Adherence to periodontal maintenance in Tehran, Iran. A 7-year retrospective study.

Periodontal disease is chronic but not life threatening. Therefore, adherence to periodontal maintenance (PM) is often not ideal. However, this service is frequently needed for the remainder of one's life in order to prevent disease progression and recurrence. This study evaluates the degree of compliance with PM in a private periodontal practice in Tehran, Iran. Data were collected and analyzed for degree of compliance from 519 patients who had completed active periodontal treatment up to 7 years earlier and who had begun PM. The patients were classified according to age, sex, diagnosis, prognosis, procedures performed, and compliance with prescribed maintenance intervals. In total, the overall rate of complete compliance was 3.3%, while 57.6% were erratic compliers, and 39.1% never returned for therapy. Female patients complied better than males. Patients who had received surgery complied better with PM than patients who had received scaling and root planing. These results confirmed that the degree of compliance following periodontal therapy is far from ideal. Although universal findings of poor compliance have been found, there may not be a universal solution to resolve the problem.     

Deflection fatigue of Ti-6Al-7Nb, Co-Cr, and gold alloy cast clasps

STATEMENT OF PROBLEM: There is little information about the deflection fatigue of clasps in relation to stress distribution. PURPOSE: The aim of this study was to investigate the fatigue resistance and permanent deformation of cast clasps made of titanium and other dental alloys and to relate the fatigue resistance with the calculated stress values. MATERIAL AND METHODS: Twenty-five Ti-6Al-7Nb, 25 Co-Cr, and 15 Type IV gold alloy clasps were subjected to cyclic deflection of preset values of 0.25 mm, 0.50 mm, or 0.75 mm, for 10 6 cycles (n = 14). Finite element models were created to calculate principal stresses within the specimens. Fatigue life, retentive force, and permanent deformation were recorded, and the fracture locations were determined microscopically. The results were characterized in relation to the stress within the clasps. One-way analysis of variance and Tamhane's post-hoc tests were used to compare the results of the 9 material-deflection groups (alpha=.05). RESULTS: Ti-6Al-7Nb clasps exhibited significantly less permanent deformation than the other clasps under relatively greater deflections, indicating better adaptation to the tooth surface. However, the fatigue life of the Ti-6Al-7Nb clasps under 0.75-mm deflection, with the stress above the alloy's 0.2% yield strength, was significantly shorter than those under smaller deflections. The gold clasps showed significantly longer fatigue life than the other clasps under the 0.50-mm deflection. High-stress areas within the fatigue clasp specimens coincided with the fracture locations. The probabilities of fatigue fracture and permanent deformation were closely related to the material strengths and the preset deflections. CONCLUSION: To minimize fatigue failures, the cast clasp should be designed with consideration of the stresses distributions within the clasps.     

Compliance with infection control programs in private dental clinics in Jordan

The aim of this study was to assess the compliance of general dental practitioners (GDPs) in the private sector in North Jordan with infection control measures. A pilot-tested questionnaire about infection control measures was distributed in March 2004 to 120 private practices. The response rate was 91.66 percent. About 77 percent of dentists usually ask their patients about medical history, 36 percent were vaccinated against hepatitis B, 81.8 percent wear and change gloves during treatment and between patients, and 54.5 percent wear and change masks during treatment and between patients. Most dental practitioners (95.4 percent) reported that they changed extraction instruments and burs between patients. All dental practitioners reported that they changed saliva ejectors between patients, but only 41.8 percent changed handpieces between patients. Approximately 63 percent (69/110) used autoclaves for sterilization, 47.3 percent (52/110) used plastic bags to wrap sterilized instruments, and only 18 percent (20/110) disinfected impressions before sending them to dental labs. Fourteen percent used rubber dams in their clinics, and only 31.8 percent had special containers for sharps disposal. Based on these responses, approximately 14 percent of general dentists in this sample were considered to be compliant with an inventory of recommended infection control measures. In Jordan, there is a great need to provide formal and obligatory infection control courses and guidelines for private dentists by the Ministry of Health and the dental association in addition to distribution of standard infection control manuals that incorporate current infection control recommendations.     

Induction of Sca-1 in the duct cells of the mouse submandibular gland by obstruction of the main excretory duct

The effect of ligation of the main excretory duct (MED) of the mouse submandibular gland (SMG) on the expression of Sca-1, a stem cell antigen, was examined by Western blotting and immunohistochemistry. By Western blotting, the expression of Sca-1 with a molecular weight of 18 kDa was identified in the normal gland. At 1 day post-ligation, the expression level of Sca-1 was strongly increased in the experimental gland and weakly in the contralateral gland, and such expression in both glands decreased at 6 days. By immunohistochemistry, Sca-1 was detected weakly in the apical membrane of excretory duct (ED) cells of the SMG under the normal condition. By duct ligation, Sca-1 became expressed strongly in most cells of the two major duct systems, i.e., the striated duct (SD) and granular convoluted tubules (GCT), but was not detected in the acinar (Ac) cells. By fluorescence-activated cell sorter (FACS) analysis, the number of side population (SP) cells in this gland was found to be increased by ligation. These results imply that Sca-1-positive cells may have a role in the duct cell proliferation in the regeneration step elicited by MED ligation-induced injury.     

The fatigue life of a cobalt-chromium alloy after laser welding

The aim of this study was to investigate the fatigue life of laser welded joints in a commercially available cast cobalt-chromium alloy. Twenty rod shaped specimens (40 mm x 1.5 mm) were cast and sand blasted. Ten specimens were used as controls and the remaining ten were sectioned and repaired using a pulsed Nd: YAG laser welder. All specimens were subjected to fatigue testing (30N - 2Hz) in a controlled environment. A statistically significant difference in median fatigue life was found between as-cast and laser welded specimens (p < 0.001). Consequently, the technique may not be appropriate for repairing cobalt chromium clasps on removable partial dentures. Scanning electron microscopy indicated the presence of cracks, pores and constriction of the outer surface in the welded specimens despite 70% penetration of the weld.     

A comparison using macroradiography of canal shapes in teeth instrumented ultrasonically and by hand

Forty teeth with severely curved canals were divided into two groups and the root canals were prepared either ultrasonically or with hand instruments. Canal shapes were compared qualitatively and quantitatively using subtraction macroradiography; this allowed the pre- and postinstrumented canal shapes to be viewed on the same print. The times to carry out instrumentation and the incidence of elbows were recorded. In addition, the following measurements were taken from the radiographs using a digitizer: apical and coronal areas, distance of elbow from canal curvature, change in width at elbow and 0.5 mm apical to it, and apical transport width. Subjective evaluation revealed that no difference was apparent between the methods as to the places where the dentin was removed; both instruments exhibited unequal dentin removal along the canal length with more removal occurring coronally. The quantitative results indicated an absence of differences in the following: the time of instrumentation, the incidence of elbows, the distance of elbow from the point of curvature, the change in width at the region of the elbow, and the apical transport width. These findings indicated that ultrasonic files behaved similarly to hand instruments when used in a filing action.     

3H]-forskolin binding sites in rat submandibular salivary glands

Specific [3H]-forskolin binding was linear as a function of the membrane protein concentration and reached steady-state by 30-40 min of incubation at 37 degrees C. Such binding was saturable and the bound radioligand could be readily dissociated by an excess of unlabelled forskolin. There was only one type of binding site, with a dissociation constant (Kd) of 0.16 microM. The concentration of the binding sites (Bmax) was 0.73 pmol/mg protein. There was no significant difference in the [3H]-forskolin binding characteristics in membranes of rats fed for 6 weeks on diets containing 10% corn oil, 8% coconut oil + 2% corn oil, or 10% menhaden fish oil.