Dentin surfaces irradiated by Er:YAG laser were irregular, scaly, or flaky and dentinal tubules were opened without smear layer, cracked or melted; whereas protrusion of peritubular dentin
was revealed due to its less amount of water compared with intertubular dentin.
Dentinal tubules are cylindrical structures located along the dentin and covered by highly mineralized peritubular dentin that provides them with rigidity.
For example, through atomic force microscopy one can calculate the nanohardness and the modulus of elasticity of specific sites, such as coronal or root inter- and peritubular dentin.
It forms a complex with the calcium rich zone of the peritubular dentin
to create a crystal plug.
The qualitative evaluation considered dentin surface characteristics, intertubular and peritubular dentin
, dentinal tubules and smear layer deposits.
Dentin tubule occlusion takes place as teeth age via continued deposition of peritubular dentin
(40) which may influence the physical properties of the dentin.
According to Kawamoto and Tsujimoto, (23) the OH radical resulting from hydrogen peroxide degradation is responsible for tooth whitening, and acts on intertubular and peritubular dentin
, destroying its organic portion, increasing permeability, (24,25) and decreasing its hardness and elasticity modulus, (2,3) which can be intensified with a greater exposure time of the tooth to the bleaching agent.
Qualitative aspects of the inter- and peritubular dentin
were also assessed, taking into consideration the presence or absence of the smear layer.
Older teeth experience gradual enlargement of peritubular dentin
and intratubular mineral deposits, which often result in narrowed or completely occluded tubules.