The effect of radiation therapy on the mechanical and morphological properties of the enamel and dentin of deciduous teeth--an in vitro study.
OBJECTIVE
To evaluate the effects of radiation therapy on deciduous teeth.


METHODS
The enamel and dentin microhardness (n = 12) was evaluated at 3 depths, both before (control) and after each 10 Gy of irradiation and up to a dose of 60 Gy. The morphology was evaluated via scanning electron microscopy (SEM) (n = 8). The data were analyzed using a two-way analysis of variance (ANOVA) and Tukey's test (α = 5%).


RESULTS
The enamel microhardness, as a whole, increased (p < 0.05) after a dose of 60 Gy (211.4 KH), mostly in the superficial enamel. There was a significant difference between the values of nonirradiated dentin microhardness (28.9 KH) compared with dentin that was irradiated with doses of 10 Gy (23.8 KH), 20 Gy (25.6 KH), 30 Gy (24.8 KH), and 40 Gy (25.7 KH) (p < 0.05). There was no difference between nonirradiated dentin and dentin irradiated with 60 Gy (p > 0.05). The highest mean value of microhardness (29.9 KH) (p < 0.05) was found in the middle dentin. The groups that were irradiated with doses of 30 and 60 Gy exhibited greater surface changes in their enamel and dentin compared with the nonirradiated groups for all regions, exhibiting an amorphous surface upon increase of the irradiation doses.


CONCLUSIONS
The enamel microhardness increased at a dose of 60 Gy, whereas the value of the dentin microhardness did not change. A progressive disruption of enamel and dentin morphology was found with the increased radiation dose.
Department of Pediatric Clinics, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão, Preto, Brazil. talimellara@hotmail.com.
Talitha
T
de Siqueira Mellara
Regina Guenka
RG
Palma-Dibb
Harley Francisco
HF
de Oliveira
Francisco Wanderley
FW
Garcia Paula-Silva
Paulo
P
Nelson-Filho
Raquel Assed Bezerra
RA
da Silva
Léa Assed Bezerra
LA
da Silva
Alexandra Mussolino
AM
de Queiroz
D003743:Dental Enamel / Q000166:cytology / Q000528:radiation effects* / Q000648:ultrastructure; D003804:Dentin / Q000166:cytology / Q000528:radiation effects* / Q000648:ultrastructure; D006244:Hardness / Q000528:radiation effects; D006245:Hardness Tests; D006801:Humans; D066298:In Vitro Techniques; D055595:Mechanical Phenomena; D008855:Microscopy, Electron, Scanning; D011878:Radiotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D014094:Tooth, Deciduous / Q000166:cytology / Q000528:radiation effects* / Q000648:ultrastructure