Side-effects of dental ceramics

[Fluorescence of zirconia-based dental ceramic materials]

The review contains information about the fluorescent properties of natural teeth, fluorescent additives, fluorescent liquids for staining zirconium dioxide, fluorescent powders, pastes, glazes, and cements for zirconia, methods for measuring fluorescence. Factors affecting the fluorescent properties of ceramics are also reported.

Determination of cytogenetic abnormalities in buccal mucosa of dental laboratory technicians

This study aims to investigate the toxic effects of metals, which dental technicians are exposed to, on the oral mucosa cells in dental prosthesis laboratories (DPL). To monitor cytotoxic effects, mutations of pyknosis, Karyolysis Karyorrhexis, binucleus, micronucleus, and broken-egg were evaluated. Experimental group comprised of a total of 30 volunteer DPL employees from various DPLs, and 30 teachers and office workers were volunteered to be a part of the control group. Age range of DPL employees and whether they consume alcohol or smoke cigarettes were also considered as sub-variables. Peripheral smear technique was applied by taking samples from the oral mucosa of the experimental group and the control group. Anomalies determined between technicians and control group were statistically significant (p < .05). However, our findings revealed that the sub-variables (ie, age range, alcohol, and smoking) did not significantly affect the anomalies.

Investigation of morphological abnormalities in red blood cells among dental laboratory technicians

A variety of materials are used in dental prosthesis laboratories (DPL), especially metal alloys and methyl methacrylate (MMA)-based monomers and polymers. These metal alloys contain elements such as cobalt, chromium, nickel, molybdenum, lead, and mercury that can have toxic effects on human health when excessive amounts of exposure occur. This study aims to investigate the cytotoxic effects of occupational exposure due to dental prosthesis manufacturing operations on erythrocyte cells. Thirty DPL workers were compared with the 30 control group and the questionnaire forms were applied including the symptoms due to their occupational exposure. Blood was taken from the experimental group and the control group into tubes with EDTA, and the erythrocyte morphologies were examined by the peripheral smear technique. Morphological anomalies determined from the experimental group and the control group are statistically significant (p < .005, p < .01). On the other hand, it was revealed that the sub-variables, namely age range, alcohol, and smoking, did not significantly affect the anomalies. With these results, it was concluded that DPL employees should strictly comply with occupational health precautions.

Radioactive potential of zirconium-dioxide used for dental applications

PURPOSE

The purpose of this study was to investigate the possible radioactive potential of zirconium dioxide (ZrO2) dental ceramics. Such information is necessary since they became an integral part of routine prosthetic rehabilitations and devoid of scientific information about their radioactivity creates some concern in the dental community.

METHODS

Four different types of commercial ZrO2 ceramics, namely Lava, Cercon, ICE Zirkon, and Everest Bio ZS were investigated before and after the sintering process. Sintering temperatures were applied according to each manufacturer's instructions. The compositions of the presintered and sintered specimens were analyzed using x-Ray Fluorescence Spectrometer (XRF). Concentrations of the elements and compounds were also measured by this method. Determination of radioactivity continued with Gamma-spectrometry measurements and Gross alpha/Beta analyses.

RESULTS

The activity of gamma and Gross alpha/beta was below minimum detection limits (MDL) for presintered and sintered ZrO2. The MDLs of gross alpha/beta counting system were 0.02 Bq/g and 0.01 Bq/g for alpha and beta radioactivity, respectively. The sintering process played only a minor role in the composition of the compounds.

CONCLUSIONS

Radioactivity of the ZrO2 ceramics studied showed negligible radionuclide activity that can be considered lower than many hazardous radioactive appliances in our environment.

Surface degradation of dental ceramics as a function of environmental pH

We tested the hypotheses that glass-ceramic veneers and overglazes degrade by ion exchange in an acidic environment, and that they degrade by breakdown of the silica network in a basic environment. Disk specimens of glass-ceramic veneer and glaze were fabricated and immersed in pH 2, 7, or 10 buffer solutions, for 1, 3, 5, 10, 15, and 30 days. Each specimen was placed in a shaker bath containing de-ionized distilled water at 80°C. Concentrations of Al(3+), Ca(2+), Zn(2+), Li(2+), and Si(4+) were analyzed by means of inductively coupled plasma atomic emission spectrometry (ICP/AES). Statistical analyses were performed by factorial ANOVA. Significant differences occurred among leached ion concentrations as a function of material type, solution pH, and exposure time. A substantial release of Si occurred at pH 10 over time, leading to a breakdown of the glass phase. At pH 2, dissolution was controlled by an ionic exchange mechanism. We conclude that ceramic veneers and glazes may be susceptible to considerable degradation in low- and high-pH buffer solutions.

[Mercury and health in the dental practice]

Mercury is a heavy metal widely used by man. It is considered very toxic causing conditions in the central nervous system, behavior disturbances, and renal and sexual disorders. For a century, mercury has been used in the dental practice for its capacity of joining metals (amalgamate), its low cost and its rapid fixing in dental pieces repair. Currently, there is much controversy about the safety of dental amalgams and it has been demonstrated it poses occupational risks to dental practitioners and their assistants. The objective of this study is review aspects related to metallic mercury toxicity for personnel involved in the dental practice and patients with dental amalgams. Routes of mercury exposure in dentistry, occupational risks and measures to prevent mercury poisoning are presented here. A literature review was conducted mostly on data from Biological Abstracts and the Science Citation Index for the period between 1990 and 2000.

Bonding to alumina ceramic in restorative dentistry: clinical results over up to 5 years

OBJECTIVES

The purpose of this clinical pilot study was to evaluate the resin bond to alumina ceramic in vivo when using a bonding method which had been shown to be successful in laboratory testing.

METHODS

Seventeen resin-bonded all-ceramic bridges and splints fabricated from a glass-infiltrated alumina ceramic were tribochemically silica coated and resin bonded to their abutment teeth. The patients were recalled every 6 months to evaluate the restorations with regard to function and possible failures.

RESULTS

Over a mean observation time of 3.8 +/- 1.6 years some ceramic fractures occurred. However, the resin bond between the teeth and the alumina ceramic always remained stable.

CONCLUSIONS

Silica coating of alumina ceramic resulted in a durable resin bond over up to 5 years.

Ceramics in dentistry: historical roots and current perspectives

This article presents a brief history of dental ceramics and offers perspectives on recent research aimed at the further development of ceramics for clinical use, at their evaluation and selection, and very importantly, their clinical performance. Innovative ceramic materials and ceramics processing strategies that were introduced to restorative dentistry since the early 1980s are discussed. Notable research is highlighted regarding (1) wear of ceramics and opposing enamel, (2) polishability of porcelains, (3) influence of firing history on the thermal expansion of porcelains for metal ceramics, (4) machining and CAD/CAM as fabrication methods for clinical restorations, (5) fit of ceramic restorations, (6) clinical failure mechanisms of all-ceramic prostheses, (7) chemical and thermal strengthening of dental ceramics, (8) intraoral porcelain repair, and (9) criteria for selection of the various ceramics available. It is found that strong scientific and collaborative foundations exist for the continued understanding and improvement of dental ceramic systems.