مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال شانزدهم شماره 1 (پیاپی 34، بهار 1382)

Statement of Problem: The Prevalence of HBsAg, among patients with Down Syndrome (DS) has been reported higher than normal population. Living in institutes, comparing to home, leads to higher probability of HBsAg prevalence. The purpose of the present study was to determine HBsAg prevalence in patients with DS and compare it with other mentally retarded patients with similar conditions, and also with healthy population in Iran. One hundred patients, with average age of 12 years, living in five institutes inTehran, were chosen. Children with DS and other mentally retarded children were considered as the first and second groups, respectively (50 members in each group). Blood samples were taken and tested (ELLSA) to determine HBsAg and HBsAb titre. For statistical analysis, Chi- Square test was used. HBsAg was positive in 8% and 4% of DS and MR groups, respectively. HBsAb was seen in 25% of DS, comparing to 32% of MR. The prevalence of HBsAg in retarded patients living in institutes was higher than normal population of Iran (less than 3%), which was not statistically significant. Consideration of sterilization principles and infection control upon dental operations, in these centers, are necessary. It is also suggested that these children, as a high- risk population, should be vaccinated against hepatitis B.

Statement of Problem: Microleakage presents the major cause for restorations failure in the oral cavity resulting in postoperative sensitivity, pulp irritation and secondary caries formation. The aim of this study was to compare two dentinal adhesive systems of fifth generation and copalite varnish in reducing microleakage of amalgam restorations in primary teeth. In this in-vitro study, 100 class V amalgam restorations were prepared on the buccal or lingual surfaces of primary molar and canine teeth. Samples were randomly divided into four groups (25 samples each). No liner was used for the first group and the second group restorations were lined with copalite varnish. Two dentin adhesives, called Syntac C and Single Bond, were used for the third and fourth groups, respectively. At the next stage, the samples were immersed in 5% fuschin solution for 24 hours, then sectioned buccolingually, and examined under a stereomicroscope for microleakage evaluation. There was a significant difference between four groups statistically (PO.000I), Comparing four groups, the first and fourth ones, demonstrated the most and the least microleakage, respectively. The present study showed that new dentinal adhesive systems caused microleakage reduction in amalgam restorations of primary teeth.

Statement of Problem: Anthropometry is applied in medical professions such as maxillofacial surgery,growth and development studies, plastic surgery, bioengineering and non- medical branches such as like shoe- making and eye- glasses industries. The aim of the present study was to determine facial and cranial ratios among Isfahan young adults. A study was done randomly on 200 boys and 200 girls, from among Isfahan young adults, with normal face patterns. Facial and cranial ratios, according to sex, were estimated and compared. The results of this study were compared with Canadian anthropometric findings by Farkas.There was no significant difference in cranial width between boys and girls but cranial length and all facial parameters (Int, cant, go-go, zy- zy, ch-ch, Ala-Ala, low.lip, Up.Iip, Sn.gn, Sto.gn, N.sto, Ngn)were greater in boys than girls. Cranial index and, , ", Cl ratios were greater in n - gn zy - zy zy - zy zy - zy. .. slo-go sn-gn sto-gn slo-gn sto-gn. .. _girls, however, -, -,, , were greater in boys, There was no significant go-go n- gn n- gn n- sto sn - gn difference about facial index between boys and girls. Comparing facial parameters between Iranian and Canadian races, low. lip, Ala-Ala and go- go were greater among Iranians, however, Int cant, Up. lip. N.gn, ch- ch, zy-zy showed a greater size among Canadians. Sn-gn ratio was greater in Canadian girls, but there was no significant difference between Iranian and Canadian boys in this regard. " " s", s° " 8°, " ~ s °, g° " 8°, ^-- ratios were greater among Isfahanian boys and girls,zy-zy zy-zy zy-zy n - gn zy-zy however, J ° ~ g", 5 ° " 8" / ° " s" ratios were greater among Canadians. Regarding 5"~g" ratio, no n- sto sn- gn n~ gn n- gn significant difference was observed between Canadian and Isfahanian girls. Considering the significant difference in the facial and cranial anthropologic ratios and sizes, among Canadian and Isfahanian young adults, the results obtained from Canadian race, should not be applied as a criteria for Iranian surgical and dental treatment plans. Due to the wide racial combinations in Iran, more studies, with wider variations, should be conducted among different Iranian races.

Statement of Problem: Central crown fractures of deciduous and permanent teeth lead to unfavorable psychological effects on both children and their parents. Moreover, it can cause malocclusion. So,recognizing tooth fracture reasons plays an important role to prevent its side effects. The aim of this study was to investigate the reason's of permanent central crown fractures in (7-12)years old children. Records of 218 children, with at least one central tooth fracture, referred to pediatric department of faculty of dentistry of Tehran University of Medical Sciences, from 1999 to 2000, were studied. All the related information about fracture such as: reason, location, time, type of occlusion, and type of fracture were recorded. It was found that falling down (45.4%) and having contact with external objects (21.6%) were the main reasons for permanent centrals fractures. The mean age of these children was 9.78±1.24 and 63.3% of them were boys. It should be noted that 41.3% of them had unsupported lip. The highest rate of fractures belonged to upper centrals. Based on Ellis classification, most fractures were of degree 3 (52.7%). There was no significant relationship between overbite and overjet with the degree of fracture (P<0.05). Dental skeletal malocclusions such as CI II, Div I, central incisors protrusion and developmental defects of tooth structure should be considered as determinant factors in tooth crown fractures.

Statement of Problem: Cephalometric findings are of high importance in making decision about orthodontic treatment plans and orthognathic surgeries. Natural head position (NHP) is considered as a useful and exact radiographic technique. The aim of the present study was to compare two techniques, namely Standard and NHP, in lateral cephalometry. In this cross- sectional study, performed in Shiraz. 138 randomly selected students {70 males. and 68 females), age ranging from (13-15). were evaluated clinically and radiographically. None of them had a history of orthodontic treatment, head and face fracture or surgical operations. Lateral cephalograms were taken in both standard and natural head position techniques, for each student. For statistical analysis, l-lest for paired samples, was done. This study showed that in anterior-posterior dimension, among angles with significant differences in two techniques, those of standard one were more reliable, whereas in vertical dimension.statistical differences showed natural technique as more useful one. Due to the fact that natural cephalometry requires more patient cooperation, more time and a higher complex technique, it is not suggested, except when different clinical and cepholomeiric findings are observed.

Statement Problem: A few studies have been conducted about bioglass posts. The aim of this study was to compare bioglass posts with prefabricated metallic posts in clinical performance of extensive composite restorations for anterior endodontically treated teeth. Sixty endodontocally maxillary anterior teeth, with horizontally or vertically destruction, were selected. Teeth were divided into two groups based on the kind of post: Metallic prefabricated parapost and bioglass post. Each group was divided into three subgroups based on anterior bite: normal, deep bite and edge to edge. Gutta-percha was removed from 2/3 of canal length for parapost and 1/3 for bioglass post. After etching with phosphoric-acid (37%) and applying dentine bonding syntac, Duo cement was used for the adhesion of bioglass post and a self cured composite (Degufil) for parapost. Restoration was done with a hybrid composite (Heliomolar). Follow up studies, radio-graphically and clinically, were done every three months for a 1.5-year period. Exact Fisher and Pearson tests were used for data analysis. Apical lesion was not observed in any of the radiographs. Post seal was increased by resin cement and dentin bonding agent. Post type did not significantly affect on the clinical success rate of the restorations. The retention of restoration, for both posts, was the same. Crown destruction had no significant effect on success rate. The type of anterior bite had a significant effect on success rate, as the total 6.6% failure rate was related to the patients with anterior deep bite. It is suggested to use metallic paraposts and bioglass posts, in extensive composite restorations for patients with deep-bite, more conservatively.

Statement of Problem: The main objective of endodontic therapy is chemomechanical cleansing of entire pulp cavity and its complete obturation with an inert material. During this procedure, the failure of detection and inadequate cleaning of a canal will result in failed endodontic therapy. Therefore, the dentist must have enough knowledge of root canal morphology to treat a tooth successfully. The aim of this study was to determine the number and type of root canals of mandibular incisor teeth. In order to do this in-vitro, descriptive study, 68 non-carious mandibular incisor teethj collected from different clinics in Yazd, were immersed in indian ink, decalcified and cleared. It was found that 55.9% of the teeth had two separate canals that in 5.5% of them, the canals merged before' apical foramen. In 4.4% of these samples, two separate canals existed along the whole root. Considering high percentage of two canals in lower mandibular incisors, during access preparation, more attempts in detection of the second canal, is emphasized.

Statement of Problem: Eugenol is the most important chemical compound of the clove tree (Eugenia aryophylata) extract. That is widely used in dentistry as a bactericidal and pain relieving agent. The aim of the current study was to evaluate the antinociceptive effect of local and systemic administration of eugenol by formalin test in rats. In this research, 56 male Wistar rats, weighing 230±20 g were divided into seven groups (n=8). Ten minutes before formalin test, different doses of eugenol (12.5,25,50 mg /in groups 2,3,4 respectively) were injected to the right hind paw of the rats subcutaneously. In- group 5 eugnol (50 mg) was. injected to the contralateral hind paw. In group 6 eugenol (100 mg/ kg) and control group (group 7), equal volume of norma! saline was injected intraperitonealy. The minutes 0-5 and 16-60 were considered as acute and chronic phases of pain in the formalin test, respectively. Data were statistically analyzed by ANOVA and Tukey's tests. The results showed that local injection of eugenol to the same paw receiving formalin caused a decrease of nociception in both acute and chronic phases of formalin test (PO.005). However, in the group that eugenol (50mg/ kg) was injected to the contralateral paw, no significant differences were observed in the pain score in comparison with the control group. Intraperitoneal injection of eugenol (lOOmg/kg) did not reduce the nociception in the acute phase, but it caused a significant decrease of nociception in tonic phase (PO.00I). It was concluded that eugenol, as a local anesthetic drug not only inhibits nociceptive impulse conduction on the peripheral pain fibers, but also centrally reduce chronic pain.

Statement of Problem: Different materials have been suggested for endodontic surgeries. One of the most important characteristics of filling materials is their biocompatibiiity. The aim of this research was to evaluate the biocompatibiiity of four different root end filling materials. In this study, 20 male Guineanpigs from English short hair breed, weighing 600-700 grams, were selected. The animals were classified into two groups. In the first group, amalgam and composite and in the second group MTA and Glass Ionomer were examined. The testing materials were shaped into cylindrical form with 1 mm diameter and 1.5 mm height. After general anesthesia, twocavities with 1mm diameter and 2 mm depth were prepared in parasymphysis area of animal jaw. The prepared materials were implanted in these cavities and the flaps were sutured. After 80 days, the animals were sacrificed and the dissected bones, with implanted materials inside them, were sent for histological evaluation. The histological findings were statistically analysed by Kruskal Wallis and xtests. No significant differences were shown in the degree of inflammation, the type of inflammatory cells adjacent to the tested materials and the type of tissue response, induced in the vicinity of these four materials during 80 days. Regarding biocompatibiiity, there was no significant difference among amalgam,composite, MTA and glass Ionomer in endodontic surgeries.

Statement of Problem: One of the important indications for the extraction of mandibular impacted third molar is to preserve the periodontal health of the adjacent second molar from the destructive effects of plaque accumulation, acute and chronic inflammation. The purpose of this study was to determine the effect of mandibular third molar surgery on the PDL of the adjacent molar. Thirty patients, referred to the department of maxillofacial surgery, Tehran University of Medical Sciences, were selected, based on the desirable conditions. They had no history of systemic diseases and their adjacent molar was healthy. Probing depth (PD) at seven points and attachment level (AL) at three points were measured preoperatively. Standardized periapical radiographics were taken regularly for all patients. All the above-mentioned procedures repeated after three months of surgery. Findings were analyzed by Paired t-test. A significant difference in probing depth (PD) was observed before and after surgery, meaning that probing depth decreased after mandibular third molar surgery. Attachment level was also decreased post operatively moreover. Intrabony defects (IBD) showed healing after surgery. Considering the limitations of the present study, impacted third molar surgery is suggested to prevent periodontal problems of the adjacent molar.