The safety of nickel containing dental alloys.

Nickel is a constituent of many dental alloys. This paper reviews mainly papers published after 1985 with regards to biological reactions to nickel in dentistry. Nickel is an allergen, but there is no evidence that individual patients are at a significant risk of developing sensitivity solely due to contact with nickel-containing dental appliances and restorations. Hypersensitivity reactions to nickel are only likely to occur with prior sensitization from non-dental contacts and even these are rare. Clinical evidence has been presented to show that small doses of nickel, e.g. from dental appliances, may induce tolerance to this allergen. The papers reviewed report low rates of release of nickel from dental alloys. Some nickel compounds, which are mildly cytotoxic, have been implicated as carcinogens by inhalation in industrial settings, but these compounds are not present in dentistry-related operations, including dental technology procedures. Nickel-containing alloys and compounds have not been associated with increased cancer risk by oral or dermal routes of exposure. It is concluded that, subject to use according to established techniques, nickel-containing dental alloys do not pose a risk to patients or members of the dental team.

Repair or replacement of amalgam restorations: decisions at a USA and a UK dental school.

Whereas replacement of failed restorations is the major treatment for adults in dental practice, repair is an important alternative with the potential to save tooth structure and increase the longevity of restorations at a lower cost. This in vitro study recorded the choices of treatment for the same set of teeth with defective Class II amalgam restorations by students and faculty at two dental schools (University of Manchester, UK and University of Florida, USA). Treatment options (monitor, refurbish, repair and replace) and reason(s) for the choice of treatment for 24 marked amalgam restorations were selected. Overall, participants more frequently chose replacement of restorations; whereas, repair was the least favored option. The reasons cited the most to replace restorations were secondary caries including unsightly appearance, partially lost restoration and tooth fracture; for repair, the major reasons included loss of part of the restoration and marginal ditching; and for refurbishment, the major reasons included poor anatomic form and marginal ditching. There was a significant difference between the students and faculties at the two sites in their choice of treatment (p<0.0001; Chi-square test). The treatment decision to "monitor" the restorations was more frequent for the Manchester site than the Florida site. Conversely, the combined treatment decisions to "refurbish, repair and replace" were more frequently chosen in Florida than in Manchester.

Effect of different application and polymerization techniques on the microleakage of proximal resin composite restorations in vitro.

This in vitro study investigated cervical microleakage of proximal resin composite restorations placed with three application and polymerization techniques. Uniform mesio-occlusal-distal (MOD) preparations featuring cervical margins above (mesial) and below (distal) the CEJ suitable for restoration with resin composite were copy milled into 33 recently extracted permanent molars. The teeth were divided randomly into three groups of 11 teeth and restored using a conventional incremental technique (Group A) and two novel curing devices (Groups B and C). After 24 hours, a dye penetration test was used to assess microleakage. Conventional placement in preparations with cervical margins in enamel had significantly lower interfacial leakage scores than those recorded for placement in preparations with margins in cementum regardless of the technique used to place the restorative material. Use of the two novel curing devices conferred no advantage in reducing microleakage irrespective of where preparation margins were placed.

The integrity of bonded amalgam restorations: a clinical evaluation after five years.

BACKGROUND: Bonded amalgam restorations have been studied extensively in vitro, but few long term clinical studies exist. The authors examined the clinical performance of bonded amalgam restorations after five years of clinical service an compared it with that of nonbonded amalgam restorations. METHODS: The authors placed 75 bonded and 62 nonbonded amalgam restorations in patients needing restorations. Most of the restorations were placed in conventional preparations; six bonded restorations were placed in nonretentive cavities. They were evaluated after a five-year period of clinical service by two trained dentists using a mirror and explorer and following modified U.S. Public Health Service criteria. RESULTS: Statistical analysis (via Fisher exact test) showed no significant differences between the two techniques when conventional preparations were used. Restorations in nonretentive preparations were successful during this period. CONCLUSIONS: Bonded and nonbonded amalgam restorations yielded similar results in conventional preparations after five years of clinical service. Bonded amalgam restorations were clinically successful in a limited number of nonretentive preparations over a five-year period. CLINICAL IMPLICATIONS: Bonded amalgam restorations can be used successfully in conventional preparations and possibly in nonretentive preparations as well, and can be expected to last at least five years.

Microleakage of amalgam cavity treatment systems: an in vitro evaluation.

PURPOSE: to evaluate the effectiveness of four cavity treatment systems for their ability to seal standardized Class V restorations of amalgam. MATERIALS AND METHODS: The Celay copy-milling machine was used to prepare twenty-five standardized Class V cavities on the buccal and palatal surfaces of maxillary premolar teeth extracted for orthodontic purposes. The cavosurface margins lay entirely within enamel. Five cavity treatment test groups were employed prior to amalgam placement: Group 1, Cervitec; Group 2, Gluma One Bond; Group 3, Panavia 21; Group 4, Copaliner Dentin Varnish and Sealant and Group 5, Control. Following restoration placement, the teeth were aged at room temperature (25 +/- 2 degrees C) in tap water for 2 months. The specimens were subsequently thermocycled (500 cycles, 5 -55 +/- 2 degrees C), immersed in a dye solution, sectioned and scored for microleakage. Scanning electron microscopy was employed to examine features of the tooth/restoration interface. RESULTS: None of the materials tested consistently prevented microleakage. No statistically significant differences were identified between the groups with respect to the microleakage scores (P > 0.05). The gingival walls exhibited significantly more microleakage than the occlusal walls (P = 0.00). No significant differences were identified between the microleakage scores obtained for the buccal and palatal cavities. Scanning electron microscopy examination failed to demonstrate a consistent pattern of interfacial appearance, showing a combination of cohesive and adhesive failure within and between test groups.