مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال بیست و پنجم شماره 4 (پیاپی 73، زمستان 1391)

The purpose of this study was to evaluate the sealing ability of different thicknesses of orthograde MTA plugs in comparison with 5 mm gutta-percha. Fifty extracted single rooted human teeth were collected. After root canal preparation, the samples were randomly divided into 4 experimental (n=10) and two control groups (n=5). In group 1, the apical 5 mm of the canals were obturated using laterally condensed gutta-percha and sealer AH26. Groups 2, 3 and 4 received 2, 3 and 4-mm thick orthograde MTA plug, respectively. Thereafter, the coronal portion of specimens was exposed to the microbial solution containing streptococcus sanguis and the root tips were placed in phenol red lactose broth. The color changes were observed within 60 days. The data were analyzed with Fisher exact test. The leakage was found in all samples (100%) in group 1 and 72.7%, 30.8% and 50% of the samples in groups 2, 3 and 4, respectively. Significant difference was found between 3 mm thickness of MTA plug and gutta percha and sealer (P=0.02). According to the findings, it seems that 3 mm thickness of orthograde MTA plug had better sealing ability than the other thicknesses of MTA plug as well as the 5 mm of gutta-percha.

One of the decisive factors on the final esthetic results of implant treatment is the abutment material. Ceramic abutments are nowadays very popular in this regard. The purpose of this study was to compare the fracture resistance of three zirconia abutments with titanium abutment. Four groups of abutments (five specimens in each) were prepared. The abutments were prefabricated titanium, prefabricated zirconia, zirconia-metal, and copy-milled zirconia abutment. After securing the abutments to the implant using a torque of 24 Ncm, they were mounted into a mounting jig using the 30º tilt. The force was applied on the assembly till the failure occured. Facture resistance and mode of failure were recorded for each specimen. The data were analyzed using One-way ANOVA. The mean values recorded for fracture resistance of different zirconia abutments varied between 426 to 688 N; however, there was no significant differences among the groups (P=0.14). Body fracture was observed only in prefabricated zirconia abutments. Screw fracture and screw bending were the common failures observed in other groups. Zirconia abutments of any type could be successfully used in regular plateform implants.

Different mechanisms have been developed for connecting abutment to implant. One of the most popular mechanisms is Tapered Integrated Screw (TIS), which is a Tapered Interference Fit (TIF) with a screw integrated at the bottom of that. The aim of this study was to investigate the mechanism of TIS and effective factors in employing TIS during design and implementation processes using an analytic method. Relevant equations were developed to predict tightening and loosening torques, contact pressure and preloads with and without bone tissue in this analysis. The efficiency is defined as the ratio of the loosening torque to the tightening torque. The effects of the change in elastic modulus and thickness of the bone on operation of this mechanism were investigated. In this study, 14 independent parameters such as taper angle, friction coefficient, abutment and implant geometry that are effective on performance of TIS mechanism were presented. The role of some factors was shown in the performance of ITI implant using sensitivity analysis. It was shown that friction coefficient, contact length, and implant radius play major roles on tightening and loosening torques and efficiency of the mechanism. Furthermore, the results revealed that the change in the elastic modulus and thickness of the bone influenced the efficiency of the mechanism less than 15%.

Internal derangement of the Temporomandibular joint (TMJ) is the most common form of Temporomandibular disorders, which represents an abnormal internal strucural and functional change of the disk, as well as an abnormal relationship of the disk to the condyle, glenoid fossa and articular eminence when the teeth are in the closed- mouth position. The aim of this study was to evaluate the correlation between eminence steepness and condyle disk movements in TMJs affected by internal derangements using magnetic resonance imaging (MRI). In this cross-sectional study, digital MRI files of 90 joints belong to 45 patients in open and closed-mouth positions were evaluated. Patients were subdivided into two groups: 64 individuals with anterior disk displacement with reduction and 26 individuals with anterior disk displacement without reduction. Appropriate oblique sagittal sections were selected and printed. Outlines of the fossa, eminence, condyle and disk were traced on matte acetate sheets and evaluated by an oral and maxillofacial radiologist and a postgraduate student of oral and maxillofacial radiology. Disk rotation, condyle rotation, condyle translation and eminence steepness were measured. The data were analyzed using T-test. In this study, no significant difference was found in measurements between the two groups, (for steepness P=0.64, for Disc rotation P=0.77, for condyle rotation P=0.28 and for condyle translation P=0.12). Disk rotation showed statistically significant correlation with eminence steepness in the anterior disk displacement with reduction group (P=0.034). Although this correlation was weak (r=0.27) no statistically significant correlations were found between other variables and eminence steepness in this group (for condyle rotation P=0.3 and for condyle translation P=0.98). Disk rotation and condyle translation had statistically significant relationship in the anterior disk displacement without reduction group (P=0.011, r=-0.49). In addition, a significant difference was found between disk rotation and condyle rotation in this group (P=0.004, r=0.54). The relationship between other variables and eminence steepness were not statistically significant (for disc rotation P=0.06, for condyle rotation P=0.72 and for condyle translation P=0.73). According to the results of the present study, there is no obvious relationship between eminence steepness and movements of the condyle- disk assembly in patients with TMJ internal derangements. Therefore, the hypothesis that a steep articular eminence of the TMJ is a predisposing factor for disk displacement without reduction could not be verified. Performing prophylactic Eminectomy as a part of patient treatment plan is doubtful and need further evaluations.

Approximately 5% of cancers involve structures of oral cavity. Partial resection of maxilla (maxillectomy) may be performed in these cases. Maxillectomy often results in significant functional disabilities such as inability in mastication, deglutition and speech with adverse impact on psychological status and social life of patients. Obturator prosthesis is a prosthodontic treatment to separate nasal and oral cavities and restore the critical above mentioned functions. The assessment of speech is considered to examine speech function restored by the treatment. The purpose of this study was to evaluate the speech in patients with resected maxilla who have been treated by obturator prosthesis from a pool of related patients in the Prosthodotnics department of dental faculty, Tehran University of Medical Sciences. The evaluation was performed with computer software using sentence intelligibility (SI) test. This cross sectional study was conducted on 10 subjects (23-66 years) referred to the Prosthodontics department of the faculty and received an obturator. After primary examination of the prosthesis, the patients completed SI test in an acoustic room under guidance of a speech therapist. The performed tests were analyzed by the speech therapist. In addition, the SI with and without the prosthesis was evaluate by lay audience. The statistical analyses were performed using Wilcoxon-signed rank test and Weighted Kappa. Significant differences were found between SI tests with and without the obturators (P<0.001). Two of 10 patients showed problems in speech function using obturator. Within the limitations of the present study, obturators had significant effect on improvement of the speech outcomes of examined patients. Improvement of the quality of life could be predicted.

Re-application of microbrush may affect the micro tensile bond strength of adhesives to dentin. The aim of this study was to evaluate the effect of re-application of microbrushes on the micro tensile bond strength of an adhesive to dentin. Thirty freshly extracted molars teeth were collected and enamel of occlusal surface were removed to expose superficial dentin. Then superficial dentin was etched, washed and partially air dried. According to the times of application of microbrush, teeth were divided into two test groups. In group 1, new microbrushs were used, but in group 2, the ones that were already used for twice were included. Ambar dentin bonding agent (FGM/Brazil) was applied to the etched dentin with microbrushes according to the manufacturer's instructions. Then the crown of teeth was built up with LLiss (FGM/Brazil) composite resin. The teeth were sectioned in buccolingual direction to obtain 1mm slabs. Then 50 hourglass- shape samples were made from 30 teeth (25 Specimens per group). The microtensile bond strength of the specimens was tested usingMTD500 (SD Mechatronik, Germany). The data were statistically analyzed by T-test. The mean values for the microtensile bond strength were 30.49±7.18 and 23.61±9.06 MPa±SD for the first and second groups, respectively. There was significant difference between the groups (P=0.005). Microbrushes should not be used for more than one cavity preparation.

The vitality pulp tests are necessary for diagnosis of pulpal disease and differentiation between endodontic and non-endodontic diseases. Thermal and electrical tests are conventional methods for evaluation of pulp vitality. The purpose of this study was to evaluate the effect of thermal changes on the tooth response to the electric pulp tester. In this study, 160 intact maxillary central incisors of 40 voluntaries were evaluated. After isolation, electric pulpal response threshold in patients were recorded. After heat and cold tests, the electrical pulp test was repeated. The degree of response was recorded. The data were analyzed using pair T-test and independent T-test. The result of this study demonstrated that the average of teeth response to the electric pulp tester before and after cold test was 1.3 and 1.7, respectively. The average was 1.4 and 1.7 before and after heat test, respectively. There was no significant difference (P<0.001) between the pulpal response before and after thermal tests (heat and cold tests). In addition, no significant difference was found between pulpal response after heat and cold tests (P=0.25). The response of tooth to the electric pulp tester was influenced by heat and cold tests.

Nursing Caries (NC) is a destructive form of caries because of incorrect nutritional habits in infants that affects deciduous teeth after eruption. Familiarity with the pattern of this type of caries and evaluation of its symmetrical or asymmetrical pattern is necessary for effective and scientific diagnosis and treatment. The aim was to assess the symmetrical or asymmetrical aspects of Nursing Caries in children between 3-5 years old. In this cross-sectional study, 10 kindergartens were randomly selected by the Tehran Welfare Organization. 115 children with NC caries entered to study after examination. Written consents were obtained from the parents. The dmfs in upper primary incisors and upper and lower primary canines, as well as the first primary molars were assessed and the caries pattern in terms of symmetrical or asymmetrical aspects was evaluated. The data were analyzed by ANOVA, LSD, Chi-square and Fisher tests. In 53.9% of the children with NC, the anterior teeth were affected symmetrically, while 46.1% indicated an asymmetrical pattern. In general, 32.2% of the teeth were affected in a symmetrical pattern and 67.8% of them in an asymmetrical pattern. About the relationship between the breastfeeding from the right or left breast and the symmetrical pattern of the NC, 51% of the children were equally breastfed from both breasts. However, in the asymmetrical NC pattern with more impact in the right side of dentition, 50% of the children had been breastfed from the left side and in children with more caries in the left side of dentition, 50% of them had been breastfed from the right side (P=0.01). NC has symmetrical and asymmetrical patterns. Direction of mother for breastfeeding affects the symmetrical and asymmetrical pattern of NC.

The aim of this study was to investigate the prevalence of diabetes and other risk factors in patients with dental infections. A cross-sectional study was conducted among 50 patients who preferred in maxillofacial word of shariaty hospital with acute dental infections in 9 months. A self-administered questionnaire was administered during a dental appointment in order to gather demographic information and recorded past history of systemic disease, OPG radiography, gingival examination, and the result of lab tests such as CBC, FBS, PT, Bilirubin, Creat, T3, T4, TSH, HIVAb and HBSAg. 28% of the subjects and diabetes, 28% Anemia, 4% Hepatitis and 4% suffered from thyroid deficiency. 28% were smokers and 18% declared using alcohol. 6% of this population was addicted to narcotic substances. There was a significant correlation between age, education, diabetes and dental infections (P<0.05). DMFT for people with dental infections without any systemic disease were 8, for diabetic patients, smokers and alcohol users were respectively 17.16, 17 and 14. Diabetes found highly prevalent in patients with dental infection and high DMFT.It indicates a need to establish a comprehensive oral health promotion program based on whole examination and blood glucose control in diabetic patients who have acute dental infection by collaboration between dental and general health care professionals. Moreover, it is recommended that all patients should be educated in dental and oral health for prevention of dental infections.

This study was conducted to assess the psychological health status of dentists in Shiraz city. In this cross-sectional study, subjects consisted of 106 dentists and 94 general practitioners (comparison group) from private and public clinics in Shiraz city. Subjects were requested to complete the standard general health questionnaire and a questionnaire on demographic variables. The data were analyzed by appropriate statistical tests. Chi-Square test and independent sample t-test were used to compare demographic and occupational variables of both groups. The questionnaires were scored and the overall score of each individual determined his/her psychological health status. Means of GHQ scores of both groups were compared using statistical tests. Both groups were similar in all demographic variables, except for age. The mean total score of GHQ-28 for both dentists (17.9) and physicians (16.34) groups were significantly lower than the cut-off point value of 23 (P <0.01). The means of scores for somatic problems, depression, anxiety and insomnia as well as unusual social performance scales were significantly different between both groups (P<0.05). A significant positive association was found between GHQ total score and job tenure. Our findings revealed that psychological health status of dentists was poorer than that of physicians. Additionally, dentist's scores were significantly different from those of their counterparts in all GHQ sub-scales.