Microbiome Changes After Laser and Chlorhexidine Disinfection in Caries Removal

Not Applicable

Not yet recruiting

• Conditions: Dental Caries
• Interventions: Procedure: Tungsten carbide bur; Drug: CHX disinfection; Device: Laser Disinfection; Procedure: Polymer bur

• Registration Number: NCT06765330
• Lead Sponsor: Mersin University

Brief Summary

The aim of this study was to investigate the effects of cavity disinfection with laser and chlorhexidine on the microbiome in cavities prepared using different caries removal methods.

Detailed Description

Prevention and treatment of dental caries, one of the most common and oldest diseases, is closely related to human health. Dental hard tissue undergoes remineralization and demineralization processes in a cycle. Caries occur when this balance is disturbed in favor of demineralization. Dental caries is the loss of minerals caused by the acid produced by microorganisms.

In conventional caries removal, high-speed rotating hand instruments are generally used to reach the lesion. In contrast, low-speed rotating hand instruments (tungsten carbide burs) remove the caries. This method involves rapid and efficient caries removal but may result in the removal of healthy tissue or affected dentin capable of remineralization. During minimally invasive procedures, more sparing and selective methods of caries removal are widely used in operative dentistry as an alternative to the conventional method. One of these methods is polymer burs produced as an alternative to conventional tungsten carbide burs. They are made of soft polymer material. It removes only infected dentin. Polymer burs are harder than carious dentin and softer than healthy dentin. Therefore, when removing carious tissue with a polymer bur, the bur remains intact, but when it comes to healthy tissue, the bur wears out. It is designed to remove only carious dentin by selectively maintaining its cutting efficiency until it encounters caries-affected dentin. In a previous study, microbiological Streptococcus mutans bacteria count reduction before and after occlusal caries removal was statistically significant with polymer burs compared to tungsten carbide burs.

In restorative dentistry, complete removal of infected caries tissue before the restoration process plays a key role in the success of the treatment. Due to the risk of removing healthy dentin tissue while removing infected caries tissue, protective cavity preparation techniques have been developed. Criteria such as color and hardness, which are considered in the decision to remove caries from dental tissue, are subjective and depend on the senses of sight and touch. Although researchers recommend the use of caries indicators based on objective data, studies have shown that indicators are only 15-40% successful in detecting the presence of microorganisms. Despite the removal of the stained tissues, the presence of microorganisms was observed in the area close to the pulp, especially in the dentinal tubules. These microorganisms remaining in the tissue may cause secondary caries formation, postoperative sensitivity, and pulpal inflammation. Studies have shown that the occlusive and sealing properties of the restoration material cannot prevent the residual bacteria in the smear layer and dentinal canals from diffusing into the pulp tissue and causing infection. Therefore, the use of antibacterial cavity disinfectants has come to the fore. Today, chlorhexidine digluconate (CHX), benzalkonium chloride, sodium hypochlorite, hydrogen peroxide, iodine solutions, phosphoric acid, fluoride, propolis, ozone, light-activated disinfection systems, and laser systems are used as cavity disinfectants.

The microbiology of dental caries is a subject that has been studied for many years. Previous studies have used traditional culture-based methods to identify bacteria associated with dental caries. The culture-based method has allowed a basic understanding of the composition of dental plaque microbiota in dental caries. Microorganisms have been isolated from carious lesions or dental plaque samples collected from a cross-sectional or longitudinal study using culture-based techniques. However, research on the oral microbiome is still incomplete as artificial media cannot fully mimic the natural environment in which oral bacteria are found, because about half of the oral microbiome cannot be cultured. Therefore, it is not possible to detect all bacteria in the sample in studies using the culture method. Molecular genetic techniques can detect and identify the microbiome without culture using the analysis of 16s rRNA found in all these prokaryotes. The 16s rRNA gene is used as a standard for the classification and identification of the microbiome because 16s rRNA gene sequences contain hypervariable regions that can provide species-specific sequences for the identification of bacteria. Although initially used to identify bacteria, 16s rRNA sequencing was later used to reclassify bacteria into new species or genera. It has also been used to identify new species that have not yet been successfully cultured. Recently, high-throughput pyrosequencing has revealed unexpectedly high diversity within the human oral microbiome. Molecular genetic techniques have been used to detect and identify microorganisms in permanent teeth, necrotic pulp and periapical lesions, and clinical samples without direct culture.

The understanding of caries microbiology has been greatly enriched in recent years by the advancement of sequencing-based technology and bioinformatic analysis. However, there are no studies in the literature evaluating microbiome analysis in combination with different caries removal techniques and cavity disinfection methods. Therefore, this study aims to review the classical concepts of microbiological aspects of dental caries and to investigate the effects of cavity disinfection with laser and chlorhexidine on the microbiome in cavities prepared using different caries removal methods.

Study Timeline

• Status Verified: 2025-01
• Study First Submitted: 2025-01-03
• Study First Submitted QC: 2025-01-03
• Last Update Submitted: 2025-01-03
• Study First Posted: 2025-01-09
• Last Update Posted: 2025-01-09
• Study Start: 2025-05-05
• Primary Completion: 2025-08-29
• Study Completion: 2025-09-15

Recruitment & Eligibility

• Status: NOT_YET_RECRUITING
• Sex: All
• Target Recruitment: 78

Inclusion Criteria

Not provided

Exclusion Criteria

Not provided

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Group 1: Non-selective caries removal with tungsten carbide bur + No cavity disinfection	Tungsten carbide bur	Access to the lesion will be achieved using a high-speed handpiece with a sterile high-speed bur (#245 bur Meisinger GmbH, Germany). The caries removal strategy towards soft dentin will be performed following the guidelines published by the International Caries Consensus Collaboration. The caries will be completely removed from the surrounding cavity walls with a tungsten carbide bur, leaving at least 2 mm of peripheral intact tooth structure for good adaptation and sealing of the restoration. Superficial necrotic caries fragments, which deform when an instrument is pressed into them and can be easily removed with little force, will be removed from the pulpal floor using a sharp sterile excavator, while soft dentin will be left at the cavity floor to avoid pulpal exposure. Following caries removal, the tooth will be restored without any cavity disinfection.
Group 2: Non-selective caries removal with tungsten carbide bur + 2% chlorhexidine disinfection	CHX disinfection	Following the caries removal protocol applied in Group 1, 2% chlorhexidine (Consepsis®, Ultradent) will be applied to the cavity for 20 seconds. The cavity will then be air-dried for 10 seconds, and the tooth will be restored.
Group 2: Non-selective caries removal with tungsten carbide bur + 2% chlorhexidine disinfection	Tungsten carbide bur	Following the caries removal protocol applied in Group 1, 2% chlorhexidine (Consepsis®, Ultradent) will be applied to the cavity for 20 seconds. The cavity will then be air-dried for 10 seconds, and the tooth will be restored.
Group 3: Non-selective caries removal with tungsten carbide bur + Er,Cr: YSGG laser disinfection	Laser Disinfection	Following the caries removal protocol applied in Group 1, the cavity will be disinfected using an Er,Cr: YSGG laser (EPIC X™, BIOLASE, USA) with 940 nm and 0.1 W output power. Then, the tooth will be restored.
Group 3: Non-selective caries removal with tungsten carbide bur + Er,Cr: YSGG laser disinfection	Tungsten carbide bur	Following the caries removal protocol applied in Group 1, the cavity will be disinfected using an Er,Cr: YSGG laser (EPIC X™, BIOLASE, USA) with 940 nm and 0.1 W output power. Then, the tooth will be restored.
Group 4: Selective caries removal with polymer bur + No cavity disinfection	Polymer bur	Access to the lesion will be achieved using a high-speed handpiece with a sterile high-speed bur (#245 bur Meisinger GmbH, Germany). The SS White Smartburs II® will be used with a low-speed handpiece at 5,000-10,000 RPM to remove carious dentin of sizes RA4, RA6, and RA8 depending on the size of the caries lesion. The instrument will be used with a circular, light force starting from the center of the carious lesion towards the periphery as recommended by the manufacturer. Caries removal will be stopped when the instrument is macroscopically worn and blunt and can no longer remove tissue. An explorator will be used to verify if any caries remain at the base of the cavity. If necessary, a new polymer bur, SmartbursII®, will be used to remove the remaining decay. After selective caries removal, the tooth will be restored without any cavity disinfection.
Group 5: Selective caries removal with polymer bur + 2% chlorhexidine disinfection	CHX disinfection	Following the selective caries removal protocol applied in Group 4, 2% chlorhexidine (Consepsis®, Ultradent) will be applied to the cavity for 20 seconds. The cavity will then be air-dried for 10 seconds, and the tooth will be restored.
Group 5: Selective caries removal with polymer bur + 2% chlorhexidine disinfection	Polymer bur	Following the selective caries removal protocol applied in Group 4, 2% chlorhexidine (Consepsis®, Ultradent) will be applied to the cavity for 20 seconds. The cavity will then be air-dried for 10 seconds, and the tooth will be restored.
Group 6: Selective caries removal with polymer bur + Er,Cr: YSGG laser disinfection	Laser Disinfection	Following the selective caries removal protocol applied in Group 4, the cavity will be disinfected using an Er, Cr: YSGG laser (EPIC X™, BIOLASE, USA) with 940 nm and 0.1 W output power. Then, the tooth will be restored.
Group 6: Selective caries removal with polymer bur + Er,Cr: YSGG laser disinfection	Polymer bur	Following the selective caries removal protocol applied in Group 4, the cavity will be disinfected using an Er, Cr: YSGG laser (EPIC X™, BIOLASE, USA) with 940 nm and 0.1 W output power. Then, the tooth will be restored.

Primary Outcome Measures

Name	Time	Method
Microbiome Changes	3 months	In all groups, dentin samples will be taken from the affected dentin at the base of the cavity as a result of three different subgroup disinfection procedures applied after the caries removal method using 2 sterile number 6 round sterile steel roun burs moistened with saline for microbial analysis. The burs will be placed in 5 ml sterile vials and stored at -80 0C until the analyses are performed. The prepared cavities will be completed with routine and standard treatment protocols. Following the finishing and polishing procedures, occlusion will be checked. The samples collected during the research process will be delivered to the A\&D Genetic Diseases Evaluation Centre (Ankara, Turkey) where DNA isolation and sequence analysis will be performed together with molecular biologists. In the method, following the extraction of total genomic DNA from clinical samples, broad-range 16S rRNA PCR will be performed and MicroSeq 500 16S rRNA Sequencing kit will be used for sequence analysis.

Trial Locations

Locations (1)

Mersin University, Faculty of Dentistry, Department of Restorative Dentistry; 🇹🇷 Mersin, Yenisehir, Turkey