Study On The Effect Of Laser Treatment Of Peri-implantitis On Osteanagenesis

[Background]The unmodified implant surface shows slower progression and higher bone level,while the inflammatory cell infiltration area in the connective tissue around modified implant surface is more extensive [1,2].Therefore,how to completely remove the plaque biofilm on modified implant surface and rebuild the biocompatibility of implant surface has become a hot research topic for scholars at home and abroad.Now there are a variety of mechanical cleaning methods that can assist surgical or non-surgical treatment,such as curette,titanium brush,ultrasonic tip,air-powder abrasive,etc.However,some studies have suggested that present mechanical cleaning methods are quite ineffective for debridement of the infected implant with rough surface[3].Some researchers believed that compared with mechanical cleaning methods,laser could significantly reduce the level of lipopolysaccharide on the implant surface,reduce the depth of peri-implant exploration and repair bone defects,which might bring new hope for the treatment of peri-implant inflammation[4,5].However,there still had some scholars believed that the effect of laser treatment for peri-implantitis is limited [6].Why there are so many differences in theevaluation of the effect of laser therapy? By comparing different literatures,we found that the laser parameters,laser types and implant surface used by different researchers were different.Whether it has different effects and on the surface and affects the effect of laser treatment of peri-implantitis still needs to be studied.[Objective]The reason for the difference in the efficacy of laser therapy for peri-implantitis remains to be clarified.The purpose of this study is to explore whether there are differences in decontamination effect and surface morphology change degree of different power and different kinds of laser on different surfaces.To further determine the surface changes caused by the ultra-high power laser,and finally determine which degree of change will affect the biocompatibility of the implant surface.This will provide evidence for the clinical use of standard laser therapy for peri-implantitis.[Methods]Firstly,the effects of Nd: YAG and Er: YAG laser with different power on different implant surface were compared.The surface most prone to damage was selected——micro-arc oxidation surfaces.Titanium discs of micro-arc oxidation surfaces were prepared and treated with laser power known to cause surface damage.Scanning electron microscopy(SEM)and energy dispersive spectrum analysis(EDS)were used to analyze the effects of different degrees of damage on surface elements and biocompatibility.Finally,effects of laser treatment for peri-implantitis was evaluated under optimal treatment conditions1.Implants with different surfaces removed due to peri-implantitis were collected from clinical practice.The implant surface was observed by SEM after treatment with Nd: YAG laser at A(2W),B(3W)and C(4W)with the same other parameters(non-contact mode,water 12,air 7,60 s).In order to further clarify whether the different effects of laser on the surface were related to the type of laser,we chose Er:YAG laser,which was with completely different action principle from Nd :YAG.Surface morphology changes were observed by SEM after treating with Er:YAG laser at A(0.6W,20 m J),B(1.2W,40 m J)and C(1.8W,60 m J).2.Titanium discs of micro-arc oxidation surfaces treated with 1.8W,60 m J Er:YAG laser was used as the experimental group,and titanium discs of micro-arc oxidation surfaces treated without laser was used as the control group.Surface morphology changes and surface element changes before and after laser treatment were compared by SEM and EDS,respectively.Rat bone marrow mesenchymal stem cells(BMSCs)were adhered to the two groups of titanium discs.The number and morphology of cells adhered to the surface were observed by SEM and confocal laser microscope.3.The mandibular anterior teeth of New Zealand rabbits were implanted with implants.Two months later,when implants achieved osseointegration,they were divided into blank control group and laser group.In both groups,the buccal 8mm bone wall was completely chipped to establish peri-implantitis model.One month later,clinical examination and inflammatory factor expression test verified the modeling success,and the blank control group received no treatment.The buccal side of the laser group received erbium-neodymium dual-wavelength laser treatment,and the lingual side of the laser group received no treatment as its own control.After 2 months,the samples were collected and the bone regeneration and re-bonding around the implant were observed by Micro CT quantitative analysis combined with hard tissue section.[Results]1.Sandblasted acid etching surface(SLA? non-hydrophilic surface and INICELL? surface)could be well decontaminated without causing surface damage under 3-4W Nd: YAG laser treatment;Oxidation surface(Tiunite? surface and micro-arc oxidation surface)had poor decontamination effect at 2W,while the decontamination effect was similar at 3W and 4W,but surface damage was caused at 4W.Under the irradiation of 0.6-1.8W Er:YAG laser,the surface morphology of sandblasting and acid-etching implants did not change,while oxidized implants surface was always damaged,and the severity of damage was positively correlated with the laser power.2.From the perspective of microscopic morphology,the influence of high power laser on oxidized surface had two forms--surface cracking and surface stripping.In the surface stripping zone,EDS analysis showed that elements O,C and P decreased,while elements Ti and N increased,with significant statistical differences(P < 0.01).However,the surface elements in the cracked area showed no significant change compared with the control group which didn’t irradiated by laser,and the difference was not statistically significant.In addition,surface exfoliation affected the adhesion of BMSCS,while surface cracking did not.3.Micro-CT reconstruction results showed that the buccal bone wall was missing in the untreated blank control group,while the buccal bone wall was regenerated in the laser treatment group,and the bone volume fraction of the laser treatment group was higher,the difference was statistically significant(P < 0.01).However,the bone volume fraction of the laser treatment side was lower than that of the control side,and the difference was statistically significant(P < 0.05).Histological observations showed that bone regeneration could occur after laser treatment for periimplantitis,but the bone did not adhere closely to the implant surface.[Conclusion]Different laser power and different laser types have different changes on different implant surfaces.Whether effects of laser treatment for peri-implantitis were affected depended on the degree of surface change.Surface stripping of implants changed the proportion of elements and the biocompatibility,while surface cracking didn’t.In the absence of the above interference,bone regeneration could occur after laser treatment of periimplantitis,but re-osseointegration was poor.