Frontiers in Dentistry

Objectives: This study aimed to compare the retention of cast posts cemented with four types of cements and assess the mode of root fracture following their removal.

Materials and Methods: In this in vitro, experimental study, 48 upper central incisors were randomly divided into 4 groups of 12, and were endodontically treated. The fabricated cast posts in each group were cemented with zinc phosphate (Masterdent), glass ionomer (GI; Meron), Meta resin cement, and Panavia SA resin cement. A device was customized for post removal by a universal testing machine similar to WAM X pliers. The retention of cemented posts was measured by the pull-out test in a universal testing machine. Next, the teeth were macroscopically and microscopically inspected regarding the occurrence and sites of catastrophic fracture, cracks, or craze lines. Quantitative and qualitative data were analyzed by ANOVA, and Chi-square test, respectively (P<0.05).

Results: ANOVA showed a significant difference in the mean retention of cements (P<0.001). Panavia provided the highest retention (278.6±34.9 N) followed by zinc phosphate (221.9±28.88 N), GI (161.3±60.7 N), and Meta (140.4±66.54 N). There was no significant difference between the groups regarding the pattern of root fracture (P=0.39). However, site and extent of fractures were significantly different among the groups (P<0.05).

Conclusion: The conventional cements provided optimal retention and caused less root damage after post removal. Thus, cements providing adequate retention and allowing easier post removal are recommended for use in endodontically treated teeth with a possibility of requiring retreatment.

Objective: This study sought to assess the frequency and severity of second molar external root resorption (ERR) due to the adjacent third molar and its correlation with the position of third molar and other related factors using cone-beam computed tomography (CBCT).

Materials and Methods: This cross-sectional study evaluated 320 second molars and their adjacent impacted third molars on CBCT scans of patients over 16 years, retrieved from the archives of Azad University Radiology Department. Presence/absence of second molar ERR, its location and severity (if present), and position of adjacent third molar were determined on CBCT scans, and recorded in a checklist. Data were analyzed using a logistic regression model.

Results: The frequency of second molar ERR was 33.4% in the mandible and 14% in the maxilla. The severity of ERR was significantly correlated with the involved jaw (P=0.001) but had no correlation with age, gender, or depth of impaction of adjacent third molar (P>0.05). The mesioangular and horizontal positions of impacted third molars had a significant correlation with the frequency of second molar ERR (P<0.006).

Conclusion: According to the results of this study, ERR occurring in second molars adjacent to third molars is common, especially in the mandible. Mesially inclined third molars have a greater potential of being associated with ERR in second molars.

Cone-Beam Computed Tomography; Root Resorption; Molar, Third; Tooth, Impacted

Objectives: This study aimed to assess the effect of casein phosphopeptide amorphous calcium phosphate (CPP-ACP) and xylitol chewing gums, and probiotic yogurt, as chemical plaque control strategies, on periodontal parameters.

Materials and Methods: This randomized clinical trial evaluated 120 eligible dental students that were randomly divided into four groups (n=30) for use of (I) CPP-ACP chewing gum, (II) xylitol chewing gum, (III) probiotic yogurt, and (IV) chlorhexidine (CHX) mouthwash. The oral hygiene index-simplified (OHI-S), Silness and Loe gingival index (GI), and Silness and Loe modified plaque index (PI) were measured before and on days 15 and 30 after using the products. Paired t-test or its non-parametric equivalent was used to analyze the parameters after the intervention compared with baseline. The study groups were compared using one-way ANOVA or its non-parametric equivalent.

Results: The OHI-S did not change over time, and most participants had a good OHI-S. The CHX group had the most favorable, and the probiotic yogurt group had the least favorable GI. Pairwise comparisons of the groups did not reveal a significant difference in GI between the CPP-ACP gum and CHX groups (P>0.05). CHX caused the greatest improvement in PI, with significant differences with other groups.

Conclusion: CHX was the most effective for improvement of periodontal parameters followed by CPP-ACP, which showed better results compared with other groups.

Objectives: This study aimed to evaluate the correlation between the opacification degree of the paranasal sinuses on computed tomography (CT) with clinical symptoms, and anatomical variations of the nose and paranasal sinuses in patients with chronic rhinosinusitis (CRS).

Materials and Methods: This descriptive prospective study evaluated 100 patients (60 males and 40 females), who were diagnosed with CRS by ENT specialists according to the clinical findings, and were scheduled for a CT scan. The patients were requested to express the severity of their symptoms using a visual analog scale. The CT scans of the paranasal sinuses were assessed for the presence of anatomical variations and scored using the modified Lund-Mackay scoring system for the opacification degree of each sinus. The correlations between the anatomical variations and sinusitis, and also between the severity of symptoms/disease severity and CT scores were statistically analyzed. P<0.05 was considered statistically significant.

Results: The most common symptoms were purulent (discolored) nasal drainage and nasal obstruction. Septal deviation was the most common anatomical variation. The maxillary and anterior ethmoid sinuses were the most commonly involved areas. The Spearman’s correlation coefficient showed a significant correlation between the sinus involvement and some of the evaluated symptoms, as well as certain types of anatomical variations (P<0.05).

Conclusion: Some specific anatomical variations of the paranasal sinuses may predispose them to sinusitis. The CT scan score can predict the severity of many symptoms such as purulent (discolored) nasal drainage, nasal obstruction, hyposmia/anosmia, halitosis, cough, and fatigue, among the other symptoms of CRS.

Objectives: This study aimed to compare the marginal fit of temporary restorations fabricated by the conventional chairside method, 3D printing, and milling.

Materials and Methods: In this in vitro, experimental study, 14 temporary restorations were conventionally fabricated over an implant abutment and analog that had been mounted in a phantom model at the site of canine tooth, using auto-polymerizing acrylic resin and putty index. In digital manufacturing, the original model was scanned, and the final restoration was designed. Fourteen temporary restorations were milled out of polymethyl methacrylate (PMMA) blocks, and 14 others were printed by a 3D printer. Temporary crowns were placed on the abutment, and images were obtained from specific areas under a stereomicroscope at x100 magnification to measure the amount of marginal gap. Data were analyzed using one-way ANOVA and Tukey’s test (α=0.05).

Results: The mean marginal gap values for the temporary crowns in the 3D printing, milling, and chairside groups were 91.40, 75.28 and 51.23 µm, respectively. The crowns that were conventionally fabricated chairside exhibited the lowest marginal gap, and the difference in this respect was significant among the three groups (P<0.05).

Conclusion: Temporary crowns fabricated by the chairside method showed significantly smaller marginal gap; however, the marginal gap of all three groups was within the clinically acceptable range.

Objectives: Research is ongoing to find safe and effective oral hygiene aids for oral self‑care in children. Mouthwashes are used to complete the process of mechanical plaque control. Lack of affordability and side effects of most commercially available mouthwashes limit their use in children. Hence, the cost-effective and easily available essential oil, lemongrass oil, when formulated as a mouthwash, may possibly serve as an adjunct to oral hygiene maintenance. The main objective of this study was to compare the efficacy of lemongrass oil and chlorhexidine (CHX) mouthwash in children.

Materials and Methods: Sixty healthy children between 9-12 years were selected. During the initial visit, the plaque pH, plaque index (PI), and gingival index (GI) were assessed, and oral prophylaxis was performed. The patients were randomized into three groups (n=20) and received 0.25% lemongrass oil mouthwash (group A), 0.2% CHX mouthwash (group B), and oral prophylaxis alone (group C). The patients were recalled after 14 and 21 days. ANOVA with post-hoc Bonferroni and paired t-test were used to analyze the results by SPSS software.

Results: Intragroup comparison of PI and GI showed a significant decrease between 14 and 21 days in groups A and B (P≤0.05). Intragroup comparison of the mean plaque pH in group A showed a significant increase at day 21 compared with baseline (P=0.028).

Conclusion: The results showed that the lemongrass oil mouthwash was effective in reducing PI and GI in children. Thus, it may be used as a good herbal alternative to CHX mouthwash.

Objectives: One of the main problems with polymethyl methacrylate (PMMA) used for the fabrication of oral removable appliances is plaque accumulation due to surface porosities. Incorporation of antimicrobial agents in this material might help tackle this problem. The aim of this study was to evaluate the antimicrobial activity of PMMA acrylic resin incorporated with propolis nanoparticles (PNPs).

Materials and Methods: Antimicrobial properties of acrylic resin incorporated with PNPs were assessed against Streptococcus mutans (S. mutans), Streptococcus sanguinis (S. sanguinis), Lactobacillus acidophilus (L. acidophilus) and Candida albicans (C. albicans). Acrylic discs were fabricated in four groups: A control group without PNPs and three experimental groups containing 0.5%, 1% and 2% concentrations of PNPs. Disc agar diffusion (DAD) test was performed to determine the antimicrobial effects of PNPs by measuring the microbial growth inhibition zones on Muller-Hinton agar plates. The eluted components test evaluated the viable counts of microorganisms in liquid medium after 24 and 72h. Finally, biofilm inhibition test assessed the efficacy of PNPs for inhibition of biofilm formation. P<0.05 was considered significant. 

Results: The acrylic discs failed to produce microbial inhibition zones in the DAD test. Discs containing 1% and 2% nanoparticles showed anti-biofilm effects on all four microbial species. The colony counts of all microorganisms significantly decreased following exposure to liquids containing nanoparticles after 24 and 72h in eluted component test.

Conclusion: PMMA acrylic discs incorporated with PNPs presented some antimicrobial properties against S. mutans, S. sanguinis, L. acidophilus, and C. albicans

Objectives: This study aimed to investigate the marginal adaptation of implant-supported three-unit fixed restorations fabricated in excessive crown height by various frameworks namely zirconia, nickel-chromium (Ni-Cr) alloy, and Polyetheretherketone (PEEK) before and after veneering.

Materials and Methods: A basic model with two implant fixtures was made to receive posterior three-unit fixed partial dentures (second premolar to second molar) in 15 mm crown height. A total of 30 frameworks were fabricated using Ni-Cr, zirconia, and PEEK (n=10). All specimens were veneered and vertical marginal discrepancy was evaluated before and after veneering using a stereomicroscope (×75). The effect of framework material and veneering on marginal discrepancy was evaluated by repeated-measures and one-way ANOVA, and paired t test (α=0.05).

Results: There was a significant difference between the groups (P<0.001) before and after veneering. The vertical marginal discrepancy of zirconia frameworks was significantly lower than that of other groups both before and after veneering (P<0.001). Statistical analysis revealed that the veneering process had a significant effect on marginal adaptation (P<0.001).

Conclusion: In implant prostheses with excessive crown height, zirconia had the greatest marginal adaptaion significantly, followed by Ni-Cr. Veneering caused a significant increase in marginal discrepancy of all the materials.

Objectives: Bond strength of composite restorations plays an important role in their success. This in vitro study evaluated the effect of a hemostatic agent on shear bond strength of universal adhesives.

Materials and Methods: Thirty-six extracted human molars were used in this study. Buccal and lingual surfaces were reduced to obtain flat dentin surfaces and were ground with a silicone paper. The samples were randomly divided into three groups (n=12) based on the application of hemostatic agent: group 1: no contamination (control), group 2: aluminum chloride application, and group 3: ferric sulfate application. Each group was then divided into two subgroups (n=6) for using G-Premio and Single Bond Universal. Resin cylinders (Filtek Z550) were bonded to dentin surfaces according to the manufacturer’s instructions. After 1000 thermal cycles, shear load was applied to the specimens using a universal testing machine at a crosshead speed of 1 mm/min until failure. Data were statistically analyzed using two-way ANOVA and Tukey’s post-hoc test (α=0.05).

Results: There were statistically significant differences in shear bond strength of the three main groups for both G-Premio and Single Bond Universal (P<0.05). When the adhesive systems were compared with each other, G-Premio showed higher shear bond strength than Single Bond Universal (P<0.05).

Conclusion: Contamination with hemostatic agents had an adverse effect on the shear bond strength of universal adhesives. Moreover, G-Premio yielded a higher bond strength than Single Bond Universal.

Keywords: Hemostatics; Shear Strength; Adhesives

Objectives: The aim of this study was to assess the shear bond strength (SBS) of zirconia ceramic to composite resin with various surface treatments following pressure changes.

Materials and Methods: Totally, 135 zirconia blocks were prepared by computer-aided design/computer-aided manufacturing technology. The samples were divided into 9 groups (n=15). Three surface treatments including sandblasting, tribo-chemical preparation, and laser application were used. For each method, 45 samples were considered and tested under different pressure conditions. Z-Prime Plus primer was used for bonding of all samples to composite cylinders. All specimens were stored in water for 24 h, underwent thermocycling, and were then placed in a pressure chamber under normal-, high-, and low-pressure conditions. Then, the SBS test was performed for each sample. Data were analyzed by two-way and one-way ANOVA (α=0.05).

Results: The SBS was significantly higher in sandblasting and tribochemical preparation compared with laser irradiation (P<0.05). There was no statistically significant difference in SBS of sandblasting and tribochemical preparation methods (P>0.05). Sandblasting, tribochemical preparation, and laser methods did not show a significant difference in SBS at different pressures (P>0.05).

Conclusion: Sandblasting and tribochemical preparation yielded a higher SBS than laser. Different pressures had no effect on SBS, irrespective of surface preparation method. 

Objectives: This study aimed to compare the colonization of Enterococcus faecalis (E. faecalis), Escherichia coli (E. coli), Streptococcus mutans (S. mutans) and Staphylococcus aureus (S. aureus) isolated from the oral cavity on different suture materials used in oral implantology.

Materials and Methods: Patients scheduled for implant surgery were included in this study. After flap approximation, the surgical site was sutured using silk, nylon, polyglactin 910 (Vicryl^®) and triclosan-coated polyglactin 910 (Vicryl^® Plus) sutures in a randomized order. Seven days after surgery, the sutures were removed and incubated in bile esculin agar (for E. faecalis), MacConkey agar (for E. coli), mitis salivarius agar (for S. mutans), and mannitol salt agar (for S. aureus) at 37°C for 24 h. The colonies were then counted. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests.

Results: Vicryl^® sutures showed the highest accumulation of E. faecalis, followed by Vicryl^® Plus, nylon, and silk. There was no significant difference between nylon and silk (P=0.5) or between Vicryl^® and Vicryl^® Plus (P=0.4). Vicryl^® Plus sutures showed the highest accumulation of E. coli followed by Vicryl^®, silk and nylon (P<0.01). Vicryl^® sutures showed the highest accumulation of S. mutans, followed by Vicryl^® Plus, silk, and nylon. Vicryl^® Plus sutures showed the highest accumulation of S. aureus, followed by Vicryl^®, nylon, and silk.

Conclusion: Nylon sutures showed the least microbial accumulation. Vicryl^® and triclosan-coated Vicryl^® Plus sutures had no advantage over the commonly used silk sutures in decreasing the number of bacteria.

Objectives: Dental caries is among the most common chronic diseases of the childhood. This study sought to assess the effect of caries experience in primary molars on caries development in the adjacent permanent first molars.

Materials and Methods: This cross-sectional study evaluated 413 students aged 7 and 8 years. Clinical dental examination was performed by two independent examiners using disposable dental instruments and a head light. Dental caries was evaluated using the International Caries Detection and Assessment System (ICDAS) for all four permanent first molars and the decayed, missing, and filled teeth (dmft) index for the primary molars. Data were analyzed using the Pearson’s Chi-squared test and Fisher’s exact test.

Results: When primary first molars were sound, 22.9% of the permanent first molars of the same quadrant were sound. When primary second molars were sound, 25.7% of the adjacent permanent first molars were sound. A carious primary second molar had a stronger correlation with development of dentin caries in the adjacent permanent first molar than a carious primary first molar (P<0.001).

Conclusion: The current results confirmed that carious primary molars can significantly affect caries development in the adjacent permanent first molars, and a carious primary second molar has a significantly greater effect than a carious primary first molar in this respect. Thus, special attention should be paid to oral hygiene and proper tooth brushing of primary molars, particularly second molars.

Objectives: Intrabony defects are among the most important signs of progression of periodontal disease. Complete tissue regeneration is the ideal goal of periodontal treatment, and regenerative methods aim to achieve this goal. New studies have reported the positive efficacy of chitosan to enhance the recovery of bony defects. This study aimed to clinically and radiographically assess the efficacy of chitosan particles for treatment of intrabony periodontal defects.

Materials and Methods: In this clinical trial, 18 intrabony three-wall periodontal defects were randomly divided into three groups (n=6). The control group only received conventional flap surgery with a sulcular incision. In the second group, low molecular weight (100,000-300,000g/mol) chitosan was used in the three-wall intrabony defects during surgery while high molecular weight chitosan particles (600,000-800,000 g/mol) were used in the third group. The probing pocket depth (PPD), clinical attachment level (CAL) and radiographic defect depth (RDD) were measured at baseline and at 6 and 12 months later. Repeated measures ANOVA, and McNemar’s test were used for statistical analysis.

Results: In both the control (P<0.001) and coarse chitosan (P=0.035) groups, a significant difference was noted in PPD before and after surgery. CAL was not significantly different among the three groups (P>0.05). No significant difference was noted on radiographs between the groups regarding the regenerated bone density.

Conclusion: Chitosan showed no positive efficacy for treatment of three-wall periodontal bone defects.

Objectives: Pulp stone is a focal calcification in dental pulp, which is often detected on conventional dental radiographs. Pulp stones can complicate easy access to the root canal and pulp chamber in root canal treatment. Orthodontic treatment may be associated with the formation of pulp stones. Therefore, this study examined the number of pulp stones pre- and post-orthodontic treatment.

Materials and Methods: In this retrospective cross-sectional comparative study, 222 digital panoramic radiographs collected from private orthodontic offices in Rasht, were divided into two groups: radiographs of patients undergoing orthodontic and non-orthodontic treatment according to the inclusion criteria. The obtained data were analyzed by SPSS via the Wilcoxon and Mann-Whitney tests (P<0.05).

Results: The difference in the number of pulp stones pre- and post-orthodontic treatment was significant (P<0.0001). The maximum number of pulp stones after orthodontic treatment was observed in second molars (P=0.016). The change in the number of pulp stones in the mandible (P=0.001) was significantly higher than that in the maxilla (P=0.002). This change was also greater in the left side (P<0.0001) than in the right side (P=0.002). The changes in the number of pulp stones was significant in females (P=0.02). Age had an insignificant effect on pulp stone formation (P>0.05).

Conclusion: This study showed the effect of orthodontic treatment on the number of pulp stones. Further studies are required to clarify the underlying mechanisms for this increase and come up with strategies to prevent it.

Objectives: Lingual foramen (LF) is an important landmark of the mandible, which should be considered in presurgical assessment. The purpose of this study was to assess the anatomical variations of the LF using cone-beam computed tomography (CBCT).
Materials and Methods: The study was conducted on 200 CBCT scans of Iranian adults. The lingual foramina (LFs) were classified into two groups by their location in the mandible namely the medial LFs (MLFs) and the lateral LFs (LLFs). The frequency of both the MLFs and the LLFs and their distance from the inferior border of the mandible were evaluated. Additionally, the diameter of the MLFs and the location of the LLFs were assessed. Data were analyzed separately for males and females.
Results: All 200 participants had at least one LF. Totally, 257 LFs were detected on 200 CBCT scans, including 223 MLFs (86.6%) and 34 LLFs (13.3%). The LLF was detected in 23 patients (11.5%). The prevalence of the LLF was higher in males and in the second premolar region. The diameter of the MLFs was less than 1mm in 81% of the cases, and males had a larger MLF.
Conclusion: There was a significant variability in the anatomy and location of the mandibular LF in Iranian adults. CBCT is recommended for preoperative imaging to determine the exact location and size of the LFs in the mandible to prevent possible surgical complications.

Objectives: This study aimed to evaluate the efficacy of ProTaper, Mtwo, and WaveOne retreatment files and Hedstrom files for removal of gutta-percha from the straight root canals using cone-beam computed tomography (CBCT).
Materials and Methods: Forty freshly extracted single-rooted and single-canal teeth were selected for this study. The teeth were decoronated, and biomechanical preparation was performed up to #30 K-file. The root canals were obturated using lateral compaction technique with gutta-percha and Resilon sealer. The teeth were then randomly divided into 4 groups, and CBCT images were obtained. All the canals were then retreated with either ProTaper retreatment files, Mtwo retreatment files, WaveOne files, or Hedstrom files. The surface area of the remaining filling material after the retreatment procedure was quantified by CBCT. Statistical analysis was performed via one-way ANOVA and the Tukey-Kramer multiple comparisons test.
Results: None of the file systems could completely remove the filling material from the canals. Data analysis revealed significant differences between the groups in the apical and middle thirds (P<0.05).
Conclusion: All the file systems left some filling material in the canals. Mtwo retreatment files had maximum efficacy for removal of filling materials in comparison with other files. WaveOne files can also be used for root canal retreatment.

Objectives: Calcium hypochlorite (CH) has been recently used as a root canal irrigant. The aim of the present study was to compare the effect of CH and sodium hypochlorite (SH), as root canal irrigants, on the push-out bond strength of fiber posts cemented with an etch-and-rinse resin cement.
Materials and Methods: In this experimental in-vitro study, 40 human anterior teeth with similar root lengths were randomly divided into five groups (N=8) according to the protocol of root canal irrigation as follows: group 1: saline (control); group 2: 2.5% SH; group 3: 5.25% SH; group 4: 2.5% CH; group 5: 5% CH. Before post placement, the post space was irrigated using the same irrigation protocol, and after that, they were irrigated by distilled water. Fiber posts were cemented with All-Bond 3 bonding and Dou-Link Universal cement. After thermocycling (1000 cycles, 5-55°C), a push-out test was performed, and data were analyzed using one-way analysis of variance and Tukey's post-hoc test with SPSS version 23 (α=0.05).
Results: The highest and lowest mean bond strengths were detected in groups 2 and 5, respectively. There was no significant difference between group 1 and the SH groups (P>0.05), but the difference between group 1 and the CH groups was significant (P<0.001). There was a significant difference between SH groups and CH groups (P<0.001).
Conclusion: Compared to SH, as a root canal irrigant, CH decreased the push-out bond strength of fiber posts cemented with an etch-and-rinse resin cement.

Objectives: In this study we assessed the cytotoxic effect of nanohydroxyapatite (NHA) incorporated into resin modified and conventional glass ionomer cements (RMGICs and CGICs) on L929 murine fibroblasts.
Materials and Methods: In this in vitro study, 0wt%, 1wt%, 2wt%, 5wt%, 7wt% and 10wt% concentrations of NHA were added to Fuji II LC RMGIC and Fuji IX CGIC powders. Eighteen samples (5×3mm) were fabricated from each type of glass ionomer, in six experimental groups (n=3): CG₀, CG₁, CG₂, CG₅, CG₇, CG_10, RMG_0, RMG₁, RMG₂, RMG₅, RMG₇, and RMG₁₀. Samples were incubated for 72h. The overlaying solution was removed and added to L929 fibroblasts. The methyl thiazolyl tetrazolium bromide (MTT) assay was performed at 24, 48 and 72h. The wavelength was read by a spectrophotometer. Data were analyzed by ANOVA and Tukey’s test.
Results: There was no significant difference in cytotoxicity of the two types of glass ionomers, with and without NHA, except for CG₀ and RMG₀ groups after 72h. RMG₀ group was significantly more cytotoxic than the CG₀ group (P<0.05). In CG groups during the first 24h, the cytotoxicity of CG₅ and CG₇ groups was significantly higher than that of CG₁; while, there was no significant difference between the RMG groups. Cytotoxicity significantly decreased in all groups after 24h (P<0.05).
Conclusion: Incorporation of NHA into Fuji II LC RMGIC and Fuji IX CGIC did not affect their biocompatibility and therefore its addition to these materials can provide favorable biological properties, especially considering its beneficial effects on the other properties of GICs.

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.

Impaction of the anterior teeth, which is less frequent in central incisors, can cause serious esthetic and subsequent psychological problems for patients during the mixed dentition period. Traumatic injury to deciduous teeth is the most common etiologic factor. Thus, treatment of maxillary incisor impaction is highly important. Nowadays, application of laser has been suggested in orthodontics and pediatric dentistry for different treatments, such as surgical exposure of impacted teeth and application of low-level laser therapy (LLLT) for acceleration of orthodontic tooth movement. In this paper, the authors present treatment of an impacted and dilacerated maxillary central incisor with laser application for its surgical exposure and LLLT for acceleration of its orthodontic traction and eruption.

Pulmonary atresia with ventricular septal defect (PA/VSD) is one of the congenital heart diseases that results in cyanosis, susceptibility to bacterial endocarditis, and increased risk of complications during general anesthesia. Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common inherited genetic disorder affecting the red blood cells. We aimed to elaborate the potential dental management for patients with this serious condition. This report presents the single-visit dental treatment of a three-year-old female with PA/VSD, G6PD deficiency and rampant caries. The complexity of dental treatments, high incidence of dental caries, lack of cooperation, and the systemic condition limit treatment options to providing service under general anesthesia and hospitalization. Careful monitoring of oxygen saturation during general anesthesia and antibiotic prophylaxis are essential due to the invasive nature of dental treatments. It appears that single-visit dental management under general anesthesia minimizes the risk of treatment of patients at high risk of bacterial endocarditis.

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.