Objectives
To assess survival/success rates and patient‐reported outcome of zirconia‐based posterior single crowns (SCs) supported by zirconia implants in a prospective two‐center study after five ...years of observation.
Material and methods
Forty‐five patients were restored with 45 zirconia implant‐supported posterior SCs composed of zirconia frameworks hand‐layered with a leucite‐reinforced feldspathic ceramic. Survival rates of SCs were assessed and technical success was evaluated according to modified United States Public Health Care (USPHS) criteria. Furthermore, patient‐reported outcome measures (PROMs) were assessed by applying visual analog scales (VAS). Wilcoxon matched‐pairs signed‐rank test, mixed‐effects ordered logistic regression, and linear mixed models were used to evaluate time effects on response variables.
Results
Forty patients were available after a mean observation period of 61.0 ± 1.4 months. One SC had to be replaced, resulting in a Kaplan–Meier (KM) survival estimate for the SCs of 97.5 ± 2.47%. Since nine reconstructions showed at least in one category a major deviation from the ideal (five major chippings, four with increased occlusal roughness, one significant crevice, and one pronounced over‐contouring), the KM success estimate was 79.3 ± 5.8%. Incidence of chipping (n = 19) and occlusal roughness (n = 35) was frequent (p < 0.001). All PROMs at prosthetic delivery except for speech (p = 0.139) showed significantly improved VAS scores (81%–94%; p < 0.001) compared to pre‐treatment evaluations. Thereafter, no decrease in satisfaction could be observed until the 5‐year follow‐up (93%–97%).
Conclusion
Veneered zirconia‐based SCs supported by zirconia implants showed high survival rates and highly satisfied patients' needs. However, significant incidence of technical complications is compromising the clinical long‐term outcome for this indication.
To date, it is unknown whether 3D printed fixed oral implant‐supported prostheses can achieve comparable soft tissue integration (STI) to clinically established subtractively manufactured ...counterparts. STI is mediated among others by gingival fibroblasts (GFs) and is modulated by biomaterial surface characteristics. Therefore, the aim of the present work was to investigate the GF response of a 3D printed methacrylate photopolymer and a hybrid ceramic‐filled methacrylate photopolymer for fixed implant‐supported prostheses in the sense of supporting an STI. Subtractively manufactured samples made from methacrylate polymer and hybrid ceramic were evaluated for comparison and samples from yttria‐stabilized tetragonal zirconia polycrystal (3Y‐TZP), comprising well documented biocompatibility, served as control. Surface topography was analyzed by scanning electron microscopy and interferometry, elemental composition by energy‐dispersive x‐ray spectroscopy, and wettability by contact angle measurement. The response of GFs obtained from five donors was examined in terms of membrane integrity, adhesion, morphogenesis, metabolic activity, and proliferation behavior by a lactate‐dehydrogenase assay, fluorescent staining, a resazurin‐based assay, and DNA quantification. The results revealed all surfaces were smooth and hydrophilic. GF adhesion, metabolic activity and proliferation were impaired by 3D printed biomaterials compared to subtractively manufactured comparison surfaces and the 3Y‐TZP control, whereas membrane integrity was comparable. Within the limits of the present investigation, it was concluded that subtractively manufactured surfaces are superior compared to 3D printed surfaces to support STI. For the development of biologically optimized 3D printable biomaterials, consecutive studies will focus on the improvement of cytocompatibility and the synthesis of STI‐relevant extracellular matrix constituents.
Aim
The aim of the present investigation was to evaluate clinically and radiographically the outcome of zirconia oral implants after 3 years in function.
Materials and methods
In 60 patients in need ...of either a single‐tooth replacement or a three‐unit fixed dental prosthesis (FDP), a total of 71 one‐piece zirconia implants were placed and immediately restored with temporary fixed prostheses. After a period of at least 2 months in the mandible and at least 4 months in the maxilla, zirconia‐based reconstructions were cemented. The implants were clinically and radiologically examined at implant insertion, prosthetic delivery, at 6 months and then yearly up to 3 years. A linear mixed model was used to analyze statistically the influence of prognostic factors on changes in the marginal bone level.
Results
Seventy‐one implants (48 in the mandible, 23 in the maxilla) inserted in 60 patients were restored with 49 crowns and 11 FDP. One patient lost his implant after 5 weeks. Five patients with one implant each could not be evaluated after 3 years. Based on 55 patients with a total of 66 implants, the mean survival rate was 98.5% after 3 years in function. A statistically significant mean marginal bone loss (0.70 mm ± 0.72 mm) has been detected from implant insertion to the 3‐year follow‐up. The largest marginal bone loss occurred between implantation and prosthetic delivery (0.67 mm ± 0.56 mm). After delivery, no statistically significant bone level change was observed (0.02 mm ± 0.59 mm). None of the investigated prognostic factors had a significant influence on changes in the marginal bone level.
Conclusions
After 3 years in function, the investigated one‐piece zirconia implant showed a high survival rate and a low marginal bone loss. The implant system was successful for single‐tooth replacement and three‐unit FDPs. Further investigations with long‐term data are needed to confirm these findings.
Polyether ether ketone (PEEK) has been introduced into implant dentistry as a viable alternative to current implant abutment materials. However, data on its physico-mechanical properties are still ...scarce. The present study sought to shed light on this topic utilizing an ex vivo chewing simulator model. A total of 48 titanium two-piece implants were allocated into three groups (n = 16 per group): (1) implants with PEEK abutments and an internal butt-joint connection (PBJ), (2) implants with PEEK abutments and an internal conical implant–abutment connection (PC), and (3) implants with zirconia abutments and an internal butt-joint connection (ZA). All abutments were restored with a non-precious metal alloy crown mimicking the upper right central incisor. A dynamic chewing simulation of half (n = 8) of the specimens per group was performed with 5 × 106 cycles and a load of 49 N at a frequency of 1.7 Hz with thermocycling between 5 and 55 °C. The other eight specimens served as unloaded controls. Surface roughness, implant–abutment connection microgaps (IACMs), and the titanium base–abutment interface microgaps (TAIMs) in the loaded groups were evaluated. Finally, a quasi-static loading test was performed in a universal testing machine with all samples to evaluate fracture resistance. Overall, 23 samples survived the artificial chewing process. One abutment screw fracture was observed in the PC group. The ZA group showed higher surface roughness values than PEEK abutments. Furthermore, ZA revealed lower TAIM values compared to PEEK abutments. Similarly, ZA was associated with lower IACM values compared to PBJ. Fracture loads/bending moments were 1018 N/704 N cm for PBJ, 966 N/676 N cm for PC, and 738 N/508 N cm for ZA, with no significant differences compared to the unloaded references. Artificial loading did not significantly affect fracture resistance of the examined materials. PEEK abutments were associated with better load-bearing properties than zirconia abutments, although they showed higher microgap values. PEEK abutments could, therefore, be feasible alternatives to zirconia abutments based on the present ex vivo findings resembling 20 years of clinical service.
Objective
To evaluate the influence of artificial aging on the transformation propagation and fracture resistance of zirconia implants.
Methods
One‐piece (with integrated implant abutment, 1P; ...regular diameter 4.1mm; n = 16) and two‐piece (with separate implant abutment, 2P; wide diameter 5 mm; n = 16) zirconia implants were embedded according to ISO 14801. A two‐piece titanium–zirconium implant (Ti‐Zr; 4.1 mm diameter) served as a control (n = 16). One subgroup (n = 8) of each system was simultaneously dynamically loaded (107 cycles; 98N) and hydrothermally aged (85°C, 58 days), while the other subgroup (n = 8) remained untreated. Finally, specimens were statically loaded to fracture. Potential crystal phase transformation was examined at cross sections using scanning electron microscopy (SEM). A multivariate linear regression model was applied for statistical analyses.
Results
The fracture resistance of 1P (1,117 SD = 38 N; loaded/aged: 1,009 60 N), 2P (850 36 N; loaded/aged: 799 84 N), and Ti‐Zr implants (1,338 205 N; loaded/aged: 1,319 247 N) was not affected significantly by loading/aging (p = .171). However, when comparing the systems, they revealed significant differences independent of loading/aging (p ≤ .001). Regarding the crystal structure, a transformation zone was observed in SEM images of 1P only after aging, while 2P showed a transformation zone even before aging. After hydrothermal treatment, an increase of this monoclinic layer was observed in both systems.
Conclusions
The Ti‐Zr control implant showed higher fracture resistance compared to both zirconia implants. Loading/aging had no significant impact on the fracture resistance of both zirconia implants. The wide‐body 2P zirconia implant was weaker than the regular body 1P implant.
Abstract
The ongoing COVID-19 pandemic has revealed alarming shortages of personal protective equipment for frontline healthcare professionals and the general public. Therefore, a 3D-printable mask ...frame was developed, and its air seal performance was evaluated and compared. Personalized masks (PM) based on individual face scans (n = 8) and a statistically shaped mask (SSM) based on a standardized facial soft tissue shape computed from 190 face scans were designed. Subsequently, the masks were additively manufactured, and in a second step, the PM and SSM were compared to surgical masks (SM) and FFP2 masks (FFP2) in terms of air seal performance. 3D-printed face models allowed for air leakage evaluation by measuring the pressure inside the mask in sealed and unsealed conditions during a breathing simulation. The PM demonstrated the lowest leak flow (p < 0.01) of inspired or expired unfiltered air of approximately 10.4 ± 16.4%, whereas the SM showed the highest (p < 0.01) leakage with 84.9 ± 7.7%. The FFP2 and SSM had similar values of 34.9 ± 18.5% leakage (p > 0.68). The developed framework allows for the time- and resource-efficient, on-demand, and in-house production of masks. For the best seal performance, an individually personalized mask design might be recommended.
Extrusion-based printing enables simplified and economic manufacturing of surgical guides for oral implant placement. Therefore, the cytotoxicity of a biocopolyester (BE) and a polypropylene (PP), ...intended for the fused filament fabrication of surgical guides was evaluated. For comparison, a medically certified resin based on methacrylic esters (ME) was printed by stereolithography (n = 18 each group). Human gingival keratinocytes (HGK) were exposed to eluates of the tested materials and an impedance measurement and a tetrazolium assay (MTT) were performed. Modulations in gene expression were analyzed by quantitative PCR. One-way ANOVA with post-hoc Tukey tests were applied. None of the materials exceeded the threshold for cytotoxicity (< 70% viability in MTT) according to ISO 10993-5:2009. The impedance-based cell indices for PP and BE, reflecting cell proliferation, showed little deviations from the control, while ME caused a reduction of up to 45% after 72 h. PCR analysis after 72 h revealed only marginal modulations caused by BE while PP induced a down-regulation of genes encoding for inflammation and apoptosis (p < 0.05). In contrast, the 72 h ME eluate caused an up-regulation of these genes (p < 0.01). All evaluated materials can be considered biocompatible in vitro for short-term application. However, long-term contact to ME might induce (pro-)apoptotic/(pro-)inflammatory responses in HGK.
Surface characteristics of implant reconstructions determine the gingival fibroblast (GF) response and thus soft tissue integration (STI). However, for monolithic implant reconstructions it is ...unknown whether the (hybrid) ceramic biomaterial type and its surface treatment affect GF response. Therefore, this investigation examined the influence of the implant reconstruction biomaterials hybrid ceramic (HC), lithium disilicate ceramic (LS), 4 and 5 mol% yttria partially stabilized zirconiumdioxide ceramics (4/5Y-PSZ) and their surface treatment - machining, polishing or glazing - on surface characteristics and GF response.
After characterization of surface topography and wettability by scanning electron microscopy, interferometry and contact angle measurement, the adhesion, morphology, metabolic activity and proliferation of GFs from six donors was investigated by fluorescent staining and a resazurin-based assay at days 1, 3 and 7. Titanium (Ti) served as control.
Biomaterial type and surface treatment affected the GF response in a topography-dependent manner. Smooth polished and glazed surfaces demonstrated enhanced GF adhesion and earlier proliferation onset compared to rough machined surfaces. Due to minor differences in surface topography of polished and glazed surfaces, however, the GF response was similar for polished and glazed HC, LS, 4- and 5Y-PSZ as well as Ti.
Within the limits of the present investigation, polishing and glazing of machined HC, LS and 4/5Y-PSZ can be recommended to support STI-relevant cell functions in GF. Since the GF response on polished and glazed HC, LS, 4- and 5Y-PSZ surfaces and the Ti control was comparable, this investigation proofed equal cytocompatibility of these surfaces in vitro.
•Biomaterial and surface treatment determine surface topography of (hybrid) ceramics.•Surface topography is the key modulator of GF function on (hybrid) ceramics.•Polishing and glazing promote STI-relevant GF functions compared to machining.•Polished and glazed HC, LS, 4- and 5Y-PSZ surfaces show comparable GF response.
Aim
To evaluate the clinical and radiological outcomes of one‐piece zirconia implants restored with single crowns (SCs) or fixed dental prostheses (FDPs) over an observation period of 5 years in ...function.
Materials and methods
In a prospective cohort investigation with two investigational centers, one‐piece zirconia implants were placed in anterior and posterior sites. After a healing period of at least 2 months in the mandible and 4 months in the maxilla with immediate provisional reconstructions, the final all‐ceramic SCs or three‐unit FDPs were cemented. Patients were followed for 5 years. Clinical parameters and radiological measurements of the implants and the neighboring teeth were assessed. For the statistical analysis, linear mixed models were applied.
Results
A total of 71 implants were placed in 60 patients. Sixty‐three implants in 53 patients could be evaluated at the 5‐year follow‐up. Six patients with a total of seven implants were counted as dropouts. One implant did not achieve adequate osseointegration and had to be removed 5 weeks after implantation. The 5‐year survival rate was calculated as 98.4% (95% CI 91.6, 99.9). The mean overall marginal bone loss from implant placement to the 5‐year follow‐up was 0.7 ± 0.6 mm. After an initial mean marginal loss before loading the implants (0.7 mm), no further statistically significant change in marginal bone level (p = .458) could be observed.
Conclusion
The investigated one‐piece zirconia implant showed a high survival rate, very stable marginal bone, and mucosal margin levels after 5 years in function. Therefore, it can be considered safe and reliable for the reconstruction of implant‐supported SCs or FDPs over a mid‐term period.
Different printing technologies can be used for prosthetically oriented implant placement, however the influence of different printing orientations and steam sterilization remains unclear. In ...particular, no data is available for the novel technology Continuous Liquid Interface Production. The objective was to evaluate the dimensional accuracy of surgical guides manufactured with different printing techniques in vertical and horizontal printing orientation before and after steam sterilization. A total of 80 surgical guides were manufactured by means of continuous liquid interface production (CLIP; material: Keyguide, Keyprint), digital light processing (DLP; material: Luxaprint Ortho, DMG), stereolithography (SLA; Surgical guide, Formlabs), and fused filament fabrication (FFF; material: Clear Base Support, Arfona) in vertical and horizontal printing orientation (n = 10 per subgroup). Spheres were included in the design to determine the coordinates of 17 reference points. Each specimen was digitized with a laboratory scanner after additive manufacturing (AM) and after steam sterilization (134 °C). To determine the accuracy, root mean square values (RMS) were calculated and coordinates of the reference points were recorded. Based on the measured coordinates, deviations of the reference points and relevant distances were calculated. Paired t-tests and one-way ANOVA were applied for statistical analysis (significance p < 0.05). After AM, all printing technologies showed comparable high accuracy, with an increased deviation in z-axis when printed horizontally. After sterilization, FFF printed surgical guides showed distinct warpage. The other subgroups showed no significant differences regarding the RMS of the corpus after steam sterilization (p > 0.05). Regarding reference points and distances, CLIP showed larger deviations compared to SLA in both printing orientations after steam sterilization, while DLP manufactured guides were the most dimensionally stable. In conclusion, the different printing technologies and orientations had little effect on the manufacturing accuracy of the surgical guides before sterilization. However, after sterilization, FFF surgical guides exhibited significant deformation making their clinical use impossible. CLIP showed larger deformations due to steam sterilization than the other photopolymerizing techniques, however, discrepancies may be considered within the range of clinical acceptance. The influence on the implant position remains to be evaluated.
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