The level of evidence in prosthodontics in relation to author's characteristics: An analysis of three leading prosthodontics journals.

Purpose: The purpose of this study was to examine the level of evidence (LOE) characteristics and associated factors that change over time in three leading prosthodontics journals. Materials and methods: Articles published in The Journal of Prosthetic Dentistry (JPD), International Journal of Prosthodontics (IJP), and Journal of Prosthodontics (JP) in 2013 and 2020 were reviewed by eight independent reviewers. After applying exclusion and inclusion criteria, the number of authors, the corresponding author's educational degree, corresponding author's origin in each clinical research article were recorded. The included articles were rated by reviewers according to the level of evidence criteria and proposed level of evidence-associated factors. Descriptive statistics, univariable, and binary logistic regression analysis were performed to investigate dependent variables and potentially associated factors. All independent variables with a significant effect were analyzed by using a multivariable test. The entry and exit alpha level were set at αE = 0.15. The statistical significance was set at α = 0.05. Results: A total of 439 articles from 3 selected journals for the years studied met the inclusion criteria. The percentages of level 1, 2, 3, 4, and 5 articles were 2.7 %, 11.4 %, 9.6 %, 13.4 % and 62.9 %, respectively. Univariable analysis results demonstrated significant associations related to the number of authors (P = 0.005), the corresponding author's educational degree (P = 0.022), and the corresponding author's geographic origin (P = 0.042). Multivariable analysis results demonstrated significant associations related to the number of authors (P = 0.002), and the corresponding author's geographic origin (P = 0.014). Conclusions: The number of authors, CA degree, and CA origin had a significant association with the LOE of included prosthodontic studies. Although there was an increase in the number of publications from 2013 to 2020, the level of evidence trend shows no improvement over the years.

Automated facial landmark measurement using machine learning: A feasibility study.

STATEMENT OF PROBLEM: Information regarding facial landmark measurement using machine learning (ML) techniques in prosthodontics is lacking. PURPOSE: The objective of this study was to evaluate and compare the reliability, validity, and accuracy of facial anthropological measurements using both manual and ML landmark detection techniques. MATERIAL AND METHODS: Two-dimensional (2D) frontal full-face photographs of 50 men and 50 women were made. The interpupillary width (IPW), interlateral canthus width (LCW), intermedial canthus width (MCW), interalar width (IAW), and intercommissural width (ICW) were measured on 2D digital images using manual and ML methods. The automated measurements were recorded using a programming language (Python), and a convolutional neural network (CNN) model was trained to detect human facial landmarks. The obtained data from the manual and ML methods were analyzed using intraclass correlation coefficients (ICCs), the paired sample t test, Bland-Altman plots, and the Pearson correlation analysis (α=.05). RESULTS: Intrarater and interrater reliability values were greater than 0.90, indicating excellent reliability. The mean difference between the manual and ML measurements of IPW, MCW, IAW, and ICW was 0.02 mm, while it was 0.01 mm for LCW. No statistically significant differences were found between the measurements obtained by the manual and ML methods (P>.05). Highly significant positive correlations (P<.001) were obtained between the results of the manual and ML methods: (r=0.996[IPW], r=0.977[LCW], r=0.944[MCW], r=0.965[IAW], and r=0.997[ICW]). CONCLUSIONS: In the field of prosthodontics, the use of ML methods provides a reliable alternative to manual digital techniques for carrying out facial anthropometric measurements.

Influence of ceramic thickness, background and cement shade on the translucency of zirconia reinforced lithium silicate and lithium disilicate ceramics.

Background: Although, the influence of cement and background shade on the final color and translucency of zirconia reinforced lithium silicate (ZLS) and lithium disilicate (LDS) ceramics has been previously investigated, there is still little data on the translucency of LDS and ZLS ceramics in decreased thickness (0.4 and 0.6 mm). The aim of this study was to investigate ceramic thickness', background and cement shades' effects on the zirconia reinforced lithium silicate (ZLS) and lithium disilicate (LDS) ceramics' translucency. Material and Methods: Totally 160 square-shaped A1 shade LDS and ZLS samples produced in 0.4 and 0.6 mm thicknesses were cemented with light and neutral shade resin cement on A2 and A3 shade composite resin backgrounds. The color notations of specimen were measured and translucency parameter (TP) values were calculated. Factorial ANOVA and Tamhane's T2 multiple comparison statistical analyzes were used. Results: Highest TP values (11.82±0.97) were obtained in ZLS specimens that were 0.4 mm in thickness, cemented on A2 background with light shade resin cement. While, the lowest TP values (9.60±0.55) were calculated in LDS samples that had 0.6 mm thickness, cemented on A3 background with neutral shade resin cement. Conclusions: Material type, thickness, and background shade affected TP values of specimens. The cement and background shade used might change the final translucency of ZLS and LDS ceramics that had 0.4 and 0.6 mm thickness. Key words:Ceramics, lithium disilicate, spectrophotometry, zirconia, dental materials.

Machine learning model to predict the width of maxillary central incisor from anthropological measurements.

PURPOSE: To improve smile esthetics, clinicians should comprehensively analyze the face and ensure that the sizes selected for the maxillary anterior teeth are compatible with the available anthropological measurements. The inter commissural (ICW), interalar (IAW), intermedial-canthus (MCW), interlateral-canthus (LCW), and interpupillary (IPW) widths are used to determine the width of maxillary central incisors (CW). The aim of this study was to develop an automated approach using machine learning (ML) algorithms to predict central incisor width in a young Turkish population using anthropological measurements. This automation can contribute to digital dentistry and clinical decision-making. METHODS: In the initial phase of this cross-sectional study, several ML regression models-including multiple linear regression (MLR), multi-layer-perceptron (MLP), decision-tree (DT), and random forest (RF) models-were validated to confirm the central width prediction accuracy. Datasets containing only male and female measurements, as well as combined were considered for ML model implementation, and the performance of each model was evaluated for an unbiased population dataset. RESULTS: Compared with the other algorithms, the RF algorithm showed improved performance for all cases, with an accuracy of 96%, which represents the percentage of correct predictions. The plot reveals the applicability of the RF model in predicting the CW from anthropological measurements irrespective of the candidate's sex. CONCLUSIONS: These results demonstrated the possibility of predicting central incisor widths based on anthropometric measurements using ML models. The accurate central incisor width prediction from these trials also indicates the applicability of the proposed model to be deployed for enhanced clinical decision-making.

Comparison of 3D accuracy of three different digital intraoral scanners in full-arch implant impressions.

PURPOSE: This in vitro study aimed to evaluate the performance of digital intraoral scanners in a completely edentulous patient with angled and parallel implants. MATERIALS AND METHODS: A total of 6 implants were placed at angulations of 0°, 5°, 0°, 0°, 15°, and 0° in regions #36, #34, #32, #42, #44, and #46, respectively, in a completely edentulous mandibular polyurethane model. Then, the study model created by connecting a scan body on the implants was scanned using a model scanner, and a 3D reference model was obtained. Three different intraoral scanners were used for digital impressions (PS group, TR group, and CS group, n = 10 in each group). The distances and angles between the scan bodies in these measurement groups were measured. RESULTS: While the Primescan (PS) impression group had the highest accuracy with 38 µm, the values of 104 µm and 171 µm were obtained with Trios 4 IOSs (TR) and Carestream 3600 (CS), respectively (P = .001). The CS scanner constituted the impression group with the highest deviation in terms of accuracy. In terms of dimensional differences in the angle parameter, a statistically significant difference was revealed among the mean deviation angle values according to the scanners (P < .001). While the lowest angular deviation was obtained with the PS impression group with 0.185°, the values of 0.499° and 1.250° were obtained with TR and CS, respectively. No statistically significant difference was detected among the impression groups in terms of precision values (P > .05). CONCLUSION: A statistically significant difference was found among the three digital impression groups upon comparing the impression accuracy. Implant angulation affected the impression accuracy of the digital impression groups. The most accurate impressions in terms of both distance and angle deviation were obtained with the PS impression group.

Evaluation of the relationship between the geriatric anxiety and COVID-19 anxiety and fear levels in geriatric dental patients during the COVID-19 pandemic.

BACKGROUND: Illness, social isolation and loneliness may cause different psychological problems in the geriatric population, including depression and anxiety. Factors such as anxiety and fear can negatively affect dental treatment processes and prognoses. Thus, in terms of dental approach to geriatric individuals, it is important to be aware of the emotional processes the elderly may have experienced during the pandemic. OBJECTIVES: This study aimed to determine the relationship between the geriatric anxiety levels and the coronavirus disease 2019 (COVID-19) anxiety and fear levels in the geriatric population. MATERIAL AND METHODS: In this correlational study, 129 geriatric individuals were selected through the convenience sampling method. To gather the data, the Geriatric Anxiety Scale (GAS), the COVID-19 Anxiety Scale (CAS), the COVID-19 Fear Scale (CFS), and a questionnaire assessing demographic variables were used. Simple linear regression and Pearson's correlation coefficients were used to evaluate the relationships between the variables. RESULTS: The sample consisted of 70.5% males and 29.5% females aged ≥65 years. The GAS total score (15.64 ±9.34) and its 3 subscale scores were strongly correlated with the CAS and CFS scores. The GAS total score and its subscale scores had a significant linear regression with both the CAS and CFS scores (p < 0.001). CONCLUSIONS: An increase in the anxiety and fear levels associated with the pandemic was observed in geriatric individuals. Thus, it should be considered that geriatric individuals may encounter some difficulties during dental treatment and prosthetic rehabilitation after the pandemic. Therefore, it is important to normalize the anxiety levels with the help of professionals, and to implement interventions such as socialization, physical activity and meditation to help balance the anxiety levels.

Level of evidence and characteristics of clinical studies published in leading prosthodontics journals.

STATEMENT OF PROBLEM: Data on the level of evidence and the characteristics of studies published in peer-reviewed prosthodontic journals are lacking. PURPOSE: The purpose of this study was to investigate the characteristics and level of evidence (LOE) scores of studies published in 3 leading peer-reviewed prosthodontic journals. MATERIAL AND METHODS: Clinical studies published in the Journal of Prosthetic Dentistry (JPD), the Journal of Prosthodontics (JP), and the International Journal of Prosthodontics (IJP) in 2013 and 2020 were included in the analysis. Abstracts, letters to the editor, book reviews, and animal and laboratory studies were excluded from the investigation. For each study, design, type and LOE scores (Levels 1 to 5), publication year, impact factor (IF) of the journals, geographic origins of the first and corresponding authors, and funding status were recorded. Level 1 and Level 2 were defined as high evidence (HE), and Level 3, Level 4, and Level 5 were defined as low evidence (LE). Descriptive statistics and logistic regression analysis were performed (α=.05). RESULTS: Among the 439 studies included in the analysis, the proportion of HE and LE studies was 14.1% and 85.9%, respectively. According to univariate and multivariate analysis results, year of publication (P=.010 and P=.029), geographic origin of the corresponding author (P<.001), and funding status (P<.001 and P=.002) were significantly associated with the LOE of a study. However, the journal IF was not associated with LOE (P=.328). CONCLUSIONS: Although the number of HE studies in 3 leading prosthodontic journals has increased over time, the total number was still limited compared with LE studies. A further improvement in the overall LOE of clinical studies in prosthodontics is needed.

Effect of variations in facial flow curves on the perceptions of smile esthetics by laypeople.

STATEMENT OF PROBLEM: Information about the effect of the facial flow concept on the smile esthetic perception of laypeople is lacking. PURPOSE: The purpose of this study was to determine the effect of the facial flow concept on laypeople's perception of smile esthetics. MATERIAL AND METHODS: Frontal full-face images of a female volunteer were digitally altered to create commissural line and transverse occlusal plane inclinations, a dental midline shift, and facial asymmetries. A questionnaire was developed, and a single researcher asked 400 evaluators to rate the attractiveness of the different smiles by using a visual analog scale. The subsequent data were analyzed by using 3-factor repeated measures ANOVA and post hoc Bonferroni tests. RESULTS: Images with commissural line and transverse occlusal plane inclinations pointing toward the green side of the facial flow curve were found to be more attractive than those with inclinations pointing to the red side (P<.001). Asymmetric facial images with the dental midline coinciding with the facial flow curve had higher esthetic scores than those without (P<.001). Images that showed parallelism between the transverse occlusal plane and commissural line inclinations were perceived as more esthetic (P<.001). CONCLUSIONS: In an asymmetric face model, the degree and direction of commissural line and transverse occlusal plane inclinations and dental midline shift influenced the perceived attractiveness of a smile.

Effect of coating on the color and surface hardness of the surface of dental ceramics.

BACKGROUND: The aim of this study was to investigate whether boron nitride (BN) and BN-chromium (BN-Cr) coatings applied with the sputtering method would change the characteristics of hardness and discoloration of the ceramic veneer surface. MATERIALS AND METHODS: In this experimental study, thirty disc-shaped cores (10 mm in diameter and 0.8 mm in thickness) were prepared. Three different ceramic systems, IPS Empress (E) (Ivoclar Vivadent, Schaan, Liechntenstein), IPS e.max Press (EP) (Ivoclar Vivadent, Schaan, Liechntenstein), and Turkom Cera (T) (Turcom-Ceramic SDN-BHD, Kuala Lumpur, Malaysia), were tested, each with n = 10. The specimens were divided into two subgroups (n = 5) according to the coating on the veneering ceramic: BN or BN-Cr. The Vickers hardness and color differences (ΔE) values were measured before and after coating. Surface analysis was performed with X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopic. The Wilcoxon signed-rank test was performed to compare hardness values. The Kruskal-Wallis test was performed to compare ΔE values among all groups. The post hoc tests was used after Kruskal-Wallis, with level of statistical significance set at P ≤ 0.05. RESULTS: BN-Cr coating statistically significantly increased the hardness of all types of ceramics (P < 0.05). BN coating did not change the hardness statistically significantly (P > 0.05). The mean ΔE values indicated clinically noticeable (over the limit of 3.7) color change in all groups except for the EP-BN and T-BN groups. CONCLUSION: Although BN-Cr coating in this thickness had a negative effect on color, it increased the hardness of the ceramics and could be useful in the palatal region.

Evaluation of the color stability of temporary materials produced with CAD/CAM.

BACKGROUND: If a temporary restoration is in the esthetic area and needs to be worn for a long time, the color stability of temporary materials becomes an important factor. OBJECTIVES: The aim of this in vitro study was to evaluate the long-term effects of various staining solutions on the color stability of different temporary materials produced with the computer-aided design and computer-aided manufacturing (CAD/CAM) technology. MATERIAL AND METHODS: In the study, the following materials were used: VITA CAD-Temp® (group 1); Ceramill® Temp (group 2); and Telio® CAD (group 3). Forty disk-shaped specimens (10 mm in diameter, 2 mm in thickness) of each material (N = 120) were produced with a CAD/CAM system. Staining solutions - of tea (A), of coffee (B) and cola (C) - and distilled water (D, control) were used, and color was evaluated before and after storing the samples in the solutions. Measurements were taken with a spectrophotometer and the color parameters (L*, a*, b*, and ΔE) were calculated according to the Commission internationale de l'éclairage system (CIELab). The results were evaluated with the two-way analysis of variance (ANOVA) and Tukey's tests (α = 0.05). RESULTS: Clinically perceivable (ΔE00 > 0.8) and statistically significant (p < 0.001) color differences were detected in all specimens. The highest ΔE00 value was found in the Ceramill Temp specimens. In addition, the highest ΔE00 values were noted for the specimens stored in cola and the coffee solution for all groups. The lowest ΔE00 value was observed for the groups stored in the tea solution. CONCLUSIONS: Clinically perceivable color changes were observed in all the specimens kept in the solutions. Color changes were greater for cola and coffee as compared to tea.

Three-Dimensional Accuracy of Conventional Versus Digital Complete Arch Implant Impressions.

PURPOSE: The accuracy of digital impressions is still controversial for complete arch implant cases. The aim of this study is to compare the accuracy of different intraoral scanners with the conventional technique in terms of trueness and precision in a complete arch implant model. MATERIAL AND METHODS: Eight implants were inserted asymmetrically in a polyurethane edentulous mandibular model with different angulations. A 3-dimensional (3D) reference model was obtained by scanning this polyurethane model with an optical scanner. First, digital impressions were made by using 3 different intraoral scanners: Carestream 3500 (DC), Cerec Omnicam (DO) and 3Shape Trios 3 (DT). Subsequently, a nonsplinted open tray impression technique was used for conventional impression group (C) and then the master casts were digitalized with a lab scanner. Each 10 STL files belonging to 4 different impression groups were imported to a reverse engineering program, to measure distance and angle deviations from the reference model. All statistical analyses were performed after taking absolute values of the data. After comparing the impression groups with one-way ANOVA, the trueness and precision values were analyzed by Tukey post hoc test and 0.05 was used as the level of significance. RESULTS: The mean trueness of distance was 123.06 ± 89.83 µm for DC, 229.72 ± 121.34 µm for DO, 209.75 ± 47.07 µm for DT, and 345.32 ± 75.12 µm for C group (p < 0.0001). While DC showed significantly lower deviation compared to DO and C, no significant difference was found between DC and DT. C showed the highest distance deviation significantly in all groups; and no significant difference was found between DO and DT groups. In angle measurements; the trueness was 0.26° ± 0.07° for DC, 0.53° ± 0.42° for DO, 0.33° ± 0.30° for DT, and 0.74° ± 0.65° for C group. There was no significant difference between the groups in terms of angular trueness (p = 0.074). In terms of the precision for distance, the results of DC 80.43 ± 29.69 µm, DO 94.06 ± 69.96 µm, DT 35.55 ± 28.46 µm and C 66.97 ± 36.69 µm were determined (p = 0.036). The significant difference was found only between DT and DO among all groups. Finally, angular precision was determined to be 0.19° ± 0.11° for DC, 0.30° ± 0.28° for DO, 0.22° ± 0.19° for DT, and 0.50° ± 0.38° for Group C. No significant difference was found between the groups, in terms of angular precision (p = 0.053). CONCLUSIONS: All digital impression groups yielded superior data compared to conventional technique in terms of trueness. DC formed the impression group with the highest trueness in both distance and angular measurements. The results of this in vitro study suggest the use of intraoral scanners compared to the conventional impression techniques in complete arch implant cases with high angulations.

Effects of gingival margin asymmetries on the smile esthetic perception of dental professionals and lay people.

OBJECTIVE: To determine the effects of different gingival margin asymmetries of anterior tooth on the smile esthetic perceptions of dentists, prosthodontists, periodontists and lay people. MATERIALS AND METHODS: A frontal close-up smile photo of a woman was used in this study. Image was digitally altered in order to create gingival margin asymmetries in left maxillary central, lateral incisors, and canines. Four stages of alterations were made in 0.5 mm increments. The final images were randomly assessed by 240 evaluators: 60 dentists, 60 prosthodontists, 60 periodontists, and 60 lay people. Questionnaire was carried out by a single researcher and each rater was asked to evaluate the attractiveness of the smile images by using the visual analog scale. Collected data were analyzed by using one-way ANOVA test with post hoc Scheffé test. RESULTS: Smiles with 0.5 mm gingival margin asymmetries were found to be more esthetic, while 2 mm gingival asymmetries were less esthetic (P ˂ .001). Lay people's esthetic scores were higher than other groups in all degrees of asymmetries (P ˂ .001). Esthetic scores of canine teeth were higher than, lateral, and central teeth (P ˂ .001). CONCLUSIONS: As the amount of asymmetries increased, esthetic scores decreased in all groups. Gingival margin asymmetries were less perceptible laterally. CLINICAL SIGNIFICANCE: This study may help dental professionals to understand which gingival asymmetries are found by patients as esthetic or unesthetic and guides them in their dental treatment, especially in the aesthetic zone.

Effect of fiber reinforcement on color stability of composite resins.

AIM: The aim of this in vitro study was to determine the effect of fiber reinforcement on the color changes of two different composite resins. MATERIALS AND METHODS: A silorane-based composite (Filtek Silorane, A2 shade) and a methacrylate-based composite (Valux Plus, A2 shade) were used in this study. Three groups of samples (control group with no reinforcements, polyethylene fiber [Ribbond THM]-reinforced composite, and glass fiber [everStick® Net]-reinforced composite groups) were prepared from each composite (n = 8). The color change was calculated between baseline and 1 day (ΔE1) and between baseline, 7 days (ΔE2), and 21 days (ΔE3) with a spectrophotometer. The data were analyzed by ANOVA, Duncan's multiple-range tests and independent sample t-test. RESULTS: Statistical analysis of variance presented the statistically significance difference between composite, fiber, and time for ΔE (P < 0.05). The Ribbond reinforced composite showed a similar color change to the control group (ΔE = 3.69), while the everStick reinforced composite showed the largest total color change (ΔE = 4.13). It was determined that the time is an effective factor on the color stability of reinforced composites (P < 0.05). CONCLUSION: The addition of fiber may lead to color change in composite resins. The amount of change may differ depending on the structural properties of the composite resin or the fiber and time.

The effect of restoration thickness and resin cement shade on the color and translucency of a high-translucency monolithic zirconia.

STATEMENT OF PROBLEM: Information regarding the influence of cements and material thickness on the final color of monolithic zirconia restorations is lacking. PURPOSE: The purpose of this in vitro study was to examine the effect of varying resin cement colors and material thicknesses on the color and translucency of a high-translucency monolithic zirconia and to compare these effects with those reported in similar studies that examined other dental zirconia materials. MATERIAL AND METHODS: Katana High Translucent (Kuraray) was used as a monolithic zirconia material. A total of 80 disk specimens (10 mm in diameter) were made in 4 different thicknesses of 0.5 mm, 1 mm, 1.5 mm, and 2 mm (n=20 per thickness). The color of the specimens (Commission Internationale de l'Eclairage [CIE] L*, a*, b* values) before cementation was measured using a spectrophotometer. Specimens within each thickness were further divided into 2 groups: transparent (n=10) and opaque (n=10). A transparent or opaque self-etch adhesive resin cement (Panavia V5) was then applied to each specimen. After cementation, the color was measured again. The translucency parameter (TP) and ΔE were calculated and evaluated with the color measurements by using descriptive statistics, correlation analysis, single specimen t test, 2-way ANOVA, and the Tukey Honestly Significant Difference (HSD) test. RESULTS: Statistically significant (P<.001) changes were found with the increasing thicknesses of the high-translucency zirconia specimens. The TP, L*, and b* values decreased, whereas the a* values increased. In both the transparent and opaque groups, statistically significant (P<.001) increases in L*, a*, and b* values and a significant decrease in TP were found with cementation. The lowest ΔE value (1.19 for 2 mm) was observed for monolithic zirconia-clear cement. The highest ΔE value (8.05 for the 0.5 mm) was observed for the monolithic zirconia and opaque cement combination. CONCLUSIONS: Material thickness and cement color affected the color and translucency of high-translucent monolithic zirconia, with effects similar to those observed with other monolithic zirconia materials.

A comparison of the fracture resistance of premolars without a ferrule with different post systems.

STATEMENT OF PROBLEM: Which type of post improves the performance of endodontically treated mandibular premolars without a ferrule remains unclear. PURPOSE: The purpose of this in vitro study was to compare the restoration of endodontically treated mandibular premolars without a ferrule by using different post systems. MATERIAL AND METHODS: Thirty extracted mandibular premolars were endodontically treated, and their crowns removed. They were divided into 3 groups with different post systems (n=10): zirconia ceramic posts (ZRPs), fiber posts (FPs), and bundled glass fiber-reinforced composite resin posts (GTPs). After post placement and core fabrication, computer-aided design and computer-aided manufacture (CAD-CAM) lithium disilicate crowns were cemented. The specimens were subjected to thermocycling and mastication simulation before a fracture test in a universal testing machine. The maximum load at which the fracture occurred was recorded, and the fractured specimens were examined by using an optical microscope. The data were analyzed for statistical differences with a 1-way ANOVA and the Tukey honestly significant difference post hoc test (α=.05). RESULTS: No statistically significant difference in fracture strength was found among the groups (P=.970). From the light microscopy examination, catastrophic failure was observed in all specimens, and there was no failure of the ceramic crowns. CONCLUSIONS: Based on the findings of this in vitro study, the choice of post material with a low or high modulus of elasticity did not prevent catastrophic failures in endodontically treated teeth without a ferrule.

An investigation of the esthetic indicators of maxillary anterior teeth in young Turkish people.

STATEMENT OF PROBLEM: Comprehensive studies evaluating the dimensions of anterior maxillary teeth in the Turkish population with respect to different esthetic parameters are lacking. PURPOSE: The purpose of this clinical study was to evaluate different proportions of teeth and compare them with current esthetic parameters such as the golden proportion, recurring esthetic dental proportion, and width-to-height ratio of central incisors and to evaluate whether the apparent contact dimension of maxillary anterior teeth follows the "50:40:30" rule. MATERIAL AND METHODS: A total of 150 Turkish dental students (81 men and 69 women) aged between 18 and 24 years participated in the study. Standardized digital photographs of the mouth were made from an anterior view. The width and length of the maxillary central incisor, apparent width of the maxillary lateral and canine teeth, and distances between contact areas of the maxillary incisor teeth were measured with software. Differences between the measured proportions and the determined esthetic parameters were assessed with the 1-sample t test (α=.05). RESULTS: The width and length proportions of the maxillary incisor teeth in both sexes were significantly different than the golden and recurring esthetic dental proportions. The width-to-height ratio for the maxillary central incisor was different from 80%, which is considered optimal, and the difference among these parameters was statistically significant (P<.001). The apparent contact dimensions on the right and left sides were not statistically significantly different (P>.05). However, the proportions did not fit the 50:40:30 ratio that has been defined as the esthetic proportion, and the differences were statistically significant (P<.001). CONCLUSION: Proportions among maxillary anterior teeth were found to be significantly different from the golden proportion and recurring esthetic dental proportion in both sexes. The proportions of apparent contact dimension were significantly different than the 50:40:30 ratio in both sexes. The width-to-height ratio for maxillary central incisor was significantly different from 80% in both sexes.

Effect of number of firings on the color and translucency of ceramic core materials with veneer ceramic of different thicknesses.

STATEMENT OF PROBLEM: Whether masking or translucency should be the goal for achieving an esthetic restoration with ceramic materials is unknown. PURPOSE: The purpose of this in vitro study was to examine the effect of the number of firings on the color and translucency of ceramic core material with different thicknesses of veneer ceramic. MATERIAL AND METHODS: Three different ceramic systems were used: IPS Empress (IE), IPS e.max Press (IEP), and Turkom Cera (TC). Ninety disk-shaped cores, 10 mm in diameter and 0.8 mm in thickness were prepared using each system (n=30). The specimens were divided into 3 subgroups (n=10) according to the thickness of the veneering ceramic: 0.5, 1.0, and 1.5 mm. The specimens were fired 1, 3, and 5 times, and the color parameters of the specimens were measured. The color measurements were repeated, and the data were statistically evaluated using 2-way and multifactorial analysis of variance, the Duncan test, and the Bonferroni post hoc test. RESULTS: The number of firings affected the translucency parameter and CIELab values. Increased porcelain thickness led to decreased translucency parameter and L* values and increased a* and b* values (P<.05). The IE system was the most translucent (P<.001). The changes with increased firing periods were not statistically significant (P>.05). The number of firings affected the color change of the IE and IEP systems but not of the translucency parameter system. CONCLUSIONS: Repeated firings and porcelain thickness affected the final color and translucency of the ceramic systems tested. These 2 factors adversely affected the esthetic result and should be considered in both the preparation and the laboratory phase.

Color changes in resin cement polymerized with different curing lights under indirect restorations.

AIM: The aim of the study was to investigate the effects of different interface materials and curing units on color changes in a resin cement material. MATERIALS AND METHODS: Three interface materials and different curing systems, quartz-tungsten-halogen and polywave and monowave light-emitting diode (LED) light curing units, were studied at two-time intervals. Polystyrene strip was used as a control group. All measurements were made on a white background for standard color measurement. According to the CIE L*a*b* color space, the baseline color values of each specimen were measured. Differences between the measurements were calculated as ΔE, ΔL, Δa, and Δb. Data were analyzed using analysis of variance (ANOVA) and Duncan's tests (α = 0.05) with SPSS 20.0 software (SPSS Inc., Chicago, IL, USA). ANOVA revealed significance for interface materials and curing units and time for ΔE (P < 0.05). RESULTS: Interaction between polymerizing units, material and time was not significant (P > 0.05). Monowave LED exhibited significantly higher color changes than the other units ([P < 0.05] [ΔE 2.94 ± 0.44]). QTH promoted composite specimens significantly less color change ([P < 0.05] [ΔE 0.87 ± 0.41]). CONCLUSION: This study concluded that color of resin cement used in the adhesion of indirect restorations was affected by curing device light and indirect restoration material type.

Effect of repair resin type and surface treatment on the repair strength of polyamide denture base resin.

The purpose of the present study was to evaluate the effects of different repair resins and surface treatments on the repair strength of a polyamide denture base material. Polyamide resin specimens were prepared and divided into nine groups according to the surface treatments and repair materials. The flexural strengths were measured with a 3-point bending test. Data were analyzed with a 2-way analysis of variance, and the post-hoc Tukey test (α=0.05). The effects of the surface treatments on the surface of the polyamide resin were examined using scanning electron microscopy. The repair resins and surface treatments significantly affected the repair strength of the polyamide denture base material (p<0.05); however, no significant differences were observed interaction between the factors (p>0.05). The flexural strength of the specimens repaired with the polyamide resin was significantly higher than that of those repaired with the heat-polymerized and autopolymerizing acrylic resins.

In vitro evaluation of long-term cytotoxic response of injection-molded polyamide and polymethyle metacrylate denture base materials on primary fibroblast cell culture.

OBJECTIVE: This study investigated the long-term cytotoxic response of thermoplastic polyamide and conventional polymethyle metacrylate (PMMA) denture base materials. MATERIALS AND METHODS: Twenty discs were prepared for each polyamide, heat and cold cured PMMA denture base resins (totally 60) and divided into four sub-groups (n = 5). Cytotoxicity was assessed with the direct cell contact method using cell viability and neutral red (NR) uptake assay. Each sub-group was tested at initial and after being aged for 24 h, 1 week and 8 weeks with artificial saliva according to ISO 10993 standards. RESULTS: There were no significantly difference among the materials and control groups after initial, 24 h and 1 week testing. In 24 h testing, only Deflex was more toxic according to the Control group (p < 0.05). After 8 weeks of aging with artificial saliva, all materials were significantly cytotoxic when compared to the control group. QC20 was more toxic than Deflex and SC Cold Cure (p < 0.05). There were significant differences between the 8 week aging group and the initial, 24 h and 1 week testing for all materials (p < 0.05). CONCLUSIONS: Cytotoxicity of all tested denture base materials increased significantly after the long-term aging. Therefore, long-term aging may be useful to determine a dental material's toxicity. Polyamide denture base material had a similar toxicity profile with conventional heat- and cold-cured PMMA.