EPA Consensus Project Paper: Accuracy of Photogrammetry Devices, Intraoral Scanners, and Conventional Techniques for the Full-Arch Implant Impressions: A Systematic Review.

PURPOSE: The objective of this systematic review was to evaluate and compare the accuracy of digital impression techniques and conventional methods for full-arch implant impressions. METHODS: An electronic literature search in the databases Medline (Pubmed), Web of Science, and Embase was performed to identify in vitro and in vivo publications (between 2016 and 2022) directly comparing digital and conventional abutment-level impression techniques. All selected articles passed through the data extraction procedure according to defined parameters in inclusion and exclusion criteria. Measurements on linear, angular and/or surface deviations were performed in all selected articles. RESULTS: Nine studies met the inclusion criteria and were selected for this systematic review. 3 articles were clinical studies and 6 studies were in vitro. Accuracy difference mean values of the trueness up to 162+/-77µm between digital and conventional techniques were reported in the clinical studies and up to 43µm in laboratory studies. Methodological heterogeneity was observed in both, in vivo and in vitro studies. CONCLUSIONS: Intraoral scanning and photogrammetric method showed comparable accuracy for registering implant positions in the full-arch edentulous cases. A tolerable implant prosthesis misfit threshold and objective misfit assessment criteria (for linear and angular deviations) should be verified in clinical studies.

EPA Consensus Project Paper: Accuracy of Conventional and Digital Workflows in Partially Edentulous Cases Restored with FPDs over Implants. A Systematic Review

PURPOSE: To compare conventional and digital workflows in terms of accuracy in partially edentulous cases restored with implant-supported restorations. METHODS: An electronic search in the databases PubMed, Scopus, Web Of Science, and CENTRAL was conducted to identify relevant publications, comparing digital and conventional workflows in partially edentulous cases restored with implant-supported prostheses. RESULTS: 18 articles were included in the systematic review. Ten of the studies were in-vitro, and eight were clinical. Sample sizes varied considerably from 20 to 100. In three studies, three implants were investigated, whereas, in all other instances, accuracy was evaluated on two implants. Substantial heterogeneity in the methodology of the selected studies is evident, which prevents summarising the accuracy outcomes. CONCLUSIONS: Digital impressions showed similar results in terms of accuracy compared to the conventional approach. There is a lack of uniform criteria for the tolerable misfit, which hampers the ability to transfer in-vitro results to clinical situations. A need for a standardised approach in the evaluation of impression and workflow accuracy is warranted to enable the systematisation and analysis of results from different studies.

The effect of different implant impression splinting techniques and time on the dimensional accuracy: An in vitro study.

BACKGROUND: Splinting of impression copings is generally recommended for complex implant-supported restorations. It can also be used in the digital workflow when a control model is needed to improve the fit of the prosthesis. However, there is a lack of knowledge on how dimensional accuracy is affected by different splinting techniques and time factors. OBJECTIVES: To evaluate the time factor on the dimensional stability of different implant impression splinting techniques used in the conventional and digital workflow. MATERIALS AND METHODS: Ten pairs of implant analogs were fixed to a stainless steel bar. Modified impression copings were connected to the analogs and eight splinting strategies evaluated (n=10): (1) type I impression plaster (PLA), (2) autopolymerizing acrylic resin, cut and rejoin technique (PTR), (3) light-cured acrylic resin, cut and rejoin technique (ILC), (4) light-cured acrylic resin, no cutting and rejoining (ILN), (5) VPS bite registration material (SBR), (6) bis-acryl bite registration material (LXB), (7) bis-acryl composite resin (PTP), (8) 3D printed splint (3DP). In each group, the position of modified impression copings was scanned with a laboratory scanner at different time points: (1) unsplinted impression copings (baseline), (2) 2 h after splinting, (3) 24 h after splinting. Modified impression coping design allowed using metrology software to measure and compare distance, vertical, angle and rotational deviations between impression copings. RESULTS: All types of splints showed dimensional deviations. After 2 h of splinting, the lowest distance deviation was recorded in PTR (15.4±6.15µm), vertical deviation - in ILC (19.2±27.37µm), angle deviation - in ILC (0.08±0.1°), rotation - in LXB (0.2±0.24°) groups. Comparing results 2 and 24 h after connection of impression copings, statistically significant deviations in the distance were recorded in groups PLA (-5.6±5.95 µm), PTR (5.5±7.01µm), ILN (19.2±14.26µm), PTP (23.8±12.55µm). CONCLUSIONS: The best dimensional accuracy was observed in the ILC group, followed by PTR and 3DP groups. CLINICAL SIGNIFICANCE: Proper selection of splinting technique and polymerization time can increase the accuracy of conventional or digital impressions. Splinting techniques with rigid materials, proper polymerization and compensating for material shrinkage seem to produce the best results.

Effect of extracellular matrix and dental pulp stem cells on bone regeneration with 3D printed PLA/HA composite scaffolds.

The demand for bone grafting procedures in various fields of medicine is increasing. Existing substitutes in clinical practice do not meet all the criteria required for an ideal bone scaffold, so new materials are being sought. This study evaluated bone regeneration using a critical-size Wistar rat's calvarial defect model. 12 male and 12 female rats were evenly divided into 3 groups: 1. Negative and positive (Geistlich Bio-Oss®) controls; 2. polylactic acid (PLA) and PLA/hydroxyapatite (HA); 3. PLA/HA cellularised with dental pulp stem cells (DPSC) and PLA/HA extracellular matrix (ECM) scaffolds. PLA/HA filament was created using hot-melt extrusion equipment. All scaffolds were fabricated using a 3D printer. DPSC were isolated from the incisors of adult Wistar rats. The defects were evaluated by micro-computed tomography (µCT) and histology, 8 weeks after surgery. µCT revealed that the Bio-Oss group generated 1.49 mm3 and PLA/HA ECM 1.495 mm3 more bone volume than the negative control. Histology showed a statistically significant difference between negative control and both (Bio-Oss and PLA/HA ECM) groups in rats of both genders. Moreover, histology showed gender-specific differences in all experimental groups and a statistically significant difference between cellularised PLA/HA and PLA/HA ECM groups in female rats. Qualitative histology showed the pronounced inflammation reaction during biodegradation in the PLA group. In conclusion, the bone-forming ability was comparable between the Bio-Oss and PLA/HA ECM scaffolds. Further research is needed to analyse the effects of ECM and PLA/HA ratio on osteoregeneration.

Comparison of the Clinical Accuracy of Digital and Conventional Dental Implant Impressions.

The aim of this study was to compare the clinical accuracy of digital and conventional dental implant impressions. Two types of implant impressions were made for each case, namely a conventional open-tray impression and a digital implant impression (DII) using a Trios IOS. Master casts were scanned using a D800 laboratory scanner and STL files were retrieved from conventional and digital workflows to be exported for comparison. The distance between center points, angulation, rotation, vertical shift, and surface mismatch of the scan bodies were evaluated and compared between conventional and digital impression techniques. Comparing digital and conventional impression techniques the following factors showed statistically significant differences: distance (73.7±75 µm), angulation (0.42±0.3°), and surface mismatch of scan bodies. The difference in conventional and digital impression techniques as regards to angulation and distance between the implants were associated with distance, angle, and vertical shift differences in scan. The mismatch of the scanned surface of scan bodies was twice higher for the intraoral scanner group. Clinicians should therefore control the implant suprastructures clinically and also using casts (e.g. printed casts) when a digital scan is planned.

The effect of laser-treated titanium surface on human gingival fibroblast behavior.

Surface modification, as a means of enhancing soft tissue integration in titanium would have significant advantages including less marginal bone resorption, predictable esthetic outcome, improved soft tissue stability, and seal against bacterial leakage. The aim of this study was to evaluate the effects of laser-roughened titanium surfaces on human gingival fibroblast (HGF) viability, proliferation, and adhesion. Titanium discs were ablated with impulse laser in four different patterns. Polished and sand-blasted titanium discs were used as control groups. Specimen surface properties were determined using optical profilometry and scanning electron microscopy. HGF behavior on modified surfaces was analyzed using cell adhesion, viability, proliferation, and ELISA assays. Results suggested that modified Ti surfaces did not affect the viability of HGFs and improved adhesion was measured in laser treatment groups after 24 h. However, proliferation study showed that the adsorbance of fibroblast cells after 72 h cultured on polished titanium was higher and comparable with that of control cells. As for focal adhesion kinase (FAK), cells grown on laser modified surfaces had higher expression of FAK as compared with polished titanium. In conclusion, tested laser-treated surfaces seem to favor HGF adhesion. There were no significant differences between different laser treatment groups.

Influence of attachment wear on retention of mandibular overdenture.

UNLABELLED: The aims of this study were: (i) to evaluate and compare retention of two-teeth (implant) supported mandibular overdenture with either stud or magnetic attachments during linear (axial) and rotational (paraxial) dislodgements; (ii) to compare retentive properties before and after wear simulation. The test group consisted of five magnetic and four stud overdenture attachments (n = 12 specimens for each attachment type). Retention in axial direction was evaluated on one-tooth (implant) model by measuring maximum retentive force (N) and range of retention (mm) during the linear dislodgement. Retention in the paraxial direction was evaluated on mandibular-overdenture model by measuring the maximum retentive force (N) during three types of rotational dislodgements - anterior, lateral and posterior. The minimum number of cycles required to simulate wear was determined by special wear test. Afterwards, the wear was simulated in the test group, and retention in axial and paraxial directions was measured again. STATISTICAL ANALYSIS: one-way anova, Scheffe post hoc and paired-samples t-tests (P < 0.05). Initially, studs had higher retention (4-11 N) than magnets (4.5-6 N) in axial direction. After the wear simulation, it had decreased from 76% to 48% for some of the studs and had become similar to the retention of magnetic attachments. Magnets had lower retention range (0.2-0.3 mm) than studs (0.5-1.1 mm). Studs provided similar or higher retention in paraxial directions than magnetic attachments both before and after wear simulation. Retentive properties of magnets decreased mostly with posterior rotational dislodgement. Retentive properties of stud overdenture attachments were less constant.