DIRECTED POLYMERIZATION SHRINKAGE VERSUS A HORIZONTAL INCREMENTAL FILLING TECHNIQUE - INTERFACIAL ADAPTATION IN-VIVO IN CLASS-II CAVITIES

Purposes: (1) To evaluate the interfacial adaptation to dentin and ena mel of Class II composite resin restorations placed in vivo with the d irected shrinkage technique, a combination of a self-curing (Bisfil 2B ) and a light-curing composite resin (AElitefil); (2) To compare this technique with a horizontal incremental filling technique, where the g ingival layer of the light-curing composite resin was cured with a tra nsparent light-tip; (3) To evaluate the effect of a hydrophilic bondin g system (All-Bond 2) on the marginal adaptation of both application t echniques. Materials and Methods: In each of 34 premolars, scheduled t o be extracted for orthodontic reasons, a mesial and a distal cavity w as restored with composite resin filling material using the directed s hrinkage technique (Bisfil 2B/AElitefil) and a horizontal incremental filling technique (AElitefil). In six groups, a hydrophilic dentin bon ding system (All-Bond 2) was applied. As control, an enamel bonding ag ent (Gluma 4) was used in one of the directed shrinkage and in one of the horizontal incremental filling groups. For conditioning of the cav ities a 10% phosphoric acid gel was used in six groups and a 32% acid gel in the other two groups. The teeth were extracted after 1 month, s ectioned and replicas of the sections were made. Quality of the interf acial adaptation was studied with a scanning electron microscope. Resu lts: On the pairwise comparisons between the two application groups, n o significant differences were found between the directed shrinkage te chnique and the horizontal incremental filling technique. The groups u sing the hydrophilic bonding system showed a significant better adapta tion, with gap-free attachment in 77%-87% of the length of the dentin margins investigated. No significant differences for adaptation to ena mel were seen between the investigated groups. The adhesive failures w ere found mostly between the hybrid layer and the composite resin, whi le the dentin was still sealed. No significant difference in interfaci al quality was seen between the cavities using the 10% or the 32% phos phoric acid conditioning. A relative high frequency of enamel fracture s, parallel to the interfaces, was found in the 10% phosphoric acid-co nditioned cavities, especially in the cervical enamel interfaces.