Steven R Armstrong

University of Iowa, Iowa City, Iowa, United States

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Publications (66)91.51 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Conventional grading of dental students' projects in preclinical courses has mainly relied on visual evaluation by experienced instructors. The purpose of this study was to compare conventional visual grading in a dental anatomy course at one U.S. dental school to a novel digital assessment technique. A total of sixty samples comprised of two sets of faculty wax-ups (n=30), student wax-ups (n=15), and dentoform teeth of tooth #14 (n=15) were used for this study. Two additional faculty members visually graded the samples according to a checklist and then repeated the grading after one week. The sample wax-up with the highest score based on the visual grading was selected as the master model for the digital grading, which was also performed twice with an interim period of one week. Descriptive statistics and signed rank tests for systematic bias were used for intra- and interrater comparisons. The intraclass correlation (ICC) was used as a measure of intra- and interrater reliability. None of the faculty members achieved the minimum acceptable intrarater agreement of 0.8. Interrater agreement was substantially less than intrarater agreement for the visual grading, whereas all measures of intrarater agreement were greater than 0.9 and considered excellent for the digital assessment technique. These results suggest that visual grading is limited by modest intrarater reliability and low interrater agreement. Digital grading is a promising evaluation method showing excellent intrarater reliability and correlation. Correlation for visual and digital grading was consistently modest, partly supporting the potential use of digital technology in dental anatomy grading.
    Journal of dental education. 12/2014; 78(12):1655-62.
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    ABSTRACT: Purpose: To directly test the effectiveness of ethanol-wet bonding (EW) in improving monomer infiltration into demineralized dentin through quantitative measurement of bis-GMA and TEG-DMA molar concentrations within hybrid layers, and to comprehensively evaluate the effect of EW and chlorhexidine on durability of resin-dentin bonds compared to conventional water-wet bonding (WW). Materials and Methods: A three-step etch-and-rinse adhesive (70% bis-GMA/28.75%TEG-DMA) was applied to coronal dentin using a clinically relevant ethanol-wet bonding protocol (EW) or the conventional water-wet bonding (WW) technique. Bis-GMA and TEG-DMA molar concentrations at various positions across the resin/dentin interfaces formed by EW and WW were measured using micro-Raman spectroscopy. The experiment was repeated at the same positions after 7-month storage in phosphate buffer solution containing 0.1% sodium azide. The μTBS and hybrid layer morphology (TEM) of bonding groups with and without chlorhexidine application were compared immediately and after 1-year storage in terms of nanoleakage, collagen fibril diameter, collagen interfibrillar width, and hybrid layer thickness. Results: Specimens bonded with EW showed significantly higher monomer molar concentrations and μTBS throughout the hybrid layer immediately and after storage, providing direct evidence of superior infiltration of hydrophobic monomers in EW compared to WW. Microscopically, EW maintained interfibrillar width and hybrid layer thickness for resin infiltration and retention. The application of chlorhexidine further preserved collagen integrity and limited the degree of nanoleakage in EW after 1-year storage. Conclusion: EW enhances infiltration of hydrophobic monomers into demineralized dentin. The results suggest that a more durable resin-dentin bond may be achieved with combined usage of a clinically relevant EW and chlorhexidine.
    The journal of adhesive dentistry 09/2014; · 0.91 Impact Factor
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    ABSTRACT: Objective: IRB-approved thirty-six month matched-pair RCT to evaluate the effectiveness of a single component one-step self-etching adhesive in non-carious class V lesions (NCCLs) as compared to gold standard etch-and-rinse 3-step system. Method: Two premolars with NCCLs mostly in dentin were randomly assigned, pumice cleaned only and restored by two clinicians in 30 adult subjects using either a self-etch 1-step or etch-and-rinse 3-step adhesive and nanofilled composite (Bond Force/Estilite Sigma Quick-BF/ESQ, Tokuyama; Optibond FL/Premise™-OPFL/P). Cotton and cord was used for isolation in all but four restorations. Esthetic (surface luster and stain, marginal stain, color match, anatomic form), functional (retention, marginal adaptation, patient’s view) and biologic properties (sensitivity, caries, tooth integrity, periodontal response, adjacent mucosa) were collected by two blinded and calibrated clinical evaluators at baseline, 6-, 12-, 24- and 36-months using Hickel et al., 2007 and 2010 criteria. McNemar’s test and Bowker's test of symmetry were used to compare restorations and Kaplan-Meier survival analysis was conducted to evaluate the survival distributions of length of overall clinical success between the two restorations (statistically significant if p<0.05, marginally significant if 0.05<p<0.10). Result: Retention over 36-months: OPFL/P one partially lost and BF/ESQ four lost restorations with all failed restorations from one clinician. 23 patients were available for recall at 36-months. Within groups as compared to baseline: BF/ESQ had significantly worse marginal stain (p=0.0186), retention (p=0.0455), marginal adaptation (p=0.0018); OPFL/P had improved periodontal response (p=0.0455). Between groups BF/ESQ had significantly better color match at baseline (p=0.0107) and significantly worse marginal adaptation (p=0.0252) at 36-months. A marginally significant difference between restoration survival (p=0.0568 log-rank test and p=0.0751 Wilcoxon test) was found with estimated 36-month probabilities of survival for BF/ESQ and OPFL/P of 0.75 and 0.92, respectively. Conclusion: OPFL/P had significantly better clinical performance in NCCLs through 36-months as compared to BF/ESQ.
    IADR General Session and Exhibition 2014; 06/2014
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    ABSTRACT: Objective: To assess the effects of ceramic opacity and thickness on delivered irradiance and energy density and degree of conversion and microhardness of the light-cured resin cement. Method: IPS e-Max ceramic discs (Ivoclar Vivadent) were fabricated in 3 thicknesses (0.5, 1.0, and 1.5mm) and 4 opacities (HT, LT, MO, HO) (n=3/per group). Light-cured resin cement (Variolink Veneer Luting Cement – shade MVO, Ivoclar Vivadent) 50µm thick was cured through these ceramics disks using a halogen curing light unit (Optilux 501, Kerr) with its energy density and irradiance measured by MARC from a fixed distance (1.5mm). Knoop hardness and Raman microscopy were used to evaluate the bottom degree of cure. Descriptive statistics were conducted. One- and two-way ANOVA with post-hoc Tukey’s HSD test and Pearson correlation test were used for the statistical analyses (alpha=0.05). Result: Significant interaction was found between ceramic thickness and opacity on resin cement degree of conversion (p<0.0001), irradiance (p=0.0062), and energy density (p=0.0078). Subsequent analyses demonstrated that there was a significant simple effect for opacity and for thickness on conversion, irradiance and energy density under different conditions of thickness and opacity. Although the curing unit used has relatively good beam homogeneity, no significant correlation was found between hardness and degree of conversion (r=0.03; p=0.8859) unless data collection locations of Raman and Knoop Hardness were taken in close proximity (R2= 0.9, p=0.0006). The calibration curve representing this correlation will be used in the final data collection. Conclusion: Ceramic opacity and thickness affect the polymerization of light-cured resin cements and need to be considered and compensated for when bonding indirect restorations. Based upon the findings of this preliminary study, the final study is ongoing.
    AADR Annual Meeting & Exhibition 2014; 03/2014
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    ABSTRACT: Ethanol-wet bonding (EW) was proposed to increase the strength and durability of the resin-dentin bond by producing a more hydrolytic resistant hybrid layer (HL) via increased infiltration of hydrophobic monomers into the acid-etched dentin. Objectives: The aim of this study is to evaluate effect of EW on same-day and 7-month molar concentration (MC) of BisGMA and TEGDMA in HL. Methods: Experimental co-monomers were prepared to construct calibration curves for MC calculation in resin-dentin bond specimens. Eight sound human molars were randomly and systematically rotated for EW and water-wet bonding (WW) treated surfaces. All teeth were flattened with a carbide bur in the CNC Specimen Former (University of Iowa) to expose coronal dentin. Sticky wax was used to build 2-mm wall on top of the midline cut to separate each tooth into 2-halves treated with EW and WW. For EW, the etched and water rinsed dentin was subsequently rinsed with absolute ethanol for 15s X 3 before primer (50%resin/50%ethanol) application. After solvent removal, pure adhesive (71%Bis-GMA/28%TEGDMA) was applied and 2-mm resin-based composite (Z100, 3M ESPE) built-up. Two 1-mm-thick resin-dentin slabs were formed per tooth and polished using a series of diamond suspensions. On each side of slabs, two locations with 3μm-thick HL were randomly selected on EW and WW treated surfaces. At each location, Raman spectra were obtained at 5 positions across the resin-dentin interface (n=64) through 100x objective lens using 8-11mW from 785 nm laser (1.5μm spot size) for 60s (micro-Raman Spectroscopy, Kaiser Optical System, Inc.). Peak area at 605 and 1610 cm-1 were used for MC calculation. Resin-dentin slabs were stored for 7-month at 37C in PBS before re-collecting the data at the same positions. Results: Positions Short-term BisGMA MC(mol/L) Short-term TEGDMA MC(mol/L) EW Mean(±SD) WW Mean(±SD) EW Mean(±SD) WW Mean(±SD) Adhesive layer 1.69A* 1.69A* 1.19(±0.62)A 1.43(±0.90)A* Adhesive-HL interface (AHI) 1.17(±0.34)A* 1.00(±0.40)B* 0.97(±0.62)A* 0.81(±0.57)A HL (1μm below AHI) 0.82(±0.30)A 0.59(±0.35)B* 0.67(±0.49)A* 0.57(±0.47)A HL (2μm below AHI) 0.56(±0.32)A* 0.33(±0.24)B* 0.42(±0.26)A* 0.39(±0.45)A* HL-tooth interface 0.35(±0.25)A* 0.20(±0.23)B* 0.30(±0.42)A* 0.17(±0.22)B* Means with the same letters showed no significant difference of BisGMA or TEGDMA MC between EW and WW (p>0.05). (*) indicates significant reduction of the mean BisGMA or TEGDMA MC after 7-month at each position within each bonding group (p<0.05). Conclusion: EW enhances infiltration (increased MC) of hydrophobic monomers into demineralized dentin.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013
  • K. HIRATA, F. QIAN, J. YAMAGAWA, S. ARMSTRONG
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    ABSTRACT: Objective: Determine enamel and dentin micro-tensile bond strength (mTBS) of an experimental self-etching, borate-initiated self-curing adhesive resin cement containing self-reinforcing (SR) multi-functional monomer (ECD-89). Method: Four adhesive resin cement groups in two curing modes: ECD-89 (ECD, experimental, self-cure/self-cure (pretreatments/resin cement) mode and self-cure/light-cure, Tokuyama Dental), Multilink Automix (MLA, self-cure/self-cure and self-cure/light-cure, Ivoclar Vivadent), CLEARFIL Esthetic Cement (CEC, light-cure/self-cure and light-cure/light-cure, Kuraray) and Calibra (CAL, self-cure/self-cure and light-cure/light-cure, Dentsply Caulk) were used to adhesively bond indirect resin-based composite ‘crowns’ (Paradigm MZ100, 3M ESPE, φ10mmX2mm, #600 SiC paper and sand blasting (50μm alumina, for 10seconds)) to occlusal dentin and buccal/lingual enamel of 160 carbide bur-cut human molars. Twenty-four hours later restored teeth were sectioned with diamond blades into 2x2mm square sticks then dumbbell shaped specimens (0.5mm2 round cross-sectional area, 1mm gage length, 0.6mm radius of curvature) were formed using a CNC Specimen Former (University of Iowa). One-half of the specimens were then tensile-tested at a crosshead speed of 1mm/min in a calibrated materials testing machine (Z2.5, Zwick), while the remaining half were placed in artificial saliva at 37 degrees C, with monthly media exchanges for mTBS testing after 1 year storage. Result: Microtensile bond strength (MPa (SD)) n=20/group Dentin‡ Enamel† ECD SC/LC 44.7 (14.1) A 35.1 (13.5) A,B,C ECD SC/SC 44.7 (12.5) A 28.8 (10.9) C MLA SC/LC 23.8 (22.2) B 36.1 (18.8) A,B,C MLA SC/SC 11.7 (11.7) C,D 29.7 (12.1) C CEC LC/LC 16.4 (14.1) C 33.9 (14.1) A,B,C CEC LC/SC 7.9 (8.5) D 31.1 (16.4) B,C CAL LC/LC 6.0 (8.6) D 46.7 (13.6) A CAL SC/SC 14.0 (10.8) C,D 43.9 (16.1) A,B ‡ means with the same uppercase letter are not significantly different using a simple random effect in Mixed Model ANOVA or † One-Way ANOVA, followed by post-hoc Tukey’s test. . Conclusion: mTBS of EDC to dentin was significantly stronger than remaining groups. mTBS to enamel was higher when phosphoric acid etching was performed (CAL) but not significantly different from ECD SC/LC, MLA SC/LC or CEC LC/LC. Acknowledgements: Sponsored by Tokuyama Dental Corp. K. Hirata is an employee of Tokuyama.
    IADR General Session 2012; 06/2012
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    ABSTRACT: Objective: Self-reinforcing (SR) adhesive has been introduced as a technology to contribute high bond efficiency with the multi-functional interaction to enamel and dentin. The purpose of this study was to evaluate the micro-tensile bond strength (mTBS) to dentin after two-years water storage and to characterize its interfacial interaction with dentin using TEM. Method: Five adhesive groups: Bond Force (BF, self-etch 1step (SE1) with SR, Tokuyama), Bond Force no-SR (NSR, experimental SE1, Tokuyama), Optibond FL (OBFL, total-etch 3step Kerr), Clearfil SE (CSE, self-etch 2step, Kuraray) and Optibond All-in-One (OBA, SE1, Kerr) were tested. 150 Extracted human molars were randomly distributed into five adhesive groups. Dentine surfaces were prepared using CNC Specimen Former (University of Iowa). The adhesives were applied according to manufacturer's instructions. Resin-based composite (Z100, 3M-ESPE) ‘crowns’, approximately 5mm in height, were incrementally formed and light-cured. Each restored tooth was sectioned into 2x2mm square sticks with diamond blades then into dumbbell-shaped specimens with the CNC (0.5mm2 round cross-sectional area, 1mm gage-length, 0.6mm radius of curvature). The specimens were stored for two-years in artificial saliva containing sodium azide (changed monthly) at 37ºC. Specimens were tensile-tested at a crosshead speed of 1mm/min in a calibrated testing machine (Z2.5, Zwick). The data was analyzed by two-way ANOVA with post-hoc Turkey's test (alpha=0.05). Additional specimens per each group were subjected to a silver impregnation protocol and nanoleakage patterns were observed under TEM. Result: The mTBS means and standard deviations are presented in the table below. Pre-test failures were included as 1MPa. Means followed by same letters (number for rows, character for columns) are not significantly different. Material (n=30) 24hr 24mo Bond Force 58.2(10.5) A,1 31.8(7.6) B,2 Bond Force no SR 38.3(17.5) B,1 18.8(11.6) C,2 Optibond FL 56.4(8.8) A,1 43.2(11.3) A,2 Clearfil SE 55.9(12.7) A,1 44.7(13.8) A,2 Optibond All-in-one 55.0(11.8) A,1 33.7(12.8) B,2 Conclusion: The bonding effectiveness of SR technology applied to a one bottled adhesive system for dentin bonding was confirmed. Mr. Yamagawa was employed by Tokuyama Dental Corp. while a visiting scientist at the University of Iowa.
    06/2012
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    ABSTRACT: Objective: Randomized controlled, matched-pair clinical study evaluated the effectiveness of two commercially available adhesive/composites restoratives in non-carious class V lesions (NCCLs). Methods: Non-carious cervical lesions (N=60) primarily in dentin on two premolars were restored in 30 adult subjects. Rubber dam was used only if retraction cord and cotton rolls were inadequate for proper isolation. Teeth were randomly assigned and only cleaned with pumice. Paired teeth were restored with one of two adhesive/resin-based composite (RBC) systems: Tokuyama Bond Force single component self-etching 1-step adhesive system with Estilite Sigma Quick supra-nanofilled RBC (BF/ESQ, Tokuyama) and Optibond FL etch-and-rinse 3-step adhesive system with Premise™, nanofilled RBC (OFL/P, Kerr). The adhesive was applied according to manufacturer’s instructions and the RBC was incrementally placed and light-cured with a QTH light (Demetron 501, Kerr). Restorations were finished with carbide finishing burs, Soflex discs and rubber polishing points. Evaluation was done at baseline, 6- and 12-mo (24- and 36-mo planned) using clinical evaluation criteria based upon Hickel et al., 2007 and 2010. This 12 month evaluation reports on: Color Match, Marginal Discoloration, Marginal Adaptation, Retention, Post-op Sensitivity. Univariate statistics were conducted. McNema’s test and Bowker’s test of symmetry were used to compare the difference in selected parameters between two restoration systems and between two time points (alpha=0.05). Results: Baseline: no significant difference between adhesive/(RBC) for any criteria except color match: Category-1 BF/ESQ (56.7%), OFL/P (30%). 12 months: 29 patients were available for recall with no difference for any criteria except marginal adaptation, Category-1 for OFL/P (85.2%) compared to BF/ESQ (66.7%) (p=0.0253, McNemar’s test). 97% of BF/ESQ and 93% of OFL/P were totally acceptable with 1 OFL/P and 2 BF/ESQ unacceptable due to retention loss. Conclusion: Preliminary 12-mo evidence supports efficacy of both the self-etching 1-step and etch-and-rinse 3-step restorative systems.
    IADR General Session 2012; 06/2012
  • K. HIRATA, S. ARMSTRONG, F. QIAN
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    ABSTRACT: Objectives: Determine dentin micro-tensile bond strength (mTBS) of an experimental self-etching, borate-initiated self-curing one-step adhesive system containing self-reinforcing (SR) multi-functional monomer (DBC510) when using direct resin-based composites, resin-based cement and core buildup restorative materials. Methods: DBC510 (DBC, experimental, self-etch self-cure one-step, Tokuyama Dental Corp.) was applied to carbide bur-cut occlusal dentin of 80 human molars using the following restorative materials: Direct Resin-based Composites (6): Estelite Sigma Quick (ESQ, Tokuyama Dental), Estelite Omega (EO, Tokuyama Dental), Esthet X HD (EXH, DENTSPLY CAULK), Herculite Ultra (HU, Kerr), Filtek Supreme Ultra (FSU, 3M) and Venus Diamond (VD, Heraeus Kulzer); Resin Cements (5): ECD-89 (ECD, experimental, Tokuyama Dental), Multilink Automix (MA, IVOCLAR VIVADENT), NX3 (NX, Kerr), CLEARFIL Esthetic Cement (CEC, KURARAY) and Calibra (CA, DENTSPLY); Core Materials (5): ECG (experimental, Tokuyama Dental), Luxa Core Z Dual (LCD, DMG AMERICA), Core-Paste XP (CPX, DenMat), Absolute Dentin (AD, Parkell) and Build IT FR (BIF, Pentron Clinical). The following day the restored teeth were diamond saw sectioned into 2x2mm square sticks then dumbbell shaped specimens (0.5mm2 round cross-sectional area, 1mm gage length, 0.6mm radius of curvature) were formed using an ultrafine diamond bur in the CNC Specimen Former (University of Iowa) then tensile-tested at a crosshead speed of 1mm/min in a calibrated materials testing machine (Z2.5, Zwick) using a glue less passive gripping device (Dircks Device). Both ANOVA and Weibull regression models were performed, both ignoring and considering the random effect of the tooth (multiple specimens per tooth) to detect a difference in bond strengths between each restorative material group. Results: Microtensile bond strength to dentin (MPa (SD))** Direct RBCs Resin cements Core buildups ESQ 51.0 (9.5) A ECD 50.0 (16.4) a ECG 50.3 (8.5) α EO 53.5 (11.3) A MA 51.6 (15.5) a LCD 48.9 (9.4) α EXH 56.1 (14.5) A NX 50.8 (12.4) a CPX 45.2 (12.7) α HU 55.7 (16.5) A CEC 51.1 (17.1) a AD 50.1 (14.6) α FSU 62.3 (17.4) A CA 58.3 (16.8) a BIF 46.0 (11.9) α VD 55.3 (17.1) A - - - - **means with the same symbol letter are not significantly different using a simple random effect in Mixed Model ANOVA with post-hoc Tukey's test (P > 0.05). n = 20 per group. Conclusions: No difference in mTBS to dentin was detected when using DBC with any of the restorative material classes. Acknowledgements: Sponsored by Tokuyama Dental Corp. K. Hirata is employee of Tokuyama.
    AADR Annual Meeting 2012; 03/2012
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    ABSTRACT: Innumerous modifications have been proposed for the microtensile test since its introduction; however, testing parameters are not often well described and wide variations in bond strength are commonly reported. The aim of this study was to evaluate the effect of the test specimen's gripping device, specimen geometry and fixation method on microtensile bond strength, failure mode, and stress distribution when using an etch-and-rinse 2-step adhesive system bonded to human dentin. Resin-based composite bonded to occlusal dentin from 21 human molars was used to fabricate dumbbell- and stick-shaped test specimens which were divided into three groups: Di - dumbbell-specimens placed in a Dircks device; GeS - stick-specimens gripped in a Geraldeli's device with Superglue; GeZ - stick-specimens gripped in a Geraldeli's device with Zapit. Specimens were tested to failure in tensile mode and the failure mode was examined under stereomicroscopy and fracture initiation sites were verified by scanning electron microscopy and energy dispersive X-ray spectroscopy. Three-dimensional models of each device/specimen were created and finite element calculations were performed. The effect of the gripping devices on the bond strength was not significant, unless the bond test areas were normalized. The failure mode was influenced by the type of device. Dircks device was less sensitive to human error than Geraldeli's, and produced a more uniform stress distribution at the dumbbell specimen adhesive layer than did the Geraldeli's device at the stick layer. Microtensile testing parameters can directly influence the results and consequently inter-study comparisons.
    Dental materials: official publication of the Academy of Dental Materials 03/2012; 28(5):e50-62. · 2.88 Impact Factor
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    ABSTRACT: This study evaluated the effect of gamma radiation on the microtensile bond strength of resin-based composite restoration to human enamel and dentin performed either before or after radiotherapy. Thirty sound human third molars were sectioned mesio-distally into buccal and lingual halves and then randomly divided into enamel or dentin groups. Enamel and dentin substrates were randomly divided into three sub-groups (n = 10): Control, which received no irradiation; specimens were irradiated before restoration protocol; and specimens were irradiated after restoration protocol. Radiation therapy was defined by application of 60-Gy dose fractionally with daily exposures of 2 Gy, 5 days a week, over 6 weeks. Restorations were carried out using Adper Single Bond adhesive system and Filtek Z250 resin composite. The specimens were sectioned producing 4 sticks per specimen and submitted to microtensile on a testing machine. Data were submitted to two-way ANOVA followed by Tukey test (p < 0.05). Failure modes were examined under optical microscopy and SEM. Bond strength to enamel was significantly higher than to dentin irrespective radiation therapy. Radiotherapy applied before restoration significantly reduced the bond strength to both substrates. A predominance of adhesive failures was detected for control groups and groups restored before radiotherapy. Cohesive failures in dentin and enamel increased when the specimens were restored after irradiation. The gamma radiation had a significant detrimental effect on bond strength to human enamel and dentin when the adhesive restorative procedure was carried out after radiotherapy.
    Supportive Care in Cancer 03/2012; 20(11):2873-8. · 2.09 Impact Factor
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    ABSTRACT: Objectives. Innumerous modifications have been proposed for the microtensile test since its introduction; however, testing parameters are not often well described and wide variations in bond strength are commonly reported. The aim of this study was to evaluate the effect of the test specimen’s gripping device, specimen geometry and fixation method on micro tensile bond strength, failure mode, and stress distribution when using an etch-and-rinse 2-step adhesive system bonded to human dentin. Methods. Resin-based composite bonded to occlusal dentin from 21 human molars was used to fabricate dumbbell- and stick-shaped test specimens which were divided into three groups: Di – dumbbell-specimens placed in a Dircks device; GeS – stick-specimens gripped in a Geraldeli’s device with Superglue; GeZ – stick-specimens gripped in a Geraldeli’s device with Zapit. Specimens were tested to failure in tensile mode and the failure mode was examined under stereomicroscopy and fracture initiation sites were verified by scanning electron microscopy and energy dispersive X-ray spectroscopy. Three-dimensional models of each device/specimen were created and finite element calculations were performed. Results. The effect of the gripping devices on the bond strength was not significant, unless the bond test areas were normalized. The failure mode was influenced by the type of device. Dircks device was less sensitive to human error than Geraldeli’s, and produced a more uniform stress distribution at the dumbbell specimen adhesive layer than did the Geraldeli’s device at the stick layer. Significance. Microtensile testing parameters can directly influence the results and consequently inter-study comparisons.
    Dental Materials 01/2012; 28:e50-e62. · 3.77 Impact Factor
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    ABSTRACT: Adequate degree of conversion (DC) of resin adhesives is critical to resin-dentin bond strength and clinical durability. Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) is a promising alternative photoinitiator compared to redox initiators based on camphorquinone for resin adhesives. Photoinitiator combinations may provide broader light absorptivity and more reactive radicals with the potential to enhance polymerization. Objectives: Evaluate effect of five photoinitiator systems on DC and resin/composite-dentin shear bond strength (SBS). Methods: DCs of hydrophilic (PMGDM/HEMA) and hydrophobic (BisGMA/TEGDMA) resins containing 5 photoinitiator systems; BAPO, BAPO/benzoyl peroxide (BAPO/BPO), camphorquinone/ethyl-4-dimethylaminobenzoate (CQ/4E), CQ/BAPO, and CQ/BPO were measured at 24-hour by FTIR using Near-infrared (NIR; 1.8mm-thick resins) for both resins and Mid-infrared (Mid-IR;25 micron-thick resins) for BisGMA/TEGDMA (n=5). 50 sound molars were randomly divided into 5 groups by photoinitiator system. All teeth were flattened and ground with #320-grit SiC papers to completely remove coronal enamel before application of a 3-step etch-and-water rinse, primer and bonding resin adhesive (35% phosphoric acid etchant, PMGDM/HEMA/50%acetone primers, and BisGMA/TEGDMA bonding resins) and a commercial resin-based composite (TPH3, Dentsply). SBS (knife-edge chisel-on-iris) was evaluated at 24-hour followed by fracture mode evaluation under a light microscope. Results: Photoinitiators DC at 24h (%) by NIR Mean SBS at 24h (MPa) Bis-GMA/TEGDMA7:3 by mass PMGDM/HEMA 3.3:1 by mass. BAPO (1%) 81.37(±0.52)A,a 76.58(±0.46)B,b 35.31(±6.87)A BAPO (1%) BPO (1%) 81.97(±0.78)A,a 79.20(±0.53)A,b 35.58(±7.56)A CQ (0.25%) 4E (1%) 76.61(±1.08)B,a 67.53(±0.55)C,b 27.22(±9.04)B CQ (0.25%) BAPO (1%) 80.06(±1.84)A,a 76.70(±1.61)B,b 21.17(±5.92)B CQ (0.25%) BPO (1%) 74.35(±0.72)C,a 58.68(±0.78)D,b 14.28(±2.35)C Groups with same upper case letters within columns and same lower case letters within rows are not significantly different (p > 0.05). NIR measured significantly higher DC of BisGMA/TEGDMA resin at 24-hour compared to Mid-IR; BAPO=59(1.6)%, BAPO/BPO=61(1.6)%, CQ/4E=54(1.5)%, CQ/BAPO=62(1.6)%, CQ/BPO=59(0.5)%. No cohesive failures were observed. Groups with lower SBS had a higher percentage of joint failures; while groups with higher SBS had a higher percentage of mixed failure. Conclusion: The use of BAPO alone and in combination with BPO and CQ increased DC of both hydrophobic and hydrophilic resins over resins containing CQ/4E. Only BAPO and BAPO/BPO demonstrated significantly higher SBS over resins containing CQ/4E. Supported by NIST, NIDCR Interagency agreement (Y1-DE-7005), ADAF PRC, and University of Iowa.
    IADR General Session 2011; 03/2011
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    ABSTRACT: Objectives: Estimate adequate light exposure duration for six commercial resin-based composites by non-liner regression analysis with the top and bottom micro-hardness. Methods: Estelite Sigma Quick (EQ, A2, Tokuyama Dental Corp.), Estelite Sigma (ES, A2, Tokuyama), Supreme Plus (SP, A2E, 3M-ESPE), Durafill VS (DV, A2, Heraeus Kulzer), Esthet-X HD (EH, A2, Dentsply) and Herculite Ultra (HU, A2E, Kerr) were evaluated. Each composite (d=3.0 x h=2.0mm) was cured for 10, 20, 30, 60, 120 or 180s (n=5) with QTH light-curing unit (Optilux500, Kerr, 591mW/cm2). Distal end of light-guide was placed 2.0mm from the composite surface with a black background. After 24h storage in 37˚C distilled water, three KHN measurements (Micromet-II Microhardness Tester, Buehler) were made for top and bottom of each specimen under 25g load for 12s. The average of three measurements was then used for the data analysis. Non-liner regression was calculated with: Y = (Ymax-c)(1-e-kt)+c; Ymax = the asymptotic maximum hardness, c = constant, k = rate parameter and t = exposure duration. The exposure duration needed for the bottom surface to achieve 80% of top-surface Ymax was estimated by inverse regression. SAS (PROC NLIN, Newton-Raphson) for Windows (SAS Institute Inc) was used for the data analysis (alpha=0.05). Results: Table shows Ymax, k and r2 for top- and bottom-surface and exposure duration needed to achieve a bottom-surface hardness that is 80% of top Ymax. Exposure duration for EQ is unable to be generated by the model because the asymptote bottom Ymax is approached more quickly than top Ymax. Conclusions: Non-liner regression methods employed were unable to predict exposure duration needed for the bottom surface of EQ to achieve 80% of top-surface Ymax due to the high rate of conversion. Manufacturer's recommended curing protocols may not achieve a bottom-surface hardness that is 80% of top Ymax. Sponsored by Tokuyama Dental Corp.
    03/2011
  • K. HIRATA, J. YAMAGAWA, F. QIAN, S. ARMSTRONG
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    ABSTRACT: Objectives: To evaluate the color stability of experimental resin based composite (RBC) UBC. Methods: UBC-001 (UBC, A2-Enamel, Tokuyama Dental Corporation, Experimental), Filtek Supreme Plus (SP, A2E, 3M-ESPE), Esthet-X HD (EX, A2, DENTSPLY), Durafill VS (DV, A2, Heraeus Kulzer), PREMISE (PM, A2, Kerr) and Venus Diamond (VD, A2E, Heraeus Kulzer) were evaluated for color stability. 96 disk-shaped specimens (N =16 per RBC, D =10mm, 2mm thick) were made by light polymerizing for 10 or 20 seconds, based on the manufacturer's recommendation, using Optilux 500 (Kerr Inc, Orange, CA, USA) at more than 800 mW/cm2. After 24 hour dark storage in distilled water at 37C the directly irradiated surfaces were ground with P800 grit SiC paper on a grinding/polishing machine (Rotopol V, Stuers, Cleveland, Ohio, USA) under continuously water cooling at 150 rpm, followed by dry polishing with a Sof-Lex disc fine and super-fine grit for 20 seconds (30,000 rpm, Upower UP500, Brasseler, USA). Each specimen was then thermocycled between 5C and 55C with the dwell time of 1 min each in distilled water. Color of each RBC was measured using VITA Easyshade compact (Model # DEASYCHP, VITA) before and after thermocycling (TC) and delta-E = (delta-a2+delta-b2+delta-L2)1/2 was used to analyze the color stability. One-way ANOVA and repeated measures ANOVA with appropriate post-hoc tests were conducted to assess the effects of composites and polishing times on the color stability, within each polishing and thermocycling step and within each composite, respectively. Results: RBC Delta-Eb (color change using black background) TC 3K TC 10K TC 20K TC 30K TC 50K UBC 0.91 (0.10)B,1 0.86 (0.15)A,B,1 1.20 (0.17)A,2 2.08 (0.17)B,3 3.20 (0.17)B,4 SP 3.45 (0.35)D,1 4.22 (0.34)E,2 4.44 (0.27)D,2 4.37 (0.29)D,2 4.43 (0.28)C,2 EX 0.55 (0.27)A,1 0.76 (0.19)A,1,2 1.74 (0.45)B,3 1.03 (0.23)A,2 1.01 (0.27)A,2 DV 0.63 (0.22)A,1 0.99 (0.23)B,2 1.34 (0.08)A,3 1.76 (0.29)B,4 2.93 (0.68)B,5 PM 1.62 (0.41)C,2 1.90 (0.33)C,2 1.90 (0.28)B,2 1.76 (0.33)B,2 1.08 (0.34)A,1 VD 1.79 (0.25)C,1 2.65 (0.33)D,2 3.33 (0.32)C,3 3.43 (0.32)C,3 3.95 (0.43)C,4 Groups within columns with same letter and within row with same number are not significantly different (p >.05). Conclusion: Color stability for all RBCs, including UBC, was within the stated clinically perceptual limit (delta-E; less than 3.3, Craig and Powers, 2002) with the exception of SP after 3,000 TC and VD after 30,000 TC challenge. Acknowledgements: Supported by Tokuyama Dental Corporation and Mr. Hirata was an employee of Tokuyama while a visiting scientist at University of Iowa.
    IADR General Session 2011; 03/2011
  • Source
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    ABSTRACT: A concise overview of an institution's aspirations for its students becomes increasingly elusive because dental education has evolving emphases on priorities like critical thinking and adapting to new technology. The purpose of this article is to offer a learner-oriented matrix that gives a focus for discussion and an overview of an institution's educational outcomes. On one axis of the matrix, common educational outcomes are listed: knowledge, technical skills, critical thinking, ethical and professional values, patient and practice management, and social responsibility awareness. On the other axis, methodologies are listed: definition, cultivation strategies, measures (summative/formative, objective/subjective), institutional coordination, and competency determination. By completing the matrix, an overview of the process by which students reach these outcomes emerges. Each institution would likely complete the matrix differently and, ideally, with active discussion. While the matrix can first be used to establish "Where are we now?" for an institution, it can also be a starting point for more extensive matrices and further discussion. Vertical and horizontal analyses of the matrix provide a unique lens for viewing the institution's learning environment.
    Journal of dental education 02/2011; 75(2):160-8. · 0.99 Impact Factor
  • Dental Materials - DENT MATER. 01/2011; 27.
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    ABSTRACT: To determine if the results of resin-dentin microtensile bond strength (μTBS) is correlated with the outcome parameters of clinical studies on non-retentive Class V restorations. Resin-dentin μTBS data were obtained from one test center; the in vitro tests were all performed by the same operator. The μTBS testing was performed 8 h after bonding and after 6 months of storing the specimens in water. Pre-test failures (PTFs) of specimens were included in the analysis, attributing them a value of 1MPa. Prospective clinical studies on cervical restorations (Class V) with an observation period of at least 18 months were searched in the literature. The clinical outcome variables were retention loss, marginal discoloration and marginal integrity. Furthermore, an index was formulated to be better able to compare the laboratory and clinical results. Estimates of adhesive effects in a linear mixed model were used to summarize the clinical performance of each adhesive between 12 and 36 months. Spearman correlations between these clinical performances and the μTBS values were calculated subsequently. Thirty-six clinical studies with 15 adhesive/restorative systems for which μTBS data were also available were included in the statistical analysis. In general 3-step and 2-step etch-and-rinse systems showed higher bond strength values than the 2-step/3-step self-etching systems, which, however, produced higher values than the 1-step self-etching and the resin modified glass ionomer systems. Prolonged water storage of specimens resulted in a significant decrease of the mean bond strength values in 5 adhesive systems (Wilcoxon, p<0.05). There was a significant correlation between μTBS values both after 8 h and 6 months of storage and marginal discoloration (r=0.54 and r=0.67, respectively). However, the same correlation was not found between μTBS values and the retention rate, clinical index or marginal integrity. As μTBS data of adhesive systems, especially after water storage for 6 months, showed a good correlation with marginal discoloration in short-term clinical Class V restorations, longitudinal clinical trials should explore whether early marginal staining is predictive for future retention loss in non-carious cervical restorations.
    Dental materials: official publication of the Academy of Dental Materials 10/2010; 27(2):114-25. · 2.88 Impact Factor
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    ABSTRACT: Objectives: Evaluate effect of light-irradiation time on Knoop hardness numbers (KHN) ratios of six resin-based composites. Methods: Estelite Sigma Quick (EQ, A2, Tokuyama Dental), Estelite Sigma (ES, A2, Tokuyama), Supreme Plus (SP, A2E, 3M-ESPE), Durafill VS (DV, A2, Heraeus Kulzer), Esthet-X HD (EH, A2, Dentsply) and Herculite Ultra (HU, A2E, Kerr) were evaluated. Each composite (d=3.0 x h=2.0mm) was cured for 10, 20, 30, 60, 120 or 180seconds (n=5) with QTH light-curing unit (Optilux500, Kerr, 591mW/cm2). Distal end of light-guide was placed 2.0mm from the composite surface with a black rubber sheet used as background. After 24hour storage in 37˚C distilled water, three KHN measurements were made for top and bottom of each specimen using Micromet-II Microhardness Tester (Buehler) under 25g load for 12seconds. KHN ratios were calculated: T/T = Top KHN [at the each curing time]/Top KHN [at 180s], B/T: Bottom KHN [at the each curing time]/Top KHN [at 180s]. One-way ANOVA with post-hoc Tukey's HSD and/or Ryan-Einot-Gabriel-Welsch Multiple Range Test were used to compare curing efficacy through six curing times for each composite (alpha=0.05). Results: Light-irradiation times required to reach 80% T/T = EQ(10s), ES(10s), SP(20s), HU(20s), EH(30s) and DV(60s). See table for curing time required to reach 80% B/T; groups with same letter are not significantly different within columns. Curing time EQ ES SP DV EH HU 10s 0.863α 0.741α 0.563α 0.419α 0.589α 0.597α 20s 0.918α,β 0.818α,β 0.753β 0.598β 0.683β 0.751β 30s 0.925α,β 0.898α,β 0.791β, 0.616β 0.788 0.819β, 60s 0.952α,β 0.950β 0.873,Ω 0.721Ω 0.851,Ω 0.874,Ω 120s 0.986β 0.986β 0.891Ω 0.757Ω 0.884,Ω 0.924Ω 180s 0.991β 0.994β 0.958Ω 0.810Ω 0.917Ω 0.923Ω Conclusion: KHN ratios were material- and curing time-dependent. EQ demonstrated the greatest and DV the lowest curing efficacy based on KHN ratios. Manufacturer's recommended curing protocols may not achieve 80% B/T KHN ratios. Sponsored by Tokuyama Dental Corp.
    IADR General Session 2010; 07/2010
  • R. MAIA, S. ARMSTRONG, S. GERALDELI, F. QIAN
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    ABSTRACT: Objectives: Compare the effectiveness of 7 contemporary adhesive systems bonded to dentin, ground and unground enamel, as well as the method of shear bond strength (SBS) specimen fabrication. Methods: 105 human third molars were randomly assigned to 7 experimental groups to evaluate the dentin SBS, while 210 bovine incisors were used for testing the enamel SBS and SEM evaluation. Additionally, three methods of SBS specimen fabrication were tested. Differences between groups were tested using one-way ANOVA with post-hoc Tukey's studentized range (alpha=0.05). Results: Adhesive Class Dentin SBS MPa (SD) G-Enamel SBS MPa (SD) UG-Enamel SBS MPa (SD) All-Bond 3 ER 3-Step 35.49 (2.76) A 38.02 (1.38) A 37.61 (1.42) A Perma Quick ER 3-Step 35.90 (2.90) A 37.98 (0.62) A 37.51 (1.01) A All-Bond 3 ER 2-Step 33.52 (3.54) A 37.31 (1.31) A 35.03 (1.66) B PQ1 ER 2-Step 34.08 (2.45) A 37.57 (0.67) A 35.00 (1.88) B Clearfil SE Bond SE 2-Step 36.32 (1.90) A 36.20 (0.95) A 36.49 (1.81) A B Peak SE SE 2-Step 34.73 (2.80) A 38.34 (1.02) A 37.91 (1.54) A Adper PromptL-Pop SE 1-Step 28.10 (2.07) B 37.23 (1.97) A 35.90 (2.02) A B ER = etch-and-rinse; SE = self-etching; G = ground; UG = unground The method of adhesive application in the Ultradent SBS jib significantly affected SBS and failure mode. Adhesive application method PQ1 Dentin SBS MPa (SD) PQ1 Predominant failure mode Peak SE Dentin SBS MPa (SD) Peak SE Predominant failure mode Cured Before JIG 34.08 (2.45) A Dentin (8/12) 34.73 (2.80) A Dentin (10/12) Cured Through JIG 32.06 (1.36) B Dentin (10/12) 32.68 (0.95) B Dentin (10/12) System Placed Within JIG 22.92 (1.28) C Adhesive (10/12) 23.85 (1.88) C Adhesive (11/12) Conclusion: One reduced step system was weaker when bonded to dentin and two reduced-step systems were weaker when bonded to unground enamel; however, other reduced systems (Peak SE and Clearfil SE Bond) were not significantly different from ER 3-Step systems. How the specimen is fabricated will determine the bond strength and mode of failure and, therefore, should be properly described and justified in research reports. Acknowledgments: Ultradent provided Materials.
    IADR General Session 2010; 07/2010

Publication Stats

633 Citations
91.51 Total Impact Points

Institutions

  • 1997–2014
    • University of Iowa
      • • College of Dentistry
      • • Department of Operative Dentistry
      • • Department of Chemical and Biochemical Engineering
      • • Dows Institute for Dental Research
      Iowa City, Iowa, United States
  • 2012
    • University of Campinas
      • Faculty of Dentistry from Piracicaba
      Conceição de Campinas, São Paulo, Brazil
  • 2008–2012
    • Universidade Federal de Uberlândia (UFU)
      UDI, Minas Gerais, Brazil
  • 2007–2008
    • Srinakharinwirot University
      • Department of Conservative Dentistry
      Krung Thep, Bangkok, Thailand
    • Jordan University of Science and Technology
      • Faculty of Dentistry
      Irbid, Irbid, Jordan
    • Georgia Health Sciences University
      • Division of Oral and Maxillofacial Pathology
      Augusta, Georgia, United States
    • United States Navy
      Monterey, California, United States