Acceptability Threshold Research Articles

Quantitative examination of factors influencing the colour reproduction ability of lithium disilicate glass-ceramics

BackgroundEffects of ceramic translucency, layer thickness, and substrate colour on the shade of lithium disilicate glass-ceramic restorations proved to be significant in several studies, however, quantitative, numerical results on the relationship between the colour difference and these parameters are still lacking. The purpose of this in vitro study was to quantitatively determine how the colour reproduction ability of a lithium disilicate glass-ceramic is affected by its translucency, layer thickness, and substrate colour.MethodsCeramic samples were prepared from A2 shade IPS e.max CAD blocks with high and low translucencies (HT and LT) in a thickness range of 0.5–2.5 mm (+/- 0.05 mm). Layered samples were acquired utilizing composite substrates in 9 shades; transparent try-in paste was used. The spectral reflectance of the specimens was assessed under D65 standard illumination with a Konica Minolta CM-3720d spectrophotometer. The CIEDE2000 colour difference (ΔE00) between two samples was analysed using perceptibility and acceptability thresholds set at 50:50%. Statistical analysis involved linear regression analysis and the Kruskal–Wallis test.ResultsAn increase in the thickness of 0.5 mm reduced the ΔE00 of the HT samples to 72.8%, and that of the T samples to 71.1% (p < 0.0001). 7 substrates with HT and LT specimens had significantly different results from the mean (p < 0.05). A thickness of 0.5 mm is not sufficient to achieve an acceptable result at any level of translucency, while the low translucency ceramic at a thickness of 1.5 mm gave acceptable results, except for severely discoloured substrates (ND8 and ND9).ConclusionsThe colour reproduction ability of lithium disilicate glass-ceramics is significantly affected by their translucency, layer thickness, and 7 substrates out of 9 substrates examined.

Design overview and usability of the codesigned My Surgical Pathway E-health tool for supporting patient self-managed surgical preparation and recovery

IntroductionSurgery plays a critical role in global health, often facing significant quality challenges such as high rates of postoperative complications, variability in patient outcomes, and inconsistencies in care pathways, due to the complex nature of the perioperative journey. The My Surgical Pathway (MSP) app is an e-health intervention designed to address these challenges by supporting self-management and integrated care throughout the entire perioperative journey. This study aims to describe the features and functions of MSP and report on the results of usability testing from both patients and healthcare workers. MethodsThis mixed-methods study evaluated the usability of the My Surgical Pathway (MSP) app using quantitative surveys, qualitative feedback, and observation data from patients and healthcare workers. Structured 2-hour user testing sessions included interaction with the MSP app, completion of the User Version of the Mobile Application Rating Scale (uMARS), and think-aloud activities. Data analysis combined quantitative and qualitative insights to identify usability issues and inform potential improvements. ResultsThe mixed-method user-testing evaluation of the co-designed e-health intervention revealed high overall app quality scores, with an average of 4.50 out of 5. All user-type interfaces received mean scores above the minimum acceptability threshold of 3.0, demonstrating the intervention's efficacy in supporting patient surgery journeys, enhancing healthcare worker coordination, and meeting diverse user needs. Notably, the highest individual item scores were for credibility of source (4.92) and interactivity (4.85), highlighting the application's reliability and engaging nature. ConclusionsThe study evaluated the 'My Surgical Pathway' (MSP) e-health intervention, co-designed with consumers and healthcare workers to support self-management of surgical care. Results indicate high user satisfaction, with an overall app quality score of 4.50 out of 5 on the uMARS tool. Users praised MSP's engagement, education, and responsiveness, highlighting its potential to improve patient experiences and clinician workflows. Recommendations for future research include expanding participant diversity and hospital settings, and employing longitudinal designs for a comprehensive evaluation.

Color stability of CAD-CAM hybrid ceramic materials following immersion in artificial saliva and wine.

To examine the color stability of 3D-printed and milled, interim, and definitive, restorative materials after immersion in artificial saliva and wine for 1, 3, and 6 months. The study used a 2 × 5 factorial design with 10 subgroups, including 2 immersion liquids (artificial saliva and wine) and 5 manufacturing technology and restorative material combinations (n = 10). Color measurements were taken using a contact-type digital spectrophotometer (CM-2600d Spectrophotometer; Konica Minolta Healthcare Americas Inc) before immersion and at 1 month (T1), 3 months (T3), and 6 months (T6) after immersion. The CIE2000 system was used to calculate quantitative measurements of color differences in ΔE00, and comparisons were made to the acceptability threshold (AT) and perceptibility threshold (PT). Repeated measures of ANOVA (α = 0.05) were used to compare differences in color changes between manufacturing technology/restorative material-immersion liquid combinations at T1, T3, and T6. To compare the effect of immersion liquid and time on the manufacturing technology/restorative material groups, the ΔE00 values were compared to the PT of 0.8 and the AT of 1.8. Wine caused significant color changes in ΔE00 values beyond the PT and AT values in all groups at all time intervals, except for the AT value of milled definitive crowns (hybrid nano-ceramic material). Wine immersion caused significant ΔE00 for all manufacturing technology/restorative material groups at all time intervals (1 month, 3 months, and 6 months) when compared to artificial saliva immersion (all p < 0.001). Upon exposure to artificial saliva, 80%-100% of samples from all groups remained within the acceptable and perceptible color change thresholds. The wine had significant chromogenic effects on all tested restorative materials, however, the milled definitive crowns (hybrid nano-ceramic material) showed the greatest color stability. For patients with heavy wine consumption, 3D-printed definitive crowns (hybrid ceramic-filled material) may show discoloration exceeding acceptable and perceptible color change limits.

Natural dentifrices: how can prolonged toothbrushing influence enamel color and surface roughness?

This study evaluated the color change (ΔE00) and surface roughness (Ra) of enamel submitted to prolonged toothbrushing with natural non-fluoride dentifrices. Five groups of bovine teeth (n=10) were brushed with a control dentifrice: (C) Colgate Total 12 – Colgate; and four natural dentifrices: (R) Restore – Jeunesse; (OG) OnGuard – doTerra; (OC) OzonCare – Philozon; and (N) Natural activated charcoal – Suavetex. Mechanical toothbrushing simulated one month (T1), six months (T2), one year (T3), and two years (T4) of product use. ΔE00 and Ra were measured before and after toothbrushing. Two-way repeated measures ANOVA and Tukey's test were performed. Dentifrice (p&lt;0.001), toothbrushing time (p=0.004), and their interaction (p=0.031) influenced color change (ΔE00). Natural dentifrices promoted similar color change and Ra to the traditional product. After six months of simulated toothbrushing, OG promoted more color changes than N and R. Only OG and R reached ΔE00 above the acceptability threshold. OC and N dentifrices generated Ra above the limit of clinical roughness from T2. Toothbrushing with natural toothpaste for up to two years causes similar enamel color changes and roughness to the traditional product.

Level of Agreement in Subjective Selection of Gingival Colour

Background and Objectives: Primary outcome: To assess the level of agreement between the objective and subjective methods for recording gingival colour in each area of the gingiva. Secondary outcome: To compare performance of the subjective visual method of gingival colour selection by a male observer and a female observer. Materials and Methods: A chromatic study was conducted on a total of 101 participants, in five gingival zones, from the free gingival margin to the mucogingival line, using a SpectroShade Micro spectrophotometer for the objective method and 21 ad hoc ceramic gingival shade tabs for the subjective method. A man and a woman of the same age, with the same amount of clinical experience in dentistry, selected the tab that most resembled the colour of participants’ gingiva. The “chromatic error” was then assessed by calculating the colour difference (using the Euclidean and CIEDE2000 formulae) between the CIELAB coordinates of the shade tab selected and the objective coordinates of the gingiva. The unweighted Kappa coefficient was used to calculate the level of agreement between observers. Results: For the male observer, the mean chromatic errors varied between ΔEab* 10.3 and 13.1 units, while for the female observer, the mean errors varied between ΔEab* 11.1 and 12.8: these differences were not statistically significant. Similarly, no statistically significant differences were found between the mean chromatic errors for the five gingival zones in either the male operator (p = 0.100) or the female operator (p = 0.093). The minimum level of agreement (unweighted Kappa) between the observers ranged from 0.1 to 0.4. Conclusions: Subjective selection of gingival colour was very inaccurate, by both the male observer and the female observer, for any area of the gingiva, with no differences identified between them. The level of agreement between the observers was low. These findings suggest that gingival colour should not be determined using solely subjective methods, given that the chromatic errors significantly exceeded the clinical acceptability threshold for gingiva (4.1 units for ΔEab* and 2.9 units for ΔE00). Both observers showed a tendency to select gingival shade tabs that were redder and bluer than the objective colours.

Perceptibility and acceptability of lightness difference of a single maxillary central incisor.

The aim of this study was to assess the lightness difference perceptibility and acceptability thresholds, for a single maxillary central incisor, and to investigate possible differences in these thresholds regarding the direction (+ΔL* vs. -ΔL*), the observer group (dentists vs. laypersons), and the gender and age of the observers. A series of images with varying lightness (L*), were created by altering the right maxillary central incisor of a male Caucasian, on a frontal view full-portrait image. Digital modification of one central incisor by 1 ΔL* unit resulted in 15 different images: one control, seven with increased and seven with decreased lightness. The images were presented in random order, on a digitally calibrated monitor, to 158 observers, grouped into 79 dentists, and 79 laypersons, who were asked to evaluate every image and answer whether they perceive a difference and if yes, whether they accept this difference. A multifactorial analysis of covariance was performed to analyze the perception and acceptance of any difference in the central incisors and to estimate the thresholds. The statistical significance level was α = 0.05. Overall, the magnitude of ΔL*, direction of ΔL*, observer group and age were each significant (p < 0.001), as was gender (p = 0.03). The effect of the magnitude of ΔL* interacted with its direction and the observer group (p = 0.045), and the effect of age interacted with the direction of ΔL*, and the gender and the group of the observers. Estimated 50%:50% perceptibility thresholds ranged from 0.1 to 2.7, and 50%:50% acceptability thresholds ranged from 2.3 to 4.5. Overall, dentists perceived lightness differences at lower magnitudes than laypersons; difference in lightness was perceived and accepted at lower magnitudes when the tooth become lighter instead of darker; and female observers perceived and accepted lightness differences at lower magnitudes compared to males. As age increased overall, differences of lightness were perceived and accepted at higher magnitudes. Perceptibility and acceptability of lightness differences of a single maxillary central incisor are affected by the magnitude and the direction of lightness change, as well as the gender, the age, and the type of the observers. Even small changes in lightness are perceivable; however, thresholds of perception and acceptance are dependent on the magnitude and the direction of change and are also dependent on the observer, with women, dentists and younger people perceiving and accepting changes at lower magnitudes of ΔL*.

Factors associated with never treatment and acceptability of mass drug administration for the elimination of lymphatic filariasis in Guyana, 2021.

Guyana remains one of four countries in the Americas endemic for lymphatic filariasis (LF). Elimination of LF requires repeated annual mass drug administration (MDA) with sufficient levels of coverage for success. This study assesses the acceptability and never treatment of LF MDA using data from a routine assessment survey in 2021. A subset of individuals, over 20 years of age (n = 2498), were selected to receive an expanded questionnaire to examine factors associated with acceptability and never treatment. Assessed factors include respondent demographics, knowledge, risk perceptions of LF, and opinions on the MDA programme. The majority (73%) of those with scores above the acceptability threshold (score ≥22.5) reported participating in MDA two or more times. Factors strongly and positively associated with scoring above the acceptability threshold include beliefs in importance of participation in MDA for their community (aOR = 2.8, 95%CI (1.1-7.2)), perception of importance of LF treatment (6.9 (3.2-14.7)), receiving treatment in 2021 (2.9 (1.5-5.4)), and the number of self-reported times taking treatment for LF (2.2 (1.1-4.4)). Ten percent of respondents participated in the MDA for the first time in 2021, while 15% reported never treatment during any round of LF MDA. Three factors were statistically associated with participation in MDA across the two levels of the models (level 1: took LF treatment once versus never, and level 2: took LF treatment twice versus never) included: 1) scoring above the acceptability threshold (aOR = 6.2, 95%CI(3.8-10.0)), 2) self-reported importance of participation in MDA for their community (7.1 (2.9-17.8)), and 3) personal beliefs that they should take LF treatment even if they are not sick (2.6 (1.7-3.9)). As Guyana moves closer to LF elimination, these results provide further insight and understanding into programmatic results and could inform further action following MDA activities-particularly if an approach is needed to address never treatment during MDA.

Effect of Simulated Gastric Juice on Color Stability of Different Artificial Teeth

Objective: The current study aimed to evaluate the gastric juice effect on the artificial teeth discoloration in patients with gastroesophageal reflux disease (GERD) under in vitro conditions.&#x0D; Methods: Three different artificial teeth (Ivostar, Vivodent PE, Phonares II) were used in the study (n=12). A spectrophotometer (VITA Easyshade Compact; VITA Zahnfabrik, Bad Säckingen, Germany) was used for initial color measurements after keeping the specimens in distilled water for 24 h. Then, they were immersed in 5% hydrochloric acid (HCl) at 37°C (pH=2) for 91 h and the color measurements were&#x0D; repeated. The CIEDE2000 formulation was used to calculate the color changes. The statistical analysis was performed with one-way ANOVA and Tukey HSD tests.&#x0D; Results: Although the color differences of Vivodent PE and Phonares II materials did not exhibit a statistically significant difference (p=.95; p &gt; .05), there was a significant difference between Ivostar and other materials (p=.02, p=.01). The 50:50% detection threshold (PT) was exceeded with Vivodent PE and Phonares II materials, while the 50:50% acceptability threshold (AT) was exceeded with Ivostar material.&#x0D; Conclusion: After exposure to gastric acid, all groups exhibited perceptible color differences. In the group of acrylic resin artificial teeth, the color difference was above acceptability threshold and would be better to improve. While the acrylic resin artificial teeth exhibited the highest discoloration, artificial teeth containing nanohybrid composite resin showed the least discoloration. These should be considered in&#x0D; the selection of artificial teeth in patients with GERD.

Color stability of pressed lithium disilicate ceramics under repeated firings evaluated by different methods.

The aim of this study was to determine and compare color differences of pressed lithium disilicate ceramic specimens after repeated firing cycles. An additional objective was to determine and evaluate correlation of CIEDE2000 values analyzed by X-Rite Color i5 Spectrophotometer, VITA EasyShade Advance 4.0 and Adobe Photoshop. Tile specimens (N=36) with 8 x 10 x 1.5mm dimensions were prepared by IPS e.max Press lithium disilicate MT Monochromatic ingots and IPS e.max Multi Press lithium disilicate Multichromatic ingots. Specimens were exposed to 7 repeated firing cycles. Color analysis was performed after the 1st, 2nd, 3rd, 5th, and 7th firing cycles. CIE L*a*b* values were measured by X-Rite Color i5 Spectrophotometer, VITA EasyShade Advance 4.0 and Adobe Photoshop. CIE DE*2000 (ΔE*00) was calculated to estimate color differences. Linear regression and multiple comparison analysis (Tukey's HSD test) showed a statistically significant (p<.001) color difference ΔE*00 after multiple firing cycles. Statistically significant differences (p<.05) were also noted in different shade groups and between different instruments used for shade evaluation. Moreover, significant differences (p<.05) were found in interactive effects between different shades tested by different instrument, different shades tested after multiple firing cycles and different instruments after multiple firing cycles. Lithium disilicate material shows significant color differences after repeated firing cycles tested by three color analysis instruments. Measuring instruments used to evaluate CIE L*a*b* color values showed significant differences in color values analysis, which may lead to altered level of interpretation, particularly to determine perceptibility and clinical acceptability thresholds.

Chlorine Water Taste Threshold and Acceptability among Indigenous and Non-Indigenous Populations in Rural Panama.

Although gains in access to water services over the past two decades have been large, more than two billion people still lack access to safely managed drinking water. This study examines and compares free chlorine taste and acceptability thresholds of rural Indigenous Ngäbe and rural Latino Panamanians to study if taste aversion may be a limiting factor in chlorination of community systems in Panama using the three-alternative forced choice test methodology. This study is the first to establish a best-estimate taste threshold for a rural Indigenous group and the only study in Latin America to report best-estimate taste thresholds using those methods. Median taste thresholds were 0.87 mg/L Cl2 for Indigenous Ngäbe participants (n = 82) and 1.64 mg/L Cl2 for Latino participants (n = 64), higher than both the minimum concentration for biologically safe water (0.2 mg/L) and the recommended concentration range in Panama (0.3-0.8 mg/L). Median acceptability thresholds were established much higher than taste thresholds at 3.45 mg/L Cl2. The results show that the ability to accurately taste chlorine may not be the limiting factor for adoption of safe water initiatives in remote and Indigenous communities.

Stereotactic Radiation Therapy in Early Non–Small Cell Lung Cancer and Interstitial Lung Disease

Patients with interstitial lung disease (ILD) and early-stage non-small cell lung cancer (NSCLC) have been reported to be at high risk of toxic effects after stereotactic ablative radiotherapy (SABR), but for many patients, there are limited alternative treatment options. To prospectively assess the benefits and toxic effects of SABR in this patient population. This prospective cohort study was conducted at 6 academic radiation oncology institutions, 5 in Canada and 1 in Scotland, with accrual between March 7, 2019, and January 12, 2022. Patients aged 18 years or older with fibrotic ILD and a diagnosis of T1-2N0 NSCLC who were not candidates for surgical resection were enrolled. Patients were treated with SABR to a dose of 50 Gy in 5 fractions every other day. The study prespecified that SABR would be considered worthwhile if median overall survival-the primary end point-was longer than 1 year, with a grade 3 to 4 risk of toxic effects less than 35% and a grade 5 risk of toxic effects less than 15%. Secondary end points included toxic effects, progression-free survival (PFS), local control (LC), quality-of-life outcomes, and changes in pulmonary function. Intention-to-treat analysis was conducted. Thirty-nine patients enrolled and received SABR. Median age was 78 (IQR, 67-83) years and 59% (n = 23) were male. At baseline, 70% (26 of 37) of patients reported dyspnea, median forced expiratory volume in first second of expiration was 80% (IQR, 66%-90%) predicted, median forced vital capacity was 84% (IQR, 69%-94%) predicted, and median diffusion capacity of the lung for carbon monoxide was 49% (IQR, 38%-61%) predicted. Median follow-up was 19 (IQR, 14-25) months. Overall survival at 1 year was 79% (95%, CI 62%-89%; P < .001 vs the unacceptable rate), and median overall survival was 25 months (95% CI, 14 months to not reached). Median PFS was 19 months (95% CI, 13-28 months), and 2-year LC was 92% (95% CI, 69%-98%). Adverse event rates (highest grade per patient) were grade 1 to 2: n = 12 (31%), grade 3: n = 4 (10%), grade 4: n = 0, and grade 5: n = 3 (7.7%, all due to respiratory deterioration). In this trial, use of SABR in patients with fibrotic ILD met the prespecified acceptability thresholds for both toxicity and efficacy, supporting the use of SABR for curative-intent treatment after a careful discussion of risks and benefits. ClinicalTrials.gov Identifier: NCT03485378.

Evaluation of the Practices of Anesthesiologists in the city of Kinshasa on the Management of Post-Operative Pain

Introduction: The management of Postoperative Pain represents a public health problem. Throughout the world, this subject is the subject of numerous studies which emphasize the need to treat pain and evaluate practices. However, despite the progress made in the understanding of pain mechanisms, analgesic techniques, and the multiple recommendations made by learned societies in many countries, Post-Operative Pain is insufficiently addressed. The objective of our work was to evaluate the practices of anesthesiologists in the field of postoperative pain management in two health institutions in the city province of Kinshasa which are the Saint Joseph Hospital of Limeté and the Ngaliema Clinic. Method: The population of our study consisted of 23 anesthesiologists, 14 of whom were the subject of our occasional sample. To collect the data, we used the survey method supported by the techniques of direct observation, interviews and documentary analysis. At the end of our survey, the data was processed using descriptive analysis by calculating percentages and the average. Results: Regarding socio-demographic characteristics, the majority of subjects surveyed were male at level A1 (graduate, equivalent of bacc+3) and with professional experience of 10 years or more. Concerning the management of Post-Operative Pain, 48.5% provided the actual management of Post-Operative Pain; 17.1% provided pre-anesthetic information. Overall, the management of postoperative pain was achieved at 32.8%. Conclusion: Referring to our acceptability threshold set at 80%, we can affirm that the management of Postoperative Pain is not provided satisfactorily by the anesthesiologists of the two hospital institutions selected for the study.

The Efficacy of Different Laser Applications on Dentin Sealing in Preventing Discoloration Induced by Mineral Trioxide Aggregate.

The aim of this in vitro study was to evaluate the effect of the pre-application of a dentin-bonding agent and the application of different lasers on the prevention of tooth discoloration caused by mineral trioxide aggregate (MTA) in the presence of blood. Sixty extracted human anterior teeth were selected, with root lengths standardized to 10 mm and root canals shaped using Gates-Glidden drills #3 to #5. The samples were divided into six groups (n = 10): Group 1 with no surface treatment and Groups 2 to 6 with Optibond universal adhesive and Neodymium yttrium aluminum garnet (Nd:YAG), Erbium yttrium aluminum garnet (Er:YAG), Erbium-chromium-yttrium-scandium-gallium-garnet (Er:Cr:YSGG), and diode laser applications, respectively. Root canals were filled with fresh human blood, and ProRoot MTA and a collagen barrier were then placed. Color changes were measured with a spectrophotometer at 0, 7, 30, 90, and 180 days post MTA placement. Color differences (∆E) were analyzed using a two-factor mixed-design ANOVA with the Sidak method (p = 0.05). All treatment groups exhibited discoloration above the acceptability threshold. Although all treatment approaches exhibited less color change compared to the control group (p < 0.05), there was no significant difference among them in terms of preventing color change (p > 0.05). It was determined that none of the methods could guarantee 100% prevention of discoloration caused by MTA-blood contact.

Photocolorimetry for full crown central incisor shade matching

Introduction The objective of this case series report is color matching of the central incisors all-ceramic crowns and determine the color difference between those crowns and contralateral or neighboring intact natural incisor using the ?Eab value from CIELab formula. Case Report The subject of this color assessment was all-ceramic crowns for central incisors for three young female patients. The intact natural incisors were used as the target shade for the all-ceramic crown. After tooth preparation and intraoral scan, everything was done at once, regarding the design of restoration and model. For these cases, we used Ivoclar ZirCAD PRIME multi A1 (Ivoclar, Schaan, Liechtenstein) block. For proper shade mapping polarized picture with grey card for digital calibration is necessary as well as one standard picture for mapping the color effects. For tooth color mapping we used the eLAB software (eLAB Prime, Freiburg im Breisgau, Germany). Highest ?Eab value for all three cases was 2.7 or less, which indicates that the color is clinically acceptable, considering acceptability threshold value of less than 2.7 (three-year follow-up confirmed acceptable color appearance. Conclusion Following recommended protocol based on the eLAB software software (eLAB Prime), clinically acceptable color of the all-ceramic crown were obtained.

Influence of different palatal morphologies on the accuracy of intraoral scanning of the edentulous maxilla: A three-dimensional analysis.

This study investigated the influence of different palatal morphologies on the accuracy of intraoral scanning (TRIOS 4) of edentulous maxillae. Six typodonts were fabricated for different palatal morphologies with flat (F), medium (M), and deep (D) palates, with palatal wrinkles (W), or smooth palates (S), resulting in six groups: WF, WM, WD and SF, SM, SD. Ten scans were performed for each group; standard tessellation language files obtained were imported into a software to measure trueness and precision in micrometer. Trueness was calculated as the mean of the standard deviation values obtained by superimposing each scan onto the reference scan. Precision was achieved by overlapping each scan with that with the best trueness in the group. Descriptive and post-hoc analyses were conducted. The mean values for trueness were as follows: WM=48.7±4.7, WD=161.7±18.4, WF=85.9±16, SM=48.1±2.4, SD=349.9±8.8, and SF=349.1±25.5. The precision values were as follows: WM=46.7±7.3, WD=46.9±9, WF=48.9±6.7, SM=46±2.7, SD=105.9±17.4, SF=72.6±10.8. Significant differences were observed for trueness between SM and SD (P < 0.001), SM and SF (P < 0.001), and WF and SF (P = 0.003); whereas for precision, significant differences were reported between WD and SD (P = 0.015). Regarding trueness and precision, no difference was found between WM and SM (P = 1.0). Medium palatal depth showed the best accuracy. The mean accuracy values were within the clinical acceptability thresholds for all palatal morphologies. The presence of rugae improved the precision of deeper palates and the trueness of flat palates. No differences were observed in the medium palates with or without rugae.

Evaluation of Effect of Tooth Brushing on the Surface Roughness of Different Implant Superstructure Materials: An In Vitro Study

Background This in vitro investigation aimed to evaluate and contrast the surface roughness of various implant superstructure materials before and after tooth brushing simulation.Objectives To evaluate the surface roughness of G1- PMMA Polymethyl Methacrylate G2- Polychrome composite and G3- Direct Metal Laser Sintering DMLS glazed Porcelain-Fused-to-Metal PFM restorative materials before and after brushing simulation.Methodology Six cuboid shaped specimens 10times10times2 mm were prepared from prepolymerized CADCAM Computer-aided design and Computer aided manufacturing PMMA CADCAM polychrome composite and conventional DMLS glazed porcelain fused metal N24. The specimens were subjected to 10000 brushing cycles simulating one year of tooth brushing using SD Mechatronik-Brushing Simulator ZM-3.8 and toothbrush amp toothpaste Colgate Palmolive Ltd. The surface roughness Ra was measured before and after brushing using Mitutoyo Surftest SJ-310 surface roughness analyzer.Results No significant change in surface roughness was found on CADCAM Polychrome composite after one year of simulated tooth brushing P gt0.05. However CADCAM PMMA and DMLS PFM demonstrated a significant increase in surface roughness P lt0.05.Conclusion Brushing led to an increase in the surface roughness of CADCAM PMMA and DMLS PFM. All surface roughness values were above the clinically acceptability threshold of 0.2 microm.

Analysis of Colour Differences Obtained by Acceptability and Perceptibility Threshold (Visual Method):-Review

Backgrounds: Various information about acceptability (AT) and perceptibility thresholds (PT) for colour differences (∆E) was reviewed in dental literatures. There is consensus that determining (∆E) is ideal for identifying AT and PT. However, there is confusion about which values should be used. The aim of this review was to determine the discrepancies in research results and the critical value of ∆E. Materials and methods: MEDLINE/PubMed and Google Scholar were screened for studies that investigated colour acceptability, perceptibility, ∆E, but were not sensitive to whether only AT or PT were used. 20 studies matched the study criteria and had been included in this review and clinical measurements were made using spectrophotometers. Result: Most studies evaluated PT using approximately ∆E = 0.8–1.7. In terms of AT which ranged between 1.8 and 3.7 as a maximum. Many recent studies evaluate AT00=1.8 according to the CIE2000 colour difference formula. Conclusion: Different formulas as ∆E00 (2000) or ∆Eab(lab) in colour expression may produce different results. The CIElAB formula (ΔEab) has greater evidence; however, current research recommends the CIE2000 formula ∆E. The absence of colourimetric control has a negative effect on overall product quality.

Effect of coffee thermal cycling on the surface properties and stainability of additively manufactured denture base resins in different layer thicknesses.

To compare the effect of coffee thermal cycling on surface roughness (Ra), Vickers microhardness (MH), and stainability of denture base resins additively manufactured in different layer thicknesses with those of subtractively manufactured denture base materials. Eighty disk-shaped specimens (Ø10×2mm) were fabricated from two subtractively (Merz M-PM [SM-M] and G-CAM [SM-G]) and three additively (NextDent 3D+ [50µm, AM-N-50; 100µm, AM-N-100], FREEPRINT Denture [50µm, AM-F-50; 100µm, AM-F-100], and Denturetec [50µm, AM-S-50; 100µm, AM-S-100]) manufactured denture base materials (n = 10). Ra measurements were performed before and after polishing by using a non-contact optical profilometer, while MH values and color coordinates were measured after polishing. Specimens were then subjected to 5000 cycles of coffee thermal cycling, all measurements were repeated, and color differences (ΔE00) were calculated. A linear mixed effect model was used to analyze Ra and MH data, while one-way analysis of variance was used to analyze ΔE00 data (α = 0.05). Ra values were further evaluated according to a clinically acceptable threshold of 0.2µm, while ΔE00 values were evaluated according to perceptibility (1.72 units) and acceptability (4.08 units) thresholds. The interaction between the material type and the time interval affected both Ra and MH (p ≤ 0.001). Tested materials had their highest Ra before polishing (p ≤ 0.029). Before polishing, AM-F-100 had the highest, and SM-M and SM-G had the lowest Ra (p < 0.001). After polishing and after coffee thermal cycling, SM-G mostly had lower Ra than those of other materials (p ≤ 0.036). SM-G mostly had higher MH than that of other materials before and after coffee thermal cycling (p ≤ 0.025). Coffee thermal cycling reduced the MH of SM-M and increased that of AM-S-100 (p ≤ 0.024). AM-N-100 had higher ΔE00 than AM-F, AM-S-100, and SM-G (p ≤ 0.009), while AM-F and SM-G had lower ΔE00 than AM-S-50 and AM-N-50 (p ≤ 0.024). Polishing reduced the surface roughness of all materials, whereas the effect of coffee thermal cycling was nonsignificant. Most of the tested materials had acceptable surface roughness after polishing and after coffee thermal cycling according to the reported threshold. Layer thickness only affected the microhardness of tested additively manufactured resins, which was material-dependent. Subtractively manufactured specimens mostly had high microhardness and that of nonreinforced subtractively manufactured resin decreased after coffee thermal cycling. When reported color thresholds are considered, all materials had acceptable color stability.

The capacity of conservative preparations for lithium disilicate glass-ceramic laminates luted with different resin cements to mask different substrate shades: A minimally invasive esthetic approach.

Demonstrate the ability of 0.5 mm thickness lithium disilicate laminates associated with resin cement to mask different substrate saturations. 60 specimens (n = 5) were prepared with CAD/CAM lithium disilicate glass-ceramic IPS e.max CAD, 0.5 mm thick, in three degrees of translucency (HT, MT and LT); cemented by Variolink Esthetic LC Light+ (L) and Neutral (N) on composite resin substrates A1 and A4 shades. Color measurements were performed by a spectrophotometer (CM-3700d -Konica Minolta). The L*, a*, b* parameters of the tri-layer structure (laminate/ resin cement/ substrate) were used to calculate color difference ( ) by CIEDE2000 formula and Translucency Parameter ( ). This study adopted = 0.8, as perceptibility threshold (PT), and = 1.8, as acceptability threshold (AT). Statistical analyses were performed by one-way ANOVA and Tukey tests (a = 0.05). Color difference between resin cement shades showed statistical differences (p < 0.0001) and > 1.8 for all groups. Color difference between substrates saturations showed a significant statistical difference (p < 0.0001) and values above AT for all groups. The demonstrated significant statistical differences (p < 0.0001). The LTL combination, the opaquest set, showed the smallest values between substrate shades differences, however, above AT. The translucency of the lithium disilicate, the substrate saturation and the resin cement opacity influenced final color of restoration. The ceramic translucency impact on final color was reduced by opaque resin cement. Furthermore, the LT lithium disilicate and the Light+ resin cement reduced the translucency of the restoration, contributing to mask saturated substrate. This study shows the influence of conservative lithium disilicate laminates with different degrees of translucency associated with resin cement on final color of saturated substrate restorations. A minimally invasive esthetic protocol for masking substrates is demonstrated by associating low translucency ceramic laminates and opaque resin cement.

Surface roughness, optical properties, and microhardness of additively and subtractively manufactured CAD-CAM materials after brushing and coffee thermal cycling.

To evaluate the surface roughness, optical properties, and microhardness of additively or subtractively manufactured CAD-CAM materials after simulated brushing and coffee thermal cycling. Two additively manufactured resins (Crowntec, CT and VarseoSmile Crown Plus, VS) and 3 subtractively manufactured materials (a reinforced composite (Brilliant Crios, BC), a polymer-infiltrated ceramic network (Enamic, VE), and a feldspathic ceramic (Mark II, VM)) were used to fabricate disk-shaped specimens (Ø10×1-mm) (n = 10). Surface roughness, Vickers microhardness, and color coordinates were measured after polishing, while surface roughness was also measured before polishing. Specimens were then subjected to 25000 cycles of brushing and 10000 cycles of coffee thermal cycling, and measurements were repeated after each time interval. Color difference (ΔE00 ) and relative translucency parameter (RTP) were calculated. Robust analysis of variance test was used to evaluate surface roughness, ΔE00 , and RTP data, while generalized linear model analysis was used for microhardness data (α = 0.05). Material type and time interval interaction affected tested parameters (p ≤ 0.002). In addition, material type affected all parameters (p < 0.001) other than surface roughness (p = 0.051), and time interval affected surface roughness and microhardness values (p < 0.001). Tested materials mostly had their highest surface roughness before polishing (p ≤ 0.026); however, there was no clear trend regarding the roughness of materials within different time intervals along with ΔE00 and RTP values within materials or time intervals. VS and CT had the lowest microhardness regardless of the time interval, while the remaining materials were listed as VM, VE, and BC in decreasing order (p < 0.001). Coffee thermal cycling only reduced the microhardness of VM (p < 0.001). Tested additively manufactured resins can be considered more susceptible to simulated brushing and coffee thermal cycling than the other materials, given the fact that their surface roughness and ΔE00 values were higher than previously reported acceptability thresholds and because they had the lowest microhardness after all procedures were complete.