Journal of Dental Medicine

The ferrule effect and the biomechanical stability of teeth restored with cores, posts and crowns: Literature review

Sara Koosha

Background and Aims: Preserving intact coronal and radicular tooth structure is considered to be crucial for the optimal biomechanical behavior of restored teeth .The ferrule effect has been extensively studied and still remains controversial from many perspectives. The purpose of this study was to summarize the results of different issues related to the ferrule effect and published in journals listed in Pub Med.

Materials and Methods: The search was conducted from 1985-2014 from Pub Med and scientific dentistry internal journals using the following key words: Ferrule, Ferrule effect, Literature review, Fracture resistance, Fatigue, Finite element analysis.

Results: The finding showed that the presence of 1.5-2 mm high and 1mm thickness ferrule had a positive effect on the fracture resistance of endodontically treated teeth.

Conclusion: The presence of ferrule effect is essential for successful endodontic treatment. If a ferrule can performed, the teeth will have poor prognosis for survival.

Dental students' satisfaction of applying a combination of lecture and work in small groups compared to applying only lecture: a quasi-experimental study

Hooman Keshavarz

Background and Aims: Choosing an appropriate style of teaching-learning by educators is a way to reach high quality education. The objective of this study conducted in Babol Dental School was to compare dental students^, satisfaction of teaching theoretical general pathology course by means of a combination of lecture and work in small groups with their satisfaction of teaching the course by means of only lecture.

Materials and Methods: This study was performed in the second semester of school year 2011-12 and 2012-13. In 2012 (intervention group, response rate=92%), the teaching of theoretical general pathology course was implemented by means of a combination of lecture and work in small groups, but in 2013 (control group, response rate=81%) by means of only lecture. An anonymous self-administered questionnaire was used to assess students^, satisfaction of the teaching methods. To compare the mean total score of satisfaction (ranging from 18 through 90) between the two groups, T-test was used.

Results: Comparing the mean total scores between the two groups revealed that students^, satisfaction of the combined teaching method was significantly higher (P<0.001). The difference of satisfaction between genders (separately for each group) was not significant in combination group and lecture group (P=0.63 and P=0.87, respectively).

Conclusion: Regarding learning, combining lecture with other teaching methods such as work in small groups may increase health sciences students' satisfaction. In regard to teaching theoretical general pathology course, our findings could confirm this hypothesis.

The relationship between study skill and academic achievement in dental students of Tehran University of Medical Sciences

Fatemeh Tirgar

Background and Aims: The purpose of the present study was to investigate the relationship between study skills and academic performance of dental students in Tehran University of Medical Sciences.

Materials and Methods: 195 dental students at dental faculty of Tehran University of Medical Sciences in 2013 participated in this descriptive-analytical study. Data were collected using Congos´ Study Skills Inventory including six subscales. Grade Point Average (GPA) indicated their academic performance. Data were analyzed using ANOVA and Tukey test.

Results: The mean score of students’ study skills were 108 out of 200 with standard deviation of 22.06±0.7. Note taking had a significant correlation with GPA (P=0.015).

Conclusion: Since no significant correlation between study skills and academic performance of the students was observed, it seems that there are other dynamics involved in their academic performance which have to be examined.

Comparative evaluation of pH, bond strength and washability in four common denture adhesives in Iran

Farinaz Khodadad Kashi

Background and Aims: Residual ridge resorption is an unpredictable, unavoidable and time-dependent process which occurs in denture-wearing patients especially those who use mandibular dentures. This process causes more problems in mandible because of its less support, tongue forces and more resorption. Inserting implants in many of these patients requires bone grafts. Overdentures are also more expensive. Denture adhesives are the last option to improve retention and masticatory function in denture-wearers with severe resorption of alveolar ridge. Nowadays only a few denture adhesives are used in Iran and there is not much information about their standard features including, pH, bond strength and washability. The objective of this study was to examine and compare the mentioned characteristics of four denture adhesives (Professional, Corega, Fittydent and Fixodent) and to introduce the most suitable denture adhesive for clinical use.

Materials and Methods: All the methodologies of ISO 10873:2010 were applied. To measure the pH value, 1±0.1g of each denture adhesive was diluted with 5g of propylene glycol and mixed with water. Using pH meter, pH of each group was measured separately for 4 times (n=4) and results were recorded. For the washability test, 4 dentures were fabricated (n=4) and each group of denture adhesives was placed on a denture according to manufacture instructions. For simulating mouth environment specimens were placed in water at 37±2 ̊C bath for 1 hour and then washed with a plastic brush. Specimens were examined for any residual adhesive and the results were recorded. For bond strength test, a sample holder was gently filled with denture adhesives and was attached to the holding arm of bond strength testing device (Santam, STM 20, Iran). Specimens were placed in 300ml water bath at 37±2 ̊C for 10 minutes, and then shaken to be dried and placed in the bond strength testing device. 10N force with 5mm/min rate was applied to the specimen. The force was maintained for 30s and then device arm was pulled back and the highest number was recorded with computer software (Santam Machine Controller v4.19, Iran). The test performed 8 times (n=8) for each adhesive and 8 results were recorded. Data were analyzed using ANOVA test for comparing the bond strength with a significant level fixed
at 0.05.

Results: Professional and Corega adhesives had more neutral pH than that of Fittydent and Fixodent which were more acidic. Washability test showed no remaining mass of any adhesive and there was not any statistically significant difference between groups (P>0.05). Fittydent and Corega adhesives showed higher bond strength than that of Professional and Fixodent and this difference was statistically significant (P<0.05).

Conclusion: Professional and Corega adhesives had less acidity. Thus they cause less harmful effects on the oral mucosa than that of Fittydent and Fixodent and should be indicated in patients with little-tolerant oral mucousa such as diabetous, iron-deficiency anemia and hypertention. All the groups had acceptable washability. Fittydent and Corega had higher bond strength than that of Professional and Fixodent. Therefore in complete-denture-wearers who require more retention as a result of severe ridge resorption, macrotruma, and maladaptiivity, Fittydent and Corega seems to be more acceptable.

Assessment of the dentoskeletal changes following the use of twin-block functional appliance and inclined anterior bite plan in the patients with class II malocclusion div 1 in 11-14 years old

Amir Hossein Mirhashemi

Background and Aims: Cl II malocclusion is one of the most common abnormalities in human societies and using a simple, affordable and accessible treatment that can be provided by general practitioners or specialists, to prevent future malocclusion complications is vital. Cl II malocclusion treatment using functional appliances such as twin block and anterior inclined bite plan have less cost, side effects and complications compared to fixed orthodontic or orthosurgery. Until now, the dentoskeletal changes resulting from the application of twin block and anterior inclined bite plan in patients with Class II malocclusion has not been evaluated. The objective of the present study was to assess the dentoskeletal changes following the use of twin-block functional appliance and inclined anterior bite plan in the patients with class II malocclusion div 1 during mixed dentition.

Materials and Methods: In this retrospective cohort trial, 60 patients with the definitive diagnosis of Class II div. 1 malocclusion having ANB>2 and FMA angel between 20 and 30 and without any previous treatment or syndrome who were treated with twin-block or inclined anterior bite plan appliance were selected and their lateral cephalometries were traced before and after treatment. Selected distance and angular landmarks were measured on the cephalograms with the good reliability (ICC=0.953) and the changes occurred in the landmarks were statistically analyzed using Student t test.

Results: Due to the increased mandibular growth, most of the landmarks experienced significant changes following the treatment with twin-block and inclined bite plan (P<0.05). The appliances corrected Class II malocclusion through improvement of mandibular length and position, maxillary and mandibular skeletal and dental relationships (decreased ANB angle and overjet) and stability of mandibular plan inclination. No significant differences were found between the devices regarding most landmarks changes (P>0.05), however, SNA (P=0.04), overjet (P=0.007) and wits appraisal (P=0.004) changed differently after using the appliances.

Conclusion: Despite with most similarities of both twin-block and anterior inclined bite plan to correct class II div. 1 malocclusion, Due to the advantages of anterior inclined bite plan such as less size, good patient cooperation and simple laboratory preparations the appliance can be used as substitute for complex functional appliances to correct class II div. 1 malocclusion before the growth spurt.

Evaluation of dye penetration in two root cutting directions in the apical microleakage assessment

Marzyeh Mirzaei

Background and Aims: Inadequate root canal obstruction has been suggested as major factor in endodontic treatment failure. On the other hand, the most common way to assess leakage is dye penetration method. In assessing the possible effect of cutting direction on the leakage, the present study was performed to investigate dye penetration in two root cutting directions.

Materials and Methods: Forty human teeth with a single root canal were used in this experimental study. Endodontic treatment was performed on the specimens and then stained with 2% methylene blue solution. The specimens were divided into two groups. Specimens in the first group were sectioned in the buccolingual dimension and the second group in the mesiodistal to evaluate the microleakage. The amount of dye penetration was measured under the stereomicroscope with a magnification of 40%. Data were statistically analyzed using Kolmogorov-Smirnov (KS) and Mann- Whitney tests.

Results: The average amount of leakage in the buccolingual and mesiodistal dimension were, 3.78±2.08 and 2.43±1.55 mm, respectively. There was statistically significant difference between the mean leakage of two dimensions (P=0.03).

Conclusion: Since the leakages in the buccolingual and mesiodistal dimensions were different, it was concluded that cutting direction could be an effective factor on the result of microleakage assessment.

Effect of laser pointer on students' levels of technical errors during intraoral radiographs

Zeinab Davoudmanesh

Background and Aims: According to concerns of technical errors in intraoral radiographs and reports of positive effects of central ray laser pointer on the students, technical errors and shortcomings of earlier research, this study was conducted at Department of Oral and Maxillofacial Radiology of Tehran Azad University to determine the role and use of laser pointer in the technical error made by students.

Materials and Methods: This clinical trials study was carried out at the Department of Radiology, Dental School of Azad Tehran University. A total of eighty students were divided into two groups of forty. In the first group the periapical technique was taught without laser guided indicator, while in the second group laser guided indicator was applied in training the students. All students took X-rays from the phantoms. Laser guided indicator is made of one low power red laser diodes.Totally 560 X-rays were taken and the technical errors and the quality of X-rays were evaluated. Data were analyzed statistically using Mann-Whitney and Chi Square tests (&alpha=0.05).

Results: The X-rays taken by students showed significant differences in cone cutting (P<0.001), and overlapping (P<0.001) between the two study groups. In the subjective review of X-ray quality, the difference was also significant (P=0.03).

Conclusion: The use of laser guided indicator as a training aid seems to be practical for easier learning of central ray adjustment and reduction of technical errors in taking X-rays by dental students.

Comparison of antimicrobial activity of sodium hypochlorite 2.5%, iodide potassium iodide 2%, and chlorhexidine 2% on the enterococcus faecalis after root canal filling

Ali Gharaati Jahromi

Background and Aims: Bacteria and their products have a major role in pulp and periapical diseases. The purpose of this study was to compare the antimicrobial activity of sodium hypochlorite, iodide potassium iodide and chlorhexidine on the enterococcus faecalis after root canal filling.

Materials and Methods: In this experimental study, 95 single canal human teeth were collected. Then after washing and cleaning and filing, the sterilization done using an autoclave. The teeth were smeared with enterococcus faecalis except five which selected as controls and then divided them into 3 groups which A randomly represented the irrigation by sodium hypochlorite, iodide potassium iodide (IKI) and chlorhexidine solution were done. The teeth were filled with gutta-percha and then incubated in a incubator for 90 days at a temperature of 37° C. The specimens were analyzed for Colony Count. Data were analyzed using Kruskal-Wallis test and Chi-Square.

Results: According to the results of this study, the correlation between the 3 groups of cultured teeth were not significant (P=0.812).The specimens which were washed by IKI had the most positive amount of cultures (23.3%) and the specimens which washed by chlorhexidine had the lowest (16.7%).

Conclusion: The results of this study showed that after the use of different wash solutions, no statistically significant difference exist in their antimicrobial activity after root canal therapy.

Evaluation of the cephalometric changes of Tweed triangle in patients with cleft lip and palate

Mohsen Shirazi

Background and Aims: Cleft lip and palate patients require orthodontic treatments during their childhood and adolescence. Tweed diagnostic triangle as well as cephalometric assessments provides important data regarding the skeletal patterns for the treatment and diagnostic purposes. The present study determined the cephalometric changes of Tweed triangle in the cleft lip and palate patients compared to normal patients.

Materials and Methods: In total, 101 cleft and palate patients as well as 95 normal individuals with the balanced age, gender and race were evaluated. All the cleft and palate patients had similar treatment histories. Radiographic clichés were obtained from both groups and the images were traced after identifying the anatomic landmarks. The studied landmarks included points, lines, and plans as well as dental and skeletal angles and distance ratios measured in radiographic images. The landmarks were statistically analyzed using Student t test.

Results: Significant differences were found between the cleft lip and palate patients and normal individuals regarding craniofacial complex morphology (P<0.001). Gender did not show significant effect on the cephalometic indices changes (except to IMPA and FMIA angles). Tweed angle changes were more in the males than that of females between normal and cleft lip and palate patients. Mandibular retrusion (decreased SNB), gonial angle opening, increased mandibular plan inclination and facial anterior height were similar in the normal and cleft lip and palate individuals while no significant differences were found between two groups regarding cranium indices (P>0.05).

Conclusion: In total, significant differences were observed between normal and cleft lip and palate individuals regarding Tweed diagnostic triangle area. These differences were decreased IMPA and increased FMA and FMIA angles. No significant differences were found in terms of other indices.

Applications of PLGA in Dentistry

Reza Masaeli

Poly (lactic-co-glycolic acid) is a biodegradable polymer which has used in a different fields of medical applications. As PLGA is approved by FDA(food and drug administration) the range of this usage is increasing in comparison to the past. Particularly, PLGA are also developed for the dental field in the form of scaffolds, films, membranes, microparticles, or nanoparticles. PLGA scaffolds have been used to regenerate damaged tissues together with stem cell-based therapy. There is solid evidence thatthe development of PLGA microparticles and nanoparticles may be beneficial to a wide range of dental fields such as endodontic therapy, dental caries, dental surgery, dental implants, or periodontology. The aim of the current paper was to review the recent advances in PLGA materials and their potential uses in Dentistry via exploring related literature during 2004 till 2016 in Science Direct and PubMed.