Mastery Learning in Preclinical Endodontics Using Customized 3D-Printed Tooth Models for Deliberate Practice: An Application of Educational Design Research.

INTRODUCTION: This study, conducted within an educational design research (EDR) framework, assessed the use of customized 3D-printed tooth models at various difficulty levels to enhance mastery learning and deliberate practice in preclinical endodontic training. METHODS: The EDR was conducted in a preclinical endodontic training involving 42 third-year students. The study focused on developing and evaluating 3D-printed tooth models customized into 3 difficulty levels to facilitate mastery learning for the access opening procedure on upper anterior teeth. To promote deliberate practice, we ensured ample availability of these models. The evaluation combined quantitative analysis, using Friedman and Wilcoxon Signed-Rank tests to assess practice volume and performance, with qualitative feedback from interviews and focus groups, analyzed via content analysis. RESULTS: There was a significant reduction in practice time across the different model levels, with students using an average of 1.5-1.8 models per level. No significant differences in performance scores were observed across levels and natural tooth (P = .333). Feedback highlighted the models' educational value in enhancing dental training, indicating their effectiveness in improving learning experiences and skill development in endodontic education. CONCLUSIONS: The innovative design of a 3D-printed tooth model system, which features 3 levels of difficulty and was developed within an EDR framework, allowed for tailored learning progressions and ample practice opportunities. This significantly enhanced the endodontic training experience and skill development by providing varied and realistic challenges.

Effect of glass-ceramic coating versus alumina air-abrasion on the bond strength and residual stress of zirconia.

OBJECTIVES: To assess the effect of glass-ceramic coated zirconia versus alumina air-abraded zirconia on the shear bond strength (SBS) of resin cement and investigate the residual stresses present on both mechanically pre-treated surfaces. MATERIALS AND METHODS: A total of 180 zirconia disks, with diameters of 10 mm and 5 mm, were divided into two groups: DCMhotbond glass-ceramic coated, followed by hydrofluoric acid etching (DCM), and alumina air-abraded (AB). All mechanically pre-treated disks were conditioned with G-Multi Primer and bonded using G-Cem Linkforce Cement. Ninety specimens were immersed in distilled water for 24 h and subsequently allocated into three groups based on aging conditions (n = 15/subgroups): immediate testing, 5000 thermal cycles, and 10,000 thermal cycles. Then, the shear bond strength was assessed, and the obtained data were subjected to analysis using a two-way ANOVA, followed by a one-way ANOVA and Tukey's HSD post hoc test (α = 0.05). The residual stresses present on both mechanically pre-treated surfaces were examined using X-ray diffraction analysis. RESULTS: The mean SBS values of the DCM and AB groups showed no significant difference under each aging condition. The SBS of DCM groups was not affected by thermal cycles, whereas the SBS of AB groups exhibited a significant decrease following thermal cycles. Glass-ceramic coated surfaces exhibited higher compressive stresses than alumina air-abrasion. CONCLUSIONS: The DCMhotbond glass-ceramic coated zirconia showed comparable bond strength to the alumina air-abrasion technique. CLINICAL RELEVANCE: The DCMhotbond glass-ceramic coating technique is a promising alternative for zirconia surface pre-treatment. However, further investigations are needed before suggesting its clinical use.

Physical Characteristics and Biocompatibility of 3D-Printed Polylactic-Co-Glycolic Acid Membranes Used for Guided Bone Regeneration.

Bioresorbable polymeric membranes for guided bone regeneration (GBR) were fabricated using the three-dimensional printing technique. Membranes made of polylactic-co-glycolic acid (PLGA), which consist of lactic acid (LA) and glycolic acid in ratios of 10:90 (group A) and 70:30 (group B), were compared. Their physical characteristics including architecture, surface wettability, mechanical properties, and degradability were compared in vitro, and their biocompatibilities were compared in vitro and in vivo. The results demonstrated that the membranes of group B had mechanical strength and could support the proliferation of fibroblasts and osteoblasts significantly better than those of group A (p < 0.05). The degradation rate in Group B was significantly lower than that in Group A, but they significantly produced less acidic environment (p < 0.05). In vivo, the membranes of group B were compared with the commercially available collagen membranes (group C). The amount of newly formed bone of rat's calvarial defects covered with the membranes of group C was stable after week 2, whereas that of group B increased over time. At week 8, the new bone volumes in group B were greater than those in group C (p > 0.05). In conclusion, the physical and biological properties of the PLGA membrane (LA:GA, 70:30) were suitable for GBR.

Influence of a Novel Lithium Disilicate Coating on Composite-Zirconia Bonding and Bond Characterization.

PURPOSE: To investigate microtensile bond strength and characterization with the novel lithium disilicate coating technique compared to conventional air abrasion. MATERIALS AND METHODS: Eight zirconia blocks were fabricated and assigned to two groups (n = 4 each): (1) Lithium disilicate coating followed by hydrofluoric acid etching and Monobond N Primer (LiDi group); and (2) alumina air abrasion (MUL group). For each group, two identically pretreated zirconia blocks were bonded together with Multilink Speed Cement and cut into 30 stick-shaped specimens (1 × 1 × 9 mm3). The 120 specimens were stored in water for 24 hours and assigned to one of three groups (n = 20/group): (1) short-term storage for 24 hours; (2) thermocycling for 5,000 cycles; and (3) thermocycling for 10,000 cycles. A microtensile bond strength test was performed and evaluated. The bond strength results were analyzed using two-way ANOVA followed by one-way ANOVA and Tukey HSD (α = .05). Energy-dispersive x-ray spectroscopy (EDS), Fourier-transform infrared (FTIR), x-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), and scanning electron microscopy (SEM) were used for chemical, crystalline phase, and failure mode analyses. RESULTS: The MUL groups recorded higher bond strength than the LiDi groups. Thermocycling significantly decreased the bond strength in both groups. Chemical analyses suggested that the lithium disilicate layer underwent hydrolysis, which compromised long-term bond strength. CONCLUSION: The bond between composite cement and alumina-abraded zirconia performed better than that with the lithium disilicate coating technique. Int J Prosthodont 2023;36:172-180. doi: 10.11607/ijp.6744.

Influence of ceramic-coating techniques on composite-zirconia bonding: Strain energy release rate evaluation.

OBJECTIVES: To compare ceramic-coating techniques versus conventional techniques on bonding between composite cements and zirconia by means of strain energy release rate (Gc, J/m2). METHODS: Two sizes of zirconia bars (30 mm × 8 mm × 1.5 mm and 14.8 mm × 8 mm × 1.5 mm) were fabricated. Two smaller bars were treated and cemented to the surface of a large bar using one of the following methods: (i) AlN-nano-structured alumina coating with RelyX Unicem 2; (ii) HOT-DCM hotbond coating with G-Multi Primer and G-Cem Linkforce; (iii) LiDi-lithium disilicate glass-ceramic coating with Monobond N Primer and Multilink Speed; (iv) COJ-tribochemical silica treatment with RelyX Ceramic Primer and RelyX Unicem 2; (v) GCEM-alumina grit blasting with G-Multi Primer and G-Cem LinkForce; (vi) MUL-alumina grit blasting with Multilink Speed; and (vii) PAN-alumina grit blasting with Clearfil Ceramic Primer and Panavia F2.0. A total of 30 bilayered specimens in each group were stored in distilled water at 37 °C for 24 h and assigned to three subgroups (n = 10/test group): short-term test, thermocycling for 5000 cycles, and thermocycling for 10,000 cycles and tested in 4-point bending configuration. Results were analysed using two-way ANOVA, followed by one-way ANOVA and Games-Howell (α = 0.05). Failure mode and surfaces were analysed using optical microscopy and SEM. RESULTS: The bonding (J/m2) of COJ and MUL groups was significantly higher than the other groups among all aging conditions. Thermocycling affected the bonding in COJ and GCEM groups. SIGNIFICANCE: Surface pre-treatments and artificial aging affect the bonding between composite cements and zirconia.

Shear Bond Strength of Composite Cement to Lithium-Disilicate Glass-coated Zirconia Versus Alumina Air-abraded Zirconia.

PURPOSE: To compare the shear bond strength of composite cement to lithium-disilicate glass-ceramic coated zirconia vs to alumina air-abraded zirconia and to analyze the residual stresses on both of lithium-disilicate glass-ceramic coated zirconia vs alumina air-abraded zirconia specimens. MATERIALS AND METHODS: One hundred eighty zirconia disks (diameters 10 mm and 5 mm, 4.5 mm thick) were divided into two groups: lithium-disilicate glass-ceramic coating followed by hydrofluoric acid etching and Monobond N Primer (LiDi) or alumina air-abrasion (AA). For each group, two different sizes of identically pre-treated zirconia specimens were bonded with Multilink Speed Cement. A total of 90 specimens were stored in distilled water at 37°C for 24 h and then assigned to three subgroups (n = 15/test group): 1. short-term test; 2. thermocycling for 5000 cycles; 3. thermocycling for 10,000 cycles. Bond strength was tested in shear mode and results were analyzed using two-way ANOVA, followed by one-way ANOVA and Tukey's HSD (α = 0.05). Failure mode and surfaces were analyzed with optical and scanning electron microscopy. X-ray diffraction was used to analyze t-m phase transformation and residual stresses on mechanically pre-treated LiDi and AA surfaces. RESULTS: The LiDi groups recorded higher mean bond strength than AA groups after thermocycling (p < 0.05). Thermocycling did not affect the bond strength of either LiDi or AA groups (p > 0.05). Most of specimens in AA groups exhibited mixed failure. Alumina air-abraded surfaces exhibited higher residual compressive stresses than did surfaces with a lithium-disilicate glass-ceramic coating. CONCLUSION: Following thermocycling, composite-zirconia bond strength of specimens with a lithium-disilicate glass-ceramic coating was greater than that of alumina air-abraded specimens.

Shear bond strength of composite cement to alumina-coated versus tribochemical silica-treated zirconia.

OBJECTIVES: To compare the shear bond strength of composite-resin cement to nano-structured alumina-coated versus to tribochemical silica-treated zirconia, and to analyze the residual stresses on both of nano-structured alumina-coated versus tribochemical silica-treated zirconia specimens. METHODS: One hundred and eighty zirconia disks (10 mm and 5 mm in diameter, 5 mm thickness) were divided into two groups: nano-structured alumina coating (H.C.Starck, AlN) and tribochemical silica treatment (CoJet) followed by RelyX Ceramic Primer (COJ). For each group, two different sizes of identically pre-treated zirconia specimens were bonded together with RelyX Unicem 2 Cement. A total of 90 specimens were stored in distilled water at 37 °C for 24 h and then further assigned to three groups (n = 15/test group): short-term test, thermocycling for 5000 cycles, and thermocycling for 10,000 cycles. Bond strength was tested in shear mode and results were analyzed using two-way ANOVA, followed by one-way ANOVA and Tukey's HSD (α = 0.05). Failure mode and surfaces were analyzed with optical microscopy and SEM. X-ray diffraction (XRD) were used for t-m phase transformation and residual stress analysis on mechanically pre-treated AlN and COJ surfaces. RESULTS: The mean bond strengths of AlN and COJ groups were not statistically different after thermocycling (p > 0.05). However, when compare to 24 h only the bond strength of the COJ groups decreased significantly after thermocycling (p < 0.05). Most of specimens in both AlN and COJ groups exhibited adhesive failure. Compressive stresses were detected on both mechanically pre-treated AlN and COJ surfaces, with significant differences in stress values. CONCLUSION: Following thermocycling, composite-zirconia bond strength of nano-structured alumina coating was comparable to that of tribochemical silica treatment.

Influence of glass-ceramic coating on composite zirconia bonding and its characterization.

OBJECTIVE: The aims of this study were to compare micro-tensile bond strength and characterize the bond of ceramic-coated versus air-abraded and chemically treated zirconia specimens. METHODS: Eight zirconia blocks were fabricated and assigned to two groups as follows: AA-alumina air-abrasion; and CC-DCMhotbond coating followed by alumina air-abrasion and hydrofluoric acid etching. For each group, two identically pre-treated zirconia blocks were applied G-Multi Primer, cemented together with G-Cem Linkforce cement and cut into 30 stick-shaped specimens (1×1×9mm3). A total of 120 specimens were stored in distilled water for 24h and then assigned to three groups: (i) short-term test, (ii) thermocycling for 5000, and (iii) thermocycling for 10,000 cycles. The specimens were tested in tensile mode. The bond strength results were analyzed using two-way ANOVA, followed by one-way ANOVA and Dunnett T3 (α=0.05). Failure mode and surfaces were analyzed with optical microscopy and SEM. The EDS, FTIR, XRD, and FIB-SEM were used for chemical, crystalline phase analyses. RESULTS: The AA groups recorded higher mean bond strength than the CC groups in all aging conditions. Thermocycling did not affect the bond strength of the AA groups, whereas the bond strength of the CC groups decreased significantly after aging. The MDP monomer and silane in G-Multi Primer chemically reacted with mechanically pre-treated AA and CC surfaces via the absorption of P-O and Si-O groups. SIGNIFICANCE: The bond strength of a conventional protocol involving alumina air-abrasion was greater than ceramic coating technique.

Influence of Nano-structured Alumina Coating on Composite-Zirconia Bonding and its Characterization.

PURPOSE: To compare microtensile bond strength and characterize the bond of nano-structured alumina-coated vs tribochemically silica-treated zirconia specimens. MATERIALS AND METHODS: Eight zirconia blocks were assigned to two groups: nano-structured alumina coating (AlN) and tribochemical silica treatment (CoJet) followed by RelyX Ceramic Primer (COJ). For each group, two identically pre-treated zirconia blocks were bonded with RelyX Unicem 2 Cement and cut into 30 stick-shaped specimens (1 x 1 x 9 mm3). A total of 120 specimens were stored in distilled water at 37°C for 24 h and then assigned to three groups (n = 20/test group): short-term test, thermocycling 5000 cycles, and thermocycling 10,000 cycles. The specimens were tested in tensile mode. The bond strength results were analyzed using two-way ANOVA, followed by one-way ANOVA and Tukey's HSD (α = 0.05). Failure mode and surfaces were analyzed with optical microscopy and SEM. FTIR and EDS were used for chemical analyses on primer-, mechanically and/or chemically pre-treated surfaces. RESULTS: The mean bond strengths of AlN and COJ groups were not statistically significantly different in all aging conditions (p > 0.05). Thermocycling significantly decreased the bond strength of both groups (p < 0.01). The AlN groups exhibited predominantly either adhesive or mixed failure, whereas the specimens in the COJ groups mainly presented either mixed or cohesive failure in composite cement. Silane chemically reacted with mechanically pre-treated COJ surface via the absorption of Si-O group. CONCLUSION: The composite-zirconia bond strength after application of a nano-structured alumina coating was comparable to that after tribochemical silica treatment.