Published online Nov 30, 2004.
https://doi.org/10.5395/JKACD.2004.29.6.532
Influence of cavity size and restoration methods on the cusp deflection in composite restoration
Abstract
The aim of this study was to measure the cusp deflection during composite restoration for MOD cavity in premolar and to examine the influence of cavity dimension, C-factor and restoration method on the cusp deflection.
Thirty extracted maxillary premolar were prepared to four different sizes of MOD cavity and divided into six groups. The width and depth of the cavity were as follows. Group 1; 1.5 × 1 mm, Group 2; 1.5 × 2 mm, Group 3; 3 × 1 mm, and Group 4-6; 3 × 2 mm respectively. Group 1-4 were restored using bulk filling method with Z-250 composite. However, Group 5 was restored incrementally, and Group 6 was restored with an indirect resin inlay.
The cusp deflection was recorded at the buccal and lingual cusp tips using LVDT probe for 10,000 seconds. The measured cusp deflections were compared between groups, and the relationship between the cube of the length of cavity wall/the cube of the thickness of cavity wall (L3 / T3), C-factor and cusp deflection or %flexure (100 × cuspal deflection / cavity width) was analyzed.
The cusp deflection of Group 1-4 were 12.1 µm, 17.2 µm, 16.2 µm and 26.4 µm respectively. The C-factor was related to the %flexure rather than the cusp deflection. There was a strong positive correlationship between the L3 / T3 and the cusp deflection. The cusp deflection of Group 5 and 6 were 17.4 µm and 17.9 µm respectively, which are much lower value than that of Group 4.
Figure 1
Configuration of the instrument for measuring cusp deflection.
Figure 2
a. The dimension of occlusal cavity and proximal box (W: Width of cavity, D: Depth of cavity, L: Length of cavity wall) b. Simplified cavity shape for calculation of the C-factor.
Diagram of prepared cavity.
Figure 3
a. Bulk cure (Group 1-4) b. Bulk cure vs. Incremental cure and Indirect Resin Inlay (Group 4, 5 and 6)
Representative curves of cusp deflection as a function of time.
Figure 4
Mean cusp deflections for each tested group.
Figure 5
b. A positive correlationship was present between the C-factor and the %flexure.
a. A positive correlationship was present between the L3/T3 and the cusp deflection.
Table 1
The prepared cavity sizes in this study
Table 2
The prepared cavity wall dimension, the L3/T3, C-factor, cusp deflection and %flexure measured.
Table 3
The results of correlation analysis between the L3/T3, C-factor, and cusp deflection or %flexure.
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