Retentive strength of two-piece CAD/CAM zirconia implant abutments

In vitro assessment of cementation of CAD/CAM fabricated prostheses over titanium bases. A systematic review

OBJECTIVES

The objective of this study is to investigate the outcomes of clinically relevant laboratory studies regarding the cementation of implant-supported restorations over ti-bases.

MATERIALS AND METHODS

The present study has been conducted according to PRISMA statement. An electronic search was performed, including publications up to March 2024, to identify studies investigating the parameters affecting the cementation between ti-bases and CAD/CAM prostheses. An assessment of the internal validity was performed, using a custom-made risk of bias tool (QUIN).

RESULTS

From the included studies, 40.1% were reported on luting systems, 25% on ti-base surface treatment, 25% on restoration surface, 21.8% on restoration material, and 18.7% on ti-base height. The majority of the included studies were associated with a medium risk of bias. In the absence of micro-retentive features, air-abrasion of ti-bases with a minimum height of 3.5 mm can be beneficial for restoration's retention. The bonding performance can vary not only between different bonding systems but also for different applications within the same system, based on a restoration's material and surface treatment as well as on ti-base height and surface treatment.

CONCLUSIONS

The height of the ti-base seems to be the prevailing factor as it constitutes the prerequisite for other modifications of the bonding surfaces to have an advantageous effect. Since the parameters that can affect bonding performance between ti-base and restoration can interact with each other, it is important for the clinician to focus on verified bonding protocols.

Effect of cement type, luting protocol, and ceramic abutment material on the shade of cemented titanium-based lithium disilicate crowns and surrounding peri-implant soft tissue: a spectrophotometric analysis

PURPOSE

The objective of the study was to analyze the impact of cement, bonding pretreatment, and ceramic abutment material on the overall color results of CAD-CAM ceramic crowns bonded to titanium-based hybrid abutments.

MATERIALS AND METHODS

For single implant restoration of a maxillary lateral incisor a total of 51 CAD-CAM-fabricated monolithic lithium disilicate crowns were fabricated and subsequently bonded onto 24 lithium disilicate Ti-base abutments, 24 zirconia Ti-base abutments and 3 resin abutment replicas as a control group. The 48 copings were cemented with three definitive and one provisional cement on both grit-blasted and non-blasted Ti-bases. The color of each restoration and surrounding artificial gingiva was measured spectrophotometrically at predefined measuring points and the CIELAB (ΔEab) color scale values were recorded.

RESULTS

The color outcome of ceramic crowns bonded to hybrid abutments and soft tissues was affected differently by cements of different brands. Grit-blasting of Ti-bases prior to cementing CAD-CAM copings affected the color results of all-ceramic crowns. There was a significant difference (P = .038) for the median ΔE value between blasted and non-blasted reconstructions at the cervical aspect of the crown. Full-ceramic crowns on zirconia Ti-base abutments exhibited significantly lower ΔE values below the threshold of visibility (ΔE 1.8). In all subcategories tested, the use of a highly opaque temporary cement demonstrated the lowest median ΔE for both the crown and the artificial gingiva.

CONCLUSION

Various cements, core ceramic materials and airborne particle abrasion prior to bonding can adversely affect the color of Ti-base supported ceramic crowns and peri-implant soft tissue. However, zirconia CAD-CAM copings and an opaque cement can effectively mask this darkening.

Effects of sterilization, conditioning, and thermal aging on the retention of zirconia hybrid abutments: A laboratory study

OBJECTIVE

To investigate the effects of sterilization, conditioning method, and thermal aging on the retentive strength of two-piece zirconia abutments.

MATERIALS AND METHODS

In total, 128 stock zirconia abutments were divided into four groups (n = 32) according to the conditioning parameters: (A) air-abrasion using 50 μm alumina particles/1.0 bar, (B) 50 μm/2.0 bar, (C) 100 μm/1.0 bar, and (D) 100 μm/2.0 bar. All abutments were bonded onto titanium bases using DTK adhesive resin and stored in water bath (37°C) for 72 h. Each group was subdivided into two subgroups (n = 16), group 1 was disinfected, whereas group 2 followed disinfection and autoclave sterilization. Half of the specimens of each subgroup (n = 8) was directly subjected to the axial retention test (groups N), while the other half was first subjected to 150 days of thermocycling followed by retention test (groups T). Statistical analysis was performed with three-way ANOVA, additional statistical analysis was performed by using separate one-way ANOVAs followed by the Tukey's post-hoc test for post hoc pairwise comparisons among groups.

RESULTS

The highest median retention strength was recorded for group B2N (1390 N), whereas the lowest strength was recorded for group C1T (688 N). No significant interaction (p ≥ 0.05) was detected between the different variables; conditioning method, sterilization, and the thermal cycling regarding the effect on the resulting retention. However, the sterilization always showed a positive effect. Thermocycling presented an adversely significant effect only in the absence of sterilization (p < 0.05), with the exception of subgroups A. For the sterilized groups, thermocycling had no statistically significant effect on the retention.

CONCLUSION

Steam autoclaving increased the retention of hybrid zirconia abutments. DTK adhesive resin for two-piece zirconia abutments performed well after sterilization and thermocycling.

Do strength of zirconia-abutment-interfaces depend on cement, zirconia type and titanium abutment dimensions?

OBJECTIVES

Part 1 of this study investigates the influence of zirconia types, chimney heights, and gingival heights on the strength of the zirconia-abutment-interface. Part 2 extends the analysis to include adhesive brands and macro-retentions.

METHODS

In Part 1, the study utilized three zirconia types (700 MPa, 1000 MPa, 1200 MPa) to fabricate 234 screw-retained zirconia crowns with varying chimney heights (3.5 mm, 4.1 mm, 5 mm) and gingival heights (0.65 mm, 1.2 mm, 3 mm) of the titanium abutments. All adherend surfaces underwent sandblasting with aluminum oxide before cementation with a specific resin cement. In Part 2, the investigation of 240 screw-retained zirconia crowns focused on a single zirconia type (1000 MPa) with chimney heights of 3.5 mm and 5 mm and a gingival height of 0.65 mm of the titanium abutments, cemented with three different resin cements. All adherent surfaces underwent sandblasting with aluminum oxide before cementation, whereas 120 out of 240 abutments received additional macro retentions. Storage in water at 37 °C for 24 h preceded the tensile test.

RESULTS

The study revealed a substantial impact of chimney height and zirconia type on the bond strength of the zirconia-abutment-interface. Neither adhesive brands nor macro retentions significantly impacted the bond strength. Fracture incidence was significantly influenced by gingival height and zirconia type in part 1, whereas in part 2 smaller chimney heights correlated with a higher fracture incidence.

SIGNIFICANCE

This study contributes insights into the complex interplay of factors influencing the zirconia-abutment-interface. The results provide a foundation for refining clinical approaches, emphasizing the importance of chimney height and zirconia type in achieving successful anterior gap implant restorations.

Fracture resistance of hybrid ceramic abutments with different restoration lengths: A pilot study

AIM

In this pilot study, the fracture resistance of hybrid abutments with different restoration lengths was investigated.

MATERIALS AND METHODS

Sixteen monolithic zirconia restorations of an upper right incisor were designed to fit a titanium base abutment. Eight central incisors had a crown length of 8 mm (T1) and the other half a length of 12 mm (T2). All crowns were cemented on the titanium base using a resin cement. After cementation, the samples were placed in a thermocycler for 5000 cycles. Fracture strength was measured using a universal test machine. Deformations and fractures of the samples were investigated.

RESULTS

The mean fracture resistance of T1 was 515 N (SD 96 N, 339-650) and 305 N (SD 57 N, 234-408) for T2 (p < 0.001). Both groups showed deformation of the titanium base, with no significant difference between both groups (p = 0.200). A difference in fracture type (p = 0.013) was observed, with significantly more screw fractures occurring in group T1 (p = 0.026).

CONCLUSION

Within the limitations of this study, hybrid restorations with standard titanium base abutments can withstand forces that have been associated with chewing, irrespective of the crown length. However, the shorter crowns demonstrated more fatal fractures.

Clinical performance of implant-supported single hybrid abutment crown restoration: A systematic review and meta-analysis

PURPOSE

To investigate survival rates and technical and biological complications of one-piece screw-retained hybrid abutments in implant-supported single crowns (SCs).

STUDY SELECTION

An electronic search was performed on five databases for clinical studies involving implant-supported single hybrid abutment crowns constructed using titanium-base (Ti base) abutments, with at least 12 months of follow-up. The RoB 2, Robins-I, and JBI tools were used to assess the risk of bias for the different study types. Success, survival, and complication rates were calculated, and a meta-analysis was performed to obtain a pooled estimate. Peri-implant health parameters were extracted and analyzed.

RESULTS

22 records (20 studies) were included in this analysis. Direct comparisons between screw-retained hybrid abutment SCs and cemented SCs showed no significant differences in the 1-year survival and success rates. For SCs using a hybrid abutment crown design, their 1-year survival rate was 100% (95% CI: 100%-100%, I2 = 0.0%, P = 0.984), and a success rate of 99% (95% CI: 97%-100%, I2 = 50.3%, P = 0.023) was calculated. No confounding variables significantly affected the estimates. The individual technical complication rate was low at 1-year follow-up. The estimated incidence of all types of complications in hybrid abutment SCs is less than 1%.

CONCLUSIONS

Within the limitations of this study, implant-supported SCs using a hybrid abutment crown design showed favorable short-term clinical outcomes. Additional well-designed clinical trials with at least a 5-year observation period are required to confirm their long-term clinical performance.

Clinical performance of monolithic lithium disilicate hybrid abutment crowns over at least 3.5 years

PURPOSE

Hybrid abutment crowns (HACs) made from monolithic ceramics represent an efficient option for single restorations on implants. However, long-term data are scarce. The purpose of this clinical trial was to evaluate the survival and complication rates of CAD-CAM fabricated HACs over a time period of at least 3.5 years.

MATERIALS AND METHODS

Twenty-five patients with a total of 40 HACs made of monolithic lithium disilicate ceramic bonded to a titanium base CAD-CAM abutment were retrospectively evaluated. All implants and screw-retained restorations were placed and manufactured in the same department of a university hospital. Only crowns that had been in service for more than 3.5 years were included in the study. HACs were evaluated regarding technical and biological complications. Functional Implant Prosthodontic Scores (FIPS) were obtained.

RESULTS

The mean observation time was 5.9 ± 1.4 years. Implant survival was 100%, and HAC survival was 97.5%. Over the observation period, one crown fracture was observed, necessitating refabricating of the restoration. Three minor biological complications were found. The overall mean FIPS score was 8.69 ± 1.12 points.

CONCLUSIONS

Within the limitations of this study, monolithic screw-retained HACs milled from lithium disilicate ceramics and bonded to titanium bases appeared to be a reliable treatment option over more than 3.5 years due to their low biological and technical complication rates.

Implant-Supported Fixed Partial Dentures with Posterior Cantilevers: In Vitro Study of Mechanical Behavior

Rehabilitation with dental implants is not always possible due to the lack of bone quality or quantity, in many cases due to bone atrophy or the morbidity of regenerative treatments. We find ourselves in situations of performing dental prostheses with cantilevers in order to rehabilitate our patients, thus simplifying the treatment. The aim of this study was to analyze the mechanical behavior of four types of fixed partial dentures with posterior cantilevers on two dental implants (convergent collar and transmucosal internal connection) through an in vitro study (compressive loading and cyclic loading). This study comprised four groups (n = 76): in Group 1, the prosthesis was screwed directly to the implant platform (DS; n = 19); in Group 2, the prosthesis was screwed to the telescopic interface on the implant head (INS; n = 19); in Group 3, the prosthesis was cemented to the telescopic abutment (INC; n = 19); and in Group 4, the prosthesis was cemented to the abutment (DC; n = 19). The sets were subjected to a cyclic loading test (80 N load for 240,000 cycles) and compressive loading test (100 KN load at a displacement rate of 0.5 mm/min), applying the load until failure occurred to any of the components at the abutment-prosthesis-implant interface. Subsequently, an optical microscopy analysis was performed to obtain more data on what had occurred in each group. Results: Group 1 (direct screw-retained prosthesis, DS) obtained the highest mean strength value of 663.5 ± 196.0 N. The other three groups were very homogeneous: 428.4 ± 63.1 N for Group 2 (INS), 486.7 ± 67.8 N for Group 3 (INC), and 458.9 ± 38.9 N for Group 4 (DC). The mean strength was significantly dependent on the type of connection (p < 0.001), and this difference was similar for all of the test conditions (cyclic and compressive loading) (p = 0.689). Implant-borne prostheses with convergent collars and transmucosal internal connections with posterior cantilevers screwed directly to the implant connection are a good solution in cases where implant placement cannot avoid extensions.

Effect of different surface treatments on the retention force of additively manufactured interim implant-supported crowns

PURPOSE

To compare the effect of different pre-cementation surface treatments and bonding protocols on the retention force of additively manufactured (AM) implant-supported interim crowns.

MATERIAL AND METHODS

A total of 50 AM interim crowns (Temporary CB resin) were cemented on implant abutments. Five groups (n = 10) were established based on the different surface pre-treatments performed in the intaglio surface of the specimens: no surface pre-treatment (Group C or control), air-abraded with 50-μm aluminium oxide particles (Group AP), air-abraded with 50-μm aluminium oxide particles followed by the application of silane (Group AMP), silane (Group MP), and air-abraded with 30 μm silica-coated aluminum oxide particles followed by the application of silane (Group CMP). Each specimen was cemented into an implant abutment using a composite resin cement (Rely X Unicem2). Afterward, the specimens underwent retention testing with a Universal Instron machine. Pull-off forces (N) and modes of failure were registered. Statistical analysis was performed using Mann-Whitney U tests with Bonferroni corrections for multiple tests (α = 0.05).

RESULTS

The median retention force values were 233.27 ±79.28 N for Group Control, 398.59 ±68.59 N for Group MP, 303.21 ±116.80 N for Group AMP, 349.31 ±167.73 N for Group CMP, and 219.85 ± 55.88 N for Group AP. The pull-off forces were significantly greater for Group MP, while the differences between the remaining groups were not statistically significant (P > 0.05). Group AP showed the lowest retention force values among all the groups. Failure modes after the pull-off testing were predominantly adhesive and substrate failure of the AM interim material.

CONCLUSIONS

The surface treatment of the intaglio AM crown tested significantly influenced the retention force values measured. Pre-treatment with an MDP-containing silane improved the retentive force values computed, whereas pre-treatment with 50-μm Al2 O3 air-particle abrasion alone is not recommended prior to cementation on a titanium-based implant abutment.

Effects of Surface Treatments and Cement Type on Shear Bond Strength between Titanium Alloy and All-Ceramic Materials

This study aimed to evaluate the effects of surface treatments and resin cement on the adhesion of ceramic and ceramic-like materials to titanium. A total of 40 specimens (5 mm diameter) of each material (lithium disilicate glass ceramic (LDGC-IPS e.maxCAD), lithium silicate glass ceramic (LSGC-VITA Suprinity) and a polymer-infiltrated ceramic network (PICN-Vita Enamic)) were fabricated using CAD/CAM technologies. In total, 120 titanium (Ti) specimens were divided into 12 groups, and half of the titanium specimens were tribochemically coated using CoJet. The titanium and all-ceramic specimens were cemented using either Self-curing adhesive cement (SCAC-Panavia 21) or a Self-curing luting composite (SCLC-Multilink Hybrid Abutment). After 5000 cycles of thermal aging, the shear bond strength (SBS) test was conducted using a universal testing machine. The failure modes of the specimens were analyzed using stereomicroscopy, and additionally, the representative specimens were observed using Scanning Electron Microscopy. ANOVA was used for the statistical analysis (p < 0.05). The post-hoc Duncan test was used to determine significant differences between the groups. The mean SBS values (mean ± STD) ranged from 15 ± 2 MPa to 29 ± 6 MPa. Significantly higher SBS values were acquired when the titanium surface was tribochemically coated (p < 0.05). The SCLC showed higher SBS values compared to the SCAC. While the LDGC showed the highest SBS values, the PICN presented the lowest. The tribochemical coating on the cementation surfaces of the titanium increased the SBS values. The specimens cemented with the SCLC showed higher SBS values than those with the SCAC. Additionally, the SCLC cement revealed a more significant increase in SBS values when used with the LDGC. The material used for restoration has a high impact on SBS than those of the cement and surface conditioning.

Evaluation of debonding force of screw-retained lithium disilicate implant-supported crowns cemented to abutments of different designs and surface treatments

STATEMENT OF PROBLEM

Straight preparable abutments provide an alternative to titanium bases (Ti-bases) for single-unit screw-retained implant-supported restorations. However, the debonding force between crowns with a screw access channel cemented to preparable abutments and Ti-bases of different designs and surface treatments is unclear.

PURPOSE

The purpose of this in vitro study was to compare the debonding force of screw-retained lithium disilicate implant-supported crowns cemented to straight preparable abutments and Ti-bases of different designs and surface treatments.

MATERIAL AND METHODS

Forty laboratory implant analogs (Straumann Bone Level) were embedded into epoxy resin blocks that were randomly divided into 4 groups (n=10 each) according to the abutment type used: CEREC group, Variobase group, airborne-particle abraded Variobase group, and airborne-particle abraded straight preparable abutment group. All specimens were restored with lithium disilicate crowns and cemented with resin cement to the corresponding abutments. They were thermocycled (from 5 to 55 °C for 2000 cycles) followed by cyclic loading (120 000 cycles). The tensile forces required to debond the crowns from the corresponding abutments were measured (N) by using a universal testing machine. The Shapiro-Wilk test of normality was used. Comparison between the study groups was done with 1-way ANOVA (α=.05).

RESULTS

Tensile debonding force values were significantly different according to the type of abutment used (P<.05). The highest retentive force value was recorded in the straight preparable abutment group (928.1 ±222.2 N) followed by the airborne-particle abraded Variobase group (852.6 ±164.6 N), and the CEREC group (498.8 ±136.6 N); the lowest value was reported in the Variobase group (158.6 ±85.2 N).

CONCLUSIONS

The retention of screw-retained lithium disilicate implant-supported crowns cemented to airborne-particle abraded straight preparable abutments is significantly higher than to non-surface treated Ti-bases and similar to airborne-particle abraded ones. Abrading abutments with 50-mm Al2O3 significantly increased the debonding force of the lithium disilicate crowns.

Mechanical stability of angulated zirconia abutments supporting maxillary anterior single crowns on narrow-diameter implants

OBJECTIVES

To investigate the fracture strength of angulated hybrid abutments supporting anterior single crowns on narrow-diameter implants (NDIs).

MATERIAL AND METHODS

Zirconia abutment with angulations of labial inclination 0° (TZ0Z), 15° (TZ15Z), 30° (TZ30Z) and palatal inclination 15° (TZ - 15Z) was designed on 3.3-mm titanium-zirconium (Ti-Zr) NDIs. Titanium abutment connected with Ti-Zr implant (TZ0T) and 0° zirconia abutment connected with pure titanium (Ti) implant (T0Z) were control groups. Thirty-six un-restored abutments and 36 abutments restored with highly translucent zirconia (HTZ) crowns were tested. Failure loads were compared among 6 groups, and bending moments were calculated for comparison between un-restored and restored abutments.

RESULTS

Failure loads of un-restored abutments were affected by the abutment angle. Sixty-seven percent samples in TZ30Z and 83% samples in TZ - 15Z group fractured at the thinnest part of the zirconia abutment and exhibited lower failure load (p < .05). Failure loads of restored abutments were close to or exceeded the maximum bite force of anterior teeth, and no differences were found among six groups (p > .05). Except TZ15Z and TZ0T group, the bending moment increased with the crown construction, especially for TZ30Z and TZ - 15Z groups (p < .001).

CONCLUSIONS

The fracture strength of hybrid abutments restored with HTZ crown on Ti-Zr NDIs exceeded the bite forces of anterior teeth for all the groups and were not affected by the abutment angle.

CLINICAL RELEVANCE

In terms of fracture strength, Ti-Zr NDIs combined with angulated hybrid abutments and HTZ crowns can be used in the anterior region.

Evaluation of the effect of anodization-colored titanium abutments and zirconia substructure thickness on zirconia substructure color: An In vitro study

BACKGROUND AND AIM

The aim of this study is to evaluate the effect of anodized titanium abutments and zirconia substructure thickness on the color of zirconia substructure.

MATERIALS AND METHODS

In this study, an electrochemical anodization setup was prepared for titanium coloring. Commercial titanium, anodization-colored yellow and pink titanium, and zirconia were used as different abutment specimens. Thirty zirconia discs in 0.7, 0.9, and 1.1 mm thickness were prepared from zirconia blocks as zirconia substructure specimens (n = 10). Zirconia substructure specimens of different thicknesses were placed on abutment specimens of different colors and L*, a*, b* values were measured with a spectrophotometer device. Color difference (ΔE) was calculated according to the CIELab formula by comparing the L*, a*, and b* values obtained on the zirconia abutment with the L*, a*, and b* values obtained on the other abutments. Statistical analyzes were performed with two-way analysis of variance and Tukey Honestly Significant Difference (HSD)test (p < 0.05).

RESULTS

The increase in the thickness of the substructure resulted in a statistically significant difference on ΔE, L*, a*, and b* values (p < 0.001). The effect of abutment color had no significant effect on ΔE values. The highest ΔE value was 18.10 at zirconia substructure with 0.7 mm thickness when paired with pink-anodized titanium abutment specimens.

CONCLUSION

The thickness of zirconia substructure and the color of titanium abutments affect zirconia substructure color.

Abutment on Titanium-Base Hybrid Implant: A Literature Review

An increase in the use of Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) technologies challenges the conventional prosthetic fabrication procedures that are practical and centered on a digital workflow for the patient, especially for dental implants. Increasing workflow of digital restoration work, considering computer-used CAM for restoration technology systems and also fast/CAM for building restoration technology; fast/CAD, also known as abut-Base, has increased interest. Studies on adaptation of different restorative materials, on titanium (Ti)-base abutments, traction, and transformed cycling have become relevant. The objective of this work was to research, through literature studies, on restoration-type abutments. A total of 24 articles were found after searching the following terms in PubMed/Medline, Scopus, and Embase databases: “ti-base AND abutment.” Twenty-one manuscripts selected from the inclusion and exclusion criteria. After an analysis of these articles, it was concluded that the Ti-base abutment and components from the same manufacturer as the Implant should be used preferably; milled monolithic crowns designed to adapt to the Ti-base the hybrid abutment-crown assembly does not affect torque maintenance after thermal aging; the saliva and cleaning protocol of the Ti-base bonding surfaces can influence the operations of the Ti-base crowns; Ti-base and Crown surface treatment is recommended for better applicability and stability results, and the superiority of resin-based cements compared with other types of cements.

Titanium Base Abutments in Implant Prosthodontics: A Literature Review

Implant abutments are essential components in restoring dental implants. Titanium base abutments were introduced to overcome issues related to existing abutments, such as the unesthetic appearance of titanium abutments and the low fracture strength of ceramic abutments. This study aimed to comprehensively review studies addressing the mechanical and clinical behaviors of titanium base abutments. A search was performed on PubMed/MEDLINE, Web of Science, Google Scholar, and Scopus databases to find articles that were published in English until December 2020 and that addressed the review purpose. A total of 33 articles fulfilled the inclusion criteria and were included for data extraction and review. In vitro studies showed that titanium base abutments had high fracture strength, adequate retention values, particularly with resin cement, and good marginal and internal fit. Although the clinical assessment of titanium base abutments was limited, they showed comparable performance with conventional abutments in short-term evaluation, especially in the anterior and premolar areas. Titanium base abutments can be considered a feasible treatment option for restoring dental implants, but long-term clinical studies are required for a better assessment.

Bond durability and surface states of titanium, Ti-6Al-4V alloy, and zirconia for implant materials

PURPOSE

Screw-retained implant crowns used as dental implants comprise a zirconia coping and titanium base bonded using resin cement. These devices are prone to debonding failures. This study investigated the bond characteristics of implant materials based on shear bond strength (SBS) and surface characteristics.

METHODS

Chemically pure (CP) titanium grade-4 (Ti), Ti-6Al-4V alloy (Ti-6Al-4V), and tetragonal polycrystalline zirconia (zirconia) were evaluated as adherent materials. Plates of each material were polished, primed for the respective resin cements, and cemented using either methyl methacrylate-based resin cement (Super-Bond) or composite-based resin cement (Panavia). The cemented samples were subjected to 10,000 thermocycles alternating between 5 and 55 °C, and the SBS were obtained before and after thermocycling. The sample surfaces were characterized based on surface observations, roughness, and free energy (SFE).

RESULTS

The SBSs of all materials bonded using Panavia were significantly compromised during thermocycling and reached zero. Although the SBSs of Ti and Ti-6Al-4V bonded using Super-Bond were not significantly affected by thermocycling, those of zirconia decreased significantly. The bond durability between zirconia and Super-Bond was improved via alumina air-abrasion, which caused no significant loss of SBS after thermocycling. Surface analyses of the air-abraded zirconia validated these results and confirmed that its surface roughness and SFE were significantly increased.

CONCLUSIONS

The bond durability between resin cement and zirconia was lower than that between Ti and Ti-6Al-4V. The alumina air-abrasion pretreatment of zirconia improved the SFE and surface roughness, thereby enhancing bond durability.

Investigation of the Effect of Abutment Angle Tolerance on the Stress Created in the Fixture and Screw in Dental Implants Using Finite Element Analysis

Today, an artificial tooth root called a dental implant is used to replace lost tooth function. Treatment with dental implants is considered an effective and safe method. However, in some cases, the use of dental implants had some failures. The success of dental implants is influenced by several biomechanical factors such as loading type, used material properties, shape and geometry of implants, quality and quantity of bone around implants, surgical method, lack of rapid and proper implant surface's integration with the jaw bone, etc. The main purpose of functional design is to investigate and control the stress distribution on dental implants to optimize their performance. Finite element analysis allows researchers to predict the stress distribution in the bone implant without the risk and cost of implant placement. In this study, the stresses created in the 3A.P.H.5 dental implant's titanium fixture and screw due to the change in abutment angles tolerance have been investigated. The results show that although the fixture and the screw's load and conditions are the same in different cases, the change of the abutment angle and the change in the stress amount also made a difference in the location of maximum stress. The 21-degree abutment puts the fixture in a more critical condition and increases the chance of early plasticization compared to other states. The results also showed that increasing the abutment angle to 24 degrees reduces the stress in the screw, but decreasing the angle to 21 degrees leads to increased screw stress and brings it closer to the fracture.

In vitro evaluation of the influence of titanium nitride coating on the retention force between components of two-part abutments

Background

Two-part abutments are typically made up of a base composed of titanium and a ceramic build-up. The long-term outcomes are affected by the mechanical durability. The purpose of the present investigation was to evaluate and compare the retention force of two-part abutment systems with titanium or titanium nitride bases—as fixed with zirconia components and with various surface treatments.

Methods

A total of 60 two-part abutments were investigated—with a titanium base (n = 30) or titanium nitride coated bases (n = 30) and bonded with zirconia ceramic build-ups. The bonding surfaces were treated with aluminium oxide blasting, with an average particle size of 110 µm. The titanium bases were then pretreated with Alloy Primer or Clearfil Ceramic Primer. The ceramic build-ups were only treated with Clearfil Ceramic Primer. For twenty test specimens, no chemical pretreatment was performed. Test specimens were classified into six groups in accordance with the pretreatment (A–F; n = 10). A resin-based luting agent was employed to attach the two parts. Specimens were then subjected to artificial thermal aging (10⁴ cycles with 5 °C/55 °C). The retention force between the two parts was then investigated with a pull-off test. The findings were analyzed by ANOVA statistics. Fracture patterns were examined by electron microscopy.

Results

In the absence of primer, titanium nitride coated bases gave significantly greater retention forces than other samples (p < 0.05). Chemical preconditioning with silane coupling agents did not effect on the retention force of coated bases.

Conclusions

The results of the current study suggested that modifying metal surfaces by coating the base with titanium nitride not only has esthetic and biological advantages, but also enhances the mechanical properties of the adhesive bond of two-part abutments.

Effects of silica sputtering on adhesion between zirconia and composite resin cores

Radiofrequency magnetron sputtering of silicon was applied onto zirconia surfaces by use of a non-doped Si wafer at 2%, 5%, 8%, and 10% oxygen volumes. Immediately after sputtering, the contact angle was practically 0 for all oxygen volume specimens. In terms of sustainability of the hydrophilicity, however, 5% oxygen volume was found to be optimal. Scanning electron microscopy and energy dispersive X-ray spectroscopy clearly suggested the presence of silica layer on zirconia surfaces. The shear bond strength of the pre-treated zirconia and resin was 35.03±4.97 MPa, which was approximately 3.5 times higher than that of zirconia without any sputtering treatment (9.26±1.21 MPa). The failure mode of the pre-treated zirconia specimen was cohesive failure, whereas that of the control specimen was observed to be interface failure.

Influence of luting space of zirconia abutment on marginal discrepancy and tensile strength after dynamic loading

STATEMENT OF PROBLEM

Although luting space is related to the marginal fit of indirect restorations, information on its influence on the marginal fit and tensile strength of zirconia abutments bonded to titanium bases is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of luting space on the marginal discrepancy and tensile strength of zirconia abutments bonded to a titanium base after dynamic loading.

MATERIAL AND METHODS

Ninety implant replicas were embedded in resin blocks to attach 4-mm-high titanium luting bases. Zirconia abutments (Ceramill Zolid FX) were fabricated with different internal luting spaces: 25 μm (G25), 50 μm (G50), or 75 μm (G75). The zirconia abutments were cemented on the titanium bases by using a resin cement (Panavia F 2.0) under a constant load of 20 N. The marginal discrepancy and internal fit of 10 random specimens from each group were evaluated with a stereoscopic microscope at ×50 magnification. The remaining specimens were submitted to the tensile strength test in which half were evaluated after dynamic loading (1.2 million cycles of 200 N at 3.8 Hz) in a mechanical fatigue machine. The tensile strength test was performed using a pullout apparatus coupled to a universal testing machine at a crosshead speed of 0.5 mm/min. The mode of failure was determined by observation at ×50 magnification under a stereomicroscope and classified into adhesive or mixed. The groups were compared by using 2-way ANOVA and the Tukey HSD test (α=.05).

RESULTS

Increase in the luting space did not influence the marginal discrepancy (P>.05). All zirconia abutments exhibited lower pullout strength after fatigue simulation (P<.05). G75 demonstrated lower tensile strength than G25 and G50 before and after loading (P<.05). Most failures were adhesive at the zirconia-cement interface.

CONCLUSIONS

The increase of the luting space to 75 μm did not influence marginal discrepancy; however, it reduced the tensile strength of a zirconia abutment bonded to a titanium base.

Optimizing the esthetic outcome by using screw-retained implant abutment crowns: A 3-year clinical follow-up

This clinical report describes a ceramic complete-mouth rehabilitation with screw-retained implant abutment crowns, optimizing esthetics by combining the properties of ceramic materials. The abutments connected a titanium insert to a computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic zirconia framework, offering improved esthetics and biologic response without negatively affecting the implant abutment interface. Lithium disilicate crowns were cemented extraorally on the abutments, resulting in a screw-retained restoration.

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.

Clinical and laboratory passive fit assessment of implant-supported zirconia restorations fabricated using conventional and digital workflow

BACKGROUND

Long-term success of implant-supported restorations can be affected by the accuracy of the prosthodontic workflow which may differ between conventional and digital techniques.

PURPOSE

The purpose was to compare the fit of two-implant-supported restorations, fabricated using conventional and digital workflows and to assess the influence of distance and angulation between the implants on the passive fit of the prosthesis. The SR test was selected to evaluate the fit of two-implant-supported zirconia restorations.

MATERIALS AND METHODS

Forty-eight zirconia two-implant-supported restorations were fabricated according to conventional (group C, n = 24) and digital (group D, n = 24) workflows. The SR parameter was calculated as a difference of rotation angles of each screw in passive and nonpassive situations. SR values between groups C and D were compared by performing measurements intraorally, on master and control casts.

RESULTS

SR intraorally in group C (16.25 ± 15.52°) was higher than it was in group D (13.85 ± 10.78°), but the difference was not statistically significant (P = .557). While measuring SR on the master cast, group C SR (6.04 ± 7.43°) had lower values than group D (13.12 ± 13.86°) (P = .0039). No statistically significant correlations were found between SR measurements and inter-implant distance or angulation. Restorations with inter-implant angle higher than 10° differed significantly from those with less than 10° angulation.

CONCLUSIONS

Digital restorations had a better fit on the control cast, which was used as a reference in this study. Angulation of more than 10° between the implants could negatively affect the passive fit of the digitally fabricated restorations intraorally.

Effect of reduced airborne-particle abrasion pressure on the retention of zirconia copings resin bonded to titanium abutments

STATEMENT OF PROBLEM

The optimal conditioning of zirconia is essential for a durable bond between zirconia copings and titanium inserts in 2-piece dental implant abutments. Low-pressure activation of the zirconia surface may be adequate for retention.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of airborne-particle abrasion (APA) of the zirconia surface with different pressures on the retention of zirconia copings bonded to titanium abutments. In addition, 2 luting systems were compared.

MATERIAL AND METHODS

Computer-aided design and computer-aided manufacturing (CAD-CAM) zirconia copings were divided into 3 groups (n=32): 0.1 MPa, 0.25 MPa, and not airborne-particle abraded surfaces with 50-μm alumina (Al₂O₃) particles. Compatible titanium abutments were airborne-particle abraded at a pressure of 0.25 MPa. All specimens were ultrasonically cleaned before bonding. Each group was divided into 2 subgroups (n=16) with different luting composite resins. A 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) containing self-adhesive luting composite resin (Panavia SA Cement Plus) and a conventional luting composite resin (Multilink Hybrid Abutment) in combination with a 10-MDP-containing universal primer (Monobond Plus) was compared. Two storage conditions were tested: in water (37 °C) for 3 days or 150 days with 37 500 thermocycles between 5 °C and 55 °C. After artificial aging, retention was measured in tension, and the failure modes were analyzed by using a light microscope and a scanning electron microscope. Statistical analysis was performed with 1-way ANOVA and the Games-Howell test for post hoc analysis (α=.05).

RESULTS

The mean retention of the airborne-particle abraded groups ranged from 576.0 N to 1049.3 N after 150 days of water storage and 37 500 thermocycles. No significant difference in bond strength was found between the 2 luting composite resin groups with airborne-particle abraded zirconia surfaces after 150 days (P<.05). Both bonding systems provided durable bond strength after 3 and 150 days. Failure mode was mainly cohesive at the titanium surfaces and predominantly adhesive at the zirconia surfaces. The retention was significantly higher if APA was used versus no APA (P<.05), while the APA pressure used made no significant difference.

CONCLUSIONS

The APA of zirconia copings at a pressure of 0.1 MPa in combination with 10-MDP-containing luting composite resins and primers is adequate for the durable bonding of zirconia copings to titanium inserts.

The Effect of Different Wax Pattern Fabrication Techniques on the Marginal Fit of Customized Lithium Disilicate Implant Abutments

PURPOSE

To evaluate the effect of different wax pattern fabrication techniques on the fit of customized pressed lithium disilicate implant abutments on titanium inserts before and after pressing. The marginal fit results of pressed lithium disilicate implant abutments were then compared with those of milled lithium disilicate abutments.

MATERIALS AND METHODS

After scanning the titanium inserts and designing an implant abutment, wax patterns were fabricated with three techniques (n = 15 each): computer-aided design/computer-aided manufacturing (CAD/CAM) milling, 3D printing and conventional layering. The marginal fit (µm) was measured using a stereomicroscope for all the wax patterns before pressing them into the lithium disilicate abutments. The pressed implant abutments were measured again for marginal fit, and the results were compared to those of the milled lithium disilicate abutments. One-way analysis of variance (ANOVA) was used to assess different wax pattern fabrication techniques in each stage before and after pressing. One-way ANOVA was also used to compare the groups of pressed and milled lithium disilicate abutments. Multiple pairwise comparisons were performed using the Tukey post hoc test in each stage.

RESULTS

There were statistically significant differences between the marginal fit of the three wax patterns groups (p < 0.001; f = 123.33), wherein the mean marginal fit was the highest for conventionally layered wax patterns (30 ± 13.09) µm. Furthermore, after pressing, there were statistically significant differences between the marginal fit of the three pressed abutments groups (p < 0.001; f = 518.62), wherein the mean marginal fit was the highest for pressed e.max abutments fabricated from conventionally layered wax patterns (25.26 ± 3.9) µm. There was no statistically significant difference between the mean marginal fit of the pressed abutments fabricated from conventional layered wax patterns and that of the milled CAD/CAM abutments. However, the mean marginal fit of the milled CAD/CAM abutments was higher than that of the pressed abutments fabricated from both CAD/CAM wax and 3D printed wax.

CONCLUSION

All the tested fabrication methods provided degrees of accuracy that lie well within accepted limits. The use of pressed lithium disilicate abutments fabricated from conventional layering wax pattern technique should provide a more consistent better marginal fit between the titanium insert and the abutment and may therefore be the preferable fabrication method.

Load-Bearing Capacity of Zirconia Crowns Screwed to Multi-Unit Abutments with and without a Titanium Base: An In Vitro Pilot Study

The static and dynamic load-bearing capacities and failure modes of zirconia crowns screwed to multi-unit abutments (MUAs) with and without a titanium base (T-base) were determined. Thirty-six monolithic zirconia crowns screwed to straight MUAs torqued to laboratory analogs (30 Ncm) were assigned to two groups (n = 18). In group A, the zirconia crowns were screwed directly to the MUAs; in group B, the zirconia crowns were cemented to the T-base and screwed to the MUAs. All specimens were aged in 100% humidity (37 °C) for one month and subjected to thermocycling (20,000 cycles). Afterwards, the specimens underwent static and dynamic loading tests following ISO 14801. The failure modes were evaluated by stereomicroscopy (20×). There was an unequivocally similar trend in the S-N plots of both specimen groups. The load at which the specimens survived 5,000,000 cycles was 250 N for both groups. Group A failed mainly within the metal, and zirconia failure occurred only at a high loading force. Group B exhibited failure within the metal mostly in conjunction with adhesive failure between the zirconia and T-base. Zirconia restoration screwed directly to an MUA is a viable option, but further studies with larger sample sizes are warranted.

Effects of Liner-Bonding of Implant-Supported Glass-Ceramic Crown to Zirconia Abutment on Bond Strength and Fracture Resistance

This study was conducted to test the hypothesis that heat-bonding with a liner positively affects the bond strength and fracture resistance of an implant-supported glass-ceramic crown bonded to a zirconia abutment produced by a computer-aided design/computer-aided milling (CAD/CAM) procedure. Lithium disilicate-reinforced Amber Mill-Q glass ceramic blocks were bonded to 3 mol% yttria stabilized tetragonal zirconia polycrystal (3Y-TZP) blocks by heat-bonding with a liner or cementation with a dual-cure self-adhesive resin cement for a microtensile bond strength test. CAD/CAM implant-supported glass ceramic crowns were produced using Amber Mill-Q blocks and bonded to a milled 3Y-TZP zirconia abutments by heat-bonding or cementation for a fracture test. A statistical analysis was conducted to investigate the significant differences between the experimental results. The mode of failure was analyzed using high-resolution field emission scanning electron microscopy. Chemical bonding was identified at the interface between the zirconia ceramic and liner. The mean tensile bond strength of the liner-bonded group was significantly higher than that of the cement-bonded group. The initial chipping strength of the liner-bonded group was significantly higher than that of the cement-bonded group, although no statistically significant difference was found for the fracture strength. The mode of failure was mixed with cohesive fracture through the liner, whereas the cement-bonded group demonstrated adhesive failure at the interface of bonding.

Two-part implant abutments with titanium and ceramic components: Surface modification affects retention forces-An in-vitro study

OBJECTIVES

Two-part abutments consist of titanium base and ceramic coping. Their long-term success is largely determined by the mechanical stability. The aim of the present study was to investigate the retention forces of two-part implant abutments. The study included zirconia and lithium disilicate ceramics copings, with different surface treatments and resin-based luting agents.

MATERIAL AND METHODS

The analysis of retention forces was based on a total of 70 test specimens. Seven surface modifications and three resin-based luting agents were employed for the bonding of components in the seven groups (n = 70). All surfaces of titanium bases-except for a control-were pretreated with aluminum oxide blasting, either alone or in combination with surface activating primers. Surfaces of ceramic copings were also treated mechanically by sandblasting, either alone or with acid etching or different primers. All specimens underwent thermal aging (10⁴ cycles, 5°C/55°C). The retention forces between the two parts were measured with a pull-off test. The results were analyzed by two-way ANOVA statistics. Fracture patterns were evaluated by light and scanning electron microscopy.

RESULTS

No mechanical pretreatment of the titanium (group 2) base resulted in the lowest retention. The combination with Monobond plus leads to the highest pull-off forces for both ceramic materials.

CONCLUSIONS

Surface modifications and resin-based agents influence the retention of components of two-part abutments. Lithium disilicate ceramic copings reached comparable results of retention to the typically used zirconia copings.

Clinical evaluation of two-piece zirconia abutments with bonded titanium inserts for implant-supported restorations

STATEMENT OF PROBLEM

Information about the long-term evaluation of 2-piece zirconia abutments (TPZAs) with bonded titanium inserts for implant-supported restorations is sparse.

PURPOSE

The purpose of this clinical study was to evaluate the clinical outcome of TPZAs with bonded titanium inserts for implant-supported restorations.

MATERIAL AND METHODS

This study retrospectively evaluated the records of patients who received implant restorations supported by TPZAs with bonded titanium inserts. The patients were recalled between January 2017 and December 2017 so that the restorations could be examined clinically and radiographically for technical and biological complications.

RESULTS

A total of 27 patients with 30 restorations and 42 zirconia abutments (ZAs) were included in the study. The patient records revealed that all implants remained integrated. However, 5 restorations supported by seven ZAs in 4 patients had to be refabricated because of abutment failure before the recall. Six of the failed abutments were in the molar area, with a combination of zirconia and titanium as the connection platform. Additional complications included screw loosening (1 patient), ceramic chipping (1 patient), and peri-implantitis (1 patient). The mean observation period was 6.6 ±1.5 years (range: 3.6 to 9.2 years).

CONCLUSIONS

After a mean observation period of 6 years after insertion, TPZAs with bonded titanium inserts appear to be a suitable treatment option in the anterior and premolar regions. However, in the molar area, the use of the same type of ZA without a complete metal-to-metal connection platform to support the restoration led to a high incidence of fracture.

Application of a standard autoclaving protocol does not harm structural integrity of two-piece zirconia abutments under detachment force testing

OBJECTIVE

Aim was to assess the influence of a standard autoclaving protocol on the retention of zirconia abutments glued on titanium bases in two-piece implant abutments.

MATERIALS AND METHODS

Twenty-four CAD/CAM-generated zirconia abutments were adhesively cemented on prefabricated titanium bases. Before mechanical and thermal aging, the specimens were divided into two groups. Group 1 was subjected to a standard steam autoclaving protocol and Group 2 remained untreated (control). The tensile strength in all specimens was evaluated by a standardized pull-off test limited to a maximum force of 1000 N.

RESULTS

Eleven samples in both groups could be subjected to pull-off testing. Ten samples in Group 1 and three samples in Group 2 failed, while all others reached the maximum pull-off force. This difference was statistically significant. The mean retention values for the failed samples were 694.53 ± 369.10 N in Group 1 and 890.78 ± 25.90 N in Group 2. This difference was not statistically significant.

CONCLUSIONS

A standard autoclaving protocol does not reduce detachment force of two-piece zirconia abutments.

CLINICAL RELEVANCE

Clinical sterilization processes as recommended by regulatory authorities seem to be harmless to the structural integrity of two-piece zirconia implant abutments, at least with regard to the retention of the components.

Historical development of root analogue implants: a review of published papers

The timetable for placing a dental implant can be crucial in the reduction of resorption of the socket after an extraction. The association of immediate implantation with an implant that copies the anatomy of the extracted root seems to add benefits in limiting the hard and soft tissue changes that may occur. The purpose of this paper is to provide an overview of the historical development of all types of root analogue implants from their beginning to the present day. To our knowledge the first individualised ones were described in 1969. Later, the use of titanium instead of the polymers that were used to start with offered better bony integration, and showed that the selection of materials was a key factor in their success. Root analogue implants made from zirconia were also described when attempts were being made to improve aesthetics in the anterior regions. The more recent introduction of digital technology such as DICOM has allowed the fabrication of these implants in less time, and the combination with digital diagnostic options such as cone-beam computed tomography facilitated the fabrication of some types of implants before extraction that could be inserted immediately into the alveolar socket with optimal and safe 3-dimensional positioning. Currently digital planning allows the clinician to design the ideal implant and abutment, which reduces the need for tissue grafting in the surgical phase and gingival conditioning in the prosthetic phase.

Retention of zirconia copings over smooth and airborne-particle-abraded titanium bases with different resin cements

STATEMENT OF PROBLEM

How cement type and the surface treatment of a titanium base affect the retention of zirconia copings on titanium bases is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the dislodging forces of zirconium oxide copings cemented on implant-supported titanium bases with different luting agents and to examine the influence of airborne-particle abrasion on titanium surfaces.

MATERIAL AND METHODS

Thirty implant laboratory analogs (BioHorizons) were fixed in metal blocks, and 30 prosthetic titanium bases (BioHorizons) were tightened with 35 Ncm of torque. Zirconium oxide copings with a luting-gap size of 30 μm were produced by using the Lava (3M ESPE) technology. The specimens were bonded to the titanium bases with 3 different resin cements (G-CEM LinkAce, RelyX U200, and Ceka Site). The specimens were kept in artificial saliva at 37°C for 24 hours and then subjected to a dynamic loading of 5000 cycles with a mastication simulator (SD Mechatronic) with thermocycling between 5°C and 55°C. The tensile force was measured by using a universal testing machine (Zwick/Roell) at a crosshead speed of 5 mm/min. After the measurement, the cement was cleaned from the titanium bases and zirconia copings. The titanium bases were airborne-particle abraded with 50-μm aluminum oxide (Al₂O₃) particles, and the bonding process was repeated. The statistical analysis included descriptive analysis, 2-way ANOVA, the Tukey post hoc, and simple main effect tests (α=.05).

RESULTS

Bond strengths were significantly different according to the cement type used and before and after airborne-particle abrasion (P<.05). The cement retentiveness before airborne-particle abrasion was as follows: G-CEM LinkAce (1338 ±69 N)>RelyX U200 (665 ±36 N)>Ceka Site (469 ±22 N). The differences among all the cement types before airborne-particle abrasion were statistically significant (P<.05). After airborne-particle abrasion, retention decreased in all the groups, and the ranking of the cements' retentiveness remained the same: G-CEM LinkAce (662 ±65 N)>RelyX U200 (352 ±21 N)>Ceka Site (122 ±17 N). After airborne-particle abrasion, the differences among all the cements remained statistically significant (P<.05). The comparison within the groups before and after airborne-particle abrasion revealed that abrading the titanium bases with 50-μm Al₂O₃ decreased the bond strength for all the tested cements.

CONCLUSIONS

The cement type had a significant influence on the retention of the zirconia copings, and abrading the titanium bases with 50-μm Al₂O₃ significantly decreased the dislodging force of the coping from the titanium base.

Effect of Bonding and Rebonding on the Shear Bond Strength of Two-Piece Implant Restorations

PURPOSE

To evaluate the rebonding strength of ceramics to titanium alloy after disassembling by heat treatment.

MATERIALS AND METHODS

A total of 40 titanium alloy (titanium-6 aluminum-4 vanadium) disks (4.0 × 6.6 mm) and 20 zirconia (Lava Plus) disks were manufactured using computer-aided design and computer-aided manufacturing (CAD/CAM) technology. Twenty heat-pressed lithium disilicate glass-ceramic (IPS e.max Press LT) disks were fabricated and used as controls. Bonding protocol for each specimen surface was performed according to manufacturer's instructions. Specimens (n = 10) of zirconia/titanium alloy (ZR) and lithium disilicate/titanium alloy (LD) were bonded using adhesive resin cement (RelyX Ultimate) and then subjected to a heat treatment (HT, 320°C, 2 minutes) to disassemble the bonding complex, cleaned with aluminum oxide airborne-particle abrasion, and rebonded following the initial protocol, group ZRHT and group LDHT, respectively. After 5000 cycles of thermal cycling, a shear bond test was conducted. A universal testing machine was used at a 5 mm/min crosshead speed. Failed specimens were examined with stereomicroscopy at 10× magnification to identify the mode of failure. One-way ANOVA and Tukey HSD tests were applied for statistical analysis of the shear bond strength data, with statistical significance at α = 0.05.

RESULTS

The mean ± SD bond strength values ranged from 28.3 ± 7.2 to 45.9 ± 9.7 MPa. Statistically significant lower shear bond strength values were obtained from the LD group (p = 0.002, F = 5.89), while no statistically significant differences in bond strength were observed between the ZR and ZRHT groups (p > 0.05). Failure mode was predominantly mixed-type failure pattern for all specimens.

CONCLUSIONS

Heat and abrasion surface treatment increased the bond strength of lithium disilicate glass-ceramics cemented to titanium alloy, but no effect was observed on zirconia/titanium alloy bonding.

Zirconia abutments in the anterior region: A systematic review of mechanical and esthetic outcomes

STATEMENT OF PROBLEM

The success of single, anterior, implant-supported restorations relies on mechanical and esthetic outcomes. Titanium has been the most commonly used material for abutments, but zirconia is increasingly chosen for its appearance despite its unclear mechanical performance. Today, manufacturers market prefabricated, computer-aided design and computer-aided manufacturing (CAD-CAM) custom and zirconia abutments with titanium connections.

PURPOSE

The purpose of this study was to systematically review the mechanical and esthetic outcomes of implant zirconia abutments used in the anterior region, considering the design changes of the past 5 years.

MATERIAL AND METHODS

An electronic search was conducted in Medline (PubMed) for studies on zirconia abutments. All clinical studies with at least a 1-year follow-up and case series (>5 abutments) published after 2013 were included. Mechanical and esthetic outcomes were collected.

RESULTS

Of the 231 retrieved studies, 20 remained for quantitative analysis. Twelve described mechanical outcomes, and 15 focused on esthetics, using mainly the pink esthetic score. Five articles reported abutment fractures and no chipping. No difference was found between prefabricated and custom abutments or internal and external implant connections regarding fractures or screw loosening. All authors reported "good to excellent" esthetic integration in terms of restorations and soft-tissue color and the presence and height of papillae. The most difficult esthetic parameters to achieve were root convexity, soft-tissue color, and texture and level of mucosa.

CONCLUSIONS

Esthetics remain the major advantage of zirconia abutment when compared with titanium, despite reservations concerning the risk of mechanical complications. Data are lacking for zirconia abutments with titanium inserts, although the prospects for this design are promising.

Effect of CAD/CAM Abutment Height and Cement Type on the Retention of Zirconia Crowns

PURPOSE

To evaluate Ti-Base abutment height and cement type on the retentiveness of zirconia-based restorations.

MATERIAL AND METHODS

Four millimeter (tall) and 2.5-mm-height (short) abutments along with temporary (provisional), glass ionomer (Meron), self-adhesive (U200), and conventional resin cement (Ultimate) were evaluated using pull-out testing (n = 10 crowns/group).

RESULTS

Tall and short abutments demonstrated similar retention for all within cement comparisons, except U200 (P = 0.032). Resin cements exhibited superior retentiveness than others (P < 0.01). Although no significant difference was evidenced between resin cements for short abutments, Ultimate evidenced higher retention than U200 for tall abutments (P = 0.043).

CONCLUSIONS

Although Ti-Base abutment height has not influenced zirconia superstructures' retentiveness, resin-based cements significantly evidenced higher retention than glass ionomer and temporary cements.

The Use of a Hybrid Pillar and Its Importance for Aesthetic Rehabilitation and Tissue Stability: A Clinical Report

In the past, aesthetics had a secondary role in implant rehabilitation. Nowadays, the search for a perfect and harmonious aesthetic has stimulated the development of new materials and techniques. Due to this aesthetic requirement, the hybrid abutment (titanium link + zirconia) emerged as an alternative to metallic pillars. The hybrid abutment made a more favorable aesthetic possible, provided reliable mechanical properties, and increased biocompatibility to the surrounding tissues. Additionally, the individual zirconia abutment improves the emergency profile and the final white aesthetics. The objective of this paper is to report a clinical case with a manufactured individualized hybrid abutment for a metal-free indirect restoration, showing the applicability, mechanical properties, and biocompatibility of the hybrid abutment.

Effects of cleaning methods for custom abutment surfaces on gene expression of human gingival fibroblasts

The aim of this study was to develop an effective method for cleaning implant abutments made by computer-aided design and computer-aided manufacturing techniques and to investigate the effect of decontamination in vitro. Briefly, a newly developed reagent (PK) and/or vacuum plasma (Plasma) were used to clean the surfaces of zirconia disks, and the effects of this decontamination were evaluated by X-ray photoelectron spectroscopy. Human gingival fibroblasts (HGFs) were cultured on sample disks for 6, 24, and 48 h. We evaluated cell attachment and gene expression of the acute inflammatory cytokines interleukin-6 and vascular endothelial growth factor A, and type 1 collagen. In the PK and PK+Plasma groups, surface contaminants were reduced by washing. In addition, HGF attachments was increased in the PK and PK+Plasma groups. Gene expressions of interleukin-6 and vascular endothelial growth factor A were lower at 6 h. Gene expression of type 1 collagen was increased at all time points after seeding. These results suggest that decontamination of implant abutment surfaces is important in initial HGF attachment and may improve the biological seal of peri-implant soft tissue.

A technique for the removal of a wedged implant abutment fragment or debonded titanium base

A technique for the retrieval of wedged implant fragments is described. The technique is suitable for fractured zirconia and metal abutments and titanium bases left behind after fracture or debonding of the custom zirconia abutment from the titanium base of an implant-supported prosthesis. This straightforward, noninvasive, technique facilitates the removal of the fragments or titanium bases without risking damage to the implant, surrounding bone, or soft tissues.

Effect of Steam Autoclaving on the Tensile Strength of Resin Cements Used for Bonding Two-Piece Zirconia Abutments

The purpose of this study was to evaluate the effects of steam autoclave sterilization on the tensile strength of two types of resin cements used to bond customized CAD/CAM zirconia abutments onto titanium bases. Forty sets of zirconia abutments cemented to screwed titanium bases of implants analogs were divided into 4 groups (n = 10). Two groups were treated with a conventional chemically activated resin cement (ML, Multilink Ivoclar Vivadent) and the other two groups with a self-adhesive dual resin cement (RelyX U200, 3M ESPE). One group from each cement was submitted to steam autoclaving. The autoclave sterilization cycle was performed after 72 hours of cementation for 15 minutes at 121°C and 2.1 Kgf/cm2. The samples were subjected to tensile strength testing in a universal testing machine (200 Kgf, 0.5 mm/min), from which the means and standard deviations were obtained in Newtons. Results showed (via ANOVA and Tukey's test; α = 0.05) that in the absence of steam autoclaving, no difference was observed in tensile strength between the cements tested: ML: 344.87 (93.79) and U200: 280 (92.42) (P = .314). Steam autoclaving, however, significantly increased tensile strength for the ML: 465.42 (87.87) compared to U200: 289.10 (49.02) (P &lt; .001). Despite the significant increase in the ML samples (P = .013), autoclaving did not affect the tensile strength of the U200 samples (P &gt; 0.05). The authors concluded that steam autoclaving increases the mean tensile strength of the chemically activated cement compared to the dual-cure self-adhesive cement. The performance of both cements evaluated was similar if the sterilization step was disconsidered.

A Current Perspective on Screw-Retained Single-Implant Restorations: A Review of Pertinent Literature

OBJECTIVE

There is a trend toward increased use of screw-retained single-implant restorations. A comprehensive literature review was undertaken to examine the data related to screw- and cement-retention and to objectively evaluate the innovations in implant dentistry that have led to this resurgence.

OVERVIEW

When comparing the two options, survival and complication rates are similar, bone and soft-tissue levels are comparable, and zirconia offers esthetic advantages for both selections. Zirconia abutments with bonded titanium inserts provide esthetic alternatives to titanium abutments for both choices. Bone- and soft-tissue responses are similar, but residual cement of cement-retained restorations is associated with significant soft- and hard-tissue complications. The potential weakness of ceramic discontinuity of screw-access openings can be lessened by the incorporation of stronger ceramic materials such as zirconia and lithium disilicate. The overriding remaining indication for cement-retained restorations is to compensate for angled implants.

CONCLUSIONS

Screw-retained single-implant crowns should be reconsidered for many clinical situations for the following reasons: Predictable retention and retrievability No potential for the biologic consequences associated with residual cement As with cement-retained restorations, the choice between metal ceramics or all ceramics Only one margin, at the implant/abutment interface A single abutment/crown ceramic margin that can extend gingivally to the implant interface Nearly imperceptible blend of a composite resin in ceramic abutment access openings One component instead of two, which may simplify the restorative process CLINICAL SIGNIFICANCE: Innovations in implant and ceramic technology now give screw-retained prostheses the potential for esthetic, functional, and biologic outcomes that are comparable to those for cement-retained prostheses, while providing the advantages of predictable retrievability and avoidance of residual cement. Angled implants, however, remain a major indication for cement-retained single-implant prostheses. (J Esthet Restor Dent 29:161-171, 2017).