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PubMedDate not supplied

Esthetic veneering of amalgam restorations with composite resin--combining the best of both worlds?

Patients are becoming more and more aware of the esthetic alternatives to dental amalgam and are asking dentists to offer solutions that are more esthetically pleasing. However, the difficulties in inserting clinically durable composite resin restorations in the posterior area are numerous. With the high-copper amalgam systems, the dental profession has had an excellent restorative material. In the past there have been attempts to combine amalgam with the esthetic qualities of composite resin. The introduction of an adhesive and opaque light-curing glass-ionomer liner has created new opportunities to bond composite resin to existing amalgam restorations on esthetically disturbing surfaces. This paper describes a simple and quick way in which unesthetic buccal and occlusal extensions of amalgam restorations can be veneered with composite resin. Preliminary six-month results of about 100 restorations are presented. This method may prevent the premature replacement of good functioning amalgam restorations with porcelain-fused-to-metal crowns or composite resin restorations for only esthetic reasons.

Color↗
PubMed1989

[Normalizing method for determining the mode of crack-propagation in amalgams and composite resins].

A normalizing method for determining the mode of crack-propagation in a phase or component of a dental amalgam or composite resin was devised. The results calculated using the method were found to be satisfactory when the method was applied to the materials. Furthermore, details of the mode of crack-propagation in the materials which cannot be seen using pictures of the cross-section structure of the materials are revealed using the method.

Composite Resins↗
PubMed1997

Surface treatment effects on amalgam repair strength.

PURPOSE: To determine whether the use of microetching and bonding agents could improve the shear bond strength between aged and freshly added dental amalgam, simulating an amalgam repair. MATERIALS AND METHODS: Aged amalgam surfaces were treated with either a carbide bur or carbide bur + microetcher (Al2O3 abrasive). Five commercially-available adhesive systems were tested. Fresh amalgam was condensed through a split mold onto each prepared amalgam surface. Two control groups were included: a positive control consisting of non-repaired amalgam, and a negative control consisting of aged specimens which received neither carbide bur nor microetching preparation prior to the addition of fresh amalgam. In addition, one group received only carbide bur and another received only carbide bur and microetching treatments, without any adhesive. Following storage and thermocycling, each specimen was tested for shear bond strength. RESULTS: The mean shear bond strength of the repaired samples treated with carbide bur alone (25.8 MPa) was not exceeded by any of the other treatments. Neither microetching nor use of an adhesive agent significantly improved amalgam-to-amalgam shear bond strength. In some cases, use of an adhesive agent significantly decreased the shear bond strength of repaired amalgam samples.

Aluminum Oxide↗
PubMed1987

Renal cortical mercury levels associated with experimental amalgam tattoos: effects of particle size and amount of implanted material.

Powdered dental amalgam that had passed through either a 106 microns or a 45 microns sieve was implanted subcutaneously in guinea pigs for periods of up to 2 yr. The renal cortical mercury levels associated with the 106 microns material were on average 16% of those produced by the 45 microns material. A reduction in the amount of 45 microns powder implanted, by a factor of 75%, resulted in a fall of only 27% in renal mercury concentrations. The marked effect of particle size on mercury release may be explained by the large increase in the proportion of implanted material that was degraded within phagocytic cells in the local lesions.

Animals↗
PubMed1997

The influence of the amalgam alloy on the survival of amalgam restorations: a secondary analysis of multiple controlled clinical trials.

Data from 14 independent controlled clinical trials on the oral behavior of Classes 1 and 2 amalgam restorations, with a follow-up between five and 15 years, were re-evaluated by secondary analysis for the influence of alloy composition on the survival of amalgam restorations. For the analysis, 3119 restorations were available, which were made from 24 different alloys by a group of seven operators. The alloys were divided into four groups according to their zinc content (zinc-containing and zinc-free) and their copper content (conventional and high-copper). During the follow-up of the trials, the restorations were annually assessed for failures, which were classified as to (1) restoration-, (2) restorative process-, and (3) patient-related reasons. With the restoration-related failures, survival functions of the restorations were estimated by alloy and alloy group. The total number of failed restorations was 481, of which 77% were restoration-related and 14% process-related. Eighty percent of the restoration-related failures were due to some form of fracture of the amalgam. Restorations of conventional zinc-free alloys had the shortest survival. After 13 years, only 25% survived. Zinc and a high copper content had an equally favorable influence on the survival rate, which was 70% after 13 years when either was present. The highest survival rates were of restorations of zinc-containing high-copper alloys: 85% after 13 years. The zinc and copper contents of the alloy contributed to the corrosion resistance of the amalgams, which in turn influenced the survival of the restoration. The current ISO Standard 1559 on alloys for dental amalgam should be modified to account for these factors that influence the survival of amalgam restorations.

Controlled Clinical Trials as Topic↗
PubMed1986

Standardizing evaluations of the clinical marginal fracture of amalgam.

In this study, we investigated both inter-examiner and intra-examiner differences in the evaluation of the marginal fracture characteristics of dental amalgam restorations. Evaluations were made by matching intra-oral photographs of the occlusal surfaces of clinical restorations to a reference set of clinical photographs illustrating increasing amounts of marginal fracture. Four amalgam alloys and five examiners provided the data base. Differences in marginal fracture indices were found among examiners and between evaluation times for the same examiners. However, these differences were reduced significantly after application of a standardization procedure.

Dental Alloys↗
PubMed1990

Exposure to mercury vapor during setting, removing, and polishing amalgam restorations.

The level of mercury vapors in the oral cavity was determined by analyzing 242 samples of intra-oral air before and after removing, setting, and polishing dental amalgam. The analysis was effected using atomic absorption spectrometry in cold vapors with the detection limit of 6 micrograms/m3. A score of 1 to 3 was assigned to each restoration to adjust the differences of the amalgam sizes. The present study showed that the vapor was released during any procedure: removing, setting, and polishing amalgam. The mean levels were between 85 and 326 micrograms/m3. However, before the restorative procedures, no mercury vapors had been detected in the oral cavity. This investigation has also demonstrated a significant direct correlation between Hg vapor concentrations in intra-oral air and the sizes of amalgam restorations during each procedure: removing, setting, and polishing. The statistic analysis showed no significant difference of mercury vapors in the oral cavity between the use or nonuse of water coolant during the amalgam polishing.

Air↗
PubMed1996

Restoration of pediatric posterior teeth.

Four categories of materials are popular for restoration of slightly to moderately carious pediatric primary teeth: amalgam, composite resin, glass ionomer and resin-modified glass ionomer. Practitioners looking for a material to replace dental amalgam for restoration of pediatric Class II areas will find that the most promising and growing technique is using resin-modified glass ionomer.

Bicuspid↗
PubMed1989

Amalgam margin breakdown caused by creep fatigue rupture.

This study was designed to determine whether the mechanical cyclic stressing that occurs during normal mastication contributes to margin breakdown of dental amalgam restorations. The method used appears to duplicate the mechanical stresses developed in vivo during mastication, as the result of tooth flexing. We evaluated one low-copper alloy--NTD--and three high-copper alloys--Dispersalloy, Phasealloy, and Tytin. We prepared simple amalgam restorations in a cavity centrally located in an aluminum beam. Each specimen received five periods of three-point cyclical loading (1.7 hertz, 4200 cycles at 37 degrees C). The margin area was subjected to SEM examination prior to and at the completion of each period of cycling. At the beginning of each period of cycling, beam deflection was set to establish a maximum theoretical stress of 1, 2, 4, 6, or 8 MPa. For all brands, cycling resulted in margin gap formation and surface wrinkling. Wrinkling in Dispersalloy occurred as a wide band of shallow wrinkles, whereas that in NTD occurred as a narrow band of deep wrinkles. At 21,000 cycles, very little void formation and fracturing had occurred in the Dispersalloy or NTD restorations. In contrast, the Phasealloy and Tytin restorations developed extensive fracturing even after 4200 cycles. Fracture surface analyses of Phasealloy and Tytin indicated that creep fatigue rupture was the fracture mechanism responsible for margin breakdown in these amalgam restorations, when subjected to cyclic compressive loading similar to that experienced during mastication.

Copper↗