Surface topography of the enamel margins of butt and beveled class V preparations

An In-Vitro Study of Microleakage Around Class V Cavities Bonded with a Self-Etching Material Versus a Conventional Two-Bottle System

Objective

To evaluate the microleakage around class V restorations restored with either a self-etching adhesive system or a conventional two-bottle adhesive system used with ‘total etch’ technique, and their recommended resin-based composites (RBC).

Methods

Two types of adhesive systems were used. A self-etching adhesive, Etch and Prime 3.0 (Degussa AG, Hanau, Germany), and a conventional two-bottle adhesive, Gluma Solid Bond (Heraeus Kulzer, Dormagen, Germany). The bonding systems were used in strict accordance with the manufacturers’ instructions, except that, with the two-bottle adhesive system, the cavities were filled with either a ‘wet’ or a ‘dry’ bonding technique, subsequent to acid-etching with 20% phosphoric acid. Etch & Prime 3.0 was used in conjunction with Degufill Mineral (Degussa, Hanau, Germany) RBC and Gluma Solid Bond with Flow Line RBC (Heraeus Kulzer, Dormagen, Germany). Standardised bucco-cervical cavities were prepared on the buccal and lingual surfaces of 15 extracted maxillary first premolar teeth; all cavity margins were in enamel. Ten of the resulting cavities (Group A) were restored using Etch & Prime 3.0 and Degufill Mineral, ten (Group B) using Gluma Solid Bond (Wet Bond), and ten (Group C) using Gluma Solid Bond (Dry Bond). Leakage scores at occlusal and gingival margins were calculated after thermocycling 500 times between baths, held at 5°C and 55°C, respectively, with 30 seconds dwell time in both. Data were analysed by the Fisher Exact Test.

Results

There was no statistically significant difference between the self-etching adhesive and conventional two-bottle adhesive systems at either the occlusal or the gingival margins. With the self-etching adhesive, there was no statistically significant difference in leakage scores between occlusal and gingival margins. There was a statistically significant difference between the occlusal and the gingival margins when a ‘wet’ or ‘dry’ bonding technique was used with the conventional two-bottle adhesive system.

Conclusions

The results suggest that the application of a conventional two-bottle bonding system used with a ‘total etch’ technique is better than that of a self-etching adhesive system. With the former, the use of a ‘wet’ bonding does not give better results than a ‘dry’ bonding technique.

Resin restorations: leakage, bacteria, pulp

Through the development of composite resin materials, the acid-etch technique and dentin adhesives, dentists can now complete perfect and permanent dental restorations--restorations with a color and shape approximating the natural tooth, with perfect marginal adaptation, and no harmful effects to the surrounding tissues, including the dental pulp. However, newer cross-sectional studies indicate that marginal defects are still the main cause of replacement of resin restorations, and that their clinical durability is shorter than that of other types. Moreover, there is no doubt that gap preventive treatments can intensify pulpal reactions to resin restorations if bacterial leakage occurs. The present thesis is based on nine previously published studies (I-IX). The aims of the studies were: to examine the possibilities of minimizing the occurrence of bacterial leakage around resin restorations through the use of various gap preventive procedures, to extend our understanding of their mode of action, and to investigate the pulpal reactions associated with restorations with and without bacterial leakage. The results of earlier research are reviewed, as well as the various methods for registration of gap occurrence around restorations. Studies I-IX are described briefly and followed by a discussion of the results, a summary and some concluding remarks.

Fracture-mechanics parameters of the composite-enamel bond

In a previous study, the critical values of the opening mode stress intensity factor (K1), its equivalent, the strain energy-release rate (G1), and the J integral (J1) (in the elastic case being equal to that of G1) were determined for resin composite. In this study, the strength of the composite-tooth interface was investigated. The critical values of K1 and J1 were measured with single-edge notched-bend (SENB) specimens of resin composite bonded to enamel, with the notch at midspan at the bonded interface. Due to enamel's anisotropy, the values of Klc and Jlc to be used in a fracture-mechanics application for failure prediction of a structure depend on the enamel prism orientation relative to the adhesive interface. Where interfacial failure is to be expected, the following values for Jlc and Klc can be used: Silux, Jlc = 145 +/- 35 Jm-2 and Klc = 0.84 +/- 0.16 MNm-3/2; P-30, Jlc = 163 +/- 13 Jm-2 and Klc = 1.02 +/- 0.07 MNm-3/2. Where enamel failure is expected or where the failure mode cannot be predicted, the following values can be applied: Silux, Jlc = 89 +/- 15 Jm-2 and Klc = 0.84 +/- 0.16 MNm-3/2; P-30, Jlc = 89 +/- 15 Jm-2 and Klc = 0.75 +/- 0.10 MNm-3/2.

Replica patterns on composite restorations performed in vitro with different acid-etch procedures and dentin adhesives

160 experimental Class V restorations using two chemically cured composite resins were inserted in extracted human teeth with conventional and modified acid-etch restorative procedures. The modifications included cavity treatment with non-composite resin, ethanol, or four different dentin adhesives. Following demineralization of the teeth the fillings were examined in the SEM concerning their replica patterns of the etched cavity walls. In vitro conditions favored resin penetration into pretreated enamel and dentin, but resulted in minor variations between different acid-etch procedures compared with those previously seen on resin restorations placed in vivo in teeth with vital pulps.

Marginal porosity of light activated composites in relation to use of intermediate low-viscous resins

The marginal porosity of four light activated restoratives (Command, Durafill, Prismafill and Silux) was investigated in extracted human teeth. It was found that the use of a low-viscous resin prior to application of the restorative materials significantly reduced the marginal porosity in both acid etched enamel cavities and EDTA-cleaned dentin cavities.