The Resistance To Fracture Of Premolar After Endodontically Treated:an In Vitro Study

Objective To compare the effect of various restorative materials as well as the role of cavity types in the fracture resistance of premolar teeth .Methods Fourty eight pairs of maxillary and mandibullar premolars extracted for orthodontic reason were selected .The teeth were noncarious and intact .They were randomly divided into six groups of eight pairs as follows:group a:mandibullar premolars,root canal therapy,MO/DO cavity, amalgam filled; group b: mandibullar premolars,root canal therapy,MO/DO cavity,light curing composite resin filled; group c:maxillary premolars, root canal therapy,MOD cavity,amalgam filled; group d:maxillary premolars,root canal therapy,MOD cavity, light curing composite resin filled; group e:maxillary premolars,root canal therapy, O cavity,amalgam filled; group f:maxillary premolars,root canal therapy, O cavity, light curing composite resin filled.T tests was used to compare the result.Results The resistance to fracture of trial teeth were lower than unaltered teeth in group a(p<0.01),but no significance was founed in group b,c,d,e,f(p>0.05).The pattern of fracture in unaltered teeth was the fracture of buccal or lingualcusp,but in tyial teeth ,the pattern of fracture was coronal-radicular vertical fracture through the filling material.Conclusions The various cavity of premolar teeth after root canal therapy were filled with light curing composite resin can obtain the equal fracture strength to the unaltered teeth.The MO/DO cavity of premolar after root canal therapy was filled with amalgam ,it's strength fracture was lower than unaltered premolar teeth (p<0.01) .The pattern of fracture in maxillary premolar after root canal therapy was different from the unaltered teeth.