مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال بیست و ششم شماره 2 (پیاپی 75، تابستان 1392)

Because of high prevalence of TMJ dysfunctions، increased promotion of diagnostic and treatment methods is necessary. In many cases، in addition to disc position، morphology of other joint components such as articular eminence can be changed and therefore the probable correlation between disc position and morphology of hard tissue components can be used for prediction of internal derangements. The aim of this study was to evaluate the correlation between the position of disc and morphology of articular eminence of TMD`s patients using magnetic resonance imaging (MRI). In this cross sectional study by evaluation of digital MRI files، ultimately 78 joint images were identified which had sufficient quality and resolution for review. Then the MRI images، were observed and evaluated by 3 oral and maxillofacial radiologists to determine the disc position (normal، anterior displacement with and without reduction، and posterior displacement) and morphology of articular eminence (Box، Sigmoid، Flattened). Ultimately the results that were reported at least by 2 observers were included as the final results and were recorded in the check list. Data were analyzed using Chi-Square test and Fisher test. In this study، no case of posterior disc displacement was found and therefore was excluded from the study. Articular eminence morphology (Flattened versus Sigmoid) showed statistically significant correlation with anterior disc displacement with and without reduction (P-values for anterior displacement with and without reduction were 0. 03 and 0. 002، respectively). No significant difference was found between the sigmoid and box types in relationship with disc displacement (P-values for anterior displacement with and without reduction were 0. 72 and 0. 70. In this study، no significant difference between the anterior disc displacement with reduction and anterior disc displacement without reduction in relationship with the morphological changes of articular eminence in any of the cases were found. The results showed that flattening of articular eminence had significant relationship with anterior disc displacement.

Failure of bonding between artificial teeth and denture base material is a considerable problem for patients who wear dentures. According to the different impact of artificial teeth and different information about resistance force of mastication and also with deficiency in researchs، this study was designed to compare the bond strength of composite and acrylic artificial teeth to auto-polymerized denture base resins with and without cyclic loading. In this experimental and in vitro study، an acrylic resin auto-polymerized (Rapid Repair، Dentsply) and four artificial teeth (Acrylic Marjan new، Composite Glamour teeth and Ivoclar acrylic and composite teeth) were used. Therefore، 8 groups of 10 specimens each were evaluated. All specimens were thermocycled for 5000 cycles، in water baths between 5 and 55 ◦ C. Half the specimens in each group were treated with cyclic loading at 50N for 14، 400 cycles at 1. 2 Hz. The shear bond strengths were measured using a Universal Testing Machine. Data were analyzed using Two-way ANOVA test. Statistical analysis demonstrated no significant effect of cyclic loading on the shear bond strength، but the type of artificial tooth affected the shear bond strength (P=0. 006). Also، the interaction between Cyclic loading and the type of artificial tooth showed no significant difference (P=0. 98). Tukey test showed that acrylic teeth (Ivoclar) had statistically higher bond strength values than that of other teeth (PGlamour=0. 02)، (PComposite ivoclar=0. 01) and (PMarjan new=0. 02). Within the limitation of this study، the predominant type of fracture in all groups was cohesive، therefore the bond strength was adequate in all teeth and the type of artificial tooth may influence the bond strength of denture teeth to denture base resin. Cyclic loading had no significant effect on the bond strength of denture teeth to the auto-polymerized acrylic resin.

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.

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).

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.

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

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. 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. 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). 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.

Regarding the diversity of reported low- back pain among dentists in different countries and lack of control group in most of the previous studies، the purpose of this study was to compare low- back pain and related risk factors between male general dentists and pharmacists to determine the relation between dentistry and development of low back pain. In this cross-sectional study، 261 male dentists were compared with 193 male pharmacists as a control group with Standardized Nordic Questionnaire (low back section). Subjects were at least one year in clinical practice after becoming qualified and did not suffer from connective tissue diseases and history of a traumatic event causing fracture in spinal column. The data were analyzed by Chi- square، T-test and logistic regression analyses. The prevalence of low back pain in the past 12 months was 54. 8% in male dentists and 36. 3% in male pharmacists (P=. 001). Logistic regression analyses، adjustmenting for occupation، age، body mass index (BMI)، smoking، working years and working hours per week، revealed that there was a significant association between being a dentist and having low- back pain (OR=2. 54، P=0. 001). Dentistry as a profession in male gender is associated with low back pain، independent of age، body mass index (BMI)، smoking، working years and working hours per week.

Today، use of adhesive systems is the most common materials in restorative dental procedures. The aim of this study was to evaluate the effect of different air-drying periods on the microtensile bond strength of composite to dentin using adhesive. 15 sound molar teeth were selected. The an occlusal surfaces of teeth were removed with silicon carbide disks (3M/USA) to reach flat surface of dentin. Then according to the air drying of solvent، the teeth were divided to five groups. After 5 sec etching and rinsing for 15 sec، the teeth were air dried for 3 sec. Then Singlebond (3M) was used with different air-drying times (0s، 2s، 5s، 10s، 30s) and cured. Then after insertion and curing of Saremco (microhybrid low shrinkage/Switzerland) composite، the teeth were thermocycled for 500 cycles. Then hour glass slabs with 1 mm2 interface was created. Specimens were then subjected to µTBS force until fracture. Data were analyzed using ANOVA and Bonferroni tests. Statistical tests showed that there were significant differences between bond strength of groups (P=0. 002). The mean of µTBS for the 2 Sec and 30 Sec evaporating time was the most and the least vawes، respectively. An optimum air-drying time for solvent evaporation was the lowest time recommended by the manufacturer. Over and under evaporation time decreased µTBS significantly.

Periodontitis does not affect on all patients by the same way. There are some risk factors in some people that make them more sensitive to progress of periodontitis. Smoking، uncontrolled diabetes، and special pathogens increase the risk of periodontitis. Other factors such as stress، depression and anxiety، are not crucial risk factors for periodontitis yet. Biologic explanation of this relation is that mental conditions and exposure to stressful situations can alter immune response. The aim of this study was to review the psychological factors of anxiety and depression associated with periodontitis. For this review article، we have searched through internet by the following keywords; periodontal disease، anxiety، depression. We have tried to cover almost all dental– related sites and journals as well as Pubmed from 1990-2010. Most published studies support a positive relationship between periodontitis and several psycho-social factors. Life style، stressful conditions، hormonal changes، nonchalance in oral hygiene، habits such as smoking are predisposing factors in periodontal diseases.

The purpose of this study was to evaluate the survival rate، mean bone loss and post operative complication of implants inserted in All-on-4 technique. The literature was searched using keywords angled implant، All-on-4، tilted implant and graftless technique in the last 10 years (2001 to 2011) and clinical trial article that evaluated survival rate and mean bone loss around axial and tilted implants in All-on-4 technique was selected and evaluated. A total of 73 articles were found by searching. After evaluation of titles and abstracts، finally 10 clinical trial، that were fully consistent with including criteria such as mean of bone loss and survival rate was selected and evaluated. Results showed that the survival rate (96-100%) and mean bone loss (0. 34-1. 9 mm) with All-on-4 technique in immediate loading is comparable with other implant support treatment plan. Comparison of implant survival and bone loss in axial and tilted implant in All-on-4 system is shown this treatment plan has consistent result with other conventional implant support prosthesis. Also، postoperative complication including fractures of the acrylic temporary prosthesis، detachment of the teeth، abutment or prosthesis screw loosening have been reported with All-on-4 technique.

Skeletal class III malocclusions are considered as one of the most complex and difficult orthodontic problems to diagnose and treat. Facial appearance and occlusion problems make the patients to seek treatment as soon as possible. The purpose of this study was to evaluate the outcomes of early treatment with facemask compared to the patients who had no treatment. For this retrospective study، 38 growing patients (mean age، 8. 5 years old) with class III dentoskeletal malocclusion were divided into 2 groups. 23 patients were treated with facemask and 15 patients who did not receive any treatment were assigned as control group. Lateral cephalograms were taken before and after treatment and dentoskeletal changes were estimated. Data were analyzed using Wilcoxon signed ranks test. The results revealed statistically significant forward displacement of maxillary bone and upper incisors (P<0. 001)، and downward-backward rotation of mandible in facemask group (P<0. 001). Increased lower facial height was seen in both treatment and untreated groups. However، in untreated group some measurements revealed forward displacement of maxillary complex as well. It seems that in class III patients treating with facemask is a better choice than ChinCap and decision making for early treatment in class III patients should be considered seriously. Moreover، specific attention to the type of patient’s skeletal discrepancy is necessary. In class III patients، facemask might be a better option than other appliances.