Journal of Mashhad Dental School
Year:2010 | Volume:34 | Issue:1 (72)|Papers Count:12

Introduction: Estimating the width of maxillary central incisor may be difficult when an artificial tooth is selected for edentulous patients. One of the ways to choose a good size for this tooth is using extra-oral landmarks in face. This study examined the relationship between mesiodistal (MD) width of maxillary central incisor and interpupillary distance (IPD) which is a stable landmark in lifetime.Materials & Methods: In this descriptive cross sectional study, 100 Iranian subjects (50 males and 50 females, mean age 23±6.3 years) without ocular and dental deformities were selected. The MD width of upper central incisor and IPD were measured three times for each subject using Boley Gauge with 0.1 mm accuracy and then, the mean values were calculated. A mathematic equation to evaluate correlation between MD width of upper central incisor and IPD was calculated and then examined in the other 20 subjects (10 males and 10 females, mean age 24.8±1.56 years) by statistically comparing the difference between calculated and real size of tooth with paired t-test. Results: In the first stage, these results were obtained: the mean MD width of maxillary central incisor was 8.6±0.4mm and the mean IPD was 62.1±2.8mm. The correlation coefficient between these two parameters was r=0.446 (P<0.05). The calculated equations for this relationship were: (Y=0.15x–0.0002x² in men and Y=0.22x–0.0014x² in women, “y” represents MD width of maxillary central incisor and “x” represents IPD). In the second stage, these equations were applicable in 90% of subjects (18 from 20 subjects) with 0.5mm of accuracy. Conclusion: IPD is a good landmark for estimating MD width of maxillary central incisor in edentulous patients.

Introduction: Gingivitis is a multifactorial disease in which host immune system and genetic factors have an important role in its pathogenesis. Genetic polymorphisms in cytokines and their receptors have been proposed as potential markers for periodontal disease. Recent studies have suggested IL-10 gene polymorphism to be involved with gingivitis in children. The aim of this study was to evaluate IL-10 gene polymorphism association with gingivitis in 8-12 year old children.Materials & Methods: In this case-control study, approved by Hamadan University of Medical Sciences, 100 children were divided into two groups of 50 controls and cases, according to the periodontal indices. An epithelial sample from buccal mucosa of each individual was prepared and DNA was extracted by Miller's salting out method. Then mutation at position - 1082 (H/L), -819 (C/T) in the IL-10 gene was detected by PCR-RFLP method and the data were analyzed by chi-square test. Results: Results showed that at position-1082, distribution of H allele in case group was 34% and for control group it was 24% (P=0.27). Distribution of L allele in two groups was 98% (P=1). Callele distribution in-819 position in case group was 36% and for the control group was 42% (P=0.54) and T allele distribution for case group was 94% and for control group was 90% (P=0.71). There was no significant difference in genotype distribution between the groups. Conclusion: This study suggests that there is no correlation between IL-10 polymorphism with gingivitis in 8-12 year old children.

Introduction: Third molars have the highest prevalence of congenital missing. Missing or presence of third molars is one of the key factors that can change the orthodontic, pediatric and surgical graft treatment. The aim of this study was to evaluate the frequency and risk factors of congenitally missing of third molars in 14-25 year old patients in Mashhad dental school.Materials & Methods: In this cross-sectional analytical study, panoramic radiographs of 120 14-25 year old patients evaluated in 2006 and the frequency of congenital missing of third molars and risk factors such as gender, hypodontia and family history was checked. The data were analyzed by Mann-Whitney and Wilcoxon tests. Results: 1. Missing of third molars was 11.2% prevalent. No statistical difference was found between male and female. 2. In patients with third molar agenesis, 60% had agenesis in other permanent teeth and 7.5% had anomaly in permanent teeth. 3. In 23.3% of patients with small size of maxilla, third molar agenesis was detected. 4. No statistical difference was found between maxilla & mandible or right & left sides in third molar agenesis. Conclusion: Frequency of congenitally missing of third molar in our society was similar to other societies and a direct relationship was found between either small size of the maxilla, anomaly or agenesis in other teeth, and agenesis of third molar.

Introduction: Several studies have been done on the effect of Thalassemia Major on craniofacial skeleton. Its effect on dental development however, has rarely been studied. The aim of this study was to evaluate dental development as well as prevalence of dental anomalies in patients with beta Talassemia Major in comparison with control group.Materials & Methods: In this case control study, apprived by ethical committee of Shiraz University of Medical Sciences, panoramic radiographs of 120 Talassemic patients were assessed. The case group consisted of 68 males and 52 females ranging in age from 8-19 with mean age of 12.98±2.66 years. 120 control individuals matched for age and sex. Radiographs were assessed for prevalence of dental anomalies and dental age. Fisher's exact test was used to compare prevalence of dental anomalies between case and control groups. Dental and chronological ages were compared using paired t-test. Independent t-test was used to compare dental ages between case and control groups.Results: Microdontia, missing, tarudontism and short spiky roots were more prevalent in Talassemic patients. There was not either a significant difference between the mean of dental and chronological ages in Talassemic patients or between mean of dental age of Talassemia and control individuals.Conclusion: According to the present study, dental anomalies are more common in Thalassemic patients in comparison with normal individuals. Dental developments as well as time of eruption however, were not affected by Thalassemia.

Introduction: Conventional radiographs are usually used for diagnosis of dental impaction, but these radiographs do not provide the dentist with complete information in 3rd dimension. In this situation, tomography or computed tomography is used for acquisition of more detailed information for localization of impacted tooth. The aim of this study was to evaluate the efficiency of tomography in localization of impacted maxillary tooth. Materials & Methods: In this descriptive study, nine orthodontic patients (5 males, 4 females, mean age 16.2 Years) with 12 impacted teeth (canine or supernumerary teeth) with diagnostically difficult impacted maxillary tooth who had undergone spiral tomography, were followed and received surgical treatment. Spiral tomography (2mm thickness with 1 and 3mm interval in mesial and distal directions) from marked point by cranex tome sordex machine (Helsinki, Finland) and Digora PSP (photostimulable phosphorus plates) were provided. After image transfer to computer, tomographic measurements were corrected by an enlargement factor×1.5. On the images, location of coronal portion of impacted tooth and the distance between tip or prominent point of coronal portion to tangent line of crestal bone in digital program to 0.1 mm accuracy was measured. The results of radiographic measurements were compared with surgical results. Results: There was a 100% agreement between tomographic and surgical findings in localization of impacted teeth. The minimum and maximum differances between measurements of surgery and tomography were 0 and 1.5 mm respectively. The mean difference was 0.6 mm.Conclusion: Spiral tomography gives us additional information about location of impacted tooth compared with conventional radiography. This method facilitates the localization of impacted tooth and also measures the distance between impacted tooth and alveolar crest with minimum difference.

Introduction: Mucoepidermoid carcinoma (MEC) and Adenoid cystic carcinoma (AdCC) are the most common salivary malignancies, and their biologic behavior has not been completely determined. Perineural and vascular invasion are effective on the biologic behavior. Therefore, the aim of this study was to evaluate perineural and vascular invasion in AdCC and MEC of major and minor salivary glands by expression of neural markers such as S-100, GFAP, NCAM and vascular marker such as PECAM-1.Materials & Methods: Formalin-fixed and parafin-embedded tissue sections of 20 cases of AdCC and 20 cases of MEC were immunohistochemically analyzed for the presence of S-100, GFAP, NCAM, PECAM-1by biotin streptavidin Novolink polymer procedure after antigen retrieval. Data were analyzed by Mann-Whitney and Fisher's exact tests.Results: All AdCCs and MECs were positive (+1®+4) for S-100. S-100 positive frequency and severity ratios in AdCC were higher than MEC (P<0.05). Two specimens of AdCC and nine specimens of MEC were positive (+1) for GFAP. GFAP positive frequency and severity ratios in MEC were higher than AdCC (P=0.013). All AdCCs and MECs were negative for NCAM and PECAM-1 (P=1).Conclusion: The presence of S-100 and GFAP in AdCC and MEC probably indicates the role of myoepithelial cells in histogenesis of theses tumors. Considering that perineural invasion in salivary gland tumors has been ascribed to myoepithelial cell, this characteristic does not necessarily indicate the poor prognosis of these tumors. As a result, according to the lack of expression of NCAM and PECAM-1 in AdCC and MEC and other findings, perineural and vascular invasion in these tumors do not appear to be different significantly.

Introduction: Today, many controversies about the most beneficial design of distal extension base partial dentures exist. Although the purpose is minimizing the stress on abutment teeth and supporting tissues, different results and theories have been reported. The purpose of this study was to analyze the stress applied on distal extended abutment in different types of conventional clasp designs.Materials & Methods: The skull of a 42 year old man was CT-Scanned with 0.6mm sections and data were used to make a 3D model of the mandible in mimics software. Then a frame work of Kenedy's class I partial denture with 3 different clasp designs (Aker's, Bar type and combination) was designed on this model. Occlusal force was applied on the saddle and stress was measured with a finite element method analysis using "cosmos works 2008" soft ware. Results: In Aker's design, stress concentration pattern showed applying distal load on abutment. The combination clasp presented identical pattern, but stress concentration was significantly lower than that of the Aker's. On the contrary, stress concentration pattern showed that bar type clasp applied mesial load to abutment. In all designs, buccal load was applied from partial denture to abutment in buccolingual dimension.Conclusion: Aker's clasp in distal extension base partial dentures applies extra stress on distal extended abutment in unfavorable (distal) direction, which is greater than tooth tolerance.

Introduction: Lateral ridge augmentations are traditionally performed using autogenous bone grafts. However, the bone harvesting procedure, whether intra orally or extra orally, is accompanied by patient morbidity. So, applying bone substitute has been suggested. The aim of the present study was to compare the stability of implants in ridges augmented with mineralized cortical cancellous allograft blocks with implants in native bone using Resonance Frequency Analysis.Materials & Methods: In this clinical trial study, approved by ethical committee of Mashhad university of Medical Sciences, nine subjects with insufficient ridge width were selected. Their ridges were augmented with mineralized cortical cancellous allograft blocks. After 6 months, implants were inserted. In control group, 9 subjects with sufficient ridge width were selected. Implants were inserted in the same place as the test group. ISQ was used for measurement of implants stability on third and sixth month after implants placement. Data were analyzed by paired and two sample t tests using SPSS version 15 software.Results: During the study period, two implants in allograft group failed. In the test group, the difference between mean ISQ at third and sixth month was statistically significant (P=0.008), but in the control group, it was not significant (P=0.065). At third month, the mean ISQ between 2 groups was not statistically significant (P=0.317), but at sixth month, the mean ISQ in control group was significantly higher than the test group (P=0.000).Conclusion: The mean ISQ in both groups were enough to load the implants. This means that mineralized cortical cancellous blocks could be used as a scaffold for growth of the bone and ridge augmentation for implant placement.

Introduction: The purpose of this study was to evaluate the accuracy of cephalometric measurements obtained from digital tracing software compared with equivalent hand traced measurements to determine the more accurate and useful method.Materials & Methods: Digital and analogue radiographic images of 30 orthodontic patients were obtained through Sandwich technique (a conventional radiographic film and a digital image are produced simultaneously). Fifteen cephalometric landmarks were identified and 10 linear and angular measurements calculated, both manually and with digital tracing software. Measurement errors were assessed for each method by duplicating measurements of 15 randomly selected radiographs using Pearson’s correlation coefficient. A paired t- test was used to detect differences between the manual and digital methods.Results: Differences between the two methods for SNA, U1-L1and Wit’s appraisal were statistically significant (P<0.05). In error measurements, an overall greater variability in the digital cephalometric measurements was found.Conclusion: The two tracing methods provided similar clinical results; therefore, efficient digital cephalometric software could be reliably chosen as a routine diagnostic tool due to its advantages (lower exposure to X-ray, image development bypass, image quality enhancement through computer).

Introduction: Tooth extraction is one of the most common and necessary measures that is done in dental practice. No doubt, it is necessary for each dentist to be familiar with possible complications of this procedure. The purpose of this report was to introduce a case of accidental replacement of mandibular third molar into the infratemporal space, which is one of the wisdom tooth surgery complications.Results: A 23-year old woman with severe limitation of mouth opening was referred to Mashhad dental school by a dentist. In the radiographic evaluation of the mandible, presence of wisdom tooth in the infratemporal space was evident. The displaced tooth caused significant limitation in mouth opening due to mechanical intraction with cronoid process. Tooth removal was done in operation room under general anesthesia and limitation in mouth opening was improved.Conclusion: Awareness of possible complications of removing teeth is a basic principle. Any dentist should be familiar with the possible complications and how to manage it.