Abstract
Endocrowns represent a conservative and esthetic restorative alternative to full coverage crowns. They can be constructed using various CAD/CAM materials that can provide a modulus of elasticity similar to that of teeth. The ability to use of such materials in composite blocks that can be easily repaired is also an advantage, provided appropriate bonding performance is ensured. This study, therefore, evaluated the marginal gap and fracture resistance of two CAD/CAM endocrown materials using two bonding protocols. Thirty-two mandibular molars were evaluated in two groups based on the material type: a Cerasmart group (GC America Inc; n = 16) acting as the control and a Ceramill COMP group (Amann Girrbach, Germany; n = 16). These groups were then classified according to the bonding protocol used: a total-etch bonding protocol (n = 8) and a self-etch bonding protocol (n = 8) implemented using RelyX ultimate adhesive resin cement (3M ESPE). The samples were then subjected to aging by simulating a 1-year thermo-mechanical process. The marginal gap results were statistically insignificant across the material and bonding protocol groups before thermo-mechanical aging. Thermo-mechanical aging significantly reduced the marginal gap distance for Ceramill COMP endocrowns cemented using the total-etch protocol (p = 0.002). No statistically significant difference was recorded for the fracture resistance in either the material or bonding protocol groups (p ≥ 0.05). Both materials and bonding protocols can, therefore, be used in the posterior region providing conservative treatment, adequate marginal gap and fracture resistance.
Highlights
Treated teeth have a higher probability of fracture than vital teeth because of their inherently poor structural integrity, with loss of root and coronal dentin resulting from previous caries and/or tooth preparation.[1,2] Ceramics with a high mechanical strength and capable of being acid etched, along with an adhesive capacity for adhesive systems and resin cements, have made it easier to restore endodontically treated teeth, without cores and intraradicular posts.[3]
After exposure to the thermomechanical aging process, the Ceramill COMP endocrowns cemented using the total-etch protocol displayed a significantly smaller marginal gap than the Cerasmart crowns (p 1⁄4 .002). When both types of endocrowns were cemented using the self-etch protocol, there was no significance difference between the marginal gap resulting from either material (p 1⁄4 .06)
The structures of the Cerasmart and Ceramill COMP endocrown materials allow for a modulus of elasticity similar to that of dentin (18 ± 2 GPa),[29] less crack propagation, and higher fracture resistance than conventional ceramics, which are more prone to fracture due to their brittle nature.[30]
Summary
Treated teeth have a higher probability of fracture than vital teeth because of their inherently poor structural integrity, with loss of root and coronal dentin resulting from previous caries and/or tooth preparation.[1,2] Ceramics with a high mechanical strength and capable of being acid etched (such as those reinforced with leucite or lithium disilicate), along with an adhesive capacity for adhesive systems and resin cements, have made it easier to restore endodontically treated teeth, without cores and intraradicular posts.[3]. Ceramics with a high mechanical strength and capable of being acid etched (such as those reinforced with leucite or lithium disilicate), along with an adhesive capacity for adhesive systems and resin cements, have made it easier to restore endodontically treated teeth, without cores and intraradicular posts.[3]. Applying computer-aided design/computer-aided manufacturing (CAD/CAM) technology to suitable ceramic blocks have made it possible to obtain accurate restorations very quickly. Cerasmart (CS) is a composite block consisting of a flexible nano-ceramic matrix with an even distribution of nano-ceramic and a composite resin containing 71% silica and barium glass nano-particles by weight, exhibiting a flexural strength of 238 MPa.[7]. Ceramill COMP (CC) is a composite CAD/CAM block consisting of strontium boroaluminosilicate glass (78% by weight) and ß 2020 The Author(s).
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