Customized Zirconia Abutments Research Articles

Effect on the Fracture Resistance of Monolithic Zirconia Custom Abutment in Different Angulation: An In Vitro Study

The study was designed to find out the effect of different angulations of monolithic Zirconia custom-made abutments on fracture resistance. In this experimental type in vitro study, a total of thirty implant analogs with a diameter of 4.3 mm and a length of 11.5 mm were obtained for the maxillary central incisor. A total of thirty abutments specimens in three groups- 0-degree, 15-degree, and 25-degree, ten in each group were fabricated with monolithic zirconium by CAD/CAM system. Each abutment was subjected to load until fracture in a Universal testing machine and data was collected to a data collection sheet. One-way ANOVA was done to compare the fracture load among the three groups and pairwise comparison was done by Tukey post hoc test. The statistical significance p-value was considered as less than 0.05. The range of fracture load of 0-degree, 15-degree, and 25-degree angulated abutments were 590.55-1305.43N, 755.89-1720.55N, and 496.68-820.88N respectively. The highest fracture resistance was shown in 15-degree angulated custom-made zirconium abutments with a mean ± SD of 1223.442 ± 317.771N and the lowest fracture resistance was shown in case 25-degree with a mean ± SD deviation of 653.139 ± 102.045N. The mean ± SD of the 0-degree abutment was 948.944±245.588N. 95% Confidence interval of the mean were 773.260-1124.627N, 996.122-1450.761N, and 580.140-726.137N were assessed in cases of 0-degree, 15-degree, and 25-degree respectively. The fracture load or fracture resistance among the three groups of custom-made monolithic zirconium abutments were significantly different. 15-degree angulated abutment had higher fracture resistance properties. straight abutment had more fracture resistance properties than that of 25-degree abutments, but less than 25-degree abutments.

Clinical assessment of different implant‐supported esthetic crown systems fabricated with semi‐digital workflow: Two‐year prospective study

To assess the clinical outcome of three esthetic implant-supported crown systems fabricated with semi-digital workflow and their influence on the clinical outcome of dental implants. A total of 30 participants had received dental implants restoring missing maxillary first/second premolars. After 6 weeks, customized zirconia abutments were early loaded. Two months later, the definitive crowns were fabricated using semi-digital workflow and cemented. According to the crown material, 3 groups were randomly allocated; group (Z): ultrahigh-translucent monolithic zirconia, group (C): resin-matrix ceramic and group (P): polyetherketoneketone veneered with light-cured composite resin. Clinical outcomes including the survival and success rates were evaluated at baseline, 6, 12, 18, and 24 months. The survival rate for all studied groups was 100%, while their success rate was 100% for group (Z) and 90% for group (C) and group (P). Based on the functional implant prosthodontic score, a statistically significant difference was detected between group (Z) and group (P) (p< 0.001) as well as between group (C) and group (P) (p= 0.01). The zirconia group had the most favorable clinical behavior, while the polyetherketoneketone had the least. All crown systems had comparable success rates with similar values of the peri-implant marginal bone loss. Using semi-digital workflow, ultrahigh-translucent monolithic zirconia, resin-matrix ceramic and polyetherketoneketone veneered with light-cured composite resin can be considered as favorable implant-supported crowns. The implant-supported crown system based on polyetherketoneketone veneered with light-cured composite resin is counted as a promising esthetic and restorative option.

The Esthetic Outcome of Interproximal Papilla Between Implant-Restored Unilateral and Bilateral Maxillary Central Incisors: A Cross-Sectional Comparative Study.

Restoring the esthetics of anterior teeth with implants is challenging. This study aimed to evaluate the esthetic outcome of interproximal papilla between implant-restored unilateral and bilateral maxillary central incisors. A total of 56 adults with implant restorations in the maxillary central incisors were enrolled, including 40 cases of unilateral incisors and 16 cases of bilateral incisors. Photographic and radiographic assessments were performed, and patient-reported esthetic satisfaction was collected. The papilla index (PI) in the unilateral group was superior to that in the bilateral group (P = .002). Patients in the two groups reported equal satisfaction regarding the final esthetic outcome (P = .470). Statistically significant differences were noted between the two groups in papilla height (P = .000), implant-implant or implant-tooth distance (P = .002), and vertical distance from the implant platform to the bone crest (P = .000). In the bilateral group, tested variables were not correlated with PI by nonparametric Spearman correlation. In the unilateral group, the multivariate binary logistic regression model showed that incomplete papilla fill was associated with abutment type (OR = 0.019), implant-tooth distance (range, 2.1 to 6.2 mm; OR = 6.435), and distance from the bone crest to the contact point (range: 3.5 to 6.9 mm; OR = 4.589). In implant-restored maxillary central incisors, PI in the unilateral group was superior to that in the bilateral group. In the bilateral group, no clinical variable was correlated with PI. In the unilateral group, the risk of incomplete papilla fill was reduced by the customized zirconia abutment and was increased by the larger implant-tooth distance and higher distance from the bone crest to the contact point.

Cemented versus screw-retained zirconia-based single-implant restorations: 5-year results of a randomized controlled clinical trial.

ObjectivesTo compare cemented and screw‐retained one‐piece zirconia‐based restorations in terms of clinical, radiographic, and technical outcomes 5 years after insertion.Materials and methodsThirty‐four patients with single‐tooth implants were randomly restored with either a cemented lithium disilicate crown on a one‐piece customized zirconia abutment (CEM, 17 patients) or a screw‐retained crown based on a directly veneered one‐piece customized zirconia abutment (SCREW, 16 patients). All patients were recalled for a baseline examination (7–10 days after crown insertion) and then annually up to 5 years. The following outcomes were assessed: marginal bone level (changes), technical, and clinical (bleeding on probing, plaque control record, probing depth, and keratinized tissue) parameters. The Mann–Whitney U‐test was used to assess differences between the two groups.ResultsAt 5 years, 26 patients (13 in each group) were re‐examined. The survival rates on the implant and restorative levels were 100% and 82.4% (equally for both groups), respectively. At 5 years, the median marginal bone level was located at −0.15 mm (IQR: −0.89 mm; 0.27 mm) (CEM) and −0.26 mm (IQR: −0.38 mm; 0.01 mm) (SCREW) below the implant shoulder (intergroup p = .9598). The median changes between baseline and the 5‐year follow‐up amounted to −0.23 mm (CEM; intragroup p = .0002) and −0.15 mm (SCREW; intragroup p = .1465) (intergroup p = .1690). The overall technical complication rate at 5 years was 15.4% (CEM) and 15.4% (SCREW) (intergroup p = 1.00). Clinical parameters remained stable over time (baseline to 5 years).ConclusionsAt 5 years, screw‐retained and cemented restorations rendered largely the same clinical, technical, and radiographic outcomes. Technical complications were frequent in both groups.

Evaluation of the Fatigue Strength of a CAD-CAM Nanoceramic Resin Crown on Titanium and Zirconia-Titanium Abutments

A computer-aided design/computer-aided manufacturing (CAD/CAM) resin block material for restoration of single-implant abutments can be milled and cemented on an optimized standard titanium abutment as a cheaper solution or, alternatively, individualization of the crown–abutment connection is required to fulfill the same mechanical requirements. The aim of this study was to evaluate how different structural and geometric configurations of the abutment influence the resistance of a nano ceramic resin crown (NCRC). During the test, 30 implants with an internal conical tapered configuration were considered. Each implant received a standard titanium abutment: in group 1, NCRCs were directly bonded to the titanium abutments; in group 2, NCRCs were cemented on a customized zirconia framework and then cemented on a standardized titanium abutment. Three crowns of each group were submitted to a static load test until failure. The remaining crowns were submitted to a fatigue test protocol with a dynamic load. The static and dynamic test showed earlier failure for group 1. In group 1, complete breaking of NCRCs was observed for all samples, with an almost total titanium abutment exposition. In the static tests, group 2 showed a mode of failure that involved only the crown, which partially debonded from the zirconia abutment. Within the limitations of the present preliminary study, it was possible to conclude that the shape of the abutment mainly influences the fatigue strength compared to the static tensile strength. The results of the performed test show that NCRC bonded to the customized zirconia abutments, and presented a 75% survival rate when compared to the same material bonded directly to a standard titanium abutment.

The effects of provisional resin cements on the color and retentive strength of all-ceramic restorations cemented on customized zirconia abutments.

This study aimed to evaluate the effects of two types of provisional resin cements on the color and retentive strength of two different all-ceramic restorations cemented onto customized zirconia abutments. Forty-two crowns were made of monolithic zirconia and lithium disilicate ceramics (n = 21 per group) and cemented on customized zirconia abutments by using two provisional resin cements of TempBond Clear and Implantlink Semi, and TempBond serving as the control (n = 7 per cement subgroup). The specimens' color was measured before and after cementation and after thermocycling. The color difference was calculated by using CIEDE2000 formula (ΔE00). The tensile force was applied to assess the retentive strength. Kruskal-Wallis, Dunn's post-hoc, and Mann-Whitney non-parametric tests were used to compare ΔE00(1) and ΔE00(2) and two-way ANOVA followed by one-way ANOVA and Tukey's HSD post hoc test and T-test were used to compare retentive strength between subgroups. In the lithium disilicate group, ΔE00 of the control subgroup (TempBond) was significantly higher than that of Implantlink Semi cements subgroup (P = 0.001). But, in the monolithic zirconia group, ΔE00 of the control subgroup (TempBond) was significantly higher than that of Implantlink Semi (P = 0.020) and TempBond Clear cements (P = 0.007). In the monolithic zirconia group, the control subgroup (TempBond) was significantly more retentive than TempBond Clear (P = 0.003) and Implantlink Semi cement (P = 0.001). However, in the lithium disilicate group, Implantlink Semi cement was significantly more retentive than TempBond Clear (P = 0.019) and TempBond (control) (P = 0.001). The final color of both restorations was significantly affected by the provisional resin cement type. The retentive strength was influenced by both the type of cement and ceramic.

Clinical performance of implant crowns with customized zirconia abutments: A prospective cohort study with a 4.5- to 8.8-year follow-up.

To assess the clinical and esthetic outcomes and patient satisfaction of screw-retained one-piece implant crowns fabricated with zirconia abutments after a 4.5- to 8.8-year follow-up. Thirty-two patients (12 women and 20 men), who received 40 implant single crowns in anterior and premolar sites, were included in this prospective study. All restorations were based on ceramic hand-veneered customized CAD/CAM zirconia abutments. The follow-up consisted of clinical and radiological examinations. The pink esthetic score-white esthetic score (PES-WES) was used to evaluate the esthetic outcome. Patients' satisfaction was assessed via visual analog scale (VAS). Implant and prosthetic survival rates were 100% and 97.5%, respectively. Mean marginal bone loss was -0.17mm (SD 1.16mm). Probing depth was ≤4mm in 98.7% and 5mm in 1.3% of the sites; 8.3% of them were bleeding on probing positive. No technical or biological complications were observed except for one abutment fracture. The mean PES-WES scores were 7.0 and 7.1, respectively. VAS scores (10-point) of 9.41 for function and 9.26 for esthetics showed high patient satisfaction. After a mean observation period of 6years and 7months, screw-retained implant crowns based on veneered customized CAD/CAM zirconia abutments with conical connection showed very good clinical performance and may be recommended for the replacement of missing anterior and premolar teeth. (ClinicalTrials.gov # NCT04370314).

Modelagem anatômica para abutment de implante personalizado de zircônia para melhorar a estética anterior: uma técnica clínica.

Abutments são usados ​​em odontologia para conectar coroas dentárias ao implante dentário. Atualmente, o pilar customizado de zircônia é o mais utilizado em restaurações, pois oferece diversas vantagens, principalmente melhor estética e prevenção de infecções. Diversas inovações são feitas nos desenhos e procedimentos dos implantes para alcançar uma melhor estética. Este artigo tem por objetivo reltatar a confecção de um novo tipo de munhão estético em zircônia. Uma nova técnica de modificação anatômica da borda incisal do abutment para confeccionado, para criar o efeito mamelo-incisal e melhorar a estética, a combinação de cores, e replicação anatômica da estrutura incisal que se assemelha ao incisivo natural. Esta técnica apresentada ajudará o técnico de prótese dentária a obter uma coroa altamente estética com fluxo de trabalho totalmente digital sem a necessidade de estratificação de porcelana.

Influence of Screw Channel Angulation on the Fracture Resistance of Zirconia Abutments: An In Vitro Study.

The aim of this study was to investigate the effect of implant screw channel angulation on the fracture resistance of zirconia abutments without artificial aging. Ten implant replicas were embedded in a jig of autopolymerizing acrylic resin. Using a surveyor and a metallic platform, the implant replicas were mounted centrally and with an angulation of 30°. A maxillary left central incisor crown was fabricated from pattern resin and scanned. The digital design of a monolithic zirconia implant abutment-crown was completed using a 3D imaging software. For all specimens of this group (ASC25 ), the screw channel was positioned at 25° to the lingual. Following fabrication, the samples were attached onto the embedded implant replicas and manually torqued to 35 Ncm as recommended by the manufacturer. The monolithic zirconia implant abutment-crowns were mounted in a metallic platform, positioned perpendicular to the indenter, and subjected to loading until failure. Crosshead speed was set at 0.5 mm/min for the universal testing machine. Data from a similar in vitro study where straight zirconia custom abutments (ASC0 ) were subjected to static load until failure was used as a control group. An unpaired Student's t-test was used to determine if fracture resistance based on load at failure and maximum load in each group were significantly different from each other (ASC25 vs ASC0 ). Statistical significance level was inferred at p ≤ 0.05 RESULTS: Group ASC25 fractured at a mean (SD) load of 215.49 (47.10) N and a mean (SD) maximum load of 420.50 (17.18) N. Group ASC0 fractured at a mean (SD) load of 534.04 (133.77) N and a mean (SD) maximum load of 762.69 (109.59) N. The difference was statistically significant for both mean load and mean maximum load at failure (p ≤ 0.05). The survival rate of 0° zirconia abutments was significantly higher than that of 25° ASC zirconia abutments. Within the limitations of this in vitro study the mean fracture load was significantly higher in the group with a straight channel angulation.

Effect of customized zirconia abutment on peri-implant tissue: a one-year prospective study

Objective: To observe the changes of peri-implant tissue around the individualized abutment that was grinded from zirconia provisional crown in one year. Methods: In this research, a prosthodontic-driven virtual implant planning and immediate provisionalization were conducted in computer assisted design software. And computer-aided design/computer-aided manufacturing (CAD/CAM) techniques were used to fabricate the zirconia provisional crown and surgical guide template before surgery. The implant was accurately placed with the surgical guide, and the zirconia provisional crown was immediately delivered after surgery. Three months later, the implant osseointegration was completed, and zirconia provisional crown was prepared intraorally to generate customized zirconia abutment for final prosthesis. The study included 30 patients with single anterior tooth loss, including 18 males and 12 females, aged from 26 to 50 years old, and the mean age was (36.2±6.1) years old. The patients were from the Center of Oral Implantology, The First Affiliated Hospital of Zhejiang University Medical College from January 2017 to February 2018. After cementation of the final prosthesis, the cases were followed up at 6 and 12 months time intervals. Implant survival rate, probing depth, bleeding on probing, marginal bone level loss and papilla index score (PIS) were recorded in every appointment. Results: The survival rate of 30 implants was 100%, and the probing depths were less than 5 mm. The bone resorption at 6 and 12 months follow-up after the final delivery was 0 (0, 0) mm and 0 (-0.2, 0) mm, respectively, and the difference was not statistically significant (P>0.05). The PIS was 3.0 (2.0, 4.0), 3.0 (2.8, 4.0) and 3.0 (3.0, 4.0) on the final delivery, 6 and 12 months after final delivery, respectively. Conclusions: Marginal bone level and bone loss were stable with this new implant clinical protocol at the one-year follow-up.

Retentive Force of Glass-Ceramic Soldered Customized Zirconia Abutment Copings with Prefabricated Titanium Bases.

Two-piece abutments consisting of customized zirconia abutment copings and prefabricated titanium bases are popular due to their biological and esthetic advantages. Glass–ceramic solder (GS) is an alternative biocompatible connective agent. This in vitro study evaluated the retentive force of GS in comparison to classical resin composite cements (RC) after artificial aging and autoclaving. Ninety specimens consisting of prefabricated titanium bases and zirconia abutment copings were fabricated. The two parts of each specimen were fixed either by RC (n = 30) or GS with a luting space of either 30 µm (n = 30) or 100 µm (n = 30). Ten specimens of each group underwent autoclaving before artificial aging (water storage, thermocycling). Twenty specimens (including the 10 autoclaved specimens) of each group were exposed to a mechanical load. The retentive force between the zirconia and titanium in all specimens was determined. A fractographic analysis was performed to analyze the fracture surfaces of the GS specimens. The RC- and GS-connected two-piece abutments showed no relevant differences, independent of the luting space. RC appears to be more vulnerable to the thermal and mechanical loads than GS. Thus, GS may be an appropriate alternative to RC for two-piece abutments, especially for patients with enhanced biocompatibility requirements.

Implant Angulation Effect on the Fracture Resistance of Monolithic Zirconia Custom Abutments: An In Vitro Study.

To investigate the fracture resistance and performance of zirconia when employed for the fabrication of implant abutments with different angulations, simulating anterior maxillary oral rehabilitation. Forty-five monolithic zirconia custom abutments of internal conical implant connection were CAD/CAM designed and fabricated. The specimens were divided into three groups (n = 15/group) according to implant-to-abutment angulation. The angulations used were; 0°, 15°, and 25°. The abutments were loaded until failure at 135° using the Universal Testing Machine (Instron, Canton, MA). Collected data were statistically analyzed using one-way ANOVA and post hoc Tukey test. Mean (±standard deviation) load at fracture of the zirconia abutments for the three groups were 962.37 ± 93.81 N (Gr15) > 718.25 ± 93.71 N (Gr25) > 534.05 ±133.77 N (Gr0). Statistically significant difference (p < 0.0001) was found between all groups; Gr0 vs. Gr15, Gr0 vs. Gr25, Gr15 vs. Gr25. Contrary to expectations, the non-angulated monolithic zirconia abutments presented the lowest fracture resistance values. Angulating the abutments 15 or 25 degrees, following the palatal resorption pattern of the premaxilla, significantly increased the in vitro fracture resistance.

Effect of Different CAD/CAM Techniques on Marginal accuracy, Color matching and Retention of Cemented versus Screw retained Implant-supported Crowns.

Purpose: Evaluating the effect of different computer aiding designing/computer aiding manufacturing techniques on marginal accuracy, color matching and retention of cemented versus screw retained implant-supported crowns. Materials and Methods: Thirty six zirconia implant supported crowns were constructed and divided according to mode of retention into two groups (n=18/group);GpI:Implants supported crowns cement retained to customized zirconia abutments. GpII : Implant-supported crowns screwed directly to implant analogs. Each of the two groups were further subdivided according to mode of veneering into three subgroups(n=6/group).(IA)Full Contoured cement retained zirconia crowns (IB)Solid Zirconia copings veneered by Hand layering&(IC)Solid Zirconia coping veneered by Heat pressed ingots.(IIA)Full contoured screw retained zirconia crowns(IIB)&(IIC)Solid Zirconia copings manufactured and veneered as cement retained but they were screwed directly to implant analog. Marginal accuracy, color matching and retention was measured. Results :Press veneered cement retained subgroup(IC)showed the biggest marginal gap value, while full contoured screw retained subgroup(IIA)showed the smallest. Cement retained hand veneered(IB)showed the highest statistically significant color matching acceptance(50% good, 16.67% fair,33.3%adjust).Screw retained group[II] showed statistically significant lower retention mean value than cement retained group[I].The highest statistically significant retention mean value was recorded by press veneered subgroups [C] . Conclusion: While cement retained showed better color matching and resistance to dislodgment than screw retained zirconia CAD/CAM implant supported crowns but the later showed better adaptation. Full contoured showed lowest marginal gap, hand veneered showed highest color matching acceptance and press veneered showed the highest retention mean values.

Titanium implant wear from a zirconia custom abutment: A clinical report

This clinical report describes damage to a 1-piece zirconia abutment where both biological and mechanical complications developed, resulting in premature loss of the implant. Scanning electron microscopy showed significant damage to the internal connection of the implant. When using 1-piece zirconia abutments with a titanium internal connection, periodic recall and identification of wear is necessary, especially in patients with repeated screw loosening.

Phase transformation and fracture load of stock and CAD/CAM-customized zirconia abutments after 1year of clinical function.

Functional loading and low-temperature degradation may give rise to impaired clinical long-term service of zirconia implant abutments. The aim of this study was to compare the fracture strength (primary outcome measure) and the volume percentage of monoclinic surface zirconia (m-ZrO2 ) of stock and CAD/CAM-customized zirconia implant abutments that functioned clinically for 1year with geometrically identical pristine controls in an ex vivo experiment. Twenty-three stock (ZirDesign™) and 23 CAD/CAM-customized (Atlantis™) zirconia implant abutments were retrieved after 1year of clinical service. They were compared with pristine copies with respect to the volume fraction of the monoclinic phase using Raman spectroscopy and their fracture load by means of a single load-to-fracture test. Failure analysis was performed using optical and SEM microscopy. After verification of normal distribution, paired t tests were used for comparison of fracture loads between pristine and clinically aged specimen. All statistical tests employed a level of significance of α=0.05. The fracture loads of the stock zirconia abutments were significantly (p<0.05) reduced to 78.8% (SD 29.5%) after one year of clinical function. For the CAD/CAM abutments, no reduction in fracture load was found. No m-ZrO2 volume percentages beyond the detection threshold of 5% were observed in any of the samples. After 1year of clinical service, no difference in fracture strength of the CAD/CAM-customized zirconia implant abutments could be demonstrated, whereas the stock zirconia abutments decreased considerably in fracture strength. No substantial tetragonal-to-monoclinic transformation was observed.

Randomized Controlled Clinical Trial Comparing Cemented Versus Screw-Retained Single Crowns on Customized Zirconia Abutments: 3-Year Results.

To assess the biologic and technical responses to cemented and screw-retained all-ceramic single-tooth implant-supported reconstructions at 3 years postinsertion. Thirty-four patients with single-tooth implants were randomly restored with either a cemented lithium disilicate crown on a customized zirconia abutment (CEM) or a screw-retained crown with a directly veneered zirconia abutment (SCREW). At baseline examination and after 3 years of loading, marginal bone level and technical parameters were assessed. Differences in marginal bone loss were tested using Mann-Whitney U test at baseline and at 3 years, and changes within each group between baseline and 3 years were tested using Wilcoxon signed rank test. The median changes between baseline and the 3-year follow-up amounted to -0.1 mm (CEM; intragroup P = .36) and -0.0 mm (SCREW; intragroup P = .58). Intergroup comparisons did not reveal statistically significant differences at 3 years (P = .20) or over time (P = .70). At 3 years, screw-retained and cemented reconstructions rendered largely the same radiographic and technical outcomes.

Randomized Controlled Clinical Trial of All-Ceramic Single-Tooth Implant Reconstructions Using Modified Zirconia Abutments: Results at 5 Years After Loading

The objective of this trial study was to assess whether submucosal veneering of internally connected zirconia abutments influences clinical, radiographic, and technical outcomes of single-tooth implant-borne reconstructions at 5 years after loading. A total of 20 patients with 20 single-tooth implants in the anterior or premolar area of the maxilla or mandible were included. The implants were randomly restored with fixed single-tooth reconstructions using either pink-veneered customized zirconia abutments (test group = 10) or nonveneered customized zirconia abutments (control group = 10). All reconstructions were adhesively cemented with all-ceramic crowns. Follow-up examinations were performed at baseline (7 to 10 days after crown insertion) and at 1, 3, and 5 years after loading, at which points the following were assessed: periodontal parameters such as probing depth (PD), bleeding on probing (BOP), and marginal bone levels, as well as technical outcomes using the modified United States Public Health Service (USPHS) criteria. Statistical comparisons were based on the Wilcoxon-Mann-Whitney test. Sixteen patients attended the 5-year follow-up. At 5 years, the implant survival rate was 100% and the prosthetic survival rate was 94.1% (one abutment fracture in the test group). Veneering of the submucosal part of zirconia abutments resulted in significantly higher mean PD values: 3.6 ± 0.4 mm (test group) and 3.0 ± 0.5 mm (control group), P = .042. Marginal bone levels at 5 years and changes up to 5 years were not significantly different between groups (P > .05). One crown exhibited an abutment fracture and two crowns a minor chipping (17.6% overall technical complication rate). Limited by a small sample size, veneering of the submucosal part of internally connected zirconia abutments led to outcomes that were less favorable biologically (PD, BOP, and KM), but similar to nonveneered abutments radiographically and technically.

Fits of Implant Zirconia Custom Abutments and Frameworks: A Systematic Review and Meta-Analyses.

The aim of this systematic review and meta-analyses was to evaluate fits of zirconia custom abutments and frameworks on implants and to identify the factors that influence their fits. An electronic search was conducted through PubMed (MEDLINE), Google Scholar, and Cochrane Central Registrar of Controlled Trials. The search was completed in August 2017. Series of meta-analyses were conducted to compare fits of zirconia custom abutments and frameworks on implants with metal abutments and frameworks. The interest variables were the interface gap and the rotational misfit of abutments and the vertical fit of frameworks. Initially, a total of 672 articles were identified from the electronic search. After applying the inclusion criteria, 17 suitable articles were selected, including 9 studies on the fit of zirconia custom abutments and 8 studies on the fit of zirconia frameworks. There is a tendency for zirconia abutments to exhibit greater interface gaps and rotational misfits than metal abutments. Abutments produced by manual-aided designs/manual-aided manufacturing (MAD/MAM) exhibited inferior fits compared with those produced by computer-aided design/computer-aided manufacturing (CAD/CAM). Proprietary abutments had superior fits compared with non-proprietary abutments. Milled zirconia frameworks had insignificantly inferior fits compared with milled metal frameworks. Within the limitations of this study, custom zirconia abutments and non-proprietary abutments appeared to exhibit slightly inferior fits compared with metal abutments or abutments produced by the same implant company. However, the clinical significance of this difference is yet to be determined. The fit of milled zirconia frameworks is generally comparable to milled metal frameworks.

Early histological, microbiological, radiological, and clinical response to cemented and screw-retained all-ceramic single crowns.

To assess the early histological, microbiological, radiological, and clinical response to cemented and screw-retained all-ceramic single-tooth implant-supported reconstructions. Patients with single-tooth implants were randomly allocated to receive a cemented lithium disilicate crown on a customized zirconia abutment (CEM) or a screw-retained crown with a directly veneered zirconia abutment (SCREW). At the screening visit, at crown insertion and at the 6-month follow-up, clinical parameters were measured at the implant and the contralateral tooth. Marginal bone levels, technical parameters, and esthetic outcomes were measured at the implants. At the 6-month follow-up, a microbiological test was performed and a soft tissue biopsy was harvested at the implants for histological analysis. Inflammatory cells and fibroblasts/-cytes were analyzed at the level of the sulcular epithelium, junctional epithelium, and connective tissue. The histological parameters were analyzed by means of a linear mixed model. Thirty-three patients completed the study, and implant and crown survival rates were 100% at 6months. Histologically, the number of inflammatory cells tended to be higher in group CEM (p>0.05). Moreover, significantly less inflammatory cells and fibroblasts/-cytes were found in the sulcular epithelium compared to the junctional epithelium and supracrestal connective tissue (p<0.001). Four patients were tested positive for periodontal marker pathogens at the 6-month follow-up, and three of them belonged to group CEM. From crown insertion to the 6-month follow-up, median marginal bone levels changed only minimally and measured 0.31 and 0.32mm in group CEM and 0.47 and 0.36mm in group SCREW, respectively. Clinical and esthetic parameters remained stable over time and were comparable between natural teeth and implants as well as between the groups. Cemented reconstructions were associated with more inflammatory cells, and more patients were diagnosed with periodonto-pathogens. Both types of reconstructions resulted in similar radiological (marginal bone levels) and clinical outcomes (bleeding on probing and probing depth).

Fracture loads and failure modes of customized and non-customized zirconia abutments

ObjectiveThis study aimed to evaluate the fracture load and pattern of customized and non-customized zirconia abutments with Morse-taper connection. Methods18 implants were divided into 3 groups according to the abutments used: Zr — with non-customized zirconia abutments; Zrc — with customized zirconia abutments; and Ti — with titanium abutments. To test their load capacity, a universal test machine with a 500-kgf load cell and a 0.5-mm/min speed were used. After, one implant-abutment assembly from each group was analyzed by Scanning Electron Microscopy (SEM). For fractographic analysis, the specimens were transversely sectioned above the threads of the abutment screw in order to examine their fracture surfaces using SEM. ResultsA significant difference was noted between the groups (Zr=573.7±11.66N, Zrc=768.0±8.72N and Ti=659.1±7.70N). Also, the zirconia abutments fractured while the titanium abutments deformed plastically. Zrc presented fracture loads significantly higher than Zr (p=0.009). All the zirconia abutments fractured below the implant platform, starting from the area of contact between the abutment and implant and propagating to the internal surface of the abutment. All the zirconia abutments presented complete cleavage in the mechanical test. Fractography detected differences in the position and pattern of fracture between the two groups with zirconia abutments, probably because of the different diameters in the transmucosal region. SignificanceCustomization of zirconia abutments did not affect their fracture loads, which were comparable to that of titanium and much higher than the maximum physiological limit for the anterior region of the maxilla.