Ragai Edward Matta

Accurate transfer of implant position to the virtual model is essential for digital implant prosthodontic workflows. Although scan body geometry and CAD software may affect this process, evidence regarding their combined effect remains limited. This in vitro study evaluated the effects of two scan body systems and three CAD software programs on implant-position transfer accuracy and assessed their interaction. An edentulous maxillary titanium model with three implants was digitized ten times for each of two scan body systems. Each data set was processed with exocad, 3shape, and DWOS. Implant-position transfer was assessed as the three-dimensional Euclidean deviation of standardized scan body reference points. Data were analyzed using a two-way mixed repeated-measures ANOVA and Holm-adjusted pairwise comparisons (α = 0.05). Scan body system, CAD software, and their interaction significantly affected transfer accuracy (p < 0.001). Medentika showed lower mean deviations than NT-Trading with all software programs, although the difference was not significant with 3shape. For NT-Trading, 3shape produced significantly lower deviations than exocad and DWOS, whereas for Medentika, exocad produced significantly lower deviations than DWOS, with no significant differences between 3shape and either exocad or DWOS. Implant-position transfer accuracy depended on the specific combination of scan body system and CAD software. These findings suggest that scan body system and CAD software should be considered jointly when evaluating implant-position transfer accuracy.

The objective was to evaluate the trueness of interocclusal registration obtained with three intraoral scanning systems versus a conventional impression and bite registration in fully dentate patients. Twenty adults with complete dentitions and Angle Class I occlusion were enrolled. Complete-arch scans were obtained with Primescan, iTero Element, and TRIOS 4, followed by bilateral virtual interocclusal registration. Conventional impressions and polyvinyl siloxane records were used to fabricate stone casts, digitized with a laboratory scanner with the record and after manual articulation in maximum intercuspation. Industrial scanner datasets served as participant-specific references. Three-dimensional deviations were analyzed by repeated-measures ANOVA and Holm-adjusted paired t-tests (α = 0.05). The conventional workflow with an interocclusal record showed the greatest deviation (797 ± 308 μm; p < 0.001). Manual articulation (331 ± 167 μm) did not differ significantly from Primescan (262 ± 120 μm), iTero Element (256 ± 101 μm), or TRIOS 4 (325 ± 168 μm) (p ≥ 0.223); no differences were found among scanners under the conditions of this study (p ≥ 0.468). Virtual interocclusal registration showed greater trueness than the conventional workflow with a physical record, whereas manual articulation performed comparably to digital workflows. These conclusions apply only to fully dentate patients with stable occlusal support and maximum intercuspation.

Scan-assisted interocclusal registration may vary with record extent and occlusal support. Using separately fabricated high-hardness vinyl polysiloxane (VPS) records, a fixed bilateral buccal intraoral scanner (IOS) acquisition protocol, optical reference articulations, and position-level three-dimensional analysis, this in vitro study compared prepared-tooth (Hard-Prep) and complete-arch (Hard-Arch) records across three support configurations and assessed a no-record IOS workflow. Ninety VPS-based and 45 no-record IOS acquisitions were analyzed. VPS records were fabricated under a 3.0 kg load; measurements used a 1.0 kg load. Overall three-dimensional deviation (dXYZ) was averaged over five mandibular positions. Log-transformed dXYZ was analyzed by ordinary least squares with Holm-adjusted contrasts. The Hard-Arch/Hard-Prep contrast was not statistically significant under bilateral extended support. Hard-Arch showed higher dXYZ under unilateral extended support (ratio, 1.75; 95% confidence interval (CI), 1.54–1.99; p < 0.001) and unilateral limited support (ratio, 1.58; 95% CI, 1.39–1.80; p < 0.001). In the no-record workflow, unilateral extended support exceeded bilateral extended support (ratio, 1.50; 95% CI, 1.31–1.72; p < 0.001), whereas unilateral limited support was lower than unilateral extended support (ratio, 0.68; 95% CI, 0.59–0.77; p < 0.001). Prepared-tooth records yielded lower deviation in both unilateral configurations, while the no-record workflow varied with support configuration.

Purpose: In dentistry, digital technologies have become firmly established in the field of oral implantology. The trueness of impressions taken using intraoral scanners as part of the digital workflow has a direct influence on the accuracy of fit of the subsequent restoration. Therefore, this in-vitro study investigates the influence of possible scanning errors on the trueness of digital implant impressions. Methods: A standardized titanium model of a maxillary alveolar ridge with three bone-level implants was digitized with two different scan body systems (Medentika and NT-Training) using an industrial high-precision scanner to generate the virtual reference models. Subsequently, three different modifications, including two different gingival heights and artificially created defects, were each digitized 15 times using two different intraoral scanners (Primescan and Trios 4) with both scan body systems. The digitized scan bodies were then matched with the scan body analogs in the Exocad software to generate the virtual working models. Trueness was examined by superimposing the virtual working models with the corresponding virtual reference model. Results: All scanning errors evaluated resulted in significantly higher deviations. Across all groups, the trueness decreased with increasing gingival height. The best results (30 ± 15 μm) were attained when scanning at the lower gingival height. The largest discrepancy (178 ± 63 μm) was found when impressions of the higher gingival height were taken. Conclusion: In the process of taking digital implant impressions, it is essential to maximize the exposure of the scan bodies. Furthermore, it is imperative to minimize defects in order to achieve optimal outcomes. Graphical

Multilayer zirconias have recently been introduced as dental biomaterials to combine improved translucency with sufficient mechanical reliability by implementing yttria-driven gradients in phase composition. Such materials can be considered functionally graded ceramics, where local phase stabilization influences strength and crack resistance. However, manufacturer-specific gradient profiles and their structure–property relationships remain insufficiently characterized. This study investigated two commercially available multilayer zirconias with distinct gradient concepts: IPS e.max^® ZirCAD Prime (continuous gradient) and KATANA™ Zirconia YML (stepwise gradient). Ten equidistant sections along the blank height were analyzed using quantitative X-ray diffraction and Rietveld refinement to quantify zirconia phase fractions and estimate local Y₂O₃ content. Mechanical behavior was evaluated by biaxial flexural strength testing (ball-on-three-balls method) and fracture toughness testing using the chevron-notched beam technique. Both materials exhibited pronounced yttria- and phase-dependent gradients consistent with their reported layer designs. Regions with increased yttria content showed higher t″ fractions and reduced fracture toughness and strength, whereas deeper regions displayed increased mechanical performance associated with higher fractions of transformable tetragonal phase. These findings emphasize that multilayer zirconias exhibit spatially dependent mechanical properties, which should be considered in biomaterial selection and restoration design, particularly when balancing aesthetic demands and fracture resistance.

Dimensional accuracy of 3D-printed implant models is essential for precise implant-supported restorations. The objective of this study was to evaluate the influence of printing orientation and model base design on the accuracy of implant position transfer. A standardized maxillary model with four implants was scanned using an intraoral scanner. Solid and hollow models were designed and printed using digital light processing (DLP) technology at orientations of 0°, 45°, and 90° (n = 10 per group). All models were digitized with a high-precision industrial scanner, and implant position deviations were determined by comparing corresponding reference points with the master model. Data were analyzed using two-way analysis of variance and post hoc tests (α = 0.05). Printing orientation significantly affected accuracy (p < 0.001). Models printed at 45° showed the highest deviations, whereas those printed at 0° and 90° exhibited comparable and superior accuracy. Model design (solid vs. hollow) had no significant influence at 0° and 90°, but hollow models were more accurate at 45° (p < 0.001). Mean deviations ranged from 131 μm to 382 μm. Printing at 0° or 90° is recommended, while 45° orientations should be avoided. Model design showed minimal effect on accuracy.

Objectives: Post-extraction remodelling of hard and soft tissues results in volume reduction, leading to aesthetic challenges in planning prosthetic restorations, particularly in the anterior maxilla. This study assessed whether atraumatic vertical extraction, versus conventional extraction, could reduce postoperative volume loss and aesthetic compromises at the extraction site and adjacent teeth. Methods: Following randomized tooth extraction with unassisted healing in the test (Benex^® extraction, n = 10) and control group (conventional extraction, n = 10), postoperative scans were conducted at 30 days (t₁), 60 days (t₂), 90 days (t₃) and 12 months (t₄). Each scan was aligned with the baseline scan (t₀), and surface comparison was performed with five regions of interest (ROIs: central, mesial, distal, papilla mesial and papilla distal). Aesthetic parameters, including recession and Pink Esthetic Score (PES) of adjacent teeth, were clinically evaluated at each follow-up appointment. Statistical analysis used a mixed linear model accounting for confounding factors such as smoking, buccal bone integrity, gingival phenotype, and provisional use. Results: Both groups showed significant volume reduction from baseline to t₃ and t₄. The largest volume loss occurred in the central ROI in both test (t₄: −65.34 ± 36.89 mm³) and control group (t₄: −70.85 ± 30.96 mm³), with no significant difference between groups. A decline in PES and recession at the adjacent teeth was noted in both groups at 12 months. Conclusions: Both groups showed significant volume reduction with aesthetic impairment at the adjacent teeth’s soft tissue.

Successful dental implant therapy relies on accurate planning and placement, e.g., through static, computer-aided implant surgery using CAD/CAM-fabricated surgical guides. This study examined production methods’ influence on surgical guide sleeve housing geometry. A model with two edentulous spaces was digitized using intraoral scanning and CBCT, and two virtually positioned implants were planned. Ten guides per group were produced using milling (MCX5), DLP printing (ASIGA and SHERA), and SLA printing (FORM), printing with 50 µm and 100 µm layers each. Each guide (n = 70) was then digitized using an industrial scanner before and after sterilization. Superimposition of the actual guide data with the reference data allowed for evaluation of deviations at the drill sleeve housing along the x-, y-, z-, and dxyz-axes. Descriptive and statistical evaluation was performed (significance level: p ≤ 0.0125). Significant differences existed among the production methods: Milling and SLA showed higher deviations than the DLP group (p < 0.001). Milled guides post-sterilization showed the highest deviations (0.352 ± 0.08 mm), while one DLP printer at 50 μm layer thickness showed lowest deviations (0.091 ± 0.04 mm). The layer thickness was insignificant, whereas sterilization increased deviation (p < 0.001). DLP produced the most precise implant surgical guides. All 3D printers were suitable for fabricating clinically acceptable surgical guides.

Material wear significantly impacts the clinical success and longevity of dental ceramic restorations. This in vivo study aimed to assess the wear behavior of IPS Empress^® glass-ceramic inlays and onlays over 14 years, considering the influence of different antagonist materials. Fifty-four indirect restorations of 21 patients were available for comprehensive wear analysis, with complete follow-up data for up to 14 years. Three-dimensional measurements relied on digitized epoxy resin models produced immediately post-insertion (baseline) and subsequently at 2, 4, and 14 years. The occlusal region on the baseline model was delineated for comparative analysis. Three-dimensional superimpositions with models from subsequent time points were executed to assess wear in terms of average linear wear and volumetric loss. Statistical analyses were conducted in R (version 4.4.1), employing Mann–Whitney U tests (material comparisons) and Wilcoxon signed rank tests (time point comparisons), with a significance threshold of p ≤ 0.05. During the entire study period, an increase in wear was observed at each assessment interval, gradually stabilizing over time. Significant differences in substance loss were found between the follow-up time points, both for mean (−0.536 ± 0.249 mm after 14a) and integrated distance (−18,935 ± 11,711 mm³ after 14a). In addition, significantly higher wear was observed after 14 years with gold as antagonist compared to other materials (p ≤ 0.03). The wear behavior of IPS Empress^® ceramics demonstrates clinically acceptable long-term outcomes, with abrasion characteristics exhibiting stabilization over time.

Objectives: Temporomandibular disorders (TMD) are often linked to changes in dental occlusion, yet the impact of therapeutic interventions remains unclear. This pilot study investigates the effects of manual therapy on occlusion in TMD patients through quantitative analysis of intraoral scans.Material and Methods: Ten individuals were diagnosed with TMD and underwent a 40‐min session of manual therapy (Group MT). Ten subjects were allocated to the healthy control group (Group C) and did not receive any therapy during the 10‐week control period. Occlusion measurements were obtained using the TRIOS 3 intraoral scanner (3Shape, Denmark) both before and after the therapy or control period. The digital models were analyzed regarding occlusal changes using the GOM Inspect Professional software (GOM, Germany). The differences in the individual axes and Euclidean distance were computed.Results: In terms of the arithmetic mean, Group MT exhibited higher deviations across all three axes () as well as in the Euclidean distance than the control group . Statistically significant differences were observed for the Y and Z axes, as well as the Euclidean distance (p < 0.05).Conclusion: Considering the limitations of this pilot study, it is reasonable to suggest that manual therapy has a significant influence on occlusion in habitual intercuspidation among TMD patients.