Implant-Abutment Contact Surfaces and Microgap Measurements of Different Implant Connections Under 3-Dimensional X-Ray Microtomography

Microgap Formation in Conical Implant-Abutment Connections Under Oblique Loading: Influence of Cone Angle Mismatch Through Finite Element Analysis

OBJECTIVES

This study evaluated different designs of the conical implant-abutment connection (IAC) and their resistance to microgap formation under oblique loads as specified by the ISO standard for testing dental implants. Also evaluated was the effect of deviations from the ISO specifications on the outcomes.

METHODS

Finite element analysis was conducted to compare the microgap formation and stress distribution among three conical IAC designs (A, B, and C) in two loading configurations: one compliant with ISO 14801 and one with a modified load adaptor (non-ISO). The different IAC designs varied in the taper, diameter, and cone height. The cone angle mismatch (Cam) between the implant and abutment was considered. A torque of 20 Ncm and oblique loads (up to 400 N) were simulated.

RESULTS

The stresses produced by the screw-tightening torque varied among the different IAC designs. The contact height was approximately 0.3 mm for Designs A and B, and less than 0.03 mm for Design C. Under oblique loads, Design A maintained IAC sealing without gap formation up to 400 N. With the ISO adaptor, gaps appeared in Design B at 300 N and in Design C at 90 N. The non-ISO adaptor resulted in gap formation at 160 N for Design B and at 50 N for Design C.

CONCLUSIONS

The IAC design and cone angle mismatch significantly influenced microgap formation, with some designs showing zero gaps even when the oblique load reached 400 N. The non-ISO adaptor increased gap formation in IACs B and C.

Effect of Cyclic Loading on the Fixture-Abutment Microgap in Short Implants Versus Standard Implants: An In Vitro Study

Objectives: This study aimed to assess the effect of cyclic loading on the amount of fixture-abutment microgap in short implants compared to standard implants. Materials and Methods: This in vitro experimental study was conducted on two groups of short and standard implants (n = 10). The microgap at the fixture-abutment interface was measured under a light microscope at ×75 magnification. The implants were mounted in an acrylic resin to simulate the jawbone. They were then subjected to cyclic loading by applying 75 N load with 1 Hz frequency along the longitudinal axis of each implant (perpendicular to the abutment surface). After 500,000 cycles, corresponding to 20 months of mastication in the oral environment, the implants were removed from the acrylic resin, and the microgap at the fixture-abutment interface was measured again under a stereomicroscope by a blinded examiner. Data were then analyzed by t-test using SPSS version 22 (α = 0.05). Results: The mean microgap was 13.59 ± 3.80 µm in the standard and 20.41 ± 11.30 µm in the short implants before cyclic loading (p=0.087). These values changed to 15.22 ± 5.44 and 24.53 ± 21.85 µm, respectively, after cyclic loading. No significant difference was noted in the amount of microgap between the standard and short implants after cyclic loading (p=0.222). Conclusion: Cyclic loading increased the amount of fixture-abutment microgap in both the standard and short implants. However, the difference in this respect was not significant between the two implant lengths. Thus, short implants could be reliably used in patients with limitations for surgery to restore function and esthetics.

Implant Mechanics, Biological Milieu, and Peri-Implantitis: A Narrative Review

Dental implants constitute an important treatment modality for rehabilitating edentulous and partially edentulous arches. With more implant systems in the market, understanding the mechanical aspects of implants is crucial in understanding this indispensable therapy. However, microflora-related factors i.e. biological factors are also crucial. Despite the tremendous success rate of dental implants, it is not averse to failure. Both mechanical and microbial aspects in seclusion or together predispose to implant failure. Newer technological advances have paved the way for advanced techniques to identify the not-so-common flora causing implant failure. This review focuses on detailed mechanical and biological aspects and the sealing agent used to seal the implant-abutment interface. It also focuses on advanced molecular techniques like metagenomics and transcriptomics. A thorough literature search was performed with selected articles from electronic databases. A combination of in-vivo and in-vitro studies were considered to provide comprehensive information on the subject. Both the biomechanical aspects like micro gap, and microleakage, as well as microbial movements play confluent roles in implant failure. The focus should be on the different aspects through which microflora can penetrate the inner parts of the implant. Also, newer culture-independent techniques of detecting previously undetected oral flora should be included in future studies.

Effect of shape and design of the internal connection of tissue-level and bone-level implants on detorque values and removal forces: An in vitro study

STATEMENT OF PROBLEM

Optimal implant stability and preventing complications such as screw loosening are paramount concerns for implant-supported prostheses. However, studies examining the influence of various internal connection designs on detorque values and removal forces, critical aspects of implant success, are lacking.

PURPOSE

The purpose of this in vitro study was to assess the impact of the shape and design of the internal connection in tissue-level and bone-level implants on the detorque value and the force required for abutment removal from the implant.

MATERIAL AND METHODS

Forty dental implants were securely mounted in 10×6×20-mm acrylic resin blocks positioned perpendicular to the surface. The implants were divided into 4 groups (n=10): bone-level SM Torx, tissue-level PSI Torx, bone-level UF Hex, and tissue-level UF Hex implants. After exposure to a dynamic loading test at 31.2 N, 2 Hz and 106 cycles, measurements were made of both detorque values and removal forces. Statistical analyses, including 1-way ANOVA with a post hoc Tukey test and Kolmogorov-Smirnov test, were conducted to assess the results (α=.05).

RESULTS

The differences in detorque values among the 4 groups were statistically similar (P=.087). In terms of removal force values, tissue-level PSI implants exhibited the highest values, while bone-level UF implants had the lowest values, with significant differences in the removal forces among the 4 groups (P<.001). Pairwise comparisons revealed significant differences among the groups (P<.001), except for the comparison between tissue-level PSI and bone-level SM implants (P=.108).

CONCLUSIONS

While detorque values remain consistent across implant types, the shape and design of the internal connection of implants has a significant impact on the removal force required for abutment detachment from the implant.

Does the index in Morse taper connection affect the abutment stability? An in vitro experimental study

The present study compared three different implant and abutment sets of type Morse taper (MT) connection, with- and without-index, were analyzed regarding their mechanical behavior without and with cyclic load application simulating the masticatory function. Ninety implant and abutment (IA) sets were used in the present study, divided into three groups (n = 30 samples per group): Group A, Ideale solid straight abutment (one piece) without index; Group B, Ideale abutment with an angle of 30-degree (two pieces) without index; Group C, Ideale abutment with an angle of 30-degree (two pieces) with index. The abutment stability quotient (ASQ) values, detorque value and rotation angle were measured before and after the cycling load. Twenty IA sets of each group were submitted to mechanical load at 360,000 cycles. The ASQ without load were 64.7 ± 2.49 for the group A, 60.2 ± 2.64 for the group B, 54.4 ± 3.27 for the group C; With load were 66.1 ± 5.20 for the group A, 58.5 ± 6.14 for the group B, 58.9 ± 2.99 for the group C. Detorque values were lower in groups B and C compared to group A (p < 0.05). In conclusion, the presence of the index did not influence the stability values. However, solid straight abutments (group A) showed higher values of stability compared to groups of angled abutments (groups B and C).

Effect of chemical and electrochemical decontamination protocols on single and multiple-used healing abutments: A comparative analysis of contact surface area, micro-gap, micro-leakage, and surface topography

INTRODUCTION

Although the combined use of chemical and electrochemical decontamination protocols can completely remove contaminants from the surfaces of one-time used healing abutments (HAs), their effectiveness in multiple-used HAs remains unknown. We aimed to investigate the effect of reused HAs frequency on the implant-HA contact surface area, micro-gap, microleakage, and surface topography following chemical and combined chemical and electrochemical decontamination protocols.

METHODS

Ninety bone level titanium implants were assembled with 90 bone level HAs, in which 80 contaminated HA samples were collected from human participants. The retrieved HAs were randomly divided into two groups according to the cleaning protocol: ultrasonication with 5.25% NaOCl solution for 15 min and steam autoclaving (group I); ultrasonication with 5.25% NaOCl solution for 15 min, followed by electrochemical cleaning and steam autoclaving (group II). The control group (group III) comprised 10 new unused HAs. The cleaning protocol was applied after each insertion as follows: (a) single-use and cleaning, (b) double-use and double cleaning cycles, (c) triple-use and triple cleaning cycles, and (d) more than triple-use and more than triple cleaning cycles. The contact surface area and micro-gap were assessed with micro-computed tomography scanning technique, microleakage test using 2% methylene blue staining, surface morphology with scanning electron microscopy, and surface elemental composition with energy-dispersive X-ray spectroscopy analysis.

RESULTS

Group Id exhibited the smallest contact surface area. The values of the micro-gap volumes and microleakage were significantly different (p < 0.001) in the descending order of Id > Ic > Ib > IId > Ia, IIa, and III. Morphological evaluation of Groups IIa, IIb, and IIc revealed that residual biological debris was optimally removed without altering their surface properties.

CONCLUSIONS

Chemical and electrochemical decontamination protocols are more effective than NaOCl cleaning methods, particularly for multiple consecutive uses with better decontamination levels, which decreases micro-gap volume and microleakage without surface alterations. Although the use of combined decontamination protocols for the contact surface area at the implant-HA interface showed comparable results with the control, change in the contact surface area was observed following the NaOCl cleaning methods. Therefore, titanium HA reuse can be considered in multiple times, if they are cleaned and sterilized using combined chemical and electrochemical decontamination protocols.

Assessment of Microgap and Microbial Leakage of Two Different Implant-abutment Interfaces: An In Vitro Study

AIM

The purpose of the current study was to evaluate Titanium and Bioneck TRI implant-abutment interfaces for microgaps and microbiological leakage.

MATERIALS AND METHODS

In this in vitro experiment, 40 dental implants were split into two groups, each of which had 20 samples. Group I: Titanium dental implant, group II: Bioneck TRI. E. coli strain was cultivated in MacConkey media for 24 hours at 37°C. To achieve a bacterial concentration of 1 × 108 colony-forming units per mL at 0.5 scale of MacFarland, the brain-heart infusion (BHI) broth was injected. The CFU count was done to evaluate the microbial leakage. The parts were first submerged, carefully cleaned in an ultrasonic bath, and then installed using a digital torque meter with a 20 N/cm preload. These were attached to a stub of approximately 13 mm using carbon tape, and the microgap evaluation was performed using a scanning electron microscope at a magnification of x1000. Unpaired t-test was used for the calculated data's statistical analysis. The p-value less than 0.05 was considered as statistically significant.

RESULTS

The maximum microbial leakage was in Bioneck TRI implants (10000 ± 0.01) followed by Titanium dental implants (8.60 ± 3.16). The mean difference was 9991.40 and there was a statistically significant difference found between the two different groups. The maximum microgap was found in the Bioneck TRI implants (9.72 ± 0.96), followed by Titanium dental implant (6.82 ± 1.10) and there was a statistically significant difference was found between the groups (p < 0.001).

CONCLUSION

The present study concluded that the microorganisms can infiltrate the microgap between the implant and abutment interface. When compared with Titanium dental implants, Bioneck TRI implants showed significantly higher levels of microbial leakage.

CLINICAL SIGNIFICANCE

A microgap between the implant and abutment connection might operate as a bacterial source, may produce inflammation, even osseointegration in danger, and subsequently alter clinical and histological parameters. Therefore, having an understanding of the compatible components aids in overcoming treatment planning challenges.

Biomechanical evaluation of abutment stability in morse taper implant connections in different times: A retrospective clinical study compared with an in vitro analysis

Objectives

Micromotion between a dental implant and abutment can adversely affect clinical performance and compromise successful osseointegration by creating a bacterial harbor, enabling screw loosening, and imparting disruptive lateral forces on the cortical bone. Thus, the aim of the present study was to measure the abutment stability evolution using resonance frequency analysis (RFA) in vivo at four different times (baseline, 3, 4, and 12 months), and compare these data obtained with the RFA measured after mechanical cycling (in vitro) corresponding to the proposed times in numbers of cycles.

Methods

To evaluate the abutment stability, RFA was performed in 70 sets of implant/abutment (IA) with a total of 54 patients (31 women, 23 men). These IA sets were divided into three groups, according to the abutment angulation: straight abutment (Abt1 group), 17-degree angled abutment (Abt2 group), and 30-degree angled abutment (Abt3 group). Abutment stability was measured immediately at implant placement and the abutment installation (T1), 3 (T2), 4 (T3), and 12 months (T4) later. For the in vitro analysis, ten sets of each group were submitted to mechanical cycling: T1 = 0 cycles, T2 = 90,000 cycles, T3 = 120,000 cycles, and T4 = 360,000 cycles. All data collected were statistically evaluated using the GraphPad Prism 5.01 software, with the level of significance was α = 0.05.

Results

In vivo, the overall data of implant stability quotient (ISQ) values obtained for all groups in each evaluation time were 61.5 ± 3.94 (95% CI: [60-63]) at T1, 62.8 ± 3.73 (95% CI, [61-64]) at T2, 63.4 ± 3.08 (95% CI: [61-64]) at T3, and 65.5 ± 4.33 (95% CI: [63-68]) at T4. Whereas in vitro, the ISQ were 61.5 ± 2.66 (95% CI: [59-63]) at T1, 63.2 ± 3.02 (95% CI, [61-65]) at T2, 63.9 ± 2.55 (95% CI: [62-66]) at T3, and 66.5 ± 2.97 (95% CI: [64-68]) at T4. In both evaluations (in vivo and in vitro), the data showed a significant difference (ANOVA test with p < 0.0001).

Conclusions

The RFA to measure the abutment stability used in this study showed that there was a progressive increase in stability among the predetermined times for the measurements, in both analysis (in vivo and in vitro). Furthermore, the values at each time point were similar, with no statistical difference between them.

Bridging the Gap with Nanoparticles: A Novel Approach

Two-piece implants unavoidably present a microgap between the implant and the abutment interface. Although numerous modalities have been attempted to overcome this situation, the implant abutment interface still remains a critical point for microbial colonization, which starts an inflammatory cascade of events eventually compromising the implants. Throughout our life, cells in all biological systems are unprotected to oxidative stress leading to the formation of Reactive oxygen species which is of concern when it comes to placing implants in patients who are periodontally compromised. This necessitates the development of alternative therapeutic modalities, which could counteract as well as prevent the microbial overload and ROS generation thereby improving the longevity of implants. To evaluate and assess the antibacterial, antioxidant and anti inflammatory effectiveness of quercetin-loaded titanium nanocomposites as coatings over healing abutments. Quercetin-loaded titanium nanocomposites were synthesized using green synthesis and confirmation was done using UV spectroscopy. Healing abutments were coated with the formulated nanocomposites, an intra-oral environment was simulated by thermocycling. Their antibacterial, antioxidant, anti-inflammatory, and cytotoxicity were assessed using standard tests. Healing abutments were coated with the formulated nanocomposites, an intra-oral environment was simulated by thermocycling. They showed potent antibacterial, antioxidant, and anti-inflammatory properties, which could prove beneficial in a variety of clinical scenarios in which there is a high risk for implant failure during early osseointegration.

Evaluation of Removal Force in Prosthetic Components of Morse Taper Dental Implants

The longevity of prosthetic rehabilitation is determined by the stability of the implant and abutment interfaces. True morse taper connections on dental restorations have been effective, however activation force still empirical. This work compared the activation strength and internal contact of Morse taper system according to the removal force. Eighty sets, composed of implants and prosthetic abutments, were evaluated with different internal contact areas; 15.12mm2 (G3.3) and 21.25mm2 (G4.3). The specimens were activated at 0° and 30°, with loads of 10, 20, 40 and 60N. The specimens were submitted to tensile test and the data to ANOVA and Tukey's tests (α=0.05). Representative specimens were examined under SEM. Removal force of G3.3 (2.15±1.33MPa) did not differed to G4.3 (1.99±1.03MPa). The activation at 0º (2.95±0.98MPa) statistically differed to 30º (1.19±0.54MPa). The 60N load was statistically superior for G3.3 and there was no statistical difference between 20N to 60N in G4.3. The values of 10N at 30o and 20N at the long axis of the morse taper implant, independent of the frictional contact area showed the best settlement.

Histological and Biological Response to Different Types of Biomaterials: A Narrative Single Research Center Experience over Three Decades

Background: In more than three decades of work of the Retrieval Bank of the Laboratory for Undemineralized Hard Tissue Histology of the University of Chieti-Pescara in Italy, many types of biomaterials were received and evaluated. The present retrospective review aimed to evaluate the histological and biological aspects of the evaluated bone substitute biomaterials. Methods: In the present study, the authors prepared a retrospective analysis after the screening of some databases (PubMed, Scopus, and EMBASE) to find papers published from the Retrieval Bank of the Laboratory for Undermineralized Hard Tissue Histology of the University of Chieti-Pescara analyzing only the papers dealing with bone substitute biomaterials and scaffolds, in the form of granules and block grafts, for bone regeneration procedures. Results: Fifty-two articles were found, including in vitro, in vivo, and clinical studies of different biomaterials. These articles were evaluated and organized in tables for a better understanding. Conclusions: Over three decades of studies have made it possible to assess the quality of many bone substitute biomaterials, helping to improve the physicochemical and biological properties of the biomaterials used in daily clinical practice.

Influence of buccal emergence profile designs on peri-implant tissues: A randomized controlled trial

BACKGROUND

The prosthetic emergence profile design might be an important factor in postsurgical mucosal recession etiology. Therefore, a restorative buccal emergence profile designed correctly might reduce gingival margin recession.

PURPOSE

To compare the marginal gingival level and the width/height (W/H) ratio between two profile configurations of single implant-supported restorations at molar sites.

MATERIALS AND METHODS

Twenty-one patients requiring a single mandibular molar tooth replacement with supracrestal mucosal thickness ≥2 mm were recruited and randomly assigned to a prosthesis buccal emergence profile design based on the buccal mucosal W/H ratio (Test Group) or maintained the original emergence profile of the healing abutment (Control Group). Assessments were made before delivery of the definitive restoration (T0), at prosthesis placement (T1), one (T2), and 12 (T3) months after loading. The gingival margin level change (△GM), initial emergence angle, buccal mucosal W/H ratio, marginal bone loss (MBL), implant failure, and complications were assessed.

RESULTS

The gingival recession in the test group (0.13 ± 0.32 mm) was significantly lower than in the control group (0.63 ± 0.38 mm) at T3 (p = 0.006). The initial emergence angle in the test group (31.4 ± 7.22 degrees) was significantly lower than the control group (40.0 ± 7.60 degrees) (p = 0.025). The W/H ratio in the test group at T2 was significantly higher than at T0 but remained stable thereafter. The W/H ratio presented a continued rising trend in the control group.

CONCLUSIONS

When the initial supracrestal soft tissue thickness was ≥2 mm, a restorative emergence profile based on the W/H ratio significantly reduced gingival margin recession. An emergence angle of 32.4 degrees showed better behavior in maintaining the gingival margin than 40 degrees.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR190002210.

Comparison of the Morse Cone Connection with the Internal Hexagon and External Hexagon Connections Based on Microleakage - Review

The gap formed at the abutment-implant interface brings about a bacterial colonization. In addition, a bacterial reservoir can be established within the implant. The build-up of microorganisms around the implant can cause soft tissue infections and bone loss around the implant, which can lead to implant failure. Our literature review aimed to evaluate the infiltration at the implant-abutment interface, comparing the Morse cone connection with the external hexagon and internal hexagon connections. A literature search using the PubMed database was performed on March 24, 2021. The search terms were combinations of "Morse cone" or "Morse taper" with each of the following terms (individually): "microleakage", "leakage", "infiltration", and "penetration". The inclusion criterion was in vitro studies comparing the Morse cone with the external hexagon and/or internal hexagon, based on infiltration at the implant-abutment interface. The exclusion criterion was the evaluation of microleakage at the implant-abutment interface after applying a sealant over this region. The search was expanded as needed. There was no limit on the year of publication, and only articles written in English were included. In addition, references cited in included articles were also included in this review when they were appropriate. This literature review concluded that, in most cases, the microleakage in the Morse cone connection was lower when compared with the external hexagon and internal hexagon connections.

The Microbial Neck: A Biological Review of the Various Implant–Abutment Connections

Aim:

This study reviews the importance of selecting implant systems with connection designs that ensure better long-term prognosis of the prosthesis, thus placed.

Materials and Methods:

An electronic search on the PubMed database was done using MeSH keywords (“dental implant OR abutment OR connection AND microleakage OR bone loss”) to review English language articles published since the year 2011, which compared the crestal bone levels and microleakage around various implant–abutment connection designs (external hex, internal hex, and Morse taper). The search screened for articles on human trials and in vitro studies to be included within the review.

Results:

Based on the inclusion and exclusion criteria applied to the preliminary search, a total of four articles were included in the review for evaluating the influence of connection type on peri-implant bone loss, while nine articles were included to study the influence on bacterial leakage across the implant–abutment interface.

Conclusion:

Based on the studies reviewed, the conical connection design proved to be the most biologically stable junctional geometry because of the better microbial seal and the lesser micromovement observed in these types of implants during functional loading. Moreover, this review even emphasizes the need for more longitudinal clinical trials to assess the microbial seal of these connection designs within the actual oral environment to evaluate long-term changes in the peri-implant tissues, and subsequently even factor the prognosis of the planned prosthetic intervention.

Behavior of implant and abutment sets of three different connections during the non-axial load application: An in vitro experimental study using a radiographic method

BACKGROUND

During the masticatory cycle, loads of different intensities and directions are received by the dental structures and/or implants, which can cause micromovements at the junction between the abutment and implant.

OBJECTIVE

The objective of this in vitro study was to evaluate the behavior of three different implant connections subjected to different load values using a digital radiography system. Additionally, the torque values for removing the abutment screws were also measured and compared.

METHODS

Ninety sets of implant and abutment (IA) were used, divided into three groups according to the type of connection (n = 30 per group): EH group, external hexagon type connection; IH group, internal hexagon connection; and, MT group, Morse taper connection.

RESULTS

MT group showed the better vertical misfit behavior at the three intensity of load applied, in comparison with EH and IH groups. In the analysis of torque maintenance (detorque test), MT group showed higher values of detorque when compared with the measured values of EH and IH groups (p < 0.001).

CONCLUSIONS

The IA sets of EH and IH groups showed a microgap in all levels of applied loads, unlike the MT group this event was not observed. In the detorque test, MT group increase in the torque values when compared to the initial torque applied, unlike EH and IH groups showed a decrease in the initially torque applied in all conditions tested. A positive correlation was detected between the misfit and detorque values.

Direct-Deposited Graphene Oxide on Dental Implants for Antimicrobial Activities and Osteogenesis

Objective

To determine the effects of graphene oxide (GO) deposition (on a zirconia surface) on bacterial adhesion and osteoblast activation.

Methods

An atmospheric pressure plasma generator (PGS-300) was used to coat Ar/CH₄ mixed gas onto zirconia specimens (15-mm diameter × 2.5-mm thick disks) at a rate of 10 L/min and 240 V. Zirconia specimens were divided into two groups: uncoated (control; Zr) group and GO-coated (Zr-GO) group. Surface characteristics and element structures of each specimen were evaluated by field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and contact angle. Additionally, crystal violet staining was performed to assess the adhesion of Streptococcus mutans. WST-8 and ALP (Alkaline phosphatase) assays were conducted to evaluate MC3T3-E1 osteoblast adhesion, proliferation, and differentiation. Statistical analysis was calculated by the Mann–Whitney U-test.

Results

FE–SEM and Raman spectroscopy demonstrated effective GO deposition on the zirconia surface in Zr-GO. The attachment and biofilm formation of S. mutans was significantly reduced in Zr-GO compared with that of Zr (P < 0.05). While no significant differences in cell attachment of MC3T3-1 were observed, both proliferation and differentiation were increased in Zr-GO as compared with that of Zr (P < 0.05).

Significance

GO-coated zirconia inhibited the attachment of S. mutans and stimulated proliferation and differentiation of osteoblasts. Therefore, GO-coated zirconia can prevent peri-implantitis by inhibiting bacterial adhesion. Moreover, its osteogenic ability can increase bone adhesion and success rate of implants.

One-Piece Titanium Implants: Retrospective Case Series

Purpose

One-piece titanium implants are not routinely used for reconstruction after tooth loss. Several limitations seemed to be apparent although the concept provides a straightforward approach for different clinical situations. A clinical documentation of five prosthetic restorations with one-piece titanium implants serving as a relevant treatment option in dental surgery is pursued. We demonstrate the feasibility and benefits of one-piece titanium implants for fixed dental prosthesis. Detailed descriptions of the technical features and the surgical approach by means of clinical cases are given. The prosthetic workflow when working with one-piece titanium implants is depicted in detail as well as examples for implant-supported tooth replacement in the posterior region and the esthetic zone. Conditions of applications regarding different timing of implant placement using the system and its limitations are discussed.

Results

Clinical cases with a follow-up period of up to 10 years are presented to prove the long-term success of one-piece titanium implants in terms of bone and soft-tissue stability respecting the biological criteria for periodontal health.

Conclusions

One-piece titanium implants represent a reliable treatment method for single-tooth replacements. Clinical success with long-time bone stability around the implantation site can be achieved. Taken into account the requirements for periodontal tissue stability, uneventful healing without extensive tissue loss is demonstrated by means of clinical cases presenting patients with periodontitis.

Mechanical Pull-Out Test of a New Hybrid Fixture-Abutment Connection: An In Vitro Study

Implant abutment connection was described among the main causes of peri-implant bone resorption. The aim of this in vitro study was to test the coupling capacity, the surface modification of a new hybrid connection and the influence of repeated connection activations caused during the main clinical and laboratory phases. A total of 40 implant-abutment screw retained systems with 10°-conical and internal hexagon connection were tested. The connection was screwed, fixed to the universal test machine, removed the screw and a pull-out test was performed. Test was repeated five times in succession. Also Scanning Electron Microscopy (SEM) was used to detect microscopically surface modification. Analysis of variance and Tukey tests were used for the statistical analysis. Pull-out test reveals a mean value of 131.35 ± 16.52 Newton Centimeter (N·cm). For each single activation, results from first to fifth were: 113.9 ± 13.02, 126.1 ± 12.81, 138.11 ± 15.15, 138.8 ± 11.90 and 140 ± 12.99 N·cm. A statistically significant difference between the measurements and an increase in the removal force was shown. The collected data supports the use of this new type of connection, resulting in a very strong interface between implant and abutment. Also, repeated activation of connection can promote a better coupling of the implant-abutment interface.

Synchrotron-based micro computed tomography investigation of the implant-abutment fatigue-induced microgap changes

OBJECTIVE

This study evaluates the effect of dynamic-loading on the microgap of the IAC when different supratructure heights are applied.

MATERIALS AND METHODS

Forty-eight dental implants (24 each of butt-joint (H) and internal-conical connections (C)) were tested in this study. Each group was further divided into three groups (n = 8) according to the applied suprastructure height (H1, C1: 10 mm, H2, C2: 14 mm and H3, C3: 18 mm). All specimens were subjected to cyclic loading in a chewing-simulator with a load of 98 N for 5 × 10⁶ chewing cycles. The microgap at the IAC was inspected before and after loading, using synchrotron-based micro computed tomography (SRμCT) and light microscopy (LM).

RESULTS

SRμCT revealed an internal microgap range between 0.26 μm and 0.5 μm in the group C, whereas the group H exhibited a microgap range between 0.26 μm and 0.47 μm prior to loading. After chewing simulation, a smaller microgap size in all groups was detected ranging from 0.11 μm to 0.26 μm (group C: 0.11μm-0.26 μm; group H: 0.21μm-0.25 μm). The LM investigation showed mean microgap values at the outer IAC junction before loading from 5.8 μm to 11.3 μm and from 3.9 μm to 7.2 μm after loading. All specimens exhibited a vertical intrusion displacement of the abutment.

CONCLUSION

Regardless of the crown height, the microgap between the abutment and implant systematically decreased after loading in both butt-joint and internal-conical connections.

A new design of a multifunctional abutment to morse taper implant connection: Experimental mechanical analysis

The objective of this study was to evaluate a new design of multifunctional abutment for Morse taper implant connections, relative to the retentive stability after the application of cyclic loads in cemented and screwed crowns. Multifunctional abutments with two different angulations in the seating portion of the crown were tested, forming 2 groups (n = 30 samples per group): Group Abut11, where Smart abutments with an angle of 11.42° were used; Group Abut5, where Ideale abutments with an angle of 5° were used. Fifteen samples from each group received cemented crowns (CC) and another fifteen screwed crowns (SC). All crown samples were subjected to the mechanical cycling test at 360,000 cycles at a frequency of 4 Hz and 150 N of the load. The samples with CC were subjected to the tensile test to remove the crowns, while in the samples with SC, the detorque value of the fastening crown screws was measured. The mean tensile strength value of CC in the Abut11 group was 131.9 ± 13.5 N and, in the Abut5 group was 230.9 ± 11.3 N; while the detorque mean value in samples with SC 5.8 ± 1.8 N for the Abut11 group and, 7.6 ± 1.1 N for Abut5 group. Significant statistical differences were found between the two groups in both situations tested (p < 0.05). The multifunctional abutments, presenting a lesser angulation of the crown-seating portion, showed higher values of retention of the CC and a lesser screw loosening of torque of the fixing screws in the SC after the application of cyclic loads when compared to the abutments with more angulation in the crown-seating portion.

Effect of sealing gel on the microleakage resistance and mechanical behavior during dynamic loading of 3 implant systems

STATEMENT OF PROBLEM

Sealing products have been produced to reduce microleakage at the implant abutment interface. However, little is known about their effectiveness and any alterations in mechanical behavior of implant systems with their application.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of a silicone sealing gel on implant abutment interface microleakage, abutment screw torque loss, and thread wear of implant systems in a simulated oral environment.

MATERIAL AND METHODS

Five specimens each of 3 implants systems (Nobel, Straumann, and WEGO) that included sealed and unsealed groups were analyzed (N=30). Before assembling the components, toluidine blue solution was injected to the implant intaglio cavity to evaluate implant abutment interface microleakage. After tightening to the recommended torque, 20 to 200 N of 30-degree off-axis dynamic force was applied at 2 Hz for 48 hours. The toluidine blue solution was extracted to test optical density values at 1, 3, 9, 24, 33, and 48 hours. Detorque values were measured before and after cycling loading, and torque loss rates were calculated. The abutment screw morphologies were observed by using scanning electron microscopy. The coefficient of friction tendency of applying sealing gel was explored with a ball-on-flat configuration. One-way ANOVA and Student t test were used for statistical analysis (α=.05).

RESULTS

The optical density value increased with the loading time, especially for Straumann group. The sealing gel decreased the implant abutment interface microleakage of Straumann assemblies after cyclic loading of 9 hours (P=.044), whereas no statistical difference was found for Nobel (P=.140) or WEGO groups (P=.402) at 6 time points. Torque loss occurred during tightening and further increased after dynamic cyclic load in each group. Among the 3 implant systems, Straumann implants reported the best antiloosening property (P<.001). The application of sealing gel reduced the initial (P=.048) and final (P=.032) torque loss rate in all the 3 systems. Scanning electron microscopy observations revealed the bottom thread tended to have more abrasion than the first thread. After applying sealing gel, less thread abrasion was found in Nobel and WEGO assemblies, whereas the protective effect was not evident for the Straumann group. The coefficient of friction of sealed group (0.17 ±0.026) was significantly (P=.012) lower than that of unsealed group (0.24 ±0.044).

CONCLUSIONS

The silicone sealing gel improved the immediate fastening and long-term antiloosening performances of 3 implant systems, decreased the implant abutment interface microleakage of Straumann system, and reduced abutment screw thread abrasion of the Nobel and WEGO systems.

The biological width around implant

PURPOSE

The concept of biological width has been proposed and widely used in oral implantation. This review aimed to summarize the biological width around implant in detail.

STUDY SELECTION

An electronic search of the literature prior to March 2019 was performed to identify all articles related to biological width in periimplant soft tissue. The search was conducted in the MEDLINE (National Library of Medicine) database accessed through PubMed with no date restriction. The following main keywords were used: "implant", "biological width", "soft tissue", "junctional epithelium", "peri-implant epithelium", "connective tissue", "gingiva", "mucosa" (connecting multiple keywords with AND, OR).

RESULTS

The identified researches focused on several aspects related to biological width in oral implantation, namely the concept, formation, remodeling, dimension, structure and function.

CONCLUSIONS

Based on of the reviewed literature, the concept, formation, remodeling, structure, dimension, and functional significances of periimplant biological width are explored in this narrative review. The formation of biological width around implant is a complex process after several weeks of healing. The biological width around implant is a 3-4mm distance from the top of the peri-implant mucosa to the first bone-to-implant contact or the stabilized top of the adjacent bone, consisting of sulcular epithelium, junctional epithelium and fibrous connective tissue between the epithelium and the first bone-to-implant contact or the stabilized top of the adjacent bone. The biological width forms a biological barrier against the bacteria, influences the remodeling of soft and hard tissue around implant and has implications for clinical aspects of dental implantation.

Measurement of gap between abutment and fixture in dental conical connection implants. A focused ion beam SEM observation

BACKGROUND

The aim of the authors was to examine the abutment-fixture interface in Morse-type conical implants in order to verify gaps at this level using a new microscopical approach.

MATERIAL AND METHODS

In this in vitro study, 20 abutment-fixture complexes were prepared by sectioning (longitudinal and cross-sectional to the long axis) with a microtome and then with a focused ion beam (FIB). This is a micrometric machine tool that uses gallium ions to abrade circumscribed areas to dig deeper into the cuts obtained with the microtome in order to eliminate cut-induced artifacts. This is because the FIB abrasion is practically free from artifacts, which are normally generated by the action of the microtome blades or other techniques. Samples were then observed by scanning electron microscopy (SEM).

RESULTS

The observation of the abraded parts with the FIB permitted measurement of the real gap between the implant-abutment components. A variable amount of gap was retrieved (from 0 to 3 μm) by the observations, confirming the non-hermetic nature of the connection. It has to be pointed out that in approximately 65% of cases, the gap accounted for less than 1 μm.

CONCLUSIONS

The reported data confirmed that the analyzed connection system allowed for minimal gap. However, from the evidence of the present analysis, it cannot be assumed that the 2 parts of a Morse-type conical implant are fused in 1 piece, which would create a perfectly matched hermetic connection.

Avaliação da interface entre o componente protético reto e a conexão interna tipo Cone Morse do implante dentário por meio da microscopia eletrônica de varredura

Resumo Introdução A interface implante-pilar protético e a formação dos seus microgaps são aspectos relevantes na transferência das cargas e na resposta biológica, estando ligadas ao sucesso da reabilitação. Objetivo Avaliar microgaps na interface entre a conexão interna do implante do tipo Cone Morse e a superfície do componente protético por meio da microscopia eletrônica de varredura (MEV). Material e método Foram utilizados 20 implantes dentários de tamanho 3,75 × 11,0mm do tipo Cone Morse com seus respectivos pilares protéticos da Singular® (Singular Implants, RN, Brasil). Os munhões retos foram acoplados aos implantes com torque de 32N/cm2 e o conjunto resultante foi emergido em base de Resina Epóxi ES260, para permitir secção longitudinal da amostra. As amostras foram analisadas e os microgaps mensurados no MEV (JEOL JCM-5700, MA, USA), e posteriormente os dados foram analisados. Resultado A média e o desvio padrão dos maiores microgaps foram observados na parte apical do implante nos lados direito e esquerdo, sendo 1,44±2,68 e 1,16±1,49 μm, respectivamente. Os menores microgaps foram na parte superior do implante nos lados direito e esquerdo, sendo 0,60±0,73 e 0,66±0,67 μm, respectivamente. Contudo, no teste de Kruskal-Wallis, não houve diferença estatisticamente significativa entre as regiões dos implantes, tanto para o lado esquerdo (p=0,692) como para o direito (p=0,865). No teste de Mann-Whitney, não houve diferenças estatisticamente significativas entre os lados para as diferentes regiões dos implantes. Conclusão Mesmo com a presença de microgaps na interface implante-pilar protético, estes apresentam tamanho inferior ao que causaria problemas biológicos e mecânicos. As amostras analisadas quanto à sua compatibilidade de encaixe foram satisfatórias.

A New Strategy Against Peri-Implantitis: Antibacterial Internal Coating

The bacterial biofilm formation in the oral cavity and the microbial activity around the implant tissue represent a potential factor on the interface between bone and implant fixture that could induce an inflammatory phenomenon and generate an increased risk for mucositis and peri-implantitis. The aim of the present clinical trial was to investigate the bacterial quality of a new antibacterial coating of the internal chamber of the implant in vivo at six months. The PIXIT implant (Edierre srl, Genova Italy) is prepared by coating the implant with an alcoholic solution containing polysiloxane oligomers and chlorhexidine gluconate at 1%. A total of 15 healthy patients (60 implants) with non-contributory past medical history (nine women and six men, all non-smokers, mean age of 53 years, ranging from 45-61 years) were scheduled to receive bilateral fixed prostheses or crown restorations supported by an implant fixture. No adverse effects and no implant failure were reported at four months. All experimental sites showed a good soft tissue healing at the experimental point times and no local evidence of inflammation was observed. Real-Time Polymerase Chain Reaction (PCR) analysis on coated and uncoated implants showed a decrease of the bacterial count in the internal part of the implant chamber. The mean of total bacteria loading (TBL) detected in each PCR reaction was lower in treated implants (81038 units/reaction) compared to untreated implants (90057 units/reaction) (p < 0.01). The polymeric chlorhexydine coating of the internal chamber of the implant showed the ability to control the bacterial loading at the level of the peri-implant tissue. Moreover, the investigation demonstrated that the coating is able to influence also the quality of the microbiota, in particular on the species involved in the pathogenesis of peri-implantitis that are involved with a higher risk of long-term failure of the dental implant restoration.

Contact analysis of gap formation at dental implant-abutment interface under oblique loading: A numerical-experimental study

PURPOSE

To develop numerical and experimental methods for investigating the formation of micro-gaps and the change in contact area at the implant-abutment interface of two different connector designs under oblique cyclic loading.

MATERIALS AND METHODS

Samples (n = 10 per group) of two-piece implant systems with the conical connection (group A) and the external hexagonal connection (group B) were subjected to cyclic loading with increasing load amplitudes up to 220 N. After loading, the samples were scanned using micro-CT, with silver nitrate as a high-contrast penetrant, and the level of leakage was assessed using a discrete scoring system. Three-dimensional finite element (FE) analyses of the two implant systems were also conducted to reveal the micro-gap formation process, especially bridging of the internal abutment screw space. The experimental and numerical results for the bridging load were then compared.

RESULTS

90% of the samples in group A showed leakage into the internal implant space at a load of around 100 N; while over 80% of those in group B did so at a load of around 40 N. This agreed with the FE analysis, which showed bridging of the internal implant space at loads similar to those measured for the two implant systems. Residual gaps of less than 1.49 μm were predicted for group A only after unloading.

CONCLUSIONS

The FE-predicted loads for bridging agreed well with those found experimentally for leakage to occur. The conical connection showed more resistance against formation of micro-gaps at the implant-abutment interface than the external hexagonal connection. Although the minimum load required to bridge the internal implant space was within the range of human biting force, the relation between bacterial invasion and micro-gaps needs further research.

In vitro assessment of connection strength and stability of internal implant-abutment connections

BACKGROUND

Various connections have been machined to improve the fit between the dental abutment and implant. In vivo, the instability created by imprecisely fitting components can cause soft tissue irritation and bacterial colonization of the implant system. The aim of this study was to quantify abutment stability under in vitro force applications.

METHODS

Abutment stability and fit were quantitatively measured after application of rotational, vertical, and horizontal forces.

FINDINGS

The abutment connection held by friction (Friction-Fit) was the only group to have 0° angular rotation. A significantly greater vertical force was required to pull the abutment from the implant for the Friction-Fit connection as compared to all other experimental groups. The abutment connection held by a mechanically locking friction-fit with four grooves (CrossFit) and Friction-Fit demonstrated significantly lower lateral movement as compared to all other connections. The remaining connections evaluated included two hexagon connections that rely on screw placement for abutment fit (Conical + Hex #1 and Conical + Hex #2), one connection with protruding slots to align with recessed channels inside the implant (Conical + 6 Indexing Slots), and an internal connection that allows for abutment indexing every 120° (Internal Tri-Channel).

INTERPRETATION

Internal connection geometry influenced the degree of abutment movement. Friction-Fit and CrossFit connections exhibited the lowest rotational and horizontal motions. Significant differences were found between Friction-Fit and CrossFit following the application of a vertical force, with the Friction-Fit requiring a significantly greater pull force to separate the abutment from the implant.

Ratio between Height and Thickness of the Buccal Tissues: A Pilot Study on 32 Single Implants

BACKGROUND

Previous studies have suggested that mucosal height is related to the bone level and soft tissue thickness. The purpose of this pilot study was to investigate the ratio between the height and width of the tissues around single implants with a conical connection and platform switching.

METHODS

All patients receiving single implants (Anyridge^®, MegaGen, Gyeongbuk, South Korea) and restored with single crowns, in a three-month period, were included in this study. After a provisionalization of 12 months, precision impressions were taken and stone casts were poured for measurements. For each implant, two values were collected at the buccal site: the mucosal height (MH), calculated from the vestibular shoulder of the implant to the upper gingival margin of the supra-implant tissue; and the mucosal thickness (MT), calculated from the vestibular shoulder of the analogue to the external mucosa point perpendicular to the implant major axis. Mean, standard deviation (SD), and confidence intervals (CI 95%) for MH and MT, as well as their ratios, were calculated. Correlation between MH and MT was assessed by Pearson's correlation coefficient, with significance level set at 0.05.

RESULTS

32 single Anyridge^® implants were eligible for this evaluation. The mean MH was 3.44 mm (±1.28), the mean MT was 3.29 (±1.46). The average of the ratio between MH and MT of the supra-implant mucosa was therefore 1:1.19 (±0.55). The relation between MH and MT was statistically significant at p ≤ 0.01 (Pearson two-tailed 95% CI).

CONCLUSIONS

Our study found a constant relationship between width and height of the peri-implant mucosa. However, our results are different from those of Nozawa et al., who found a ratio of 1:1.5 between height and thickness of the peri-implant tissues. This may be determined by the different sample and follow-up period, as well as by the implants used in our study.

Morse taper implant macrodesign, loading protocol and site of installation – retrospective study of 5,601 implants

Abstract Introduction The long-term implant-supported prosthetic rehabilitation monitoring is extremely important in evaluating parameters that could interfere in the success of the treatment. Objective To evaluate the influence of macrodesign (shape of the body and apex), length and diameter, insertion torque, site of installation as well as the loading protocol, on long-term survival rates. Material and method The data obtained was from the medical records of rehabilitated patients who had had at least one Morse taper implant surgery done at ILAPEO School between 2006 -2012. Incomplete medical records, from which it would have been impossible to extract all data essential to complete the study, were excluded. Result A total of 1,142 patient’s medical records comprised the sample; documenting the progress of 5,601 implants, done in both jaws and mandibles. The final survival rate was 98.31%, over an average time of 37.54 months. The type of implant most used was cylindrical (70.33%). The mean installation torque most evidenced in the study was between 41 and 50 Ncm. A logistical regression analysis showed that none of the following variables, site of installation, body and apex shape designs and length, had any significant statistical influence on implant loss. Torque increase and diameter influenced implant loss while immediate loading favored implant maintenance. Conclusion It can be concluded that Morse taper implants present a long-term survival rate that can be lowered by excessive torque, as well as by the diameter of the implant.

The Conometric Concept: A Two-Year Follow-Up of Fixed Partial CEREC Restorations Supported By Cone-In-Cone Abutments

PURPOSE

To evaluate the performance of definitive, implant-supported, lithium disilicate fixed dental prostheses (LS₂ FDPs) manufactured with a computer-assisted design/computer-assisted manufacturing (CAD/CAM) system. All patients received two-unit restorations placed in posterior regions, supported by osseointegrated implants with cone-in-cone connection abutments.

MATERIALS AND METHODS

Two implants (Ankylos) were placed into healed sites or fresh extraction sockets in the maxillary/mandibular posterior regions of partially edentulous patients. Definitive digital impressions were made 3 months after surgery. Twenty-four patients received fixed  monolithic LS₂ restorations manufactured with the CEREC system. All restorations were connected to the implants using cone-in-cone connection abutments. Peri-implant pocket depths were recorded for 2 years at each follow-up visit. Esthetic, functional, and biologic United States Public Health Services (USPHS) parameters modified by the FDI World Dental Federation study design were assessed yearly until the last follow-up appointment. The opposing dentitions were identified by type of restoration and supporting structures at the time of placement of the definitive restorations and at the 2-year follow-up visits.

RESULTS

One patient (4.16%) moved to an unknown location during the study. A total of 23 FDPs (95.8%) supported by 46 implants reached the 2-year follow-up. None of the prostheses failed, or became loose or detached. No significant difference involving probing levels between the experimental times were found.

CONCLUSIONS

The results of this research indicated that the abutment-prostheses connection using a cone-in-cone approach was successful within the 2-year period of this study. None of the studied monolithic LS₂ glass-ceramic prostheses milled using the CEREC CAD/CAM system fractured or became detached.

The influence of implant-abutment connection on the screw loosening and microleakage

Background

There are some spaces between abutment and implant body which can be a reservoir of toxic substance, and they can penetrate into subgingival space from microgap at the implant–abutment interface. This penetration may cause periimplantitis which is known to be one of the most important factors associated with late failure. In the present study, three kinds of abutment connection system, external parallel connection (EP), internal parallel connection (IP), and internal conical connection (CC), were studied from the viewpoint of microleakage from the gap between the implant and the abutment and in connection with the loosening of abutment screw.

Methods

We observed dye leakage from abutment screw hole to outside through microgap under the excessive compressive and tensile load and evaluated the anti-leakage characteristics of these connection systems.

Results

During the experiment, one abutment screw for EP and two screws for IP, out of seven samples in each group, were fractured. After the 2000 cycles of compressive tensile loadings, removal torque value (RTV) of abutment screw represented no statistical differences among three groups. Standard deviation was largest in the RTV of EP and smallest in that of CC. The results of microleakage of toluidine blue from implant–abutment connection indicated that microleakage generally increased as loading procedure progressed.

The amount of microleakage was almost plateau at 2000 cycles in CC, but still increasing in other two groups. The value of microleakage greatly scattered in EP, but the deviation of that in CC is significantly smaller. At 500 cycles of loading, there were no significant differences in the amount of microleakage among the groups, but at 1000, 1500, and 2000 cycles of loading, the amount of microleakage in CC was significantly smaller than that in IP. Throughout the experiment, the amount of microleakage in EP was largest, but no statistical difference was indicated due to the high standard deviation.

Conclusions

Within the limitation of the present study, CC was stable even after the loading in the RTV of abutment screw and it prevented microleakage from the microgap between the implant body and the abutment, among the three tested connections.

Influences of microgap and micromotion of implant-abutment interface on marginal bone loss around implant neck

OBJECTIVE

To review the influences and clinical implications of micro-gap and micro-motion of implant-abutment interface on marginal bone loss around the neck of implant.

DESIGN

Literatures were searched based on the following Keywords: implant-abutment interface/implant-abutment connection/implant-abutment conjunction, microgap, micromotion/micromovement, microleakage, and current control methods available. The papers were then screened through titles, abstracts, and full texts.

RESULTS

A total of 83 studies were included in the literature review. Two-piece implant systems are widely used in clinics. However, the production error and masticatory load result in the presence of microgap and micromotion between the implant and the abutment, which directly or indirectly causes microleakage and mechanical damage. Consequently, the degrees of microgap and micromotion further increase, and marginal bone absorption finally occurs. We summarize the influences of microgap and micromotion at the implant-abutment interface on marginal bone loss around the neck of the implant. We also recommend some feasible methods to reduce their effect.

CONCLUSIONS

Clinicians and patients should pay more attention to the mechanisms as well as the control methods of microgap and micromotion. To reduce the corresponding detriment to the implant marginal bone, suitable Morse taper or hybrid connection implants and platform switching abutments should be selected, as well as other potential methods.