Polymerization degree and cementation methods of two different self-adhesive luting cements used for glass fiber postcementation.

AIM: Aim of this study was to evaluate two different luting cements and how their clinical procedures influence the postcementation quality. METHODS: Thirty-six freshly extracted mono-radicular teeth (N.=18) were treated endodontically and randomly divided into two groups. Posts were cemented respectively with two different self adhesive luting cements: Group A - RelyX Unicem (3M Espe) and Group B - Multilink Sprint (Ivoclar-Vivadent) following the manufacturers' instructions. Teeth were then thermocycled according to protocol ISO/TR 11405 and were immersed 24 hours in 2% methylene-blue solution. Each tooth was sectioned by a diamond-coated saw (Isomet-Buhler) from CEJ to apex. Each slice was examined for the presence or absence of gutta-percha remnants, voids, bubbles, dye infiltration degree and polymerization grade of the luting agent. Findings were evidenced by stereoscopic microscopy (30x) and Micro-Raman spectroscopy. Mann-Whitney and ANOVA statistical analyses were performed for all results. RESULTS: No statistical significances were evidenced for gutta-percha presence, dye infiltration and polymerization degree. Voids were present mostly in Group B and bubbles in Group A. Both differences were statistically significant. CONCLUSION: Materials and protocols for glass fiber posts cementation are fundamental for the clinical success. Self adhesive luting cements, if used correctly, could be an acceptable and quick luting agent for postcementation.

Indirect resin composite restorations: evaluation of polymerization of luting agents by means of micro-Raman spectrophotometry.

AIM: The degree of conversion of a luting composite cement influences its clinical performance. Aim of the study was to evaluate the degree of conversion of 4 different composite cements by means of micro Raman spectrophotometry. METHODS: Forty-four cylindrical onlays of different and defined thickness (1, 2, 3, 4 mm) were built using a custom made template. The onlays were made in composite material (Signum, Heraeus; shade A 3,5) and cemented onto a glass plate with different luting materials: dual curing (Variolink II, Calibra) and light curing (Venus flow, Tetric flow). The lamp tip was shielded in order to have the light reach the cement only through the onlay. Samples were divided into 12 groups (N.=3), differing in onlay thickness and luting material. Each sample was examined in three spots by a micro-Raman spectrophotometer (Dilor Hr-Labram). The conversion degree was evaluated by analyzing the variations in intensity of the 1638 cm(-1) aliphatic peak (C=C), characteristic of all Bis-GMA containing materials, related to the invariant 1608 cm(-1) (C-C of the aromatic ring). RESULTS: All materials show good polymerisation results below 1 mm and 2 mm onlays. Below onlays thicker than 3 mm a constant degree of conversion throughout the surface of samples could not be found: spots with satisfactory polymerisation and spots with insufficient polymerisation were found. CONCLUSIONS: Onlay thickness has a key role in cement conversion. The thicker the onlay, the less predictable the conversion.