5.5-year-survival of CAD/CAM resin-based composite restorations in severe tooth wear patients.

OBJECTIVES: Aim of this prospective study was to assess full mouth rehabilitation of severe tooth wear patients using minimally invasive CAD/CAM resin-based composite (RBC) restorations and direct veneers by evaluating restoration survival up to 5.5-years. METHODS: Twenty-two patients with generalized severe tooth wear with functional and/or esthetic problems were included. Following minimally invasive preparation, CAD/CAM RBC restorations (LAVA Ultimate,3M) were adhesively luted, direct RBC veneers (Filtek Supreme XTE, 3M) were applied in the aesthetic region. Patients were recalled after 1m,1y,3y,5y and seen in between recalls by their general dentists or at the clinical study center if complaints occurred. Failures were categorized as F1 (severe deficiencies requiring replacement/extraction), F2 (localized deficiencies requiring re-cementation/repair) and F3 (small chippings requiring refurbishment/monitoring). Survival of indirect restorations was evaluated using lifetables and Kaplan-Meier-graphs, distinguishing between failure categories and tooth type (front teeth=FT, premolars=PM, molars=M). F1 + F2 and F1 + F2 + F3 failures were analyzed using Cox regression on the variables tooth type/ location, age, gender and VDO increase (p < 0.05). RESULTS: 568 indirect restorations and 200 direct veneers in 21 patients evaluated for up to 5.5-years. For indirect restorations, 96 failures were recorded (F1:6;F2:41;F3:49) and annual failure rates were 0.29%(FT), 1.56%(PM), 2.93%(M) for F1 +F2 and 0.53%(FT), 2.42%(PM), 6.11%(M) for F1 + F2 + F3. Reasons for failure were chipping fracture (48), adhesive fracture (32), complete debonding (7), caries (4), endodontic treatment (1) and reasons unknown (documentation general dentists, 4). Molar tooth type had a statistically significantly increased probability of failure compared with front teeth and premolars for F1 + F2 + F3 (p < 0.006). Direct veneer restorations showed 18 failures (F1:2;F2:9;F3:7). SIGNIFICANCE: Minimally invasive CAD/CAM RBC restorations combined with direct RBC veneers showed an acceptable clinical mid-term survival for restorative rehabilitation of severely worn dentitions.

A Prospective Comparative Analysis Regarding the Assessment of Oral Mucosal Disease Using a Validated Questionnaire to Improve the Teaching of Dental Students.

Structured examination and treatment are essential in medicine. For dental students, a structured approach to the assessment of oral mucosal lesions is missing thus far. To validate an approach, a structured questionnaire was compared with the habitually used free description of oral lesions (white lesions, ulcers, hyperplasia). Thirty-three dental students were divided into two groups (Group 1 (n = 17) used the free description; Group 2 (n = 16) used a guided questionnaire) to characterize mucosal lesions in patients and make a tentative diagnosis. Although no difference was found between the groups regarding the suspected diagnosis or the histopathological findings, there was a significant advantage of the structured questionnaire in all aspects of the description compared to the free description (p = 0.000018). Thus, a structured description is an important aspect in the evaluation of oral mucosal changes, and a guided questionnaire should be implemented in the study of dentistry.

Evaluation of wear behavior of dental restorative materials against zirconia in vitro.

OBJECTIVES: To evaluate two-body wear (2BW) and three-body wear (3BW) of different CAD/CAM and direct restorative materials against zirconia using a dual-axis chewing simulator and an ACTA wear machine. METHODS: 3 CAD-CAM resin-based composite or polymer infiltrated ceramic network blocs, 1 lithium disilicate CAD-CAM ceramic (LS2), 3 direct resin composites, amalgam and bovine enamel were tested. For 2BW, 8 flat specimens per material were produced, grinded, polished, stored wet (37 °C, 28d) and tested (49 N, 37 °C, 1,200,000 cycles) against zirconia. For 3BW, specimens (n = 10) were stored accordingly, and tested against a zirconia antagonist wheel (3Y-TZP, d = 20 mm, h = 6 mm; 200,000 cycles, F = 15 N, f = 1 Hz, 15% slip) in millet seed suspension. Wear resistance was analysed in a 3D optical non-contact profilometer, measuring vertical wear depth and volume loss for 2BW and mean wear depth and roughness (Ra) for 3BW. Vickers hardness (15 s, HV2) was measured. Statistical analysis was performed using non-parametric tests (Mann-Whitney-U test, p < 0.05). RESULTS: 2BW and 3BW have a different impact on material surfaces. Similar wear resistance was observed for direct and indirect resin based materials with analogous filler configurations in both methods. Bovine enamel exhibited the best wear resistance in 2BW, but the least wear resistance in 3BW against zirconia. Regarding 2BW, a direct/indirect composite material pair of the same manufacturer showed the significantly highest mean volume losses (2.72/2.85 mm³), followed by LS2 (1.41 mm³). LS2 presented the best wear resistance in 3BW (mean wear depth 2.85 µm), combined with the highest mean Vickers hardness (598 MPa). No linear correlation was found between Vickers hardness and both wear testing procedures. The zirconia antagonists showed no recordable signs of wear. SIGNIFICANCE: Dental restorative materials behave differently in 2BW and 3BW laboratory testing. Vickers hardness testing alone cannot hold for a correlation with wear behavior of materials. Micromorphological investigation of material composition can reveal insights in wear mechanisms related to variations in filler technologies.

Fourteen years clinical evaluation of leucite-reinforced ceramic inlays luted using two different adhesion strategies.

OBJECTIVES: Aim of the present prospective study was to clinically evaluate the long-term performance of two different luting-materials for leucite-reinforced glass-ceramic inlays/onlays after 14 years. METHODS: A total of 83 IPS-Empress-inlays/onlays were placed in 30 patients. Restorations were luted according to two different strategies: 43 restorations were fixed with a self-adhesive resin-cement (RelyXUnicem, RX), 40 restorations were inserted with VariolinkII-low (SV) after pretreatment with an etch-and-rinse multi-step adhesive. Recalls were performed after two weeks (n=83), two years (n= 82), four years (n=74) and 14 years (n=54). Two independent calibrated examiners evaluated all restorations using modified USPHS-criteria. Statistical analysis was performed using pairwise Mann-Whitney-U-test and Friedman-test (p < 0.05). RESULTS: After 14 years, 54 restorations in 22 patients were evaluated (eight patients equalling 29 inlays not available). Ten restorations had to be replaced (failure rate 12%); four (SV-group) showed bulk fractures and two (RX-group) exhibited marginal fractures at the 14-year recall. Overall, the SV-group revealed significantly better results regarding discoloration of the luting gap (p<0.05) compared to the RX-group. No statistically significant differences were computed between SV and RX for the remaining criteria at the respective recalls (p>0.05). However, statistically significant deteriorations were detected for both luting procedures over 14 years regarding "colour match", "marginal integrity" and "tooth integrity" (p<0.05). CONCLUSIONS: The self-adhesive resin-cement RelyXUnicem showed similar clinical performance to a conventional multi-step luting-procedure after 14 years for most of the test parameters with a slightly inferior performance of RelyXUnicem regarding discoloration of the luting gap. CLINICAL SIGNIFICANCE: The current study presents unique in-vivo long-term data on two adhesion-strategies for indirect ceramic single-tooth restorations. Differences in performance of the two luting methods after being challenged for 14 years in the oral environment are highlighted. However, the overarching survival rate justifies the recommendation of both methods for clinical routine.

Viscosity and stickiness of dental resin composites at elevated temperatures.

OBJECTIVE: To investigate the influence of pre-heating different classes of dental resin composites on viscosity and stickiness at five different temperatures. METHODS: Six flowable, five conventional packable, and one thermo-viscous bulk-fill resin composites were heated up to 54°C in a plate-plate rheometer to determine their complex viscosity. Normal force measurements were carried out for the six packable materials to determine the unplugging force and unplugging work (stickiness) over the same temperature range. Data were analyzed using Kolmogorov-Smirnoff test, one-way ANOVA and Tukey Post Hoc test with α=0.05 as level of significance. RESULTS: At 23°C packable composites showed viscosity between 6.75 and 19.14kPas, while flowable composites presented significantly lower viscosities between 1.31 and 2.20kPas. Pre-heating led to a drop of 30-82% in the viscosity of packable materials. The thermo-viscous material dropped to the level of flowables at 45 and 54°C thus behaving as a packable composite at room temperature with flowable-like viscosity at higher temperatures. No statistically significant differences for viscosity were observed among flowable composites at any temperature. The unplugging force decreased for packable composites, while their unplugging work generally increased at elevated temperature. At 23°C unplugging force was measured between 7.50 and 19.18N, while pre-heating up to 54°C led to values between 2.9 and 6.2N. Regarding unplugging work at 23°C the calculated values were between 3.0 and 8.9×10-3J and at 54°C between 8.8 and 13.0×10-3J. SIGNIFICANCE: Pre-heating significantly reduced viscosity of highly viscous resin composites, while no influence was shown for flowable composites. In general stickiness, measured as unplugging work, increased at elevated temperatures. The thermo-viscous material showed low viscosity comparable to flowable composites at 45 and 54°C, yet its stickiness did not increase significantly compared to the values at 23°C.

Fracture toughness of dental incremental composite-composite interfaces at elevated temperatures.

The aim of the present laboratory study was to mechanically characterize the interface between two dental resin-based composite (RBC) increments, and to investigate if elevated temperatures have an influence on the quality of the interface mimicking clinical filling procedure. Four RBCs (CLEARFIL MAJESTY™ Posterior, Kuraray (CMP)/Filtek™ Supreme XTE, 3M (FSX)/Grandio®SO, VOCO (GSO)/VisCalor® bulk, VOCO (VCB)) were tested with a fracture toughness test using Chevron notched beams (KI,CNB) at 23, 37 and 54 °C. KI,CNB specimens (3 × 4x25mm) with a V-shaped notch at the incremental interface were loaded until failure in a 4-point bending set-up. Failure modes were characterized using light microscopy, microstructural interface was analyzed using SEM. Statistical analysis was performed using Kolmogorov-Smirnoff test, two-way ANOVA and Tukey Post-Hoc test (p = 0.05). Mean KI,CNB ranged between 0.73 ±0.14 MPam0.5 (VCB, 23 °C) and 1.11 ± 0.11 MPam0.5 (FSX, 23 °C). The tested conventional highly filled RBCs presented fracture toughness at the incremental interface comparable to the cohesive strength of the bulk materials. VCB showed reduced interfacial fracture toughness at 23 and 37 °C, but performed well at elevated temperature of 54 °C.

New Approaches in Bonding to Glass-Ceramic: Self-Etch Glass-Ceramic Primer and Universal Adhesives.

PURPOSE: To investigate the tensile bond strength of silane-containing universal adhesives and self-etch glass-ceramic primer to lithium disilicate glass ceramics (LS2). MATERIALS AND METHODS: 960 rectangular LS2 bars (7 mm x 3 mm x 9 mm, IPS e.max CAD, Ivoclar Vivadent) were manufactured and divided into 4 groups (n = 240). Group 1 was etched with ~5% hydrofluoric acid (HF) for 20 s (VITA Ceramics Etch, Vita Zahnfabrik), group 2 was etched with ~5% HF for 20 s and silanized (ESPE Sil, 3M Oral Care), group 3 was pre-treated with a self-etching glass-ceramic primer (Monobond Etch & Prime, Ivoclar Vivadent, and group 4 received no pre-treatment. Three universal adhesives (iBOND Universal, Heraeus Kulzer; Scotchbond Universal Adhesive, 3M Oral Care; Futurabond U, Voco) were applied to the differently pre-treated surfaces, with Heliobond (Ivoclar Vivadent) serving as control. The bars from each group were paired and luted perpendicularly, forming a square bonded area of 9 mm2, using Variolink II (Ivoclar Vivadent) with a constant pressure of 10 N, followed by light curing (40 s at 800 mW/cm2, Elipar Trilight, 3M Oral Care). The resulting specimens were stored for 24 h at 37°C in distilled water. Half of the specimens of each group were submitted to tensile bond strength testing, the other half were thermocycled ([TC] 5000 cycles, 5°C/55°C, 30-s dwell time) before testing. Data were analyzed using three-way ANOVA (α = 0.05). RESULTS: Group 2 (HF etched and silanized) and group 3 (self-etching glass-ceramic primer) reached significantly higher mean bond strengths than did groups 1 (only HF etched) and 4 (no pre-treatment). CONCLUSION: Additional silanization of HF-etched LS2 statistically signficantly improved the tensile bond strength of the silane-containing universal adhesive (Scotchbond Universal). The self-etching glass-ceramic primer Monobond Etch & Prime achieved mean bond strengths that did not differ significantly from HF-etched and silanized specimens.

Bulk-fill resin composites: polymerization properties and extended light curing.

OBJECTIVES: The aim was to evaluate the polymerization properties of bulk-fill resin composites using two different light-curing protocols, in terms of degree of conversion (%DC), Vickers hardness (HV), polymerization volume shrinkage (PVS) and polymerization shrinkage stress (PSS) and compare them to conventional condensable and flowable resin composites. MATERIALS AND METHODS: Filtek BulkFill (FBF, 3MESPE, Germany), SDR (Dentsply, Germany), TetricEvoCeram BulkFill (TBF, Ivoclar-Vivadent, Liechtenstein), Venus BulkFill (VBF, Heraeus, Germany), X-traBase (XTB, Voco, Germany), FiltekZ250 (3MESPE) and Filtek Supreme XTE Flowable (FSF, 3MESPE) were investigated. Light-curing was performed for 30 s or according to manufacturers' instructions (1200 mW/cm2, Bluephase20i, Ivoclar-Vivadent). For %DC and HV, discs (n=5) of 2 or 4 mm in thickness were prepared and stored for 24h in distilled water at 37°C. %DC was determined by FTIR-ATR-spectroscopy. %DC and HV were measured at the top and bottom of the specimens. PVS was measured using Archimedes method (n=6). PSS measurements (n=10) were carried out using 5 mm diameter PMMA rods as bonding substrates with a specimen height of 1 mm in a universal testing machine. Data were analyzed using one- and two-way ANOVA (α=0.05). RESULTS: Except Z250 in the manufacturers' light-curing mode, all materials showed no significant inferior %DC at 4 mm thickness. When light cured for 30 s Z250 had no significant differences in %DC at 2 or 4 mm when compared to top. FBF, TBF, FSF and Z250 displayed significant reduced HV at 4 mm in both curing modes. Z250 and TBF showed the lowest PVS and FSF the highest PSS in both curing modes. SIGNIFICANCE: All investigated bulk-fill composites obtained sufficient polymerization properties at 4 mm depth. Enhanced curing time improved the investigated polymerization properties of bulk-fills and Z250.