Evaluation of national dental curriculum in Iran using senior dental students' feedback.

BACKGROUND: Dental curriculums require regular revision to stay up to date in scientifical and societal fields. Senior dental students are among the main stakeholders of such curriculums. The present study investigated the opinions of Iranian senior dental students regarding the adequacy of their dentistry program and the national dental curriculum in training a competent dentist, the program's content, and its structure. METHODS: A previously designed and validated questionnaire on the opinion of senior dental students regarding curriculum adequacy was sent to a representative in each of the country's dental schools. Before the COVID pandemic terminated data collection, a total of 16 schools (438 students) managed to respond (37%). The questionnaire asked the students to assess the adequacy of the training received in curriculum's theoretical and practical competencies with the help of a five-point Likert scale that ranged from "Completely inadequate" to "Completely adequate". It also questioned them on its teaching methods and intensity. SPSS software version 24 and Chi-square test served for statistical analysis. RESULTS: In total, the study has 438 participants, 245 female and 193 male. Significant sex differences were spotted in the responses concerning both theoretical and practical training. Regarding general training adequacy, 50 (22.6%) female students and 50 male ones (30.7%), P = 0.08 agreed that the program was acceptable. The numbers for students of old (more than 15 years of activity) and new schools were 47 (21.7%) and 53 (31.7%), respectively (P = 0.03). Nearly one-third deemed the teaching methods appropriate. Regarding the duration of curriculum phases, 33 students (8.3%) believed that basic science required extension, while 108 (28.6%) and 266 (69.1%) reported such need for pre-clinical and clinical phases. The school's years of activity emerged as significant, as 38.1% of students from new schools versus 21.7% of those from old ones deemed the extension of pre-clinical phase necessary (P < 0.001). CONCLUSION: A significant number of Iranian senior dental students found the undergraduate dental curriculum inadequate regarding competencies, content, and teaching. Further investigations will determine whether it's the curriculum or its implementation that warrants revision.

Effect of fluoride varnish on glass ionomer microhardness changes in endogenous acid erosion challenge.

OBJECTIVE: This study aimed to assess the effect of fluoride varnish on glass ionomer microhardness changes after endogenous acid erosion challenge. METHODOLOGY: In this study, 40 conventional glass ionomer (CGI; Fuji IX) and 40 resin-modified glass ionomer (RMGI; Fuji IILC) discs were fabricated and divided into 4 subgroups (n = 10) for immersion in synthetic gastric acid or saliva for 27 h with/without fluoride varnish application. The surface microhardness was measured at baseline and after immersion, and the change in microhardness was calculated. Data were analyzed using analysis of variance and T-test. RESULTS: A reduction in microhardness was noted in all subgroups following immersion. The lowest change in microhardness of both CGI and RMGI occurred in artificial saliva. In CGI groups, the highest reduction in microhardness occurred in synthetic gastric acid with fluoride varnish application, and the reduction was significantly different from that of the CGI group with fluoride varnish application (p value = .01). In RMGI groups, the highest reduction in microhardness was noted in synthetic gastric acid without fluoride varnish application, and the reduction was significantly different from that of the other groups (p value < .05). CONCLUSIONS: Exposure to synthetic gastric acid caused a significant reduction in microhardness of RMGI. Varnish application significantly decreased the acid susceptibility of RMGI, but not that of CGI.

Push-out bond strength of calcium-silicate cements following Er:YAG and diode laser irradiation of root dentin.

This study aimed to compare the effects of diode and Er:YAG laser irradiation of root dentin on push-out bond strength of mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM) cements. An in vitro experimental study was conducted on 90 dentin discs, cut out of freshly extracted human teeth. The discs were instrumented to obtain 1.3-mm lumen diameter. Then, they were randomly divided into six groups (n = 15). Groups 1 and 4 subjected to diode laser (Wiser, Doctor Smile, Italy) (980 nm, 1 W, continuous mode) for 10 s and filled with MTA and CEM cements. Groups 2 and 5 subjected to Er:YAG laser (Deka, Italy) (2940 nm, 1 W, 10 Hz, 230 µs) for 10 s and filled with MTA and CEM cements. Groups 3 and 6 (control groups) were filled with MTA and CEM cements without laser irradiation. After 7 days, push-out bond strength test was performed using a universal testing machine in order to evaluate the adhesion of the biomaterials to dentin. The samples were evaluated under a light microscope at × 40 magnification to determine the mode of fracture. Data were analyzed using two-way ANOVA. The highest push-out bond strength (8.76 ± 3.62 MPa) was noted in group 1 (diode/MTA), which was significantly higher than the other groups (P < 0.001). The lowest bond strength (2.61 ± 0.81) was noted in group 6 (control/CEM). Diode laser significantly increased the bond strength of both cements (P < 0.05), but Er:YAG laser irradiation only increased the bond strength of CEM and had no significant effect on MTA (P = 0.603). The bond strength of MTA control group was higher than that of CEM control group (P = 0.001). Push-out bond strength of endodontic cements can be affected by dentin conditioning with diode 980 nm and Er:YAG laser. Nine hundred eighty-nanometer diode laser irradiation is recommended to increase the bond strength of endodontic cements particularly the CEM cement to dentin.

The Effect of BC Sealer, AH-Plus and Dorifill on Push-out Bond Strength of Fiber Post.

INTRODUCTION: Dentinal canal walls are in direct contact with endodontic sealers prior to post space preparation and luting cements after post space preparation. This direct contact may affect the bond strength of intraradicular posts to root dentin. This study aimed to assess the effect of three different sealers on the bond strength of fiber posts to root dentin. METHODS AND MATERIALS: The canals of 56 extracted single-rooted human premolars after selection and decoronation were prepared. For obturation of the canals, specimens were randomly divided into four groups (n=14) according to the type of sealer used in conjunction with gutta-percha: group 1 (control) without any sealer; group 2 with AH-Plus sealer (resin based); group 3 with Dorifill sealer (ZOE-based); and group 4 with BC Sealer (calcium silicate-based). Nine mm-deep post space was prepared in the canal of each specimen. Intraradicular fiber posts were cemented using dual-cure resin cement (Panavia F2.0). Sections of 1 mm thickness were made at the coronal, middle and apical thirds of the post space of each specimen. The push-out bond strength of post to root dentin was measured in a universal testing machine. The data were analyzed using one-way ANOVA and post-hoc Tukey's test. RESULTS: The mean push-out bond strength in the coronal third was significantly lower in Dorifill group compared to AH-Plus (P=0.004). This value was significantly lower in BC Sealer group than AH-Plus (P=0.000) and control group (P=0.03). In middle and apical thirds, the mean push-out bond strength was not significantly different among the four groups (P=0.407, P=0.065, respectively). The mean push-out bond strength was significantly lower in apical than coronal third in AH-Plus group (P=0.001). CONCLUSION: Application of BC Sealer and Dorifill decreased the mean push-out bond strength of intracanal post to root dentin in the coronal third in comparison to AH-Plus.

Comparison of Apical Transportation with the Use of Rotary System and Reciprocating Handpiece with Precurved Hand Files: An In Vitro Study.

INTRODUCTION: Success of root canal treatment depends on several factors; among which, maintaining the original canal path during mechanical preparation is extremely important. This in vitro study aimed to compare apical transportation using RaCe NiTi rotary system and precurved stainless steel (SS) hand files in a reciprocating handpiece. METHODS AND MATERIALS: Mesiobuccal canals of 40 extracted human mandibular first and second molars with 20 to 45° curvatures and 3 to 7 mm curve radius were chosen for this study. After working length determination, the teeth were divided into two groups (n=20). Root canals were prepared with RaCe in group 1 and NSK handpiece and precurved SS hand files in group 2 up to #30 with 2% taper in both groups. Radiographs were taken of teeth before and after instrumentation from buccolingual and mesiodistal directions. The images were superimposed using Adobe Photoshop CS3 software. Degree of straightening and amount of apical transportation at 0, 0.5, 1, 2, 3, 4 and 5 mm levels short of the working length were determined using digital subtraction radiography. The student's t test was used to compare the degree of straightening and Mann Whitney test was applied to compare apical transportation (millimeters) between the two groups. RESULTS: No significant difference was noted between the two groups on buccolingual or mesiodistal views in degree of straightening and apical transportation on buccolingual view (P>0.05). However, on mesiodistal view, NSK reciprocating handpiece caused greater apical transportation at 0. 0.5 and 1 mm levels (P<0.05). CONCLUSION: The RaCe system and precurved SS files in reciprocating handpiece were highly similar in terms of degree of straightening and apical transportation. Thus, engine-driven NSK reciprocating handpiece can be used as an efficient adjunct for root canal preparation.

Evaluation of the antibacterial activity of a conventional orthodontic composite containing silver/hydroxyapatite nanoparticles.

BACKGROUND: One of the most important complications of fixed orthodontic treatment is the formation of white spots which are initial carious lesions. Addition of antimicrobial agents into orthodontic adhesives might be a wise solution for prevention of white spot formation. The aim of this study was to evaluate the antibacterial properties of a conventional orthodontic adhesive containing three different concentrations of silver/hydroxyapatite nanoparticles. METHODS: One hundred and sixty-two Transbond XT composite discs containing 0, 1, 5, and 10 % silver/hydroxyapatite nanoparticles were prepared and sterilized. Antibacterial properties of these composite groups against Streptococcus mutans, Lactobacillus acidophilus, and Streptococcus sanguinis were investigated using three different antimicrobial tests. Disk agar diffusion test was performed to assess the diffusion of antibacterial agent on brain heart infusion agar plate by measuring bacterial growth inhibition zones. Biofilm inhibition test showed the antibacterial capacity of composite discs against resistant bacterial biofilms. Antimicrobial activity of eluted components from composite discs was investigated by comparing the viable counts of bacteria after 3, 15, and 30 days. RESULTS: Composite discs containing 5 and 10 % silver/hydroxyapatite nanoparticles were capable of producing growth inhibition zones for all bacterial types. Results of biofilm inhibition test showed that all of the study groups reduced viable bacterial count in comparison to the control group. Antimicrobial activity of eluted components from composite discs was immensely diverse based on the bacterial type and the concentration of nanoparticles. CONCLUSIONS: Transbond XT composite discs containing 5 and 10 % silver/hydroxyapatite nanoparticles produce bacterial growth inhibition zones and show antibacterial properties against biofilms.

Evaluation of Salivary Leptin Levels in Healthy Subjects and Patients with Advanced Periodontitis.

OBJECTIVES: Leptin is a hormone-like protein produced by the adipose tissue. It plays an important role in protection of host against inflammation and infection. Some studies have reported changes in leptin levels in the gingival crevicular fluid (GCF), saliva and blood serum of patients with periodontal disease compared to healthy individuals. The aim of the present study was to compare the salivary leptin levels in patients with advanced periodontitis and healthy individuals. MATERIALS AND METHODS: In this case-control study, the salivary samples of healthy individuals and patients with advanced periodontitis with clinical attachment loss >5mm were obtained using a standardized method and the leptin levels were measured in the salivary samples by means of ELISA. The effects of the periodontal status and sex on the salivary leptin levels of both groups were statistically analyzed by two-way ANOVA. RESULTS: The means ± standard deviation (SD) of salivary leptin levels in healthy subjects and patients with advanced periodontitis were 34.27±6.88 and 17.87±5.89 pg/mL, respectively. Statistical analysis showed that the effect of sex on the salivary leptin levels was not significant (P=0.91), while the effect of advanced periodontitis on the salivary leptin levels was significant compared to healthy individuals (P<0.0001). CONCLUSIONS: In patients with advanced periodontitis, the salivary leptin levels were significantly lower compared to healthy individuals. Thus, assessment of salivary leptin can be done as a non-invasive and simple method to determine the susceptibility of patients to advanced periodontitis.

Treatment of Symptomatic Geographic Tongue with Triamcinolone Acetonide Alone and in Combination with Retinoic Acid: A Randomized Clinical Trial.

OBJECTIVES: Geographic tongue or migratory glossitis is an inflammatory disorder with unknown etiology. Considering the accompanied burning pain, taste dysfunction, and lack of definite cure, it is important to treat this condition symptomatically. The objective of the current study was to compare the efficacy of a combination of 0.05% retinoic acid and 0.1% triamcinolone acetonide with that of triamcinolone acetonide alone for treatment of symptomatic geographic tongue. MATERIALS AND METHODS: This randomized controlled double-blind clinical trial was performed on 28 patients with symptomatic geographic tongue, who were referred to two dental clinics. Participants were randomly divided into two groups and treated with triamcinolone alone or retinoic acid plus triamcinolone for 10 days. Patients were assessed for the level of pain, burning sensation and size of lesion at the beginning and at the end of the study. Participants were followed up for two months after cessation of treatment (at the end of each month). SPSS 11 was applied to compare the two therapeutic modalities. RESULTS: Twenty-eight participants with a mean age of 40 years were evaluated including Seven (25%) males and 21(75%) females. There was a positive family history of geographic tongue in 21 patients. Despite the diminished pain and burning sensation as well as smaller size of lesions following treatment (P<0.05), no statistically significant differences were found between the two groups (P> 0.05). No side effect was reported. CONCLUSIONS: The combination of triamcinolone and retinoic acid was not more effective than triamcinolone alone for symptomatic treatment of geographic tongue.

Comparison of Cleaning Efficacy and Instrumentation Time in Primary Molars: Mtwo Rotary Instruments vs. Hand K-Files.

INTRODUCTION: Pulpectomy is the preferred treatment for restorable primary teeth with symptomatic irreversible pulpitis or periradicular lesion. Considering the rather new application of rotary files for pulpectomy of primary teeth, the aim of this study was to compare the cleaning efficacy and instrumentation time of hand K-files and Mtwo rotary system for preparation of human primary molars. METHODS AND MATERIALS: This experimental study was conducted on 100 extracted primary maxillary and mandibular intact molars with no resorption. Access cavities were prepared and India ink was injected into the root canal on a vibrator using an insulin syringe. Canals were then divided into 5 groups (n=20): in group I, canals were instrumented using K-files up to #25 for mesial and buccal canals and #30 for palatal and distal canals. In group II, canals were prepared using Mtwo rotary files (15/0.05, 20/0.06 and 25/0.06 for mesial and buccal canals and 15/0.05, 20/0.06, 25/0.06 and finally 30/0.05 for distal and palatal canals). In group III, root canals were only irrigated with saline. Groups IV and V were the positive and negative control groups, respectively. The time required for cleaning and preparation of the canals for each of the specimens in groups I, II and III was recorded. RESULTS: The mean score of cleanliness of Mtwo was not significantly different from K-file group (P>0.05). However the mean instrumentation time in Mtwo group was significantly shorter (P<0.001). CONCLUSION: Although there were no differences regarding the cleaning efficacy of either system, Mtwo rotary files were far more time efficient.

Effect of chloroform, eucalyptol and orange oil solvents on the microhardness of human root dentin.

OBJECTIVES: This study aimed to assess the effect of chloroform, eucalyptol and orange oil solvents on the microhardness of human root dentin. MATERIALS AND METHODS: Sixty-eight single-rooted single-canal extracted human premolar teeth were used. Tooth crowns were separated from the roots at the cementoenamel junction (CEJ). Roots were buccolingually sectioned into mesial and distal halves. Specimens were randomly divided into 5 groups, with 20 teeth in each solvent group and 4 teeth in each control group. Primary microhardness of specimens was measured using Vickers microhardness tester. Specimens were exposed to solvents for 15 minutes and were subjected to microhardness testing again. Data were recorded and analyzed using repeated measure ANOVA. RESULTS: No significant difference was found in dentin microhardness before and after exposure to solvents in any of the orange oil, eucalyptol, chloroform or saline groups (P=0.727). None of the experimental groups showed any significant difference in terms of dentin microhardness reduction (P=0.99) and had no significant difference with the negative control group. CONCLUSION: This study showed that chloroform, eucalyptol and orange oil as gutta percha solvents did not decrease the microhardness of root dentin. Thus, none of the mentioned solvents has any superiority over the others in terms of affecting dentin properties.

Cone-beam Computed Tomographic Assessment of Canal Centering Ability and Transportation after Preparation with Twisted File and Bio RaCe Instrumentation.

OBJECTIVE: Use of rotary Nickel-Titanium (NiTi) instruments for endodontic preparation has introduced a new era in endodontic practice, but this issue has undergone dramatic modifications in order to achieve improved shaping abilities. Cone-beam computed tomography (CBCT) has made it possible to accurately evaluate geometrical changes following canal preparation. This study was carried out to compare canal centering ability and transportation of Twisted File and BioRaCe rotary systems by means of cone-beam computed tomography. MATERIALS AND METHODS: Thirty root canals from freshly extracted mandibular and maxillary teeth were selected. Teeth were mounted and scanned before and after preparation by CBCT at different apical levels. Specimens were divided into 2 groups of 15. In the first group Twisted File and in the second, BioRaCe was used for canal preparation. Canal transportation and centering ability after preparation were assessed by NNT Viewer and Photoshop CS4 software. Statistical analysis was performed using t-test and two-way ANOVA. RESULTS: All samples showed deviations from the original axes of the canals. No significant differences were detected between the two rotary NiTi instruments for canal centering ability in all sections. Regarding canal transportation however, a significant difference was seen in the BioRaCe group at 7.5mm from the apex. CONCLUSION: Under the conditions of this in vitro study, Twisted File and BioRaCe rotary NiTi files retained original canal geometry.

Evaluation of shear bond strength of orthodontic brackets bonded with nano-filled composites.

OBJECTIVES: The purpose of this study was to evaluate the shear bond strength (SBS) of orthodontic brackets bonded with two types of nano-composites in comparison to a conventional orthodontic composite. MATERIALS AND METHODS: Sixty extracted human first premolars were randomly divided into 3 groups each containing 20 teeth. In group I, a conventional orthodontic composite (Transbond XT) was used to bond the brackets, while two nano-composites (Filtek TM Supreme XT and AELITE Aesthetic Enamel) were used in groups II and III respectively. The teeth were stored in distilled water at 37°C for 24 hours, thermocycled in distilled water and debonded with a universal testing machine at a crosshead speed of 1 mm/min. The adhesive remnant index (ARI) was also evaluated using a stereomicroscope. RESULTS: AELITE Aesthetic Enamel nano-composite revealed a SBS value of 8.44±2.09 MPa, which was higher than Transbond XT (6.91±2.13) and Filtek TM Supreme XT (6.04±2.01). Statistical analysis revealed a significant difference between groups II and III (P < 0.05). No significant difference was found between groups I and III, and between groups I and II (P > 0.05). Evaluation of ARI showed that Transbond XT left fewer adhesive remains on teeth after debonding. CONCLUSION: Results of this study indicate that the aforementioned nano-composites can be successfully used for bonding orthodontic brackets.

Effect of nicotine on orthodontic tooth movement in rats.

INTRODUCTION: Although the detrimental health effects of cigarettes are well known, many people, including some orthodontic patients, continue to smoke. Nicotine can affect bone resorption and apposition. Therefore, the aim of this study was to investigate the effect of nicotine on orthodontic tooth movement. METHODS: Thirty-two adult male Sprague-Dawley rats were randomly divided into 3 experimental groups and 1 control group. With the rats under general anesthesia, 5-mm nickel-titanium closed-coil springs were placed between the maxillary right first molars and first incisors. Injections of nicotine were administered daily for 13 days: group A, 0.5 mg per kilogram; group B, 0.75 mg per kilogram; and group C, 1 mg per kilogram. Group D, the control group, received injections of 0.1 mL of normal saline solution. At the end of the experimental period, the rats were killed, and interproximal tooth movements were measured. RESULTS: The mean amounts of tooth movement were 0.47 mm in group A, 0.62 mm in group B, 0.78 mm in group C, and 0.21 mm in group D. Statistical analysis with analyis of variance (ANOVA) test showed significant differences between all groups. The most movement occurred in group C, and group D had the least movement. CONCLUSIONS: Nicotine accelerates orthodontic tooth movement, and this effect is dose-dependent. Nicotine's role in accelerating tooth movement might be related to its effect of accelerating bone resorption.

Effect of acidic environment on the push-out bond strength of mineral trioxide aggregate.

INTRODUCTION: Reduced surface microhardness and decreased sealing ability have been shown after the placement of mineral trioxide aggregate (MTA) in an acidic environment. In this study, the effect of an acidic environment on the push-out strength of MTA was evaluated. METHODS: Eighty root dentin slices from freshly extracted single-rooted human teeth were sectioned and their lumen instrumented to achieve a diameter of 1.3 mm. One gram of tooth-colored ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN) was mixed with 0.33 g of distilled water and introduced into the canals of the root-dentin slices and treated with ultrasonic energy. The specimens were then randomly divided into four groups (n = 20) and wrapped in pieces of gauze soaked in phosphate buffer saline solution (pH = 7.4) and butyric acid buffered at pH values of 4.4, 5.4, or 6.4, respectively. They were then incubated for 4 days at 37 degrees C. The push-out bond strengths were then measured using a universal testing machine. The slices were examined under a light microscope at x40 magnification to determine the nature of the bond failure. The data were analyzed using one-way analysis of variance and the Tamhane post hoc test. RESULTS: The greatest mean push-out bond strength (7.28 +/- 2.28 MPa) was observed after exposure to a pH value of 7.4. The values decreased to 2.47 +/- 0.61 MPa after exposure to a pH value of 4.4. There were significant differences between the groups (p < 0.001). Inspection of the samples revealed the bond failure to be predominantly adhesive. CONCLUSION: The force needed for displacement of MTA was significantly lower in samples stored at lower pH values.