J Korean Acad Prosthodont.  1999 Apr;37(2):143-167.

THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS OF STRESS DISTRIBUTION IN PORCELAIN LAMINATE VENEERS WITH VARIOUS AMOUNTS OF INCISAL COVERAGE AND TYPES OF INCISAL FINISH LINE UNDER TWO LOADING CONDITIONS

• Ryoo KH
• Lee SH
• Yang JH
• Chung HY

Abstract

The success of porcelain laminate veneer depends on the bond strength between tooth structure and ceramic restoration and the design of tooth preparation. In particular, incisal coverage and incisal finish line are the two most important factors in long-term fracture resistance. Although the majority of clinicians are practicing incisal coverage and there are various opinions on the geometrical ratio between the clinical crown length of the remaining tooth structure and the length of incisal extension in porcelain laminate veneer and the optimal incisal finish lines, scientific evidence still leaves much to be desired. The purpose of this study was to determine the effects of the amounts of incisal coverage and the types of incisal finish line on th stress distribution in maxillary anterior porcelain laminate veneers under two different loading conditions. Three-dimensional finite element models of a maxillary anterior porcelain veneer with different amounts of incisal coverage ; 0, 1, 2, and 3mm and different incisal finish lines ; feathered edge, incisal bevel, reverse bevel and lingual chamfer with various amounts of lingual extension were developed. 300N force was applied at the point 0.5mm cervical of the linguoincisal edge in two loading conditions ; A) 125 degrees, B) 132 degrees. tensile and compressive stress in ceramic and shear stress in the resin cement layer wee analyzed using three-dimensional finite element method. The results were as follows : 1. The types of incisal finish line had more influence on the stress distribution in porcelain laminate veneer than the amounts of incisal coverage. 2. In case of no incisal coverage, incisal beveled laminate exhibited more evenly distributed tensile stress than feathered edged laminate. And in case of incisal coverage, reverse beveled laminate and lingual chamfered laminate with 1mm lingual extension exhibited more evenly distributed tensile stress than lingual chamfered laminates with 2 mm and 3mm lingual extension. 3. As long as the lingual chamfer goes, less tensile stress was found at the incisal edge, while much more tensile stress was found at the lingual margin area in proportion to length of lingual extension. 4. Under 125 degree load, tensile stress in porcelain laminate veneer had increased compared with that under 132 degree load and the difference exhibited by the change of the amount of tooth support was larger. 5. The types of incisal finish line and the distance from the incisal finish line to the loading point had more influence on the shear stress distribution in the resin cement layer than the amount of incisal coverage. In contrast loading condition had little influence.

MeSH Terms

Animals
Ceramics
Crowns
Dental Porcelain*
Feathers
Finite Element Analysis*
Resin Cements
Tooth
Tooth Preparation
Ceramics
Dental Porcelain
Resin Cements