Effect of margin design, cement polymerization, and angle of loading on stress in porcelain veneers

Abstract

Statement of problem. The clinical failure of porcelain veneers may result from stresses induced in the porcelain during mastication. Purpose. This study investigated whether applied stresses were large enough to cause porcelain fracture, examined the influence of the margin design, and examined whether a lack of bond in the middle, cervical, or incisal area would have any influence on stress distribution. Material and methods. A 2-dimensional finite element model was made. Location and magnitude of maximum compressive and tensile stresses were calculated in porcelain veneer. Results. Small differences in stress were observed in the margin portion for various cervical designs under the same conditions. An increase in stresses appeared for all situations and in all reading points with a more transverse angulation of load. A significant difference appeared between full bonding and a lack of adhesion in the middle portion, or cervical and incisal areas, of the veneer. Conclusion. A chamfer or shoulder preparation is recommended for porcelain veneer preparations. Careful evaluation of occlusal forces and how these forces affect the facing is indicated. It is important to receive a full bonding between the tooth and facing. (J Prosthet Dent 1999;82:518-24.)