Intraoral Esthetic Repair of Dental Restorations

Intraoral Esthetic Repair of Dental Restorations

R O N A L D E . G O L D S T E I N , D D S " SHANE N . W H I T E , B D F N I S C , MS, MA+

any restorations are M replaced for reasons unre- lated to recurrent disease. Repair of superficial parts of otherwise sound dental restorations is often desirable, both to correct current defects and to prevent future problems. This approach conserves tooth structure, decreases patient suffering, and reduces health care costs. Long-term clinical trials of direct amalgam and composite restorations have shown that up to half of all unsatisfactory restorations have been replaced due to fracture, wear, unsatisfactory con- tour or anatomic form, marginal discrepancies, staining, open con- tacts, o r color mismatch.'-' Porcelain fracture and marginal discrepancies are common causes of early failure of crowns and fixed partial dentures.'-"' This article reviews current repair techniques and suggests appropriate clinical pro roco 1 s .

I S 0 I. A l ' I 0 N

Rubber dam isolation is strongly recommended, whenever possible, for adhesive procedures. Isolation can prevent salivary contamination,

allow moisture control, protect soft tissues from acids, prevent inhalation of airborne abrasives, and retract soft tissues. Moreover, a uniform-colored background facili- tates achieving the chosen shade.

R E I ' A I K M E T H O D S

Many intraoral methods have been used to prepare the surfaces of restorations for adhesive bonding. These methods can be divided into two groups. The first group of techniques roughens restoration surfaces to create micromechanical retention. Methods include roughening with a diamond bur, sandblasting, high-energy a brasion, etching with strong acids, and tin plating. The second group of techniques promotes adhesion of restorative composites to the roughened surfaces. These include silane coating and treating with multipurpose adhesives. The best results are obtained using a combination of techniques. Predictable results can now be achieved in a single routine office visit.

Roughening with Diamond Burs A diamond bur can be used to roughen most restorative surfaces, but this method is not as effective as other techniques and should not be relied on."-" Burs can also be used to create macromechanical retentive undercuts, but excessive removal of tooth structure or restoration should be avoided. Surface preparation using multi- fluted carbide finishing burs or smooth finishing diamond burs should be avoided.

Sandblasting Sandblasting can improve retention to fractured porcelain, exposed cast metal, or composite surfaces*lz,".1' Lh This not only creates micromechanical roughening, but also produces compositional changes and increases surface energy, thus increasing wetability by adhesives." Small intraoral sandblasters are now available (Micro Etcher, Danville Engineering, Danville, CA). Optimal effects are obtained using large (50 to 100 pm) alumina particles at high pressures (80 to 100 psi). The sandblaster should

,-Chicid Professor of Oral Kehahl~i tat lo~, Schooi of Dentistry, Medical Cidlege of Georgia. Adjunct Clinical Professor of I'rosthodontrcs a t Boston University, Visiting Professor of Oral and Maxillofacial Imaging and Continuing Education at t h University of Southern California School o f Dentistry, 1.0s Angeles, Californra, Adjunct Professor of Restoratnw Dentistry ut The University of Texas Health Science Center at Sun Antonio, 'Texas, and Private Practice, Atlanta, Georgiu .Assistant Professor and Director ~f Clinical Research, Department of Restorative DentistrylSiomaterials, School o f Dentistry, University of Southern Califimria, Los Angeles, California v o i 11h41- 7 . N I I Z ~ R ~ K i 219

hit raoral Esthetic Repair of Dcrital Restorations

Figure I . A scanning electron micrograph (X2000 original magnification) of a hybrid composite (Herculite XRV, Kerr) that has been treated using high-energy abrasion (KCP 2000, American Dental Technology). Exposure of individual filler particles has created an extremely retentive surface.

be attached to the main air supply line before it is down regulated to approximately 40 psi for hand- pieces. Since the patient’s eyes and airway must be protected, rubber dam isolation and protective gog- gles are recommended.

differs from conventional air abrasion in several ways.Lx.” Higher pressures and smaller nozzles are used to increase particle velocity and energy. The equipment also has con- sidera ble reserve volume to ensure that pressure does not drop during use. For most restorative materials, that the best results are obtained by using 50 pm alumina abrasive a t the medium setting.’’ Optimal results are obtained when the tip of the nozzle is held a t an angle several millimeters back from the surface. It is recommended that both patients and clinicians wear protective eye- wear. Clinicians should wear masks and patients’ airways should be isolated by rubber dam.’l High-volume evacuation should be used for removal of abrasive and saliva, but the system’s own integral high-

High-Energy Air Abrasion Recently, a surface preparation method using high-energy a brasion has become available (American Dental Technology, Troy, MI, Sunrise Technologies, Freemont, CA, Kreativ Inc., Albany, OR).’* This technique enhances adhesion to a very wide variety of restorative materials (Figures 1 and 21, as well as to enamel and The high-energy air abrasion technique Figure 2. A scanning electron micrograph ( X l 000 original magnification)

of a stainless steel surface that has been treated using high-energy abrasion ( K C P 2000). Despite the soft and tough nature of stainless steel, micromechanical retention has been created.

volume evacuation system should be used primarily for dry, airborne abrasive. The abrasive need only be directed at the target area for very short periods, and a uniform change in surface texture is sufficient. Prolonged application times are unnecessary and will remove too much restorative material. This system is very quick and easy to use.

Etching Thirty-seven percent phosphoric acid is used to etch enamel adjacent to repairs. Weaker acid solutions (e.g., 10% phosphoric acid or 2.5% nitric acid) can be used to condition adjacent dentin prior to bonding; that is, to open up tubules and remove the smear layer and other debris.

Several acids can be used to etch porcelain. They act by differentially dissolving porcelain components to create micromechanical undercuts. Hydrofluoric acid, usually used at 8% to 10% concentrations for 2 to 4 minutes, is highly effective.”-’4.”-” However, it is also extremely dangerous and must be used with careful isolation and great caution. A weaker 2.5% solution of hydrofluoric acid, which may be less dangerous, is also effective (Porcelock, Den-Mat, Santa Maria, CA).” Acidulated phosphated fluoride, applied in the form of a 1.2% fluoride gel for an extended time, ha only limited ability to etch porcelain. IL,14,1 i 3 3 Phosphoric acid enamel etchant can be used to clean

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exposed porcelain surfaces and make them more receptive to silane. However, phosphoric acid has no etching effect on porcelain. Acid etching is the most important step in feldspathic porcelain re~air , ’~,’~.~’ but it is much less effective on stronger, highly crystalline ceramics such as In-Ceram (Vita Zahnfabrik, Bad Sackingen, Germany), Empress (Ivoclar-Vivadent, Amherst, NY) or Dicor (Dentsply York Division, York, PA).24,25 Sandblasting or high- energy abrasion is the primary method of roughening high-strength ceramic^.^^^^' It may be prudent to replace damaged high-strength all- ceramic restorations, rather than to attempt major repairs.

Sandblasting prior to etching increases surface roughness and allows the etchant to penetrate deeper into the surface defects on all porcelains and ceramic materials.”~l‘~Zh

Some acids may be used to etch the glassy filler in composites, but they may not be very effective in improving bond strength and may stain or damage some conipos- ites.lx,’y As well as attacking the filler, acids tend to damage the polymeric matrix and the interface between filler and matrix.

When several different acids are to be used to treat different adjacent materials, the strongest one should be used first (e.g., 10% hydrofluoric acid on porcelain), followed by

the intermediate acid (e.g., 37% phosphoric acid on enamel), and finally the weakest acid (e.g. 2.5% nitric or 10% phosphoric acid on dentin). The repair should be thor- oughly washed using airlwater spray for at least 10 seconds after each acid application.

Tin Plating Intraoral tin plating may be used to coat precious metals with a layer of sharp retentive tin oxide crystals.’L~L‘l This may be preferred to conventional sandblasting alone, which is less effective on precious metals. However, high-energy abrasion is effective on precious or homogeneous metals such as Type 111 gold and titanium.” Tin plating may stain adjacent tooth-colored materials. Sandblasting prior to tin plating is recommended. ” Several small tin platers suitable for intraoral use are commercially available (Micro Tin, Danville Engineering; Kerr, Glendora, CA).

Silane Organosilane coupling agents have the ability to form covalent bonds with siliceous glassy composite filler and with resinous polymer^.'".^" These bonds are stable, but may be slow to form. Tests on the enhance- ment of repairs by silane coupling agents have produced conflicting and often disappointing

This may be due to the susceptibility of organosilanes to hydrolysis by moisture and to their slow reaction

results. I I . l l , lh . lY. lh .~h.?Y4 I

hit raoral Esthetic Repair of De I I t a1 Rcs t o r*ations

Figure 3 . incisor.

A composite and enamel fracture on an upper right central

kineticS.Lf,.17.42 Isolation during the bonding procedure may not be sufficient protection for silane, because composites quickly absorb water from the oral en~ironment .~ ' Therefore, silane treatment may be best suited to laboratory or manu- facturing procedures where it will not he exposed to moisture until fully reacted. Currently, silanation can be regarded as an optional step for intraoral repairs. It may not be very effective, but it will not be deleterious.

Mdu$urgo~w Boadaag Agents Solvent-based primers containing surface active monomers wet the restorative material and penetrate into micromechanical surface irregk larities. I2.i 1.1 ~.I;.IX,LII,LI.L1.L6,1I,14~;~,,444h

These surface active monomers can then copolymerize with composites. Suggested materials include Tenure (Den-Mat), All-Bond (Bisco, Itasca, IL), C&B Metabond (Parkell, Farmingdale, NY), Scotchbond

Figure 4. (Ivoclar- Vivadent). Remaining composite and adjacent enamel has been treated with high-energy abrasion (KCP 2000).

The incisor has been isolated using a Quick Dam

MP Plus (3M, St. Paul, MN), Syntac (Ivoclar-Vivadent) and Prime and Bond (Caulk/Dentsply). Again, a micromechanically retentive surface is needed, isolation is critical and the manufacturers' instructions must be followed carefully. Figures 3,4, and 5 show the repair of a fracture in which a multipurpose bonding agent was used.

Figure S. The tooth has now been treated with a multipurpose bonding agent (All-Bond, Bisco), restored with a hybrid composite (2 100, 3M), shaped with 30-hladed carbide burs (ET9UF, Brassler), and polished with flexible discs (Sof-Lex, 3M).

' 2 2 I Y Y ~

C L F A N I N G A N 1) L j E L R E A S I N G

Clean, dry surfaces are essential for adhesion. Sandblasting, high- energy abrasion and acid etching will all remove superficial debris and salivary contaminants. However, it is also essential that acid gels and abrasive particles be completely washed off conditioned surfaces. Oil from lubricated hand- pieces or compressors can be removed by carefully cleaning with acetone or a commercial degreas- inddrying agent such as Dry-Bond (Den-Mat).

Figure 6. of a porcelain laminate.

A traumatic porcelain fracture on the incisal edge

(: o M I' o s I T E P L A <: t:, M E N 'i-

Several types of composite may be used for different repairs. Hybrid composites should be used if resistance to occlusal stresses is necessary, such as for incisal angles (Figures 6, 7, and 8). Suggested hybrid materials include Herculite XRV (Kerr, Glendora, CA), Prisma TPH (Caulk/Dentsply), ZlOO (3M) and Aelitefil (Bisco). Figure 7.

high-energy abrasion for several seconds. Porcelain and adjacent enamel are treated by

Microfilled materials should be used when optimal esthetics and polishability are needed but stress resistance is less important (e.g., gingival fractures). Microfills can be used to veneer hybrids or fractured porcelain. Suggested microfills include Durafil (Heraeus Kulzer, Irvine, CA), Silux Plus (3M), Perfection (Den-Mat) or Rename1 (Cosmedent, Chicago, IL).

Figure 8. acid, and the enamel etched with 37% phosphoric acid. A multipurpose bonding agent (Tenure, Den-Mat), and a hybrid composite (Prisma TPH, CaulklDentsply) completed the repair.

The porcelain was etched with 10% hydrofluoric

l r r l moral kktlietic Repair of Derital Restorations

Fluoride-releasing materials, or resin-modified glass ionomers, can be used when the patient is at risk for caries. These materials are gen- erally weaker, less wear-resistant, less polishable, and less dimension- ally stable than conventional composites. However, they possess sustained fluoride release, acceptable esthetics, and acceptable adhesive properties. Suggested resin-modified glass ionomers include Fuji I1 LC (GC America, Chicago, IL), Vitremer (3M), Dyract (Caulk/Dentsply), Geristore (Den-Mat) and Photac-Fill (ESPE Premier, Norristown, PA).

Opaque composites may be used to hide exposed metal. Some resinous materials such as Panavia (J Morita, Tustin, CA), Geristore (Den-Mat) or Resinomer (Bisco) are adhesive on their own, but can be enhanced by a multipurpose bonding agent.” Layers of trans- lucent composite should be added and cured incrementally, allowing internal characterization and avoiding excessive polymerization shrinkage. If possible, polymerization should be initiated by directing the curing light through the tooth, rather than from the external surface, thus initiating curing at the tooth/composite interface and allowing some stress relaxation during polymerization. The composite must be protected from moisture until fully cured. After complete curing, the composite can be recontoured using fine diamonds or inultifluted carbide

Figure 9. porcelain laminates have become ditched, hut the restorations are otherwise satisfactory.

T h e occlusal margins of these five-year-old

Figure 10. abrasion, and deeply stained fissures explored. The margins have been coated with a n unfilled resin (Fortify, Bisco), and the fissures restored with a hybrid composite (Rename1 Hybrid, Cosmedent).

T h e margins have been treated with high-energy

Figure 2 I . will continue to provide many years of serrtice.

The repaired restorations, with intact margins,

finishing burs (ET, Brassler, Savannah, GA) and polished using abrasive discs (Soflex, 3M; Flexidiscs, Cosmedent; and Super- Snap, Shofu, Menlo Park, CA) or very fine diamond polishing paste. Recuring the composite after finishing may improve its physical properties.

D I $ ( U I S I O N

Table 1 gives suggested protocols for repair of various materials. These repair procedures were suggested by consideration of the scientific literature and by clinical experience. Other opinions and procedures may be valid. New information, materials, or technologies may influence future protocols. In all cases, a combination of techniques provides the best results. Since many adhesive techniques are operator-sensitive, the simplest effective protocol should be chosen.

These adhesive techniques may be applied in many imaginative ways to solve many different problems; for example, a porcelain veneer could be bonded to a bridge pontic that had lost its porcelain facing. New types of restorations will demand novel solutions to brand- new problems.

Repair techniques vary widely in their ability to produce durable bonds to different materials. For example, bond strengths to porcelain may be so strong as to exceed their cohesive strength, but bonds

to repaired amalgam are usually weak. Therefore, if possible, conventional retention and resistance form should be used to augment the adhesive repair. Each clinical repair should be evaluated sepa- rately. Figures 9, 10, and l l show a combination approach taken to porcelain laminates with ditched margins.

Little long-term clinical data exists on the performance of repaired restorations. We should advise our patients with caution, because many lab studies have shown that bond strength decreases after stor- age, artificial aging, or fatig~e.'",'~." (However, one clinical study of repaired amalgams has achieved a loo%, 1-year success rate.46) Our patients must be fully informed as to the risks of failure. We cannot yet give our patients any estimates of repair longevity. We must also stress the importance of continued follow-up and maintenance therapy. This will allow early diagnosis of problems and may lead to less invasive interceptive treatments.

When making treatment decisions, we must evaluate the consequences of possible future failure of the repair. These may often be less seri- ous than the potential consequences of failure of a completely new replacement restoration. However, we must be careful to fully diagnose any restoration-related disease, such as deep caries or periodontal disease, before opting for repair instead of replacement.

If a damaged restoration can be removed from the mouth, many more adhesive repair techniques are possible. Such restorations could be cleaned using ultrasonic or steam cleaning. Additional techniques include silane coating, silica coating (Silicoater, Hereaus Kulzer and Rocatec, ESPE Premier), oxidization, electrolytic etching, and plasma spraying. Composite repairs could be post-cured using heat, pressure, and more intense light sources.

C: 0 N C 1. U S I 0 N S

Preventive repair of existing restorations has the potential to conserve tooth structure, reduce patient suffering, and decrease treatment costs. Many new techniques for intraoral repairs are now available. Lack of clinical data limits our ability to predict the long-term performance of repairs.

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Intraoral Esthetic Repair of Dental Restorations