Research On The Expression Of Collagen I And Cathepsin D In The Process Of Implant-bone Interface Healing Remodeling Influenced By Submerged And Nonsubmerged Implants

BackgroundWith the development of the time and society, that more and more people require toimprove the quality of life and pay more attention to oral problems, makes the implantdenture become the main approach for the treatment of the dentition defect or edentulousjaws. A direct structural and functional connection between implants and bone tissues,osseointegration, is an important indicator assessing the success of implants.Clinically,the non-submerged implants in the clinical application are gradually increasedto reduce the operation frequency and the treatment time. However, conventionalsubmerged implant is the best choice for the patients with poor initial stability afterimplanting and poor quality of alveolar bone. As implants are implanted into jaw,osseointegration and dynamic remodeling of bone tissues begins until ultimate balanceoccurs, which is regulated by related factors from autocrine and paracrine in bonemicroenvironment.Although It was reported that the expression of collagen I and Cathepsin D in thebone-implant interface was higher than any other place, the exact mechanism remainsunknown. Hence, the present study was to investigate the dynamic change and themolecular mechanism of the remodeling process of collagen I and Cathepsin D in theimplant-bone interface during healing period by comparing the submerged andnon-submerged implant directly. ObjectiveThe aim of this study was to discuss the effects and mechanism of the remodelingprocess of collagen I and Cathepsin D in the implant-bone interface during healing periodof submerged and non-submerged implant.Materials and Methods1. Preparation of titanium implantsPure-titanium-made screw-shaped implant with10mm in Length and3.75mm indiameter, abutment with4mm in height, central screw connecting implant with abutmentwere used in this study.2. Experimental animalsEight healthy male18-20-months old mongrel dogs, weighing between13-15kgwere used in this study.3. Tooth extractionDogs were general anaesthetized with3%sodium pentobarbital via intramuscularinjection of1ml/kg. And then the crowns were slit with emery sheet. After the fourthpremolars and first molar in mandibular were extracted using elevators and forceps fromthe socket as atraumatically as possible, tooth sockets were scraped and wounds weresutured.4. Implant placement3months after extraction, each dog was implanted6implants into its mandibular:3submerged implants were implanted into the left part and3non-submerged implants wereimplanted into the right. In summary,48implants were implanted into8dogs(24submerged implants and24non-submerged implants).5. Preparation of the tissue specimens2dogs were sacrificed in each period (1week,2weeks,1month and3months)after implanting respectively. After the bone segments wrapping implants were taken out,they were slit out at the position that is10mm outside the implants. And then thespecimens were performed decalcification with100g/L EDTA for3months, dehydrationusing ethyl alcohol with concentration gradient, embedding with petroleum wax, Buccolingual slitting with4μm in thickness, adhesion onto slides with APES coating andpreparation for Immunohistochemistry.6. Experimental MethodsAvidin-Biotin peroxidase comlexs (ABC) immunohistochemistry method wasperformed for experiment.7. Control groupNegative control: Blocking serum (10%normal goat serum) was used to replaceprimary antibody.8. Image and statistical analysisHPIAS-1000color graphic analyzer (Olympus, BX40) was used for image analysisand paired t test was used for statistical analysis.Results1.The collagen I and Cathepsin D in the implant-bone interface in submerged and non-submerged experimental groups were significantly higher than that in control groups.Meanwhile the experimental groups had regulatory rules.2. The grey level of collagen I which was91.25±2.48in the implant-interface insubmerged experimental groups increased in1week,and reached peak at112.71±0.57after1month.Then it dropped to81.29±0.81and was not significantly different fromthe normal level after3month.3. The grey level of collagen I which was90.72±1.82in the implant-interface innon-submerged experimental groups increased in1week,and reached peak at113.98±0.51after1month.Then it dropped to81.04±0.52and was not significantlydifferent from the normal level in3month.4.The grey level of Cathepsin D which was84.38±1.05in the implant-interface insubmerged experimental groups increased in1week,and reached peak at102.53±1.03after2weeks.Then it dropped down to75.21±0.66and was not significantlydifferent from the normal level after3month.5.The grey level of Cathepsin D which was86.81±0.52in the implant-interface innon-submerged experimental groups increased in1week,and reached peak at 114.49±2.28after2weeks.Then it dropped down to75.84±1.83and was not significantlydifferent from the normal level in3month.6.No significant difference were found in the expression of collagen I and Cathepsin Dbetween the submerged and non-submerged experimental groups at each time point inthis study.ConclusionThe expression of collagen I and Cathepsin D in the implant-bone interface wasClearly positive in both the submerged and non-submerged implants during healingperiod. Meanwhile, the expression of collagen I and Cathepsin Dwh.ich showed an effecton the remodeling of the interface.changed according to the healing period. As theeffect of the remodeling of the interface went on, no significant differences were foundbetween the submerged and non-submerged implant groups.