The effect of pre-ceramic soldering on marginal and internal fit of 4-unit zirconia frameworks and monolithic zirconia fixed dental prostheses.

The aim of this study is to evaluate the effect of pre-ceramic soldering on the marginal and internal fit of 4-unit zirconia fixed dental prostheses (FPDs) that have two abutments and two pontics. 4-unit zirconia frameworks (Zirkonzahn ICE Translucent) (Z Group) and monolithic zirconia (Zirkonzahn Prettau) (M Group) FPDs were manufactured. Groups were divided into two groups (n = 10) control (ZC and MC) and soldering (ZS and MS). Samples of ZS and MS groups were cut into two pieces under cooling water and soldered with a bonding material (DCM Zircon HotBond). The marginal and internal fit of the restorations were measured from 36 points of each sample and cement space volume was calculated using reverse engineering software (Geomagic Design X). The mean and standard deviations were submitted to Generalized Linear Mixed Model (GLMM) analysis (α = 0.05). Statistical differences between groups before and after pre-ceramic soldering on point measurements were found. In total cement spacing measurements, a significant difference was found amongst all groups (P < 0.05). However, in premolars, a statistically significant difference was found between ZC and ZS groups and MC and MS groups (P < 0.05). All discrepancies after pre-ceramic soldering were found to be lower than before.

In Vitro Comparison of the Accuracy of Conventional Impression and Four Intraoral Scanners in Four Different Implant Impression Scenarios.

PURPOSE: The aim of this study was to compare the trueness and precision of four intraoral scanners (IOSs) and splinted open-tray conventional implant impression (SOCI) in partial and total edentulism. MATERIALS AND METHODS: Four gypsum models (Model A-implants at mandibular right second molar, right second premolar, and right canine; Model B- implants at mandibular right canine, left central incisor, and left canine; Model C-implants at mandibular right second molar, right second premolar, right canine, left central incisor, and left canine; and Model D-implants at mandibular right second molar, right second premolar, right canine, left central incisor, left canine, left second premolar, and left second molar) were prepared, and four different IOSs (Aadva IOS, CS 3600, Trios 3, and Emerald) and one polyvinyl siloxane (PVS) were used. Reference models were digitized with a high-resolution industrial scanner, and data were superimposed. Root mean square (RMS) values were calculated by software and defined as deviation values after superimposition. The oneway analysis of variance (ANOVA) test and Tukey honest significant difference (HSD) test were performed to analyze the data (P < .05). RESULTS: For Models A and B, the truest impressions were made with Aadva, followed by CS 3600, PVS, Trios 3, and Emerald, respectively, while for Model C, the truest impressions were made with CS 3600, followed by Aadva, PVS, Trios 3, and Emerald, and for Model D, the truest impressions were made with Aadva, followed by CS 3600, PVS, Emerald, and Trios 3 (P < .05). There was no statistical difference between groups for precision in Models A, B, and C (P > .05); however, PVS showed lower precision values than other groups in Model D (P < .05). CONCLUSION: In partial edentulism, IOSs are true and precise as SOCI except Emerald. However, the trueness of IOSs is not favorable in total edentulism cases. SOCI with PVS in total edentulism treated with implants is less precise than IOSs.

The Effect of Preceramic Soldering on Fracture Resistance of 4-Unit Zirconia Fixed Dental Prostheses.

PURPOSE: Preceramic soldering of zirconia may deliver better fitting restorations. However, there is not sufficient evidence regarding the influence of preceramic soldering of zirconia restorations on mechanical strength. The aim of this study was to evaluate the effect of preceramic soldering on the fracture load of 4-unit zirconia fixed dental prostheses (FDPs). MATERIALS AND METHODS: Eighty samples of 4-unit FDPs between maxillary right first premolar and maxillary right second molar were prepared and two restorative materials were used as a framework (Z) and monolithic restoration (M). The samples were divided into two subgroups as control (C) and study (S). The restorations of study groups (S) were divided into two pieces and soldered with a bonding material (DCM HotBond Zirkon). The groups were divided into two subgroups for thermal cycle (T) application. After soldering and thermal cycling application, 4-point bending test was applied to the samples at a cross-head speed of 1 mm/min in a universal testing machine and the fracture load was recorded. The data was analyzed statistically, and the level of significance was set at α = 0.001. RESULTS: Statistically significant differences were found among the groups, based on the results of maximum failure loads (p < 0.001). The highest mean failure load was observed in the ZCT(-) group (1094.1 + 139.77 N), while the lowest mean failure load was obtained in the ZST(+) group (627.7 + 82.14 N). No significant difference was found among the groups MC and MS, MC, and ZC groups (p > 0.001). Thermal aging application caused lower fracture resistance in control and soldering groups (p < 0.001). CONCLUSIONS: The preceramic soldering applications affected zirconia group negatively. However, the values were above the clinically acceptable static load bearing capacity for posterior teeth. Soldering did not cause a statistically significant difference for the fracture strengths of monolithic zirconia groups. Thermal cycling affected the fracture strength of zirconia and monolithic zirconia restorations negatively.

Evaluation of anxiety-provoking situations related to clinical training in dental education.

INTRODUCTION: The aims of this study were to evaluate the situations that cause anxiety in clinical training and to discuss the precautions that can be taken to reduce clinical anxiety in dental education. MATERIALS AND METHODS: This multi-centred survey-based study was created through Google Docs, and 3rd, 4th and 5th grade dental students were included. The students were asked to rate their reactions on a 4-point Likert scale "not anxious" to "very anxious" for 27 questions related to academics, communication and interaction, diagnosis, dental treatments, deficiencies and mistakes in the treatments. RESULTS: 1332 students were reached, and 1320 students completed the questionnaire. Whilst extracting wrong tooth (3.53 ± 0.83), getting infected by patient (3.39 ± 0.85) and getting diagnosis wrong (3.31 ± 0.83) were identified as the 3 most anxiety-provoking situations, taking panoramic radiograph (1.48 ± 0.71) and communication with patients and dental assistants/nurses (1.76 ± 0.87; 1.64 ± 0.76) were identified as 3 situations that cause the least anxiety. Female students reported higher anxiety levels than male students in most of the questions (p < .05). A statistically significant difference was observed between the grades of the students (p < .05). 3rd grade students showed statistically higher anxiety levels than higher grades in 16 out of 27 questions. No statistical significance was observed according to the status of the university (p > .05). CONCLUSION: Questions related to diagnosis, delivery of the dental treatments, deficiencies and mistakes in the treatments caused higher anxiety levels amongst dentistry students. As experience and time in the clinical training increase, the anxiety level of the students decreases. Orientation programmes and establishing an effective communication between grades are recommended. Also, gender-based solutions must be taken into consideration.

Stainability of different ceramic materials against mouth rinses and effect of polishing after staining.

STATEMENT OF PROBLEM: Mouth rinses are known to stain tooth surfaces. However, their staining effect on different ceramics after prolonged use and the effect of polishing after staining are still unclear. PURPOSE: The purpose of this in vitro study was to evaluate the stainability of different ceramic materials against different mouth rinses and the effect of polishing on staining. MATERIAL AND METHODS: Forty disk-shaped specimens were prepared from each material (total of 160 specimens): lithium disilicate (IPS e.max CAD), zirconia-reinforced lithium disilicate (VITA SUPRINITY PC), leucite-reinforced feldspar (GC Initial LRF), and resin matrix ceramic (CERASMART). Baseline color measurements (T0) were recorded with a clinical spectrophotometer (VITA Easyshade V). The specimens were immersed in chlorhexidine gluconate (CHX) 0.2% mouth rinse (Klorhex), (KLO) chlorhexidine gluconate 0.1% mouth rinse (Eludril) (ELU), a daily mouth rinse (LISTERINE Cool Mint) (LIS), artificial saliva (CON) continuously for 7 days (T1), 14 days (T2), and 28 days (T3). Discoloration values (ΔE) between the immersion time points (T0,T1,T2,T3) were calculated by using the following formula: ΔE= ([ΔL∗]2 + [Δa∗]2 + [Δb∗]2)1/2. After the immersion process, specimens were polished and ΔE values remeasured. The Kruskal-Wallis and Mann-Whitney U tests were performed (α=.05) and were adjusted by postanalysis Bonferroni testing. RESULTS: KLO caused the highest ΔE values in all groups. IPS e.max CAD had the lowest ΔE values, and CERASMART showed the highest ΔE values against all of the solutions (P<.05). However, polishing caused a decrease in the ΔE values in all groups. CONCLUSIONS: Prolonged use of mouth rinses may cause color change in different ceramic materials. Polishing affected the color change and resulted in a decrease in ΔE values. Mouth rinses containing CHX should be recommended with caution for daily use.