Dental color standards: shade tab arrangement.

PURPOSE: The aim of this study was to analyze the shade tab arrangement of two popular dental shade guides, suggest possible improvements, and propose clinical guidelines. MATERIALS AND METHODS: Data were recorded using a colorimeter set to standard illuminant source C and CIE L*a*b* system. The manufacturers' shade tab arrangement as well as the possible improvements in the arrangement of shade tabs of Vitapan Classical and Vitapan 3-D Master (Vita Zahnfabrik, Bad Säckingen, Germany) shade guides were examined by regression analysis. RESULTS: Certain shortcomings in the manufacturers' arrangement of both color standards were observed. The Vitapan 3-D Master arrangement was more consistent, but with a decrease in lightness, tab saturation decreased as well in four of its five groups. When Vitapan Classical and Vitapan 3-D Master tabs were arranged according to deltaE* in relation to the lightest tab, r2 was 0.98 and 0.96, respectively. After dividing the total deltaE* range into four equal segments for the newly established Vitapan Classical guide, r2 was 0.91, 0.95, 0.68, and 0.94, respectively. Corresponding r2 values for Vitapan 3-D Master were 0.96, 0.94, 0.90, 0.94, and 1.0. CLINICAL SIGNIFICANCE: Total color difference in relation to the lightest tab, followed by the tab division into an adequate number of groups, is recommended as a possible and universally applicable mode of tab arrangement in dental color standards.

Color of restorative materials after staining and bleaching.

This study determined the effect of a 10% carbamide peroxide bleaching agent on the removal of stain from restorative materials. Color changes (delta E*) of three restorative materials [compomer (Dyract); composite (TPH Spectrum); hybrid ionomer (Fuji II LC)] when exposed to juice/tea, chlorhexidine (CH), and water (control) for 120 hours were studied. Stained specimens were treated for two 2-hour periods with a bleaching agent (Platinum Tooth Whitening System) with and without the active ingredient. Color was measured at baseline, after staining, and after treatment using the CIE L*a*b* color system relative to CIE standard illuminant A (incandescent light) as measured by a reflection spectrophotometer. Means and standard deviations (n = 5) were calculated and data were analyzed by four-way ANOVA. All variables and interactions were statistically significant. Color changes caused by CH and water were not perceptible (delta E* < 3.3). After two 2-hour treatments, the following occurred with specimens stained with cranberry juice/tea: paste with and without active ingredient perceptibly changed color of stained composite. The stained hybrid ionomer perceptibly changed color after treatment with paste containing active ingredient but did not change after exposure to paste without active ingredient. The stained compomer was not perceptibly different with either treatment. Platinum successfully removed stains from the composite and hybrid ionomer tested.

Discoloration of a compomer by stains.

This study evaluated the color stability of a polyacid-modified composite (compomer) upon exposure to stains. Five disks were prepared for immersion in each of five stains: coffee, chlorhexidine, cola, red wine, and water as a control. Color measurements were made on a reflection spectrophotometer at baseline, after 24-hour incubation, and after 24, 48, and 72 hour immersion in each stain. At 24 hours, perceptible color changes occurred for specimens in red wine and coffee. After 48 hours, perceptible color changes occurred for specimens in cola. Chlorhexidine and water caused no perceptible color changes. A compomer is susceptible to staining by coffee, red wine, and cola.

Development of a priority list of chemical mixtures occurring at 1188 hazardous waste sites, using the HazDat database.

Under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA or Superfund) section 104 mandate, as amended by the Superfund Amendments and Reauthorization Act (SARA) of 1986 USC 9604 (i)(2), the Agency for Toxic Substances and Disease Registry (ATSDR) is to identify individual substances and combinations of substances that pose the greatest public health hazard at hazardous waste sites. This has led to certain mandated activities of the Agency, including development of toxicological profiles, identification of data gaps, and, ultimately, establishment of a research agenda. The Agency has also developed HazDat, a database that captures pertinent information from public health assessments conducted at hazardous waste sites. As a preliminary step, data from sites have been analysed to identify the combinations of chemicals found in various environmental media. The most frequently found combinations were perchloroethylene (PERC) and trichloroethylene (TCE) in water (23.5% of sites); chromium (Cr) and lead (Pb) in soil (20.5%); benzene and toluene in air (3.5%); PERC, 1,1,1-trichloroethane (1,1,1-TCA) and TCE in water (11.6%); Cr, cadmium (Cd) and Pb in soil (12.0%); and benzene, PERC and TCE in air (2.2%). The findings of this analysis can be enhanced by factoring into the algorithm paramenters such as toxicity, source contribution, and likelihood of human exposure similar to that used for the Agency's priority list of 275 single substances. Assessment of the impact of chemical mixtures on human health is a formidable task, and estimating the toxicity of such mixtures, including the role of chemical interactions, is an equally demanding challenge. Because limited experimental data exist for chemical interactions, alternative methods such as predictive approaches and in vitro techniques are needed to address the many substances and their potential combinations.

Complex mixtures: hazard identification and risk assessment.

Regarding risk evaluation of complex mixtures, the Working Group discussed the following topics: evaluation of the mixture as a whole, fractionation of the mixture, identification of the 'top ten' chemicals, and composite standards. It was concluded that no standard methodology for hazard identification and risk assessment of complex mixtures yet exists, but assessment of complex mixtures must proceed, using all available information, methods, technology, expertise and experience. The development of a decision tree for tackling complex mixtures was recommended, and the need to move forward with instituting standards for mixtures, especially in job-oriented situations, was emphasized.

The misdiagnosis of temporomandibular disorders in lateral pharyngeal space infections--two case reports.

Two cases of lateral pharyngeal space infections which were initially misdiagnosed as temporomandibular disorders (TMD) are presented and discussed. Such symptomatology as chronic facial pain, trismus and decreased inter-incisal opening provide many viable different diagnoses. It is important for the clinician to evaluate these different diagnoses in a logical manner. Conservative therapy is advised in the initial treatment of many TMDs, therefore other diagnoses with a greater potential for morbidity should be ruled in or out before the diagnosis of TMD is considered. The symptomatology of lateral space infections and the relevance of this entity to clinical dentistry are discussed.

Differential uptake of HRP by intact axon terminals versus transected axons: a study on bulbospinal fibers in the dorsolateral funiculus.

A comparison was made of the amount of HRP uptake from transected versus intact axonal endings of rostral ventromedial medulla (RVMM) and locus coeruleus cells projecting via the dorsolateral funiculus in the rat. We found that retrograde labelling in the RVMM was reliably different between treatments, while locus coeruleus retrograde labelling was highly variable and not reliably different. HRP applied to intact endings retrogradely labelled approximately twice as many RVMM cells, including 25 times as many 5-hydroxytryptamine (B3) cells, as HRP applied to transected axons. In this first quantitative assessment of HRP uptake from transected versus intact endings, reliable differences have been found. These results have implications for the neural circuitry involved in pain modulatory systems.