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science & practice14 EAO Annual Scientific Congress 2015 · 24 September Crestal bone stability around dentalimplantsremainsoneofthe most important features of suc- cessfulimplanttreatment.Besides major clinical advantages for the patient, stable marginal bone pro- videstheclinicianwithpsycholog- ical comfort and satisfaction, be- causeofthepositivelong-termout- come (Fig. 1). Therefore, we all need to be aware of possible causes of loss of crestal bone sta- bility and exercise every method to prevent bone resorption. For almost one decade, plat- form switching has been consid- eredtobethemosteffectivewayto achieve this outcome. It is so effec- tivethatalmostallimplantcompa- nies have implemented platform switching as an essential feature ofimplantmanufacture.Ithasgen- erally be concluded that implant design is more important than the biology itself. However, recent clinicalresearchconductedbyour group has found that soft-tissue thickness is an important factor in preserving crestal bone stability around implants. It was deter- mined that if vertical soft-tissue thickness is 2 mm or less, there will be crestal bone resorption of 1.5 mm in extent during formation of a biological seal between the soft tissue and the implant, abutment or restoration surfaces (Fig. 2). Furthermore, it was clearly shown that even implants with platform switching could not maintain bone if at the time of im- plant placement vertical soft tis- sue was thin (Fig. 3). That returns us to the discussion of whether bi- ologyorimplantdesignismoreim- portant. Well, we need to under- stand that vertical soft-tissue thickness is a prerequisite of the biological width around implants. Biological width around implants startstoformatthetimeofhealing abutment connection and is com- plete after eight weeks. This bio- logical seal is the only barrier pro- tecting the osseointegrated im- plantfromthecontaminatedintra- oral environment and hence most important. Thus, there is a direct connection between the peri-im- plant mucosa of an edentulous alveolar ridge and peri-implant soft tissue. It seems that the soft-tissue thickness required to protect the underlying bone around implants is approximately 4 mm, which is longer than the biological width around teeth. There are two ways in which biological width around implants is formed: with crestal bone loss or without bone resorp- tion. Which one would you like your patient to have? Or which one would you like your mother to have?Thatisthequestionweallas cliniciansshouldanswersincerely. So if we diagnose thin vertical tissue at the time of implant place- ment, what should we do? There arenocurrentguidelinestofollow; however,weneedtodosomething, because crestal bone resorption will otherwise result. This is espe- cially important for short im- plants, which are increasingly be- ing used. Today, an implant of 8mm in length is no longer consid- ered short, and we have sufficient data to determine that implants of 6mm in length work as well as longer ones do in the posterior of both jaws. However, imagine the outcome if a 6mm implant is placed in the posterior mandible, where thin vertical soft tissue is frequently present. We would have approximately 2mm of bone resorption, due to biological width formation, leaving only two-thirds of the implant surface to become osseointegrated. Such a circum- stance poses a risk of implant fail- ure, considering the prosthetic su- perstructure and implant–crown ratio. Some implant manufactur- ers have launched implants of 4mm in length, making soft-tissue thicknessevenmoreimportantfor users of these products. So what should the approach be?Thereareseveraloptions,some of them already researched clini- callyandsomebasedonclinicalex- perience without any objective ev- idence. An initial thought may be to place the implant deeper sub- crestally(Fig.4).Firstly,theremust be adequate distance from the alveolar nerve to position the im- plant sub-crestally in a safe man- ner. It is advised that the implant stop at least 1 mm from the nerve. Extensive sub-crestal position- ing of the implant, of course, does notpreventcrestalboneloss,asthe microgap at the implant–abut- mentinterfacewillformaninflam- matory infiltrate, which will cause bone resorption anyway; however, it is likely that the implant will not have soft-tissue recession or rough surface exposure, which usually follow bone resorption. It is well known that the exposure of the rough implant surface enhances plaque accumulation and the de- velopment of peri-implantitis. In other words, the future of such an implant would only depend on the scrupulouscleaningabilitiesofthe patient, what is usually not the case. Another option might be recon- touringoftheboneduringbasicim- plantbedpreparation,especiallyif a narrow ridge is present. Careful reduction and smoothening of the narrow ridge will not only provide a flat bone surface and a suffi- ciently wide area of bone for im- plantpositioning,butwillincrease soft-tissuethicknessaswell(Fig.5). Whiletheconceptofboneremoval to preserve the bone might be ac- ceptable to some clinicians, there is no strong clinical evidence that this procedure increases soft-tis- sue thickness and reduces crestal bone remodelling. Consequently, we might think in another direction and consider a third option, vertical reconstruc- tion of the soft-tissue thickness, which in my opinion is the most logical approach. Increasing soft- tissue thickness vertically com- pensatesforthelackofverticaltis- sue. Already in a 2009 paper, we suggested that clinicians “con- sider the thickening of thin mu- cosa before implant placement”; therefore, this concept is not en- tirely new.1 The idea is to place some sort of autogenous, allo- geneic or xenogeneic material over the implant to increase soft- tissue thickness after healing. A connective tissue graft is con- sidered the gold standard for soft- tissue augmentation around im- plants. However, this technique has some serious disadvantages, such as donor site morbidity and thedifficultyoftheharvestingpro- cedure. Therefore, allogeneic sub- stitutes might be considered a vi- able option to replace autogenous grafts in vertical soft-tissue recon- struction. The use of an acellular dermal matrix is thus far the only approach backed by solid clinical research, including a controlled clinical prospective study.2 In this study, implants were placed in three groups of patients with (a) thin vertical tissue, (b) thick verti- cal tissue or (c) thin vertical tissue augmented with an acellular der- mal matrix material (AlloDerm, BioHorizons).Radiographicassess- mentshowedareductionofcrestal bone loss from 1.74mm in the thin- tissue group to 0.32mm in the aug- mented group. In addition, soft- tissue thickness increased by 2.33mm,from1.50mmto3.83mm, after augmentation with the allo- graft (Figs. 6a & b). This research provesthatthelackofverticalsoft- tissue thickness required for bio- logical width formation without crestal bone loss can be compen- sated for by the use of an acellular dermal matrix material at the time of implant placement. Inconclusion,itmustbeempha- sisedthatdiagnosisofthinvertical soft tissue is very important in im- plant treatment. Only by acknowl- edging that tissue thickness is an importantfactorcanwefollowpro- tocols that allow us to reconstruct vertical peri-implant tissue and re- duce crestal bone loss. Editorialnote:Alistofreferencesis available from the publisher. Vertical reconstruction of soft peri-implant tissues By Dr Tomas Linkevičius, Lithuania Fig. 1: Crestal bone stability around the implant and abutment (Tapered, BioHorizons). Fig.2:Thinverticalsofttissuemeasured at the crest (≤2mm). Fig. 3: Crestal bone loss around an im- plant with platform switching. Fig. 4: Sub-crestal placement of an im- plant (Tapered Plus, BioHorizons). Fig.5:Flatteningoftheridgefortheregu- lar matching connection implant (green) will increase soft-tissue thickness. The implant is placed supra-crestally to iso- late the microgap and thin polished col- lar. Figs. 6a & b: Original vertical soft-tissue thickness (a); soft-tissue thickness after augmentation with an acellular dermal matrix (b). 1 2 3 4 5 6a 6b Dr Tomas Linkevičius 12 34