Fracture force of CAD/CAM resin composite crowns after in vitro aging
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The aim of this in vitro study was to investigate the influence of material, preparation, and pre-treatment on the aging and fracture force of CAD/CAM resin composite molar crowns.
Materials and methods
CAD/CAM molar crowns (n = 80) were milled from four resin composites (Block HC, Shofu; Lava Ultimate, 3 M; Grandio Blocs, Voco; and Tetric CAD, Ivoclar Vivadent, with/without sandblasting). Extracted human teeth were prepared with optimal preparation (height 6–8 mm, angle 6–8°) or worst-case preparation (height 3.5–4 mm, angle 10–15°). Both groups were prepared with a 1-mm deep cervical circular shoulder. Crowns were adhesively bonded after corresponding tooth treatment required for the individual adhesive systems (Table 1). Specimens were aged for 90 days in water storage (37 °C) and subsequently subjected to thermal cycling and mechanical loading (TCML 3000 × 5 °C/3000 × 55 °C, 2 min each cycle, H20 distilled; 1.2 × 106 cycles à 50 N, 1.6 Hz). De-bonding and fracture force was determined. Statistics: one-way-ANOVA; post hoc Bonferroni, α = 0.05.
Four crowns of Lava Ultimate with worst-case preparation de-bonded during TCML. Individual crowns without sandblasting treatment (3x Tetric CAD with optimal preparation; 1x Tetric CAD with worst-case preparation) de-bonded during water storage. One crown of Grandio Blocs with optimal preparation showed a small chipping during TCML. All other crowns survived TCML and water storage without failure. Fracture forces differed between 1272 ± 211 N (Lava Ultimate) and 3061 ± 521 N (Tetric CAD). All Grandio Blocs and Tetric CAD crowns revealed significantly (p ≤ 0.023) higher fracture forces than Block HC or Lava Ultimate crowns. No significantly different (p > 0.05) fracture forces were found between optimal or worst-case preparation/fit groups.
De-bonding during water storage and TCML was dependent on material and crown pre-treatment. Therefore, surface roughening seems strongly required. Fracture forces were not influenced by preparation but by the type of material.
Clinical success and de-bonding of CAD/CAM resin composite crowns is strongly influenced by the type of material and its pre-treatment.
KeywordsCAD/CAM Resin composite Resin-based material Preparation Fit CAD/CAM bloc Dental material TCML Aging Storage
The authors thank Ivoclar Vivadent for supporting this investigation.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors./All applicable international, national, and/or institutional guidelines for the care and use of animals were followed./All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
For this type of study, formal consent is not required.
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