Microbiological aspects of human mandibular subperiosteal dental implants

Microbiological Aspects of Human Mandibular Subperiosteal Dental Implants

1. Scientific Reference

• Study Title: Microbiological Aspects of Human Mandibular Subperiosteal Dental Implants
• Authors: Thomas E. Rams, Burton E. Balkin, Thomas W. Roberts, Arthur K. Molzan
• Scientific Journal: Journal of Oral Implantology
• Year of Publication: 2013
• DOI: 10.1563/AAID-JOI-D-11-00023

2. Scientific Background

Mandibular subperiosteal implants represent a historical therapeutic option intended for patients with severe mandibular atrophy and complete edentulism. Although their use has become less common with the development of modern endosseous implants, some devices remain functional for many years in certain patients.

One of the major challenges associated with these restorations concerns the occurrence of infectious complications around transmucosal abutments. These inflammatory lesions, often compared with the concept of peri-implantitis observed around endosseous implants, may lead to progressive deterioration of peri-implant tissues and, in some cases, implant removal.

Despite the clinical importance of these biological complications, limited microbiological data were available regarding subperiosteal implants. This study was conducted within a research context aimed at better understanding the role of bacterial biofilm in maintaining peri-implant health or in the development of infections associated with this specific type of implant rehabilitation.

3. Study Objective

The primary objective of the authors was to compare the clinical, microbiological, and biological characteristics of mandibular subperiosteal implants affected by peri-implantitis with those of subperiosteal implants maintaining long-term clinical stability and peri-implant health.

The study specifically sought to identify potential differences in the composition of the submucosal microbiota and in certain inflammatory markers associated with the clinical status of the implants.

4. Methodology

This research corresponds to an observational clinical study including microbiological and biochemical analyses.

Eleven generally healthy adults wearing complete mandibular subperiosteal implants were included. Three patients presented peri-implantitis lesions, whereas eight patients exhibited prolonged peri-implant stability. The implants had been functioning for approximately 10 to 22 years, depending on the subjects studied.

The authors performed clinical evaluations including plaque index, gingival index, probing depth, bleeding on probing, and suppuration. Submucosal microbiological samples were subsequently analyzed by bacterial culture in order to identify several species associated with periodontal and peri-implant diseases. An analysis of interleukin-1β (IL-1β) levels in peri-implant crevicular fluid was also performed in a subgroup of five patients.

5. Main Results

Implants affected by peri-implantitis exhibited significantly higher plaque and gingival index scores than clinically healthy implants. Suppuration and bleeding on probing were observed at all affected sites, with a mean probing depth of 6.6 mm.

From a microbiological perspective, the authors observed a substantially greater anaerobic bacterial load in peri-implantitis-affected implants. Species belonging to the red complex, particularly Porphyromonas gingivalis and Tannerella forsythia, were found exclusively or predominantly in peri-implant lesions. Several bacteria from the orange complex, such as Prevotella intermedia/nigrescens, Parvimonas micra, and Campylobacter rectus, were also more frequently detected in diseased implants.

In contrast, implants demonstrating long-term peri-implant health were more frequently colonized by viridans streptococci and Actinomyces species, which are considered more compatible with a balanced microbiota. A trend toward higher IL-1β concentrations was also observed in peri-implantitis cases.

6. Clinical Analysis

This study provides valuable insight into a relatively under-documented area of dental implantology. Despite significant structural differences between subperiosteal implants and modern endosseous implants, the microbiological profiles observed during peri-implantitis episodes showed notable similarities to those described around conventional implants affected by peri-implant inflammation.

The results suggest that the composition of the bacterial biofilm may play a major role in the clinical evolution of subperiosteal implants. A high prevalence of anaerobic bacteria known for their involvement in periodontal diseases was associated with situations involving loss of tissue stability, whereas a flora dominated by species compatible with oral health was observed in long-term stable cases.

For clinicians involved in the follow-up of edentulous patients rehabilitated with subperiosteal implants, these findings reinforce the importance of plaque control and peri-implant maintenance. They also suggest that microbiological analysis may contribute to a better understanding of certain late biological complications.

However, caution is warranted when interpreting the results. The study is based on a very limited number of patients, and its cross-sectional design does not allow a causal relationship to be established between the observed bacterial composition and the development of peri-implantitis. The findings describe an association but do not demonstrate that these microorganisms are the sole cause of the disease.

7. Clinical Applications

The data presented may be relevant for practitioners responsible for the long-term follow-up of patients with mandibular subperiosteal implants, particularly in situations of severe bone atrophy where this type of rehabilitation has historically been used.

This study highlights the value of regular monitoring of peri-implant tissues, control of supragingival biofilm, and early detection of inflammatory signs. The findings may also contribute to discussions regarding the use of microbiological approaches in the assessment of biological implant complications.

Finally, these observations emphasize the importance of implant maintenance protocols in complex implant-supported rehabilitations for completely edentulous patients.

8. Level of Evidence, Limitations, and Transparency

This publication corresponds to a small observational clinical study combined with microbiological and biochemical analyses.

The level of evidence should be considered limited due to the small number of participants (11 patients in total, including only 3 with peri-implantitis). The authors also acknowledge that the exclusive use of bacterial culture methods constitutes a limitation, as some species may not be detected through this approach. Furthermore, the cross-sectional study design does not permit demonstration of a cause-and-effect relationship.

Regarding transparency, no conflicts of interest are declared in the information provided. The authors indicate that the work received support from the Paul H. Keyes Professorship in Periodontology at the Temple University School of Dentistry.

9. Key Points of the Study

• Study Type: Observational clinical study with microbiological and biochemical analyses.
• Level of Evidence: Low to moderate.
• Population Analyzed: 11 adults with mandibular subperiosteal implants.
• Number of Patients: 11.
• Number of Implants: Not specified in the information provided.
• Follow-up Duration: Implants had been functioning for approximately 9 to 22 years depending on the patients.
• Primary Outcome Evaluated: Relationship between peri-implant clinical status and submucosal microbiota.
• Main Result: Implants affected by peri-implantitis exhibited a higher bacterial load and a greater prevalence of species associated with periodontal diseases.
• Scientific Conclusion: The composition of the peri-implant microbiome and plaque control appear to be associated with the clinical status of mandibular subperiosteal implants.
• Potential Limitations: Small sample size, cross-sectional design, and bacterial identification based primarily on culture methods.

10. Scientific Impact

This study occupies a particular place in the literature due to the limited number of investigations dedicated to mandibular subperiosteal implants and their biological complications. It provides original microbiological data that help characterize bacterial environments associated with health or disease around these devices.

Beyond the specific context of subperiosteal implants, the reported observations reinforce the concept that certain microbiological signatures observed around endosseous implants may also be found in other implant systems. The study therefore contributes to bridging knowledge derived from periodontology and implantology.

Although its scope remains limited by the small sample size, this work opens perspectives for larger studies using modern microbiological methods to better understand the biological mechanisms involved in peri-implant complications associated with complex rehabilitations in edentulous patients.

11. Editorial Conclusion

This study highlights an association between the clinical status of mandibular subperiosteal implants and the composition of the peri-implant microbiota. Implants affected by peri-implantitis harbor a greater number of bacteria recognized for their involvement in peri-implant inflammatory diseases, whereas long-term stable implants are associated with a microbial flora more compatible with health. Although the findings are based on a limited sample size, they emphasize the importance of biofilm control and peri-implant monitoring in the management of complex implant rehabilitations.