The effects of amalgam restorations on plasma mercury levels and total antioxidant activity

Objective

This study evaluated the effects of amalgam restorations on plasma mercury levels and total antioxidant activities (TAA).

Design

The study was comprised of 48 subjects ranging in age from 20 to 32 years. Of these, 33 had dental amalgam restorations and 15 had no dental amalgam restorations. In those patients with amalgams, the total number of amalgam restorations and surfaces were counted, and the total and occlusal areas (mm²) of restorations were measured using a Counting Measurement Machine. Blood samples were collected from all participants. Plasma mercury levels were measured using an Atomic Absorption Spectrometer and Hydride System, and plasma TAA levels were measured using an Antioxidant Assay Kit. Statistical analysis was performed using the SPSS 10.01 software program. Data was evaluated by t test and correlation analysis.

Results

Plasma mercury (P-Hg) levels were found to be significantly higher in subjects with amalgam restorations when compared to subjects without amalgams (p < 0.01); the differences in P-TAA levels between subjects with and without amalgams were not found to be statistically significant (p > 0.05). No significant correlations were found between P-Hg concentrations and P-TAA levels (p > 0.05). Significant positive correlations were found between P-Hg concentrations and the number of amalgam restorations (p < 0.01), number of amalgam surfaces (p < 0.05), total amalgam surface area (p < 0.05) and amalgam occlusal surface area (p < 0.01). However, no significant correlations were found between these parameters and P-TAA (p > 0.05).

Conclusions

The results of our study showed that dental amalgams are a major source of plasma mercury; however, amalgam restorations were not found to have a significant effect on plasma-total antioxidant activities.     

Transverse molar movements during growth

The purpose of this study was to evaluate changes in molar crown torque and intermolar arch width from the time of permanent first molar eruption to early adulthood. Molar crown torque and intermolar arch width were measured in 36 untreated subjects with Class I occlusion from the Iowa Facial Growth Study at approximate ages 7.5, 10.3, 12.9, 16.5, and 26.4 years. On average, the mandibular first and second molars uprighted buccally by 5.0 degrees and 7.5 degrees, respectively. Mandibular first and second molar intermolar width increased by 2.2 and 0.78 mm, respectively. On average, maxillary first and second molars uprighted lingually by 3.3 degrees and 5.9 degrees, respectively. Maxillary first and second intermolar width increased by 2.8 and 2.0 mm, respectively. Results of statistical analysis by the Wilcoxon signed rank test indicate that (1) maxillary molars erupt with buccal crown torque and upright with age, whereas mandibular molars erupt with lingual crown torque and upright with age (P <.01), and (2) molar crown torque changes are accompanied by concurrent increases in maxillary and mandibular intermolar width (P <.01).     

The Role of Abutment-Attachment Selection in Resolving Inadequate Interarch Distance: A Clinical Report

A critical factor that needs to be evaluated during the diagnosis and treatment planning phase for patients seeking an implant-tissue-supported overdenture or metal-resin implant fixed denture is the presence of adequate interarch distance. The amount of interarch distance is critical to the selection of appropriate implant abutments and attachments for both implant-tissue-supported overdentures and metal-resin implant fixed complete dentures. This clinical report describes a patient with complications related to the failure to diagnose inadequate interarch distance, and the methods used to resolve the patient's chief complaint. A guide for abutment-attachment selection using one commercially available implant system is given.     

Co-ordinated treatment of secondary cleft deformities

Secondary cleft deformities result from the cumulative effects of functional and morphological abnormalities. Treatment choices should be based on a comprehensive plan which is designed to minimize treatment time and iatrogenic effects and which is based on sound physical and psychosocial objectives. Conventional orthodontic and orthognathic surgical principles can be modified and applied to a variety of facial cleft problems. Direct surgical correction of secondary deformities instead of prosthetic or orthodontic compensation expands treatment possibilities and optimizes treatment results.     

A Comparison of an Accelerated Technique for Casting Post-and-Core Restorations With Conventional Techniques

Purpose This project compares an accelerated technique for the casting of post-and-core restorations with four traditional techniques. The accelerated technique uses two phosphate-bonded investments and the traditional techniques use a gypsum- and a phosphate-bonded investment. The study measures and compares the differences between the seating of the casting and the seating of the acrylic resin pattern. The effects of the techniques on the fit of castings with and without a ferrule are also compared. Materials and Methods Six groups of 10 castings were made from plastic patterns formed on a stainless steel test die. A different investment and/or burnout method was used for each group. Each group had two subgroups: ferruled and nonferruled. The fit of the plastic patterns was measured at two time intervals after forming, 2 weeks and 3 months. The patterns were invested immediately after the 3-month measurement, and the difference in fit of the castings was calculated. An ANOVA and Tuckey-Kramer test were done to determine the statistical validity. Results The seating of the patterns after 3 months of storage was consistently worse than the 2-week measurements of fit. The ferrule and nonferrule patterns were not statistically different in seating. Measurement of the castings showed that the ferruled castings seated significantly worse than the nonferrule castings. The difference in the seating of the castings as compared with the patterns was considered clinically unacceptable, showing a range of 0.301 mm to 0.528 mm. The nonferrule castings showed a significant difference in seating among groups. The difference ranged from - 0.099 mm to 0.322 mm. Conclusions The castings of the ferrule subgroups were considered clinically unacceptable and were not analyzed for significance. Among the nonferrule castings, the group using a gypsum investment and conventional technique for investing and burnout but no ring liner showed the best seating. The accelerated technique was intermediate in seating with a difference of 0.148 mm from the seating of the patterns. This group was significantly different from the two best groups but not from the remaining three groups.     

Actinobacillus actinomycetemcomitans serotype e--biotypes, genetic diversity and distribution in relation to periodontal status

Actinobacillus actinomycetemcomitans isolates from 356 individuals were screened for identification of serotype e in order to investigate its distribution in relation to periodontal status. From subjects with serotype e, 1–6 isolates per subject ( n =61) were genotyped using arbitrarily primed–polymerase chain reaction (AP-PCR) and apaH gene polymerase chain reaction–restriction fragment-length polymorphism (PCR-RFLP) analysis to determine the genetic heterogeneity within the serotype. Furthermore, one serotype e strain per subject was tested for fermentation of 8 carbohydrates for biotyping. Among patients with adult periodontitis ( n =219), localized juvenile periodontitis ( n =55) and other forms of early-onset periodontitis ( n =18) serotypes b, a and c, respectively, were the most frequently detected serotypes. Non-periodontitis subjects ( n =64) were predominantly colonized with serotype c. Serotype e was found in 30 (14%) adult periodontitis patients, 2 (11%) early-onset periodontitis patients and in 5 (8%) non-periodontitis individuals, but in none of the 55 localized juvenile periodontitis patients. AP-PCR distinguished 3 and apaH gene PCR-RFLP analysis 2 genotypes among the 61 A. actinomycetemcomitans serotype e isolates, one genotype per subject. The AP-PCR genotypes 1 and 3 represented the apaH genotype 1 and the AP-PCR genotype 2 the apaH genotype 2. On the basis of variable fermentation of galactose and xylose, 3 biotypes among A. actinomycetemcomitans serotype e were established. Contrary to the absence of A. actinomycetemcomitans serotype e in localized juvenile periodontitis patients, its detection frequency was comparable among other forms of periodontitis and periodontal health. Clinical serotype e isolates form at least 2 genetic types and 3 biotypes.     

The Accuracy of Implant Verification Casts Compared With Casts Produced From A Rigid Transfer Coping Technique

Purpose Prosthodontic techniques for implant-supported prostheses continue to evolve in an effort to facilitate treatment and minimize costs. Because research has shown no impression transfer technique to be without error, some clinicians have attempted to control the fit of prosthetic frameworks by reorienting sections of patterns or frameworks intraorally, fabricating a verification cast, and completing the prosthesis to fit such a cast. One manufacturer has attempted to meet both impression-making and verification-cast objectives by providing metallic impression copings (MICS) with extensions that allow contact between the copings for rigid fixation with acrylic resin before impression making. The purpose of this study was to determine the accuracy of casts produced from the MICS transfer process compared with casts produced from sectioned frameworks, where both techniques used a low-polymerization-shrinkage acrylic resin polymer to rigidly join the sections. Materials and Methods Using stainless steel measurement spheres as a reference point on each implant analog, the distances between analogs on the experimental casts were compared with the distances measured on the master cast. Seven casts were produced for each group and measured with a machinist's microscope at a 4-μm level of precision. Results The results revealed that the MICS transfer exhibited a mean error of 41 μm, which was significantly less than the verification-cast group mean error of 57 μm (p < .01, Student's t test). Conclusions Given these results, clinicians can consider the rigid transfer technique as provided in the MICS transfer to be more accurate than the verification technique as outlined in this study.     

Dental Caries in Homeless Adults in Boston

Objectives : Information about the oral health status of the homeless is limited. The purpose of this study is to characterize the dental caries status among users of a dental treatment and referral program at homeless shelters in Boston, MA. Methods : Persons attending the program during a one-year period were assessed for evidence of dental caries experience by a single examiner. DMFT counts were abstracted from patient records. Results : The population examined (n=73) was 66 percent male with a mean age of 36 years. The racial composition was 51 percent African-American, 34 percent Caucasian, and 14 percent Hispanic. The 70 dentate people examined had a mean DFT of 11.1 (SD=6.1). The mean percent of DFT that was DT per person was 55.7 percent. Untreated caries was detected in 91.4 percent of those examined. Conclusions : These findings show evidence of previous dental services utilization by these homeless individuals, but demonstrate a high need for preventive and restorative dental therapy.