Physicochemical and microscopic characterization of implant-abutment joints

Surface, microstructural and mechanical characterization of contemporary implant abutment screws

OBJECTIVES

The aim of the present work was to evaluate six commercially available abutment screws by characterising roughness parameters, microstructure and mechanical properties.

METHODS

Six abutment screws from each implant system, were used. The surface roughness parameters (Sa, Sq, Ssk, Sku, Spk, Sk and Svk) were identified by an optical interferometric profiler. Microstructural observations and crystallographic analysis were performed using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscopy (EDX) device for elemental analysis and an X-ray diffractometer (XRD), respectively. The Martens Hardness (HM), Indentation Modulus (EIT), elastic index (ηIT) and Vickers hardness (HV) of all specimens were determined by instrumented indentation testing (IIT). The results were analyzed by one-way ANOVA and Tukey multiple-comparison tests (a=0.05).

RESULTS

EDX and XRD showed the abutment screws to be mixed α- and β-phase titanium alloys. Microstructural analysis revealed a fine homogeneous microstructure without porosity, consisting of fine dispersoid rods of β-phase embedded in a continuous α-phase matrix. Statistically significant differences were found among the mechanical properies and surface roughness parameters apart from Sq, Spk and Svk.

CONCLUSIONS

The tested abutment screws showed significant differences in the probed properties, and, thus, differences in their clinical behaviour are anticipated.

Titanium particles in peri-implantitis: distribution, pathogenesis and prospects

Peri-implantitis is one of the most important biological complications in the field of oral implantology. Identifying the causative factors of peri-implant inflammation and osteolysis is crucial for the disease's prevention and treatment. The underlying risk factors and detailed pathogenesis of peri-implantitis remain to be elucidated. Titanium-based implants as the most widely used implant inevitably release titanium particles into the surrounding tissue. Notably, the concentration of titanium particles increases significantly at peri-implantitis sites, suggesting titanium particles as a potential risk factor for the condition. Previous studies have indicated that titanium particles can induce peripheral osteolysis and foster the development of aseptic osteoarthritis in orthopedic joint replacement. However, it remains unconfirmed whether this phenomenon also triggers inflammation and bone resorption in peri-implant tissues. This review summarizes the distribution of titanium particles around the implant, the potential roles in peri-implantitis and the prevalent prevention strategies, which expects to provide new directions for the study of the pathogenesis and treatment of peri-implantitis.

Micro-CT Evaluation of Microgaps at Implant-Abutment Connection

The assessment of microgaps at the implant-abutment interface is an important factor that may influence clinical success. Thus, the aim of this study was to evaluate the size of microgaps between prefabricated and customised abutments (Astra Tech, Dentsply, York, PA, USA; Apollo Implants Components, Pabianice, Poland) mounted on a standard implant. The measurement of the microgap was performed using micro-computed tomography (MCT). Due to 15-degree rotation of samples, 24 microsections were obtained. Scans were performed at four levels established at the interface between the abutment and the implant neck. Moreover, the volume of the microgap was evaluated. The size of the microgap at all measured levels varied from 0.1 to 3.7 µm for Astra and from 0.1 to 4.9 µm for Apollo (p > 0.05). Moreover, 90% of the Astra specimens and 70% of the Apollo specimens did not exhibit any microgaps. The highest mean values of microgap size for both groups were detected at the lowest portion of the abutment (p > 0.05). Additionally, the average microgap volume was greater for Apollo than for Astra (p > 0.05). It can be concluded that most samples did not exhibit any microgaps. Furthermore, the linear and volumetric dimensions of microgaps observed at the interface between Apollo or Astra abutments and Astra implants were comparable. Additionally, all tested components presented microgaps (if any) that were clinically acceptable. However, the microgap size of the Apollo abutment was higher and more variable than that of the Astra one.

Mechanical, Chemical, and Biological Properties of 3D-Printed Abutments: A Systematic Review

Aim:

A systematic review of the methods of 3D printing and the materials used so far for the manufacture of abutments was performed to evaluate whether their clinical use is indicated through the mechanical, chemical, and biological analyses carried out.

Materials and Methods:

An electronic search conducted by three independent reviewers was carried out in the PubMed, Web of Science, Cochrane Library, Science Direct, and Lilac databases. The inclusion criterion was researching articles in English that contained as subject the manufacturing of abutments through 3D printing/additive manufacturing. Any meta-analyses, reviews, book chapters, abstracts, letters, conferences papers, and studies without abutments printed were excluded.

Results:

We found 780 references, which after applying the exclusion criteria resulted in the final inclusion of seven articles for review. The studies had a high heterogeneity, showing different materials and methodologies to manufacture abutments, which makes a comparison between them difficult, and for this reason it was not possible to carry out a meta-analysis with the data found.

Conclusions:

Even with the limitations found in the present research, it is possible to conclude that printed abutments have adequate mechanical, chemical, and biological properties that can indicate their clinical use. 3D printing presents high accuracy and speed and can produce customized abutments according to each case.

Healing Abutment Distortion in Implant Prostheses: An In Vitro Study

Little has been studied regarding the repeated usage of healing abutments and their effects on the distortion of dental implant-healing abutment hex surfaces. Additionally, implant manufacturers do not provide specific guidelines on how many times a healing abutment can be used before discarding. Therefore, we evaluated the effect of repeated screwing-unscrewing of implant-healing abutment on the healing abutment hex surface and screw head. A total of 12 Biomate implants with 4 mm diameter and 13 mm length were inserted into a synthetic bone block. The standard healing abutments of 3 mm diameter and 4 mm length were screwed onto each implant using a torque ratchet at a final torque of 30 Ncm. Immediately, the abutments were unscrewed at 30 Ncm. Then, screwing-unscrewing was repeated for 4, 8, 16, 24, 32, 40, 80, 160, 320, and 400 times and the healing abutments were scanned under the scanning electron microscope for any distortion. Distortion was graded as 0, 1, 2, and 3. Data were analyzed using SPSS 24.0. Descriptive statistics were calculated. One-way ANOVA with post hoc using Tukey’s HSD test was performed to analyze the difference in distortion at different screwing-unscrewing times. A significant level was selected at p-value = 0.05. It was found that distortion healing abutments screws were seen after 32 times screwing and unscrewing. There was a significant difference in the distortion (p-value < 0.05) after 24 times of repeated usage of healing abutment and at 160, 320, and 400 times. No surface distortions were observed at the healing abutment screw head at 4, 8, 16, 24, 32, 40, 80, 160, 320, and 400 cycles of screwing-unscrewing. It can be concluded that repeated screwing and unscrewing of the implant-healing abutments causes damage to the healing abutment hex surface. The distortion of healing abutments screws was seen after 32 times screwing and unscrewing. No surface distortions were observed on the healing abutment screw head until 400 times of screwing and unscrewing. Hence, the clinician should be cautious while using the healing abutments repeatedly.

Fatigue Resistance of Cast-on Implant Abutment Fabricated with Three Different Alloys

OBJECTIVES

 This study aimed to evaluate fatigue resistance of cast-on implant abutment using three alloys.

MATERIALS AND METHODS

 Forty specimens of implant-supported crowns were prepared; Group 1 (TA) stock titanium abutments, Group 2 (GS) abutment cast with 40% gold alloy, Group 3 (GP) abutment cast with palladium alloy, and Group 4 (CN) abutment cast with nickel-chromium alloy. Specimens were cyclic loaded at 20 Hz, starting from 200 N (5,000 cycles), followed by stepwise loading of 400, 600, 800, 1,000, 1,200, 1,400, 1,600, and 1,800 N (30,000 cycles/step). Specimens were loaded until failure or reached 245,000 cycles.

STATISTICAL ANALYSIS

 The withstand cycles were analyzed using one-way analysis of variance and Weibull survival analysis. Fracture surfaces were examined using scanning electron microscopy.

RESULTS

 The results of withstand cycles were TA (189,883 ± 22,734), GS (195,028 ± 22,371), GP (187,662 ± 22,555), and CN (200,350 ± 30,851). The statistical analysis showed no significant difference between the groups (p = 0.673).

CONCLUSION

 Although CN has higher Weibull characteristic strength which means greater durability, its lower Weibull modulus demonstrated less structural reliability. Consistent failures at implant fixture level were also found in CN group.

Pull-off resistance of a screwless implant-abutment connection and surface evaluation after cyclic loading

PURPOSE

The aim of this study was to investigate to what extent cyclic load affects the screwless implant-abutment connection for Morse taper dental implants.

MATERIALS AND METHODS

16 implants (SICvantage max) and 16 abutments (Swiss Cross) were used. The screwless implant-abutment connection was subjected to 10,000 cycles of axial loading with a maximum force of 120 N. For the pull-off testing, before and after the same cyclic loading, the required force for disconnecting the remaining 6 implant-abutment connections was measured. The surface of 10 abutments was examined using a scanning electron microscope 120× before and after loading.

RESULTS

The pull-off test showed a significant decrease in the vertical force required to pull the abutment from the implant with mean 229.39 N ± 18.23 before loading, and 204.30 N ± 13.51 after loading (P<.01). Apart from the appearance of polished surface areas and slight signs of wear, no visible damages were found on the abutments.

CONCLUSION

The deformation on the polished abutment surface might represent the result of micro movements within the implant-abutment connection during loading. Although there was a decrease of the pull-off force values after cyclic loading, this might not have a notable effect on the clinical performance.

Ion Release from Dental Implants, Prosthetic Abutments and Crowns under Physiological and Acidic Conditions

Ion release from dental implants and prosthetic restoration can affect osteointegration and implant viability over a long period of time. Therefore, the aim of this study was to study the ion release from implants and crowns, with and without intermediate anodized abutments, in two different media, simulating clinical conditions. The implants, intermediate prosthetic abutments and Cr–Co crowns were divided into two groups depending on the media: Hanks’ solution and 1% lactic acid, simulating body fluids and microbiologically conditioned fluids, respectively. The study followed the ISO 10271:2011 and 10993-15:2000 standards modified to simulate the replacement of fluids in the oral environment. The ions’ release was measured by inductively coupled plasma mass spectroscopy (ICP-EOS), and only aluminum, chromium, cobalt, titanium and vanadium were identified. Ion concentration was higher in lactic acid than in Hanks’ solution at all time points (p < 0.05). Only vanadium showed a very low ion release in lactic acid, with no statistically significant differences from the ion release in Hanks’ solution (p = 0.524). Both anodized abutments and the immersion medium influenced the release of ions and affected the corrosion of these structures. The presence of an intermediate anodized abutment also affected ion release, as the level of ions was lower in groups with this component.

Remnant oral biofilm and microorganisms after autoclaving sterilization of retrieved healing abutments

OBJECTIVE

The purpose of this study was to evaluate the sterilization effectiveness against biofilms on retrieved healing abutments used in implant dentistry.

BACKGROUND

A large number of clinicians reuse healing abutments to decrease treatment costs although it can promote infection due to the presence of remnant biofilm biomass.

METHODS

One hundred and eighty-five titanium healing abutments previously used for 3 months in oral cavity were assessed in this study. Abutments were submitted to cleaning, chemical disinfection, and autoclave sterilization according to clinical guidelines. The abutments were aseptically placed into glass tubes containing specific bacterial growth medium and then incubated for 10 days. From glass tubes with bacterial growth, 100 µl medium was transferred to Schaedler's agar for morphological identification and counting of strict anaerobes and to Columbia blood agar for presumptive identification of facultative anaerobes after incubation. Isolated strains were then identified at species level by enzymatic and biochemical tests within API microorganism detection platform. Also, polymerase chain reaction (PCR) was performed for identification of undefined strains.

RESULTS

After the standard cleaning and sterilization procedures, fifty-six (approximately 30%) retrieved abutments showed the presence of remnant biofilm biomass. The bacteria identified into the remnant biofilms covering the abutments were representative of the commensal oral microbiota including Aggregatibacter actinomycetemcomitans, Prevotella intermedia, and Enterococcus faecalis.

CONCLUSION

Although some healing abutments did not reveal the existence of bacteria, organic components from biofilm biomass are still strongly adhered on the retentive micro-regions and surfaces of abutments and therefore that would support the accumulation of biofilm including pathogenic species leading to patients' cross-infections. Further studies should be performed on the assessment of different materials, design, and connections of the healing abutments associated with clinical disinfection procedures in implant dentistry.

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.

Potential Causes of Titanium Particle and Ion Release in Implant Dentistry: A Systematic Review

Implant surface characteristics, as well as physical and mechanical properties, are responsible for the positive interaction between the dental implant, the bone and the surrounding soft tissues. Unfortunately, the dental implant surface does not remain unaltered and changes over time during the life of the implant. If changes occur at the implant surface, mucositis and peri-implantitis processes could be initiated; implant osseointegration might be disrupted and bone resorption phenomena (osteolysis) may lead to implant loss. This systematic review compiled the information related to the potential sources of titanium particle and ions in implant dentistry. Research questions were structured in the Population, Intervention, Comparison, Outcome (PICO) framework. PICO questionnaires were developed and an exhaustive search was performed for all the relevant studies published between 1980 and 2018 involving titanium particles and ions related to implant dentistry procedures. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed for the selection and inclusion of the manuscripts in this review. Titanium particle and ions are released during the implant bed preparation, during the implant insertion and during the implant decontamination. In addition, the implant surfaces and restorations are exposed to the saliva, bacteria and chemicals that can potentially dissolve the titanium oxide layer and, therefore, corrosion cycles can be initiated. Mechanical factors, the micro-gap and fluorides can also influence the proportion of metal particles and ions released from implants and restorations.