Amalgam alternatives-microleakage evaluation of clinical procedures. Part II: direct/indirect composite inlay systems

Interim and temporary restoration of teeth during endodontic treatment

One of the main aims of endodontic treatment is to eliminate micro-organisms from within the root canal system. A further aim is to prevent the ingress of any further bacteria during and after treatment. These aims are usually achieved by various means and stages throughout the treatment process. Endodontic treatment is usually performed on teeth that have lost the integrity of the external coronal tooth structure which has allowed bacteria to enter the tooth and ultimately reach the pulp space. Further opening of the tooth occurs when an endodontic access cavity is made to allow treatment to be performed. Hence, there will always be a need for interim and temporary restoration of teeth undergoing endodontic treatment. Many different materials and techniques have been proposed, and these proposals have been based on many research reports. The purposes of this article are to review the literature regarding the use of interim and temporary restorations, and to provide recommendations regarding such restorations for clinicians to follow when providing endodontic treatment.

Amalgam type, adhesive system, and storage period as influencing factors on microleakage of amalgam restorations

STATEMENT OF PROBLEM

The penetration of oral fluids and bacteria at the interface between the preparation walls and amalgam restorations, known as marginal microleakage, continues to be a problem in restorative dentistry. Microleakage may result in secondary caries and the irritation of the pulp.

PURPOSE

This study evaluated the effect of amalgam type, adhesive system, and storage period on microleakage of amalgam restorations.

MATERIAL AND METHODS

Eighty human premolars and molars were divided randomly into 8 equal groups of 10 teeth each. A combination of 2 different types of amalgam alloys (Spherodon and Nogama-2) and 2 bonding agents (Resinomer and High-Q-Bond) were used to restore Class V preparations. After thermocycling for 750 cycles (4 degrees C and 60 degrees C for 1-minute dwell times), the teeth were stored in a corrosive solution (modified Fusayama solution). The mean depth of fuchsin dye penetration was evaluated after an immersion period of 14 days and 180 days. The data were analyzed with a 3-way analysis of variance model and Wilcoxon paired signed rank test (alpha=.05). Main effects (aging time, amalgam, and adhesive), as well as possible interactions, were included in the model.

RESULTS

Significant differences were found in all analyzed combinations. The 3-way interaction between time, restoration, and adhesive was significant (P=.04 and P=.015 for the cervical and occlusal margin, respectively). After long-term storage, dye penetration values decreased in all groups and reached a lower level compared with short-term storage (range of 0.42 mm to 0.83 mm versus 0.61 mm to 3.6 mm for the long and short term, respectively).

CONCLUSION

An adhesive bonding agent may affect microleakage in the short term. However, in the long term the effect of the adhesive does not appear to be the dominant factor in reducing microleakage around amalgam restorations.

Investigations of thermal property gradients in the human dentine

An investigation of the adaptation of dentine to temperature variation was conducted with the aid of digital moiré interferometry and thermomechanical analysis. The moiré interferometric patterns provided direct evidence of two major phases of thermally involved deformation in dentine. An initial phase of expansion was followed by contraction at higher temperatures. Significant gradients in thermal strain and the coefficient of thermal expansion were identified. Close agreement was found between the response of dentine to thermal changes as observed by moiré interferometry and that detected by thermomechanical analysis. This study highlights the biological adaptation of dentine to thermal variations.