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The authors conducted a survey of dentists reporting tooth avulsions from basketball net accidents. Although the number of people injured was small, the dental injuries were serious. In many cases, multiple teeth were avulsed as a result of the maxillary anterior teeth becoming entangled in the basketball net while the patients were attempting to slamdunk a basketball either on a lowered backboard or from a raised take-off area. The authors present recommendations for preventing tooth avulsions resulting from basketball net entanglement.

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The purpose of this project was to determine the amalgam surface roughness following finishing and polishing procedures. Nine high-copper amalgams were tested. They were hand-condensed in a 3 x 3 x 30 mm mold. Each sample was divided into four sections, and each section was finished by one of four methods: carving only; carving and then burnishing 15 minutes after carving; carving and then polishing at the prescribed times; or carving, burnishing 15 minutes after carving, and then polishing at the prescribed times. Each bar of amalgam had these surface treatments done at either 1, 3, 6, or 24 hours. The results indicated surface roughness may be more dependent on particle size, shape, and distribution of the individual high-copper amalgams than the polishing time or the surface treatment performed.

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Ceramic materials exposed to a liquid environment may be subject to stress corrosion and/or time-delayed failure. The intent of this project was to evaluate the susceptibility of a magnesia alumina spinel (Cerestore) to stress corrosion and degradation. Bars 2.5 x 2.5 x 30.0 mm were prepared according to manufacturer's instructions. Specimens were aged in distilled water or air at 37 degrees C. The modulus of rupture was evaluated at zero, six, and 12 months in four-point loading at loading rates of 0.05, 0.5, and 5.0 mm/min. The modulus of rupture of each specimen was tested in its respective aging medium. The data were analyzed by one-way analysis of variance with a multiple-means comparison test, linear regression analysis, and Weibull statistics. The pooled data sets of specimens aged in water vs. those aged in air showed a significant difference in the respective modulus of rupture (air, 108.50 +/- 16.11; water 96.94 +/- 15.04 MPa). The one-way analysis of variance showed no significant difference between the aging times zero, six, and 12 months in each respective aging medium. The Weibull analysis also showed no difference between the Weibull constants, 7.66 air vs. 7.64 water, but a significant difference between the characteristic strengths, 115.22 air vs. 103.02 water. This study indicates that distilled water has a significant degradative effect on a magnesia alumina spinel, more likely affecting the mode of fracture rather than the stress corrosion characteristics.

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Possible correlations between the presence or position of cavity linings and the incidence of caries were studied in a sample of 57 extracted permanent teeth with amalgam fillings. Linings could be detected if their thickness was greater than approximately 20 microns, and if they were observed on 74% of the teeth. On 53% of the teeth caries were found adjacent to the restorations, and on 11% not adjacent to the restorations. The incidence of adjacent caries on the teeth with lined cavities was not lower than on the unlined ones. In 36% of the teeth with linings, evidence was found for washout of linings which had been present at the cavosurface margin. These teeth showed a significantly higher incidence of adjacent caries than the unlined ones. Carious sites associated with washout of linings were found in 31% of the lined specimens.

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The object of this study was to determine for amalgam restorations the relationship between marginal breakdown and (i) over- or undercarving; (ii) the amalgam margin angle (AMA); and (iii) the incidence of carious occlusal enamel adjacent to the restoration. Fifty-two extracted human teeth with occlusal amalgam fillings from the Chicago (C) area and forty-three teeth from the Jerusalem (J) area, were examined with a probe. Employing common clinical criteria, it was found that replacement of the fillings was indicated due to extensive marginal defects, in 45% of the C teeth, and 41% of the J teeth. The occlusal amalgam margins and the incidence of caries adjacent to these margins were studied on facio-lingual sections. The incidence and the average AMA values for six margin types were measured on random sections and were found to be: all margins (100%, 67 degrees); intact flush margins (31%, 69 degrees); fractured flush margins (21%, 56 degrees); undercarved margins which fractured (22%, 74 degrees), or did not fracture (9%, 80 degrees) near the cavity margin; margins with amalgam deficiencies (12%, 62 degrees); and margins with separation between enamel and amalgam by remnants of linings (5%). Marginal breakdown was found in 42% of the margins and was associated mainly with flush carving at low AMAs, and with broken flashes resulting from undercarving. Occlusal carious enamel was detected on 19% of the J teeth and none of the C teeth. Sixty-three per cent of these lesions were associated with fractured undercarved margins.

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