Trueness, precision, time-efficiency and cost analysis of chairside additive and subtractive versus lab-based workflows for manufacturing single crowns: An in vitro study

Effect of manufacturing trinomial and preparation design on the fabrication and fit accuracy of additively and subtractively manufactured resin-based overlay restorations

OBJECTIVE

To evaluate the effect of the manufacturing trinomial (technology, printer, and resin) and preparation design on the fabrication and fit accuracy (trueness and precision) of additively manufactured (AM) resin-based overlays compared to subtractively manufactured (SM) overlays.

METHODS

Six mandibular right first molar typodont teeth were prepared with varying designs: (A) 1 mm occlusal reduction, (B) 1.5 mm occlusal reduction, (C) B + contrabevel finish line, (D) B + chamfer finish line, (E) C + proximal box, and (F) D + proximal box. Overlays were fabricated using AM-IX (tilting stereolithography), AM-VS (digital light processing), or SM-EN and digitized for fabrication (overall, external, intaglio, marginal) and internal fit accuracy analyses. Data were analyzed with two-way analysis of variance and Bonferroni-corrected post-hoc tests (α = 0.05).

RESULTS

The interaction between the manufacturing trinomial and preparation design affected fabrication accuracy of overall, external, and intaglio surfaces, and the precision of marginal surface deviations and average gaps (P ≤ 0.034). AM-IX overlays mostly had higher overall, external, and marginal fabrication accuracy, whereas SM-EN overlays mostly had lower accuracy across these surfaces (P ≤ 0.019). Preparation designs A, B, and C mostly led to lower overall, external, and intaglio surface trueness within SM-EN overlays (P ≤ 0.014). AM-IX overlays had the lowest and preparation design E led to the highest gaps (P ≤ 0.023).

CONCLUSIONS

AM overlays fabricated with tilting stereolithography mostly had higher fabrication and fit accuracy. Increased axial preparation improved fabrication trueness but did not consistently enhance fit.

Comparison of accuracy in internal, marginal, and external regions of ceramic copings fabricated via milling, DLP printing, and heat-pressing methods

OBJECTIVE

The present study aimed to evaluate the accuracy of ceramic copings fabricated by milling, DLP printing, and heat-pressing methods.

METHODS

A central maxillary incisor coping was designed after scanning a typodont model. Thirty specimens were fabricated using milling (MCC), DLP printing (PCC), and heat-pressing methods (HCC) (n = 10 per group). All the specimens were scanned with a lab scanner. The scanned data were segmented into external, internal, and marginal regions and analyzed using 3D measurement software. The accuracy of each group was evaluated and Root mean square (RMS) deviations were calculated. For statistical analysis of the measurements, the Kolmogorov-Smirnov test was conducted to assess the normality and homogeneity of variance among the three groups and the results. As equal variances were not observed (p < 0.05), a nonparametric Kruskal-Wallis test was conducted, followed by post-hoc analysis using the Bonferroni-adjusted Mann - Whitney U test (α = 0.016).

RESULTS

The MCC group recorded RMS values of 14.29 ± 1.80 µm and 15.80 ± 2.36 µm in the internal and marginal regions, respectively, with lower deviation (p < 0.001). The PCC group showed the highest RMS in the internal region at 39.43 ± 4.59 µm (p = 0.684). The HCC group's RMS value was highest in the external region at 55.53 ± 5.71 µm (p < 0.001). Statistical analyses indicated significant differences in RMS values in external and internal regions but not in the marginal region (p = 0.143). All the RMS values remained within the clinically acceptable range.

CONCLUSION

This study confirmed that different fabrication techniques significantly influence the dimensional accuracy of ceramic copings. The MCC group showed lower RMS values whereas the PCC and HCC groups exhibited higher RMS values. However, all RMS values remained within the clinically acceptable range.

CLINICAL SIGNIFICANCE

This study assessed the trueness and precision of ceramic copings made by different fabrication methods. The MCC group exhibited the greatest precision in both the internal and marginal regions. In contrast, the PCC group, while requiring additional research and validation in marginal areas, displayed enhanced accuracy and reproducibility in the external region compared to the HCC group.

Additively manufactured zirconia periodontal splint integrated prosthesis: A proof-of-concept

OBJECTIVES

To provide a digital workflow for designing custom zirconia periodontal splints using material jetting (MJ) technology to support and rehabilitate periodontally compromised anterior teeth.

METHODS

Initially, the maxillary and mandibular teeth were scanned using a Trios3 intraoral scanner (IOS). Subsequently, the periodontal splint was digitally designed using a computer-aided design software. Then, a zirconia periodontal splint was produced using MJ technology with a three-dimensional (3D) printer (Carmel 1400C). Additionally, the trueness of the periodontal splint was analyzed using 3D detection software (Geomagic Control X 2018). Finally, the periodontal splint was adhered using resin cement.

RESULTS

In terms of trueness, the intaglio surface and the prosthesis of the periodontal splint matched well, whereas the lingual surface showed some deviation areas. The trueness root mean square (RMS) value of the splint was 57.7 μm and the deviation remained within ± 200 μm. For clinical treatment, the periodontal splint was precisely bonded and achieved the effect of supporting and rehabilitating periodontally compromised anterior teeth. After six months of treatment, the follow-up results showed that the splint remained intact, with no further absorption of the alveolar bone.

CONCLUSIONS

Additively manufactured zirconia periodontal splints exhibit good trueness and aesthetics. Periodontal splints can achieve precise bonding and maintain long-term bonding stability, and can help stabilize loosened teeth and prevent further absorption by the alveolar bone.

CLINICAL SIGNIFICANCE

This proof-of-concept outlines a digital workflow for designing zirconia periodontal splints using MJ technology to improve outcomes of periodontitis treatments. Moreover, the adhesive stability and efficacy of periodontitis treatment using the periodontal splint were preliminarily verified.

Trueness of multichromatic versus monochromatic veneers printed using tilted stereolithography technology at different build angles? An in vitro study

OBJECTIVES

To evaluate the influence of shade (monochromatic vs multichromatic) and build angle on the trueness of veneers printed using tilted stereolithography technology (TSLA).

METHODS

A maxillary central incisor typodont tooth model was prepared to receive a butt-joint full veneer with 0.3 mm labial and 2 mm incisal reduction. The preparation was digitized using laboratory scanner (T310; Medit) to design the veneer restoration. Sixty veneers were fabricated using Tilting Stereolithography (TSLA) 3D-printing technique (Dfab; DWS). Thirty veneers were printed in monochromatic shade (N = 30) (IrixMax monochromatic A2; DWS) and thirty veneers in multichromatic shade (N = 30) (A1-A3.5) using hybrid resin-ceramic material (IrixMax Photoshade A1-A3.5; DWS). In each group, three subgroups were defined based on the build angle (N = 10): 90°, 75° and 45° angles. Trueness was evaluated quantitatively and qualitatively using metrology software (Geomagic Control v2020; 3DSystems). Two-way Analysis of Variance (ANOVA) test with Tukey post hoc test for multiple comparisons were used to detect the differences in root mean square estimate (RMSE) between the test groups (α =0.05).

RESULTS

Two-way ANOVA revealed a statistically significant interaction between different build angles and material shade on RMSE in butt-joint veneer preparation design (P = .001). Multichromatic shade showed significantly higher RMSE values when printed at 45° (P=.010) compared to monochromatic one.

CONCLUSIONS

Build angle and material shade have an influence on the trueness of veneers printed using TSLA technique. 45° build angle with multichromatic shade material resulted in the highest RMSE deviation values. Therefore, clinicians should be cautious with the selected print angle when printing a multichromatic resin-based veneers.

STATEMENT OF CLINICAL RELEVANCE

Advances in material science and 3D-printers resulted in the introduction of a chairside TSLA 3D-printer that can be used for the fabrication of multichromatic, resin-based veneer restorations. Both build angle and material shade influence the dimensional accuracy of TSLA printed veneer restorations. To print highly accurate multichromatic restorations and increase the number of printed parts per print cycle, 45° build angle should be avoided.

Effect of manufacturing trinomial and restoration thickness on the fabrication trueness, fit, and margin quality of additively manufactured resin-based ultrathin laminate veneers

OBJECTIVE

To evaluate the effect of the manufacturing trinomial (manufacturing technology, three-dimensional printer, and material) and restoration thickness on the fabrication trueness, fit, and margin quality of additively manufactured resin-based ultrathin laminate veneers (LVs) by comparing to those produced subtractively.

METHODS

Reference LVs were designed from the scan files of two identical maxillary central incisor typodonts prepared for 0.3 mm and 0.5 mm LVs. LVs were manufactured additively with resins of different compositions, either using a tilting stereolithography (Irix Max [AM-IX] and Irix Plus [AM-IP]) or a digital light processing printer (VarseoSmile Crown Plus [AM-VS] and Tera Harz TC- 80DP [AM-GR]), and subtractively (Tetric CAD [SM-TC]) (n = 10). All LVs were digitized to evaluate their fabrication trueness and fit. The margin quality was assessed through visual examination. The trueness and fit data were analyzed with two-way analysis of variance and Tukey tests, while the chi-squared test was used to evaluate the margin quality (α = 0.05).

RESULTS

The interaction between the main factors and the manufacturing trinomial affected the fabrication trueness and fit, while restoration thickness affected the fit of tested LVs (P ≤ 0.001). AM-IP mostly had the lowest deviations, followed by AM-IX, and mostly had the lowest gaps (P ≤ 0.037). Thinner LVs had lower gaps (P < 0.001). Tested LVs mostly had slightly rough margins with small defects.

CONCLUSIONS

LVs fabricated with the tilting stereolithography printer mostly had higher trueness. Using AM-IP or fabricating 0.3 mm LVs improved the fit. Nevertheless, all tested LVs had clinically accep fit.

CLINICAL SIGNIFICANCE

Ultrathin laminate veneers fabricated with the manufacturing trinomial involving tested tilting stereolithography printer and resins may require less clinical adjustments. In addition, one of the resins (AM-IP) within this manufacturing trinomial or fabricating 0.3 mm laminate veneers may improve the fit.

Effect of surface conditioning on the adhesive bond strength of 3D-printed resins used in permanent fixed dental prostheses

OBJECTIVES

Although pre-treatment parameters for subtractive computer-aided design/computer-aided manufacturing (CAD/CAM) materials have been thoroughly investigated, data regarding additive restorative materials designed for permanent use in the oral cavity are scarce. This study investigated the effects of abrasive materials and blasting pressure on the bond strength of 3D-printed resins used in permanent restorations.

METHODS

A total of n = 44 test specimens additively manufactured from Formlabs' `Permanent Crown Resin' were prepared. Three groups with n = 11 specimens were airborne-particle abraded with 50 µm aluminium oxide at 1 bar, 2 bar or 3 bar. The control group did not receive any further airborne-particle abrasion after post-processing with 50 µm glass beads. Cylindrical superstructures were bonded to the prepared surfaces using RelyX Unicem 2. The bonded specimens were then subjected to artificial ageing via thermocycling. Subsequently, shear bond strength (sbs) tests were conducted. Data were analysed with the Kruskal-Wallis test (α = 0.05).

RESULTS

After post-processing with glass beads, average shear bond strength values of 10.13 ± 7.62 MPa were achieved. When using aluminium oxide and 1 bar blasting pressure, significantly higher average sbs values of 25.57 ± 7.04 MPa were revealed (p = 0.009). The bond strength increased with higher blasting pressures (28.14 ± 6.35 MPa at 2 bar (p = 0.005); 30.15 ± 6.46 MPa at 3 bar (p < 0.001)). However, the shear tests revealed increased failure within the specimen base at higher blasting pressures.

CONCLUSION

Bond strength significantly improved when airborne-particle abrasion with aluminium oxide was applied. However, increased airborne-particle abrasion pressure led to more failures at the base plate level of the specimens.

CLINICAL SIGNIFICANCE

Aluminium oxide increases the adhesive strength of 3D-printed dental restorative materials. Although the adhesive bond increased slightly with increasing airborne-particle abrasion pressure, the 3D restorative materials also exhibited an increased failure rate within the restorative material in the shear bond strength test with increasing blasting pressure.

Effect of Air Particle Abrasion and Primers on Bond Strength to 3D-Printed Crown Materials

Two 3D-printed crown materials (Crown and Ceramic Crown) were examined to determine the best surface treatment and primers for bonding. Discs of the two materials were printed and mounted with their "intaglio" surfaces untouched. Half the specimens from each group were sandblasted with 50 µm alumina. Then, specimens were divided into four groups (n = 10): Gr1-no further treatment; Gr2-one coat of silane; Gr3-one coat of universal adhesive; Gr4-one coat of silane, then one coat of universal adhesive. Bond strength specimens were prepared with an Ultradent shear bond strength apparatus using Filtek Supreme composite. Specimens were stored for 8 weeks in 37 °C water. The specimens were debonded with a circular notched-edge blade applied at 1 mm/min, and the shear bond strength was calculated. The data were compared with a two-way ANOVA (factors: surface treatment and primer) and a Tukey post hoc analysis for both materials independently, with p < 0.01 considered meaningful. The filler content (burned ash) and resin content (FTIR) of the materials were determined. For both materials, factors surface treatment and primer were significant (p < 0.01), but their interaction was not (p = 0.43 for Crown and p = 0.34 for Ceramic Crown). Alumina air particle abrasion improved the bond strength for both materials. The Tukey post hoc analysis grouped primer treatments into the same statistically different groups for both materials: Gr1 and Gr2 < Gr3 and Gr4. The filler percentage of Crown was 32.7% and Ceramic Crown was 48.2%. Resin content was similar for both materials. The most effective method to bond to 3D-printed crowns (regardless of filler percentage) was to sandblast with 50 µm alumina and apply a layer of adhesive (with or without previous application of silane).

Zirconia crowns manufactured using digital light processing: Effects of build angle and layer thickness on the accuracy

OBJECTIVES

This study investigated the effects of build angle and layer thickness on the trueness and precision of zirconia crowns manufactured using digital light processing (DLP) technology.

MATERIALS AND METHODS

Single crowns were fabricated from zirconia using DLP technology. The crowns were manufactured with three different representative build angles (0°, 45°, and 90°) and two different layer thicknesses (30 μm and 50 μm). After printing, the specimens were non-contact-scanned, and their accuracy was assessed using a 3D analysis software. Root mean square (RMS) values were used to determine trueness and precision. Color maps were generated to detect deviations within the specimens. Statistical analyses were conducted using two-way ANOVA.

RESULTS

Build angle and layer thickness significantly affected trueness and precision (p < 0.05). At a 30-μm layer thickness, the crowns printed at angles of 0° (32.2 ± 3.2 μm) and 45° (33.9 ± 2.4 μm) demonstrated the best marginal trueness compared to those in other groups (p < 0.05). Notably, those printed at an angle of 90° exhibited the best intaglio surface trueness (37.4 ± 4.0 μm). At a 50-μm layer thickness, the crowns printed at an angle of 90° exhibited the lowest accuracy concerning marginal and intaglio surface aspects (27.7 ± 8.2 μm).

CONCLUSIONS

Both the build angle and layer thickness significantly affected the dimensional accuracy of DLP-printed zirconia crowns, with the 30-μm layer thickness offering superior trueness. Optimal results were achieved using build angles of 0° and 45° in conjunction with thinner layers, minimizing marginal defects.

CLINICAL SIGNIFICANCE

All zirconia crowns produced at different build angles and layer thicknesses satisfied clinical requirements. Specific combinations of these factors realized the fabrication of single crowns that possessed the highest accuracy.

Longevity and risk factors of CAD-CAM manufactured implant-supported all-ceramic crowns - A prospective, multi-center, practice-based cohort study

OBJECTIVES

The aim of this prospective, multi-center, practice-based cohort study was to analyze factors associated with the success of implant supported all-ceramic single-unit crowns, made by computer-aided-design/computer-aided-manufacturing (CAD-CAM).

METHODS

All-ceramic crowns placed in a private practice-based research network (Ceramic Success Analysis, AG Keramik) were analyzed. Data from 567patients with CAD-CAM implant supported all-ceramic crowns placed between 2008-2023 by 54dentists were evaluated. Firstly, all crowns with at least one follow-up control were included (n = 907). Secondly, all crowns being followed up for ≥ 5years and all failures were included (n = 151). At the latest follow-up visit, crowns were considered as successful (not failed) if they were still in function without the need for additional therapy. Multi-level Cox proportional hazards models were used to evaluate the association between a range of predictors and time of success.

RESULTS

Within a mean follow-up period (SD) of 2.5 (2)years (first scenario) and 6.2 (1.2)years (second scenario) [maximum:12years], 27crowns failed (annual failure rate [AFR]:0.74 %). The main failure types were decementation, (n = 11), fracture of the ceramic (n = 4) or Ti-Base (n = 4). In 5-year-scenario, crowns fabricated in the laboratory had 26times lower failure rate than those fabricated chairside (95 %CI:0.0-0.7;p = 0.038). Furthermore, the use of a silane (HR:0.051;95 %CI:0.0-0.5;p = 0.014) and etching of the ceramic (HR:0.053;95 %CI:0.0-0.8;p = 0.035) resulted in a significantly higher risk for failure than their non-use.

SIGNIFICANCE

For CAD-CAM manufactured implant supported all-ceramic crowns, high success rates were found in up to 12-year evaluation. Furthermore, after 5years, no patient-or implant-level factors, but operative-level factor (i.e.fabrication method, use of silane/etching) were significantly associated with failure. The study was registered in the German Clinical Trials Register (DRKS-ID: DRKS00020271).

Artificial intelligence and mixed reality for dental implant planning: A technical note

AIM

The aim of this work is to present a new protocol for implant surgical planning which involves the combined use of artificial intelligence (AI) and mixed reality (MR).

METHODS

This protocol involves the acquisition of three-dimensional (3D) patient data through intraoral scanning (IOS) and cone beam computed tomography (CBCT). These data are loaded into AI software which automatically segments and aligns the patient's 3D models. These 3D models are loaded into MR software and used for planning implant surgery through holography. The files are then exported and used to design surgical guides via open-source software, which are 3D printed and used to prepare the implant sites through static computer-assisted implant surgery (s-CAIS). The case is finalized prosthetically through a fully digital protocol. The accuracy of implant positioning is verified by comparing the planned position with the actual position of the implants after surgery.

RESULTS

As a proof of principle, the present protocol seems to be to be reliable and efficient when used for planning simple cases of s-CAIS in partially edentulous patients. The clinician can plan the implants in an authentic 3D environment without using any radiology-guided surgery software. The precision of implant placement seems clinically acceptable, with minor deviations.

CONCLUSIONS

The present study suggests that AI and MR technologies can be successfully used in s-CAIS for an authentic 3D planning. Further clinical studies are needed to validate this protocol.

Effect of thickness on the translucency of machinable and printable ceramic-glass polymer materials

OBJECTIVES

To assess the translucency of machinable and printable ceramic-glass polymer materials with different thicknesses.

METHODS

Five ceramic-glass polymer materials were tested: one 3D-printable material, Permanent Crown resin (3D), two machinable materials available at low translucency (LT) and high translucency (HT) levels, VITA Enamic (VE) HT/LT, and Cerasmart 270 (CS) HT/LT. A total of 100 specimens were produced across 10 subgroups (n = 10) with thicknesses of 1 mm and 1.5 mm. The colour coordinates of the specimens were measured against black and white backgrounds using a spectrophotometer. Translucency was quantified using the Relative Translucency Parameter (RTP), calculated via the CIEDE2000 formula. A two-way ANOVA followed by post-hoc tests with Bonferroni correction (α = 0.05) was used for statistical analysis.

RESULTS

The RTP for both thicknesses were ranked as follows: CSHT > VEHT > CSLT > 3D > VELT. The RTP of the 3D was lower than that of the HT machinable materials (CSHT and VEHT) for both thicknesses (p < 0.05). No significant difference was observed between the RTP of 3D and CSLT at 1.5 mm (p = 1.000); however, at 1 mm, the RTP of the 3D was lower than that of the CSLT (p < 0.05). Notably, the 3D showed the least translucency difference with a 0.5 mm increase in thickness.

CONCLUSIONS

Printable ceramic-glass polymer materials demonstrated lower translucency than HT machinable ceramic-glass polymer materials. Both the thickness and type significantly influenced the translucency of the LT machinable counterparts compared to the printable ceramic-glass polymer material.

CLINICAL SIGNIFICANCE

Printable ceramic-glass polymer resins may be a suitable option for minimally invasive procedures, especially when attempting to mask undesirable-coloured abutments. When selecting HT machinable ceramic-glass polymers, clinicians should pay greater attention to the abutment colour and thickness of the restorative material.

3D-printed short-span hybrid composite implant-supported restorations fabricated through tilting stereolithography: A retrospective clinical study on 85 patients with 1 year of follow-up

PURPOSE

To report the clinical results obtained with fixed short-span (single crowns [SCs] and fixed partial prostheses [FPPs]) implant-supported hybrid composite restorations fabricated through tilting stereolithography (TSLA).

METHODS

This retrospective clinical study included 85 patients who had been restored with 95 fixed short-span implant-supported hybrid composite (Irix Max®, DWS Systems) restorations (70 SCs and 25 FPPs up to three units) fabricated with TSLA. The full-digital model-free workflow was based on intraoral implant scanning, computer-assisted design (CAD) and 3D printing using TSLA (Dfab®, DWS Systems). The primary outcomes were the marginal adaptation, the quality of the occlusal and interproximal contact points, and the chromatic integration of the restorations, assessed independently by two experienced operators (a prosthodontist and a periodontist). A score from 1 to 5 (with 5 as the highest value, 4 for satisfactory quality, 3 for acceptable quality, and 2 and 1 as the lowest values, expressing unsatisfactory quality) was assigned by each operator to each restoration at delivery. The secondary outcomes were the survival and success of the restorations at the 1-year follow-up. The restoration was defined as successful in the absence of any complications throughout the follow-up period. A statistical analysis was conducted.

RESULTS

For the quality of the marginal closure and occlusal and interproximal contact points, the 3D-printed hybrid composite restorations scored highly; the aesthetic integration was satisfactory. One year after placement, all restorations survived, with a low incidence (4.2 % overall, 5.7 % SCs) of complications (two abutment screw loosenings, two decementation of the restorations, and one upper portion of the hybrid abutment decemented from the titanium base), for a success rate of 95.8 %.

CONCLUSIONS

Within the limits of this study (retrospective design, follow-up limited to 1 year from the delivery, and only cemented restorations included) fixed short-span implant-supported hybrid composite crowns and bridges fabricated through TSLA were clinically precise, presenting a low incidence of complications at 1 year.

STATEMENT OF CLINICAL RELEVANCE

The use of TSLA printing technology can open new perspectives for the treatment of small edentulous gaps with definitive implant-supported prosthetic restorations.

Accuracy of the intaglio surface of 3D-printed hybrid resin-ceramic crowns, veneers and table-tops: An in vitro study

OBJECTIVES

The present study aims to examine the influence of the build angle on the accuracy (trueness and precision) of 3D printed crowns, table-tops and veneers with a hybrid resin-ceramic material.

METHODS

One crown, on table-top and one veneer were printed in five different build angles (0°, 30°, 45°, 60°, 90°) (n = 50) with the digital light processing (DLP) system (Varseo XS, Bego) using hybrid resin (Varseo Smile Crownplus A3, Bego). All printed restorations were scanned using the laboratory scanner (D2000, 3Shape) and matched onto the initial reference design in metrology software (Geomagic Control X, 3D Systems). The root mean square error (RMSE) was calculated between the scanned and reference data. The data was statistically analyzed using the Tukey multiple comparison test and Wilcoxon multiple comparison test.

RESULTS

The crown group showed higher trueness at 30° (0.021 ± 0.002) and 45° (0.020 ± 0.002), and table-tops at 0° (0.015 ± 0.001) and 30° (0.014 ± 0.001) (p < 0.0001). Veneers demonstrated higher trueness at 30° (0.016 ± 0.002) (p < 0.0001). All three restoration types demonstrated the lowest trueness at a 90° build angle and portrayed deviations along the z axis. The veneer and table-top groups showed the lowest precision at 90° (veneers: 0.021 ± 0.008; table-tops: 0.013 ± 0.003). The crown group portrayed the lowest precision at 45° (0.017 ± 0.005) (p < 0.0001).

CONCLUSION

The build angle of DLP-printed hybrid resin-ceramic restorations influences their accuracy.

CLINICAL SIGNIFICANCE

Considering the build angle is important to achieve a better accuracy of 3D-printed resin-ceramic hybrid restorations. This may help predict or avoid the interference points between a restoration and a die and minimize the clinical adjustments.