Azeez Al-Ibrahim, Hasan Subhi
(2015)
Evaluation of gypsum-chitosan as a biomaterial in dental pulp protection.
Masters thesis, Universiti Sains Malaysia.
Abstract
In dentistry, preservation of vital pulp tissue through pulp therapy is a
challenging clinical approach. In the procedure of direct pulp capping, the exposure
site is sealed by dental material to maintain the vitality of the pulp and induce
reparative dentin formation. Several materials such as calcium hydroxide and mineral
trioxide aggregate have been used and investigated for dental pulp capping with
limitations. Thus, chitosan (CHT) and calcium sulfate (pure gypsum - Gyp)
incorporated with bone morphogenetic protein 2 (BMP-2) were chosen in this study
to exploit their advantages and develop a biomaterial with high biological and
mechanical characteristics. Gyp is highly biocompatible, moldable and used as
carrier of antibiotic. CHT is biocompatible, has antibacterial activity and enhances
tissue growth. BMP-2 induces differentiation of pulp cells into odontoblasts and
reparative dentin formation. The aims of this study were to prepare an experimental
gypsum-based biomaterial and to study the effects of the biomaterial with several
concentrations of CHT (10%, 5%, 2.5%, 1%, and 0% chitosan solution) on setting
time (min), pH value, compressive strength (MPa), solubility (%), antibacterial
activity against cariogenic bacteria, and the proliferative activity of SHED. In
addition, BMP-2 was incorporated with Gyp-CHT and its effect was evaluated on
alkaline phosphatase activity (ALP) of SHED. The adhesion and proliferation of
SHED on the experimental biomaterial was also observed by scanning electron
microscope (SEM). Commercial dental liner Dycal and Fuji IX were prepared
according to manufacturer’s instructions and selective properties were evaluated for
comparison purpose. For the experimental biomaterials the results of setting time
were ranged between 4.1 and 6.6 min which is considered acceptable for clinical
application. The pH values after 24 hours were ranged 5.7 and 6.4 which is suitable
for application as pulp capping. The compressive strength increased with higher
CHT concentration in the biomaterial which ranged between 2.63 and 5.83 MPa. The
solubility rate decreased with CHT incorporation compared to that without CHT
except for Gyp-CHT 10% which showed the highest solubility. The experimental
biomaterial showed potent antibacterial activity against S. mutans and S. sobrinus,
which was more evident with greater CHT concentration and comparable with other
lining materials. The biomaterial showed good cell compatibility to SHED in both
direct and indirect MTS tests. The biomaterial tended to increase the release of ALP
outside the cells. The experimental biomaterial induced the ALP activity of SHED
with higher activity in biomaterial incorporated with BMP-2. SEM observations
showed that the seeded SHED were apparently healthy, well adhered and were
spread on the surface through proliferative activity. The in vitro results of this study
suggest that the physical and mechanical properties of gypsum based chitosan
biomaterials were acceptable in relation of pulp capping biomaterials. The ALP
activity of SHED which is an indicator of mineralization was significantly higher in
Gyp-CHT-BMP-2 biomaterials compared to Dycal. Antibacterial properties of
experimental biomaterials were found comparable with the commercial materials.
Thus, the crystalline gypsum impregnated with CHT and BMP-2 organic matrices
may have the potential for application in vital pulp therapy.
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