مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال نوزدهم شماره 2 (پیاپی 47، تابستان 1385)

In addition to the camera, other accessories such as retractors and mirrors are necessary for intraoral photography. They enable directly inaccessible subjects, to be viewed and photographed easily. Gaining adequate view, by suitable retractors and mirrors, is the most important step, requiring skill and patient cooperation to achieve successful results. Composition, visualization of the final photograph and a carefully controlled clinical technique must be practiced in order to produce rapid, precise and reproducible clinical photographs. There are many procedures to be followed and precautions to be taken in order to obtain good quality, reproducible dental photographs. Failures can be avoided by following a distinct procedure. This article focuses on clinical equipments such as retractors, mirrors and intraoral photography.

Achieving adhesion between restorative materials and dentin as a wet and dynamic surface is an important topic in restorative and especially in conservative dentistry. Adhesion of new dentin bonding systems depends on the formation of hybrid layer and micromechanical retention. Nevertheless, an ideal adhesive system has not yet been introduced. Recent studies reveal an increase in bonding stability when the collagen is removed from demineralized dentin surfaces. This study investigates the effect of collagen removal on the shear bond strength of four single bottle dentin bonding systems regarding their structural differences. This experimental study was performed on 56 intact human premolar teeth. Smooth surfaces of dentin were prepared on buccal & lingual aspects of teeth, providing 112 dentin surfaces. The dentin surfaces were etched with 37% phosphoric acid for 15 seconds and then rinsed. The specimens were divided into 8 groups. Single bottle adhesive systems [Single Bond (3M), One-Step (Bisco), Prime & Bond NT (Dentsply), and Excite (Vivadent)] were then applied on the dentin surfaces of 4 groups using the wet bonding technique. In the other 4 groups, the demineralized dentin surfaces were treated with a 5.25% solution of sodium hypochlorite for one minute in order to remove the surface organic components. The adhesive systems mentioned before were applied to these 4 groups with the same wet bonding technique. A cylinder of Z100 (3M) dental composite with a 3 mm diameter and 2 mm height was placed on the adhesive covered dentin surface of all groups and light-cured (400 mW/cm2, 40 sec on each side). The specimens were kept in distilled water at room temperature for one week and then thermocycled for 3000 times (5-55 oc). Shear bond strength of specimens was measured using an Instron (1495) universal mechanical testing machine with cross-head speed of 0.5 mm/minute and chisel form shearing blade. Data were analyzed by Two Way ANOVA and Tukey HSD tests with p<0.05 as the limit of significance. The mean & standard deviation of shear bond strengths (in Mpa unit) of all groups were as follows: One-Step = 19.60 1.83 One-step +H = 19.72 2.01 Single Bond =21.44 3.94 Single Bond +H =18.26 2.85 Prime&Bond NT=26.51 5.02 Prime&Bond NT+H =26.98 5.70 Excite =29.78 3.85 Excite +H =19.07 9.94 Analysis of the results revealed that the use of 5.25% sodium hypochlorite for one minute on the surface of demineralized dentin significantly decreased the shear bond strength of Excite and Single Bond (P<0.05). For Prime & Bond NT and One-Step, shear bond strength increased with this treatment but was not statistically significant (P>0.05). Based on the results of this study, collagen removal from demineralized dentin surface caused a significant decrease in shear bond strength of alcohol & water/alcohol based bonding systems, while the bonding strength of the acetone based systems was not affected. Therefore, the effect of collagen removal on shear bond strength depends on the bonding system applied and its solvent type.

Recent advances in technology have permitted manufacturers to produce endodontic files from NiTi alloy and rotary systems. According to manufacturers, these files maintain original canal shape better than hand files and reduce treatment time. The aim of this study was to compare a new rotary system (Race) with an older one (Profile) in maintaining the original shape of curved canal and the working length as well as the procedural accidents rate. In this experimental study, 40 polyester blocks with curved canals (45), were fabricated and divided into 2 groups. After primary working length determination and staining with methylene blue, photographs were taken. Canal preparation was done with Profile and Race rotary systems according to manufacturers and working length was measured again. Canal staining by eosin was performed and photographs were taken for the second time. The two images were superimposed and changes in canals anatomy in 5 sections were recorded. Data were analyzed by t test with p<0.05 as the limit of significance. There was no significant difference in inner and outer canal walls transportation between 2 groups (P> 0.05). Changes in working lengths and procedural accidents were similar in the studied groups (P> 0.05). Based on the results of this study, changes in canal anatomy and working length of simulated severely curved canals as well as procedural accidents rate are similar in two rotary systems and both are suitable for canal preparation.

In this paper, an unusual case of pigmented dentigerous cyst in a 37-year-old Iranian man with multiple dentigerous cysts of maxilla and mandible is reported. In addition to the characteristic histopathologic features of dentigerous cyst, numerous melanin granules which were distributed throughout the epithelial lining of one of these cysts were also noted. The histochemical study using Fontana’s staining indicated that the pigment was melanin and many of the cells containing melanin were immunohistochemically positive for S-100 protein. Although no firm conclusion could be drawn from the present case regarding melanin origin in dentigerous cyst, the possible histogenesis of melanocytes in odontogenic lesions is discussed.

Achieving appropriate seal in canal obturation is the main goal of endodontic therapy. However, in some cases, it can not be obtained by non-surgical procedures alone. Retrograde surgery is one of the most common procedures in endodontics. Apical seal improvement can be obtained by root end filling and decreasing the root end resection angle (bevel angle). The aim of this study was to investigate the role of bevel angle on apical microleakage following the use of amalgam and MTA as root end filling materials. In this experimental study, 128 extracted human teeth were instrumented and obturated by lateral condensation technique. The teeth were divided into two groups and the apical root resection was performed by high speed fissure bur (one group perpendicular to the long axis of the teeth and the other 45 to the long axis. The 3 mm root end cavity was prepared by ultrasonic device. Each group was divided into two subgroups: One filled with amalgam and the other with MTA. Teeth were incubated for 72 h, covered by two layers of nail polish (except for apical 3mm) and submerged in methylene blue for 48 h. Teeth were washed under tap water and mesiodistally dissected by low speed disc. Dye penetration was evaluated by stereomicroscope. Data were analysed by two way ANOVA and Tukey tests with p<0.05 as the limit of significance. The results showed that retrofill material type had a significant effect on microleakage and MTA was superior to amalgam in this respect. Bevel angle failed to show any significant effect on apical microleakage. Based on the results of this study, it seems that the use of MTA instead of amalgam in clinical practice can improve the success rate of endodontic surgery whereas the bevel angle can be determined based on the status of each individual case However, increasing the bevel angle seems to increase microleakage due to exposure of more dentinal tubules.

One of the most important structural factors that facilitate patient’s acceptance of full denture, is adequate and appropriate retention. The objective of this study was to evaluate the retentive ability of four denture adhesives in vitro: Safe Saze-Gum Sealing-Denstet-Corega. This experimental study was conducted in vitro on the basis of measurement of adhesion and cohesion forces between acrylic disk and glass, with denture adhesive applied between them. At first the retentive ability of alcohol, water and artificial saliva was measured and recorded as control. Then the retention ability of different adhesives mixed once with water and next with artificial saliva was measured and compared. The procedure was repeated 7 times for each denture adhesive with 7 similar acrylic disks. Data were analyzed using. ANOVA and paired t test with p<0.05 as the limit of significance. Comparison of four powder denture adhesives showed that the highest retentive ability was observed in Denstet and the lowest in Safe-Saze. The retentive ability of Gum-Sealing was higher than Corega. Based on the results of this study, significant differences exist among the retention ability of different denture adhesives.

The need for recrimping precrimped stainless steel crowns by the dentist in clinic is controversial. This study aimed to evaluate the rate of marginal circumference and marginal thickness change of precrimped stainless steel crowns after recrimping. In this experimental study, 30 primary photos were taken from margins of 30 S.S.Cs (3M, Ni-Cr) related to tooth 85 with a digital camera fixed at a determined distance. Margins of crowns were crimped by 114 and 137 pliers with a controlled force (0.2 N) and then 30 secondary photos were taken in the same conditions. The circumference of crown margins in primary (group A) and secondary (group B) photos were assessed by a digitizer system. Comparing the circumferences of crown margins in primary and secondary photos showed a significant decrease after crimping. Thickness of 30 random points on the crown margins of a crown similar to mentioned cases was measured by SEM (×150). Then similar procedures including taking a primary photo, crimping and taking a secondary photo was done for the sample crown. After significant reduction in margin circumference, thickness of 30 other random points on the crown margin were measured by SEM. Data were analyzed by paired sample t-test with p<0.05 as the limit of significance. The mean marginal circumference of precrimped stainless steel crowns was reduced by 7.3% which was significant (P<0.001). On the other hand the mean marginal thickness of sample stainless steel crown showed 18µ increase. According to the results of this study, marginal circumference of precrimped stainless steel crowns (3M, Ni-Cr) showed a significant decrease after crimping. It is concluded that crimping the stainless steel crowns even for precrimped ones seems necessary.

Orthodontic ligature cutting pliers are expensive. Methods of sterilization should be safe considering patient's health as well as lifetime of orthodontic pliers. The purpose of this study was to compare the wear of orthodontic ligature cutting pliers after sterilizing with dry heat or steam autoclave. In this experimental study, thirty ligature cutting pliers from 3 different factories (Dentarum-Germany, RMO and ETM-USA) were sterilized in either dry heat or steam autoclave. The amount of wear at the tip of each plier in both groups was measured with a stereomicroscope and digital photomicrography. Wear was defined as the difference of the initial length and the length after 10, 20, 30 cycles of sterilization measured by the distance from a reference line on the tip of the plier. Three way ANOVA was used to compare wear between the two sterilization groups. P<0.05 was considered as the limit of significance. The amount of wear of the ligature cutting plier's tip after 10, 20 and 30 cycles in dry heat sterilization was 1.0±0.16, 0.98±0.22 and 0.94±0.31 mm respectively. These figures were 1.16±0.15, 1.16±0.13 and 1.15±0.14mm for steam heat sterilization. The higest wear was observed after 20 cycles of sterilization in autoclavce whereas the lowest was seen in dry heat sterilization after 30 cycles. The differences between the two studied groups were statistically significant (P<0.0001). In addition, increasing sterilization cycles decreased the rate of wear in both groups. Based on the results of this study routine autoclaving caused more damage and wear at the tip of the pliers than dry heat sterilization.

Several biomaterials have been presented for regeneration of intraosseous defects and Bio-Oss is one of the most accepted materials in this field. Neo-Oss may be the first and only regenerative material made in Iran which few studies have been published about it. The aim of this study was the histologic evaluation of Neo-Oss in comparison with Bio-Oss in experimental rabbit calvarial defects. This was an interventional in vivo study. After elevating muccoperiosteal flap 18 standard defects (3×6mm) in frontal & parietal bone were made by round bur on the calvarium of 6 New Zealand rabbits. Defects were randomly assigned to one of the following treatments: 1-No graft (control), 2-Bio-Oss graft 3-Neo-Oss graft. After 4 weeks the animals were killed and histologic sections prepared. The studied variables consisted of inflammation, type of regenerated bone, thickness of bony trabeculation and foreign body reaction. Data were analyzed by Friedman test with p<0.05 as the limit of significance. The results showed that Bio-Oss was effective for bone regeneration. Inflammation (P= 0.026) and foreign body reaction (P= 0.002) in Neo-Oss was significantly more than Bio-Oss group. Thickness of terabecula in Neo-Oss group (66.7% thin) was significantly different from Bio-Oss (100% thick) and control group (50% thin 50% thick) (P= 0.006). In Neo-Oss group, granulation tissue containing giant cells was observed and the rate of resorption during 4 weeks was high. Based on the results of this study, the healing capacity of Neo-Oss in comparison with Bio-Oss is not acceptable.

Human and animal studies linking fluoride with diminished intelligence have been published. Although adverse effects of high intake of fluoride on intelligence and mental acuity continue to be reported, they are still controversial. The aim of this research was to investigate the relationship between fluoride in drinking water and children's intelligence. In this cross sectional study, 41 children were selected from the high fluoride area with 2.5mg/l (ppm) fluoride in the drinking water and 85 children were selected from low fluoride area with 0.4mg/l (ppm) fluoride in the drinking water. The intelligence quotient (IQ) of each child was measured by the Raven's test. The history of illnesses affecting the nervous system, head trauma, birth weight (2.5kg or  2.5kg), residental history, age and sex of children were investigated by questionnaires completed by the children's parents. Data were analyzed by Chi-Square test with p<0.05 as the limit of significance. In the high fluoride area the mean IQ of children (87.911) was significantly lower than in the low fluoride area (98.912.9) (P=0.025). Based on the findings of this study, exposure of children to high levels of fluoride may carry the risk of impaired development of intelligence.

Giant cell granuloma is a relatively common benign proliferative lesion of the oral cavity. This lesion has a marked gender predilection with more prevalence in females and tendency to rapid growth and recurrence during pregnancy. The aim of this study was the evaluation of specific receptors of sex hormones in giant cell granuloma. In this cross-sectional study, twenty five cases of formalin fixed paraffin embedded giant cell granulomas were retrieved from the oral pathology archive of dental school Isfahan University of Medical Sciences. Also twenty five normal oral mucosa biopsies resected during different surgical procedures were prepared as control group. Cases were immunohistochemically stained for estrogen and progesterone receptors using the biotin-streptavidine method. Data were analyzed by SPSS package. Staining for ER/PR markers were negative for the mononuclear stromal cells and multinucleated giant cells in all cases. The epithelial cells and connective tissue stromal cells of the control group were also negative for these receptors. Based on the results of this study, immunostaining for ER/PR was negative in all cases. These findings suggest that in most cases development and growth of this lesion is not directly related to these hormones. However further studies with more sensitive techniques are recommended.

Adenoids are normally large in children and their size starts to reduce during adolescence. Hypertrophic adenoids could be associated with allergic reactions. Enlarged adenoids result in nasal breathing difficulties and the child is forced to switch to mouth breathing. Airway obstruction causes postural alterations of jaw, tongue and head, and due to persistent obstruction, patient’s appearance changes to adenoid face. Evaluation of nasopharyngeal space in lateral cephalometic view is a simple and repeatable method for determination of the size and shape of adenoids and nasopharyngeal space which can provide a simple measurement of nasopharyngeal obstruction. The roof of nasopharyngeal space is covered by the sphenoid bone. Thus changes of nasorespiratory resistance by hypertrophic adenoids may affect the cranial base angles. In this study, the relationship between adenoid hypertrophy and cranial base angles was investigated. In this descriptive-analytic study, lateral cephalometric views of 7 to 14 y/o patients from the files of orthodontic centers in Rasht city were selected. The radiographs with proper resolution were separated for this research. Adenoid to nasorespiratory ratio (A/N Ratio) was determined by Fujioka method and categorized in three groups: A (A/N 0.8), B (0.5. ...