Differences in micromorphology of the implant–abutment junction for original and third-party abutments on a representative dental implant

Comparative in vitro evaluation of microgap in titanium stock versus cobalt-chrome custom abutments on a conical connection implant: Effect of crown cementation and ceramic veneering

OBJECTIVE

To compare the implant-abutment connection microgap between computer-aided design and computer-aided manufacturing (CAD/CAM) milled or laser-sintered cobalt-chrome custom abutments with or without ceramic veneering and titanium stock abutments with or without crown cementation.

MATERIAL AND METHODS

Six groups of six abutments each were prepared: (1) CAD/CAM cobalt-chrome custom abutments: milled, milled with ceramic veneering, laser-sintered, and laser-sintered with ceramic veneering (four groups: MIL, MIL-C, SIN, and SIN-C, respectively) and (2) titanium stock abutments with or without zirconia crown cementation (two groups: STK and STK-Z, respectively). Abutments were screwed to the implants by applying 30 Ncm torque. All 36 samples were sectioned along their long axes. The implant-abutment connection microgap was measured using scanning electron microscopy on the right and left sides of the connection at the upper, middle, and lower levels. Data were analyzed using the Kruskal-Wallis test (p < .05).

RESULTS

Mean values (μm) of the microgap were 0.54 ± 0.44 (STK), 0.55 ± 0.48 (STK-Z), 1.53 ± 1.30 (MIL), 2.30 ± 2.2 (MIL-C), 1.53 ± 1.37 (SIN), and 1.87 ± 1.8 (SIN-C). Although significant differences were observed between the STK and STK-Z groups and the other groups (p < .05), none were observed between the milled and laser-sintered groups before or after ceramic veneering. The largest microgap was observed at the upper level in all groups.

CONCLUSIONS

Titanium stock abutments provided a closer fit than cobalt-chrome custom abutments. Neither crown cementation nor ceramic veneering resulted in significant changes in the implant-abutment connection microgap.

Mechanical strength of stock and custom abutments as original and aftermarket components after thermomechanical aging

OBJECTIVES

The study aimed to assess the impact on the mechanical strength and failure patterns of implant-abutment complexes of choosing different abutment types, designs and manufacturers, aiding in selecting the optimal restorative solution. Stock and custom abutments from original and aftermarket suppliers were subjected to thermomechanical aging.

MATERIAL AND METHODS

Stock and custom abutments from the implant manufacturer (original) and a aftermarket supplier (nonoriginal) were connected to identical implants with internal connection. Custom abutments were designed in a typical molar and premolar design, manufactured using the workflow from the respective suppliers. A total of 90 implants (4 mm diameter, 3.4 mm platform, 13 mm length) equally divided across 6 groups (three designs, two manufacturers) underwent thermo-mechanical aging according to three different regimes, simulating five (n = 30) or 10 years (n = 30) of clinical function, or unaged control (n = 30). Subsequently, all samples were tested to failure.

RESULTS

During aging, no failures occurred. The mean strength at failure was 1009N ± 171, showing significant differences between original and nonoriginal abutments overall (-230N ± 27.1, p < .001), and within each abutment type (p = .000), favoring original abutments. Aging did not significantly affect the failure load, while the type of abutment and manufacturer did, favoring original and custom-designed abutments. The most common failure was implant bending or deformation, significantly differing between original and nonoriginal abutments and screws. All failure tests resulted in clinically unsalvageable implants and abutments.

CONCLUSIONS

Within the limitations of this study, original abutments exhibited a higher mechanical strength compared to the nonoriginal alternative, regardless of the amount of simulated clinical use. Similarly, custom abutments showed higher mechanical strength compared to stock abutments. However, mechanical strength in all abutments tested was higher than average chewing forces reported in literature, thus components tested in this study can be expected to perform equally well in clinical situations without excessive force.

Prosthetic design and choice of components for maintenance of optimal peri-implant health: a comprehensive review

Current research has identified features of the prosthetic design with potential to significantly impact the long-term health of peri-implant tissues, while the choice of prosthetic components is also shown to be critical in an effort to reduce long-term complications of implant therapy. Overcontouring of the prosthesis emergence profile has been associated with marginal bone loss, recession and peri-implantitis, while the mucosal emergence angle is shown to have a strong association with peri-implant tissue inflammation. Further elements of interest include convexity/concavity of the restoration, the prosthetic connection and the different geometric configurations of junctions, as well as the peri-implant tissue dimensions. With regards to implant components, the choice between original and third-party-manufactured components might come with implications, as differences in material and microgeometry might impact precision of fit and overall performance, potentially leading to complications. Scrutiny of the specifications and manufacturing is essential when third-party-manufactured components are considered.The aim of this narrative review was to summarise the current evidence with regards to the restorative features of the implant prosthesis and also the selection of prosthetic components which can have implications for the long-term success of the implant therapy. Furthermore, the review aimed at interpretating current scientific evidence into meaningful strategies and recommendations to implement in clinical practice of implant dentistry.

Dental Implant Abutment Screw Loss: Presentation of 10 Cases

Re-tightening the loosened dental implant abutment screw is an accepted procedure, however the evidence that such screw will hold sufficiently is weak. The purpose of this study was material analysis of lost dental implant abutment screws made of the TiAlV alloy from various manufacturers, which became lost due to unscrewing or damaged when checking if unscrewed; undamaged screws could be safely re-tightened. Among 13 failed screws retrieved from 10 cases, 10 screws were removed due to untightening and 3 were broken but without mechanical damage at the threads. Advanced corrosion was found on nine screws after 2 years of working time on all surfaces, also not mechanically loaded. Sediments observed especially in the thread area did not affect the corrosion process because of no pit densification around sediments. Pitting corrosion visible in all long-used screws raises the question of whether the screws should be replaced after a certain period during service, even if they are well-tightened. This requires further research on the influence of the degree of corrosion on the loss of the load-bearing ability of the screw.

Proposal regarding potential causes related to certain complications with dental implants and adjacent natural teeth: Physics applied to prosthodontics

PURPOSE

Complications can and do occur with implants and their restorations with causes having been proposed for some single implant complications but not for others.

METHODS

A review of pertinent literature was conducted. A PubMed search of vibration, movement, and dentistry had 175 citations, while stress waves, movement, and dentistry had zero citations as did stress waves, movement. This paper discusses the physics of vibration, elastic and inelastic collision, and stress waves as potentially causative factors related to clinical complications.

RESULTS

Multiple potential causes for interproximal contact loss have been presented, but it has not been fully understood. Likewise, theories have been suggested regarding the intrusion of natural teeth when they are connected to an implant as part of a fixed partial denture as well as intrusion when a tooth is located between adjacent implants, but the process of intrusion, and resultant extrusion, is not fully understood. A third complication with single implants and their crowns is abutment screw loosening with several of the clinical characteristics having been discussed but without determining the underlying process(es).

CONCLUSIONS

Interproximal contact loss, natural tooth intrusion, and abutment screw loosening are common complications that occur with implant retained restorations. Occlusion is a significant confounding variable. The hypothesis is that vibration, or possibly stress waves, generated from occlusal impact forces on implant crowns and transmitted to adjacent teeth, are the causative factors in these events. Since occlusion appears to play a role in these complications, it is recommended that occlusal contacts provide centralized stability on implant crowns and not be located on any inclined surfaces that transmit lateral forces that could be transmitted to an adjacent tooth and cause interproximal contact loss or intrusion. The intensity, form, and location of proximal contacts between a natural tooth located between adjacent single implant crowns seem to play a role in the intrusion of the natural tooth. Currently, there is a lack of information about the underlying mechanisms related to these occurrences and research is needed to define any confounding variables.

Titanium-base abutments may have similar long-term peri-implant effects as non-bonded one-piece abutments

Design A single-centre (private practice), prospective, longitudinal, split-mouth, single-blind, randomised controlled clinical trial reported peri-implant parameters of individualised abutments bonded to titanium (Ti) bases during a five-year follow-up. The study complied with the ethical principles of the Helsinki Declaration and the CONSORT (Consolidated Standards of Reporting Trials) guidelines. It was approved by the Medical Ethical Committee of the University of Freiburg (013/1630) and registered in the German Clinical Trials Register (DRKS00006163).Case selection The included subjects had to be over 17 years of age, have an American Society of Anaesthesiologists score of 1, be a non-smoker, have a full-mouth plaque index (PI) below 20%, full-mouth bleeding index (BI) 20%, and planned with at least two dental implants but not adjacent to each other. Participants were excluded if they required simultaneous augmentation, were pregnant or breastfeeding, or had a history of periodontitis. Marginal bone loss (MBL) was the main clinical outcome, while local bleeding on probing (BoP), probing pocket depth (PPD), plaque Index (PI), local recession (REC), and relative attachment level (RAL) were also evaluated. The study timeline consisted of a screening (visit 1) and implant surgery (visit 2). Stage two was three months after implant surgery (visit 3), impression was two weeks after stage two (visit 4), followed up by baseline with a standardised radiograph (visit 5), one-year follow-up with radiographic and clinical parameters (visit 6), two-year follow-up (visit 7), three-year follow-up (visit 8), four-year follow-up (visit 9) and five-year follow-up (visit 10). In total, 24 subjects received two bone-level implants (Conelog, Camlog Biotechnologies, Basel, Switzerland) in the same arch and region up to 1 mm subcrestally. Their implant-abutment connection was an internal 7.5 degree conical connection platform-switch. Each subject received two abutments (one control and one test) as per the split-mouth design. The control abutments consisted of individualised, one-piece, computer-aided design/computer-aided manufacturing (CAD/CAM) titanium abutments, whereas the test abutments were CAD/CAM titanium abutments bonded to Ti-bases. The decision which implant was restored and in which way was made by a coin flip. The surgeon, patient and prosthodontist were blinded regarding the treatment allocation.Data analysis Descriptive measures and quantitative parameters were obtained from means, standard deviations, minimum and maximum values and 95% confidence intervals. The means of clinical parameters (six sites per implant) were MBL, BoP, PPD, PI, REC, and RAL. Paired t-tests were used for intragroup comparisons at different intervals as well as for intergroup comparisons within each time point. All data collected were considered until participants dropped out (that is, intention-to-treat principle). The significance level alpha was set to 0.05. The post-hoc power calculation of the MBL intergroup comparison dammed this trial as underpowered (power = 34%).Results All implants were osseointegrated after the healing stage and no implants were lost during the trial. Two subjects dropped out (one after the two-year follow-up and the other at the last appointment). Regarding MBL, no significant intergroup differences were found between the abutment groups. Nonetheless, significant intragroup differences were found at several visits (visit 6 to visit 10) compared to the baseline MBL (visit 5), indicating continuous bone level alterations. Concerning the BoP, no significant differences were identified. In terms of PPD, significant intergroup differences were found at visits 9 (p = 0.006) and 10 (p = 0.024), favouring Ti-base abutments. There were significantly intergroup differences in terms of REC (p = 0.014) at visit 10, with higher values in the one-piece abutment group. No differences were found in terms of PI.Conclusions A preliminary conclusion of this underpowered trial was that Ti-base abutments have a similar long-term effect to one-piece abutments on human peri-implant tissues.

Mechanical properties and marginal fit of prefabricated versus customized dental implant abutments: A comparative study

INTRODUCTION

Dental implant abutments play an important role in the health and aesthetics of soft and hard tissues around implants.

PURPOSE

To compare mechanical properties and marginal fit of prefabricated and customized dental implant abutments and provide references to evaluate the relationship between abutment choice and clinical indications.

METHODS

Titanium abutments were randomly divided into prefabricated and customized abutments. Static and dynamic loads were applied according to ISO14801:2016. Mechanical properties, including fracture strength, fatigue strength, rotational torque value, and torque loss rate, were measured. The biological properties of the implant abutments were assessed using an internal marginal fit. The samples were sliced, and the internal marginal fit was examined using a scanning electron microscope before and after cyclic loading. The length of the tight contact was calculated at the level of the conical connection, lower internal connection, and screw threads. Microleakage was evaluated by immersing the samples in 1% methylene blue and measuring the absorbance.

RESULTS

The fracture strengths of the prefabricated abutments were greater than those of the customized abutments before and after cyclic loading. The average fatigue strengths of the prefabricated and customized abutments were 350 and 300 N, respectively. The removal torque loss of the customized abutments was significantly greater than that of the prefabricated abutments. Significant differences were found in conical connection before loading, while the screw threads showed substantial differences between the two groups after loading. Microleakage in the customized abutments was significantly higher than that in the prefabricated abutments before and after loading.

CONCLUSIONS

Prefabricated abutments showed superior mechanical and biological properties compared with customized abutments in vitro, suggesting a greater risk of mechanical and biological complications occurring with the use of customized abutments. This study provides a reference for the clinical selection of implant abutments.

Original vs compatible stock abutment- implant connection. An in vitro analysis of the internal accuracy and mechanical fatigue behaviour

PURPOSE

To assess the internal accuracy and mechanical behaviour under cyclic loading after artificial aging of implantsupported crowns restored with original stock abutments and two compatible non-original stock abutments.

METHODS

Forty-eight original internal hexagon connection implants were connected to different stock abutments. The samples were divided into three groups depending on the manufacturer of the abutment components (one original, two non-originals).Firstly, samples were cross-sectioned and observed by using Scanning Electron Microscope (SEM) to evaluate the internal accuracy in three different implant-abutment interface locations (platform, internal and screw). Further, cyclic fatigue loading was carried out according to the ISO Norm 14801 using dynamic testing machine under sinusoidal loads for 2,000,000 cycles at test frequencies of 2 Hz in air after thermocycling with 10,000 cycles at 5 °C and 55 °C in artificial saliva for aging simulation.

RESULTS

Original abutment components presented the highest percentage of surface with tight contact with the implant in the three implant-abutment interfaces studied. Additionally, original configuration showed highest fatigue limit value and fatigue strength exponent (280 N and -0.054) than non-original 1 (225 N and -0.109) and non-original 2 (200 N and -0.101).

CONCLUSION

Original abutment components provide better fit and mechanical results under cyclic loading than nonoriginal configurations. The results obtained in this study seem to suggest that the use of the original stock abutments to implants leads to a more homogeneous load distribution between the components that can influence the long-term success of the restorations.

Accuracy of Original vs. Non-original Abutments Using Various Connection Geometries for Single Unit Restorations: A Systematic Review

PURPOSE

To ascertain whether the compatibility of non-original abutments (NOAs) with dental implants is influenced by the type of implant connection i.e. internal or external, and whether certain combinations of componentry may be as compatible as the original components.

METHODS

A structured literature search was conducted using 3 electronic databases (MEDLINE®, The Cochrane Library, and Web of Science Core Collection) for studies reporting on the use of non-original abutments published between 1995 and 2020. This was supplemented with hand searching in relevant journals and references, as well as searching grey literature. Relevant studies were selected according to specific inclusion criteria. Data was collected for the following parameters: precision of fit, microleakage, micromorphological differences, micromotion, rotational misfit, screw loosening, maximum load capacity, fracture resistance, tensile strength, compressive strength and in-vivo implant and prosthesis outcomes.

RESULTS

The electronic searching and hand search yielded titles and abstracts of 5617 studies following de-duplication; 40 studies were finally selected. Overall, original abutments showed better precision of fit, ability to resist microleakage, prevention of rotational misfit and micromotion, and fatigue strength compared with non-original abutments. Some non-original abutments on external connections were comparable with original abutments in terms of precision of fit and resistance to screw loosening and may be associated with less catastrophic failures than those on internal connections.

CONCLUSION

Original abutments present more predictable outcomes than non-original abutments with regards to the parameters investigated. However, it seems that external connections can provide some level of compatibility in terms of precision of fit and may also exhibit less catastrophic failures than NOAs on internal connections. This may be due to increased rotational freedom external connections provide. There is a lack of information regarding the influence of connection geometry on many aspects of compatibility and therefore the current clinical recommendation should be to use original abutments. More laboratory studies comparing non-original abutments on different implant connections are required. In addition, there is a need for long-term in vivo studies providing data on the clinical performance of non-original abutments. This article is protected by copyright. All rights reserved.

Mechanical Performance of Chairside Ceramic CAD/CAM Restorations and Zirconia Abutments with Different Internal Implant Connections: In Vitro Study and Finite Element Analysis

(computer-aided design-computer-aided manufacturing) CAD/CAM monolithic restorations connected to zirconia abutments manufactured with a chairside workflow are becoming a more common restorative option. However, their mechanical performance is still uncertain. The aim of this study was to evaluate the mechanical behavior of a combination of a zirconia abutment and monolithic all-ceramic zirconia and lithium disilicate crown manufactured with a chairside workflow, connected to titanium implants with two types of internal connection—tube in tube connection and conical connection with platform switching. They were thermally cycled from 5 °C to 55 °C and were subjected to a static and fatigue test following ISO 14801. The fractured specimens from the fatigue test were examined by SEM (scanning electron microscopy). Simulations of the stress distribution over the different parts of the restorative complex during the mechanical tests were evaluated by means of (finite element analysis) FEA. The mechanical performance of the zirconia abutment with an internal conical connection was higher than that of the tube in tube connection. Additionally, the use of disilicate or zirconia all-ceramic chairside CAD/CAM monolithic restorations has similar results in terms of mechanical fracture and fatigue resistance. Stress distribution affects the implant/restoration complex depending on the connection design. Zirconia abutments and monolithic restorations seem to be highly reliable in terms of mechanical resistance.

Original versus nonoriginal cast-to-gold abutment-implant connection: Analysis of the internal fit and long-term fatigue performance

STATEMENT OF PROBLEM

Restoring implants with nonoriginal abutments is common. However, studies that evaluated compatible abutments with long-term fatigue performance are lacking.

PURPOSE

The purpose of this in vitro study was to assess the internal fit and the cyclic fatigue life after artificial aging of 3 implant-abutment configurations restored with 1 original and 2 compatible nonoriginal cast-to-gold abutments.

MATERIAL AND METHODS

Forty-eight original internal hexagon connection implants were connected to 3 different brands of abutments (n=16): 1 original to the implant system and the other 2 with nonoriginal abutments. Internal fit and the percentage of surface with tight contact were assessed by scanning electron microscopy in 12 cross-sectioned specimens (n=4) at 3 different areas (platform, internal, and screw). Thirty-six implant-abutment-crown specimens (n=12) were immersed in artificial saliva and thermocycled for 10 000 cycles between 5 °C and 55 °C. Subsequently, a cyclic load test, as per International Organization for Standardization (ISO) Standard 14 801, was completed in a universal testing machine at 2 Hz in air.

RESULTS

The original abutments presented the best fit and highest percentage of tight contact in the internal areas. In addition, the original abutments showed the lower cyclic fatigue strength degradation and the highest long-term success.

CONCLUSIONS

Occlusal loads are transferred more homogenously through the system when original abutments are used because of the better fit between the internal components, leading to increased fatigue resistance.

Three-dimensional positional accuracy of intraoral and laboratory implant scan bodies

STATEMENT OF PROBLEM

In the implant digital workflow, scan bodies provide the 3D position of digital implants in the virtual dental arch. However, limited evidence is available on scan body accuracy, selection, and usage.

PURPOSE

The purpose of this in vitro study was to evaluate the 3D positional accuracy of 4 intraoral and 6 laboratory scan body systems to the implants and laboratory replicas of an implant system under various torque magnitudes.

MATERIAL AND METHODS

Ten test groups comprising 4 intraoral (I): Medentika L-Series (MS), Straumann CARES Mono (SM), Core 3D (CO), Straumann RC (SS); and 6 laboratory (L): Nobel Procera Pos Locator (NP), Sirona InPost (SR), Amann Girrbach (AG), Straumann CARES Mono (SM), Core 3D (CO), Straumann RC (SS) scan bodies were derived from 7 scan body systems. Of these, 3 systems (SM, CO, SS) are used for both intraoral and laboratory applications. The scan bodies were tested on Straumann Bone Level Regular CrossFit implants or laboratory replicas. Eight test groups allowed for the variation of torque application (5, 10, and 15 Ncm), while 2 test groups (NP, SR) were hand positioned only. Prefabricated metal abutments (ME) for both implants and laboratory replicas served as controls. A coordinate measuring machine measured four 3D positional accuracy variables: vertical linear distortion (d_z), 2D tolerance displacement (d_r), global linear distortion (d_R), and scan body height discrepancy (ΔH) (n=10). The data were analyzed with 2-way analysis of variance tests and post hoc analysis with Tukey tests (α=.05).

RESULTS

For both intraoral and laboratory test groups, 2-way ANOVA found that the system had a significant effect on all distortion variables (P<.001), while torque magnitude had a significant effect only on d_z and ΔH (P<.001). Overall, mean d_z ranged from 5 ±12 μm for L-AG at 15 Ncm to 23 ±14 μm for L-AG at 5 Ncm. Mean d_r ranged from 5 ±4 μm for I-SM at 15 Ncm to 73 ±41 μm for L-SS at 10 Ncm, and mean d_R ranged from 11 ±6 μm for I-SM at 10 Ncm to 74 ±41 μm for L-SS at 10 Ncm. Mean ΔH ranged from -5 ±10 μm for I-SM at 15 Ncm to 23 ±14 μm for L-AG at 5 Ncm. Among intraoral test groups, for d_z and ΔH, all the test groups except for I-SM at 15 Ncm and I-MS at 10 and 15 Ncm were significantly more positive than the control (P<.001). For d_r, I-SS at 5, 10, and 15 Ncm was significantly different from the control (P<.001). For d_R, only I-SS at 5 Ncm was significantly different from the control (P<.001). Among laboratory test groups, for d_z and ΔH, L-AG at 5 Ncm and L-CO at 15 Ncm were significantly more positive than the control (P<.001). For d_r, L-SS at 10 and 15 Ncm were significantly different from the control (P<.001). For d_R, only L-SS at 10 Ncm was significantly different from the control (P<.001). Intraoral and laboratory systems show comparable 3D positional accuracy.

CONCLUSIONS

Overall, I-SS and L-SS were the least accurate. The system tested had a significant effect on 3D positional accuracy, while torque magnitude had no consistent effect across all systems.

Reproducibility of laboratory scanning of multiple implants in complete edentulous arch: Effect of scan bodies

OBJECTIVES

To evaluate the reproducibility of complete arch scanning with multiple implant scan bodies using a laboratory scanner.

METHODS

A master model of edentulous maxillary arch with 6 implants was fabricated. PEEK scan bodies were inserted into the model and consecutively scanned using a dental laboratory scanner (N = 10, Group C). Another 10 scans were performed with each scan body detached and reinserted into the same site between each scan (Group CR). The last group of scanning was performed with the scan bodies detached and randomly repositioned between each scan (N = 10, Group RR). Virtual models were created and the inter-implant distances and angles were measured using an inspection software. Accuracy of the complete arch scans was calculated and compared using Two-Way ANOVA (⍺ = 0.05).

RESULTS

Significant greater distance distortion was found in CR (27.6 ± 18.9 μm) and RR (34.2 ± 25.0 μm). No significant difference in angular distortion was found among 3 groups. The greatest distance distortion was found in the anterior and cross-arch region of the arch. The smallest angular distortion was found in the first scanned sextant, with increasing distortion along the scanning path of the arch. The distance precision was significantly reduced in group CR and RR, while the angular precision was significantly reduced in group RR only.

CONCLUSION

Reproducibility of complete arch scanning was significantly affected by repositioning of the scan bodies using a laboratory scanner. Repeated and random repositioning of the scan bodies would decrease the reproducibility of the spatial position and angle of the virtual implant. The distortion appeared to be small and within the clinical tolerance.

CLINICAL SIGNIFICANCE

High-precision transfer of the implant information from intra-oral environment to dental laboratory is a prerequisite for the success of implant-supported prosthesis. Although laboratory scanners seem to be accurate, their accuracy is also affected by the precision and attachment procedure of the implant scan bodies and that has always been overlooked.