Frontiers in Dentistry
Volume:1 Issue: 3, Summer 2004

Statement of Problem: Following the increasing use of composites in restoring anterior and posterior teeth, problems due to its technique sensitivity have become a major concern. One of these problems is the possibility of contamination of dentin with saliva, blood and/or gingival fluid in different stages of bonding procedure, even with application of different methods of isolation. However, by introduction of Single-bottle dentin adhesives, the contamination possibility reduced to two stages. Scientific documents show that saliva contamination reduces bond strength of composites to dentin. Application of simple and efficient methods for reducing or eliminating saliva contamination enables clinicians to carry out dental treatment without any concern about deterioration of clinical longevity of restoration. This study was designed to compare the effect of different decontamination methods on the shear bond strength of composite to dentin using a “Single-bottle” adhesive. Seventy-two extracted sound human molars and premolars were selected. Enamel of buccal surface was ground flat to expose dentin. The teeth were divided into 9 groups of 8 each. In control group (1) the adhesive “Excite” was used according to the manufacturer, without any contamination. Conditioned and saliva contaminated dentin was (2) rinsed and blot dried, (3) rinsed, dried and re-etched. In groups 4, 5, 6 uncured adhesive was saliva contaminated and then: (4) only blot dried (5) rinsed, blot dried with adhesive reapplication and (6) resurfaced with bur, rinsed, dried and followed by repeating the whole process. In groups 7, 8, 9 cured adhesive was contaminated with saliva and then: (7) rinsed and dried (8) rinsed, blot dried with adhesive reapplication (9) same as group (6). Then “Tetric Ceram” composite cylinders were bonded to dentin surfaces. Samples were thermo cycled in 5°C and 55°C water, 30 seconds in each bath with a dowel time of 10 seconds for 500 cycles. Finally, samples were sheared using Instron testing machine and shear bond strength data were subjected to one way ANOVA analysis, and Tukey HSD PostHoc. Mode of failure of samples was examined under Stereomicroscope (×40) and using Log-rank survival data analysis. No statistically difference between mean shear bond strength of groups 1,2,3 was observed (P=0.543). Comparison of groups 4,5,6 with group 1 showed that shear bond strength of group 4 was significantly lower (P<0.001). Mean shear bond strength of groups 1,7,8,9 were not significantly different (P=0.150). The major mode of failure was cohesive either in composite or dentin bonding. Blot- drying of saliva-contaminated uncured Single-bottle adhesive significantly decreased shear bond strength of composite to dentin. In other contamination protocols, the effect of treatments applied did not differ.

Statement of Problem: Dental caries is one of the common diseases in the world. It is an infective disease which is caused by loss of minerals and destruction of dental tissues. One of the most effective ways to diagnose the interproximal caries is radiography. Bitewing radiography is the best way for caries diagnosis. The aim of this study was to evaluate the prevalence of the interproximal caries in dental students of Islamic Azad University. This research was a cross sectional study that was conducted on 89 students of the Azad University consisting of 48 females and 41 males who were selected by random sampling. For each individual student left and right posterior bitewing radiographs were taken with a standard method (the interproximal spaces were between 6-7,5,6 and 4,5). Thus 12 interproximal spaces were examined in each individual. The most proximal cavitation surfaces were detected in the upper Jaw. Results revealed that 6 individuals (6.7%) were totally caries free and 83 individuals (93.3%) showed interproxmal caries. Out of 1068 proximal spaces which had been studied 794 Spaces (73.4%) were caries free and 274 surfaces (25.7%) had caries. The high incidence of proximal caries and the possibility of missing them in the routine examinations make the bitewing radiographs an effective procedure for diagnosis.

Statement of Problem: Low- fusing compound (type 1) is used for border molding and impressions. Flow and reproducibility of surface detail are two important characteristics of these materials. There are no valid data available comparing domestic and imported brands. The Purpose of this study was to evaluate these two properties of four different products including Kerr (Kerr Manufacture MI 98174-2600), Harvard (Hoffman Harvard Dental GMb H Germany); Kymia (Kymia dental company 713 Iran); and Pishro (Pishro 72534 Iran). All procedures were followed according to ADA and BS-Standard. Total number of 48 samples were divided into 8 groups (6 in each group). Twenty disks were fabricated for impression tests. The specimen dimensions were 40 mm (diameter) and 6mm (thickness). Standard test blocks were used to test the specimens. The Willcoxon test showed significant difference in flow rate between materials tested with the best result for Kerr (P<0.05). Kerr flow was 85% and under 5% at 45°C and 37°C, respectively. There were great deviations from standards value at 45°C. For the rest of the samples at 37°C; except Kymia the flow rate for 3 materials (Kerr; Harvard Pishro) were almost acceptable. The impression test results revealed that only Kerr was able to record the details at 45°C. Kerr flow is exactly what ADA standards specify. But the flow rate for three materials exhibit a great distance from these standards. In impression test only Kerr was able to record the details

Statement of Problem: Avulsion is one of the most serious emergencies in dental office. Avulsed teeth should be stored in a medium that supports the periodontal ligament cells viability. In some clinical situations, preserving media, contained growth factors and mitogenic products may be used for repair of traumatized (Periodontal Ligament) tissues. It has been previously reported that levodopa (L-dopa) accelerates healing by increasing the growth hormone level. In this study, the local effect of L-dopa, on human periodontal ligament fibroblast (HPLF) cells was evaluated. Samples were taken from impacted or semi-impacted third molar teeth, which didn’t show inflammatory reaction. The cells obtained from periodontal ligament of these teeth, were cultured in appropriate medium. The passage number between 3-6 was taken for further experiments. The viability of HPLF cells, which treated, by L-dopa were evaluated by trypan blue dye exclusion and neutral red assay. Results indicate that low concentration of L-dopa produces significant increase in number of these cells in comparison with control group. These results confirmed previous study about direct action of L-dopa on the viability of HPLF cells. On the basis of this study and previous reports, presence of L-dopa in preserving media may be useful in increasing the self-life transferring HPLF cells.

Statement of Problem: Among periodontal defects, the furcation involvement represents one of the most chalenging scenarios due to the difficulty of achieving a predictable improvement regardless of the type of periodontal therapy. Moreover, the presence of furcation involvement has been demonstrated to considerably affect tooth prognosis. Thus, treatment of furcation defects is a challenge in clinical periodontics. The aim of periodontal treatment is not only to control infection but also to regenerate periodontal tissues lost as a consequence of periodontal disease. The purpose of this study was to compare Bio-oss (Bo), an anorganic bovine bone Xenograft, in combination with coronally positioned flap to open flap debridment surgery with coronally positiond flap alone in human mandibular class II furcation defects. In this clinical trial and interventional study 24 furcations, which provided 12 pairs of similar periodontal defects were evaluated. Each defect was randomly assigned to treatment with Bio-Oss in combination coronally positioned flap or open flap debridment and coronally positioned flap alone. Following basic therapy, baseline measurements were recorded including probing depth (PDD), clinical attachment level (CAL), gingival recession (REC), keratinized gingiva (KG) and closed horizontal probing depth (CHPD). After 6 months, all sites were re-entered and hard tissue measurements were recorded. Hard tissue measurements were performed during surgery to determine open horizontal probing depth (OHPD) and open vertical probing depth (OVPD). The data was analyzed using t-test paired sample. Vertical probing depth reduction of 3.17±1.32 mm and horizontal probing depth reduction of 4.42±1.02 mm were noted for the BO group, with 2.87±0.83 mm and 2.31±0.49 mm reductions, respectively, noted for CPF alone. Both surgical procedures resulted in statistically significant probing depth reduction and gain clinical attachment levels, with no significant difference between groups. Recession didn''t have significant differences between groups. Hard tissue measurements (after Re-entry) showed 4.17±1.66 mm of vertical furcation bone fill (OVPD) for test group (BO) and 0.83±0.72 mm for CPF alone. The test (BO) group had 3.87±0.88mm of horizontal furcation bone fill (OHPD), and the CPF group had 1.21±0.8mm. There was a statistically significant difference between test (BO) group and CPF group in all soft and hard tissue measurements with the exception of attachment level, recession, and keratinized gingiva. The use of Bio-oss improved horizontal and vertical defect resolution in mandibular class II furcation defects.

Statement of Problem: The restoration of the teeth should have enough ability to withstand masticator forces while preserving as much tooth structure as possible. The purpose of this study was to compare the effects of light-heat cured composite with light cured composite restorations on fracture resistance of the restored teeth. Forty healthy maxillary premolar teeth were chosen, endodontic treatment performed in 30 of them. MOD cavities were prepared in all of them to weaken tooth structures. Then, they were divided into 3 groups each of which contains 10 specimens. The groups were as follows: Group 1: unprepared teeth (sound teeth acted as control) Group 2: restored teeth with direct light cured composite resin. Group 3: restored teeth with light-heat cured composite resin as inlay without any cementing surface treatment Group 4: restored teeth with light-heat cured composite resin inlays with cementing surface treatment. Finally all samples were subjected to compressive load by testing machine. The data were analyzed using ANOVA and Duncan tests. There was a significant difference in fracture resistance between 4 groups (P<0.001) except groups 2 and 3. The mean fracture load for groups 1,2,3 and 4 were 98.96±16.05, 58.72±15.33, 54.04±15.56 and 78.36±9.83 kgf respectively. Using light-heat curing method and cementing surface treating of composite resin will increase fracture resistance of endodontically treated maxillary premolars.

Statement of Problem: Amalgam is the most widely used dental restorative material. However, because of continuous low-level release of Mercury from amalgam fillings, its safety has been questionable. The aim of this study was the evaluation of concentration of Mercury in saliva before and after amalgam fillings and its relation with numbers and surfaces of amalgam fillings. In an analytic interventional study we surveyed concentration Mercury in saliva before and after amalgam fillings. Twenty-five Patients (9 male, 16 female) who referred to oral medicine department of Tehran university of medical science and Haj- Abdol- Vahab medical center who had no amalgam fillings were selected and the samples of saliva (5cc) was collected before fillings. After that all of posterior decayed teeth were filled in an appointment with amalgam and, 24 hours later, the second samples of saliva (5cc) was collected. The amount of saliva Mercury before and after filling was measured and its difference was analyzed by paired t- test. In this study the mean of Mercury in saliva was 0.00896 µg/ml before and 0.16404 µg/ml after amalgam fillings. The mean of number of fillings was 1.96 and mean of size of surfaces was 76.43 mm2 and mean of consumption amalgam was 4.1 units. There was no significant correlation between age (P=0.677), sex, number of fillings (P=0.055), number of surface of filling (P=0.059) and size of surfaces of fillings (P=0.072), with Mercury levels in saliva after amalgam fillings. There was a significant relation between Mercury level of saliva after fillings and amalgam amount (P= 0.036). Therefore amalgam may be designate a significant source for Mercury release in saliva. Since this is a preliminary study, it needs supplementary evaluations in saliva, blood and urine in different periods after amalgam fillings.

Statement of Problem: Chondrosarcoma is a tumor which includes 10 percent of the bone primary tumors. Its prevalence is half of the osteosarcoma and two times of Ewing’s. The mean age of the patients ranges between 30-50 years of old. There is no significant sex or race predilection. The most common complaint is the presence of a painless and enlarging mass. Its clinical course is described as slow-growing lesion with local invasion and recurrence, no or delayed metastasis, almost long survival. The aims of this study were as follows: the determination of prevalence of reported Chondrosarcoma in cancer institute Imam Khomeini hospital and faculty of dentistry of Tehran University of medical sciences, comparison of jaw Chondrosarcoma to the body one, evaluation of sex, age, clinical and histological parameters and prevalence of different locations in body. In this study the biopsy notes of all kinds of chondrosarcoma of the body in cancer institute (212 cases) and the extracted files of the patients with the jaws chondrosarcoma in cancer institute and department of oral pathology of faculty of dentistry, University of Tehran medical sciences (23 Cases) were evaluated. In this retrospective statistical study the proportion of the patients with the jaws conventional chondrosarcoma to the patients with conventional Chondrosarcoma of the body was 8.57%. The mean age of the total patients and the patients with jaws chondrosarcoma were 36.21 and 38.87 years, respectively. Men were somehow more involved. Pelvic was the most common location of the tumor. Maxilla involvement was 3-4 times more than mandible. Microscopic manifestation and tumor grading suggested a low grade lesion in jaws. Local recurrence in jaws was 33.3%. The most common site of involvement of chondrosarcoma was pelvic and maxillary involvement was more common than mandible. Its prevalence was in the posterior site of the jaws.

Statement of Problem: Many attempts have been made in order to evaluate the amalgam corrosion behavior as an indicator of biocompatibility. The aim of this study was to evaluate and compare the initial corrosion of four different brands of dental amalgams. Four different types of commercial high copper dental amalgam were studied. A special mold was used and twenty-one samples of each type of commercial dental amalgams were prepared. X-ray diffraction technique was used to investigate the microstructure of freshly prepared specimens. Electrochemical potentiodynamic tests were performed in physiological solutions in order to determine and compare the corrosion behavior of freshly prepared sample of four brands of dental amalgams. The physiological solutions were the Ringer’s solution and physiological normal saline. Five replicate tests on each group of specimens were performed. Tafel extrapolation and linear polarization methods determined corrosion potentials and corrosion current densities. The mean value and standard deviations of the results were calculated. The mean values were statistically compared by ANOVA and Duncan methods at 95% level of confidence. Gamma-2 phase was present in freshly prepared sample of each type of commercial amalgam. The results showed statistically significant differences between the mean corrosion current density values of freshly prepared sample of four brands of amalgams (P<0.05). The freshly prepared specimen of Sybraloy dental amalgam possesses the higher initial corrosion resistance than the other three, and Cinaalloy dental amalgam possesses the lowest corrosion resistance. This trend is independent to the type of physiological environment. Initial corrosion resistance of each type of commercial dental amalgam is much less than its corrosion resistance that could be obtained after one week. From the viewpoint of the corrosion behavior as an indication of biocompatibilty and for prediction of biocompatibily of the amalgam restoration, it is necessary to pay attention to the initial corrosion of dental amalgam.

Statement of Problem: Blindness as a disability seems to produce difficulties to reach an ideal heath status of the teeth. Moreover ordinary educational health programmes for this group of population, especially children, are not successful. Investigate the dental health status of these children and to see if they are really different with the normal population. All sixty three 12- year- old blind children in three institutes were studied. A general questionnaire, as well as a dental questionnaire including some information on the first molars, were completed by these children. The average DMFT and DMFS of the first molars were 3.30± 1.19 and 6.22±3.95 respectively. DMFT was higher in the lower molars, Compared with to the upper ones. However, DMFS was higher in the upper molars. The present study shows that the values of these indices, among blind children, are close to those of normal population, indicating that under controlled health condition and good education, acceptable values for DMFT and DMFS will be obtained.

Statement of Problem: Nowadays Mineral Trioxide aggregate (MTA) is widely used for root end fillings, pulp capping, perforation repair and other endodontic treatments. Investigations have shown similar physical and chemical properties for Portland cement and Root MTA with those described for MTA. The aim of this in vitro study was to evaluate the tissue reaction to implanted MTA, Portland cement and Root MTA in the mandible of cats. Under asepsis condition and general anesthesia, a mucoperiosteal flap, following the application of local anesthesia, was elevated to expose mandibular symphysis. Two small holes in both sides of mandible were drilled. MTA, Portland cement and Root MTA were mixed according to the manufacturers, recommendation and placed in bony cavities. In positive control group, the test material was Zinc oxide powder plus tricresoformalin. In negative control group, the bony cavities were left untreated. After 3,6 and 12 weeks, the animals were sacrificed and the mandibular sections were prepared for histologic examination under light microscope. The presence and thickness of inflammation, presence of fibrosis capsule, the severity of fibrosis and bone formation were investigated. The data were submitted to Exact Fisher test, chi square test and Kruskal- Wallis test for statistical analysis. No statistically significant differences were found in the degree of inflammation, presence of fibrotic capsule, severity of fibrosis and inflammation thickness between Root MTA, Portland cement and MTA (P>0.05). There was no statistical difference in bone formation between MTA and Portland cement (P>0.05). However, bone formation was not found in any of the Root MTA specimens and the observed tissue was exclusively of fibrosis type. The physical and histological results observed with MTA are similar to those of Root MTA and Portland cement. Additionally, all of these three materials are biocompatible. However, in order to replace Root MTA and Portland cement type I as less expensive and suitable substitutes for MTA, more longer- term studies with larger number of samples are suggested.