Journal of Dental School
Volume:22 Issue: 4, 2004

The antibacterial activity of three endodontic sealers, a Ca(OH)2 based sealer (apexit) a Zoe based sealer (Drofill) and a resin based sealer (AH26) was assessed on the growth of an anaerobic bacteria (peprostreptococcus spp.) using the Agar diffusion test (ADT). Thirty brain heart diffusion agar plates were incubated with peptostreptococcus anaerobics. Each plate was divided into two separate areas. In one area, 0.1ml droplet of a given fresh sealer and in the other area a dry material of the same sealer were placed, such that each plate had two areas with the same sealer in two forms of fresh and dry (setform). There were ten plates for each of the three sealers. The plates were placed into anaerobic jars and incubated at 37°C. After varying periods, zone of inhibition of bacterial growth were observed, measured and compared by t and Paired T-test. There was no statistically significant differences between the activity of AH26 and drofill in the fresh form(P>0.05). However there were significant differences between (the two sealers in set form) (P<0.05) Drofill was more antibacterials in the set form than AH26. All sealers were more active when fresh than ages. It is likely that the eugenol in the Dorifill and the formaldehyde in the AH26 are responsible for their greater antimicrobial activity.

Root fracture is a clinical problem which often is difficult to detect and diagnose. As the root fracture detection is based on demonstration of a fracture line or lines, radiographic examination is important. The aim of this study was to compare diagnostic efficacy of direct digital radiography with conventional radiography for detecting experimental root fractures. This study was based on observational diagnostic method which eighty one extracted single rooted human teeth were endodontically instrumented and divided into two groups, a control group of 40 teeth and a fractured group of 41 teeth in which root fractures were produced with Instron machine. Each tooth was imaged using the parallel technique with a CCD-based digital system and E-speed film. The images were interpreted by three experienced oral and maxillofacial radiologists without prior knowledge of the distribution of the root fractures. Three image groups were taken: conventional film, digital images and enhanced digital images. Sensitivity, specificity, false negative and false positive percentage, accuracy of each method in comparison with golden standard (visual examination of fractured and intact teeth) were analyzed. The degree of agreement in detecting root fractures with each imaging system compared with each other was expressed as the kappa value. The sensitivity, specificity and accuracy for root fractures in conventional radiography were 73.2%, 87.5% and 80.2% respectively, in direct digital radiography were 78%, 77.5% and 77.8% respectively and in enhanced direct digital radiography were 82.9%, 85% and 84% respectively. The most sensitive was enhanced direct digital radiography and the most specific was conventional radiography. There was fair to good agreement between conventional radiography and digital radiography (k=0.68), fair to good agreement between enhanced digital radiography and conventional radiography (k=0.73) and excellent agreement between digital radiography and enhanced digital radiography (k=0.90). The diagnostic efficacy of Conventional radiography, digital radiography and enhanced digital radiography in detecting root fractures was comparable with each other.

The aim of this study was to determine the effect of the artificial layer produced by oxalate potassium on permeability of human root's dentine comparing with the smear layer produced by root canal therapy. Seventy extracted mandibular premolars which had one root also the canal was direct without any resorption, decay nor advanced periodontal disease, were chosen. The end of the roots were completely sealed and no calcification nor breakage were observed in them. Samples were divided into four groups randomly: two test groups and two control groups. Each test group consisted of 30 samples and control groups contained 5 samples each. In order to measure permeability of dye through dentin, the spreading cabinet method was used and the amount of 2% methylen blue penetrated thorough the canal wall was calculated after 72 hours. Samples were evaluated by spectrophotometer with wave length of 640. In negative control group, no penetration was observed and also in the other three groups no statistical significant difference in dye permeability was observed. The greatest amount of permeability was in the absence of smear layer. Natural smear layers were second and artificial smear layer created by applying oxalate potassium was third. Therefore oxalate potassium can be applied in infectious canals after removal of smear layer which is full of micro-organisms and poisonous products in order to reduce dental tubule's penetration. However sufficient investigations should be conducted in-vivo regarding tissue biocompatibility and harmlessness of this compound.

Bond failure is not an unusual happening. It may occur well before the end of the treatment, in which rebonding becomes a neccesity. This study investigates the shear bond strength of two different resin systems on rebonded brackets. Thirty non-carious human adolescent upper premolar teeth were bonded and rebonded. No mix and two paste Composit resin systems and Edgewise premolar brackets (American Orthodontics) with a slot size of 22 were used in the present study. Testings were performed with an instron machine at a cross-head speed of 1 mm/min. The debonding force was exerted through a full dimension rectangular 17×25 stainless steel looped wire, engaging the entire bracket slot, so that the point of force application was at the same distance from the bracket – resin interface in all cases. The shear bond strength of each tooth was recorded. Following the initial test, the resin remnants of the enamel surface was removed with a tungsten carbide bur then, the enamel surface, polished and retreated with 37% H3Po4 for 15 seconds. The residual resin at each bracket base was reduced to a minimum thickness with a green stone. The whole procedure of bonding and debonding was repeated again and data was recorded. Means and standard deviations for each group was completed and analyzed by t-test and paired t-test. The results of the paired t-test for the no-mix and two paste resin systems indicate that the difference between the shear bond and rebond strength is not statistically significant. The t-test showed that the bond and rebond strengths of the no-mix systems is not statistically different from that of two paste systems. The analysis of the bond failure showed that the great majority of the bond failures occurred at the bracket-resin interface. The strength of the bond determined in vitro seems to be sufficient to withstand bond failure, but because of the aggressive environment of the oral cavity caution must be exercised, when attempting to extrapolate results to the clinical setting.

Injuries of the anterior teeth are frightful events for child and his parents. This study evaluates the knowledge of primary school teachers about dental trauma. In this study 384 teachers of Tehran primary schools have been evaluated. Tehran is divided to five areas and in each area, eight schools have been randomly selected. Then ten teachers in each school have been selected in the same way. Questionnaire which contained information about management of avulsion, crown fracture, complete crown loss, teachers’ degree, duration of teaching, taking first aid courses and previously facing any dental trauma were presented to the teachers. The data was analyzed by Microsoft SPSS 10 and Chi square test. Out of 384 teachers: 15.5% were aware of avulsion management, 42.7% about crown segment fracture and 68.5% about complete crown loss. There was significant relation between teacher’s knowledge and previous history of trauma in children (P<0.01). Awareness increased as the teaching skill and duration increased. There was no significant relation between the amount of awareness comparing the teachers’ degree and taking first aid courses. Teachers’ knowledge in management of dental injuries especially about avulsion was little, and there is a great necessity of making it public through school books and media.

The purpose of this study was to evaluate the micro-shear bond strength of two kinds of resin-based cements with fluoride release with the usage of five adhesive systems to enamel and dentin. Bovine flat enamel or dentin surfaces were used in this study. Micro cylinders of resin cement with Xeno Cem Plus (XCP) or Panavia Fluoro Cement (PFC) were bonded to enamel or dentin as followed: XCP or PFC as instructions prior to the usage of their own adhesive systems, Xeno CF II+XCP, SE Bond+PFC, or Clearfil Liner Bond II (CLB) + PFC. After the storage in 37oC water for 24 hrs, micro-shear bond test was applied for all the test groups. The data were statistically analyzed using two-way analysis of variance (ANOVA). After two-way ANOVA, one-way ANOVA and multiple comparisons with Fisher’s PLSD test were made. Are given as follow (enamel and dentin, mean±SD in MPa) XCP, 13.7±4.0 and 15.5±9.2 PFC, 23.7±10.6 and 15.0±7.3 XCP+XCF II, 35.4±11.5 and 17.1±4.0 PFC+SE, 54.2±9.8 and 41.7±12.0 PFCCLB, 31.39±3.09 and 15.09±4.35. ANOVA (α=0.05) analyze revealed the usage of SE Bond under PFC significantly increased the bond strength to both enamel and dentin. Bonding of Xeno CFII was only improved the bonding to enamel with the application of XCP. Light-cure adhesive systems significantly improve the bonding of current resin cements.

Perfect facial symmetry is exceedingly rare. In most individuals one side of the face is larger than the other side. Asymmetries large enough to be easily noted on clinical examination are important for patients and orthodontists, because of functional and esthetic problems. The purpose of this study was to determine the prevalence of mandibular asymmetries in high school students. Eight hundred twenty students were selected randomly from 14 high school including 400 girls and 420 boys in north eastern Tehran province. The diagnostic criteria for skeletal asymmetry was chin deviation more than 2mm from a vertical reference plane confirmed by unilateral cross-bite or different right–left cuspid relationship. For functional asymmetries, apparent lateral shift of the mandible from most retruded position to maximum intercuspation and for dental asymmetries, midline shift accompanied by missing teeth or early loss of teeth was noted. 44.6% of girls and 46.4% of boys demonstrated at least one form of asymmetry. The prevalence of skeletal, dental and functional asymmetry in girls was 20%, 21% and 10% respectively, while for boys the prevalence was 23.6%, 20.9% and 7.6%. In 62.5% of students with skeletal asymmetry chin was deviated to the right side. There was a positive correlation between history of trauma r=0.39 and unilateral mastication r=0.22 with asymmetry. The signs and symptoms of TMD was significantly more prevalent in students with skeletal asymmetry than others. Asymmetry of lower third of the face is a common finding. Early diagnosis and proper treatment planning prevents further functional and aesthetic problems.

The purpose of this investigation was to evaluate the effect of 16% carbamide peroxide bleaching agent on enamel surface morphology. Twenty-five bovine incisor teeth were selected. The specimens were subjected to 16% carbamide peroxide for a period of two weeks 8 hours daily. A control area on each tooth was covered and sealed. The specimens were examined under a scanning electron microscope. Fisher’s exact test was used for underestanding the correlation between surface roughness and bleaching (a=0.05). Bleaching agent, presented varying degrees of alteration in tooth surface from slight (44.4%) to moderate (38.9%). The control group and only 14.7% of experimental specimens showed no alteration. Statistical analysis, Fisher’s exact test recognized that there was a correlation between bleaching agent and enamel surface morphology (P<0.05). 16% caramide peroxide could cause slight and moderate alterations in enamel surface. Although severe alteration was not observed.

B thalasemia had been reported as a highly, prevalent genetic disorder in the Middle East region associated with some dental and periodontal complications. This study was designed to evaluate the frequency of dental and periodontal problems in thalasemic sufferers. A group of 100 B thalasemic patients referred to the Hematology wards in selected university hospitals in north eastern region of Tehran were investigated for rise in upper lip, prominecy of the cheek, pale mucosa, premaxillary expansion, crudely saddled nose, dental caries rate and periodontal status. Data were recorded and rates were compared with their percentile. Early diagnose of the disease was shown to play important introductions of future complications including orofocial region. This was due to on time commencement of the blood transfusion leading to a more natural growth. Appropriate and on time blood transfusions in thalasemic children could clearly prevent many of the future orofocial complications.

Dental caries is one of the most common and costly chronic diseases in the world. Many studies have reported socio-economic status (S.E.S) as an important factor predisposing caries. This investigation was carried out to evaluate the effect of differences in socio-economic status of parents as a multidimensional factor on caries development in a group of 8-year-old children in Tehran during the year 2000. A total of 1024 children were randomly selected from 99 primary schools throughout the greater Tehran.The prevalence of dental caries was recorded using the “DMFT” and “dmft” indices. S.E.S was assessed through evaluating, parent's educational level, father's job. Collected data was then analyzed using Chi-square and oneway ANOVA tests, in association to a regression analysis. Results showed that, the mean caries prevalence in primary teeth (d) to be at 2.4±2.4 and 4.6±2.3 in the highest and lowest socio-economic status respectively. This value was at 2.1±2.4 and 4.5±2.3 in children of highly educated mothers and illiterate ones, respectively. There were similar findings for the effect of the other factors determining S.E.S, on caries prevalence of the children. Regression Analysis showed that, mother's education was as important as the other factors to determine the family's S.E.S. This was in fact found to be the most effective factor on caries prevalence.(PV=0.01). S.E.S is an important factor on caries prevalence, with mother's educational level being the main determining factor on S.E.S.

The aim of this study was to compare the effects of A) a flame heated endo plugger, B) GatesGlidden drills and C) GPX drills on the apical seal for the purpose of post space preparation. The crowns of sixty six extracted maxillary central teeth were removed from CEJ by a diamond disc and the root canals were prepared and obturated with guttapercha and sealer (Ah26) using lateral condensation technique. Six teeth were used as positve and negative control groups and the other sixty teeth were divided into 3 groups, each group containing 20 teeth. The post space in these 3 groups was made by either A/a hot plugger, B/# 3or# 4 Gates glidden drills and C/# 40 or # 50 GPX drills and apical dye leakage in each group was measured by stereomicroscope and the Anova test was used to compare the mean amount of dye leakage between groups. Between these 3 groups, the minimal mean dye leakage was related to the hot plugger group and the maximum mean leakage was observed in Gates glidden drill group. There was significant statistical difference between the groups (P=0.005). The GPX drills for the purpose of post space preparation affect apical seal less than Gates glidden drills.

The aim of this research was to evaluate the effect of surface treatment, clinical performance and the condition and position of the dental restoration on the corrosion behavior of dental amalgam. Commercial amalgam namely Oralloy was selected to prepare 21 flat amalgam samples. After triturating and condensation, the samples were divided into three groups and each group was finished by using one of the three clinical procedures carving, carving-burnishing, carving-burnishing-polishing. A special cylindrical mold was used in order to simulation of the inter-proximal areas and proximal surfaces of the dental restorations. Stainless steel matrix band was placed on the internal mold surfaces and amalgam paste was compacted in the mold and 14 cylindrical samples were prepared. Electrochemical tests were performed at a temperature of 37±1oC in normal saline in order to determine the corrosion behavior of dental amalgam samples. Tafel extrapolation and linear polarization methods determined corrosion potential and corrosion current densities. The mean value and standard deviations of the results were calculated. The mean values were statistically compared by ANOVA and Duncan methods at 95% level of confidence. The results showed statistically significant differences between the mean corrosion current density values of three different groups of dental amalgam(P<0.05). The carved group showed more corrosion resistance in comparison with the sample near the matrix band (P<0.05) as an index of the proximal surfaces of the dental restorations. Even a simple clinical performance could effect on the corrosion resistance of dental amalgam. The proximal surfaces of the class II restorations are not only susceptible to concentration cell corrosion but also possess less corrosion resistance.

A variety of systemic agents being able to arrest the progression of periodontal disease have been studied for progression in periodontal therapy. Metronidazole usually used as a systemic and local antibiotic for treating periodontitis in Iran. During recent years an increasing number in antibiotic resistance has been documented. The purpose of the present study was to evaluate the minimal inhibitory concentration of metronidazole against clinical isolates of Porphyromonas gingivalis from adult periodontitis in Iran. This experimental study was performed on samples of 62 patients. The samples were taken by sterile paper points. Isolated bacteria were determined by conventional methods and MIC (minimal inhibitory concentration) determination was carried out according to the agar dilution method recommended for anaerobic bacteria by NCCLS (M11-A5). The range of final antibiotic concentration was 0.0625μg/ml to 16μg/ml. The results were analyzed by interval estimates. Thirty six strains of P. gingivalis were isolated from 62 patients. 16.7%, 55.5% and 27.8% of isolated strains were susceptible to the metronidazole with final concentration of 1, 0.5 and 0.25μg/ml of metronidazole, respectively. Therefore, all strains were susceptible to metronidazole. This is the first report to testing the sensitivity of P. gingivalis to Metronidazole in Iran. Fortunately, all 36 isolated strains of P. gingivalis were sensitive to metronidazole and this antibiotic may be used for treating P. gingivalis related infection in Iran.

Transition of dentition from late mixed dentition to early permanent stage has an impact on dental arch length, circumference also width and depth of arch. Recognition of these changes and prediction of it's pattern is important in treatment planning especially because there are differences between genders that should be considered. This study was designed to evaluate the variations between Iranian(residence of Qazvin city) normal girls and boys in arch dimensions and area. This was a longitudinal descriptive study on 26 normal occlusion adolescents with mean age of 12±1 years at the commencement and 16±1 years at the end of study (12 girls & 14 boys). The individuals had normal occlusion defined by Moyers. Study casts were taken from the sample during 1998 and 2002 respectively. The casts were trimmed according to Profitt. Two photographs were taken from the occlusal view of each with 20 cm distance and vertical to it's midline. After superimposition of the two dental arches on the midline and registration on best fit of incisal edges and mesiobuccal cusp of first molar, changes of depth and width at molar and canine regions were calculated based on genders. Variations in the shape and area of the dental arch were also studied. Mean, SD and confidence interval of the landmarks in each sex was calculated and compared for differences by means of t test. The size and area of arch was always larger in boys and this difference increased by age. In maxilla and mandible, molar width increased in boys but decreased in girls. In maxilla, reduction of canine depth was seen only in boys. There are significant differences between normal arch dimension and area between boys and girls that should be considered in treatment planning. Keywords:

Different intraoral methods are introduced to faciliate the movement of molars distally, which in most cases their major disadvantage is the undesirable movement of the anchorage unit.This study was undertaken to evaluate the effect of a new design of the maxillary molar distalizer using palatally anchorage to assess the anchorage loss. The survey was carried out on 10 patients with the mean age of 14.5 years old. A new fixed intraoral appliance was developed in order to achieve maxillary molar distalization. The appliance was consisted of two parts: The anchorage unit having of a wide Nance button with two Adams clasps on the first premolars and the active unit was composed of a NiTi open Coil spring on the 0.018" stainless steel wire. The patients were followed for total period of 6 weeks in 2 weeks interval time. Lateral cephalograms, study models and copies of the maxillary casts were provided and analyzed prior and after molar distalization by superimposition of the cephalograms and copies respectively. T-test was used to evaluate the changes after distal movement of the molar. The results showed that maxillary first molars were distalized with an average of 1.75mm without any extrusion. Distal tipping of the first molars was found to be 4.35°. Maxillary first premolars and incisors moved forward by 0.7mm and 0.67mm respectively. The first premolars with an average of 0.58mm extrusion were tipped by 6.17°. Distal outrotation of the first molars were showed to be 3.4° while mesial out-rotation of the first premolars were not significant. Intermolar width was increased by 2.26mm and interpremolar width was decreased by 1.58mm. This study showed that the designed appliance could be considered as one of the non-compliant appliances for maxillary molar distalization. No extraoral appearance, patient cooperation and acceptability and applying a light-continuous force could be considered as the other advantages of the appliance.

In the two-step putty wash impression technique after providing first impression, sometimes there are defects in the impression that can be corrected by rewash (reline), although there are different opinions regarding this technique. This study was performed by experimental method on laboratory model. In addition to ten impressions from a laboratory model with routine putty-wash technique (single wash) as control group, another ten impressions were taken with rewash (double wash) technique for evaluation. Then die stones were poured and 20 stone models were provided. Different dimensions of all stone models were compared with lab model and the results were analyzed by t – test. The height of die in the rewash impression technique comparing with control group decreased but its p-value was not statistically significant. Meanwhile in the rewash technique, there was a significant decrease in die diameter and the distance between two dies increased due to shrinkage. 1-Rewash impression technique leads to reduction in die diameter. 2- When there is an undercut below finishing line, die diameter significantly decrease in rewash technique. 3- Rewash technique is debatable because of reduction in tooth diameter, so it is not advisable.

Glass fiber reinforced composite (GFRC) for the fabrication of esthetic fixed partial dentures (FPDs) have been recently developed. The aim of this invitro study was to measure and to compare the bond strength of GFRC and base metal as framework used in maxillary anterior resin-bonded FPDs. Twenty resin-bonded FPDs were made with GFRC and base metal. The specimens were stored for 2 weeks at 37°±1°C in distilled water, thermo cycled (5°-55°C, x 2500) and statically loaded to fracture. The instron universal testing machine measured bond strength of the specimens. A metal cone with 1.0mm tip cut vertically to the center of labial surface of pontic with 1.0mm/min speed to debond of prosthesis from abutment teeth. The debonding force was recorded in Newtons. The mean and standard deviation for bond strength of GFRC RBFPDs were 113±45 and for base metal RBFPDs were 43±32 Newtons. ANOVA showed that bond strength between the two groups were statistically significant (P≤0.0009). Although more clinical experience is needed it is possible to use, fiber reinforced composite materials for metal-free prostheses to obtain excellent esthetic qualities.

To investigate the relationship between craniofacial skeletal structure and occlusion. Data were obtained from lateral cephalometric radiographs and study casts of 60 patients with various malocclusions, with the mean age of 13.3±1.5 years. Thirteen angular and 14 linear skeletal measures as well as 5 occlusal measures including overjet, overbite, molar relation, maxillary and mandibular crowding were applied. Relations were examined by use of univariate and multivariate statistical methods. Simple correlation analysis between individual skeletal measures and individual occlusal characteristics showed that the strongest linear correlation exists between overbite and Pal-GoMe angle (r=-0.451, P-value≤0.01). Stepwise multiple regression was carried out for quantitative occlusal variables. The prediction formula for overjet had the highest multiple R and R2 values (multiple R=0.654, R2= 0.428), which shows that multiple skeletal features explained 43% of the variance in overjet. Individually and in combination, skeletal measures were poorly associated with individual features of occlusion, so that variations in skeletal structure account for at most 43% of the variations in occlusion.

Lichen planus (LP) is a common chronic immunologic inflammatory epidermal and mucocutaneous disorder involving skin, oral mucosa and both sometimes, the main cause of which is still unknown. Due to the importance and it’s prevalence, this study was carried out in order to assess the association of oral and dermal lesions in patients referring to Dermatology Clinic of Tehran Razi Hospital during summer of 2001. In this descriptive study, a total of 101 patients with individual involvement of LP in skin or mucosa were selected among 6510 patients referred to Tehran Razi Hospital-Dermatology Clinic. The selected cases were subjected to further and exact clinical examination along with interview, while in suspected lesions, the conducted histopatologic tests obtained by biopsy were used for the evaluation. A questionnaire was completed for each patient after taking history and physical examination, including history of systemic diseases, interacting medication, smoking habits, presence of oral and dermal lesions, the onset of mucosal and skin lesions and the treatment period, oral lesion’s signs and the patients complaint, involvement location, form, manner of distribution, oral lesion history as well as existence of amalgam restorations along side the lesion chi-square used to assess differences for variables. The study revealed 34 percent association of oral and dermal lesions in the study population, while individual dermal lesion were observed in 61.1 percent of patients and individual oral lesions in 4.9 percent. The incidence of oral LP lesions was slightly higher in females in comparison to males (40.4 percent in females and 37.3 percent in males). About 20 percent of patients who gave history of oral LP, reported smoking cigarettes, while there was no case of pipe smoking or different smoking habits. Patients with dermal lichen planus reported a time between 1-6 months passing from their appearance, while the cases with oral lichen planus were unaware of the beginning time of lesions. The most reported symptom of oral lichen planus in the study population was the burning sensation, while the buccal mucosa was the most common site of involvement and reticular form was the high prevalent. High incidence of dermal and oral lichen planus association revealed throughout the study calls the attention for complete systemic examinations of the patients. As this study was carried out in the dermatology clinic, it seems that other studies in dental schools as well as throughout the public will be of necessity and importance to verify the results. According to this study, there was not a significant statistical relationship between LP and other variables.

More than 30 years has passed since introduction of glass-ionomer cement as a dental restorative material, luting cement and liner. Although they are sensitive to moisture and desiccation during the initial setting stages, relative poor physical properties because of chemical bonding to tooth substrate, and long-term esthetic quality, they are recommended for restoring anterior and posterior primary teeth, cervical lesions and root caries of permanent teeth. In this study, shear bond strength of Fuji II was compared with of ariadent glass-ionomer cements. Thirty intact extracted primary molars were prepared for this study. Selected teeth were divided in two groups of 5. Sample were free of caries, fracture, crack, discoloration or any structural abnormality. The dentin of buccal surface of teeth were exposed by microtome apparatus. The surface was conditioned by polyacrylic acid (10%) for 20 seconds. Glass ionomer cements (Fuji II, and Ariadent) were prepared in a plastic cylinders (15 of each) and attached to the dentin of teeth horizontally. Shear bond stength of materials was measured by instron (Model 1159). Mean shear bond strength of Ariadent cement was 4.2 1.9 Mpa while 7.4 1.5 Mpa was of Fuji II cement (P=0.000). Failure mode was similar between two cements (P=ns). The most prevalent type of failure mode was cohesive failure leaving a firmly attached thin and homogenous layer of cement to dentin, in both groups. It appears that shear bond strenght of Ariadent cement to primary tooth is much lower than of Fuji II.