Journal of Dentistry, Shiraz University of Medical Sciences
Volume:12 Issue: 3, 2011

Statement of the problemProblem: The application of nickel-titanium arch wires is very common in the first stage of orthodontic treatment. The aim of this study was to evaluate the effect of activation value on load-deflection properties of two types of nickel-titanium archwires. The changes that occurring ed in bending properties of these wires after recycling were also assessed. In this in vitro study, 80 specimens from single-strand Ni-Ti (Rematitan “Lite”) and multi-strand Ni-Ti (SPEED Supercable) wires were selected and subjected to a three point bending test in the “as-received condition” and “after 2 months immersion in a simulated oral environment and autoclave sterilization”. The wires were activated up to 3 or 6 mm distances and unloading forces were recorded using Zwick testing machine. The data were analyzed by using T-test. Rematitan “Lite” showed significantly greater force than Supercable at both 3 and 6 mm activations (p <0.05). The single-strand nickel titanium wire showed lower forces at 6 mm activation compared with 3 mm activation. In contrast, severe activation of multi-strand Ni-Ti wire caused a longer plateau range and, consequently, the unloading forces of this wire at 1.5, 1.0 and 0.5 mm deflections were higher in severe activation than in moderate activation. The effect of recycling on bending properties of Ni-Ti wires was not clinically considerable. Application of a multi-strand Ni-Ti wire is useful when a very light force is needed for tooth alignment. The magnitude of forces exerted in three point bending test depended on the amount of wire activation. The tested wires can be reused at least once.

Statement of Problems: The first step to decrease the patient's exposure to unnecessary radiography radiation is the proper prescription of radiography. The purpose of this study was to evaluate the knowledge of general dental practitioners as to proper prescription of intraoral radiography and panoramic views. In this study, a questionnaire on the dentist's knowledge about the proper prescription of dental radiography was used. A total of eighty one general dental practitioners filled in the questionnaire. Statistical analysis of the dentist's awareness and its relationship with graduate round off period was done carried out by Chi-square, Mann Whitney and Fishers exact tests using SPSS software. The Knowledge of general dental practitioners as to panoramic radiography was moderate and that of those who graduated more than five years ago (Group 1) was 42.8%. The knowledge of the recently graduated general dental practitioners graduated less than 5 years ago (Group 2) was 50%. As to preference of application of panoramic radiography and intraoral periapical radiography in diagnosis of oral and dental diseases, group 1 gave 100% correct answers compared to 83.3% in group 2. The dentist's knowledge regarding the proper prescription of radiography did not have a significant difference. Adequate instruction for dentists in this regard seems to be necessary.

Statement of Problem: Oral lichen planus (OLP) is a chronic inflammatory disorder which can specially be painful in atrophic, erosive and ulcerative forms. In this area, different treatment plans with different results have been evaluated The aim of this article is to compare the effect of aloe vera gel and local triamcinolone in treatment of oral lichen planus lesions. In this double blind research, 50 patients (13 males and 37 females) having oral lichen planus lesions were selected and randomly divided into two groups. The first group received 70% aloe vera gel and the second group, 0.1% local triamcinolone. Both groups used the drug locally 3 times a day for 8 weeks. All the patients were under follow up every 2 weeks. Clinical evaluation and pain reduction was evaluated by Thongprasom and VAS methods in both groups. Data were evaluated by repeated measure technique. 20 patients of the triamcinolone group showed good response to treatment and 3 patients had complete remission during the treatment period. In aloe vera group, 9 patients had good response and no one showed complete remission (p <0.001). No significant lesion was seen in both groups during the treatment period Application of aloe vera gel is suggested in treatment of erosive and atrophic lichen planus lesions in comparison with steroids. However, according to the results of this study, the use of steroid instead of aloe vera in treating ulcerative lichen planus lesions is a better and more appropriate choice.

Statement of Problem: Various forms of fluoride-contained products are used to increase the resistance of the tooth against caries for preventive purposes. Furthermore, studies demonstrated higher fluoride uptake with varnish and gel among the wide range of products.

This study compared fluoride uptake of Duraflor® varnish (Practicon Dent, USA) with fluoride gel (APF, Sultan®), used on the enamel surface of the intact teeth.

In this experimental in-vitro study, 20 intact pre-molar teeth extracted for orthodontic purposes were randomly assigned to two groups of 10 teeth. The teeth were sectioned into two mesial and distal halves as the control and experimental sides. Defined semi-circular areas on the enamel surface of the experimental halves were treated with gel or varnish for 1 hour. The sample halves were stored in artificial saliva for 24 hours at 37°c, etched for 30 seconds by 0.5 M perchloric acid, and washed by 0.2 m KOH after each etching process. Biopsies of the samples were obtained by Acid Etch Enamel Biopsy technique and the fluoride and calcium concentrations were calculated by potentiometer and spectrophotometer, respectively. Kolmogorov-smirnov, Paired t-test and Student t- test were used for statistical analyses.

The results demonstrated an increase in the enamel fluoride content after exposure of the teeth to both Duraflor® varnish and APF gel (Sultan®). The results of the paired t-test revealed significant differences between the experimental and control halves in both groups (varnish: p =0.002, gel: p =0.039). The fluoride uptake value in varnish and gel groups was 2069.78 ppm and 1050.99 ppm, respectively. The student t-test showed a statistically significant difference (p =0.01).

Both APF gel and Duraflor® varnish increased the fluoride content of the tooth enamel after application, although Duraflor® varnish had a higher fluoride uptake level than APF gel.

Statement of Problem: Pulpotomy is the most common pulp treatment in primary teeth. Final restoration of the pulpotomized primary molar can affect the success rate of treatment.

The aim of this study was to evaluate the success rate of formocresol pulpotomy in primary molars restored with stainless steel crowns as compared to those restored with amalgam.

In this randomized clinical trial study, 110 primary molars to be treated with pulpotomy were treated by a conventional pulpotomy technique. Then these teeth were randomly divided into 2 groups: amalgam and crown. 55 teeth were restored by stainless steel crown and 55 by amalgam. The clinical and radiographic evaluation was done at 6-12-24 months. The data were analyzed by Exact Fisher test.

During the 6 months of evaluation, no clinical and radiographic failure was seen. In the 12 months of follow up in the amalgam group, 1 case showed swelling and furcal radiolucency. During the 24 months of evaluation, mobility was seen in 2 teeth in the crown group, and in the amalgam group radiolucency was seen in 1 case, mobility in 1 case, and internal resorption in 1 tooth. Exact Fisher test showed that there was no significant difference in the success rate of pulpotomized molars restored by stainless steel crown and amalgam.

If the tooth is selected correctly for pulpotomy, SSC and amalgam restoration can be used as the final restoration.

Statement of Problem: Determining the appropriate Working Length (WL) is an important factor in the success of root canal therapy. Several methods are available for this purpose but radiography is the mostly used one. The aim of this study was to compare the conventional and self -developing films with a Gold standard in estimation of the working length. In this descriptive study, radiographs were obtained with conventional and self-developing films from 45 mesiobuccal maxillary molar root canals which were mounted on a phantom head. Conventional films were processed automatically and self-developing films manually in accordance with manufacturer’s instructions. The radiographs were examined by three endodontologists and one oral and maxillofacial radiologist under double-blind conditions. Actual working lengths were measured on each tooth (Gold standard) and then measurements from each film type were compared together and against the Gold Standard. The data were analyzed using t-test and paired t-test. The average difference in WL between the conventional and self-developing films measured against the Gold standard was 0.33 mm and 0.14 mm, respectively. No significant difference was found between these two types of films and the Gold standard (p =0.06 and p =0.7, respectively). Also, there was no significant difference between these two types of films for estimation of the working length (p =0.4). Although there was no significant difference between these two types of films, the assessment shows that self-developing films produced more accurate results in estimation of the working length. It is concluded that in the absence of dark room and processing solutions, self-developing films can be suitably used instead of conventional films.

Statement of Problem: Many authors have claimed that pulpal inflammation may occur following periodontal diseases. Appropriate diagnosis of different lesions that have affected the dental pulp or periodontium is critical for prevention of unnecessary or harmful treatments; this must be taken into account before treatment. The purpose of this study was histological evaluation of the pulp in the teeth with advanced periodontitis. 30 permanent single teeth root that had advanced periodontitis with attachment loss ≥ 5 mm at least in one surface were used. The teeth were not maintainable and did not have caries, restoration and any sign of primary trauma from occlusion and did not receive any periodontal professional treatment in the past 6 months with no background of trauma. After clinical and radiographical examination and confirmation of the existence of advanced periodontitis, the teeth were extracted. Then cracks were created in the teeth by special clips. After fixation of the teeth in 10% formalin solution and decalcification by 10% nitric acid, the sections were prepared and stained by hematoxylin and eosin and then evaluated from histological perspectives. The data were analyzed by Spearman correlation coefficient ANOVA, t-test and Kruskal wallis tests. In this survey, we did not find any significant correlation between clinical findings and histopathological situation. The relationship between clinical attachment loss and pulp diagnosis was statistically significant (p =0.043). Also there was a statistically significant relationship between clinical attachment loss and calcification in the pulp (p =0.014). According to the result of this research, it seems that periodontal condition affects the pulpal condition and it should be considered in future treatments on these teeth.

Statement of Problems: Several methods have been presented for the prediction of mesiodistal width of the unerupted canines and premolars. Nowadays, application of digital methods is suggested in dental analysis in orthodontics.

The aim of this study was to design a software for space analysis and comparison of the accuracy of tooth measurements by digital and manual methods in an Iranian population.

By using Delphi and C++ programming languages, a software was designed. After insertion of 2 dimensional scanned images of dental casts, the software can predict mesiodistal width of the unerupted canines and premolars by using 12-variable regression equations based on the incisors and first molars. After providing 2 dimensional images of 125 dental casts in permanent dentition (75 females and 50 males), the prediction accuracy of regression equations was investigated. By providing 2-dimensional images of dental casts in 50 patients with mixed dentition, the accuracy of dental measurements was evaluated through the designed software. Moreover, the time duration of manual and digital measurements was evaluated. Data was analyzed in SPSS, version 17, using paired sample t-test for comparing the manual and digital measurements and evaluation of interobserver and intraobserver errors.

Prediction of the width of the canines and premolars by the designed software was not significantly different from manual measurement of those teeth on dental casts with digital Caliper (p >0.05). There were no significant differences between manual and digital measurement of mesiodistal width of the teeth (p >0.05). Also, there were no significant differences between intra-observer and inter-observer measurements and the speed of measurements in digital and manual methods. However, the time duration and speed of space analysis with these two methods were significantly different.

The designed software has a good accuracy in prediction of unerupted canines and premolars with equations and it is an efficient tool for predicting the mesiodistal width of the teeth as to the time duration or speed.

Statement of Problem: There are many controversies regarding the usable number of rotary files in the literature. The aim of this study was to compare three Rotary Systems in Terms of Number of Severely Curved Root Canals Preparation, Till Either Defect or Fracture. In this in vitro study, 60 mandibular or maxillary molar mesial roots with a mature apex and a curvature of 35-80º were evenly divided into three groups according to their radius and curvature angle. The Pruett method was used to define the curvature degree. In all the three groups, cleaning and shaping were accomplished with a working length of 16mm.Then, the number of the prepared canals until any defect or fracture (using a 8x magnifier) was recorded and canal preparation was done with the same devices in the remaining canals. Chi-square test was applied for inters categorical variables comparisons. Kaplan-Meier curves were used to display the number of prepared canals till any defect or fracture with further comparison by a log-rank test. To compare the curve angle and radius, Kruskal-Wallis test was used. p.value of less than 0.05 was considered as statistically significant. The average number (±SD) of the prepared canals leading to defect or fracture in flexmaster, Hero and Race systems was 11.87 (±2.07), 13.28 (±2.46), and 9.66 (±1.92), respectively (p <0.05). Overall, 20 devices were found to be fractured or defective, among which 7 had defects and 13 had fractures. The rates of defects in Hero, Race and Flexmaster were 50%, 33.3% and 28.6% with the fracture rate of 50%, 60% and 71.4%, respectively (p > 0.05). Hero system showed higher numbers of prepared canals and revealed less fracture rate. Meanwhile, Race system revealed the least number of prepared canals with the highest rate of the fracture. However, there were no statistically significant differences between the systems.

Statement of Problem: Bonding agent composition for impregnation of fiber may increase the flexural strength of fiber-reinforced composites by means of increasing adhesion. Investigating the impact of filler of four commercial bonding agents with different hydrophobicity on the flexural strength of a fiber-reinforced composite. In this experimental study, six groups (N=15 per group) of polyethylene fiber-reinforced composite specimens were prepared. In group 1, the positive control group, the samples were prepared using composite and without fiber, whereas in group 2, as the negative group, fiber-reinforced composite without any bonding agent resination was used. The fibers in group 3 to 6 were resinated with Single bond 2, Single bond, Resist, and all bond 3, respectively. Firstly, the fiber was placed in the base of the specimen preparation mold. Then the mold was filled with composite and cured. The specimens were stored in distilled water for 24 hours. In the next step, the flexural strength was measured in Three-point bending test with Instron machine at cross- head speed of 1 mm/min. Failure mode of the specimens was observed with stereomicroscope. At last, statistical analysis was performed using ANOVA and LSD post hoc tests (p < 0.05). Ono-way ANOVA test was used for evaluating the relationship among the groups, and for pair-wise comparison, LSD post-hoc test was used. One-way ANOVA test showed a significant difference among the groups. The All bond 3 group showed a significantly higher flexural strength than the other groups (p <0.001). Groups 3 to 6 had significantly higher flexural strength than flexural strength of the control groups (p <0.05). The choice of bonding agent can have a significant impact on the flexural properties of the fiber-reinforced composite. When filled hydrophobic bonding agent was used for impregnation of the fiber, compared to negative control group, flexural strength increased 4 fold.

Statement of Problem: One of the most important procedures in the rehabilitation of an edentulous space in the anterior segment is the selection of an appropriate size of the anterior teeth in order to achieve the perfect esthetic results. The purpose of this study was to examine the correlation between horizontal measurements of the face and width of the maxillary anterior teeth. In this descriptive-analytical and cross-sectional study, the face and teeth of the 77 subjects (39 women and 38 men aged between 20-30) with no facial and dental deformities were examined. Some horizontal dimensions of the face including IC (intercanthal), IP (interpupillary), BZW (bizygomatic width), IA (interalar), and ICm (Intercomussural) width and perceived width of the teeth were calculated with AutoCAD software with 0.1 mm accuracy on the photos. The actual width of the teeth was calculated with a digital caliper by 0.1 mm accuracy on the maxillary casts. The data were analyzed in SPSS software using the Pearson correlation coefficient and t-test. Except for the IC and the sum of the actual width of the six maxillary anterior teeth on the cast, the rest of the measurements were significantly different by gender (p < 0.05). All the correlations between facial measurements and width of the teeth were bigger than when they were separated by gender. In women, the correlation between IC and the six anterior teeth in the front view (SANTF) was the highest one (r = 0.436, p = 0.005). However, the highest correlation was related to the ICm and SANTF in men. (r = 0.0501, p =0.001) Within the limitation of this study, the results suggest that except for the BZW, the rest of the facial measurements including IC, IP, IA and ICm can be used as a preliminary criterion for determining the width of the maxillary anterior teeth of the edentulous patients.

A 22 year old female with chief complaint of tenderness of the masticatory muscles and joint sound referred to pProsthodontic dDepartment of ….Shiraz Dental School. The patient expressed the history of nocturnal bruxism and pain in the masticatory muscles in early morning that decreased with time. In extraoral examination, there was no facial asymmetry and masseters of both sides were tender with palpation. In intraoral examination, excessive wear of the anterior and posterior teeth and several wear fascets on the posterior teeth wear were found. Overjet was 0 mm and overbite was -1mm which was due to excessive wear of the anterior teeth. There was a single click while opening and closing the mouth in the right TMJ, but both right and left TMJs were tender during examination. There were interferences in the centric relation both in the arc of closure and line of the closure.At first, stabilization appliance was made for the patient to relax the masticatory muscles and to reduce their pain. The patient wore the appliance for 4 months. Then occlusal equilibration was done for her in order to achieve bilateral, even and simultaneous contacts in the centric relation. After that without increasing the OVD, the upper and lower anterior teeth were reconstructed with composite resin so that in the excursive movements the anterior teeth could exclude the posterior teeth out of the occlusion. This treatment approach is affordable for patients because it minimizes the need for orthodontic and extensive prosthodontic treatments.