Journal of Dental Medicine

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Different techniques for local anesthesia are used in the mandible. The purpose of this study was to determine the effects of inferior alveolar dental nerve blocks by comparing the two akinosi and conventional techniques. 80 patients (aged 15-60 years old) were randomly divided into tow groups for extracting the mandibuler posterior teeth by akinosi and conventional techniques. Patients were all injected with 1.8 ml of Lidocaine 2% plus Adernaline j^nnnn .Then the Pain Sensation during injection,positive aspiration, beginning time of anesthesia, duration of anesthesia depth of anesthesia, and the anesthesia of soft tissue related to sensory nerves were evaluated. The results showed that the pain sensation in conventional technique was significantly higher than that of akinosi technique. The number of positive aspirations in conventional technique (12,5%) was higher than that of akinosi (5%) but not significantly different. The long buccal nerve anesthesia in akinosi technique (75%) was significantly higher than that of conventional technique. There was no significant difference between the two techniques for the depth of anesthesia. The success rate was 87.5% in conventional technique and 80% in akinosi technique. The average time of lips anesthesia in conventional technique was 3 minutes compared with 4 minutes in akinosi technique, which was not significantly different from each other. However, the beginning time of aneshtesia in tongue was significantly lower in conventional technique. No significant difference in the duration of anesthesia in lips and tonques between the two techniques was observed.

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Statement of Problem: Considering that the role of collagen fibers in dentin adhesion has not been thoroughly established yet, the removal of exposed collagen fibers with a deproteinization agent such as sodium hypochlorite following etching may facilitate access of adhesive resins to a substrate that is more penetrable and less sensitive to water content which in turn would lead to a more durable bonding system. Furthermore, due to sodium hypochlorite clinical application as a cleanser or canal irrigator, its effects on the surface before etching may influence adhesive bonding strength.

Purpose: The goal of this study was to evaluate the effects of a two-minute 5.25% NaOCL application on composite restorations microleakage, using two different adhesive systems.

Materials and Methods: In this interventional experimental study, on seventy-two extracted boving incisors class V cavities were prepared on dentinal surfaces. The specimens were then randomly divided into six equal groups: A1) Acid etch (AE) dentin bonding Scontchbond Multipurpose Plus (SBMBP), A2) AE/ dentin bonding One Step (OS), B1) NaOCL/ AE/SBMPp, B2) NaOCL/AE/OS, C1) AE/NaOCL/SBMPp, C2) AE/NaOCL/OS. After bonding procedures according to the manufacturer’s instructions, cavities were restored using Z100 composite. Then, the specimens were thermocycled for 500 times in water baths of 5 and 55C. After thermocycling, the specimens were immersed in a 0.2% solution of basic fuchsin for 24 hours. A buccolingual section at the center of each restoration was obtained and examined with a stereomicroscope to evaluate color penetration into cavities. The data were subjected to two-way variance analysis.

Results: The microleakage of group B was significantly less than those of A and C (P<0.001). No significant difference was found between groups A and C (P=0.73). There were also no significant differences within groups A, B and C (P=0.852). No interaction was observered between dentin bondings and surface treatment (P=0.946).

Conclusion: The findings of this study revealed that NaOCL application after etching, for hybrid layer removal, did not make any difference on microleakage as compared with conventional bonding systems. However, its application before etching improved the seal of restoration. Additionally, there was not any significant difference between two different dentin bondings.

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Background and Aim: Root filling materials are usually in close contact with living tissues. So their biological properties like mutagenicity and cytotoxicity are important. These properties help us determine the potential damage to periapical tissues, or potential DNA mutations, and malignant transformation of the cells. The aim of this study was to evaluate the mutagenicity and cytotoxicity of four root canal sealers: AH Plus (Dentsply, DeTrey), Ketac-Endo Aplicap (3M ESPE), Sankin Apatite III (Sankin K.K), and Tubli-Seal EWT (Kerr).

Materials and Methods: In this experimental in vitro study fresh and set specimens from AH Plus, Ketac-Endo Aplicap, Sankin Apatite III, and Tubli-Seal EWT were immersed in culture medium for 1, 2 and 7 days. Cytotoxicity was assessed using tetrazolium bromide reduction assay (MTT) after 1, 2 and 7 days exposure of diluted extracts to L929 cells. Extracts of sealers in phosphate buffer saline (PBS) were used to examine the mutagenic effects by sos-umu test according to standard procedures. Data were analyzed using one way ANOVA, Kruskall Wallis, Mann Whitney and Post hoc tests with P<0.05 as the level of significance.

Results: Extracts of all freshly mixed sealers were cytotoxic. Ketac-Endo Aplicap and Sankin Apatite III showed the lowest toxicity respectively and Tubli-Seal EWT the highest. In contrast to other sealers, the cytotoxicity of Tubli-Seal showed no decrease with time. -galactosidase did not increase significantly thus none of the sealers showed mutagenic effects.

Conclusion: Based on the results of this study, Tubli-Seal EWT showed the highest cytotoxicity with time. Other sealers showed decreasing cytotoxicity with time. No mutagenicity effects was observed in none of  tested materials.

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Background and Aim: Several agents were used for pulpotomy in primary molars. Formocresol is the most common drug in this procedure. In some studies it has been shown that, this material has potential some side effects, so it is essential to find other alternatives. The aim of this study was to evaluate clinical and radiographic success rates of mineral trioxide aggregate and formocresol.

Materials and Methods: In this randomized clinical trial study, 70 carious primary teeth of 4 to 7-year-old children were pulpotomized, and remaining pulp was dressed with Root MTA and formocresol. The clinical and radiographic follow up evaluations were performed at 6, 12 months by a blind dentist. The data were analyzed by Fisher's exact test.

Results: At the end of 1-year follow-up period, in formocresol group sinus tract and tenderness to percussion were seen in 2 teeth, internal resorption was seen in 1 tooth, and furcation radiolucency was seen in 2 teeth. Clinical and radiographic signs of failure were not seen in any case of (Iranian) Root MTA group.

Conclusion: Based on the results of this study, Iranian MTA can be used for pulpotomy in primary molars.

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Background and Aims: Formocresol is one of the most common pulpotomy medicaments for primary teeth. Because of its systemic and local side effects, it may be essential to use another material instead of formocresol. The aim of this study was to evaluate the histopothalogy of pulp after pulpotomy teeth with sodium hypochlorite and formocresol.

Materials and Methods: In this randomized clinical trial, 22 canine teeth that must be extracted because of orthodontic treatment were selected. The teeth were randomly divided into 2 groups (n=11) and pulpotomized with formocresol or sodium hypochlorite. These teeth were extracted after 2 months and pulpal response was evaluated according to the degree of inflammation and extent of pulpal involvement. Dentinal bridge formation was also evaluated. The data were analyzed by Mann-Whitney test.

Results: In formocresol group, mild inflammation was seen in 4 and moderate inflammation in 3 and severe inflammation in 4 cases. In sodium hypochlorite group mild inflammation was seen in 6 cases and moderate inflammation in 4 cases and severe inflammation in 1 case. Mann-Whitney test revealed that this difference was not statistically significant (P>0.05). In formocresol group, necrosis was seen in 5 cases, but abscess and internal resorption were not seen in any cases. In sodium hypochlorite group, internal resorption was seen in 3 cases but necrosis and abscess were not seen in any cases.  Mann-Whitney test showed that the difference between two groups was significant in terms of necrosis (P=0.02). In sodium hypochlorite group, dentinal bridge was formed in 3 cases however, no dentinal bridge formation was seen in formocresol group. Mann-Whitney test showed that this difference was not significant statistically (P>0.05).

Conclusion: Based on the results of this study, sodium hypochlorite can be used as a pulpotomy agent in primary teeth.

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Background and Aims: Accurate bone measurements are essential for determining the optimal size and length of proposed implants. The radiologist should be aware of the head position effects on image dimensions in each imaging technique. The purpose of this study was to evaluate the effect of mandibular plane angle on image dimensions in linear tomography.
Materials and Methods: In this in vitro study, the vertical dimensions of linear tomograms taken from 3 dry mandibles in different posteroantenior or mediolateral tilts were compared with actual condition. In order to evaluate the effects of head position in linear tomography, 16 series of images while mandibular plane angle was tilted with 5, 10, 15 and 20 degrees in anterior, posterior, medial, or lateral angulations as well as a series of standard images without any tilt in mandibular position were taken. Vertical distances between the alveolar crest and the superior border of the inferior alveolar canal were measured in posterior mandible and the vertical distances between the alveolar crest and inferior rim were measured in anterior mandible in 12 sites of tomograms. Each bone was then sectioned through the places marked with a radiopaque object. The radiographic values were compared with the real conditions. Repeat measure ANOVA was used to analyze the data.
Results: The findings of this study showed that there was significant statistical difference between standard position and 15º posteroanterior tilt (P<0.001). Also there was significant statistical difference between standard position and 10º lateral tilt (P<0.008), 15º tilt (P<0.001), and 20º upward tilt (P<0.001). In standard mandibular position with no tilt, the mean exact error was the same in all regions (0.22±0.19 mm) except the premolar region which the mean exact error was calculated as 0.44±0.19 mm. The most mean exact error among various postroanterior tilts was seen in 20º lower tilt in the canine region (1±0.88 mm) and for various mediolateral tilts the most exact error was seen in the canine region in 20º upper tilt (2.9±2 mm).
Conclusion: The mean exact errors in various regions and various 5º to 20º posteroanterior and mediolateral mandibular tilts were in the range of acceptable values (≤1 mm) except for the canine region. However, this effect is more considerable in mediolateral tilt compared with posteroanterior tilt, posterior region compared with anterior region, and upper tilt compared with lower tilt.

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Background and Aims: In the last decade, several studies have reported the isolation of stem cell population from different dental sources, while their mesenchymal nature is still controversial. The aim of this study was to isolate stem cells from mature human dental pulp and follicle and to determine their mesenchymal nature before differentiation based on the ISCT (International Society for Cellular Therapy) criteria.
Materials and Methods: In this experimental study, intact human third molars extracted due to prophylactic or orthodontic reasons were collected from patients aged 18-25. After tooth extraction, dental pulp and follicle were stored at 4°C in RPMI 1640 medium containing antibiotics. Dental pulp and follicle were prepared in a sterile condition and digested using an enzyme solution containing 4mg/ml collagenase I and dispase (ratio: 1:1). The cells were then cultivated in α-MEM medium. Passage-3 cells were analyzed by flow cytometry for the expression of CD34, CD45, CD 73, CD90 and CD105 surface markers.
Results: Dental pulp and follicle were observed to grow in colony forming units, mainly composed of a fibroblast-like cell population. Flow cytometry results showed that dental pulp and follicle are highly positive for CD73, CD90 and CD105 (mesenchymal stem cell markers) and are negative for hematopoietic markers such as CD34 and CD 45.
Conclusion: In this study we were able to successfully confirm that dental pulp and follicle stem cells isolated from permanent third molars have a mesenchymal nature before differentiation. Therefore, these two sources can be considered as an easy accessible source of mesenchymal stem cells for stem cell research and tissue engineering.

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Background and Aims: Reliable bonding between tooth substrate and zirconia-based ceramic restorations is always of great importance. The laser might be useful for treatment of ceramic surfaces. The aim of the present study was to investigate the effect of laser irradiation on the shear bond strength of zirconia ceramic surface to dentin.

Materials and Methods: In this experimental in vitro study, 40 Cercon zirconia ceramic blocks were fabricated. The surface treatment was performed using sandblasting with 50-micrometer Al2O3, CO₂ laser, or Nd:YAG laser in each test groups. After that, the specimens were cemented to human dentin with resin cement. The shear bond strength of ceramics to dentin was determined and failure mode of each specimen was analyzed by stereo-microscope and SEM investigations. The data were statistically analyzed by one-way analysis of variance and Tukey multiple comparisons. The surface morphology of one specimen from each group was investigated under SEM.

Results: The mean shear bond strength of zirconia ceramic to dentin was 7.79±3.03, 9.85±4.69, 14.92±4.48 MPa for CO₂ irradiated, Nd:YAG irradiated, and sandblasted specimens, respectively. Significant differences were noted between CO₂ (P=0.001) and Nd:YAG laser (P=0.017) irradiated specimens with sandblasted specimens. No significant differences were observed between two laser methods (P=0.47). The mode of bond failure was predominantly adhesive in test groups (CO₂ irradiated specimens: 75%, Nd:YAG irradiated: 66.7%, and sandblasting: 41.7%).

Conclusion: Under the limitations of the present study, surface treatment of zirconia ceramics using CO₂ and Nd:YAG lasers was not able to produce adequate bond strength with dentin surfaces in comparison to sandblasting technique. Therefore, the use of lasers with the mentioned parameters may not be recommended for the surface treatment of Cercon ceramics.

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Background and Aims: Since impression materials usually contact with saliva, blood, and oral soft tissues, their microbial contamination are harmful in immunocompromised patients. The aim of the present study was to determine the bacterial and fungal contamination in common impression materials.

Materials and Methods: In current lab trial study, 5 different samples from each 4 impression materials were homogenized in 1 ml Tween 80 and then 100µl of each sample were cultured onto blood agar, EMB, or sabouraud dextrose agar. Bacterial and fungal cultures were incubated at 37º C and 30º C, respectively. The isolated bacterial and fungal colonies were enumerated and identified using specific diagnostic media and tests. Data were analyzed using Kruskal-Wallis test.

Results: Totally 75% of samples had one or several bacterial contaminations. Iranian alginate and Speedex (putty) were the most contaminated samples. On the other hand, Speedex (light body) and foreign alginate showed lower contamination. Species of Micrococcus, Staphylococcus, Bacilluses, Corynebacteria, gram negative Citrobacter, Actinomycetes and Neisseria were isolated from the analyzed impression materials. Aspergillus, Penicillium, Alternaria, Cladosporium and Sepdonium were the fungi isolated from impression materials. Statistical significant difference was shown between bacterial contamination of Iranian and foreign alginates (P=0.001). There was no statistical significant differences between the bacterial and fungal isolated colonies (CFU/gr) of 4 tested impression materials (P=0.21).

Conclusion: Several opportunistic bacteria and fungi were isolated from impression materials especially from Iranian alginate and Speedex putty which indicated their contamination.

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Background and Aims: Accurate recording of implant location is required to achieve passive fit and have the implants without stress concentration. The aim of this in-vitro study was to evaluate the dimensional and angular accuracy of open-tray and closed-tray impression techniques using polyether impression material and also to assess the surface detail reproduction of the tooth while impression making.

Materials and Methods: One reference metal model with 2 implants (Implantium) on the position of the maxillary second premolar and first molar and one molar tooth for evaluation of surface details was prepared. 27 polyether impressions of these models were made (9 using open-tray, 9 using closed-tray techniques and 9 were made just of the surface of the teeth without any implants). Impressions were poured with ADA type IV stone. Coordinate Measuring Machine was used for measuring the dimensional accuracy and video measuring machine for surface detail reproduction. All of these measurements were compared with the measurements on the reference model. Data were analyzed by and compared by T-test and One-way ANOVA.

Results: There was a significant statistical difference between open-tray and closed-tray techniques (P<0.001). There was no significant difference in the surface detail reproduction of open-tray and Closed-tray techniques and impression making with or without the implants (P>0.05).

Conclusion: The accuracy of open-tray impression technique was more than closed-tray technique. The surface detail reproduction of the tooth was not affected by impression technique.

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Background and Aims: Calcium hydroxide has a pronounced antimicrobial activity against most of the bacterial species found in infected root canals and endodontic infections. It is one of the most frequently used intracanal medications in endodontic therapy. The objective of this study was to determine the antimicrobial efficacy of six calcium hydroxide formulations (mixed with saline, lidocaine 2%, chlorhexidine 2%, chlorhexidine 0.2%, Iodine Potassium iodide (IKI) 2%, and glycerin) on Enterococcus faecalis using agar diffusion test.
Materials and Methods: Twelve culture plates were incubated with Enterococcus faecalis. Five cavities were made in each plate with 5 mm diameter and 4 mm depth. Two plates were randomly considered for each calcium hydroxide formulation and filled completely with creamy mixture of tested materials. The plates were incubated at 37ºC for 48 hours. The diameter of inhibition zone around each well was recorded in millimetres and data were submitted to ANOVA and Tukey tests.
Results: The results of this study showed that all tested calcium hydroxide pastes had good antimicrobial activity. The antimicrobial activity of calcium hydroxide mixed with lidocaine, chlorhexidine 2% and IKI 2% were significantly greater than that of calcium hydroxide mixed with saline (P<0.001). No significant differences in the antimicrobial  were found between the other groups (P>0.01).
Conclusion: Considering the results of this study, lidocaine 2%, chlorhexidine 2% and IKI 2% are suggested to be used for preparation of calcium hydroxide paste. Further studies with different methods are needed for confirming these results.

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Background and Aims: Periodontitis is one of the most common oral diseases with the various incidence rates in different populations. A number of bacteria are considered as the major etiologic agents of periodontitis. The aim of the present study was to determine the prevalence of periodontopathogen bacteria in patients using both PCR and culture techniques.
Materials and Methods: In this study, one-hundred patients (including 62 females and 38 males with an average age of 49±11.5 years) with adult periodontitis referred to periodontics department of School of Dentistry/Tehran University of Medical Sciences were investigated. The samples were taken and sent immediately to the laboratory for culture and molecular evaluation. The PCR was performed using specific primers and the statistical analysis of data was performed using SPSS statistic software and McNemar test.
Results: The results demonstrated that the total detection rate in culture method was 64%. The rate of Aggregatibacter actinomycetemcomitans (Aa) was 28% which was significantly higher than that of Porphyromonas gingivalis (Pg) (6%) and Prevotella intermedia (Pi) (3%). 27% of cases showed mixed bacterial growth. 65% of patients were positive using molecular method. The rate of Aa (30%) was significantly higher than that of Pg (7%) and Pi (5%). The mixed PCR positive rate containing of Aa, Pg and Pi was (23%).
Conclusion: In this study, it was found that most of the bacteria isolated using culture and molecular methods were Aa, Pg and Pi, respectively. Although the detection frequencies of both techniques were similar, the specificity, sensitivity and bacterial detection speed of the PCR technique is obviously higher. Therefore, the use of molecular techniques is strongly recommended. However, both techniques seem to be suitable for microbiological diagnostics.

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Background and Aims: One of the decisive factors on the final esthetic results of implant treatment is the abutment material. Ceramic abutments are nowadays very popular in this regard. The purpose of this study was to compare the fracture resistance of three zirconia abutments with titanium abutment.

Materials and Methods: Four groups of abutments (five specimens in each) were prepared. The abutments were prefabricated titanium, prefabricated zirconia, zirconia-metal, and copy-milled zirconia abutment. After securing the abutments to the implant using a torque of 24 Ncm, they were mounted into a mounting jig using the 30º tilt. The force was applied on the assembly till the failure occured. Facture resistance and mode of failure were recorded for each specimen. The data were analyzed using One-way ANOVA.

Results: The mean values recorded for fracture resistance of different zirconia abutments varied between 426 to 688 N however, there was no significant differences among the groups (P=0.14). Body fracture was observed only in prefabricated zirconia abutments. Screw fracture and screw bending were the common failures observed in other groups.

Conclusion: Zirconia abutments of any type could be successfully used in regular plateform implants.

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Background and Aims: The marginal integrity of fixed restorations always is a major matter of concern for dental clinicians. Any cause of distortion, including veneering processes, in the marginal integrity is supposed to be detrimental for long-term success of fixed dental prostheses. The aim of this in vitro study was to compare the marginal adaptation of two different full ceramic restoration systems (Zirkouzahu&Cercon) and possible changes in marginal integrity following the multiple veneering process.

Materials and Methods: Twelve all-ceramic crowns in the form of coping were fabricated on a pre-made standard metal die with finish line of shoulder preparation from two commercial systems: Cercon® and Zirkonzahn®. The specimens were not cemented. The Crown/Die discrepancy were measured by means of a precise stereo microscope (accuracy±0.1 μm), at various points (n=12) selected along circumferential margin of the restorations. Same procedure was accomplished after applying the veneering porcelain. The mean gap dimensions were calculated and data were analyzed by multivariate (b) test.

Results: Mean marginal gap dimensions before and after veneering porcelain firing cycles, for Cercon® were (59.67±13.46 µm) and (63.75±14.16 µm) and for Zirkonzahn® were (65.81±24.37 µm) and (64.74±21.94 µm), respectively. Hotelling trace Multivariate(b) test method showed that the rate of mismatching marginal integrity in two groups (Cercon® and Zirkonzahn®) had no significant difference before and after porcelain firing (P>0.05).

Conclusion: Within the limitation of this study, the marginal integrity of both systems were seems to be within the clinically acceptable standard dimension, i.e. 120μm.The marginal gap of both all-ceramic systems were not affected by veneering porcelain firing cycles.

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Background and Aims: Endodontically treated teeth are prone to fracture because they loose a big amount of their structure. The treatment plan of those teeth is completed when they are rehabilitated with a strong and functional restoration. The purpose of this study was to evaluate the fracture resistance of endodontically treated teeth restored with amalgam cuspal coverage in comparison with other restorative techniques.

Materials and Methods: 40 human healthy maxillary premolars were divided into 4 groups: group1 (S): sound teeth, group 2(Co): endodontically treated teeth with MOD cavity restored with bonding and composite, group 3(Am-B): endodontically treated teeth with MOD cavity restored with bonding and amalgam and group 4 (Am-CC): endodontically treated teeth with MOD cavity restored with amalgam cuspal coverage. Then the restorations were stored in water and room temperature for 100 days at then thermocycled for 500 cycles between water baths at (5.5 ± 1) and (55 ± 1) ⁰ C. The fracture resistance was evaluated by universal testing machine (Instron, 1195 UK) with the compressive force of about 2000 N in 0.5 mm/min. The fracture modes were evaluated in four groups by a stereomicroscope. Statistical analysis (Scheffe test) was done for all groups (P<0.05 was considered as the level of meaningfulness).

Results: The highest fracture resistance was found in group 4 (Am-CC) (976 ± 23.27 N) that had no significant difference with sound tooth (P>0.05). The lowest fracture resistance was found in group 2 (Co) (384 ± 137.4 N) that had no significant difference with group 3 (Am-B) (P>0.05). The fracture resistance in group 4 was significantly higher than group 2 (Co) and 3 (Am-B). The fracture mode in group 1 was cohesive within tooth and in group 2 (Co) and 3 (Am-B) was mixed cohesive and adhesive, and in group 4 was cohesive within in restorative material.

Conclusion: The highest fracture resistance was found in teeth that received amalgam cuspal coverage.

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Background and Aims: Apoptosis or programmed cell death plays an important role in the pathogenesis of many diseases. Previous studies suggest that apoptosis is involved in the pathogenesis of periodontal disease, on the other hand it is also suggested that diabetes mellitus enhances apoptosis of connective tissue cells. Thus, we measured expression of proteins which are relevant to apoptosis in the gingival tissue of diabetic patients with chronic periodontitis in comparison to non diabetic individuals.

Materials and Methods: 25 patients with diabetes and chronic periodontitis and 16 non diabetic controls were included in this study. 4 weeks after scaling and root planning and oral hygiene instructions, periodontal surgery was done and gingival tissues obtained during surgery, were sent to lab to investigate expression of Fas, P53, Bcl-2 and Survivin using real-time PCR technique. Data were analyzed using Mann-Whitney and Chi-squared.

Results: Pro-apoptotic proteins (Fas, P53) were significantly (P<0.05) higher in gingival tissues of diabetics (9.5×10^-6, 2.4×10^-6, respectively) in comparison to non diabetics (9.4×10^-7, 5.6×10^-7), whereas the difference in expression of anti-apoptotic proteins (Bcl-2, Survivin) between 2 groups was not significant (9.7×10^-8, 3.5×10^-7 in comparison to 1.4×10^-7, 3.1×10^-7, respectively)( P =0.91, P =0.29 respectively).

Conclusion: Apoptosis was increased in gingival connective tissue of diabetic patients with chronic periodontitis in comparison to non diabetic ones. Therefore , intervention in expression or function of pro-apoptotic proteins (Fas, P53) could be a new goal in the treatment of periodontal disease of diabetic patients.

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  Background and Aims: The aim of this review article was to present the information have been published, regarding the functional properties of Zirconia until today.

  Materials and Methods: A review of the literature was carried out in MEDLINE database using key words (Dental ceramic, Zirconia, 3Y-TZP, Clinical performance, Machining and Transformation toughening). These searches were limited to the articles published after the year 2000.

  Conclusion: Despite excellent clinical results in short-term studies, there is still a major need to have more clinical and laboratory long-term information about zirconia restorations.

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  Background and Aims: The main cause of erosion is acid exposure . Side effects of erosion necessitate therapeutic agents’ uses. The aim of this study was to investigate the effects of nano- hydroxy apatite in tooth remineralization following exposure to soft beer.

  Materials and Methods: This in vitro experimental study was conducted on 18 human impacted third molars that had been surgically extracted. The microhardness of specimens was measured. Then teeth were exposed to soft beer and their secondary microhardness was measured. The teeth were divided into 2 groups (water and nano-hydroxy apatite solution) and were placed on 9 orthodontics appliances and delivered to 9 volunteers. These volunteers placed the tooth on one side in water for 5 minutes and the tooth in opposite side in nano-hydroxyapatite solution. This application was repeated 6 times a day for 10 days. The microhardness of teeth was measured again. Data were analyzed using Paired T-test.

  Results: The tooth enamel microhardness reduced after exposure to soft beer significantly (P=0.04). The microhardness of 9 teeth after being in water showed significant changes (P=0.012). The microhardness of 9 teeth significantly changed after exposure to nano -hydroxyapatite solution (P=0.001) .

  Conclusion: Based on the results of this study, 10% solution of nano- hydroxy appatite could restore the erosive lesions .

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  Background and Aims: The importance of quality in medical education makes the need for better standards in educational systems in the center of interest as the basis for certification. Standards needed to be evaluated by program administrators before the implementation phase. The purpose of this study was to evaluate the general dentistry standards program in Islamic republic of Iran from dental schools view point.

  Materials and Methods: This descriptive study was performed during the year 2011 and 2012. A list of 16 faculties was introduced by the dental secretariat of the Ministry of Health and Medical Education. A check list was conducted based on the basic standards of undergraduate dental program that consisted of the importance and feasibility of each standard. The checklist was evaluated by sixteen dental schools representatives and asked their faculty members and reported back to the dental secretariat of the Ministry of Health. Results were reported in descriptive statistics manner.

  Results: Data were collected from 14 dental schools. (Response rate=87%). All of the criteria were essential with more than 85% agreement of the faculties. There were more than 70% of criteria that were not feasible in less than one year.

  Conclusion: The dental standard program was widely accepted by the faculties over the country. However, it seemed that by the faculties it would fail if used as accreditation base line.

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  Background and Aims: The aim of this descriptive longitudinal study was to determine the type of teeth that were more prone in accidental bracket debonding and also to investigate the relationship between broken bracket bond and intervening factors such as age, type of malocclusion and sex.

  Materials and Methods: We used a pilot study to determine the correct sample size for this study. According to the pilot study which consisted of 20 records of patients, it was concluded that 576 patient’ records was needed. The mean time for a bracket before it fails was also measured using Kaplan-Meier method. Cox regression analysis was done to examine the effect of age, gender, and class of malocclusion on each tooth with broken bracket. Data were analyzed using the software SPSS 20.

  Results: Results showed that the percentage of unexpected broken bracket bond for each tooth varied and they were significantly related only in second premolars in both jaws with malocclusion that was different for each tooth (P=0.037, P=0.004).

  Conclusion: Maxillary second premolars and mandibular second premolars had the highest rate of unexpected broken bracket bond in CL II CL I malocclusion respectively. Age, gender and malocclusion had no effect on the unexpected broken bracket bond for other teeth.