J Korean Acad Conserv Dent JKACD Journal of Korean Academy of Conservative Dentistry 1225-0864 2093-8179 The Korean Academy of Conservative Dentistry 10.5395/JKACD.2010.35.1.030 Basic Research The effect of the amount of interdental spacing on the stress distribution in maxillary central incisors restored with porcelain laminate veneer and composite resin: A 3D-finite element analysis Hong Junbae 1 Tak Seung-Min 2 Baek Seung-Ho 1 http://orcid.org/0000-0001-9641-5507 Cho Byeong-Hoon 1 Department of Conservative Dentistry, School of Dentistry, Seoul National University, Seoul, Korea. Mechanical Aerospace Engineering, Gyeongsang National University, Jinju, Korea. Corresponding Author: Byeong-Hoon Cho. Department of Conservative Dentistry, School of Dentistry, Seoul National University, 275-1 Yeongeon-Dong, Jongno-Gu, Seoul, 110-768, Korea. Tel: 82-2-2072-3514, Fax: 82-2-2072-3859, chobh@snu.ac.kr 01 2010 31 01 2010 35 1 30 39 30 12 2009 04 01 2010 04 01 2010 Copyright © 2010 Korean Academy of Conservative Dentistry 2010

This study evaluated the influence of the type of restoration and the amount of interdental spacing on the stress distribution in maxillary central incisors restored by means of porcelain laminate veneers and direct composite resin restorations.

Three-dimensional finite element models were fabricated to represent different types of restorations. Four clinical situations were considered. Type I, closing diastema using composite resin. Labial border of composite resin was extended just enough to cover the interdental space; Type II, closing diastema using composite resin without reduction of labial surface. Labial border of composite resin was extended distally to cover the half of the total labial surface; Type III, closing diastema using composite resin with reduction of labial surface. Labial border of the preparation and restored composite resin was extended distally two-thirds of the total labial surface; Type IV, closing diastema using porcelain laminate veneer with a feathered-edge preparation technique. Four different interdental spaces (1.0, 2.0, 3.0, 4.0 mm) were applied for each type of restorations.

For all types of restoration, adding the width of free extension of the porcelain laminate veneer and composite resin increased the stress occurred at the bonding layer. The maximum stress values observed at the bonding layer of Type IV were higher than that of Type I, II and III. However, the increasing rate of maximum stress value of Type IV was lower than that of Type I, II and III.

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Finite element models of each type of restorations. a. Type I, b. Type II, c. Type III, d. Type IV.

Load angulation. 50 N of load was applied at 125° angles (tearing force) with the tooth's longitudinal axis at the palatal surface of the crown.

von Mises stress distribution patterns of each type of restoration. These figures represent stress distribution at the tooth side of bonding layer. a. Type I with interdental space of 2.0 mm. b. Type II with interdental space of 2.0 mm. c. Type III with interdental space of 2.0 mm. d. Type IV with interdental space of 2.0 mm.

Line graphs of maximum von Mises stress values at the cervical area of the tooth side of bonding layer. Horizontal axis means interdental space. Vertical axis means von Mises stress values (MPa).

Maximum von Mises stress values in Type II restoration which was restored with porcelain laminate veneer instead of composite resin.

Three-dimensional finite element models simulating composite resin and porcelain laminate veneer restorations, with or without tooth preparation, for restoring the interdental spaces ranging from 1 mm to 4 mm

*The tooh model was reduced by 0.5 mm up to 2/3 of labial surface for type III model and up to distal surface for type IV model.

Each finite element model was designed as restoring half the space of the amount of interdental space (0.5, 1.0, 1.5, 2.0 mm) because opposite tooth model was under symmetrical condition.

Mechanical properties of materials used

Maximum von Mises stress within each model with varying interdental spaces (Unit: MPa)

The maximum values were obtained at the cervical area near the line angle between the labial surface and mesial surface.