Journal of Dental School
Year:2003 | Volume:21 | Issue:3|Papers Count:20

Background & Aim: Canal preparation is the hardest and most time consuming stage of the root canal therapy, particularly in curved narrow canals. The main error that occurs in these canals is overwidening. The aim of this study was to compare the quantity of curved canal dislocation after using two types of endodontic files made of nickeltitanium (NT) and stainless steel (SS).Method &Materials: In addition we used two kinds of movements in our study to evaluate their effects on quality of canal preparation. 40 same acrylic blocks with 40 degrees gradual curve were made and were divided into 4 groups of 10. I) Nitiflex (NT) with Filing movement, 2) Nitiflex with Watch-winding movement, 3) Flexofile (SS) with Filing movement, 4) Flexofile with Watch-winding movement. Canal shapes were stored in the computer memory before doing any' preparation. Then the canals were prepared in all groups with Passive Step-Back technique. Canal shapes were storcld in the computer memory again. Primary and secondary pictures were I I superimposed with an especial computer program. The quantity of removed material from the inner and outer canal walls was evaluated in 11 sections trom the apex to the 10 millimeters above it (beginning of the curve). At last the results were analyzed with Kruskal-Wallis variance analysis.Results: The quantity of material removed with SS files was significantly more than NT files (P<O.OS).Also the NT files prepared the canal more suitable.Conclusion: We concluded that for curved canal preparation first must used (NT) file with both filling and (WW) motion in 1.3 apically and for preparation in 2.3 coronally used (SS) file with anticurvature filling were more suitable.

Aim: In this study oral and teeth's health status of 12 and 15years old boys of Tehran deaf's schools was evaluated in order to planning treatment programs.Methods & Materials: one hundred and three 12 and 15 year deaf student were examined and DMFT, CPITN, dental treatment needs and also prevalence of malocclusion, fluorosis and traumatic injuries of teeth were determined.Results: In this study, the average of DMFT was 3.59±2.4 and the percent of caries free was %10. Evaluation of CPITN showed that the average of healthy sextants in 12 years old children was 4.75±1.23 and in 15 years old was 4.56±1.60 %92 of the students needed to have a kind of dental treatment and %64 needed to learn oral hygiene instructions.Conclusion: The high prevalence of tooth decay and dental needs of this population shows that hearing loss can be an effective factor in the oral health.

Aim: To compare the shear bond strengths of composite to enamel using enamel bond, one -step, two step adhesive systems and without bonding.Material & Methods: SDI enamel bond, Etch &prime 3.0 (one-step), Excite, Single bond, Prime & bond (two-step) were evaluated. Sixty sound human premolars were divided into six subgroups for each of five adhesives. (N=10).Small flat areas on the buccal surfaces of all teeth were ground in enamel with diamond disk. In all groups, except Etch & prime 3.0, the surface was etched for 15 seconds with 37% phosphoric acid, rinsed with water for 10 seconds.Each bonding system was applied according to its manufacture's directions. After adhesive application, Heliomolar composite restorative materials were applied in 3.8-mm diameter plastic molds to the completed specimens were stored in water for one week before testing. Shear bond strengths were measured using an instron testing machine (3710-016). Data were subjected to one way ANOVA and Tukey's multiple comparison tests.Result: Mean shear bond strengths observed in this study were between 8.17±1.97 Mpa (without bonding) to 19.22±4.99 Mpa (SDI enamel bond). The mean shear bond strength of the subgroup without bonding was significantly lower than all other subgroups. The mean shear bond strength of SDI enamel bond was significantly different than the mean shear bond strength of Prime & Bond, but there was no significant difference for other subgroups with each other and with SDI enamel bond.Conclusion: The results of this study suggest that mean shear bond strength for SDI enamel bond is higher than the other adhesive systems. Unusing of bonding shows significantly lower bond strengths than the other adhesives. There were no significant difference bond strength between one-step and two step adhesive bondings.

Aim: A basic tenet in endodontic therapy is the thorough cleaning and shaping of the root canal system, while maintaining the original canal configuration. It has been demonstrated that the files tend to straighten once introduced into the curved, resulting in excessive removal of dentin on the outside wall of the curvature which is called apical transportation (AT). The purpose of this study was to compare the amount of AT resulting from three instrumentation techniques.Method &Material: The study was done on 45 extracted human roots with 20-43o curvature. All roots were prepared by rotary (profile) and hand (balanced - force, step-back) techniques. The resulting AT was measured by double exposure radiographic projection method and by using computer analysis through Photoshop 5.5 software.Results: There was no statistically significant difference of AT between three experimental groups (P<0.05) and no difference between two measurement methods (P<0.05).Conclusion: Under the condition of this study, it seems that step back to be as effective as profile and balanced- force in preparing curved root canals.

Background & Aim: The aims of this study were to determine the ratio of the powder to liquid of Acropars (Iranian made self-cured temporary crown and bridge acrylic resin) and comparison of pulp chamber increasing temperature during acrylic setting between Acropars (Marlic Co.) and Trim II (Bosworth Co.)Method & Material: This study is done through the experimental and single blind method. A temperature, which connected to a digital thermometer, was placed in pulp chamber and surrounded by amalgam. After that temporary restorations by Trim II and Acropars acrylic resin were made over the teeth and temperature changes were recorded every 30 seconds.Results: Results showed that there was no significant difference between the amounts of increasing temperature in Acropars. But produced temperature in Trim II was 3.6±0.3oC and for Acropars was 4.±0.3oC. This difference of increasing temperature of 25% is significant (P<0.01).Conclusion: The provisional restorations made by Trim II acrylic resin would change the pulp chamber temperature significantly less than those which made by Acropars resin.

Aim: The aim of this study was to evaluate the prevalence of dental caries in 6 - years - old children of Khomein town.Method & Material: The present study was descriptive and crosses- sectional. A total of 7I3 student of this age, 485 in the city (245 boys, 240 girls) along with 227 students in the rural regions (119 boys and 108 girls) were selected for the study.Results: The results showed the prevalence of caries free about 18.7% in primary dentition and 19.2% in permanent dentition and the total percent of 18%.The prevalence of caries free was higher in boys than girls. The mean of dmft and DMFT in total was 4.02 and 0.15. The most dental treatment need was Cl 11 restorations (31.25%). Caries free prevalence in the city (19.2%) was more than rural areas (15.2%).Conclusion: The results of this study showed high difference between WHO standards and what found in the studied area, showing great needs for providing dental services and health instructions.

Background &Aim: The lnterocclusal Distance (IOD) is essential for health of muscles and other pacts of masticatory system. It has also a certain rule in esthetics, Function and comfort of pat-ients.Method & Material: In this study the reproducibility of IOD after immediate increase of vertical dimension was evaluated. 16 Dentate subjects with class I occlusion that has no history of tempromandibular and muscle disorders were selected. Full occlusal splints were made for each subject and IOD were measured before and after splint insertion. The Variance and Duncan tests were used to analyze the results.Results: There was no significant difference between IOD before and after splint insertion.Conclusion: It seems that muscles can adapt with increasing of vertical dimension and these changes have no effect on IOD.

Aim: The purpose of this study was to evaluate the effect of IRAN formulated miconazole Lacquare on denture stomatitis in patients who were residents of Kahrizac Geriatric center in 1999(1378).Material & Method: This double-blind clinical trial study was conducted on 38 patients (mean age 77±12) In two parallel group: miconazole group A and control group B. Denture stomatitis was diagnosed by inspection of palatal mucosa for erythema and positive fungal culture on base day, then on days I and 7 according to their groups, the miconazole lacquare or placebo was applied on denture Inner surfaces. Follow up examination took place on days 7, 14 and 21 by preparation of specimen from palatal mucosa and Denture.Results: Data revealed that application of IRAN formulated miconazole lacquare significantly reduces the number of candida colonies (P<0.05) and palatal erythema (P<0.01).Conclusion: Due to results, Iran formulated miconazole lacquare is an effective agent on denture stomatitis.

Aim: Considering that the use of intracanal medicaments in teeth with necrotir; pulp, periapical lesion, or exudating canals is evident, this study was performed to evaluate the ca ++ and OH- diffusion through root dentin using calcium hydroxide paste as intracanal dressing.Method & Materials: 52 single - rooted teeth were selected. The canals were enlarged to size 60 master apical file and flared to size 1ra. External defects were created on the coronal one- third of the root surface. 17%EDTA and 5% sodium hypochlorite were used to eliminate the smear layer.Ali surfaces except the external defects were sealed and the teeth were, placed in normal saline. Ten teeth were selected as th.e control group and after three days, ca+2 concentrations and the pH in the saline were determined. 42 remaining teeth were divided to three groups with 14 teeth in each one (A,B, C groups).Calcium hydroxide powder and distilled water were mixed to make calcium hydroxide paste. This paste was placed in root. cenal of 42 teeth. Ca++ concentration and pH of normal saline were determined after 24 hoursin group A, after 48 haul's in group B and after one week in group C.Results: The ca++ concentration and pH in all three groups (A, Band C) were significantly .different from control group. The most ca++ release and pH was seen in group C that was significantly different from groups A and B.Conclusion: In order to gain the maximum effect of calcium hydroxide as an intracanal dressing it is recommended to be used for 1 week.

Background & Aim: It is essential to use a reliable retrofill material in surgical endodontics in order to gain successful results. Past investigations showed that none of the available materials are ideal. Amalgam has been accepted as a retrofill material for many years. MTA has been suggested as a better replacement for amalgam recently. There has not been any report on MTA usage in human. The aim of this study was to evaluate the clinical and radiographic success of amalgam and MTA as a retrofill material.Method & Material: In order to evaluate the clinical and radiographic success of amalgam and MTA as a retrofill material we followed 56 patients (72 roots) who had received surgically retrofilled treatment during the past three years.Results: In respect to the standard criteria for success and failure related to endodontics we found that 84.3% (43 roots) of amalgam refrofilled roots and 71.4% (15 roots) of MTA were categorized as successful cases.5.9% (3 roots) with amalgam and 14.3%(3 roots) with MTA were classified as failure treatment. 9.8% (5 roots) with amalgam and 14.3% (3 roots) \\ith MTA were considered uncel1aincases.Statistical analysis using chi square test revealed that there was not any significant differences (P>0.05) between amalgam and MTA as a retrofill material.Conclusion: Further investigations need to carry out in order to compare the success and failure of MTA and anialgam in human. Our clinical study showed no significant difference between MTA and Amalgam as a retrofill material.

Aim: To achieve Andrews six keys of occlusion is a component of treatment goals of each orthodontist. Present study was carried out in order to evaluate six keys in 40 dental casts with normal occlusion.Method & Material: In this descriptive, cross- sectional study molar relationship, existence of space between teeth and dental rotation was evaluated and curve of spee, crowns angulation and inclination of teeth was measured.Results: The results of this study showed that although Andrews normal keys exist in our samples, some differences are observed including the following: I) The mean of angulations and inclination angles of crown of some teeth weren't similar to Andrews samples and these differences are statistically significant 2) The curve of spee wasn't completely flat in any of our samples 3) In some cases a small space (lower than 0.5mm) existed distal to the lower canine or mesial to the upper canine.Conclusion: The differences that been- observed between results of present and Andrews' study can be due ethenic difference between two groups samples.

Background & Aim: There are different recommendations on how to use oral hygiene instruction in dental patients.The purpose of this study was to compare the amount of dental plaque formation following practical versus verbal oral hygiene instruction.Method & Material: This study was carried out on 36 dental students age 19-20years old, who was matched and then randomly divided into 3 groups of experimental, positive control and negative control. Experimental group patients were instructed verbal and practical tooth brushing, in positive control group only oral hygiene was instructed verbally and in negative control group no oral hygiene instruction was done.Results: The changes in plaque index before instruction and 2 months after baseline in experimental group and positive control group were statistically significant. However no significant difference was found in negative control group. A comparison of changes in plaque indexes between experimental group and positive control group following 2 months showed statistically different results between these 2 groups, however the result was better in experimental group than control group.Conclusion: It can be concluded from the results of this study that practical methods of brushing is better than verbal oral hygiene instruction in removing the dental plaque.

Aim: Determining and remaining within the confines of the working length of the root canal during instrumentation are recurrent problems in endodontics. Currently, electroniv apex locators are being used to determine working length and hence, decrease the number of radiographs taken. The purpose of this study is to compare clinically the radiography and an electronic apex locator "apex finder".Method & Material: In this invitro study, 140 root canal (in 99 teeth), were measured by the apex-finder and then radiographed. The working lengths obtained by the apex-finder and those obtained by radiographs were recorded and compared. In addition, this study was undertaken to evaluate the influence of intracanal conditions (dryness or wetness), pulp and periapical status, patient's age and type of teeth, on the root canal length measurements.Results: In 79.3% of the root canals (at least in one of dry or wet conditions), the apex- finder measurements were within ±0.5 mm of the radiographic findings. Furthermore, intracanal conditions have influenced the validity of findings, but not the other factors.Conclusion: Apex finder with good accuracy is useful for determining working length of the root canal in pregnant women, disorder muscle patent with complex root anatomy. Application of this apex finder recommend for determining canal length.

Background & Aim: One of the common problems of removable prosthesis is separating of the acrylic teeth from the acrylic resin base because of improper occlusal forces, accidents and errors in laboratory procedures. The purpose of this study was evaluation of bonding strength of different Iranian acrylic resin teeth (Super Nevoclar, Berelian, Marjan and Urum dent) to Acropars acrylic denture base material.Method & Material: For this research, 84 plastic teeth (canine of four different types of Iranian teeth) were selected.These teeth were divided in four groups according the type of the teeth. The teeth processed on acrylic blocks. They were loaded by instron set until the fracture. The forces of fracture of the teeth were recorded and analyzed. Analysis of variances and Duncan test were used for data analysis.Result: The results showed that there was significant difference between Berelian acrylic teeth and the other groups (P<O.05).Berelian teeth had the greatest bonding strength between four groups.Conclusion: The use of Berelian acrylic teeth reduces the chance of separation of acrylic teeth from acrylic resin base.In the case of the super Nevoclar teeth, surface treatment of ridgelap portion is recommended.

Aim: One of the problems which repaired complete denture is refracturing at the same repaired point. To solve this problem, different methods have been introduced. The following study will show the success rate of these methods.Method & Material: In this study has been used 40 test specimens (15.3.70 mm) in 4 groups and all of them made of heat cure acrylic material. Three of the four groups have been cut and beveled at the center. The first group was repaired with selfcure Acrylic material. In second group, monomer has been applied the edges for 180 seconds, and in third group chloroform has been applied for 5 seconds to achieve etching and then repaired. All 3 groups have been compared with the fourth group for transverse strength on ANOVA and t- test.Results: The result of this study determined the transverse strength in second and third groups, to be increased than the first group. However a significant difference was found in third group (P<0.05) and the transverse strength was about 97% of the fourth group.Conclusion: This study showed that, using of chloroform for 5 seconds were caused the most reinforcement in repaired acrylic resin than other methods.