RECONSTRUCTION OF FRACTURED PERMANENT INCISORS IN SCHOOLCHILDREN USING LAMINATE VENEERS ( REVIEW )

Crown fractures as a part of traumatic injuries are common among schoolchildren. They create serious functional, esthetic and psychological problems. The clinicians must deal with sometimes small patient’s age, need of high esthetics in the front part and the choice of exact treatment plan. Repeated reconstructions are needed in many cases because of compromised results as time passed by. Achievement of promising restoration that preserves its esthetics and strength is the greatest desire for both children and their parents. In this review are collected data for the usage of laminate veneers for restoring fractured incisors in schoolchildren. A critical analysis of proposed from different authors improvements and objections has been made. These methods summarize succession in the right therapeutic approach.


• Advantages and disadvantages
The clinicians prefer and recommend definite kind of veneer according to the clinical case.Most often cited in the literature advantages and disadvantages of the veneers are shown on table 1.
Introduction of enamel etching technique and elaboration of hybrid and microfilled composite resin materials gives opportunity for more conservative restoration of fractured teeth connected with application of minimal tooth preparation.In 1975 the first porcelain veneers have been placed after testament of the connection with tooth structures (16).Development of the adhesive systems leads to creation of more stabile linkage between bonding surfaces and tooth structures.(4,6).

• Indications
Indications for utilization of veneers are pretty large.There are evidences for their usage in tooth fractures, diastema, teeth with malformations, change of position, discolorations (4).Veneers are indicated in restoration of fractured permanent teeth at children for strength improvement and achievement of satisfied esthetics (11).

Vestibular surface
The choice for tooth preparation depends on the material used, extent of discoloration or shape changes as well as the correlation between upper and lower jaw.
In utilization of porcelain veneers according to the first data the teeth remained intact.Even now some authors do not recommend tooth preparation (17,19).According to the contemporary literature most satisfied results are performed when the preparation is measured, removing hard tissue in two plates -vestibule-gingival (0,5-0,75 mm) and vestibule -incisal (1-1,2 ìì) (14,17,19).
Gingival margin Preparation design for direct and indirect veneers most often finishes with chamfer edge gingival and interproximal (17,19).Thus enough space is ensured to represent all color features of natural teeth.
In the past gingival margin has been placed 0,5-1 mm subgingivaly.The contemporary tendencies report favorable gingival reply when the margins of tooth preparation are placed to margo gingivalis (14,17,19).
In the past it has been claimed that tooth preparation for veneers should remain in the enamel (6).With the dynamic improvement of bonding to dentin it is acceptable the margins of tooth preparation to finish in dentin (8,14).This fact vastly extended clinical cases in which to put successfully veneers to the teeth.It should also be mentioned that even best adhesive materials can not compensate wrong preparation.When the preparation margins include the cement the followed microleakage can influence veneer's retention (8).
Incisal edge According to Walls et al. there are four basic preparation designs for incisal edge (fig. 1) (20).The influence of these preparations upon veneers' retention has been examined through the years.According to the investigations made there is no need for incisal preparation at direct composite veneers, except in cases when veneers are used to provide incisal guidance.In this case it is necessary to ensure preparation form strong enough to prevent fracture of separate segments.The incisal edge should be reduced with 1 mm and the preparation to finish lingual with enamel bevel (10).Bevel's width depends on the retention necessary for neutralization of applied from incisal guidance force (10).
Preparation of incisal edge for porcelain veneers should not exceed 2 mm, as wider porcelain thickness can fracture the veneer.

Indirect porcelain veneer
Direct-indirect composite veneer -conservative approach -excellent esthetics -very good gingival reply -conservative approach -excellent esthetics -excellent gingival reply -complete polymerization -easy reparation -acceptable price -requires two appointments -requires more preparation -technical difficulties -difficult reparation -high price -requires technical skills -requires prolonged time -requires extra appliances b) "Feather" preparation, the veneer is taken up to the height of the incisal edge but the edge is not reduced; c) "Beveled" preparation, a buco-palatal bevel is prepared across the full width of the preparation and there is some reduction of the incisal edge; d) Preparation of "incisal overlap", in which the incisal edge is reduced and the preparation extended palatal Very important conclusions are made in the study of Magne and Duglas.The authors point out significant strength improvement of restored with veneers fractured incisors when replacing the missing tooth structures with composite resin for optimization of incisal edge preparation (12).Other investigations accept the fact that composite resin restoration should be made not more than 2 to 3 years before veneer placement, in order to reduce the negative influence upon traction resistance (7).
Lingual overlap of the preparation margins starts an argument between clinicians.In one of his investigations Magne (13) develops experimental scientific setting and optimizes preparation design with the principles of engineering mechanics.He strives for proposing the best decision for neutralizing of the inherent in techniques and materials loading.The conclusions of this investigation show most satisfied results in incisal reduction up to 2 mm, without lingual overlap.This preparation design diminishes risk for incisal fracture as well as the loading that stand both tooth and material (5).

Proximal finishing lines
It suggested by some authors that proximal finishing lines should not extend beyond contact point in the incisal third of the tooth.It means to preserve the contact point with the adjacent teeth (8,20).
According to the published in the literature data when the preparation has sharp edges this leads to concentration of different forces on that place and cracks and fractures of the veneer may occur (3,8,15).Smooth and rounded internal angles of the preparation will help to reduce stresses at the preparation edges and prevents from fractures (10,20).
Every reduction design for veneer is based on certain principles that help fracture resistance Adhesive bonding of veneers to tooth structures ensures the strength of the whole complex.Thickness up to 2 mm also diminishes fracture probability.It is necessary to achieve adequate incisal guidance which exists normally or is provided by planned tooth preparation (13).
Composite veneers can be made directly on the tooth or direct-indirectly with the help of plaster models and extra polymerization light box.Lack of laboratory procedures facilitates the method and makes it preferable at small children (10).Porcelain veneers are made by dental technician in laboratory conditions (20).
• Placement and luting Before placement tooth surfaces are thoroughly cleaned with pumice.Placement and luting of direct composite veneers is made after etching of the enamel and usage of adhesive system.The procedure follows up the manufacturer's instructions as a clinical protocol.
Placement of porcelain veneers begins also with cleaning of the surfaces.The porcelain veneer is tried in on the dental surface by the help of specific paste that is colored in some shades.The paste should match the tooth color.It is possible to do this procedure with the luting resin (20).Porcelain veneers can be fixed with dual cement which hardening is catalyzed chemically and by luting activation.Acid etching with hydrofluoric acid, washing and drying is performed on both tooth surface and internal part of the veneer.After that prior to placement of the veneer to its internal surface is applied a silane-coupling agent.Dentine bonding agent is applied and the veneer is loaded with luting agent.The excess of resin round the periphery of veneer can best be removed at that stage with metal instrument.The suggested cure time is at about 60 sec.Most important in performing the adhesive technique is the moisture control.Placement of rubber dam and retraction cord can be helpful in prevention of contamination (20).
Direct-indirect veneers are placed and luted in the same way as porcelain ones without applying of silanecoupling agent (10) • Finishing and polishing The last stage is finishing and polishing the margins.Finishing and polishing contribute for smooth and harmonious transition from tooth to restoration.It is important to eliminate any occlusal interference (20).For this purpose a system of carbide and diamond burs, polishing disks (Soflex discs) and polishing pastes are used.(9) • Prognoses Composite veneers can stand unchanged from 2 up to 13 years in good hygiene and minimal harmful habits (9).Microfilled veneers tend to wear with time and loose their gloss (2).Some resin materials have included small bubbles that can appear on the surface and fill with food or plaque stains.That leads to early repair of the veneer (18).
Direct-indirect veneers have long live longevity than the direct veneers.Their strength and abrasion stability is improved and the polymerization shrinkage is minimal (10).
Composite veneers can be easily repaired when occurring some of the problems mentioned.That makes them economically favorable (10).
Reconstruction of fractured children's teeth with composite veneers improves esthetics and preserves tooth structures.Some authors place them as temporary restoration until development completion and replace them with porcelain veneers (20).According to a clinical study of Welbury, made on 289 composite veneers of child and adolescence, followed up for 3 years, the average strength of the veneers is 35, 6 month (21).
Porcelain veneers are with best esthetic and mechanical properties and show low fracture degree.Unlike Address for correspondence: Dr. Ani Beltcheva, PhD Department of Pediatric Dentistry, Faculty of Dental Medicine, Medical University, Plovdiv, Bulgaria Å-mail abeltcheva@yahoo.comcomposite veneers they can not be repaired (1,3).Porcelain veneers do not chance their color with time and have no leakage of water soluble dyes.Marginal adaptation and luting technique pay an important role for the degree and time after which a marginal discoloration will appear (15).Patient's hygiene is also of great importance.A serious disadvantage of porcelain veneers is their high price (8).

CONCLUSIONS
Elaboration of veneers on teeth with compromised esthetics and function is a conservative method that improves appearance, modifies contour without reducing hard tissues as for the whole tooth crown.In that context the method is minimal invasive and indicated for children.Even in the period of growth and development, when children are at high risk for tooth trauma, fractured teeth can be successfully restored with minimal tooth preparation utilizing composite veneers.Knowledge of the methods for making and applying composite or porcelain veneers for restoration of fractured permanent teeth at schoolchildren is useful advantage of dental doctor for mastering the esthetic and functional problems of the young patients.

Fig. 1 .
Fig. 1.Appearance preparation of incisal according to Walls et al. a) "Window" preparation, the veneer is situated close to but not up to the incisal edge;b) "Feather" preparation, the veneer is taken up to the height of the incisal edge but the edge is not reduced; c) "Beveled" preparation, a buco-palatal bevel is

Table 1 .
Advantages and disadvantages of different kinds veneers, utilized for restoration of permanent teeth DOI: