Porcelain Laminate Veneers 1 Tariq Alghazzawi, BDS, MS, MSMtE, PhD Assistant Professor and Materials Engineer Departme

1. Porcelain Laminate Veneers (1)Tariq Alghazzawi, BDS, MS, MSMtE, PhDAssistant Professor and Materials Engineer Department of Prosthetic Dental Sciences�College of DentistryTaibah University 

2. Temperature for Oral Environment The minimum and maximum temperatures intraorally between 0o C and 58.5o C and suggested a range of 0o C to 67o C for the thermocycling tests of dental materials.

3. Mechanical Properties of Tissues and Materials

4. 3D-FEM Model and Loading Conditions

5. Introduction of Laminate Veneers Since their introduction by Pincus in 1930, PLVs have become a popular dental procedure.

6. The Success Rate of Veneer Aristidis GA, Dimitra B. Five-year clinical performance of porcelain laminate veneers. Quintessence Int 2002;33(3):185�9. Friedman MJ. A 15-year review of porcelain veneer failure�a clinician�s observations. Compend Contin Educ Dent 1998;19(6):625�8, 30, 32 passim; quiz 38. Aristidis GA, Dimitra B. Five-year clinical performance of porcelain laminate veneers. Quintessence Int 2002;33(3):185�9. Friedman MJ. A 15-year review of porcelain veneer failure�a clinician�s observations. Compend Contin Educ Dent 1998;19(6):625�8, 30, 32 passim; quiz 38.

7. Restoring Lost Enamel Porcelain veneers have been considered to biomimetically restore the mechanical behavior of the crowns of teeth on which they are placed, i.e. they mimic or recover the biomechanics of the original tooth by means of the restorative material/technique. As a consequence, besides achieving natural appearance of the smile, the stress distribution in a tooth restored with porcelain veneers was similar to that of a sound tooth

8. Laminate Veneer Thickness The ratio between the thickness of the restoration and the luting cement appears to have a relevant influence on the stress distribution in laminate veneers Magne P, Kwon KR, Belser UC, Hodges JS, Douglas WH. Crack propensity of porcelain laminate veneers: a simulated operatory evaluation. J Prosthet Dent 1999;81:327�34. White SN, Yu Z, Kipnis V. Effect of seating force on film thickness of new adhesive luting agents. J Prosthet Dent 1992;68:476�81. Thin restorations with poor internal fit result in higher stresses at both the surface and interface of the restorations Magne P, Versluis A, Douglas WH. Effect of luting composite shrinkage and thermal loads on the stress distribution in porcelain laminate veneers. J Prosthet Dent 1999;81:335�43.

9. Laminate Veneer Thickness In order to obtain optimal physical properties, a minimal thickness of 0.6mm is required for indirect laminate veneers Meijering AC, Peters MCRB, DeLong R, Pintado MR, Creugers NH. Dimensional changes during veneering procedures on discolored teeth. J Dent 1998;26:569�76. Insufficient tooth reduction could lead to an overcontoured final restoration, whilst excessive reduction results in an increased reliance upon dentin bonding systems to effectively retain and seal the restoration Naeije M, Loon LAJ. Craniomandibular function and disfunction. Bohn Stafleu Van Loghum 1998:39�56.

10. Tooth Preparation 52% of the preparations for porcelain veneers caused exposure of dentin at the level of the gingival margin Dumfahrt H, Schaffer H. Porcelain laminate veneers. A retrospective evaluation after 1 to 10 years of service: part II�clinical results. Int J Prosthodont 2000;13:9-18. This observation can be due to a thin enamel thickness available at the apical third of the buccal surface of anterior teeth Ferrari M, Patroni S, Balleri P. Measurement of enamel thickness in relation to reduction for etched laminate veneers. Int J Periodont Restor Dent 1992;12:407�13.

11. Effect of Occlusion Functional and parafunctional forces may cause Failure of the adhesive interfaces, Microleakage Staining Postoperative sensitivity Secondary caries

12. Tooth Morphology Regarding tooth morphology, the palatal concavity and the incisal areas of maxillary anterior teeth are considered to be high stress concentration areas during tooth function Highton R, Caputo AA, Matyas J. A photoelastic study of stresses on porcelain laminate preparations. J Prosthet Dent 1987;58:157-61. This fact is physiologically compensated for by having increased enamel thickness in these zones Nicholls JI. Tensile bond of resin cements to porcelain veneers. J Prosthet Dent 1988;60:443-7. Magne P, Oh WS, Pintado MR, DeLong R. Wear of enamel and veneering ceramics after laboratory and chairside finishing procedures. J Prosthet Dent 1999;82:669-79.

13. Tooth Morphology The enamel removed during tooth preparation should be compensated for with a material having enamel-like properties to restore the original biomechanical behavior of a tooth.

14. Failures The most frequent failure factors associated to porcelain veneers are: Fracture (main reason) Barghi N, Berry TG. Post-bonding crack formation in porcelain veneers. J Esthet Dent 1997;9:51-4. Microleakage Debonding

15. Failures The magnitude and the angle of incisal load greatly influence the long-term success of ceramic veneers. The connection of resin cement to dentin may be the weakest link in bonding porcelain veneers

16. Fractures Clinical observations on the use of ceramic veneers reported that cohesive fracture of porcelain mainly concerned the incisal edge of the restoration, because of a greater stress concentration in this area during function

17. Authors indicate that the fracture energy concentrates at the level of the adhesive interface between the composite resin cement and enamel. Lin CP, Douglas WH. Failure mechanisms at the human dentin-resin interface: a fracture mechanics approach. J Biomech 1994;27:1037-47. The shearing stress makes the veneer slide, concentrating compression stress in the weakest areas (incisal or gingival margin) Troedson M, Derand T. Shear stresses in the adhesive layer under porcelain veneers. A finite element method study. Acta Odontol Scand 1998; 56:257-62. This occurrence can create microcracks, propagation of which causes fracture or detachment of veneers Yoshikawa T, Sano H, Burrow MF, Tagami J, Pashley DH. Effects of dentin depth and cavity configuration on bond strength. J Dent Res 1999;78: 898-905. Fracture of Laminate Veneers

18. Most fractures are caused by adhesive failure at the porcelain/cement interface. Walls AW. The use of adhesively retained all-porcelain veneers during the management of fractured and worn anterior teeth: part 2. Clinical results after 5 years of follow-up. Br Dent J 1995;178:337-40. Porcelain is rigid and does not deform with the stresses of polymerization shrinkage of a composite resin cement, creating stress at the interface. Peumans M, Van Meerbeek B, Yoshida Y, Lambrechts P, Vanherle G. Porcelain veneers bonded to tooth structure: an ultra-morphological FE-SEM examination of the adhesive interface. Dent Mater 1999;15:105-19. Fracture of Laminate Veneers

19. Factors Affecting the Success of Laminate Veneers Many factors influence the long-term success of porcelain veneers such as: Tooth surface Porcelain thickness Type of luting agent and adhesive system Marginal adaptation Periodontal response Tooth morphology Functional and parafunctional activities Geometry of the preparation