Effect of Model Resin and Shaft Taper on the Trueness and Fit of Additively Manufactured Removable Dies in Narrow Ridge Models.

Effect of model resin and shaft taper angle on the trueness and fit of additively manufactured removable dies in narrow ridge casts Purpose. To evaluate how model resin and shaft taper affect the trueness and fit of additively manufactured removable dies in narrow ridge casts. MATERIAL AND METHODS: A typodont model with a prepared mandibular molar was scanned to design virtual dies with different shaft tapers (0-degree (straight), 5-degree, and 10-degree tapered). Fifteen dies and one hollowed cast per taper were additively manufactured from two resins (G-PRINT 3D Model, GP and DentaMODEL, DM). Dies and casts were digitized to evaluate their trueness (root mean square (RMS)). The fit of the dies was evaluated with crown portion's RMS when seated in the cast and with distance deviations. Kruskal-Wallis and Mann-Whitney U tests were used to analyze data (α =.05). RESULTS: GP dies had lower overall, root, and base RMS, while DM dies had lower crown RMS (P≤.016). Straight dies had the highest overall, root, and base RMS within GP (P≤.030). Ten-degree dies had the lowest overall and base RMS, lower crown RMS than straight, and lower root RMS than 5-degree dies within DM (P≤.047). When the dies were seated, GP had lower crown portion RMS within 5- and 10-degree dies, and 5-degree dies had the highest RMS within DM (P≤.003). GP had lower distance deviations within 5- and 10-degree dies. Five-degree dies had the highest deviations within DM (P≤.049). CONCLUSIONS: GP dies mostly had higher trueness and better fit. Straight dies mostly had lower trueness within GP. Ten-degree taper mostly led to higher trueness within DM. The shaft taper affected DM dies' fit.

Fatigue behavior of implant-supported cantilevered prostheses in recently introduced CAD-CAM polymers: An in vitro study.

STATEMENT OF PROBLEM: Cantilevered complete arch implant-supported prostheses are commonly fabricated from zirconia and more recently from strength gradient zirconia. Different polymer-based materials indicated for definitive fixed prostheses that could be used with additive or subtractive manufacturing have also been marketed recently. However, knowledge on the long-term fatigue behavior of cantilevered implant-supported prostheses made from these polymer-based materials and strength gradient zirconia is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the fatigue behavior of implant-supported cantilevered prostheses of recently introduced computer-aided design and computer-aided manufacturing polymers and zirconia. MATERIAL AND METHODS: A master standard tessellation language file of a 9×11×20-mm specimen with a titanium base (Ti-base) space that represented an implant-supported cantilevered prosthesis was used to fabricate specimens from additively manufactured interim resin (AM), polymethyl methacrylate (SM-PM), nanographene-reinforced polymethyl methacrylate (SM-GR), high-impact polymer composite resin (SM-CR), and strength gradient zirconia (SM-ZR) (n=10). Each specimen was prepared by following the respective manufacturer's recommendations, and Ti-base abutments were cemented with an autopolymerizing luting composite resin. After cementation, the specimens were mounted in a mastication simulator and subjected to 1.2 million loading cycles under 100 N at 1.5 Hz; surviving specimens were subjected to another 1.2 million loading cycles under 200 N at 1.5 Hz. The load was applied to the cantilever extension, 12-mm from the clamp of the mastication simulator. The Kaplan-Meier survival analysis and Cox proportional hazards model were used to evaluate the data (α=.05). RESULTS: Significant differences in survival rate and hazard ratio were observed among materials (P<.001). Among tested materials, SM-ZR had the highest and AM had the lowest survival rate (P≤.031). All materials had a significantly higher hazard ratio than SM-ZR (P≤.011) in the increasing order of SM-GR, SM-PM, SM-CR, and AM. CONCLUSIONS: SM-ZR had the highest survival rate with no failed specimens. Even though most of the tested polymer-based materials failed during cyclic loading, these failures were commonly observed during the second 1.2 million loading cycles with 200 N. All materials had a higher hazard ratio than SM-ZR.

Influence of scan extension and starting quadrant on the accuracy of four intraoral scanners for fabricating tooth-supported crowns.

STATEMENT OF PROBLEM: Multiple factors can influence the accuracy of intraoral scanners (IOSs). However, the impact of scan extension and starting quadrant on the accuracy of IOSs for fabricating tooth-supported crowns remains uncertain. PURPOSE: The purpose of the present in vitro study was to measure the influence of scan extension (half or complete arch scan) and the starting quadrant (same quadrant or contralateral quadrant of the location of the crown preparation) on the accuracy of four IOSs. MATERIAL AND METHODS: A typodont with a crown preparation on the left first molar was digitized (T710) to obtain a reference scan. Four scanner groups were created: TRIOS 5, PrimeScan, i700, and iTero. Then, 3 subgroups were defined based on the scan extension and starting quadrant: half arch (HA subgroup), complete arch scan starting on the left quadrant (CA-same subgroup), and complete arch scan starting on the right quadrant (CA-contralateral subgroup), (n=15). The reference scan was used as a control to measure the root mean square (RMS) error discrepancies with each experimental scan on the tooth preparation, margin of the tooth preparation, and adjacent tooth areas. Two-way ANOVA and pairwise multiple comparisons were used to analyze trueness (α=.05). The Levene and pairwise comparisons using the Wilcoxon Rank sum tests were used to analyze precision (α=.05). RESULTS: For the tooth preparation analysis, significant trueness and precision differences were found among the groups (P<.001) and subgroups (P<.001), with a significant interaction group×subgroup (P=.002). The iTero and TRIOS5 groups obtained better trueness than the PrimeScan and i700 groups (P<.001). Moreover, half arch scans obtained the best trueness, while the CA-contralateral scans obtained the worst trueness (P<.001). The iTero group showed the worst precision among the IOSs tested. For the margin of the tooth preparation evaluation, significant trueness and precision differences were found among the groups (P<.001) and subgroups (P<.001), with a significant interaction group×subgroup (P=.005). The iTero group obtained best trueness (P<.001), but the worst precision (P<.001) among the IOSs tested. Half arch scans obtained the best trueness and precision values. For the adjacent tooth analysis, trueness and precision differences were found among the groups (P<.001) and subgroups tested (P<.001), with a significant interaction group×subgroup (P=.005). The TRIOS 5 obtained the best trueness and precision. Half arch scans obtained the best accuracy. CONCLUSIONS: Scan extension and the starting quadrant impacted the scanning trueness and precision of the IOSs tested. Additionally, the IOSs showed varying scanning discrepancies depending on the scanning area assessed. Half arch scans presented the highest trueness and precision, and the complete arch scans in which the scan started in the contralateral quadrant of where the crown preparation was obtained the worst trueness and precision.

Fabrication trueness and marginal quality of additively manufactured resin-based definitive laminate veneers with different restoration thicknesses.

OBJECTIVES: To evaluate how restoration thickness (0.5 mm and 0.7 mm) affects the fabrication trueness of additively manufactured definitive resin-based laminate veneers, and to analyze the effect of restoration thickness and margin location on margin quality. METHODS: Two maxillary central incisors were prepared either for a 0.5 mm- or 0.7 mm-thick laminate veneer. After acquiring the partial-arch scans of each preparation, laminate veneers were designed and stored as reference data. By using these reference data, a total of 30 resin-based laminate veneers were additively manufactured (n = 15 per thickness). All veneers were digitized and stored as test data. The reference and test data were superimposed to calculate the root mean square values at overall, external, intaglio, and marginal surfaces. The margin quality at labial, incisal, mesial, and distal surfaces was evaluated. Fabrication trueness at each surface was analyzed with independent t-tests, while 2-way analysis of variance was used to analyze the effect of thickness and margin location on margin quality (α = 0.05). RESULTS: Regardless of the evaluated surface, 0.7 mm-thick veneers had lower deviations (P < 0.001). Only the margin location (P < 0.001) affected the margin quality as labial margins had the lowest quality (P < 0.001). CONCLUSION: Restoration thickness affected the fabrication trueness of resin-based laminate veneers as 0.7 mm-thick veneers had significantly higher trueness. However, restoration thickness did not affect the margin quality and labial margins had the lowest quality. CLINICAL SIGNIFICANCE: Laminate veneers fabricated by using tested urethane-based acrylic resin may require less adjustment when fabricated in 0.7 mm thickness. However, marginal integrity issues may be encountered at the labial surface.

Effect of Hydrothermal Aging on the Flexural Strength and Microhardness of Materials Used for Additive or Subtractive Manufacturing of Definitive Restorations.

PURPOSE: To evaluate the flexural strength (FS) and microhardness of various CAD/CAM restorative materials intended for definitive use. The effect of hydrothermal aging on the mechanical properties of these materials was also investigated. MATERIALS AND METHODS: A total of 210 bar-shaped specimens (17 × 4 × 1.5 mm ± 0.02 mm) were fabricated via either subtractive manufacturing (SM) methods-reinforced composite resin (SM-CR), polymer-infiltrated ceramic network (SM-PICN), fine-structured feldspathic ceramic (SMFC), nanographene-reinforced polymethyl methacrylate (PMMA; SM-GPMMA), PMMAbased resin (SM-PMMA)-or additive manufacturing (AM) methods with urethane acrylate-based resins (AM-UA1 and AM-UA2). Specimens were then divided into two subgroups (nonaged or hydrothermal aging; n = 15). A three-point flexural strength test was performed, and five specimens from the nonaged group were submitted to microhardness testing. Specimens were subjected to 10,000 thermal cycles, and the measurements were repeated. RESULTS: Regardless of aging, SM-CR had the highest FS (P < .001), followed by SM-GPMMA (P ≤ .042). In nonaged groups, AM-UA2 had a lower FS than all other materials except SM-FC (P = 1.000). In hydrothermal aging groups, AM specimens had lower FS values than other materials, except SM-PMMA. With regard to microhardness, there was no significant difference found between any of the tested materials (P ≥ .945) in the nonaged and hydrothermal aging groups. CONCLUSIONS: The effect of hydrothermal aging on FS varied depending on the type of restorative material. Regardless of aging condition, SM-CR showed the highest FS values, whereas SM-FC had the highest microhardness. Hydrothermal aging had no significant influence on the microhardness of the tested materials.

Verifying the seating of a 3D-printed removable die using elastomeric matrices: A dental technique.

Computer-aided design and computer-aided manufacturing systems enable digital designing and 3-dimensional (3D) printing of definitive casts with removable dies. However, the fit of the removable dies should be without interferences for their accurate positioning in the cast. Given that the accuracy of additive manufacturing depends on design- and manufacturing-related factors, verifying the accuracy of the position of 3D-printed removable dies in their cast is essential to fabricate positionally accurate definitive prostheses, which would enable minimal or no laboratory and clinical adjustments. This dental technique article presents a straightforward approach to verify the seating of a 3D-printed removable die by using verification matrices made of a polyvinylsiloxane interocclusal registration material.

Dimensional Stability of Additively Manufactured Diagnostic Maxillary Casts Fabricated with Different Model Resins.

PURPOSE: To evaluate the effect of model resin type and time interval on the dimensional stability of additively manufactured diagnostic casts. MATERIALS AND METHODS: Ten irreversible hydrocolloid impressions and 10 impressions from an intraoral scanner were made from a reference maxillary stone cast, which was also digitized with a laboratory scanner. Conventional impressions were poured in type III stone (SC), while digital impressions were used to additively manufacture casts with a nanographene-reinforced model resin (GP) or a model resin (DM). All casts were digitized with the same laboratory scanner 1 day (T0), 1 week (T1), 2 weeks (T2), 3 weeks (T3), and 4 weeks (T4) after fabrication. Cast scans were superimposed over the reference cast scan to evaluate dimensional stability. Data were analyzed with Bonferroni-corrected repeated measures ANOVA (α = .05). RESULTS: The interaction between the main factors (material type and time interval) affected anterior teeth deviations, while the individual main factors affected anterior teeth and entire-cast deviations (P ≤ .008). Within anterior teeth, DM had the lowest deviations at T3, and GP mostly had lower values at T2 and lower deviations at T3 than at T0 (P ≤ .041). SC had the highest pooled anterior teeth deviations, and GP had the highest pooled entire cast deviations (P < .001). T3 had lower pooled anterior teeth deviations than at T0, T1, and T4, and higher pooled entire cast deviations than T1 were demonstrated (P ≤ .027). CONCLUSIONS: The trueness of nanographene-reinforced casts was either similar to or higher than that of other casts. Dimensional changes were acceptable during the course of 1 month.

Effect of Polymerization Unit, Polishing, and Coffee Thermocycling on the Color and Translucency of Additively Manufactured Resins Used for Definitive Prostheses.

PURPOSE: To evaluate the effect of polymerization unit, polishing, and coffee thermocycling on the color and translucency of additively manufactured polyurethane-based resins with different viscosities. In addition, their color behavior was compared with the color of the shade tab throughout the fabrication steps and aging. MATERIALS AND METHODS: Disk-shaped specimens (Ø10 × 2 mm) were fabricated from polyurethane-based resins with different viscosities (Tera Harz TC-80DP and C&B permanent; n = 30 per material). Baseline color coordinates were measured after cleaning. The specimens in each resin group were divided into three subgroups (n = 10 per subgroup) to be polymerized with different polymerization units (Otoflash G171 [FLN], Wash and Cure 2.0 [CLED1], and P Cure [CLED2]), polished, and subjected to coffee thermocycling. Color coordinates were remeasured after each process. Color differences (ΔE00) and relative translucency parameter (RTP) values were calculated. Data were statistically analyzed (α = .05). RESULTS: Time points and polymerization units affected the ΔE00 for each material (P ≤ .049). ΔE00 of each polymerization unit pair had significant differences within and among different time points within each material (P ≤ .024). ΔE00 (when compared with the shade tab) and RTP were mostly affected by polymerization units and time points within both materials (P ≤ .042). CONCLUSIONS: Tested polymerization units, polishing, and coffee thermocycling affected the color difference and translucency of tested resins. Color differences ranged from moderately unacceptable to extremely unacceptable, and the differences in translucency values mostly ranged from perceptible to unacceptable, according to previous thresholds. In addition, tested resin-polymerization unit pairs had unacceptable color differences when compared to the shade tab. CLED1 may enable higher color stability for tested resins.

Biomechanical Analysis of One-Piece Post and Cores in Different Materials: Can High-Performance Polymers Be an Option?

PURPOSE: The aim of this finite element analysis was to evaluate the stress distribution along a premolar's root dentin, its post, and post luting agent when materials with different elastic modulus are used to fabricate one-piece post-and-cores in 2 different design. MATERIALS AND METHODS: Two 3D virtual models (for cylindrical and conical post designs) of a mandibular premolar restored with one-piece post-and-core restorations were obtained by using a software. A total of eight post-and-core materials (polyether-ether-ketone (PEEK), polyether-ketone-ketone (PEKK), glass fiber-reinforced polyether-ether-ketone (GFR-PEEK), carbon fiber-reinforced polyether-ether-ketone (CFR-PEEK), gold-palladium alloy (Au-Pd), titanium (Ti), zirconia (Zi) and chromium-nickel (Cr-Ni)) were tested. Maxiumum principals stress (MPS) in the post, post luting agent, and root dentin were determined. A load of 150 N was applied to the buccal cusp in linguo-labial direction at an angle of 45° oblique to the longitudinal axis of the crown. RESULTS: The highest MPS value in post structure was observed with Cr-Ni material for both post designs. Similarly, the highest MPS value in the post luting agent was observed for Cr-Ni, the material with the highest elastic modulus. However, in the root dentin, the highest value was observed in PEEK, the material with the lowest elastic modulus. CONCLUSION: Post material and design influenced the stress concentration in the post, post luting agent, and root dentin. The stress at root dentin was slightly higher for polymeric materials. Cylindrical post design revealed lower stresses than conical post design at root dentin for all post-and-core materials tested.

Implementation of triple-scan protocol to evaluate the fit of complete-arch implant-supported fixed prostheses.

Passive fit is essential for multiple-unit implant-supported prostheses. Conventional methods to assess the passivity of complete-arch implant-supported prostheses do not allow 3-dimensional (3D) visualization and quantification of misfit. This report describes the marginal and internal fit evaluation of a complete-arch implant-supported prosthesis by using the triple-scan protocol involving a scanner and a 3D analysis freeware. This technique allows researchers, clinicians, or dental technicians to detect and quantify 3D prosthetic misfit, which may facilitate the preparation for dental appointments and objective measurement of misfit for research studies.

Tooth morphology, internal fit, occlusion and proximal contacts of dental crowns designed by deep learning-based dental software: A comparative study.

OBJECTIVES: This study compared the tooth morphology, internal fit, occlusion, and proximal contacts of dental crowns automatically generated via two deep learning (DL)-based dental software systems with those manually designed by an experienced dental technician using conventional software. METHODS: Thirty partial arch scans of prepared posterior teeth were used. The crowns were designed using two DL-based methods (AA and AD) and a technician-based method (NC). The crown design outcomes were three-dimensionally compared, focusing on tooth morphology, internal fit, occlusion, and proximal contacts, by calculating the geometric relationship. Statistical analysis utilized the independent t-test, Mann-Whitney test, one-way ANOVA, and Kruskal-Wallis test with post hoc pairwise comparisons (α = 0.05). RESULTS: The AA and AD groups, with the NC group as a reference, exhibited no significant tooth morphology discrepancies across entire external or occlusal surfaces. The AD group exhibited higher root mean square and positive average values on the axial surface (P < .05). The AD and NC groups exhibited a better internal fit than the AA group (P < .001). The cusp angles were similar across all groups (P = .065). The NC group yielded more occlusal contact points than the AD group (P = .006). Occlusal and proximal contact intensities varied among the groups (both P < .001). CONCLUSIONS: Crowns designed by using both DL-based software programs exhibited similar morphologies on the occlusal and axial surfaces; however, they differed in internal fit, occlusion, and proximal contacts. Their overall performance was clinically comparable to that of the technician-based method in terms of the internal fit and number of occlusal contact points. CLINICAL SIGNIFICANCE: DL-based dental software for crown design can streamline the digital workflow in restorative dentistry, ensuring clinically-acceptable outcomes on tooth morphology, internal fit, occlusion, and proximal contacts. It can minimize the necessity of additional design optimization by dental technician.

Load bearing capacity of 3-unit screw-retained implant-supported fixed dental prostheses with a mesial and distal cantilever on a single implant: A comparative in vitro study.

OBJECTIVES: To assess the mechanical durability of monolithic zirconia implant-supported fixed dental prostheses (iFDP) design on one implant, with a distal and a mesial extension cantilever bonded to a titanium base compared to established designs on two implants. MATERIALS AND METHODS: Roxolid Tissue level (TL), and tissue level x (TLX) implants were used to manufacture screw-retained 3-unit iFDPs (n = 60, n = 10 per group), with following configurations (X: Cantilever; I: Implant, T: Test group, C: Control group): T1: X-I-X (TL); T2: X-I-X (TLX); T3: I-I-X (TL); T4: I-I-X (TLX); C1: I-X-I (TL); C2: I-X-I (TLX). The iFDPs were thermomechanically aged and subsequently loaded until fracture using a universal testing machine. The failure load at first crack (Finitial) and at catastrophic fracture (Fmax) were measured and statistical evaluation was performed using two-way ANOVA and Tukey's post-hoc tests. RESULTS: The mean values ranged between 190 ± 73 and 510 ± 459 N for Finitial groups, and between 468 ± 76 and 1579 ± 249 N for Fmax, respectively. Regarding Finitial, neither the implant type, nor the iFDP configuration significantly influenced measured failure loads (all p > 0.05). The choice of implant type did not show any significant effect (p > 0.05), while reconstruction design significantly affected Fmax data (I-I-Xa < X-I-Xb < I-X-Ic) (p < 0.05). The mesial and distal extension groups (X-I-X) showed fractures only at the cantilever extension site, while the distal extension group (I-I-X) showed one abutment and one connector fracture at the implant/reconstruction interface. CONCLUSION: Results suggest that iFDPs with I-X-I design can be recommended regardless of tested implant type followed by the mesial and distal extension design on one implant abutment (X-I-X).

Effect of coffee thermocycling on the surface roughness and stainability of denture base materials with different chemical compositions manufactured with additive and subtractive technologies.

OBJECTIVE: To evaluate the effect of coffee thermocycling (CTC) on the surface roughness (Ra ) and stainability of denture base materials with different chemical compositions fabricated by using additive and subtractive manufacturing. MATERIALS AND METHODS: Disk-shaped specimens were additively (FREEPRINT denture, AM) or subtractively (G-CAM, GSM and M-PM, SM) fabricated from three pink denture base materials in different chemical compositions (n = 10). Ra was measured before and after polishing, while color coordinates were measured after polishing. Specimens were subjected to CTC (5000 cycles) and measurements were repeated. Color differences (ΔE00 ) after CTC were calculated. Ra among different time intervals within materials was evaluated by using repeated measures analysis of variance (ANOVA), while 1-way ANOVA was used to evaluate the Ra of different materials within each time interval and the ΔE00 values. Color coordinates within each material were compared by using paired samples t-tests (α = 0.05). RESULTS: Ra before polishing was the highest for all materials (p < 0.001), while SM had its lowest Ra after CTC and AM had its lowest Ra after polishing (p ≤ 0.008). Before polishing, AM had the highest Ra among the materials (p < 0.001). After polishing, SM had higher Ra than AM (p < 0.001). After CTC, GSM had the lowest Ra (p ≤ 0.048). SM had the lowest (p ≤ 0.031) and AM had the highest (p < 0.001) ΔE00 . CTC decreased the a* and b* values of SM and AM (p ≤ 0.017), and increased the L* values of AM (p < 0.001). CONCLUSIONS: Polishing significantly reduced the surface roughness of all materials. CTC did not increase the surface roughness of materials above the clinically acceptable threshold. Only AM had perceptible color change when previously reported threshold values for denture base materials were considered. CLINICAL SIGNIFICANCE: Tested denture base materials may have similar surface stability after coffee thermocycling. However, subtractively manufactured denture base materials may have improved color stability when subjected to long-term coffee consumption.

Effect of Material Thickness and Coffee Thermocycling on the Color Stability and Translucency of Additively and Subtractively Manufactured Resin-Based Materials for Definitive Restorations.

PURPOSE: To evaluate the effect of material thickness and coffee thermocycling on the optical properties of definitive resin-based materials created via additive manufacturing (AM) and subtractive manufacturing (SM). MATERIALS AND METHODS: Specimens were prepared in three thicknesses (1, 1.5, and 2 mm) from three AM (3D-CB, 3D-TH, and 3D-CT) and two SM (G-CAM and VE) resin-based materials (n = 15 per material and thickness combination). Color coordinates of each specimen were measured after polishing and after 10,000 cycles of coffee thermocycling. Color differences (ΔE00s) and relative translucency parameter (RTP) values were calculated. After logarithmic transformation, ΔE00 values were analyzed with two-way ANOVA, while RTP values were analyzed with generalized linear model test (α = .05). RESULTS: 3D-TH had the highest pooled ΔE00 and G-CAM had the lowest (P ≤ .004). 3D-CB had higher pooled ΔE00 than VE and 3D-CT (P ≤ .002). For the SM group, the 1.5-mm and 2-mm 3DCT specimens and 1-mm 3D-TH specimens had lower ΔE00 than 1.5-mm and 2-mm 3D-TH specimens (P ≤ .036). Most of the AM specimens and 1-mm VE specimens had higher ΔE00 than 2-mm G-CAM specimens (P ≤ .029). Further, most AM specimens had higher ΔE00 than 1.5-mm G-CAM specimens (P ≤ .006). RTP values increased in order of 3D-CT, G-CAM, VE, 3D-CB, and 3D-TH specimens (P < .001). Increased thickness and coffee thermocycling mostly reduced RTP (P < .001). CONCLUSIONS: 3D-TH typically had higher color change values than SM specimens, while G-CAM typically had lower color change values than AM specimens. Only the 1.5-mm and 2-mm 3D-TH specimens had unacceptable color changes. Thickness and coffee thermocycling mostly reduced the translucency.

Fabrication Trueness, Intaglio Surface Adaptation, and Marginal Integrity of Resin-Based Onlay Restorations Fabricated by Additive and Subtractive Manufacturing.

PURPOSE: To evaluate the fabrication trueness, intaglio surface adaptation, and marginal integrity of resin-based onlay restorations made via additive manufacturing (AM) or subtractive manufacturing (SM). MATERIALS AND METHODS: An onlay restoration was designed (DentalCAD Galway 3.0) and saved as an STL file to generate a design STL file (DO-STL). Using this design, 45 onlays were fabricated either with AM (3D-printed resin for definitive [AM-D; Tera Harz TC-80DP] and interim [AM-I; Freeprint temp] restorations) or SM (composite resin, Tetric CAD) technologies. Onlays were scanned with an intraoral scanner (CEREC Primescan SW 5.2), and the scans were saved as test STL files (TO-STLs). For trueness evaluation, TO-STLs were superimposed over the DO-STL, and root mean square (RMS) values of overall and intaglio surfaces were measured (Geomagic Control X). For the intaglio surface adaptation and marginal integrity, a triple-scan protocol was performed. Kolmogorov-Smirnov, one-way ANOVA, and post-hoc Tukey honestly significant difference tests were used to analyze data (α = .05). RESULTS: RMS values of intaglio and overall surfaces, intaglio adaptation, and marginal integrity varied among test groups (P < .001). AM-D had the greatest overall surface RMS (P < .001), while SM had the greatest intaglio surface RMS (P < .001). SM had the highest average distance deviations for intaglio surface adaptation and marginal integrity, whereas AM-D had the lowest (P < .001). CONCLUSIONS: AM-D onlays showed lower overall trueness than AM-I onlays and SM definitive onlays. However, AM-D onlays presented high intaglio surface trueness, intaglio surface adaptation, and marginal integrity.

Influence of intraoral scanner and finish line location on the fabrication trueness and margin quality of additively manufactured laminate veneers fabricated with a completely digital workflow.

STATEMENT OF PROBLEM: Knowledge of the fabrication trueness and margin quality of additively manufactured (AM) laminate veneers (LVs) when different intraoral scanners (IOSs) and finish line locations are used is limited. PURPOSE: The purpose of this in vitro study was to evaluate the fabrication trueness and margin quality of AM LVs with different finish line locations digitized by using different IOSs. MATERIAL AND METHODS: An LV preparation with a subgingival (sub), equigingival (equi), or supragingival (supra) finish line was performed on 3 identical maxillary right central incisor typodont teeth. Each preparation was digitized by using 2 IOSs, (CEREC Primescan [PS] and TRIOS 3 [TS]), and a reference LV for each finish line-IOS pair (n=6) was designed. A total of 90 LVs were fabricated by using these files and urethane acrylate-based definitive resin (Tera Harz TC-80DP) (n=15). Each LV was then digitized by using PS to evaluate fabrication trueness (overall, external, intaglio, and marginal surfaces). Each LV was also qualitatively evaluated under a stereomicroscope (×60), and the cervical and incisal margin quality was graded. Fabrication trueness and cervical margin quality were evaluated by using 2-way analysis of variance, while Kruskal-Wallis and Mann Whitney-U tests were used to evaluate incisal margin quality (α=.05). RESULTS: The interaction between the IOS type and the finish line location affected measured deviations at each surface (P≤.020). PS-sub and TS-supra had higher overall trueness than their counterparts. and the subgingival finish line resulted in the lowest trueness (P≤.005). PS and the subgingival finish line led to the lowest trueness of the external surface (P≤.001). TS-sub had the lowest intaglio surface trueness among the TS subgroups, and PS-sub had higher trueness than TS-sub (P<.001). PS-sub and PS-supra had higher marginal surface trueness than their TS counterparts (P<.001). TS resulted in higher cervical margin quality (P=.001). CONCLUSIONS: Regardless of the IOS tested, subgingival finish lines resulted in the lowest trueness. The effect of IOS on the measured deviations varied according to the surface evaluated and finish line location. The cervical margin quality of AM LVs was higher when TS was used.

Stainability and translucency of potassium aluminum sulfate applied computer-aided design and computer-aided manufacturing materials after coffee thermocycling.

OBJECTIVE: The purpose of this in vitro study was to evaluate the effect of potassium aluminum sulfate (alum) application on the stainability and translucency of computer-aided design and computer-aided manufacturing (CAD-CAM) materials after coffee thermocycling (CTC). MATERIALS AND METHODS: Disk-shaped specimens (Ø10 × 1 mm; N = 200) were fabricated by using additively (Crowntec [CT] and Varseo Smile Crown Plus [VS]) and subtractively manufactured (Brilliant Crios [RCR], CEREC Block [FC], and Vita Enamic [VE]) CAD-CAM materials and polished. All specimens were randomly divided into two groups as alum applied and control (n = 10). All specimens were then subjected to CTC (10,000 cycles at 5-55°C) and color coordinates were measured at each time interval. Color differences (ΔE00 ) and relative translucency parameters (RTPs) were calculated and the data were statistically analyzed (a = 0.05). RESULTS: Among tested time intervals, alum applied specimens had their lowest ΔE00 after alum application (p ≤ 0.006), except for FC (p = 0.177). In addition, alum applied RCR had lower ΔE00 values than its control specimens (p = 0.029). Alum applied specimens had their lowest RTP after CTC (p < 0.001) and alum application decreased the RTP of CT (p = 0.010). CTC reduced the RTP of all materials in control groups (p < 0.001). Alum applied CT had higher RTP than its control specimens (p = 0.049). CONCLUSIONS: Alum application's effect on color change varied depending on the material and alum mostly resulted in clinically acceptable changes in translucency. CTC led to unacceptable color and translucency changes based on previously reported threshold values. CLINICAL SIGNIFICANCE: Optical properties of CAD-CAM materials and the sustainability of these properties over time is critical for longevity. Alum may improve the color stability of reinforced composite resin when subjected to long-term coffee consumption.

Antimicrobial activity, surface properties, and cytotoxicity of microencapsulated phytochemicals incorporated into three-dimensionally printable dental polymers.

OBJECTIVES: This study aimed to investigate the antimicrobial properties of three dimensionally-printed dental polymers (3DPs) incorporated with microencapsulated phytochemicals (MPs) and to assess their surface characteristics and cytotoxicity. METHODS: MPs derived from phytoncide oil and their specific chemical components were introduced into suspensions of three microbial species: Streptococcus gordonii, Streptococcus oralis, and Candida albicans. Optical density was measured to determine the microbial growth in the presence of MPs for testing their antimicrobial activity. MPs at 5% (w/w) were mixed with dental polymers and dispersants to 3DP discs. These microbial species were then seeded onto the discs and incubated for 24 h. The antibacterial and antifungal activities of MP-containing 3DPs were evaluated by counting the colony-forming units (n = 3). The biofilm formation on the 3DP was assessed by crystal violet staining assay (n = 3). Microbial viability was determined using a live-dead staining and CLSM observation (n = 3). Surface roughness and water contact angle were assessed (n = 10). Cytotoxicity of MP-containing 3DPs for human gingival fibroblast was evaluated by MTT assay. RESULTS: MPs, particularly (-)-α-pinene, suppressed the growth of all tested microbial species. MP-containing 3DPs significantly reduced the colony count (P ≤ 0.001) and biofilm formation (P ≤ 0.009), of all tested microbial species. Both surface roughness (P < 0.001) and water contact angle (P < 0.001) increased. The cytotoxicity remained unchanged after incorporating MPs to the 3DPs (P = 0.310). CONCLUSIONS: MPs effectively controlled the microbial growth on 3DPs as evidenced by the colony count, biofilm formation, and cell viability. Although MPs modified the surface characteristics, they did not influence the cytotoxicity of 3DPs. CLINICAL SIGNIFICANCE: Integration of MPs into 3DPs could produce dental prostheses or appliances with antimicrobial properties. This approach not only provides a proactive solution to reduce the risk of oral biofilm-related infection but also ensures the safety and biocompatibility of the material, thereby improving dental care.

Evaluation of Prosthetic Complications with Metal-Acrylic Resin Implant-Fixed Complete Dentures: A Medium- and Long-Term Retrospective Analysis with Up to 13 Years of Follow-up

PURPOSE: To present prosthetic complications observed in the medium and long term in patients treated with metal-acrylic resin implant-supported fixed complete dentures (MAIFCDs). MATERIALS AND METHODS: A total of 87 patients who were treated with MAIFCDs were included. Acrylic resin (denture teeth and base) fracture, screw loosening (prosthetic or abutment), screw (prosthetic or abutment), and framework fracture were analyzed for descriptive statistics. Product-limit survival estimates were used for the cumulative no-complication rate (CNCR) of prostheses. All results were assessed using α = .05. RESULTS: The average observation time was 42.9 months (range: 19 to 153). Of 597 implants, 8 mandibular (44.4%) and 10 maxillary implants (55.6%) failed. In total, 29 patients (33.3%) experienced no complications in an average of 7 years, and 58 patients (66.6%) experienced at least one complication. The average time for the first complication to occur was 23 months (range: 1 to 97 months). The average number of complications was 5.9/patient. Acrylic resin complications were the most frequent, followed by screw loosening, screw fracture, and framework fracture. Of those patients with complications, 9 (16%) had maxillary MAIFCDs with an average of 4 complications. In total, 28 patients (48%) had only mandibular MAIFCDs with an average of 5 complications, and 21 patients (36%) had both arches treated with MAIFCDs with an average of 9 complications. Mandibular MAIFCDPs in women had a higher CNCR compared to maxillary MAIFCDs of both women and men and when both arches of women were treated with MAIFCDs (P < .05). CONCLUSIONS: The CNCR of MAIFCDs differed depending on the arch treated and sex. Mandibular MAIFCDs in women had a lower complication rate than MAIFCDs in other arch-sex pairs. Acrylic resin related complications were commonly observed as well as prosthetic screw loosening.