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PURPOSE: The purpose of this diagnostic study was to assess the accuracy and time efficiency of a digital method to draw the denture foundation extension outline on preliminary casts compared with the conventional technique. MATERIALS AND METHODS: A total of 28 preliminary edentulous casts with no anatomical landmarks were digitized using a laboratory scanner. The outlining of the entire basal seat of the denture was performed on preliminary casts and digitized. Casts with no extension outline were digitized and outlines were drawn using software (DWOS, Straumann). The accuracy of the extension outlined between both techniques was evaluated in the software (GOM Inspect; GOM GmbH) by file superimposition. Specificity and sensitivity tests were applied to measure accuracy. The paired t-test (95% CI) was used to compare the mean total area and the working time. RESULTS: The accuracy ranged from 0.57 to 0.92. The buccal and labial frenulum showed a lower value in the maxilla (0.57); while the area between the retromolar pad and buccal frenulum (0.64) showed a lower score in the mandible. The maxillary denture foundation and the working time for both arches were significantly longer for the digital method (P < .001). CONCLUSION: The denture foundation extension outline exhibited a sufficiently excellent accuracy for the digital method, except for the maxillary anterior region. However, the digital method required a longer working time.

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OBJECTIVE: To evaluate the thermocycling effect of 3D-printed resins on flexural strength, surface roughness, microbiological adhesion, and porosity. MATERIALS AND METHODS: 150 bars (8 × 2 × 2 mm) and 100 blocks (8 × 8 × 2 mm) were made and divided into 5 groups, according to two factors: "material" (AR: acrylic resin, CR: composite resin, BIS: bis-acryl resin, CAD: CAD/CAM resin, and PRINT: 3D-printed resin) and "aging" (non-aged and aged - TC). Half of them were subjected to thermocycling (10,000 cycles). The bars were subjected to mini-flexural strength (σ) test (1 mm/min). All the blocks were subjected to roughness analysis (Ra/Rq/Rz). The non-aged blocks were subjected to porosity analysis (micro-CT; n = 5) and fungal adherence (n = 10). Data were statistically analyzed (one-way ANOVA, two-way ANOVA; Tukey's test, α = 0.05). RESULTS: For σ, "material" and "aging" factors were statistically significant (p < 0.0001). The BIS (118.23 ± 16.26A) presented a higher σ and the PRINT group (49.87 ± 7.55E) had the lowest mean σ. All groups showed a decrease in σ after TC, except for PRINT. The CRTC showed the lowest Weibull modulus. The AR showed higher roughness than BIS. Porosity revealed that the AR (1.369%) and BIS (6.339%) presented the highest porosity, and the CAD (0.002%) had the lowest porosity. Cell adhesion was significantly different between the CR (6.81) and CAD (6.37). CONCLUSION: Thermocycling reduced the flexural strength of most provisional materials, except for 3D-printed resin. However, it did not influence the surface roughness. The CR showed higher microbiological adherence than CAD group. The BIS group reached the highest porosity while the CAD group had the lowest values. CLINICAL RELEVANCE: 3D-printed resins are promising materials for clinical applications because they have good mechanical properties and low fungal adhesion.

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STATEMENT OF PROBLEM: Providing a removable partial denture (RPD) can be a complex, time-consuming, and error-prone procedure. Computer-aided design and computer-aided manufacturing (CAD-CAM) techniques have shown promising clinical outcomes; however, the influence of manufacturing techniques on the properties of RPD components is unclear. PURPOSE: The purpose of this systematic review was to determine the accuracy and mechanical properties of RPD components fabricated with conventional and digital methods. MATERIAL AND METHODS: This study followed the guidelines of the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) and was registered on the international prospective register of systematic reviews (PROSPERO) database (CRD42022353993). An electronic search was conducted on PubMed/MEDLINE, Scopus, Web of Science, and the Cochrane Library in August 2022. Only in vitro studies comparing the digital with the lost-wax casting technique were included. The quality of the studies was assessed by using the methodological index for nonrandomized studies (MINORS) scale. RESULTS: Of the 17 selected studies, 5 evaluated the accuracy of RPD components as well as the mechanical properties, 5 studies evaluated only the component accuracy, and another 7 evaluated only the mechanical properties. The accuracy was similar regardless of the technique, with discrepancies within clinically acceptable values (50 to 426.3 µm). The surface roughness was higher for 3D-printed clasps and lower for milled clasps (P<.05). The metal alloy significantly influenced the porosity, with the highest number of pores obtained by casting for Ti clasps and by rapid prototyping for Co-Cr clasps. CONCLUSIONS: In vitro studies showed that the digital technique provided similar accuracy to that of the conventional technique within a clinically acceptable range. The manufacturing technique influenced the mechanical properties of RPD components.

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This technical report describes a novel workflow for complete denture fabrication designed to abbreviate the necessary steps for dental prostheses delivery by using a 3-appointment protocol in which preliminary impressions are made in the first session together with the registration of maxillary lip support, occlusal plane, and reference lines for tooth arrangement. A trial denture is fabricated with conventional or computer-aided design and computer-aided manufacturing procedures and is evaluated in the second appointment for esthetics, the definitive impression, and the maxillomandibular relationship record to provide precise references for definitive denture fabrication.

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STATEMENT OF PROBLEM: The direct digitalization of completely edentulous arches rehabilitated with multiple implants still represents a limitation regarding obtaining accurate images for prosthetic purposes. PURPOSE: The purpose of this systematic review was to present the factors that may influence the accuracy of intraoral scanning of completely edentulous arches. MATERIAL AND METHODS: This review was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria and registered with International Prospective Register of Systematic Reviews (PROSPERO) (CRD42020171021). Three examiners performed an electronic search in the Medline/PubMed, Cochrane Library, Scopus, and Web of Science databases for articles published up to January 2021. RESULTS: The electronic search resulted in 11 498 studies. After removing duplicates, 11 347 studies remained. Twelve studies were selected (10 in vitro and 2 in vivo) according to the eligibility criteria. Several factors were found to influence the performance of intraoral scanners (Carestream Dental and TRIOS, 3Shape presented the best results), the intraoral scanning technique (Promoting physical paths that join the digitization bodies can increase the accuracy of transferring the position of the implants), environmental conditions (temperature: 20 °C to 21 °C, air pressure: 750 to 760 ±5 mmHg, air humidity: 45%, angle and distance between the implants: up to 15 degrees and 16 to 22 mm, and the material of the scan body: PEEK more accurate). CONCLUSIONS: The accuracy of the intraoral scanning of completely edentulous arches is affected by factors such as the type of intraoral scanner, scanning technique, environmental conditions, angle and distance between implants, and material of the scan bodies.

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INTRODUCTION: The preparation of parallel axial wall guide planes in abutment teeth is essential for providing a correct path of insertion and removal axis for removable partial dentures (RPDs). With the introduction of digital resources, new alternatives to the conventional method can be used to manufacture guide preparation for guide planes. AIMS: To describe the use of computer-aided design/computer-aided manufacturing (CAD/CAM) technology for the manufacture of guide planes to guide the reduction of the axial walls of abutment teeth according to the insertion and removal axis of the RPD. METHODS: This technique used the "bite splint" module of the Dental Wings software for the virtual planning of guide planes, to promote the construction of axial walls parallel to the abutment teeth. This was performed from the virtual design on a standard tessellation language (STL) file obtained by intraoral scanning, which determined the best trajectory for insertion and removal of the metallic structure. CONCLUSION: Digital technology allows the design and production of guide planes for the preparation of abutment teeth, simplifying the conventionally used technique, with precision and speed.

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OBJECTIVE: To investigate the incidence and risk factors for non-adaptation of the conventional mandibular complete denture (CMCD). MATERIALS AND METHODS: A total of 108 edentulous patients were rehabilitated with complete dentures (CDs) and followed up at 3- and 6-month intervals. Adaptation was confirmed based on chewing, phonetics, and comfortable swallowing with the CDs. The risk factors among sociodemographic and patient-centered factors were analyzed. Statistical analyses included the chi-square test and then a multivariate analysis. RESULTS: After 3 months, 38.0% of patients showed non-adaptation to CMCDs. Non-adaptation was significantly associated with the absence of previous mandibular denture experience (p = 0.042), ulcerations after 15 days of rehabilitation (p < 0.001), and a reduced posterior mandibular ridge (p = 0.035). After 6 months, this incidence decreased to 14.1%. The factors associated with non-adaptation were ulcerative lesions after 15 (p < 0.001) and 30 (p < 0.001) days of the delivery of CDs and the non-regular use of mandibular CDs (p < 0.001). CONCLUSION: The incidence of non-adaptation was higher after 3 months, with reduction after 6 months. Sociodemographic variables did not influence the adaptation. After 3 months, the absence of previous experience, traumatic ulcers, and reduced mandibular ridges hindered the adaptation of patients to mandibular CDs. After 6 months, only the occurrence of ulcerative lesions and non-regular wear of dentures were risk factors for non-adaptation. CLINICAL RELEVANCE: A considerable number of patients have difficulties in adapting to the mandibular dentures. Identifying the factors of non-adaptation of the dentures will contribute to increasing the predictability of this critical adaptation period.

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STATEMENT OF PROBLEM: The digitalization of completely edentulous arches presents limitations because of the lack of anatomic structures for best-fit alignment during the image generation process of the scanner's software program. PURPOSE: The purpose of this clinical study was to evaluate a new device for intraoral scanning and to analyze its usefulness in capturing the 3-dimensional (3D) position of implants in edentulous mandibular arches. MATERIAL AND METHODS: The 3D positions of 40 implants in 10 participants with fixed interim mandibular prostheses were evaluated by comparing 3 scanning techniques. Images were generated in 2 experimental groups, with digital scan bodies (group SC) and with the scanning device (group SD) and in a control group (group CT) in which images were obtained by laboratory scanning of casts produced from splinted impression copings. The standard tessellation language (STL) files were superimposed by using a reverse engineering software program to measure the 3D coordinate system. Variations in implant linear displacements (Δx, Δy, and Δz), total 3D displacement (Δx2+Δy2+Δz2), and angle projections (ΔθXY, ΔθXZ, and ΔθYZ) were statistically analyzed (α=.05). The distances between the implants were also measured. The Spearman correlation coefficient (α=.05) was used to find the correlation between the 3D coordinates and the distances between the implants. RESULTS: Group SD had lower values for linear displacement than group SC; however, this difference was not statistically significant except for implant #2. The overall evaluation showed a significant difference with better accuracy for group SD. Concerning angular displacements, group SD showed lesser angular variation for the 3 projection planes. For the distances between the implants, significant differences were only observed for the "all" assessment in which group SD behaved similarly to group CT, while group SC showed the highest values (P<.05). No correlation was detected between the axes (x, y, and z) and the distances between the implants. CONCLUSIONS: The evaluated scanning device led to improved trueness for linear, angular displacements, and distances between implants in mandibular edentulous arches.

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OBJECTIVE: The aim of this study was to evaluate the factors influencing edentulous patients' willingness about mandibular implant-supported complete denture. MATERIALS AND METHODS: A cross-sectional study was carried out with 117 bimaxillary edentulous patients wearing removable complete dentures (CDs). Patients were assessed concerning denture-related items (number of previous mandibular CDs, previous denture wearing period, dentures maker professional, and regular wearing of previous mandibular dentures) and individual-related aspects, such as mandibular edentulousness period, mandibular bone height, and willingness to the use of mandibular implant-supported complete denture. Masticatory performance was evaluated by the median particle diameter. Mandibular bone height and satisfaction were assessed using a validated method. The Chi-square test was used for data analysis and prevalence ratios were adjusted by using multivariate Poisson regression, both with 95% confidence interval. RESULTS: A total of 78 participants (66.7%) were interested in mandibular implant-supported overdenture (mean age 65.33 ± 9.49). Masticatory performance was not influenced by choosing mandibular implant-supported complete denture. The preference about mandibular implant-supported complete denture was correlated with longer mandibular complete denture experience (p = 0.021) and it was significantly associated with dissatisfaction about retention (p = 0.005). CONCLUSION: Previous experience with mandibular complete dentures and dissatisfaction about retention influence the willingness about mandibular implant-supported overdenture. CLINICAL RELEVANCE: Many factors are associated with rehabilitation preferences for edentulous patients and mandibular implant-supported complete denture is one of the available alternatives. Therefore, this study has demonstrated the factors influencing the decision to replace a mandibular conventional complete denture by dental implant treatment based on patient's outcomes. Such finding may be considered as a relevant aspect towards shared decision-making for prosthodontic rehabilitation of edentulous patients.

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STATEMENT OF PROBLEM: Removable partial dentures (RPDs) are traditionally made by casting, a complex, error-prone, and time-consuming process. Computer-aided design and computer-aided manufacturing (CAD-CAM) RPD systems may simplify the clinical steps and minimize errors; however, the accuracy of CAD-CAM RPD systems is unclear. PURPOSE: The purpose of this systematic review was to determine whether CAD-CAM systems are accurate for the manufacturing of RPD frameworks. MATERIAL AND METHODS: A literature search was conducted through Medline-PubMed, Scopus, Lilacs, Web of Science, and Cochrane Library databases using specific keywords for articles published up to November 2019. Three reviewers obtained data and compared the results. All studies evaluated the framework accuracy or fit of prostheses fabricated with conventional and digital techniques. RESULTS: A total of 7 articles, 2 clinical studies, and 5 in vitro studies that complied with the inclusion criteria were evaluated. One in vitro study compared indirect (extraoral) and direct (intraoral) scanning for partially edentulous ridges and shows that digital scans were better than conventional impressions in terms of trueness. In the other studies included, although the frameworks analyzed had clinically acceptable discrepancies (<311 µm), the material influenced the fit. Polyetheretherketone (PEEK) showed better fit than traditional metal cast RPDs. Co-Cr alloy RPDs produced by rapid prototyping exhibited the highest discrepancies when produced by sintering laser melting. CONCLUSIONS: The results show that the digital technique for RPD frameworks is accurate. In the studies included, the analyzed frameworks had clinically acceptable gaps, but the results were heterogeneous among studies because the articles used different measurement methods with small sample sizes. Few studies discussed the long-term clinical performance. The digital technique for RPD frameworks was accurate because the misfits and mismatches found in in vitro and clinical studies were within the acceptable clinical limit for RPDs.

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STATEMENT OF PROBLEM: Parallel dental implants improve prosthesis longevity and facilitate the impression making steps when compared with angled implants. The effect of implant angulation on the accuracy of casts generated by using intraoral scanners has not been fully investigated. PURPOSE: The present systematic review addressed following the patient, intervention, control, and outcome (PICO) question: Does implant position affect the intraoral scanning accuracy of arches that will receive complete-arch implant-supported fixed dental prostheses? MATERIAL AND METHODS: A bibliographic search was performed in the Medline-PubMed, Scopus, Web of Science, and Cochrane Library databases by using specific descriptors for studies published until July 2020. All studies evaluated the intraoral scanning accuracy of arches rehabilitated with multiple implants through implant linear and/or angular deviation. RESULTS: Eight in vitro studies that met the eligibility criteria were evaluated. Five publications showed lower linear and angular displacements for the digital scans compared with the conventional technique. Two studies showed that the digital scan presented higher angular and linear distortions than the conventional technique. Only 1 study did not find differences between the 2 recording methods. CONCLUSIONS: Digital scanning is reliable. However, caution is needed concerning its indication, especially in patients where the angles between implants are greater than 15 degrees. The association of the implant angulation with the clinical factors needs to be further investigated. The absence of clinical evidence and methodological heterogeneity limited the results of this study.

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PURPOSE: To evaluate the periodontal conditions and integrity of abutment and non-abutment teeth of patients evaluated 7 years after insertion of the removable partial denture (RPD). MATERIALS AND METHODS: Twenty-two patients (17 women, 5 men) were assessed at the moment of denture insertion and 7 years later. The following items were verified in each assessment: bleeding on probing (BP), probing depth (PD), gingival recession (GR), and mobility (M), comparing direct and indirect abutment teeth, and the teeth not involved in the denture design. Tooth integrity was also evaluated and classified as intact when no caries or fractures were observed. The Kruskal-Wallis test was used to reveal statistical significance between the groups (p = 0.05) as well as the Bonferrroni-corrected Mann-Whitney test for post hoc comparison. The Wilcoxon test was used for evaluation within the group over time. Fisher's exact test was applied to cross data about abutment integrity. RESULTS: Statistically significant differences were found for GR (baseline, p < 0.001; 7 years, p < 0.001) and PD (baseline, p = 0.001; 7 years = 0.004) between the three groups at baseline and after 7 years of follow-up. Mean BP and M values increased from initial assessment to after 7 years of RPD use in every group, but no statistically significant difference was found between the groups. For abutment integrity, a statistically significant difference (p = 0.028) was observed, and the direct abutment exhibited more (33.3%) caries and fractures. CONCLUSION: RPDs generated more periodontal damage to direct abutments, since higher gingival recession probing depth indexes, and presence of caries and fractures were observed in comparison to indirect abutments and non-abutments.

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OBJECTIVES: To evaluate the change in masticatory efficiency and quality of life of patients treated with mandibular Kennedy class I removable partial dentures (RPDs) and maxillary complete dentures at the Department of Dentistry of the Federal University of Rio Grande do Norte. MATERIALS AND METHODS: A total of 33 Kennedy class I patients were rehabilitated with maxillary complete dentures, and mandibular RPDs were selected for this non-randomized prospective intervention study. The patients had a mean age of 59.1 years. Masticatory efficiency was evaluated by colorimetric assay using fuchsin capsules. The measurements were conducted at baseline and 2 and 6 months after prosthesis insertion. Quality of life was evaluated using the Oral Health Impact Profile (OHIP-14) at baseline and 6 months after denture insertion. The Kolmogorov-Smirnov normality test was applied. Masticatory efficiency was evaluated by repeated measures ANOVA. Oral health-related quality of life was compared using the paired t test. RESULTS: There was no statistically significant difference in masticatory efficiency after denture insertion (p = 0.101). Significant differences were found (p = 0.010) for oral health-related quality of life. A significant improvement in psychological discomfort (p < 0.01) and psychological disability (p < 0.01) was observed. Mean difference value (95 % confidence interval) was 6.8 (3.8 to 9.7) points, reflecting a low impact of oral health on quality of life, considering the 0-56 range of variation of the OHIP-14 and a Cohen's d of 1.13. CONCLUSION: According to the results of the present study, rehabilitation with Kennedy class I RPDs and complete dentures did not influence masticatory efficiency but improved oral health-related quality of life. CLINICAL RELEVANCE: The association between the patient's quality of life and the masticatory efficiency is important for treatment predictability.

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