V.K. KALAVACHARLA’s research while affiliated with University of Alabama at Birmingham and other places

Objectives: Lithium disilicate is a glass-containing ceramic for all-ceramic restorations. During fabrication or before bonding to the preparation, alumina oxide abrasion or HF acid-etching may be used to create micromechanical retention. Few studies have investigated how HF etching or abrasion affects the flexural strength of lithium disilicate ceramics. This study measured and compared the flexural strength of e.max CAD following alumina abrasion at differing pressures and acid-etching at differing concentrations and times. Methods: Bars of e.max CAD (9 groups of 10 - 22mm x 2.5mm x 2.5mm) were prepared; polished sequentially (180, 320, and 600 paper); and fired following manufacturer’s instructions. 4 groups were particle abraded (30µm alumina from 10mm at 8psi, 15psi, 30psi, or 45psi for 10s). 2 groups were etched with 5% HF (20s or 2 minutes). Two groups were etched with 9.5% HF (20s or 2 minutes). The control was polished and fired only (no treatment). Specimens were loaded using a three point flexural test to failure in an Instron (1mm/min crosshead speed). ANOVA and Dunnett’s t-test determined intergroup differences (p= 0.05). Results: Compared to the control, the 15psi, 30psi, and 45psi abraded groups produced significantly lower flexural strengths (p<0.05). The 8psi treated group was not statistically different from the control (p>0.08). The 5% and 9.5% HF etched groups were not significantly different from the control (p>0.05). Group Mean Flexural Strength (MPa) Deviation (MPa) Control 376.8 80 8 psi 305.3 29 15 psi 278.9 39 30 psi 240.6 31 45 psi 241.9 14 5% HF (20s) 313.7 62 5% HF (2min) 333.8 46 9.5% HF (20s) 303.5 39 9.5% HF (2min) 353.5 67 Conclusions: Alumina particle abrasion higher than 15psi significantly reduced e.max CAD flexural strength. HF etching is recommended to increase micromechanical retention and clean the intaglio surface of the restoration prior to bonding.

Objective: Measure 24hr and thermocycled shear bond strength (SBS) of universal bonding agents tested on etched enamel, uncut enamel and dentin surfaces. The line of universal bonding agents produced by several companies are intended to bond to enamel, dentin, glass ceramic, zirconia, noble and non-precious alloys, and composites without using a primer. Method: Enamel and dentin surfaces were polished (320-grit SiC-paper/4mins) and the root was cut off. Following surface treatments according to each manufacturer’s instructions, bonding agent was applied, Z100 composite cylinders (d=1.5mm) were bonded and light-cured (40 sec, Elipar/S10/3M-ESPE/1000mW/cm2). Half (n=10) were debonded after 24hrs storage/37°C (Instron-1mm/min) and the rest were debonded after thermocycling (10,000cycles/5-50°C/15sec dwell time). Data were analyzed with ANOVA and Tukey/Kramer post-hoc tests (p=0.05). Result: MPa/ (Mean ± SD) for SBS Table 1. All surfaces 320-grit SiC-paper finished. Same letters in a column are not statistically different (p>0.05) Universal Bonding Agents Treatments 24 Hours Thermocycled 10,000 cycles Scotchbond Universal Enamel 30.3±2.9 AB 24.9±7.7AB Dentin 30.5±2.5 AB 23.5±10.3 AB Prime & Bond Enamel 33.4±5.3A 36.6±7.7 A Dentin 33.3±5.8 A 33.4±7.2 A Bisco Universal Enamel 27.8±6.6 ABC 29.7±4.4 AB Dentin 26.6±4.5 BC 21.4±6.2 BC Conclusion: The highest mean bond strength in the etched enamel and dentin were seen in Prime & Bond. Thermocycling etched enamel showed no significant decrease in bond strength when compared to that of 24-hour group. Storage treatment had no significant effect.

Lithium disilicate is an etchable ceramic used for bonded restorations. Objectives: To measure 24hr and thermocycled shear bond strength (SBS) of Scotchbond Universal to e.max CAD after silane and hydrofluoric acid surface treatments and salivary contamination and cleaning. Methods: e.max CAD blocks were sectioned, polished (180, 320-grit SiC-paper/4mins), finished (0.5 Al2O3 slurry/2mins) and cleaned (ultrasonic/distilled water/15seconds). Following surface treatments (Table.1) and bonding agent application (20sec), Z100 composite cylinders (d=1.5mm) were bonded and light-cured (40 sec, Elipar/S10/3M-ESPE/1000mW/cm2). Half (n=10) were debonded after 24hrs storage/37C (Instron-1mm/min) and the rest were debonded after thermocycling (10,000cycles/5-55C/15sec dwell time). Contact angles were measured for all groups. Saliva collected from a single participant (2hrs postprandial) was pipetted onto the etched and silanated surface (0.04ml/3min/air dried-1min). SBSs were measured (Table1). Data was analyzed with ANOVA and Tukey/Kramer post-hoc tests (p=0.05). Results: MPa/ (MeanSD) for SBS Table.1 silane-RelyX (20 sec) ceramic primer unless mentioned, HF= Hydrofluoric acid (20 sec). Same letters in a column are not statistically different (p>0.05) Treatments 24Hours Thermocycled 10,000 cycles No HF No Silane 7.22a 1.82a No HF Silane 11.94a 12.65b HF Silane 1 Coat Heat Dried 36.75b,c 33.2c,e Silane 2 Coats Heat Dried 34.17b 29.55e 9.5% HF (1 min) Silane 41.55b,c,d 37.55c,d Monobond Plus (1 min) 38.37b,c,d 38.95c,d Salivary Contamination and Cleaning Protocols 5% HF + Silane contaminated with Saliva + Air drying No Treatment 40.53b,c,d 35.58c,d,e 35 % H3PO4 (15 sec) + Silane 41.55c,d 40.35d Alcohol (1 min) + Silane 42.85d 38.83c,d Bond strength decreased after thermocycling for the groups in italics. Saliva and the cleansing protocols did not affect the silane. Conclusions: HF etching and silane application should be applied for a durable bond. The hydrophobic surface produced by silane application resisted salivary contamination. Supported in part by 3M ESPE.

Objectives: To compare the shear bond strength of three resin cement and two commercially available resin cements onto 4 substrates (IPS e.max-CAD, Co-Cr alloy, ground enamel and dentin). Methods: Ceramic blocks (IPS e.max-CAD/Ivoclar Vivadent) were sectioned (4mm), polished (320-grit SiC) and finished (0.5 Al2O3 slurry). Human molars were wet-ground (320-grit) to obtain flat enamel and dentin surfaces. Metal alloy surfaces were air abraded (50 Al2O3/15sec) using KaVo RONDO flex 2013 at a distance of 10mm. IPS e.max-CAD was etched (5% HF/20 seconds), rinsed (distilled water), air dried and silanated (Monobond Plus/Ivoclar Vivadent). Pre-cured Z100/3M ESPE composite resin cylinders were bonded to the prepared surfaces using three cements following manufacturer's instructions with a constant load of 110gms. They were light cured using Elipar S10 (3M ESPE/950-1000mW/cm). Samples were stored (370C/24 hrs), thermocycled (5-50C/15s dwell time/1,600cycles), mounted on a steel fixture and subjected to compressive load until failure (1mm/min) using Instron (5565). Data were analyzed using ANOVA and Tukey HSD post-hoc tests (p=0.05). Results: MPa (MeanSD) Same letters in the same column are not statistically different (p>0.05). Enamel Dentin e.max Metal Alloy Light-Cure Self-Cure Light-Cure Self-Cure Light-Cure Self-Cure Light-Cure Self-Cure DAD Dual-Cure Permanent Resin Cement/Septodont Confi-Dental Division 22.94A 15.96A 29.95.9A 15.35A 36.68A,B 27.54A,B 15.77A 64.6A Multilink Automix/Ivoclar Vivadent 17.65B 13.45A 27.28.5A 18.76A 41.55A 24.45A 378B 16.35B,C Nexus3/Kerr 18.25A,B 14.03A 30.38.2A 20.96A 30.47B 29.86B 23.17C 19.910C Conclusions: Light cure vs Self Cure: Shear bond strength decreased for the cements below when used in self cure mode (Mann-Whitney test). Enamel: Nexus3 (p=0.013) and DAD (p=0.004) Dentin: Nexus3 (p=0.007), Multilink Automix (p=0.02) and DAD (p=0.0001) e.max: Multilink Automix (p<.0001) and DAD (p=0.006) Base metal: Multilink Automix (p<.0001) and DAD (p=0.001). This study was supported in part by a grant from Septodont.

Objectives: To measure and compare compressive strength, yield strength and wear resistance of a giomer, BEAUTIFIL Flow Plus, to flowable composite resins, PREMISE hybrid and SureFil SDR flowable. Methods: Compressive and yield strength: Specimens (n=10) were prepared using a Teflon split mold (d=4mm/h=8mm) following manufacturers' instructions for light curing (Elipar S10/3M ESPE/1100mW/cm) and stored (distilled water/370C/24hours). They were placed vertically between the hard steel plates of an Instron (Model/5565) and a compressive load applied (0.75mm/min) until failure. Compressive and yield strength was calculated from the stress strain curve created by the Instron Software. Wear resistance: Eight flat disc specimens (n=8) of each material (d=10mm/h=2mm) were prepared in 2mm increments using a flexible mold following manufacturers' instructions, light-cured (Elipar S10/3M ESPE/1100mW/cm2) and stored (distilled water/370C/24hours). They were mounted in brass holders (d=15mm/self-cured acrylic), polished (600-, 1000- and 1200- grit SiC paper) and finished (0.05 alumina slurry+polishing cloth). A load of 75N applied using stainless steel tips (d=4.70mm) for 200,000 cycles/1.2Hz in the Alabama Wear machine with 50 PMMA beads as media. Surfaces were scanned using a non-contact 3D profilometer (PROSCAN2000/Scantron/UK) and superimposed (ProForm/Scantron/UK) to determine wear depth and volume. Data was analyzed using ANOVA and Tukey/Kramer post-hoc tests (p=0.05). Results: (MeanSD) Same letters are not statistically different (p>0.05) Material/Manufacturer Wear Compressive and Yield Strength (MPa) Volume (mm³) Depth (m) Beautifil Flow Plus F00/SHOFU 0.0310.006A,C 94.78A 178.836A,C Beautifil Flow Plus F03/SHOFU 0.0430.007A,B 106.815A,C 185.927A,B,C Premise hybrid/KERR 0.0310.016A,C 64.118B 115.323D SureFil SDR/DENTSPLY 0.0520.005B 126.69C 16225C Conclusions: Within the limitations of this study, Beautifil Flow Plus F03 and F00 showed similar compressive strength, yield strength and wear with commercially available flowable composites. They also showed similar wear properties with Hybrid material. Funded in part by a grant from Shofu Dental Corporation .

Wear of posterior restorative materials is a significant clinical problem over the life of the restoration. Objectives: To measure and compare the in vitro wear of three glass ionomer restorative materials (Riva Self-Cure LV/SDI, ChemFil Rock/Dentsply, Fuji IX/GC) and (control) a resin composite (Z100/3M ESPE) restorative material. Methods: Eight flat disc specimens (n=8) of each material (d=10mm/h=4mm) were prepared using a flexible mold following each manufacturers' instructions. The capsules of glass ionomer materials were mixed in an amalgamator OptiMix (Kerr) for 8 seconds at 4,000rpm. ChemFil Rock was mixed for 12 seconds and placed in the flexible mold covered with a glass slide and allow to set. The composite resin was placed in 2mm increments in the same mold and light-cured with an Elipar S10 curing light (3M ESPE/1020mW/cm2). Specimens were stored in distilled water (24h/37C), mounted in brass holders (d=15mm/self-cured acrylic resin), polished with a series of abrasive disc (320-, 600- and 2000- grit SiC paper) and finished (0.05 alumina slurry+polishing cloth). The wear test was conducted on a modified UAB wear machine with a 2mm slide for 300,000 cycles using stainless steel tips (d=4.70mm) with load of 50N at 50cycles/min. 50 PMMA beads were used as the third body media (15g beads+9g water). Restorative materials were scanned before and after wear using a non-contact 3D profilometer (PROSCAN2000/Scantron/UK) to determine loss of restorative material (wear-depth and volume) by superimposing the two images (ProForm software). Data were analyzed with ANOVA and Tukey/Kramer post-hoc test (p=0.05). Results: (MeanSD) Material Volume (mm3) Depth (m) Riva Self-Cure LV/SDI 0.40.1 52.813 ChemFil Rock/Dentsply 0.30.06 40.311 Fuji IX/GC 0.20.08 24.512 Z100/3M ESPE 0.020.002 73 Conclusions: Z100 produced significantly less wear than any of the glass ionomer materials tested (p<.0001). Fuji IX had significantly less wear than Riva self-cure LV (p<0.05). No other differences were found.