Specific polymerization contraction may be viewed as a primary deficiency of composite resins, being responsible for inducing a series of negative clinical consequences, such as: dental deformation and fractures at enamel level, adhesive failure and post-surgical dental sensitivity, secondary carries, cohesive microfissures with marginal fracture or restoration mass fractures.
The aim of the study was to evaluate the level of marginal sealing by a colorimetric method, in occlusal restorations from composite resins, performed by five techniques of material’s application inside the cavity. The experiments were performed on 50 posterior (premolars and molars), healthy human teeth, which had been extracted due to various (orthodontic, parodontal, prophilactic) causes. The 50 occlusal cavities thus prepared were randomly distributed into 5 groups, according to the method applied for inserting the material, as follows: A – the closed sandwich technique; B – the technique of horizontal layers; C – the technique of vertical layers; D – the technique of cuspidian construction; E – the monoblock technique). Marginal adjustment was evaluated by measuring the depth of the colouring agent penetration, by optical microscopy. Statistical tests applied: U Mann Whitney i Kruskal-Wallis. The results obtained demonstrated that none of the insertion methods applied led to perfect sealing at the margins of the occlusal cavity. Apparently, the best method was that of cuspidian restoration, followed by the closed sandwich one. The monoblock insertion technique induced the most severe marginal percolation. It is known that the insertion technique may influence the degree of polymerization contraction of posterior composite resins employed in direct coronary restorations.
- composite resins
- occlusal restorations
- polymerization contraction