•Phase transformation of alumina-toughened zirconia (ATZ) does not affect fracture load of ATZ implants.•Carbon fiber-reinforced (CRF) screws represent a valid option for screw-retention of ...metal-free implants.•Loading had no influence on gap size of the IAC of zirconia implants assembled with a CRF screw.
To investigate the long-term stability of a metal-free zirconia two-piece implant assembled with a carbon fiber-reinforced (CRF) screw by means of transformation propagation, potential changes in surface roughness, the gap size of the implant-abutment connection, and fracture load values.
In a combined procedure, two-piece implants made from alumina-toughened zirconia were dynamically loaded (107 cycles) and hydrothermally aged (85°, 60days). Implants made from titanium (Ti) and a titanium–zirconium (TiZr) alloy with a titanium abutment screw served as control. Transformation propagation (ATZ) and gap size of the IAC were monitored at cross-sections by scanning electron microscopy (SEM). Furthermore, changes in surface roughness of ATZ implants were measured. Finally, implants were statically loaded to fracture. Linear regression models and pairwise comparisons were used for statistical analyses.
Independent of the implant bulk material, dynamic loading/hydrothermal aging did not decrease fracture resistance (p=0.704). All test and control implants fractured at mean loads >1100N. Gap size of the IAC remained stable (<5μm) or decreased. None of the CFR screws fractured during static or dynamic loading. Monoclinic layer thickness of ATZ implants increased by 2–3μm at surfaces exposed to water, including internal surfaces of the IAC. No changes in surface roughness were observed.
Combined hydrothermal aging and dynamic loading did not affect the above-mentioned parameters of the evaluated two-piece ATZ implant. Mean fracture loads >1100N suggest a reliable clinical application.
The aim of this study was the development of a novel in-vitro method to evaluate the intraoral release of wear particles with a diameter< 1 µm from dental restorative materials.
Test fixtures for a ...dual-axis chewing simulator (CS-4.8, SD Mechatronik, Feldkirchen-Westerham, Germany), consisting of three components to mount the specimens and a solvent (distilled water) as well as a zirconia antagonist to transfer the masticatory forces onto the specimen was developed. Ceram.x Spectra™ ST HV (CS) and Filtek™ Supreme XTE (FS) specimens (n = 3) were fixed into the mounts and immersed in 25 ml solvent. All specimens were subjected to 500.000 wear cycles with a load of 49 N. The particle size distribution of the suspensions were examined by dynamic light scattering (DLS). The collected particles were characterised by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). For wear quantification, the surfaces of the specimens were photo-optically scanned and the wear was measured. For the statistical analysis, one-way ANOVA and post-hoc Scheffé tests were applied.
DLS showed particle diameters< 1 µm (CS: 18.06 nm-1.64 µm, FS: 72.30 nm-2.31 µm). SEM/EDS indicated an association between the detected elements and the materials' composition. FS showed significantly higher volume loss (p = 0.007) and maximum depth of the wear profile (p = 0.005) than CS, but no significant differences in the surface loss (p = 0.668).
The novel method is able to detect material dependent particles to the size of nanoscale after in-vitro abrasion.
A polyolefin with certified biocompatibility according to USP class VI was used by our group as feedstock for filament-based 3D printing to meet the highest medical standards in order to print ...personal protective equipment for our university hospital during the ongoing pandemic. Besides the chemical resistance and durability, as well as the ability to withstand steam sterilization, this polypropylene (PP) copolymer is characterized by its high purity, as achieved by highly efficient and selective catalytic polymerization. As the PP copolymer is suited to be printed with all common printers in fused filament fabrication (FFF), it offers an eco-friendly cost-benefit ratio, even for large-scale production. In addition, a digital workflow was established focusing on common desktop FFF printers in the medical sector. It comprises the simulation-based optimization of personalized print objects, considering the inherent material properties such as warping tendency, through to validation of the process chain by 3D scanning, sterilization, and biocompatibility analysis of the printed part. This combination of digital data processing and 3D printing with a sustainable and medically certified material showed great promise in establishing decentralized additive manufacturing in everyday hospital life to meet peaks in demand, supply bottlenecks, and enhanced personalized patient treatment.
Aim
This 3‐year report of a prospective long‐term cohort investigation aimed to evaluate the clinical and radiographic outcomes of a one‐piece zirconia oral implant for single‐tooth replacement.
...Materials and Methods
Sixty‐five patients received a 1‐stage implant surgery with immediate temporization. Standardized radiographs were taken at implant insertion, after 1 year, and after 3 years to monitor peri‐implant bone levels. A univariate analysis of the association of different baseline parameters on marginal bone loss from implant insertion to 36 months was performed. Soft‐tissue parameters were evaluated at prosthesis insertion, after 6 months, after 1 year, and at the 3‐year follow‐up.
Results
After 3 years, six posterior site implants were lost, giving a cumulative survival rate of 90.8%. The mean marginal bone loss was 1.45 mm; 35% of the implants lost at least 2 mm bone, and 22% more than 3 mm. The univariate analysis did not identify any parameter associated with marginal bone loss. Probing depth, clinical attachment level, and bleeding index increased over 3 years, and plaque index decreased.
Conclusions
The low survival rate of the presented ceramic implant and especially the high frequency of advanced bone loss are noticeable but remain unexplained.
Objective
To evaluate the impact of reducing the radiographic field of view (FOV) on the trueness and precision of the alignment between cone beam computed tomography (CBCT) and intraoral scanning ...data for implant planning.
Materials and Methods
Fifteen participants presenting with one of three clinical scenarios: single tooth loss (ST, n = 5), multiple missing teeth (MT, n = 5) and presence of radiographic artifacts (AR, n = 5) were included. CBCT volumes covering the full arch (FA) were reduced to the quadrant (Q) or the adjacent tooth/teeth (A). Two operators, an expert (exp) in virtual implant planning and an inexperienced clinician, performed multiple superimpositions, with FA‐exp serving as a reference. The deviations were calculated at the implant apex and shoulder levels. Thereafter, linear mixed models were adapted to investigate the influence of FOV on discrepancies.
Results
Evaluation of trueness compared to FA‐exp resulted in the largest mean (AR‐A: 0.10 ± 0.33 mm) and single maximum discrepancy (AR‐Q: 1.44 mm) in the presence of artifacts. Furthermore, for the ST group, the largest mean error (−0.06 ± 0.2 mm, shoulder) was calculated with the FA‐FOV, while for MT, with the intermediate volume (−0.07 ± 0.24 mm, Q). In terms of precision, the mean SD intervals were ≤0.25 mm (A‐exp). Precision was influenced by FOV volume (FA < Q < A) but not by operator expertise.
Conclusions
For single posterior missing teeth, an extended FOV does not improve registration accuracy. However, in the presence of artifacts or multiple missing posterior teeth, caution is recommended when reducing FOV.
In most cases, prosthetic rehabilitation of patients suffering from microstomia is inconvenient for the patient and challenging for both the dentist and dental technician. In such cases, conventional ...impression-taking requires an individualized tray design and modified impression techniques, amplifying the risk for impression and cast deformation and thereby compromising the final outcome. An intraoral scanner (IOS) might overcome these limitations due to its reduced size compared to an impression tray. In the present case history report, a microstomia patient was successfully restored with a telescopic prosthesis by digitizing both retaining teeth and the palate with an IOS.
Long-term edentulism associated with vertical loss of alveolar bone might lead to increased suprastructure height. This study aimed to evaluate the effect of suprastructure height on the stability of ...the implant-abutment connection by investigating the stability of two different two-piece titanium implants with internal hexagonal or conical connections under simulated oral loading conditions.
A total of 48 specimens were used. The specimens were divided into 2 groups according to their implant-abutment connection (group H: internal hex connection, group C: conical connection). Each group was further divided into 3 groups according to the applied suprastructure height (H1; C1: 10 mm, H2; C2: 14 mm and H3; C3: 18 mm) (n = 8). All specimens were subjected to a cyclic loading force of 98 N for 5 million simulated chewing cycles. Then, all implants that survived the chewing simulation were quasi-statically loaded until failure. The monotonic-failure load and monotonic-bending moment at failure were evaluated.
After the dynamic chewing loading, the implants showed the following survival rates: group H: 95.8%; group C: 100%. The implant suprastructures revealed survival rates of 100% and 91.5% for groups H and C, respectively. After the artificial chewing simulation of 5 million cycles, some implants in the groups with higher crowns (14 mm and 18 mm) showed crack formation and plastic deformations under the light microscope. Regarding monotonic-failure load, implants with shorter suprastructures (10 mm) revealed higher resistance to failure (C1: 1496 and H1: 1201 N) than longer suprastructures (18 mm) (C3: 465 and H3: 585 N) which was expected. The mean monotonic-bending moment values at failure ranged from 400.7 Ncm to 673.3 Ncm.
Implant-supported restorations with increased crown height are considered stable for an extended time period (5 million cycles which equals approximately 20 years clinical service) and a reliable treatment option in case of increased inter-arch distance. There was no difference in stability of the two internal connections. Nevertheless, the integrity of implant components might be impaired when crowns with increased heights are applied.
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To determine the clinical and patient-reported outcomes of bi-layered, all-ceramic posterior single crowns (SCs) supported by zirconia implants in an uncontrolled, prospective, multicenter study.
In ...two centers, 60 patients received 71 one-piece zirconia oral implants to be restored with either SCs (n=49) or three-unit fixed dental prostheses (n=11). Of these patients, 45 implants were restored with all-ceramic, zirconia-based posterior SCs (one per patient). Survival rates of implants and reconstructions were assessed, and technical success was evaluated according to modified U.S. Public Health Service (USPHS) criteria. Furthermore, patient-reported outcome measures (PROMs) were assessed by applying visual analog scales (VAS). Kaplan-Meier (KM) plots and log-rank tests were used for success/survival analyses. The Wilcoxon matched-pairs signed-rank test was used to evaluate time effects on response variables (PROMs, USPHS criteria).
Forty patients with 40 SCs could be evaluated after 36.7±1.2months. No SC was replaced, resulting in 100% survival. The KM success estimate was 87.5% (two chippings, one restoration margin, and one contour were rated Charlie). In general, the incidence of chipping (p=.0005) and occlusal roughness (p=.0003) was frequent. Compared with the pre-treatment patient surveys (67–93%), all surveys at prosthetic delivery except for speech (p=.139) showed significantly improved VAS scores (81–94%; p<.0001). Thereafter, no decrease in satisfaction could be observed over time until the 3-year follow-up (86–93%; p≥.390).
Veneered, zirconia-based SCs supported by zirconia implants satisfied patients’ needs highly. However, significant incidence of chipping and roughness of the veneering ceramic may compromise the clinical long-term outcome for this indication.
Posterior, zirconia-based SCs supported by zirconia oral implants entirely survived the follow-up period of 3 years, but two major chippings, one a significant marginal opening and one pronounced over-contouring, resulted in a reduced KM success estimate of 87.5% after 36 months of observation.
Several attachment systems for implant-supported removable dental prostheses (ISRDPs) are currently available. The bar attachment option includes cast or milled alloyed male and female parts. ...Replaceable slide attachments made from elastic materials can be inserted into the female part of the bar to counter loss of friction that develops due to wear. Another approach involves milling the female part from organic thermoplastic polymers. In the present case history report, an edentulous maxilla was restored with a digitally fabricated ISRDP with the female part of the bar milled from polyether ether ketone (PEEK) polymerized into a zirconia framework.
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