Claus-Peter H. Ernst

Determination of polymerization shrinkage stress by means of a photoelastic investigation.

OBJECTIVE This study examined the polymerization stress of different established composite resins (Tetric Ceram, Vivadent; EsthetX, Surefil, Dentsply/DeTrey; Clearfil AP-X, Clearfil Photo Posterior, Kuraray; Prodigy Condensable, sds Kerr; Filtek P 60, 3M ESPE; Solitaire 2, Heraeus-Kulzer) by means of a photo-elastic investigation and investigated six new, experimental composite resins, which have been claimed to exhibit less polymerization shrinkage (InTen-S, Vivadent; K 112, K 051, Dentsply/DeTrey; Compox, Pluto, Hermes 3M ESPE). METHODS Cylindrical cavities (phi 5 mm) in Araldit B epoxide resin plates (40 x 40 x 3 mm3) were pretreated with the Rocatec system to ensure bonding of the composite resin. Ten composite resin specimens of each material, embedded in the Araldit plates, were exposed for 60 s (Elipar TriLight, Standard-mode, 800 mW/cm2). Polymerization contraction stress data (MPa) were calculated at 4 min and 24 h after exposure, based on the diameter of the isochromatic curves of first order obtained from the Araldit-plates. The statistical analysis was carried out with the Wilcoxon test (5% level). RESULTS After 24 h, the calculated mean polymerization stress values were 4.4+/-0.1 MPa for Tetric Ceram, 4.6+/-0.1 MPa for EsthetX, 3.7+/-0.1 MPa for Z 250, 4.6+/-0.1 MPa for Clearfil AP-X, 4.1+/-0.1 MPa for Prodigy Condensable, 4.0+/-0.1 MPa for Filtek P 60, 4.5+/-0.1 MPa for Surefil, 4,5+/-0.1 MPa for Clearfil Photo Posterior, 5.4+/-0.04 MPa for Solitaire 2, 3.2+/-0.1 MPa for In Ten-S, 3.9+/-0.1 MPa for K 112, 3.1+/-0.04 MPa for K 051, 3.2+/-0.1 MPa for Compox, and 2.0+/-0.1 MPa for Hermes. CONCLUSIONS The new and experimental composite resins In Ten-S, K 051, Compox, and Hermes showed significantly less polymerization shrinkage stress than the controls (p < 0.0005, Bonferroni correction). For the experimental material Pluto, no determination of isochromatic rings was possible.

Retentive strengths of cast gold crowns using glass ionomer, compomer, or resin cement.

PURPOSE The retention forces of a newly developed compomer cement (Dyract Cem), a glass ionomer cement (Ketac Cem Aplicap), and a resin cement (F21) were examined. MATERIAL AND METHODS Cemented cast gold crowns were removed along the path of insertion with a Zwick universal testing device. The impact of both a cured and a noncured additional bonding layer that were applied to the inner surface of the crowns was examined across the Dyract Cem group. RESULTS The mean adhesive strength was measured at 2.36 +/- 0.69 N/mm2 in the Ketac Cem group, at 0.60 +/- 0.28 N/mm2 in the F21 group, and at 1.85 +/- 0.94 N/mm2 in the Dyract Cem group, respectively. The application of an additional bonding layer to the inner surface of the crowns did not significantly improve the retentive strength of Dyract Cem; the respective mean strengths were observed at 1.46 +/-0.33 N/mm2 for the uncured and at 1.70 +/- 0.76 N/mm2 for the cured bonding layers. CONCLUSIONS Dyract Cem and Ketac Cem showed significantly higher retentive strengths than F21 (p < 0.001, Wilcoxon test, 5% level). No significant difference was found in bond strength between Ketac Cem and Dyract Cem.

In vivo validation of the historical in vitro thermocycling temperature range for dental materials testing

In dental research, restorative materials have been regularly subjected to alternating in vitro thermal stress in investigations since the 1950s, in order to simulate in vivo alternating temperature stress and to artificially stress them in vitro. The provocation temperature is mostly 5°C for cold provocation, and 55°C for hot provocation. These temperatures are determined quite arbitrarily based on very few examinations in vivo. Extensive temperature data for the approximal space of teeth, which is decisive for the success of fillings adhesively attached to dentin, has so far not been addressed. The objective of this study was to examine the interproximal temperature characteristics created in the space of all teeth in vivo with thermal alternating stress, and therefore to validate the in vitro standardized thermal alternating stress of 5–55°C. Fifteen study participants with healthy teeth were used to determine the temperature in each inter-dental space, resulting from hot/cold provocation in the upper and lower jaw, from the central incisor to the second molars. This was performed by a thermal element (cable sensor GTF 300, Greisinger Electronic GmbH, Regenstauf, Germany). The temperature sensor was attached with dental floss into the interproximal space and the temperature was recorded by the computer. The participants in the pilot test had to state when they were able to sip an 85°C hot drink. That particular temperature value was taken for hot provocation as maximum temperature reference. Cold ice water (0°C) was used for cold provocation as minimum temperature reference. The respective recordings with a total of 14 measurements for each individual were performed simultaneously in the upper and lower jaw. The study participants were to start with hot provocation, followed by cold provocation. This cycle was repeated at least once with an individual dwell time. The highest recorded approximal space temperature was 52.8°C in the lower jaw, between the first and the second premolar. The lowest temperature of 13.7°C was recorded in two participants in the upper jaw, between the 1st and 2nd incisor, and between the two central incisors. The mean of the maximum temperatures was 43.8±3.7°C, and the mean of the minimum temperatures 24.2±4.6°C. The mean initial temperature was 35.2±1.3°C. None of the recordings reached either the upper threshold (55°C) or the lower threshold (5°C). This study showed that the actual thermal stress in the interproximal space of teeth is slightly lower than the one used in in vitro examinations. For class II cavities, most of the alternating temperature stress limits selected at 5–55°C cover the actually occurring temperature interval quite well.

Marginal integrity of different resin-based composites for posterior teeth: an in vitro dye-penetration study on eight resin-composite and compomer-/adhesive combinations with a particular look at the additional use of flow-composites

OBJECTIVE To determine improvements in marginal adaptation of resin-based composite restorative systems by means of flow-composites (Solitaire 2/Gluma Solid Bond, Solitaire 2/Flow Line/Gluma Solid Bond, Point 4/Optibond Solo Plus, Point 4/Revolution/Optibond Solo Plus) and to determine the equality of simplified bonding systems (Solitaire 2/Gluma Comfort Bond, Tetric Ceram/Tetric Flow/Excite, Dyract AP/Prime & Bond NT/NRC, Pertac II/Prompt-L-Pop) in marginal gap formation. METHODS The marginal dye penetration (2% methylene-blue) was investigated separately for the approximal boxes of Class II mod-cavities with one cervical margin of the approximal box within enamel, the other within cementum. The surface analysis determined the percentage of dye-penetrated cervical and lateral margins of the approximal boxes, while the in depth investigation reported the mean dye penetration (mm) at both different cervical margins. RESULTS After thermocycling (5000 x , 5-55 degrees C) the percentage of dye penetration at the cervical cementum margins ranged from 16.5 +/- 5.9% (Solitaire/Flow Line/Gluma Solid Bond) to 82.8 +/- 5.7% (Pertac II/Prompt L-Pop), for the cervical enamel margins from 10.1 +/- 5.2% (Dyract AP/NRC/P & B NT) to 72.7 +/- 7.9% (Pertac II/Prompt L-Pop), and for the lateral enamel margins of the approximal boxes from 4.8 +/- 2.3% (Dyract AP/NRC/P & B NT) to 53.9 +/- 6.8% (Pertac II/Prompt L-Pop). In the in-depth dye penetration investigation the mean dye penetration ranged from 0.2 +/- 0.2 mm (Point 4/Revolution/Optibond Solo Plus) to 1.7 +/- 0.2 mm (Pertac II/Prompt L-Pop) at the cementum margins. At the enamel margins only Pertac II/Prompt L-Pop and Solitaire 2/Gluma Solid Bond showed mean in depth dye-penetrations deeper than 0.1 mm. SIGNIFICANCE Pertac II/Prompt-L-Pop showed a statistically significant (significance level alpha = 0.05, Wilcoxon test) higher percentage of dye-penetrated margins than most of the other restorative systems.

Minimal exposure time of different LED-curing devices

OBJECTIVES The purpose of the study was to investigate the shortest possible exposure time of different LED-curing devices for five different resin composites in a clinically relevant in vitro-model, where a 7 mm distance from the light guide tip to the bottom side of the cavity was compiled. METHODS Resin composite samples (Tetric EvoCeram A3, Filtek Supreme XT A3B, Premise A3, CeramX Mono M5, QuiXfil) were filled in three increments of 2mm thickness each in stainless steel moulds (Ø=5 mm, h=6 mm, n=9). The samples were incrementally exposed to different blue LED-curing devices (Bluephase, Bluephase C8, Bluephase 16i/Ivoclar Vivadent, L.E. Demetron II/sds Kerr, Elipar FreeLight 2/3M ESPE, Smartlite PS/DENTSPLY, Translux Power Blue/Heraeus) according to the manufacturers recommendations at a distance of 7 mm from the bottom of the cavity to simulate a class II-curing situation. Surface hardness was measured (Zwick Z2.5/TS1S) 10 min post-exposure at the bottom surfaces of the resin sample. A bottom/top-surface hardness ratio of 80% of a reference sample (2mm thickness, 40s), was defined as clinically acceptable for safe curing. A descriptive statistical analysis was carried out. RESULTS The curing devices Bluephase, Bluephase C8, Smartlite PS and Translux Power Blue could cure all composite resins investigated sufficiently in the exposure time recommended by the manufacturers (10-20s). The curing device Bluephase 16i and L.E. Demetron II only cured the composite Quixfil sufficiently in the exposure time recommended by the manufacturer. FreeLight 2+ allowed a 10s exposure time for all materials except Ceram X Mono (20s). SIGNIFICANCE When incrementally exposed, all resin composites investigated were polymerized sufficiently at a maximum of 20s exposure time.

In-vitro shear bond strength of self-etching versus traditional adhesives for orthodontic luting.

Object:To determine the enamel shear bond strength (SBS) of various established (Resulcin® Aqua Prime & Monobond N [RA], Prompt™ L-Po™ III [PLP]) and experimental (AC-Bond [AC], AC-Bond + Desensitizer [ACD]) self-etching adhesives in comparison to fourth (Total Etch, Primer and Bonding have separate liquids; OptiBond® FL [FL]) and fifth-generation (Total Etch, Primer and Bonding “One Bottle”; Excite® [EX], Gluma® Comfort Bond [CB]) adhesives.Materials and Methods:All adhesives were applied on flattened human enamel surfaces following the manufacturers’ instructions and light-cured using a quartz-tungsten-halogen curing device. 3.5 × 2.0 mm Tetric Ceram® A2 composite cylinders were sheared off (Zwick Universal-testing-machine 1445, 1 mm/min) after thermocycling (5–55 °C, 5000×). Normal distribution was tested for all groups and analysis of variance was conducted. The t-test (5% level, Bonferroni-correction) was used for statistical analysis to evaluate intergroup differences.Results:Shear bond strength in enamel: Resulcin® Aqua Prime & Monobond N: 27.0 ± 5.8 MPa, Prompt™ L-Pop™ III: 15.9 ± 3.4 MPa, AC-Bond: 28.1 ± 4.4 MPa, AC-Bond + Desensitizer: 22.2 ± 4.1 MPa, OptiBond® FL: 33.2 ± 3.2 MPa, Excite®: 30.5 ± 5.1 MPa, Gluma® Comfort Bond: 30.1 ± 3.7 MPa.OptiBond® FL demonstrated significantly higher SBS (p < 0.002) in enamel than Resulcin® Aqua Prime & Monobond N, AC-Bond, AC-Bond + Desensitizer and Prompt™ L-Pop™ III. Resulcin ® Aqua Prime & Monobond N performed significantly better than Prompt™ L-Pop™ III, but did not differ from AC-Bond or AC-Bond + Desensitizer. The SBS values of Excite® and Gluma® Comfort Bond were both on the same level of significance as AC-Bond and Resulcin® Aqua Prime & Monobond N, but the former showed superior results to AC-Bond + Desensitizer and Prompt™ L-Pop™ III. Prompt™ L-Pop™ III yielded significantly lower SBS-values than all the other products evaluated.Conclusion:Resulcin® Aqua Prime & Monobond N and AC-Bond did not differ significantly from established 5th-generation products. Further in-vivo studies are required to investigate intra-oral stability and resistance against changing forces and force directions.ZusammenfassungZiel:Ziel der Studie war es, die Scherhaftung (SBS) verschiedener etablierter (Resulcin® Aqua Prime & Monobond N [RA], Prompt™ L-Pop™ III [PLP]) und experimenteller (AC-Bond [AC], AC-Bond + Desensitizer [ACD]) selbstkonditionierender Adhäsive im Vergleich zu Adhäsiven der vierten (Total Etch, Primer und Bonding als separate Lösung; OptiBond® FL [FL]) und fünften Generation (Total Etch, Primer und Bonding als „One Bottle“-Produkt; Excite® [EX], Gluma® Comfort Bond [CB]) am Schmelz zu evaluieren.Material und Methodik:Sämtliche Adhäsive wurden den Herstellerangaben entsprechend auf plane humane Schmelzflächen appliziert und mittels Halogenlampe polymerisiert. 3,5 × 2,0 mm große Tetric-Ceram®-A2-Kompositzylinder wurden nach Thermocycling (5–55 °C, 5000×) abgeschert (Zwick Universal-Testmaschine 1445, 1 mm/min). Die Gruppen wurden auf Normalverteilung geprüft und es wurde eine Varianzanalyse durchgeführt. Weiterhin wurde zur Analyse von Gruppenunterschieden der t-Test für nicht verbundene Stichproben herangezogen (5%-Niveau, Bonferroni-Korrektur).Ergebnisse:SBS am Schmelz: Resulcin® Aqua Prime & Monobond N: 27,0 ± 5,8 MPa, Prompt™ L-Pop™ III: 15,9 ± 3,4 MPa, AC-Bond: 28,1 ± 4,4 MPa, AC-Bond + Desensitizer: 22,2 ± 4,1 MPa, OptiBond® FL: 33,2 ± 3,2 MPa, Excite®: 30,5 ± 5,1 MPa, Gluma® Comfort Bond: 30,1 ± 3,7 MPa.OptiBond® FL zeigte signifikant höhere SBS Werte (p < 0,002) am Schmelz als Resulcin® Aqua Prime & Monobond N, AC-Bond, AC-Bond + Desensitizer und Prompt™ L-Pop™ III. Resulcin® Aqua Prime & Monobond N schnitt signifikant höher ab als Prompt™ L-Pop™ III, wies aber keinen Unterschied zu AC-Bond und AC-Bond + Desensitizer auf. Excite® und Gluma® Comfort Bond lagen beide auf dem gleichen Signifikanzniveau wie AC-Bond und Resulcin ® Aqua Prime & Monobond N, zeigten gleichzeitig aber höhere Ergebnisse als AC-Bond + Desensitizer und Prompt™ L-Pop™ III. Prompt™ L-Pop™ III zeigte signifikant niedrigere SBS-Werte als alle anderen untersuchten Materialien.Schlussfolgerung:Resulcin® Aqua Prime & Monobond N und AC-Bond unterschieden sich nicht signifikant von den etablierten Produkten der fünften Generation. Zusätzlich sind In-vivo-Studien nötig, um die intraorale Stabilität sowie die Resistenz gegenüber wechselnden Kräften und Belastungsrichtungen zu untersuchen.

The Influence of Subjective Norm on the Usage of Smartglasses

One factor hindering people’s usage of smartglasses seems to be that of Subjective Norm. More specifically, there are multiple reports of people using Google Glass being criticized in public, due to the general public’s perception that their privacy is at risk because of the device’s integrated recording functionalities. In this article, we empirically evaluate the influence of Subjective Norm on smartglasses usage. After collecting 111 completed online questionnaires about one specific pair of smartglasses, Google Glass, and applying a structural equation modeling approach, our findings indicate that smartglasses are at least partly utilitarian technologies whose usage is influenced by Perceived Usefulness. Furthermore, although we could not confirm a direct positive influence of Subjective Norm on the Actual System Use of smartglasses, we confirmed an indirect positive influence of Subjective Norm on Actual System Use through Perceived Usefulness. These findings suggest that smartglasses manufacturers need to emphasize the instrumental benefits of their devices. In addition, the manufacturers need to address users’ potential negative perceptions of smartglasses stemming from users’ beliefs that the general public has a negative opinion of the device.

Does Perceived Health Risk Influence Smartglasses Usage

The World Health Organization has warned populations about illnesses that can develop due to radiation. Since smartglasses, which are worn on the head right next to the brain, can emit radiation, their usage might be hindered by the Perceived Health Risks people associate with such devices. In this article, we empirically evaluate the topic by studying the influence of Perceived Health Risk on smartglasses usage. After collecting 109 completed online questionnaires about one specific pair of smartglasses, Microsoft HoloLens, and applying a structural equation modeling approach, our findings indicate that smartglasses are at least partly hedonic technologies whose usage is influenced by Perceived Enjoyment. Furthermore, although we could not confirm a direct negative influence of Perceived Health Risk on the Behavioral Intention to Use smartglasses, we confirmed an indirect negative influence of Perceived Health Risk on Behavioral Intention to Use through Perceived Enjoyment. These findings suggest that smartglasses manufacturers need to emphasize the hedonic benefits of their devices as well as address people’s potential negative perceptions of these devices in terms of their health.

Risk Hurts Fun: The Influence of Perceived Privacy Risk on Social Network Site Usage

Some studies suggest that Perceived Privacy Risk exerts no influence on the Actual System Use of a Social Network Site (SNS). However, the potential indirect relationships between Perceived Privacy Risk and Actual System Use through its central antecedents have so far been overlooked. In this paper, I postulate that Perceived Privacy Risk exerts a negative influence on the Perceived Enjoyment of SNSs, one of the central antecedents of Actual System Use. After surveying 415 students and applying a structural equation modeling approach, I confirmed an indirect negative effect of Perceived Privacy Risk on Actual System Use through Perceived Enjoyment. Overall, my study suggests that SNS service providers need to actively manage people’s perceptions of privacy risk.

Success Comes to Those Who Are Successful: The Influence of Past Product Expectation Confirmation on Smartwatch Usage

Due to smartwatches’ usual strong functional dependence on other devices from the same manufacturer, we believe that Past Product Expectation Confirmation—which we describe as the extent to which a person believes that his/her expectations were satisfied by a specific manufacturer’s product portfolio in the past—influence people’s usage of smartwatches. After collecting 229 completed online questionnaires about the Apple Watch, and applying a structural equation modeling approach, our findings indicate that smartwatch usage is positively influenced by Perceived Usefulness. Past Product Expectation Confirmation was found to have a direct positive influence on the Behavioral Intention to Use smartwatches as well as an indirect positive influence on the Behavioral Intention to use smartwatches through Perceived Usefulness. These findings emphasize the importance of having strong product portfolios so that manufacturers can launch equally successful products in the future.