Effects of a blended design of closed-book and open-book examinations on dental students' anxiety and performance.

BACKGROUND: While closed-book examinations (CBEs) have traditionally been implemented in dental education, open-book examinations (OBEs) are being introduced for the purpose of acquiring higher levels of knowledge and promoting long-term memory. This study examines whether it is effective to use a blended assessment of CBEs and OBEs for dental students to reduce test anxiety and enhance academic performance. METHODS: Using a quasi-experimental research method, a blended assessment that combined CBEs in class and OBEs online was designed for a dental course. In 2020, when the pandemic was at its peak, student assessment was ineffective, and the 2020 cohort was omitted for our study; instead, two cohorts of predoctoral dental students (N = 178) enrolled in Restorative Dentistry in the spring semesters of 2019 and 2021 were included in the study. These students were informed about the experimental design, and they provided written consent for data collection, thereby voluntarily participating in the survey. Their self-perceived responses to open-ended survey questions on assessment methods were qualitatively analyzed. RESULTS: There was no significant difference in test anxiety between the CBEs and OBEs at the p-values of 0.001 in all items. Traditional and blended assessment showed a similar trend of lower scores in midterm exams compared to higher scores in final exams, thus discriminating against students' performances. In particular, a low-achieving group was better predicted by a blended assessment. An analysis of the students' self-perceived responses produced highly topical themes, including exam burden, learning effects, and fairness issues. CONCLUSIONS: This study confirmed the feasibility of blended assessment that can be implemented in online and in-person educational environments. Moreover, it can be used as the groundwork to develop new models of assessment in dental education.

In vivo real-time temperature measurement on the surface of intact and gold-restored teeth during consumption of hot and cold drinks.

This study aimed to measure real-time temperature changes in gold-restored teeth compared with intact teeth during the intake of hot and cold drinks. Sixteen molars, including eight natural intact teeth and eight restored teeth with gold inlays, were selected from the participants. Custom-made thermocouple sensors were attached to the coronal third of the buccal surface of teeth. Participants consecutively consumed hot and cold drinks according to a standardized regimen. Resting, maximum, and minimum temperatures; time to reach peak temperatures; and heating and cooling velocities were obtained. Statistical analysis was performed using independent two-sample t-test. Teeth with gold restorations showed a significantly higher maximum temperature (44.7 °C [SD 2.9]) than did natural teeth (40.5 °C [SD 1.2]) during hot water drinking and showed a lower minimum temperature (25.0 °C [SD 4.9]) than did natural teeth (31.5 °C [SD 3.1]) during cold water drinking. The heating and cooling rates for the teeth with gold restorations were two and three times higher than those of the natural teeth. Gold-restored teeth showed greater temperature change than intact teeth in terms of magnitude and velocity in response to temperature changes induced by hot and cold drinks.

Influence of different inlay configurations and distance from the adjacent tooth on the accuracy of an intraoral scan.

STATEMENT OF PROBLEM: Clinical guidelines for obtaining accurate scan data during the intraoral scanning of inlay cavities with various configurations and interproximal distances are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of interproximal distance and cavity type on the accuracy of digital scans for inlay cavities, including proximal cavities. MATERIAL AND METHODS: Four artificial teeth with 4 types of inlay cavities designed based on the buccolingual width and gingival level of the proximal box were installed in a mannequin at distances of 0.6, 0.8, and 1.0 mm from the adjacent teeth. Reference scans of the 4 artificial teeth were obtained by using a laboratory scanner. The CEREC Primescan AC was used to acquire digital scan data (each n=10). Standard tessellation language (STL) files were analyzed with a 3-dimensional analysis software program. The mean deviation values were measured with a 3-dimensional best-fit alignment method to evaluate the accuracy of the digital scan data. Statistical analyses were performed by using 2-way ANOVA and the Bonferroni multiple comparison test (α=.05). RESULTS: As per the interproximal distance, the 1.0-mm group showed significantly higher trueness than the 0.6-mm group (P<.05). As the interproximal distance increased, the maximum positive deviation significantly decreased (P<.05). Maximum negative deviation and precision of the scan data were not significantly different among the distance groups (P>.05). Cavity type had a significant influence on the trueness and precision of the scan data (P<.05). In particular, the narrow long cavity type had an adverse effect on the precision and maximum positive deviation of scan data. CONCLUSIONS: During the intraoral scanning of class II inlay restoration, interproximal distance and cavity type affected the accuracy of an intraoral scan. As the interproximal distance increased, the trueness of the acquired digital images increased and the maximum positive deviation significantly decreased. The narrow long cavity type negatively affected the mean maximum positive deviation and precision of scan data.

How light attenuation and filler content affect the microhardness and polymerization shrinkage and translucency of bulk-fill composites?

OBJECTIVES: The purpose of this study was to investigate the microhardness, polymerization shrinkage, and translucency of bulk-fill composites (BFCs) which have different light attenuation properties and filler contents. MATERIALS AND METHODS: Five BFCs [Filtek Bulk Fill (FB), SureFil SDR (SS), Venus Bulk Fill (VB), SonicFill (SF), and Tetric N-Ceram Bulk Fill (TB)] and two resin-based composites (RBCs) [Tetric N-Ceram (TN) and Filtek Z350XT Flowable (ZF)] were chosen. Numbers of transmitted photons, refractive index, microhardness at different thicknesses, polymerization shrinkage, and translucency parameter (TP) were evaluated. RESULTS: Attenuation coefficients (ACs) based on measured photons ranged from -0.88 to -1.90. BFCs, except SF, had lower AC values than TN or ZF, and BFCs, except TN, had smaller refractive index decreases between top and bottom surfaces. Regardless of an exponential decrease in photon counts, microhardness decreased linearly as specimen thickens. Moreover, microhardness of BFCs showed smaller top-to-bottom decreases (11.5-48.8 %) than TN or ZF (57.3 and 71.5 %, respectively). BFCs with low filler contents showed lower microhardness and higher polymerization shrinkage than those of high filler contents. Also, BFCs had significantly higher (p < 0.001) TP values than TN or ZF. CONCLUSION: BFCs attenuated light less than RBCs. However, some BFCs had much lower top surface microhardness and higher polymerization shrinkage than tested RBCs. CLINICAL RELEVANCE: Despite the convenience of bulk filling, careful selection of BFC is advised because some BFCs have worse microhardness and polymerization shrinkage than RBCs due to their lower filler contents.

Temperature changes in bulk-fill resin composite during photopolymerization.

PURPOSE: To investigate the temperature changes at multiple sites within bulk-fill resin composites and in the pulp chamber during photopolymerization in the tooth cavity. METHODS: Class 1 cavities (n = 5) prepared in extracted third molars were filled with SureFil SDR Flow, a newly developed bulk-fill composite. After securing the specimens in a water bath at 36.5 degrees C, eight thermocouples were used to measure the temperature at the bottom center (BC), middle center (MC), top center (TC), bottom edge (BE), middle edge (ME), and top edge (TE) of the restoration; the pulpal aspect of the dentin (PD); and the center of the curing light tip (CL) during photopolymerization. RESULTS: The maximum temperature values (degrees C) differed among the measurement sites. TC exhibited the greatest temperature increase (72.3 ± 2.4), followed by MC, BC, TE, TE, ME, CL, and BE. The lowest temperature was observed at PD (41.1 ± 1.9). The peak temperatures within the composite were observed during the early stage of light-curing, while CL and PD exhibited the highest temperature at the end stage of light-curing.

Dentin wear after simulated toothbrushing with water, a liquid dentifrice or a standard toothpaste.

PURPOSE: To investigate the influence of dentifrices with and without abrasives on the wear and surface topography of human dentin following simulated toothbrushing in vitro. METHODS: 24 dentin specimens were prepared and randomly allocated to a liquid dentifrice (Garglin Gum-Guard), conventional dentifrice (333 Clinic Total Care), and control (distilled water) groups. Specimens were subjected to simulated toothbrushing of 50,000 repeated strokes under a 150 g-load. The dentin surface was profiled in each specimen using a profilometer before and after toothbrushing. The mean surface roughness (Ra) of the specimens was calculated and compared by one-way ANOVA and Tukey's post-hoc test (α = 0.05). The dentin surfaces were further examined by scanning electron microscopy (SEM). RESULTS: The Ra values were similar between the liquid dentifrice and control groups (P > 0.05), and was significantly higher in the conventional dentifrice group (P < 0.001). On SEM examination, patent dentin tubules were observed in the conventional dentifrice and liquid dentifrice groups, but were not observed in the control group.

Quantitative microleakage analysis of endodontic temporary filling materials using a glucose penetration model.

OBJECTIVE: The purpose of this study was to analyze the sealing ability of different temporary endodontic materials over a 6-week period using a glucose penetration model. MATERIALS AND METHODS: Standardized holes were formed on 48 dentin discs from human premolars. The thicknesses of the specimens were distributed evenly to 2 mm, 3 mm and 4 mm. Prepared dentin specimens were randomly assigned into six groups (n = 7) and the holes in the dentin specimens were filled with two kinds of temporary filling materials as per the manufacturers' instructions as follows: Caviton (GC Corporation, Tokyo, Japan) 2 mm, 3 mm, 4 mm and IRM (Dentsply International Inc., Milford, DE) 2 mm, 3 mm, 4 mm. The remaining specimens were used as positive and negative controls and all specimens underwent thermocycling (1000; 5-55°C). The sealing ability of all samples was evaluated using the leakage model for glucose. The samples were analyzed by a spectrophotometer in quantitative glucose microleakage test over a period of 6 weeks. As a statistical inference, a mixed effect analysis was applied to analyze serial measurements over time. RESULTS: The Caviton groups showed less glucose penetration in comparison with the IRM groups. The Caviton 4 mm group demonstrated relatively low glucose leakage over the test period. High glucose leakage was detected throughout the test period in all IRM groups. The glucose leakage level increased after 1 week in the Caviton 2 mm group and after 4 weeks in the Caviton 3 mm and 4 mm groups (p < 0.05). CONCLUSIONS: Caviton had better sealing ability than IRM in the glucose penetration model during 6 weeks. Temporary filling of Caviton to at least 3 mm in thickness is necessary and temporary filling periods should not exceed 4 weeks.

Cytotoxicity of four denture adhesives on human gingival fibroblast cells.

OBJECTIVE: The purpose of this study was to compare the cytotoxicity of four denture adhesives on human gingival fibroblast cells. MATERIALS AND METHODS: Immortalized human gingival fibroblasts were cultured with one of four different denture adhesives, Polident, Protefix, Staydent or Denfix-A, which was placed in insert dishes (10% w/v concentration) for 48 h. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and flow cytometric apoptosis assay were used to evaluate cell viability and apoptosis rates. The fibroblasts were also examined under a scanning electron microscope. RESULTS: The MTT assay showed that all denture adhesives resulted in a significantly lower cell viability compared to the control cells propagated in normal culture medium (p < 0.05), with Staydent demonstrating the lowest cell viability. According to the flow cytometric apoptosis assay, Staydent and Protefix showed significantly higher apoptosis rates than the control group (p < 0.05), whereas Polident and Denfix-A did not demonstrate any significant differences (p > 0.05). Staydent showed the highest apoptosis rate. Scanning electron microscopy showed that the cells of the Staydent group underwent cytoplasmic membrane shrinkage, with cell free areas containing residual fragments of the membrane of dead cells. CONCLUSIONS: The four denture adhesives evaluated in this study imparted cytotoxic effects on human gingival fibroblast cells. Staydent showed the highest toxicity.

Influence of preparation design on fit and ceramic thickness of CEREC 3 partial ceramic crowns after cementation.

OBJECTIVE: This study investigated the influence of preparation design on the marginal and internal gap and ceramic thickness of partial ceramic crowns (PCCs) fabricated with the CEREC 3 system. MATERIALS AND METHODS: Sixteen extracted human mandibular molars were prepared according to two different preparation designs (n = 8): a retentive preparation design with traditional cusp capping (Group I) and a non-retentive preparation design with horizontal reduction of cusps (Group II). PCCs were fabricated from IPS Empress CAD with the CEREC 3 system. The parameters for luting space and minimum occlusal ceramic thickness were set to 30 µm and 1.5 mm, respectively. The fabricated PCCs were cemented to their corresponding teeth with self-adhesive resin cement and were then scanned by micro-computed tomography. The marginal and internal gaps were measured at pre-determined measuring points in five bucco-lingual and three mesio-distal cross-sectional images. The ceramic thicknesses of the PCCs were measured at the measuring points for cusp capping areas. RESULTS: Group II (167.4 ± 76.4 µm) had a smaller overall mean gap, which included the marginal and internal gap measurements, than that of Group I (184.8 ± 89.0 µm). The internal gaps were larger than the marginal gaps, regardless of preparation design. Group I presented a thinner ceramic thickness in the cusp capping areas than the minimum occlusal ceramic thickness parameter of 1.5 mm. CONCLUSION. Preparation design had an influence on fit, particularly the internal gap of the PCCs. Ceramic thickness could be thinner than the minimum ceramic thickness parameter.

Effects of non-thermal atmospheric pressure pulsed plasma on the adhesion and durability of resin composite to dentin.

This study investigated the effect of low-power, non-thermal atmospheric pressure plasma (NT-APP) treatments, in pulsed and conventional modes, on the adhesion of resin composite to dentin and on the durability of the bond between resin composite and dentin. A pencil-type NT-APP jet was applied in pulsed and conventional modes to acid-etched dentin. The microtensile bond strength (MTBS) of resin composite to dentin was evaluated at 24 h and after thermocycling in one control group (no plasma) and in two experimental groups (pulsed plasma and conventional plasma groups) using the Scotchbond Multi-Purpose Plus Adhesive System. Data were analyzed using two-factor repeated-measures anova and Weibull statistics. Fractured surfaces and the bonded interfaces were evaluated using a field-emission scanning electron microscope. Although there were no significant differences between the plasma treatment groups, the plasma treatment improved the MTBS compared with the control group. After thermocycling, the MTBS did not decrease in the control or conventional plasma group but increased in the pulsed plasma group. Thermocycling increased the Weibull moduli of plasma-treated groups. In conclusion, plasma treatment using NT-APP improved the adhesion of resin composite to dentin. Using a pulsed energy source, the energy delivered to the dentin was effectively reduced without any reduction in bond strength or durability.

Shear bond strength of dual-cured resin cements on zirconia: The light-blocking effect of a zirconia crown.

Abstract Background/purpose: The presence of restorative material between resin cement and the light-curing unit can reduce light transmission. This study aimed to evaluate the effect of the light-blocking effect of zirconia crown on shear bond strength (SBS) between three dual-cured resin cements and the zirconia surface. Materials and methods: Sixty zirconia specimens were prepared and divided into three groups according to the type of resin cement [RXU (RelyX Ultimate); SC2 (SmartCem2); MEC (Maxcem Elite Chroma)]. Each group was further divided into two subgroups, with or without a 1-mm-thick zirconia crown (n = 10). The specimens were light-cured from five different directions for 20 s each. All specimens were thermocycled 5000 times and subjected to SBS testing, followed by scanning electron microscope examination. Results: The presence of a 1-mm-thick zirconia crown had no significant effect on the SBS in all resin cements. However, the SBS was significantly affected by type of resin cement. RXU showed the highest SBS (8.35 MPa with crown; 8.57 MPa without crown), followed by SC2 (5.48 MPa with crown; 5.57 without crown) and then MEC (3.37 MPa with crown; 4.04 MPa without crown. Fractured surfaces exhibited varying degrees of mixed failure patterns. Conclusion: A 1-mm-thick zirconia crown material between the light source and the dual-cured resin cement did not significantly influence the SBS of the resin cements on the zirconia substrates. RXU exhibited the highest SBS regardless of zirconia crown coverage. With sufficient light-curing, dual-cured resin cements can be a good choice for zirconia crown cementation.

Effect of dentin surface conditions and curing mode of resin cement on the dentin bond strength.

This study investigates the effects of dentin's drying time, roughness, and curing modes of resin cement on bond strength. Forty human teeth were divided into eight groups based on three experimental factors: dentin's roughness by 240-or 600-grit SiC paper (coarse or fine), dentin wetness with air-drying time (5-s or 10-s), and Single Bond Universal adhesive's curing mode by co-curing with RelyX Ultimate cement or light-curing separately (co-curing or light-curing). The micro-tensile bond strength of fifteen resin-dentin stikcs per groups was measured. Failure mode and adhesive layers were observed using stereoscopic and confocal laser scanning microscopy, respectively. The curing mode of the adhesive layer affected the bond strength of the dentin-resin cement (p<0.05). In particular, the light-curing mode exhibited a significantly higher bond strength than the co-curing one (p<0.05). The bond strength between the resin cement and dentin was improved in the 5-s drying groups than in the 10-s drying groups.

Post-polymerization of three-dimensional printing resin using a dental light curing unit.

Background/Purpose: In vat photopolymerization, post-polymerization of the three-dimensional (3D) printing resin is necessary to ensure the optimum physical properties of the printed objects. This study aimed to evaluate the potential use of a handheld polywave light-emitting diode (LED) dental light-curing unit (LCU) for post-polymerizing 3D printed resins by measuring the microhardness and biaxial flexural strength of the post-polymerized resin. Material and methods: 3D printed 1- and 2-mm-thick disks were irradiated with a dental LCU at 3200 mW/cm2. Post-polymerization was repeated either on one side from the top surface: two cycles (T2), four cycles (T4), and eight cycles (T8), or on both sides from the top and bottom surfaces: one cycle (T1B1), two cycles (T2B2), and four cycles (T4B4) for each side. The microhardness and biaxial strength of the disks were compared to those post-polymerized by a conventional desktop polymerizing unit (PC) and those without post-polymerization (NC). Results: Microhardness of the disks varied between the top and bottom surfaces of the 1-mm and 2-mm-thick disks, depending on the post-polymerization methods. T8 and T4B4 produced comparable microhardness on the top surface to PC for both thicknesses. In contrast, PC, T2B2, and T4B4 exhibited the highest microhardness on the bottom surface. Except for NC, the 1-mm-thick disks had a higher biaxial flexural strength than the 2-mm-thick disks. T4B4 resulted in the highest biaxial flexural strength for both thicknesses, which was comparable to that of the desktop polymerizing unit. Conclusion: The microhardness and biaxial flexural strengths of the post-polymerized 3D-printed disks increase with polymerization time. With sufficient polymerization from both sides, the polywave LCU has the potential to be a viable alternative to desktop polymerization units.

Comparison of the stress distribution in base materials and thicknesses in composite resin restorations.

Resin-based composite materials are commonly used for restorations, but their dimensional changes during the polymerization could cause various clinical problems. This study evaluated the influence of a base of different materials and thicknesses on the stress magnitude and distribution in a second maxillary premolar with an MOD resin composite restoration using three-dimensional finite element analysis. A sound tooth without cavity was considered as the control group (ST), and another group was restored with composite resin without applying a base material in a MOD cavity (CR). The other three groups were restored with composite resin along with the following base materials: glass ionomer cement, low-viscosity resin, and tricalcium silicate, respectively (CR-GIC, CR-LR, and CR-TS). These three groups were further divided into two subgroups according to the thickness of the base layer: thin (0.5 mm) and thick (1.0 mm). The stress distribution was compared using the maximum principal stress after polymerization shrinkage and vertical loading with 600 N on the occlusal surface. Group ST showed the lowest stress value, and its stress propagation was confined to outer enamel surfaces only. Group CR demonstrated the highest stress distribution in the tooth-restoration interface with increased failure risk on marginal areas. The thin and thick subgroups of the three groups with a base layer had lower stress levels than Group CR. The base materials reduced the marginal stress caused by polymerization shrinkage of composite resin in MOD cavities. Different base materials and thicknesses did not affect the stress distribution.

Intratubular crystal formation in the exposed dentin from nano-sized calcium silicate for dentin hypersensitivity treatment.

The aim of this study is to evaluate intratubular crystal formation from the experimental material consisting of dicalcium silicate (C2S) and tricalcium silicate (C3S) with nano-scaled particle size. A total of twenty-four specimens were made by isolating 8 mm of the cervical part centered at the cementoenamel junction of extracted premolars. Twelve specimens were not treated and considered as control. The experimental material was applied to the other twelve specimens by brushing for 10,000 strokes. Each group was randomly divided into four subgroups according to the period of immersion in phosphate buffer saline (PBS) for 1, 30, 60, and 90 days each. The specimens were sectioned longitudinally and examined with scanning electron microscopy and energy dispersion X-ray spectroscopy. The intratubular crystal were formed in PBS and densely filled the dentinal tubules over time. The crystal formation occurred at a depth of more than 50 µm from the dentin surface. The Ca/P ratio of formed intratubular crystals was 1.68 after 3 months. The experimental material consisting of C2S and C3S with a nanoscale particle size can form hydroxyapatite-like crystals in dentinal tubules in PBS, and there is a possibility of reducing dentin hypersensitivity by blocking the dentinal fluid flow.

Lipopolysaccharide penetration analysis of two different resin cement systems to dentin and ceramic surface.

Background/purpose: One of the challenges in adhesive ceramic restorations is deterioration of tooth-cement-ceramic interfaces. This study was to quantitatively investigate lipopolysaccharide (LPS) penetration through adhesive ceramic restorations. Materials and methods: Standardized holes were formed on ceramic (IPS Empress CAD, Ivoclar Vivadent) and human dentin discs. Prepared discs were randomly assigned to experimental groups (n = 6/group): SC, self-adhesive resin cement (SmartCem 2, Dentsply Sirona) bonded to ceramic discs; ST, self-adhesive resin cement bonded to dentin discs; VC, etch-and-rinse resin cement (Variolink II, Ivoclar Vivadent AG) bonded to ceramic discs; VT, etch-and-rinse resin cement bonded to dentin discs. The specimens underwent thermocycling (10,000 cycles; 5-55 °C) then LPS penetration test until 5-weeks. A mixed effect analysis using R statistical language was performed for data analysis. Results: Dentin and ceramic bonded with etch-and-rinse resin cements (groups VT and VC) showed significantly less penetration than those with self-adhesive resin cement (groups ST and SC) (P < 0.05). ST showed significantly lower penetration than SC (P < 0.05), that showed similar penetration with positive control (P > 0.05). VC showed minimal penetration during observed time of period (P < 0.05). Scanning electron microscope observations showed different interfacial characteristics among the groups. Conclusion: Within the limitation of this study, etch-and-rinse resin cement showed less LPS penetration than self-adhesive resin cement on both ceramic and dentin surfaces.

Effects of virtual body-representation on motor skill learning.

Motor learning is often hindered or facilitated by visual information from one's body and its movement. However, it is unclear whether visual representation of the body itself facilitates motor learning. Thus, we tested the effects of virtual body-representation on motor learning through a virtual reality rotary pursuit task. In the task, visual feedback on participants' movements was identical, but virtual body-representation differed by dividing the experimental conditions into three conditions: non-avatar, non-hand avatar, and hand-shaped avatar. We measured the differences in the rate of motor learning, body-ownership, and sense of agency in the three conditions. Although there were no differences in body-ownership and sense of agency between the conditions, the hand-shaped avatar condition was significantly superior to the other conditions in the rate of learning. These findings suggest that visually recognizing one's body shape facilitates motor learning.

Effect of cyclic thermal stress on the fatigue life of teeth restored with gold inlay.

This study aimed to evaluate the stress distribution that results from temperature changes in teeth restored with gold inlay and to predict the fatigue life of the teeth. A thermal load regimen for finite element analysis (FEA) was established in an in vivo experiment, in which participants with gold inlays drank hot and cold water. An extracted human maxillary molar was converted into a 3D FEA model. The tooth models with Class I and II preparations were restored with gold inlay in the experimental groups. The stress distribution was analyzed under the thermal loads. Also, lifetime prediction was conducted using Basquin's formulation. The gold inlay groups showed a higher stress distribution than the preparation-only groups regardless of the type of preparation. The Class II gold inlay group showed the shortest fatigue life of 2.48×1011 cycles, whereas the Class I preparation group showed the longest fatigue life of 4.49×1016 cycles.

Influence of Dentin Surface Roughness, Drying Time, and Primer Application on Self-adhesive Composite-Cement Bond Strength.

PURPOSE: To investigate the effect of roughness and drying time of dentin as well as the number of coats of a self-adhesive composite-cement primer on the bond strength of self-adhesive composite cement. MATERIAL AND METHODS: Sixty human teeth were prepared and assigned to 12 groups (n = 5), according to three experimental factors: 1) dentin surface roughness, rough or fine, as achieved by 250- and 600-grit silicon carbide papers, respectively; 2) dentin wetness based on air-drying time (5 or 10 s); and 3) the self-adhesive composite-cement primer applications (no-coat, 1-coat, and 2-coat). Composite resin blocks were made with hybrid composite resin (M1 GraceFil) and cemented with G-CEM ONE (both GC). Cement-dentin sticks (12) were prepared, and the microtensile bond strength (µTBS) test was performed. Failure modes were observed with a stereomicroscope (40X), and bonding interfaces were evaluated with confocal laser scanning microscopy (CLSM). Statistical analysis was performed using three-way ANOVA and Tukey's post-hoc comparisons test (α = 0.05). RESULTS: Dentin roughness (250-grit > 600-grit, p = 0.000), drying time (5-s drying > 10-s drying, p = 0.000), and primer application (no-coat < 1-coat = 2-coat, p = 0.000) had significant effects on bond strength. These factors also showed significant interactions with each other (p = 0.003). The highest µTBS (31.8 ± 3.1 MPa) was observed in the 1-coat/fine roughness/10-s drying group and the lowest µTBS (13.4 ± 2.7 MPa) in the no-coat/coarse roughness/5-s drying group. CLSM showed higher penetration of cement in the primer-coated groups compared to that in the no-coat groups. CONCLUSION: Bond strength between the self-adhesive composite cement and dentin was higher in the fine-roughness dentin group than in the coarse-roughness dentin group, and in the 5-s drying group compared to the 10-s drying group. Applying a primer to dentin improved bond strength of the self-adhesive composite cement.

Did Clinical Reasoning and Knowledge Questions During Team-Based Learning Enhance Dental Students' Performance in Esthetic Dentistry?

The aim of this study was to assess whether clinical reasoning and factual knowledge questions used in team-based learning (TBL) enhanced dental students' performance in esthetic dentistry. Ninety-seven third-year dental students enrolled in esthetic dentistry in a dental school in Korea in 2018 were assigned to 16 teams consisting of five or six students each. A four-step TBL sequence (pre-study, readiness assurance test, appeal/feedback, and final test) was designed to examine how clinical reasoning and knowledge questions affected academically high- and low-achieving students. The analysis was conducted with 87 students' data because ten students failed to answer some questions. The results showed that team performance in TBL was consistently better than individual performance. The TBL sessions enhanced students' critical thinking skills, though it did not affect their knowledge acquisition. The clinical reasoning questions especially benefited the academically low-achieving students. Overall, TBL was an effective method for teaching these dental students using small-group learning in esthetic dentistry. Team-based cooperative learning facilitated a deeper understanding of esthetic dentistry because students were motivated to think critically and solve problems rather than simply memorize factual knowledge.