Clinical Evaluation Of Class II Restored With Definite And Amalgam: 12 Month-Results R. Lorenzi*, M. Anselmi, G. Dondi Dall’Orologio (Dept. Of Dental Materials And Operative Dentistry, University Of Bologna, Italy) Despite reservations about using resin composites in the posterior regions, promising long -term clinical results have been reported, even with evaluations not often homogenous.   The aim of the present study was to evaluate the clinical behavior of a new class of materials, ormocer, characterized by a reduced volumetric polymerization shrinkage of 1.88%, as claimed by the manufacture and showed by independent researches.   A total of 120 patients, ranging in age between 20 and 65 years with at least two class II cavities were recruited and enrolled according with the inclusion criteria: 66 premolars and 54 molars were restored with a self-etching bonding system, Etch & Prime 3.0 (Degussa) and Definite (Degussa), in 72 cases of medium or deep cavities a GIC liner (Vitrebond 3M) was used. For cavity preparation and finishing, carbide and diamond burs (Komet), 80.000-100,000 r.p.m. were used. All cavities had margins lying in enamel, restorations were placed under rubber dam by 4 operators and were in occlusion. Definite was applied with a layering technique and each layer was light-cured for 40 sec. from the occlusal surface; finishing and polishing was done at the same appointment.   120 cavities were treated with Permite (SDI) or Dispersalloy (Dentsply) dental amalgam: in 105 cases the GIC liner was used. Cavities and amalgam restorations were done according with conservative concepts and the polishing was performed at the recall. Restorations were evaluated with the USPHS criteria, modified by Van Dijken, at baseline, 6 months and 12 months, for the parameters of retention, color stability, anatomic form, abrasion resistance, marginal adaptation, marginal discoloration, surface texture, caries and postoperative sensitivity.   ANOVA Statistical analysis was performed at 95% of significance (P<0.05).   At 12-month recall 5 patients were lost, 112 Definite restorations were scored alfa or 0, 2 bravo or 2 for color stability, 2 bravo or 1 for anatomic form, marginal adaptation and discoloration and surface texture; 107 amalgams were scored alfa or 0 and 8 bravo or 1. For the post-operative sensitivity two Definite and five amalgam restorations showed a level 4 (intermittent, not diminishing).   There was no significant difference between Definite and amalgam (P>0.05).   The short term results indicated that the new material represented an acceptable substitute for amalgam within one year of clinical observation: long term durability must be demonstrated.