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
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
PURPOSE
This in vitro study evaluated the influence of the presence of saliva in varying levels on the trueness and scanning time of complete-arch intraoral scans for implant-supported prostheses, considering different scan body heights, splinting protocols, and scanners.
MATERIALS AND METHODS
A three-dimensionally (3D)-printed edentulous maxillary model with six implants and multi-unit abutments was digitized using a metrology-grade industrial scanner (Artec Micro), using polyetheretherketone scan bodies (ISBs) of two heights (short: 4.5 mm and tall: 8.0 mm). The model was also scanned with three intraoral scanners (IOSs) (TRIOS 5 [TR], NeoScan 1000 [NS], and Primescan [PS]) under two splinting wire aids (splinted and non-splinted) and dry or artificial saliva-moisturized (lightly or highly) conditions. A total of 192 scans (n = 8 per experimental condition) were analyzed. Scanning time was recorded with a stopwatch, and trueness was analyzed as root mean square (RMS) deviation when industrial and IOS scans were aligned using Geomagic Control X. Data were analyzed with Kruskal-Wallis, Mann-Whitney U, and Bonferroni-adjusted pairwise comparisons (α = 0.05).
RESULTS
Saliva significantly affected trueness and scan time, with higher moisture levels resulting in greater deviations (p < 0.001) and longer acquisition times for all tested IOSs (p < 0.001). IOS type, ISB height, and scan-aid also had significant effects on scan trueness (p < 0.001). TR presented the lowest RMS values, followed by PS and NS. Under moisture conditions, short ISBs and non-splinted configurations produced more reliable scans (p < 0.001). Short ISBs consistently reduced total scanning time compared with tall ISBs (p < 0.001). PS demonstrated the shortest scanning times under dry and highly moisturized conditions, whereas NS combined with short ISBs showed the fastest acquisition under light moisture conditions.
CONCLUSION
The simulation of intraoral saliva presence compromised scan trueness, particularly when moisture level increased. Clinically, minimizing saliva presence during scans and selecting appropriate-height ISBs can enhance trueness for digital implant scans. Although scan-aid may reduce scanning time, its use should be limited to situations in which stabilization is critical, such as long edentulous arches or long interimplant distances, as these conditions may increase optical deviations in the presence of saliva. These findings support the refinement of clinical protocols for complete-arch implant scans, emphasizing saliva control and careful scan strategy selection to improve trueness of digital edentulous scans.
C. S. Galvao, Fabiana Silveira Ramalho Moreira, Annie Karoline Bezerra de Medeiros et al.· Journal of Prosthodontics· 0 citations