Considerations in measuring the electrical potentials of metallic restorations in vivo.

Many variables are believed to affect the accurate measuring of metallic restoration electrical potentials. This study examined the effects of intra- versus extra-oral location of the reference electrode, the type of metallic probe used to make contact with the restoration, and scratching and brushing of the restoration surface. Dental amalgam restorations were measured in 40 human subjects. Results showed that only the location of the reference electrode affected the central tendency of the potential. The study discusses the significance of some experimental variables in the accurate measuring of metallic potentials and the need to consider individual subject differences when statistically analysing for the central tendency of a sample.

Photopolymerization of composite resin using the argon laser.

Because of the dental profession's increased utilization of light-cured restorative materials, there has been a corresponding increase in research into the light sources used to initiate polymerization. The argon laser is one promising source, as the wavelength of light emitted by this laser is optimal for the initiation of polymerization of composite resins. The literature reflects a strong divergence of opinion about many aspects of the effectiveness of laser curing compared to conventional light curing. Research indicates that the argon laser offers a greater depth and degree of polymerization, less time required and an enhancement of the physical properties of composite resins polymerized. These advantages are offset by reports that the increased polymerization caused by the laser results in increased shrinkage, brittleness and marginal leakage. Dentists interested in the new technology need to monitor ongoing studies.

Connective tissue response to root surfaces resected with Nd:YAG laser or burs.

PROBLEM: The Nd:YAG laser beam may be used for root resection, but the tissue compatibility of the resulting root surface has not been confirmed. OBJECTIVE: This study assessed the connective tissue response over time to implanted root segments with Nd:YAG laser-cut or bur-cut surfaces. STUDY DESIGN: Endodontically treated roots of 25 extracted human teeth were cross sectioned to form 3.5 mm thick disks by alternating a water-cooled Nd:YAG laser with a high-speed water-cooled tungsten fissure bur. A total of 63 disks were implanted into the dorsal subcutaneous tissue of 16 rats, then recovered with the surrounding tissue after periods of 3, 7, 14, 28, 60, and 90 days, and processed for light microscopic examination. Tissue against the cut surfaces was assessed for intensity and extent of inflammation and fibrous capsule thickness. RESULTS: A two-factor analysis of variation showed statistically significant (p < 0.05) differences between the laser-cut and bur-cut surfaces. CONCLUSION: Tissue repair about the root surfaces resected with Nd:YAG laser was delayed when compared with those resected with a bur.