Manuel António Sampaio-Fernandes

Objectives: To characterize, by micro-computed tomography, internal defects, porosity, and radiopaque particle distribution in two three-dimensionally printed photopolymer denture base resins (NextDent Denture 3D Plus and NextDent Base) and to descriptively explore the influence of build orientation (0°, 45°, and 90°) for Denture 3D Plus. Methods: In this descriptive in vitro pilot study, standardized specimens (10×10×2 mm) were designed (Meshmixer) and printed by liquid crystal display technology. Denture 3D Plus was printed at 0°, 45°, and 90°, and Base at 90°. One specimen of three per group was randomly selected for micro-computed tomography scanning. Reconstructed volumes were segmented to assess internal defects, porosity, and radiopaque particle volume. Data were analyzed descriptively. Results: No microcracks, fractures, inclusions, contamination, or interlayer delamination were detected within the resolution limits of the scanning protocol. Porosity was below the detection threshold in NextDent Base at 90° and very low in Denture 3D Plus at 0° (0.001%), 45° (0.0001%), and 90° (0.0003%). Radiopaque particles were dispersed throughout the resin matrix. Because the analyzed regions of interest differed in volume, particle volume fractions were not directly comparable, and no orientation-related trend could be inferred. Conclusions: Within the limitations of this single-specimen-per-group pilot design, the scanned specimens showed no detectable internal defects and very low porosity. These findings should be interpreted as preliminary micro-computed tomography observations. Controlled studies with adequate sample sizes, standardized regions of interest, and validated segmentation protocols are required before material- or orientation-related conclusions can be drawn.

Sports mouthguards play a crucial role in preventing orofacial injuries. Vacuum thermoforming with ethylene-vinyl acetate is the most common fabrication method; however, digital workflows and 3D printing have introduced promising alternatives. This in vitro study aimed to compare mouthguards produced by vacuum thermoforming and 3D printing in terms of precision, trueness and impact resistance. A maxillary plaster model was used to fabricate two groups: thermoformed mouthguards (GTherm, n = 3; Playsafe Triple Light, Erkodent™) and 3D-printed mouthguards (GPrint, n = 3; high-impact polystyrene via fused deposition modeling). The internal surfaces were scanned with a Medit T500, and precision and trueness were assessed by superimposing STL files using Geomagic software. Ten specimens of each material underwent Charpy impact testing. Data were analyzed with GraphPad Prism. The GPrint group exhibited higher precision (median RMS = 57.8 µm) than GTherm (median RMS = 812 µm), although the difference was not statistically significant (p = 0.10). Trueness in GPrint was within acceptable limits (median RMS = 118 µm). In the Charpy test, impact strength was significantly higher in thermoformable-based specimens than in printed ones (mean 17.33 ± 1.96 vs. 14.33 ± 0.65 kJ/m², respectively). Within the study’s limitations, 3D-printed HIPS mouthguards showed superior precision and acceptable trueness, whereas thermoformed mouthguards demonstrated significantly greater impact resistance.

Peri-implant infections pose a significant challenge in dental implantology. This study aimed to develop and characterize a chitosan–vancomycin coating for titanium surfaces, focusing on drug loading, release kinetics, antimicrobial performance, and cytocompatibility. Grade 4 titanium discs were coated with a chitosan film using the dip-coating technique and subsequently loaded with vancomycin through immersion in an aqueous solution. Coating morphology was examined by scanning electron microscopy (SEM). Vancomycin loading was quantified by spectrophotometry, and release kinetics were monitored over 144 h (6-day). Antimicrobial activity was assessed through agar diffusion assays against Staphylococcus aureus. Cytocompatibility was evaluated using human mesenchymal stem cells (hMSCs), whose metabolic activity, adhesion, and morphology were assessed over a 19-day culture period by resazurin assay and SEM. SEM analysis revealed a uniformly distributed, smooth, and crack-free chitosan film, which remained stable after drug loading. The coating exhibited a biphasic release profile, characterized by an initial burst followed by sustained release over six days, which maintained antimicrobial activity, as confirmed by inhibition zones. hMSCs adhered and proliferated on the coated surfaces, displaying normal morphology despite a transient reduction in metabolic activity on vancomycin-containing films. These findings support the potential of chitosan–vancomycin coatings as localized antimicrobial strategies for implant applications, warranting further in vivo and mechanical evaluations.

Background/Objectives: Stability, retention, and support are removable partial denture (RPD) biomechanical principles. The literature shows contradictory opinions on indirect retention in RPDs, but no solid scientific evidence exists. This in vitro research aims to analyze indirect retainers’ (IRs) influence on forces transmitted to abutment teeth of a Kennedy Class I mandibular RPD. Methods: Bilateral distal-extension mandibular RPDs—differing only in the presence or absence of an IR on tooth 44 (IR model vs. nonIR model, respectively)—were installed on an acrylic master model. Tensile forces were applied perpendicularly to the occlusal plane on the longest free-end saddle’s distal aspect. Electronic speckle pattern interferometry (ESPI) measurements were obtained with and without an IR. The three-dimensional out-of-plane displacements of both models were acquired. Results: Abutment teeth 46 and 47 contralateral to the longest distal extension suffered more deformation under displacement forces when an IR was used. In turn, the IR’s influence on the deformation values of the abutment tooth 34 adjacent to the larger edentulous area depended on the intensity of the tensile force exerted: low-intensity forces resulted in reduced deformation, while higher-intensity forces resulted in higher deformation. Conclusions: This study’s findings indicate that indirect retention promotes better tensile force distribution in the existent teeth. However, they also question the IR’s role in protecting abutment teeth against excessive torque forces. This study’s preliminary results highlight the need for research on indirect retention principles using new methodologies, namely, in silico and ex vivo studies, and their experimental and clinical validation.

This in vitro study aims to compare the trueness of digital impressions obtained using two intraoral scanners (IOS) and one photogrammetry device for full-arch implant-supported rehabilitations. According to the Caramês Classification I, three models were produced with Straumann implants arranged in different spatial distributions: Option A with six implants and Options B and C with four implants each. The three models were scanned using a 12-megapixel scanner to create digital master casts. For each reference model, 30 digital impressions were acquired: 10 with the 3Shape Trios 3 intraoral scanner, 10 with the Medit i500 intraoral scanner, and 10 with the PIC Dental photogrammetry device. Trueness was assessed through best-fit superimpositions between the digital master casts and the corresponding virtual models. The Shapiro–Wilk test was applied to assess the normality of the data distribution, and Levene’s test was used to evaluate the homogeneity of variances. The non-parametric Kruskal–Wallis test was employed to compare group differences, with post hoc adjustments made using the Bonferroni correction. A significance threshold of p = 0.05 was adopted for all statistical tests. Statistically significant differences were observed in the root mean square values among the three devices. The Medit i500 demonstrated the highest trueness, with a median (interquartile range) deviation of 24.45 (18.18) µm, whereas the PIC Dental exhibited the lowest trueness, with a median deviation of 49.45 (9.17) µm. Among the implant distribution, the Option C showed the best trueness, with a median deviation of 19.00 (27.83). Considering the results of this in vitro study, intraoral scanners demonstrated comparable trueness, whereas the photogrammetry-based system exhibited lower trueness values. Additionally, a smaller number of implants and reduced inter-implant distances were associated with improved trueness in digital impressions for full-arch implant rehabilitation.

The objective of this in vitro study is to evaluate and compare the precision of digital impressions obtained using intraoral scanners and photogrammetry devices for full-arch implant-supported oral rehabilitation. Three reference models were created with various spatial distributions of Straumann implants, according to the Caramês I Classification: (i) option A with six implants; (ii) option B with four implants; and (iii) option C with four implants. Thirty digital impressions were taken for each of the reference models: ten with the Intraoral 3Shape Trios 3 scanner, ten with the Medit i500 intraoral scanner, and ten with the PIC Dental photogrammetry device. Intra-group best-fit overlaps were performed between the virtual models obtained, and accuracy was evaluated using root mean square (RMS) values. A significance level of p = 0.05 was defined. Mean values were statistically analyzed using the Kruskal–Wallis test. All scanners studied showed high precision, with RMS values similar for each implant distribution. The PIC Dental photogrammetry device demonstrated the best results for the CCI A and B distributions, with mean values of 11.28 µm and 14.44 µm, respectively. For the CCI C distribution, the 3Shape Trios 3 scanner achieved the best result, with a mean value of 5.96 µm. Among all devices, the implant distribution showing the highest RMS values was the CCI B, with mean values between 14.44 µm and 16.96 µm. The PIC Dental device was the only method that did not exhibit statistically significant differences in RMS values across the different distributions studied, indicating that its performance is unaffected by distribution variations. No statistically significant differences (p < 0.05) were observed in the RMS values among the three types of scanners. Overall, a smaller number of implants and closer distribution between them resulted in improved precision for digital impressions in full-arch implant rehabilitation.

Background/Objectives: This study aimed to compare the cost and time implications for implant-supported prosthesis comparing three digital impression techniques: digitization with an intraoral scanner, digitization of the conventional impression (without dental casts) and digitization of the stone models. Methods: To assess the time and cost of digital impression techniques on implants, time records on intraoral scans were consulted and three models were created with one, two and six implants to assess extraoral procedures time. Costs were evaluated based on material consumption, time expenditure and operator-related expenses. Time was recorded in three stages: (1) impression-taking, (2) model fabrication and (3) overall workflow completion. Statistical analysis was performed using ANOVA to compare cost and time differences across workflows. Results: Intraoral scanning presented a reduction in chair-side time between 4 and 20% when compared to extraoral techniques. For the three clinical situations evaluated, the intraoral scanning always presented the lowest cost. The extraoral digitization of impressions showed a reduction between 51.9% and 53.6% in laboratory time and between 3.5% and 7.6% in total cost compared to stone models digitization. Conclusions: The findings of this study indicate that intraoral scanning is a more cost-effective and time-efficient alternative to traditional impression methods, providing advantages in terms of reduced material use and shorter procedural durations.

Direct scanning of silicone impressions is a valid technique. However, studies in implant-supported rehabilitations are lacking. This in vitro study aims to compare the trueness of impressions obtained with two types of silicone and their corresponding stone casts, using two laboratory scanners in a full-arch implant rehabilitation. A master cast with six dental implants was scanned with a 12-megapixel scanner to obtain a digital master cast. Ten implant impressions were made using two silicones (Zhermack and Coltene) with the open-tray technique. The impressions and stone casts were scanned by two extraoral scanners (Identica T500, Medit; and S600 ARTI, Zirkonzhan). Trueness was assessed by comparing linear and angular distances in digital casts with the master cast. A p < 0.05 significance level was considered. The results showed that for the linear measurements, 72% were higher than the master cast measurements, and no consistent pattern was observed in the angular measurements. The greatest deviations were detected between the most posterior implants, with mean values ranging between 173 and 314 µm. No significant differences were found between scanners. However, differences were observed in the distances between silicones (46.7%) and between impressions and stone casts (73.3%). This work demonstrates that the direct scanning of silicone impressions yields results comparable to those obtained from scanning gypsum casts in full-arch implant-supported rehabilitation.

This pilot study aimed to compare the fit accuracy of cobalt–chromium (Co-Cr) and polyether ether ketone (PEEK) removable partial denture frameworks, produced by digital technologies. Two study models of previously prepared Kennedy’s Class I and Class III mandibular dental arches were scanned. For each model, two frameworks were digitally designed and manufactured using a Co-Cr alloy via the selective laser melting (SLM) technique, and using PEEK via the milling technique. A qualitative assessment of the framework’s fit accuracy to the corresponding study models was carried out using calibrated endodontic instruments and image amplification. Best-fit superimpositions between the reference design and the scanned frameworks were performed using the Geomagic Control X version 2018, 3D Systems software, allowing the expression of trueness by calculating the root mean square (RMS) value. Higher fit accuracy was observed for the milled frameworks, with the Class I PEEK framework showing the best fit accuracy to the corresponding model. RMS values were Class I—148.3 μm for Co-Cr and 69.2 μm for PEEK; Class III—107.2 μm for Co-Cr and 59.7 μm for PEEK. In the experimental conditions used, the milled PEEK frameworks showed better fit accuracy and higher trueness than the SLM-printed Co-Cr ones in both Kennedy classes.