Removable Partial Dentures with Polyetheretherketone Framework: The Influence on Residual Ridge Stability.

PURPOSE: To provide, in a clinical case-control study, 1-year data on edentulous residual ridge dimensional changes for patients wearing removable partial dentures (RPD) with Polyetheretherketone (PEEK) framework, fabricated with a digital workflow, and a control group of untreated patients. MATERIALS AND METHODS: Ten patients were treated with PEEK RPD, and six controls were studied. Intraoral scans at baseline (T0) and after a median period of 1 year (T1) were superimposed, trimmed, and reoriented (T0r and T1r), moved to a metrology software, and realigned. A curve (C0) was then traced on T0r, along the residual ridge crest; its projection (C1) on T1r was obtained. The mean distance C0-C1 was the dependent variable of interest and represented the 1-year changes in the height of the edentulous ridge. In addition, mean 3D distance between T0 and T1 at each edentulous area was measured. Differences in these outcomes measured between RPD treated and control groups were statistically assessed. RESULTS: Twenty-six and 14 edentulous areas were investigated in the RPD treated and control groups, respectively. No significant differences were observed for potentially confounding variables, such as median follow-up time (12.5 vs. 13 months, respectively), the alignment accuracy between T0r and T1r (0.01 mm vs. 0 mm, respectively), the median number of remaining teeth (6 vs. 8.5, respectively), and the median length of edentulous areas (25.5 mm vs. 22.8 mm, respectively). For the outcomes of interest, no statistically significant difference was seen in the mean distance between C0 and C1 (i.e., changes in residual ridge height: -0.39 ± 0.52 mm vs. -0.52 ± 0.54 mm, respectively) or in the mean 3D distance at corresponding points of the denture bearing areas (-0.3 ± 0.46 mm vs. -0.4 ± 0.35, respectively). CONCLUSIONS: Although 1 year is a relatively short observation period, this clinical study shows that there are no short-term differences in edentulous residual ridge height and overall dimensions between patients wearing PEEK RPD, fabricated with a digital workflow, and controls without an RPD.

A single procedure for the registration of maxillo-mandibular relationships and alignment of intraoral scans of edentulous maxillary and mandibular arches.

PURPOSE: The presented technique describes the intraoral scanning workflow to capture scans of edentulous arches and occlusion rims, align them as per maxillo-mandibular relationships registered in the occlusion rims, and incorporate data for tooth arrangement. METHODS: On preliminary intraoral scans of the edentulous arches, design the baseplates for the occlusion rims, make a 3D print of them and finalize by adding wax. Use occlusion rims to make jaw relation record and definitive intraoral scans. Use the "Pre-preparation scan" function to link scans of occlusion rims to scans of edentulous arches and align each other. CONCLUSIONS: Making and aligning, in a single procedure, intraoral scans of the edentulous arches and occlusion rims incorporating maxillo-mandibular relationships and information for tooth arrangement, allow to proceed directly with the denture design, thus, being sensible from the treatment time efficiency point of view. The technique is applicable to both partial and complete edentulous maxillary and mandibular arches. Nonetheless, care should be taken in stabilizing occlusion rims, whose shape is characterized by a reduction in size of the baseplates. In addition, its accuracy in comparison with the current clinical best practice based on conventional procedure requires to be addressed by further research.

Three-dimensional differences between intraoral scans and conventional impressions of edentulous jaws: A clinical study.

STATEMENT OF PROBLEM: Using intraoral scans for removable dentures has been questioned because of a suggested lack of accuracy. However, data regarding the accuracy of digital intraoral complete-arch scans are sparse, present some methodological issues, and mostly come from in vitro studies on dentate casts, which are very different from edentulous arches. PURPOSE: The purpose of this clinical study was to evaluate 3D differences between intraoral scans (IOS) and conventional impressions of edentulous arches by means of digital analysis. MATERIAL AND METHODS: Ten maxillary and 10 mandibular edentulous arches were investigated. For each of them, IOS was performed, and a custom tray was digitally designed based on these scans. Trays were built by using a 3D printer and used to make a conventional impression with a polysulfide impression material. The conventional impression was scanned immediately by using the same intraoral scanner and by the same dentist. Standard tessellation language (STL) files of IOS and the scans of the corresponding conventional impressions (CIS) were superimposed with a 2-phase best-fit alignment in a reverse engineering software program. The corresponding full-scan, 3D mean distance was measured. This procedure was repeated after trimming the IOS and CIS to eliminate peripheral areas not present in both files, as well as nonmatching areas caused by practical aspects related to obtaining the IOS (mobile tissue stretching) and the conventional impressions (mobile tissue compression and folding at the margin of impression), which could have impaired alignment and, consequently, measurement accuracy. The mean distance between the full and trimmed IOS and CIS was statistically investigated, and subgroup analysis was performed for the maxillary and mandibular arches. The statistical significance of the differences between the 2 impression methods was also investigated. RESULTS: The full-scan mean distance between the IOS and CIS (-0.19 ±0.18 mm) was significantly different from that of the trimmed scan mean distance (-0.02 ±0.05 mm), with no significant differences for maxillary and mandibular arches. The differences between the IOS and CIS were statistically significant for full scans; they were not significant for trimmed scans, except for the maxillary subgroup. CONCLUSIONS: The mean distance between the IOS and CIS may be significantly different if they are not properly superimposed. The mean distance (-0.02 ±0.05 mm) between the IOS and CIS falls within the range of mucosa resilience. Thus, 3D differences between the IOS and CIS can be attributed to the different physics behind the 2 impression methods and not to defects in accuracy of one method compared with the other. The size of the measured difference between the 2 impression methods was not statistically significant and was not clinically significant for removable denture fabrication.

Intraoral scans of edentulous arches for denture design in a single procedure.

Digital denture design requires anatomic information, an accurate maxillomandibular relationship, and parameters to guide tooth arrangement. Capturing all these data by intraoral scanning makes their immediate digitization, integration, and transfer to the computer-aided design workflow possible, which can be started without an additional procedure. The presented technique describes the digital workflow to automatically align intraoral scans of completely or partially edentulous maxillary and mandibular arches according to the maxillomandibular relationships registered in digitally designed occlusion rims adapted on the patient.

Digital versus conventional workflow for the fabrication of multiunit fixed prostheses: A systematic review and meta-analysis of vertical marginal fit in controlled in vitro studies.

STATEMENT OF PROBLEM: Limited evidence is available for the marginal fit of multiunit fixed dental prostheses (MFDPs) fabricated with digital technologies compared with those fabricated with conventional techniques. PURPOSE: The purpose of this systematic review and meta-analysis was to answer the following question: Does digital workflow for the fabrication of tooth-supported or implant-supported MFDPs provide better marginal fit than the conventional workflow? MATERIAL AND METHODS: PubMed, SCOPUS, EBSCO, and Web of Science databases were searched for controlled in vitro studies addressing direct comparison of the fit of MFDPs produced with digital or conventional workflows and excluding studies addressing interim restorations, MFDPs on mixed abutments (teeth and implants), or studies in which reproduction of the basic master cast was performed in 1 group. Vertical and horizontal marginal fit were the primary outcomes; meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, with subgroup analysis for tooth- or implant-supported MFDPs. RESULTS: Four studies published between 2011 and 2015 met the inclusion criteria and were included in the review. They investigated 3-unit partial fixed dental prostheses, exhibited a high degree of heterogeneity, and reported data only regarding vertical marginal fit. MFDPs fabricated with digital techniques presented a nominally higher vertical marginal discrepancy than those fabricated with the conventional technique, but the mean difference (MD) (19.8 µm, 95% confidence interval [CI]: -12.1; 51.7) has no statistical significance. The same is also applicable to subgroup analysis for a tooth-supported (MD=45.8 µm, 95% CI: -45.4; 137.0) or implant-supported (MD=14.7 µm, 95% CI: -38.6; 68.1) MFDP. CONCLUSIONS: Digital technologies offer a reliable alternative to conventional techniques for the fabrication of tooth- or implant-supported 3-unit fixed partial dentures; additional studies with up-to-date technologies and for prostheses with more than 3 units are recommended to provide stronger evidence.