مجله دانشکده دندانپزشکی مشهد
سال چهل و یکم شماره 1 (پیاپی 100، بهار 1396)

Researchers have reported conflicting results in terms of the effects of tooth bleaching on mechanical properties of enamel. This study aimed to evaluate the effect of at-home bleaching and laser-assisted in-office bleaching on microhardness of enamel.
In this experimental study, 18 healthy bovine incisors were selected and divided into two groups. Home-bleaching with 15% carbamide peroxide was applied for the first group for eight hours a day over 15 days. On the other hand, in-office bleaching was performed on the samples of the second group using 40% hydrogen peroxide and a GaAlAs diode laser (wavelength 810 nm), applied to accelerate tooth bleaching at settings of 2 W as a continuous wave in non-contact mode. This process was performed for three sessions over 15 days. Specimens were stored in Fusayama Meyer artificial saliva during the study. Vickers hardness test was performed to assess the microhardness of the specimens before and after bleaching in both groups. Data analysis was performed using paired and independent t-tests, and P-value of less than 0.05 was considered statistically significant.
While hardness of enamel decreased after both at-home bleaching and laser-assisted in-office bleaching, this reduction was not significant (P>0.05). No significant difference was observed between the study groups in terms of enamel hardness before and after the bleaching procedures (P>0.05).
According to the results of this study, none of the bleaching methods had a significant impact on mineral properties of intact enamel. Therefore, both procedures could be recommended as conservative methods for treatment of discolored teeth.

Given the considerable attention to research in recent years, review and elimination of errors in any research are of great importance. With respect to the scant review articles within the field of dentistry, especially randomized controlled clinical trials, this study aimed to collect and review these articles.
All randomized controlled clinical trials published in the Journal of Dental School, Mashhad University of Medical Sciences, Mashhad, Iran during 2003-2015 were collected and scored based on CONSORT checklist. Data analysis was performed in SPSS version 20. Central tendency and dispersion of the obtained scores were calculated. Accordingly, all articles were classified as weak, medium, good and excellent.
Among 514 collected articles, 64 were clinical trials, 40 of which were randomized controlled clinical trials. Most clinical trials (seven papers) were published during 2003-2009, whereas only one paper was published in 2012, 2005, 2004 and 2013. Mean and standard deviation of percentage of scores of all articles was 57.79±13.61. In addition, the highest mean score was obtained in 2014.
According to the results of this study, given the importance of randomized controlled clinical trials, it seems necessary to overcome the mentioned shortcomings and increase the quality of these studies.

Implementing orthodontic treatment can cause severe caries in teeth in the shape of light spot. The present study planned to evaluate the ability of green tea varnish in the prevention of caries caused by fixed orthodontic.
In the present experimental study, a total number of 45 premolar healthy teeth were selected and categorized into 3 equal groups (N=15) after placing brackets on them. Group 1 (control group): after placing brackets, teeth received no treatment. Group 2: green tea varnish was applied around the brackets in 48 hours intervals for a 21 days period of time. Group 3: green tea varnish was applied around the brackets in 24 hours intervals for a 21 days period of time. After this period, the 40 Micron sections were prepared cervical than the location of the brackets in order to study the avarage of caries depth in micrometers using polarized light in three points at a distance of 500 Micron from each other. The measurment data were analyzed by the SPSS 16.0 software using Kruskal-Wallis and Mann-Whitney nonparametric statistical tests. A significance level of 0.05% was considered.
The average and standard deviation of the caries depth in groups 1, 2, and 3 is 452.03±290.72, 44.91±92.92 and zero respectively. The control group have the most caries depths compared to other groups. Results of groups 1 and 2 had no significant differenc (P=0.878); but, the groups 1 and 2 and also grous 1 and 3 had significant difference with each other (P The results of this study showed that the utilization of green tea varnish in 21-day period at 24 and 48 hours intervals reduces tooth caries around the orthodontic brackets.

Molar-incisor hypomineralization (MIH) is a rapidly destructive type of enamel defects of systemic origin. The aim of the present study was to investigate the prevalence of MIH and the potential predictive factors among the children within the age group of 6-13 years in Rasht, Iran.
The prevalence of MIH was determined through clinical examination of 1043 children aged 6-13 years. At In the next stage, 235 subjects with MIH and their matched controls were evaluated for determining the probable etiologic risk factors. The data were collected using questionnaire and interviews entailing some questions about the late pregnancy problems, birth time problems, and the diseases at the first three years of life. The data analysis was performed using the Chi-square, Fisher’s exact, and Mann-Whitney U tests through the SPSS version 17. The p-vale less than 0.05 was considered statistically significant.
According to the results of the study, the prevalence of MIH was 19.9%, and the sole molar involvement was 17.4%. On average, every child had 2.18 hypomineralized teeth involving 1.9 molars and 0.28 incisor. There was no significant difference between the two genders in terms of the prevalence and intensity of the MIH (P=0.54, X2=0.36). Furthermore, no significant difference was observed between the private and public school students regarding the prevalence of this defect (P=0.51, X2=0.47). As the results indicated, the enamel defects were more common in the lower molars, compared to those in the upper ones (P As the findings of the present study revealed, the MIH had a high prevalence. However, most of the defects were mild, and the mean of the MIH-affected teeth was two teeth per child. The opacities were the main type of defect. None of the investigated variables was associated with the MIH. Further studies are recommended to investigate the etiologic factors including the genetic background to determine the predisposing factors.

Dental trauma is one of the most common causes for visit to the dental office. The prognosis of dental trauma depends on the basic measures taken immediately after the trauma. This study aimed to evaluate the knowledge of parents toward this issue.
This cross-sectional study was conducted on 500 parents of children aged 8-12 years, selected using a two-stage sampling (cluster-quota). A standardized questionnaire was prepared and filled by the participants, validity and reliability of which were evaluated after localization. Data analysis was performed using ANOVA and t-test (α=0.05).
In this study, mean parental knowledge was equal to 5.25±2.01. A slight direct and significant difference was observed between parental awareness and educational level of the parents (r=0.165, P According to the results of this study,low level of knowledge toward traumatic avulsed teeth was observed in the participants. It is recommended that awareness of parents be raised through training programs.

Feldspathic porcelains and zirconia crowns are the most applied dental ceramic materials. Teeth wear against these ceramics has turned into a major concern. Primary surface roughness of these ceramics can have a significant impact on enamel abrasion. This study aimed to detect an association between enamel abrasion and surface roughness of dental ceramics.
In this laboratorial study, polished zirconia samples, polished feldspathic porcelains, and polished and glazed feldspathic porcelains were prepared (N=11). In addition, human natural premolar teeth were provided as antagonist. Afterwards, mounted tooth samples were photographed by a stereo microscope in a fixed position and the distance from the cusp tip to the reference point was measured. Surface roughness of all samples was evaluated before the test using a profilometer device. Following that, ceramic samples were tested against dental samples. Moreover, 11 tooth samples (control group) were tested against another 11 tooth samples in chewing simulator device with 120000 masticatory cycles (equal to six months of chewing). Afterwards, tooth samples were photographed again and differences between the measurements were recorded. Data analysis was performed in SPSS version 20 using the kruskal-Wallis test and scatter diagram graphs, and P-value of less than 0.05 was considered statistically significant.
In this study, mean and standard deviation of surface roughness rate in polished porcelain, polished and glazed porcelain, polished zirconia ceramics and control group were 1.48±0.083, 1.20±0.126, 0.535±0.086 and 0.039±0.006 micrometers, respectively. According to the results, a statistically significant difference was observed between the level of surface roughness in the study groups (P According to the results of this study, higher level of surface roughness of ceramics increased tooth abrasion.

Sandwich technique is one of the most common methods in dentistry, in which resin-modified glass ionomers are used with composite restorations due to special features, such as fluoride release and adhesion to tooth structure. This study aimed to assess shear bond strength between resin-modified glass ionomer and composite using bonding agents with different solvents.
In this in vitro study, 80 resin-modified glass ionomer samples (GC FUJI 2LC) were prepared. Composite was adhered to glass ionomer without the use of bonding agent in the first group and with the use of bonding agents in other three groups (single bond, one step plus and TG bond). After preserving the samples in distilled water in incubator at the temperature of 37.5°C for one week, shear bond strength of the subjects was measured using universal testing machine. Data analysis and comparison of the groups were performed using one-way analysis of variance and tukey post hoc.
In this study, the maximum amount of bond strength was observed in TG bond group (12.99 Mpa), whereas the lowest amount was found in the control group (5.3 Mpa). Results revealed a statistically significant difference between the groups in terms of mean shear bond strength (P=0.001).
According to the results of this study, the maximum shear bond strength between resin-modified glass ionomer and composite resin was related to TG bond. This could be due to the presence of water in the composition of bonding agent, which acted as a moisturizing agent of glass ionomer and led to greater adhesion of composite to glass ionomer.

Dental anxiety is defined as psychological reaction to stress caused by dental interventions. This type of anxiety is common among patients, assessment of which could be beneficial in psychiatric treatments. This study aimed to evaluate the psychometric properties of dental anxiety inventory (DAI).
Material & In total, 300 students from Islamic Azad University of Khoy, Khoy, Iran with a history of dental treatment were selected by random sampling. Participants filled the DAI after obtaining written informed consents. Data analysis was performed in SPSS and LISREL.
The results of exploratory factor analysis revealed one factor. In addition, the exploration for DAI in Iranian population was confirmed through confirmatory factor analysis. Moreover, internal consistency of this inventory was demonstrated at Cronbach’s alpha (α=0.94) and split-half (r=0.95).
According to the results of this study, DAI contains sufficient psychometric properties for Iranian population and could be used by professionals to evaluate dental anxiety.

Patient awareness of options available in changing the color of natural dentition has created an increase public demand. Bleaching is the least expensive esthetic treatment option. This process can be performed by several energy sources, which accelerate the effect of bleaching materials, such as hydrogen peroxide, in office. Laser particles used for this purpose usually facilitate the absorption of laser light by the gel, leading to the conversion of light energy to thermal energy causing accelerated bleaching material effects.
Case Report: In this paper, a 35-year-old female patient with a history of dental fluorosis referred to dental college with complaints of tooth discoloration. Given the reports on severe tooth sensitivity during home bleaching, office bleaching was carried out using the laser source of Er:YAG laser (Fontona Dualis XS, USA), with a power of 4.2 watts less than the enamel threshold. This process resulted in 2-3 shade change from A3.5 to A1 after three minutes and 15 seconds of treatment. Patient reported no discomfort or sensitivity during and after the procedure, which was due to the short duration of the process and application of primary use of unfocused laser light.
According to the results of this study, application of Er:YAG laser resulted in the removal of tooth discoloration with bleaching gels in the office. Since the Er:YAG laser is an standard device used for many dental procedures, there was no need for purchasing a new laser device. Therefore, Er:YAG laser could be used along with bleaching gels as an effective and minimally invasive method to whiten teeth.

Papillon-Lefevre syndrome (PLS) is a rare autosomal recessive disorder. Clinical manifestations of this disease are hyperkeratosis of the palms and soles and rapidly progressive periodontitis, which result in premature loss of deciduous and permanent teeth. Early diagnosis and correct treatment of this discover could prevent the involvement of permanent teeth and promote periodontal condition, which leads to longer maintenance of deciduous teeth and prevention of alveolar ridge breakdown and prosthetic problems.
Case report: Our case was a 4-year-old boy presented with PLS, hyperkeratosis of the palms and soles and rapidly progressive periodontitis, which had led to the loosening of deciduous teeth. The case has been followed for four years. Evidence-based treatment of the patient resulted in stabilized periodontal condition and the possibility of partial removable prosthodontics for aesthetic and functional reasons. In addition, periodontal condition of permanent teeth of the patient was favorable after the eruption.
Due to periodontal disease, dentists are often the first to diagnose this syndrome. Early diagnosis and treatment of PLS is of paramount importance due to the possibility of preventing the involvement of permanent teeth.