بررسي مقايسه اي گير و مقاومت به شكست ترميم كمپلكس آمالگام و MOD در دندان مولر اول منديبل (Invitro)

An in vitro comparative study between amalgam complex and MOD restorations in first molar mandibul teeth

Objective: Due to the lack of retention and possible fracture resistance of amalgam and cavity preparation, several methods were suggested and evaluated. The aim of this study was to evaluate whether box preparation could reinforce the retention and fracture resistance of amalgam complex restorations. Materials and Methods: Forty eight non caries human first molars were selected and mounted in acrylic resin, the specimens were then randomly divided into 4 groups of 12 specimens. Two different restorative configurations were evaluated in groups. Groups 1 and 2: Standardized MOD cavity preparation was made using a diamond bur with a high speed hand piece with air/water spray. The depth of the occlusal isthmus was 3 mm and proximal margins located above the cement enamel junction (CEJ). All box walls 10 degree of divergence against the occlusal plane. Groups 3 and 4: cavity preparation was made using a diamond bur with high speed hand piece with air/water spray. The occlusal surface of specimens were ground to 3 mm occlusal to the CEJ and then four boxes were prepared on buccal , lingual, mesial and distal surfaces. Specimens in groups 2 and 4 were used for retention test and specimens in groups land 3 used for fracture resistance test. In groups 2 and 4 were used for evaluation the retention of restoration. All groups were restored with amalgam. Each specimen was loaded in an universal testing machine at a cross-head speed of lmm/min until fracture occur. Data were analyzed with t- test. Results: The mean fracture resistance of groups 1 & 3 was: group 1784.3 N and 880.4 N respectively (P<0/05). The mean retention force of groups 2 and 4 was: 218.8 N and 317.4 N (P<0/05). Discussion: In our study there was significant difference (P<0.00) between the fracture resistance of groups 1&3 and there was significant difference (P<0.000) between the retention of group 2. The retention in group 4 was significantly increased compare to the group 2, and fracture resistance in group 3 was significantly decreased compared with the group 1.