This document discusses various methods for evaluating the depth of cure of dental resin composite materials, including thickness measurements, scraping technique, hardness tests, atomic force microscopy, glass transition temperature measurements, and degree of conversion measurements using differential scanning calorimetry and Fourier transform infrared or micro-Raman spectroscopy. No single technique can fully characterize the complex curing behavior, so a combination is typically used to evaluate factors like light absorption, scattering, filler properties, and how well material cures at different depths.

1. Evaluation Methods of Depth of
Cure for Dental Resin Composite
Restorative Materials.

2. Introduction
• The physical, mechanical and biocompatibility
properties of photo-cured resin composites
depend on the degree of cure (conversion)
during polymerization.
• Hence its clinical success
• Unfortunately dentist has no mean to
measure the cure of resin beneath the surface
(inner layers) or the depth of cure.

3. Depth of Cure
• Definition:
– The thickness of photo-polymerizable resin composite
that is “adequately” cured.
• Factors Affecting: (limitations)
• Light absorption
• Light Scattering
• Amount, size, type of fillers.
• Shade.
• Photo-initiator type and
concentration.
• Reflective index mismatch.
• Light irradiation source.
• Light irradiation duration.

4. Methods of Measurement (evaluation)
Types of Methods
Thickness
measurements
(ISO 4049)
Scraping Technique
Hardness
Elastic modulus
Vicker Hardness Test
Atomic Force
Microscope
Glass transition temp.
Degree of Conversion
DSC , FTIR ,
Micro-Raman
Spectroscopy

5. Scraping Technique (ISO 4049)
• No determination of the
degree of polymerization.
• Doesn’t tell the thickness
to expect bottom
adequate cure.
• Overestimate depth of
cure.
• Can only be used to
compare curability of
different composites.

6. Hardness Ratio (Vickers Indentation)
• Limitations:
– Indentation bigger
than distance between
fillers.
– Top surface not usually
fully cured.
– No quantitative
information on
unreacted radicals.
Can only be used as an indirect approximation

7. FTIR and Micro-Raman Techniques
• Based on interaction between electromagnetic
radiation and natural vibrations of the chemical
bonds among atoms that compose the matter.
• 2 conditions:
– Coincidence between frequencies
– Change in dipole moment
• Stiffness of the bond specify the frequency.

8. Fourier Transform Infra-Red
Spectroscopy

9. Micro-Raman Spectroscopy

10. FTIR and Micro-Raman Techniques
• Detect the carbon double bonds vibrations at
different wavelengths.
• by comparing the intensities of aliphatic to
aromatic bands, degree of conversion can be
measured.

11. • In the absence of an isolated stable band (internal
reference), a calibration curve for the monomer that
composes the composite should be made.
FTIR and Micro-Raman Techniques

12. • Bands overlap and it becomes difficult to identify
the baseline and separate each band area.
• Better use band height over area for calculating
the absorption difference
FTIR and Micro-Raman Techniques

13. Micro-Raman Spectroscopy
• Advantages over FTIR:
– Not sensitive to H2O vibration band.
– Can do scanning over surface.
– No special sample preparation.
– Easy to use.
• Limitations:
– Not very sensitive to small changes in vibration
intensity.

14. Atomic Force Microscope (AFM)
Small changes in in conversion result in marked differences in elastic modulus

15. Julian G. Leprince, Philippe Leveque, Bernard Nysten,
Bernard Gallez, Jacques Devaux, Gaetane Leloup. New
insight into the “depth of cure” of dimethacrylate-
based dental composites. Dental Materials, Volume
28, Issue 5, May 2012, Pages 512-520.

16. Differential Scanning Calorimetry (DSC)
• To detect the glass transition (Tg) temperature
of the cured composite resin at different depth.
• This identify the state of the cured composite if
gel state or vitrified state.

17. Julian G. Leprince, Philippe Leveque, Bernard Nysten, Bernard Gallez, Jacques Devaux, Gaetane Leloup.
New insight into the “depth of cure” of dimethacrylate-based
dental composites.
Dental Materials, Volume 28, Issue 5, May 2012, Pages 512-520.

18. References
• BK Moore et al. Depth of cure of Dental Resin Composites. Operative Dentistry, 2008, 33-4.
• C. Pianelli, J. Devaux, S. Bebelman, G. Leloup. The Micro-Raman Spectroscopy, a Useful Tool to Determine
the Degree of Conversion of Light-Activated Composite Resins. J Biomed Mater Res (Appl Biomater) 48:
675–681, 1999.
• Moraes L G P, Rocha R S F, Menegazzo L M, Araújo E B De, Yukimitu K, Moraes J C S. Infrared Spectroscopy:
A Tool For Determination Of The Degree Of Conversion In Dental Composites.J Appl Oral Sci.
2008;16(2):145-9.
• Julian G. Leprince, Philippe Leveque, Bernard Nysten, Bernard Gallez, Jacques Devaux, Gaetane Leloup.
New insight into the “depth of cure” of dimethacrylate-based dental composites. Dental Materials,
Volume 28, Issue 5, May 2012, Pages 512-520.
• Ronald D. Jackson. The truth about depth of cure. http://www.dentistrytoday.com/viewpoint/9867-the-
truth-about-depth-of-cure.

19. Thank You

20. • Hardness measurment is more sensitive to
detect small changes in degree of conversion
than FTIR after network is crosslinked.