Retention Forces of Monolithic CAD/CAM Crowns Adhesively Cemented to Titanium Base Abutments-Effect of Saliva Contamination Followed by Cleaning of the Titanium Bond Surface

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.

Do all ceramic and composite CAD-CAM materials exhibit equal bonding properties to implant Ti-base materials? An Interfacial Fracture Toughness Study

OBJECTIVES

To compare the interfacial fracture toughness (IFT) with or without aging, of four different classes of CAD-CAM ceramic and composite materials bonded with self-adhesive resin cement to titanium alloy characteristic of implant abutments.

METHODS

High translucent zirconia (Katana; KAT), lithium disilicate-based glass-ceramic (IPS. emax.CAD; EMX), polymer-infiltrated ceramic network material (PICN) (Vita Enamic; ENA), and dispersed filler composite (Cerasmart 270; CER) were cut into equilateral triangular prisms and bonded to titanium prisms with identical dimensions using Panavia SA Cement Universal. The surfaces were pretreated following the manufacturers' recommendations and developed interfacial area ratio (Sdr) of the pretreated surfaces was measured. IFT was determined using the Notchless Triangular Prism test in a water bath at 36 °C before and after thermocycling (10,000 cycles) (n = 40 samples/material).

RESULTS

IFT of the materials ranged from 0.80 ± 0.25 to 1.10 ± 0.21 MPa.m1/2 before thermocycling and from 0.71 ± 0.24 to 1.02 ± 0.25 MPa.m1/2 after thermocycling. There was a statistical difference between IFT of CER and the two top performers in each scenario: KAT and EMX before aging, and KAT and ENA after aging. Thermocycling significantly decreased IFT of EMX. The Weibull modulus of IFT was similar for all materials and remained so after thermocycling. Sdr measurements revealed that ENA (7.60)>Ti (4.97)>CER (2.85)>KAT (1.09)=EMX (0.96).

SIGNIFICANCE

Dispersed filler CAD-CAM composite showed lower performance than the other materials. Aging only affected IFT of Li-Si glass-ceramic, whereas zirconia and PICN performed equally well, probably due to their chemical bonding potential and surface roughness respectively.

Post sterilization of intraoral scan body and the effect it has on the axes and distances between three adjacent implants: in-vitro study

BACKGROUND

The purpose of this pilot in-vitro study was to assess the effect of sterilization on the intra-implant axis, inter-implant axis, intra-implant distance and inter-implant distance of three implants in a straight line by using laboratory scanner (LBS) versus intra-oral scanner (IOS) with intra-oral scan bodies (ISB).

METHODS

A printed 3D model with three internal hex analogs in the positions 15#,16#,17# was used. Zirkonzhan (ZZ) intra-oral scan body (ISB), two-piece titanium was used. The ZZ ISBs were scanned by 7 Series dental wings (LBS) and 30 times by Primescan (IOS) pre sterilization and 30 times post sterilization. For each scan (pre and post) stereolithography (STL) file was created and a comparison between all the scans pre sterilization and post sterilization were superimposed on the laboratory scan by using a 3D analyzing software. A Kolmogorov-Smirnov test performed followed by Wilcoxon Signed Ranks tests. (p < 0.05) Results: Post sterilization of the ZZ ISB, the mean errors were significantly increased for the inter-implant distances (p < 0.0005), intra-implant distances 1,2,3 (p < 0.0005), intra-implant axis 1,3 (p < 0.0005) and inter-implant axes 13,23 (p < 0.05). In contrast, the mean errors for intra-implant axis 2 (p < 0.0005) and inter-implant axis 12 (p < 0.0005) were significantly reduced.

CONCLUSIONS

ZZ ISB showed changes in all four parameters after sterilization. The middle ISB had the largest changes in mean error regarding all four parameters. Sterilization process may affect the three-dimensional (3D) structure of the ZZ ISB after three cycles. There is a lack in the literature in this field and there is a need for further studies to explore the effect of sterilization (multiple cycles) on different ISBs and for creating an approved guidelines regarding the amount of sterilization for each ISB in the industry.

Fatigue behavior of implant-supported cantilevered prostheses in recently introduced CAD-CAM polymers: An in vitro study

STATEMENT OF PROBLEM

Cantilevered complete arch implant-supported prostheses are commonly fabricated from zirconia and more recently from strength gradient zirconia. Different polymer-based materials indicated for definitive fixed prostheses that could be used with additive or subtractive manufacturing have also been marketed recently. However, knowledge on the long-term fatigue behavior of cantilevered implant-supported prostheses made from these polymer-based materials and strength gradient zirconia is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the fatigue behavior of implant-supported cantilevered prostheses of recently introduced computer-aided design and computer-aided manufacturing polymers and zirconia.

MATERIAL AND METHODS

A master standard tessellation language file of a 9×11×20-mm specimen with a titanium base (Ti-base) space that represented an implant-supported cantilevered prosthesis was used to fabricate specimens from additively manufactured interim resin (AM), polymethyl methacrylate (SM-PM), nanographene-reinforced polymethyl methacrylate (SM-GR), high-impact polymer composite resin (SM-CR), and strength gradient zirconia (SM-ZR) (n=10). Each specimen was prepared by following the respective manufacturer's recommendations, and Ti-base abutments were cemented with an autopolymerizing luting composite resin. After cementation, the specimens were mounted in a mastication simulator and subjected to 1.2 million loading cycles under 100 N at 1.5 Hz; surviving specimens were subjected to another 1.2 million loading cycles under 200 N at 1.5 Hz. The load was applied to the cantilever extension, 12-mm from the clamp of the mastication simulator. The Kaplan-Meier survival analysis and Cox proportional hazards model were used to evaluate the data (α=.05).

RESULTS

Significant differences in survival rate and hazard ratio were observed among materials (P<.001). Among tested materials, SM-ZR had the highest and AM had the lowest survival rate (P≤.031). All materials had a significantly higher hazard ratio than SM-ZR (P≤.011) in the increasing order of SM-GR, SM-PM, SM-CR, and AM.

CONCLUSIONS

SM-ZR had the highest survival rate with no failed specimens. Even though most of the tested polymer-based materials failed during cyclic loading, these failures were commonly observed during the second 1.2 million loading cycles with 200 N. All materials had a higher hazard ratio than SM-ZR.

Influence of sterilization on the retention forces of lithium disilicate and polymer-infiltrated ceramic-network crowns bonded to titanium base abutments: An in-vitro study

OBJECTIVES

The aim of this study was to evaluate the effect of sterilization on the retention forces of lithium disilicate (LD) and polymer-infiltrated ceramic network (PICN) crowns bonded to titanium base (Ti-base) abutments.

MATERIALS AND METHODS

Forty LD and 40 PICN crowns were milled and then bonded to 80 Ti-bases with two resin composite cements: Multilink Hybrid Abutment (mh) and Panavia V5 (pv) for a total of 8 groups (n = 10). Half of the specimens (test) underwent an autoclaving protocol (pressure 1.1 bar, 121°C, 20.5 min) and the other half not (control). Restorations were screw-retained to implants, and retention forces (N) were measured with a pull-off testing machine. The surfaces of the Ti-bases and the crowns were inspected for the analysis of the integrity of the marginal bonding interface and failure mode. Student's t-test, chi-square test, and univariate linear regression model were performed to analyze the data (α = 0.05).

RESULTS

The mean pull-off retention forces ranged from 487.7 ± 73.4 N to 742.2 ± 150.3 N. Sterilized groups showed statistically significant overall higher maximum retention forces (p < .05), except for one combination (LD + mh). Sterilization led to an increased presence of marginal gaps and deformities compared to no-sterilization (p < .001), while no statistically significant relationship was found between failure mode and sterilization (p > .05).

CONCLUSIONS

Sterilization may have a beneficial effect on the retention forces of LD and PICN crowns bonded to titanium base abutments, although it may negatively influence the integrity of the marginal bonding interface.

Effect of adhesive system, resin cement, heat-pressing technique, and thermomechanical aging on the adhesion between titanium base and a high-performance polymer

STATEMENT OF PROBLEM

Even though polyetheretherketone (PEEK) has become popular for various prosthetic indications, a standard adhesive protocol to bond the PEEK to titanium bases has not been yet established. How the heat-pressing technique performs in this respect is also not clear.

PURPOSE

The purpose of this in vitro study was to investigate the effect of an adhesive system-cement combination, the heat-pressing technique, and thermomechanical aging on the retention force between titanium bases and PEEK specimens.

MATERIAL AND METHODS

Sixty 9×11×20-mm PEEK specimens with a titanium base slot integrated into the design were milled to simulate an implant-supported PEEK framework for a cantilevered fixed prosthesis. The specimens were assigned to 8 groups (n=10) according to the titanium base primer (MKZ or Monobond) and resin cement (DTK or Multilink hybrid) used and with or without thermomechanical aging. Twenty PEEK specimens were directly heat-pressed on titanium bases, and half of the specimens were not subjected to thermomechanical aging (n=10). For nonaged groups, the PEEK specimen complex was tightened to an implant analog and secured on a custom-made pull-off device. Retention forces were measured by using the pull-off tensile test in a universal testing machine, and the maximum tensile bond strength (MPa) was calculated. The aged groups were subjected to 5000 cycles of thermal aging (5 °C to 55 °C), and the specimens were clamped to load the extension (cantilever) for 1 200 000 cycles with 120 N and 200 N at 1.5-Hz frequency. After aging, the pull-off test was performed for those specimens that survived thermomechanical aging. A nonparametric Kruskal-Wallis test was used to determine whether there was a difference among the groups, followed by pairwise Wilcoxon rank tests with Bonferroni correction. The Wilcoxon rank test was used to analyze the effect of thermomechanical aging in each adhesive system-cement or heat-press group (α=.05 for all tests).

RESULTS

None of the specimens failed during cyclic loading. According to the Kruskal-Wallis test, the effect of the PEEK-Ti base bonding technique on the retention force in the nonaged (P=.019) and thermomechanically aged groups was significant (P=.010). In the nonaged groups, the heat-pressing technique resulted in a higher retention force than when the specimens were bonded by using the Monobond-Multilink hybrid combination (P=.031). Thermomechanical aging did not significantly affect the results (P>.241). All failures were adhesive, with cement remaining only on the Ti-bases.

CONCLUSIONS

All bonding protocols tested resulted in a stable bond between PEEK and Ti-bases, as all specimens survived thermomechanical aging. The heat-pressing technique resulted in mean bond strength values similar to those obtained with the tested adhesive system-cement combinations with 1 exception; the nonaged heat-pressed groups presented higher bond strength than the Monobond-Multilink hybrid combination. Failure types indicated that the weaker bond was between the PEEK and the cements tested rather than between the titanium base and the cements, regardless of the adhesive system-cement combination.

Prosthetic complications with monolithic or micro-veneered implant-supported zirconia single-unit, multiple-unit, and complete-arch prostheses on titanium base abutments: A single center retrospective study with mean follow-up period of 72.35 months

BACKGROUND

The influence of prosthetic design on prosthetic complications when monolithic or micro-veneered zirconia prostheses are supported with titanium base (ti-base) abutments is not well-known.

PURPOSE

The purpose of this single center, retrospective study was to assess the prevalence of prosthetic complications with monolithic or micro-veneered single-unit, multi-unit, and complete-arch zirconia prostheses supported with ti-base abutments (implant level or multi-unit abutment level).

MATERIAL AND METHODS

This study retrospectively evaluated the electronic health record (EHR) of participants who received either monolithic or micro-veneered implant-supported single-unit, multi-unit, and/or complete-arch prostheses supported by ti-base or zirconia-ti-base hybrid abutments delivered between the years 2010 and 2021. Data were analyzed by using logistic regression and Exact Mantel-Haenszel chi-square test (α = 0.05) to assess the clinical performance of prostheses and complications including crown decementation, feldspathic porcelain chipping, prosthesis fracture, zirconia-ti-base hybrid abutment decementation, abutment screw loosening, screw fracture, abutment fracture, implant loss, and prosthesis remake.

RESULTS

The study included 94 participants (50 female, 44 male) with a mean age of 59.5 years (range: 24-101 years of age). The retrospective EHR evaluation yielded 82 single-unit, 51 multi-unit, and 20 complete-arch prostheses on 325 implants. Among 153 prostheses delivered, 108 were micro-veneered (47 single-unit, 41 multi-unit, and 20 complete-arch prostheses) and 45 were monolithic. The average duration was 72.35 months (6.02 years) with a follow-up period of 5-132 months. From the time of insertion to the time of EHR review, of 153 prostheses, 78.43% did not exhibit any prosthetic complication. However, 33 prostheses (21.57%) from 29 participants (30.85%) had at least one prosthetic complication. Only four patients (4.25%) experienced two or more prosthetic complications. Prosthetic design affected the probability of having a complication (p = 0.005); complete-arch prostheses had higher probability (p ≤ 0.028). Single-unit prostheses had lower probability of complication than multi-unit prostheses (p = 0.005). The most commonly observed complication was fracture of veneering material (5.88%) followed by prosthetic screw loosening (4.57%) and decementation between the zirconia and the ti-base abutment (2.61%). Micro-veneered complete-arch prostheses had higher probability of having chipping than that of not having (p < 0.001), and other micro-veneered prosthetic designs had similar probability of chipping with that of complete-arch prostheses (p ≥ 0.082). Frequency of chipping was affected by veneering (p < 0.001). Monolithic prostheses had lower probability of chipping than micro-veneered prostheses, regardless of the prosthetic design (p < 0.001).

CONCLUSIONS

The frequency of prosthetic complications varied depending on prosthetic design. Complete-arch prostheses had the highest probability of complications while the single-unit prostheses had the lowest. Micro-veneered prostheses had higher probability for chipping than monolithic prostheses. Probability of chipping was similar for micro-veneered single-unit, multi-unit, and complete-arch zirconia prostheses.

A multicenter randomized controlled clinical pilot study of buccally micro-veneered lithium-disilicate and zirconia crowns supported by titanium base abutments: 1-year outcomes

OBJECTIVES

To investigate survival rates, technical and biologic outcomes of buccally micro-veneered all-ceramic single implant crowns.

MATERIAL AND METHODS

Sixty subjects randomly received immediately or early placed implants. Crowns out of lithium-disilicate (n = 30) and zirconia-ceramic (n = 30) were bonded to titanium-base-abutments. Restorations were inspected at baseline (BL) and during follow-up visits (6, 12 months). Technical and biologic parameters were recorded. Data were analysed descriptively. Differences between groups were tested with Student's t-test. Paired T-test was used when comparing data from the same implant or tooth over time. Linear model repeated measures were used to test differences between materials over time. Differences in counts were evaluated using Pearson Chi-square test. The level of significance was at p < .05.

RESULTS

After a mean observation time of 13.2 ± 2.4 months, 54 restorations were re-examined. The implant survival rate was 98.3%, and the restoration survival rate was 100%. One early implant failure occurred. Two minor chippings occurred in lithium-disilicate restorations. No chippings or fractures occurred in any zirconia restorations at 1 year (0%). The technical complication rate was 3.7%, with 7.7% complications among the lithium-disilicate restorations and no differences between the two materials (p = .558). At 1-year follow-up, mean Bleeding on Probing (BOP) was higher at implants (0.27 ± 0.3) than adjacent teeth (0.17 ± 0.18) (p = .046) with no differences between materials (p = .36). Differences in pocket probing depth (PPD) between implants and adjacent teeth were significant (p < .01). Jemt Index improved significantly from BL to 1-y-follow-up (p < .001).

CONCLUSIONS

Preliminary results were good, suggesting that the ceramic type does not impact technical and biologic parameters.

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.

Retentive Strength of CAD/CAM-Fabricated All-Ceramic Crowns Luted on Titanium Implant Abutments Using Different Ceramic Materials and Luting Agents: An In Vitro Study

Objectives: This study aimed to determine the retentive strength of monolithic hybrid-all-ceramic crowns luted on titanium implant abutments. Material and Methods: In total, 450 crowns (75 each of Mark II, Empress CAD, e.max CAD, Suprinity, Enamic, Celtra Duo) were milled using a CAD/CAM system. The crowns were cemented onto sandblasted titanium implant abutments using five luting agents (Multilink Implant, Variolink II, RelyX Unicem, Fujicem, and Panavia 2.0). After thermocycling was performed (5000 cycles: 5−55 °C, 30-s dwell time), the crowns were removed using a universal testing machine. The location of luting-agent residue on the abutment and inner crown surfaces was evaluated. Analyses of variance (ANOVA) with the Bonferroni correction were performed to evaluate differences of retentive strength depending on the crown material and the kind of the luting agent. Results: The retentive strengths for the different ceramic materials were Vita Mark II: 652N-759N (SD:134N-146N), Empress CAD: 681N-822N (SD: 89N-146N), e.max CAD: 784N-1044N (SD: 109N-176N), Vita Enamic: 716N-1177N (SD: 132N-220N), Vita Suprinity: 867N-1488N (SD: 202N-278N), and Celtra Duo 772N-1335N (SD:151N-229N). After the removal trials, the visual documentation showed different adhesive residue location depending on the ceramic materials. Furthermore, the pull-off force was dependent on the choice of adhesives. No significant differences were found between different luting agents and the ceramic material Vita Mark II and Empress CAD. EmaxCAD showed significant differences with Unicem and FujiCem compared to Panavia, as did VitaSuprinity, VitaEnamic, and Celtra Duo (p < 0.001). Conclusions: The ceramic material used seems to influence the retentive strength and the use of certain luting agents results in a higher retentive strength for some ceramic materials.

Scanning Electron Microscopy Analyses of Dental Implant Abutments Debonded from Monolithic Zirconia Restorations Using Heat Treatment: An In Vitro Study

Aim: The aim of this in vitro study is to present a debonding protocol developed to remove a screw-retained, monolithic, zirconia restoration from its titanium-base abutment, and to microscopically evaluate the abutment integrity at both the prosthetic and connection levels. Materials and Methods: A total of 30 samples were tested. Each sample consisted of a monolithic zirconia restoration bonded on a titanium link abutment. Five different shapes were designed and fabricated. Randomly, one-third of the Ti-link abutments were subjected to an anodizing process. Then, all the zirconia samples were bonded to the Ti-link abutments according to a pre-established protocol. Forty-eight hours later, the samples were debonded according to the experimental protocol. The outcomes were evaluated by a visual inspection with an optical microscope, scanning electron microscopy (SEM), and chemical composition analysis. Results: Thirty samples were collected and visually analyzed. Seven samples were randomly evaluated via scanning electron microscopy. In all the examinations, no relevant changes were reported. Chemical composition analysis also relieved no changes in the chemical structure of the titanium. Conclusions: The titanium-base abutments do not alter the structure and properties of the material, not creating phase changes or the birth of oxides such as to induce fragility. Further clinical studies with longer follow-up periods are needed to confirm these preliminary results.

Laboratory Fracture Resilience of Hybrid Abutments Used in Oral Rehabilitation: A Systematic Review

When implants are required in prosthodontics treatment, one of the most important decisions is the choice of the final crown and the type of connection to the implant through the abutment. Hybrid abutments are becoming a primary choice. They are projected and produced with materials whose properties guarantee the required mechanical features (including resistance) and take advantage of the hybrid abutment crown retention between screw and cement. However, a review of the mechanical resistance of the different abutment types and associated materials is still lacking. This review aimed to study the in vitro mechanical efficiency of the hybrid abutments used in oral rehabilitation. Methods: A systematic review was conducted using the PubMed, B-on, and Google Scholar databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: 75 articles were identified from all databases, and 33 were selected after abstract screening. Thus, 21 studies were included in the review after full-text reading. Among the materials used for crowns, lithium disilicate was, aesthetically, the primary choice for its aesthetic and moderate strength. On the other hand, zirconia showed the best fracture resistance. Regarding the different kinds of abutments, there is still some lack of knowledge about the best design. Conclusions: Within the limitations of this systematic review, we can conclude that hybrid pillars are an excellent choice for oral rehabilitation through implants, showing improved resistance when including materials such as zirconia and lithium disilicate.