Enamel and Dentin Microhardness and Chemical Composition After Experimental Light-activated Bleaching

At a Glance

Metadata	Details
Publication Date	2015-03-06
Journal	Operative Dentistry
Authors	Eva Klarić, Mario Rakić, Ivan Sever, O. Milat, Matej Par
Institutions	Institute for Tourism, Institute of Physics
Citations	66
Analysis	Full AI Review Included

Technical Analysis and Documentation for 6CCVD

Executive Summary

This research investigates the mechanical and chemical degradation of dental hard tissues following light-activated bleaching, specifically evaluating high-concentration peroxide gels in combination with advanced light sources, including an experimental femtosecond laser system.

Advanced Illumination Tested: The study utilized state-of-the-art light sources, including a Mercury Metal Halide lamp (ZOOM2), high-power 405 nm LED, organic LED (OLED), and a Ti:sapphire Femtosecond Laser (770 nm center wavelength).
Negligible Light Activation Effect: The study concluded that light activation itself did not significantly contribute to microhardness reduction or chemical degradation; rather, the peroxide concentration (up to 38% HP) and high gel acidity were the primary detrimental factors.
Extreme Material Requirements: The laser system employed high-power density (800 mW/cm²) and femtosecond pulses (700-950 nm range), demanding extreme optical quality and thermal management from system components.
Measurement Standards: Mechanical evaluation relied on Vickers diamond microhardness testing, while elemental analysis utilized high-energy (10,000 keV) Energy-Dispersive X-ray Spectroscopy (EDS).
6CCVD Value Proposition: The requirement for high-durability optics operating at 770 nm and excellent thermal management for high-power LEDs/Lasers directly necessitates the use of high-purity, optically transparent CVD Single Crystal Diamond (SCD) components.

Technical Specifications

Hard data extracted from the study detailing experimental conditions and results.

Parameter	Value	Unit	Context
Femtosecond Laser Center Wavelength	770	nm	Ti:sapphire oscillator (Spectra-Physics)
Femtosecond Laser Power Density	800	mW/cm²	Activation energy for bleaching
ZOOM2 Light Source Power Density	2,000	mW/cm²	Mercury metal halide source
LED Wavelength	405	nm	Used for light activation
High Peroxide Concentration (HP)	38	%	Hydrogen Peroxide (BOOST gel)
Lowest Observed Dentin Microhardness	40	% Reduction	Achieved with 25% HP gel
pH of Most Acidic Bleaching Gel	3.20	-	25% HP gel (below enamel critical level 4.5)
EDS Spectroscopy Energy	10,000	keV	Used for elemental analysis (Ca, P, O, F, C)
Baseline Enamel Microhardness (Median)	37.81	Vickers (IQ: 37.01-38.92)	Prior to treatment
Maximum Post-Treatment Microhardness Loss	< 3	% Deviation from Baseline	After two-week ACP/Artificial Saliva restoration

Key Methodologies

A concise overview of the experimental procedures, focusing on the equipment and specific recipes.

Specimen Preparation:
- 125 human third molars were dissected into quarters (enamel/dentin).
- Surfaces were polished using water-cooled carborundum discs (4000 grit) and micro-polish powders (down to 0.05 µm) to achieve a standardized 3 x 3 mm area.
Bleaching Treatment Recipe:
- Five commercial peroxide/carbamide peroxide gels were tested (10% CP to 38% HP).
- Application protocol: Gels applied 2 times for 15 minutes each session.
Advanced Light Activation Sources:
- Bleaching performed with no light (control) and activated by four light sources: ZOOM2, 405 nm LED, OLED, and Femtosecond Laser.
- Femtosecond Laser Configuration: A 532 nm green pump laser stimulated a Ti:sapphire oscillator, generating femtosecond pulses centered at 770 nm (700-950 nm range).
pH Measurement:
- Gel pH measured at room temperature (24°C) for 20 minutes (e.g., 25% HP measured 3.20).
Microhardness Measurement:
- Vickers diamond microhardness tester (Leitz Miniload2).
- Load parameters: 100g applied for 10 seconds.
Chemical Composition Analysis:
- Energy-Dispersive X-ray Spectroscopy (EDS) (JEOL JSM 7000F) performed at 10,000 keV.
Post-Bleaching Treatment:
- Specimens stored for two weeks in either deionized water or restoration medium (Artificial Saliva + Amorphous Calcium Phosphate (ACP)).

6CCVD Solutions & Capabilities

6CCVD provides the high-performance CVD diamond materials required to develop, stabilize, and measure next-generation optical and mechanical systems used in this type of high-energy research.

Applicable Materials

To replicate or extend this research, especially concerning the high-power optics and analytical windows, the following 6CCVD materials are required:

Research Requirement	6CCVD Recommended Material	Technical Rationale & Specifications
High-Power Laser Optics (770 nm)	Optical Grade Single Crystal Diamond (SCD)	Essential for stabilizing the Ti:sapphire oscillator. SCD provides zero birefringence, high purity, and superior thermal conductivity (up to 2200 W/mK) for managing thermal lensing and drift in high-power femtosecond systems. Available in thicknesses from 0.1 µm up to 500 µm.
High-Density LED/OLED Thermal Management	Polycrystalline Diamond (PCD) Heat Spreaders	The high-power density of the ZOOM2 and LED sources (up to 2,000 mW/cm²) necessitates robust heat spreading. 6CCVD offers PCD wafers up to 125mm diameter for integration with active thermal components, ensuring operational stability and longevity.
EDS Spectroscopy Windows	Thin SCD or PCD Membranes	Used as robust, chemically inert windows for the EDS detector (JSM 7000F) analyzing Ca, P, and F content at 10,000 keV. Diamond membranes provide optimal X-ray transparency and durability against corrosive environments.
Mechanical Test Components	Ultra-Hard Single Crystal Diamond (SCD)	For ensuring precision and longevity in Vickers microhardness indenter tips, especially critical when testing complex material changes caused by chemical exposure.

Customization Potential

The experiment relies on highly specified components for high-power laser delivery and precise material analysis. 6CCVD offers specialized manufacturing capabilities to meet these precise engineering demands:

Custom Dimensions and Shapes: While the paper used 3x3 mm samples, 6CCVD can supply SCD or PCD optics with custom geometries, laser-cut features, and large formats (PCD up to 125mm) necessary for scaling research applications or developing commercial devices.
Precision Polishing: Achieving accurate microhardness and chemical analysis requires superior surface preparation. 6CCVD guarantees Ra < 1nm for SCD optics and Ra < 5nm for inch-size PCD wafers, providing superior component quality for optical and test apparatus interfaces.
Metalization Services: 6CCVD provides in-house metalization (including Au, Pt, Pd, Ti, W, Cu) for bonding, mounting, or creating electrodes needed for the integration of high-power LED/OLED chips onto diamond heat spreaders.

Engineering Support

This study underscores the intersection of advanced laser physics, chemical engineering, and materials science. 6CCVD’s in-house PhD team provides consultative support for projects involving:

High-Power Laser Optics: Assistance with material selection and design for stabilizing high-energy (femtosecond pulse) or high-average-power optical systems across the UV to IR spectrum (405 nm to 950 nm tested here).
Thermal Management Solutions: Design optimization for using CVD diamond as heat spreaders in high-density LED arrays and organic electronic devices similar to the PPML OLED engineering prototype utilized in this project.
Corrosion Resistance: Specifying chemically inert diamond components for use in harsh chemical or acidic environments (like the low-pH peroxide gels used here) prevalent in medical or industrial applications.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

SUMMARY Objectives To evaluate 1) the influence of five bleaching agents (with additional light activation) on enamel and dentin surface microhardness and chemical composition and 2) the remineralizing potential of artificial saliva and amorphous calcium phosphate (ACP). Methods and Materials The study was conducted on 125 human third molars dissected into quarters for separate enamel and dentin measurements. The bleaching process was performed with 38% and 25% hydrogen peroxide (HP) and 30%, 16%, and 10% carbamide peroxide (CP) gels two times for 15 minutes each time. All bleaching gels were tested alone and in combination with ZOOM2, light-emitting diode (LED), organic LED, and femtosecond laser. A total of 25 bleaching combinations (n=10) were evaluated. Microhardness was measured by a Vickers diamond. Chemical analysis was performed using energy-dispersive X-ray spectroscopy. Results Bleaching agents used in the absence of light activation caused a significant reduction in enamel and dentin surface microhardness (p&lt;0.001), ranging from 8% for 16% CP to 40% for 25% HP. The effects of different light activations were negligible. After two-week treatment with ACP and artificial saliva, maximum deviation from baseline microhardness was just 3%. Such treatment increased the concentrations of calcium, phosphorus, and fluorine. Conclusions An increase in peroxide concentration and gel acidity negatively affected microhardness and concentrations of calcium and phosphorus in enamel and dentin. ACP and artificial saliva stimulated the remineralization of hard tissues.

Tech Support

Original Source

DOI: https://doi.org/10.2341/14-148-l

References

2005 - Subsurface microhardness of enamel and dentin after different external bleaching procedures
2012 - Microhardness change of enamel due to bleaching with in-office bleaching gels of different acidity [Crossref]
2011 - Effect of carbamide peroxide and hydrogen peroxide on enamel surface: An in vitro study [Crossref]
2011 - Postoperative sensitivity after two in-office bleaching methods
2001 - Effect of 10% carbamide peroxide bleaching materials on enamel microhardness
2009 - Effect of different bleaching systems on the ultrastructure of bovine dentin [Crossref]
2004 - Pulp reaction to vital bleaching
2008 - Effect of fluoride containing bleaching agents on enamel surface properties [Crossref]
2008 - Remineralization of enamel subsurface lesions in situ by the use of three commercially available sugar-free gums [Crossref]