Seven-year clinical performance of CEREC-2 all-ceramic CAD/CAM restorations placed within deeply destroyed teeth.

OBJECTIVES: Adhesively luted all-ceramic restorations represent a promising way to preserve and stabilize weakened tooth substance, but little information is published about the clinical performance of extensive all-ceramic restorations. MATERIALS AND METHODS: A total of 78 large CEREC 2™ single-tooth all-ceramic restorations had been placed in 35 patients. After 7 years, 59 teeth in 25 patients were reevaluated according to USPHS or modified USPHS criteria regarding aesthetic properties, e.g., "anatomic form," "color match," and "marginal discoloration"; functional properties, e.g., "marginal integrity," wear expressed by the criteria "proximal contact" and "static/dynamic occlusal relationship"; and biological properties, e.g., "tooth vitality" and "secondary caries". Additionally, the "proportion of margin below/above cemento-enamel junction" was included. RESULTS: Two restorations had failed prior to the 7-year recall, one due to a bulk fracture of the restoration and one due to poor marginal integrity (rated "Charlie") after 4 years. Other six restorations were rated as failure at the 7-year evaluation (three restorations revealed secondary caries, one was bulk fracture of the Cerec 2 restoration, and two failures were related to endodontic problems resulting in extraction or amputation of one root, respectively), resulting in a failure rate of 13.1% after 7 years. A total of 96.4% of the restorations revealed sufficient ratings for esthetic properties "anatomic form," "color match," "marginal discoloration," and "marginal integrity". CONCLUSIONS: The survival rate of 86.9% at the 7-year recall demonstrates that adhesively luted all-ceramic CAD/CAM-generated restorations are suitable for restoration of extended coronal defects. CLINICAL RELEVANCE: CAD/CAM-generated all-ceramic restorations facilitate the reconstruction of deeply destroyed teeth irrespectively of the location of the cavity margins.

Marginal integrity: is the clinical performance of bonded restorations predictable in vitro?

PURPOSE: In vitro testing of dental materials is daily routine for the preclinical investigation of restoratives. Although clinical trials remain the ultimate instrument, preclinical screenings are still important. However, it is still not fully understood whether clinical performance is predictable in the lab. The aim of this paper is to combine known facts and recent results to answer the question concerning in vitro predictability of clinical marginal integrity and related outcome. MATERIALS AND METHODS: (a) The literature in the field from 1990-2005 was analyzed regarding marginal integrity in vitro and in vivo, especially in frequently cited papers. (b) Five different adhesives, a 4-step etch-and-rinse adhesive (Syntac), a 3-step etch-and-rinse adhesive (OptiBond FL), a 2-step etch-and-rinse adhesive (Single Bond), a 2-step self-etching adhesive (Clearfil SE Bond), and a 1-step self-etching adhesive (Xeno III) were used for bonding of a resin composite (Tetric Ceram) in Class I cavities (n = 8 in vitro and n = 8 in vivo). In vitro, the restorations were thermomechanically loaded (TML; 100,000 with 50 N and 2500 cycles of 5 degrees C/55 degrees C) according to a previously published protocol. Replicas of restorations were analyzed initially and after TML (in vitro) and two years of clinical service (respectively). RESULTS: (a) Marginal integrity is reliably predictable in laboratory in vitro studies by simulating clinical circumstances. However, marginal analyses of direct restorations in vitro still suffer from not being able to determine a lower boderline, ie, actually worse in vitro results may still result in acceptable restorations in vivo. (b) The in vitro-in vivo comparison revealed significantly better marginal adaptation in (enamel) margins when etch-and-rinse adhesives were used for bonding. After 2 years of clinical service, restorations bonded with self-etching adhesives did not clinically fail but exhibited significantly more marginal gaps. CONCLUSION: Clinical behavior of restoration margins is predictable. However, marginal adaptation is only one among several important aspects in restorative dentistry, ie, clinical outcome is not predictable from marginal integrity alone.

Characterisation of resin-dentine interfaces by compressive cyclic loading.

The aims of this in vitro study were to evaluate the ultra-morphological changes in resin-dentine interfaces after different amounts of thermomechanical load (TML), and to determine the corresponding microtensile bond strengths (microTBS). Enamel/dentine discs with a thickness of 2 mm were cut from 24 human third molars and bonded with four adhesives involving different adhesion approaches: Syntac (Ivoclar Vivadent; used as multi-step etch-and-rinse adhesive), Clearfil SE Bond (Kuraray; two-step self-etch adhesive), Xeno III (Dentsply DeTrey; mixed all-in-one self-etch primer adhesive system), and iBond (Heraeus Kulzer; non-mixed all-in-one self-etch adhesive). The resin-dentine discs were cut into beams (width 2 mm; 2 mm dentine, 2 mm resin composite) and subsequently subjected to cyclic TML using ascending amounts of mechanical/thermal cycles (20 N at 0.5 Hz of mechanical load and 5-55 degrees C of thermal cycles: for 0/0, 100/3, 1,000/25, 10,000/250, 100,000/2,500 cycles). Loaded specimens were either cut perpendicularly in order to measure microTBS (n=20; crosshead speed: 1 mm/min) or were immersed in an aqueous tracer solution consisting of 50 wt% ammoniacal silver nitrate and processed for ultra-morphological nanoleakage examination using transmission electron microscopy (TEM). microTBS were significantly decreased by increasing amounts of TML for all adhesives (p<0.05). Bond strengths after 0 vs. 100,000 thermomechanical cycles were: Syntac: 41.3/30.1 MPa; Clearfil SE Bond 44.8/32.5 MPa; Xeno III 27.5/13.7 MPa; iBond 27.0/6.2 MPa. Relatively early, a certain amount of nanoleakage was observed in all groups by TEM, which was more pronounced for Xeno III and iBond. The incidence of nanoleakage remained stable or was even reduced with increasing load cycles for all adhesives except iBond, where exact failure origins were detected within the adhesive and at the top of the hybrid layer.

Effect of surface treatment on the shear bond strength of three resin cements to a machinable feldspatic ceramic.

The aim of this study was to evaluate the shear bond strength of three resin cements to Vita Mark II ceramics under different pretreatments of the ceramic surface and to examine whether simplified pretreatment procedures would result in satisfying results compared to the state of the art. RelyX Unicem (RXU), Calibra (CAL), and Variolink II (VAR) were used as resin cements and bonded to machine milled feldspatic disks, pretreated in five different ways. (1) no pretreatment of the ceramic surface; (2) surface etched with hydrofluoric acid (HF); (3) ceramic surface silanized; (4) ceramic surface etched (HF) and silanized, (5) ceramic surface etched (HF), silanized, and covered with Heliobond. The shear bond strengths were measured initially, after 5000 and 10,000 thermocycles (TC). After 10,000 TC for CAL only procedure 5 resulted in a reliable adhesion median value of 10.7 MPa. VAR showed median values of 24.6, 17.2, and 18.1 MPa for pretreatments 5, 3, and 4, respectively. RXU performed 25.9, 22.0, and 11.0 MPa for procedures 5, 4, and 3, respectively. For procedure 2, RXU revealed the significantly highest value with 15.4 MPa (U-test, p = 0.05). Only RXU-luted specimens of procedure 1 survived the 10,000 thermocycles. The results revealed that a simplification of the ceramic pretreatment for VAR and RXU might be possible.

A comparative study of two CEREC software systems in evaluating manufacturing time and accuracy of restorations.

This study compared the manufacturing times and the accuracy of proximal and occlusal contacts on restorations produced by two different versions of CEREC 3 software, COS and 3D. Fourteen casts containing pre-existing inlay and onlay preparations of premolars and molars were mounted on articulators. A bite registration was made in maximum intercuspation. Optical impressions of the preparation and the bite registration were made. The Wilcoxon signed rank test was applied for a statistical analysis of time expended in the different design and manufacturing steps of both software versions. The chi-square test was applied for the statistical analysis of proximal and occlusal contacts.

Mechanical properties and three-body wear of veneering composites and their matrices.

Fatigue as one of the major factors affecting three-body wear of resin composites is influenced by mechanical properties of the resin matrix. The aim of this in vitro study was to determine three-body wear (ACTA methodology), fracture strength, and Young's modulus of four veneering composites (Artglass old and new formula, Vita Zeta LC Composite, Targis) and one direct restorative composite (Z 100). Furthermore, three-body wear of the pure matrices of the materials was tested. The wear results were compared to Amalgam as reference material. It should be computed whether there exists a correlation between the wear results of resin composite and matrix alone. Wear of the veneering composites was significantly higher than of Z100 (13 microm) and Amalgam (14 microm; p < 0.01, Mann-Whitney U-test). Mean fracture strengths of indirect composites ranged from 127.5 MPa (Targis) to 71.6 MPa (Vita Zeta LC). The elastic moduli of the composites were between 2.9 and 12.8 GPa. The matrix wear rates did not differ significantly. Three-body wear results of complex resin composites are highly influenced by their filler content, filler particle size distribution, kind of filler particles, shape, and their silanization to the matrix. Due to this fact, three-body wear testing is an essential testing method and cannot be replaced by testing single material components.

Clinical performance of large, all-ceramic CAD/CAM-generated restorations after three years: a pilot study.

BACKGROUND: Adhesively luted all-ceramic restorations preserve and stabilize weakened tooth structure, but there is little published information about the clinical performance of large, all-ceramic restorations. METHODS: In this pilot study, the authors placed 58 large, single-tooth, all-ceramic restorations in 26 patients using a computer-aided design/computer-aided manufacturing, or CAD/CAM, system (CEREC 2, Sirona Dental Systems GmbH, Bensheim, Germany). They documented the maximum height of the restoration and remaining cementoenamel junction, or CEJ. In 21 cases, rubber dam isolation was not possible during adhesive luting. They re-evaluated the restorations after three years according to the U.S. Public Health Service criteria. RESULTS: After three years, the authors rated 56 (97 percent) of the 58 restorations as Bravo or better in regard to marginal integrity, secondary caries (four could not be rated), discoloration and anatomical form. One restoration was rated as Charlie because of poor marginal integrity, and one restoration had to be replaced owing to a bulk fracture. The authors rated the adequacy of proximal contact and occlusal relationships as acceptable-to-good for all restorations. Neither the extent of the remaining enamel at the cavity margin nor application of a rubber dam had any statistically significant influence (chi2 test, P > .05) on the clinical performance of the restorations after three years. CONCLUSIONS: At the three-year recall appointment, the authors found that the adhesively luted all-ceramic restorations had successfully repaired large coronal defects, irrespective of the cavity margin location (that is, coronal or apical to the CEJ). CLINICAL IMPLICATIONS: Tooth-colored, all-ceramic CAD/CAM-generated restorations are an alternative to conventional restorations if large coronal defects need to be treated.