Frontiers in Dentistry
Volume:7 Issue: 2, Spring 2010

Exposure to mercury can occur in occupational and environmental settings.During clinical work with dental amalgam, the dental personnel are exposed to both metallic mercury and mercury vapor. The aim of the present study was to investigate blood mercury level (BML) and its determinants among dentists practicing in Hamadan city, Iran. This cross sectional study was done on all dental practitioners of Hamadan (n=43). Dentists were asked to complete a questionnaire, and then 5 ml blood samples were obtained from them. After preparation, mercury concentration of each sample was measured by cold vapor atomic absorption device. Pearson correlation test and regression models served for statistical analysis. The mean blood concentration of mercury was 6.3 μg/l (SD=1.31 range 4.15- 8.93). BML was positively associated with age, years in practice, working hours per day, number of amalgam restorations per day, number of amalgam removal per week, sea food consumption, working years in present office, using amalgam powder, using diamond bur for amalgam removal, dry sterilization of amalgam contaminated instruments, and deficient air ventilation. BML of dentists in Hamadan was higher than standards. Working hours and number of amalgam restorations per day were significantly correlated with blood mercury.

The aim of this study was to evaluate the bond strength between metal brackets and non-glazed ceramic with three different surface treatment methods. Forty-two non-glazed ceramic disks were assigned into three groups. Group I and II specimens were etched with 9.5% hydrofluoric acid. Subsequently in group I, silane and adhesive were applied and in group II, bonding agent was used only. In group III, specimens were treated with 35% phosphoric acid and then silane and adhesive were applied. Brackets were bonded with light-cured composites. The specimens were stored in water in room temperature for 24 hours and then thermocycled 500 times between 5°C and 55°C. The difference of tensile bond strength between groups I and III was not significant (P=0.999). However, the tensile bond strength of group II was significantly lower than groups I, and III (P<0.001). The adhesive remnant index scores between the three groups had statistically significant differences (P<0.001). With the application of scotch bond multi-purpose plus adhesive, we can usephosphoric acid instead of hydrofluoric acid for bonding brackets to non-glazed ceramicrestorations.

The aim of the present study was to evaluate the efficacy of two caries detector dyes in the diagnosis of dental caries. Twenty extracted human posterior teeth without pulpal exposure were sectioned mesiodistally through the center of the lesions using a water-cooled disk.The tooth halves were randomly divided into two groups and treated with Caries Detector(CD) and Caries Check (CC) detector dyes. Access cavities were prepared followed bycaries removal and dye application. All cavities were arbitrarily divided into two right andleft sections and excavation of the stained areas was performed on the left parts, while the right sections remained untouched. Bacterial penetration into dentinal tubules was evaluated using Gram-stained decalcified sections under light microscopy. Sensitivity andspecificity of both dyes were calculated. The sensitivity of CD and CC were 74% and 71%, respectively. The specificity obtained for both dyes was 100%. Considering the low sensitivity of the dyes evaluated in the present study, it seems that they may not be reliable when used as the sole diagnostic technique for detection of carious lesions in posterior teeth.

This experimental in vitro study compared marginal adaptation of indirect composite, glass-ceramic inlays and direct composite. Seventy-five recently extracted human molars were randomly divided into three groups (n=25) and mesio-occluso-distal cavities with the same dimensions were prepared in the teeth. Indirect composite and glass-ceramic inlays were fabricated following manufacturer''s instructions and the marginal gap was measured by a stereomicroscope at magnification 40× before cementation. After cementation of inlays and restoring the third group by direct composite, all the specimens were thermocycled and the marginal gaps were measured exactly as previously described. Repeated measure ANOVA and post-hoc Tukey test were used for pairwise comparison of occlusal, proximal, and gingival marginal gaps in each group. One-way ANOVA and post-hoc Tukey test were used for comparison of mean marginal gap in the three groups and for comparison of marginal gap before and after cementation in inlays, paired T-test was used. The marginal gap of direct composite (19.96 μm) was significantly lower than that of indirect composite inlay (48.47 μm), which in itself was significantly lower than that of glass-ceramic inlay (60.96 μm). In all the restorations, marginal gap in the gingival margin was significantly higher than occlusal and proximal margins. The marginal gap of inlays did not change after cementation and thermocycling. This study indicated that the marginal gaps of the evaluated restorations are less than 100 μm, which is clinically acceptable.

Preservation of unsupported occlusal enamel after removal of underlying carious dentin may result in maintenance of aesthetics as well as wear resistance against the opposing enamel. This study investigates the influence of different restorative materials and bonding agents on reinforcement of unsupported enamel in molars and compares it with sound dentin. In this in vitro study, forty- five extracted human molars were selected and randomly divided into five groups of nine. All lingual cusps were cut off. The dentin underlying the buccal cusps was removed in all groups except the positive control.The negative control group received no restorations. After application of varnish and Panavia F, spherical amalgam (Sina) and after application of Single-Bond (3M), compositeresin (Tetric Ceram) was used to replace missing dentin.All specimens were thermocycled, then mounted in acrylic resin using a surveyor. Lingualinclination of facial cusps was positioned horizontally. Load was applied by an Instronmachine at a crosshead speed of 10 mm/min until fracture.Data were subjected to ANOVA (one way) and Post hoc Test (Duncan). Statistically significant differences were found between the five groups (P<0.001); however, no significant difference was revealed between bonded amalgam andthe positive control groups (P=0.762). Composite and amalgam had the same effect(P=0.642), while the composite and negative group had no significant difference(P=0.056). Bonded amalgam systems (Panavia F) could reinforce the undermined occlusal enamel effectively.

Vertical bone loss evaluations in the Nobel Biocare Replace® Select Tapered TM implant system in the human after one-year loading time. This retrospective cross-sectional study was performed on 31 patients (14 men, 17 women; mean age, 60.39 years) receiving 170 implants (mean, 5.48 for each patient) of Groovy and Non-groovy designs in the Nobel Biocare Replace® Select Tapered TM system. The marginal bone loss was measured at mesial and distal aspects of the implants on OPG x-rays after one-year follow-up. The data regarding the patient''s gender, age, history of disease, smoking, bone type at implant location, loading time of prosthesis and implant, implant design, diameter and length were recorded by the patients'' records and interview. The data were subjected to multiple linear regression and Pearson coefficient ratio regarding different factors. The mean (standard deviation) distal, mesial and overall bone loss was 0.688 mm (0.851), 0.665 mm (0.849) and 0.935 mm (0.905), respectively in the studied implants. No significant differences were found regarding implant location, bone quality at the implant region, implant design and bone graft reception. In addition, no significant correlation was found between the occurred bone loss and implant diameter, length and number of used splints. Due to the criteria mentioned for implant success in term of bone loss values after one-year loading time, Noble Biocare Replace® Select Tapered TM implant system is an acceptable treatment option for implant restorations in this regard.

The aim of this cross-sectional analytic study was to evaluate the diagnostic efficacy of panoramic-based indices of the mandible (Mental Index-MI, Mandibular Cortical Index-MCI and Panoramic Mandibular Index-PMI) and to determine their correlation with bone mineral density (BMD) of the femoral neck and lumbar vertebrae (L2-L4) in order to assess the possibility of using these parameters as indicators of osteoporosis. The mandibular indices of 67 women over 35 years old were measured from panoramic radiographs, and bone densitometry was performed in the femoral neck and lumbar vertebrae (L2-L4), using DXA (Dual Energy X-ray Absorptiometry) technique. The patients were divided into three categories of normal, osteopenic and osteoporotic in each skeletal region. One-way ANOVA and ROC curve analyses were applied.The results were considered statistically significant when the P-value was less than 0.05. Comparing the mean BMD in the femoral neck in women between C1 and C3 subgroups of MCI, a significant difference was detected (P=0.04). The mean PMI in the three skeletal subgroups was not different according to the skeletal region (P>0.05). We found a significant difference in mean MI between normal and osteopenic subgroups in the femoral neck (P=0.042). Using radiomorphometric indices of the mandible (MCI-MI) may be useful in determining the skeletal status of the patients, but is not sufficient for precise evaluation.