Abstract
Aim: To evaluate the fracture resistance of roots restored with CAD/CAM-fabricated posts, receiving or not intracanal laser treatment, compared with glass fiber posts under mechanical cycling. Methods: Twenty-seven endodontically treated, single-rooted teeth were divided into 3 groups: group 1 (control), prefabricated glass fiber posts relined with resin composite; group 2, CAD/CAM-fabricated intraradicular posts using Resin Nano Ceramic (RNC) blocks; and group 3, CAD/CAM-fabricated intraradicular posts using RNC blocks in canals irradiated with a 940-nm diode laser (100 mJ, 300-um optic fiber, coronal-apical and apical-coronal helical movements, speed of 2 mm/second, 4 times each canal). After cementation of the coping, cyclic loading was applied at an angle of 135° to the long axis of the root, with a pulse load of 130 N, frequency of 2.2 Hz, and 150,000 pulses on the crown at a point located 2 mm below the incisal edge on the lingual aspect of the specimen. Every 50,000 cycles, the specimens were evaluated for root fracture occurring below or above the simulated bone crest. Results were analyzed by one-way ANOVA followed by Tukey’s test (p<0.05). Results: Group 1 was the least resistant, while groups 2 and 3 were the most resistant. Group 1 differed significantly from groups 2 and 3 (p<0.01), but there was no difference between groups 2 and 3 (p<0.01). Conclusion: Treatment of the intracanal surface with diode laser had no influence on fracture resistance of roots restored with CAD/CAM-fabricated posts, but a longer cycling time is required to evaluate the real benefits of diode laser irradiation.
Highlights
Treated teeth are at increased risk of fracture due to loss of healthy tooth structure, which may result from inadequate access cavity preparation, carious lesions, and/or extensive restorations[1]
Twenty-seven endodontically treated, single-rooted teeth were divided into 3 groups: group 1, prefabricated glass fiber posts relined with resin composite; group 2, CAD/CAM-fabricated intraradicular posts using Resin Nano Ceramic (RNC) blocks; and group 3, CAD/CAM-fabricated intraradicular posts using RNC blocks in canals irradiated with a 940-nm diode laser (100 mJ, 300-um optic fiber, coronal-apical and apical-coronal helical movements, speed of 2 mm/second, 4 times each canal)
Treatment of the intracanal surface with diode laser had no influence on fracture resistance of roots restored with CAD/CAM-fabricated posts, but a longer cycling time is required to evaluate the real benefits of diode laser irradiation
Summary
Treated teeth are at increased risk of fracture due to loss of healthy tooth structure, which may result from inadequate access cavity preparation, carious lesions, and/or extensive restorations[1]. In order to improve crown retention and stress distribution on the remaining tooth structure, the use of intraradicular posts fabricated from different materials is indicated[2]. Metal alloys are the oldest materials, but their high modulus of elasticity (100-200GPa) is much higher than the dentin (18GPa), what can lead to root fracture. Prefabricated carbon and glass fiber posts have a lower modulus of elasticity-similar to dentin- and are presented in different diameters and tapers. Even when the most adjustable post to the prepared root canal is selected, the film thickness of the luting cement may be higher, which reduces fracture resistance[3]. With the development of the CAD/CAM system, intraradicular posts can replace the intracanal and coronal portions in one piece, reducing the resin-cement interface, shortening clinical time, and enhancing adaptation[4]
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