| BACKGROUND:Based on the principle of osseointegration, implant dentistry hasmade tremendous progress in the pass 40 years. Today,implant-supported protheses are widely accepted as a reliable treatmentmodality for the rehabilitation of fully and partially edentulous patients.Prospective clinical studies have demonstrated over 90% of survivaland success rates after up to 10 years of follow-up.Recent years, the vast improvements in surgical technologies andprocedures of dental implants have been achieved, which makes theindications of dental implant much wider. The area which was thoughtimpossible previously can be implanted successfully through thecreation of improved bone quality and quantity with such procedures asmaxillary antroplasty and repositioning. Now, quality assurance hasbecome an important goal in clinical dental practice.However, there are still many problems. Complications may beginwhen implant is inserted into bone. Failure of implants may be caused by technological factor and related complications, however most of thefailure cases were caused by peri-implantitis associated withbiomechanical factors.Peri-implantitis refers to inflammation of tissues surrounding dentalimplants. It is one of the main causes of implant failure, due tosubsequent loss of supporting bone around implant with peri-implantitis.Inflammation in peri-implantitis is caused by excessive loading, poororal hygiene,pathogenic bacteria. Out-of-control bony defect mayinduce implant denture failure. In order to increase survival rate,prophylaxis and treatment of peri-implantitis become emphasis andnodus in clinical research area. To explore treatment method and skillof peri-implantitis, and to summarize and extend appropriates relatedclinical experience, there is a very long way to go.To ensure the long-term function of implant denture, it requires thetechnology to re-construct the bone defects in peri-implantitis.The ultimate goal of membrane barrier technologies is the restitutionof the supporting tissues that were lost as a consequence ofinflammatory disease or trauma. With the advent of membrane barriertechniques and materials, more predictable restoration of the functionof the bone is being achieved. Membrane barrier techniques are basedon the biologic behavior of different tissues during wound healing. Thegoal of membrane barrier procedures is to guide proliferation of thedifferent tissues during healing after therapy. Cells that have thecapability to form bone, cementum, and periodontal ligament mustoccupy the defect to stimulate regeneration of tissues. The progenitorcells reside in the periodontal ligament or alveolar bone or both, which remain around the bony defect. Placement of a physical barrier betweenthe gingival flap and the defect before flap repositioing and suturingprevents gingival epithelium and connective tissue from contacting thespace created by the barrier. It also facilitates repopulation of the defectby regenerative cells. Although most of the early studies wereconcerned with the treatment of periodontal defects, the principles ofmembrane barrier techniques are to facilitate augmentation of alveolarridge defects, to improve bone healing around dental implants, toinduce complete bone regeneration in peri-implantitis treatment.Past 10 years there are limited amounts of experimental reports in theworld adopting GBR technique to treat bony loss in peri-implantitis.Some clinical studies have shown that bone-reconstruction was gainedin some cases, the other didn't.OBJECTIVES:The objectives of this study are to evaluate the effects of treatmentwith GBR techniques for peri-implantitis bone defects in animal modeland in clinical cases. Ultimately, the investigation on the effects oftreatment with GBR techniques for peri-implantitis will establishscientific basis for clinical therapy of peri-implantitis bone defects, andto provide appropriate procedures for long-term success of implantdentures.METHODS:Part 1, Effects of GBR on experimental peri-implantitis bone defect.1.1 To establish peri-implantitis model in beagle dogs.Mandibular first, second and third premolar and first molar of 2beagle dogs were extracted, 3 CDIC pure titanium implants wete bilaterally inserted into the posterior mandible in each dog.1.2 To establish animal osseointegration implant model in beagle dogs.1.3 To observed the bone defectAfter healing-abutment connection, silk ligatures were placed aroundthe healing-abutments and then plaque was accumulated. Peri-implantbone defects was detected by direct measurement during operation.1.4 Re-osseointegration of peri-implanttitis bone defects.Ligatures and abutments were removed after 1 month and the bonedefects were randomly assigned to one of the following treatments:Control group: debridement alone.Experiment group 1: debridement plus BME-10X collagen membraneand Bio-Oss graft;Experiment group 2: debridement plus BME-10XAT collagenmembrane associated with osteoinduction active material (OAM).1.5 To obtain inferior maxilla sample with implants.The dogs were sacrificed after 6 months, the inferior maxilla sampleswere taken, Methylmethacrylate was used for infiltration andembedding. The cutting surface of specimen (bone and dental implant)was glued to glass slide with cyanoacrylate adhesive. The 150μmsection was obtained by Leica SP1600, then the thickness of thesections were reduced to 30μm by hand-grind.1.6 Evaluation by clinical parameters and histologyThe histology changes and osteoanagenesis were observed by lightmicroscope with different enlargement sizes, and analyzed by medicalimage analysis system.Part 2, Clinical effects of GBR on peri-implantitis defect. 1. The patients with serve peri-implantitis were selected. A total of 10dental implants with 2 different surface coatings (9 titaniumplasma-sprayed(TPS); and 1 hydroxyapatite(HA)with peri-implantitisof above 5mm vertical bone loss were enrolled. Superstructures andabutments were removed after 7 day treatment of antibiotics and thebony defect were treated with debridement plus GBR.2. Five dental implants (machine turned surface [MTS]) with activeretrograde peri-implantitis were also enrolled, Superstructures andabutments were removed after 2 day treatment of antibiotics and thebony defect were treated with debridement plus GBRRESULTS:Part 1, Effects of GBR on experiomental peri-implantitis bone defect.1. General state of healthTwo dogs both survived, the osseointegration was formedsuccessfully for all 12 implants. The newly formed bone tissue wasobserved around the implants during re-entry.2. Evaluation by clinical parametersThe bone contact levels at mesiai, distal, buccal and lingual sideswere measured. There was no statistics difference between each group(P＞0.05) before therapy. In all groups, the bone resorption levelsurrounding implants approached 40%. After treatment, the boneformation differed significantly between the different treatment groups.The bone formation in the animals treated with Bio-Oss or OAM wasbetter than control. These results indicted that Bio-Oss and OAM canpromote bone formation in peri-implantitis bone defects.3. Bone histomorphology examination There were significant differences between 3 groups on boneformation and bone contact level (P＜0.05). The groups usingdebridement plus absorbable membrane associated with Bio-Oss orOAM resulted in greater amount of regeneration than the group usingdebridement alone.Under the light microscope, there is abundant new bone formationaround implant shoulder in the experiment groups, Bio-Oss or BMP wassubstituted by newly formed woven bone and lamellar bone. Haversiansystem was formed with direct contact to the implant. The new boneformation in blank grounps is much less, the fibrous connective tissuebetween implant and bone can be observed.Part 2, Clinical effects of GBR on peri-implantitis bone defects.1. Complete bone regeneration had been found in bone defect zones ofall nine implants with TPS surface. Implants had excellent stability, but1 implant with HA surface had no regenerated bone.2. Five implants with MTS surface demonstrated considerable boneregeneration after treatment of GBR.CONCLUSIONS:1. Experimenttal peri-implantitis can be induced through silk ligaturesin submarginal position.2. The thickness of section (bone and dental implant) can be reduced to30μm by hand-grind. This method could provide good preservation ofmineralized and cellular area for the study of interface analysis ofdental implants.3. Inflammation induced peri-implant bone defect can be regenerated byGBR. 4. Peri-implant circumferential bone loss with TPS surface coating canbe regenerated by GBR technique. Further clinical evaluation ofperi-implant circumferential bone loss with HA surface coating isnecessary before final conclusions about the effect of GBR can bemade.5. Active retrograde peri-implantitis bone loss with MTS surface canregenerated by GBR technique.
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