مجله تحقیق در علوم دندانپزشکی
سال بیست و یکم شماره 4 (پیاپی 82، زمستان 1403)

Cementation for attaching crowns to implants has found wider use due to various reasons, including clinical advantages and aesthetic preservation. However, cement-retained prostheses have drawbacks such as the possibility of excess cement and its leakage into the surrounding tissues of the implant, which can lead to inflammatory complications in these tissues. The use of the extra-oral cementation technique can minimize excess cement. Accordingly, in this laboratory study, two extra-oral methods, PIA (Putty Index Analogue) and LBA (Light Body Analogue), and the conventional intra-oral cementation method were compared in terms of the amount of excess cement leakage when placing a crown on an implant model.

In this laboratory study, 30 zirconia frameworks were fabricated on three abutment-analogue sets for three study groups. The control group underwent the conventional intra-oral cementation method. The LBA group used a light body condensation silicone. The PIA group used a silicone putty for cementation. In each group, after cementation, the excess cement around the abutment-crown connection was manually removed using a dental scaler and weighed with a digital scale with an accuracy of ±0.01 mg.

The excess cement in the control group was reported as 85.23 ± 13.07 mg, in the LBA group as 1.70 ± 0.55 mg, and in the PTA group as 7.11 ± 1.45 mg. The average excess cement in the LBA and PTA groups was significantly lower than in the control group (both groups with p value < 0.001). However, the difference in average excess cement between the LBA and PTA groups was not statistically significant (p value = 0.265).

The extra-oral cementation techniques, PIA and LBA, significantly reduced the amount of excess cement compared to the conventional technique in implant-based restorations, which may limit the adverse effects of excess cement on surrounding tissues..

Recognizing a combination of fluoride that has the most enamel uptake and consequently, the most resistance to decaying agents, is one of the most important concerns of preventive dentistry. Among the topical methods, fluoride varnishes are very effective in preventing and controlling caries in permanent teeth. The aim of this invitro study is to compare two types of sodium fluoride varnish (V Varnish and MI Varnish) on the rate of fluoride uptake into permanent tooth enamel.

In this experimental invitro trial, 34 permanent posterior teeth were selected that had at least one circle with a diameter of six millimeters on the buccal and lingual surfaces with healthy enamel and no cracks, enamel defects, decay and fillings. Each tooth was first sectioned from the CEJ by a D&Z diamond disk and then divided into two buccal and lingual halves. Samples were divided into two groups, and certain surfaces were randomly stained on the buccal or lingual surface of the teeth randomly by V Varnish or MI Varnish. They were then stored in artificial saliva for 24 hours at 37° C. For using acid etch enamel biopsy method the teeth were etched for 30 seconds with 1M per chloric acid. After etching the window surfaces were washed by 0.2 KOH.Their calcium and fluoride content were then measured by spectrophotometer and potentiometer devices, respectively. Finally, the data was analyzed using SPSS version 20 software. The P-Value of the tests was considered less than 0.05.

In summary, enamel fluoride uptake in the specimens exposed to MI Varnish was slightly higher than V Varnish(P=0.09), but there was no significant difference between them and the amount of calcium in biopsy solutions of V Varnish samples was slightly higher than MI Varnish, but there was no significant difference between them(P>0.79).

It seems that V Varnish and MI Varnish are equally effective in the fluoride uptake into permanent teeth enamel.

The base of most dental prostheses is made of metal, and some of these metals can possibility dissolve in the oral cavity, which is a conductive environment for corrosion, and the body can eventually absorb it. These alloys have been proven to be harmful for human health. In this research, an attempt was made to investigate the release rate of metal ions (chromium, cobalt and molybdenum) from Sintron alloy in the environment of acidic artificial saliva under laboratory conditions.

In this experimental study, 6 disk-shaped samples of Sintron alloy with a thickness of 3 mm and a diameter of 10 mm were prepared with the help of CAD/CAM machine. In this experiment two artificial saliva environments (acidic with a pH of 3.5 and neutral) were used. The samples were incubated for 7 days at 37 degrees Celsius in a sterile Falcon closed environment. At the end of this period, the samples are taken out and artificial saliva samples were analyzed to check the release rate of metal ions (chromium, cobalt and molybdenum) by spectroscopic method (ICP-AES). Finally, with the help of statistical methods, the results were analyzed and checked.

There was no significant difference in the release rate of chromium and cobalt ions in acidic and neutral artificial saliva, but the release rate of molybdenum ions in acidic pH was significantly higher than in neutral conditions.

According to the results of the present research, the release rate of chromium, cobalt and molybdenum ions caused by Cintron alloy in acidic and neutral artifial saliva is insignificant, indicating its biocompatibility. In acidic pH, the release rate of molybdenum ions caused by Cintron alloy was higher than that of chromium and cobalt ions.

Considering the increased microbial load of Streptococcus mutans in patients with orthodontic appliances and the high prevalence of caries in these patients, the aim of this study was to compare the adhesion of Streptococcus mutans to orthodontic composites in various saliva types under laboratory conditions at the Tehran Islamic Azad University of Medical Sciences in 1401-1402.

This research was done experimentally and in vitro.  This study was conducted on light-cured composite Sci-pharm and American Orthodontics (6 samples per group). After preparation and sterilization, samples were immersed for 2 hours in one of the artificial saliva compositions with normal or acidic pH. Then, the samples were incubated in a suspension of Streptococcus mutans bacteria for 2 hours. The samples were washed with normal saline and sonicated in 0.9% saline solution to detach the bacteria adhered to the samples. After serial dilution and bacterial culture on brain heart infusion broth, the total number of formed colonies was counted and calculated. The results were graphed using Microsoft Excel software, and the statistical difference between groups was analyzed using two-way ANOVA with a significance level of 0.05 (p < 0.05) in SPSS (last version) software.

The adhesion of Streptococcus mutans in acidic and normal saliva to Sci-pharm composites is greater than American Orthodontics composites (P =0.000). The adhesion of Streptococcus mutans to composites in acidic saliva is higher (P = 0.003).

American Orthodontics composite exhibits greater resistance to Streptococcus mutans colonization and the adhesion of streptococcus mutans to composites is higher in acidic saliva.

Radiography is one of the most important paraclinical methods for an accurate diagnosis and treatment plan selection in dentistry. This study aims to assess the level of awareness among final-year dental students about the principles of prescribing the appropriate radiographic techniques and related factors in the year 2021.

In this descriptive-analytical study conducted cross-sectionally, a total of 79 final-year dental students participated. A two-part questionnaire was designed according to previous studies and reference books. It consisted of a first section with demographic variables, students’ grades in Radiology Theory 1 and 2, and Diagnostic Radiology 4, and a second section consisting of 20 questions to evaluate students' awareness. The validity of the questionnaire was confirmed by experts according to the content validity index higher than 0.79 and content validity reliability of 0.62. Pearson correlation coefficient and regression test were used for data analysis

The mean age of the students was 25.16 ± 1.83 years. The average awareness score was 13.85 ± 2.07 out of 20, with a minimum and maximum of 9 and 18, respectively. A positive and significant correlation was observed between the grades in Radiology Theory 1 (r=0.24, p=0.019), Radiology Theory 2 (r=0.28, p=0.011), Diagnostic Radiology 4 (r=0.25, p=0.023), and the average awareness score of the students. With each year increase in age, a significant decrease in awareness level by 0.32 was observed (p=0.010).

In this study, the level of awareness among final-year dental students about the principles of prescribing appropriate radiographic techniques in dentistry was evaluated as moderate to low, indicating the need for intervention through changes in the type of education.

Face masks and respirators are used to filter inhaled air, which may contain airborne droplets and high particulate matter (PM) concentrations. The respirators act as a barrier to the inhaled and exhaled air, which may change the nasal airflow characteristics and air-conditioning function of the nose. This study aimed to evaluate the serum oxygen levels following the use of three-layer, five-layer and N95 masks after intervals of 1,2,3 hours in dental students of Azad University.

This cross-sectional analytical study was performed on 38 dental students of Islamic Azad University in 2020-2021. Initially, their arterial oxygen content was measured 20 minutes before the start of the study and at rest using a pulse oximeter. Then, for three days, the students put three-layer, five-layer and N95 masks on their faces, respectively, and after 1, 2 and 3 hours, their arterial oxygen level was measured by a pulse oximeter. SPSS software and one-way ANOVA, repeated measures ANOVA, Bonferroni and Tukey tests were used to analyze the data (p <0.05).

After one, two and three hours wearing the mask, the highest mean percentage of serum oxygen in the blood was present in the three-layer mask, the five-layer mask and the N95 mask, respectively. The mean serum oxygen saturation percentage one hour after wearing the mask was not significantly different between the groups without mask, three-layer, 5-layer and N95 masks (p <0.05). At two and three hours, the percentage of blood serum oxygen in the groups of three-layer, 5-layer and N95 masks was significantly lower than before the study (p <0.001). At two hours, the percentage of serum oxygen in the groups of three-layer masks was significantly higher than the five-layer masks (p = 0.027) and N95 (p = 0.014). At three hours, the percentage of serum oxygen in the blood in the three-layer mask groups was similar to the five-layer and N95 masks (p <0.05). In all three types of face masks, the evaluation time had an effect on the percentage of serum oxygen saturation in the blood (p <0.05). The mean percentage of serum oxygen in the blood before the study was not significantly different from one hour after wearing the mask (p <0.05). However, the mean percentage of serum oxygen in the blood at two hours (p <0.001) and three hours (p = 0.005) after wearing the mask was significantly lower than before the start of the study. The mean percentage of serum oxygen in the blood was not significantly different between one hour and two and three hours of wearing a mask (p <0.05).

After two or three hours of wearing face masks, the level of serum oxygen in the blood decreased. Respiratory consequences of decreased blood oxygen saturation can be harmful. Therefore, to prevent such consequences, it is recommended to take preventive measures.

  One of the important clinical challenges in root canal treatment is the treatment of immature teeth. Following the stop of root formation, the tooth will have thin dentin walls and will be prone to cervical fracture.  In vital pulp therapy (VPT), due to the preservation of the pulp, there is a possibility of completing and repairing the dentin pulp complex and increasing the dentin's thickness and length. In this report, VPT for hypoplastic immature permanent teeth (turner's tooth) has been investigated.

Case Report: 

The patient was a five-year-old girl whose premolar tooth had severe caries due to a preapical infection caused by the corresponding primary tooth. Due to the incompleteness of the root, after the coronal pulp was removed, MTA was placed, and vital pulp therapy was performed. In the two-year follow-up, the tooth had normal clinical signs, and the length and thickness of the root increased favorably.

Conservative pulp treatments, like VPT, can be suitable treatment options for necrotic, immature permanent teeth.

Syphilis is one of the oldest sexually transmitted diseases known.  The incidence of syphilis has increased worldwide in the last decade, despite the fact that the treatment of this infection can be done easily. The causative agent of this sexually transmitted disease is the bacterium Treponema pallidum subspecies pallidum (TPA). (1) Syphilis oral lesions, the most common extragenital sign of infection, are a diagnostic challenge for dentists, who are usually the first to examine oral lesions. Biopsy is sometimes the first examination, but histological findings are considered non-specific.

Case: 

In the present study, we present a new case with the oral manifestations of syphilis along with the occurrence of extra teeth.

Our results show that careful monitoring and appropriate interdisciplinary cooperation during the treatment stages sometimes will not lead to the desired result in terms of aesthetics and function, because the desired abnormality is not correctable.