ABSTRACT
Tooth fracture is a common complication following MOD restorations.This study sought to assess the effect of different cusp coverage patterns on fracture resistance of maxillary premolar teeth in MOD composite restorations. In this invitro experimental study, 40 human maxillary sound premolar teeth were chosen and stored in Chloramine solution. Using bleaching shield, an over impression was made from each tooth and then wide MOD cavities were prepared. The teeth were randomly divided into 4 groups of 10 each: Group A, without cusp coverage; Group B, with 1.5 mm palatal cusp coverage; Group C, with 1.5 mm buccal cusp coverage; and group D, with 1.5 mm both buccal and palatal cusp coverage. The cavities were restored using Z100 composite resin and the prepared over impressions [in order to restore the normal anatomy of teeth]. The teeth were then stored in water at 37°C for 24h and their fracture resistance was assessed using Universal Testing Machine. The load at fracture was recorded in N. Data were analyzed using one-way ANOVA and Tukey's test with 95% CI. The mean fracture strength was 873.11 +/- 243.5 N in group A, 750.53 +/- 270.7 N in group B, 824.22 +/- 330.2 N in group C and 1499.25 +/- 305 N in group D. The results showed that the fracture resistance of MOD restorations with the coverage of both cusps was significantly more than that of other groups [P<0.05]. MOD restorations with cusp coverage in maxillary premolar teeth increased the fracture strength of teeth against compressive forces. However, covering only one cusp had no significant effect on fracture strength
Subject(s)
Humans , Composite Resins , Bicuspid , Maxilla , Tooth FracturesABSTRACT
The aim of this study was to measure the shear bond strength of composite resin to human dentin surface bonded with three different bonding systems. The crown surface of 66 extracted human third molar teeth were abraded with trimer in a wet environment until the dentin surface was exposed, and they were polished with silicon carbide paper 400 and 600 grit. Then, all the smooth smear layer samples were randomly classified into three equal groups. We used bonding according to the instruction of the manufacturer [the first group Single Bond, the second group BC Plus and third group Charm Bond]. Then, the composite resin was bonded to the tooth surface by plastic tube [diameter: 1.8 mm, height: 5mm].Finally, shear bond strength was determined by universal testing machine [LMT 100]. The variance analysis [ANOVA] P value=0/000 revealed the mean of shear bond strength is different between three groups. The mean shear bond for first, second and third groups are 15.25 MP, 6.84 MP, 8.59 MP, respectively. The multiple comparison with THKEY test showed that there is different significance between group one and the other two groups which did not differ significantly. All in all, we found out that greatest shear bond strength to dentin is the American Single Bond, which is better than Korean product [BC Plus and charm Bond]