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.

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.

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.

Cameo and intaglio surface stability and variability of additively, subtractively, and conventionally manufactured occlusal devices after long-term storage.

STATEMENT OF PROBLEM: Additive and subtractive manufacturing have become alternative technologies for fabricating occlusal devices. However, knowledge of the long-term stability of occlusal devices fabricated using these recent technologies is limited. PURPOSE: The purpose of this in vitro study was to evaluate the cameo and intaglio surface stability and variability of additively, subtractively, and conventionally manufactured occlusal devices after 18 months of storage. MATERIAL AND METHODS: A standard tessellation language (STL) file of a dentate maxillary typodont was used to design a master occlusal device. The STL file of this design was used to fabricate occlusal devices additively either with a digital light processing (AM-1) or a continuous liquid interface production (AM-2) printer, subtractively with 2 different 5-axis milling units (SM-1 and SM-2), and conventionally (TM-HP) (n=10). STL files of each device's cameo and intaglio surfaces were generated using a laboratory scanner after fabrication and after 18 months of storage in a moist environment. These generated files were imported into an analysis software program (Geomagic Control X) to analyze the dimensional stability of tested devices by using the root mean square method. The average deviation values defined the variability of measured changes over time. Cameo and intaglio surface deviations were analyzed using the Kruskal-Wallis and Dunn tests, while the variability of measured deviations was analyzed with 1-way analysis of variance and the Tukey HSD tests (α=.05). RESULTS: Significant differences were observed among tested devices when the intaglio surface deviations and the cameo surface variability were considered (P<.001). SM-2 had significantly higher intaglio surface deviations than AM-1, SM-1, and AM-2 (P≤.036). Among the test groups, AM-1 had the greatest cameo surface variability (P≤.004). CONCLUSIONS: SM-2 resulted in lower intaglio surface stability than the additive and the other subtractive manufacturing technologies, while AM-1 led to the highest cameo surface variability among the test groups.

Effect of internal connection type and screw channel angle on the screw stability of anterior implant-supported zirconia crowns.

OBJECTIVES: To investigate the effect of implant-abutment connection and screw channel angle on screw stability by comparing a newly introduced and an established connection, before and after cyclic loading. MATERIALS AND METHODS: Implants (N = 44) with Torcfit (TF) or Crossfit (CF) connection were divided to be restored with a straight (CFS and TFS) or an angled screw access channel (CFA and TFA) titanium-base abutment (n = 11). CFA and TFA received screw-retained crowns, whereas CFS and TFS received hybrid zirconia abutments and cement-retained crowns. The initial torque value (ITV) of each complex (ITVI ) and removal torque value (RTV) after 24 h (RTVI ) were measured. Screws were replaced with new ones, ITVs were recorded again (ITVF ), and crowns were cyclically loaded (2.4 million cycles, 98 N) to measure RTVs again (RTVF ). Percentage torque loss was calculated. Data were analyzed (α = 0.05). RESULTS: ITVs were similar among groups (p ≥ .089). CF led to higher RTVs (p ≤ .002), while CFS had higher RTVI than CFA (p = .023). After 24 h, CFS had lower percentage torque loss than TF, while CFA had lower percentage torque loss than TFA (p ≤ .011). After cyclic loading, CF led to lower percentage torque (p < .001). CONCLUSION: The implant-abutment connection affected the removal torque values. However, no screw loosening occurred during cyclic loading, which indicated a stable connection for all groups. Screw access channel angle did not affect screw stability after cyclic loading.

Effect of coffee thermocycling on the surface roughness and stainability of nanographene-reinforced polymethyl methacrylate used for fixed definitive prostheses.

STATEMENT OF PROBLEM: A nanographene-reinforced polymethyl methacrylate (PMMA) has been introduced for definitive prostheses. However, knowledge on the surface roughness and stainability of this material is lacking. PURPOSE: The purpose of this in vitro study was to compare the surface roughness and stainability of nanographene-reinforced PMMA with those of a prepolymerized PMMA and a reinforced composite resin after coffee thermocycling. MATERIAL AND METHODS: Disk-shaped specimens (Ø10×1.5-mm) were prepared from 3 different A1-shade millable resins (prepolymerized PMMA [M-PM; PMMA]; nanographene-reinforced PMMA [G-CAM; G-PMMA]; reinforced composite resin [Brilliant Crios; RCR]). Surface roughness (Ra) values were measured before and after conventional polishing by using a noncontact profilometer. Initial color coordinates were measured over a gray background with a spectrophotometer after polishing. Specimens were then thermocycled in coffee for 5000 cycles. Measurements were repeated after coffee thermocycling, and color differences (ΔE00) were calculated. Ra values among different time intervals were analyzed by using either the Friedman and Dunn tests (RCR) or repeated measures analysis of variance (ANOVA) and Bonferroni corrected paired samples t tests (PMMA and G-PMMA), while Ra values within a time interval were analyzed by using either the Kruskal-Wallis and Dunn tests (before polishing) or 1-way ANOVA and Tukey HSD (after polishing) or Tamhane T2 tests (after coffee thermocycling). ΔE00 values were analyzed by using 1-way ANOVA and Tukey HSD tests, while color coordinates of the specimens after polishing and after coffee thermocycling were compared by using paired samples t tests (α=.05). RESULTS: All materials had their highest Ra values before polishing (P≤.011), while differences after polishing and after coffee thermocycling values were nonsignificant (P≥.140). PMMA had higher Ra than RCR before polishing (P=.002), and RCR had higher values than G-PMMA after polishing and after coffee thermocycling (P≤.023). RCR had the highest ΔE00 (P<.001). Polishing increased the b∗ values of PMMA, and coffee thermocycling increased the a∗ values of G-PMMA and all values of RCR (P≤.012). CONCLUSIONS: The tested materials had similar and acceptable surface roughness after polishing. The surface roughness of materials was not affected by coffee thermocycling. Considering the reported color thresholds, all materials had acceptable color change, but the computer-aided design and computer-aided manufacturing composite resin had perceptible color change after coffee thermocycling.

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

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

Trueness of crowns fabricated by using additively and subtractively manufactured resin-based CAD-CAM materials.

STATEMENT OF PROBLEM: Advancements in digital dental technologies have enabled the use of different resin-based materials that can be fabricated either additively or subtractively. However, knowledge on the fabrication trueness of these materials is scarce. PURPOSE: The purpose of this in vitro study was to investigate the trueness of crowns fabricated by using different resin-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials. MATERIAL AND METHODS: A complete crown for a mandibular right first molar with a 30-µm cement space was designed in standard tessellation language (STL) format. This master STL (MC-STL) was used to fabricate 40 complete crowns with 4 different resin-based CAD-CAM materials and either additive (Crowntec [MS]) or subtractive techniques (Brilliant Crios [BC], breCAM.monoCOM [PMMA], and G-CAM [GR]; n=10). All crowns were digitized with an intraoral scanner (CEREC Primescan SW 5.2) to generate their STL files (TC-STLs). MC-STL and TC-STLs were transferred into a 3-dimensional analysis software program (Medit Link v2.4.4), and a trueness (overall, external, occlusal, intaglio occlusal, and marginal) analysis was performed by using the root mean square (RMS) method. The Kruskal-Wallis and Dunn tests were performed to analyze data (α=.05). RESULTS: The test groups had significantly different deviations on all surfaces (P≤.001). MS crowns had higher overall (P≤.007) and external surface (P≤.001) deviations than GR and PMMA crowns, while the differences between GR and PMMA crowns were not significant (P≥.441). BC crowns had higher external surface deviations than GR crowns (P=.005), higher occlusal deviations than GR and MS crowns (P≤.007), and higher intaglio occlusal deviations than GR and MS crowns (P≤.009). However, BC crowns had lower marginal deviations than MS and GR crowns (P≤.018). CONCLUSIONS: The brand of resin-based CAD-CAM materials affected the trueness of crowns. Additively manufactured crowns (MS) mostly had lower overall and external surface trueness than the other groups. Nevertheless, the deviation values of occlusal, intaglio occlusal, and marginal trueness were generally small; thus, the effect of the tested materials on clinical crown fit may be negligible.

Effect of printing layer thickness on the trueness and fit of additively manufactured removable dies.

STATEMENT OF PROBLEM: Additive manufacturing is commonly used for the fabrication of definitive casts with removable dies. However, how the trueness and fit of removable dies are affected by printing layer thickness is lacking. PURPOSE: The purpose of this in vitro study was to investigate the trueness and fit of additively manufactured removable dies printed in different layer thicknesses. MATERIAL AND METHODS: A mandibular cast with a prepared right first molar tooth was digitized (CEREC Primescan), and its standard tessellation language (STL) file was imported into a software program (DentalCAD 3.0). A removable die (D-STL) and a hollow cast with (M-STL) or without the die (SM-STL) were designed. D-STL and SM-STL were imported into a nesting software program (Composer), and 45 removable dies in 3 layer thicknesses (100 µm, 50 µm, and 50 to 100 µm) (n=15) and 1 cast (100-µm) were additively manufactured. Each removable die (TD-STLs), the cast with each die (TM-STLs), and the cast without the die (TSM-STL) were digitized by using the same scanner. All STL files were imported into a software program (Medit Link v 2.4.4), and TD-STLs were superimposed over D-STL. The root mean square (RMS) method was used to analyze the trueness of the dies at 2 different areas (crown and root portion) and as a complete unit (overall). Overall RMS values of the cast with and without the die were also calculated after superimposing TM-STLs over M-STL. The fit of the dies in the cast was evaluated by using a triple-scan protocol to measure deviations at 5 different points (point M: most mesial point of the margin; point TM: tip of the mesial cusp; point O: deepest point of the occlusal fossa; point TD: tip of the distal cusp; point D: most distal point of the margin) on the crown portion. One-way ANOVA and Tukey honestly significant difference tests were used to evaluate data (α=.05). RESULTS: The RMS values of removable dies showed significant differences at each area (P≤.002). The 50- to 100-µm group had higher overall RMS values than the 100-µm group (P=.017). The 100-µm group had the highest RMS values for the crown portion (P≤.019), while the 50-µm group had the highest RMS values for the root portion (P<.001). The 50-µm group had the lowest RMS values for the crown portion when the die was in the cast (P<.001). Except for point TM (P=.228), significant differences were observed among the test groups at all points (P<.001). The 50-µm group had the lowest distance deviations at points M, TD, and D (P≤.005), while the 100-µm group had the highest distance deviations at points O and D (P≤.010). CONCLUSIONS: Removable dies fabricated by using a 100-µm or 50- to 100-µm combined layer thickness had trueness that was either similar to or better than that of dies fabricated with a 50-µm layer thickness. When the die was on the cast, the 50-µm layer thickness resulted in the best crown portion trueness. However, because the deviation differences among groups were clinically small, the 100-µm layer thickness can be considered for the efficient fabrication of removable dies when the tested printer and resin are used.

Influence of chairside surface treatments on the shear bond strength of PEKK polymer to veneering resin materials: An in vitro study.

STATEMENT OF PROBLEM: High-performance thermoplastics have been adopted as an alternative restorative material to metal or ceramics. However, a straightforward surface modification process to provide a durable bond strength between the polymer and the veneering material is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the shear bond strength (SBS) of different veneering resin materials to polyetherketoneketone (PEKK) after different surface treatments. MATERIAL AND METHODS: Rectangular (7×7×2 mm) PEKK specimens (N=120) were randomly allocated to the following 6 groups (n=20): untreated (Cnt); nonthermal plasma (NTP) treated; tribochemical silica airborne-particle abrasion with 30-µm silica-modified Al2O3 (Tbc); abraded with a coarse-grit diamond rotary instrument (Ab); tribochemical silica airborne-particle abrasion + plasma treated (Tbc_NTP); abraded + plasma treated (Ab_NTP). After a bonding agent (PEKK Bond) was applied to the specimens, each group was divided into 2 subgroups according to the applied veneering resin materials: polymethylmethacrylate (PMMA) and nanohybrid composite resin (NHC, n=10). The specimens were stored in water for 24 hours at 37 °C and subjected to the SBS test by using a universal testing machine, and failure modes were evaluated using a stereomicroscope. Two-way analysis of variance (ANOVA) was performed followed by the Tukey honestly significant difference (HSD) test to statistically analyze the data (α=.05). RESULTS: The 2-way ANOVA showed that surface treatment methods, veneering material, and their interactions were significantly different on the SBS values (P<.001). The highest SBS values were determined for the Tbc and Tbc_NTP treatment groups not only for PMMA (10.71 to 11.63 MPa) but also for NHC (19.80 to 20.60 MPa) veneering resin materials (P<.05). CONCLUSIONS: The bonding capacity of PEKK to the PMMA and NHC veneering resin materials can be significantly improved by using tribochemical silica airborne-particle abrasion alone or with nonthermal plasma surface treatment techniques. Furthermore, using NHC veneering resin material is recommended over PMMA.

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.

Fracture resistance of additively or subtractively manufactured resin-based definitive crowns: Effect of restorative material, resin cement, and cyclic loading.

OBJECTIVE: To evaluate how restorative material, resin cement, and cyclic loading affect the fracture resistance of resin-based crowns fabricated by using additive or subtractive manufacturing. METHODS: A right first molar crown standard tessellation language (STL) file was used to fabricate 120 crowns from one subtractively manufactured polymer-infiltrated ceramic network (SM) and two additively manufactured resin composites (AM-B and AM-S) (N = 40). These crowns were randomly divided into 4 groups within each material according to the dual-polymerizing resin cement to be used (RX and PN) and the aging condition (n = 10). After cementation, the crowns without cyclic loading were subjected to fracture testing, while the others were first cyclically loaded (1.7 Hz, 1.2 million cycles, and 49-N load) and then subjected to fracture testing. Data were analyzed with generalized linear model analysis (α = .05). RESULTS: Fracture resistance of the crowns was affected by material, resin cement, and cyclic loading (P ≤ .030). However, none of the interactions significantly affected fracture resistance of tested crowns (P ≥ .140). Among tested materials, SM had the highest fracture resistance, whereas AM-B had the lowest (P ≤ .025). RX led to higher fracture resistance, and cyclic loading decreased the fracture resistance (P ≤ .026). SIGNIFICANCE: Tested materials can be considered reliable in terms of fracture resistance in short- or mid-term (5 years of intraoral simulation) when used for single molar crowns with 2 mm occlusal thickness. In the long term, polymer-infiltrated ceramic network crowns cemented with RelyX Universal may provide promising results and be less prone to complications considering higher fracture resistance values obtained.

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 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.

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.

Effect of computer-aided design and computer-aided manufacturing technique on the accuracy of fixed partial denture patterns used for casting or pressing.

OBJECTIVES: To evaluate the effect of additive and subtractive manufacturing on the accuracy (trueness and precision) of fixed partial denture patterns (FPDPs) used for casting or pressing. MATERIALS AND METHODS: A 3-unit complete coverage FPD on mandibular right first premolar and first molar teeth was virtually designed. Using the design data, FPD patterns were fabricated from an additively manufactured resin (PR, ProArt Print Wax) and 2 CAD-CAM wax discs (YW, ProArt CAD Wax Yellow and BW, ProArt CAD Wax Blue) (n = 10). Each pattern was then digitized with a scanner (CEREC Primescan) and evaluated for 3D surface deviation at 4 different surfaces (overall, external, marginal, and intaglio surfaces) by using a 3D analysis software (Medit Link). Root mean square (RMS) values were automatically calculated. Data were analyzed by using Kruskal-Wallis and Dunn's post hoc tests for trueness and precision (α= 0.05). RESULTS: Significant differences were found among the RMS values for overall (P<.001) and each surface (P≤.040) evaluated. PR had the highest overall (P≤.011) and intaglio surface (P≤.01) deviations, while the difference between YW and BW was not significant (P≥.199). PR had the highest (P≤.027) and BW had the lowest (P≤.042) external surface mean RMS values. BW had higher mean marginal RMS value than YW (P=.047). For precision, significant differences were observed among test groups only for marginal RMS values (P=.002). PR had lower precision than BW (P=.002). CONCLUSIONS: BW and YW FPDPs mostly had higher trueness compared with PR FPDPs. However, considering relatively smaller deviations at marginal and intaglio surfaces and the fact that patterns mostly had similar precision, clinical fit of FPDs fabricated by using tested patterns may be similar. CLINICAL SIGNIFICANCE: Definitive 3-unit fixed partial dentures fabricated by using tested patterns may be similar. However, FPDs fabricated with tested additively manufactured resin patterns might result in more chairside adjustments than those fabricated with tested subtractively manufactured wax patterns.

Effect of number of supports and build angle on the fabrication and internal fit accuracy of additively manufactured definitive resin-ceramic hybrid crowns.

OBJECTIVES: To evaluate the effect of number of supports and build angle on the fabrication and internal fit accuracy (trueness and precision) of additively manufactured resin-ceramic hybrid crowns. METHODS: A mandibular first molar crown was designed and nested on the build platform of a printer either with a 30° angle between the occlusal surface and the build platform (BLS (less support) and BMS (more support)) or its occlusal surface parallel to the build platform (VLS (less support) and VMS (more support)) to fabricate additively manufactured resin-ceramic hybrid crowns (n = 14). After fabrication, supports were removed by a blinded operator and all crowns were digitized with an intraoral scanner. Fabrication accuracy (overall, external, intaglio occlusal, occlusal, and marginal) was evaluated by using root mean square (RMS) method, while internal fit was evaluated with triple scan method. RMS, average gap, and precision of these data were analyzed (α= 0.05). RESULTS: VLS had higher overall deviations than BLS and VMS (P≤.039). VMS had higher occlusal deviations than BLS (P=.033). While BMS and BLS had higher marginal deviations than VLS (P≤.006), BMS also had higher values than VMS (P=.012). BLS led to higher precision than VMS (intaglio occlusal and occlusal surfaces) and VLS (occlusal surface) (P≤.008). VLS led to higher precision than BMS (marginal surface) (P=.027). Average gap values were similar (P=.723); however, BLS resulted in higher precision than VLS (P=.018). CONCLUSIONS: Considering their high marginal and occlusal surface trueness, and similar internal occlusal deviations and average gaps (trueness), clinical fit of resin-ceramic hybrid crowns fabricated with tested parameters may be similar. Reduced number of supports and angled orientation may lead to higher precision of fit. CLINICAL SIGNIFICANCE: Tested resin-ceramic hybrid-printer pair may be used to fabricate crowns with reduced number of supports to maintain occlusal surface integrity without compromising the fabrication accuracy and fit.

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 (Ø10x2 mm) were fabricated from polyurethane-based resins with different viscosities (Tera Harz TC-80DP and C&B permanent) (N=30). Baseline color coordinates were measured after cleaning. The specimens were divided into 3 to be polymerized with different polymerization units (Otoflash G171, FLN; Wash and Cure 2.0, CLED1; CARES P Cure, CLED2) (n=10), 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). CONCLUSION: 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.

Additive or subtractive manufacturing of crown patterns used for pressing or casting: A trueness analysis.

OBJECTIVES: To investigate the effect of subtractive and additive manufacturing techniques on the trueness of crown patterns used for pressing or casting. MATERIAL AND METHODS: A complete-coverage mandibular right first molar crown was designed in standard tessellation language (STL) format. This STL served as the control (C-STL) and was used to fabricate 30 crown patterns in 3D-printed resin (PR, ProArt Print Wax), millable wax suitable for casting (BW, ProArt CAD Wax Blue), and millable wax suitable for pressing (YW, ProArt CAD Wax Yellow) (n = 10). Subtractively manufactured patterns were fabricated by using a 5-axis milling unit (PrograMill PM7), while 3D-printed patterns were fabricated by using a digital light processing-based 3D printer (PrograPrint PR5; Ivoclar Vivadent, Schaan, Liechtenstein). All fabricated patterns were digitized by using an intraoral scanner (CEREC Primescan SW 5.2) to generate test-STLs. C-STL and test-STLs were transferred into a 3D analysis software (Medit Link v 2.4.4). Trueness evaluation was performed at 4 different surfaces (external, intaglio with margin, marginal, and intaglio without margin) and for complete scan meshes (overall) by using the root mean square (RMS) method. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests (α = .05). RESULTS: RMS values varied significantly at all surfaces (P < .001), except for marginal surface (P = .151). PR had the highest RMS values at external surface (P ≤ .007), intaglio surfaces (with (P ≤ .003) and without margin (P ≤ .005)), and overall (P ≤ .01). No significant differences were observed between YW and BW (P ≥ .223). CONCLUSION: Patterns fabricated by using subtractive manufacturing exhibited high trueness. The deviation values, in general, were small, particularly at intaglio and marginal surfaces; thus, clinical difference in crown-fit may be negligible using additive or subtractive technique. CLINICAL SIGNIFICANCE: The fit of definitive crowns may be similar when tested crown patterns are additively or subtractively manufactured. However, crowns fabricated by using tested 3D-printed resin patterns may require more chairside adjustments compared with those fabricated by using subtractively manufactured wax patterns.

Is Tele-Dentistry an Effective Approach for Patient Follow-up in Maxillofacial Surgery.

PURPOSE: To explore the feasibility and diagnostic accuracy of the tele-dentistry for the follow-up of different diagnostic groups of Turkish patients in maxillofacial surgery. MATERIALS AND METHODS: In this study, follow-up patients were allocated to four groups as dental implant, minor surgical procedure, infection-medication-related osteonecrosis of the jaws (MRONJ) and temporomandibular joint disorder (TMD). In all groups, remote examination via video call and subsequently face-to-face clinic examination were performed. The quality and accuracy of the video call were scored by the same investigator. Also, patient satisfaction regarding the video call was evaluated with a questionnaire. RESULTS: Twenty-one patients (12 females, 9 males) between 18 and 71 years (38.90 ± 17.88) participated in the study. A strong preference of 71% and 95% toward video call by patients was seen in the questionnaires performed after video call and face-to-face examination, respectively. Regarding the rating of the clinician, no significant differences were found between groups in terms of the quality and accuracy of video call (p ≥ 0.05). CONCLUSION: Remote follow up of diagnostic groups which can benefit from tele-dentistry pose a promising remedy that is reliable as in-person visits and also can reduce the clinical visits in routine clinical practice.