Quintessence International, 07/1997

A new polymer glass, Artglass, is utilized for esthetic modification of an existing porcelain-fused-to-metal fixed partial denture. The masking ability of the polymer glass is demonstrated. A procedure is described for simultaneous adhesion of the Artglass to multiple intraoral surfaces.

A robot system simulating three-dimensional brushing motions as a function of time has been developed. In association with a typodont and either artificial plaque or chromogenic stain, the robot system can be used to assess the plaque removal efficiency or the cleaning effectiveness of toothbrushes. In particular, the influence of different brush head designs of powered toothbrushes was examined. The study compared the plaque removal efficiency of a cup-shaped brush head (Braun Oral-B EB 5) and a modified brush head (Braun Oral-B EB 9) that incorporates longer filaments on the outer ring, designed for additional interdental penetration. A specially designed artificial plaque was applied to the plastic teeth of typodonts. Artificial teeth were cleaned by the robot system for a 2-minute period with a wet brush hea d without a dentifrice. The remaining plaque was assessed visually by two independent examiners, with a modification of the global Plaque Index. In comparison to the EB 5, the new brush head significantly reduced artificial plaque overall. In vitro data demonstrated the ability of the robot system to reveal reproducible significant differences of the cleaning effectiveness of powered toothbrushes.

Three retention systems, 4-META adhesive, Silicoating, and a conventional retention beads system, were used for resin-metal bonding. For each group, 40 standard specimens were prepared (20 for microleakage testing and 20 for tensile strength testing). Wax patterns were prepared, invested, and cast with a nickel-chromium alloy. The metal surfaces of the specimens were sandblasted with 250-um aluminum oxide. Dentacolor Opaque was placed and set in a light curing unit for 90 seconds. Dentacolor resin composite w as placed and set in the same unit for 90 seconds. The bonded specimens were subjected to thermocycling process in baths of 5 degrees C and 55 degrees C with 30-second dwell time. The tensile strength test specimens were stored in water, and the microleakage test specimens were stored in 5% basic fuchsin dye for 2 days. The means of the tensile strength test groups were not significantly different. However, the differences in microleakage among groups were found to be statistically significant. As a result, 4-META and Silicoating systems were found to be better than the conventional retention beads system, which allowed the greatest microleakage.

The presence of several canals in each root has been established as a normal morphology of the root canal system. Two case reports are presented to describe maxillary first molars with multiple canal system morphology in the palatal root. Both teeth exhibited two canals in the palatal root, although with different morphologic manifestations. One of the molars exhibited two canals in the mesiobuccal root as well.

This article provides a decision flowchart that can serve as a guide to selecting the optimum restorations for endodontically treated teeth. The process begins with an assessment of the endodontically treated tooth to determine its restorability. The restorable tooth is then evaluated for the amount of remaining coronal tooth structure. Anterior teeth with minimal or moderate coronal damage do not require complete coverage or a post and core. However, anterior teeth with significant coronal damage will require complete coverage plus a post and core. Posterior teeth with minimal coronal damage may be treated conservatively with partial-coverage restorations. For posterior teeth with moderate damage and those with curved roots, amalgam or resin composite foundations are used to support complete-coverage restorations. Posterior teeth with significant coronal damage require a post and core and a complete-coverage restoration.

Microabraded enamel acquires a highly polished surface of mineralized tissue. The purpose of this study was to determine if microabraded enamel surfaces are more resistant to demineralization. Twenty extracted permanent incisors were used in the experiment. Four treatment modalities were investigated: (1) microabrasion in conjunction with a topical fluoride treatment, (2) topical fluoride treatmen, (3) microabrasion, and (4) no treatment. All surfaces, following their respective treatment regimen, were stored in artificial saliva for 2 months and then exposed to an artificial caries system for 5 days. Teeth treated with microabrasion followed by a 4-minute application of 1% neutral topical sodium fluoride exhibited significantly less enamel demineralization when subjected to an artificial caries challenge than did teeth that underwent microabrasion alone, topical fluoride treatment alone, or no treatment at all.

The purpose of this study was to compare the degree and pathway of microleakage in bonded amalgam restorations utilizing fluorescent dyes with scanning laser confocal microscopy and 45Ca radioisotope with autoradiographs. Mesial slot preparations with enamel cervical margins and distal preparations with dentin margins were prepared in extracted human molars. Four liners, Copalite (control), All-Bond 2/Resinomer, Amalcoden, and Panavia 21, were used. Teeth were restored with Dispoersalloy or Tytin. After thermocycling, 7 days' storage, and staining, the degree of microleakage was measured on an ordinal scale, Dental adhesive liners minimized microleakage; the ranking was, from most to least effective, All-Bond 2, Panavia 21, and Amalcoden. The control exhibited the greatest microleakage. Microleakage occurred most frequently at the liner-tooth interface. No significant difference was observed between amalgams. The high corerlation between the results of the fluorescent and radioisotope studies indicated that these two microleakage tests can be directly compared.

It is very difficult to prepare structures of heterogeneous materials, material interfaces, or sensitive biologic samples. The usual grinding, cutting, or fracturing methods are mostly material destructive because of resulting shear strengths. Ion beam slope cutting allows microcuts to be accurately placed into subsurface areas. The material reduction is based on the principles of ion sputtering, whereby atoms are removed in the area of ion incidence. The spped of removal depends on the sputtered material, amounting to several micrometers per hour. Apprxomiately 40 biologic dental specimens of various origin were examined. Depending on the incidence angle of the ion beam, the typical structures of ion etching can be reduced or intensified. Both variants are used to obtain a precise judgment of morphologic details or an exact topography of failures.