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ORIGINAL ARTICLE |
https://doi.org/10.5005/djas-11014-0023
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Comparative Analysis of Microbial Leakage in Implant Recess of Three Different Internal Implant Abutment Connections: An In Vitro Study
1–3,6Department of Prosthodontics, Dr HSJ Institute of Dental Sciences & Hospital, Panjab University, Chandigarh, India
4,5Department of Microbiology, Dr HSJ Institute of Dental Sciences & Hospital, Panjab University, Chandigarh, India
Corresponding Author: Shefali Singla, Department of Prosthodontics, Dr HSJ Institute of Dental Sciences & Hospital, Chandigarh, India, Phone: +91 9417194185, e-mail: shefali_singla@yahoo.com
How to cite this article: Kumar L, Singla S, Rehan S, et al. Comparative Analysis of Microbial Leakage in Implant Recess of Three Different Internal Implant Abutment Connections: An In Vitro Study. Dent J Adv Stud 2023;11(3):102–105.
Source of support: Nil
Conflict of interest: None
Received on: 08 September 2023; Accepted on: 05 October 2023; Published on: 30 December 2023
ABSTRACT
Objective/Introduction: Bacterial infiltration at implant abutment junction is a potential risk for soft tissue inflammation and bone loss around the implant. Potential colonization of microgap is related to precision of fit at the mating interfaces of implant and abutment and is dependent on structural geometry of implant abutment connection. Considering the limited information regarding differences in microbial penetration at the junction in implants with degree of taper in internal connections, this study conducted comparative analysis of microbial seal of three different implant abutment connections—1.5 mm internal hex (IH), 4° tapered, and 11° conical hex (CH) implants.
Materials and methods: Three study groups with 18 implant abutment assemblies in each, included 1.5 mm IH (BioHorizon®), 4° taper (4° CH) internal conical connection (Ankylos®), and 11° taper (11°CH) connection (Neobiotech® Active) implants. Each assembly was suspended in Escherichia coli as well as Enterococcus faecalis suspension in brain heart infusion (BHI) separately and incubated at 37°C for 3 days. Wash from respective implant internal recess was assessed for microbial contamination.
Results: Internal hex group showed significantly higher E. coli (44.4%) and E. faecalis (50.0%) leakage than 4°CH and 11°CH groups. The difference in microbial leakage in 4°CH (11.1%) and 11°CH (16.7%) for both the study microbes was statistically insignificant (p = 0.630), thus partially accepting the null hypothesis.
Conclusion: The type of connection significantly influences microbial leakage at implant abutment junction with internal connection more conducive to bacterial infiltrations than conical connection implants. However, degree of taper of conical connection does not have a significant effect on bacterial permeability of the implant abutment connection.
Keywords: Bacterial infiltration, Dental implants, Implant abutment connection, Implant recess, Internal hex, Microbial leakage.
INTRODUCTION
Implants are commonly used in the treatment of partially and completely edentulous patients. The implant–abutment interface (IAI) is the connection between the implant and abutment which can be either single piece or a two-part system.
In a two-part implant abutment system, a microgap is present at IAI, through which the seepage of fluid and micro molecules from the saliva, crevicular fluid, and bacteria occurs during cyclic loading of the implant supported crown.1 The presence of bacteria in the internal recess of implant and penetration of the bacteria through microgap may increase the risk of soft tissue inflammation and bone loss around the implant.2 Potential colonization of microgap is probably related to precision of fit between implant components and loading forces when implants are in function.3
According to Binon et al., the microgap between IAI varies between different implant systems and reported to be 20–50 μm.4 Jansen et al. found this microgap to be 5 μm, whereas according to Callan et al. microgap varies between 30 and 135 μm.5,6 The type of implant–abutment connection (IAC) plays significant role in bacterial leakage and the subsequent peri-implant inflammation. External hex and internal hex (IH) connections are slip-fit joints with a microgap of 20–25 μm, whereas conical tapered connections are a tube in tube friction fit connections with much narrower gap of 2–3 μm and a cold welding which delays and even prevents bacterial infiltration.4,7 Microgap in conical connection implants depends on degree of taper of the mating components which varies from 4 to 11 degrees in most conical connection implants. Various studies have reported higher degree of bacterial infiltration in IH connection implants as compared to conical connection implants.1,8–10 Schmitt et al. in their systematic review reported conical connection implants to have lesser microgap and better stability and microbial seal than butt joint.11
There is limited information regarding differences in microbial penetration of the microgap of implants with different degree of taper in friction fit connection implants. This in vitro study aims to comparatively evaluate the sealing ability of three different IAC—1.5 mm IH, 4° tapered and 11° conical hex (CH) implant. Null hypothesis was that there is no difference in microbial permeability of IH connections and conical connection implants with different degree of taper.
MATERIALS AND METHODS
A total of 54 implant abutment assemblies with three different implant connections (n = 18 in each subgroup) were used in this study.
Preparation of Implant Abutment Complexes
For each group, 18 sterile implants (BioHorizon®, Ankylos® C/by Dentsply Sirona, IS-II Active Neobiotech®) with 1.5 mm IH group, 4° tapered (4° CH) group, and 11°CH group connection, respectively, were taken and the respective abutments were screw tightened using 30, 15, and 30 Ncm torque as per respective manufacturer recommendation using the cordless auto torque driver (MEG TorQ by Megagen® South Korea).
Preparation of Samples for Microbiological Analysis
The implant abutment complexes were placed in vertical position in the Eppendorf tube and Escherichia coli bacterial suspension in brain heart infusion (BHI) was added in Eppendorf tube with micro-pipette such that implant abutment junction was dipped (Fig. 1). Each implant in Eppendorf tube with bacterial suspension was incubated at 37°C for 30 days. The bacterial suspension (E. coli) was replaced every 4th day to prevent the overgrowth of the bacteria in the media. After 30 days of above procedure, the composite sealing the screw access hole and plugging material was removed.
Fig. 1: Implant abutment complex in vertical position
Sample from Implant Internal Recess
Abutments were unscrewed carefully and implant fixture recess was rinsed with premeasured quantity of saline in a sterile syringe. The saline was immediately drawn up and transferred into a sterile Eppendorf tube having peptone water. The wash from implant recess was then planted on MacConkey Agar for microbial analysis.
Same procedure as above was followed for implant abutments assemblies of all the groups using Enterococcus faecalis suspension in vertical position of the assemblies in the Eppendorf tube.
RESULTS
Microbial contamination of implant recess in each assembly was assessed and the data collection was analyzed statistically using Chi-square test.
Microbial Analyses of Wash from 3 IAC
Internal hex connection implants (Group IH) showed significantly higher E. coli (44.4%) and E. faecalis (50.0%) infiltration than 4°CH and 11°CH connection implants (Tables 1 and 2).
| Presence of bacteria in implant recess | ||||
|---|---|---|---|---|
| Presence of E. coli | Presence of E. faecalis | |||
| Absent | Present | Absent | Present | |
| Connections | ||||
| IH | ||||
| Count | 10 | 8 | 9 | 9 |
| % within connection | 55.6 | 44.4 | 50.0 | 50.0 |
| 4° CH | ||||
| Count | 16 | 2 | 16 | 2 |
| % within connection | 88.9 | 11.1 | 88.9 | 11.1 |
| 11o CH | ||||
| Count | 15 | 3 | 15 | 3 |
| % within connection | 83.3 | 16.7 | 83.3 | 16.7 |
| p-value | 0.043 | 0.016 | ||
| p-value | |||
|---|---|---|---|
| E. coli | E. faecalis | ||
| IH vs 4° CH | 0.026 | 0.011 | Significant |
| IH vs 11° CH | 0.070 | 0.034 | Significant |
| 4° CH vs 11° CH | 0.630 | 0.630 | Non-significant |
DISCUSSION
The present study confirms low bacterial permeability of conical hex IAC with 4° as well 11° taper and high prevalence of bacterial penetration of internal slip fit connection implants, thus rejecting the first part of the null hypothesis. However, microbial leakage difference between 4° and 11° tapered conical connection implants was found statistically insignificant (p > 0.05). Potential colonization of microgap at implant abutment junction (IAJ) is related to IAC type, precision of fit and connecting torque.10 Loading forces further increase the microgap but their influence is not uniform in all connections and host sites. Internal conical connection implants are reportedly more stable with a tighter connections than butt joint connections like IH.9,10,12–14
Lesser taper in morse connection creates better seal due to friction lock between the mating components.15 Microbial ingress of internal conical connection with varying degree of taper (4° and 11°) has been evaluated in present study over an observation period of 30 days. Several studies have depicted two-way microbial leakage into and out of implant abutment internal recess in in vitro setups.5,9,13,14,16–18 Inward microbial ingress method simulating in vivo condition was used in the present study.
Gram-negative anaerobic bacteria have been found surrounding the failing implants in higher counts as compared to healthy implant sites.19,20 Escherichia coli, a Gram-negative facultative anaerobic rod with 1–2 μm length and 0.5 μm radius, was chosen as contaminating bacteria for this study because of its motility, easy handling, and its short generation time of 20 minutes. Also, it has been isolated from periimplantitis lesions.9 Another non-motile Gram-positive facultative anaerobe, E. faecalis with 0.5–1 μm dimensions was also used to check the bacterial ingress into IAC due to small size and non-motile nature. Morse taper implant connections have a much lesser microgap of 2–3 μm than 10 μm of slip fit connections.21 This fact was taken into consideration while choosing organism of <2 μm so that bacteria could penetrate even the supposedly tight-fitting conical connections.
Previous studies investigated microbial leakage over a period of 14 days which was reported sufficient for leakages through IAC by Aloise et al.9 However, Tripodi et al. in 2012 showed that microleakage occurred after 22 days in morse taper connection so microbial leakage in the present study was evaluated over observation period of 30 days.22
Cyclic loading in clinical set ups differentially influences degree of micro leakage and further increase the number and type of bacteria.23 The present study aimed to establish differential microbial leakage in three IACs and required consistent conditions. Hence, cyclic loading was excluded from the study protocol.
The present study reported significantly higher microbial leakage in IH group than 4° and 11° conical connection implants (p < 0.05). These results are supported by previous studies by Tripodi et al. and D’Ercole S, who had reported that conical connection implants depicted less microbial leakage than IH connection implants.22,24–26 Tesmer et al. reported that only 30% of internal conical connection implants showed microleakage as compared to 90–100% microleakage in trilobed connection.10 Khajavi A in 2020, reported higher microleakage in Argon conical connection implant as compared to Zimmer slip fit IH connection.27 One degree taper in IH of Zimmer implant abutment surfaces imparts them with high degree of friction lock seal that accounts for better microbial seal.
Our study establishes limiting effect of internal conical connection on microbial leakage at IAJ with both 4° and 11° taper implants effecting similar microbial seal. Aloise et al.,9 Deconto et al.,28 and Alves et al.29 had also reported insignificant difference in microleakage in different conical connection implants. The present study confirmed equally low permeability of conical connections with different taper between mating components over slip fit hexagonal connections over a period of 30 days.
CONCLUSION
The type of connection significantly influences microbial leakage at implant abutment junction with internal connection more conducive to bacterial infiltrations than conical connection implants. However, degree of taper of conical connection does not have a significant effect on bacterial permeability of the IAC.
Further research is required to validate the result of this study by increasing the sample size and cyclic loading of the samples. Similar in vivo studies need to be conducted to correlate the results in laboratory setups with clinical results.
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