One-piece Zirconia Research Articles

Evaluation of tensile bond strength of two different cements used for luting zirconia coping to one-piece zirconia implant - An in vitro study

Aim: The purpose of this in vitro study was the evaluation of the tensile bond strength of two different cements used for luting zirconia coping to one-piece zirconia implant. Settings and Design: The study was designed in an in vitro study setting. Materials and Methods: A one-piece zirconia implant was scanned on laboratory scanner, and thirty zirconia implants were milled by computer aided manufacturing (CAM). Subsequently, the abutment surface of each zirconia implants were scanned in laboratory scanner and coping with a hole was designed by computer-aided designing software, which was used for milling by computer-aided manufacturing (CAM). After various surface treatments of abutment and intaglio surface of coping, fifteen sets were cemented by glass ionomer cement (Group I) and the other fifteen sets by adhesive resin cement (Group II). All thirty samples after thermocycling were dried and pulled out in a universal testing machine, and tensile retention force is noted in pounds per square inch (psi). Statistical Analysis Used: Values for tensile retention force were tabulated for both the groups. Mean and standard deviation are calculated. Independent t-value and P value were calculated. Results: The least tensile retention force was reported in Group I (165.86 ± 25.74 psi). Maximum tensile retention force was received for Group II (396.81 ± 78.32 psi). Independent t-test was applied from which t-value calculated was 10.85 and P value obtained was 0.001, which means that there exists a very high difference in tensile bond strength of cement in Group I and Group II. Conclusions: Better tensile retention forces were observed in samples cemented with adhesive resin cement when compared to samples cemented with glass ionomer cement.

The Fracture Resistance Comparison between Titanium and Zirconia Implant Abutments with and without Ageing: Systematic Review and Meta-Analysis.

Implant abutments are essential components of implant prosthetic restorations. The golden standard for abutment material is titanium; however, due to its properties, the esthetic result can be compromised. The most popular esthetic material alternatives are one- and two-piece zirconia. The study aimed to answer the questions of whether zirconia abutments can be used interchangeably with titanium in both anterior and posterior regions and how aging of the abutment affects durability. For this study, an electronic search of MEDLINE (PubMed) and Scopus (Embase) was conducted. The PRISMA guidelines were followed, and a systematic review was registered with PROSPERO. The search revealed 4031 results, of which 17 studies were selected. The strongest material for abutments is titanium, closely followed by two-piece zirconia. One-piece zirconia abutments were the weakest. The cyclic loading above 1,000,000 cycles decreased the fracture resistance of the abutments. Differences in implant diameter, angulation, and restoration affected the fracture strength of all compared materials. The main mode of failure for titanium abutments was screw bending or screw fracture. One-piece zirconia most often presented catastrophic failure with internal hexagon fracture below the implant neck. Two-piece zirconia exhibits a combination of failure modes. Two-piece zirconia abutments may be suitable for use in the posterior region, given their comparable fracture resistance to titanium abutments. Despite the fact that one-piece zirconia is capable of withstanding forces that exceed those exerted during mastication, it is recommended that it be employed primarily in the anterior dentition due to its propensity for unfavorable failure modes.

Effects of screw channel angulation on the fracture resistance of one-piece zirconia crown with titanium base.

The design of the angulated screw channel in implant restorations allows the possibility to correct angulation discrepancies, especially in the anterior maxilla. However, the effects of varied screw channel angulations on fracture resistances and fracture patterns of the implant restorations are still uncertain, and thus the aim of this study. Angulated screw channel monolithic zirconia crowns (Nobel Biocare) with three different angulation groups-straight (ASC1), 15° (ASC15), and 25° (ASC25)-were digitally designed from a left central incisor prototype scan. Following fabrication, 10 samples of each group were individually mounted onto implant replicas embedded in standardized type V stone gypsum cylinder jigs (25mm × 25mm). All screws were manually torqued to 35 Ncm according to the manufacturer's recommendation, and screw access openings were subsequently sealed with resin composite. To mimic the off-axis loading of the central incisor, the specimens were then loaded at a cephalometric interincisal relationship of 135° between the long axis of the crown and the Instron force applicator, with crosshead speed set at 0.5mm/min. Fractured abutment surfaces were examined, and selected specimens were further evaluated by scanning electron microscopy. Screw torque values were also measured after the catastrophic loading. One-way ANOVA was used to compare load-to-fracture values between groups, with the statistical significance set at 0.05 (p values). The mean load-to-fracture values in descending order were 331.24N (±34.00N) in ASC15, 325.22N (±35.50N) in ASC25, and 302.04N (±45.10N) in ASC1, with no statistically significant differences between groups. Considerable screw torque losses were found in all groups after catastrophically loading. The average torque loss was 84% in ASC1, 86% in ASC15, and 94% in ASC25. 16 out of 30 specimens experienced screw loosening; one ASC1 screw underwent slight deformation. Crowns of all tested groups exhibited cohesive fracture patterns at the screw-metallic-zirconia interfaces. Within the limitations of this in vitro study, one-piece monolithic zirconia implant crowns with varied screw channel angulations shared similar fracture-strength and fracture-mode characteristics. The zirconia-titanium base junctions exhibited the weakest link of all restorations.

Single Crown Restorations Supported by One-Piece Zirconia Dental Implants: Case Series with a Mean Follow-Up of 58 Months

The main aim of this case series was to report the clinical and radiographic outcomes of 22 one-piece zirconia dental implants positioned in 19 patients to restore single edentulisms and followed up for at least 2 years. The mean observation period was 58.18 months. At the last follow-up visit, no issues, such as foreign body sensation, discomfort or pain, were reported by the patients. No implant showed signs of infection with suppuration or implant mobility. Marginal bone levels (MBL) were assessed through standardized dental radiographs and a dedicated software. The mean distance between the implant head and the first detectable bone to implant contact was calculated at the mesial and distal aspect of each implant. The mean MBL at baseline was 1.82 ± 0.63 mm while the mean MBL at the last follow-up visit was 2.57 ± 0.72 mm. The results obtained in the present case series over a mean follow-up period of 58.18 months (range 27–96) showed that one-piece zirconia dental implants could be an alternative option to support single crowns in patients requiring metal-free restorations. Nevertheless, further better-controlled research featuring an adequate study design and longer follow-up is needed in order to clarify advantages and limitations which are related to this treatment modality.

One-piece versus two-piece zirconia abutment supported single implant crown in the esthetic region: 3-Year results from a split-mouth randomized controlled clinical trial.

To compare the clinical, radiographic, and immunological outcomes between one-piece versus two-piece zirconia abutments supported single implant crowns in the esthetic region. The study followed a split-mouth, double-blind, and randomized controlled clinical design for a duration of 3 years. Twenty-two eligible patients with 44 implants were randomly assigned to two groups: Group 1 (one-piece zirconia abutment with zirconia base, n = 22) and Group 2 (two-piece zirconia abutment with titanium base, n = 22). The primary outcome was the technical complication rate. Additionally, survival rates, cytokines concentrations in peri-implant crevicular fluid (PICF), peri-implant conditions, marginal bone loss, and pink/white esthetics score (PES/WES) were assessed as secondary outcomes. Twelve of 22 patients attended the 1-year follow-up (due to the COVID pandemic), and 19 patients attended the 3-year examination. Two abutments in Group 1 were fractured after 10 and 12 months in function. Additionally, one screw loosening occurred in Group 1 at 1-year follow-up. The 3-year technical complication rate was significantly higher in Group 1 than that in Group 2 (15.79% vs. 0%, p < .001). The 3-year implant survival rate was 100% in both groups. The concentration of IFN-γ in PICF was significantly upregulated in Group 2 (p = .018). Furthermore, the IL-6 concentration was positively correlated with BOP% (p = .020). Two-piece zirconia abutments exhibited superior technical performance compared to one-piece designs during a 3-year follow-up in the anterior region. However, further long-term research is necessary to verify the immunological stability of two-piece zirconia abutments.

Evaluation of one-piece zirconia dental implants: An 8-year follow-up study

ObjectivesLong-term studies of modern zirconia implants are still insufficient. This prospective 8-year follow-up study investigated one-piece zirconia implants.Materials and methodsPatients who had received a one-piece zirconia dental implant (PURE ceramic implant, Institut Straumann GmbH, Basel, Switzerland) were included in this study. Next to the implant survival and success rates, the radiographic and clinical implant parameters were assessed.ResultsThe overall survival rate of 67 zirconia implants in 39 patients was 100%. The overall success rate was 89.6%. Around the immediate zirconia implants, the success rate was 94.7%, and around the delayed implants, 87.5%. The immediate implants showed a significantly higher bone crest compared to the delayed implants (p = 0.0120). According to the pink esthetic score, the immediate implants revealed more favorable esthetic results compared to the delayed implants after an 8-year follow-up (p = 0.0002).ConclusionsAfter 8 years, the one-piece zirconia implants presented an 89.6% success rate. Regarding the timing of implantation, in individual cases, immediate implantation can have slight advantages over delayed implantation.Clinical relevanceImmediate implants can also be considered for zirconia implants and should not be excluded on principle.

The clinical use of computer aided designed/computer aided manufactured titanium nitride coated implant abutments: Surgical and prosthetic considerations-A case series.

To describe the clinical use of nitride-coated titanium CAD/CAM implant abutments in the maxillary esthetic zone in two patients with high esthetic and functional demands and, to highlight the advantages of nitride-coated milled titanium abutments when compared to stock/custom titanium, one-piece monolithic zirconia, and hybrid metal-zirconia implant abutments. Due to the inherent mechanical and esthetic clinical challenges, single implant-supported reconstructions in the maxillary esthetic zone are a complex restorative treatment. While CAD/CAM technology has been suggested to enhance and ease implant abutment design and manufacturing, implant abutment material selection remains as a critical decision affecting restoration's long-term clinical outcomes. To date, considering the esthetic disadvantages of conventional titanium implant abutments, the mechanical limitations of one-piece zirconia abutments and the manufacturing time and costs associated with hybrid metal-zirconia abutments, no abutment material can be considered "ideal" for all clinical scenarios. Due to their biocompatibility, biomechanical characteristics (hardness and wear resistance), optical properties (yellow color), and peri-implant soft tissue esthetic integration, the use of CAD/CAM titanium nitride-coated implant abutments has been suggested as a predictable implant abutment material in mechanically challenging but esthetically demanding clinical situations, as the maxillary esthetic zone. Two patients requiring a combined tooth-implant restorative treatment in the maxillary esthetic zone were treated using CAD/CAM nitride coated titanium implant abutments. The principal advantages of TiN coated abutments include comparable clinical outcomes to stock abutments, optimal biocompatibility, adequate fracture, wear, and corrosion resistance, reduced bacterial adhesion, and excellent esthetic integration with adjacent soft tissues. Clinical reports and short term mechanical, biological and esthetic clinical outcomes indicate that CAD/CAM nitride coated titanium implant abutments can represent a predictable restorative alternative to stock/custom and metal/zirconia implant abutments and be considered a clinical relevant option in mechanically challenging but esthetically demanding situations, as often found in the maxillary esthetic zone.

Long-Term Stability of Hydrothermally Aged and/or Dynamically Loaded One-Piece Diameter Reduced Zirconia Oral Implants

The aim of this in vitro study was to evaluate the long-term stability of one-piece diameter reduced zirconia oral implants under the influence of loading and artificial aging in a chewing simulator as well as the fracture load in a static loading test. Thirty-two one-piece zirconia implants with a diameter of 3.6 mm were embedded according to the ISO 14801:2016 standard. The implants were divided into four groups of eight implants. The implants of group DLHT were dynamically loaded (DL) in a chewing simulator for 107 cycles with a load of 98 N and simultaneously hydrothermally aged (HT) using a hot water bath at 85 °C. Group DL was only subjected to dynamic loading and group HT was exclusively subjected to hydrothermal aging. Group 0 acted as a control group: no dynamical loading, no hydrothermal ageing. After exposure to the chewing simulator, the implants were statically loaded to fracture in a universal testing machine. To evaluate group differences in the fracture load and bending moments, a one-way ANOVA with Bonferroni correction for multiple testing was performed. The level of significance was set to p < 0.05. In the static loading test, group DLHT showed a mean fracture load of 511 N, group DL of 569 N, group HT of 588 N and control group 0 of 516 N. The average bending moments had the following values: DLHT: 283.5 Ncm; DL: 313.7 Ncm; HT: 324.4 Ncm; 0: 284.5 Ncm. No significant differences could be found between the groups. Hydrothermal aging and/or dynamic loading had no significant effect on the stability of the one-piece diameter reduced zirconia implants (p > 0.05). Within the limits of this investigation, it can be concluded that dynamic loading, hydrothermal aging and the combination of loading and aging did not negatively influence the fracture load of the implant system. The artificial chewing results and the fracture load values indicate that the investigated implant system seems to be able to resist physiological chewing forces also over a long service period.

One-Piece Zirconia Oral Implants for Single Tooth Replacement: Five-Year Results from a Prospective Cohort Study

The intention of this 5-year prospective cohort investigation was to clinically and radiographically investigate the outcomes of a one-piece zirconia implant system for single tooth replacement. Sixty-five patients received a total of 66 single-tooth implants. All implants immediately received temporary restorations and were finally restored with all-ceramic crowns. Follow-ups were performed at the prosthetic delivery, after 1, 3, and 5 years. Peri-implant and dental soft-tissue parameters were evaluated and patient-reported outcomes recorded. To monitor peri-implant bone remodelling, standardised radiographs were taken at the implant insertion and at the 1-, 3-, and 5-year follow-ups. In the course of 5 years, 14 implants were lost, resulting in a cumulative implant survival rate of 78.2%. The mean marginal bone loss from the implant insertion to the 5-year follow-up amounted to 1.12 mm. Probing depth, clinical attachment level, bleeding, and plaque index increased over time. In 91.5% of the implants, the papilla index showed levels of 1 or 2, respectively. At the end of the study, the patient satisfaction was higher compared to the pre-treatment measurements. Due to the low survival rate after five years and the noticeably high frequency of advanced bone loss observed in this study, the implant has not met the launch criteria, as it would have not been recommended for routine clinical use.

Immediate placement of one-piece zirconia implants with or without xenograft into the buccal gap. Soft tissues as secondary outcomes of an experimental in vivo study.

To histologically evaluate soft tissue healing following immediately placed one-piece zirconia implant and grafting a xenograft into the buccal gap. The third and fourth premolars (PM3 and PM4) in both quadrants of the mandible of nine dogs were used for this experiment. Those teeth were removed flapless and implants were placed into the distal sockets in a lingual position. In one side of the jaw, the gap between the implant and the socket walls was grafted (test) while no grafting was performed in the contralateral side (control), randomly selected. After 6months of healing, biopsies were obtained and prepared for histological analysis. Soft tissue measures like supracrestal soft tissue height (STH), length of barrier epithelium (BE), and connective tissue (CTC) were measured at buccal and lingual surfaces. The marginal mucosa was in a coronal position on the test side compared with the control side. At the buccal surface, the BE was longer in the test side than in the control side, while the CTC was longer in the control side than in the test side. For the STH (BE + CTC), the difference between the groups was not statistically significant. The placement of a xenograft into the gap between a 1-piece zirconia implant and the buccal wall in dogs modified the process of soft tissue healing, providing less soft tissue recession. The gap size seems to have a modifying effect on the application of this protocol.

In Vitro Investigation of Material Combinations for Meso- and Suprastructures in a Biomimetic Approach to Restore One-Piece Zirconia Implants

The aim of this study was to find a suitable material combination to avoid cement excess in the marginal region of one-piece zirconia implant-supported restorations by means of a hybrid crown consisting of a meso- and a suprastructure. One-piece zirconia implants (n = 120) were embedded in epoxy resin. Microfilled resin composite mesostructures (n = 60), designed as caps, were bonded on the implant abutment with a primer only. A molar crown was constructed and cemented with a resin cement on top of the mesostructure as a suprastructure out of feldspar ceramic (n = 12), lithium-disilicate (n = 24), or zirconia (n = 24). Fracture load (n = 6) and retention force (n = 6) were measured immediately after storage in distilled water at 37 °C for 24 h, as well as after an additional exposure to artificial aging in a chewing simulator and simultaneous thermal cycling. For the measurement of the fracture load, monolithic crowns made of the employed restorative materials and identical in shape to the hybrid crowns served as controls (n = 6 each). Fracture load values for feldspar ceramic and lithium-disilicate hybrid crowns were slightly higher than those for the respective monolithic crowns at baseline and after aging, which was statistically significant only for feldspar crowns after aging. In contrast, fracture load values for zirconia monolithic crowns were higher than those for zirconia hybrid crowns, which was only statistically significant after aging. Artificial aging reduced the fracture load of feldspar and lithium-disilicate crowns both for hybrid and monolithic crowns. The effect was only statistically significant for lithium disilicate hybrid crowns. The fracture load for hybrid and monolithic zirconia crowns was increased by artificial aging without reaching statistical significance. The retention force of lithium-disilicate and zirconia hybrid crowns was not affected by artificial aging. Taking into account retention force and fracture load, lithium-disilicate hybrid crowns showed promising results.

One-Piece Zirconia Oral Implants for the Support of Three-Unit Fixed Dental Prostheses: Three-Year Results from a Prospective Case Series.

The objective was to investigate the clinical and radiological outcome of one-piece zirconia oral implants to support three-unit fixed dental prostheses (FDP) after three years in function. Twenty-seven patients were treated with a total of 54 implants in a one-stage surgery and immediate provisionalization. Standardized radiographs were taken at implant placement, after one year and after three years, to evaluate peri-implant bone loss. Soft-tissue parameters were also assessed. Linear mixed regression models as well as Wilcoxon Signed Rank tests were used for analyzing differences between groups and time points (p < 0.05). At the three-year evaluation, one implant was lost, resulting in a cumulative survival rate of 98.1%. The mean marginal bone loss amounted to 2.16 mm. An implant success grade I of 52% (bone loss of ≤2 mm) and success grade II of 61% (bone loss of ≤3 mm) were achieved. None of the evaluated baseline parameters affected bone loss. The survival rate of the zirconia implants was comparable to market-available titanium implants. However, an increased marginal bone loss was observed with a high peri-implantitis incidence and a resulting low implant success rate.

Survival and Fracture rates of One-Piece Zirconia Implants: A Systematic review

Introduction: The implementation of endosseous showed expected outcomes related to survival and successful oral management. Nowadays, interest in achieving an excellent esthetic outcome increased in implant dentistry. Dental implants’ aesthetic outcomes demand understanding of fundamental biological principles and proficiency in various surgical procedures. Titanium alloys and titanium are the gold standards as a material of choice. Evaluate the rate of survival and fracture by dental implants of one-piece zirconia with a year follow-up history. Methodology: This study was based on a systematic review, carried out through PubMed, Embase and Medline databases considering clinical studies only from 2016–2022 published data. Results: Eleven articles were selected out of 1024 initially. Evaluated a total number of 658 one-piece implants, with follow-ups from 1–7 years. The comprehensive survival and fracture rate of one-piece zirconia implants is 87.7 % and 4.9% after at least a year of function. Z-system Zirconia implants showed the highest fracture rate among other systems. Conclusion: Zirconia dental implants are a promising solution to replace missing tooth/teeth, especially in the case of Titanium allergy, or in patients with sub-optimal soft tissue conditions can lead to poor esthetic results. However, more clinical practice is required to determine the effective implants with fewer complications.

Clinical and radiographic prospective study of customized one-piece titanium and one-piece fusion-sputtered zirconia implants: five-year mean follow-up

BackgroundTo evaluate the clinical and radiographic assessment of customized fusion-sputtered one-piece zirconia implants.MethodsTwenty-eight patients received either fusion sputtered one-piece zirconia implants (n = 14) or one-piece titanium implants (n = 14). All implants were one-piece designs. After 4 months of immediate loading, all implants were restored with a monolithic zirconia crown. All implants were evaluated at baseline, 6 months, 1 year, 2 years, and 5 years. Implant mobility, plaque index, and gingival index evaluations were performed. The measurements of marginal bone level were calculated radiographically.ResultsAll implants were well maintained through the evaluation period with a 100% survival rate without any clinical complications. Regarding gingival index, there was no statistically significant difference (P = .364) between zirconia (3.3 ± 0.7 mm) and titanium (3.5 ± 0.6 mm) implants, after 5 years. There was no statistically significant difference (P = .470) between zirconia (1.77 ± 0.039 mm) and titanium (1.80 ± 0.28 mm) implants regarding marginal bone loss, after 5 years.ConclusionsOne-piece fusion-sputtered zirconia implant represents a reliable treatment modality in replacing a missing tooth in the esthetic zone.

A short-term prospective study to evaluate the clinical performance of endosseous zirconia implants

Background: Endosseous zirconia implants have been established as an alternative to conventional titanium implants, especially in the aesthetic zone. This pilot study aimed to evaluate the outcome of rehabilitation with zirconia implants, in a subset of the Indian population, involving varying clinical scenarios. Methods: A total of 10 one-piece zirconia implants were placed in seven patients requiring rehabilitation of missing teeth. The survival rate and marginal bone levels were evaluated at six months and 12 months following implant placement. Results: Five implants were placed in the maxilla and five in the mandible, including well-healed sites, extraction sockets, a single cantilever in the lower anterior region, and a full-arch rehabilitation. During the observation period, two early implant failures were noted resulting in a survival rate of 80%. Mean marginal bone loss of 0.73mm was seen one year following implant placement, with maximum bone loss occurring in the first six months. Conclusion: The results of this study encourage the use of endosseous zirconia implants in diverse clinical scenarios with careful case selection. However, long-term studies are needed to further validate these findings.

Implant deformation and implant-abutment fracture resistance after standardized artificial aging: An in vitro study.

Zirconia abutments have been widely adopted in clinical implant practice. The unique mechanical properties of zirconia may significantly affect the long-term prognosis of implant treatments. The purpose of this study was to investigate the influence of abutment material on implant deformation and fracture resistance of internal conical connection implant-abutment complexes of two diameters after standardized artificial aging. Thirty original abutments (one-piece titanium, one-piece zirconia, zirconia with alloy base) with two diameters (regular, narrow) were connected to internal conical connection implants and subjected to a standardized artificial aging process consisting of thermal cycling and mechanical cyclic loading. Microcomputed tomography (μCT) scans of implant bodies were performed before and after aging. 3-dimensional images of implant bodies were generated from the μCT scans and aligned for before and after aging to calculate the volumetric deformation amount. Finally, fracture resistance was measured using a mechanical static loading test for the surviving aged and 30 brand-new specimens. All specimens survived artificial aging. No significant difference in implant deformation was found in the regular groups (p=0.095). In narrow groups, the one-piece zirconia group showed significantly less deformation (p < 0.0001). For fracture resistance, no significant decrease was observed after aging in any group (p > 0.05). One-piece zirconia abutments showed significantly lower strength than the other two materials for both diameters (p < 0.0001). In the regular diameter system, abutment material had no significant influence on the tested mechanical property degradation after simulated long-term oral use. The mechanical performance of narrow diameter one-piece zirconia abutments differed from the other two materials. For optimal performance, one-piece zirconia abutments should be adopted only in anterior regions.

German S3 guideline on the use of dental ceramic implants

PurposeBased on the excellent long-term data, dental implants made of titanium are considered the international implantological standard for replacing missing teeth. However, ceramic implants made of zirconia (ZrO2) have experienced a renaissance in the last 15 years due to constant innovations in materials and products, with material properties and soft tissue- and osseointegration behavior comparable to those of titanium. However, one limitation concerning ceramic implants is the lack of reliable long-term data, especially in the case of two-piece implant systems. As there is an increasing demand for ceramic implants from practitioners and patients, the German Society for Implantology (DGI) has decided to develop a guideline on the use of dental ceramic implants at the highest available evidence level with the involvement of experts in this field.MethodsStatements and recommendations were prepared after conducting a systematic literature search and an independent assessment process involving the relevant clinical literature from 2008 to 2021. The adopted recommendations and statements are summarized in this guideline.Results and conclusionsIt confirms the feasible use of one-piece zirconia implants as an addendum/alternative to titanium implants. No final conclusion regarding the application of two-piece ceramic implant systems could be drawn on the basis of the existing data, thus its use can only be recommended after the patient has been informed in detail about the lack of long-term clinical data.

Fatigue resistance and fracture strength of narrow-diameter one-piece zirconia implants with angled abutments.

Zirconia implants are assumed to satisfy the esthetic requirements that titanium implants cannot meet, however, there are not enough studies in the literature about narrow-diameter and angled zirconia implants that can be preferred especially in the anterior region. This in vitro study aimed to evaluate the fatigue resistance and fracture strength of narrow-diameter zirconia implants with angled abutments. Forty-eight one-piece experimental zirconia implants and monolithic zirconia crowns were produced from 3-YTZP blanks. The implant diameters (3.0 or 3.7 mm) and the restoration types were determined according to three intraoral regions (upper central incisors, lower central incisors, and upper canine), and abutments were designed as straight or 15° angled. The samples were subjected to chewing simulation corresponding to 5 years of clinical performance and then the static loading test. The survival rates of groups were measured by the Kaplan-Meier log-rank test, and the fracture load values were estimated by using Kruskal-Wallis and Mann-Whitney U tests (p < 0.05). All 3.0 mm diameter implants failed the fatigue test. The fatigue resistance of the implants with angled abutments was significantly lower than the straight abutments, and different crown designs were found to affect survival rates significantly. The fracture strengths of the surviving groups were above the maximum physiological chewing forces, and the differences were not significant. The implant diameter, abutment angle, and restoration type have a significant effect on the fatigue behavior of zirconia implants. The fracture strengths of the one-piece zirconia implants with a 3.7 mm diameter and a 15° abutment angle are above the chewing forces for the anterior intraoral region.

Effects of abutment height and type of cements on bond strength of monolithic zirconia single crowns luted to one-piece zirconia implants.

To test the bond strength of one-piece zirconia implants with either standard or reduced height using different luting agents and pretreatments of the ceramic crowns' inner surfaces. Twenty monolithic CAD/CAM-fabricated zirconia single crowns were cemented onto 10 one-piece zirconia implants with either 5-mm or 4-mm abutment height (Z-Look3 Evo SLM, Z-Systems) using 13 different luting agents. After water storage, the crowns were removed using a specially developed test fixture in a universal testing machine (Z010, Zwick/Roell). The maximum force was recorded (N), and the force per area was calculated (MPa). The statistical evaluation was performed using univariate analysis of variance (SPSS version 25.0, IBM). A mean of 4.19 MPa (SD 2.90) at 5 mm and 3.89 MPa (SD 2.85) at 4 mm was obtained for all luting agents. The highest values were achieved for a resinmodified glass-ionomer cement, with 12.37 MPa (4 mm)/12.00 MPa (5mm). The lowest values were shown for a long-term temporary material, with 0.73 MPa (4 mm)/1.07 MPa (5 mm). Only a polycarboxylate cement (P < .001) and a glass-ionomer cement (P = .006) showed statistically significant differences, in favor of the reduced abutment height. The latter did not significantly reduce bond strength for any of the materials examined. Implants with a reduced abutment height are clinically suitable. Pretreatment of the crowns' inner surfaces with ceramic primer showed to be advantageous.

EAO Position Paper: Current Level of Evidence Regarding Zirconia Implants in Clinical Trials.

Titanium oral implants are still considered "state of the art" in implant dentistry, with well-documented survival rates. However, their grayish color and high prevalence of peri-implant infections have resulted in controversial discussion as to whether tooth-like-colored, metal-free zirconia ceramic implants provide sufficient potential to be considered equal regarding treatment outcomes. The present position paper has been composed upon invitation by the European Association of Osseointegration in order to provide an update on the current level of evidence regarding zirconia implants in clinical trials. To date, most available and scientifically documented zirconia implant systems are one-piece implants that require an experienced surgeon and prosthodontist due to the restricted flexibility in cases of compromised angulation or vertical positioning. Taking this limitation into account, there is evidence of a comparable outcome for one-piece zirconia implants compared to titanium implants for the fixed replacement of one to three missing teeth. In contrast, currently available clinical data evaluating two-piece zirconia implants with an adhesively bonded implant-abutment interface suggest an inferior outcome. Data evaluating the clinical applicability of screw-retained solutions, even if revealing sufficient fracture resistance in laboratory investigations, are still missing. High survival rates were reported for all-ceramic reconstructions supported by zirconia implants, but with increased technical complications; ie, fractures of the ceramic veneer in the case of bilayered restorations. Sufficient clinical evidence for recommending monolithic approaches is limited to single crowns.