مجله دانشکده دندانپزشکی مشهد
سال چهل و ششم شماره 2 (پیاپی 121، تابستان 1401)

Lichen planus is a chronic inflammatory disease with an immunological base involving mucosal skin. However, the etiology and pathogenesis of this disease are still unknown. Zinc is one of the most essential elements needed by the body that acts as a cell membrane stabilizer and is necessary for boosting the immune system. Due to very limited studies with conflicting results, the present study was performed to compare serum zinc levels in patients having erosive and atrophic oral lichen planus with healthy individuals.

This case-control study was conducted on two groups (n=20 each), including patients with erosive and atrophic oral lichen planus and healthy volunteer subjects being similar in age and gender to the case group. After selecting patients based on the criteria for admission and obtaining informed consent from the candidates, individuals were referred to the Blood Transfusion Organization for the evaluation of zinc levels in the blood. The test results were then examined and delivered to the patient. Mann-Whitney test was used to analyze the data.

The mean age scores of the participants in the case and control groups were obtained as 46.7±16.9 and 41.5±10.1 years, respectively, which was not statistically significant (P=0.056). In the case and control groups, 6 and 5 individuals were men, respectively, and the rest participants were women in both groups. The mean serum zinc levels were estimated at 84.21±19.6 and 76.9±20.8 µg/dl in the case and control groups, respectively, which did not show a statistically significant difference with the Mann-Whitney test (P=0.2).

Despite lower serum zinc levels in patients with erosive and atrophic oral lichen planus, this element was still within normal limits and appeared not to play a role in the pathogenesis of the disease.

Considering the importance of microleakage in posterior composite restorations for recurrent caries and pulpitis in formerly repaired teeth, this study aimed to evaluate and compare the microleakage rate of class II composite restorations in two methods Open sandwich and Snowplow.

In this study, a total of 64 premolar teeth with a class II cavity whose margins were extended 1 mm below dentin and cement joint were prepared and divided into two groups. In the first group, a layer of 1 mm thick resin-modified glass ionomer (RMGI Fuji II LC) was placed on the gingival floor and cured. The cavity was then etched with phosphoric acid gel, washed, and a bonding agent was applied. Then resin composite (Z250 3M ESPE) was incrementally applied in the cavities. In the second group, the cavity preparation was performed in the same way as that in group A. Afterward, 1 mm thick flowable composite (Filtek Z350 3M) was placed on the gingival floor, without curing. A layer of 1 mm thick resin composite was then added and packed. Both layers were then cured at once. The prepared teeth underwent 3000 times thermocycling and were placed in methylene blue for 72 h for evaluation of microleakage rate. The teeth were then cut mesiodistally. The samples of both groups were examined under a stereomicroscope, and the mean microleakage in both groups was compared using the Mann-Whitney test.

In the first group, based on the degree of dye penetration, the average amount of microleakage was observed in 10.66% of the samples. In the second group, the average amount of microleakage was 5.25%, using the Snowplow technique. Moreover, in the Open sandwich technique, dye penetration level in 34.4%, 12.5%, 34.4%, and 18.8% of samples was zero, one, two, and three, respectively. Moreover, in the Snowplow group, dye penetration level in 46.9%, 25%, 25%, and 3.1% of samples was zero, one, two, and three, respectively. The level of significance was set at 0.05.

Based on the obtained results, Snowplow and Open sandwich techniques are not effective for complete elimination of the microleakage of posterior composite restorations. The rate of microleakage in tooth restoration interface in class II restorations using the Snow-plow technique was more compared to the Open sandwich technique.

In recent years, laser-assisted surgery has become commonplace in dentistry, especially in soft tissue surgeries. The present study aimed to investigate the complications and patient satisfaction after removing exophytic lesions by laser surgery.

A total of 12 patients requiring removal of peripheral exophytic lesions such as reactive hyperplasia and mucosal surgery were examined to participate in the present study.

This surgical procedure had the maximum patient satisfaction (84%) and almost all patients (91.7%) had no postoperative pain. After three weeks, the wound site healed in all patients, although a case of mucosal recurrence was observed in this study.

Laser surgery is quite successful due to the absence of pain, maximum patient satisfaction, and wound healing in all patients which is consistent with the results of previous studies, although this method requires a more complete evaluation.

Three-dimensional (3D) printing is a layer-by-layer fabrication method used to manufacture 3D models of complex structures. This technology has multiple methods, materials, and equipment. The present study aimed to investigate the use of 3D printers in manufacturing dental prostheses, various processing methods, materials, and the accuracy of each.

A standard search method was used in PubMed and Google scholar databases. The inclusion criterion was articles published in English in the field of manufacturing dental prostheses by additive methods between 2015 and 2020.

A total of 2,250 articles were retrieved from databases, using the keywords "3D printing" OR "Additive manufacturing" OR "Rapid prototyping" AND "Dental prostheses" OR "Dental Prosthetics" OR "Digital dentistry".According to the exclusion criteria, 27 articles (3 review, 2 in vivo, and 22 in vitro studies) related to 3D printing technology in prostheses were selected. 3D. In dentistry, stereolithography (SLA), Selective Laser Melting (SLM), Fused Deposition Modeling (FDM), and Material jetting (inkjet) have been so far used to make surgical guides, implants, casts, special trays, removable prostheses, casting patterns, metal frameworks, and fixed prostheses.

The advent of 3D and digital technology has had a significant impact on the reconstruction of teeth and prosthetic works. The quality of prostheses made by this technology is clinically acceptable; therefore, they can replace conventional methods. The printing methods and materials used in dentistry are improving every day, and for the successful application of this technique, we need a complete and up-to-date familiarity with the method of using the materials, limitations, and benefits of this new technique.

In recent years, using metal alloys has been expanding in dentistry, especially in dentures. Further research is needed on ion release in these alloys considering the potential harm to human health.
A total of 20 disk-shaped samples and two acidic environments with pH of 4.2 and 6.5 were used in the present study. Half of the samples without simulation of porcelain firing and the other half after the simulation were incubated for 7 days at 37 ° C in a closed sterile centrifuge tube containing 7.5 ml of acidic solution with pH of 4.2 and 6.5. Finally, the solution was analyzed by spectroscopic method to evaluate the amount of ions released from the Cintron alloy. The results were analyzed using ANOVA by SPSS software.
In the samples placed in solutions with pH of 4.2 and 6.5, the amount of released ions after firing was significantly higher than that without the firing process. Furthermore, the amount of released ions in a solution with a pH of 6.5 is significantly less than that in pH of 4.2 in samples without firing simulation. However, the amount of released ions in a solution with a pH of 6.5 is significantly higher than that in pH of 4.2 in the samples after firing.
The results demonstrate that porcelain firing changes the nature of alloys leading to the release of more chromium, cobalt, and molybdenum ions. Also, increasing the acidity of the environment before firing causes more ions to be released, while after firing, the ions are released less in a more acidic environment.

Squamous cell carcinoma is one of the most common malignancies in the oral cavity. The number and distribution of mast cells affect the pathogenesis of oral squamous cell carcinoma (OSCC). Mast cells can produce enzymes, such as matrix metalloproteinase-9 (MMP-9) that can affect OSCC growth and the aggressive behavior of tumors. This study investigated the mast cell density and immunohistochemical expression of MMP9 in OSCC.

In this descriptive study, 10 paraffin blocks of OSCC were selected from the pathology department archive in the Dentistry College of Jundishapur University of Medical Sciences and Imam Khomeyni Hospital in Ahvaz, Iran. Afterward, 4-µm sections were cut from paraffin blocks and stained using the immunohistochemical method for MMP9 expression and using toluidine blue for mast cell count. The expression of MMP9 in the epithelium and connective tissue was investigated, and the number of mast cells was counted in five high-power fields.

In this study, MMP9 was expressed (over 50%) in eight cases in the epithelium and nine cases in connective tissue. In one case, MMP9 was not expressed in the epithelium. No statistically significant association was observed between immunohistochemical expression of MMP9 in connective tissue and the mean number of mast cells in OSCC connective tissue. One of the specimens was excluded from this study due to the low amount of tumor tissue.

Expression of MMP9 in the connective tissue of all cases may indicate the aggressive behavior of OSCC; however, this expression may not be related to mast cell density or may be suppressed with a high number of mast cells.

Color matching between a zirconia-based ceramic restoration and a natural tooth is a common clinical challenge. This in-vitro study aimed to assess the effects of the number of firing cycles and zirconia core translucency on the color stability and surface roughness in two zirconia-based ceramic systems.

A total of 60 disk-shaped zirconia specimens (10×1 mm) were prepared in high and low translucencies (n=30 per group), veneered with 1mm ceramic layers, and subjected to 3, 5, and 7 firing cycles in three respective subgroups (n=10). Color stability (∆E) and surface roughness (Ra(µm)) parameters were measured after soaking the specimens in coffee solution and using a spectrophotometer and profilometer, respectively. Data were analyzed using two-way ANOVA and Tukey’s post hoc test (α=0.05).

The number of firing cycles affected the Ra value in both zirconia-based ceramic systems (P<0.001); however, it did not affect the color change (P=0.253). The surface became significantly smoother by increasing the number of firing cycles from 3 to 5 and from 3 to 7 (P<0.001). Zirconia core type significantly affected the color stability after soaking in coffee solution (P<0.001); however, it did not affect the surface roughness (P=0.189). High-translucency zirconia core sub-groups had a more stable color, compared to samples in low-translucency groups.

Multiple firings of veneering porcelain did not affect the color stability of the two zirconia-based ceramic systems; however, the color stability in the zirconia core system with low translucency was significantly lower than that in the high-translucency zirconia core system. The surface roughness in both zirconia core systems was reduced with increasing the number of firing cycles. However, zirconia core translucency had no effect on the surface roughness of restorations.

The most effective strategy to prevent the transmission of Covid-19 is social distancing. Close contact between professor and student is inevitable in traditional methods of dental education. Therefore, newer methods should be used to avoid unnecessary contacts while continuing the training. The present study aimed to evaluate the educational method using online classes and videos on preclinical endodontics from the perspective of professors and undergraduate students.
The Practical Principles of Endodontics course was taught to 67 undergraduate students on two levels P1 and P2 (31 students in P1 and 36 students in P2). In each session, students watched a professionally produced demo video with a verbal explanation. The main points were stated by the instructor during and after watching the videos. Then the students' questions were answered before the practice. The students of P2 had passed their P1 course in the traditional method in the previous semester; therefore, comparing traditional and new teaching methods was possible.
A total of 67 students and 12 professors completed the questionnaire. The degree of agreement in three groups (students of P1, students of P2, and professors) was statistically different in 6 of 7 similar questions (P<0.05). In general, students of P2 and professors gave higher scores to these questions.
According to the results of the present study, the achievements of this educational method included students' satisfaction with the proper observance of infection control protocols during the pandemic and the effectiveness of this teaching method. According to the professors, this method positively affects the performance of the students and reduces their iatrogenic errors.

Autism is a neurodevelopmental disorder whose symptoms appear during infancy or early childhood. Autism spectrum disorder is characterized by impairments in social interaction and communication, restricted behavioral patterns, and unusual sensory sensitivities. Few studies have been conducted to investigate the dental problems of autistic children, rendering conflicting results. Regarding this, the present study aimed to compare 3-12-year-old autistic with normal children in terms of the decayed, missing, and filled teeth (DMFT) index in Sari city.

This cross-sectional study was conducted on autistic and healthy children (n=70 each) in the age range of 3-12 years old in 2020. The age and gender of the participants, the educational level of parents, and the number of children were recorded in both groups. The DMFT index was compared in children with autism and healthy children. The data were analyzed using the Mann-Whitney U and Chi-square tests. A p-value less than 0.05 was considered statistically significant.

According to the results of the study, the educational level of parents (maternal education P=0.279, paternal education P=0.295), age (P=0.832), gender (P=1.00), and the number of children (P=0.397) were not significantly different between the two groups; however, d and DMFT indices (P<0.001) were significantly higher in the group of children with autism than in the group of healthy children.

The DMFT index was significantly higher in autistic children than in healthy children. Therefore, it is essential to implement preventive programs at home and in the clinics to improve the oral health of children with autism.

Removal of teeth and residual roots is one of the most common dental surgeries which is sometimes accompanied by complications such as root displacement to adjacent anatomical spaces. The present study aimed to report a rare case of tooth root displacement to the pyriform area.

The patient was a 56-year-old woman who was referred to Mashhad School of Dentistry following extraction of the maxillary premolar root by closed method and improper pressure by the dentist which transferred the root to the soft tissue of the pyriform sinus.

Observing the principles of prevention, selecting a qualified patient, and appropriate techniques and devices for tooth extraction are important The possibility of errors and complications increases during work if the correct surgical method is not used and the surgeon has insufficient experience.