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Authors: Dr. Arjun Jawahar Sharma, Dr. Rahul Nagrath

INTRODUCTION

Ceramic veneer restorations have proven to be durable and aesthetic restorative procedure for treatment of teeth in the front area of the mouth. Ceramic veneers are more conservative than crowns , and maintain the biomechanics of an original tooth with a success rate of approximately 93% over 15 years of clinical use.

Restorative aesthetic dentistry should be practiced as conservatively as possible. The use of adhesive technologies makes it possible to preserve as much tooth structure as is feasible while satisfying the patient’s restorative needs and aesthetic desires. With indirect restorations, clinicians should choose a material and technique that allows the most conservative treatment; satisfies the patient’s aesthetic, structural, and biologic requirements; and has the mechanical requirements to provide clinical durability.1

Based on their strength, longevity, conservative nature, biocompatibility, and aesthetics, veneers have been considered one of the most viable treatment modalities since their introduction in 1983.2 Aesthetic veneers in ceramic materials demonstrate excellent clinical performance and, as materials and techniques have evolved, veneers have become one of the most predictable, most aesthetic, and least invasive modalities of treatment.3 For this reason, both materials and techniques provide the dentist and patient an opportunity to enhance the patient’s smile in a minimally invasive to virtually noninvasive way. Initially used to treat various kinds of tooth discoloration, porcelain laminate veneers have been increasingly replaced by more conservative therapeutic modalities, such as bleaching and enamel microabrasion.4 However, this evolution has not led to a decrease in indications for veneers, as materials and techniques continue to be developed. Ceramic veneers are considered the ultimate option for a conservative aesthetic approach because they leave nearly all of the enamel intact before the veneer is placed.5

Since its introduction more than two decades ago,6,7 etched ceramic veneer restoration has proven to be a durable and aesthetic modality of treatment. The clinical success that the technique has found can be attributed to great attention to detail in a set of procedures, including planning the case, with the correct indication; conservative preparation of the teeth; proper selection of ceramics to use; proper selection of the materials and methods of cementation; and proper planning for the ongoing maintenance of these restorations.6 Accordingly, this article discusses the aspects of ceramic laminate veneers restoration that involve materials, applications, and techniques, in order to address some concerns about newer trends, materials, and methods as they relate to the continued success of this modality of treatment.8,9,10

 

ADVANTAGE

DISADVANTAGE

  • Less invasive – requires minimal preparation.
  • Color and surface texture can be matched with natural teeth.
  • Good biocompatibility with gingiva at the margins of the restoration.
  • Excellent durability – as it has good bond strengths between ceramic, composite and tooth.
  • Resistance to abrasion,wear and solvent attack.

 

  • Uniform and minimal preparation required makes it difficult to execute.
  • No alterations possible once the veneer is ready.
  • Bonding procedure is time consuming technique sensitive and governs the success.
  • Due to their fragility, may lead to fractures while try-in or cementation.
  • Proper selection of underlying cement is critical for effective final result.
  • It is difficult to repair.

 

 

INDICATIONS

CONTRA INDICATIONS

  • Correction of alternations in tooth shape or position.
  • Changes in morphology of teeth with microdontia or tooth transposition.
  • Presence of diastemas and/or poor incisalembreasures.
  • Repair of incisal fractures.
  • Extensive anterior dental restorations.
  • Enamel alterations (abrasion, attrition, abfraction).
  • Change in tooth color.
  • Anterior guide rehabilitation.
  • Repair of crown and bridge.
  • Teeth having insufficient crown material:
  • If the teeth are composed of dentin and cementum crowning may well be the preferable treatment.
  • Young permanent teeth
  • Parafuncitonal habits
  • Severe periodontal involvement and crowding.
 

CASE REPORT

A 27 years old female patient reported to Department of Prosthodontics, K.D dental college and hospital, Mathura. Patients chief complaint was of yellowish, uneven upper and lower teeth and fractures front tooth since few years.

The patient was a foreign national and gave dental history of proximal restorations i.r.t 11,12,21,22. Intraoral examination revealed patient had proximal composite restorations i.r.t11,12,21,22. The overall oral hygiene was good. The radiographic investigations were done.

Patient was explained about the treatment modalities of having orthodontic opinion / re-restorations with composite / ceramic veneers with their advantages and disadvantages. Ceramic laminate veneers was decided as definitive treatment plan.

TREATMENT PLANNING
 
 
 
 
 
 
 

TECHNIQUES

Preparation of teeth The preparation of the teeth greatly influences the durability and color (translucency and tonality) of the ceramic restoration, since the tooth preparation will determine the inner superficial contour and the thickness of the ceramic material. This stage is determined by the evaluation of the condition of the teeth, the indications of the clinical situation, and the material chosen (feldspathic or glass ceramic).15,18 Concepts regarding the preparation of teeth for porcelain veneers have changed over the past few years. Although early concepts suggested minimal or no tooth preparation, current belief supports removal of varying amounts of tooth structure.4,7,18 The preparation design for laminate veneers should simultaneously allow an optimum marginal adaptation of the final restoration and demonstrate utmost respect for the hard tissue morphology. Enamel reduction is required to improve the bond strength of the resin composite to the tooth surface. In doing so, the aprismatic surface of mature unprepared enamel, which is known to offer only a minor retention capacity, is removed.7,18 In addition and when possible, care must be taken to maintain the preparation completely in enamel to realize an optimal bond with the porcelain veneer. Although the results of the newest generation dentin adhesive systems are very promising, the bond strength of porcelain bonded to enamel is still superior when compared with the bond strength of porcelain bonded to dentin.6,7 Thus, one of the main objectives of the technique is to maintain the entire contour in intact enamel whenever possible, because the better the adhesion between the veneer and the prepared tooth, the better the stress distribution in the system enamel–composite–ceramic.18

The types of preparation differ only at the incisal region of the tooth. At the cervical third, the gingival margin of the veneer must be located at the same level as the gingival crest or lightly subgingival for the anterior teeth. In this region, it is difficult to obtain a preparation with suitable depth while preserving intact enamel; therefore, in this place, the wear must be approximately 0.3 mm. At the medium third, the preparation may achieve 0.5–0.8 mm.3,18 At the incisal third, the preparation may be modified. The options include the “window” preparation, the most conservative and maintain enamel in incisal third, which results in a visible line between enamel, resin, and ceramic; in addition, the remaining structure is more prone to fracture. The other possibility is the “feather” preparation, which recovers the incisal of the tooth, maintaining its format. The critical points of this technique are the difficulty in positioning the ceramic restoration at the moment of its cementation and in matching the optical properties of the remaining incisal structure. So, to obtain adequate color properties at the incisal third of the laminate veneers, the preparation needs to allow a thickness of ceramic of 1.5–2.0 mm, and this is possible with the “overlap” preparation. At the proximal region, the preparation must follow the papilla and extend until interproximal contact.18

SUBSTRATE TREATMENT

The ceramic veneer technique includes the bonding of a thin porcelain laminate to the tooth surface, enamel and/or dentin, using adhesive techniques and a luting composite to change the color, form, and/or position of anterior teeth. The success of the porcelain veneer is greatly determined by the strength and durability of the bond formed between the three different components of the bonded veneer complex: the tooth surface, the porcelain veneer, and the

luting composite.7 Because of the improvements to adhesive procedures, it is expected that the biomechanical and structural integrity of the enamel-dentin complex could be partially mimicked using porcelain veneers. The success of bonding to teeth relies on suitable preparation and conditioning of the involved surfaces, the ceramics, and the mineralized dental tissues.30,31

Tooth surface (enamel and dentin) The enamel surface must be conditioned with phosphoric acid (37%). This procedure increases the surface energy of the structure, which leads to a perfect wetting of the surface with the bond. At this stage, care must be taken to avoid contamination with saliva and breath moisture, which can reduce the surface energy of the enamel. Therefore, isolation with a rubber dam is highly recommended, which lowers stress input during the clinical procedure.32 While the etching of enamel with phosphoric acid leads to a “frosty” surface – a sign of a successful procedure, because of its inorganic composition and perfect etchability – the effect of dentin-bonding agents on dentin is difficult to control, due to its different composition of inorganic and organic parts and tubular structure. It is difficult to obtain the correct dryness or wetness of the surface, which is elementary for a successful bond. Different kinds of dentin-bonding agents deal with surface wetness and the obtaining of a hybrid zone in various ways. Multiple bonding-agent generations and different concepts also lead to confusion in dental practices. Last but not least, dentin-bonding systems are highly sensitive to technique, especially when perfect moisture control cannot be guaranteed.33

In cases of dentin exposition, sealing this structure with a dental bonding agent is suggested immediately after the completion of tooth preparation and before the final impression itself10,31 because the newly prepared dentin is ideal for the adhesion.25 This technique, called the “resin-coating technique,” consists of interposing a layer of low viscosity resin between the dental substrate and the luting cement.35,36 This procedure seems to produce an increase in the union strength and a reduction of crack formation, bacteria infiltrations, and postoperative sensitivity, as it allows for acid conditioning of the enamel while avoiding the conditioning of the dentin and allowing better control of the conditioning of the enamel. A substantial clinical advantage is that this measure protects the pulpodentinal organ and prevents sensitivity and bacterial leakage during the provisional phase. The use of a conventional adhesive with three steps or auto conditioning with two steps, with polymerization of the adhesive separated from the composite resin, is recommended.

Ceramic Effective etching of the ceramic surface is considered an essential step for the clinical success of indirect ceramic-bonded restorations and direct ceramic repair procedures. Alteration of the surface topography by etching will result in changes in the surface area and in the wetting behavior of the porcelain. This may also change the ceramic surface energy and its adhesive potential to resin. Differences in ceramic composition will also produce unique topographic changes after etching procedures. The enhancement of bonding through modification of the internal porcelain surface is advocated in order to increase the intimacy of the bond; this may be achieved by exposing the porcelain surface to acid or by air abrasion with alumina particles. The aim of pre-cementation surface modification of the porcelain is to increase the surface modification of the surface area available for bonding and to create undercuts that increase the strength of the bond to the resin luting cement.20

Silanization of etched porcelain with a bifunctional coupling agent provides a chemical link between the luting resin composite and porcelain. A silane group at one end chemically bonds to the hydrolyzed silicon dioxide at the ceramic surface and a methacrylate group at the other end copolymerizes with the adhesive resin. Single-component systems contain silane in alcohol or acetone and require prior acidification of the ceramic surface with hydrofluoric acid to activate the chemical reaction. With two-component silane solutions, the silane is mixed with an aqueous acid solution to hydrolyze the silane, so that it can react directly with the ceramic surface.19,20

Ceramic composition and surface treatment protocols

Ceramic

Conditioning

Feldspathic

9.5% hydrofluoric acid for 2 to 2.5 min; 1 min washing; silane application

Leucite-reinforced

9.5% hydrofluoric acid for 60 s; 1 min washing; silane application

Lithium disilicate-reinforced

9.5% hydrofluoric acid for 20 s; 1 min washing; silane application

 

SUMMARY AND CONCLUSION

Currently, the properties of ceramics indicate that they are materials capable of mimicking human enamel and their mechanical properties are expanding their clinical applications. As indicated in this case report it is to conclude that the clinical success of laminate veneers depends on both the suitable indications of the patient and the correct application of the materials and techniques available for that, in accordance with the necessity and goals of the aesthetic treatment.

REFERENCES
  1. McLaren EA, Whiteman YY. Ceramics: rationale for material selection. CompendContinEduc Dent. 2010;31(9):666–668.
  2. McLaren EA, LeSage B. Feldspathic veneers: what are their indications? CompendContinEduc Dent. 2011;32(3):44–49.
  3. Radz GM. Minimum thickness anterior porcelain restorations. Dent Clin North Am. 2011;55(2):353–370.
  4. Belser UC, Magne P, Magne M. Ceramic laminate veneers: continuous evolution of indications. J Esthet Dent. 1997;9(4):197–207.
  5. Strassler HE. Minimally invasive porcelain veneers: indications for a conservative esthetic dentistry treatment modality. Gen Dent. 2007;55(7):686–694.
  6. Calamia JR, Calamia CS. Porcelain laminate veneers: reasons for 25 years of success. Dent Clin N Am. 2007;51:399–417.
  7. Peumans B, Van Meerbeek B, Lambrechts P, Vanherle G. Porcelain veneers: a review of the literature. J Dent. 2000;28:163–177.
  8. MEDLINE® [database on the Internet] Bethesda, MD: National Library of Medicine; nd. Available from: http://www.ncbi.nlm.nih.gov/pubmed/Accessed January 9, 2011

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