Effect of Conventional Adhesive Application or Co-Curing Technique on Dentin Bond Strength.

The aim of this in vitro study was to assess the effect of two different adhesive application methods on shear dentin bond strength (ISO 29022) using three various adhesive systems. A mid-coronal section of 77 intact third human molars with fully developed apices was made to create flat bonding substrates. The materials used in the study were Excite F (Ivoclar Vivadent), Prime&Bond Universal (Dentsply Sirona) and G-Premio Bond (GC). The application of each adhesion system was performed in two different ways. In the first group, the bonding agent was light cured immediately after the application (conventional method), while in the second group the adhesive and composite were cured concurrently ("co-curing" method). A total of 180 specimens were prepared (3 adhesives × 2 method of application × 30 specimens per experimental group), stored at 37 °C in distilled water and fractured in shear mode after 1 week. Statistical analysis was performed using ANOVA and Weibull statistics. The highest bond strength was obtained for Prime&Bond conventional (21.7 MPa), whilst the lowest bond strength was observed when co-curing was used (particularly, Excite F 12.2 MPa). The results showed a significant difference between conventional and co-curing methods in all materials. According to reliability analysis, the co-curing method diminished bond reliability. Different application techniques exhibit different bond strengths to dentin.

Estimating Attribute-Specific Willingness-to-Pay Values from a Health Care Contingent Valuation Study: A Best-Worst Choice Approach.

BACKGROUND: Willingness-to-pay (WTP) studies frequently use a contingent valuation (CV) method to determine the economic value of a good or service. However, a typical CV study is able to estimate the WTP for a good as a whole, but provides no information about the marginal WTP for different attributes of a good. OBJECTIVE: The aim was to estimate marginal WTP for different attributes of a CV scenario. METHODS: By using the data from an additional best-worst choice (BWC) experiment, we disaggregated the holistic WTP values for dental care, estimated using the CV method, into attribute-specific WTP values. The study was conducted at the School of Dental Medicine, University of Zagreb, Croatia. Dental school patients were surveyed from March 2016 to January 2017, and their WTP for dental care was estimated using either a CV survey (n = 242), which also included a BWC task, or a discrete choice experiment (DCE) survey (n = 275). RESULTS: The largest marginal welfare estimate (€13.5) was obtained for the improvement in treatment explanation, followed by the improvements in staff behavior (€8.1) and waiting time in the office (€7.2), and by the changes in dental care provider (€3.4). These estimates were generally highly similar to the traditional marginal WTP estimates obtained with a traditional multi-profile DCE, after adjusting DCE estimates for non-attendance to the cost attribute. CONCLUSION: Our BWC-CV framework may serve as a valuable alternative for estimating marginal WTP values for health care attributes when the choice behavior of respondents raises concerns for the validity of DCE estimates.

Estimating willingness-to-pay for health care: A discrete choice experiment accounting for non-attendance to the cost attribute.

RATIONALE, AIMS, AND OBJECTIVES: The literature suggests that discrete choice experiments (DCEs) are a preferable method for estimating willingness-to-pay (WTP) values, as they may avoid some biases often observed in contingent valuation surveys, such as protest and strategic behaviour. However, the choice studies have demonstrated that attribute non-attendance may be a serious issue that leads to biased WTP estimates. METHOD: A DCE was used to estimate patients' WTP for dental care at the dental school clinic. The endogenous attribute attendance (EAA) model was used to estimate WTP for dental care attributes, while accounting for non-attendance to the cost attribute. RESULTS: The EAA model revealed that almost every second respondent had ignored the cost attribute when making choices, indicating that patients were very sensitive to other characteristics of dental care. Dental care providers should pay particular attention to providing a detailed explanation of treatment to their patients, as this was the most valued attribute of dental care. The welfare estimates from the EAA model, which accounted for non-attendance to the cost attribute, were more than two times lower than welfare estimates from a traditional multinomial logit model and mixed logit model estimated in WTP space. CONCLUSIONS: The findings raise concerns for derived WTP estimates in DCE studies that did not consider non-attendance to the cost attribute during the estimation process. Non-attendance to the cost attribute overestimates WTP values, even if being motivated by the true preferences of respondents.

Valuing the delivery of dental care: Heterogeneity in patients' preferences and willingness-to-pay for dental care attributes.

OBJECTIVES: To examine the amount of heterogeneity in patients' preferences for dental care, what factors affect their preferences, and how much they would be willing to pay for improvement in specific dental care attributes. METHODS: A discrete choice experiment (DCE) was used to elicit patients' preferences. Three alternative dental care services that differed in the type of care provider, treatment explanation, dental staff behavior, waiting time and treatment cost were described to patients. Patients (n=265) were asked to choose their preferred alternative. The study was conducted at a public dental clinic of the School of Dental Medicine, University of Zagreb. Mixed logit and latent class models were used for analysis. RESULTS: On average, the patients would be willing to pay €45 for getting a detailed explanation of treatment over no explanation. This was the most valued attribute of dental care, followed by dental staff behavior with marginal willingness-to-pay (WTP) of €28. Dental care provided by the faculty members and private dental care were valued similarly, while student-provided care was valued €23 less. Patients also disliked longer waiting time in the office, but this was the least important attribute. Four classes of patients with distinct preferences for dental care were identified. Older and/or more educated patients tended to give relatively less importance to treatment explanation. Higher education was also associated with a higher propensity to substitute faculty dental care with the private care providers. CONCLUSIONS: Large heterogeneity in patients' preferences was detected. Understanding their preferences may improve the delivery of dental care. CLINICAL SIGNIFICANCE: Dental care providers should pay particular attention to providing a detailed treatment explanation to their patients. Dental care for older and/or more educated patients should be more attentive to interpersonal characteristics. Faculty dental care provided by faculty members could be price competitive to private care, and student-provided care more affordable.

Effects of bleaching agent on physical and aesthetic properties of restorative materials.

To investigate the effects of bleaching agent on microhardness, color and light transmission of different restorative materials. Specimens (n=20) of Tetric EvoCeram (TEC), Tetric EvoCeram Bulk Fill (TECBF) and Equia Fill (EQUIA) were treated with either 40% hydrogen peroxide Opalesence Boost or destilled water for 45 min. Specimens were stained in tea solution or stored in deionized water for one and two weeks. Color, microhardness and light transmission were monitored at the baseline, after the bleaching and after the tea immersion or storage in deionized water. After the bleaching a significant reduction in surface microhardness (p<0.001) was recorded for all materials. Clinically visible color change (ΔE>3) was observed after the bleaching and after treatment in tea solution, but only in EQUIA samples. The absorption coefficient was the largest for the samples stained in tea solution. Bleaching can affect the microhardness and color of fillings; therefore, they should be sometimes replaced.

Accounting for measurement reliability to improve the quality of inference in dental microhardness research: a worked example.

OBJECTIVES: Dental microhardness experiments are influenced by unobserved factors related to the varying tooth characteristics that affect measurement reproducibility. This paper explores the appropriate analytical tools for modeling different sources of unobserved variability to reduce the biases encountered and increase the validity of microhardness studies. MATERIALS AND METHODS: The enamel microhardness of human third molars was measured by Vickers diamond. The effects of five bleaching agents-10, 16, and 30 % carbamide peroxide, and 25 and 38 % hydrogen peroxide-were examined, as well as the effect of artificial saliva and amorphous calcium phosphate. To account for both between- and within-tooth heterogeneity in evaluating treatment effects, the statistical analysis was performed in the mixed-effects framework, which also included the appropriate weighting procedure to adjust for confounding. The results were compared to those of the standard ANOVA model usually applied. RESULTS: The weighted mixed-effects model produced the parameter estimates of different magnitude and significance than the standard ANOVA model. The results of the former model were more intuitive, with more precise estimates and better fit. CONCLUSIONS: Confounding could seriously bias the study outcomes, highlighting the need for more robust statistical procedures in dental research that account for the measurement reliability. The presented framework is more flexible and informative than existing analytical techniques and may improve the quality of inference in dental research. CLINICAL RELEVANCE: Reported results could be misleading if underlying heterogeneity of microhardness measurements is not taken into account. The confidence in treatment outcomes could be increased by applying the framework presented.

Real-time local experimental monitoring of the bleaching process.

OBJECTIVE: The purpose of this article was to investigate a new setup for tooth bleaching and monitoring of the same process in real time, so to prevent overbleaching and related sideeffects of the bleaching procedure. BACKGROUND DATA: So far, known bleaching procedures cannot simultaneously monitor and perform the bleaching process or provide any local control over bleaching. MATERIALS AND METHODS: The experimental setup was developed at the Institute of Physics, Zagreb. The setup consists of a camera, a controller, and optical fibers. The bleaching was performed with 25% hydrogen peroxide activated by ultraviolet light diodes, and the light for monitoring was emitted by white light diodes. The collected light was analyzed using a red-green-blue (RGB) index. A K-type thermocouple was used for temperature measurements. Pastilles made from hydroxylapatite powder as well as human teeth served as experimental objects. RESULTS: Optimal bleaching time substantially varied among differently stained specimens. To reach reference color (A1, Chromascop shade guide), measured as an RGB index, bleaching time for pastilles ranged from 8 to >20 min, whereas for teeth it ranged from 3.5 to >20 min. The reflected light intensity of each R, G, and B component at the end of bleaching process (after 20 min) had increased up to 56% of the baseline intensity. CONCLUSIONS: The presented experimental setup provides essential information about when to stop the bleaching process to achieve the desired optical results so that the bleaching process can be completely responsive to the characteristics of every individual, leading to more satisfying results.

Temperature rise during experimental light-activated bleaching.

The purpose of this study was to evaluate the surface and intrapulpal temperatures after treatments with different bleaching gels subjected to different types of light activation. A K-type thermocouple and infrared thermometer were used to measure the temperature increase during the 15- or 30-min treatment period. Light-emitting diode with a center wavelength of 405 nm (LED405), organic light-emitting diode (OLED), and femtosecond laser were tested and compared to ZOOM2. The tooth surface was treated with five bleaching agents and Vaseline which served as a control.The generalized estimating equation (GEE) model was applied for testing the differences in temperature increase. The ZOOM2 light source led to the largest increase in mean pulpal and tooth surface temperatures of 21.1 and 22.8 °C, followed by focused femtosecond laser which increased the pulpal and surface temperatures by up to 15.7 and 16.8 °C. Treatments with unfocused femtosecond laser, LED405, and OLED induced significantly lower mean temperature increases (p < 0.001 for each comparison with ZOOM2 and focused femtosecond laser), both in the pulp chamber (up to 2.7, 2.5, and 1.4 °C) and at the tooth surface (up to 3.2, 3.4, and 1.8 °C). Significant differences between pulp chamber and tooth surface measurements were obtained for all types of bleaching gel, during treatments with ZOOM2 (p < 0.001), LED405 (p < 0.001), and unfocused (p < 0.001) and focused femtosecond laser (p ≤ 0.002). Different bleaching agents or Vaseline can serve as an isolating layer. Focused femtosecond laser and ZOOM2 produced large temperature increases in the pulp chamber and at the tooth surface. Caution is advised when using these types of light activation, while LED405, OLED, and unfocused femtosecond laser could be safely used.

Optical effects of experimental light-activated bleaching procedures.

OBJECTIVE: The purpose of this study was to evaluate the efficiency of experimental light-activated bleaching procedures. BACKGROUND DATA: The improved color effect may be attributed to the potential photochemical effect of light-emitting diode (LED405), organic LED (OLED), and femtosecond laser rather than to the photothermal effect of conventional lights used for tooth bleaching. MATERIALS AND METHODS: Specially made pastilles of hydroxylapatite were immersed in green tea for 8 h and randomly divided into four groups (n=50) specified by the type of light source applied during a 30 min bleaching treatment: LED405, OLED, and femtosecond laser, or its absence (control group). Each group was treated with five bleaching gels: 10%, 16%, and 30% carbamide peroxide (CP), and 25% and 38% hydrogen peroxide (HP). Changes in color were determined by red-green-blue (RGB) colorimeter and ultraviolet-visible-near-infrared (UV/Vis/NIR) spectroscopy. RESULTS: Regardless of the applied bleaching gel, LED405 produced a larger increase in the value of RGB index than did OLED and bleaching without light activation (p<0.05). Femtosecond laser also produced significantly better results in combination with 16% CP and 38% HP. Furthermore, application of a bleaching agent with a higher concentration of peroxide boosted the value of the RGB index. Spectroscopic measurements revealed similar results, although treatments with OLED were rated relatively better than in RGB analysis. CONCLUSIONS: The mechanisms of light-activated bleaching procedures had a significant effect on the color change. The bleaching activation with LED405 and higher concentrations of peroxide in bleaching agents promoted better whitening effect.

Surface changes of enamel and dentin after two different bleaching procedures.

Bleaching agents have effect on chemical/physical and morphological structure of enamel and dentin that must be taken into account when this therapy is used. The aim of this in vitro study was to evaluate the effects of two bleaching agents containing a high concentration of hydrogen peroxide for professional use on human enamel and dentin surface and to evaluate the potential remineralizing effect of amorphous calcium phosphate gel (ACP). Twenty-five human third molars were divided into two groups and dissected in half and both surfaces were bleached with either ZOOM2 or Opalescence BOOST for 3 x 15 minutes. Vickers microhardness of enamel and dentin was measured before, after the bleaching treatment, and after treatment with artificial saliva and ACP gel or 2-week storage in deionized water. Surface microstructure was evaluated using scanning electron microscopy. The mixed model ANOVA and Wilcoxon Rank Sum test were used. Both bleaching agents showed significant reduction in surface microhardness (p < 0.001 for both BOOST and ZOOM2 application). ZOOM2, which had a lower pH value showed greater decrease in surface microhardness (p = 0.005) compared to BOOST. Post-treatment with artificial saliva and ACP showed significant increase in surface microhardness (p < 0.001). After the bleaching procedure, enamel and dentin surface microstructure showed mild or slight alterations with no loss of superficial structure. In conclusion, both bleaching agents resulted in reduction in surface enamel and dentin microhardness. Treatment with ACP led to increase in surface microhardness, improved surface roughness, and enhanced remineralization of the hard dental tissues.