Biomimetic Preparation And Characterization Of The Novel Micro/Nano-bioactive Glasses For Pulp Repair

The pulp is easy to be damaged when it suffers from the decay or trauma, thus affectingthe health and function of the teeth. So saving the vital pulp or inducing pulp-dentineregeneration is the research hotspot in the field of endodontology. As a third-generationbiomaterial, bioactive glass (BG) has biocompatibility, bone conductivity and inductivity. BGis the ideal biomaterial for bone tissue regeneration. Given the similarity of bone and toothformation, BG could have the potential to be applied to dentin regeneration. However, theproblems for traditional BG are still unsolved, such as the severe agglomeration, irregularshape and uncontrolled size of BG particles, which would weaken their bioactivity andphysicochemical properties when used for tissue regeneration. Because of the uniquemicro/nano-structure, human natural tissues show the absolute advantages of biologicalfunction when compared with the traditional synthetic materials. Hence, based on theperspective of bionics, this study used sol-gel method combining template self-assemblytechnology to synthetize the novel micro/nano-bioactive glass (MNBG) with controlled shape,structure, size and composition, to study the forming mechanism of micro/nano-structure. Wealso studied physicochemical properties and apatite-forming ability of MNBG andinvestigated the effects of particle shape, size and composition on biocompatibility of MNBGwhen cultured with human dental pulp cells (HDPCs). The study also observed the effects ofbioactive glass on the odontogenic differentiation of dental pulp cells via transplantedcomplexes of BG with pulp tissues into the dorsum of immune-deficient mice. Main researchwork and conclusions are as follows:(1) We synthetized bioactive glass with different shapes from sphere to short rod and tolong rod by sol-gel method combining template self-assembly technology using CTAB astemplate agent. The shape and size of particles were controlled by adjusting theconcentrations of CTAB and ammonium hydroxide, respectively. LRBG showed the higherapatite-forming ability compared with SRBG and SBG. Biocompatibility of BG whencultured with HDPCs was depended on the concentrations of BG particles,200μg/mL wasnot conducive to cell proliferation while100μg/mL was suitable. When cultured HDPCswith BG at the concentration of100μg/mL, SBG showed the higher proliferation and ALP differentiation compared with SRBG and LRBG.(2) Monodispersed micro/nano-bioactive glass spheres (MBGS) with controllable sizeless than1μm were successfully fabricated by improved sol-gel method using dodecylamine(DDA) as a hydrolysis catalyst and structural formation template. The size of particles werecontrolled by adjusting the concentrations of DDA. The apatite-forming ability and ionrelease rate increased with MBGS size decreased. And when cultured HDPCs with MBGS atthe concentration of100μg/mL, MBGS with smaller size showed the higher proliferation andALP differentiation.(3) Based on the preparation technology of chapter three, we synthetized bioactive glassdoped Sr (BG-Sr) by using SrO replaced with CaO. The results showed that doping moderateSr, BG still exhibited regularly spherical morphology and favorable mono-dispersibility, andthe size, crystal structure and chemical constitution were not changed obviously. However,the apatite-forming ability decrease with the amount of Sr. The concentration of Sr had aneffect on the proliferation, ALP differentiation and mineralized nodule, Sr-BG with6mol%ofSr exhibited appropriate bioactivity with optimal cell proliferation, ALP activity andmineralized nodule, while Sr-BG with15mol%of Sr presents the inhibition.(4) Hollow mesoporous bioactive glass spheres (HMBGS) were successfully synthetizedby using CTAB as a template agent based the sol-gel method. The bioactive glass spherespresented a process from hollow to solid and the particle size decreased as the CTABconcentrations increased. HMBGS also possessed high specific surface area(444.003~609.512m2/g) and good apatite-forming ability.(5) In order to make further investigation the effects of bioactive glass on theodontogenic differentiation of dental pulp cells in vivo, we mixed the45S5BG,58S BG andmonodispersed micro-nano bioactive glass spheres (MBGS) with pulp tissues of nude mouse,respectively, and then transplanted complexes of BG with pulp tissues into the dorsum ofimmune-deficient mice for6weeks, finally observed via HE and Masson staining. The resultsdemonstrated that all the samples have biocompatibility without the presence of inflammatorycells, and can promote the secretion of extracellular matrix and dental pulp cellsmineralization. compared with45S5BG and58S BG, MBGS possessed stronger inducingcells mineralization ability.