مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال نوزدهم شماره 4 (پیاپی 49، زمستان 1385)

Object photography in dentistry including dental instruments, models, teeth and gross specimens has some special features and needs special consideration. These objects are usualy very small, highly usually reflective and often with very bright surfaces. They need special lighting and other accessories for acceptable results. On the other hand, in laboratories and dental clinics we havent enough time for taking photographs. The purpose of this article is to introduce the principles of object photography in dentistry.

Many studies have shown that microorganisms are the main cause of pulpal diseases and the main purpose of root canal therapy is their elimination from the root canal system. Antiseptic agents are used to reduce bacteria but their antibacterial activities differ from in vivo to in vitro studies and might be inactivated by dentin and its components in root canal space. This study was designed to investigate the effect of dentin on antibacterial activity of different antimicrobial agents. In this experimental study, two antibacterial agents (sodium hypochlorite and chlorhexidine) with different concentrations were used in four experimental groups: Group 1: dentin, Group 2: demineralized dentin with EDTA, Group 3: dentin matrix and Group 4: dentin mineral component. The species used in this study was Entrococcus faecalis. Different concentration of agents were added to mixture of each experimental group and bacteria. At the baseline and after one and 24 hours, samples were collected and cultured. After incubation period, colonies were counted. Data were analyzed by Tukey test with p<0.05 as the limit of significance. 2% and 0.2% chlorhexidine, and 5% sodium hypochlorite solutions at the three studied times eliminated Entrococcus faecalis completely. 1% sodium hypochlorite eliminated all bacteria in 1h and 24 hs. Statistical analysis showed significant differences between experimental and control groups (P<0.05). Sodium 1% hypochlorite at time 0, could reduce bacteria significantly (P<0.05) but didn’t eliminate them completely. Inactivation of intracanal antiseptics was not observed in this study. As elimination of bacteria occurred, application of these antibacterial agents are recommended in endodontic treatment. Further investigations on other antibacterial agents, other concentrations and shorter time intervals are recommended.

Stainless steel crown (SSC) is the most durable and reliable restoration for primary teeth with extensive caries but its metalic appearance has always been a matter of concern. With advances in restorative materials and metal bonding processes, composite veneer has enhanced esthetics of these crowns in clinic. The aim of this study was to evaluate the shear bond strength of SSC to composite resin using different surface treatments and adhesives. In this experimental study, 90 stainless steel crowns were selected. They were mounted in molds and divided into 3 groups of 30 each (S, E and F). In group S (sandblast), buccal surfaces were sandblasted for 5 seconds. In group E (etch) acidic gel was applied for 5 minutes and in group F (fissure bur) surface roughness was created by fissure diamond bur. Each group was divided into 3 subgroups (SB, AB, P) based on different adhesives: Single Bond, All Bond2 and Panavia F. Composite was then bonded to specimens. Cases were incubated in 100% humidity at 37°C for 24 hours. Shear bond strength was measured by Zwick machine with crosshead speed of 0.5 mm/min. Data were analyzed by ANOVA test with p<0.05 as the limit of significance. There was no statistical interaction between surface treatment and adhesive type (P>0.05) so the two variables were studied separately. No significant difference was observed in mean shear bond strength of composite among the three kinds of adhesives (P>0.05). Similar results were obtained regarding surface treatments (P>0.05). Based on the results of this study, treating the SSC surface with bur and using single bond adhesive and composite can be used successfully to obtain esthetic results in pediatric restorative treatments.

With the introduction of different bondable restorative materials in dentistry, various methods have been suggested to enhance the polymerization and shear bond strength of these materials. The aim of this study was to determine the effects of different methods of enamel conditioning on bond strength of orthodontic brackets and on the bracket/ adhesive failure mode. In this experimental in vitro study, brackets were bonded to thirty-six bovine incisor teeth with different protocols according to the manufacturer's instructions as follows: Group 1: conventional multistep adhesive (n=12); Group 2: self-etching primer system (n=12); Group 3: acid+self-etching primer system (n=12). Specimens were loaded in a universal testing machine (Instron, Canton and Mass) and the mode of failure was recorded. Data were analyzed by ANOVA and Kruskall-Wallis tests with p<0.05 as the limit of significance. The mean shear bond strength was 11.7 ± 4.2, 10.5 ± 4.4, and 10.9 ± 4.8 MPa for group 1, 2, and 3 respectively. There was no significant difference in bond strength among the three groups (P=0.800). No significant difference was observed among the three groups with respect to residual adhesive on the enamel surfaces (P=0.554). Based on the results of the present study, the use of self-etching primers may be an alternative to conventional phosphoric acid pre-treatment in orthodontic bonding.

Although toothbrushing is still the most effective method in plaque reduction, it is insufficient for total plaque removal. Considering this limitation, it is suggested that toothbrushing could be aided by chemical methods. For this purpose, it is advised to use some kind of mouthrinses before toothbrushing to increase the rate of microbial plaque removal. Several prebrushing mouthrinses are available in the market and comparing their efficiency is valuable for dentists. The aim of this study was to investigate and compare the effect of two prebrushing mouthrinses, Plax and Irsha, on dental plaque reduction. This clinical trial was carried out as an interventional and triple blind protocol, using completely random block design. For this purpose, questionnaire and initial examination chart was filled for 50 healthy volunteers between the age of 18 and 40 years and finally 30 individuals were selected based on the inclusion/exclusion criteria. If scaling and polishing was necessary, it was performed at least 2 weeks before starting the main program. Then, each volunteer participated in a 4 steps program, including one step toothbrushing without use of mouthrinse and three steps toothbrushing after use of one of the mouthrinses (Plax, Irsha, Placebo). Data were analyzed by SPSS software using factorial analysis, ANOVA and Tukey’s multiple comparison tests with p<0.05 as the limit of significance. Toothbrushing without use of mouthrinse decreased the amount of plaque, significantly (P<0.0001). Use of mouthrinse without toothbrushing decreased the amount of plaque significantly (P<0.0001). The amount of plaque reduction after use of various mouthrinses (Plax, Irsha, Placebo) showed no statistical differences (P=0.761). Use of the mouthrinses before toothbrushing, had no statistically significant effect on the final results after toothbrushing (P=0.331). According to the findings of the present study, although using mouthrinses decrease the amount of dental plaque significantly, but the prebrushing mouthrinse didnt show statistically significant effect on final result after toothbrushing.

Unlike other bones of the head and neck, hyoid bone has no bony articulations. It is connected to mandible, cranium and pharynx through muscles and ligaments. During treatment with functional appliance in patients with class II div1 malocclusion, mandible is positioned in inferior and anterior direction. Regarding the relation between hyoid and mandibular bone, alterations of hyoid bone position can be a result of functional appliance therapy. The aim of this study was to evaluate the changes of hyoid bone position following treatment with Farmand functional appliance in patients with class II div 1 malocclusion. In this before-after clinical trial, 28 patients with class II div 1 malocclusion which were under treatment with Farmand functional appliance for 11 months were selected. Facial growth in vertical, normal or horizontal direction was determined by cephalometric measurement. Data were analyzed with Paired-t test to compare the differences of mean values pre and post treatment. Variance analysis was used to compare the three growth patterns. P<0.05 was considered as the limit of significance. Hyoid bone shifted significantly forward in horizontal dimension (P<0.01) and non-significantly upward in vertical dimension. There was no significant difference among the three studied groups with respect to hyoid bone position alterations in horizontal dimension but significant difference was observed between horizontal and vertical growth pattern in vertical dimension (P<0.05). There was significant correlation between decrease of ANB angle and forward movement of hyoid bone. Based on the results of this study, treatment with Farmand functional appliance (Fa II) leads to significant alterations in the position and anterior displacement of the hyoid bone.

Many methods and techniques of canal preparation work well in large and relatively straight canals. However, in severely curved canals, the complexity increases markedly, and techniques rendering good results in usual cases may be unsuccessful. The aim of this study was to compare the effect of five root canal preparation techniques on original canal anatomy in simulated severely curved canals. In this experimental in vitro study, 100 simulated canal blocks with similar hardness were made from polyester. The degree of curvature was 45º with a radius of 2.55 mm and a straight part of 8mm. The blocks were prepared with five different techniques (20 canals in each group) as follows: 1-Stepback 2- Passive step back 3- Balanced force using flex-R files 4- Balanced force using Ni-Ti hand instruments 5- Hybrid using a rotary Ni-Ti system (XtremRace). Digital photographs were taken from pre- and post instrumentation colored canals. Then images were superimposed and analyzed by an image editing software. The amount of removed material from the inner and outer canal walls was measured at five levels: 1-The canal orifice (O) 2-The halfway between the orifice and the beginning of the curve (HO) 3-The beginning of the curve (BC) 4-The apex of the curve (AC) and 5-The endpoint of preparation (EP). Additionally, the time of instrumentation, instrument failure and changes in working length were recorded. Data were analyzed by ANOVA and Kruskall-Wallis tests with p<0.05 as the limit of significance. Mean transportation was towards the outer aspect of the curve at the EP in all canals but there were no significant differences between the studied groups. At the BC point, all of the canals were transported towards the inner aspect of the curve and there were significant differences for both transportation values & direction among different groups. The highest amount of transportation was in step back and the lowest, in hybrid group. The highest transportation value was in step back and the lowest in balanced force group. Fractured and deformed instruments were observed in Flex-R files. The shortest canal preparation time was seen in XtremRace and the slowest, in Passive step back groups (P<0.001). Based on the results of this study, changes in canal curvature were less with techniques using nickel titanium instruments and the fastest technique with least transportation was XtremRace.

Nanoleakage can cause discoloration around restoration margins, secondary caries, postoperative sensitivity and finally loss of restoration, thus adequate hybrid layer is of primary importance in prevention of nanoleakage in adhesive restorations. Because of structural differences between primary and permanent dentin, evaluation of nanoleakge in primary teeth is very important. The aim of this study was to evaluate the nanoleakage in composite restorations following application of self -etch and total-etch adhesives in primary and permanent teeth. In this experimental study, Cl V cavities were prepared in buccal surfaces of 20 extracted primary molars and 20 extracted premolars. Each group was divided into 2 subgroups: In group (A), Gluma One Bond and in group (B), iBond adhesive materials were applied. After silver nitrate staining, specimens were mesiodistally sectioned and polished and then SEM examination was carried out to measure the nanoleakage. Data were analyzed statistically using, ANOVA and Duncan tests with p<0.05 as the limit of significance. Factors tested had no significant effect on each other. Primary teeth showed more nanoleakage than permanent teeth (P<0.05). Mean nanoleakage was significantly higher in cervical than occlusal margins (P<0.05) and also in iBond than in Gluma One Bond in primary teeth (P<0.05). In permanent teeth, the lowest nanoleakage was observed in Gluma One Bond. The result of this study indicates that the use of total etch dentin adhesives (Gluma One Bond) in bonded restorations results in less nanoleakage in primary and permanent teeth.

Handpieces are in current use in dental practice. Cross contamination from these instruments is very high because of their direct contact with blood and saliva. The purpose of this study was the evaluation of antiviral effects of different disinfectants on dental handpieces. In this experimental study, the effects of 5 groups of different materials and methods of sterilization and disinfection on virus elimination from dental handpieces were evaluated. Groups were as follows: 1- autoclave 2- Solarsept 3- Unisepta 4- Sodium hypochlorite (2% solution of household bleach) 5- Sanosil. 14 handpieces in each group were washed, dried and autoclaved, then contaminated with polio and Herpes Simplex virus type I. Samples were washed with sterile distilled water. Antiviral agents were applied according to the manufacturer or previous investigations. After washing with water, the instruments were washed with MEM (Minimum Essential Medium) and two samples of cell culture from each handpiece were prepared. In each group one handpiece was treated as control. The results were recorded after one week. The percent of negative cell cultures in each group were as follow: A- For Poliovirus: 1- Autoclave: 100%. 2- Solarsept: 28.6%. 3- Unisepta: 0%. 4- Sodium hypochlorite: 28.6%. 5- Sanosil 92.9%. B- For Herpesvirus: 1- Autoclave: 100%. 2- Solarsept: 100%. 3- Unisepta: 100%. 4- Sodium hypochlorite: 57.1%. 5- Sanosil: 100%. According to our findings autoclave is the best method for virus elimination from dental handpieces. Sanosil with 92.9% efficiency was the best solution. Solarsept, hypochlorite with special method and Unisepta had the lowest effectiveness.

Microscopic differentiation between well differentiated squamous cell carcinoma and verrucous carcinoma is very difficult. As these lesions have different clinical course and treatment a reliable method to help distinguish between them is necessary. The basement membrane in oral verrucous carcinoma is generally intact whereas in oral squamous cell carcinoma is mostly discontinuous. This structure can be studied by different methods. The aim of this study was to differentiate these lesions with special staining of basement membrane. In this tests evaluation study, a total of 26 cases consisting of 15 oral squamous cell carcinomas and 11 oral verrucous carcinomas were retrieved from Cancer Institute of Imam Khomeini hospital archive of pathology and their paraffin blocks were cut and stained with Periodic Acid Schiff method. Slides were studied with light microscope to evaluate the continuity of basement membrane. Sensitivity and specificity of this method were calculated. The sensitivity of this method for differentiating oral squamous cell carcinoma from oral verrucous carcinoma was 100% whereas the specificity was 90.9%. Positive predictive value was 93.75% and negative predictive value 100%. Based on the results of this study, the sensitivity of this test for diagnosis of oral squamous cell carcinoma was high (100%). Further studies are needed to evaluate the use this method for distinguishing oral verrucous carcinoma from oral squamous cell carcinoma.

Vital pulpotomy in primary teeth is performed to maintain the vitality of the pulp and tooth until normal exfoliation. Different materials such as zinc oxide- eugenol, calcium hydroxide and formocresol are used in this procedure. The aim of this study was to evaluate the application of formocresol (FC) and mineral trioxide aggregate (MTA) in pulpotomy of primary molars. In this clinical trial, one hundred and twenty six children (aged 5 to 9 years old) with dental caries that were candidate for pulpotomy were selected and randomly divided into two groups. After removing the roof of the pulp chamber, coronal pulp was cut at the orifices and bleeding controlled. In control group, formocresol was applied for 5 minutes. In case group, MTA paste was used as pulpotomy agent. The crowns of both groups were restored with amalgam and the teeth were evaluated clinically and radiographically after 3 and 6 months follow up. Data were analyzed by Fisher test with p<0.05 as the limit of significance. No sign of clinical failure was observed after 3 and 6 months follow-up. Comparison between the two methods revealed no significant difference in radiographic findings of the teeth and surrounding tissues after 3 months follow-up. However, after 6 months follow-up, internal resorption was observed radiographically in four cases of formocresol group. Based on the results of this study, pulpotomy with MTA showed more successful results than formocresol radiographically. MTA is recommended as a good substitute for formocresol in pulpotomy of primary molars.

Extensive studies on the epidemiology of teeth and oral diseases are an important part of health care programs specially for hearing impaired groups. For adequate programming in this field, proper situation analysis is mandatory. The aim of this study was to assess the DMFT (decayed missed filled teeth) of 12 years old students attending hearing impaired schools in Tehran and exploring the relation between sex, hygiene and hearing threshold with the index. This cross sectional descriptive study was based on examining 12 years old (± 6 month) students (117 cases) attending hearing impaired schools in Tehran. A questionnaire was filled for each case. T, Chi-square and Kruskall-Wallis tests were used to analyze the results with p<0.05 as the limit of significance. The mean DMFT in these students was 3.07. Mean DMFT in students with very severe hearing loss was 2.99. Mean ranked DMFT in girls and boys was similar (56.09 in boys and 61.96 in girls). Mean ranked DMFT in students who didn’t use floss (66.40) was higher than those who used floss (46.71). Mean ranked DMFT in students who seldom brushed, was the highest (72.82) and in students who brushed once a day was the lowest (51.26). The DMFT index in hearing disabled children was 3.07. Regular brushing and flossing reduced the index.