Implant decontamination: the challenge of surface integrity

Therapeutic success in implant periodontology relies on a critical balance: eliminating the biofilm while preserving the integrity of the titanium surface, a sine qua non condition for successful re-osseointegration. For the practitioner, the difficulty lies in choosing a decontamination method that does not alter the biocompatibility necessary for bone neoformation. This study addresses a major clinical variable: the influence of the bone defect geometry on treatment efficacy.

Objectives and hypotheses: defect angulation at the heart of the study

The primary objective was to quantify the morphological changes of the implant surface after laser decontamination using atomic force microscopy (AFM). The second objective aimed to evaluate the biological response of human osteoblasts (Saos-2) in terms of adhesion, differentiation, and mineralization. The researchers tested the hypothesis that the angle of an intrabony defect (15°, 30°, 60°, and 90°), modeled via 3D printing, directly affects the efficacy of an Er, Cr:YSGG laser (50 mJ, 1.5 W, 30 Hz). The study seeks to determine whether the defect morphology dictates not only the safety of the irradiation but also the quality of the cellular response on the treated surfaces.

Experimental methodology

This in vitro study is based on a customized peri-implantitis model, designed by 3D printing to simulate different anatomical configurations. The experiment involved a total of 26 implants: 24 previously contaminated test implants and 2 native implants serving as a control group.

The test implants were divided into four distinct experimental groups, defined by the angulation of the simulated infra-bony defect:

• Group 1: 15° angulation;
• Group 2: 30° angulation;
• Group 3: 60° angulation;
• Group 4: 90° angulation.

The decontamination procedure was performed using an Er, Cr: YSGG laser equipped with a side-firing tip. The treatment parameters were standardized: energy of 50 mJ (power of 1.5 W, frequency of 30 Hz), air/water spray (50% / 40%), for a protocol of 5 cycles of 5 minutes each.

The analyses focused on two major areas:

• Surface morphology: use of atomic force microscopy (AFM) profilometry to evaluate implant integrity and roughness after treatment.
• Biological response: biocompatibility assessment via human osteoblast culture (Saos-2). Measurements targeted cell attachment, differentiation, and mineralization, including alkaline phosphatase (ALP) activity as well as gene and protein expression of osteoprotegerin (OPG) and RANKL ligand.

Surface integrity and roughness (Profilometry/AFM)

Profilometry and atomic force microscopy (AFM) analysis shows that the Er, Cr: YSGG laser decontamination protocol (1.5 W, 30 Hz, 50 mJ) preserves the morphological integrity of the implants. No significant difference was observed between the surface roughness of the native implants (control group) and that of the four tested groups (15°, 30°, 60°, 90°).

A notable observation concerns the angulation of the defect: a slight reduction in surface roughness was recorded specifically for the group presenting a 60-degree bone defect compared to the other infra-bony defect configurations.

Biological response and osteogenic markers (Saos-2)

The evaluation of biocompatibility via human osteoblastic cell culture (Saos-2) reveals a favorable cellular response in all decontaminated groups, although the pristine native implant maintains a superior response. Biological results vary according to the angulation of the defect:

• Enzymatic activity: The group with a 60° defect displayed the highest alkaline phosphatase (ALP) activity.
• Protein and gene expression: Osteoprotegerin (OPG) expression was maximal in the 60° group.
• Resorption markers: Soluble receptor activator of nuclear factor-kB ligand (sRANKL) levels, at both protein and gene levels, were lowest in the 60° group.

The following table summarizes the biological response observed according to the angulation of the peri-implant defect:

In summary, the angulation of the defect directly influences the residual roughness after laser treatment and, by extension, the osteogenic response. The 60-degree defect appears to offer the most favorable environment for cell attachment and differentiation after Er, Cr: YSGG laser decontamination.

Analysis of results and clinical impact

The data from this study (NCT05137821) demonstrate that the Er, Cr: YSGG laser, used with a side-firing tip, succeeds in decontaminating implant surfaces without significantly altering their roughness. Major clinical fact: the angulation of the bone defect directly influences the biological response. The 60° defect is distinguished by a slight reduction in surface roughness associated with maximal enzymatic activity (ALP) and osteoprotegerin (OPG) expression, thus promoting a superior osteogenic environment compared to 15°, 30°, or 90° angles.

Limits and perspective

While these results are promising, the study presents inherent limitations due to its experimental design: it is an in vitro model using Saos-2 cells and 3D-printed models. Real clinical behavior, within a complex bacterial biofilm and a human inflammatory environment, remains to be confirmed. Furthermore, the authors highlight a concrete reality: even when successfully decontaminated, the surface of a "used" implant never reaches the biological performance of a new (prine) implant, which explains the complexity of achieving total re-osseointegration in daily practice.

Implications for the practice

For the practitioner, this study validates the efficacy of the Er, Cr: YSGG laser (50 mJ, 1.5 W/30 Hz) as a tool of choice for preserving implant integrity during decontamination. It suggests that the morphology of the peri-implant defect is not only a surgical challenge for grafting, but a determining factor in the quality of the local cellular response post-treatment.

Summary of results

This study demonstrates that the Er, Cr: YSGG laser (1.5 W, 30 Hz) preserves the surface integrity of contaminated implants, regardless of the infra-bony defect angle (15° to 90°). The results highlight an optimal osteogenic response in 60° defects, characterized by maximal ALP activity and OPG expression, promoting the differentiation of Saos-2 osteoblasts.

Concretely, for the practitioner:

• Substrate preservation: Use the Er, Cr: YSGG laser (side-firing tip, 5 cycles of 5 min) to decontaminate without altering the implant roughness, ensuring the maintenance of its initial biocompatibility.
• Defect analysis: Anticipate better re-osseointegration kinetics in 60° angular defects, where the geometric environment appears to optimize the mineralizing response compared to narrower or wider angulations.
• Expectation management: Although the protocol is effective, remember that a decontaminated surface remains biologically inferior to a native implant; complete regeneration remains a greater clinical challenge than a primary placement.

Technical lexicon of the study

Er, Cr: YSGG (Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet): Solid-state laser used for implant decontamination. In this study, it is set at 1.5 W and 30 Hz with a side-firing tip to preserve surface integrity.

Infrabony defect: Angulation of the peri-implant bone lesion (tested here at 15°, 30°, 60°, and 90°). The study demonstrates that this geometry influences cleaning efficiency and subsequent cellular response.

Atomic Force Microscopy (AFM): High-resolution profilometry technique used to analyze morphological changes and implant surface roughness after laser decontamination cycles.

Alkaline phosphatase (ALP): Enzyme marker of osteoblastic activity. High ALP activity on treated implants, particularly in 60° defects, indicates successful cell differentiation and biocompatibility.

OPG / RANKL: The ratio between osteoprotegerin (OPG) and receptor activator of nuclear factor-kB ligand (RANKL). The study measures their gene and protein expression to evaluate the balance between bone formation (promoted by OPG) and resorption (induced by RANKL).

Saos-2: Human osteoblast cell line used as a biological model to evaluate adhesion, proliferation, and bone mineralization on implant surfaces after laser treatment.

Information intended for healthcare professionals. This content may contain errors or truncated summaries. We recommend always verifying with the original source article. Delynov disclaims all responsibility regarding the use of this information. This document is not intended for patients or the general public.