Journal of Islamic Dental Association of IRAN
Volume:20 Issue: 3, 2008

Increased fracture rate of different rotary NiTi files has influenced the prognosis of root canal therapies. Torsion fatigue is one of the most important factors influencing the fracture rate of these rotary instruments; due to increased contact area between file and canal walls. The manual glide path is one of the recommended methods to decrease this problem. The purpose of this study was to investigate the influence of manual glide path on fracture or separation rate of NiTi rotary instruments. This experimental study was conducted using 160 root canals of human molar teeth with mild curvature of 15 to 35 degrees. Samples were divided into two groups. In group one manual glide path was carried out with k-type SS#10-20. The final preparation was performed with Mtwo files using crown down technique. The root canals in group two were instrumented with Mtwo files without prior application of manual glide path procedure. Data were collected and analyzed using ANOVA, Mann-Whitney and Mantel-Cox tests. Based on the results of this study, the three variables under investigation in both groups showed significant differences with each other when the defect (P=0.039); fracture or defect (P=0.005), and number of prepared canals (P=0.042) were compared. Survival analysis of Kaplan-Meier demonstrated that, the safety probability after preparation of 10 canals were 81.5% and 53.7% in group one and two respectively. The Mantel–Cox test showed significant difference between the two groups in terms of file working time (P=0.002). Based on these results, the fracture and defect can considerably be decreased when using SS hand files for preparation of apical third, before using NiTi rotary instruments. Key words: Manual glide path - Defect - Fracture - NiTi rotary files. Corresponding Author: Dr. Zarrabi MH., Professor, Endodontics Department and member of Dental Research Center, Faculty of Dentistry, Mashhad University of Medical Sciences. Mashhad, Iran.

Esthetic is one of the major demand of orthodontic patients. Therefore, esthetics orthodontics with special attention to soft tissue is considered as a new philosophy and approach. The purpose of this study was to investigate the correlation between selected hard tissue structures and soft tissue profiles. The sample was composed of 36 pre-treatment lateral cephalograms from 14-18 year-Old Iranian girls with class II Div 1 malocclusion. They had all their permanent teeth in the dentition, with no apparent syndrome. The cephalograms were taken with the same machine, and similar magnification for all. Eleven cephalometric hard and ten soft tisuue landmarks were measured. Analysis of data was conducted using Pearson correlation and multiple regression procedures. A significant correlation was observed between some of the dento-skeletal parameters and soft tissue structures. In the upper lip, the thickness in the base was related to the angle of ANB (P= 0.032) and upper incisors position (P= 0.032), whereas, the vermilion was affected by the position of the lower incisors (P= 0.032). The basal soft tissue thickness of the lower lip was related to the position of lower incisors (P= 0.015), while in the vermilion, was related to the position of upper incisors (P= 0.001). The upper lip height was associated with Witt's app (P= 0.003) and lower incisor position (P= 0.037), whereas, the lower lip height was affected by FMA (P= 0.019) and the lower incisor position. Mentolabial angle had the highest coefficient with hard tissue structures such as FMA, ANB, and position of the upper and lower incisors. No relationship was detected between chin height, nasolabial angle and hard tissue parameters. According to correlations between soft tissue and dentoskeletal structures that tend to compensate for hard tissue problems; both factors should be considered when diagnosing or treating orthodontic patients.

The locally delivered antibiotics are used as adjunct therapy together with scaling and root planning for periodontitis conditions. The aim of this study was to evaluate the microbiological effectiveness of locally delivered xanthan-based CHLO-SITE gel as an addition to scaling and root planning in treatment of cases with moderate to advanced chronic periodontitis. A randomized controlled split-mouth clinical trial method was used in this investigation. A total of 20 subjects were recruited from patients referring to dental clinics at the School of Dentistry, Shaheed Beheshti University of Medical Sciences. These cases were all met by the study’s inclusion criteria. Participation was voluntary and consent forms were obtained prior to study initiation. One quadrant with pocket depth of 4-6 mm was assigned as the experimental site and the opposite quadrant with similar condition selected as control randomly. After scaling and root planning on both sides, the CHLO-SITE, a xanthan-based gel was injected into the gingiva of the experimental sites. The pocket samples were taken from both sides at baseline, 1 and 3 months after treatment initiation. The samples were exposed to MacConkey, blood agar and nutrient agar mediums and colony counts (CC) were determined. The data were analyzed using Wilcoxon Signed Rank and Friedman tests. At baseline, the CC of the experimental and control sites were 2690000 and 2645000 respectively with no significant difference. At 1 month follow up, the CC was 13850 and 151610 at experimental and control sites respectively with a significant difference (p<0.027). The CC was 13400 at experimental sites, while it was 143555 at control sites after 3 months follow up. The difference between the two groups was statistically significant as well (p<0.05). This observation showed intensive CC reduction during the first follow up period, while the decrease was slightly less after 3 months follow up. Based on the results of this investigation, it was revealed that, subgingival injection of xanthan-based CHLO-SITE gel after scaling and root planning in patients with chronic periodontitis, may cause significant decrease in the colony counts compared with scaling and root planning alone.

OPN gene has been shown to play an important role during bone resorption. The significant expression role of OPN gene in bone resorption hypothesizes the increased quantity of this glycoprotein during bone resorption induced by orthodontic tooth movement. The aim of this study was to assess the expression of OPN gene in rat bone resorption induced by orthodontic tooth movement. In an experimental study, fixed Ni-Ti closed coil springs were applied for mesial movement of the maxillary left first molars in 13 male 8-week-old Wistar rats. The animal's right maxillary first molars were used as internal controls of the study. The rats were sacrificed 21 days after application of orthodontic appliances. The scratched materials from mesial sides of the alveolar bone were used for PCR evaluation. The collected data were subjected to Wilcoxon Signed Rank Test. Densitometry analysis of OPN coding mRNA on electrophoresis gel exhibited significant increase in gene expression on resorptive (mesial) side of the alveolar bone (P<0.001). The authenticity of PCR assessments was verified by GAPDH gene. Based on the results of this investigation and considering the study limitations, OPN gene expression increases during bone resorption induced by orthodontic tooth movements.

Biocompatibility of dental materials can help in their proper handling and usage in dental clinics. Zonalin is a foreign brand, reinforced Zinc Oxide Eugenol in two forms of liquid and powder. Zoliran is a similar compound produced in Iran. The purpose of this in-vivo study was to compare the biocompatibility of the two cements by using an animal model. This experimental study was conducted using twelve 3-4 month-old female rats weighing 150-200 grams. The two cements (Zonalin and Zoliran) were implanted into subcutaneous tissues of each rat. Zonalin was implanted in two sites on the left side of the body and Zoliran in two sites on the right side. The area in the center of the four sites was used as the control site, which was opened and sutured without any implantation. Biopsies were taken after 3, 15, 30 and 60 days intervals (3 rats were used at a time). The tissues were fixed in buffered formalin, sectioned and stained with Hematoxylin and Eosin according to standard methods. No considerable differences in the inflammatory responses were observed between the two materials at all time intervals. Similarly, no significant tissue response was noted for each material over time. The inflammatory response at test locations was always higher than the control sites at all time intervals. Although mild inflammation was observed, both materials under investigation appeared to be biocompatible and well tolerated.

If restorative materials have significant difference in thermal properties when compared with natural tooth structure, these thermal difference can produce noticeable thermal stresses, and may result in tooth fracture and leakage in the restoration which means failure in post and core treatment. The purpose of this study was to investigate the influence of thermal difference in combination of post and core materials used in endodontically treated maxillary central incisors. The finite element study model was used for this investigation. A 3-dimentional finite element model of a maxillary central incisor with a ceramic crown, a post, core, and supporting tissues were constructed. Three combinations of post, core and crown were used: 1) zirconium post/ composite core/ IPS Empress II crown; 2) carbon fiber post/ composite core/ IPS Empress II crown; and 3) gold post/ gold core/ IPS Empress II crown. For thermal change evaluation, the teeth were kept in 36ْ C and for cold evaluation a cold irritant at 0ْ C were applied on the outer surface of the model for seven seconds. Thermal gradients in the models with zirconium and carbon fiber post and composite core were more than the model with gold post and core after seven seconds. The maximum thermal stresses were seen in restoration rather than the surrounding tissues. Temperature changes can produce thermal stresses and the gold post and core generated the lowest thermal stress in restoration and dentin than other non metallic restorations.

Sandwich technique with glass ionomer (GI) has been recommended to overcome gingival microleakage. The study objectives were to compare open and closed sandwich techniques and evaluate GI injection in sandwich restorations. Sixty extracted sound premolar teeth were divided into 4 groups (n=15). A Class II cavity with gingival margin below CEJ was prepared on each tooth. Teeth were restored using glass ionomer (Fuji II LC), adhesive (Single Bond) and resin composite (Z250) as follows: Group 1, Open sandwich, GI injection; Group 2, Open sandwich, placing GI by a probe; Group 3, Closed sandwich, GI injection; Group 4, Closed sandwich technique, placing GI by a probe. Dye penetration was performed by using fushin after thermocycling. Teeth were sectioned then dye penetration was evaluated (0-3 scores) under a stereomicroscope. Statistical analysis was conducted using Kruskal Wallis and Mann-Whitney U tests. The least microleakage was observed in closed sandwich technique with GI injection and the most microleakage was observed in open sandwich using GI by a probe. When comparing the handling techniques, it was shown that using a syringe was significantly better than using a probe (P<0.05). There was no statistical difference between open and closed sandwich techniques although the mean dye penetration happened less in closed technique. According to the results of this study, injection of GI into cavity is recommended because of better access and superior adaptation of GI with cavity walls.

The reproduction of superstructures that exhibits the best passive fit when connected to multiple abutments is one of the major objectives in making implant supported prosthesis. Taking accurate impression is the most important requirement in order to ensure passive fit. The aim of this study was to review selected databases in search of journal articles describing the best implant impression techniques or their modifications that can increase the accuracy of the impression and finally a passive supra-structure reproduction. Language restriction was applied in order to select articles in English language only. Based on our strategy, search started from Cochrane Oral Health Group’s Trials Register, followed by searching PubMed and Medline databases. Hand searching was conducted for several dental journals. We checked the bibliographies of relevant clinical trials and review articles in search of studies that may not have been included in those hand searched journals. Several implant manufacturers’ product catalogues as well as their instruction manuals were searched for relevant information. A total of 92 articles were identified. Twelve of them were case-report articles that presented modified techniques. Another 50 presented detailed statistical comparison and were suitable for inclusion in this review. No RCT and Meta analysis papers were identified. Based on the reviewed articles it can be suggested that: Direct or open tray technique is more accurate procedure than indirect or close tray technique for duplicating oral conditions in the master cast. Polyether and polyvinylesiloxane (PVS) impression materials are more suitable for taking impression of dental implants. In case of multiple implants, splinted technique showed no advantages over non splinted techniques.

The enamel bond strength of resin containing materials is reduced right after bleaching. The aim of this study was to investigate the neutralizing effect of an antioxidant agent on bond strength of bleached enamel, using composite resin (Z100, 3M, ESPE, USA) and a resin modified glass ionomer (Vitremer, 3M, ESPE, USA) in this investigation. Likewise, it is intended to compare the results of this procedure with delayed bonding (for one week) effects. Ninety-six human sound 3rd molars were divided into eight groups. After initial preparations, the buccal enamel surface of the specimens in groups one and five were immediately bonded with composite resin (CR) and resin modified glass ionomer (RmGI) cylinders. The samples in other groups were all bleached six hours a day for five days consecutively. The specimens in groups two and six were bonded with CR and RmGI immediately after bleaching. The specimens in groups three and seven were immersed in distilled water at 37◦C for one week and groups four and eight, were exposed to 10% sodium ascorbate hydro gel for ten hours after bleaching and they were bonded with CR and RmGI immediately. Using DARTEC machine, the shear bond strength (SBS) were recorded for all samples. Data analyses were conducted by using One-way ANOVA and Tukey statistical tests. The mean SBS value in group two was significantly lower than other CR groups (P=0.045). RmGI did not bond to bleached enamel (group six).There was no significant difference between other RmGI groups (P>0.05). Both One week delay and application of 10% sodium ascorbate hydro gel before bonding can significantly increase the bond strength of composite and resin modified glass ionomer to bleached enamel.

Odontodysplasia is a rare disorder that may involve both primary and permanent dentition. This condition affects both enamel and dentin simultaneously. It is usually a localized lesion but, sometimes can be classified as generalized depending on the number of affected teeth in the oral cavity. Case report: A case of generalized Odontodysplasia in a 2.5-year-old girl, together with radiographic, pathologic characteristics as well as treatment together with a literature review is presented in this article.The primary molars were covered with SS-Crown, and anterior teeth were restored with composite resins.

Giant cell containing jaw lesions, are similar in most microscopic aspects but different in biological behavior. The aim of this study was to evaluate the biological characteristics of these lesions by using AgNOR as a cell proliferation marker. This descriptive study was conducted on 42 specimens, that were selected by convenient sampling method. The Hematoxylin & Eouzinofyle (H & E) technique were used for lama staining, and they were reviewed by maxillofacial pathologist. The sample blocks were separated and prepared for silver nitrate staining according to Ploton method. AgNOR cell counting was performed for selected visual fields of microscope. The counting was performed by looking at 100 cells in a given field using Nikone YS100 light microscope under 1000x magnifications. ANOVA statistical test was used in order to compare the group mean AgNOR differences. From 42 specimens under investigation, the one and only case of GCT was eliminated. In 21 cases of CGCG, the mean average cell count stained with AgNOR was 0.85 (±0.29). The mean average cell count was 0.76 (±0.32) In eight cases of ABC. In six cases of Cherubis, the average count was 0.87 (±0.10) and in six cases of Brown tumors, the average count of witch was 0.82 (±0.16) for NOR. No significant difference was detected between the mean AgNOR count and their clinical characteristics. In jaw lesions containing Giant cells, no considerable difference in mean AgNOR was detectable.

Several treatment methods have been suggested for reduction of dentin hypersensitivity such as Nd:YAG laser and Seal & Protect sealant materials. However, the effects of these methods have not been yet evaluated on dentin microhardness. The aim of this study was to compare the effect of Nd:YAG laser and Seal & Protect sealant on microhardness of dentin by using Vickers indicator. This in-vitro experimental study was conducted on forty-five freshly extracted human third molars. The buccal enamel surface was removed in order to expose the underneath dentin. Samples were randomly divided into three groups. Group one, received no treatment as controls, group two were exposed to Nd:YAG laser (1 W,10 Hz, 2 min) and the samples in third group were treated by Seal & Protect. Indentations were performed using Vickers indentor at 100 gr. load. Finally the average hardness number was calculated and statistical analysis was done with ANOVA and LSD tests. The results of this study demonstrated that Nd:Yag laser irradiation can increase dentin microhardness. However, it was not statistically significant (P>0.05) when compared with control group. Low level dentin microhardness was detected in Seal & Protect group when compared to other groups (P=0.01). Also, there was significant difference between the Nd:Yag laser and Seal & Protect groups (P<0.05). Nd:YAG laser irradiation for treatment of dentin hypersensitivity didnt decrease dentin microhardness. In contrary, using Seal & Protect can decrease dentin microhardness. Key words: Dentin Microhardness - Nd:YAG laser - Seal & Protect- Dentin hypersensitivity. Corresponding Author: Dr. Shirani F., Assistant Professor, Department of Operative Dentistry, Faculty of Dentistry, Isfahan University of Medical Sciences. Isfahan, Iran.