Journal of Dental Medicine

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According to different studies - especially geometric ones - different factors have been proposed that can affect horizontal dimension parameters. The aim of this study is claimed on the title. The study is of a descriptive and cross- sectional type.Fourteen lateral cephalogerams were selected to the sample consisted of 21 boys and 19 girls with the mean age of 9.83 years who suffered from different skeletal & dental malocclusion and were selected by simple sampling method.The linear parameters of wit's and wylie (which depend on occlusal & FH planes), the harvold parameter (which is independent of reference planes) & the proportional parameter of Schwartz were selected & their correlation with angular parameter of ANB were evaluated.

The results showed:1- All of the horizontal analyses showed statistically significant correlation.2- The ANB parameter showed high correlation with wit's, wylie, harvold & shawartz analyses and the correlation between ANB & wit's was higher than others.

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Odontoma is an odontogenic lesion with epithelial and mesenchymal origin and is composed of differentiated dental parts. Than because of abnormal organization of mature tissues. It seems that it is a hamartoma rather than real tumor. Odontoma is seen in two types of compound & complex.Out of 57 studied cases, 31 cases (54.2%) were of complex type 12 cases (21 %) were compound & 8 cases were of cystic. The age of incidence ranged from 5.5 to 68 years. The mean age in complex odontoma was 27 years & compound type was 19 years. There was no significant difference regarding the sex in the complex type. In compound odontoma women were affected 2 times more than means.Complex type are found in mandibular posterior era ereas more and compound type in anterior regions .In this studied found 12 cases impaction teeth.

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: One of the main aspects of orthodontic treatments is hard and soft tissue changes and their effects on patients appearance.Fixed orthodontic treatment with extraction of upper first premolars to camulfalge of ci II malocclusion is very common,however there is not sufficient studies about lip and incisors changes after this procedure. For evaluating of vertical changes of upper, lip and incisors following retraction of upper incisors, fifteen adult Iranian patients aged 15 to 24 years who sought treatment for their CI II DI malocclusion were treated. Standard edgewise technique(0.018") following extraction of four first premolars were used.A cephaiometric study was undertaken to determine the vertical change in upper incisors and upper lip. For this evaluation, thirty linear and angular measurements were utilized.Results show that: 1- The upper incisors were intruded (X=0.83mm).2- The upper lip length was increased(X~1.2mm).3- The occlusal plane, rotated upward (Anteinclination).4- The palatal plane rotated downward and backward (Retroinclination).This study shows that the standard edgwise appliance has the capacity of reduction of incisor protrusion significantly without extruding them.

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In recent years many patients have been received radiotherapy for head and neck tumors and a large number of them have been survived for some years.The side effects of radiotherapy in oral region are mucositis, ulcers, fungal and viral infections and salivary glands dysfunction. Among these, mucositis is the most important one.A randomized double blind clinical trial was performed in radiotherapy department of Tehran Imam Khomeini Hospital to determine chamomile mouth rinse effects on mucositis after radiotherapy.The patients are selected randomly from those with oral oropharyngeal or nasopharyngeal cancers.Data showed that chamomile administration could decrease mucositis rate significantly,

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Guided Tissue Regeneration (GTR) is the most recent and common method for regeneration of class II forcation molars. However, it requires membrane, which seems expensive for most of the patients. In order to overcome this problem, Coronally Position Flap (CPF) procedure may be applied which arresting the epithelial cell down growth, follow the same aim. This study is aimed to compare GTR technique utilizing bioresorable collagen membrane and CPF utilizing citric acid. Nine patients with grade II forcation defects were selected. Defects were bilateral that randomly assigned into two groups: GTR and CPF groups. Measurements recorded at baseline and after surgery (6 months). Paired-T test was performed on these data. The following results were obtained after 6 months: In both groups significant reduction in probing pocket depth were measured in GTR and CPF groups, 1.55 Ind 1.88 mm, respectively. Also, open vertical probing depth: 0.33, 1.11 mm. Reduction in forcation weight in both groups was 0.22 mm. Bone fill was observed in 0.33% and 51% of defects. No recession was observed in GTR group, in CPF was 0.11 mm. Loss of attached gingiva was 0.34 and 0.78 mm, respectively. No significant difference was found between clinical parameters except OHPD. Comparison of means at the day (0 and 180) in each group showed the success for regeneration of forca. Considering the results, it can be concluded that CPF may substitute for GTR technique.

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Carious lesions are usually found by dentists, using bitewing radiographs, and according to the depth of the lesions, the treatment plan is designed. At the present, this technique is the most accepted one and is used generally. But it is not a perfect technique and there are some errors in determining of depth of proximal carious lesions. These errors are mainly related to the use of new high-speed films with broad density and lower voltages. In this study, dentin thickness under proximal caries in bitewing radiography was compared with its real thickness, in tooth structure. Twenty-four teeth samples with proximal caries were used. Before and after removal of carious lesions bitewing radiographs were taken and then each tooth was sectioned occlusogingivally and the thickness of dentine under proximal caries and on bitewing radiographs were measured under microscope with 0.01 mm accuracy. Mean value of dentine thickness in tooth structure was 41% of its mean thickness in bitewing radiographs, showing 59% difference (reduction). Therefore, more care should be taken in using standard technique and interpreting of bitewing radiographs by clinicians. Clinical examinations also should be performed in ideal conditions, and patients should be clinically and radiographically examined every six months.

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Different techniques for local anesthesia are used in the mandible. The purpose of this study was to determine the effects of inferior alveolar dental nerve blocks by comparing the two akinosi and conventional techniques. 80 patients (aged 15-60 years old) were randomly divided into tow groups for extracting the mandibuler posterior teeth by akinosi and conventional techniques. Patients were all injected with 1.8 ml of Lidocaine 2% plus Adernaline j^nnnn .Then the Pain Sensation during injection,positive aspiration, beginning time of anesthesia, duration of anesthesia depth of anesthesia, and the anesthesia of soft tissue related to sensory nerves were evaluated. The results showed that the pain sensation in conventional technique was significantly higher than that of akinosi technique. The number of positive aspirations in conventional technique (12,5%) was higher than that of akinosi (5%) but not significantly different. The long buccal nerve anesthesia in akinosi technique (75%) was significantly higher than that of conventional technique. There was no significant difference between the two techniques for the depth of anesthesia. The success rate was 87.5% in conventional technique and 80% in akinosi technique. The average time of lips anesthesia in conventional technique was 3 minutes compared with 4 minutes in akinosi technique, which was not significantly different from each other. However, the beginning time of aneshtesia in tongue was significantly lower in conventional technique. No significant difference in the duration of anesthesia in lips and tonques between the two techniques was observed.

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The idea of using chemical agents in removal of obstructions on the walls of root canals has been existing since years ago. Successful attempts in this area have been made with the introduction of RC-Prep materials in root canal preparations. The aim of this study was to compare the decalcifing potency of two chelating agents in root canal preparations. 30 extracted canines were divided in three groups for use of Re- Prep materials. Group A Rc-Prep (Primer) made in USA, group B Re- Prep (RC-CTF) made in Iran, and group C as control. Root canals were prepared using standard method followed by washing with 5% sodium hypochloride. Then the teeth were divided into two sections of mesial and distal by a special cutting device. The amount of calcium on polished sections was measured using an elemental analysis method (electron beam probe system). The mean value data were analysed using one‌way Analysis of Variance (ANOVA). The mean values for the measured calcium were group A: 28713±1129, group B: 39441+680, and group C: 54458±2024 . Statistical analysis showed that the mean value for group A was significantly different from other groups. There was also significant difference in the mean values for group B and C. The results indicate that the decalcifing potency for Rc-Prep (Primer, USA) is significantly higher (PO.001) than that of Rc-Prep (RC-CTF).

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 Polymerization shrinkage of light cure composite resins causes many complications in conservative and esthetic restorations. The objective of this in-vitro study was to evaluate the polymerization shrinkage, degree of conversion and the amount of filler in IDM and tetric ceram composites. Ten disk shaped, uncured specimens (8mm×1.547mm) of each composite were placed on glass slide in the center of the metal attached to it. Then specimens were light cured for 60s from underneath. After 30 minutes, the thickness of specimens, using a micrometer and the percent of the polymerization shrinkage of each sample were measured. Statistical analysis was carried out by t-test (P<0.05). Also the degree of conversion of specimens was evaluated with FTIR and the mineral filler content was measured by burning in electric oven. Polymerization shrinkage in IDM and tetric ceram was not significantly different. Degree of conversion and mineral filler content in tetric ceram was greater than that of IDM.

It is assumed that the low degree of conversion in IDM is due to its chemical composition and filler content. Also, the similarity in linear polymerization shrinkage between IDM and tetric ceram may be caused by the low degree of conversion in IDM.

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Electromyographic (EMG) investigations about the activities of the muscles have been the focus of attention for many years. In the field of orthodontics, investigators, among other things, tried to evaluate correlation between EMG activity, occlusal relationships and craniofacial morphology to analyze the effect of muscular activity, as an etiological factor in malocclusion. The purpose of the present investigation is to analyze the effect of EMG activity of temporal and masseter muscles quantitatively in skeletal class III malocclusion. 26 patients (9 to If years old), with class III malocclusion were selected and their EMG activity of temporal and masseter muscles in rest position, centric occlusion, clenching, mastication and swallowing were compared with 20 normal children at the same age range. Then the statistical correlation between 13 cephalometric parameters and EMG activities were analyzed and then the regression analysis was performed and the results were as follows:
1- The mean amplitude of masseter and temporal muscles activity in rest position, centric occlusion, mastication, and clenching in class III samples were greater than normal group (PO.05).
2- The mean duration of masseter and temporal muscles activity in rest position and centric occlusion in class III samples were more than normal group (PO.05).
3- According to regression analysis, a linear correlation was observed between ANB angle and temporal muscle activity in rest and centric occlusion that was not observed in other cases.
The findings of this study showed that difference in temporal muscle activity in class III malocclusion, in comparison with the normal group, is correlated with skeletal morphology of the face, but according to other investigations it is not ture for the masseter muscle.

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Conventional cephalometric analysis, based on intracranial reference line SN and Frankfurt plan, sometimes leads to incorrect diagnostic findings and unpleasant theraputic results, especially in orthosurgery patients, mainly due to the instability of the mentioned references. Natural head position (NHP) is the standardized orientation of the head that its record in lateral cephalometric radiographs, provides us with extracranial references. The aim of this study is to evaluate the necessity for providing a lateral cephalogram in NHP for diagnosis and treatment of severe malocclusion (orthosurgery) in comparison with mild to moderate malocclusions. For this reason, 28 orthodontic and 26 orthosurgery patient's cephalograms, in natural head position, were selected. Diagnosis and treatment planning were based on clinical evaluation and cephalometric analyses especially Harvold and Tweed ones. Each group, based on their growth pattern, was divided vertically and horizontally. The angles between SN and TH planes with TH (True vertical Sine) were measured. Then, the correlation between the angles in two groups and also in relation to the severity of malocclusion, were analyzed in vertical and horizontal directions. The results of two groups were compared by the independent t-test. The findings of this study showed that:1- The SN line was found to be more inclined than FH line and in orthodonthic patients, FH plan is a more reliable reference than SN.2- In orthosurgery patients, the SN-TH and FH-TH angles were strongly different statistically.3- Variation in SN-TH angle, in patients with vertical growth pattern, was high in both groups of patients.These conclusions prove the necessity of a lateral cephalogram in NHP for all orthosurgery patients and those orthodontic patients with vertical growth pattern.

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Nowadays, bone mass estimation, through imaging methods, is widely used in metabolic diseases diagnosis and treatment. One of these methods is called "optical densitometry" which estimates bone density by measuring the intensity of the transmitted light on different parts of a radiographic image. Digital radiography systems act similarly by determining grey levels of the image. The aim of this study is comparing two different methods of optical densitometry and a digital system densitometry known as radiovisiography. 45 samples, containing urografin with three different concentrations, were imaged, by both radiovisiogrphy (RVG) and conventional film systems. To determine the densitometry of films and radiovisiography images, optical densitometry and bone densitometry option of the RVG software, were applied respectively. Data were analyzed and compared for their reliability (repeatability) and correlations with concentration. In RVG densitometry system, the correlation with concentration is moderate (r=0.42) and intra samples and intra group reliability are 97.68% and 88.19%. Moreover, in conventional optical film densitometry, correlation with concentration (r=0.987) is high, intra samples and intra group reliability is high, intra samples and intra group reliability are 99.97% and 99.84%, respectively. According to the results, it is suggested that conventional film optical densitometry is more precise and reliable than RVG densitometry.

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Esthetics is one of the prosthetic treatment goals. Correct selection of anterior teeth, regarding size and appearance, results in a successful treatment. The goal of the present research was to investigate the relationship between interzygomatic width and maxillary anterior teeth width in order to find a better determinant for artificial anterior teeth selection. In this study, the interzygomatic width and maxillary central incisors width and also the width of six maxillary anterior- teeth, in 71 subjects (29females and 42 males) were measured. The results showed a significant difference in maxillary anterior teeth width, comparing men and women, (P<0.05). These measurement in people under study, are less than Europeans. The interzygomatic width was also more in men than women (PO.05), which is, less than of European race. The ratio between interzygomatic and central maxillary incisor width was 15:1 which is less than 16:1 that is used in clinic. Thus, it is recommended to pay more attention to anterior teeth selection, especially in young patients.

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Dentine bonding systems are usually unfilled, and so their shrinkage may be significant. High shrinkage may cause internal stress at the interface between resin-composite restoration and the dentine substrate. Failure of the adhesive interface may be observed due to the interna! stress. The aims of this study were:A) To obtain a suitable method for measuring the kinetics of polymerisation shrinkage in unfilled resm at different thicknesses, particularly for thin films.B) Consideraing the effect of thickness on shrinkage.Scotchbond Multipurpose (3M) adhesive bond resin was used. To overcome the particular challenges presented by thin films, a filled-ring measurement procedure was used. Also, a non-contact laser analogue displacement sensor system was developed and applied to measure polymerisation shrinkage. Regression analysis was performed on a complete data set. Non-linear regression analysis established a logarithmic relationship between polymerisation shrinkage and layer thickness. The method applied in this study was found to be sensitive and accurate procedure for determining photo-polymerisation shrinkage of thin films. Polymerisation shrinkage increased with logarithmic of the adhesive thickness.

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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.
Aim: The aim of this study was to determine the number and type of root canals of mandibular incisor teeth.
Materials and Methods: 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.

Results: 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.
Conclusion: Considering high percentage of two canals in lower mandibular incisors, during access preparation, more attempts in detection of the second canal, is emphasized.

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Statement of Problem: The construction of dental materials has been developing inside the country.Cold- cured acrylic resins are of such materials which are used in removable prostheses.
Purpose: The aim of this study was to compare the dimensional changes of two types of cold-cured acrylic resins, Acropars and Meliodent.
Material and Methods: Forty acrylic discs, with diameter of 13.7 mm, were made of Acropars and Meliodent acrylic resins (20 samples in each group). Then, each group was randomly divided into two parts. The first group was kept in usual environment, whereas the samples of the second group were placed in the boiling water for five minutes. The dimensional changes of the samples, at different intervals and seven days post curing, were measured by light microscope and recorded. Variance analysis was used to analyze the results.
Results: Acropars resins, comparing to Meliodent ones, showed a considerable dimensional changes,which was statistically significant. Boiling of Acropars resins, for five minutes, lead to a significant shrinkage. The maximum shrinkage occured at 24 hours post curing.
Conclusion: If the tray is made of Acropars acrylic resin, it is recommended to take impression, 24 hours
after its setting.

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Statement of Problem: Halitosis refers to the unpleasant mouth odor leading to problems for the patient and his associates. Dentists with enough knowledge about the halitosis incidence with oral causes are able to plan and prevent it effectively.

Purpose: The aim of the present study was to determine the rate of halitosis incidence with oral causes among high school and guidance schoolgirls aged 13-17 years old in Ghazvin. Moreover, the relationship between some etiologic factors such oral hygiene, coated tongue with unpleasant mouth odor was investigated.

Material and Methods: The number of 700 female students, aged 13-17 years old was studied and 14 factors were recorded on a questionnaire for each subject. The related data were collected through direct clinical examination.
Results: The incidence of halitosis in this population was 28.9%. In addition, mouth odor was significantly associated with independent variables such as gingivitis, coated tongue, systemic disease and taking medicine,consumption odor producing materials and the level of oral hygiene.
Conclusion: The most important factor causing malodor was poor oral hygiene. Also in other investigations gingivitis, coated tongue, tonsilitis, dental calculus and malocclusion were diagnosed as the most important causes for oral halitosis.

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Statement of Problem: Computer Sciences, in radiology, like other fields, is of high importance. It should also be noted that the accuracy of the technique and work conditions affects the radiographs information considerably. There for, in order to get more accurate diagnostic information, it seems necessary to investigate different digitized radiographic techniques and to compare them with the conventional technique.
Purpose: The aim of this study was to compare the accuracy of conventional and digitized radiographic images by three digitization techniques in proximal caries detection.
Material and Methods: In this research study, sixty extracted human canines, premolars and molars were mounted in blocks and imaged on E-Kodak film, similar to bitewing radiographs. Ten bitewing radiographs were then scanned at 600 d.p.i with flat bed scanner and a digital camera, then digitized at 300 d.p.i with another digital camera. The digitized images were displayed randomly on a high-resolution monitor. Six
observers assessed the caries status of 120 proximal surfaces by conventional and digitized images. The observer's scores were compared with the results of the macroscopic examination. Reliability of each technique was calculated. Data were analyzed using chi-square and ANOVA tests.
Results: No significant differences were detected between different techniques in intact proximal surfaces and enamel caries diagnosis. However, digital techniques were more sensitive in dentin caries detection (P<0.05).
Conclusions: When conventional film images are digitized, medium resolution (300 d.p.i) seems to be sufficient. At this resolution the file size is decreased and there is no significant loss of the information necessary for caries diagnosis.

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Statement of Problem: Panoramic radiography seems necessary at examination, diagnosis and treatment plan phases of removable prostheses treatment since most of the patients who request removable prostheses treatment have retained root fragments, impacted teeth, cycts and tumors that might not otherwise be detected.
Purpose: The aim of the present study was to investigate the incidence rate of retained roots, impacted teeth and suspected pathologic conditions in panoramic radiographics of patients referred to removable prosthodontics departments of four dental schools and five public centers.
Materials and Methods: In this case series study, 1232 panoramic radiographs were analyzed to detect retained root fragments, impacted teeth and pathologic conditions.

Results: From among 850 panoramic radiographs of patients seeking complete denture, the incidence rates of impacted teeth, retained roots and pathologic lesions were 1.3%, 9.5% and 4.0% respectively.Also from 382 panoramic radiographs of removable partial denture patients the corresponding measures were 2.9%, 11% amd 0.1%.
Conclusion: Due to the significant and evident problems in residual ridge, as well as pathologic conditions of the remaining teeth structures and their supporting tissues as partial prosthesis base, the necessity for panoramic radiographics in edentolous and semi- edentulous patients is reemphasized.

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Statement of Problem: Hepatitis C is a relatively common infection which can be transmitted through accidental inoculation consequently dentists are highly at the risk of exposure to this virus.
Purpose: The aim of this study was to determine prevalence of Hepatitis C among the dentists of Yazd and to evaluate their knowledge about the existing ways for the transmission and prevention of this infection.
Materials and Methods: In this descriptive- analytic study which was performed periodically (2002), the sera of all dentists practicing in Yazd were tested (104 samples) in the laboratory of Yazd blood transfusion organization initially by 1st generation of Elisa for Anti HCV followed by Riba on positive samples to confirm the results. Meanwhile a questionnaire assessing their knowledge about hepatitis was completed the by the dentists. Data were analyzed by ANOVA and t test.
Results: None of the one hundred and four samples of sera were positive for Anti HCV. Mean score of their knowledge was 14.80 (of 20). The knowledge of 92.1% of them was at moderate to high level. No significant difference was observed between Yazd's dentists knowledge about hepatitis C in different age, gender and length of professional experience groups.
Conclusion: According to this study, the absence of HCV among the dentists of Yazd is mainly attributed to the low prevalence of HCV infection among general population, though it can also be an indicative of the knowledge and excellent performance of the dentists to prevent the transmission of infection through blood and saliva.