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Dental Tribune Nordic Edition | 3/201512 TRENDS&APPLICATIONS Crestal bone stability around den- tal implants remains one of the most important features of suc- cessful implant treatment. Besides major clinical advantages for the patient, stable marginal bone pro- vides the clinician with psycholog- 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 stability and exercise every method to prevent bone resorption. Foralmostonedecade,platform switching has been considered to be the most effective way to achieve this outcome. It is so ef- fective that almost all implant companies have implemented platform switching as an essential feature of implant manufacture. It has generally be concluded that implant design is more important than the biology itself. However, recentclinicalresearchconducted by our group has found that soft- tissue thickness is an important factor in preserving crestal bone stability around implants. It was determined that if vertical soft- tissue thickness is 2 mm or less, there will be crestal bone resorp- tion of 1.5 mm in extent during formation of a biological seal be- tween the soft tissue and the im- plant, 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 implant placement vertical soft tissuewasthin(Fig.3).Thatreturns us to the discussion of whether biology or implant design is more important. Well, we need to un- derstand that vertical soft-tissue thickness is a prerequisite of the biological width around implants. Biological width around implants starts to form at the time of heal- ing abutment connection and is complete after eight weeks. This biological seal is the only barrier protecting the osseointegrated implant from the contaminated intra-oralenvironmentandhence most important. Thus, there is a direct connection between the peri-implant mucosa of an eden- tulous alveolar ridge and peri- implant soft tissue. It seems that the soft-tissue thickness required to protect the underlyingbonearoundimplants 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? That is the question we all as clinicians should answer sincerely. So if we diagnose thin vertical tissueatthetimeofimplantplace- ment, what should we do? There are no current guidelines to fol- low; however,we need to do some- thing, because crestal bone re- sorption will otherwise result. This is especially important for short implants, which are increas- ingly being used. Today, an im- plant of 8 mm in length is no longer considered short, and we have sufficient data to determine that implants of 6 mm in length work as well as longer ones do in the posterior of both jaws. How- ever, imagine the outcome if a 6 mm implant is placed in the posterior mandible, where thin vertical soft tissue is frequently present. We would have approxi- mately 2 mm of bone resorption, duetobiologicalwidthformation, leaving only two-thirds of the implant surface to become osseo- integrated. Such a circumstance poses a risk of implant failure, considering the prosthetic super- structure and implant–crown ra- tio. Some implant manufacturers have launched implants of 4 mm in length, making soft-tissue thickness even more important for users of these products. Sowhatshouldtheapproachbe? There are several options, some of them already researched clinically and some based on clinical expe- rience without any objective evi- dence. An initial thought may be to place the implant deeper sub- crestally (Fig. 4). Firstly, there must beadequatedistancefromthealve- olar nerve to position the implant sub-crestally in a safe manner. 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 not prevent crestal bone loss, as the microgap at the implant– abutment interface will form an inflammatory infiltrate, which will cause bone resorption any- way; however, it is likely that the implant will not have soft-tissue recession or rough surface expo- sure, which usually follow bone resorption. It is well known that theexposureoftheroughimplant surface enhances plaque accu- mulation and the development of peri-implantitis. In other words, the future of such an implant would only depend on the scrupu- louscleaningabilitiesofthepatient, what is usually not the case. Another option might be recon- touring of the bone during basic implant bed preparation, espe- cially if a narrow ridge is present. Careful reduction and smoothen- ing of the narrow ridge will not only provide a flat bone surface and a sufficiently wide area of bone for implant positioning, but will increase soft-tissue thickness aswell(Fig.5).Whiletheconceptof boneremovaltopreservethebone might be acceptable to some cli- nicians, there is no strong clinical evidence that this procedure in- creases soft-tissue thickness and reduces crestal bone remodelling. Consequently, we might think in another direction and consider athirdoption,verticalreconstruc- tion of the soft-tissue thickness, which in my opinion is the most logical approach. Increasing soft- tissue thickness vertically com- pensates for the lack of vertical tissue. Already in a 2009 paper, we suggested that clinicians “consider the thickening of thin mucosa 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 considered the gold standard for soft-tissue augmentation around implants. However, this technique has some serious disadvantages, such as donor site morbidity and the difficulty of the harvesting procedure. Therefore, allogeneic substitutes might be considered a viable option to replace autoge- nous grafts in vertical soft-tissue reconstruction. The use of an acel- lular dermal matrix is thus far the only approach backed by solid clinical research, including a con- trolled clinical prospective study.2 In this study, implants were placed in three groups of patients with (a) thinverticaltissue,(b)thickvertical tissueor(c)thinverticaltissueaug- mented with an acellular dermal matrix material (AlloDerm, Bio- Horizons). Radiographic assess- mentshowedareductionofcrestal bone loss from 1.74 mm in the thin-tissue group to 0.32 mm in the augmented group. In addition, soft-tissue thickness increased by 2.33 mm,from1.50 mmto3.83 mm, after augmentation with the allo- graft (Figs. 6a & b). This research proves that the lack of vertical soft- tissue thickness required for bio- logical width formation without crestal bone loss can be compen- sated for by the use of an acellular dermalmatrixmaterialatthetime of implant placement. Inconclusion,itmustbeempha- sised that diagnosis of thin vertical 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 reduce crestal bone loss. Editorialnote:Alistofreferencesisavail- able from the publisher. Dr Tomas Linke- viçiusisanAsso- ciate Professor at the Institute of Odontology at Vilnius Uni- versity in Lithu- ania. He can be contacted at linktomo@ gmail.com. Fig.1:Crestalbonestabilityaroundtheimplantandabutment(Tapered,BioHorizons).—Fig.2:Thinverticalsofttissuemeasured at the crest (≤2mm).—Fig. 3: Crestal bone loss around an implant with platform switching.—Fig. 4: Sub-crestal placement of an implant (Tapered Plus, BioHorizons).—Fig. 5: Flattening of the ridge for the regular matching connection implant (green) will increase soft-tissue thickness. The implant is placed supra-crestally to isolate the microgap and thin polished collar.— Figs.6a&b:Originalverticalsoft-tissuethickness(a);soft-tissuethicknessafteraugmentationwithanacellulardermalmatrix(b). 1 Vertical reconstruction of soft peri-implant tissues By DrTomas Linkevičius,Lithuania 2 3 4 5 6a 6b DTNE0315_12_Linkevicius 02.11.15 11:05 Seite 1 23 45 DTNE0315_12_Linkevicius 02.11.1511:05 Seite 1