Werner J. Finger

Monomers with low oxygen inhibition as enamel/dentin adhesives

OBJECTIVES This study was conducted to investigate the depths of polymerization inhibition by oxygen, the shear bond strengths to enamel and dentin, and the marginal adaptation in dentin cavities of experimental adhesives containing BisGMA/HEMA of mixtures of low-inhibition BisGMA-dicarbonate with HEMA or with HEMA-carbonate at ratios of 100/0, 80/20, 60/40, 50/50, and 40/60 by weight. METHODS The inhibition layer thickness was determined microscopically as non-polymerized surface film thickness on three samples each. For bond strength testing, composite cylinders were bonded to enamel and dentin following H3PO4 conditioning with the adhesives dissolved in acetone; marginal adaptation was evaluated in cylindrical dentin cavities. Five specimens each were stored in water for 24 h prior to testing. Shear bond strength results were compared by ANOVA and Duncans test (p < 0.05), the maximum gap widths by Kruskal-Wallis, ANOVA and Wilcoxons two-sample test (p < 0.01). RESULTS Inhibition layer thickness was significantly smaller for modified than for conventional BisGMA/HEMA monomers and increased significantly with HEMA content. In the BisGMA-dicarbonate/HEMA-carbonate group, the inhibited layer was thinner than 1 micron. Apart from the 40 and 50% BisGMA-dicarbonate/HEMA-carbonate mixtures, enamel bond strengths were not significantly different. The highest bond strengths to dentin were 15 and 12 MPa at 50 BisGMA and 50 BisGMA-dicarbonates/HEMA, respectively. The average bond strength for the BisGMA-dicarbonate/HEMA-carbonate group was 5 MPa. Adhesives with 40 and 60% HEMA in the conventional and 40 to 60% HEMA in the dicarbonate/HEMA group showed significantly better marginal adaptation than all others (p < 0.05). SIGNIFICANCE Carbonate-modified low-inhibition monomers have no advantage as enamel/dentin adhesives compared with conventional BisGMA/HEMA-based resins.

Self-etching primers--an alternative to the conventional acid etch technique?

AbstractMaterial and Methods: The aim of the present in vitro study was to evaluate the bonding capacity of three self-etching primers (Clearfil™ SE Bond [SE], Clearfil™ Linder Bond 2V [CLB], Novabond® [NOVA]) to enamel. Two adhesive systems with a separate phosphoric acid etching procedure (Gluma® Comfort Bond [GLU], Kurasper™ F [KU]) served as controls. 60 human incisors were used to evaluate shear bond strengths of composite cylinders to enamel. Results: Significant differences were found between the groups (p < 0.001). The mean value for groups, GLU, KU, CLB and SE was 24 MPa. The shear bond strength recorded for the Novabond® system was significantly lower (17 MPa). Conclusion: The results of the present investigation indicate that enamel bonding especially with the self-etching primers CLB and SE is an effective as conventional phosphoric acid etching.ZusammenfassungMaterial nd Methode: Ziel der vorliegenden In-vitro-Untersuchung war es, das Anbindungspotential von drei selbstkonditionierenden Primern (Clearfil™ SE Bond [SE], Clearfil™ Liner Bond 2V [CLB], Novabond® [NOVA] an Schmelz zu überprüfen. Als Kontrollgruppen dienten zwei Adhäsivsysteme, die sich der Ätztechnik mit Phosphorsäure bedienen: Gluma® Comfort Bond (GLU) und Kurasper™ F (KU). An 60 menschlichen Inzisivi wurde die Scherbindungsfestigkeit von Zylindern aus Bracketadhäsiv an Schmelz bestimmt. Ergebnisse: Es ergaben sich signifikante Unterschiede in den einzelnen Präparategruppen: GLU, KU, CLB und SE lagen bei 24 MPa und unterschieden sich nicht signifikant. Signifikant niedrigere Scherfestigkeiten (17 MPa) wurden für das Novabond®-Adhäsivsystem ermittelt. Schlussfolgerung: Mit der vorliegenden Untersuchung konnte gezeigt werden, dass insbesondere mit CLB und SE ähnlich gute Verbundfestigkeiten erreicht werden wie nach der Anwendung herkömmlicher Systeme mit Phosphorsäurekonditionierung.

Factors influencing marginal cavity adaptation of nanofiller containing resin composite restorations

OBJECTIVES The aim of this study was to investigate the effects of polymerization contraction, shrinkage stress and Youngs modulus of nanofiller containing resin composites on early marginal adaptation of restorations in cavities. METHODS Six nanofiller containing and two reference resin composites were studied. Marginal gap widths of restorations in cylindrical 4.2mm wide and 1.5mm deep dentin cavities, non-bonded or bonded with a self-etch adhesive, and in Teflon cavities of same dimensions were determined 15 min after irradiation (n=8). Polymerization shrinkage strains were measured using the bonded-disk (n=8) and a strain gage method (n=8). For determination of contraction stress the composites (n=10) were bonded to and cured in Araldit molds using a photoelastic method. Flexural moduli of the restoratives were studied according to ISO specification 4049 (n=5). Statistical analysis was performed with one- and two-way ANOVA, Kruskal-Wallis ANOVA test and post hoc tests (p<0.05). RESULTS Only two nanofiller composites (Kalore, GC, Japan) and Venus Diamond (Heraeus Kulzer, Germany) showed consistently gap-free margins in bonded dentin cavities. The mean gap widths in non-bonded and in Teflon cavities were 6.1-12.8 and 14.1-25.5 μm, and linearly correlated (r(2)<0.85). Significant linear relationships were observed between strain, stress and marginal gap widths in non-bonded and Teflon cavities (p<0.01). Flexural moduli (15 min) were between 1.66 and 8.63 GPa. SIGNIFICANCE Marginal cavity adaptation of restorations in bonded dentin cavities reflects complex interactions between adhesive bonding on the one hand, and polymerization contraction strain, stress and elastic modulus, on the other.

Two- and three-body wear of composite resins

OBJECTIVE The aim of the present study was to investigate two- and three-body wear of microfilled, micro-hybrid and nano-hybrid composite resins using a ball-on-disc sliding device. METHODS One microfilled (Durafill VS), one micro-hybrid (Filtek Z250), one hybrid (Clearfil AP-X), one nanofilled (Filtek Supreme XT), and two nano-hybrid (MI Flow, Venus Diamond) composite resins were examined. The composites were filled in a cylindrical cavity, and light polymerized. After storage in 37°C distilled water for 7days, all specimens were tested with a custom-made ball-on-disc sliding device with a zirconia ball as antagonist (50N loads, 1.2Hz, 10,000 cycles) immersed in water, poppy seed slurry and polymethyl methacrylate slurry, respectively. Maximum wear depth and volume loss of worn surfaces were quantified by a digital CCD microscope and analyzed with two-way analysis of variance. RESULTS The interactions between composite resin and condition of their maximum wear depth and volume loss were significant (p<0.01). The abrasive wear produced at three-body loading with poppy seed slurry was very large for the microfilled composite, and small for all other composites tested. In contrast, two-body wear of the microfilled composite, and one nano-hybrid composite was very low. SIGNIFICANCE The ball-on-disc sliding device used is considered suitable to simulate sliding of an antagonist cusp on an opposing occlusal composite restoration, either in the two- or the three-body wear mode. All tested materials except for the microfilled composite showed low surface wear when exposed to poppy seed as the third-body medium.

Effect of two desensitizing agents on dentin permeability in vitro

Abstract Objective The aim of this in vitro study was to investigate the effect of two desensitizing agents and water on hydraulic conductance in human dentin. Material and Methods GLUMA Desensitizer PowerGel (GLU) contains glutaraldehyde (GA) and 2-hydroxyethyl methacrylate (HEMA), and Teethmate Desensitizer (TD) is a powder comprising tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) that is mixed with water. Deionized water was used as a negative control (CTR). Thirty discs with a thickness of 1.2 mm were cut from the coronal dentin of the third molars and cleaned with 0.5 M EDTA (pH 7.4). After being mounted in a split-chamber device, the discs were pressurized with water at 1 kPa and 3 kPa in order to measure flow rates with a highly sensitive micro-flow sensor and to calculate hydraulic conductance as a baseline value (BL). Following the application of GLU, TD, and CTR (n=10), hydraulic conductance was remeasured with intermittent storage in water after 15 min, 1 d, 1 w, and 1 m. Reduction in permeability (PR%) was calculated from hydraulic conductance. Data were statistically analyzed using nonparametric methods (α<0.05). Representative discs were inspected by SEM. Results PR% for GLU and TD were 30-50% 15 min and 1 m after their application. Post hoc tests indicated that PR% of CTR was significantly greater than those of GLU and TD at all time points tested. The PR% of GLU and TD were not significantly different. SEM examinations showed noncollapsed collagen meshes at the tubular entrances after GLU, and crystalline precipitates occluding the tubular orifices after TD, whereas CTR specimens showed typical patterns of etched dentin. Conclusions The present study on hydraulic conductance in dentin discs treated with two chemically different desensitizing agents and water as a control demonstrated that both products may be characterized as effective.

All-in-one self-etch model adhesives : HEMA-free and without phase separation

OBJECTIVE Aim of this study was to design HEMA-free all-in-one self-etch model adhesives without phase separation, and to investigate their efficiency on extracted human teeth. MATERIALS AND METHODS Compositions of adhesives in mass% (1): UDMA (25), 4-META (20), H(2)O (0, 1, 2, 5, 10, 20, 35, and 45), balance of acetone or ethanol. (2): UDMA (35), 4-META or 4-MET (28), H(2)O (0, 2, 4, 5, 6, and 8), balance of acetone. Phase separation was evaluated on samples exposed to ambient atmosphere. Conventional shear bond strengths (SBS, n=8) were determined on human enamel and dentin. Marginal adaptation (MGW, n=8) was assessed in cylindrical butt-joint dentin cavities. RESULTS Solutions (1) and (2) with 5 and 8% or less water content, respectively, showed no phase separation. SBSs on enamel were not different within the acetone- or ethanol-group and between the adhesive groups (1). Water content of adhesives (2) was a significant determinant of enamel SBSs, groups with 4-META or 4-MET were not different (p>0.05). Dentin SBSs with adhesives (1) were not different (p>0.05) within solvent groups, yet higher for acetone-dissolved adhesives (p<0.05). Dentin SBSs with adhesives (2) were different by water content and functional monomer (p<0.05). MGW for solutions (1) were smaller with acetone-dissolved than with ethanol-dissolved adhesives (p<0.001). Acetone solutions between 2 and 45% water content produced almost perfect marginal adaptation. Marginal adaptation of adhesives (2) was almost perfect at 5 through 8% water content. CONCLUSIONS Simplified HEMA-free self-etch adhesives without phase separation were prepared without compromises on bonding efficiency to enamel and dentin.

Clinical trial of tooth desensitization prior to in‐office bleaching

The aim of this clinical trial was to compare tooth sensitivity during and after bleaching with hydrogen peroxide gel following application of GLUMA Desensitizer PowerGel or placebo. Forty-six subjects with sound maxillary incisors and canines were enrolled. Tooth shades were determined by comparison with a Vitapan Classic Shade guide. GLUMA Desensitizer PowerGel and placebo were randomly applied to the labial surfaces of the left or right anterior teeth for 1 min, which were then rinsed and dried. Then, Opalescence Boost PF 40% gel was applied onto labial enamel for 15 min. Sensitivity scores [recorded on a 10-point visual-analog scale (VAS)] were determined before, at 5, 10, and 15 min during, and 1, 24, 48 h and 1 wk after, the bleaching treatment. Shades were determined postbleaching and after 1 wk. Prebleaching application of GLUMA Desensitizer PowerGel significantly reduced tooth sensitivity during and after bleaching when compared with treatment with placebo. The whitening effects immediately and 1 wk after bleaching were significant when compared with the prebleaching shades. In conclusion, tooth pretreatment with GLUMA Desensitizer PowerGel for 1 min prior to 15 min of in-office bleaching with 40% hydrogen peroxide gel was highly effective in reducing tooth sensitivity during and after bleaching.

Randomized controlled clinical trial on the efficacy of dentin desensitizing agents

Abstract Objective. To investigate the effects of four dentin desensitizers on pain reduction in hypersensitive cervical dentin lesions. Materials and methods. The trial was designed as a randomized, controlled, four-arm, single-masked study. Fifty subjects with at least one hypersensitive lesion in each of the four quadrants were allocated. The requested pre-operative pain, determined as a response to 2-s air-blast (AB) and probe scratching (PS), was ≥5 on a VAS scale, 0 = no through to 10 = worst pain. Randomly each subject received each of the four treatments: MS Coat One F (MSC, Sun Medical, Japan), Nanoseal (NAN, Nishin, Japan), Teethmate Desensitizer (TMD, Kuraray Noritake, Japan) and Gluma Desensitizer PowerGel (GLU, HeraeusKulzer, Germany). The investigator assessed blindly the pain response using the two stimuli and recorded the patients’ VAS scores before and immediately after application, after 1 week and after 1, 3 and 6 months. Statistical data treatment. ANOVA and post-hoc testing (p ≤ 0.05). Results. Forty-nine subjects completed the trial. Pre-operative dentin hypersensitivity (DH) for the groups was not significantly different. All desensitizers reduced DH significantly throughout the 6-months observation. ANOVA revealed significant differences among VAS scores, obtained with the desensitizing agents (p < 0.001). Ranking by post-hoc testing was: MSC > NAN > TMD > GLU (p < 0.05). Upon PS NAN and TMD showed slight but significant regain of sensitivity after 6 months. For GLU PS scores immediately after application and after 6 months were not significantly different, whereas recalls after 1 week, 1 month and 3 months revealed significantly lower scores. Conclusion. The calcium phosphate-based TMD and GLU proved highly effective in reducing sensitivity.

In vitro dentin permeability after application of Gluma® desensitizer as aqueous solution or aqueous fumed silica dispersion

Objectives To assess and to compare the effects of Gluma® Desensitizer (GDL) with an experimental glutaraldehyde and HEMA containing fumed silica dispersion (GDG) on dentin permeability using a chemiluminous tracer penetration test. Material and Methods Twenty disc-shaped dentin specimens were dissected from extracted human third molars. The dentin specimens were mounted in a split chamber device for determination of permeability under liquid pressure using a photochemical method. Ten specimens were randomly selected and allocated to the evaluation groups Gluma® Desensitizer as aqueous solution and glutaraldehyde/HEMA as fumed silica dispersion, respectively. Dentin disc permeability was determined at two pressure levels after removal of smear with EDTA, after albumin soaking, and after application of the desensitizing agents. Two desensitizer-treated and rinsed specimens of each group were examined by scanning electron microscopy (SEM) for surface remnants. Results Comparatively large standard deviations of the mean EDTA reference and albumin soaked samples permeability values reflected the differences of the dentin substrates. The mean chemiluminescence values of specimen treated with GDL and GDG, respectively, were significantly reduced after topical application of the desensitizing agents on albumin-soaked dentin. The effects of GDL and GDG on permeability were not significantly different. Treated specimens showed no surface remnants after rinsing. Conclusions The experimental desensitizer gel formulation reduced dentin permeability as effectively as the original Gluma® Desensitizer solution.

In vitro evaluation of the wear resistance of composite resin blocks for CAD/CAM

UNLABELLED The aim of the study was to investigate two- and three-body wear of CAD/CAM blocks. Four composite resins, one hybrid ceramic and one feldspar ceramic block material were examined. Six specimens each were tested in a ball-on-disc wear device fitted with a zirconia ball (50 N load, 1.2 Hz, 50 k cycles) in water for two-body and in poppy seed slurry for three-body wear evaluation. Volume loss after each 10 k cycle was quantified using a digital CCD microscope. STATISTICAL ANALYSIS ANOVA and Tukeys multiple comparisons (α=0.05). Two-body wear for composite resin blocks was small, hybrid ceramic and ceramic blocks showed larger volume loss. Threebody wear was very low for all materials. All CAD/CAM block materials investigated displayed low wear compared to previous data for direct posterior composites carrying out the same wear test. The block materials are considered suitable for fabrication of single full crown restorations on premolar teeth.