Scanning electron microscopic analysis of adherent bacterial biofilms associated with peri-implantitis

Abstract

Objectives: Peri-implantitis (PI) is caused by bacteria in the peri-implant space but the consensus on microbial profile is still lacking. Current microbial sampling of PI lesions has largely focused on analyzing bacterial species that have been shed from the implant surface and captured in the pocket fluid. The purpose of the present study was to investigate the morphotypes of bacteria in biofilm covering the implant threads and explore whether certain morphotypes were associated with PI.

Methods: Fourteen failed implants were removed and instantly processed for scanning electron microscope analysis. The implants were imaged at three equally divided sub-crestal levels of the exposed area. Bacterial morphotypes were identified and quantified by three examiners. Mobility and years in function were correlated to the presence of different morphotypes.

Results: The implants demonstrated the presence of variable bacterial morphotypes that did not correlate to disease progression in our study. Some implants were dominated by filaments and others showed the presence of combinations of cocci/rods or spirilles/spirochetes. In general, all implants showed variable morphologic biofilm composition. However, individual implants tended to have similar composition throughout the entire implant. Rods and filaments were dominant morphotypes throughout the surfaces and cocci showed increased presence toward the apical third. There were some differences in the biofilm morphology with mobility and time in function.

Conclusions: The profiles of bacterial biofilm morphotypes in failing implants with similar clinical presentations were highly variable. While there were significant differences between implants, similar morphotypes in individual implants were often found throughout the entire surface.

Keywords: bacteria; biofilm; peri-implantitis.

Figure 1

Radiographic images of a set of implants removed due to severe bone loss. These implants represent different thread type (aggressive [a], regular [b, c, e, f] or mild [d]), surface characteristics (oxidized [a–c, f] or SLA [d, e]), level of placement (bone [a–c, e, f] or tissue level [d]) and abutment fit (butt joint [b–d, f] or platform‐shifting [a, e]) and splinted (b and f) and nonsplinted (d and e) adjacent implants. SLA, Sand‐blasted, large grit, acid‐ etched.

Figure 2

Relative distributions of each morphotype in each location and all combined surfaces. (a) Relative distribution of each microbiome morphotype combined with all samples. (b) Relative distribution of each morphotype combined with all samples in each location of implants. (c) Relative distribution of morphotypes at each implant location combined with all samples. N = 14.

Figure 3

Relative distribution of morphotypes related to implant mobility, and more or less than 10 years of function. (a) Relative distribution of morphotypes in mobile and nonmobile implants. Mann–Whitney test, p < .05 between nonmobile versus mobile on rods, filaments, and spirochete/spirilla. N (nonmobile) = 9, N (mobile) = 5. (b) Relative distribution of morphotypes in Years in function, <10 years versus ≥10 years. Mann–Whitney test, p < .05 between <10 years versus 10 years and up on rods, filaments, and spirochete/spirilla. N (<10 years) = 7, N (10 years and up) = 7.

Figure 4

High resolution scanning electron microscopy images on the surfaces of the failed implants. (a, b) The images of the coronal third surfaces of failed implants show abundant rods and spirochetes (a) and bristle‐brush formations (b); (c, d) the images of the middle third surface of failed implants show curved rods (vibrios) with flagellas (c) and rods and filaments (d); (e, f) the images of the apical third surfaces of failed implants demonstrate the presence of corn‐cob formations with central filament coaggregating with cocci (e) and rods and filaments (f). Images were in 5000x magnification (magnification bar included in each image).

Figure 5

Coaggregate structures of the biofilm on the surfaces of failed implants. (a, b) Corncobs on the coronal third areas of failed implants (a, 1000x; b, 5000x); (c, d) test‐tube brush formations on the middle third areas of failed implants (c, 2000x; d, 5000x); (e, f) hedgehog structures on the middle third areas of failed implants (e, 5000x; f, 8000x).

Figure 6

Pseudo‐colored scanning electron microscope images of native biofilm on the surfaces of the failed implants. (a) Rods (blue) around the pores of the anodized implant surfaces (pink; 10,000x). The matrix is colored purple. (b) Cocci (pink) along with filaments (purple) embedded in matrix (brown) (25,000x). (c) Hedgehog formation with cocci (blue), rods (purple) around matrix (green) (8000x). (d) Morphotype of vibrio (curved rods, orange/brown) covered with vesicles and elongated fimbriae/flagella (green) (20,000x). (e) Multiple strands of the corncob formation with filaments (purple) and cocci (blue) (5000x). (f) Unknown morphotype (purple) with filamentous morphotypes (yellow), cocci (green), and matrix (pink) (12,500x).