مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال بیست و دوم شماره 4 (پیاپی 61، زمستان 1388)

Considering advantages and disadvantages of mineral trioxide aggregate (MTA), Calcium Enriched Mixture (CEM) cement has been developed recently. The purpose of this study was to compare the apical microleakage of the root-end cavities prepared by ultrasonic or Er,Cr:YSGG laser and filled with MTA or CEM cement. Eighty single-rooted, extracted human teeth were instrumented and obturated. Root-end resection was made by removing 3 mm of the apex. The teeth were randomly divided into two experimental (n=30) and two positive and negative control (n=10) groups. After that, the retrograde cavities were prepared using ultrasonic or Er,Cr: YSGG Laser. According to the root-end filling materials (MTA or CEM cement), each group was then divided into two subgroups. Finally, specimens were cleared for assessing the amount of apical dye (Indian ink) penetration. The data were analyzed using Kruskall-Wallis and Dunn tests. Laser/CEM cement group showed significantly the lowest mean apical dye penetration. There were no statistically significant differences between Laser/MTA, ultrasonic/MTA and ultrasonic/CEM cement groups. Based on the findings of this study, CEM cement demonstrated lower rate of apical leakage compared with MTA, when the root-end cavities prepared with Er,Cr:YSGG Laser. The sealing ability of MTA was not different following root-end preparation by ultrasonic or Er,Cr:YSGG Laser.

In spite of the advances achieved in the field of dentin adhesives, the longevity of bond to dentin is still a challenge. According to recent studies, Matrix Metaloproteinase (MMP) inhibitors can increase clinical longevity of bonding and decrease leakage. The aim of this study was to evaluate the amount and pattern of doxycycline release from an experimental dentin adhesive containing this MMP inhibitor. In this experimental study, specimens containing 0.25 and 0.5 loading percent of doxycycline in an experimental monomer were prepared in cylindrical moulds of 12 mm diameter and 2 mm thickness. The adhesive monomer was composed of 12 wt% Bis-GMA, 10 wt% TMPTMA, 28 wt% HEMA and 50 wt% ethanol. Camphorquinone and amine were used as initiators. Addition of 0.25 and 0.5 w% doxycycline showed linear release in both groups. Increasing the loading percent of doxycycline caused more release. The release continued during the test period. Doxycycline release was observed from the experimental adhesive. Further studies in this field will help in preparing adhesive systems with more clinical longevity.

Root canal obturation is of great importance in root canal treatment. Its purpose is to eliminate microleakage, re-entry and growth of micro-organisms in the root canal system. The aim of this study was to compare coronal salivary microleakage in obturated root canals using lateral compaction, single cone gutta-percha and System B vertical compaction methods. In this in-vitro study, 80 single rooted, human extracted teeth were randomly divided into 3 experimental groups (n=20) and 2 positive and negative control groups (n=10). The specimens in each experimental group were obturated by using cold lateral compaction, single cone obturation, or continuous wave of condensation (system B). After that, coronal saliva leakage was evaluated. Data were analyzed using Survival analysis and Log-rank test. The results showed that all the specimens in the positive control group showed evidences of leakage during the first 7 days of study. None of the specimens in negative control group showed leakage during the 30-days period of the experiment. Survival test and log-rank test showed that at the end of the 30 days, there was significantly less resistance to coronal salivary leakage in single cone method compared with lateral compaction (P=0.039) and continuous wave of condensation (P=0.019) groups. No significant difference was observed between lateral compaction and System B vertical continuous method (P=0.564). Based on the results of this study, lateral compaction and system B groups showed higher resistance against the coronal leakage compared with single cone group.

In this in-vitro study, the effect of multiple adhesive coating on the microshear bond strength of composite to dentin and surface microhardness of dentin after treatment with four adhesives (One Step Plus, One Step, Single Bond, Single Bond 2) were evaluated.

One hundred intact human molars were cut to obtain disks of dentin having 2 mm thickness. For the microshear bond test, sixty disks were randomly divided into four groups. In each group one type of adhesive was used. In one half of a disk two layers and in another half six layers of adhesive were applied. Cylinders with 1mm height was filled with a composite and light cured. The cross-head speed was 0.5 mm/min. Vickers microhardness was tested on forty dentin disks which divided into four groups and prepared in the same manner used for microshear bond test. Data were analyzed by Two-way ANOVA and Tukey tests.

The highest and lowest bond strength were recorded as 29.49 ± 5.74 MPa (One Step Plus; 6 layers), and 21.23 ± 4.83 MPa (One Step Plus; 2 layers), respectively. The results indicated that One Step Plus bond strength in 6 Layers was significantly higher than 2 layers. The highest and lowest dentin hardness values were39.08 ± 8.34VHN (Single Bond; 2 layers) and 28.53 ± 5.98 VHN (One Step Plus; 6 layers). None of the adhesives exhibited significant difference in hardness with regards to the layers applied (P>0.05). Presence of filler in adhesives had no significant effect on bond strength (P=0.05) whereas caused significant decrease in the dentin microhardness (P<0.05). In addition, type of solvent had significant effect on the bond strength and bond strength was significantly higher in acetone-base adhesives (P<0.05). However, dentin microhardness was significantly higher in the ethanol-base adhesives (P<0.05).

Multiple adhesive coating had no influence on the microshear bond strength of composite to dentin and dentin surface microhardness. It was dependent on the type of adhesive used.

Insolubility has been stated as one of the important characteristics of the materials which are used as sealers in the endodontic treatments. The aim of this study was to evaluate the solubility of four endodontic sealers (ZOE, Dorifill, AH26 and Tubliseal).

Five specimens from each sealer with similar size were prepared. After first weighing, the samples were stored individually in bottles containing 50 ml of distilled water at 37ºC. After 7 days, the specimens weighed and changes in the weight of each sample recorded with a digital scale. The data were analyzed by ANOVA and Post-hoc Tukey HSD tests.

The results of this study indicated that Dorifill had the maximum solubility among all sealers with weight loss of 2.8%. Tubliseal and ZOE showed the weight loss of 1.4% and 2.3%, respectively. AH26 showed weight gain of 1.9% during 7 days. There were no significant differences in the mean weight changes between Dorifill, Tubliseal and ZOE groups (P>0.05). A significant difference was found between the mean weight changes of AH26 and that of the other groups (P=0.000).

From the results of this study, all tested sealers were in the standard limit of solubility, and thus, it could confirm this physical property of sealers for clinical applications.

Metal-free and fiber-reinforced composite (FRC) restorations have drawn considerable attention and interest in recent years for restoring in the posterior area due to their improved esthetics. Fracture resistance is one of the most important mechanical properties of materials because of 500-600 N load of occlusion. The restorations should tolerate this load. The purpose of this in vitro study was to compare the fracture resistance of FRC with that of zirconia all-ceramic for posterior partial dentures. Forty extracted human intact teeth (20 first premolars and 20 first molars) selected for fabricating 10 pairs of fiber-reinforced composite and 10 pairs of zirconia all-ceramic bridges. After receiving standard tooth preparation, the teeth were mounted with 7.5 mm distance between each other. The bridges were made and cemented on the teeth. Then the restorations were stored in 37ºC water for 30 days. The fracture resistance was measured using mechanical testing machine with cross-head speed of 1mm/min. Data were evaluated by Independent Sample T test. The mean fracture resistance in the ceramic group was 1329.41 N and for the F.R.C group was 1118.528 N with significant differences between them (P=0.034). The failure modes were mainly cohesive at pontic area for ceramic samples, but adhesive for FRC samples at pontic area. Both systems showed sufficient fracture resistance for using in posterior area.

Despite the significant improvement in dentistry, pain after endodontic therapy is still of concern for patients. Non-steroidal anti-inflammatory drugs are the most commonly prescribed oral analgesics used for dental pain relief after root canal treatment. The purpose of this study was to compare the effectiveness of Ibuprofen versus slow-released Diclofenac Sodium in controlling pain following root canal treatment. In this randomized clinical trial, mandibular molars with irreversible pulpitis in 90 patients were selected. The patients were divided into three groups (Ibuprofen, slow-released Diclofenac Sodium and placebo). After examination patients filled in the consent form. Then they received one of the mentioned drugs. After inferior alveolar nerve block, access cavity was prepared and the root canals were prepared using passive step back method. The canals were dried and temporary filling material was placed. Then the pain evaluation form (visual analog scale) was explained and delivered to the patients. Data were analyzed using Repeated Measurement ANOVA, Kruskal-wallis and Man-Whitney U tests. The mean pain intensity in slow-released Diclofenac Sodium group was 0.87 0.95, 1.17 1.10 for Ibuprofen group, and 2.14 1.70 for placebo group. The differences between groups were statistically significant (P<0.001). The effect of Ibuprofen in controlling post endodontic pain in the first 2 hours was more than slow-released Diclofenac Sodium (P=0.01), but in 10, 18, and 36 hours after treatment, slow-released Diclofenac Sodium was more effective than Ibuprofen (P<0.001). Premedication with single dose of slow-released Diclofenac Sodium can control post endodontic pain for a longer period of time compared with Ibuprofen.

The objective of the present study was to investigate knowledge and attitude of senior dental students towards HIV/AIDS. Its result could help in promotion of education. This educational research was carried out in two state dental schools in Tehran. The senior dental students in Tehran and Shaheed Beheshti dental schools were asked to fill in a self-administered questionnaire regarding their age, gender, parent's job, knowledge and attitudes towards treatment of patients with HIV/AIDS in Autumn semester 2007. Fifty five dental students (83%) including 27% male and 73% female in Shaheed Beheshti and fifty five dental students (85%) including 34% male and 66% female in Tehran dental schools were participated. The score for knowledge and attitude of the students were calculated separately. The data were analyzed using Independent sample t-test. The mean percentage of knowledge and attitude scores were 76.5% (at rang 1-3) and 50% (at range 1-5), respectively. Nearly all of the students believed that all patients should be considered as HIV positive in dental practice, while 49% preferred to refer HIV positive patients. Knowledge and attitude of students were not significantly associated with the gender and knowing HIV positive person (P>0.05). There is a need to improve knowledge and attitudes of dental students towards HIV/AIDS. It is suggested to emphasize on this subject in dental schools curriculum in Iran.

There are several risk factors in dentistry professional environment. Carelessness about occupational health regulation endangers dentist's life. Erconomics in dentistry is a scientific approach which introduces the latest ergonomic principles in dental profession. It discusses about physical and mental stresses. Ergonomic programs eliminate dentist physical and mental challenges and provide practical solution to establish efficient and comforting environment. This study reviewed the role and effectiveness of Ergonomics in dental profession. We used related journals, books and ergonomics websites to write this article. Many of researchers believe that awkward body posture and low movement are the sources of occupational disorders. Therefore, knowledge of ergonomics risk factors in dental office design is very important. Dentist's body posture and dental equipment evaluations are important factors in dental ergonomics. The most logical approach to design dental equipment for utilizing ergonomics principles is consideration of the dentist posture and type of movements and activities. In conclusion, dentists should be informed about dental ergonomics regulation and its different aspects. Furthermore, academic developments and research projects can be useful in this area.

Soft tissue management with providing the esthetic for restoration of a single implant in the anterior maxilla is of great importance. Tissue training helps to develop a proper emergence profile and natural tooth appearance. The aim of this article was to report a nonsurgical management of undesirable contours of soft tissue around maxillary anterior implants to achieve an optimum appearance. A 23-year-old female with congenital missing of maxillary lateral incisors, after completion of a fixed orthodontic treatment and gain enough space, received 2 dental implants. After second phase surgery and healing period, construction of the restorations was not possible through conventional method because of severe soft tissue collapse. In this case, soft tissue contours were corrected using a provisional restoration and then final restoration was made and delivered. Tissue training with a provisional restoration helps to re-establish normal gingival tissue contours and interdental papillae around the restoration of maxillary anterior implants.