Discussion
tumor, fracture, friable, dehydration, Velo et al., tooth
TUMOR, MINERALIZATION, DEHYDRATION, FRAGILITY, HEAD AND NECK CANCER, HYDROXYAPATITE
The null hypothesis was rejected because RDT altered the dentinal tubular morphology,
modified the inorganic composition of the intra-radicular dentin, and affected the
integrity of the collagen fibers in the root dentin. A greater number of obliterated
dentinal tubules was observed after RDT, demonstrating its deleterious effect on the
tooth structure and corroborating the previous results by Velo et al. Obliteration of the dentinal tubules has been associated with the deposition of
residues resulting from cutting the dentin As for the alteration of collagen fibers, approximately 20% of the dentin is composed
of organic matrix mainly composed of collagen, and RDT can influence the integrity
of type IV collagen in the organic matrix, resulting in the fragility of this
structure and favoring the fracture of the dental element The structure of the intra-radicular dentin is composed of dentinal tubules that
extend from the pulp to the cement-dentin junction In our study, most of the irradiated teeth showed low collagen integrity, whereas, in
the control group, the collagen fibers remained intact in 77.8% of the cases,
corroborating other studies The literature regarding the microscopic evaluation of the effects of RDT on collagen
structure is scarce. However, histological studies are important because they allow
a better understanding of this structure, and the Masson trichrome and picrosirius
red stains under polarization allow the evaluation of collagen fibers The effects of RDT on the obliteration of dentinal tubules and alteration in the
structure of collagen fibers may be due to fiber fragmentation resulting from
dehydration and the action of free radicals, leaving the tissue dehydrated and
friable RDT is also associated with increased matrix metalloproteinase expression and
activation in other organs Alterations in the organic matrix of the intra-radicular dentin can negatively affect
the microhardness of the dentin structure RDT can also influence the inorganic components of dentin, as observed in our study
with the reduction in Ca, P, and Mg after RDT. Additionally, Ca reduction has also
been observed in root dentin The Ca/P ratio determines the average mineralization of hydroxyapatite. In our study,
an increase in this value was observed after RDT, which may explain the obliteration
of dentinal tubules from an increase in peritubular dentin, which is more
mineralized. However, this increase in hydroxyapatite in the intra-radicular dentin
does not necessarily mean an increase in the mechanical strength of the analyzed
region, because ions are released from the interaction between water and radiation,
inducing the formation of a type of hydroxyapatite that is more susceptible to
degradation In this study, a reduction in Mg was observed. Mg is associated with tooth
biomineralization The radiation dose used was based on RDT treatment for head and neck cancer, which
usually involves a total dose of 70 Gy in the tumor region Studies on the deleterious effect of RDT on tooth structure are controversial Due to the lack of a standardized methodology to assess the effects of RDT on tooth
structure, it becomes difficult to compare our results with those of other studies,
which is a limitation of the present study. Moreover, different doses of RDT can
generate different effects, and in our study, we evaluated the maximum dose
treatment prescribed for a patient with head and neck cancer.RDT can cause deleterious effects on the intra-radicular dentin, such as obliteration
of dentinal tubules, alteration in inorganic components, and harmful effects on the
collagen fibers of the root dentin. This can interfere with the effectiveness of
dental procedures such as root canal filling in endodontic treatments, and these
changes must be considered when choosing endodontics or restorative materials.
However, further studies are needed to better understand the deleterious effects of
RDT, and protocols must be defined to minimize clinical consequences.