مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال سی و سوم شماره 1 (پیاپی 102، بهار 1399)

The vertical growth pattern of the face depends on several factors. One of these factors can be the muscle strength of the jaw. Maximum occlusal force (MOF) can be considered as an index to measure the function of the muscles of the masticatory system. Despite the various studies, the relationship between the facial pattern and muscle function is still controversial. According to soft tissue paradigm theory, muscle can affect the shape and form of bones of the jaw, face and head. The aim of this study was to determine the relationship between the maximum occlusal force and head and face growth pattern in dental students of Shahed University in Tehran.

81 dental students (40 males and 41 females) were participated. MOF was measured with a loadcell designed for this purpose, and the anthropometric points of the face and head were measured with digital caliper. Two-way ANOVA and Tukey HSD tests were used to determine the effect of facial and head patterns on the maximum occlusal force. Statistical analysis was performed by SPSS23.

The mean MOF in males was 480 N and in females 320 N. Head forms in our sample research were 54.32% Brachycephale, 32.09% Mesocephale, and 13.58% Dolicocephale. The form of the face was 23.45% euprosopic, 39.5% mesoprosopic, and 37.03% leptoprosopic. According to the statistical analysis, the relationship between the maximum occlusal force and leptoprosopic form of face was statistically significant (P=0.02). However, there was not significant relationship between the maximal occlusal force and none of the three type of head forms (P=0.813).

MOF was related to the leptoprosopic pattern of face, and these individuals had less bite power. No relationship between the maximum occlusal force and head forms and neither between the head pattern and facial pattern was found in this study. The maximum occlusal force in men was higher in all three facial patterns than that of women, although this relationship was not significant.

Erosion is the chemical dissolution of a tooth by acid without bacterial involvement. The purpose of the current study was to investigate the effect of resin infiltration (Icons), MI paste plus, and Nd:YAG laser on the enamel microhardness.

40 enamel samples were obtained from the third molar tooth. Primary microhardness was measured in all specimens. Then, erosion was created using hydrochloride acid on the surfaces of enamel and the microhardness values were measured. The samples were randomly divided into four groups. G1: MI paste plus, G2: MI paste plus+ Nd:YA laser, G3: ICON without etching, G4: ICON with etching. Erosion was induced again by hydrochloric acid and then subjected to thermocycling. Finally, the microhardness of the samples was measured. Statistical analysis was performed using SPSS23 software, one-way ANOVA, multiple Tukey and T-test comparisons. P<0.05 was considered as a significant level.

The microhardness increased in the third stage compared to the second stage in all groups, which was statistically significant (P<0.000). Also, the comparison of the increase of microhardness among groups, except second group with the fourth group, was statistically significant.

All the materials used in this study significantly increased the microhardness of the eroded enamel.

Periodontitis is one of the most common causes of damage to the gums and retaining structures of the teeth. Matrix protein, a metalloproteinase, is known as intermediate collagenase and the enzyme collagenase fibroblast, which is encoded in humans by the MMP-1 gene. The aim of this study was to investigate 1G/2G polymorphism in the MMP-1 gene and its association with the periodontal disease in the Iranian patients.

In this study, 50 patients with periodontal disease and 50 patients were selected as the control group in Kerman city. DNA was extracted from a person's blood sample using a kit. The desired primers were controlled by the NCBI site. Then, with the Tetra arms PCR technique, the desired polymorphism was multiplied. In the next step, the samples were transferred to electrophoresis gel and examined. The results were analyzed with SPSS software using T-test or Squer Chi-(X2).

The percentage of 1G/1G genotype in the patients group was 8% and for the controls group was 0%. The percentage of 2G/2G genotype for the patients group was 24% and for the controls group was 18%. In addition, the 1G/2G genotype frequency was 68% for the patients group, and for the controls group was 82% (P=0.83). The results of Tetra-arms PCR genotyping of the samples were confirmed by sequencing.

The findings indicated that in Iranian patients, MMP-1 -1607 1G/2G (rs1799750) was not significantly associated with periodontal disease. It is recommended to take more samples from different parts of Iran to confirm the results.

The inferior alveolar nerve block (IANB) is the most frequently used technique for mandibular anesthesia. Due to the many factors which can cause its failure, the aim of this study was to evaluate the efficacy of experience and knowledge in the success rate of IANB technique.

 In this study, 115 students of Shiraz Dental school were participated in two groups. One group contained 53 novice students and another group 62 students with one year experience in IANB injection. Each student accomplished injection once and then success or failure of the injection was examined. In order to evaluate the students’ knowledge, each student was asked to fill out a questioner including six questions related to the instruction of the injection. Data were then collected, coded, and analyzed by SPSS18 using Chi square with a significant level of 0.05.

The rates of knowledge in novice and experienced group were 71.6% and 86.3%, respectively. The success rates of IANB were 47.1% in novice group and 64.3% in experienced group. The success rates of IANB and knowledge were significantly higher in the experienced group compared with the novice group. (P=0.02 and P=0.01, respectively) There was no significant difference between male and female (P=0.06).

The results showed that knowledge and experience could play an important role in the success rate of IANB technique.

Due to the very high importance of assessing the clinical performance of students, choosing the best assessment tool and method is one of the most important goals and tasks in medical education. The objective of this study was the development of a checklist for the assessment of dental students’ clinical skills in the clinical complete denture course. The second aim was to determine the validity and reliability of the checklist, and The third aim was the evaluation of raters’ and students’ satisfaction.

The checklist was developed in expert panel sessions, and the validity and reliability of the checklist were assessed with CVI (content validity index) test-retest and inter-rater reliability methods, respectively. Students (n=15) were evaluated with a developed checklist. At the end of the session, the satisfaction level of staff and students were assessed. The obtained information was reported descriptively with the expression of mean and standard deviation and in the form of relative and absolute frequencies.

The content validity index (CVI) of the checklist was 0.96. The reliability of the checklist confirmed with a high Intraclass Correlation Coefficient (>0.8) (between 0.82-0.97 ((P<0.05). The coefficient of agreement in inter-rater reliability was 0.99. Raters’ and students’ satisfaction earned a high percentage of satisfaction.

The designed checklist has the optimal features of a good students’ clinical performance assessment tool; it seems that using this checklist can be an excellent alternative method to a global rating scale to assess the clinical skills of dental students in the complete denture courses.

Immediate implant placement following tooth extraction is a treatment with many advantages. Alveolar bone preservation after immediate implant, need minimum of 2 mm thickness in buccal bone plate. The aim of this study was to evaluate the thickness of buccal cortical bone of maxillary premolars by Cone Beam Computational Tomography (CBCT) technique.

In this descriptive epidemiological study, Cone Beam Computed Tomography image was obtained from 29 patients(male and female) referred to the radiology department of Jundi Shapoor dental school of Ahvaz from 1393 (Mehr) to 1394 (Shahrivar) for implant insertion. The thickness of buccal cortical bone was measured in 3 and 5 mm optical to the CEJ and root apex, perpendicular to the longitudinal axis. All the measurements were done by two oral and maxillofacial radiologists, separately. Data were analyzed by SPSS 22 software, descriptive statistics, and T-Test.

The thickness of buccal cortical bone in second premolar was significantly more than 1 mm (P=0.001), but in first premolar, the thickness was close to 1 mm (P=0.29).

The results of this study showed that immediate implant insertion could be done in the maxillary second premolar area with more predictability compared to the first premolar area.

Some of the post-operative complications of impacted third molar surgery, one of the most prevalent surgeries in oral field, are known to be infection, erythema, trismus and pain. Antibiotic prescription to prevent post-operative infection under some particular circumstances, is acceptable but under debate considering their disadvantages. In the present study, we examined the infection rate in patients taking no or 2 types of antibiotics distinctively after impacted mandibular third molar surgery.

In this double blind clinical trial, 90 patients within the age range of 18 to 34 were dedicated to 3 groups (group 1: 2 capsules of placebo on surgery day and 1 for 4 days, group 2: Amoxicillin 500 mg every 8 hours for 5 days, group 3: Azithromycin 250 mg, 2 capsules on surgery day and 1 capsule for 4 days). All subjects were treated by a sole surgeon, protocol, surgical technique, and flap type and the same amount of osteotomy. In addition to aforesaid drugs, the patients received chlorhexidine and Gelofen 400 mg. At the day 7 postoperative, cases were examined to evaluate the infection (trismus, erythema and halitosis). Data were analysed using Chi-Square test and the groups were compared by Kruskal-Wallis test.

Three signs of infection (halitosis, erythema and trismus) were compared in patients. Symptoms of halitosis and erythema were more indicated in first group, but the ultimate statistical analyses among the 3 groups from halitosis and erythema viewpoint showed no significant difference (P=0.072, P=0.149). Although, no severe trismus was reported, the most moderate trismus incidence was in group 2 and mild trismus was exhibited in group 1. In group 3, no trismus occurred. On the whole, the trismus frequency among groups was statistically significant (P=0.004).

Comparing infection symptoms of the three study groups emphasized the fact that only trismus rate was statistically significant (P=0.004). On balance, the results of this study indicated that antibiotics did not have significant impact on the reduction of most postoperative complications, especially on infection.

Elastomeric chains are known as a current device with the purpose of dental movement in orthodontic treatments. The aim of this study was to compare the elastomeric behavior and force degradation rate between different elastomeric chains existing in Iran in different time durations.

11 different elastomeric chains used in this study were: Class One, ASTAR, G&H, TSNPT, MIB (French and Chinese type), Ultra Chain and both American, Ortho Technology (simple and memory type). All chains were stretched upon to exert 150 g force and then force degradation rate in 6 time duration (1, 3, 24 hours and 3, 7, 21 days) and modulus of elasticity (MOE) in 2 time duration (start and 21 days) were investigated. All Data were analyzed statistically by ANOVA, Tukey, Games-Howel tests.

All chains up to the 21th day showed a significant decrease in MOE except for the G&H, ClassOne, simple orthotechnology and a significant force degradation except for the American (memory type). The most significant force degradation rate was in ASTAR gray (P<0.05) and the least in MIB (French), Ultra Chain, and American (P<0.05).

All chains showed significant time-dependent force degradation (mostly in the first day). Only, this rate was not significant in any time duration for the American (memory). In all groups, the most force degradation rate belonged to ASTAR gray and the least to Ultra Chain, MIB (French) and American after 21th day.