OBJECTIVE
This study evaluated the influence of polymerization units and support bar design on the trueness and fit of complete-arch implant-supported frameworks fabricated using digital light processing (DLP) additive manufacturing (AM) and compared their performance with a subtractively manufactured (SM) control.
METHODS
A maxillary complete-arch framework was designed and fabricated using six conditions combining two polymerization units (xenon-flash light under nitrogen [XFN] and light-emitting diode [LED]) and three support bar designs (no-bar, Y-shaped bar, horizontal-bar), along with an SM reference framework (n = 10). Fabrication trueness was evaluated by analyzing surface deviations across predefined regions (overall framework, occlusal, non-occlusal, and abutment surfaces) and by measuring linear abutment-level and interimplant distance deviations using metrology software. Marginal gap, used as a fit indicator, was assessed using a digital triple-scan protocol. Test and control group differences were analyzed by one-way ANOVA (Dunnett), and those across AM groups by two-way ANOVA (Bonferroni; α = 0.05).
RESULTS
Support bar design significantly influenced trueness (p < 0.001); no-bar frameworks generally demonstrated the highest trueness. The polymerization unit showed limited main effects on trueness, although a significant effect was observed for overall RMS (p = 0.024). For linear deviation, interimplant distance, and marginal gap, outcome-dependent polymerization unit × support bar design interactions were identified (p < 0.05). XFN polymerization yielded lower linear deviations at selected implant sites, whereas LED polymerization was associated with lower interimplant distance deviations and reduced marginal gaps at specific locations.
CONCLUSIONS
Support bar design was the primary factor influencing dimensional trueness, with no-bar configurations generally demonstrating higher trueness. Polymerization unit effects were outcome- and geometry-dependent, with no consistent overall difference between XFN and LED.
CLINICAL SIGNIFICANCE
Under the tested laboratory conditions, omitting support bars was associated with lower surface deviations in DLP-printed frameworks. However, the site- and geometry-dependent marginal gap findings do not establish a clinically preferable support or polymerization protocol and require mechanical and clinical validation.
Manuel Aeschbacher, Steven Sonderegger, S. A. Mosaddad et al.· E -journal of dentistry· 0 citations
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.
Mohamed El Gedaily, Mustafa Borga Donmez, Munir Demirel et al.· The International Journal of...· 0 citations
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.
Steven Sonderegger, Pedro Molinero Mourelle, Manuel Aeschbacher et al.· E -journal of dentistry· 0 citations
