PURPOSE. The objectives of this study were to evaluate the fracture strength and fracture patterns of provisional crowns fabricated from different materials and techniques after receiving stress from a simulated oral condition. MATERIALS AND METHODS. A monomethacrylate-based resin (Unifast Trad) and a bis-acryl-based (Protemp 4) resin were used to fabricate provisional crowns using conventional direct technique. A milled monomethacrylate resin (Brylic Solid) and a 3D-printed bis-acrylate resin (Freeprint Temp) were chosen to fabricate provisional crowns using the CAD/CAM process. All cemented provisional crowns (n=10/group) were subjected to thermal cycling (5,000 cycles at 5°-55ºC) and cyclic occlusal load (100 N at 4 Hz for 100,000 cycles). Maximum force at fracture was tested using a universal testing machine. RESULTS. Maximum force at fracture (mean ± SD, N) of each group was 657.87 ± 82.84 for Unifast Trad, 1125.94 ± 168.07 for Protemp4, 953.60 ± 58.88 for Brylic Solid, and 1004.19 ± 122.18 for Freeprint Temp. One-way ANOVA with Tamhane post hoc test showed that the fracture strength of Unifast Trad was statistically significantly lower than others (P<.01). No statistically significant difference was noted among other groups. For failure pattern analysis, Unifast Trad and Brylic Solid showed less damage than Protemp 4 and Freeprint Temp groups. CONCLUSION. Provisional crowns fabricated using the CAD/CAM process and the conventionally fabricated bis-acryl resins exhibited significant higher fracture strength compared to conventionally fabricated monomethacrylate resins after the aging regimen. Therefore, CAD/CAM milling and 3D printing of provisional restorations may be good alternatives for long term provisionalization.
Polyelectrolyte multilayer (PEM) film can modify the surface properties of materials to improve cellular responses. In this study poly(diallyldimethylammonium chloride) (PDADMAC), poly(sodium 4-styrene sulfonate) (PSS) and poly(4-styrenesulfonic acid-comaleic acid) sodium salt (PSS-co-MA) were assembled into PEM {(PDADMAC/PSS)4/PDADMAC+PSS-co-MA} film on glass surfaces and its ability on affecting osteoblast functions were examined. PSS-co-MA film showed an increase roughness and more wettable surface as compared to glass. When the osteoblast cell line, MC3T3-E1, was seeded on the surfaces, no differences were observed in cell attachment or spreading on either PSS-co-MA film or glass at 4-16 hours. However, increases in alkaline phosphatase activity (day-5 and 7) and the expression of osteocalcin mRNA/protein at day-13 were observed. Cells cultured on PSS-co-MA film developed a faster rate of calcium deposition at day-15 compared to control. In conclusion, PSS-co-MA film enhanced osteoblast differentiation and could be used to promote mineralization and improve osseointegration for dental implants.
To compare and evaluate the effects of different indirect composite onlay and/or core buildup materials on the fracture resistance and fracture mode of restored endodontically treated premolars. Methods: Two conventional handmade indirect composite resins (SR Nexco (NC) and Ceramage (CM)) and two core buildup materials, dual-cure composite resin (MultiCore Flow (MC)), and short fiber-reinforced composite resin (EverX Posterior (EXP)), were selected. Sixty maxillary premolars were randomly divided into six groups (n=10). Group 1 included intact teeth (INT; negative control). Mesio-occluso-distal cavity preparation and endodontic treatment was performed on the remaining premolars. Group 2 was restored with polymer-reinforced zinc oxide eugenol intermediate restorative material (IRM; positive control), whereas the experimental groups (groups 3-6) were restored with core buildup material and indirect composite onlay (MC_NC, MC_CM, EXP_NC, and EXP_CM). The specimens received compressive loading using a universal testing machine, at 45° to the long axis with a crosshead speed of 0.5 mm/min until fracture. Fracture modes were visually analyzed. Fracture resistance was measured and statistically analyzed using two-way and one-way ANOVA (α=0.05). Results: Only the type of indirect composite onlay affected the fracture resistance of the experimental groups (P=0.009). The MC_CM group showed the highest fracture resistance, which was significantly higher than that of the MC_NC group (P=0.031). No statistically significant differences were found between the INT group and other experimental groups(P>0.05). All groups had a greater incidence of restorable than unrestorable failures. Conclusion:The type of indirect composite onlay affected the fracture resistance of restored endodontically treated maxillary premolars.
Effect of different surface treatments of human occlusal sclerotic dentin on micro-tensile bond strength to resin composite core material Kwansirikul A, Sae-Lee D, Angwaravong O, Angwarawong T. Effect of different surface treatments of human occlusal sclerotic dentin on micro-tensile bond strength to resin composite core material. Eur J Oral Sci 2020; 128: 263-272. © 2020 Eur J Oral SciThe objectives of this study were to evaluate the micro-tensile bond strength (lTBS) of composite bonded to human occlusal sclerotic dentin following different surface treatments to determine the sclerotic dentin morphology. Human molars without (normal dentin; group 1) or with occlusal wear (sclerotic dentin; groups 2-5) were divided and subjected to different surface treatments, including the normal protocol for the Contax self-etch bonding system (group 1 and 2); doubled etch-prime time (group 3); pre-conditioning with 37% phosphoric acid before normal protocol (group 4); or pre-conditioning with 37% phosphoric acid before doubling the selfetching time (group 5). All teeth were restored with composite (Luxacore Z dual), sectioned into stick specimens and stored for 24 h in water before specimens were subjected to the lTBS test (n = 50 per group). The lTBS of normal dentin was not statistically significantly different from that of the sclerotic dentin groups, except for the doubled etch-prime time group which showed lower lTBS. Sclerotic dentin pre-treated with phosphoric acid resulted in less sclerotic casts and wider dentinal tubules, while doubled etch-prime time did not alter the morphology, as shown by scanning electron microscopy. In conclusion, the use of 37% phosphoric acid before applying self-etch bonding resulted in more tubule openings and a significantly higher lTBS when compared with the doubled etch-prime time group.
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