PROVISIONAL RESTORATION IN FIXED

PARTIAL DENTURE

DR IRFAN

INTRODUCTIONIt is important that the prepared tooth or teeth be protected and that patient be kept comfortable while a cast restoration is being fabricated by successful management of this phase of the treatment, the dentist can gain the patients confidence and favourable influence for the ultimate success of the final restoration.If the provisional restoration is not up to the mark, it may lead to unnecessary repairs as well as nead to treat gingival inflammation and it can further prolong the treatment schedule.

One of the foremost reasons to be careful during preparation of provisional restoration is that due to unforeseen events such as lab delays or patients unavailability it has to function for extended period so it has to be adequate to maintain patients health in other words it should be healing matrix for the surrounding gingival tissue and adjacent gingival mucosa.

It can be said that provisional restoration is frequently the patient’s first impression of final prosthesis so it should be representative of the final esthetic result. In some cases it is used to help correct the etiologic factors of T.M.J or periodontal disease.

SYNONYMS

Provisional restoration,Treatment restoration (Temporization), Interim prosthesis, Provisional prosthesis.

The word provisional means established for the time being pending a permanent arrangement . This type of a restoration has also been known for many years as temporary restoration . Unfortunately temporary often convey the notion that requirement are unimportant . Experience reveal that time effort expended fulfilling the requisites of provisional restoration are well invested.

Definition A fixed or removal prosthesis designed to enhance esthetics stabilization and function for a limited period of time after a which it is to be replaced by definitive prosthesis.(GPT-7 1999) .

A PROVISIONAL MATERIAL SHOULD SATISFY FOLLOWING CRITERIAConvenient handling: adequate working time,easily moldability, rapid setting time.Bicompatibility: nontoxic, nonallergic, nonexothermic.Dimensional stability during solidification .Ease of contouring and polishing .Adequate strength and abrasion strength.Good appearance,transclucent,color controllable,colour stable.Good patient acceptance,non irritating ,odorless.Ease of adding to or reparing .Chemical compatibility with provisional luting agent.

Requirements of a Provisional Restoration:

1. Fit: a temporary crown must fit closely at the finish line of the preparation. This will help prevent tooth sensitivity and promote health of the surrounding gingiva. In the picture at right, the provisional restoration will be worn for an extended period of time while the tissues heal from periodontal surgery. Note that the margins of the temporary fit closely to the finish line of the preparation.

This provisional has overextended margins that have caused gingival irritation. This inflammation will progress during the time that the provisional is worn and could result in necrotic tissues or bone destruction around the tooth

2. Occlusion: The provisional should establish or maintain adequate occlusal contacts. Without occlusal contacts, the prepared tooth may extrude. This will make the permanent restoration too high in occlusion and further adjustment of the final restoration may result in an occlusal surface that is too thin or that is perforated. Occlusal contacts on the provisional must not be too high. This will cause occlusal disharmony and may result in tooth sensitivity.

3. Proximal contacts: The provisional must establish or maintain adequate proximal contacts to prevent movement of the prepared tooth in a lateral direction. Without proximal contacts, the tooth may drift. This will result in a permanent restoration that will not fit due to excessive of deficient proximal contacts. Proximal contacts must be present also to prevent food impaction in those areas.

Adequate esthetics: The temporary must have adequate contours, color, translucency and texture. This is especially important in anterior teeth. Because acrylic tends to darken and discolor over an extended period of time, a different provisional restorative material may need to be selected if the temporary is to be worn for a long period. A smooth polished surface is important for esthetics as well as plaque removal

5. Proper contours: A provisional must have proper contours for esthetics and for gingival health. The emergence profile must be the same as the original tooth to facilitate plaque removal. Embrasure areas must be contoured to allow for the interdental papilla. In a fixed partial denture, the pontic must be contoured so that it is as self cleansing as possible.

The photo at right shows an improperly contoured fixed partial denture. There is not enough embrasure space. The dental papilla are impinged upon and signs of gingival inflammation are present.

At left is an example of tissue damage that can occur from overcontoured or overextended margins on a provisional

6. Strength: The strength of most provisional materials is far less than gold alloy. Provisionals must be of adequate thickness to withstand occlusal forces without cracking. In a fixed partial denture, the connector area may need to be slightly enlarged to prevent breakage.

Materials Material used to fabricate provisional

restorations can be classified as acrylics or resin composites. Subcategories are based on method of polymerization (e.g., chemically activated, light activated, dual activated).Acrylics These materials have been used to make provisional restorations since the 1930s and usually consist of a powder and liquid. They are the most commonly used materials today for both single-unit and multiple-unit restorations. In general, their popularity is due to their low cost, esthetics, and versatility.

They produce acceptable short-term (i.e., three months) provisionals but tend to discolor over time. Other disadvantages include an objectionable odor, significant shrinkage and heat generation during setting, and messiness during mixing. The three types of acrylics are polymethyl methacrylates,poly-R’ methacrylates(where R’ represents either ethyl,vinyl,or isobutyl groups), and epimines.

Type Brand Manufacturer Advantages Disadvantages

Poly(methylmethacrylate

AlikeCr & Br Resin

Dura lay

GC America LD Caulk Reliance

Dental Lang Dental Parkell Biomaterials

Good marginal fit

Good transverse strength

Good polishabilityDurability

~ High exothermic heat increase

Low abrasion resistance

Free monomer toxic to pulp

High volumetric shrinkage

Poly( ethyl methacrylate)

JetSnap

Parkell Biomaterials Good polishability

Minimal exothermic heat increase

Good stain resistance

Low shrinkage

Surface hardnessTransverse strength

Durability

Fracture toughness

Poly(vinylethyl

methacrylate)

Trim Harry Bosworth Good polishability

Minimal exothermic

heat increaseGood

abrasion resistance

Good stain resistance

Surface hardnessTransverse strength

EstheticsFracture toughness

Bis-acryl composite

Pro temp II ESPE-Premier Good marginal fit

Low exothermic

heat increase Good

abrasion resistance

Good transverse strength

Low shrinkage

Surface hardnessLess stain resistance

Limited shade selection Limited polishability

BrittleMarginal fit

VLC uerthane

dimethacrylate

Triad Dentsply York High surface hardness

Good transverse

sirengthGood

abrasion resistance

Controllable working timeColor stability

Less stain resistanceLimited shade selection

ExpensiveBrittle

1 . Polymethyl MethacrylatesPolymethyl MethacrylatesAdvantages -low cost ,good wear resistance ,good esthetics ,high polishability ,good color stability .Disadvantages- significant amount of heat given off by exothermic reaction , high degree of shrinkage (about 8%) ,strong, objectionable odor -short working time , hard to repair , radiolucent 2 Poly-R' Methacrylates (R' = ethyl, vinyl, isobutyl) Advantages -low cost ,less heat given off during reaction than polymethyl methacrylates , less shrinkage than polymethyl methacrylates Disadvantages -extended working time ,less esthetic than other currently-marketed materials , poor wear resistance ,poor color stability , strong, objectionable odor hard to repair ,radiolucent

3.Epimines These were the first two-paste acrylics, commercially introduced in 1968 as Scutan (ESPE). Although Scutan had relatively low shrinkage and heat production, it was weak and could not be altered or repaired.

4 . Bis-Acryl Composites Bis-acryl provisional materials are resin composites and represent an improvement over the acrylics because they shrink less, give off less heat during setting, and can be polished at chairside. Conveniently, the majority of these products are provided in cartridges for use in an automix dispenser gun. However, there are at least two types of guns for provisional materials, so you should not assume compatibility between one manufacturers cartridges and another manufacturers gun.

Provisionals made with bis-acryl resins can be polished to a smooth finish, but are generally not glossy like the acrylics. They also have a pronounced air-inhibited layer that should be removed (usually with alcohol-saturated gauze) prior to finishing and polishing. Although they are provided in fewer shades than the acrylics, they can be characterized using flowable or traditional resin composites. The bis-acryl composites can be subcategorized according to method of activation (e.g., chemically activated, visible light activated, or dual activated).

Advantages -less shrinkage than acrylics ,minimal heat generated during setting reaction ,relatively high strength ,minimal odor ,excellent esthetics ,most products use automix delivery ,can be repaired or characterized using resin composite ,easy to trim , good color stability Disadvantages - radiopaque ,greater cost than acrylics ,some do not have a rubbery stage ,viscosity cannot be altered ,sticky surface layer present after polymerization ,may be more brittle than acrylics

Chemically-Activated Composites Chemically-activated resin composite

provisional products include Protemp 3 Garant (3M ESPE), Integrity (Dentsply/Caulk), Temphase (SDS/Kerr), InstaTemp (Sterngold), and Luxatemp (Zenith/DMG).

Specific Product Information Protemp 3 Garant is available in four shades (A1, A3, B1, B3). A specially designed dispenser syringe of AddOn, a low-viscosity light-cured resin, is also included with the product. AddOn is used to correct voids or defective margins of the provisionals. Provisional restorations made with Protemp 3 Garant are said to be more fracture resistant that those made with other composite products. 3M ESPE also claims that the restorations have excellent marginal adaptation and are fast and easy to polish.

Integrity is available in three shades (A1, A2, A3.). Two sizes of mixing tips are available: a small size for single-unit temporaries and a larger tip for multiple temporaries and fixed partial dentures. The product has a snap set and should be used expeditiously; place it in the mouth within 45 seconds and remove it in another 45 seconds..Visible Light-Activated (VLA) Composites Very few provisional materials are available that are polymerized solely by exposure to a light curing unit. One, however, is Revotek LC, introduced by GC America in 2002.

Specific Product Information Revotek LC is a VLA, single-component, sculptable resin composite. It is supplied in a Putty Stick form in a lightproof plastic tray. To make a provisional restoration, a small portion of the material is cut from the stick and adapted to the preparation directly in the mouth. It is then sculpted using hand instruments after which the patient is instructed to occlude into it to establish a functionally-generated occlusal scheme. The Revotek LC provisional is then light-activated for 10 seconds in the mouth, removed, and given a final 20-second light exposure. After finishing and polishing, the restoration is cemented with a temporary cement. Revotek LC is available in only one shade (B2).

Dual-Activated Composites One example is Unifast (GC America), which goes through a chemically-activated, rubbery, setting stage and is then VLA for final set. Other such products have appeared in the past such as TempCare (3M) and Provipont DC (Ivoclar Vivadent) but have since discontinued.Preformed materialsPreformed provisional crowns or matrices usually consist of tooth-shaped shells of plastic, cellulose acetate, or metal. They are commonly relined with acrylic resin to provide a more custom fit before cementation, but the plastic and metal crown shells can also be cemented directly onto prepared teeth using a stiff luting material following adjustment. .

They are commercially available in various tooth sizes and are usually selected for a particular tooth anatomy. Nonetheless, available sizes and contours are finite which makes the selection process important for clinical success. Compared with custom fabricated restorations, this treatment method is quick to perform but is more subject to abuse and inadequate treatment outcome. This can result in improper fit, contour, or occlusal contact for a provisional restoration

Polycarbonate resinPolycarbonate resin is commonly used for preformed crowns and possesses a number of superior properties relative to polymethyl methacrylate materials.These crowns combine microglass fibers with a polycarbonate plastic material. Practitioners commonly use polycarbonate resin shell crowns as a matrix material around a prepared tooth that is relined with acrylic resin to customize the fit. This material possesses high impact strength, abrasion resistance, hardness, and a good bond with methyl-methacrylate resin.

MetalMetal provisional materials are generally esthetically limited to posterior restorations. Aluminum shells provide quick tooth adaptation due to the softness and ductility of the material, but this same positive quality can also promote rapid wear that results in perforation in function and or extrusion of teeth.

An unpleasant taste is sometimes associated with aluminum materials. Iso- Form Crowns (3M Dental Products, St. Paul, Minn) are manufactured with high-purity tin-silver and tin-bismuth alloys. Like aluminum, they possess reasonable ductility and can be contoured quickly, but the occlusal table is reinforced so they are more resistant to wear related failure. For longer-term use, nickel chrome and stainless steel crowns are available but may be more difficult to adapt to a prepared tooth.

INFLUENCE OF MATERIAL PROPERTIES ON TREATMENT

OUTCOMEMarginal accuracyAccurate marginal adaptation of resinous provisional restorations to the finish line of a prepared tooth assists in protecting the pulp from thermal, bacterial, and chemical insults. The accuracy could be significantly improved by relining the restoration after the initial polymerization.

A number of studies have focused on the effects of thermocycling

on provisional crown margins.They reported that

(1) acrylic resin provisional crowns demonstrated dimensional

degeneration and enlarged marginal gaps resulting from

thermocycling and occlusal loading;

(2) marginal gap changes were greater after hot thermocycling

than cold thermocycling;

(3) improved marginal accuracy of PMMA provisional

restorations occurred when a shoulder finish line was used

compared with a chamfer marginal design;

(4) light-polymerized materials provided significantly improved marginal accuracy relative to auto polymerizing PMMA resin after thermocycling. In contrast, Keyf and Anif concluded that the marginal discrepancy found with bis acryl resin was significantly greater with a shoulder finish line after 1 week relative to a chamfer design . composite materials would provide a better marginal fit relative to unfilled polymethyl methacrylate because of less polymerization contraction, but marginal fit is not the only factor affecting the overall retentive quality of provisional restorations.

Nearly 20% improvement in the retention of interim crowns made with polymethyl methacrylate compared to those fabricated with composite materials. They concluded that polymerization shrinkage occurring with the polymethyl methacrylate material might have allowed for a tighter fit of the restoration on the prepared tooth, which had a direct influence on improved retentive quality.

Color stabilityColor stability

In esthetically critical areas it is desirable for remain color stable over the course of provisional treatment. Discoloration of provisional materials can produce serious esthetic complications, especially when long term provisional treatment is required. Modern provisional materials use stabilizers that decrease chemically induced color changes, but these materials are susceptible to other factors that will promote staining..

When provisional materials contact pigmented solutions such as coffee or tea, discoloration is possible. Porosity and surface quality of provisional restorations as well as oral hygiene habits, can also influence color changes.

Crispin and Caputo studied the color stability of provisional materials. They found that methyl methacrylate materials exhibited the least darkening, followed by ethyl methacrylate and vinyl-ethyl methacrylate materials. They also reported that increases in surface roughness induced increases in material darkening and pressure polymerizing did not influence discoloration relative to air polymerizing.

Koumjian included a visible light-polymerized material in their investigation. They placed test materials into the flanges of complete dentures and concluded that for short time periods of 5 weeks or less, all materials demonstrated acceptable color stability . They stated, however, that the Triad VLC material exhibited more adverse color change relative to other materials at the end of 9 weeks.

Yannikakis et al immersed provisional materials in various staining solutions for up to 1 month. They reported that all materials showed perceptible color changes after 1 week. The methyl methacrylate materials exhibited the best color stability and bis-acryl materials the worst.

Gingival response

Inflammation and recession of the free gingival margin associated with provisional treatment is a common occurrence. Donaldson reported the following observations regarding gingival recession: (1) the presence of a provisional restoration lead to at least some recession at about 80% of the free gingival margin sites evaluated; (2) the degree of recession was time dependant; (3) placement of the definitive treatment commonly lead to gingival recovery; (4) 10% of subjects demonstrated recession in excess of 1 mm; and (5) in the presence of gingival recession, only one third of subjects demonstrated complete gingival recovery.

In a separate report, Donaldson indicated that the occurrence of gingival recession before provisional treatment was directly linked to further recession observed after the completion of definitive prosthodontic treatment. He also found a direct relation between the degree of pressure applied by a provisional restoration and gingival recession. An anatomically contoured provisional restoration caused less recession than did a non anatomically contoured one. periodontal inflammation associated with provisional treatment could be expected to be a reversible process provided that the amount of gingival irritation is minimal and provisional treatment occurs over a short time span.

PULPAL RESPONSE

Dental pulp inflammation can be caused by either thermal or chemical insult resulting from materials used to produce direct provisional restorations. The results of the study suggest the possibility of thermal damage to dental pulp tissue and odontoblasts during direct provisional fabrication, They suggested that by use of air and water coolants, as well as by use of a matrix material, that can dissipate heat rapidly, the pulp temperature rise might be reduced. Additionally, the amount of heat rise is dependent on the quantity of provisional restorative material used

Temperature rise was greatest with polymethyl methacrylate and vacuum adapted templates; least with bis-acryl and relined resin shells; and intermediate temperature increases were recorded with polyethyl methac rylate materials and either irreversible hydrocolloid or polyvinylsiloxane impression materials used as a matrix for holding acrylic resin provisional material against a tooth. The authors also identified that fixed partial denture provisional restorations produced a greater temperature rise than did single-unit provisional restorations.

Grajower et al showed that faster polymerizing acrylic resin materials could generate higher temperatures than slower polymerizing resins.

They indicated that external heat dissipation might be enhanced with a water spray or by polymerization of restorations in silicone impressions. Additionally, this external heat dissipation caused retardation in the polymerization, which further decreased heat production. The retardation resulted from the cooling effect of the spray and not the water itself, since moisture quickens the polymerization of autopolymerizing acrylic resins that contain tertiary amine accelerators. The authors concluded that (1) provisional acrylic resin restorations might be fully polymerized on prepared teeth by appropriate methods such as in impressions or with external cooling, without causing excessive heating of the dental pulp;

(2) removal of a provisional restoration before complete polymerization, leading to potential deformation of the acrylic resin material, is therefore unnecessary; and (3) a thin insulating layer should be applied to a prepared tooth before contact with non polymerized acrylic resin to avoid chemical .

Hypersensitivity

Hypersensitivity from provisional materials has been reported but appears to be rare. Autopolymerizing methacrylate materials have greater potential for producing allergic contact stomatitis than similar heat-polymerized materials. The residual monomer in the material has been implicated as the causative factor. One report showed that the residual monomer content in heat-polymerized acrylic resin ranges from 0.045% to 0.103%. Autopolymerized acrylic resin has a residual monomer content of 0.185%. Over time residual monomer is gradually leached out, leaving a fraction that is tightly bound to the resin materia1.

Allergic reaction to provisional materials will demonstrate the following features: (1) the patient has had previous exposure to the provisional material; (2) the reaction conforms to a known allergic pattern, such as redness, necrosis, or ulceration; (3) the reaction resolves when a provisional restoration is removed; 4) reaction recurs when a provisional restoration is replaced; and 5) a patch test for the material is positive. Patch testing has demonstrated less response with light-polymerized materials relative to autopolymerizing acrylic resin. In direct material processing methods are recommended for individuals showing evidence of hypersensitivity.

Strengthening provisional materials

The studies clearly favors acrylic resin as the material of choice for provisional restorations. Most resins used for provisional restorations are brittle. Repairing and replacing fractured provisional restorations is a concern for both clinician and patient because of additional cost and time associated with these complications. Failure often occurs suddenly and probably as a result of a crack propagating from a surface flaw. The strength and serviceability of any acrylic resin, especially in long span interim restorations, is determined by the material's resistance to crack propagation. Crack propagation and fracture failure may occur with these materials because of inadequate transverse strength, impact strength, or fatigue resistance.

Physical properties of strength, density, and hardness may predict the longevity of provisional restorations. Donovan et al examined methods to improve the longevity of these restorations using variable indirect polymerization techniques. They compared methyl methac rylate material strength, porosity and hardness under the following polymerization conditions: (1) in air; (2) under water; (3) under air pressure; and (4) under water and air pressure. They found that polymerization with a pressure vessel with air and water had the greatest influence on increasing strength and reducing porosity.

Heat-polymerization of acrylic resin materials can be used when provisional restorative treatment will be required for extended periods of time or when additional strength is required. This indirect laboratory process results in materials that are denser, stronger, more wear resistant, more color stable, and more resistant to fracture than their autopolymerizing counterparts. Both heat-polymerized acrylic resin and metal provisional restorations should last longer than autopolymerized restoration, but the expense and time required for indirect fabrication can make them less cost effective for routine use

Zuccari et al studied methods to promote a stronger resin matrix "by decreasing crack propagation. They reported that when admixed zirconium oxide powders were added to unfilled methyl methacrylate resin, the resultant composite material exhibited significant improvements in the modulus of elasticity, transverse strength, toughness, and hardness, even though water sorption over time had a negative influence on mechanical properties.

In a study describing a negative influence on the strength of provisional materials, Chee et al studied the effect of chilled monomer on the working time for 3 autopolymerizing acrylic resins. They found that the working and setting times increased by up to 4 minutes when chilled monomer was used, but the transverse strength for the materials were decreased by 17%.

Provisional luting materials

Provisional luting agents should possess good mechanical properties, low solubility, and tooth adhesion to resist bacterial and molecular penetration. The most important function of these materials is to provide an adequate seal between the provisional restoration and prepared tooth. This is necessary to prevent marginal leakage and pulpal irritation. There are a variety of luting materials used for interim purposes. The most common include (1) calcium hydroxide; (2) zinc-oxide and eugenol; and (3) noneugenol materials. Generally, all of these possess poor mechanical properties that likely worsen over time.

This can have a negative influence on marginal leakage but also provides an advantage by allowing easier dislodgment and removal of provisional restorations from teeth.

The retentive requirements for provisional luting materials are that they be strong enough to retain a provisional restoration during the course of treatment but allow easy restoration removal when required. This paradoxical necessity for good retentive and sealing quality and easy restoration retrieval may lead to a compromise in material behavior, particularly regarding mechanical properties.

Baldissara et al recommended that interim restorations be frequently evaluated and used for only short periods of time. Literature reports advise that if provisional treatment is required over a protracted time period, it is best to remove and replace the provisional luting agent on a regular basis. Some of the most commonly used cements with provisional prostheses are those containing zinc-oxide and eugenol. They provide sedative effects that reduce dentin hypersensitivity and possess antibacterial properties. Unfortunately, free radical production necessary for polymerization of methacrylate materials can be significantly hampered by the presence of eugenol found in eugenol based provisional luting materials.

This can interfere with the acrylic resin polymerization and hardening process .They can also be incompatible with some resin-based definitive luting agents for the same reason.

Eugenol-free provisional luting materials are commercially available and have gained popularity due to the absence of resin-softening characteristics .

Gegauff and Rosenstiel, however, reported that Temp- Bond (Kerr Dental, Orange, Calif) a zinc-oxide and eugenol based cement did not appear to have a significant adverse effect on the polymerization of acrylic resins. They postulated that the softening effect of eugenol on acrylic resin is dependent on the presence of unreacted eugenol, which may be minimal in Temp-Bond cement .

CLINICAL CONSIDERATIONS FOR PROVISIONAL TREATMENT INVOLVING

NATURAL TEETH

The fabrication of provisional restorations is extensive . Virtually all teeth receiving cast restorations require provisional restorations. Properly executed provisional restorative treatment rarely fails and dislodgment or fracture usually indicates that their form is unacceptable or that a tooth preparation is inadequate. Provisional restorations should be smooth, highly polished, and alterable and for this reason custom made provisional restorations most consistently meet the biological,functional, and esthetic needs of a patient.

Provisional restorations as part of comprehensive treatment

Provisional restorations are not devoid of interactions with other modes of therapy. Patients often have periodontal, endodontic, orthodontic, or surgical needs in conjunction with their prosthodontic treatment. Provisional restorations produce outcomes that range from microscopic tissue effects to psychological factors that change a patient's behavior. Provisional restorations can provide patients with an increased confidence in treatment.

Diagnostic provisional treatment

In the simplest situations, complete oral and extraoral clinical examinations, as well as radiographic evaluation, may be all that is necessary before commencing prosthodontic treatment. In more complex treatments, however, provisional restorations provide a means of designing, improving, and assessing the occlusion, esthetics, and contours for definitive restorations, as well as to determine their effects on gingival health, phonetics, and patient adaptability before the initiation of the definitive treatment. Provisional restorations fit into 2 categories: (1) those that fit within an arch of fundamentally intact teeth that provide reference for their occlusion, contours, and esthetics; and

Those that become the reference for the entire prosthesis. Provisional treatment for patients with more complex prosthodontic needs demands fabrication and articulation of diagnostic casts and completion of a diagnostic wax-up in the maxillomandibular relationship in which definitive treatment is to be performed.

Occlusal diagnosis and treatment

Casts of provisional restorations mounted opposite definitive casts transfer contours, clinical crown dimensions, and maxillomandibular relationships from a patient to a dental laboratory for developing occlusal factors, especially anterior guidance, for fixed prosthodontic treatment.

Sometimes treatment feasibility can only be tested via full-arch provisional restorations and occlusal problems are best diagnosed during a functional testing period with provisional treatment .

Esthetic and phonetic diagnosis and treatment

Provisional restorations assist development and assessment of esthetic and phonetic values of the planned fixed prosthesis. Matrixes created from a diagnostic waxing or from casts of provisional restorations are useful tools for producing specific contours in a definitive prosthesis or communicating those concepts to the dental laboratory.

In certain situations phonetics and esthetics of a planned prosthesis can be assessed before tooth preparation by use of vacuum or pressure-formed matrixes that hold autopolymerizing acrylic resin between unprepared teeth and proposed tooth contours to provide intraoral treatment simulation.

Periodontal treatment and maintenance

Periodontal treatment is commonly part of comprehensive prosthodontic care. These provisional restorations provide a matrix against which the tissue heals, guiding the generation of correct soft tissue architecture. According to Shavell, tooth preparations and provisional restorations should be completed with retraction cord in place.

It has been recommended that when the duration of the periodontal treatment is less than 6 months, the use of acrylic resin provisional restorations . Poorly fabricated provisional restorations have consequences for fixed prosthodontic treatment including gingival recession difficulty making impressions; difficulty fitting the definitive restorations; soft tissue damage; and inefficient use of time at prosthesis insertion

Slightly convex facial and lingual contours of provisional restorations and a flat emergence profile are effective in promoting gingival health. Good periodontal health can be created by developing the appropriate contour and good gingival adaptation and embrasure space of the prosthesis.. Embrasure spaces that are too broad can cause food impaction and blunting of the papilla .

Types of provisional restorations: Many different types of procedures are used to construct provisional. Provisional construction can be categorized into two main methods: 1 - Custom temporaries - those that are made with a matrix derived from the original tooth or a modified diagnostic cast. Custom temporaries can

be constructed in three different manners:

Direct: these are constructed with a matrix lined with provisional material that is placed directly on the prepared tooth

Indirect: these are constructed by placing the filled matrix over a model of the prepared tooth, thus the provisional is constructed out of the patient's mouth.

Indirect-Direct: these are made by forming a temporary in an indirect manner and then relining this directly in the patients mouth. This method is useful when constructing temporary bridges because most of the work can be done in the laboratory.

2- Prefabricated temporaries - these are preformed crowns that can be purchased and may be modified to fit a prepared tooth. In most cases these require relining with an acrylic material.

Direct fabrication. For select patients, a denture tooth secured in position and orthodontic wire may be a suitable provisional restoration for a missing mandibular incisor. For urgent situations, in the absence of any matrix or opportunity to create a matrix, a provisional restoration can be fabricated by adapting a block of freshly mixed acrylic resin directly to a tooth. After the acrylic resin block has polymerized, the tooth contours can be carved with acrylic resin burs of choice and the restorative margins perfected intraorally.Most patients, however, require a more conventional approach. Fabricating provisional restorations directly on teeth using the "direct method" is suitable for single units and up to 4-unit fixed partial denture provisional restorations,

Three techniques encompass virtually all of the literature on direct provisional restorations: (1) use of a pre manufactured provisional sheIl (2) use of an impression material ,or pressure or vacuum formed translucent matrix and (3) use of a custom, pre fabricated acrylic resin shell. Direct provisional restorations made particularly of PMMA and, to a lesser degree, polyethyl methac rylate (PEMA) must be cooled if the material is allowed to polymerize completely on a tooth; polymethyl methacrylate can increase pulpal temperatures as much as 7°C. Cooling the material during polymerization by its removal at initial polymerization and allowing complete polymerization to be completed while it is off the tooth,

cooling with air-water spray, periodic removal, and flushing with water and use of a "heat sink" matrix material such as alginate will limit temperature increases to less than 4°C, minimizing the exothermic risk .

Indirect fabrication. The indirect method has been indicated to fabricate multiple unit provisional restorations to (1) avoid exposure of a patient to adverse properties of provisional acrylic resins; (2) optimize the properties of provisional acrylic resins; (3) allow the use of materials that are difficult to polymerize intraorally; (4) make significant contour or occlusal changes; and (5) provide for the fabrication of hybrid provisional restorations.

Indirect techniques generally use either approximate tooth preparations made on a duplicate cast or a cast of the actual tooth preparations made after the clinical procedure has been accomplished. One advantage of the indirect technique is that it can be allocated to auxiliary personnel. Fabricating a provisional restoration wholly or in part using an indirect method reduces exposure of oral tissues to monomer, heat, shrinkage, and reduces the volume of volatile hydrocarbons inhaled by a patient. Creating an indirect acrylic resin shell of an unprepared tooth that is later relined intraorally is one method of reducing patient exposure.

It has been reported that provisional restorations fabricated indirectly have superior margins to those from direct techniques because the acrylic resin polymerizes in an undisturbed manner. Polymerizing autopolymerizing acrylic resin under heat and pressure improves the physical properties of the material. Reinforcing the vacuum or pressure formed matrix allows it to be secured to the cast on which the provisional shell is polymerized.

Indirect method (Alginate impression technique)The overimpression frequently is made in the patient's mouth while waiting for the anesthetic to take effect. However, if the tooth to be restored has any obvious defects, the overimpression should be made from the diagnostic cast .When the alginate has set, the overimpression is removed from the diagnostic cast and checked for completeness. Thin flashes of impression material that replicate the gingival crevice are removed to insure that there will be no impediments to the complete seating of the cast into the overimpression later .

The impression is wrapped in a wet paper towel and placed in a zip lock plastic bag for later use.When the tooth preparation is completed, another quadrant impression is made in alginate. This impression is poured up with a thin mix of quick-setting plaster . Mix tooth-colored acrylic resin in a dappen dish with a cement spatula. Place the resin in the over impression so that it completely fills the crown area of the tooth for which the provisional restoration is being made .

Seat the prepared tooth cast into the over impression, making sure that the teeth on the cast are accurately aligned with the tooth impressions.

Once the cast has been firmly seated and the excess resin has been expressed, hold the cast in place with a large rubber band.

It is important that the cast be oriented securely in an upright position so that the space between the cast and the impression that is filled with the resin forming the provisional restoration will not be distorted. If the cast is torque to one side by the rubber band, the cast may be forced through the soft tissue in some areas resulting in a provisional restoration that may be thin in those areas and thicker than desirable in others. The force used to seal the cast into the alginate impression is critical.

DIAGNOSTIC CASTSDIAGNOSTIC CASTS

PUTTY INDEX TECHNIQUE

Diagnostic wax-up doneDiagnostic wax-up done

Putty index made from the Putty index made from the diagnostic wax up.diagnostic wax up.

Trimmed acrylic shells oriented in the Trimmed acrylic shells oriented in the putty indexputty index

Auto polymerizing resin filled in Auto polymerizing resin filled in the putty indexthe putty index

The index stabilized on the The index stabilized on the prepared sectional cast.prepared sectional cast.

Finished and cemented Finished and cemented provisionals.provisionals.

2TEMPLATE METHODTo make a template, place a metal crown form or a denture tooth in the edentulous space on the diagnostic cast . All of the embrasures should be filled with putty to eliminate undercuts during adaptation of the resin template.To facilitate removal of the template, a thin strand of putty can be placed around the periphery of the cast and on the lingual surface of the cast, apical to the teeth . Use a large acrylic bur to cut a hole through the middle of the cast (midpalatal or midlingual). Place a 5 x 5-inch sheet of 0.020-inch-thick resin . Turn on the heating element of the machine and swing it into position over the plastic sheet .

As the resin sheet is heated to the proper temperature, it will droop or sag about 1.0 inch in the frame. If you are using coping material, it will lose its cloudy appearance and become completely clear. The cast should be in position in the center of the perforated stage of the vacuum forming machine. Turn on the vacuum.Grasping the handles on the frame that holds the heated coping material, forcefully lower the frame over the perforated stage . Turn off the heating element and swing it off to the side. After approximately 30 seconds, turn off the vacuum and release the resin sheet from the holding frame . if a vacuum forming machine is not available, it is still possible to fabricate a template for a provisional restoration.

Place the softened sheet over the cast. Forcefully seat the tray of silicone putty over the coping material . To accelerate cooling, blow compressed air on the plastic sheet and the impression tray. After about a minute, snap the tray off the cast . If the silicone putty sticks to the resin sheet, the putty can be easily removed by pulling it off in quick jerks. Rapid separation causes the silicone putty to exhibit brittleness that will result in easy removal. Replace the putty in its original container for later re use. Separate the template from the diagnostic cast.

Upon completion of the preparations, make an alginate impression of them and pour it in fast-setting plaster. Trim the cast so that it includes only one tooth on either side of the prepared teeth. Try on the template to verify its fit .Coat the cast with separating medium and allow it to dry. Mix the acrylic resin in a dappen dish and place some on protected areas of the cast, such as interproximal spaces and in grooves and boxes. As the resin begins to lose its surface gloss and becomes slightly dull, fill the area for which the provisional fixed partial denture is being made . Place some extra bulk in the portion that will serve as the pontic.

Wrap rubber bands around the template and cast, being careful not to place them over the abutment preparations, lest they cause the template to collapse in that area . Place the cast in a pressure pot if one is available. Otherwise, place it in warm (not hot) tap water to hasten polymerization. Remove the fixed partial denture from the cast. Do not.hesitate to break the cast if necessary. Trim off the excess acrylic resin. Use discs to trim the axial surfaces down to the margins. Remove the saddle configuration that was created by the crown form in the edentulous space . The pontic should have the same general shape that the pontic on the permanent prosthesis has.

Shell-Fabricated Provisional RestorationA thin shell crown or fixed partial denture can be made from any of the acrylic resins, and then that shell can be relined indirectly on a quick-set plaster cast. It also can be relined directly in the mouth. If the reline is done directly, a methacrylate other than poly(methyl) should be used. This technique can save chair time because the restoration is partially fabricated prior to the preparation appointment Care must be taken not to make the shell too thick. If too thick, the shell will not seat completely over the prepared teeth and it will need to be trimmed internally.

This can be time-consuming and defects any advantage gained by making it before the preparation appointment .

An overimpression is made from a diagnostic wax-up before the preparation appointment. Trim off thin flashes of impression material created by the gingival crevice to produce an extra bulk of resin near the margins. Use a plastic squeeze bottle with a fine tip to deposit one drop of monomer on the facial and one drop on the lingual surface of the overimpression. Keep the monomer near the gingival portion of the impression to prevent excess from accumulating in the incisal or occlusal area. Extend the coverage by the resin to one tooth imprint on either side of the teeth being restored.

When the teeth have been prepared, make a quadrant alginate impression and pour it with a thin mix of quick setting plaster. Trim off excess plaster on a model trimmer. Save one tooth on either side of the prepared tooth, if possible. Remove areas of the cast that duplicate soft tissues.

Try the shell gently on the cast to make sure it seats completely without binding. If it does bind, relieve the inner surfaces of the shells until the restoration seats completely and passively. Liberally coat the tooth preparations on the cast with separating medium and make sure it is dry before mixing the acrylic resin.

Monomer and polymer can be added directly to the shell and mixed there. The resin also can be mixed in a dappen dish and then transferred to the shell, completeIy filling each tooth. Seat the shell onto the prepared teeth on the cast. Wrap a rubber band around the shell and cast, and place them in a plaster bowl full of hot tap water for approximately 5 minutes, preferably in a pressure pot. The use of a pressure pot will significantly increase the strength of the restoration .

If the direct technique is employed, seat the shell on the prepared teeth in the mouth A matrix can be made in many different ways. Most are from sheets of plastic that are heated and formed over the diagnostic cast. Then the matrix is filled with acrylic resin and placed over the prepared teeth in the patient's mouth.

Technique used in the fabrication Technique used in the fabrication of provisionals using light cured of provisionals using light cured

resin.resin.

DIAGNOSTIC WAX UP & IMPRESSION.

Resin placed on the finish line for Resin placed on the finish line for better adaptation.better adaptation.

Template is filled with light cured Template is filled with light cured resin.resin.

PREFABRICATED CROWNPolycarbonate Crowns: These are available in incisors, canines and bicuspids. There is a range of sizes for each tooth form.It should be relined with acrylic in order to provide a good internal fit. After lining with acrylic, they may be trimmed to provide a good marginal adaptation and further adjusted into proper occlusion.

MOLD SELECTION FOR MOLD SELECTION FOR TEMPORARY POLYCARBONATE TEMPORARY POLYCARBONATE

CROWNSCROWNS

SIZING IT UPSIZING IT UP

IMPROVING FIT WITH RESINIMPROVING FIT WITH RESIN

Cemented temporary in placeCemented temporary in place

Ion Crown Formers: These are

shells made of cellulose acetate

and are available in all tooth

forms. These shells come in

various sizes for each tooth form

and are lined with acrylic resin.

After the acrylic resin has

polymerized, the cellulose shell

is peeled away from the crown.

This usually necessitated the

further addition of acrylic in the

areas of the proximal contacts.

Tin Silver: Tin Silver preformed crowns are available for posterior teeth. This alloy is very soft and the margin of the crown can be flexed prior to seating with a swaging block. This produces a close marginal fit after the shell is trimmed with a bur. These should also be lined with acrylic resin to provide good internal adaptation and retention of the temporary.

Aluminum Shell Crowns: Similar to the tin silver, aluminum shell crowns are available in the anatomic form as shown here, or in a cylindrical form that requires extensive occlusal contouring. Adjusting occlusion on an aluminum crown lined with acrylic sometimes results in perforation of the aluminum into the layer of acrylic beneath it as shown here

Provisional treatment for all ceramic veneer restorations

All-ceramic restorations including laminate veneers have become a large part of dental practice. Most of what has been published regarding provisional treatment for veneers has focused on technical procedures. Provisional veneers are indicated when (1) esthetics and intelligible speech are important; (2) mandibular incisors are veneered; (3) dentin is exposed; (4) proximal contacts are broken; (5) maxillary teeth are inverted lingually and the veneer surface affects occlusion; (6) the preparation margin invades the gingival sulcus; and (7)the final veneer is dependent on patient approval of form, color, contour, and position.

Provisional restorations allow patients to have a trial period for making notes about esthetics so that their desires can be taken into account with the definitive veneer . Preparations for porcelain veneers may not have mechanical retentive features and thus one concern regarding a provisional restoration is tooth attachment while avoiding irreversible contamination or alteration of the luting surface of a prepared tooth.

Elledge advocated placing 2 small dimples on opposing surfaces of the preparation to provide mechanical retention for the provisional veneer that is luted with a cement of the clinician's choice. One method that avoids excess cement while sealing the margin area is the "peripheral seal technique" that

uses a 3-second etch of the preparation periphery and then bonding a provisional restoration primarily at the etched periphery. Similarly, a colored luting resin may facilitate removal of excess resin and reduce contamination of a tooth surface. Another technique known as the "spot etch" method incorporates provisional restorations that are luted with light polymerized acrylic resin to an etched spot near the center of the preparation. In an in vitro study of surface contamination associated with provisional bonding, a polyurethane isocyanate surface treatment left the cleanest tooth structure whereas a noneugenol provi sional cement left: significant but removable residue; a dual polymerizing resin cement left tenacious residue that could only be removed with a bur .

A variety of methods for fabrication of veneer provisional restorations have been reported and are not unlike the methods advocated for conventional provisional restorations including, a removable "splint,"with hand formed visible light-polymerized materials, polycarbonate provisional crowns, acrylic resin shells, and splinting together adjacent provisional veneers.

Esthetics

Patients may be highly motivated by esthetics and instant improvement can be achieved through provisional restorations. Custom colored provisional restorations made with mixtures of acrylic resin powders creating an incisal polymer, a body polymer, and a cervical blend are easier to fabricate with an indirect method. Esthetically enhanced provisional restorations can fabricated with visible light-polymerized labial veneers or denture tooth facings in conjunction with acrylic resin Gingival architecture and tissue contour are among the many factors other than materials that influence esthetics.

Anterior provisional restorations should provide the following esthetic benefits: (1) optimum periodontal health; (2) visualization of the anticipated esthetic outcome; (3) ability to test the incisal edge position and cervical emergence; (4) development of appropriate anterior guidance; and (5) determination of the need for periodontal surgery. Methods for improving or customizing colors also include coloring provisional luting cements and coloring a provisional restoration with porcelain stains and visible light-polymerized acrylic resin. In Custom color guides for provisional restorations have also been recommended.

REMOVAL OF PROVISIONAL RESTORATION

The provisional is removed when the patient returns for the definitive restoration or for continued preparation. The prepared tooth or foundation must be avoided. Risk of this can be minimized if removal forces are directed parallel to the long axis of the preparation. The Backhans or hemostatic forceps are effective for obtaining purchase on a single unit.A slightl buccolingual rocking motion will help break the cement seal. Damage can occur when a FPD is being removed. If one abutment retainer suddenly breaks loose, the other abutment can be supported to severe leverage.

Care must be exercised to remove the prosthesis alongthe path of withdrawl. Sometimes it is helpful to loop dental floss under the connector at each end of the FPD, providing a more even force distribution for removal.

RECEMENTATION OF PROVISIONAL RESTORATION

If provisional is to be recemented clean out the bulk of cement with aspoon excavator then place the provisional in a cement dissolving solution in an ultrasonic cleaner. Line it with a fresh mix of resin if necessary (as when a toothpreparation has been modified, eg).The internal surface is relieved slightly and painted with monomerto ensure good bonding of the new lining.

SUMMARY

Although provisional restorations are usually intended for short term use and then discarded, they can be made to provide pleasing esthetics, adequate support, and good protection for teeth while maintaining periodontal health. They may be fabricated in the dental office or in laboratory from any of several commercially available materials and by a number of practical methods. The success of fixed prosthodontics is often depends on the care with which the provisional is designed and fabricated.

In 1990, Ernest DaBreo et al gave "clinical report on a provisional restoration for a patient with cleft lip and palate. The provisional prosthesis provides on alternative treatment option that allows the dentist to plan the definitive restoration while providing the patient with a temporary but esthetic and functional restoration.

In 1991, Conrad Bodai described expedient and effective interim restoration for compromised posterior teeth.The restoration can beethyl methacrylate, visible-lightactivated resin, and a Bis-acrylplaced quickly, exhibits excellent adaptations provides exceptional retention and maintains proximal and occlusal contacts.

Review OF LITERATURE

In 1991, Jack Koumi Jian et al did a study on the 'Colour stability of provisional materials in view. Colour stability of provisional restorations is an important quality of the resin used, particularly for extensive reconstruction over a long period of time.This study evaluated the invitro discoloration of seven resins over a 9 week period. Resin specimens were prepared and placed in the facialflange of maxillary complete dentures and the lingual flange of a mandibular complete dentures. Patients were given tooth brushes and tooth paste and told not to use any chemical agents for choosing the dentures. Observations were made at 1, 5 and 9 weeks,

No change was detected at the first two evaluations. At the 9 week evaluation, four materials, methyl methacrylate, polyminylethyl methacrylate and bis-arylcomposite resin showed significantly less staining than did the other three resins tested. All materials tested were acceptable from the standpoint of colour stability for short term (5 weeks or less) provisional restorations. Therefore, the dentist using provisional restorations for a short period of time may consider other properties of the materials, such as resistance of fracture, marginal accuracy, rase of fabrication and cost.

In 1991, Millstein et al studied the effect of aging an temporary cement retention in vitro. The primary function of temporary cements isto act as an interim cementing media for provisional or fixed restorations. Temporary cements may be medicated and are often used for toothsedation as well as for retention. Retention of restorations cemented with temporary cement varies. Some cements are adhesive and others are '"'work in retention. In addition, cement retention may vary over time. this study determined:1. The retentive properties of four temporary cements. 2. The effects of aging on temporary cement retention Retention of restoration was studied at 1 and 6 week intervals. Retention varied with the 4 cements tested, and one cement (Temp-bond)became significantly less significant over time

In 1992, Timothy M. Campbell and Nagy described the use of avinyl polysiloxane to make interim restorations.The rationals andprocedures is described. vinyl polysiloxane is a commonly used impression material that flows readily, is accurate and sets to a fins consistency- properties that are useful a for this procedure .

In 1992, Douglass B. Roberts described a method of making indirect interim restorations using flexible costs. A procedure isdescribed for making interim restorations from a cast and dies made of polyvinyl siloxane impression, material. The use of these flexible castsand dies facilitate the removal of the polymerised resin from the cast especially in arches that have significant undercuts caused by anatomicfor or tooth alignment. The rapid set of the polyvinyl materials reducesthe time involved in making, the indirect interim restorations.Thepolyvinyl cast is reusables if necessary. The polyvinyl cast is reusables if necessary. One disadvantage of this procedure is the cost of the material.

William H. Lienberg in 1994 described a technical procedure of wire reinforced light cured glass ionomer resin provisional restoration. aprocedure to use round practical provisional restorations is presented. The viability of the use of glass ionomer resin cement and the need forembrasure perfection in provisional restoration where extensive coronal destruction has occurred. The inherent disadvantage of the procedure is the need to involve occlusal surfaces of the proximal teeth; thus its use isrestricted to mouth in which the adjacent teeth are to receive simultaneous restorative treatment.

THANK YOU