Frontiers in Dentistry

Objectives: The aim of the present study was to compare shear bond strength (SBS), adhesive remnant index and enamel cracks in bonding and rebonding of brackets to enamel, conditioned with erbium-doped yttrium aluminium garnet (Er:YAG) laser and conventional acid-etching.
Materials and Methods: Fifty-two bovine lower incisors were randomly divided into four groups consisting of group 1 (acid-conditioning in both bondings), group 2 (acid-conditioning in first and laser-conditioning in second bonding), group 3 (laser-conditioning in first- and acid-conditioning in second bonding), and group 4 (laser-conditioning in both bondings). After bracket placement, the samples were thermocycled and tested for SBS in both bonding procedures. Adhesive remnant index scores and enamel cracks were also determined. Tukey's test and one-way analysis of variance was used for statistical analysis (P<0.05).
Results: Mean SBS in the first bonding was 23.59MPa in groups 1 and 2, and 6.9MPa in groups 3 and 4. (P<0.001). The acid-etched teeth had a significantly lower SBS in rebonding, regardless of the reconditioning method (P<0.001). The SBS of the teeth conditioned with Er:YAG laser in the first bonding did not show significant changes in rebonding, although mean SBS was higher compared to the first bonding (P=0.675). Bonding most often failed at the enamel-adhesive interface and enamel cracks were observed in a few teeth.
Conclusion: The method of primary enamel preparation can affect SBS in rebonding. Based on our results, the mean SBS of Er:YAG-conditioned groups was clinically acceptable in bonding and rebonding, although it was lower compared to the acid-etched samples.

Objectives: This study aimed to determine the self-declarative performance of general dentists in prescription of analgesics and antibiotics for patients requiring root canal treatment (RCT).
Materials and Methods: In this cross-sectional study, 400 general dentists participating in the 55^th International Annual Scientific Congress of the Iranian Dental Association (2015) were randomly selected, and requested to complete a questionnaire about their performance regarding prescribing analgesics and antibiotics for patients requiring RCT. The frequency and percentage of answers to each question were calculated and reported.
Results: The most commonly prescribed analgesics included ibuprofen (100.0%), Gelofen (100.0%), Novafen (68.5%) and acetaminophen (24.8%). After RCT, dentists prescribed ibuprofen (100.0%), Gelofen (98.3%), dexamethasone (35.3%), Novafen (27.3%) and acetaminophen/codeine (15.8%) in decreasing order of frequency. Antibiotic prescription was minimum (48.5%) for cases with painful (moderate or severe) irreversible pulpitis (vital tooth) before the treatment and maximum for cases of pulp necrosis with acute apical periodontitis, edema, and preoperative symptoms (moderate or severe) (97.3%). For non-allergic patients, the most frequently prescribed antibiotics were amoxicillin 500 mg (93.3%), cefixime 400 mg (81.3%), amoxicillin/metronidazole 250 mg (71.8%), co-amoxiclav 265 mg (36.3%) and injectable penicillin (0.5%). For allergic patients, dentists prescribed clindamycin 300 mg (84.0%), cephalexin 500 mg (15.8%), azithromycin 500 mg (13.5%), and erythromycin 500 mg (10.8%). Sex and graduation date had no significant effect on the results (P>0.05).
Conclusion: Antibiotic prescription is excessive by general dentists, and their performance regarding the proper and logical prescription of antibiotics in RCT should be improved.

Objectives: The aim of this study was to evaluate the influence of varying dentin and enamel layer thicknesses of two nano-composite resins on color match of composite resins and lithium disilicate dental ceramic.
Materials and Methods: Twenty-six specimens of two types of nano-composite resins, Opallis and Vittra, were fabricated using the two-layered technique with different thickness ratios of enamel and dentin composites (A2 shade) with a total thickness of 1.2mm. Thirteen discs of the same shade and thickness of IPS e.max Press LT (low translucency) lithium disilicate dental ceramic were also fabricated. Specimen color was measured with a spectrophotometer. The difference in color (ΔE₀₀) of composite and ceramic specimens, and the translucency parameter (TP) of all specimens were calculated. Data were analyzed using multi-factor ANOVA (P<0.05).
Results: The color difference (ΔE₀₀) values of composites and ceramic were not clinically acceptable in any areas of either of the two composites (ΔE₀₀>2.25). But ΔE₀₀ between the two composite resins was in the clinically acceptable range (ΔE₀₀<2.25). The mean TP value of IPS e.max Press was greater than that of Vittra and lower than that of Opallis.
Conclusion: In similar thicknesses, composite resins with any enamel/dentin thickness ratio could not successfully simulate the color and translucency of IPS e.max Press LT ceramic.

Objectives: The purpose of the present study was to assess the level of job satisfaction among dentists in Tehran, according to background determinants, working environment elements, and type of workplace in 2018.
Materials and Methods: In this cross-sectional study, 350 dentists, selected by convenience sampling, completed a validated Persian job satisfaction questionnaire in a dental congress (with about 1100 participants) in Tehran, and in 59 dental clinics. The questionnaire included 39 structured questions (in 12 domains) on job satisfaction, reporting the satisfaction level according to a 5-point Likert scale. The level of satisfaction was measured by summing the weighted scores of each domain. The mean job satisfaction score (out of 100) was reported according to demographic factors (age, gender, level of income, years of experience, marital status, and number of children), working environment elements (number of assistants, number of colleagues, type of workplace), and stress score (8 questions). Linear regression was applied for statistical analysis.
Results: The mean score of job satisfaction was 70±10. The analysis showed that women, dentists with a low income, those working in the public sector, and those with higher stress scores had lower job satisfaction scores (P<0.05). The number of dental assistants, number of colleagues, age, work experience, marital status, number of children, and monthly number of patients had no significant correlation with job satisfaction (P>0.05).
Conclusion: The level of job satisfaction was mainly related to individual determinants. Improving job satisfaction can foster the whole dental care system and working environment elements.

Objectives: This study investigated the efficacy of theobromine in comparison with 0.05% sodium fluoride solution for remineralization of initial enamel caries lesions (IECLs).
Materials and Methods: Ninety non-carious extracted premolars were sectioned longitudinally into buccal and lingual segments. Caries-like lesions were induced in each segment using acidified gel.  Forty-five buccal segments were used for surface microhardness (SMH) test, and 45 buccal segments were used for energy-dispersive X-ray spectroscopy (EDS). The lingual segments were used as the control group for EDS and SMH test. The baseline SMH was measured with a Vickers hardness tester, and the baseline calcium content was analyzed by EDS. Each test group was divided into three subgroups for treatment with (1) artificial saliva, (2) 1.1 mol/L theobromine, and (3) 0.05% sodium fluoride. Remineralization and demineralization were done by daily pH cycling to simulate the oral environment. Samples in each group were immersed in treatment solutions for 1 min before and after the remineralizing cycle. After a 7-day cycle, the SMH test and EDS analysis were performed again. Data were analyzed using one-way ANOVA, Tukey’s post-hoc test, and paired sample t-test (P<0.05).
Results: All treatments effectively remineralized the IECLs (P<0.05), and theobromine caused the maximum increase in SMH, which was significantly higher than the value in sodium fluoride group (mean value of 36.56±4.95 versus 23.25±3.92; P=0.000). EDS showed the highest calcium deposition in theobromine group (3.82±1.83wt%).
Conclusion: Theobromine is an effective cariostatic agent, and can be considered as a safe alternative to fluoride in preventive dental care.

Objectives: This study aimed to evaluate the thermal stability and monomer elution of bulk fill composite resins cured at different irradiation distances.
Materials and Methods: Forty cylindrical-shaped (3×4mm) specimens were fabricated from two composite resins (X-tra fil, X-tra base) and cured from 0 and 7mm distances. In 9 specimens, the degree of conversion was determined by the release of monomers. For this purpose, after curing of composites, they were immersed in 5 mL of 99.9% methanol and stored at 37°C for 24h. The eluted monomer was then analyzed by gas chromatography (GC). Also, thermal stability of one sample from each group was assessed by thermogravimetric analysis (TGA) at a rate of 10°C/min. Data were analyzed using two-way ANOVA and Tukey’s post-hoc test (P<0.05).
Results: X-tra fil had significantly higher degree of conversion than X-tra base (P=0.001). Specimens cured at 7mm distance had significantly lower degree of conversion compared with those cured at 0 mm distance (P=0.001). The interaction effect of composite type and distance of light curing unit from the surface of samples was statistically significant (P=0.001). Regarding the TGA results, the lowest and the highest percentages of weight loss were detected in X-tra fil cured at 0 mm distance and X-tra base cured at 7mm distance, respectively.
Conclusion: X-tra fil composite cured at 0mm distance had the highest degree of conversion and thermal stability, and X-tra base composite cured at 7mm distance had the lowest values.

Objectives: This study aimed to evaluate the in vitro antifungal efficacy of addition of silver nanoparticles (SNPs) to Mucopren® silicone soft liner material.
Materials and Methods: Twenty disc samples (8 × 2 mm) of Mucopren® silicone soft liner containing 0wt% (control), 0.5wt%, 1wt%, 2wt%, and 3wt% SNPs were fabricated. Samples were powdered and added to 150 mL of Sabouraud dextrose agar culture medium and placed on separate culture dish plates. Each plate was inoculated with 10⁶ colony forming units per milliliter (CFUs/mL) of Candida albicans (PTCC 5027) according to the CLSI protocol, and incubated at 37℃. The colony count was verified at 24 h, and the antifungal effect of the samples was evaluated according to the percentage of viable cells in the 2 subgroups with/without thermocycling. Data were analyzed using SPSS version 20 via ANOVA and t-test (P<0.05).
Results: All experimental groups showed higher antifungal activity than the control group, and this effect was dose-dependent (P<0.05). The lowest colony count was recorded in the 3wt% group. Thermocycling had no significant effect on the antifungal efficacy, except in 0.5wt% concentration of SNPs (P=0.013).
Conclusion: Addition of SNPs to Mucopren soft liner conferred antifungal effects. Further mechanical stability and toxicity studies are still required.

Objectives: Toothpastes and mouthwashes contain chemicals that may be harmful to oral tissues. This study assessed the cytotoxicity and antibacterial activity of toothpastes and compare the Iranian and foreign toothpastes and mouthwashes available in the Iranian market in this respect.
Materials and Methods: Twenty samples (13 toothpastes and 4 mouthwashes) were selected. The cytotoxicity of 1, 10, and 50 mg/mL of toothpastes and 0.05, 2 and 10 µL of mouthwashes was measured after 1, 15 and 30 min of exposure to human gingival fibroblasts, each in triplicate. The methyl thiazolyl tetrazolium (MTT) assay was used for cytotoxicity testing. The serial dilution method was utilized to determine the minimum inhibitory concentration (MIC) of each sample against Lactobacillus acidophilus (L. acidophilus) and Streptococcus mutans (S. mutans). Two-way ANOVA and Tukey’s test were used for data analysis.
Results: A significant difference in cytotoxicity was noted among different products (P=0.00). The difference in cytotoxicity of each sample was not significant at 1, 15 and 30 min (P=0.08). The obtained MIC for all toothpastes and mouthwashes was between 0.0039 mg/mL and 0.0156 mg/mL, except for Sensodyne toothpaste and Oral B mouthwash.
Conclusion: Some brands of toothpastes have higher cytotoxicity due to their composition, and their cytotoxicity should not be overlooked. The antibacterial activity of the samples was almost equal when they were in contact with L. acidophilus and S. mutans except for the Irsha mouthwash, Sehat, Darugar and Bath toothpastes. The antibacterial effect of toothpastes and mouthwashes increased with an increase in exposure time.

Objectives: Intraoral scanners have shown promising results when used as an adjunct or alternative to conventional impression techniques. This study compared the accuracy of digital impression taking using an intraoral scanner versus the conventional technique.
Materials and Methods: In this in-vitro experimental study, a typodont molar tooth was prepared as the standard model and scanned by TRIOS intraoral scanner. Ten digital impressions were fabricated as such and intraoral scans were sent to the manufacturers. In the conventional method, using addition silicone impression material, a stone die was fabricated. Using a computer-aided design/computer-aided manufacturing scanner, the die was scanned, and the data were transferred to the software. After the fabrication of frameworks, the replica technique was used. The replicas’ thickness (indicative of the gap between the framework and the model and the accuracy of impression taking) was 12 points. The data were analyzed using student's t-test.
Results: The mean thickness of replicas (gap between the internal surface of frameworks and the standard model) at the three points in the buccal, lingual, mesial, and distal sections in the digital impression technique was lower than that in the conventional technique (P<0.0001). In other words, the accuracy of impressions taken by the digital method was significantly higher than those taken by the conventional method.
Conclusion: Intraoral digital scanner had significantly higher accuracy than the conventional method in all points. Thus, the digital method can be reliably used as an adjunct or alternative to the conventional method to increase the accuracy of impression taking.

Objectives: Traumatic dental injuries (TDIs) commonly occur in sport clubs. The knowledge and performance of fitness trainers play an important role in management of such injuries. This study sought to assess the effect of an educational pamphlet on knowledge level and performance of fitness trainers about TDIs in Tehran in 2018.
Materials and Methods: In this interventional study, a pamphlet was designed to enhance the knowledge level of fitness trainers. Ninety-five fitness trainers were randomly divided into two groups of intervention and control (n=49 in the control group and n=46 in the interventional group), and were requested to fill out a valid and reliable researcher-designed questionnaire about TDIs before and 1 month after pamphlet distribution. The questionnaire consisted of three domains of demographic information, knowledge questions, and performance questions. The results were analyzed using SPSS 25 via the Chi-square test and repeated measures ANOVA considering the intervention as the between-subject factor.
Results: The knowledge score of fitness trainers about TDIs was not adequately high in the intervention or the control group before the intervention. After the intervention, the performance of participants improved in both groups. This increase was significantly greater in the intervention group (P=0.035). There was no significant difference between the two groups in the knowledge domain (P=0.185).
Conclusion: Educational pamphlets can effectively enhance the knowledge level of fitness trainers about TDIs. However, the magnitude of this effect was not significant in our study. Future studies are recommended to compare the efficacy of educational pamphlets with other educational tools.

Objectives: This study aimed to assess the effect of tea on color stability of enamel lesions treated with resin infiltrant (RI).
Materials and Methods: This in vitro, experimental study evaluated 30 extracted human third molars with no caries, cracks, or enamel defects. Enamel-dentin samples measuring 5 x 5 x 3 mm were prepared from the buccal surfaces of the teeth by a microtome. The samples were divided into three groups of 10 namely sound enamel, demineralized enamel, and demineralized enamel plus RI. White spot lesions (WSLs) were artificially created by immersing the samples in hydroxyethyl cellulose demineralizing gel with a pH of 4.5 for 4 days. Next, Icon RI was applied on the samples in group 3. The baseline color of the samples was measured using a spectrophotometer. They were immersed in tea solution 3 times a day, each time for 15 min, for a period of 2 weeks and then underwent colorimetry again. Data were analyzed using one-way ANOVA.
Results: The maximum color change (∆E) was noted in demineralized enamel plus RI group (38.59±6.13) with significant differences with sound enamel (20.00±2.94) and demineralized enamel (25.27±7.47) groups (P<0.05). The difference between the latter two groups was not significant (P>0.05).
Conclusion: Within the limitations of this in vitro study, the results showed that tea solution caused clinically unacceptable color change in all groups. However, the color stability of WSLs treated with RI was significantly lower than other groups following immersion in tea solution.

Objectives: Marginal and internal fit of restorations are two important clinical factors for assessing the quality and durability of computer-aided design/computer-aided manufacturing (CAD/CAM)-fabricated monolithic zirconia restorations. The purpose of this study was to evaluate the marginal and internal fit of CAD/CAM zirconia crowns with two different scanners (i3D scanner and 3Shape D700).
Materials and Methods: Twelve extracted sound human posterior teeth were prepared for full zirconia crowns. Two different extraoral scanners namely i3D scanner and 3Shape D700 were used to digitize type IV gypsum casts poured from impressions. The crowns were milled from presintered monolithic zirconia blocks by a 5-axis milling machine. The replica technique and MIP4 microscopic image analysis software were utilized to measure the marginal and internal fit by a stereomicroscope at ×40 magnification. The collected data were analyzed by paired t-test.
Results: The mean marginal gap was 203.62 μm with 3Shape D700 scanner and 241.07 μm with i3D scanner. The mean internal gap was 192.30 μm with 3Shape D700 scanner and 196.06 μm with i3D scanner. The results of paired t-test indicated that there was a statistically significant difference between the two scanners in marginal fit (P=0.04); while, there was no statistically significant difference in internal fit (P=0.761).
Conclusion: Within the limitations of this study, the results showed that type of extraoral scanner affected the marginal fit of CAD/CAM fabricated crowns; however, it did not have a significant effect on their internal fit.

For many years oral esthetic problems treated by dentists were limited to those involving the teeth without giving consideration to the gingiva. However, today it is well established that these structures should be in balance to appear esthetically pleasing. More than 3mm gingival show during smiling is considered as ‘excessive gingival display’ also known as “gummy smile”, which is not attractive. The current case series, presents three patients with gummy smile managed by lip repositioning surgery, each with 1 year follow up. Our objective was to introduce lip repositioning as a successful treatment modality to decrease gingival show using a simple and conservative surgical approach.

Giant cell fibroma (GCF) is a relatively rare lesion in the oral cavity. Despite having unique microscopic features, it can be easily misdiagnosed clinically as any common hyperplastic lesion. This report presents a case of a 21-year old male with a lesion involving the papilla between the mandibular central incisors. The lesion was excised completely under topical anesthesia using a 980 nm diode laser. On histopathological examination of the excised tissue, no thermal damage or any other alteration was observed, while the features were suggestive of GCF. Healing of the gingiva was uneventful and without any signs of recurrence. Apart from the widely known advantages of the diode laser, it also appears to maintain the integrity of biopsy specimens, if used with appropriate settings. This advantage may play a vital role in the biopsy of rare lesions where the diagnosis is entirely based on accurate histopathological examination.

On March 11^th, 2020, WHO declared COVID-19 a pandemic. This disease is caused by SARS-CoV-2, a virus that can be spread by symptomatic or asymptomatic carriers through contact, droplets and airborne transmission. Because of the transmission routes of this virus, dental treatments are considered “high risk” procedures, both for patients and operators. Italy was one of the most affected European countries and experienced a long lockdown period. Guidelines were provided by the Italian Health Ministry for a safe reopening of dental practices. In this article those guidelines are reported and compared with the available literature. The Italian model for reopening dental practice appears to be coherent with the indications provided by WHO and is supported by several studies.