The purpose of this paper was to compare the bond strengths of the self-adhesive luting cements between ceramics and resin cores and examine their relation to the cement thickness. Three self-adhesive luting cements (Smartcem, Maxcem, and G-CEM) and a resin cement (Panavia F 2.0) for control were used in the paper. The thickness of the cements was controlled in approximately 25, 50, 100, or 200
Esthetic dentistry, including ceramic restorations, is now a great demand from the patients. CAD/CAM technology in dentistry has also become popular. One of the technologies, CEREC system, since its development in 1985, has improved the software and hardware for easier operation and better adaptation. The current CEREC 3 system can fabricate more precise inlays, onlays, crowns, and veneers. In a review on the CEREC restorations, Fasbinder summarized the postoperative sensitivity, restoration fracture, color match, margin adaptation, clinical longevity, and clinical performance [
Vitablocs Mark II (Vita Zahnfabrik, Germany), conventional feldspathic ceramic, is generally used in the CEREC system. The ceramic restorations are usually cemented with resin-based composite luting agent, after surface treatments necessary for the bonding. In the CEREC restoration, the luting material may be charged of two functions as a luting material and a restorative material to adhere between the tooth substrates and CEREC restoration with good mechanical properties and reliable bond capacity [
Recently, newly developed resin luting cements called “self-adhesive luting cements” have been commercialized from several manufacturers. These materials feature that the adhesion is possibly achieved to various surfaces without surface pretreatment such as air-abrasion and/or HF-etching. However, there is little information on the performance of self-adhesive luting cements in the CEREC restorations without surface pretreatment.
Commercial 3 self-adhesive luting cements (Smartcem, Maxcem, and G-CEM) and a control cement (Panavia F 2.0) were used to bond two selected adherends, a ceramic block and resin core in this study (Table
Composition of the commercial resin-based composite luting cement.
Product name (Shade) | Lot no. | Composition | Manufacturer |
---|---|---|---|
Smartcem (Natural) | R0707B1 | Base Paste: HEMA, 4-MET, PEM-F, Initiator, Inhibitor, others Catalyst Paste: 1,3-Butanediol dimethacrylate, Sulfuric acid salt, Tertiary amine, Inhibitor, others | DENTSPLY-Sankin, Tochigi, Japan |
Maxcem (Clear) | 2855305 | Base Paste: UDMA, Camphorquinone, Fluoroaluminosilicate glass, others Catalyst Paste: Bis-GMA, TEGDMA, Glycerophosphatedimethacrylate, Barium aluminoborosilicate glass, others | SDS Kerr, Orange, USA |
G-CEM (A2) | 0702061 | Powder: Fluoroaluminosilicate glass, Initiator, Pigment Liquid: 4-MET, Phosphoric acid ester monomer, UDMA, Dimethacrylate, water, Silicon dioxide, Initiator, Inhibitor | GC, Tokyo, Japan |
Panavia F 2.0 Paste (Brown) | 0293AB, 0155AA | Paste A: MDP, Methacrylate monomer, Filler, Initiator Paste B: Methacrylate monomer, Filler, NaF, Initiator, Pigment | Kuraray Medical, Tokyo, Japan |
HEMA: 2-hydroxyethyl methacrylate; 4-MET: 4-methacryloxyethyl trimellitate; PEM-F: 5-methacryloxyethyloxy cyclophosphazene monofluoride; UDMA: urethane dimethacrylate; Bis-GMA: bisphenol-A-glycidyl dimethacrylate; TEGDMA: triethyleneglycol dimethacrylate; MDP: 10-methacryloyloxydecyl dihydrogen phosphate.
Before cementation with Panavia F 2.0, specimens were etched with K-etchant and silanated with Clearfil SE primer and Porcelain Bond Activator.
Schematic illustration of the procedure for core resin preparation.
The surface of the core resin block was covered with masking tapes (transparent tape with a circular hole, 6 mm in diameters) to standardize cement thickness: 25, 50, 100, and 200
The procedures for each resin-based composite luting cement.
Smartcem | Maxcem | G-CEM | Panavia F 2.0 |
hand-mixed for 20 sec | auto-mixed | hand-mixed for 20 sec | |
cemented and held for 2 min | cemented and held for 90 sec | cemented and held for 90 sec | hand-mixed for 20 sec |
irradiated for 30 sec | irradiated for 20 sec | irradiated for 10 sec | cemented and held for 2 min |
irradiated for 20 sec |
Schematic illustration of the procedure for
After measuring
The results of the
The means and standard deviations (SD) of
Microtensile bond strength (MPa).
Smartcem | Maxcem | G-CEM | Panavia F 2.0 | |
---|---|---|---|---|
25 | 15.38 (4.06)a, b, c, d | 13.75 (5.91)a, b, c, d | 12.53 (8.68)a, b, c | 45.32 (8.72)e |
50 | 17.85 (5.64)b, c, d | 16.38 (6.17)a, b, c, d | 22.60 (6.40)d | 46.35 (7.76)e |
100 | 9.55 (2.38)a, b | 20.16 (1.90)c, d | 16.98 (3.53)a, b, c, d | 43.72 (6.16)e |
200 | 8.70 (2.63)a | 16.41 (3.88)a, b, c, d | 13.72 (2.74)a, b, c, d | 39.39 (9.21)e |
Mean (SD). Same letters denote no significant difference (
Panavia F 2.0 gave the stable and higher
SEM analysis revealed that fracture mode was dominantly cohesive failure in the cement regardless of the type of cement and cement thickness.
In this study, adhesion between ceramics and core resin was examined, simulating the luting between CEREC restorations and resin abutments.
Mazzitelli et al. concluded that the predominance of acid-base reactions or radical polymerization might explain the different responses to substrate wetness and raise concerns regarding their universal application both on vital and pulpless teeth [
Ceramic surface is usually sandblasted or abraded with diamond bar, and/or etched (e.g., phosphoric acid or hydrofluoric acid) prior to silane treatment [
All self-adhesive luting cement used in the study contains phosphoric ester monomer. Besides, 4-MET is added in both Smartcem and G-CEM. These functional acidic monomers possibly contribute to the adhesion. Further, The dominant fracture mode, that is, cohesive failure within the cement regardless of the bland of the cements, indicates that tensile stress concentrated to the cement body rather than the bonding interfaces. This implies that the mechanical property of the resin matrix mainly contributes to the bonding performance of the cements.
Han et al. reported that the pH values of 3 self-adhesive luting cements, Smartcem, Maxcem, and G-CEM, were lower than 4 at 90 seconds after mixing; G-CEM was the lowest (pH 1.8) and Smartcem was the highest (pH 3.6) [
The results of the study also suggested that the thickness of cements affected the
G-CEM contains UDMA as a cross-linking monomer, owing to a lower molecular weight and to the greater flexibility of the urethane linkage [
Usually, there is a relatively large discrepancy between a CEREC restoration and cavity walls due to the accuracy of the optical impression and milling. The space must be filled with luting cement. Therefore, the varied bond strength by the cement thickness could be disadvantageous for the longevity of the restoration.
Further study should be carried out to investigate the between mechanical properties of the self-adhesive luting cements and their bonding capacity, and also longevity of the bonding.
Three self-adhesive luting cements showed lower
The authors appreciates DENTSPLY-Sankin (Tochigi, Japan), Sybron Dental Specialties Japan (Tokyo, Japan), GC (Tokyo, Japan), and Kuraray Medical (Tokyo, Japan) for supplying them with the materials used in this paper.