Microbiological Evaluation of the Effectiveness of Different Surface Decontamination Protocols for Dental Implants Using the Polymerase Chain Reaction Method

Background and Rationale Contemporary dental implantology represents a reliable and predictable treatment method for partial or complete tooth loss. However, despite high success rates, complications such as peri-implantitis can lead to implant loss, significantly impacting patients functionally, emotionally, and financially. Peri-implantitis is an inflammatory condition affecting the soft and hard tissues surrounding an osseointegrated dental implant, with a prevalence of approximately 20% among patients undergoing implant therapy.

The primary etiological factor for peri-implantitis is the formation of a bacterial biofilm on the exposed surface of the implant. Biofilm formation is a complex, multi-step process involving the colonization of bacteria from around the implants, natural teeth, and other areas of the oral cavity. The oral biofilm associated with peri-implantitis is characterized by high microbial diversity. While no single specific bacterium has been identified as exclusively present in peri-implantitis biofilms, the long-term presence of this biofilm stimulates a host immune response, leading to chronic inflammation and subsequent tissue destruction.

The Clinical Challenge One of the most demanding and critical tasks in the treatment of peri-implantitis is the complete removal of the biofilm and the prevention of its recurrence. The presence of deep peri-implant pockets, restricted access to all implant surfaces, and the inherently rough, threaded topography of dental implants make mechanical and chemical decontamination exceptionally challenging.

Traditionally, mechanical tools such as curettes, sonic and ultrasonic instruments, air-polishing devices, and rotating titanium or chitosan brushes have been utilized to remove hard and soft deposits. A key clinical requirement is to achieve this with minimal damage or alteration to the implant surface. To address this, chemical agents (e.g., sterile saline, hydrogen peroxide, citric acid, EDTA, phosphoric acid, and chlorhexidine gluconate) are often employed alongside mechanical methods.

Recently, novel modalities have emerged to minimize surface damage while maximizing antimicrobial efficacy:

Antimicrobial Photodynamic Therapy (aPDT): Based on a photochemical reaction between a photosensitizer, oxygen, and a specific light wavelength, this therapy generates reactive oxygen species that induce bacterial cell death.

Electrolytic Cleaning (GalvoSurge): This method utilizes an electrolytic process to actively lift and eliminate bacterial biofilms from rough titanium surfaces, demonstrating promising in vitro results.

Study Objectives This prospective clinical trial is designed to evaluate and compare the antimicrobial efficacy of two novel implant decontamination protocols-Laser PDT and Electrolytic Cleaning (GalvoSurge)-against the widely accepted gold standard of 0.2% chlorhexidine gluconate rinsing. The primary focus is assessing the reduction of the microbiological load on the implant surface immediately following decontamination and prior to regenerative bone surgery.

Methodology and Clinical Protocol The study will be conducted at the School of Dental Medicine, University of Zagreb, within the Department of Oral Surgery. All surgical procedures will be performed by the same specialist in oral surgery to ensure procedural consistency.

The trial will enroll 90 bone-level dental implants affected by peri-implantitis but deemed viable for retention in the dental arch. Implants with vertical bone loss are excluded from this study. Eligible participants are restricted to healthy, non-smoking individuals classified as ASA I or II, with no systemic comorbidities. Pre-operative assessment will include Cone Beam Computed Tomography (CBCT) imaging.

The clinical workflow for each implant is as follows:

Flap Elevation: A mucoperiosteal flap is raised to expose the contaminated implant surface.

Baseline Sampling (Sample 1): A sterile swab is taken directly from the implant surface for initial PCR analysis to establish the baseline microbiological load.

Randomization and Intervention: Implants are randomly assigned to one of three treatment arms (n=30 per arm):

Group 1: Decontamination using Laser PDT (riboflavin photosensitizer + blue laser) followed by a sterile saline rinse.

Group 2: Decontamination using the GalvoSurge electrolytic system followed by a sterile saline rinse.

Group 3 (Active Control): Decontamination using a 0.2% chlorhexidine gluconate rinse.

Post-Treatment Sampling (Sample 2): Immediately following the decontamination protocol, a second sterile swab is taken for PCR analysis.

Regenerative Procedure: The surgery concludes with a classic Guided Bone Regeneration (GBR) procedure, utilizing autologous bone particles, a xenograft, and a collagen membrane fixed in place with titanium pins.

Microbiological Analysis

Samples will be analyzed using a validated real-time Polymerase Chain Reaction (RT-PCR) method targeting five specific periodontopathogenic bacteria:

Aggregatibacter actinomycetemcomitans

Porphyromonas gingivalis

Prevotella intermedia

Treponema denticola

Tannerella forsythia

The primary outcome is the change in the microbiological load. Results will be expressed as a semi-quantitative score (-, +, ++, +++), which will be numerically coded for statistical evaluation. The change is calculated as the difference between the post-treatment and pre-treatment values for each specific implant.

Sample Size and Statistical Analysis Plan The study is designed as a prospective comparative trial with repeated measures. Sample size estimations were based on available in vitro studies demonstrating a large effect size for electrolytic decontamination compared to standard methods.

Power Calculation: Assuming a conservative large standardized effect size (Cohen's d ≈ 0.9), a two-sided significance level of α = 0.05, and a test power of 80%, a minimum of 25 implants per group is required to detect statistically significant differences between the test groups and the control group. To account for potential sample loss or unusable swabs, the enrollment target was increased to 30 implants per group (90 implants total).

Data Analysis: Statistical significance is set at 95% (p < 0.05). Normal distribution of the data will be assessed descriptively and via formal tests.

For normally distributed data, a one-way Analysis of Variance (ANOVA) will be utilized, followed by post-hoc comparisons of each test group against the control group.

If assumptions for parametric testing are not met, appropriate non-parametric alternatives will be applied.

Differences between baseline and post-treatment values within individual groups will be analyzed using tests for dependent samples.

Qualitative outcomes (e.g., the positive or negative presence of the target pathogens) will be evaluated using categorical data methodologies.