IntroductionAn overdenture may be defined as a removable prosthesis that covers the entire occlusal surface of a root or implant. Such prosthesis has found ever-increasing applications in prosthodontics, which may be a reflection on population trends and the demand for better treatment. The concept of the overdenture covers a number of possible solutions for patients with nearly all the teeth missing. Common to all is the combined periodontal and mucosal support and the similarity of the external form to that of complete dentures.Definition (according to Glossary of prosthodontics terms 1999)A removable partial denture or complete denture that covers and rests on one or more remaining natural teeth, the roots of natural teeth, and/or dental implants.Synonyms- Overdentures (English)- Hybrid prosthesen (German)- Overlay dentures.- Telescopes dentures.- Biologic dentures.- Overlay prosthesis.- Superimposed prosthesis.HistoryThe overdenture, a complete or partial denture prosthesis constructed over existing teeth or root structure, is not a new concept in a technical approach to a prosthodontic problem. Indeed, its use dates back over 100 years.

In 1856, Ledger had described a prosthesis resembling an overdenture. True, his restorations were referred to as “plates covering fangs

1888 Evans had described a method of using roots actually to retain restorations. In 1896 Essig had described a telescopic-like coping. At around the same time Peeso

was also making what appeared to be removable telescopic prosthesis”. 1906–WILLIAM HUNTER put forward his focal sepsis theory and this dealt a great

blow to the overdenture mode of treatment. The main point of contention was that the exposed roots act as foci of infection.

1916‐PEESO was employing removable telescopic crowns. Later on, the bar type of construction was developed.

MILLER (1958 ) published his classic article where the retention of previously unusable teeth and their advantageous use in overdenture treatment was explained as a basic tenet in management.

Prieskal(1968)described various commercially available overdenture attachments

RATIONALE FOR THE OVER DENTURE CONCEPT

Extraction of all natural dentition and replacement with a complete denture is not the most desirable treatment. Preventive prosthodontics emphasizes the importance of any procedure that can delay or eliminate prosthodontic problems. The over denture is a logical method for the dentist to use in preventive prosthodontics..

The sequelae after the extraction of all the teeth make complete denture progressively less effective. Among these sequel area. The loss of discrete tooth. proprioceptionb. The progressive 'loss of alveolar bonec. The transfer of all occlusal forces from the teeth to the oral mucosa.From physiologic view point the roots provide not only periodontal ligament Support but also

Directional sensitivity Tactile sensitivity to load Dimensional discrimination' Canine response Proprioception and salivary secretion Decreased perception in older individuals

GoalsThe overdenture accomplishes three rather obvious, but tremendously important goals.1. Maintaining teeth as a part of residual ridge:This enables the patient to have a denture that has far more support than any other conventional dentures. Instead of soft movable tissues, the denture sits on teeth “pilings” enabling the denture to withstand far more occlusal load with out movement. Retentive device may or may not be incorporated into the denture-tooth contact.2. Decrease in the rate of bone resorption:Alveolar bone is preserved for the support of the teeth. If the teeth are removed the alveolar bone starts resorbing consistent with the length of time the teeth have been missing. Moreover, the insult of complete dentures also quickens the process atan alarming rate.3. Increase in manipulative skills in handling the denture:The preservation of the teeth also preserves the periodontal membrane that surrounds them. This preserves the proprioceptive impulses supplied by the periodontal membrane. Thus, a very important part of myofacial nervous complex is retained. The patient is aware of the occlusal contact. This fine discrimination enables an over denture patient to control the force of occlusion in very much the same manner as a person with natural teeth.

Requirements1. Maintenance of health:

The health of the underlying tooth structure should be maintained, without which the overdenture cannot sustain. Teeth used as abutments must be evaluated for their periodontal conditions. An increased crown-to-root ratio, extensive bone loss, and mobility do not necessarily negate the use of a tooth for an abutment. However without question the periodontal condition must be treated first, with whatever means.2. Reduction in crown-to-root ratio:The reduction of crown has an immediately favorable effect on tooth mobility because of the decrease in length of lever arm delivering the torque to the mobile tooth. In addition tooth mobility has lessened under long-term overdenture use provided that the periodontal health has been maintained.3. Basal seat tissue:The tissue covering the basal seat should be in good condition so that a well fitting base can distribute the load over as wide an area as possible. Intimate tissue contact is also necessary to prevent food and plaque accumulation under the base.4. Simplicity of construction:It should be simple to construct and maintain. In many areas due to the lack of available space, sections of the overdenture base are quite thin. If metal reinforcement is not used, fracture of the base and prosthetic teeth is common. The overdenture should be constructed in such a way that its repair is relatively unremarkable.5. Ease of manipulation:The base should be easily manipulated by the patient. The use of a retaining device becomes a struggle for the patient to insert and remove. This cause unwanted forces to seriously damage the base or the abutment teeth. Therefore, proper consideration should be given in selecting the course of treatment.6. Other Requirements:An overdenture which fulfills allof the above requirement should also fulfill those requirements of any conventional denture. Therefore matters such as adequate tissue coverage, underextension and overextension of bases, jaw records, harmonious occlusion and esthetics cannot be compensated because an overdenture is being constructed.

ClassificationA. According to the nature of support:- Tooth supported.- Implant Supported.B. According to indication spectrum:- Immediate overdentures.- Transitional overdentures.- Definitive overdentures.C. According to the method of abutment preparation:- Non-coping.- Coping.- Attachments.IMMEDIATE OVER DENTURE:

An immediate overdenture is constructed for insertion immediately after removal of some natural teeth of which many hopeless abutment teeth. are treated and the over denture is inserted as an immediate replacement. The immediate over denture modified as required. It can be worn for several years under favourable circumstances.TRANSITIONAL OVER DENTUREA transitional over denture is obtained by converting an existing removable partial denture to over denture. REMOTE OVER DENTUREA remote over denture is an over denture other than transitional or immediate. It is usually constructed for insertion at some time "remote" from the removal of hopeless natural teeth.

Based on the method of abutment preparation1. Non coping abutments with simple tooth modification with endodontic treatment without endodontic treatment2. Abutment with Coping3. Abutment with Attachments4. Submerged vital rootsNON COPING (AFTER ENDODONTIC TREATMENT) Selected abutments are reduced to a coronal height of 2 mm to 3 mm and then contoured to a convex or dome shaped surface. Most teeth require endodontic therapy and the final step is prepared conservatively to receive an amalgam or composite restorationWITHOUT ENDODONTIC THERAPY : The remaining teeth are merely reshaped to eliminate undercuts and reduce the vertical height if necessary to create more inter ridge space for the over denture.ABUTMENT WITH CAST COPING:Cast metal coping with a dome shaped surface and chamfer finish line at the gingival margin are fabricated and cemented. These are 2 distinct types of copings1.Short 2.LongThe short coping: These are 2-3 mm long and normally require endodontic therapy since the required coronal tooth reduction would expose the pulp. Attached to the coping is a post fitted to the canals. Long coping :These are normally 5 to 8 mm long. an attempt is made to circumvent endodontic therapy by a conservative reduction with a ellipsoidal shaped coronal coping and an increased crown root ratio

ABUTMENTS WITH ATTACHMENTS:Most attachments are secured to the abutment by cast coping. The objective of any attachment is to improve retention of the denture base.Because of the factors like time, cost and risks the procedure should be reserved for patient with a favourable prognosis. Here the low caries index, proper home care, periodontal health and inter ridge distance are absolutely necessary.SUBMERGED VITAL ROOTS : This is of current research interest. It attempts to obviate some basic problem associated with the more conventional over denture abutments. In these cases selected vital roots are transacted and -reduced to 2mm below the crestal bone and then covered by a mucoperiosteal flap.

ADVANTAGES:1. Preservation of alveolar bone:Preserving the teeth retains not only the alveolar bone supporting the teeth but also the alveolar bone adjacent to the teeth.2. Preservation of proprioceptive response:The preservation of periodontal membrane under the overdenture gives the patient a sense of discrimination not possible with conventional dentures.3. Support & Stability:The natural tooth stops of an over denture provide for a static, stable base unparalleled by any conventional denture. The overdenture literally does not move.When compared with a conventional denture, we can see the rather obvious advantage of function.4. Retention:Usually sufficient by merely over laying the teeth. However in some cases it may be desirable to increase the retention. This can be done by either using attachments or by resilient liners.5. A simple approach to the problem patient:In the past, patients with congenital defects, such as cleft palate, partial anadontia,microdontia, amelogenesis imperfecta, and so on, had a rather detailed lenghty and expensive procedure. But with the advent of overdenture concept a reasonable relatively fast, and inexpensive mode of treat became possible. They can be restored back to function esthetics and comfort.6. Periodontal maintenance:Because the abutment teeth are easily accessible and because any form of splinting seldom is involved the patient is able to take a vigorous home care to maintain periodontium in an optimum state of health.7. Patient acceptance:Patients are most receptive and appreciative of this treatment because they experience a striking improvement in function and esthetic while still maintaining some of their own teeth. Hence the psycologic scarring some patients incur because of the loss of all their natural teeth is decreased. Moreover in some cases were retentive attachments are given; extension of the denture bases can be reduced.8. Convertability:The overdenture is designed so that if for some reason overlaid teeth must be extracted the overdenture can readily be converted to accept the alteration. Even if all the teeth are lost the overdenture, can be converted to a conventional complete denture.9. Cost:There is a large initial cost, mainly due to periodontal and endodontic treatment and occasionally due to cast coping or due to retainer device. However, when weighing total service involved, the ease of maintenance in years to come, the low percentage of remakes, and the alternative treatment of extensive fixed and removable partial dentures, the cost of an overdenture is very favorable.10. Harmony of arch form:The construction of a complete upper denture opposed by a lower removable partial denture is common. Many times this results in excessive resorption of bone that directly opposes the

lower natural teeth. This problem and others similar to it can be prevented by originally retaining some of the natural teeth on the arch with complete denture. Even teeth that are hypermobile, if treated periodontally, can serve as abutments for an overdenture for many years and drastically reduce the resorptive process of the alveolar ridge that opposes the natural dentition.11. Minimal post insertion problems:Due to a stable base more accurate jaw records improves occlusion thereby patient comfort by drastically reducing the trauma of a denture base to supporting tissue.Hence minimal post insertion adjustment required.

DISADVANTAGES:1. Caries Susceptibility:The most pressing problem encountered is the breakdown of abutments due to caries. Even following endodontics and teeth that have copings are also affected.Meticulous home care along with fluoride therapy in clinics is required to overcome this.2. Bony undercuts:Because of the limited path of insertion, the bony undercuts usually found labial to the abutment causes problem for the close adaptation to the underlying tissue.Blocking out the undercuts results in a space where food traps and eliminates peripheral seal. In many cases the denture borders are cut out at the height of contour, jeopardizing the peripheral seal and esthetics. Surgical interventions to eliminate the undercut are contraindicated because; the bone involved is the supporting alveolar process of overlaid tooth.3. Overcontour:Due to the bony undercuts the flanges may have to be constructed by blocking the undercuts, which results in overcontouring and improper lip fullness and does not interact well with the facial musculature there by patient rejectance.4. Undercontour:Due to limited path of insertions and presence of undercuts, the denture base are not possible to extend to important areas such as retromylohyoid space on the mandible and the post molar pocket on the maxilla sacrificing their desirable qualities.5. Encroachment of the interocclusal distance:When an overdenture is made, especially one with some form of internal attachment, the available interocclusal distance of a standard denture usually cannot be compromised and so a struggle ensues to place the entire overdenture within proper dimension. The placement of an attachment, the artificial tooth, and the necessary acrylic to retain the attachment and tooth over the natural root is an exercise in selection and grinding to achieve the proper form within the parameter of available inter- ridge distance.6. Esthetics:Optimum esthetics is a goal to which we all strive and the proper case selection and subsequent implementation of treatment must be carefully carried out if we are to achieve this goal. An overcontoured or undercontoured flange, a compensated occlusal plane in light of a space problem or an overbulked denture due to insufficient space for attachment and tooth replacement do little for esthetics.

7. Periodontal breakdown:Periodontal disease is one of the principal reasons that a patient is in need of such a treatment as an overdenture. Carelessness leads to continuation of this pre-existing condition and jeopardize the success of the treatment. Plaque accumulation, inflammation, pocket formation, loss of supporting bone, and decrease in attached gingiva are all potential sequelae that may occur if the overdenture is not maintained properly. Greater effort on the part of patient and dentist required to maintain the prosthesis.8. Expense:Greater expense is directly related to the extent of preprosthetic treatment, the use of retentive attachments, and the post placement course. Savings are possible through the use of directly mounted attachments, elements or by dispensing with attachments altogether. In spite of these patients with very low financial status it is contra indicated.

INDICATIONS:1. Young patients with history of loss of teeth.2. If a patient can practice or learn adequate oral hygiene to significantly delay or prevent rapid carious or periodontal breakdown.3. If in an arch atleast one tooth can be remained so that, preservation of bone in that area is better than none.4. The remaining teeth would be more severely damaged by a different type of treatment.5. The prognosis for wearing complete dentures is poor because of extreme ridge resorption, xerostomea, exaggerated gag reflex, insufficient learning ability, psycologic factors etc.6. If periodontal condition and carious susceptibility is less and if present should be able to treat the conditions by whatever means possible.7. Abutment teeth located in an area where a maximum support and preservation of alveolar bone is possible.8. Patient with anomalies such as cleft palate, microdontia, amelogenesis, imperfecta, dentinogenesis imperfecta, partial anadontia etc.9. In patients who have the psychological fear missing all of their natural teeth.10. If no other type of prosthetic treatment promises a cost-effectiveness ratio.11 in patient with combination syndrome12 For patients with a poor prognosis for complete denture.

High. palatal vault and ridge slope Poorly defined sublingual fold space In Class III tongue position Knife edged ridge that will provide inadequate support.

Contraindications:

1. When a patient cannot economically afford or cannot or will not give the necessary time for the procedures.2. Poor candidates such as mentally or physically handicapped people for whom plaque control and good oral hygiene are difficult.3. Contra indications for periodontal and endodontic treatment.Periodontal:

Class III mobility with no bone support and which cannot be corrected. Soft tissues and osseous defects, which cannot be corrected. Patient who will not keep the retained teeth free of plaque. Failure to establish a sufficient zone of attached gingiva by mucogingival or

grafting procedure. Excessive reduction of the adjacent residual alveolar ridge as a result of

elimination of osseous defects and the establishment of normal architecture.

Endodontic: Vertical fracture of roots Mechanical perforation of the roots Internal resorption that has perforated through the side of the root. Broken instrument in the root canal Horizontal fracture of the root below the bony crest.

4. More specific contraindications are the diagnostic findings such as: Bony undercuts which results in over or undercontouring of the flanges. Compensated occlusal curves Probability of over bulked prosthesis. Lack of vertical space. All the above mentioned which causes an altogether compromise in esthetics,

comfort, stability etc.

DIAGNOSIS AND TREATMENT PLAN:FUNDAMENTALS:The foundation of every prosthetic plan is a comprehensive clinical and radiological examination and diagnosis. For overdenture treatment, the health of the remaining teeth and the periodontium must also be thoroughly evaluated, vitality testing performed and radiographs scrutinized. The health history interview is of great importance frequently the non-clinical factors are more decisive for the feasibility of overdentures than are the clinical conditions.

-Panoramic radiographs provide an excellent over view for treatment planning, however intra oral films of individual teeth are indispensable for evaluating critical details.

o Examination charts are used to record all clinical findings. Such as:

o Tooth mobility

o Probing depths

o Width of attached gingiva

o Inflammatory condition of the marginal gingiva and plaque index as

parameters of the periodontal condition.o Vitality of the teeth.

o Condition of the hard tissue.

PLANNING PROCESS:When planning treatment for patients who will have very few teeth remaining after the preprosthetic treatment phase, all conceivable courses of action must be considered. The treatment plan is divided to three phases.Phase I - Teeth that can be retained are identified, this goes hand in hand with indications.Phase II - Determining the usefulness and/or necessity of retaining those teeth that can be saved. Based on this results treatment options are worked out and discussed with patients. Out of this emerge the provisional treatment plan and the necessary preliminary treatment initiated.Phase III - Determination of the definitive treatment plan in regard to number of abutments and type of construction. This can be established only after the reevaluation of the provisional plan and at the end of the preliminary treatment. The final decision on the details of construction is not made until after the final try in of the trial denture.

A. Negative evaluation decision: No overdentureB. Positive evaluation decision: Provisional treatment planC. Provisionally negative reevaluation Further preliminary decision: treatment.D. Definitive negative re-evaluationdecision: Abandon overdenture treatmentE. Positive re-evaluation decision: Definitive treatment plan.

Evaluation criteria & Patient Selection:I Clinical factors:Perhaps the two most significant decisions in successful overdentures are selecting the proper type of patient and establishing a careful mode of treatment that will satisfy both the patient and dentist.a. Possibility of fixed or removable partial dentures:If the remaining natural teeth are capable of supporting a fixed or removable prosthesis, then this form of treatment must be considered the primary plan of treatment. There are many disadvantages of an overdenture that can be easily avoided if this type of treatment is adopted.b. Endodontic therapy:It must be ruled out that successful endodontics can be performed because a tooth usually must be treated endodonticaly. Ideally a patient with single rooted teeth is best candidate even though multirooted teeth can be used. A two-or four weak interval before commencing any further treatment on the tooth is good to rule our endodontic complications.

3 main advantages

The crown root ratio can be made more favourable.Reduction of the clinical crown provides an interocclusal distance more favourable for the placement of the artificial tooth in an esthetically acceptable position and in more favorable relation to the opposing teeth.For securing attachments.Careful evaluation of the possibility of F.P.D or R.P.D must be done. CONTRA INDICATIONS FOR ENDODONTIC TREATMENTi. Vertical fracture of the root (or) roots.ii. Mechanical perforation of the root canal.iii. Internal resorption that has perforated through the side of the root.iv. Broken instrument in the root canal.v. Horizontal fracture of the root below the bony crest.Vi. Posterior teeth that are tilted more than. 25 degrees..

c. Periodontal condition of the abutment teeth:Periodontal evaluation is a critical stage in the construction of an overdenture. Optimum periodontal health to ensure the longevity of teeth is required.Inflammation, pocket formation, bony defects and a poor zone of attached gingiva must all be eliminated before commencing treatment. An adequate amount of attached gingiva is need for the abutments. If this is not present it should be rectified through periodontal surgery.d. Caries:The presence of high caries index and the creation of a situation that will easily promote a caries environment are two of the most devastating sequelae to improper patient selection. If abutment teeth are caries prone, we must think our selves’ whether it can be easily removed and crown restored, and then to create a caries free environment. The restoration should be properly prepared and polished moreover the patient must be instructed to strictly follow meticulous home care along with regular visits.e. Young patients:Careful evaluation should be made in selection of young patients for overdentures.Here their needs and failures can be much greater. Because of the length of time the overdenture will be in service, failure of the denture is an eventuality that must be anticipated. Proper tooth treatment and home care become more critical.f. Location of abutment teeth:Teeth are most useful in areas of maximum occlusal force and ridge resorption potential. The anterior aspect of the residual ridge especially that of mandible, is very susceptible to change, so canines and premolars or valuable teeth to preserve in this area. Upper anterior teeth that oppose natural lower teeth prevent the destruction of the anterior maxillary ridge, when utilized in maxillary overdenture. Mandibular canines are most often utilized because they are usually the last teeth to be lost. If only a single tooth remains that should be remained if possible. If canines and premolars are present it is better to retain canine and second premolars because, it gives better support and favorable oral hygiene.

Two teeth in each quadrant presents an ideal situation in which stress is distributed over a rectangular area.Eg : Cuspid 2nd premolar and/o-r second molar in each quadrant

The tripod is the next most favourable form for support and stabiliy The use of two teeth in each arch or one arch has met with satisfactory results

g. Economics:Finally the extend of treatment necessary to save an abutment tooth must be considered taking in to account the expenditure of time and economic reality.Therefore in the treatment plan, we should evaluate the situation, as it exists; teeth that already have endodontics, teeth that could be reduced without endodontics, single rooted rather than multirooted teeth, and the minimum number of teeth needed to achieve support and bone preservation should be kept to hold the line on cost so that this form of treatment can be viable.

II Non-clinical factors:The results of the clinical evaluation must be considered along with the nonclinical factors in order to form an overall judgment. Foremost among the non-clinical factors are the wishes, expectations and demand of the patient. Against these must be weighed other factors, which can be considered parameters of feasibility, such as: the patient’s attitude towards the situations, financial resources, and information from health history.

Based on this comprehensive evaluation a provisional treatment strategy must be formulated to provide the patient with one or more treatment options to suit his/her individual need and abilities.

PRELIMINARY TREATMENT:Before a patient can be successfully treated with an over denture, it is usually necessary to improve the condition of the tissues through a preparatory phase that includes periodontal, prosthetic, surgical and endodontic procedures. Those procedures which will contribute to the health and maintenance of the periodontium around the abutment teeth are of paramount importance.A. Periodontal Procedures:The initial periodontal treatment is the most important part of the entire preparatory phase. Its progress determines whether the periodontium of the abutment teeth selected in the preliminary plan can be restored to a sufficiently healthy condition to bear the load of an overdenture and whether the patients level ofcooperation sufficient to make this type of treatment feasible and reasonable.Periodontal treatment divided into two phases:- Initial therapy.- Surgical therapy.1. Initial therapy or hygiene phase:The initial treatment includes steps to produce a cleaner oral environment through dental prophylaxis, scaling and root planning, excavation of caries and placement of temporary

restorations, elimination of iatrogenic gingival irritation, elimination of trauma due to inadequate dentures, and instruction in oral hygiene procedures.After the plaque induced gingivitis has subsided, subgingival root surfaces are cleaned and polished through deep scaling and root planning, but not under direct vision in this phase. The pocket epithelium and infiltrated subepithelial connective tissues are removed through closed soft tissue curettage. Then the results of preceding treatment steps to be evaluated.

2. Periodontal surgery:After evaluating the effectiveness of the initial therapy and patient cooperationany necessary surgical therapy is instituted. They include:- Root planning with direct visual access- Surgical reduction of periodontal pockets by gingivectomy and/or flap procedure.- Surgical crown lengthening- Widening of the attached gingiva through mucogingival surgery.

B. Preliminary prosthetic Procedures:The purpose of prosthetic procedure during the preliminary treatment is to help bring the denture bearing tissues and the neuromuscular system in to the best possible condition for acceptance of the overdenture. They are performed in conjunction with other therapeutic measures.

They are:1. Early conversion to a provisional overdenture:The periodontium of the remaining teeth is often found to be injured by unsupported clasps, lingual connectors and parts of the base of a partial denture. Very few of these denture components can be modified so that they no longer traumatize the denture supporting tissue. Root support of the modified prosthesis is accomplished at the same time, resulting in a reduction of the forces born by the residual ridge.Periodontal therapy and prophylaxis of the prospective abutments for the future overdenture can be carried out at this point.2. Modification of an existing removable partial denture:One of the indications for the replacement of a partial denture with an overdenture is tissue damage and related problems caused by wearing the partial denture. Overextension, underextension and imprecise adaptation of existing denture bases produce load concentrations on certain areas of the residual ridge and mucosa. This leads to recurring points of pressure and friction, inflammatory hyperplasia, or generalized inflammation of mucosa. It can also be caused by incorrect occlusion, or by the chemical toxins from accumulations of plaque on the tissue side of the denture.The oral mucosa can be conditioned by correcting the border extensions and temporarily relining the dentures. Relining eliminates the mechanical and chemical irritants for a period of time. Correction of occlusion can be made by making new jaw relations.

3. Initial prosthetic treatment:Whenever possible, an abrupt transition from natural dentition with no prosthesis to complete dentures or overdentures should be avoided. A removal partial denture can be given to the patient during the initial therapy; so that the patient gets accustomed to the wearing of dentures. Moreover this can be converted in to an immediate over denture. This type of treatment can be instituted only if the remaining abutments are capable to receive clasps.4. Functional diagnostic measures:Some patients may present with extreme reduction of vertical dimension of occlusion as the result of ridge atrophy or abrasion of artificial or natural teeth. This cannot be corrected in the new dentures “by raising the bite” unless the patient has good neuromuscular adaptability. Planned increases in the vertical dimension either by giving bite splints or raising the bite in existing dentures can be given over a period of several weeks or months till the neuromuscular reflex adapts to it. Patient adaptability can be checked by utilizing various parameters, such as the patients subjective oral condition, phonetics, masticatory ability and functional disturbances, parafunctional activity, abrasion and physiognomy. An increase in the vertical dimension must be thoroughly evaluated before it is used as the basis for the final dentures.C. Surgical procedure:The list of surgical procedures that might become necessary in preparing a patient for overdenture encompasses almost the entire range of oral surgery. In about 25% of all cases, radiographs reveal findings that require surgical interventions such as fractured root tips, impacted teeth, cysts and other pathology within or upon the book. The most frequent surgical procedure is the extraction of hopeless teeth. As these procedures are been undertaken, opportunity should be undertaken to improve the periodontal condition of salvageable adjacent teeth by open or closed scaling, wedge excisions or flap operations.D. Endodontic procedures:A high percentage of all prospective overdenture abutment teeth will require endodontic treatment. The only exceptions to this are vital abutments that will be covered with telescope crowns, heavily abraded vital teeth that will remain untreated, and non-vital teeth that already have root fillings. In all other cases endodontic treatment is necessary because the tooth will be shortened close to the level of the gingiva, or because part of the root canal will be needed to receive a dowel (“post”) or screw, or because the tooth is non vital and either has no root canal filling or an inadequate one. In selecting the filling materials, it must be kept in mind that the root canal will have to be reentered later in the course of treatment in order to place a dowel. Therefore, silver point, resin based cements or other canal filler that become completely hard, unless used in combination with guttapercha points, are contraindicated. Guttapercha points can be used with following precautions.- The guttapercha must not be completely removed from apex.- Special care must be taken not to push the guttapercha points beyond the apex.Therefore a radiograph with dowel in place is always indicated. As a rule, endodontic treatment is performed either before or concomitantly with any necessary periodontal treatment.

Abutment configuration:The number and position of the teeth in the arch, influences the support and stability. Two teeth in each quadrant probably present a situation in which stress is been distributed in a rectangular area. The tripod is the next most favorable form of support and stability. The use of two teeth in each arch or one tooth in one arch has met with satisfactory results when the patient has been educated in what to expect from treatment.

Design options and Support possibilities:There are various options available to the dentist for support and retention of overdenture. In addition to the more complex and expensive designs, there are also simple designs that place less financial burden on patients. The way in which the remaining teeth or roots are treated and integrated in to the construction depends on the type of design selected. The root may have only a denture-supporting function, or they may serve to provide both support and retention for the overdenture.

Various techniques:1. Simple tooth modification and reduction:In this procedure remaining teeth are merely reshaped to eliminate undercuts and reduced in vertical height, if necessary to create more inter ridge space for the overdenture. The requirements for this modality is low caries index good oral hygiene sufficient vertical space and the pulp must have receded sufficiently. After the final impression a master cast is poured, surveyed for undercuts and a denture is constructed.2. Tooth reduction and cast copings:Minimal tooth reduction is done and a cast coping is placed, so as to prevent sensitivity and caries. The requirements for this treatment are the same with simple modification and the tooth must be periodontally stable. The coping is called “thimble” shaped coping or “telescope” copings.3. Non coping abutment:Selected root abutments are reduced to a coronal height of 2 to 3 mm and then contoured to a convex or dome shaped surface. Most teeth require endodontic therapy and in the final step are prepared conservatively to receive an amalgam or composite type restoration. It is indicated when there is normal coronal height to the teeth and normal interocclusal distance with little or no loss of vertical dimension.4. Abutment with copings:Here a casting is placed on tooth instead of placing a simple amalgam restoration in the root canal. The casting may be used because of fear of recurrent delay on the exposed dentin when there is a history of carious involvement. If home care is not drastically improved, then the placement of a cast coping does little to prevent carious lesions. Cast copings may be short or long. Short cast copings are 2-3 mm long and normally require endodontic therapy because the required coronal root reduction would expose the pulp. Retention is gained from short posts that are placed within the root canal. The post is short because of the possibility of

removal of the casting, if caries could develop or if only support & stability is required from abutments.

5. Abutment with attachment copings:Usually requires endodontic therapy, and has long posts about 5-8mm long into the root canal. This approach is reserved for the situation in which not only stability is desired but also in which a significant improvement in retention is desired. The main requirement of this is a drastic reduction in the crown-root ratio, sufficient vertical space & a good periodontal support. Retentive attachments are soldered on to the copings after final try-in.6. Submerged vital roots:This additional abutment category is included because of the past research and interest. Selected abutment roots are transected and reduced to 2mm below the crestal bone and then covered by mucoperiosteal flap. This is done to prevent caries, gingivitis periodontitis etc. The results are both discouraging and encouraging. The two major postoperative problems are the development of dehiscence and pulpal pathosis. The use of submerged vital tooth is not been successful and not recommended now.

Classification of supportive devices:A. Supporting elements (non retentive)1. Root sealed with amalgam, composite, or glass ionomer cement.2. Gold copings without attachment.B. Retentive attachments1. Single attachments.- Attachments mounted directly in to root canals with no copings.- Attachments soldered to copings.2. Bar attachments.3. Telescope attachmentsRetentive attachments:A retentive attachment for an overdenture consists of two separable parts- a male part and a female part. The male part is fixed to the abutment tooth and the female part is fixed within the denture base.

Functions:Basically the same functions as the clasps of partial denture:- Securing the prosthesis against forces that tend to lift it.- Providing periodontal support for the prosthesis.- Transferring the forces of muscles of mastication from the prosthesis to the periodontium in a merely axial direction as possible.- Distributing shearing forces.- Stabilizing and splinting the abutment teeth.

Retentive mechanism:Is by friction between male and female components. The retentive force of an anchoring element should amount to at least 400g in order to ensure adequate retention. However it must not exceed 1000g, because excessive tensile force on the abutment tooth may result in damage to periodontium.Two types:-Rigid-Non rigidA. Rigid Attachments:A retentive attachment is considered to be rigid if it grasps the abutment tooth bodily and permits no movement between anchor and prosthesis except for rotation along its long axis.Advantages:- Reduction of the load on the edentulous ridge during function and parafunction.- Minimum tipping of abutment teeth when subjected to lateral forces.Disadvantages:Applied forces and movements of the denture are transmitted almost entirely to the abutment teeth.B. Non-rigid attachments:A retentive attachment is Considered to be non rigid when it permits rotational movements of the denture around the anchor in one or more planes, or vertical bodily movements. The greater the number of non-rigid attachments used in the same denture, the more limited will be the movement of each.

Advantage:- Reduced effect of tipping force on the abutment teeth (Principal of shortening)Disadvantage:- Greater stress on the tissues supporting the denture (Ridge resorption)- Greater tipping of the teeth under lateral forces.Selection of appropriate attachments:In most cases the final selection of the appropriate attachment can be made only after the denture has been tried in patients mouth. The amount of vertical and faciolingual space available to house the retentive element after the teeth are set influences the selection of retainers. However it is all upon operator’s choice to select the retentive device, which is most suitable.Rigid attachments should be used whenever possible because they place lower demands on the edentulous ridge during function and parafunction and requires fewer repairs than non-rigid attachments.Indications of non-rigid attachments:1. When the geometric distribution of the remaining teeth is unfavorable for the stability of the denture. This can give rise to unfavorable tipping and rocking movements, especially if the soft tissue support is more resilient and/or less expanded than normal.Unfavorable geometric distribution of the remaining teeth

2. When only a short dowel can be used to anchor the coping. If a rigid attachment were used over a short dowel, uncontrolled movement of the denture might loosen the dowel from the root.

The idea behind non rigid attachments is to lessen the torque the prosthesis exerts on the periodontium of the abutment teeth by shortening the clinical crowns of the natural teeth flush with the gingiva and providing a loose connection between the denture and the remaining root. This is the principle of prophylactic shortening. The movable attachment shortens the lever arm of the torque acting on the abutment tooth.Attachments anchored directly in the root canal space without copings are well suited as retainer for interim overdentures. These are cases in which the roots are too periodontally weakened to justify the placement of expensive attachments, but can still be called upon to serve as transitory denture retainers. Such limited duration treatment is also indicated for elderly patients because they can be provided at less expense and facilitate the adaptation to complete denture. One disadvantage is that the omission of protective coping increases the risk of carious destruction and root fracture. There is a limited indication, for resilient eg: where the remaining teeth are in a topographically unfavorable arrangement and the soft tissues are highly compressible. In either of these situations the overdenture must be checked frequently after placement so that any possible harmful movement of the denture can be eliminated.

Single attachment versus bar attachment:Whether the overdenture abutments are to be left separate or are to be connected by a bar depends primarily on the number, distribution and periodontal condition of the remaining roots. In many cases both type of retainers can be used with equal chances of success. This preference depends upon the operator experience.Indications for single attachments:- Only one tooth remaining.- Diagonal position of the abutment.- Spans too long to be bridged by bars.- In sufficient space above the residual ridge to accommodate the attachments. In such cases placement of a bar often causes the anterior portion of the denture base to lie too far to the lingual and encroach upon the tongue space.

Arches that are markedly V shaped or acute in front. Prefabricated bars, unlike individual retainer, often restrict the tongue space enough in the labiolingual direction to cause disturbances of speech and mastication. This is because bars must be straight, at least in the portion where the clip attaches, and therefore cannot follow residual ridge closely enough. One exception to this is a bar that is round in cross section and is grasped by short clips. This can be made to conform to the arch form more precisely and thus restrict the tongue space to a lesser extent.

Considerations during alignment of single attachments:1. The alignment of stud attachments with one another.2. The alignment of stud attachments with the path of insertion of denture.3. The taller the attachments, the more difficult the alignment may be.

Indications for bar connectors:- Periodontally weakened abutment teeth with increased mobility where primary splinting by means of a bar is desirable. True primary splinting can be accomplished only by using a non-linear connecting bar spanning more than two abutments.- Roots that will accommodate only very short dowels, especially when greater than normal movement is expected because of the distribution of the abutment, the nature of denture foundation, or anticipated ridge resorption beneath the mucosa borne denture segments.- Bar connectors offer greater mechanical stability and more wear resistance than single attachments.- Tipped teeth that could hardly be considered for single attachments because of the eccentric loading can become useful abutments when joined by bars.NB (A bar connecting a strong abutment to a mobile, periodontally weakened root can act as a lever arm with devitalizing effects on the stronger abutment if the dynamics of the prosthesis are unfavorable).Preparation of the abutment teeth:Preparing the remaining teeth to receive an overdenture takes place only after initial therapy is completed and its results can be clearly evaluated. In formulating the definitive treatment plan, it is decided how the overdenture is to be supported by the remaining teeth. It is thus determined how these teeth must be prepared. For telescopic retainers they may be prepared according to the usual rules for cast full crowns.

a. Telescopic crownb. Root copingc. No copingd. Dowel copinge. Directly mountable retentive element

a. Preparations for supporting elements with no dowel copings:The amount of shortening is determined by the vitality of the tooth by the anticipated load the root will carry and by spatial relations. Vital teeth can be shortened and remain vital only if pulp had receded other wise devitalization is always necessary. If the root is intended to resist lateral forces, atleast 3mm of height should be left. If the root is to be served only for support then, it can be shortened to a level of 1mm above the gingiva. Root should never be reduced beyond gingival crest because the space will tend to fill in with hyperplastic gingival tissue.- Rounden the sharp edges:The surface of the shortened tooth is given a slightly spherical, dome shape. This preparation shape corresponds best with denture movement induced by loading which is usually a rocking movement. The edge between the occlusal and axial root surfaces is rounded. No attempt is made to parallel the axial walls.- Sealing the orifice of the root canal:If the tooth had been endodontically treated the canal is sealed occlusally with amalgam or glass ionomer cement.b. Preparation for directly mountable prefabricated retentive elements:They are devices with out coping that can be screwed and cemented directly into endodontically treated roots. They are used for temporary fixation of overdentures.All systems are based on a spherical retentive element attached to a threaded post. For each system there are special standardized sets of instrument. (Post space drill, seat milling bur, and threaded cutter or tap). The preparation varies from system to system.In case of Dalbo-Rotex anchor, the canal of the endodontically treated and shortened tooth is drilled to depth 1-2mm greater than the length of the screw of the selected Dalbo-Rotex, using the corresponding Rotex root canal enlarger. If a long necked Dalbo-Rotex is to be used, a cavity 1-1.5mm deep is prepared in the face of root using counter sink drill. This serves to receive the base of the anchor. When short necked is used the root face is simply ground flat.

The enlarged root canal is reamed with a standardized Rotex canal trimmer used in Thomas finger wrench. The Dalbo-Rotex is screwed clockwise into the post space with the finger wrench under moderate pressure. The screw cuts its own threads in to the canal walls. Then the anchor is backed out of the canal. The post space is now coated with 2-inch phosphate cement and the Dalbo-Rotex again screwed back. First it is turned anti clockwise until it falls into the previously cut threads and then clockwise until completely seated. After the cement has hardened the cavity above the base of the anchor is seated with glass ionomer cement or amalgam. The female portion is incorporated directly in to the denture base with autopolymerizing acrylic resin.c. Tooth preparation for Dowel-copings:A dowel coping that is to serve as a connection between abutment tooth and denture base must fulfill a number of criteria that depends essentially on an adequate tooth preparation. The preparation is therefore a very exacting task in which the periodontal, functional, esthetic and technical implication must be considered.According to current concepts tooth preparation that results in subgingival crown margins is undesirable. Supra gingival preparations are also preferred for dowel copings, because they cause less gingival irritation and leave easily cleansable margins.Requirements for supragingival margins:- The sound tooth structure available for preparation must extend atleast 1.5mm above the gingiva.- There must be little danger of rapid caries formation at the margins of the coping.- Visible coping margins especially in the maxillary anterior region, must not present esthetic problems. As s rule supragingival preparation margin can be made in lingual and proximal surfaces.Requirements for partially subgingival preparations:- Esthetics demands a subgingival margin. The preparation finish line and the margin of the coping may be placed 5mm subgingivaly if and only if the coping can be tapered to a fine margin and be finished with at most care.- Supragingival margins would not allow adequate space for concealed attachment.- Caries activity is high.Tooth preparation for dowel coping must shorten the root enough to create ample space for a retentive element, but must at the same time leave enough tooth structure to provide sufficient retention for the coping. Retention is achieved by means of a standardized prefabricated dowel that precisely fits the walls of the enlarged root canals and by preparing the external surface of the root approximately parallel with long axis dowel.Steps:- After the tooth has been shortened to about 2mm above the gingival margins the roots canal is prepared with a standardized drill set to receive a root dowel, which is usually tapered. The post space is refined with hand. The length and angulation of the inserted dowel can be monitored radiographically.- The external root surface is prepared nearly parallel to the axis of the dowel with a light chamfer as finish line. The preparation is kept supra gingival wherever possible. In many case the preparation will have to extend subgingivaly partly or even completely around the root.

- Shortening the preparation is now done to its final length, approximately 1-1.5mm above the gingival margin.- Facially shortening is accomplished through placement of round occlusal shoulder so that, its outer edges about .25mm above the gingival margin.- Occlusal box is prepared where the cross sectional dimension of the root allows it.This serves to increase retention, enlarge the area were the coping is cast to the post and it provides a certain amount of reserve space for the mounting element. The remaining root walls must not be reduced to a thickness less than 1mm or the risk of root fracture would be too great.- A Bevel is placed between the box walls and occlusal surface.

d. Preparation for thimble shaped or telescope prosthesis:Abutment for telescopic prosthesis will be covered by two layers of metal while facial surfaces may require facings as well. All these require extensive preparation and planning, as a poorly executed abutment preparation is one of the most common mistakes. The results of such errors are thin inner copings that become perforated after a period of use, together with a bulky and unsightly removable prosthesis.Occlusal reduction of 2-3mm is the minimal requirement. Although height and size of the inner coping must influence retention, the principal factor for retention appears to be it’s taper, assuming that the outer casting is accurately adapted. If the convergence angle of the axial walls is 6 degrees or less, a significant amount of retention can be provided.Problems with tooth preparation and consequences:The rules for preparing dowel coping cannot be followed consistently in all cases.Often compromises must be made because of periodontal attachment loss and root caries. These affect not only the abutment tooth itself but also the shape of the coping and denture base.a. Loss of attachment:If there is loss of attachment on the facial surface but no root caries, the preparation margin should be kept supragingival. By doing this the root coping can be given the optimal form for function and periodontal health. If the denture base is kept away from the periodontium, the bare root surface will be exposed even with the denture in place. If this causes any esthetic problem, then base may be made to conceal the root surface. Because this design is disadvantageous it should be used in areas with high priority on esthetics.

b. Root caries:Caries that extends subgingivaly must be exposed through periodontal surgery to provide access so that the cavity can be excavated down to sound dentin. When root caries is confined to the facial surface, removal of caries and preparation for a root coping will result in a finish line that are at different levels. This makes it difficult to achieve the described concavity on the surface of the coping and a nearly right-angled transition from occlusal surface to the axial surface. This results in fabrication of coping, which is too steep, and there will be increased danger of fracture of the neck of the artificial tooth it will have to be thin and narrow where it terminates the facial margin of the coping.c. Caries at entrance of the root canal:

Preparation problems are also encountered when carious destruction is present at the entrance of the root canal. This necessitates the enlargement of occlusal box or a dowel, which is too large in relation to the diameter of the root to be used so that its sides will be in apposition with sound dentin. This results in weakening of roots and formation of root cracks and related bony pockets in that area. Usually the diagnosis of a cracked root is not made until the tooth is extracted.d. Mistakes made when preparing a tooth for dowel coping:- Shortening the abutments below the level of the gingiva. The gingiva reacts to this with hyperplastic proliferation.- Making the outer axial walls overtapered or divergent from the long axis of the dowel. This reduces retention, causing the coping to come loose from the root. It must be either recemented repeatedly or remade, if there is still enough tooth structure remaining to allow modification of the preparation.Impression procedures:A. Impressions of the abutment teeth:Impressions of the prepared teeth are used to make dies on which patterns for dowel- copings can be formed. NB (No special impression technique is required for teeth that will not be fitted with dowel, or copings or those that receive directly mountable retentive elements. It is only necessary that their form and position be reproduced on the working cast on which the denture will be processed. For this they can simply be recorded in the overall impression of the arch).a. Single- tooth impression in a copper band:It is one of the oldest techniques practiced. It can be performed with either a thermoplastic material (Impression compound) or an elastomeric material. The copper band must be trimmed to terminate at the preparation finish line where it must fit the tooth precisely. Use of a thermoplastic impression material permits an immediate check of parallelism between the external preparation and the root dowel. Any undercuts will cause the hardened impression compound to break as it is removed from the tooth. When an elastic material is used the preparation cannot be checked until it has been reproduced in the stone die.

b. Single tooth impression with injectable elastomer:A prefabricated dowel with an adhesive head is used. In this technique, the gingival sulcus must first be treated with retraction cord wherever the finish line is subgingival. After removal of the retraction cord a light-bodied elastomer can be injected around the root. A partial arch custom tray is filled with more viscous elastomer and then seated to complete the impression of the abutment. Care must be taken that both the dowel and tooth must not be contacted by the tray.c. Multiple tooth impression with elastomer:When multiple roots in the same arch are to be fitted with dowel-copings, they can all be included in the same impression. Such a group impression requires the use of special root dowels. These have lathe-cut polished cylindrical heads, that are unretentive. Such post can be repositioned precisely in the impression if they should pull out as the impression is removed from the mouth. This happens frequently when the dowel axes in the prepared roots

are not parallel with one another. Dowels furnished with the retentive heads separate from the impression less frequently, but when they separate, they can never be repositioned accurately. The procedures are the same used for single tooth. Single tooth and multiple tooth impressions can be poured in extra hard die stone, or they can be electroplated with silver or copper and filled with acrylic resin to form dies. The die forms the basis for fabrication of the dowel copings.

B. Combined full arch impression:To fabricate an overdenture that will be supported by dowel-copings with retentive elements requires a working cast that reproduces the edentulous ridge and the same time hold the dowel-copings in their correct positions. The latter must be incorporated into definitive working cast because the retentive elements are attached to them only after the denture has been set up on the working cast and tried in the mouth.a. Two stage technique:In this two-stage procedure the impression of the edentulous jaw segments and the incorporation of the root coping are done in separate steps. The coping is fabricated on the die, cast in gold and fitted with an acrylic resin transfer device. The root copings are tried in the mouth and any necessary corrections are made. Accurate seating of the copings is evaluated using indicator paste.First stage:A custom tray is fabricated with the same extension as for complete denture. It is windowed or fenestrated at the areas of abutments, so that it doesn’t touch both the coping and transfer device. A zinc oxide eugenol impression is made of the edentulous segment following the criteria for a complete denture. The impression is evaluated and necessary corrections are done.Second stage:The tray is reseated on the arch and a light body elastomer or impression plaster is admitted through the windows under visual control. If the procedure is carried out correctly, a smooth transition between the two impression components can be achieved. If the dowel copings remain in the tooth it can be repositioned accurately.

b. One stage technique with dowel copings:Edentulous segments and dowel-copings can also be included simultaneously in a single-stage full-arch impression. Elastomer is the only suitable material for these techniques. It allows root copings to be accurately repositioned in the impression if they should remain on the roots when the impression is removed. This sometimes occurs in cases with strongly retentive preparations or divergent roots.The custom tray used for a one-stage impression is not fenestrated over the abutments as in the two-stage technique. Because it must fit over root copings and transfer devices mounted there on with out touching them, it will be bulky. Under some circumstance, this can lead to an undesirable lifting of the movable mucosa from the underlying bone as the impression is made.NB (The two stage combined impression is a more involved and time consuming procedure, but it produces the best impression of the edentulous segments. The one stage technique is

somewhat less time consuming than the two-stage technique but the major disadvantage is the errors cannot be corrected and it should be remade).c. One stage technique with supporting elements:- For designs that rest on abutment teeth without root copings, the full-arch impression is made as soon as the abutments are prepared.- When root copings without retentive elements have been used, the impression is made after final cementation of the copings. There is no need to incorporate this type of root coping in to the working cast because they will not be processed further.The full arch impression is made in a custom tray which covers all the ridge except for any under cut areas near the abutment teeth that could not be utilized for the future denture base. Anyway the impression is made using a zinc oxide eugenol or elastomer impression materials.d. One stage technique for existing retentive element:A single step full arch impression in zinc oxide-eugenol paste or elastomer can be used for overdenture that will rest on pre-existing retentive elements. Transfer matrices are set in place on the involved retentive elements and picked up in the impression. This makes it possible to incorporate retentive element analogs in the working cast. In this situation also, a custom tray is formed similar to those used for complete dentures. The tray must not touch the root copings and the transfer matrices.Areas of the ridge that are undercut relative to the path of insertion of the retentive elements should not be included in the impression.Jaw relation records:Recording maxillomandibular relation for an overdenture is no different than for making a complete denture. Registration of the occlusal vertical dimension is followed by the determination of the horizontal relations through intraoral and extraoral registrations using a central bearing pin.The shape of the base for the occlusion rim must correspond to that of the future overdenture, ie; it should not cover the facial marginal gingiva in the abutment regions. This improves the stability of the rim. In a few selected cases the rim can be temporarily fixed to the abutments for greater stability. Such situations are:- When there are dowel-copings and retentive elements already present from previous treatment.- When directly mountable retentive elements have been inserted prior to registering jaw relations. With an overdenture, erroneous registration of the horizontal relations will have its first destructive effect on the abutment teeth. The displacement of the dentures when they occlude will result in shearing or lifting forces on the abutments if they are fitted with retentive attachments. This frequently leads to increased tooth mobility and, in extreme cases, the loss of the abutment teeth.Tooth arrangement:Tooth arrangement in overdentures should strictly follow the rules of arrangement in complete dentures. The basic considerations in establishing the occlusion for conventional complete dentures are:- The occluding rows of artificial teeth will provide optimum chewing efficiency.- Functional stability of the prosthesis.- Comfort in chewing without exerting injurious forces on the denture-bearing tissues or adversely affecting esthetics or phonetics.

The dentures, which tip, slide or generate heavy horizontal forces during function, will accelerate resorption of the ridges. Therefore the occlusion must be designed to minimize the tipping and sliding movements when chewing forces are applied. In case of an overdenture, part of the force of mastication is transmitted to, or absorbed by the periodontium of the abutment teeth in direct proportion to how rigidly and retentively the denture is attached to the abutments. Forces that causes tipping or displacement of the denture will push and tug against the abutment teeth of an overdenture that has retentive attachments. This type of force places the most stress on the periodontium and can contribute to an increase in tooth mobility. Therefore the same occlusal concept used for complete dentures must also be used for overdentures in order to minimize the non-physiologic effects of occlusal forces, The greater the quantitative and qualitative loss of periodontium has occurred the more closely must the rules be followed. They are:- Position of artificial teeth with in the envelopes of action of tongue, cheeks and lips.- Harmony between cuspal inclines and movement of mandible.- Multilocal autonomous stabilizing contacts.Incorrect occlusal form may not itself damage the periodontium but a poor oral hygiene, improperly formed root copings and denture base add to this. Because one cannot be sure that the patient maintains oral hygiene, the occlusion must be designed according to the above-mentioned criteria for the sake of avoiding the traumatic effects. Moreover an over denture may have to be converted in to conventional complete denture when remaining teeth are lost. The less the existing prosthesis has to be modified, the easier it will be for the patient to adapt to the new edentulous condition. If the occlusal form already complies with the requirements for a complete denture, the corresponding reflex pathways and denture stability will have already been established.Final try-in:As with a complete denture, the try in of waxed up- overdenture allows for evaluation and adjustment of all the prosthetic parameters before the denture is completed. In this regard, the following points must be observed:- Vertical dimension, position of the occlusal plane, and occlusal form should not be compromised by the use of construction elements. The criteria for complete dentures have priority.- The trial denture base should conform as closely as possible to the shape of the final denture base, even around the abutment teeth. Facings must be ground to fit precisely on roots or root copings. Only in this way can extension, functional stability, and the relation of the future denture base to the lips and cheeks be judged.- The lingual or palatal form of the base must be firmly established, including the areas adjacent to the abutment teeth. The functionally crucial tongue space must not be compromised during the subsequent fabrication procedures.Mounting of the attachments:The final selection and mounting of retentive elements are made after the evaluation of trial denture. Along with the other considerations in selecting the suitable elements, the amount of space available for an attachment can now be reliably evaluated. Construction elements must always take a subordinate role to the prosthetic conditions. Facial and lingual indices of the final wax up of the overdenture are made with plaster or silicone putty. With the lid of an

index it is possible for the first time to accurately judge the amount of space available for an attachment. Only now is the final decision made concerning which attachment to use. Using mounting rods in a surveyor or, the selected attachment components are mounted as near thecenters of the root copings as possible. The axis of an attachment should line up with axis of the root as far as possible. Final checkup with the index is made to see the ample space available for female recipient. Single retainers are preferred over bar attachments and small, slender retentive elements may be selected instead of larger ones if tongue space is not to be reduced.Dowel copings:Requirements:- Not impede plaque control.- Not encourage the accumulation of plaque.- Not mechanically irritate the gingival.- Not interfere with proper shaping of super structure.- Have the greatest possible retention to the tooth.- Be solid.To meet these requirements the coping’s margins, axial surfaces, occlusal surfaceand internal surface must possess certain characteristics.a. Occlusal surface:- Concave and meeting the axial surface at nearly a right angle.- Where the margins are sublingual, meeting the axial surfaces .25mm above the gingiva.Objectives:- Accurate fit of the artificial tooth and its cast backing against coping.- Sufficient thickness of the artificial tooth at the facial shoulder to minimize the risk of fracture.- No direct contact between super structure and gingiva.b. Axial surface:Slightly divergent occlusally.Objectives:- Restoration of original root contours.- Avoidance of overcontouring, which would promote the accumulation of plaque and make cleaning more difficult.c. Coping margin:- Supra gingival wherever possible.- 0.5mm subgingival where esthetics dictates.- Fine extensions thinly worked.Objectives:- No promotion of plaque accumulation- No mechanical irritation of the gingiva.d. Internal surface:- Negative reproduction of the prepared surface of the abutment tooth.- Surfaces nearly parallel to the axis of the dowel and to each other, in conjunction with an occlusal box.Objectives:

- Retention of the coping to the tooth.- Stability of the coping, by enlarging the interface where the coping is cast to the dowel.Designing of the base:Criteria for designing the base:The design of the overdenture base must closely follow that of a conventional complete denture in the edentulous areas. Overdentures that are born by elements that provide support only are shaped like complete dentures in the abutment tooth areas as well, with a continuous vestibular flange for improved retention. The design of the base is governed primarily by periodontal and functional criteria, particularly near abutment teeth with retentive attachments. This means the root coping and denture base must be considered as a unit in form and function.Requirements:- Not unnecessarily promote plaque accumulation.- Not mechanically traumatize the marginal gingiva.- Not impede the performance of good oral hygiene.- Not interfere with normal function of the tongue, lips and cheeks.- Not interfere with esthetics or speech.- Permit modifications and additions with moderate technical effort.Designs that leave the periodontium uncovered:Two types of designs:- Bases that are circumdentally open.- Bases that are facially and proximally open.A circumdentally open overdenture design is characterized by the reduction of the base around the abutment teeth. The base doesn’t cover the gingiva, and the artificial teeth are prepared to fit directly upon the roots or the dowel copings. It is only possible to keep the base of an overdenture circumdentally open in connection with a custom cast-reinforcing framework. Studies have shown that circumdentally open designs do not result in a significant reduction in plaque accumulation. The temperature of gingival sulcus under an open base is less than those with closed bases. Therefore from periodontal standpoint, an overdenture base that is circumdentally open is desirable.Contraindication of open denture bases:- Increased risk of fracture of the base in spite of reinforcement when there is insufficient space above the abutment teeth and when the lingual vestibule is shallow.- Unfavorable spatial relationships that do not permit extensive proximal openings.- Esthetic considerations (eg: large proximal embrasure between maxillary anterior teeth where there is extensive gingival recession).- Increased food impaction in the open proximal spaces.- Speech problems such as sigmatism (difficulty with “s” sound and escape of saliva during speech).- Poor prognosis for the abutment teeth, making probable an early conversion to a complete denture.The amount of opening around abutments is determined for each individual by weighing the advantages and disadvantages.Basic rules of overdenture base design:

1. Cover as little of the marginal gingiva as possible.2. Border the proximal spaces with metal.3. The greater the number of abutment teeth and the better their prognosis, the more open the construction may be.Denture base design and the periodontium:- A base designed so that it does not cover the gingiva precludes direct mechanical trauma of the marginal gingiva by the denture base.- A base not covering the periodontium reduces plaque retention around the abutments by preventing entrapment of food. It permits free circulation of saliva and a certain degree of self-cleansing.- A base that is open around each abutment makes it possible to clean the proximal surfaces of the root copings with inter proximal brushes with the prosthesis in place. The proximal surfaces of the base serve as guiding surfaces that automatically direct the bristles of the interproximal brush toward the gingival margin. In this way cleansing of smaller abutments is made easier.- A base design that leaves the periodontium uncovered prevents a suction effect from beighn induced by the movement of prosthesis which, combined with inadequate coping shape and poor oral hygiene, would otherwise lead to hyperplastic proliferation (Suction hyperplasia) of gingiva.- This design prevents undesirable vacuum retention in maxillary overdentures with retentive attachments. The torquing and pulling forces necessary to overcome the combined retention of suction and retentive elements can traumatize the periodontium. Hence one of the reasons why base not extrude to the vibrating line.Denture base design and function and esthetics:One of the challenges in designing a denture base is to compensate for tissue lost through post extraction resorption without encroaching upon function and appearance. No appreciable resorption takes place around the roots left in the jaw to serve as abutments. Because of this, these areas require no bulk of material to compensate for tissue loss. The normal position and function of the lips and cheeks as well as their natural relation to the residual ridge are maintained only when the denture base does not cover the ridge facial to the abutment teeth.Functional disturbances due to facial overbulked denture bases:- Increased food entrappement under the base.- Greater difficulty for the cheek muscles to position.- Interference with lip movement during speech and lifting forces to the teeth that are fitted with retentive attachments, resulting in damage to the periosteum.The utilization of retentive attachments must not hinder or prevent forming the denture base to its functionally or esthetically optimum shape. As accessories they must always be subordinate to the prosthetic requisites.Design of the base in edentulous areas:In edentulous areas when compared to complete dentures some modification are required.- Any overextension that might be indicated in a complete denture must be avoided.- In readily visible areas the artificial teeth may directly abut the edentulous ridge for a better esthetic effect, provided there are no large tissue defects to be filled in by the base.

- In some types of ridges eg “club shaped” the path of insertion of the retentive attachments dictates the extensions. The base must end at survey line or else, it may lead to food entrapment.- For a maxillary denture the posterior extension should not extend till vibrating line if retentive attachments used.Cast reinforcing frameworks:These presence of mechanical attachments and interruption of the denture flange near abutments reduce the cross sectional area of the denture and increase the danger of fracture. This weakness cannot be compensated by increasing the thickness of the base by acrylic. Even by using prefabricated metal reinforces can cause thickness of the base resulting in muscular interferences. Hence custom-made reinforcement should be given especially with cobalt chromium alloys. They have best physical properties that ensure high deformation resistance in thin section of 0.5-1mm.a. Circumdentally open design:It is possible to keep the denture base completely away from the abutments only if the body of the denture is comprised entirely of reinforcing framework in the abutment region.Advantages:- The base cannot traumatize the gingiva around the abutments.- It is possible to clean the abutments with out removing the denture.- Psychologically, the minimal extension of the base with its fixed prosthesis like elegance is an advantage.Disadvantages:- The fabrication is technically very complex.- The risk of fracture is greater especially when adequate thickness is impossible because of restricted space or when excessive loads are encountered such as during bruxism.- The possibilities of modifying and adding are limited when the abutment teeth are lost.Indications:Abundant space over the abutment and a good prognosis for the remaining roots.b. Facially and Proximally open design:Overdentures that are open facially and proximally have enough rigidity only if they incorporate custom cast reinforcing frameworks.Advantages:- Relatively less involved technical construction.- Reduced risk of fracture.- Ease of modification when abutment is lost.- Seldom causes any problem with phonation.Disadvantage:- Increased difficulty in cleaning the abutment teeth and root copings, especially the proximal and lingual surfaces.- Greater extension of the denture base hence psychological discomfort.- The exposed metal parts in the inner surface of the framework are difficult to reline.Indications:- Poor prognosis for the abutments- Unfavorable spatial relations around the abutments.

- Speech problems, and extensive tissue loss in the anterior region that must be compensated with the base.Placement or insertion:The following points must be checked prior to insertion:Alignment of the denture base with root copings.Small misalignments are caused due to the polymerization shrinkage between the root coping and their contact surfaces, in the denture base. This leads to premature contact between the base and coping and resultant rocking. The attachments will not fit together accurately. These problems have to be relieved.Occlusion:The resulting changes in occlusion due to polymerization shrinkage should be corrected.Border extensions:The extension of the base as established at wax try in may change during finishing of the denture, either inadvertently or for technical reasons, and must be evaluated during placement. Checking of extensions carried out before any retentive elements are cemented.After the above things are evaluated and correction are made dowel copings with retentive elements may be permanently cement. The denture is inserted in mouth and checked for final occlusal discrepancies. This should be corrected and the patient is thought to master the skill of insertion and removal before leaving the clinic.Maintenance and follow up care:a. Oral hygiene instruction:Motivating and instructing the patient in the care of the overdenture is of the at most importance for its long-term success. Periodontal treatment and careful attention to the details of design and construction are rational only if rapid periodontal or carious breakdown of the abutment teeth can be decreased or preserved by proper oral hygiene.- A normal toothbrush with moderately hard, rounded, synthetic bristles is used for preliminary cleaning of the abutments.- Toothbrush takes care of only the occlusal surface of the coping and the gingiva hence it must be followed with a single fluted interdental brush to cleanse the axial surfaces of the coping and the sulcus.

Unfortunately this is not always accomplished especially with older patients due to: -- Oral hygiene is considered increasingly unimportant by many elderly people.- Changing eating habits and reduced flow of saliva favors accumulation of plaque.- Extreme difficulty in cleaning the construction element.- Diminishing vision in increasing age.- Longer time to function and decreased learning efficiency.b. Care of the abutment teeth:Accomplished by regular tooth brushing followed by interdental brushing of the abutment teeth, both with and without root copings and the marginal gingiva. Dental floss is used only to clean under interdental bars and between root copings that are soldered together.If mechanical cleaning is impossible or inadequate, chemical aids can be used.- Fluoride in gel form can be applied directly to the exposed roots or indirectly by placing, it inside the denture over the abutments. It can also be used (.025%) as a daily rinse.

- Chlorhexidine used in a .1-.2 % solution as daily rinse or in a gel to be applied inside the denture base or the female attachment.The patient must be informed about the side effects associated with prolonged use, such as changes in taste sensation, burning mouth, mucosal desquamation, and staining.c. Care of the overdenture:The overdenture is mechanically cleansed with an ordinary toothbrush or special denture brush with toothpastes with low abrasives and non-alkaline soaps. Denture cleansers can be used as an adjunct with this. (Peroxide based). To disinfect the denture from candidiasis it is treated with .2% chlorhexidine solution or salicylate (.05%) for 10-15 minutes every day.d. Recall visits and Examinations:Patient recall for early detection of periodontal and carious lesions is extremely important for overdenture patients. The first recall is scheduled for 3 months after placement of the prosthesis. After that when oral hygiene is optimum, periodontal resistance is good and no problems with prosthetic interactions, the interval can be as great as 12 months; in all other cases, a recall every 6 months should be adequate.The following points should be checked during recall visits and appropriate treatment should be given together with oral hygiene instructions.- Root caries detection through visual probing and radiographs.- Periodontal conditions.- Patient’s cleaning.- Pocket depths.- Tooth mobility.- Width of attached gingiva.- Degree of inflammation of marginal gingiva.- Radiographic evaluation.- Evaluation of occlusion.- Evaluation of fit of the denture.- Ridge resorption and associated rocking.- Fractures of the overdenture base due to- Casting defects.- Inadequate thickness- Excessive misdirected forces- Damage to the attachments:- Due to wear- Contact with opposing teethConversion of an overdenture to a complete denture:Over denture, which has only the facial and proximal surfaces open, can easily be corrected by relining with autopolymerizing resin either directly or indirectly. But the circumdental design involves problems due to a great deal of exposed framework. A second stage impression will be necessary if extensive denture base to be added facially and lingually. The metal work in the former anterior abutment regions will not give necessary retention hence retention loops should be made on to the framework for acrylic retention.Implant overdentures:Definition:

Implant: according to glossary of prosthodontic terms 1999.The fabrication of complete dentures, particularly mandibular ones, for maladaptive elderly patients is complex and difficult. It is therefore essential that simplified implant techniques are developed that may be applied to all elderly patients.Considerations:1. A reduction in the number of prescribed implants: two in the mandible and four in the maxilla.2. A short surgical intervention to minimize patient and tissue stress.3. Avoidance of restriction in patient selection, because overdentures with implant support are an option for most elderly edentulous patient.4. Implant abutment availability does not compensate for technically and functionally inadequate dentures. Traditional and impeccable complete denture fabrication techniques must be combined with the required surgical protocol.5. Denture design should not be compromised by the location of implants and their connection to retention devices.6. The dentist may consider managing both the patients surgical and prosthodontics needs.Contraindications:1. Patient feels comfortable with present complete dentures and has no functional complaints.2. Residual ridge is not adequate in width and/or height for the implant placement.3. Communication with patient is not possible because of senility or mental disorders.4. Patient has history of substance abuse.5. General health conditions preclude a minor surgical intervention.6. Local anesthesia with vasoconstrictor is contra indicated.7. Patient has an unfavorable medical history (Therapy with immunosuppressive, intake of corticosteriods or antibiotics for prolonged period of time, brittle metabolic disease history).Implant systems, Presurgical evaluation, and Treatment planning:Various commercial implant systems are used worldwide. Branemark and Bonefit- ITI implant systems are the most common types; both types are made up of titanium and consist of two-part design. The implant body and set of abutments. The Branemark implant is screwed and Bonefit is available in both cylindrical and screwed type. The treatment planning protocol is the same for all edentulous patients but radiographs may be required to determine more accurately location and number of implants to be placed.Specific objective when treatment planning a patient for implant supportedoverdentures:a. To determine the optimum location and number of implants in the context of the morphologic accepts of the residual ridge.b. To design a favorable distribution of occlusal stresses on the implants and the prosthesis bearing tissues.c. To avoid discrepancies between the designs of the dentures, implant’s location, and denture’s retentive devices.1. The clinical oral assessment provides:Information about shape, width, height of the residual ridges and soft tissue condition. Horizontal vertical jaw relation examined and space available for retention devices is

assessed. Bone mapping done to find out the mucosal thickness and contours of maxillary bone.2. Panoramic radiographs:Are made to scout anatomical structures, possible pathological findings, and to access bone density. Templates with metallic markers of known diameter may be used to measure the alveolar bone hight on radiographs and to predetermine a favourable location of the implants with respect to the topography of the residual ridge and anatomic landmarks such as mandibular nerve or the maxillary sinus. Cephalometric tracing used for determining faciolingual dimensions plus the lingual aspect of the residual mandibular bone and the shape of the maxillary ridge. CT Scans are also used.3. Examination of existing dentures:To decide whether they are adequate for temporary use during the healing phase is important. The transmucosal aspect of Bonefit- ITI implants during the healing phase may pose a problem, because to prevent inadvertent loading in patients who are not willing to remain without denture during healing period may not be controlled. New dentures should be made prior to surgery. Old dentures are examined for esthetic merits plus the presence of loss of vertical dimensions of occlusion.4. The number of implants placed:The number of implants placed for overdenture support differs in the mandible and the maxilla and is influenced by residual jaw morphology. Maxillary overdenture requires the placement of a minimum of three to four implants usually joined with connecting bars. Two implants in selected cases can be placed but contraindicated in loose trabecular bone, and curved shape of the ridge. The implant length should be minimum of 10mm or longer. Several implants should be preferred when bone sites preclude placement of 10mm or longer fixures. In maxillary ridge short bar segments connecting multiple 1mplant units are preferred to follow the ridges without encroaching palatal space. Mandibular overdenture will have adequate support by two implants. When the anterior ridge is straight or slightly curved, a bar is used to connect which is parallel to the patients arbitrary hinge axis. The interimplant distance should exceed 12 mm to provide sufficient space to accommodate retentive components. When curvature of mandibular ridge is more, then placement of more than two implants are recommended and then connected with bars there by converting it to entirely implant supported. Patients with advanced mandibular ridge resorption will have to be given shorter implants hence more than two implants have to be given for adequate support.Surgical procedure and osseointegration:The surgical protocol is well documented and aims at placing titanium tooth analogs into predetermined host sites to fulfill prosthodontic design objectives. A surgical template is used to ensure optimal alignment and location of the implants. The patient premedicated and surgery carried out atraumatically. Postoperative care is composed of standard analgesia plus use of ice packs and chlorhexidine mouthwash. After 7-10 days sutures removed depending on the process of wound healing of the soft tissue. The denture is relined and given to patient. Incase of single stage surgery, the area corresponding to the implant site is relieved in denture and relined. The patient is motivated on oral hygiene both mechanical and chemical and the relining is done at regular intervals. Healing phase is about 3-4 month, for mandibular implants and 6 months for maxillary implants.

Denture design:The design and fabrication of implant-supported overdentures follow the principles of fabricating complete dentures. It should have well fitting base and properly extended flanges. The denture base can be reduced slightly in its extensions when desired due to the immobility of the denture or incase patient object prosthesis bulk.Tooth Set up:The rules should closely follow that of complete denture and not to interfere with protection of implant from over loading.Clinical and laboratory procedures:The preliminary impression is made in stock trays and alginate. The custom acrylic tray requires opening for accommodating transfer copings placed on implants. The final impression is made and removed and laboratory implant analoges are connected to the transfer copings. The master cast is poured with the analogues insitu. The subsequent steps are similar to the conventional complete dentures. An exception is the inclusion of retentive elements in the fitting surface of the prosthesis. The bar is cast soldered to the prosthetic copings and tried in the mouth. The same orientation index is used to cast the metal framework, necessary after final soldering of the bar. The female part of the bar clip should never be soldered to the framework.Guidelines for selecting retentive anchoring devices:Consideration:1. No of supporting implants and their distribution over the ridge.2. Type and size of the single attachment or bars.3. Length of the bar segments.4. Number of female retainers.5. Degree of atrophy of the residual ridge.A resilient retention mechanism is widely recommended for anchorage of overdentures to implants based on the assumption that this will protect implants from overload.

Anchorage devices Used:Single elements SplintedSingle retentive anchors (stress-breaking mechanism) U shaped bar (rigid) Single magnet anchors (stress- breaking mechanism) Round clip bar Individual cast telescopic copings (rigid mechanism) Egg shaped Dolder barIndications for Single Attachment:- When implants are placed underneath a patients already worn dentures that is one that do not have to be remade.- Patients with impaired manual dexterity.- Used as a temporary methods after post surgical healing phase and prior to insertion of technically time consuming prosthetic reconstructions.Indications of bars:- Patients with frequent complaint of lack of retention when single attachment is used.

- Recommended for maxillary overdenture atrophic residual ridges in the mandible and mandibles with more than two implants due of pronounce ridge curvature.Maintenance care:Although periimplant tissues do not appear to be as vulnerable to plaque byproducts as periodontal tissues, nuisance variety responses may develop and should off course be avoided. The objective of regular recalls for all overdenture patients is to maintain the health of the oral tissues, particularly the periimplant tissues, and to check the denture with regards to its fit, stability and occlusion. Growth of hyperplastic soft tissues around implants are particularly underneath the bars has been recorded. It has to be corrected by vigorous massage and surgical excision of the overgrowth. Rest all procedures are similar to those mentioned in tooth supported over denture.Discussion:Teeth may be lost because of trauma, caries, periodontal disease, congenital defects and iatrogenic treatment. Once the teeth are lost, the residual alveolar bone undergoes a period of accelerated resorption there after. The concept of overdentures helped to retain some natural teeth, which helped to bring down the rate of bone loss and increase the retention and stability of the complete denture. This can also boost up the satisfaction of patient.Overdentures are designed to distribute the masticatory load between the edentulous ridge and the abutments. Tooth supported overdenture transfers occlusal forces to the alveolar bone through the periodontal ligament of the retained roots. Proprioceptive feed back from the periodontal ligament to the muscles of mastication may act to prevent occlusal over load and there by prevent bone resorption because of the excessive forces. The relationship of complete dentures to osseointegrated implants resembles the clinical situation of overdentures retained by natural tooth roots and copings. Inspite of lack of a periodontal ligament, periodontal receptors appear to be adequately compensated for in the resultant sensory, motor feed back system via receptors in the oral mucosa, bone, temporomandibular joint, and muscle spindles. It seems that the masticatory ability of implant-supported overdentures is greater importance of oral function than the presence of a periodontal ligament itself. Patients with implant report high functional satisfaction and subjective feeling of sense of having natural teeth. Although tooth and implant abutment attachment mechanism differ, their prosthetic role is identical. They provide enhanced prosthesis retention and stability and their influence on adjacent bone levels appears to be smaller. Studies have shown that mandibular overdentures retained by implants maintain bone height, in the area where it is located. However resorption of the posterior residual ridge was increased when compared with similar sites in patients treated with implant-supported prosthesis. It seems therefore prudent to suggest that younger edentulous patients would benefit most from fixed prosthesis supported by implants where as, overdentures should be recommended routinely for elderly edentulous patients.Comparative studies have been conducted taking into consideration the advantages and disadvantages of tooth supported over dentures, conventional complete dentures and implant supported over dentures.- Pacer and Bowman (1975) compared occlusal force discrimination between complete denture and overdenture wearers. They found that the overdenture patient posses more typical sensory function i.e. closer to the natural teeth than a complete denture wearer

- Shannon and Crown 1975 have concluded through their investigation that frequent application of low-concentration stannous fluoride to exposed dentin as a homecare mouthwash.- Crum and Rooney in a five-year study (1978) compared bone loss between patients with conventional dentures and patients with overdentures. They found out that by retaining the mandibular canines in the use of an overdenture, the resorption of the alveolar bone surrounding these were reduced by 8 times. In addition the alveolar bone between the canines and posterior to it were also preserved in both height and width.- Toolson and smith (1978) in a 2 year longitudinal study has shown that fluoride therapy had markedly reduced the caries incidence.- Kroone et al 1979 found out that the temperatures in the gingival sulcus are significantly higher under closed bases that cover the gingival margin than with open designs.- Bissada et al found that this gingival reaction was always most severe where the denture base covered the gingival margin and least severe in uncovered gingival margins. The reactions were more pronounced under acrylic resin than under polished metal.- Freidline and wear 1981 described a technique to block out a bony labial under at through the use of free soft tissue palatal graft.- Bolender smith and Toolson 1984 said that bare root surfaces should not be left opposing natural teeth. They saw incidence of longitudinal root fracture is high.- Morrow 1984 opposing hare surfaces should not be used on a long term basis because, dentin to dentin contact can produce high rate of wear.- Renner et al in 1984 conducted a four-year study and concluded that 50 percent of the roots that were used as overdenture abutments remained immobile. Also 25 percent of the roots that were mobile initially became immobile and 25 percent of the roots that were mobile became less mobile.- Kunder and Palla 1988 stated that circumdentally open design helps in cleansing of the abutment, which is often having small copings.- A study conducted by Timo et al described salivary fluoride levels after topical fluoride application was found to significantly reduce caries susceptibility in overdenture abutments.

- A study conducted by Thayer and Caputo concluded that the best design for uniform distribution of occlusal forces of remaining structures was the conventional amalgam plug design, but this provided less effective retention and stability than other designs.Conclusion:The concept of the overdenture covers a number of possible solutions for patients with nearly all the teeth missing. Common to all is the combined periodontal and mucosal support and the similarity of the external form to that of complete dentures. The benefits of the comprehensive preventive dentistry are becoming available to more people in many countries. This raises, the question of whether, in the future, overdenture will still be part of the armamentarium of reconstructive dentistry. At the present time, the answer is an unequivocal “Yes”. Because of peoples changing attitudes toward their health, improved therapeutic methods and increasing life expectancy, we can predict that more people will require denture at an advancing stage of their life.References:

Textbook references:1. Zarb, Bolender, Carlsson. Boucher’s prosthodontic treatment for edentulouspatients. 11th ed. Mosby- Year Book, Inc; 1997.2. Sheldon Winkler. Essentials of complete denture prosthodontics. 2nd ed. IshiyakuEuro America, inc; 1996.3. Arthur O. Rahn, Charles M. Heartwell, Jr. Textbook of complete dentures. 5th ed.Lea & Febiger, 1993.57

4. John J. Sharry. Complete denture prosthodontics. McGraw-hill book company, inc;London.5. Harold W. Priskel. Overdentures made easy. Quintessence publishing co ltd; 1996.6. Alfred H. Geering, Martin Kundert, Charles C.Kelsy. Complete denture andoverdenture prosthetics. Geory thieme verlay; 1993.7. Glossary of prosthodontic terms. 1999.Journal references:1. Chris C.L. Wyatt. The effect of prosthodontic treatment on alveolar bone loss: areview of literature. J Prosthet Dent 1998; 80: 362-6.2. Salivary fluoride level in overdenture wearers after topical fluoride gel application.Int J Prosthodont 1997; 10: 553-61.3. Timo O. Nahari, Marielle E. Greetman. Changes in the edentulous maxilla inpersons wearing implant retained mandibular overdentures. J Prosthet Dent 2000;84: 43-9.4. Prevention of bone loss edentulous patients. Eur J Prosthodont Restor Dent 2003;June 11 (2): 715. Residual ridge resorption in the edentulous maxilla in patients with implantsupported mandibular overdentures: an 8-year retrospective study. Int JProsthodont 2003; 16(3): 295-300.6. Posterior mandibular ridge resorption in patients with conventional dentures andimplant overdentures. Int J Oral Maxillofac Implants 2003; 18(3): 447- 52.