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(2009) Mark abstract SUMMARYThe loss of a single tooth in the esthetic area is for most patients a traumatic event.Nowadays, several treatment modalities are available to replace the failing tooth, such as aresin-bonded restoration or a conventional fixed partial denture. However, since theintroduction of implants several decades ago and the increasing body of evidence on thepredictability of this alternative, the popularity of the single-tooth implant has increasedtremendously. Originally, an initial period of 3 to 6 months of submerged healing wasadvocated, followed by a second surgical intervention to uncover the implant. Yet, thisprolonged treatment time may be considered an important reason to abandon the implantsupportedrestoration as the treatment of choice by some patients. In light of this argumentseveral clinicians became tempted to insert implants shortly to immediately after extractionand to restore likewise following implant placement (chapter 1).In chapter 2 a review on immediate replacement of a failing tooth in the premaxilla showedthat implant survival and even managing the hard tissue levels seem predictable. Survivalrates in this limited number of studies were at least comparable to the original protocol andpresented promising peri-implant bone loss not surpassing 1 mm. Yet, in the past decade thecriteria for success have changed in the interest of an esthetic treatment outcome and assuch, the influence of soft tissue changes became of critical importance. Although the papillalevels seemed predictable since these are hardly influenced by the surgical/restorativeprotocol, maintenance of the midfacial soft tissue levels seemed less predictable. Ascurrently available information on this topic is very scarce, the clinician should be reservedwhen considering immediate implant placement and provisionalization for replacing singlemaxillary teeth in the esthetic zone. At the very least, a number of guidelines andprerequisites need to be taken into consideration.The overall aim of this thesis was to elucidate these guidelines and prerequisites, and toevaluate the short-term esthetic outcome of immediate single-tooth implant restorations inthe anterior maxilla. Key questions in this respect relate to patient selection, implantselection and treatment protocol (chapter 3).In reference to proper patient selection, the gingival biotype is of particular interest for theclinician, as patients with a thin-scalloped gingival biotype present a higher risk for estheticcomplications. Based on this knowledge patients with a thin gingival biotype weresystematically excluded from the conducted studies on immediate tooth replacement. Theprevalence of the different gingival biotypes was investigated in chapter 4. Out of a largegroup of young adults 3 clusters with specific features could be identified using simplediagnostic methods. A clear thin gingiva was found in about one third of the sample inmainly female subjects with slender teeth, a narrow zone of keratinized tissue and a highlyscalloped gingival margin corresponding to the features of the previously introduced ‘thinscallopedbiotype’. A clear thick gingiva was found in about two thirds of the sample inmainly male subjects. About half of them showed quadratic teeth, a broad zone ofkeratinized tissue and a flat gingival margin corresponding to the features of the previouslyintroduced ‘thick-flat biotype’. The other half could not be classified as such. These subjectsSummary 152showed a clear thick gingiva with slender teeth, a narrow zone of keratinized tissue and ahigh gingival scallop.Another important issue relates to the implant characteristics, which was included in chapter5. Recently, implant companies have introduced two-piece implants with micro-texturedcollars in the interest of hard tissue preservation and/or soft tissue integration. However,these arguments may be premature. At present, it is unclear whether micro-roughenedimplant necks reduce crestal bone loss. A possible effect may be overruled by theestablishment of a biologic width or by other factors influencing crestal bone remodeling. Inaddition, the orientation and attachment of the collagen fibbers in the peri-implant mucosaare little different as the surface roughness varies at the level of the implant neck. Byconsequence, micro-roughened implant collars do not provide an obvious advantage. Whatis more, the long-term impact of these modified collars on the initiation and progression ofperi-implant pathology is currently unknown. In conclusion, the clinician should be reservedwhen using these modified implants. Consequently only screw-type tapered implants with amicro-roughened body and machined collar were adopted in our studies.In our one-year prospective clinical study (chapter 6) all patients underwent the samestrategy; that is mucoperiosteal flap elevation, immediate implant placement, insertion of agrafting material between the implant and the socket wall and the connection of a screwretainedprovisional restoration. The objective of the study was to assess implant survival,hard and soft tissue response and esthetic outcome. Short-term results on implant survivaland hard tissue alterations were at least comparable to the outcome of the conventionalprocedure. Papilla loss and midfacial soft tissue shrinkage were limited to approximally 0.5mm after one year of observation. Based on these preliminary promising results theproposed treatment protocol was considered a viable solution for well-selected cases.However, as hard and soft tissue alterations are a continuous event further long-termevaluation is required.In chapter 7, the influence of the restorative procedure on the esthetic treatment outcomeof the immediate single tooth implant in the anterior maxilla was assessed. Whether theimplant was immediately restored or not had no influence on the osseointegration or boneremodeling process. However, it had a significant impact on the soft tissues surrounding theimplant. If the implant was not immediately provisionalized, papillae were lost and took upto one year to attain the same height as when the implant was immediately restored. Evenmore important for esthetics was the additional loss of midfacial soft tissue by 0.75 mm onaverage, which showed a permanent character during the study period. By consequence, ifthe condition of the selected case permits it, immediate provisionalization should be advisedto minimize midfacial soft tissue shrinkage.Chapter 8 is attributed to the suprastucture, and gives a detailed description of fourrestorative key elements essential to obtain an optimal esthetic outcome. A first one is toinstantly provisionalize the immediate single-tooth implant in light of optimal soft tissuepreservation. Second, the provisional restoration should meet a number of morphologicalprerequisites. A third restorative factor includes the accurate replication of the soft tissuearchitecture for the permanent restoration in order to avoid subsequent soft tissue changes.Summary 153And finally a fourth factor decisive for success relates to the choice of the abutmentmaterial.This thesis showed that the immediate replacement of a failing tooth with an implant andscrew-retained restoration is a viable treatment concept. It is an appealing strategy for aswell the patient as the clinician. However, careful patient selection, treatment planning andexperienced clinicians seem of critical importance to obtain optimal esthetics. Futureresearch should consider long-term prospective and controlled clinical studies in order todocument the overall outcome of this treatment strategy.

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Autor: Tim De Rouck



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