Accuracy of surgical guides manufactured with four different 3D printers. A comparative in vitro study.

OBJECTIVES: The aim of this study was to assess the accuracy of surgical guides manufactured with four different 3D printers.. METHODS: Forty-eight surgical guides (BlueSky Plan, BlueSky Bio) were produced using four different 3D printers, with strict adherence to each manufacturer's instructions. The printers used were three digital light processing (DLP) printers (SolFlex170, VC; Nextdent5100, ND, and D30+Rapidshape, RS) and one stereolithographic (SLA) printer (Formlabs3B+, FL). The study evaluated the trueness and precision of the overall surface, the region of interest (RoI) (occlusal and guide zone), the repeatability in several batches, and the guide hole's diameter and xyz axes. The printed guides were digitized and compared with the CAD design control specimen (Control X, Geomagic). Descriptive statistics and Kruskal-Wallis tests with post-hoc Mann-Whitney tests were performed (α=0.05). RESULTS: Differences in trueness and precision were found between groups in the overall zone and RoI (p = 0.00). The ND group demonstrated the highest repeatability. Only the RS group exhibited a comparable guide hole diameter to the master specimen (5.27±2.12 mm; p = 0.104). No statistical differences were observed between groups in the x and z axes. However, in the y-axis, the VC group displayed statistically significant differences (p = 0.01). CONCLUSIONS: The results showed that the DLP groups had better overall accuracy, while the SLA group had the best results in the RoI. The manufacturer's workflows demonstrated a high reproducibility between batches in the RoI. The RS group had values most similar values to the guide hole diameter of the master specimen, with minimal deviations in guide hole orientation. CLINICAL SIGNIFICANCE: Implant position can be affected by the accuracy of the 3D printed surgical guide. Therefore, it is critical to analyze the final dimensions and the direction of the guide hole using available printing technologies.

Material and abutment selection for CAD/CAM implant-supported fixed dental prostheses in partially edentulous patients - A narrative review.

Restorative material selection has become increasingly challenging due to the speed of new developments in the field of dental material science. The present narrative review gives an overview of the current indications for implant abutments and restoration materials for provisional and definitive implant-supported fixed dental prostheses in partially edentulous patients. For single implant restorations, titanium base abutments for crowns are suggested as an alternative to the conventional stock- and customized abutments made out of metal or zirconia. They combine the mechanical stability of a metallic connection with the esthetic potential of ceramics. For multiple-unit restorations, conical titanium bases especially designed for bridges are recommended, to compensate for deviating implant insertion axes and angulations. Even though titanium base abutments with different geometries and heights are available, certain clinical scenarios still benefit from customized titanium abutments. Indications for the definitive material in fixed implant restorations depend on the region of tooth replacement. In the posterior (not esthetically critical) zone, ceramics such as zirconia (3-5-Ymol%) and lithium-disilicate are recommended to be used in a monolithic fashion. In the anterior sector, ceramic restorations may be buccally micro-veneered for an optimal esthetic appearance. Lithium-disilicate is only recommended for single-crowns, while zirconia (3-5-Ymol%) is also recommended for multiple-unit and cantilever restorations. Attention must be given to the specific mechanical properties of different types of zirconia, as some feature reduced mechanical strengths and are therefore not indicated for all regions and restoration span lengths. Metal-ceramics remain an option, especially for cantilever restorations.

The Accuracy of Full-Arch Intraoral Optical Impressions (IOS): Clinical Pilot Study of the Influence of the Scan Strategy, Operator, and Intraoral Scanner.

PURPOSE: To investigate the influence of a novel scanning strategy-using two new intraoral scanner devices with different operators-on the full-arch scanning accuracy for a dentate maxilla. MATERIALS AND METHODS: Two scanning strategies, a test and a control strategy, were used to produce full-arch impressions of the dentate maxilla of a study patient. Two intraoral scanning (IOS) devices were used. Five expert operators performed a total of 40 scans. The scan time was recorded for each. A reference model was obtained from the patient's maxillary arch with an analog impression. The model was later scanned with a high-precision laboratory scanner to create a digital reference model (DRM). The scanning accuracy was analyzed with 3D-analysis software using a root mean square (RMS) calculation method, and qualitative analysis was executed using machine learning software. RESULTS: The mean RMS result for the test strategy was 82.8 ± 16 µm compared to 81.5 ± 16 µm for the control strategy. The mean RMS results were 84.7 ± 15 µm for Primescan (PS) and 79.6 ± 17 µm for 3Shape (3S). As such, the scanning strategies and IOS devices did not influence the scanning accuracy. Yet, a significant difference was found when the two strategies' scanning times were compared (P = .001), as well as the IOS devices (P = .001). The operator was found to have no influence on the scanning strategy. CONCLUSIONS: The accuracy of digital impressions is not influenced by different strategies, devices, or operators, in contrast with the scanning time, which is influenced by both strategies and devices.

The influence of titanium-base abutment geometry and height on mechanical stability of implant-supported single crowns.

AIM: This study aimed to investigate the influence of titanium base (ti-base) abutment macro- and micro-geometry on the mechanical stability of polymer-infiltrated ceramic network (PICN) screw-retained implant-supported single crowns (iSCs). MATERIALS AND METHODS: Twelve specimens per group were used, comprising six different implant/ti-base abutment combinations restored with PICN iSCs: Nb-T (gingival height [GH]: 1.5 mm, prosthetic height [PH]: 4.3 mm), CC (GH: 0.8 mm, PH: 4.3 mm), CC-P (GH: 0.8 mm, PH: 7 mm), Nb-V (GH: 1.5 mm, PH: 6 mm), St (GH: 1.5 mm, PH: 5.5 mm), and Th (GH: 0.5 mm, PH: 9 mm). The specimens underwent thermo-mechanical aging, and those that survived were subsequently subjected to static loading until failure. The data were analyzed using a one-way ANOVA test followed by Tukey post hoc test (α = .05). RESULTS: All specimens survived thermo-mechanical aging without complications, namely, visible cracks, debonding, or screw loosening. Th group demonstrated the highest strength values among all the groups, with significant differences compared to Nb-T (p < .05), CC (p < .001), and St (p < .001). Additionally, CC-P group exhibited significantly superior fracture strength results compared to CC (p < .05) and St (p < .05). CONCLUSION: The choice of ti-base, particularly prosthetic height, had a significant influence on fracture resistance of PICN iSCs. Nevertheless, the height or geometrical features of the ti-base did not exhibit a significant influence on the mechanical behavior of the iSC/ti-base assembly under thermomechanical loading, as all specimens withstood the aging without complication or failure.

Influence of age, training, intraoral scanner, and software version on the scan accuracy of inexperienced operators.

PURPOSE: To evaluate the effect of operator age on the scan accuracy (trueness and precision) of inexperienced operators when compared with experienced operators, and how training, intraoral scanner (IOS), and software version affect scan accuracy. MATERIAL AND METHODS: Thirty-four operators were sorted into groups: G1 (operators <25 years old, no experience), G2 (operators >40 years old, no experience), and G3 (experienced IOS operators). They conducted partial-arch scans before and after a 4-session training with two IOSs (Trios 3 and True Definition) and two software versions. These scans were compared with the reference scans obtained from conventional impressions and a laboratory scanner (IScan D103i) to evaluate trueness (mean root mean square values) and precision (standard deviation of root mean square values) with a software program (Geomagic Control X). Kruskal-Wallis and post-hoc Dunn's tests were used to evaluate the effect of age on the scan accuracy of inexperienced groups when compared with experienced operators, while the effect of training, IOS, and software version on scan accuracy was evaluated with Wilcoxon or Mann-Whitney U tests (α = 0.05). RESULTS: Before training, G1 and G2 scans had similar accuracy (p ≥ 0.065). After training, G1 scans had higher accuracy when IOS data was pooled and had higher precision with TD (p ≤ 0.004). Training increased the scan accuracy (p < 0.001), while newer software increased the trueness of inexperienced operator scans (p = 0.015). CONCLUSIONS: Age affected the scan accuracy of inexperienced operators after training, indicating that extended training may be required for older operators. Training increased the scan accuracy, and newer software increased the trueness of inexperienced operator scans.

Occlusal adjustment of 3-unit tooth-supported fixed dental prostheses fabricated with complete-digital and -analog workflows: A crossover clinical trial.

AIM: This prospective crossover clinical trial aimed to compare the complete-digital and -analog workflows in terms of occlusal adjustment of 3-unit tooth-supported fixed dental prostheses, operator, and patient preferences. MATERIALS AND METHOD: This study included twelve patients receiving fourteen 3-unit posterior FDPs. 2 FDPs were made for each restoration site: one fabricated in complete-digital workflow comprising intraoral scan with static bite registration (Trios 3) and a monolithic zirconia FDP (test); the other fabricated in complete-analog workflow comprising conventional impression/face-bow transfer and a porcelain-fused-to-metal FDP (control). The FDPs (n=28) were intraorally/provisionally fixed, and quadrant-like intraoral scans were taken for every FDP before & after their occlusal adjustments. Pre- and post-adjustment scans of each FDP were then superimposed using best-fit alignment (GOM Inspect) to measure the volumetric occlusal adjustment amount (mm3) (3Matic) (Mann Whitney U, α=0.05). The patient and operator experience for digital and analog workflows were evaluated using visual analog scales (Wilcoxon test, α=0.05). RESULTS: Mean occlusal adjustments were 7.63 mm3 [±7.02] and 25.95 mm3 [±39.61] for test and control groups, respectively. The volumetric adjustment difference was clinically noticeable but not significant (P=0.12). The impression and digital workflow adjustment were perceived more favorably by both operator (P=0.003, P=0.046, respectively) and the patients (P=0.003, P=0.002, respectively). CONCLUSIONS: Within the limitations of this clinical study, the complete digital workflow with digital static bite-registration provided high occlusal accuracy for short-span tooth-supported FDPs. In addition, the patient and operator preferences significantly favored the digital workflow. CLINICAL SIGNIFICANCE: Complete-digital workflow employing intraoral scanning and model-free fabrication of monolithic-Zr short-span tooth-supported FDPs offers an effective treatment modality with sufficient occlusal accuracy. Therefore complete-digital workflow is a valid alternative for complete-analog workflow comprising conventional impression, face-bow transfer, and use of a semi-adjustable articulator.

Influence of customized over-scan body rings on the intraoral scanning effectiveness of a multiple implant edentulous mandibular model.

OBJECTIVES: To evaluate the effectiveness of intraoral scanning with identical multiple implant scan bodies (ISB) using customized over scan body rings (COR) as an auxiliary system. METHODS: Six printed rings with different diameters and shapes were attached at different levels to each identical ISB of an edentulous mandibular master model. The master model was scanned using an intraoral scanner (Primescan CEREC) until valid digital models for the COR group (n=10) and for the unmodified ISB (UN) group (n=10) were obtained. The total scanning times and the number of rescans required was registered. To assess differences between scanning efficiency the Student T-test and Mann Whitney U-Test were applied. A Coordinate Measuring Machine (CMM) was used to register the reference model. To evaluate accuracy discrepancies between the test scans (n=20) and the reference model, Geomagic Control X was used. Mann Whitney U-test was applied to calculate statistically significant differences. RESULTS: To achieve a valid model, an average of 4.70 rescans / repetitions were required for the UN group, whereas for the COR group required an average of 1.40 rescans (p<.001). Mean total scanning time was 201.10 s and 542.40 s for the COR and UN group, respectively (p=.001). No statistically significant differences were found between the groups in terms of accuracy (p>.05) with respectively COR and UN values; mean linear trueness 34.38 µm and 31.14 µm, mean linear precision 22.94 µm and 18.51 µm, mean angular trueness 0.12° and 0.14°, mean angular precision 0.075° and 0.08°. CONCLUSION: The use of the COR system may increase the scanning efficiency of multiple implants with similar ISBs without impacting the accuracy.

Influence of age and scanning system on the learning curve of experienced and novel intraoral scanner operators: A multi-centric clinical trial.

OBJECTIVES: To evaluate the effect of age and intra-oral scanner (IOS) on the learning curve of inexperienced operators. METHODS: Thirty-four operators pertaining to 1 of 3 groups: (G1) students ≤ 25 years (y), (G2) dentists ≥ 40y, and (G3) a control group of experienced IOS operators (no age limitation), were included. All participants performed baseline and final quadrant scans on a volunteer subject, before and after a training program of 3 sessions, with two different IOS: TRIOS 3 (S1) and True Definition (S2). Baseline and final scanning times were registered in seconds. A Pearson correlation was applied to evaluate the correlation between age and scanning time. An ANOVA of repeated measures test was applied to evaluate inter-group (G1, G2, G3) and inter-system performance. Significance level was set at a = 0.05. RESULTS: Age and scanning time for inexperienced operators showed a weak positive correlation for final scanning time (r = 0.29, p < 0.05). When comparing groups and filtering by IOS, S1 failed to show differences between groups (p > 0.05). With S2, the control group demonstrated a better performance than G2 (p < 0.05), while G1 only demonstrated a better performance than G2 at final scanning time (p = 0.005). Overall, the type of IOS had a significant impact on the scanning time (p < 0.001). CONCLUSION: Results from this study indicate that age and type of IOS have an impact on the performance and learning curve of inexperienced IOS operators. CLINICAL SIGNIFICANCE: Gaining knowledge on how different aspects, such as age, experience or IOS system, influence the learning curve to IOSs is relevant due to the financial and strategical impact associated with the acquisition of an IOS.

Soft tissue integration of different abutment surfaces: An experimental study with histological analysis.

OBJECTIVE: To evaluate whether abutment surface and surface bio-activation have an effect on soft tissue morphogenesis. MATERIALS AND METHODS: 36 patients (36 implants) were included. Abutments were randomly divided into 4 groups (n = 9): Smooth Surface-MAChined (MAC), Ultrathin Threaded Microsurface (UTM), MAC Plasma of Argon activated (Plasma-MAC), and UTM Plasma of Argon activated (Plasma-UTM). After 2 months of healing, soft tissue samples were collected and prepared for histological analysis. The margin of the peri-implant mucosa (PM), the apical extension of the barrier epithelium (aJE), and the apical location of the abutment (AM) were identified. Significances of differences among groups were tested by means of the Kruskal-Wallis test and between pairs of results by means of the Mann-Whitney test. RESULTS: The mean (SD) vertical dimension of the mucosa was 2.5mm (1.0), including a connective tissue portion (CTP) of 0.8mm (0.8) in the MAC group; 3.6mm (0.2) with a CTP of 1.6mm (0.4) in the Plasma-MAC group; 3.2mm (1.0), with a CPT of 0.5mm (0.6) in the UTM; and 3.3mm (0.8), with a CPT of 0.9mm (0.7) in the Plasma-UTM group. Statistically significant differences were observed in the aJE-AM height and PM-aJE profile among the four experimental groups (p = .042 and p = .039, respectively). The Mann-Whitney test indicated differences between the Plasma-abutments and the untreated abutments both for PM-AM (p = .025) and AjE-AM (p = .021). The differences appeared more evident when the preoperative soft tissue thickness was ≤2mm. CONCLUSIONS: Within its limits, the study demonstrated a favorable effect of the plasma treatment on the connective tissue portion tissues. Plasma-MAC group highlighted the best performance. This behavior appeared strictly correlated with the soft tissue thickness.

Esthetic Outcomes of Implant-Supported Single Crowns Related to Abutment Type and Material: A Systematic Review.

PURPOSE: To systematically review the influence of abutment material and configuration on the soft tissue esthetic outcomes of implant-supported single crowns (iSCs) after 3 years. MATERIALS AND METHODS: An electronic search on MEDLINE (PubMed) from January 2000 to July 2019 was conducted for clinical trials with no language restrictions. The focus question was: In partially edentulous patients with iSCs, does the abutment material (metal vs ceramic) or the configuration (standardized vs customized) have an effect on the soft tissue esthetic outcomes? Randomized controlled trials, controlled clinical trials, and prospective or retrospective case series with at least 10 patients and a minimum of 3 years of follow-up were included. The esthetic outcomes Pink Esthetic Score (PES), PES/White Esthetic Score (WES; ie, modPES), Papilla Index (PI), soft tissue recession, and papilla height change were extracted. Meta-analysis was performed when applicable. RESULTS: Of the 6,399 titles identified, 27 studies were included. Combined mean PES/modPES scores, translated into a scale of 0 to 100, were 68.8 for ceramic, 74.2 for metal (P = .392), 71.9 for customized, and 71.3 for standard (P = .981) abutments. Mean soft tissue recession was also similar between the abutment groups, abutment material (P = .850), and configuration (P = .849), ranging from -1.09 mm to +0.59 mm gain. Papilla height changes ranged from -1.22 mm to +1.0 mm gain. The reported mean PI was 2.16 for customized, 2.06 for standard (P = .552), 2.01 for ceramic, and 2.28 for metallic (P = .04) abutments. CONCLUSION: This systematic review showed that the abutment material and configuration had minimal impact on the evaluated soft tissue esthetic outcomes. Future research focusing on the included parameters in a randomized controlled manner is needed to validate the present findings.

A Systematic Review and Meta-Analysis of the Influence of Abutment Material on Peri-implant Soft Tissue Color Measured Using Spectrophotometry.

PURPOSE: To systematically review the current literature on the influence of abutment material (metal vs ceramic) and soft tissue thickness on peri-implant soft tissue discoloration in partially edentulous patients restored with implant-supported single crowns. METHODS: An electronic MEDLINE search was performed to identify randomized controlled clinical trials (RCTs) up to and including March 2017. The search was complemented by a manual search of related bibliographies. Selection of studies was made independently by two reviewers based on the inclusion criteria. Spectrophotometric data (ΔE values) and soft tissue thickness values were extracted, and, whenever applicable, a meta-analysis using a random-effects approach was performed. RESULTS: The search resulted in 208 titles and 30 abstracts. Full-text analysis was performed for 13 articles, resulting in 6 included RCTs. Meta-analysis of a total of 266 abutments revealed significantly lower ΔE values for ceramic abutments when compared to the overall metal abutments (z test value = 1.99, P = .05), with a mean difference of 1.41 (95% CI 0.02, 2.80). Nonsignificant differences were found between titanium and zirconia (z test value = 1.59, P = .11). Limited information on the correlation between soft tissue thickness and ΔE values was found. Hence, it was not possible to perform a meta-analysis of this question. CONCLUSION: The color outcome of the peri-implant soft tissue might be influenced by the abutment material. Ceramic abutments appear to provide an improved color matching between peri-implant soft tissues and soft tissues around natural teeth when compared to metallic abutments. These findings support the preference for all-ceramic or "white" abutments in esthetically demanding cases.

Clinical Recommendations for Implant Abutment Selection for Single-Implant Reconstructions: Customized vs Standardized Ceramic and Metallic Solutions.

The present paper presents clinical guidelines for the selection of the abutment material and level of customization for single-implant reconstructions. A systematic literature search was conducted previous to a Consensus Conference, resulting in two systematic reviews. One review focused on esthetic clinical outcomes, including esthetic indices and linear measurements, and the second focused on peri-implant soft tissue color outcomes, evaluated with spectrophotometry. The outcomes of esthetic indexes and linear measurement were highly heterogenic, hence, a meta-analysis was not feasible. All-ceramic and customized solutions showed a trend for improved results of the esthetic outcomes. Regarding soft tissue color outcomes, all-ceramic abutments induced significantly less soft tissue color changes. Both metallic and all-ceramic abutments/standard and customized components may result in clinically and esthetically acceptable reconstructions.

A systematic review of the influence of the implant-abutment connection on the clinical outcomes of ceramic and metal implant abutments supporting fixed implant reconstructions.

OBJECTIVES: The objective of this systematic review was to assess the influence of implant-abutment connection and abutment material on the outcome of implant-supported single crowns (SCs) and fixed dental prostheses (FDPs). METHODS: An electronic Medline search complemented by manual searching was conducted to identify randomized controlled clinical trials, prospective and retrospective studies with a mean follow-up time of at least 3 years. Patients had to have been examined clinically at the follow-up visit. Failure and complication rates were analyzed using robust Poisson regression, and comparisons were made with multivariable Poisson regression models. RESULTS: The search provided 1511 titles and 177 abstracts. Full-text analysis was performed for 147 articles resulting in 60 studies meeting the inclusion criteria. Meta-analysis of these studies indicated an estimated 5-year survival rate of 97.6% for SCs and 97.0% for FDPs supported by implants with internal implant-abutment connection and 95.7% for SCs and 95.8% for FDPs supported by implants with external connection. The 5-year abutment failure rate ranged from 0.7% to 2.8% for different connections with no differences between the types of connections. The total number of complications was similar between the two connections, yet, at external connections, abutment or occlusal screw loosening was more predominant. Ceramic abutments, both internally and externally connected, demonstrated a significantly higher incidence of abutment fractures compared with metal abutments. CONCLUSION: For implant-supported SCs, both metal and ceramic abutments with internal and external connections exhibited high survival rates. Moreover, implant-supported FDPs with metal abutments with internal and external connections for also showed high survival rates.

Clinical evaluation comparing the fit of all-ceramic crowns obtained from silicone and digital intraoral impressions.

OBJECTIVES: The aim of this study is to compare the fit of all-ceramic crowns fabricated from conventional silicone impressions with the fit of all-ceramic crowns fabricated from intraoral digital impressions. METHODS: Twenty patients with 26 posterior teeth with a prosthetic demand were selected for the study. Two crowns (Straumann-Zerion) were made for each preparation. One crown was fabricated from an intraoral digital impression system (IDI group; Cadent-iTero), and the other crown was fabricated from a conventional one-step silicone impression (CI group; Express Penta Putty and Body Light). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation with ultra-flow silicone (Express Ultra Light Body). Each crown was embedded in resin to stabilize the registered interface, cut in 2-mm-thick slices in a buco-lingual orientation. Internal misfit was measured in microns using stereomicroscopy with a magnification of ×40. Measurements were taken at different landmarks: margin, chamfer angle, axial, crest, and occlusal fosse. After checking for normality, data was analyzed using paired Student's t test (α = 0.05). RESULTS: Fit values were significantly affected by the impression technique (p = 0.000). Mean internal misfit and mean marginal misfit were 111.40 µm (SD = 54.04)/80.29 µm (SD = 26.24) for the crowns of the IDI group and 173.00 µm (SD = 92.65)/133.51 µm (SD = 48.78) for the CI group. CONCLUSION: All-ceramic crowns fabricated from intraoral digital impressions with parallel confocal technology demonstrated a clinically acceptable internal and marginal fit as conventional impression. CLINICAL SIGNIFICANCE: Intraoral digital impressions as initial step to the digital workflow could further improve the marginal adaptation of all ceramic single crowns. TRIAL REGISTRATION: http://www.isrctn.com/ISRCTN16111844.

Clinical evaluation comparing the fit of all-ceramic crowns obtained from silicone and digital intraoral impressions based on wavefront sampling technology.

OBJECTIVE: The aim of this study was to compare the fit of ceramic crowns fabricated from conventional silicone impressions with the fit of ceramic crowns fabricated from intraoral digital impressions. METHODS: Twenty-five participants with 30 posterior teeth with a prosthetic demand were selected for the study. Two crowns were made for each preparation. One crown was fabricated from an intraoral digital impression system (IDI group) and the other crown was fabricated from a conventional two-step silicone impression (CI group). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation with ultra-flow silicone. Each crown was embedded in acrylic resin to stabilise the registered interface and then cut in 2mm thick slices in a buco-lingual orientation. The internal gap was determined as the vertical distance from the internal surface of the crown to the prepared tooth surface at four points (marginal gap, axial gap, crest gap, and occlusal fossa gap) using stereomicroscopy with a magnification of 40×. Data was analysed by using Wilcoxon signed rank test (α=0.05). RESULTS: Internal adaptation values were significantly affected by the impression technique (p=0.001). Mean marginal gap was 76.33 ± 65.32 µm for the crowns of the IDI group and 91.46 ± 72.17 µm for the CI group. CONCLUSION: All-ceramic crowns fabricated from intraoral digital impressions with wavefront sampling technology demonstrated better internal fit than crowns manufactured from silicone impressions. CLINICAL SIGNIFICANCE: Impressions obtained from an intraoral digital scanner based on wavefront sampling technology can be used for manufacturing ceramic crowns in the normal clinical practice with better results than conventional impressions with elastomers.