The Effect Of SEHi On Promoting Bone Preservation In Extraction Sockets In SD Rat

Objective:In clinical dentistry,the alveolar bone loss occurs in an irreversible and progressive way after tooth extraction due to dental caries,periodontal disease or trauma.It takes three months or longer time for bone remodeling within tooth extraction socket Soft and hard tissue conditions in extraction area directly affect the dentures’ function and aesthetics.Especially in the process of implantation,the gingival biotype and adequate of bone height,width and bone mineral density are essential for denture.Currently bone graft surgery,biomedical materials grafting,maxillary sinus elevation,guided tissue regeneration,growth factors and tissue engineering techniques are common used for bone augmentation,which greatly increases the repair difficulty and time,the burden and infection risk of in patients.It is urgent for a conservative and efficacious therapy for long-term alveolar bone preservation.Recently,the alveolar bone regeneration has been the hot research in oral field.Nowadays researchers are looking for new methods to find out a new agent with better physiological feature which can preserve or improve postextraction alveolar bone dimensions.Recently it has been found that the epoxyeicosatrienoic acids(EETs)synthesized from arachidonic acid can regulate pain,inflammation,angiogenesis,and tissue regeneration.But EETs is hydrolyzed by soluble epoxide hydrolase(sEH)in short time.The soluble epoxide hydrolase inhibitor(sEHi)can inhibit hydrolysis of EETs to increase EETs concentration in vivo indirectly.The current study aimed to study the effect of sEHi on promoting bone formation in extraction sockets in SD rat for offering a new therapeutic tool to preserve bone loss after tooth extraction.Materials and Methods:The female SD rats(n=20)were randomly divided into four groups(n=5/group).The maxillary and mandibular first molars were extracted respectively,then gelatin sponge with sEHi was put into right extraction socket and gelatin sponge with PBS was put into left extraction socket.The 10μl sEHi(20 μM)was injected submucously every three days in the right side of tooth extraction for 3,4,5 weeks from 1 week after extraction.The same volume of PBS was injected in another side.Rats were sacrificed on 4th week and 5th week after extraction.The maxillary and mandibular bone specimens were collected and fixed in 4%paraformaldehyde for 48 hrs.Cone Beam Computed Tomagraphy(CBCT)analysis were performed.The specimens were decalcified,dehydrated and embedded in paraffin for slices for HE staining.Results:1.Gross view:The soft tissues began to heal at 2 weeks post-extraction.No significant difference was observed between the experimental side and the control side.Three weeks post-extraction,the experimental side mucosa healed primarily with smooth and resilient appearance.The control side mucosa remained swelling with food in extraction.Four weeks post-extraction,the experimental side mucosa healed with normal gingiva.The control side mucosa did not heal.The mucosa of both sides healed completely and appeared same on 5 weeks post-extraction.2.HE staining:Four weeks after extraction,the trabecular was arranged regularly,bone mineral density was as normal as usual.Alveolar ridge crest height was same with the second molar’s cemento-enamel junction.The bone formation was not worse in control side than in experimental side with bone resorption and inflammatory granulation tissue.3.CBCT results:The trabecular bone structure in experimental side was more compact than that in control side.4 weeks after extraction,the height of alveolar crest changed little without notable bone resorption.The alveolar bone loss in the control side was clearly observed.There were statistical significance in BV/TV,BS/TV,Tb.Th and Tb.N in experimental side compared with control side.Conclusion:1.The sEHi promote soft tissue healing in extraction area.2.The sEHi can reduce alveolar bone resorption and promote bone regeneration in extraction socket in SD rats.3.The sEHi can promote local microcirculation by raising EETs via inhibiting sEH,which has potential for extraction site preservation and bone regeneration.