Manufacturing trueness, internal fit, and planned-to-intraoral spatial concordance of monolithic zirconia crowns fabricated with two commercial ti-base systems: a clinical cross-sectional study

The effect of build angle and intraarch connector design on the accuracy and fit of additively manufactured complete-arch implant-supported interim fixed prostheses.

OBJECTIVES To evaluate the effect of intraarch connector design and build angle on the fabrication trueness and precision, and overall accuracy, of additively manufactured (AM) compared to subtractively manufactured (SM) frameworks in high-impact polymer composite (HIPC) for complete-arch implant-supported prostheses on four implants. MATERIALS AND METHODS A typodont model with four implants and their multiunit abutments were digitized and an implant-supported complete-arch framework was designed. Three design files (no bar, horizontal bar, Y-shaped bar) were used to fabricate AM specimens using a glass-filler-reinforced composite resin in three different build angles (0°, 45°, 90°) (n=10). Ten SM frameworks fabricated from HIPC served as the control group. All frameworks were digitized and superimposed. Trueness and precision were evaluated in separate regions, as well as linear abutment and interimplant distance deviations. Marginal gaps were evaluated after seating the frameworks with one screw inserted in left posterior abutment. Data were statistically analyzed (α = 0.05) RESULTS: Both build angle and intraarch connector design significantly affected trueness, precision, linear deviations, and marginal gaps. Compared to the control group, test groups mostly showed similar or lower accuracy. No clear pattern among other test groups was observed. Marginal gaps differed significantly among groups (p<0.05), ranging from 50.2 µm at the right posterior abutment in the 0°-no-bar group to 573.7 µm at the left anterior abutment in the 90°-horizontal-bar group. 0° no-bar mostly showed the lowest surface deviation, lowest linear deviation, and least marginal gaps (p<0.05). CONCLUSIONS Within the limitations of this single-system in vitro study, AM complete-arch implant-supported interim fixed prostheses in a 0° no-bar configuration demonstrated accuracy comparable to SM HIPC. The marginal gaps found in some groups were beyond clinical acceptability. Printing such prostheses in 45° and 90° configurations using the tested printer, resin, and post-processing combination cannot be recommended. CLINICAL SIGNIFICANCE The differences in marginal gaps found between the groups showed magnitudes beyond clinical acceptability and therefore additive manufacturing of complete-arch implant-supported interim fixed prostheses using build angles other than 0°and/or incorporating intraarch connectors should be approached with caution.

Accuracy of scannable anatomic healing abutments for implant-supported crown and fixed partial prostheses: An in vitro comparison with conventional scan bodies.

STATEMENT OF PROBLEM Accurate digital implant scanning is critical for the fit, function, and biological stability of implant-supported restorations. Anatomic scannable healing abutments (AHAs) have been proposed as an alternative to conventional scan bodies (SBs) to simplify digital workflows and facilitate the development of an adequate emergence profile. However, their accuracy in crown and short-span fixed dental prosthesis scenarios remains insufficiently investigated. PURPOSE The purpose of this in vitro study was to compare the trueness and precision of implant position detection obtained using AHAs versus SBs in single-crown and short-span fixed dental prosthesis configurations. MATERIAL AND METHODS Two partially edentulous maxillary models were digitally designed and 3-dimensionally (3D) printed: 1 with a single molar edentulous site and 1 with a 3-tooth posterior edentulous span. Implant analogs were placed in the models to simulate a single implant site and a 3-unit implant fixed dental prosthesis site. AHAs (test group) or SBs (control group) were connected to the analogs. A desktop scanner was used to obtain baseline scans for each group, while 15 consecutive intraoral scans per group were acquired using an intraoral scanner. Linear (mesiodistal, buccolingual, coronoapical), angular, and overall 3D deviations at the implant platform center were calculated and analyzed using the t test and Mann-Whitney U test. RESULTS For the single-crown model, AHAs demonstrated significantly better mean 3D trueness than SBs (20 µm and 74 µm; P<.001), as well as better angular deviation (0.11 degrees and 0.44 degrees; P<.001). Precision was also better for AHAs, with a mean 3D deviation of 10 ±5 µm compared with 67 ±37 µm for SBs (P<.001). In the 3-unit fixed dental prosthesis model, AHAs consistently showed better trueness and precision at both premolar and molar positions. At the molar site, mean 3D trueness was 24 µm for AHAs versus 103 µm for SBs (P<.001), and mean 3D precision was 22 ±9 µm versus 79 ±54 µm (P<.001). CONCLUSIONS AHAs demonstrated significantly higher trueness and precision than SBs for implant position detection in single-crown and short-span fixed dental prosthesis scenarios.

Effect of varying intraoral scanner tip size, tooth location and preparation design on the marginal and internal fit of 3D-printed zirconia crowns.

Adjustment Efficiency and Internal Fit of Screw-Retained Zirconia Crowns on Additively Manufactured Dental Casts: An In Vitro Study on the Effect of Printing Layer Thickness and Digital Implant Analog Design.

PURPOSE To evaluate how the layer thickness of additively manufactured casts and implant analog design influence the adjustment efficiency and internal fit of screw-retained zirconia crowns, compared with those adjusted on conventional stone casts. MATERIALS AND METHODS A master mandibular model with an implant and its antagonist were digitized to additively manufacture implant casts with 50 µm or 100 µm layer thicknesses and either proprietary friction-retained (S) or third-party screw-retained (N) analogs (S-50, S-100, N-50, N-100), along with their corresponding maxillary casts. Conventional stone casts (CNV) served as the control (n = 10). Screw-retained zirconia crowns were fabricated for each cast, and the duration of interproximal and occlusal contact adjustments was recorded. Crown fit on the master model was evaluated using the triple-scan protocol, followed by a qualitative assessment of interproximal and occlusal contacts. Crowns with heavy contacts were readjusted and timed, then reevaluated to determine whether interproximal adjustments affected the fit. Comparisons among resin casts were performed using a generalized linear model with Bonferroni-adjusted post hoc tests, while comparisons with CNV casts were made with 1-way analysis of variance and Dunnett's tests. Qualitative contact data were analyzed using the chi-square test (α = .05). RESULTS Crowns on 50 µm-layer casts needed less adjustment and exhibited smaller gaps than those on 100 µm-layer casts; S analogs led to smaller gaps (P ≤ .010). Compared to CNV, 50 µm-layer casts led to lower adjustment duration and S-50 led to lower internal gaps (P ≤ .020). Only mesial interproximal contacts differed significantly on the master model (P = .001); crowns from S analog casts showed normal contacts, while at least 50% those from other casts had light contacts. At least 50% of the crowns exhibited normal distal contacts, and those with heavy contacts (3 on the mesial and 16 on the distal side) showed improved fit after adjustment. No occlusal adjustments were required on the master model. CONCLUSIONS Reduced printing layer thickness and the use of proprietary friction-retained analogs improved the adjustment efficiency and internal adaptation of screw-retained zirconia crowns.

In Vivo Assessment of Complete-Arch Implant Impressions Using a Clinical Seating Score: A Proof-of-Principle Case Report.

OBJECTIVE Accurate transfer of implant positions is critical for achieving passive fit in complete-arch implant-supported prostheses. This clinical case report describes the comparison of eight implant-position acquisition workflows and their influence on the clinical seating of mandibular complete-arch frameworks. The Clinical Seating Score (CSS) was used to assess clinical seating and was compared with three-dimensional deviations. METHODS A patient receiving mandibular All-on-4 rehabilitation was treated with four implants placed using dynamic navigation. After a 3-month healing period, implant positions were recorded using eight workflows: conventional open-tray impression, intraoral scanning with conventional PEEK, reduced-height titanium, horizontal-arm, centrally oriented, and reverse scan bodies, intraoral photogrammetry, and extraoral photogrammetry. Eight titanium frameworks were fabricated using standardized CAD/CAM procedures and evaluated intraorally by a single experienced clinician using the CSS (0-6), which assessed framework rocking, screw-tightening tension, and a modified Sheffield test. A Clinical Acceptability Bonus (+1) was assigned when predefined clinical deliverability criteria were met. The framework with the highest CSS was used as the reference for three-dimensional deviation analysis. RESULTS Intraoral photogrammetry produced the highest CSS (6 + 1) and was used as the reference framework. Centrally oriented scan regions and extraoral photogrammetry also produced clinically acceptable seating. Conventional impressions and workflows using conventional PEEK, horizontal-arm, or reverse scan bodies showed greater variability in clinical seating. Deviations of approximately 50-60 μm were generally associated with clinically acceptable seating, whereas discrepancies exceeding approximately 70-80 μm were associated with lower CSS values. These observations suggest that the clinical effect of implant-position discrepancies may vary according to their spatial direction. CONCLUSIONS Within the limitations of this single clinical case, the CSS provided a structured approach for assessing the clinical seating of complete-arch implant frameworks. Intraoral photogrammetry demonstrated the most favorable clinical seating, while other workflows showed variable outcomes. The proposed CSS and observed deviation ranges should be considered exploratory and require validation in larger clinical studies. CLINICAL SIGNIFICANCE The CSS may potentially provide a simple and standardized chairside method for evaluating the passive seating of complete-arch implant frameworks. This approach may help clinicians identify clinically relevant misfits before delivery of the definitive prosthesis and support more predictable decision-making during framework verification.

Monolithic Zirconia Versus Porcelain-Fused-to-Metal Implant-Supported Fixed Dental Prostheses in the Posterior Region: 3-Year Results of a Randomized Controlled Clinical Trial.

OBJECTIVES To compare the clinical, biological, and technical outcomes of posterior three-unit implant-supported fixed dental prostheses (iFDPs) fabricated from monolithic zirconia (MonoZR) or porcelain-fused-to-metal (PFM). MATERIALS AND METHODS In this prospective randomized controlled trial, partially edentulous patients requiring a posterior three-unit iFDP supported by two implants were randomly assigned to MonoZR or PFM iFDPs. The primary outcome was ceramic fracture. Secondary outcomes included prosthesis survival, complication-free survival, marginal bone level (MBL) changes, peri-implant clinical parameters, and USPHS ratings. Follow-up examinations were performed at 1 and 3 years. Statistical analyses included Kaplan-Meier estimates, Fisher's exact test, and linear mixed-effects models (α = 0.05). RESULTS Fifty-five patients received iFDPs at baseline (MonoZR: n = 28; PFM: n = 27), and 45 completed the 3-year follow-up. Two prosthesis failures occurred, one in each group, both associated with implant loss, with no difference in survival between groups (p = 1.00). Veneering ceramic chipping occurred only in the PFM group (3/23; 13%) and not in the MonoZR group (0/22) (p = 0.11). Complication-free survival, peri-implant clinical parameters, and MBL changes did not differ significantly between groups (p > 0.05). Plaque index and bleeding on probing increased over time, while probing depth and MBL remained stable. Both groups showed high clinical acceptability according to USPHS criteria. CONCLUSIONS Both MonoZR and PFM posterior three-unit iFDPs demonstrated high survival and favorable biological outcomes after 3 years. MonoZR showed no chipping events and may represent a promising alternative to PFM for posterior implant-supported restorations. TRIAL REGISTRATION German Clinical Trials Register: DRKS00011039.