Journal of Dental Medicine
Year:2011 | Volume:24 | Issue:2 (67)|Papers Count:10

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 aMEM medium. Passage-3 cells were analyzed by flow cytometry for the expression of CD34, CD45, CD73, 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.

Background and Aims: Considering the great incidence of implant failures due to high stresses around implant and at bone-implant interfaces, the aim of this study was to compare the effects of three different implant-macro designs on the quantity and distribution pattern of stresses around implants.Materials and Methods: In this experimental in vitro study, three types of implants including Biohorizon (4×10.5 mm), Iler (4×10 mm), and Swiss Plus (4.1×10 mm) were studied by applying photo-elastic method. The implants were placed within photo-elastic models with dimensions of 50×50×10 mm. Then through open tray impressed method, crowns for each implant were constructed and cemented. Vertical and oblique loads of 100 N and 150 N were applied on the cemented crowns within polariscope machine. Then the photographs were evaluated using Isochromatic Fringe Characteristics table.Results: Under vertical loads of 100 N and 150 N, the values for Biohorizon, Iler, Swiss Plus fixtures at the cervical region were (2.35, 3.60) N, (2.50, 3.10) N, and (1.39, 2.35) N, respectively; and in apical region the values were (1.63, 2.35) N, (1.82, 2.35) N, and (2.50, 3.10) N. Under oblique loads, the measures at the cervical region were (4.00, 5.00) N, (1.82, 5.00) N, and (5.20, 6.00) N; and in apical region were (1.39, 2.00) N, (4.00, 2.35) N, and (2.35, 3.00) N, respectively for mentioned implants.Conclusion: Under vertical loads, the lowest cervical stresses were observed in Swiss Plus fixture and the lowest apical stress values were recorded for Biohorizon fixture. Under oblique loads, the lowest cervical stresses were found in Iler implant and lowest apical stresses were recorded for Bohorizon.

Background and Aims: Cephalometric measurements cannot be performed for screening purposes, therefore orthodontists usually have to use either photographic or anthropometric measurements in such occasions. Finding a valid and reliable alternative could be of great value. The purpose of this study was to evaluate the correlation between McNamara’s cephalometric unit difference and a proposed soft tissue equivalent.Materials and Methods: An anthropometric ruler was redesigned and used in this study. Soft tissue measurements were performed on 36 randomly selected specimens by two investigators. The soft tissue measurements included external auditory meatus to subnasale (Ext-Sn), external auditory meatus to soft tissue pogonion (Ext-Pog), and the difference between them (UDMA´). These measurements were considered as equivalents to cephalometric indices in McNamara’s anteroposterior measurements, including maxillary (Co-A) and mandibular (Co-Gn) unit length and their difference (UDMA), respectively.Results: All soft tissue variables had an intra-class correlation coefficient (ICC) above 0.90. There was a high and significant correlation between cephalometric and anthropometric measurements (P<0.01). The ICC between (Ext-Sn) and (Co-A) was 0.890, 0.869 between (Ext-Pog) and (Co-Gn), and 0.819 between UDMA´ and UDMA.Conclusion: The proposed anthropometric method showed a good correlation with cephalometric equivalents and the results show that this method could be used for screening purposes, especially when a low-cost, non-invasive method is required. However, it cannot be considered as a substitute for cephalometry in diagnostic and treatment purposes.

Background and Aims: The aim of this study was to evaluate the effect of application of two types of primers over bracket bases on the shear bond strength (SBS) and mode of bond failure.Materials and Methods: In this study, 75 human premolar teeth were divided into three equal groups. In group 1 (control), after surface preparation of enamel by conventional method (acid etching+primer) brackets were bonded with Transbond XT composite. In group 2 (TX), brackets were bonded to enamel same as the first group but Transbond XT primer were used on bracket bases before placement of composite. In group 3 (PL), Transbond plus primer was applied on bracket bases before placement of composite. After 24 h, the SBS test was performed by universal testing machine at crosshead speed of 0.5 mm/min. Then, adhesive remnant index (ARI) scores and percentage of cohesive fracture were determined using stereomicroscopy. SBS data were analyzed by one-way ANOVA and Duncan tests. Kruskal-Wallis and Mann-Whitney tests were used to analyze ARI and cohesive fracture results.Results: There was significant difference in SBS values among the groups (P<0.001). The highest SBS was shown in TX group and the lowest was seen in PL group. There was no significant difference between control and TX groups in ARI scores (P=0.199). No significant difference was found in cohesive fracture values between the groups (P=0.093). Both the control and TX groups showed significant difference in ARI scores and cohesive fracture compared with the PL group in all of the comparisons (P<0.001).Conclusion: Application of Transbond XT primer over bracket base affects the bond strength and failure mode. Transbond XT primer increased the bond strength but Transbond plus primer decreased it.

Background and Aims: Use of glass ionomer cements in pediatric dentistry is increasing and limited information exists with regard to the effect of salivary contamination on the shear bond strength of glass-ionomer to dentin in primary teeth. The aim of this study was to evaluate the effect of salivary contamination on the shear bond strength of two types of glass ionomer cements to dentin in primary teeth.Materials and Methods: A total of 36 human extracted primary molars were used in this study. The specimens were divided into two groups for each material and then further subdivided into three groups: group 1: uncontaminated, group 2: contaminated with saliva, group 3: contaminated, washed and air dried. The specimens in groups I, II, III were bonded to glass-ionomer and in groups IV, V, VI to resin modified glass-ionomer. Shear bond strength was measured using an Instron machine at 1 mm/min cross head speed. Data were analyzed with ANOVA and T-test.Results: There were significant differences in the mean shear bond strength among groups I (7.09±0.8) & II (5.17±1.88) (P=0.04), Groups IV (7.17±1.52) & V (4.85±1.03) (P=0.01), and groups V & VI (6.62±1.43) (P=0.04). On the other hand, there were no significant difference among groups II & III (6.38±1.01) (P=0.19) and groups I & IV (P=0.91).Conclusion: Results showed that salivary contamination can decrease the mean shear bond strength of glassionomer and light-cured glass-ionomer to dentin in primary teeth.

Background and Aims: Considering the application of recycled metallic brackets in orthodontic treatments and probably more resultant metal ion release, which can cause cytotoxic side effects, this study was set up to assess the effect of recycling process of orthodontic brackets on metal ion release.Materials and Methods: In this experimental study, 80 Discovery direct bond brackets (Dentarum, Germany) were divided into 2 groups, new and recycled brackets (n=40), then each group was divided into two subgroups (one-week and 6-months subgroups) (n=20). The specimens were maintained in buffered solution of NaNHNo3 (pH=7) at 37oC in an incubator. After periods of one week and 6 months immersion, 0.5 mL of each solution was analyzed by spectrophotometry for the quantity of released Nickel (Ni), Chromium (Cr), and Cobalt (Co) ions. The data were analyzed using two way ANOVA analysis.Results: After one week, the quantity of Ni, Cr, and Co ions released from new brackets were 0.65, 1.4, and 0.75 (ppb), respectively. The values for recycled brackets were 142, 2.61, and, 1.43 (ppb). These findings indicated significant difference between two groups (P<0.001). After six months, the quantity of Ni, Cr, and Co ions released from new brackets were 1200, 3.4, and 2.4 (ppb) and from recycled brackets were 2330, 6.9, and 10.8 (ppb), which showed significant difference between two groups (P<0.001).Conclusion: Application of recycled brackets in long fixed orthodontic treatments can lead to metal ion release, specifically Nickel. Thus, the use of recycled brackets in long orthodontic treatments is not recommended.

Background and Aims: Occupational burnout is a psychological syndrome resulting from continuous tensions which causes absence, conflict, job changing, etc. In spite of much effort done in optimizing the work conditions and satisfying the employed persons, the dentists still suffer from this incident. The purpose of this study was to determine the degree of occupational burnout in Birjand dentists and to provide an approach.Materials and Methods: In this descriptive-analytical study by the census method, 38 dentists were investigated using Maslach questionnaire. Average values were compared with chi-square and comparison among the groups was performed by Tukey test using SPSS software. P40.05 was considered as the level of significance.Results: In this study, there were 68.4% men and 31.6% women with average age of 37.9±7.6 years and average work experience of 12.5±7.3 years, 15.8% single and 84.2% married. Frequency of exhaustion, intense depersonalization, and intense feeling of being unsuccessful was 21.1%, 81.6%, and 100%, respectively. There were no significant differences between occupation burnout dimensions and the other variable, such as gender, sports, marital status, and workday hours (P>0.05).Conclusion: Protection of this stratum, providing educational programs and creating job variations are necessary for optimizing the work environment. Future studies with more sample size are suggested to determine the effect of factors.

Fabrication of dental prosthesis for patients with microstomia has long been a problem for dentists. Microstomia is defined as an abnormally small oral orifice. Prosthetic rehabilitation of microstomia patients presents difficulties at all stages, from the preliminary impressions to fabrication of prosthesis. This study described a method for making impressions for patients with limited opening of the oral cavity which the use of a full-size impression tray was not possible.