JOURNAL OF ISLAMIC DENTAL ASSOCIATION OF IRAN (MAJALLAH-I-DANDANPIZISHKI)
Year:2005 | Volume:16 | Issue:4 (52)|Papers Count:14

Background and aim: One of the most important problems in disinfecting alginate impressions is the dimensional changes caused by hydrocolloid nature of alginate. The aim of this study was to determine and compare the dimensional changes of two irreversible hydrocolloid impression materials (Iralgin- Alginoplast) disinfected by immersion in sodium hypochlorite solution.Materials and Methods: One metal model consisting of one platform and two partial conical dies was made and- 80 impressions were then prepared using two kinds of alginate impressions materials. The impressions were divided into four groups. In groups 1 and 3, impressions were first rinsed for 15 seconds and immersed in 0.525% sodium hypochlorite solution and finality were poured by type III dental stone. In groups 2 and 4, impressions made by these two materials were only rinsed by tap water for 15 seconds and kept in 10% moisture for another 10 minutes and then were, poured by type III dental stone. Different dimensions of samples in four groups were measured by digital caliper and compared using variance analysis and Duncan tests.Results: Diameters, heights and outer distances of all samples showed significant differences with the metal model (P=0.049), however; inner distances did not have any significant difference (P=0.269).Moreover, significant differences, in diameter and height, were found between case and control groups.Conclusion: In all four groups, diameters and outer distances increased and heights decreased compared to the metal model which are in agreement with the similar studies. Ali such changes were estimated less in Iralgin than Alginoplast.

Background and aim: Considering slight asymmetry between the left and right sizes of body along with the right and left sides of the face, the goal of this study was to measure and compare the total size of teeth in dental arches among high school students with normal occlusion.Materials and Methods: In this cross-sectional study, 60 samples (30 females and 30 males), age ranging from 16 to 18 years old, were selected among mashhad high school students based on random cluster sampling method. Data were collected through direct observation, impressions, preparing and measuring study models using an informational form. Mesiodistal widths of 1440 teeth, from the first molar in one side to the other in another side, were measured and collected in each quadrant. Data were subjected to SPSS software, Paired t-test and t-test for independent groups.Results: The average of total teeth size was as follows:1. Upper right side in boys was smaller than the left but the difference was not significant (P.V=0.82).2. Upper right side in girls, the same as boys, was smaller than the left but the difference was not significant (P.V=0.125).3. Lower jaw of boys was larger in the right side than the left but the difference was not significant (P.V=0.456).4. Lower jaw of girls was larger in the right side than the left but the difference was not significant (P.V=0.125).5. Total size of teeth of the upper right side in boys was larger than girls and the difference was significant (P.V =0.003).6. Total size of teeth of the upper left side in boys was larger than girls and the difference was significant (P.V=0.002).7. Total size of teeth in the lower right side in boys was larger than girls and the difference was significant (P.V=0.039).8. Total size of teeth in the lower left side in boys was larger than girls and the difference was significant (P.V =0.021).9. Total size of teeth in the upper jaw (right & left) in boys (91.37mm) was larger than girls (88.65mm) and the difference was significant (P.V=0.005).10. Total size of teeth in the lower jaw (right & left) in boys (84.4mm) was larger than girls (81.17mm) and the difference was significant (P.V=0.000).Conclusion: Total size of teeth, in the right and left sides, was not symmetric in both genders but the differences were not significant.

Background and aim: Finite element method is one of the highly precise methods to evaluate periodontal responses to orthodontic forces. The goal of the present study was to investigate the PDL response of anterior maxillary teeth (central, lateral, canine) during the application of intrusive forces using FEM.Materials and Methods: Solid works software was used to translate bidimensional images of the mentioned maxillary teeth into tridimensional ones. Then, PDL and alveolar bone were simulated around teeth and anterior teeth were positioned in an ideal arch with appropriate tip and torque and rectangular wire was placed rigidly on labial surfaces of teeth.These models were then modified to "Finite element model" by MSC-NASTRAN software. Intrusive forces were applied mesially on the anterior wire and induced stresses were analyzed by MSC-PATRAN. Results: The maximum stress was observed in the PDL of lateral incisors (2.53x10-3N/mm2) and the minimum stress was in the PDL of canines (9.07.x10-5N/mm2).Conclusion: Applying the intrusive forces in midline maximum stresses were focused on the apical part of lateral incisor and the minimum stresses were in the apically third of canine.

Background and aim: Mechanical fracture is a common cause for the failure of three-unit dental bridges, particularly the all-ceramic ones.The goal of the present study was to evaluate the effects of convergent angles of the abutments on the peak and distribution of mechanical stresses within the prosthesis and at the restoration abutment interface of a three-unit all-ceramic bridge using finite element method.Materials and Methods: The cloud points of three-D geometrical data of the second premolar and first and second molar teeth were obtaind using ATOS Scanner system and utilized for the reconstruction of a surface model of the three-unit bridge in CATIA software. Data were than transferred to I-DEAS software for mesh generation and finite element analysis. Two EF models were developed with convergent angles corresponding to the up and low defined range including 171900 and 168700 tetraherdal solid four-node elements, respectively.The models were subjected to two different prosthesis materials and three different load cases.Results: The maximum tensile stresses occurred on the gingival surface of the second premolar retainer and at the tooth/restoration interface on the marginal distal surface of the second molar abutment. The peak tensile stress was relatively lower for the model with the higher convergent angle but the difference was not significant. Changing the prosthesis material from IE2 to Dicor decreased the stresses within the prosthesis.Conclusion: Higher safety factor was found for IE2 due to its higher mechanical strength. Moreover, it was proved that load condition played an important role on the mechanical stress observed.

Background and aim: Acrylic resins are nowadays widely used in denture teeth and denture bases. The quality of these materials is mostly judged based on their physical-mechanical and chemical properties. The goal of this study was to compare the bonding strengths of Ideal-Makoo, Acrydent, Acradent and Ivoclar denture teeth with acrylic bases according to ISO 3336 standard.Materials and Methods: In order to compare different groups based on the standards, six anterior teeth of each set should be evaluated. Following samples comparison with the standards, the number of samples should be increased. Totally, 120 Samples were examined in the present study (n=30). Having the samples being fixed on the mold, tensile bond strength test was performed using universal testing machine (made By HOUNSFIELD. H 10 KS company). The fracture force was recorded and analysed by one-way ANOV A test.Results: The average bonding strength of most of the teeth was within the standard range and could fulfill patients' needs. According to ANOVA analysis (P=0.049), there were significant differences in the applied forces between four groups. Ivoclar showed the minimum force.Conclusion: The mean tensile forces of Iranian teeth were similar and almost 34% more than Ivoclar teeth.

Background and aim: Tensile bond strength of endodontic sealers to dentin is an indicative of sealer's adhesion to dentin. Due to the fact that Gutta-percha is not bonded to dentin walls, the adhesion of a root canal sealer to dentin is an important issue in endodontics. The goal of this study was to compare the tensile bond strength of two sealers, AH26 and Dorifill, with dentin.Materials and Methods: In this experimental study, 30 extracted human first and second molars, with no occlusal carries, were stored in 0.9% Nacl. The enamel was removed 1mm below the central occlusal groove. The roots were cut at 2mm below the CEJ. Wire hooks, made of orthodontic wire (0.5mm), were fixed to dentin surfaces and sealers.Aluminum cylinders were used to place sealer on the dentin surface and stabalized with two drops of wax. Two groups of sealers (AH26, Dorifill) were placed within the cylinders (n=15). The lower end of the wire hook was lowered into the soft unset sealer. After 24 hours, wax drops were removed and each specimen was tested by zwick tester at the speed of 2mm/min. Data were subjected to Independenl samples t-test.Results: The mean tensile bond strength values were 1.855±0.383Mpa for AH26and 0.135±0.04 Mpa for Dorifill attributing higher tensile bond strength to AH26 than Dorifill.Conclusion: Applying AH26 in root canal therapy would be more successful than dorifill.

Background and aim: In dental radiography, there are specific potentials to transmit infection. The goal of this research was to investigate radiographic films and tubes microbiologically in private and pudic dental radiographic centres in the city of Yazd.Materials and Methods: In this cross-sectional descriptive study (2001), all 13 public and private centers with totally 21 dental radiography machines were investigated. First, sample was collected from different areas of radiography tubes and films' covers by a sterile wetswap. All samples were kept in Tayoglycolate culture media and then put in 37°C incubator in microbiology laboratory. The cloudiness was checked every 24 hours. Data were analyzed using Extended Fisher test.Results: In samples collected from public radiography centers, microbial infections with pseudomonas aeruginosa, Staphylococcus epidermidis, Aspergillus niger and alkagenous were detected probably resulted from hospital infections and healthy carries among hospital personnel.In private centers infections with microbes such as Neisseria sicca, Staphylococcus epidermidis and Bacillus subtilis were detected, a probable consequence of normal flora in the environment.Films' covers in public centers were infected with Staphylococcus aureus, staphylococcus hemolyticus, Neisseria sicca nd Staphylococcus epidermidis probably due to contact with healthy carriers.Conclusion: The methods applied in Yazd radiographic centers, especially the public ones, are completely different from the standards recommended by ADA and CDC. Therefore, our society is definitely exposed to cross-sectional infections along radiographic clinics.

Background and aim: Adrenaline application causes fluctuations in blood pressure. As drugs containing Adrenaline are frequently used in dentistry, the goal of this research was to evaluate blood pressure changes following the injection of anesthetic drugs containing Adrenaline.Materials and Methods: In this case-cross over study, a total number of 150 patients referred to Dental Faculty, Tehran University of Medical Sciences, for tooth extraction in the upper jaw, having no systemic and psychologic disease, were selected. Their blood pressures were recorded before and 15 minutes after injection. The selected patients were randomly assigned in three groups as follows:Group 1: using 1 carpool.Group 2: using 2 carpools.Group 3: using 3 carpools.Results: t-test showed no statistically significant changes in systolic pressure in groups 1 and 2, but it was significant in group 3. Diastolic pressure changes were not statistically significant in all three groups.Conclusion: Using one, two or three carpools of Adrenaline causes slight changes in blood pressure which can be ignored.

Background and aim: The goal of this study was to compare dentofacial cephalometric measurements in two mouth breathing groups, age ranging from 7 to 5 years, with anterior (nasal cavity) and posterior (nasoplaryngeal) obstructions.Materials and Methods: In this study, a sample of 79 subjects, having no orthodontic treatment, including 39 patients with posterior obstruction and mean age of 10.87 years and 40 patients with anterior obstruction with the mean age of 10.97 years, were selected. Type of obstruction was diagnosed by an ENT specialist. For each patient a standard lateral cephalogram was taken. After tracing, 15 cephalometric variables were measured and data were subjected to statistical t-test.Results: Among 15 dentofacial variables, 6 of them including 1 to FH (Ideal), 1 to NA, 1 to SN, Y-Axis, Go. Me-SN, and inclination angles revealed significant differences between two groups. In anterior obstruction group 1 to FH (Ideal), 1 to NA and 1 to SN angles were significantly higher than the other group showing more protrusion tendency of its upper centrals. In nasopharyngeal obstruction group, significant increase of Y-Axis and Go. Me-SN angles showed more mandible backward rotation where as significant increase of Inclination angle showed maxilla forward rotation. The average of other dentofacial variables: Ar-Go-S-IMP A. 1 to FH-ANB-SNB-SNA and LH did not show any significant difference.Conclusion: Dentofacial morphology is affected by the type of nasal obstruction (anterior or posterior) in mouth breathing patients.

Background and aim: Periodontal diseases are one of the most prevalent diseases among human population and of them gingival recession has a high prevalence.The goal of this study was to compare the amount of root coverage by two techniques: Guided tissue regeneration (GTR) with a bioabsorbable bovine collagen membrane (Biomend) and the connective tissue graft with Harris technique.Materials and Methods: In this controlled clinical trial, twenty anterior and premolar teeth were selected. All samples had Miller class I and II gingival recession. Following oral hygiene instruction and reevaluation of all teeth, they were randomly assigned to treat with either guided tissue regeneration (GTR) or connective tissue graft (CTG). In order to insert a connective tissue graft, Harris technique was used. Guided tissue regeneration technique was performed via a sulcular and two oblique incisions. The full thickness flap was replaced by a blunt dissection to expose the bone and then the apical protion was dissected by a sharp dissection. The later dissection was continued in a manner to facilitate the coronally repositioned flap. A bioabsorable membrane was adapted in the area so as at least 3mm of the apical and lateral were covered by the membrane. Finally, the nap was sutured coronally by sling sutures. Patients were visited in one and two weeks, one and six months periods. Information about recession depth (RD), probing depth (PO), the width of attached gingiva and the amount of root coverage was recorded at the base line and six months after surgery. The gathered data were analyzed using wilcoxaon Signed Ranks test, U-Mann-Whitney test and SPSS software.Results: The mean root coverage, after six months, were (71.22±10.2) % for GTR procedure and (80.67±16.06)% for the connective tissue graft technique. The difference was not statistically significant (P=0.134).Both procedures produced similar reductions in recession and probing depth but the connective tissue graft procedure gained a greater increase in keratinized tissue comparing to GTR technique (3/4mm vs 0/1mm respectively). The difference was statistically significant (P< 0.001).Conclusion: Both techniques can be successfully applied in the treatment of periodontal recession defects but when an increase in keratinized tissue is desirable, the connective tissue graft technique is preferred to GTR technique. On the contrary, if keratinized tissue increase is not required, an absorbable membrane, due to the lack of need to a donor tissue, is more suitable.

Background and aim: Despite improvements in the properties of composites, glass ionomers and other tooth colored materials, a number of problems still exist in their clinical application including: post-operative sensitivity, microleakage, technique sensitivity and color change.Different methods have been already presented to recuce microleakage. The aim of this study was to compare the microleakage of different restoration methods in posterior CIV cavities.Materials and Methods: On the buccal surfaces of 90 extracted human teeth, due to orthodontic treatment, periodotal problem or impaction, CIV cavities with gingival margin on CEj were prepared.The samples were randomly divided into 5 groups and restored as follows:A: Copalait varnish (Harvard) and amalgam (Cinalux)B: Dentin bonding agent (Exite) and amalgam (Cinalux)C: Dentin bonding agent (Exite) and light cure composite resin (Tetric ceram)D: Resin modified glass ionomer (Fuji II LC) and dentin bonding agent (Exite) and light cure composite resin (Tetric ceram)E: Dentin bonding agent (Exite) and flowable composite (Tetric flow) and light cure composite resin (Tetric ceram)Restorations were polished, thermocycled in 1600 cycles and immersed in 0.5% basic fushin. Samples were then sectioned and studied under a stereomicroscope to evaluate bye penetration. Data were subjected to Kruskal- Wallis test.Results: All groups showed some degrees of microleakage. According to Kruskal-Wallis statistical analysis, differences between groups were significant (P=0.000000< 0.05).Group C showed the maximum and group D Showed the minimum microleakage. Mann-Whitney analysis was used to compare pairs of groups. Results significant differences between groups as (A <B), (A<C), (B>D), (C>D), (D<E), however; no statistical difference was found between (A,D), (A,E), (B,C), (B,E), (C,E) groups.Conclusion: Proper characteristics of glass-ionomer such as its tendency for dentin bonding may be a factor to reduce micro leakage in cervical restorations. It is suggested to use glass-ionsmer under composite restorations in cases that esthetics and secondary caries prevention are important. In cases tath esthetics is not important and economic factor plays a role and the patient is not susceptible to recurrent caries, amalgam is ercommended.

Background and aim: Hygiene training is considered as the first step in health care as well as the most important duty of the health system personnel who are responsible to offer the initial health principles in rural socities. The aim of this study was to evaluate the knowledge of health system personnel on oral hygiene in Yazd and Taft in 2000.Materials and Methods: In this cross-sectional descriptive study, data were collected from 134 subjects (62 males and 72 females) through a questionnaire including 16 questions about tooth structure, primary dentition and principles of oral hygiene instruction. Results were analyzed using SPSS software and t-test.Results: In 58.5% of the subjects, the knowledge was good and in 29.6% the knowledge was fair, 11.9% had poor knowledge. t-test showed statistically significant relationship between knowledge and gender attributing more knowledge to females than males (P.V=0.002).Knowledge was declined by increasing age and ANOV A statistical test showed significant differences between various age groups (P.V =0.0001). There were not any significant differences between groups according to service record and training place although with increasing service record, knowledge has declined.Conclusion: Despite a lot of shortages, the knowledge level of Yazd health system personnel generally second to be good on oral health topics.