OBJECTIVETo assess effects of different class II cavities on stresses of amalgam and composite resin restoration.

METHODSFive kinds of class II MO cavities were prepared on the first molars of mandibles. The cavities were filled by amalgam and composite resin, respectively. The stresses were analyzed by using three-dimensional finite element method, after vertical and lateral pressures were loaded on the teeth.

RESULTSThe stresses were greater in traditional cavities than those in reformed cavities when 100 N vertical and lateral pressures were loaded on the teeth. But the pressing stress and shearing stress in cavities filled by amalgam were smaller in traditional cavities than those in reformed cavities. The stresses were smaller in cavities filled by resin than those in cavities filled by amalgam significantly, when the cavities were designed with slot retention groove, without slot retention groove and as plate form. The stresses were smaller in two kinds of slot and plate cavities than those in traditional and reformed cavities.

CONCLUSIONIt is better to design cavity with slot retention groove for amalgam restoration and to design cavity without slot retention groove for composite resin restoration.

Composite Resins ; standards ; Dental Amalgam ; standards ; Dental Cavity Preparation ; methods ; Dental Models ; Dental Restoration, Permanent ; methods ; Dental Stress Analysis ; methods ; Finite Element Analysis ; Humans ; Mandible ; Molar