INTRODUCTION

Preventive Prosthodontics emphasizes the importance of any

procedure that can delay or eliminate the future Prosthodontic problems.

The overdenture is a logical method for the Dentist to use in preventive

Prosthodontics. It is further emphasized that alveolar bone with its

overlying mucosa was never intended to receive the full force of

complete denture. So, what is this overdenture?

DEFINITION:

G P T 1999

1. Overdenture is defined as a removable partial denture or a

complete denture that covers and rests on one or more remaining natural

teeth, the roots of natural teeth, and/or dental implants.

2. A prosthesis that covers and is partially supported by natural teeth,

natural tooth roots, and/or dental implants – called also Overlay denture,

overlay prosthesis, superimposed prosthesis.

Heartwell

A tooth supported complete denture is a dental prosthesis that

replaces lost or missing natural dentition and associated structures of the

maxilla and/or mandible and receives partial support and stability from

one or more modified natural teeth.

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History

The overdenture prosthesis constructed over existing teeth or tooth

structure is not a new concept in a technical approach to a prosthodontic

problem. Its use dates back over 100 years.

In 1861, Barker reported on the proceedings of the American Dental

convention in New Haven, Connecticut. Dr. Butler, Dr. Roberts, Dr.

Atkinson, Dr. Sutton and Dr. Hayes participated in a symposium entitled

– “Surgical preparation of the mouth for artificial dentures – should the

roots would enable fabrication of complete dentures superior to that

obtained after extraction of all roots. Hayes reported the results of

fabricating a complete denture over two roots in the maxillary arches and

12 years later, they were still in place contributing to the comfort of the

patient.

Since that convention, many more than hundred journal articles on the

retention of roots/teeth to support a complete denture have appeared.

In 1945, Black of Louisville, Kentucky provided complete denture for a

14-year old girl with a congenital absence of the permanent teeth. Four

maxillary and four mandibular teeth were retained and crowns were fitted

to the molars. In 1972, 27 years later the mandibular deciduous molars

were still intact supporting a complete mandibular overdenture.

During the Second World War, many dentists in a military service

used overdentures in the treatment of inadequate or mutilated dentitions.

Boos reported such a treatment in the July 1948 issue of the Dental

Digest.

In 1952, the article by Rehn advocated the retention of a single front tooth

for denture support.

In 1958, Miller reported that retention of a few teeth under

complete dentures allowed the weak teeth to regain healthy status. This

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foresight was of prime importance in convincing the profession that the

overdenture was a superior treatment modality. In 1969, Lord and Teel

reported 7 years of successful treatment with overdentures.

The Gerber series of root cap attachments was developed in 1954 and for

20 years, clinically successful hybrid prosthesis have been fabricated with

the Gerber attachments.

As new materials and products such as plastic tooth material, soft

liners, fluorides were introduced, the potential for this type of treatment

increased materially. Methods were simplified and at present

overdenture, treatment can be provided at a little additional cost over the

conventional complete denture.

RATIONALE OF OVERDENTURES

Retention of any tooth for an overdenture preserves a portion of one of

the major sensory inputs i.e. input from the periodontal propioceptors,

which contain information about the magnitude and direction of the

occlusal forces as well as about the size and consistency of the food

bolus. This along with the input of other receptors in the mouth, muscles,

TMJ contribute to the overall response. The periodontal receptors input

are also protective against occlusal overloading. Extraction of all teeth

results in total loss of all input from periodontal ligament receptors;

where as use of an overdenture preserves the sensory input.

Studies show that the natural anterior teeth give more discreet sensory

input, but posterior teeth should also be retained for overdentures

whenever feasible even though their sensory input is lesser.

It is also known that the retention of teeth for overdentures provide

better sensory feed back regarding masticatory performance.

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Studies show that the use of an overdenture preserves alveolar

bone, especially in the area of the retained teeth. In this area, resorption

occurs very rapidly after extraction of teeth.

From the physiologic view point the rationale for preserving tooth

roots are:

1. SENSITIVITY OF ANTERIOR TEETH:

Sensory input from the periodontal receptors is one of the

major determinants of masticatory function, and the roots of the teeth

offer more discrete discriminatory input than does the oral mucosa.

Retention of natural teeth for an overdenture preserves some of the

sensory input from the periodontal receptors, which is more precise than

that able to be obtained from the oral mucosa.

Kawamura (1964), Grossman (1964), and Grossman and associates

(1965) agreed that the sensitivity in the anterior part of the mouth,

particularly the periodontal ligament of the anterior teeth, tongue tip, and

mucosa, was acute.

There is a greater concentration of sensory receptors in the anterior part

of the mouth (Kawamura, 1964), and these signals from the periodontal

and mucosal receptors are important in controlling and determining biting

force.

2. DIMENSIONAL PERCEPTION:

Dimensional perception is the discrimination of the different

thickness of objects between the occlusal surfaces of the teeth. Kawamura

and Watanabe (1960) found that patients with natural dentition could

discriminate differences at the 2 mm range better than those with artificial

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dentures. These findings emphasized the importance of conservative

procedures and the importance of the retention of natural teeth.

3. CANINE RESPONSE:

Kruger and Michel (1962) said that the canines have more neurons

than any other teeth. So, it acts as very important proprioceptive organ

which can lend support to the retention for the overdenture.

4. DIRECTIONAL SENSITIVITY

Jerge (1963, 1965) reported that the receptors in the periodontal

ligament were directionally sensitive. He said that the receptors are

arranged around a tooth in such a way as to respond to pressure

regardless of the direction from which it is applied. Directional sensitivity

is one of the most important elements in the interaction of the masticatory

system. It means that the periodontal receptors have a functional

individuality and that the relationship of the tooth to its periodontal

ligament is highly important from a sensory standpoint. Therefore, teeth

should be retained for use with an overdenture to preserve the directional

sensitivity.

5. PROPRIOCEPTION AND SALIVARY SECRETION:

Kapur and Collister (1970) studied food texture discrimination and

concluded that the periodontal receptors played an indirect role in the

masticatory salivary reflex by regulating the range and type of the

masticatory stroke. They stated that absence of the periodontal ligament

in denture wearers appeared to result in impairment of the mechanism

regulating parotid gland stimulation during mastication.

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6. PERCEPTION OF NONVITAL TEETH:

The majority of natural teeth used to support overdentures are devitalized

and treated endodontically. Perceptual studies showed that vital and

devitalized teeth had equal sensory input capabilities (Stewart, 1927;

Adler, 1947).

7. PERCEPTION OF TEETH WITH REDUCED ALVEOLAR

SUPPORT:

Often teeth selected for use with overdentures may have lost bone

support. These studies showed that the tooth still had a proprioceptive

input capability even though much of the bone support was lost.

8. DECREASE OF PERCEPTION IN OLDER INDIVIDUALS:

There is generalized decrease in perception as age increases and the

use of an overdenture is an attempt to retain every possible sensory

element at the time the patient may experience a generalized decrease in

the sensory capacity.

Advantages of overdentures

Equally effective and superior method of treatment: In many situations,

overdenture gives better service than alternative methods of treatment,

especially in patients with congenital defects (oligodontia, microdontia,

cleft palate etc.) and for class III patients with a prognathic jaw not

amenable to surgical an orthodontic treatment.

Simplicity of construction: The procedure used in constructing

overdentures are the same as those for complete dentures, and the

retained teeth or roots provide stability to the bases during registration of

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maxillomandibular records. Also they aid in determining the correct

vertical dimension of occlusion and in proper tooth placement.

Ease of maintenance: Repairs, alterations or refitting of the overdenture

can be done readily in the same manner as with conventional complete

dentures.

Stability: Stability is comparable to that obtained with fixed or

removable partial dentures and the retention of four abutments

contributes greatly to this stability.

Retention: Generally retention is excellent because of the better stability

of overdentures.

Esthetic excellence: The extensive selection of artificial denture teeth

and the many possible arrangements for these aids in creating an esthetic

effect.

Open palate possible: The maxillary denture of many patients can be

roofless if necessary, especially where anterior and posterior teeth are

saved

Reasonable cost: The time required for creating an overdenture and thus

the cost can be less than for alternative procedures.

Familiar Procedures: The procedure used are similar to those used for

conventional complete dentures.

Ease in making measurements: When teeth are retained for immediate

overdentures, the vertical dimensions of occlusion can be maintained

accurately.

Ideal Occlusion: Esthetically acceptable occlusion can be provided.

Excellent patient acceptance: This is attributable to the knowledge that

the patient still has his own teeth.

Less trauma to the supporting tissues: The hard tooth surface of the

retained teeth supports the dentures and inhibits resorption of the residual

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ridge, which may occur when all the teeth are removed, and conventional

complete dentures provided. Less soft tissue trauma also occurs.

Stabilization of existing structures: Although tissues under a long span

without tooth support may resorb, little change occurs at the site of

retained teeth, thus maintaining the vertical dimensions and the lip

support.

Minimal adjustment: Little adjustment is required due to the stability

and support provided to the overdenture by the retained teeth.

Possibility of using attachments or soft liners: This is done when soft

tissue or bony protuberances necessitate considerable relief of the denture

and it is difficult to maintain a seal. Attachments or soft liners can be

used.

Transitional or training dentures: Even though the patient may loose

the retained teeth or roots or both in a short time the overdenture is not

only stable but also retentive for the period of use, but is also excellent

for transitional or training in preparation for receiving a complete

denture.

Conversion to complete denture: The tissue coverage and border

extensions are usually the same for overdentures as for complete dentures

making it easy to compensate for the loss of one or all of the retained

teeth. The spaces can be filled in or the dentures can be relined or

rebased.

Reversibility: When making overdentures over a complete natural

dentition, it may be necessary to alter the existing teeth. Therefore, the

procedure is reversible, and removal of denture puts the teeth back in

their original states.

Ease in Cleaning: All surfaces of the abutment are accessible to

cleaning, and the denture being removable is easier to clean than a fixed

partial denture.

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Proprioceptive response: There is more efficient neuromuscular

coordination.

Distribution of forces of mastication: Forces are distributed more

uniformly over the roots and denture supporting tissues.

Disadvantages of overdentures

The overdenture treatment is more expensive than conventional denture

treatment due to the endodontic therapy usually required and the

subsequent restoration of the teeth with alloys or gold copings.

Frequently teeth to be retained also need periodontal therapy.

The overdenture is bulkier than the fixed 0r removable partial dentures.

Many patients do not like any removable appliance and therefore may

prefer a fixed partial denture.

If the patient does not keep the retained roots or teeth and the

overdenture clean, caries and periodontal disease may progress.

Maintenance problems

:

•Copings may become loose

• Attachment wear, loss and breakage

•Alveolar ridge resorption

• Overdenture breakage

• Oral hygiene problems

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Indications:

In situations where retention is difficult to obtain

a.

a. Xerostomia

b. Absence of alveolar residual ridge

c. Loss of maxilla or partial loss of mandible

d. Congenital deformity (i.e. Cleft palate)

For patients with poor prognosis for complete dentures

a.High palatal vault and ridge slope

b. Poorly defined sublingual fold space

c. In class III tongue patients

d. Knife edge ridge

When pronounced vertical overlap is required to produce the desired

esthetic result.

Unilateral overdenture can be given to provide good function and

esthetics when a large amount bone and soft tissues have been lost on one

side of the arch

Patient with badly worn out teeth.

When complete denture will be opposed by retained mandibular

anterior teeth preventing combination syndrome.

Contraindications:

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Uncooperative: Under motivated patients

Psychologically some patient cannot accept removable prosthesis

Mentally and physically compromised

When patient cannot economically afford

Contraindications for periodontally involved teeth

•Class III Mobility

• Uncorrectable soft tissue and osseous defects

• Failure to establish sufficient zone of attached gingival

Contraindications for Endodontically involved teeth

•Vertical fracture

• Mechanical perforation of root

• Broken instrument

• Horizontal fracture of root below bony crest

Clinical evaluation

The examination includes: Patient history, Study casts, clinical

examination, and Radiographs. It is very difficult to make a correct

diagnosis to determine if the overdenture is indicated for the patient or the

problems can be solved by alternative techniques. This is ascertained by

taking a proper history of the patient’s medical background and past

dental history. The past dental history indicates the patients experience

with previous removable appliances and his attitude towards the

treatment. Study casts accurately mounted on an articulator show the

occlusal relationship of the teeth and arches, the vertical spaces between

arches and location of bony undercuts.

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They also help in determining the amount of tooth reduction required, the

types of coping and often the types of attachments that can be used for

particular condition. Accurate study casts can also be used for

fabrications of interim overdentures when necessary.

Clinical examination includes examination of the entire oral cavity. All

soft tissues are evaluated and teeth are evaluated thoroughly. Occlusal

relationships are studied and periodontal and endodontic evaluation is

carried out. Potential abutments are evaluated for mobility, crown root

ratio etc.

Radiographic examination is done to evaluate presence of

pathological conditions, presence of retained roots, bone loss, root

curvatures, root canals are noted.

Diagnosis includes: Clinical evaluation and selection of abutments,

abutment location, bone support, proximal space between abutments,

number of teeth available, masticatory load and opposing dentition and

the type/design of prosthesis required.

TREATMENT PLANNING:

The patient who has only few retainable natural teeth may present

difficult treatment questions for the dentist. Johnston and associates

(1965) stated that “a bridge is indicated whenever there are properly

distributed and healthy teeth to serve as abutments, provided these have

suitable crown-root ratio and that after radiographic, diagnostic cast and

oral examinations seem capable of sustaining the additional load. When

indicated, fixed partial dentures are treatment of choice. A few retainable

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teeth generally are scattered throughout the arch, and invariably they are

involved periodontally with unfavorable crown-root ratios, the

overdenture option should be considered.

The treatment planning include evaluation of all potential abutments for:

•

• Periodontal status

• Endodontic status

• Caries management

• Positional considerations

• Economics

PERIODONTAL STATUS:

It is best to select abutments that are in an acceptable state of

periodontal health but, often it is necessary to use teeth that are less than

ideal. Abutment should have minimum mobility, have adequate bone

support and be amenable to any indicated periodontal treatment.

Periodontal pockets, inflammation, bony defects and poor zone of

attached gingiva must all be eliminated before commencing the treatment.

A common periodontal requisite with overdenture abutment teeth is that

an adequate zone of attached gingival is mandatory. This can be

accomplished with periodontal surgery utilizing either a free gingival

graft or apically repositioning split thickness flap. This results in a band

of attached gingiva adjacent to abutment tooth. It should be understood

that reduction of clinical crown-root ratio will be favorable in reducing

any existing mobility.

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ENDODONTIC CONSIDERATIONS:

There are mainly two advantages,

• The crown-root ratio can be made more favorable

• The reduction crown provides for an interocclusal

distance more favorable to placing the artificial

tooth in an esthetically acceptable position.

CARIES MANAGEMENT:

The presence of high caries index and the situation that will create a

caries environment are the devastating sequalae to improper overdenture

patient selection. An active caries process can lead to a recurrence of in

unprotected abutment teeth or gingival to coping margins and this can

lead to failure of the overdenture.

POSITIONAL CONSIDERATIONS:

1. Preference for anterior over posterior teeth because alveolar ridge of

anterior teeth appears to be more vulnerable to reduction compared to

posterior alveolar ridge.

2.

Two teeth in each quadrant presents an ideal situation in where stress is

distributed over a rectangular area. Two canines and two second

premolars present an ideal situation. The tripod is next most favorable

form for support and stability. The use of two teeth in each arch or one

tooth in one arch has met with satisfactory results.

Morrow recommends to use isolated teeth as abutments because they

return to healthy state readily and are easier for the patient to maintain

hygiene.

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The upper anterior teeth should be retained if opposed by natural

lower anterior teeth to prevent the destruction of the anterior maxillary

ridge when utilized in a maxillary overdenture.

Mandibular cuspids are most often utilized since they are usually last

tooth to fall.

ECONOMICS:

Endodontic treatment, cast copings, attachments and overdenture itself

may workout expensive, so economics of the patient should be

considered.

Types of over dentures

I. Overdentures for congenital and acquired defects:

Many patients with congenital and acquired defects cannot be

treated successfully with orthodontic or surgical therapy, nor can they be

treated with conventional procedures – either fixed or removable.

However there has been a high degree of success in treating these patients

with complete dentures over their existing teeth. The congenital defects

most frequently treated with over dentures are:

Cleft palate

Micordontia

Oligodontia

Cleidocranial dystosis

Class III patients with prognathic mandible.

The acquired defects most frequently treated by this usually results from

accidents, disease or misuse.

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II. Transitional overdentures:

A Transitional or interim overdenture is made from an existing

removable partial denture, the patients own teeth or from both.

Frequently, the entire procedure can be done while the patient waits, or

part of it can be done before the extraction visit. The objective is to do

the most for the patients with the least of trauma.

Advantages:

1. Less expensive

2. Smooth transition

3. Minimal interference with function and appearance

Disadvantages

1.Border extension, esthetics, occlusion, support and stability of the

R.P.D. often are inadequate, particularly after many years of use, making

satisfactory conversion difficult.

2.Weaker overdenture

3.Therefore, the converted prosthesis is considered as interim or

temporary overdenture, to be replaced after a suitable transitional period.

Conversion using patient’s teeth

The patient derives a tremendous psychological boost by having his teeth

removed, but leaving with them still in his mouth; even through they are

in an overdentures. This is a more economical method.

III. Immediate overdentures

An immediate overdenture is an overdenture constructed for insertion

immediately after the removal of natural teeth. It may be used as an

interim prosthesis. The immediate overdenture enables a dentist to use a

simplified construction technique that allows flexibility in planning

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treatments as requirements change. Many times with good oral hygiene

and regular professional supervision an immediate overdenture may have

a long life. Sometimes, it can be a prognostic aid before a more

comprehensive overdenture procedure. If prognosis is poor and response

to treatment is poor and immediate denture can be converted into a

serviceable complete denture.

IV. Remote overdentures

A remote overdenture is an overdenture other than transitional or

immediate. It is usually constructed for insertion at sometime remote

from the removal of hopeless natural teeth. The remote overdenture

usually placed on well healed ridges usually after a period of satisfactory

experience with an interim overdenture which may be transitional or

immediate. Although remote overdentures can be entirely constructed of

resin, metal bases are frequently used.

Metal base overdentures:

A metal base overdenture is complete denture with a cast metal base that

is supported and stabilized by selected natural teeth with contours that are

modified for the purpose by preparation and placement of copings.

V. Removable partial denture:

A superior removable partial overdenture can be made for may patients

by reducing some of the remaining teeth coronally so that the prosthesis

can be fabricated over them.

VI. Implant overdentures

A wide variety of implant types and procedures have been used with an

overdenture as the means of a final restoration. The osseointergrated

approach of implants with its use of titanium metal and rather

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sophisticated techniques of placement has proven to be viable and worthy

procedure. Although it is used mostly with fixed type of prosthesis, on

occasion single fixtures are placed on each side of the midline and an

overdenture is fabricated over fixture.

DOWEL DESIGNS

There are mainly 5 categories:

1. Customized cast dowels

2. Prefabricated resin patterns

3. Prefabricated metal dowels

4. Threaded dowels

5. Dowel systems

1. CUSTOMIZED CAST DOWELS

When a dowel and coping are waxed together and cast as a unit the

discrepancy is the same as when making an inlay and crown in the same

casting. If the expansion for the coping were sufficient, the dowel would

be oversized, the coping could not seat, and the dowel could fracture the

root during either try-in or cementation because of the wedge effect and

the hydrostatic pressure of the cement. This factor can be reduced by

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preparing cement -release groove down the long axis of the dowel. If the

dowel were undersized, the coping would seat properly, but the dowel

would be retained by cement only.

2. PREFABRICATED RESIN PATTERNS

The prefabricated dowel patterns are provided with a matched set of burs

for preparing the dowel space. The cross sectional strength of a pattern

dowel is considerably less than that of a prefabricated metal dowel of the

same size, for the metal dowels are drawn from a high fusing alloy,

different than that used for the copings, and do not have the potential

porosity and fracture of a cast dowel.PREFABRICATED METAL

DOWELS

The prefabricated metal dowels have a big advantage over the two

previous systems because of the exact fit and high metallurgic strength in

the cross sectional area; they require minimal enlargement of the canal

space and strengthen the tooth rather than weaken it. The prefabricated

metal dowels have matched sets of burs for exact fit of the preparation.

The dowels are machined from high-fusing wrought metal that is

specially alloyed for dowel usage. Most of these dowels have cement

release grooves, which avoid the possible risk of incomplete seating or

root fracture during cementation.

3. THREADED DOWELS

Threaded dowels provide mechanical fixation in addition to cementation.

The VK and Kurer systems offer excellent retention with the threading.

4. DOWEL SYSTEMS CLASSIFICATION OF

OVERDENTURESHeartwell:I . NoncopingII.

CopingIII.AttachmentsI. NONCOPING

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OVERDENTURES:Selected 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 followed by

amalgam or composite restoration.II.COPING

OVERDENTURES:Coping TypesA coping fitted to a prepared

abutment is called a primary coping. The sleeve, or coping, that fits

over this primary coping is referred to as a secondary coping.There

are four basic types of primary copings:1. Long copings (6-8

mm).2. Medium copings (4-6mm).3. Medium-short copings (2-4

mm).4. Short copings (1-2 mm).1. Long Copings (6-8 millimeters

for vital teeth):The long coping is an excellent restoration,

applicable to many overlay techniques. It may be used simply to

provide stability and retention under a telescopic overdenture.2.

Medium Copings (4-6 millimeters for vital and non-vital

teeth):Medium sized copings may be used with vital teeth where

the pulp has receded or with non vital teeth having adequate bone

support. Medium sized copings are not generally designed as

individual copings for retention of the overlay prosthesis. They are

generally connected with some type of bar attachment. Or, they

may also be used with auxiliary plunger or pressure button

attachments. They are conical with greater taper on all surfaces,

particularly the facial surface when used with bar attachments. If

used with a plunger button attachment, the surface engaged by the

plunger is flattened.3. Medium short copings (2-4 mm for

nonvital teeth):Medium short copings are indicated for nonvital

teeth; where a more favorable crown root ratio is desired than that

possible with medium or long copings. This coping form (and

preparation) is indicated when: it is difficult to obtain auxiliary

retention of the coping on the abutment with a dowel or parallel

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pins (the proximal walls of the preparation should be very closely

parallel for maximum frictional fit of the coping); numerous

neighboring abutments are to be splinted, thus permitting better

embrasure formation than possible with very short copings; used

with bar attachments. 4. Short Copings (1-2 millimeters for non-

vital teeth):Short copings are fabricated to conform to the

curvature of the alveolar ridge, with a very low profile. They are

indicated for maximum favorable crown-root ratio. Such short

copings are particularly suited to various types of stud attachments,

but may also be used effectively with many forms of bar

attachments.The best possible coping for a specific abutment

depends on the amount of alveolar support, whether or not the

abutment is vital, and the function of the coping.Coping Form and

Portion of Root Supported by BoneIII. Overdenture with

Attachments:The attachments essentially increase the crown-root

ratio and then torque. Or apply horizontal or vertical dislodging

forces to the root abutments. Here, low caries index, proper home

care, periodontal health and inter ridge distance are absolutely

necessary.ATTACHMENTS FOR OVERDENTURESThe

ultimate objective of the prosthetic service is to return the patient to

as near a normal function as possible. The basic overdenture

concept is to preserve the residual soft and hard tissues.

Mechanical stabilization can be improved by incorporating the use

of attachments and retentive devices with the basic principles of

complete denture design.BASIC PROSTHETIC DESIGNIt is

important to realize that the causes of failure inherent in the

complete denture prosthesis are not overcome by using attachment

fixation. The use of attachments does not authorize the

abandonment of basic principles. Failures of the hybrid prosthesis

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(overdenture with attachment fixation) occur not because of the

attachments but because of improper attachment selection and

failure of the dentist to develop maximum denture base extension,

atmospheric seal, and, for mandibular bases, coverage of the

retromolar pad. Availability of the proprioceptive elements in the

attachment retained overdenture permits use of gnathologic

procedures and, in some instances, anterior disclusion of the

posterior teeth as well as the relevant instrumentation desired. Use

of the attachment introduces another factor in basic prosthetic

design, that is, the demand for an exact attachment prosthesis

relationship. For each type of attachment the demand differs,

depending on the availability or desirability of resiliency and the

overall adaptation of the denture base over the soft and hard tissues

of the denture bearing area. TOOTH PREPARATIONTooth

preparation varies with the type of support to be provided. If there

is sufficient tooth structure, that is, 3- to 8 mm of clinical crown for

lateral stability of the overdenture, there are several methods of

preparation.The coping is waxed to a minimal occlusal thickness of

1 mm with the exception of the bulk of the inlay seat.

TELESCOPE CROWNS:The telescope crown is a prosthodontic

retainer for a fixed or removable prosthesis and usually consists of

the conical preparations with a like casting and a secondary

telescope casting that is embedded in a prosthesis or is an abutment

or crown itself. It is a system used to stabilize an overdenture

where 4 mm or more of clinical crown is available. The advantage

of the telescope crown or telescope preparation over the standard

overdenture is the increased stabilization and retention of the

denture while using remaining vital or nonvital teeth without

dowels or screws.TELESCOPE OVERDENTURE:The

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telescoped overdenture is an excellent alternative to routine

complete dentures. But what exactly is a telescoped or coping

overdenture? As the name implies, a telescoped overdenture fits

over natural teeth with that portion of the overdenture fitting like a

sleeve. These supporting abutments may simply be endodontically

treated teeth reduced slightly, shaped, smoothed, polished and left

in this manner to support this denture; or, these roots or teeth may

be restored with metal copings. The size of these primary copings,

the copings on the teeth, may be medium or long. They may be

designed only to provide support, or to provide support and

retention.Advantages:1. Conserve the alveolar ridge2. Provide

support and often retention 3. Retains some natural

proprioception4. Emotionally accept the overdenture 5. Easy

modification possible 6. Auxiliary retention devices can be added

7. Easy to master 8. Less expensive than attachment fixation

overdenturesDisadvantages:1. Retention is fixed, and not variable2.

Retention must be modified frequently 3. The overdenture is bulky

and less esthetic 4. Expensive than a conventional complete

dentureA Telescopic Overdenture Treatment Procedure:Following

is a case of advanced periodontal disease and extensive breakdown

of the natural dentition. The teeth were devitalized and restored

with short and long copings to support an overdenture in the

following manner:1. Examination, diagnosis and treatment plan.2.

Study casts for fabrication of interim overdentures.3. Prophylaxis,

soft tissue curettage and home care instructions.After healing, the

preparations were modified to receive medium or long copings.

Short copings are to be placed on the two centrals. The other

abutment teeth were prepared to receive long or medium copings.

The overall preparation for the longer copings was tapering with a

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rounded occlusal or incisal. chamfer, or small shoulder with a

beveled marginal preparation, is prepared. This marginal

preparation is determined primarily by the type of primary and

secondary coping. If the secondary coping was a crown rather than

a hollowed denture tooth, then the shoulder preparation must be

more substantial. The final preparation of the teeth should result in

a tapered cone shaped abutment rather than a rounded occlusal or

incisal. This preparation should extend to the gingival sulcus as for

a full crown preparation. Sufficient tooth structure was removed

facially to make room for the coping and set up of the anterior

teeth, thus ensuring a more esthetic result. The short anterior

abutments were prepared for dowel post retention. Completed

castings ready for cementation. Long copings for retention and

stability and short copings for support and stabilityCopings

cementedNow an impression was taken of the denture bearing

mucosa and copings to produce a master cast for fabrication of

the overdenture.Master casts articulated with accurate interocclusal

recordsCoping undercuts are blocked out with plaster A metal

framework with a horseshoe like major connector was fabricated

on a refractory model Resin denture teeth were hollow ground to fit

closely to the copings for maximum esthetics A resin secondary

coping of a telescoped overdenture does have some advantages

over a metal secondary coping particularly where no auxiliary

retentive means are used. It is easier to adjust the retention by

adding autopolymerizing resin to the previously relieved secondary

coping spaces and relining the coping spaces directly in the mouth.

Relining and/or RebasingAs the alveolar ridges resorb, the

overdenture will begin to rock and direct damaging lateral stresses

to the abutment teeth. Now the prosthesis must be adjusted for a

24

better fit by relining or rebasing. This is a simple procedure and

performed similar to any complete denture relining or rebasing

procedure: 1. Hollow out the secondary resin coping to provide

adequate room for the impression material; 2. Paint an adhesive

material on the denture base; 3. Load the tissue area of the

overdenture with an elastic impression material; 4. Insert the

overdenture in position and have the patient close gently into

occlusion as you muscle trim; 5. Now the overdenture is relined or

rebased similar to any complete denture technique and ready for

use.ATTACHMENTS:Bar compared to stud fixationThe

splinting of two or more teeth with a bar produces stability similar

to the rigid stud type attachment when the overdenture is in place.

The question that arises immediately is: if the denture base is so

well developed that the bar serves only as a fixation device, what is

the difference in the result of splinting obtained in the stud

prosthesis and in the bar prosthesis. Theoretically, there is no

difference, but the stud type allows independent movement, and, if

one tooth is especially weak, the strong tooth can serve as the

fulcrum point for movement of the weaker tooth in the

prosthesis.With bar units and joints, many times the bar splints in

more than one plane. Instead of the prosthesis moving one tooth,

all or none move under a functional load. With bar fixation, a

stronger and a weaker tooth can be splinted with the result that the

stronger tooth strengthens the weaker tooth and the weaker tooth

weakens the stronger tooth. In making the overdenture; only the

stud, the bar, and some of the accessory attachments are of interest.

ATTACHMENTS CAN BE CLASSIFIED ACCORDING TO

SHAPE, DESIGN, AND PRIMARY AREA OF USE AS

FOLLOWS: (Mensor)Coronal1.

25

Intracoronal attachments2. Extracoronal attachmentsRadicular3.

Telescope stud attachments (pressure buttons) 4. Bar attachmentsa.

Jointsb. UnitsAccessory5. Auxiliary attachmentsa. Screw unitsb.

Pawl connectorsc. Boltsd. Stabilizers/balancerse. Interlocksf.

Pins/screwsg. RestsAccessory5. Auxiliary attachmentsa. Screw

unitsb. Pawl connectorsc. Boltsd. Stabilizers/balancerse.

Interlocksf. Pins/screwsg. Rests STUD (PRESSURE BUTTON)

ATTACHMENTS:Most of the stud-type attachments can be

considered to be "snap fasteners" and are the simplest in concept.

They can be resilient or non resilient.RESILIENT STUDSResilient

attachment systems are selected to perform a compensatory service

and to act as a safety valve for any overload situation. No two

resilient attachment systems should oppose each other unless the

attachments in the maxillary prosthesis are locked out of function,

for the maxillary prosthesis receives additional support from the

palatal coverage. This situation arises when two hybrid prostheses

oppose each other or a mandibular appliance opposes the maxillary

denture. When the mandibular appliance opposes a natural

dentition, some provision should be made for movement so that

maximal tissue contact of the denture base can be achieved under

maximal load. In the well developed denture base with careful

positioning of the attachments, the need for a resilient system

becomes questionable. No attempt should be made at equilibrating

or establishing permanent records or relining procedures without

locking the resilient attachments out of function, because the base

would move and produce incorrect markings of the

interferences.The retained root with an attachment offers retention

and positional or directional orientation for the appliance. When

there is either inadequate technique or inability to develop a well

26

fitting denture base, the resilient attachment gives some leeway to

acceptance of the prosthesis by allowing more base contact and

support during function. NONRESILIENT STUDSThe

nonresilient stud attachments are used when interocclusal space is

limited. They should be used when the teeth are stable or when the

dentist does not desire movement or potential movement of the

overdenture.When to Use a Resilient Stud?A resilient attachment

permits the tissue to compress slightly before any load is

transmitted to the abutment. It is usually preferred: When there

are only a few abutments. When abutments have minimal bone

support. For tissue tooth supported prosthesis. When

functioning opposite natural dentition. When functioning against

a nonresilient appliance (do not use opposite another resilient

appliance). When multi-directional (stress-broken) action is

desirable. When there is a minimum denture base. When to use a

non Resilient stud Attachment ?A non resilient attachment will

not allow vertical movement (however it may permit rotational

movement) When no vertical movement is indicated. When an

all-tooth supported prosthesis is desired. When a tooth-tissue

supported appliance is desired. With strong abutments having

maximum bone support (one-half or more). When functioning

against a resilient prosthesis When a large, well-fitting denture

base is possible. When there is little interocclusal space

Opposite a complete denture.Some Stud Attachments:1. Dalla

Bona 2. Intrafix3. Ancrofix 4. Gerber5. Gmur6. Rotherman 7.

Huser8. Schubiger 9. CekaThe Gerber Attachment The Gerber

stud system is a versatile stud attachment used routinely. It consists

of a male post soldered to the coping and a retentive female

secured within the denture base of the overlay prostheses. The

27

Gerber attachment is furnished in two different types - a resilient

and non-resilient form.The male post consists of two parts - a

threaded base, which is soldered to the diaphragm of a coping, and

a removable sleeve with a retentive undercut The resilient

female consists of a housing, coiled spring, C-spring, a retention

sleeve and lock screw. The non-resilient female has a female

housing, C spring and a screw cap and no copper shim and coil

spring.Convenient tools are also used in the fabrication - female

screwdriver, male screwdriver, paralleling mandrel, heating bar,

and a soldering cornal Step-by-Step Technique:1. All treatments

must start with a thorough oral examination. This examination

should include patient history, visual examination, radiographs and

periodontal probe evaluation. Accurate study casts mounted on

an appropriate articulator are also helpful.2. A thorough oral

prophylaxis and home care instructions are completed before any

other treatment is performed.3. Fabricate an interim overdenture on

the diagnostic casts for insertion after reduction of the clinical

crowns, endodontics, extractions and periodontal surgery.4.All the

teeth are reduced to one to two mm above the gingiva5.

Endodontics is performed6. Partial preparation of the teeth7.

Extraction of hopeless dentition8. Hollow out recesses in the

interim overdenture 9. Now that the teeth have been initially

reduced, the hopeless dentition removed, and the interim

overdenture ready for insertion, periodontal therapy can be

completed in a relaxed manner with relative patient comfort.

10.After several weeks of healing, complete endodontics (if not

completed).11.Insert the interim overdenture with a soft relining

material 12.After tissue healing and maturation (2-3 months)

complete abutment preparations for short copings with post

28

retention. 13.Master cast with removable dies14.Copings waxed

on individual dies shaped to conform to the alveolar ridges. Resin

dowels were used as dowel patterns15.Position the finished

castings on the cast (lock them together with Duralay); invest and

solder them to form a splinted substructure 16.Preliminary

intraocclusal relation records for a trial set-up of denture teeth. The

anterior teeth are oriented with a plaster core. This helps to

accurately position the male attachment on the copings 17.Position

the male attachment on the coping. Consider the following factors

when determining the position of the male posts:Is there sufficient

vertical space? - Place the posts over abutments with the

most bone support. - Position the males slightly lingual. This

provides more room for the anterior denture teeth. -

Utilize abutments in different planes for maximum

retention, stability and support . - The attachments must be

parallel to each other and to the path of insertion of the

overdenture18.Lock the cast on the surveying table. Loosen the

male sleeves and Place in the paralleling mandrel. Find the most

advantageous position for the posts. Tilt the surveying table so that

the studs will be aligned to the path of insertion of the

prosthesis.19.Sticky-wax the male base to the coping 20. Male

sleeve is being removed21.Male stud sticky waxed to the coping

with sleeve removed22.Screw the soldering cornal onto the

threaded base. It acts as an extension arm for the screw to aid in

soldering 23.Cover half of the soldering cornal and coping with

soldering investment. 24.Finished copings with attachments

assembled and soldered, positioned on the abutments25.Take an

accurate muscle trimmed master impression "pulling" the coping

substructure, on the abutments, to form the master cast for the

29

overdenture fabrication 26. 3-4 thickness of x - ray foils are

adapted to all copings for spacing. 27.Block out all undercuts

around the foil spacer and copings with plaster 28.Place a small

amount of Vaseline inside each female then snap it (with its copper

shim) onto the male 29.Paint a thick mix of auto-polymerizing

resin at the male-female joint. This will prevent processed denture

acrylic resin from being forced into the attachment during denture

packing procedures 30.Design the framework with a major

connector for support and a minor connector for the acrylic denture

base. Fabricate and finish 31.Take accurate occlusal records and

mount the casts on an appropriate articulator for the denture setup

and denture is fabricated 32.Females locked inside. All excess

plaster and resin is removed. Use the female screwdriver to

disassemble the female, remove the copper shim and reassemble.

This activates the attachment making it resilient. 32.The

overdenture is ready for insertion Cement the copings onto the

roots and insert the overdenture Non-Resilient GerberThe non-

resilient Gerber attachment technique is similar to that described

above but with one exception. As it is non-resilient, the

overdenture and female rest on the tissues, copings and male posts

in a passive position; no spacing is necessary. Therefore, do not

place spacers over the copings. (Of course, the non-resilient Gerber

has no copper shim spacer.)Maintenance Consideration Relining

or RebasingAlveolar resorption will eventually cause the denture

to rock about the abutments. This rocking will increase the rate of

resorption; abutment bone support will be continually lost. Such

destructive action may even cause dislodgement of the copings,

breakage of attachments, or even the splitting of the abutment. The

appliances should be relined or rebased to eliminate these stressful

30

forces.Procedure for relining Remove the internal parts of the

female with the female screwdriver. Carefully set aside all internal

parts to be reassembled later. Screw the relining heating tool into

the female. Heat the end of the bar in a Bunsen burner flame. The

heat transfer will soften the acrylic around the female, making it

easy to remove Grind out several millimeters of the acrylic resin

within the female recess. Place the female attachments (with their

copper shims in place) over the posts in the mouth. Place an

adhesive on the tissue side of the overdenture, fill the prosthesis

with an elastic impression material and take the impression using a

routine complete denture relining impression technique. Have the

patient close into occlusion while the impression material sets.Male

relining jigInsert the special male relining jigs (transfer males) into

the females until a definite snap is felt The set cast, with the

overdenture, is articulated to a special relining jig. The relining or

rebasing procedure is similar to a conventional denture relining or

rebasing technique. Separate the articulator and remove the cast

from the overdenture impression. The cast has the transfer males in

the same location as in the mouth The cast and attachment

management is handled like the initial fabrication technique: the

spacers are placed over the stone copings; females (with their

copper shims) are placed on the males; all undercuts are blocked

out with plaster; the denture teeth are repositioned on the cast via

the relining jig, and the overdenture is fabricated by any

conventional denture procedure Advantages of the Gerber

attachment1. It provides adequate retention, stability and support.2.

Its retention is light and easily adjustable with springs adjustable

and readily replaced.3. All of its post sleeves are interchangeable

and replaceable, with the exception of the male screw base.4. It can

31

be used in conjunction with bars. 5. It can be processed directly

into the overdenture or positioned in the mouth with

autopolymerizing resin. Disadvantages of Gerber attachment1. It is

a complex attachment and maintenance problems are relatively

common. The male sleeve may become loose. The internal parts of

the female may dislodge when the retaining screw unthreads.2. Its

large vertical dimension makes it impractical for minimal

interocclusal space.3. It requires an assortment of tools for

fabrication and maintenance.4. The attachments must be parallel. 5.

The Gerber permits very little rotational action, so torquing of

abutment teeth will occur with alveolar resorption. Dalla Bona

AttachmentThe Dalla Bona is a simple stud attachment making an

excellent overdenture attachment available in a resilient or

nonresilient series. It is useful when there is minimal vertical space

and where rotation, resilience and retention are desired. It consists

of a single piece male stud soldered to the coping and a single unit

female processed within the denture. It is available in two types:

1.Cylindrical 2.Spherical One form even has an internal coiled

spring much like the resilient Gerber. This spring helps control

vertical movement. The Dalla Bona series is an excellent

attachment. Dalla bona attachments on two cuspids makes it

excellent overdenture arrangementSpherical Bona with undercut

for retentionMale is a solid stud, female is a single component with

retentive lamellae. A clear Teflon ring covers the female

lamellaeRestored roots with copings and spherical

bonasCylindrical Dalla BonaThe cylindrical male post has parallel

walls without an undercut. The female lamella fits snugly over the

male posts, providing frictional retention. A PVC ring fits around

the female lamellae. This aids in fabrication, and permits the

32

lamellae to flex. The cylindrical Dalla Bona must be parallel;

therefore, the male posts must be assembled using a paralleling

mandrel and surveyor.Spherical Dalla BonaThe spherical Dalla

Bona is similar to the cylindrical, but the male post is spherical.

This sphere provides a retentive undercut which is engaged by the

retentive lamellae of the female. If a spacer is used during

fabrication, this attachment will be resilient; without the spacer, it

will be nonresilient.Advantages1. Their overall length varies

between 3.3 millimeters (cylindrical), to 3.7 millimeters

(spherical), so it is suitable for short interocclusal spaces.2. It

provides firm, definite retention.3. It can be processed into the

overdenture in the laboratory or mounted in the mouth using

autopolymerizing resin.4. It is less expensive than the Gerber.5.

Parallelism of the spherical Bona is less critical than that of the

cylindrical Bona.Disadvantages1. The retentive action of the

female is very stiff and difficult to adjust.2. The collar that retains

the female housing in the prosthesis is too small. Therefore the

female may become loose with normal adjustments and use. 3. The

males must be parallel, particularly in the cylindrical form.4. There

may be some torquing and tipping of the abutment.Spherical Dalla

Bona TreatmentDiagnosis, treatment and management using the

Dalla Bona are very similar to that described for the Gerber.Step

by step procedure 1. The various clinical steps depend on the

existing conditions. They would normally include examination,

diagnosis, home care, initial preparation, endodontics, extractions,

periodontics, interim overdentures, final preparations and casts

with removable dies for coping fabrication.Casts with the

removable dies are fitted with the resin dowel pattern coping

pattern is waxed To improve the soldering procedure, cut a ditch in

33

the diaphragm of the coping. This ditch aids the flow of solder

under the stud base With the cast on a surveying table, use a

paralleling mandrel to position the male studs parallel to each

other. Located slightly lingual. Now sticky wax them into position.

Add a short strip of round wax to one side of the waxed base. This

will produce flame vent holes within the investment material. This

also aids the soldering procedure Preheat in an oven to 1400

degrees F. Flame solder the male to the coping by adding solder in

the prepared ditch. The copings with their soldered attachments are

now polished and ready for assembly. Preheat in an oven to 1400

degrees F. Flame solder the male to the coping by adding solder in

the prepared ditch. The copings with their soldered attachments are

now polished and ready for assembly. is withdrawn from the

abutments with an accurate muscle trimmed impression to become

integral part of the master castThe female snapped on to the stud.

The Teflon ring is positioned firmly on the baseBlock out all

coping undercuts with plaster The casts are articulated on an

appropriate articulator with accurate occlusal records for set up

of the denture teeth.The overdenture, with an all-metal base is

processed and finished for insertion with the female retained inside

the denture base The Rotherman AttachmentThe Rotherman is

another excellent stud attachment.The Rotherman consists of a

solid stud (that is soldered to the coping) and a clasp like female

(that is mounted in the overdenture. Like many stud attachments, it

is available in both resilient and nonresilient designs. The resilient

form has a taller male and is supplied with special spacers.The

Rotherman is particularly applicable where interocclusal space is

limited, as the nonresilient design has a vertical dimension of just

1.1 millimeter and the resilient just 1.7 millimeter. The Rotherman

34

anchorage has a short solid stud( non resilient right, resilient left)

and a double armed clasp. The clasp has bar for retention within

the denture baseNon resilient left and resilient right with aluminum

spacerThe male features a definite undercut on just one side of the

cylinder. A scribe line on the occlusal indicates the position of

maximum undercut. The male must be soldered to the coping so

that this line (and the undercut below it) is positioned facially. This

way, the female's clasp arms will reach around from lingual to

engage the undercut and the bar like retentive lug will fall in the

lingual portion of the denture. There it will not interfere with the

tooth setup and will be locked in thicker resin.The Rotherman is

the easiest of all attachments to solder, for it comes with solder

built into the center of the male. The technician need only position

the male on the coping and then hold it in a flame until the solder

flows.BAR ATTACHMENTSAs the name suggests, bar

attachments consist of a metal bar that splints two or more

abutments and a companion mechanism processed within the tissue

area of the overdenture. This mechanism snaps on the bar to retain

the prosthesis.Bar attachments are available commercially in a

wide variety of forms or they can easily be "custom"

fabricated.Types of Bar Attachments Bar units

Bar joints This bar has parallel walls providing rigid fixation with

frictional retention. It can be used for retention with long, medium

or short copings, but only when the appliance is to be an all tooth

supported appliance (i.e. where no stressbroken or rotational action

is indicated). It is never used when a bar joint is indicated (when

rotational or vertical action is necessary); however, a bar joint can

be used whenever a bar unit is indicated.The Bar JointThe action

of this attachment provides rotational or vertical movement. In

35

other words, it is a stress broken attachment. It has a rounded or

semi rounded contour so the retention clip and prosthesis can rotate

slightly during mastication. The Dolder BarAn ideal bar

attachment is the Dolder bar. It is well designed for splinting two

or more abutments to provide support, stability and retention for

the overdenture.This bar attachment is manufactured in two forms

a bar joint and a bar unit. It is also available in two different

diameters and lengths.Dolder bar jointThe pear shaped bar joint is

designed to provide vertical and rotational action so it is indicated

where a stress-broken, resilient attachment is desired. It can also be

used as a bar unit for an all tooth supported prosthesis by

fabricating the overdenture without planned vertical

movement.Dolder bar unitThe bar unit is in the form of an

inverted U with parallel walls. It does not permit rotational or

vertical movement; therefore it only provides retention and

support, but maximizes the masticatory load on the

abutments.Typical Dolder bar Treatment:• Endodontics,

extractions and periodontal surgery were completed prior to

starting the operative process. Tooth preparations were started only

after healing. Reduce the endodontically treated cuspids to one to

two millimeters above the gingiva. Diamond bur is used to

prepare the abutments with a bevel or chamfer margin. X

indentation is made. The copings can be retained with posts, or

parallel pins. As the two cuspids will be splinted with the bar joint,

the posts (used in this case) must be parallel to each other. The

para-post system was used to prepare these parallel "sized" holes to

receive the impression posts. Enlarge the canal opening with a

number six or eight bur to one half of the bur head depth. This adds

strength to the dowel casting union here.Fabricate a customized

36

impression tray on the study cast. Prepare holes in the tray over the

root preparations. The impression posts will pass through these

holes.Take a muscle trimmed impression of the teeth and soft

tissue areas. The previously positioned impression posts are

withdrawn with the impression Plastic dowels used as dowel

patterns Short coping patterns are waxed to conform to

curvature of the alveolar ridge The copings are finished, but are

left with a short section of the sprue on each casting which will be

removed later. These retained sprue posts aid in the assembly of

the bar to the copings for soldering Set up the denture teeth and

check with the patient for occlusal harmony, vertical dimension

and esthetics Cut the bar to fit between the copings. The bar should

be positioned slightly lingual Connect the bar to the copings (the

short sprue stubs help here) with Duralay, or sticky wax. Invest and

solder to the copings. The metal spacer is positioned over the bar

and the retentive shell is snapped on the bar securing the spacer.

Space must also be provided over the copings. Block out all

undercuts around the copings with plaster and cover the flanges of

the retentive shell Consequence of excessive block outWith a

small brush, sparingly paint a semidry mix of auto polymerizing

acrylic resin (such as Duralay) to cover the end of the spacer and

shell Framework is constructed and secured on the cast Use the

stone index to reposition the anterior teeth and complete the

denture set-up The denture is waxed, festooned, flasked, processed

and finished. The coping bar assembly is removed but the retentive

shell is retained within the tissue side of the denture Cement the

Dolder bar/coping assembly into position. The overlay denture is

inserted for use. Overdenture FunctionLet us now consider the

function of this overdenture. Freedom for vertical movement,

37

provided by the auxiliary wire spacer and lead foil covering the

copings during fabrication, allows approximately 0.5 to 1.0

millimeter of space for movement during function At rest, the

overdenture sits passively only on the alveolar tissues. A space is

present between the bar-coping assembly and the shell tissue side

of the overdenture. There is maximum retention now since the clip

engages the bar undercut During mastication, the denture moves

vertically. Now it is supported by both the alveolar tissues and the

root supported coping bar substructure. Adjusting

Retention:Retention of the overdenture is easily increased or

decreased by adjusting the flanges of the shell to provide desirable

retention.Relining/Rebasing TechniqueAs the alveolar ridge

resorbs, the overdenture settles and rocks on the Dolder bar

assembly. These excessive masticatory loads direct damaging

torquing stresses to the abutments. When this occurs, the following

rebasing procedure should be followed.1. With a small round bur,

carefully remove the acrylic around the shell, and remove the shell.

It will be used later.2. Remove additional acrylic above the area of

the copings and bar using a straight

handpiece with a number eight bur. This additional space will

accommodate the impression material.3. Dry the denture and paint

the tissue areas with an impression adhesive.4. Using the elastic

impression material of your choice, take an impression of the tissue

bearing areas, copings and Dolder bar. The patient should close

gently into occlusion, as you muscle trim the impression material.

When a large space is present under the bar or between the

copings, it should be blocked out with soft wax or cement prior to

taking the impression. Otherwise, tearing away of the impression

material from these voids, when the impression is removed, will

38

distort and destroy the accuracy of fit when the prosthesis is

rebased.5. The impression is poured with model stone. 6. The cast

with the overdenture attached is mounted in a relining jig. The

teeth are indexed in the opposing member and the jig is opened

after the plaster has set.7.The overdenture is removed from the cast

leaving a reproduction of the soft tissue, the copings and Dolder

bar.. 8. The denture teeth are removed from the overdenture and

are positioned in their appropriate slot in the plaster index. 9. The

cast is now treated as if you are fabricating a new overdenture i.

e,•Place three to four layers of X-ray foil over each coping as a

spacer.•Place the metal spacer over the mold of the bar.•Snap the

retentive shell into position over the spacer and plaster bar.•Using

plaster, block out the retentive flanges of the shell and all

undercuts.•Block the ends of the shell and spacer with resin.•

Reposition the cast on the relining jig; wax the teeth into position;

wax the denture base; festoon, flask, pack, cure and finish the

overdenture as in any complete denture technique.•The rebased

overdenture is now ready for insertion.The Dolder Bar UnitThe

Dolder bar unit is an excellent attachment when an all tooth

supported, non rotational acting overdenture is desired. This bar

design may be indicated if there are numerous abutments -

especially if they are located in three planes; i.e. posterior and

anterior abutments.The Hader Bar SystemThe Hader system is an

excellent bar attachment. Similar to the customized bar, the Hader

system consists of a plastic bar pattern with gingival extension and

small plastic clips that are processed into the overdenture. This

system has some advantages over others; the plastic bar pattern's

gingival extension can be trimmed to conform to the ridge. In

addition, worn clips can be easily replaced at chair side using a

39

special seating tool.Components of the Hader system are (from left

to right).•Plastic bar pattern (1.8 mm diameter, vertical height 5.7

mm).•Plastic clips (5 mm long, 3 mm thick, 4 mm high).•Modeling

riders used in processing to create a slot for the clips.•Clip seating

tool.Hader Bar Technique•Take an impression of the prepared

abutments, pour a cast and trim the dies as you would any bar

retained overdenture.•Wax the coping pattern on the dies.•Cut the

bar pattern to fit between the coping patterns.•Heat the bar pattern

and adapt it to the ridge curvature.•Trim the gingival portion of the

bar pattern to fit the alveolar ridge.•Wax the plastic pattern directly

to the coping patterns for a single casting, or for greater accuracy,

cast separately and solder to the copings7.The completed

substructure pattern is sprued, invested, cast and finished. 8.Seat

the substructure on the cast for completion of the overdenture

9.Position modeling riders on the bar where clips will attach. These

riders are removed after the prosthesis is fabricated, leaving a

preformed seat to receive the plastic clips for retention. 10.Using

plaster, block out all undercuts around copings and below the

round portion of the bar 11.When the overdenture is finished,

remove the modeling riders with pliers or a sharp instrument 12.

Use the special seating tool to insert the plastic clip into the slots

formed by the modeling rider 13.The denture is now ready for use

Metal clips for retentionIf a metal rider is preferred, it should be

incorporated into the prosthesis when it is initially fabricated.

Instead of using the modeling rider, substitute the metal rider

Advantages of the Hader System1. The plastic bar pattern is

easily adapted to differences in the surface of the gingival ridge

and gingival curvature.2. The plastic bar pattern simplifies the

laboratory technique by eliminating a soldering step.3. Plastic

40

riders give adequate retention and are easily replaced.4. Its

rotational joint action relieves stresses from the abutment teeth.The

main disadvantage of this system is its plastic rider which cannot

be altered for additional retention. However, the adjustable metal

riders can be used to eliminate this problem. In addition, there is no

provision for developing vertical function with the overdenture.

Commercial retentive clips can be used with these customized

bars.AUXILLARY ATTACHMENTSIn addition to bars and

studs, other attachment systems are applicable for overdenture

prostheses. These auxiliary attachments may be in the form of

screws or spring loaded plunger attachments.SCREWS:Schubiger

Screw AttachmentAn excellent screw attachment often used in

overdenture technique is the Schubiger. This attachment is a very

versatile screw-type system, used with Gerber and bar

combinations.Plunger-Type AttachmentsAuxiliary retention for

an overlay prosthesis is often desirable and it may be added to

various coping or bar systems. Plunger type units such as the

Ipsoclip, Presso-matic and IC attachments can add additional

retention Review of literaturePaul A. Miller ( 1958) gave special

emphasis on preservation of tissues with support of artificial teeth.

The use of teeth as support for dentures is aimed at reducing the

load on the osseous portions of the denture bearing area and

minimize the process of resorption.Dolder E. J. in 1961 advocated

the bar joint denture. The denture is adapted primarily to the

situation with which only a few teeth remain. The basic

construction procedures consist of (1) Shortening and capping the

residual teeth to render the crown: root length ratio more favorable

and (2) Splinting the abutments with a straight bar affixed to the

cemented copings which serves, at the same time, as the bearing

41

shaft for the complete denture.Robert J. Crum and R. J. Loiselle

(1972) in his review of literature reveal that discrete sensitivity that

exists in the separate components of masticatory system. It also

demonstrates the necessity for total integration of each component

of the masticatory system and signals the importance of preserving

the natural teeth. Merrill C. Mensor (1973) advocated the use of E

M attachment selector which consists of 8.5 by 11 inch color coded

selector cards. It is compendium of attachments and connecting

units available through out the world and it contains 30 points of

information for each of more than 105 different attachment

systems, this is a total of over 3000 points of information. Each of

the cards numbered to correspond with 5 attachment

classifications.Joseph T. Quinlivan (1974) said that retention is a

problem for overlay dentures over simple copings when only two

teeth remain. This is particularly a problem when treating a

mandibular arch, which has a more limited basal seat area. He

advocated RCT of the abutment teeth; pulp space to be enlarged

with a Gates Glidden drill and finally with a safe sided para post

drill. Then he advocated used ball and socket type of attachment

for overdenture on the teeth reduced I mm above the

gingiva.Wayne R. frantz (1975) described the construction of tooth

supported dentures where the natural tooth was utilized and the

acrylic resin for denture base processed directly to the prepared

cast. He said that abutment teeth with their coping may result in 3-

5 mm above the gingiva which causes undue stress and torque on

the teeth. He advocated natural teeth to be reduced 1-2 mm above

gingiva fill the pulp chamber with amalgam and give a very high

polish and construct the denture.A. B. Warren and A. A. caputo

(1975) conducted a study to determine and compare the transfer of

42

forces to the alveolar bone for five different abutment designs for

the tooth supported dentures and concluded that there was a direct

relationship between the stability and retention that each design

provided and the amount of stress and torque transferred to the

supporting structures. Attachments that used parallelism or

undercuts for retention tend to produce the most severe stress

conditions in the supporting alveolus.H Thayer and A A Caputo

(1977) provided the following guidelines in the selection of

specific designs for overdenture abutments:1.The Dolder bar,

which exhibits more cross-arch involvement than the Zest anchor,

will share the occlusal load across the arch, between the abutments

and the supporting structures. 2.The posterior edentulous regions

will receive some physiologic stimulation with the Dolder bar, for

it shares more stress here than the Zest anchor. 3. The forces on the

Dolder bar produce stress directed more apically than that from the

Zest anchor. Since this force is better tolerated, use of the Dolder

bar may be indicated for a short-rooted tooth with less supporting

bone.4. The greater stress concentrated around the abutment teeth

by the Zest anchor makes use of this design in a tooth that is

periodontally sound and has a long root structure well imbedded in

supporting bone seem logical.Merrill C. Mensor (1978) said that

when selecting an attachment it is essential to consider the skill of

the dentist – laboratory teem as well as dexterity of the patient and

to use the easier system that will still improve stabilization. He

advocated the use of E M gauge and E M attachment selector to

reduce confusion in selection attachments. Robert J. Crum and

George E. Rooney (1978) conducted a 5 year clinical study to

determine the amount of bone loss in the anterior part of the

maxillae and the mandible in two groups of patients: one group

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with complete maxillary dentures and mandibular overdentures and

other group with complete maxillary and mandibular dentures. The

result show that group –I demonstrated less alveolar bone reduction

than group –II.H. H. Thayer and A. A. Caputo (1979) concluded

that a) The more retentive tissue bar and extra coronal attachments

produces higher stress concentrations b) The Hader bar produced

less torquing forcesc) The Ancrofix appeared to share the forces of

occlusion between the abutments and the posterior edentulous

regions.Gary D.Derkson and Michael Macentee ( 1982) conducted

a study to observe the therapeutic effect of 0.4% stannous fluoride

gel on the periodontium and the tooth structure of overdenture

abutments and they found that 0.4% stannous fluoride gel is an

effective agent in reducing the progress of gingivitis around

overdenture abutments.Conclusion: To conclude it would not be a

repetition to say that overdenture is a preventive dentistry concept

which has been brought into Prosthodontics. The alveolar bone and

its overlying mucosa was never intended to receive the full force of

the complete denture. Even though the technique resembles those

of complete dentures, there are important differences. The

prognosis of the restoration is likely to be influenced by numerous

factors like: 1) Selection of patient2) Treatment planning3)

Preparation of the mouth4) Execution of the prosthodontic work5)

MaintenanceFinally it is reasonable to conclude that retention of

the part of the natural dentition affords the overdenture patient a

gain in neuromuscular performance thereby having an edge over

his edentulous counterpart.References1.Brewer AA, Morrow RM:

Overdentures, ed 2. St Louis, CV Mosby, 1980.2.Crum RJ,

Rooney GE Jr: Alveolar bone loss in overdentures: A 5-year study.

J Prosthet Dent 1978;40:610-613.3.DerksonGD, MacEntee MM:

44

Effect of 0.4% stannous fluoride gel on the gingival health of

overdenture abutments. J Prosthet Dent 1982; 48:23-26.4.Ettinger

RL, Taylor TD, Scandrett FR: Treatment needs of overdenture

patients in a longitudinal study: Five-year results. J Prosthet Dent

1984;52:532-537.5.Mensor MC Jr: Attachment fixation of the

overdenture: Part II. J Prosthet Dent 1978;39:16-20.

45

6.Quinlivan JT: An attachment for overlay dentures. J Prosthet Dent

1974;32:256-261.7.Thayer HH, Caputo AA: Occlusal force transmission

by overdenture attachments. J Prosthet Dent 1979;41:266-271.8.Thayer

HH, Caputo AA: Effects of overdentures upon the remaining oral

structures. J Prosthet Dent 1977;37:374-381.9.Winkler .S . Essentials of

complete denture Prosthodontics, second edition,2000, 384-402.10.Paul

A. Millar: complete denture supported by natural teeth. J Prosthet Dent

1958;8:924.11.Dolder E. J: The bar joint mandibular dentures. J Prosthet

Dent 1961;11:689.12.12.Wayne R Frantz: The use of natural teeth in

overdentures. J Prosthet Dent 1975;34:135-140.13.A B Warren and

Caputo: Load transfer to alveolar bone as influenced by abutment designs

for tooth supported dentures. J Prosthet Dent 1975;33:137.

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