Recording maximal intercuspation and border positions of the mandible with intraoral scanner using the acquisition software's multi-occlusion function.

PURPOSE: This in vitro study was conducted to investigate the accuracy of intraoral scanner (IOS) for recording maximal intercuspal position (MIP) and border positions of the mandible. MATERIALS AND METHODS: Maxillary and mandibular master casts were articulated in MIP, protrusive, and lateral interocclusal position sequentially on a semi-adjustable articulator. For each articulation relation, sites of occlusal contacts (SOCs) and sites of clearance (SCs) were identified on the master casts with articulating paper (reference sites). IOS was used to take full arch scans and nine virtual interocclusal records (VIRs) for virtual articulation of models. Virtual SOCs and SCs were detected with 3D processing software and compared to those identified with the articulating paper. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each articulation relation. RESULTS: For MIP, IOS showed adequate sensitivity and NPV of 100%, and specificity and a PPV of 99%. For protrusive position, the IOS showed a sensitivity and a NPV of 100%, a high PPV of 86%, and a specificity of 83%. For lateral positions, the specificity and the PPV were high (93% and 79%, respectively), but the sensitivity and the NPV were below the clinically acceptable limits (28% and 56%, respectively). CONCLUSION: IOS displayed clinically acceptable accuracy for recording MIP and protrusive border mandibular position. However, IOS had less accuracy for lateral border mandibular position.

Randomized clinical trial of zirconia laminate veneers sintered by using conventional versus speed process: 1-year follow-up.

STATEMENT OF PROBLEM: The application of highly translucent multilayered zirconia ceramic in minimally invasive esthetic dentistry allows the achievement of both esthetics and strength with minimal thickness. Clinical studies that have assessed the performance of zirconia ultrathin veneers sintered with the conventional and speed procedure are lacking. PURPOSE: The purpose of this clinical study was to evaluate the effect of speed sintering processes on the translucency and clinical performance of zirconia laminate veneers. MATERIAL AND METHODS: Four participants had their teeth restored with 32 ultratranslucent zirconia laminate veneers. Based on the zirconia sintering procedure, the participants were randomly allocated into 2 groups. The teeth were prepared by selective reduction over trial restorations. Zirconia veneers were milled from multilayer zirconia blanks and sintered either by speed sintering or conventional sintering as specified by the manufacturer's recommendations. The intaglio surface of the veneers were airborne-particle abraded with 50-µm aluminum-oxide, and the veneers were then adhesively bonded to the teeth with translucent light-polymerizing resin cement. The modified California Dental Association (CDA)/Ryge criteria were used to assess participants at baseline and every 3 months for 12 months. The translucency and the color difference of the tooth before and after veneer restoration were evaluated. For statistical analysis, the Pearson chi squared test, independent t test, and paired t test were used (α=.05). RESULTS: Translucency and color differences were significantly higher in the conventionally sintered group (P<.05). No restorations were lost. No significant differences were found between the 2 groups in the CDA/Ryge criteria or color parameter after follow-up intervals (P>.05). The primary qualitative changes observed at the final recall were marginal integrity and marginal discoloration. The color match and zirconia surface were rated Alfa. CONCLUSIONS: After 1 year of follow-up, both conventional and speed sintered ultrathin zirconia laminates showed satisfactory functional, esthetic, and color stability outcomes.

Translucency of recent zirconia materials and material-related variables affecting their translucency: a systematic review and meta-analysis.

BACKGROUND: Recent forms of translucent zirconia material have been developed, offering a wide range of options and varieties for enhancing aesthetics, making it a preferred choice in the field of prosthetic dentistry. However, there is insufficient understanding regarding the recent types of zirconia materials and their optical behavior. Understanding the variables that influence the translucency of zirconia and identifying strategies to enhance its esthetics are crucial. PURPOSE: The current systemic review highlights a comprehensive understanding of different zirconia generations in relation to their optical characteristics and evaluates material-related variables affecting their translucency. METHODS: The present review studied in-vitro studies that evaluated the optical characteristics of different yttria content of yttria stabilized materials. The topics explored were: (1) the different zirconia material generations and their optical behavior; (2) material-related factors that affect their translucency. The research was restricted to online publication in the English language from July 1, 2010, to July 31, 2023, using PubMed, Scopus, and Science Direct resources. The search key terms and their combinations were "zirconia," "translucent zirconia," "cubic zirconia," "highly translucent zirconia," "yttria partially stabilized zirconia," "monolithic zirconia," "translucency," "optical properties," and "light transmission." RESULTS: The data obtained from fifty-three studies addressed the optical characteristics of various zirconia generations. They reported that changing yttria content had a significant impact on translucency. Different kinds of zirconia ceramics of the same generation have varying translucencies. Achieving optimum aesthetics with monolithic zirconia is challenging due to factors related to material aspects such as the presence of additives, point defects, microstructure, thickness, phase distribution, and sintering conditions. CONCLUSIONS: Newly developed monolithic dental zirconia ceramics have improved aesthetics and translucency. However, additional research is necessary to evaluate their performance and long-term durability. TRIAL REGISTRATION: This systematic review was registered in PROSPERO, under number CRD42023474482.

Preparation of ultrathin translucent zirconia laminate veneers using 3D printing reduction guides.

Minimizing and controlling the amount of tooth reduction during the preparation of ultrathin laminate veneers is a challenge for minimally invasive dentistry. The use of reduction guides is advised to reach the optimal space required for the definitive restoration without excessive reduction. The digital production of a reduction guide used to control tooth preparation for ultrathin laminate veneers is described.

Effect of sintering time on microstructure and optical properties of yttria-partially stabilized monolithic zirconia.

OBJECTIVES: To evaluate the impact of speed sintering on the microstructure and optical properties of 3 and 5 mol% yttria-partially stabilized monolithic zirconias. METHODS: 120 plate-shaped zirconia specimens (10x10x 0.4 mm) were prepared from three commercial 5 mol% yttria-partially stabilized zirconia blocks (5Y-PSZs); Katana UTML (Kuraray Noritake), Cercon xtML (Dentsply Sirona), and Zolid FX white (Amann Girrbach), and two commercial 3 mol% yttria-partially stabilized zirconia blocks (3Y-PSZs); Lava Plus (3 M ESPE) and InCoris (Sirona, GmbH). Specimens were either conventional sintered (CS) using a 7-hour program or speed sintered (SS) using a quick 90-minute program. The microstructure was inspected with a scanning electron microscope (SEM), and phase fractions were detected using x-ray diffraction analysis (XRD). Translucency (TP00), and contrast ratio (CR) were obtained using a spectrophotometer (VITA Easyshade V). Color difference (ΔE00) between both sintering processes was calculated with the CIEDE2000 formula. ΔE00 up to 1.8 was set as the acceptability threshold. Data were analyzed using two-way ANOVA, Krusakll-Wallis, and Mann-Whitney U tests. (n = 12, α = .05). RESULTS: Grain size was significantly decreased after SS for all tested materials (P < .0001). The average grain sizes of 5Y-PSZs were significantly larger than those of 3Y-PSZs. The atomic structure, microstructure, and transparency of CS and SS were all affected by the amount of yttria, the size of the crystals, and tetragonality. SS significantly reduced TP00 (F = 7135.95, P < 0.0001) and increased CR (F = 453.21, P < 0.0001). The CS Katana presented the highest TP00 and lowest CR value. ΔE00 between the CS and SS groups were clinically acceptable except for Lava, which had values above the set threshold (1.89). SIGNIFICANCE: SS altered the grain size and internal structure of the tested materials, which was reflected in translucency.

Effect of mouth rinses on the stainability of monolithic lithium disilicate glass-ceramics with different surface treatments: An in vitro study.

STATEMENT OF PROBLEM: Mouth rinses have been reported to cause tooth surface discoloration. However, information regarding their effect on the stainability of monolithic glass-ceramics with different surface treatments is lacking. PURPOSE: The purpose of this in vitro study was to assess the effect of mouth rinses on the color change of milled and pressed monolithic lithium disilicate glass-ceramics with different surface treatments. MATERIAL AND METHODS: Fifty-six Ø12×1.5-mm disk specimens were fabricated using 2 different processing techniques: milling and pressing. Each group was subdivided into 2 subgroups according to surface treatments: glazed and polished. Specimens were then immersed in 2 different types of mouth rinse (n=7): chlorhexidine (CHX) and Listerine (LST). Color parameters were assessed using a digital spectrophotometer. Color difference (ΔE00) was calculated and compared with perceptibility (ΔE00=0.8) and acceptability (ΔE00=1.8) thresholds. The data were analyzed using ANOVA and Tukey post hoc tests (α=.05). RESULTS: The color difference (ΔE00) was significantly affected by the type of processing technique, surface treatment, and mouth rinse (P<.001) and their interaction (P=.008). All ΔE00 values were below the selected clinical acceptability threshold (ΔE00=1.8). Milled groups (ΔE00=1.13) showed greater discoloration than pressed groups (ΔE00=0.86). Glazed specimens (ΔE00=0.70) were more resistant to discoloration than polished specimens (ΔE00=1.28) and immersion in CHX (ΔE00=1.09) led to more discoloration than immersion in LST (ΔE00=0.89). CONCLUSIONS: The color of milled and pressed monolithic lithium disilicate glass-ceramics with different surface treatments was affected by using CHX and LST mouth rinses. Glazed lithium disilicate glass-ceramics showed less staining compared with those that were polished. Specimens immersed in CHX showed more discoloration than those immersed in LST.

Effect of pattern materials and fabrication techniques on the color of a pressed lithium disilicate ceramic: An in vitro study.

STATEMENT OF PROBLEM: Pattern materials and their fabrication techniques have been reported to affect the marginal accuracy and internal fit of pressed lithium disilicate ceramic restorations. However, information regarding their effect on the color of such restorations is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the color of a pressed lithium disilicate glass-ceramic fabricated from wax or resin patterns by using conventional and milling techniques. MATERIAL AND METHODS: Fifty-six Ø14×1.5-mm disk pattern specimens were divided into 4 groups based on the pattern material and fabrication technique: conventional wax pattern group (CW), conventional resin pattern group (CR), milled wax pattern group (MW), and milled resin pattern group (MR). Lithium disilicate specimens were fabricated by using the lost wax technique. The CIELab values were measured with a spectrophotometer (VITA Easyshade Advance). The ΔE00 values were calculated and compared with perceptibility (ΔE00=0.8) and acceptability (ΔE00=1.8) thresholds to interpret the color differences. The 2-way ANOVA and Tukey post hoc tests were used to analyze data (α=.05). RESULTS: Two-way ANOVA revealed that ΔE00 was significantly affected by the pattern material (P<.001), fabrication technique (P=.034), and their interaction (P<.001). The ΔE00 of the CW group (0.76 ±0.04) was clinically imperceptible. No significant difference in the ΔE00 values was found between the reference and the MW (1.48 ±0.13) and MR (1.51 ±0.15) groups (P=.926), which were both clinically perceptible and acceptable. The highest ΔE00 was that of the CR group (2.06 ±0.22). CONCLUSIONS: The color of the pressed lithium disilicate ceramic was influenced by the wax and resin pattern materials fabricated by using conventional or computer-aided design and computer-aided manufacturing (CAD-CAM) techniques. Only the CW pattern group showed color differences below the clinically perceptible threshold (ΔE00=0.8). The CR pattern group showed the highest color differences, which were not clinically acceptable.

A device to facilitate separation of components of combined screw- and cement-retained implant-supported crowns.

This article describes a technique to separate parts of cemented implant-supported restorations with a screw hole. A device was designed by using a computer-aided design (CAD) program and was milled in a milling center. The restoration was heated to 400 °C and then subjected to controlled mechanical force with the help of the device to separate the cemented parts.

Fabrication of a CAD-CAM custom healing abutment guided by a conventional dental radiograph for delayed loaded dental implants: A dental technique.

This article describes a technique for fabricating a custom anatomic healing abutment for delayed loaded implants by using the computer-aided design and computer-aided manufacturing (CAD-CAM) technology from a polymethyl methacrylate (PMMA) blank. The dimensions of the custom healing abutment are measured from a conventional dental radiograph and diagnostic casts. The healing abutment is used in the second surgical stage to guide soft tissue healing. The resulting soft tissue contour guides the design of the mucosal part of the custom implant abutment.

Effect of additional pressing on the color and translucency of pressable ceramic materials: An in vitro study.

STATEMENT OF PROBLEM: Whether reusing the buttons of pressable ceramic materials affects their color or translucency is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of additional pressing on the color and translucency of 3 different lithium disilicate ceramic brands. MATERIAL AND METHODS: Seventy-two disk-shaped ceramic specimens (Ø14×1.5 mm) were divided into 2 groups: pressed group and additionally pressed group, each containing 36 specimens. These groups were further divided into 3 subgroups: lithium disilicate (LDS), lithium disilicate with high-density micronization technology (LDS-HDM), and zirconia-reinforced lithium silicate (ZLS). Pressing was performed in the press group yielding 36 pressed specimens. Additional pressing was performed by using the buttons resulting from the press group, yielding 36 additionally pressed specimens. Color differences and translucency between pressed and additionally pressed groups were measured with a portable spectrophotometer (VITA Easyshade Compact). The translucency parameter (TP) was measured on black and white backgrounds. Color differences between the 2 groups were analyzed statistically by using the Kruskal-Wallis nonparametric test followed by the Dunn-Sidek method for individual comparison among means of all groups (α=.05). RESULTS: A statistically significant difference was found in color after additional pressing among the 3 tested materials (P=.005). After additional pressing, color difference (ΔE) values were found between the LDS group (3.78 ±1.11) and the ZLS group (3.03 ±1.44). These ΔE values were beyond the selected clinical perceptible threshold (ΔE=2.6). However, the LDS-HDM group had a ΔE value of 1.80 ±1.22, which is considered clinically not perceivable. Furthermore, LDS showed a statistically significant decrease in translucency after additional pressing (P=.002). However, after additional pressing, ZLS and LDS-HDM showed no statistically significant differences in translucency (P>.05). CONCLUSIONS: The colors of the 3 tested materials were affected by additional pressing. Only LDS-HDM showed color changes below the selected clinically perceptible threshold (ΔE=2.6). Furthermore, only LDS showed a significant decrease in translucency.

Evaluation of color duplication in metal-ceramic complexes using visual and instrumental shade-matching systems.

This study was designed to evaluate color differences (DE) between intended and fabricated shades of various metal-ceramic complexes using visual and instrumental shade determination. Forty-two master disks were made to represent every tab in two shade guides. The shades of the master disks were determined visually and instrumentally. Accordingly, 84 experimental disks were fabricated. Color measurements of the master and fabricated disks were performed using a spectrophotometer. Visual shade determination showed a significantly lower DE value than the instrumental shade determination. However, all groups showed DE values exceeding 2.75, which could be considered perceivable and therefore clinically unacceptable. A reliable shade duplication of an existing metal-ceramic restoration cannot be ensured, regardless of the method of shade assessment.

The effect of two fit-indicating materials and various subsequent cleaning methods on the retention of simulated crowns.

STATEMENT OF PROBLEM: Different cleaning methods are recommended to remove residual fit-indicating materials before definitive cementation. There is little information in the dental literature regarding the effect of these cleaning methods on the eventual retention of crowns. PURPOSE: The purpose of this investigation was to evaluate the effect of various cleaning methods on the retention of simulated crowns after using disclosing wax and silicone as fit-indicating materials. MATERIAL AND METHODS: One hundred and ten specimens were divided into 11 groups (n=10) according to the fit indicators used (silicone and disclosing wax) and the methods of cleaning as follows: Group C, no fit indicator with airborne-particle abrasion and steam cleaning (control); Group S+0, silicone with no cleaning; Group S+CH, silicone with chemical cleaning; Group S+ST, silicone with steam cleaning; Group S+US, silicone with ultrasonic cleaning in distilled water; Group S+AA+ST, silicone with airborne-particle abrasion and steam cleaning; Group W+0, disclosing wax with no cleaning; Group W+CH, disclosing wax with chemical cleaning; Group W+ST, disclosing wax with steam cleaning; Group W+US, disclosing wax with ultrasonic cleaning in distilled water; Group W+AA+ST, disclosing wax with airborne-particle abrasion and steam cleaning. Solid acrylic resin blocks were machined to form the specimens. Each specimen consisted of a cylinder and a rod. The specimens were invested and cast using a nickel chromium alloy. The rod and the internal surface of the cylindrical part of each specimen were airborne-particle abraded using 100-mum aluminum oxide powder. After application of fit indicators and subsequent cleaning, all the rods were cemented into their perspective cylinders using zinc phosphate cement at a constant load of 5 kg for 10 minutes. Specimens were randomly assigned to all groups before cementation procedures. The sequence of cementation of all specimens was also performed randomly regardless of the groups to which they were assigned. The specimens were then stored in water at 37 degrees C for 1 month. All specimens were mounted in a universal testing machine and the rods were then pulled out of their respective cylinders at a crosshead speed of 0.05 mm/min. The ultimate load required for separation was recorded and expressed as MPa. The resultant data were statistically analyzed using 2-way ANOVA for fit-indicating materials/cleaning methods, and Tukey honestly significant difference (HSD) tests (alpha =.05). RESULTS: Two-way ANOVA showed significant interaction between the effects of fit-indicating materials tested and the method of cleaning on retention (P<.001). The Tukey HSD test indicated that wax and silicone fit indicators significantly reduced retention if not properly cleaned (P<.001). Retention was significantly improved when wax was used compared to silicone, regardless of the cleaning method (P<.001). Airborne-particle abrasion coupled with steam cleaning produced the highest retention values with both fit indicators tested (P<.001). However, when wax was used there was no significant difference between steam cleaning and airborne-particle abrasion along with steam cleaning. CONCLUSIONS: Wax and silicone fit indicators significantly reduced retention of simulated crowns if not properly cleaned. Airborne-particle abrasion, in addition to steam cleaning, was necessary to clean silicone. However, steam cleaning alone was sufficient for cleaning wax.

Full-mouth rehabilitation following treatment of temporomandibular disorders and teeth-related signs and symptoms.

The literature is replete with theories regarding temporomandibular disorders (TMD). However, there is a paucity of information concerning perceived malocclusion and other teeth-related signs and symptoms after full-mouth rehabilitation. This clinical study was designed to evaluate the perception of TMD patients concerning perceived malocclusion and other teeth-related signs and symptoms after full-mouth rehabilitation guided by the Mental Analog Scale (MAS). Among 38 patients referred for full-mouth rehabilitation, 20 were diagnosed as having TMD after reviewing a questionnaire, recording the major complaints and symptoms, in addition to performing comprehensive clinical examination. Nonsurgical therapy was performed, including fabricating an anterior programming device, a centric relation occlusal device and finally full-mouth rehabilitation by means of placing crowns on all upper and/or lower teeth. All full-mouth rehabilitation procedures were performed using a fully adjustable articulator and mandibular movements were recorded following pantographic tracings. After full-mouth rehabilitation, the patients were followed up at 1, 2, 4, 6, 9, and 12-month intervals, and the major signs and symptoms were recorded along with adjunctive teeth-related signs and symptoms. Fisher exact probability tests were applied to analyze the results (P<.05). Statistical comparisons of the MAS responses before and after treatment (at 1-month recall) showed significant improvement (P<.05) for all teeth-related signs and symptoms except for bruxism (P=.0699). Further improvement was noted at the 4-month recall period. However, these improvements were not statistically significant for all teeth-related signs and symptoms. No further change was noted after the 4-month recall period. There was a marked reduction in perceived malocclusion and adjunctive teeth-related signs and symptoms during function, only after performing occlusal equilibration of the final restorations.

Intrarater repeatability of shade selections with two shade guides.

STATEMENT OF PROBLEM: Color research has shown that shade guides do not always represent the color of natural teeth. Moreover, visual evaluation has been found to be unreliable and inconsistent. PURPOSE: This investigation evaluated the effects of 2 shade guides on the intrarater repeatability (reliability) of prosthodontists and general practitioners with regard to shade selection. MATERIAL AND METHODS: Ten prosthodontists and ten general practitioners (all men, 35-45 years old) with an average practice experience of 14 years participated in this study. Examiners were tested to eliminate color blindness. Each clinician used Vita Lumin Vacuum and Vitapan 3D-Master shade guides to determine the shades of the maxillary right canines of 20 patients following a standard protocol. The identification codes of the shade tabs were masked to prevent shade memory. All teeth were polished before each shade selection, and the selection process was standardized for controlled lighting and procedures. Shade selections were randomly repeated 1 month later by the same practitioners on the same group of patients in accordance with the same shade-selection protocol. Analysis of variance and t tests for individual comparisons among means were performed (P<.05). RESULTS: Significant interactions were found between the effects of shade guide system and specialty training on intrarater repeatability (P<.0001, analysis of variance). The intrarater repeatability of prosthodontists was significantly higher than that of general practitioners when the Vita Lumin Vacuum shade guide was used (P<.0001, t test). Use of the Vitapan 3D-Master shade guide significantly improved the intrarater repeatability of general practitioners compared with the Vita Lumin Vacuum shade guide (P<.0005). This improvement was not significant, however, among prosthodontists (P=.2861). CONCLUSION: Within the limitations of this study, the prosthodontists demonstrated superior intrarater repeatability in shade selection, especially when the Vita Lumin Vacuum shade guide was used. Use of the Vitapan 3D-Master shade guide notably improved intrarater repeatability among the general practitioners.