Journal of Dental Medicine
Year:2009 | Volume:22 | Issue:3 (60)|Papers Count:11

Background and Aim: Evaluation of shear bond strength and micro leakage of bonding agents is important as these properties play main roles in adhesion of composite to dental tissues. Micro leakage results in bacterial penetration into dentin tubules and enamel surfaces and causes sensitivity and recurrent caries followed by destruction of composite filling Insufficient shear bond strength results in early failure of filling in low masticatory forces. The main goal of this study was to compare the micro leakage and shear bond strength of an experimental adhesive and Scotch bond multi-purpose (MP) adhesive system.Materials and Methods: In this experimental study, sixty extracted caries free human molar teeth were randomly assigned into 4 groups of 15 each for shear bond strength. Variables were bonding agents, enamel and dentin. Twenty teeth assigned into 2 groups of 10 each were used for valuation of the micro leakage. Micro leakage and shear bond strength were performed according to ISO TR 11405. All data were analyzed with parametric and nonparametric tests according to their normality distribution. Also, Weibull distribution performed on data.Results: Data obtained from both micro leakage and shear bond strength tests showed no significant difference between the experimental bonding and Scotch bond MP bonding (P>0.05). Furthermore, there was no significant difference between the micro leakage of occlusal and gingival parts of both bondings (P>0.05).Conclusion: Experimental adhesive bonding showed acceptable results regarding micro leakage and shear bond strength. It may be concluded that the experimental dentin bonding had a comparable performance quality with that of commercial system.

Background and Aim: Due to the complications associated with fixation by Titanium screws and plates in Bilateral Sagittal Split Ramus Osteotomy (BSSRO) surgery, the use of resorb able polymers has been increasingly recommended. Since there are not enough studies on this issue, this study aimed to assess the most appropriate stress distribution in fixation with resorb able screws after BSSRO surgery by Finite Element Analysis (FEA).Materials and Methods: This experimental study was performed on simulated human mandible using Ansys and Catia softwares. The osteotomy line was applied to the simulated model and experimental loads of 75, 135 and 600 N were respectively exerted according to the natural direction of occlusal force. The distribution pattern of stress was assessed and compared for fixation with one resorb able screw, two resorb able screws in vertical pattern, two resorb able screws in horizontal pattern, three resorb able screws in L pattern and three resorb able screws in inverted backward L pattern using Ansys software. Results: Among the four simulated fixations, L pattern showed the highest primary stability. Two screws in vertical pattern were also associated with sufficient primary stability and less trauma and cost for patients. One screw did not provide enough stability under 600 N.Conclusion: Polymer-based resorb able screws (polyglycolic acid and D, L polylactide acid) provided satisfactory primary stability in BSSRO surgery.

Background and Aim: Sodium hypochlorite can remove the organic phase of the demineralized dentin and it produces direct resin bonding with hydroxyapatite crystals. Therefore, the hydrolytic degradation of collagen fibrils which might affect the bonding durability is removed. The aim of this study was to evaluate the effect of collagen fibrils removal by 10% NaOCl on dentin shear bond strength of two total etch and self-etch adhesive systems.Materials and Methods: Sixty extracted human premolar teeth were used in this study. Buccal surface of teeth were grounded until dentin was exposed. Then teeth were divided into four groups. According to dentin surface treatment, experimental groups were as follows: Group I: Single Bond (3M) according to manufacture instruction, Group II: 10% NaOCl+ Single bond (3M), Group III: Clearfil SE Bond (Kuraray) according to manufacture instruction, and Group IV: Clearfil SE Bond primer. After that, the specimens were immersed in 50% acetone solution for removing extra monomer. Then the specimens were rinsed and dried. 10% NaOCl was applied and finally adhesive was used. Then composite was bonded to the treated surfaces using a 4´2 mm cylindrical plastic mold. Specimens were thermocycled for 500 cycles (5-55oC). A shear load was employed by a universal testing machine with a cross head speed of 1mm/min. The data were analyzed for statistical significance with One-way ANOVA, Two-way ANOVA and Tukey HSD post-hoc tests.Results: The mean shear bond strengths of groups were as follows: Single Bond=16.8±4.2, Clearfil SE Bond=23.7±4.07, Single Bond+NaOCl=10.5±4.34, Clearfil SE Bond+NaOCl=23.3±3.65 MPa. Statistical analysis revealed that using 10% NaOCl significantly decreased the shear bond strength in Single Bond group (P=0.00), but caused no significant difference in the shear bond strength in Clearfil SE Bond group (P=0.99).Conclusion: Based on the results of this study, NaOCl treatment did not improve the bond strength in self-etch adhesive and caused a significant decrease in the bond strength of total etch adhesive system.

Background and Aim: Decreasing the hardness of dental restorative composites after curing in oral environment can influence their clinical durability. The aim of this study was to evaluate the effect of food-simulating liquids such as 25%, 50%, 75 % ethanol and 50 % heptane on surface hardness of two composites – (Gradia and P60) after curing and immersing time of 24 hours and 7 days.Materials and Methods: 45 specimens of each composite were prepared in a stainless steel mold with 6 mm diameter and 2 mm depth.5 specimens of each composite were tested for micro hardness immediately after curing as the control group. The other specimens of each composite were randomly divided into eight groups. Each specimen was immersed in one of the following solutions 25%, 50%, 75 % ethanol and 50 % heptane for either 24 hours or 7 days. Then the specimens were taken out of the solutions and washed and dried and transferred to the refrigerator until performing the test. In standard conditions, surface micro hardness of specimens was evaluated by the micro hardness device based on Vickers. The data were analyzed by one way ANOVA 3 way ANOVA and Tukey Post Hoc tests. The level of significance was set at p<0.05.Results: Surface hardness of P60 composite was higher than that of Gradia. An analysis of variance in gradia and p60 showed significant difference between the control and all the other groups (P<0.05) except the 25% ethanol (P=0.514). After 24 hours all the solutions had significant effect on Gradia (P<0.05) except 50% and 75% ethanol (P=0.793). After 7 days all the solutions had significant effect on Gradia except 50% and 25% ethanol (P=0.385) and 50% and 75% ethanol (P=0.150) According to P60 after both 24 hours and 7 days all the solutions had significant effect on the hardness.50 % heptane increased the hardness (P=0.00).75% ethanol significantly decreased the hardness (P=0.000) followed by 50% (P=0.001) and 25% ethanol (P=0.007).Conclusion: Based on the results of this study, the effect of time was not significant. P60 showed to be more resistant.75% ethanol had much more effect followed by 50% and 25% ethanol. Heptane increased the mean surface hardness.

Background and Aim: Impaction of maxillary cuspids is the most common after third molars with 1% to 3% prevalence. Localization of these impacted teeth may affect orthodontic or surgical treatment plan. Therefore, different techniques have been introduced to localize impacted canines. The present study was conducted to compare the accuracy of panoramic, tube shift and panoramic plus palpation in determination of the position of maxillary impacted canine.Materials and Methods: 47 patients (20 females, 27 males) with the age of more than 12 years (mean age of 25.4 years old) whom referred to Dental School, Tehran University of Medical Sciences, with at least one impacted maxillary canine included. An oral and maxillofacial radiologist localized impacted canine first by using panoramic then tube shift technique blindly. After that, an oral and maxillofacial surgeon localized the canine by panoramic and palpation of the area before surgery. Data obtained from radiologist and surgeon were compared with true location of canine after surgery. Statistical analysis was done using sensitivity and specificity.Results: Among total 47 impacted maxillary canines, 11 cases (23.4%) showed buccal impactions and 36 cases (76.6%) palatal impactions. Sensitivity (ability of technique to localize palatal impaction) of all of the techniques were same (100%) but specificity (ability of technique to localize buccal impaction) of tube shift (100%) was more than two others (0%).Conclusion: The tube shift technique was the most accurate technique to localize maxillary unerupted canines compared to the others. Due to the ability of panoramic and panoramic with palpation in prediction of palatal canine impactions and failure of these techniques to predict buccal impactions, both methods are not suitable in localization of impacted maxillary canines and they must be used as adjunctive techniques.

Background and Aim: The usage of free gingival grafts for vestibuloplasty is a routine procedure. The free gingival procedure requires harvesting the graft from a donor site which increases morbidity and the risk of surgical complications. In addition, adequate amount of donor tissue may not be available. Acceptable results of Alloderm application as a substitute for autogenous soft tissue grafts are: Not exposing the patient to an additional surgery, no donor site morbidity, unlimited availability, decreasing the bleeding during the surgery, decreasing the surgical complications, and better color match. The aim of this study was to evaluate the maintenance of the vestibular depth in vestibuloplasty with mucosal graft and Alloderm.Materials and Methods: Both methods of anterior mandibular vestibuloplasty by Clark, utilizing Alloderm and mucosal grafts, were employed in ten clinical cases. During the surgeries, half the prepared recipient sites received Alloderm, while the remaining half received auto grafts in a randomized fashion. Immediately, 1, 3, and 6 months postoperatively, the variables of graft rejection, depth of vestibule and the degree of relapse were evaluated. SPSS software was used for analysis of the data and the methods used for “statistical tests" were as follows: Friedman Method, Paired sample t-test, Smirnov-kolmogrove Method. (The statistical significance level was established at P-value<0.05).Results: The mean difference of the relapse measurements in both methods throughout the survey did not have significant predictive value (P>0.05). Similar results were achieved for the mean difference of depth of the vestibule.Conclusion: In patients undergoing Vestibuloplasty, Alloderm could be material of choice to be utilized as autogenic soft tissue grafts in pre-prosthesis procedures.

Background and Aim: The objective of this study was to measure and compare the tissue absorbed dose in thyroid gland, salivary glands, eye and skin in maxillofacial imaging with panoramic, conventional linear tomography, cone beam computed tomography (CBCT) and computed tomography (CT).Materials and Methods: Thermo luminescent dosimeters (TLD) were implanted in 14 sites of RANDO phantom to measure average tissue absorbed dose in thyroid gland, parotid glands, submandibular glands, sublingual gland, lenses and buccal skin. The Promax (PLANMECA, Helsinki, Finland) unit was selected for Panoramic, conventional linear tomography and cone beam computed tomography examinations and spiral Hispeed/Fxi (General Electric, USA) was selected for CT examination. The average tissue absorbed doses were used for the calculation of the equivalent and effective doses in each organ.Results: The average absorbed dose for panoramic ranged from 0.038 mGY (Buccal skin) to 0.308 mGY (submandibular gland), linear tomography ranged from 0.048 mGY (Lens) to 0.510 mGY (submandibular gland), CBCT ranged from 0.322 mGY (thyroid glad) to 1.144 mGY (parotid gland) and in CT ranged from 2.495 mGY (sublingual gland) to 3.424 mGY (submandibular gland). Total effective dose in CBCT is 5 times greater than panoramic and 4 times greater than linear tomography, and in CT, 30 and 22 times greater than panoramic and linear tomography, respectively. Total effective dose in CT is 6 times greater than CBCT.Conclusion: For obtaining 3-dimensional (3D) information in maxillofacial region, CBCT delivers the lower dose than CT, and should be preferred over a medical CT imaging. Furthermore, during maxillofacial imaging, salivary glands receive the highest dose of radiation.

Background and Aim: Extracted teeth used in preclinic should be disinfected. The aim of this study was to evaluate the effects of some disinfectants on microorganisms cultured from pulp chamber of extracted teeth.Materials and Methods: In this experimental study 54 intact human teeth were collected. After access cavity preparation, 108 B. streothermophillus endospors were inoculated into pulp chamber. Then cavities were sealed with a temporary restorative material. Teeth were divided into 5 groups of 10 each. The teeth were then stored in these disinfectants: 5.25% hypochlorite sodium, 5% Microten, 5% Deconex, 2% Glutaraldehyd, and 10% Formalin for 48 hours. Two teeth were autoclaved as negative controls and two were stored in normal saline as positive controls. The teeth were then sectioned in cervical area and cultured in Trypticase Soy Broth. After three days turbidity in tubes was evaluated. Statistical analysis was done by Fisher's exact test.Results: None of these solutions were able to prevent microorganism growth in all samples, however, Formalin was better in six cases than that of other disinfectants. Differences between these five groups were not statistically significant (P=0.384).Conclusion: Sterilization of the teeth with autoclave is the only absolute method for disinfecting the root canals of extracted teeth and disinfectants are not reliable for this purpose.

Background and Aim: In recent decades many guidelines has been conducted by radiation protection organizations about radiation protection in dentistry. This study was designed to evaluate the observance of these guidelines in educational clinics of all dental schools in Iran.Materials and Methods: In this cross-sectional study a questionnaire based on National Radiation Protection guidelines was conducted. The questionnaire consisted of questions about radiation protection principles in dental radiography that is needed for patients and personnel protection and quality control of radiological instruments. The questionnaires were completed by the responsible person of each radiology department of dental schools (18 schools). After gathering the data, the results were compared with radiation protection standards.Results: There was proper condition in the case of the existence of radiation protection facilities, such as lead apron, thyroid shield and lead impacted walls. However, personnel rarely use these facilities. Usage of high speed films and existence of automatic processor in dental schools was an appreciable point. The main problem was related to the lack of regular quality control programs.Conclusion: The observance of radiation protection regulations in radiology departments of dental schools was proper. But majority of departments had no regular quality control programs, and the use of digital systems in dental radiography was not common.

Background and Aim: School health workers have an important role in education and prevention of common oral and dental diseases. An organized program can be helpful in training and shaping the proper behavior. This study has evaluated the knowledge, attitude and practice of schools health workers in Tabriz about oral and dental health in 2007-2008.Materials and Methods: This cross-sectional and descriptive study was performed in primary schools in Tabriz. Questionnaires were sent to the schools that had health workers. Levels of the knowledge, attitude and practice of the health workers who had answered this questionnaire were evaluated. SPSS software and independent T-Test and Paired- Sample T-Test were used for analyzing the results.Results: Fifty eight out of 64 school health workers were women. Mean age of school health workers was 45 years. Forty four of school health workers had passed special course about oral health and dental health.49 of them had passed special educational course the mean of acquired knowledge score was 6.77 out of 10 and women’s scores were significantly higher. Also women had more work experience than men. The mean of acquired attitude and practice scores were 7.42 and 7.14 out of 10, respectively.Conclusion: Findings show that performing of the educational courses during work and experience has an effective role in the scales of the health workers. Progress in this situation can be achieved by retraining programs and accessible pamphlets.