CARIES PREVENTIONDr.alhadi 19.2.2009

The caries process is well understood

Featherstone et al 2000

Primary caries preventive agents are

fluoride and fissure sealant.

(Ogaard B 1990)

laser

LASER APPLICATION IN PREVENTIVE DENTISTRYMaiman 1960 ruby Stern and Sognnas first in long

list of investigators. To use ruby to reduce subsurface demineralization

These studies were primitive :optical properties of dental tissues at respective laser wavelength and the laser pulse shape and characteristic were not investigated

SCATTERING AND ABSORPTION PARAMETERSMaterials with high absorption

coefficient>100 cm-1 the laser energy is absorbed within 100µm of the surface and converted to heat .

further penetration of heat is done via heat conduction and it is determined by thermal conductivity and heat capacity of the tissue

Mineral component of enamel and dentin is carbonated hydroxyapetite it contain calcium ,sodium ,phosphate ,carbonate ,hydroxyl and fluoride ion.

Water content of enamel is 12% and of dentin is 25%

Carbonate content 3% and 5% (E&D) Absorption band for water is

3µm ,hydroxyl 2.8µm ,carbonate 7µm

,and phosphate 9-11µm

MECHANISM OF LASER IRRADIATION AND IMPROVED CARIES RESISTANCE

Change in enamel composition:

Theories range from physical seal achieved by melting the surface through partial fusion and recrystaliztion of enamel prisms ,to change in enamel composition only

CREATION OF MICROSIVE OR MICROPORE SYSTEM

The creation of micro pores act as site for re-precpitation or means of trapping of calcium ,phosphate and fluoride.

The loss of water ,carbonate and organic substances from enamel would have caused the formation of microspaces.

It has been shown that irradiation with an argon laser produces a changes in the surface layer of enamel by producing micro porosities admixed with globular surface coating .

So there is an enhanced uptake of fluoride ,calcium and phosphate from endogenous and exogenous sources in lased dental hard tissues

THE CARIES PREVENTING EFFECT OF CO2 LASER

CO2 produces radiation in the infrared region that coincides closely with some of apatite absorption bands.

Mainly phosphate groups has strong absorption at 9-11µm

There are four vibrational emission bands which are centered at 9.3,9.6,10.3 and 10.6µm

In contrast to most other laser wavelength scattering is negligible in dental enamel at mid IR wavelengths 3-12µm.

so the energy deposition is determined by (a) the absorption coefficient and (b) tissue reflectance.

absorption coefficient of enamel at 9.6µm is 8.000 cm and for 10.6µm is 800 cm.

caries inhibition by CO2 is affected by wavelength ,pulse duration ,pulse number, repetition rate ,pulse energy and spot size.

The caries preventing effect of Argon lasers. The caries preventing effect of Nd:YAG laser. The caries preventing effect of

Er:YAG,Er,Cr:YSGG,Ho:YAGan