implants - international magazine of oral implantology

implantfailure.Basedonthe concept, progressive load- ing needs to be employed to allow the bone to form, re- model and mature to resist stress without detrimental bone loss by staging appli- cation of diet, occlusal con- tacts, prosthesis design and occlusal materials.36 Apple- tonetal.reportedadecrease in crestal bone loss in pro- gressively loaded implants, compared with implants without progressive load- ing, within a similar healing and loading period. In addi- tion, digital radiographs indicated an increase in bone density in the crestal 40% of the implant in the progressive loaded crowns.37 Greater crestal bone loss ob- servedatthefirstyearoffunctioncomparedwithfollowingyearscanbeexplained by a reduced occlusal overload or increased resistance to occlusal overload after the first year of function including a functional adaptation of the oral muscula- ture,wearoftheprosthesismaterial,and/oranincreaseinbonedensityafteracer- tain time period. _Peri-implantitis Peri-implantitisisoneofthetwomaincausativefactorsofimplantfailureinlater stages. A correlation between plaque accumulation and progressive bone loss around implants has been reported in experimental studies and clinical studies. Tonetti and Schmid reported that peri-implant mucositis is a reversible inflamma- tory lesion confined to peri-implant mucosal tissues without bone loss. Peri-im- plantitis however begins with bone loss around dental implants.18 Clinical features of peri-implantitis were described by Mombelli as including ra- diographic evidence of vertical destruction of the crestal bone, formation of a peri- implant pocket in association with radiographic bone loss, bleeding after gentle probing,possiblywithsuppuration,mucosalswelling,rednessandnopaintypically.38 In an experimental study evaluating the pattern of ligature-induced breakdown of peri-implant and periodontal tissues in beagle dogs, significantly greater tissue de- structionwasdemonstratedclinically,radiographically,andhisto-morphometrically atimplantareasthanattoothsites.Itwasalsofoundthatsignificantlyfewervascu- lar structures existed at implant sites compared with periodontal tissues. The difference in collagen fibre direction (parallel to the implant surface and perpendicular to tooth surface) and amount of vascular structure may explain thefasterpatternoftissuedestructioninperi-implanttissuesthanperiodontaltis- sues. Literature has shown that peri-implantitis is similar in nature to periodonti- tis in that the microbiota of peri-implantitis resemble the microbiota of periodon- titis; however, there has been no evidence that peri-implantitis induces crestal bone loss during healing and in the first year of function at a faster rate than fol- lowing years. Early crestal bone loss may result in an environment favourable for anaerobic bacterialgrowth,thuspossiblycontributingtomorebonedestructioninfollowing years.Inthemajorityofimplantshoweverthebonelossisdramaticallyreducedaf- ter the first year of prosthesis loading. Therefore, peri-implantitis as the main causative factor for early implant bone loss may not be justified. AD