The Effect Of Different Preparation Designs And Cement Type On The Fracture Resistance Of All-Ceramic Cantilever Anterior Fixed Partial

Abstract

This research was designed to study the effect of different preparation designs and cement type on the fracture resistance of all ceramic cantilever anterior fixed partial dentures.

A right maxillary lateral incisor was removed from the upper arch of an acrylic typodont, the socket of the upper lateral incisor was closed with pink modeling wax to stimulate an edentulous area of a missing lateral incisor bounded by maxillary right central and canine acrylic teeth. Three identical maxillary right canine acrylic teeth were selected from the refill teeth of the typodont. Each tooth was prepared to receive a different all ceramic retainer design; a full coverage, three quarter and a modified three quarter all ceramic retainer.

A total 30 all ceramic zirconia cantilever bridges were constructed and divided according to retainer design into three groups (10 bridges each);full coverage(10 samples),three quarter retainer(10 samples), and modified three quarter retainer (10 samples).

Each group (10 samples) was further divided according to the cement type into two subgroups; subgroup 1 (resin cement) (5 samples) and subgroup 2 (glass ionomer cement) (5 samples).

The fitting surfaces of retainers were sandblasted with 50 µm AL2O3 at a maximum pressure of 2.5bar for 30 seconds at an approximate distance 2 cm.

Thirty epoxy resin (chemopoxy 150 transparent) dies were fabricated by introducing the polymerizing resin into an addition silicone mold (3M Express putty and light) of the master dies. The adhesive resin Rely X and Medifill glass ionomer cement were used for cementation of the restorations. The restorations were seated slowly with gentle finger pressure for 1 minute. In case of glass ionomer cement: the excess cement was removed after complete setting of cement. While in case of resin cement: the excess was removed using sponge pellets immediately and each cement surface/margin was light cured for 40 seconds.

The samples were subjected to lateral loading using a universal testing machine (Lloyd instrument LR 5K).The cross-head speed was 0.5 mm/min. The very first discontinuity resulting from an early crack, debonding or catastrophic failure of bridge and/or die was detected.

The recorded data were collected and tabulated for evaluation. Data analysis was performed in several steps. Initially, descriptive statistics for each group results. Two factorial analysis of variance ANOVA test of significance comparing variables affecting mean values (preparation design and cement). One way ANOVA followed by pair-wise Tukey’s post-hoc tests were performed to detect significance between preparation groups. Student t-tests were performed to detect significance between cement groups. Chi square test was used to compare modes of failure. Statistical analysis was performed using Graph-Pad Prism-4 statistics software for Windows. P values ≤0.05 are considered to be statistically significant in all tests.

The results revealed that the full coverage retainer design had shown to have the significantly highest mean fracture resistance, while the modified partial coverage retainer showed to be significantly higher than the partial coverage retainer only. No significant difference between full and modified partial coverage groups. While no significant differences of fracture resistance mean values between resin cement and glass ionomer.