Avicenna Journal of Dental Research
Volume:15 Issue: 2, Jun 2023

Panoramic imaging is a technique to create images of facial structures. Various factors affect the preparation of a high quality and proper panoramic image, such as the patient’s proper position. The aim of this study was to investigate positional errors in panoramic images based on the dentition type of patients referring to oral and maxillofacial radiology department of Tabriz Dental School

This cross-sectional study was conducted in Radiology Department of Tabriz Dental School in 2017-18. Dentition of patients (primary, mixed, permanent, complete edentulous) was determined by radiography. 410 radiography per group (1640 samples) were selected from the archives of Radiology Department by simple random sampling method. one radiologist evaluated all the images in the same condition and in a semi-dark room, in a 21-inch DELL monitor, regarding the presence of each of the positioning errors. Radiographs that were repeated due to positioning errors and poor diagnostic quality were classified as unacceptable radiographic images.

In primary, mixed, permanent and edentulous dentitions, not attaching the tongue to the palate were the most errors in the radiographies, with 50.4%, 65.6%, 64.3% and 64.8%, respectively. The presence of 2 errors (563 radiographies, 34.3%) had the highest frequency. 123 radiographies (7.5%) were free of errors. Primary dentition with 95 radiographies (23.2%) had the highest unacceptable radiographies, and edentulous dentition with 29 radiographies (7.1%) had the lowest unacceptable radiographies. Chi-square test indicated that this finding was statistically significant (P <0.001).

Positioning error has high prevalence in radiographic images, the most common of which is not attaching the tongue to the palate during radiography. In the primary dentition period, the number of acceptable radiographs was lower than the other periods.

 This study compared the amount of residual cement at the margin of implant-supported crowns cemented using the polytetrafluoroethylene (PTFE) tape, replica technique, and conventional cementation technique.

 In this in vitro experimental study, a mandibular model underwent full-arch scanning. The right first molar tooth was eliminated on the scan using Exocad software, and a regular implant analog was modelled using the Exocad model creator. The designed abutment was then printed. The implant analog was fixed in place with acrylic resin and scanned using a scan body. A full-zirconia custom abutment was then designed by Exocad. Abutments were fabricated using zirconia and sintered. Twenty-seven resin crowns were fabricated for the abutments, and their fit was assessed. Nine crowns were conventionally cemented by filling half of the crown space with cement, 9 crowns were cemented using PTFE tape, and the remaining 9 were first placed on a resin replica and then cemented on the abutments. The residual cement was weighed using a digital scale, and the groups were compared by one-way ANOVA and LSD test (α=0.05).

 The amount of residual cement was significantly different among the three groups, indicating that the amount of residual cement was the highest in conventional cementation, and the lowest in the replica group (P < 0.05). Pairwise comparisons showed significant differences between all groups (P < 0.05).

 The replica technique followed by the PTFE tape resulted in the minimum amount of residual cement at the margin of implant-supported cement-retained crowns and are preferred for use in the clinical setting.

 The methods of increasing the longevity of dental burs by improving the mechanical properties of these surfaces, can increase their longevity. This study assessed the effect of diamond-like carbon (DLC) coating applied by the physical vapor deposition (PVD) technique on wear of diamond and tungsten carbide (TC) burs.

 In this in vitro study, 30 diamond and 30 TC burs were evaluated in four groups, including TC burs without coating (control), TC burs with a 3.5-µm DLC coating applied by the PVD technique, diamond burs without coating (control), and diamond burs with a 3.5-µm DLC coating applied by the PVD technique. The burs were weighed by a digital scale, underwent the pin-on-disc wear test, and were weighed again. The weight loss indicated the degree of wear in each group. For qualitative assessments, the surface of the burs was inspected under a stereomicroscope at×4 and×10 magnifications before wear, halfway through the test, and after the test. Finally, the data were analyzed by two-way ANOVA (α=0.05).

 The effect of DLC coating was significant on the wear of burs (P=0.032), but the effect of the type of bur and their interaction effect on wear were not significant (P=0.151). A significant difference existed in wear among the four groups (P < 0.001), and the wear of coated burs was significantly lower than that of non-coated burs (P=0.012). Stereomicroscopic assessments revealed some residual diamond particles, the impression of dislodged particles and the path of wear on the surface of diamond burs, and the path of wear on the surface of TC burs.

 Overall, the DLC coating of diamond and TC dental burs by the PVD technique could increase their wear resistance irrespective of the bur type.

 Due to its invasiveness and length, bimaxillary orthognathic surgery causes highly excruciating pain in the oropharyngeal area for the patient. There are several ways to reduce this pain, including prescribing painkillers and anti-inflammatory drugs. The aim of this study was to evaluate the effect of photobiomodulation by a 940-nm laser on reducing pain in the oropharyngeal area after bimaxillary orthognathic surgery.

 This randomized clinical trial study was performed on 40 patients aged 17-40 years who were candidates for bimaxillary orthognathic surgery referred to the Department of Oral and Maxillofacial Surgery of Besat hospital in 2021. All patients in the intervention group underwent the photobiomodulation of the oropharyngeal area with a 940-nm diode laser immediately after the end of bimaxillary orthognathic surgery. Sore throat, jaw pain, pain when swallowing, and stridor were recorded in the first to fifth days after surgery. Finally, changes in the mean score of indices were compared within and between the two groups using repeated measure analysis of variance.

 The mean age of patients in the intervention and control groups was 22.4±4.38 and 25.15±5.48 years, respectively (P=0.09). The pain score in the four areas studied in both intervention and control groups had a decreasing trend over time, which was statistically significant (P<0.001). In addition, the difference in the trend between the two groups was statistically significant so that in the intervention group, the decreasing trend was more severe (P<0.05). Eventually, a significant interaction was observed between the type of intervention and time in all four areas (P<0.05).

 The results showed that the use of a 940-nm diode laser led to a significant reduction in all four areas of sore throat, pain when swallowing, and stridor after bimaxillary orthognathic surgery.

 Different histochemical stains have been applied to demonstrate the cytotoxic and genotoxic effects of cigarette smoking on cells. Feulgen and Papanicolaou were the most popular stains to demonstrate nuclear abnormalities. The aim of this study was to compare Feulgen and Papanicolaou stains in demonstrating the cytotoxic and genotoxic effects of cigarette smoking on exfoliated oral mucosa cells.

 A total of 31 cigarette smokers and 15 non-smokers were included in this case-control study. Using a wooden spatula, two samples were taken from each participant. The samples from the left buccal mucosa were stained with Feulgen and the right mucosa with Papanicolaou. The mean number of micronuclei and the number of cells with pyknosis, karyorrhexis, and karyolysis were determined on Feulgen and Papanicolaou-stained slides. The number of counted cells with pyknosis, karyorrhexis, and karyolysis in 1000 cells/subject was recorded. The mean number of micronuclei was determined by the number of counted micronuclei per 1000 cells per subject.

 The number of micronuclei was not significantly different between Feulgen and Papanicolaou stained samples (P=0.27). Demonstration of karyolysis (P=0.73) and karyorrhexis (P=0.24) was not significantly different between Feulgen and Papanicolaou staining methods. The Feulgen was significantly more effective in demonstrating pyknosis compared to Papanicolaou (P=0.02).

 Feulgen and Papanicolaou stains had similar effectiveness in demonstrating DNA alterations (micronucleus) and cellular death features (karyorrhexis and karyolysis). Feulgen was preferable to display pyknosis than Papanicolaou.

 The incidence and mortality rates of salivary gland tumors have increased according to previous evidence. No study has so far focused on the trend of clinical and histopathologic patterns of salivary gland tumors in Iran. Therefore, the aim was to investigate the incidence and clinico-histopathologic trend of salivary gland tumors in a retrospective, cross-sectional, institutional study from 2010-2019 in Amir Alam hospital.

 The archived medical records were collected from patients with the histopathologic diagnosis of benign and malignant salivary gland tumors from Amir Alam hospital, Tehran during (April-April) 2010- 2019. Demographic data and histopathologic features, including tumor size, lymph node involvement, vascular invasion, perineural involvement, and histopathologic differentiation were retrieved, and the samples were categorized and reviewed based on the new classification of head and neck tumors. Finally, the frequencies of characteristics were determined and expressed as numbers (percentage values).

 Of 1203 salivary gland tumors, 77.6% and 22.4% were benign and malignant, respectively. The incidence of benign tumors was increased from 37 (22.2%) in 2010 to 178 (364.9%) in 2019. In the collection of the total samples, the incidence of malignant tumors was relatively steady from 23 (13.8%) samples in 2010 to 27 (55.35%) in 2019. However, an increase in the incidence of tumors with low-grade differentiation was found from 12.5% in 2010 to 80% in 2019.

 The incidence of benign and malignant salivary tumors with a higher degree of malignancy had an increasing trend in Amir Alam hospital during 2010-2019.

 Academic dishonesty is the most important educational concern. According to previous studies, it is more common in several groups of students. To prevent academic dishonesty, it is important to know the extent of the problem. Accordingly, this study was designed to investigate the behaviors, attitudes, and interpretations of dental students regarding exam fraud in the 2015-2016 academic years.

 For this purpose, a three-part questionnaire was prepared, including demographic characteristics and specific questions. The specific questions included students’ behavior, attitudes, and interpretation in the form of three scenarios. A total of 163 questionnaires were collected, and the statistical analysis was performed using SPSS, version 20. The Mann-Whitney U test and the Kruskal-Wallis test were used to analyze the data.

 The students consisted of 90 males (55.2%) and 73 females (44.8%), and their average age was 22.72±2 years (22.3±2.87 and 23.23±2.37 years for boys and girls, respectively). The results revealed that around 65.6% of students were generally aware of the fraud problem in the faculty and knew the cheaters (63.1%). Further, 55.2% of students believed that instructors should prevent cheating during the exam. Data analyses demonstrated that there were no significant differences between boys and girls in all research variables. Finally, the average behavior proportion and attitude of the first-year students were higher than those of other students.

 Based on the findings, the rate of fraud was high in dentistry schools and possibly in other medical schools, highlighting the importance of the creating culture in changing students’ attitudes.

Adenoid cystic carcinoma (ACC) is a slowly developing malignant tumor of the salivary glands, occurring more commonly in minor salivary glands and rarely in parotid glands. It has the potential of retrograde perineural spread to the adjacent structures and spaces. Here we report a rare case of ACC of the parotid gland extended to the infratemporal fossa with perineural and vascular invasion, reflecting the advanced stage of the disease. After consulting with ENT specialists and radiation oncologists, palliative surgery was performed followed by adjuvant radio/chemo therapy.