OBJECTIVES The purpose of this in vitro study was to compare the effect of simulated endodontic access preparation on the failure loads of lithium disilicate crowns and resin-matrix ceramic (RMC) crowns. MATERIALS AND METHODS Eighty maxillary first premolar crowns were manufactured by using four different CAD/CAM blocks (n = 20): lithium disilicate (LD; IPS e.max CAD), resin nanoceramic (RNC; Lava Ultimate), flexible nanaoceramic (FNC; GC Cerasmart), and polymerinfiltrated ceramic (PIC; VITA Enamic). Half of each group was accessed and repaired to simulate endodontic treatment. After cyclic loading, all specimens were loaded to failure. Data were analyzed with two-way ANOVA followed by Tukey-HSD test ( = .05). RESULTS The load to failure results showed significant differences for material types (P < .001), but not for endodontic access simulation (P = .09). The highest and lowest mean failure loads were obtained for LD (1546 N) and PIC (843 N), respectively. CONCLUSION The endodontic access preparation was not found to affect the fracture strength of LD and RMC crowns. The LD showed higher fracture strength than RMC crowns. Even though significant differences were noted for failure loads regarding different crown materials, all could reasonably withstand masticatory forces. CLINICAL SIGNIFICANCE The endodontic access preparation through a restoration is known to be a common challenge in clinical practice. Maintaining a repaired LD or RMC crown is feasible and replacement may not be necessary.
Purpose An in vitro study to compare the adaptation of denture bases fabricated with 4 different techniques using volumetric 3‐dimentional (3D) analysis. Material and Methods Edentulous maxillary and mandibular casts were scanned, and standardized denture bases were designed using CAD design software. The same standard tessellation language (STL) data were used to produce the denture bases with 4 different fabrication methods: compression molding (CM), injection molding (IM), PMMA milling (PM), and 3D printing (3D) (n = 11/group). Milled wax denture bases were used to fabricate CM and IM groups. Denture bases placed on edentulous casts were scanned using micro‐computed tomography (micro‐CT). Volumetric gap between denture base and cast was calculated from 6 locations for maxilla (anterior ridge crest, posterior ridge crest, labial vestibule, buccal vestibule, palate, and posterior palatal seal) and 3 locations for mandible (intermolar, molar, and retromolar) in addition to overall gap measurements for edentulous arches. The data were analyzed with factorial analysis of variance (ANOVA), 1‐way ANOVA, and post‐hoc Duncan tests. Reproducibility of fabrication methods with regard to each location was assessed using Z test (α = 0.05). Results In the maxilla, the highest and lowest palatal gap measurements were recorded for CM (898.44 ± 87.73 mm3) and PM (357.16 ± 57.68 mm3) (p = 0.05). The highest gap measurements for CM and 3D were at palate and, for IM and PM were at posterior ridge crest. In mandible, the volumetric gap measurements for CM were the highest and for PM were the lowest irrespective of location (p = 0.05). PM group showed the best reproducibility and adaptation with the lowest overall mean gaps for both edentulous arches (p = 0.05). Conclusions Denture bases milled from PMMA blocks showed better adaptation than 3D printed, or wax milled and conventionally fabricated denture bases for both maxillary and mandibular arches. PMMA milling is a reproducible technique that enables the construction of accurate dentures. Clinicians should be cautious about the palatal gap when the compression molding technique is used. Micro‐CT is a valid technique for evaluating the denture base adaptation.
Since the late 1930s, polymethyl methacrylate (PMMA) has been used as a base material for complete dentures. 1,2 Fabrication techniques for complete dentures have included compression molding (pack and press), fluid resin (pour) technique, and injection molding, 2,3 with compression and injection molding being the most commonly used polymerization methods. 4 The pour technique has the advantage of decreased processing time; however, disadvantages including denture tooth movement during polymerization and lack of bonding between denture teeth and the base material have been reported. 3 By combining the advantages of heat-polymerization with the reduced processing time of the pour technique, injection molding may increase the accuracy and stability of the denture bases; however, this technique is more expensive than the other conventional processing techniques. 3 Additional polymer materials instead of PMMA have been used as denture base, and urethane dimethacrylate (UDMA)-based, visible light-polymerized resin (Eclipse; Dentsply Sirona) has been claimed by the manufacturer a
Adaptation is an important factor for the clinical success of restorations. However, no studies are available evaluating the adaptation of primary crowns. The aim of this study was to compare the adaptation of crowns fabricated by CAD/CAM technology versus prefabricated fiberglass primary crowns. Typodont maxillary central, canine, and mandibular molar teeth were prepared to serve as master dies after the size of Figaro crowns was determined ( n = 10 ). Master dies were scanned with an intraoral scanner, and 10 identical CAD/CAM crowns were fabricated from resin-ceramic blocks. Figaro and CAD/CAM crowns were placed on the corresponding master dies and scanned via micro-CT. Three-dimensional volumetric gap measurements were performed to evaluate the overall adaptation. A total of 255 location-based linear measurements were allocated into 4 categories: marginal, cervical-axial, middle-axial, and occlusal. Statistical analyses were performed with factorial ANOVA, repeated measure ANOVA, and LSD tests ( α = 0.05 ). CAD/CAM crowns showed significantly lower overall and location-based gap measurements than Figaro crowns regardless of tooth number ( p < 0.05 ). For all groups, mean marginal discrepancies were lower than occlusal measurements ( p < 0.05 ). Both crown types showed higher marginal gaps for molar teeth than for canine and central incisors with no significant difference between them ( p > 0.05 ). CAD/CAM-fabricated crowns showed better marginal and internal adaptation than prefabricated Figaro crowns.
Introduction: The root canal system must be mechanically instrumented and chemically cleaned using various antimicrobial irrigants in a sequential manner or in combination for the elimination of necrotic pulp tissue and reducing the number of root canal bacteria. For this reason, new methods and materials are continuously being developed to achieve the objectives of endodontic treatment.Materials and Methods: E. faecalis (ATCC 29212) and C. albicans (ATCC 90028) standard strains were used for this study. Colonies of E. faecalis and C. albicans were harvested from the agar plates and suspended in 4 mL of phosphate buffered saline (PBS). Microorganisms were diluted to obtain a suspension of approximately 108 colony-forming units/mL (CFU/mL) in sterile PBS using McFarland standard tubes no. 0.5.Results: After a two-minute contact time, all alexidine (ALX) concentrations used in this study eradicated all E. faecalis strains, while chlorhexidine (CHX) didn’t kill 100% of E. faecalis at 0.25% and lower concentrations even after a five-minute contact time. ALX also eradicated C. albicans at all concentrations even after a one-minute contact time. CHX showed antifungal activity against C. albicans at all concentrations higher than 0.031% after a one-minute contact time.Conclusion: A 0.0156% concentration of ALX can be a good alternative to CHX as an irrigation solution in endodontic treatment when used for one minute against E. faecalis and C. albicans.
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