Clinical Evaluation of Combined Manual Pre-treatment and Negative-Pressure Cleaning for Dental Implant Instrument Reprocessing

Summary

This study evaluates a combined manual pre-treatment and negative-pressure cleaning process for dental implant instruments, demonstrating improved cleaning quality and higher qualification rates while significantly reducing manual operation time. The approach enhances standardization, efficiency, and safety in instrument reprocessing, supporting its practical adoption in clinical sterilization workflows.

Abstract

This study evaluates a combined manual pre-treatment and negative-pressure cleaning process for dental implant instruments to improve cleaning quality and efficiency. A total of 200 contaminated dental implant toolkits were randomly assigned to a control group (traditional manual cleaning) or an experimental group (manual pre-treatment combined with negative-pressure cleaning), with 100 toolkits in each group. Cleaning quality was assessed using visual inspection, magnification, residual blood detection, and ATP fluorescence testing, and cleaning time was recorded.

The experimental group demonstrated higher qualification rates across multiple indicators compared to the control group, including improved outcomes under magnification and residual blood testing, as well as a higher complete qualification rate. Manual cleaning time was significantly reduced in the experimental group (6.48 ± 2.78 min) compared to the control group (28.94 ± 2.57 min). Although total processing time increased due to automated cleaning cycles, manual handling time was markedly reduced.

Overall, the combined approach improves cleaning quality, reduces manual workload, and enhances standardization. This approach enhances efficiency, standardization, and safety in clinical instrument reprocessing.

Introduction

With the continuous development of dental implant technology, implants have become an important treatment option for patients with missing teeth due to their excellent restorative function and aesthetic appeal. The instruments used in implant surgeries have complex structures and intricate geometries, which place high demands on cleaning quality¹. Inadequate cleaning can result in residual organic or inorganic materials that not only affect the effective contact of sterilization agents^2,3 but also form bacterial biofilms, reducing sterilization effectiveness and potentially causing hospital-associated infections, thus threatening patient safety⁴. Cleaning is a critical prerequisite for effective disinfection and sterilization of reusable medical devices, particularly those with complex geometries and lumens, as retained organic soil (e.g., protein and blood) can persist despite apparent cleanliness and compromise downstream sterilization performance⁵.

These processes are essential to remove organic and inorganic contaminants and reduce microbial load, thereby supporting safe and effective instrument reprocessing in high-risk clinical settings⁶.

Furthermore, improper cleaning may cause instrument damage, shorten their lifespan, and increase maintenance and replacement costs⁷. Dental implant instrument sets usually include various instruments, such as implants, drills, and guide sleeves, along with their specialized containers, making cleaning significantly more challenging than for regular surgical instruments. Complex design features (e.g., narrow lumens or intricate shapes) have been shown to act as barriers to effective cleaning, increasing the risk of residual soil and biofilm accumulation even after manual or semi-automated cleaning processes¹.

Currently, most Central Sterile Supply Departments (CSSDs) still use manual scrubbing or spraying disinfectants for cleaning, which has issues such as low efficiency, long cleaning times, high personnel dependence, and inconsistent execution, making implant instruments a major challenge in clinical cleaning work⁸. Previous studies have consistently reported persistent contamination in complex instruments despite standard cleaning procedures, with residual organic and microbial contamination frequently detected even after routine reprocessing, particularly in devices with intricate geometries and lumens that hinder effective cleanings^9,10. Although multiple automated and semi-automated cleaning technologies have been introduced to improve consistency and reduce dependence on manual performance, studies indicate that residual soil/debris within lumened or complex instruments remains a persistent problem in real-world reprocessing, even after routine cleaning, supporting the need for improved methods and objective verification in CSSD settings^9,11. However, standardized and validated cleaning strategies for dental implant instrument sets remain limited.

Recent advances in automated reprocessing systems, including ultrasonic-assisted and washer–disinfector technologies, have improved standardization; however, their effectiveness may still be limited in removing tightly adhered contaminants within narrow lumens or complex instrument geometries due to incomplete fluid penetration and insufficient mechanical disruption under standard pressure conditions^12,13.

In addition, reports focusing on CSSD quality and safety continue to document operational challenges that reinforce the need for workflow standardization and technology-supported cleaning approaches, including clear manufacturer instructions and validated reprocessing procedures tailored for instrument complexity¹⁴. While pulsed vacuum/negative‑pressure cleaning devices have gained increasing attention, evidence specific to dental implant instrument sets remains limited, and comparative evaluations using multiple cleaning quality indicators and time‑efficiency metrics are still insufficient. Therefore, a clear research gap exists regarding the effectiveness of pressure-assisted automated cleaning systems specifically for dental implant instrument sets, particularly in terms of their ability to improve cleaning consistency, reduce manual workload, and enhance cleaning outcomes across multiple objective indicators.

This study aims to systematically evaluate a combined manual pre-treatment and negative-pressure cleaning workflow for dental implant instrument sets, which enhances fluid penetration and contaminant removal in complex instrument geometries, with the goal of improving cleaning quality, reducing manual workload, and enhancing process standardization in CSSD practice.

Based on preliminary clinical application, a combined manual pre-treatment and negative-pressure cleaning approach has shown potential to improve cleaning efficiency and reduce manual operation time; therefore, this study systematically evaluates its effectiveness in improving cleaning quality, reducing manual workload, and enhancing process standardization. Unlike conventional automated cleaning systems, the proposed approach integrates manual pre-treatment with negative-pressure-assisted cleaning, which enhances fluid penetration, promotes cavitation effects, and enables pressure-driven flushing within narrow lumens and facilitates more effective removal of contaminants from complex surfaces and internal lumens. This study conducts a comparative evaluation of this method to determine its effectiveness in clinical instrument reprocessing.

Protocol

Study Design and Ethical Considerations

This study was reviewed by the Ethics Committee of the Affiliated Stomatological Hospital of Anhui Medical University and was determined not to require formal ethical approval, as it involved only the reprocessing of medical instruments and did not include patient interaction or identifiable patient data. The study was conducted in accordance with institutional guidelines and relevant regulations. Accordingly, the requirement for informed consent was waived.

From July to December 2024, a total of 200 dental implant instrument sets were retrieved from the Disinfection Supply Center of the Affiliated Stomatological Hospital of Anhui Medical University. These were randomly divided into two groups using a random number table: the control group (traditional manual cleaning) and the experimental group (manual pre-treatment combined with a negative-pressure cleaning device), with 100 instrument sets in each group.

This study was designed as a prospective, randomized comparative study conducted under routine Central Sterile Supply Department (CSSD) operational conditions. Dental implant instrument sets (typically consisting of implant drills, guide sleeves, implant drivers, torque wrenches, and associated surgical accessories; composition varied depending on clinical procedure requirements), including variations in instrument geometry such as smooth surfaces, hinged components, and narrow lumens that may influence cleaning difficulty, were included in the study.

Randomization and Blinding

Randomization was performed using a computer-generated random number table to ensure equal allocation of instrument sets between the two groups. Allocation was conducted by a designated staff member not involved in outcome assessment. Cleaning quality evaluations were performed by trained personnel blinded to group assignment (evaluators were independent of the cleaning procedures and not involved in group allocation. Instrument sets were coded prior to evaluation to ensure blinding, and all assessments were conducted under standardized conditions using predefined evaluation criteria).

Cleaning Equipment and Procedures

One manual cleaning workstation (including washing tank, enzymatic cleaning tank, rinsing tank, and final rinsing tank), one ultrasonic cleaning machine (frequency: 40 kHz; temperature: 40–45 °C), one negative-pressure cleaning and disinfection device (vacuum level: -0.08 to -0.095 MPa; operating temperature: 48–62 °C; ultrasonic frequency: 40 kHz; cycle duration: 58 min; pulse cleaning mode enabled), one boiling machine (93 °C ± 1 °C), one drying cabinet (70–80 °C), one set of pressure steam spray guns with auxiliary devices, three high-pressure water guns (pressure: 0.2–0.3 MPa), and three calibrated digital timers. The negative-pressure cleaning and disinfection device operates based on vacuum-assisted cleaning principles, enhancing fluid penetration, ultrasonic cavitation, and pulse-driven flushing to improve contaminant removal.

All cleaning procedures were performed by trained CSSD personnel with ≥ 2 years of experience, following institutional protocols to minimize operator-dependent variability and ensure consistent execution across procedures.

Cleaning Method for the Control Group

The recovered implant instrument sets were first categorized and disassembled into their smallest components, followed by rinsing under running water for 2–3 min (flow rate ~2 L·min^-1) to remove visible contaminants. All manual cleaning steps were performed according to standardized operating procedures by trained personnel to ensure consistency across operators. The instruments were then manually brushed using a soft nylon brush (diameter 2–5 mm depending on lumen size) to remove residual debris like blood stains and rust. This was followed by immersion in a multi-enzyme cleaning solution (3.75 mL·1000 mL^-1; temperature: 35–40 °C) and brushing for 6 min (timed using a calibrated timer). Enzymatic cleaning was followed by intensive rinsing using a high-pressure water gun (0.2–0.3 MPa; 2–3 min) to remove chemical residues. A final rinse with purified water was performed for ≥ 1 min. This was followed by wet heat disinfection at 93 °C for 2.5 min. Finally, the instruments were dried in a drying cabinet (70–80 °C) and transferred to the inspection and packaging area.

Cleaning Method for the Experimental Group

The recovered implant instrument sets were first categorized and disassembled into their smallest components and rinsed under running water (2–3 min) to remove visible contaminants. The instruments were then subjected to primary cleaning using a negative-pressure cleaning and disinfection device for 58 min based on vacuum-assisted cavitation, pulse flushing, and perfusion mechanisms to enhance cleaning of internal lumens and complex geometries (standardized cycle including vacuum ultrasonic cleaning, pulse flushing, vacuum perfusion, and vacuum drying). Operational parameters were as follows: Vacuum level: -0.08 to -0.095 MPa; Temperature: 48–62 °C, and Ultrasonic frequency: 40 kHz, which were selected to optimize cavitation intensity, fluid penetration, and contaminant removal efficiency under reduced-pressure conditions. Instruments that failed to meet the required cleanliness standards after the initial cycle underwent secondary cleaning using the same negative-pressure cleaning and disinfection procedure, followed by routine inspection. If the instruments still did not meet the qualification standards after secondary cleaning, a tertiary cleaning cycle was performed using the same method, and this process was repeated until all instruments complied with the established quality standards, ensuring consistent cleaning performance across repeated cycles under controlled pressure-assisted conditions.

Observation Indicators

The cleaning efficiency indicator is cleaning time measured in minutes using calibrated digital timers and recorded for each cleaning stage, including manual cleaning time for the first cleaning, total cleaning time for the first cleaning, manual cleaning time for the secondary cleaning, total cleaning time for the secondary cleaning, manual cleaning time for fully qualified cleaning, and total cleaning time for fully qualified cleaning.

Cleaning time was recorded using calibrated digital timers. Manual cleaning time was defined as the duration from initiation of manual handling to completion of manual cleaning steps. Total cleaning time was defined as the duration from initial rinsing to completion of drying. For instruments requiring repeated cleaning cycles, time was recorded cumulatively until qualification criteria were achieved.

Cleaning quality was evaluated using visual observation, five-fold magnification lens detection, residual blood testing, and ATP fluorescence testing using predefined and standardized thresholds for cleanliness assessment to ensure objective and reproducible evaluation¹⁵. The cleaning quality indicators are the qualification rate expressed as percentages of instrument sets meeting predefined criteria, including the qualification rate for the first cleaning and the qualification rate for the secondary cleaning. Visual observation is performed using a magnifying lens with light to check for visible blood stains, dirt, water scale, and rust on the surface of the instruments; those without such visible contaminants are considered qualified. Instruments were inspected under standardized lighting conditions (≥ 1000 lux (measured using a calibrated lux meter to ensure standardized inspection conditions)) at a distance of approximately 30 cm. ATP fluorescence testing was performed by swabbing predefined instrument surfaces and lumens, followed by measurement using an ATP luminometer. Results were obtained within 30 s, and values ≤ 45 RLU were considered qualified.

Complete qualification was defined as an instrument passing all four assessment methods simultaneously: visual observation, 5× magnification visual observation, residual blood detection, and ATP fluorescence detection. Instruments failing any one of these criteria were classified as not completely qualified.

Definitions and Descriptions of Various Observation Methods

Visual Observation: Visual inspection was performed using the naked eye to detect visible contaminants such as blood stains, dirt, water scale, and rust on instrument surfaces¹⁶.

Inspection was performed using a 5× magnifying lens to detect smaller contaminants on instrument surfaces and within lumens¹⁷.

For residual blood detection method, a sterile swab was used to sample the instrument surface (~2 cm²), followed by application of detection solution according to the manufacturer’s instructions. A color change within 30 s was considered a positive result, while absence of color change was considered qualified.

A sterile swab was applied to predefined instrument surfaces and lumens and inserted into an ATP detector to measure Relative Light Units (RLU)¹⁸. This method evaluates cleaning effectiveness by measuring ATP content, as all living cells contain a constant amount of ATP, and ATP is released when bacterial cells lyse^19,20. An RLU value ≤ 45 was considered qualified²¹.

Process Checkpoints

After each cleaning cycle, instruments were evaluated using visual and instrumental methods. Instruments failing any criterion were subjected to subsequent cleaning cycles until qualification standards were met.

Reproducibility Consideration

All procedures were conducted under controlled CSSD conditions using standardized workflows and predefined equipment parameters to ensure reproducibility across repeated trials, including minimized operator-dependent variation through standardized training and protocol adherence.

Safety Considerations

All contaminated instruments were handled using appropriate personal protective equipment, including gloves, masks, and protective eyewear. High-pressure rinsing procedures were performed with splash protection to minimize occupational exposure.

Waste Disposal

Used cleaning solutions and contaminated materials were disposed of in accordance with institutional biomedical waste management protocols and local regulatory requirements.

Statistical Methods

Statistical analysis of the data was performed using SPSS software. Categorical data were expressed as frequency and composition ratio (%), and group comparisons were conducted using the χ² test or Fisher’s exact probability test. Continuous data were expressed as mean ± standard deviation (x̄ ± s), and group comparisons were made using independent sample t-tests (after confirming normality of data distribution using the Shapiro–Wilk test). Homogeneity of variance was assessed using Levene’s test prior to application of the t-test. The significance level was set at α = 0.05, with two-tailed testing. A p-value < 0.05 was considered statistically significant. All materials and equipment used in this study are listed in the Table of Materials.

Results

Comparison of Cleaning Quality Between the Two Groups

In visual observation, the qualification rate of the control group was 94%, while the qualification rate of the experimental group was 99% (Table 1; Figure 1). The difference between the two groups was not statistically significant (χ² = 1.546, p = 0.214). In the 5x magnification visual observation, the qualification rate was significantly higher in the expe...

Discussion

Cleaning dental implant instruments presents significant challenges due to their complex structures, multiple components, and lumen-containing designs²². It demands high professional standards from personnel, equipment, and facilities, and increases the risk of infection for surgical patients. This has long been a key issue in hospital infection control and the improvement of cleaning efficiency^23,24. The combination of manual pre-treatmen...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
ATP fluorescence detector	Hygiena LLC, USA / 3M Company, USA	SystemSURE Plus (ATP-100) / Clean-Trace LM1	Used for ATP-based contamination detection
ATP test swabs	Hygiena LLC, USA	UltraSnap™ (US2020)	Compatible with ATP fluorescence detector
Cleaning indicator strips	3M Company, USA	Clean-Trace™ Test Strips (CTS100)	Used for process validation of cleaning efficacy
CSSD workbench	Belimed AG, Switzerland	WD290 IQ series	Instrument processing workstation
Dental implant instrument toolkits	Straumann Group, Switzerland / Nobel Biocare, Switzerland	Various (kit-specific)	Retrieved after implant surgery; used as study samples
Drying module (integrated system)	Shinva Medical Instrument Co., Ltd., China	SQ-Z series	Integrated drying unit in automated system
Enzymatic detergent	Ruhof Corporation, USA	Endozime® AW Plus (345SPD)	Used for manual pre-cleaning
Five-fold magnifying lens (5×)	Olympus Corporation, Japan	5× Loupe (ME-5X)	Used for magnified visual inspection
Negative-pressure cleaning and disinfection device	Shinva Medical Instrument Co., Ltd., China	SQ-D Series Pulsed Vacuum Washer Disinfector	Automated cleaning and disinfection system
Personal protective equipment (PPE)	Ansell Ltd., Australia	Microflex® 93-260	Gloves used during manual cleaning
Residual blood detection reagent/test kit	Healthmark Industries, USA	HemoCheck™ (HCK100)	Used for detecting residual blood contamination
Running water source	Hospital CSSD water system	Not applicable	Standard CSSD rinse water supply
Soft cleaning brushes	Healthmark Industries, USA	BRS-100 series	Used during manual cleaning
Temperature monitoring probe	Testo SE & Co., Germany	Testo 110	Used to monitor cleaning temperature (48–62 °C)
Timer / digital stopwatch	Casio Computer Co., Japan	HS-80TW	Used for recording cleaning duration
Ultrasonic cleaning machine	Branson Ultrasonics, USA	Branson 5800	Used for ultrasonic cleaning step
Water quality test kit	Merck KGaA, Germany	Aquamerck® Kit	Ensures water quality for cleaning processes
SPSS statistical software		21.0 software	Statistical anlysis software