Evaluation of radiographic predictors to assess the rate of mandibular residual ridge resorption.

Sixty healthy clinical edentulous patients (thirty male and thirty female) were chosen for the study. Panoramic and lateral cephalometric radiographs were taken of each patient. The amount of bone loss was estimated from the panoramic radiographs as per the formula proposed by Wical and Scoop. The rate of mandibular residual resorbed ridge (RRR) expressed as percentage of bone loss per year was then computed. The correlation between the mandibular RRR and gonial cortical thickness and the percentage of cortical bone at the symphysis was tested. These parameters were also compared between the male and female patients. The rate of mandibular RRR, expressed as percentage of bone loss per year, was found to be indirectly correlated with the cortical thickness at gonion as measured from the panaromic and the lateral cephalometric radiographs. The values of students 't' test for mean differences between the female and the male patients with respect to the rate of mandibular RRR and the cortical thickness at the gonion were found to be statistically significant.     

Adjustment of the occlusal vertical dimension in the bite-raised guinea pig

In humans, the inappropriate occlusal vertical dimension (OVD) causes several orofacial disorders, such as bruxism and pain in the masticatory muscles and temporomandibular joint. However, it is still unclear how strictly the OVD is adjusted. To answer this question, we studied the temporal change of the OVD in bite-raised young guinea pigs. The OVD was raised by fixation of a bite-raising appliance to the lower incisors, and increased by either 3 or 1.5 mm at the first molars. After the space produced between the upper and lower molars was filled within 10 days due to eruption of the molars, the appliance was removed. In the bite-raised animals, the raised OVD was reduced until it attained that observed in the control animals, after which the OVD increased according to cranial growth. These results show that the OVD is developmentally changed and strictly controlled.     

Exposure of implants using a modified multiple-flap transposition vestibuloplasty

AIM: To introduce a minimally invasive operation to improve the condition of the soft tissues around the implants in an atrophied mandible, at the same time, as uncovering the implants. PATIENTS AND METHOD: A multiple-flap transposition vestibuloplasty was done in 11 patients after the insertion of four implants in the interforaminal region of an atrophied mandible. Improvement in soft tissues and successful exposure of implants and attached gingiva were evaluated during a follow-up period of 55 months. All the patients were operated on local anaesthesia as outpatients. RESULTS: Adequate exposure of implants and an area of attached gingiva 4-9 mm wide were attained. There was no bleeding on probing or local infection. CONCLUSION: The transposition multiple-flap vestibuloplasty is a simple and minimally invasive method of improving the condition of soft tissue after insertion of implants. It does not limit the patients' routine activities and avoids staged operations.     

Prevalence and trends in enamel fluorosis in the United States from the 1930s to the 1980s

BACKGROUND: The National Survey of Dental Caries in U.S. School Children: 1986-1987 conducted by the National Institute of Dental Research, or NIDR, remains the only source of national data about the prevalence of enamel fluorosis. The authors analyze these data and describe changes in the prevalence of enamel fluorosis since the 1930s, as reported by H. Trendley Dean. METHODS: A sample of children comparable to those described in the 1930s was selected from the NIDR data set among children living in households served by public water systems during the child's first eight years of life. The type of water system (that is, natural, optimal and suboptimal) for each household had been recorded in the NIDR data set using data from the 1985 U.S. Fluoridation Census. The NIDR data set included information about the children's history of fluoride exposure obtained from parents. RESULTS: In the 1986-1987 period, the prevalence of enamel fluorosis (ranging from very mild to severe) was 37.8 percent among children living in residences with natural fluoride (0.7 to 4.0 parts per million fluoride ions, or F-), 25.8 percent in the optimal fluoride group (0.7 to 1.2 ppm F- and 15.5 percent in the suboptimal fluoride group (< 0.7 ppm F-). The largest increase in fluorosis prevalence from the 1930s to the 1980s was in the suboptimal fluoride group (6.5 to 15.5 percent). CONCLUSIONS AND CLINICAL IMPLICATIONS: Exposure to multiple sources of fluoride may explain the increase in enamel fluorosis from the 1930s to the 1980s. The exposure to fluoride from sources such as dietary supplements has decreased since the 1980s because of reductions in the recommended dosage, but these changes occurred too late to have an effect on the study cohort. Evidence of simultaneous use of systemic fluorides indicates the need to reinforce guidelines for the appropriate use of fluorides and promote research on measuring total fluoride exposure.     

A simple model to demonstrate the electronic apex locator

AIM: To describe and evaluate a newly developed model for demonstrating and teaching the use of electronic apex locators. SUMMARY: A phantom model, master jaw model and extracted human teeth were used to construct the demonstration model with alginate impression material as the periapical conductive medium. The model was validated in a series of length determinations with apical foramina enlarged to 0.20, 0.30 and 0.45 mm diameter, and the stability of the model was evaluated up to 45 h after construction. All evaluations were conducted with the Root ZX apex locator with 2.65 and 5.25% NaOCl in the canals. Most length measurements were within 1 mm of actual root length (range: -2.2 to +0.21 mm) and did not change significantly over 45 h for teeth with foramina of 0.3 mm or less. Measurements for teeth with wide (0.45 mm) apices were stable up to 28 h. NaOCl concentration did not significantly affect the readings. KEY LEARNING POINTS: A simple, inexpensive model can be manufactured from plastic dental jaws, natural teeth and alginate impression material to demonstrate electronic working length measurement. The model is stable for many hours and provides consistent results with different concentrations of NaOCl in the canal and various apical diameters. The model is a useful teaching aid but needs further evaluation and refinement before use in research applications.     

Preoperative radiochemotherapy and radical resection for stages II to IV oral and oropharyngeal cancer: grade of regression as crucial prognostic factor

The purpose of this study was to assess the prognostic value of histological response to preoperative radiochemotherapy in an established multimodal therapy concept for advanced oral and oropharyngeal cancer. Two hundred and twenty-two patients who underwent preoperative radiochemotherapy (RCT: 50 Gy, mitomycin C and fluorouracil) and radical surgery were retrospectively evaluated. Resected tumours of all patients were histologically analysed and response to RCT was classified in histopathological grades of regression (RG). In a multivariate statistical analysis, RG was compared with established factors regarding their predictive value for overall and disease-specific survival. The 5-year overall survival probability in the different groups of histopathological regression grades were: RG1 (no vital tumour): 73.4%, RG2 (minimal tumour remnants encompassing less than 5%): 72.1%, RG3 (5-50% vital tumour cells): 41.9%, RG4 (more than 50% vital tumour): 37.9%. For disease-specific survival probability no significant differences were found between both groups of "responders" (RG1 and RG2) nor between "non-responders" (RG3 and RG4), whereas responders and non-responders differed significantly from each other (log-rank test; p < 0.001). T-classification, N-classification and disease stage, histological grading, tumour site, age, and sex had less prognostic value than RG in a Cox regression model. In the neoadjuvant multimodal therapy concept, histological response to preoperative RCT is a crucial prognostic factor even when surgical R0-resection is accomplished. Thus, non-responders have to be regarded as high-risk patients for recurrence and may benefit from further therapy.     

The effects of up to 240 days of tacrolimus therapy on the gingival tissues of rats--a morphological evaluation

BACKGROUND: Tacrolimus, an immunosuppressive drug used in organ transplantation, has been reported not to induce gingival overgrowth. However, prevalence studies are limited, and the methods used for assessing gingival overgrowth varies among studies. OBJECTIVE: The purpose of this study was to evaluate the effects of up to 240 days of tacrolimus therapy on gingival tissues of rats. MATERIALS AND METHODS: Rats were treated for 60, 120, 180 and 240 days with daily subcutaneous injections of 1 mg/kg body weight of tacrolimus. After histological processing, the oral and connective tissue, volume densities of fibroblasts (Vf), collagen fibers (Vcf) and other structures (Vo) were assessed in the region of the lower first molar. RESULTS: After 60 and 120 days of treatment with tacrolimus, gingival overgrowth was not observed. The gingival epithelium, connective tissue, as well as the values for Vf, Vcf, and Vo were similar to those of the control rats (P>0.05). After 180 and 240 days of the treatment, gingival overgrowth was associated with a significant increase in the gingival epithelium and connective tissue as well as an increase in the Vf and Vcf (P<0.05). CONCLUSIONS: Within the limits of the experimental study, it may be concluded that the deleterious side effects of tacrolimus on the gingival tissues of rats may be time-related.