Long-Term Stability of Contour Augmentation in the Esthetic Zone: Histologic and Histomorphometric Evaluation of 12 Human Biopsies 14 to 80 Months After Augmentation
- Autores: Simon S. Jensen, Dieter Bosshardt, Reinhard Gruber, Daniel Buser
- Localización: Journal of periodontology, ISSN 0022-3492, Vol. 85, Nº. 11, 2014, págs. 1549-1556
- Idioma: inglés
- Enlaces
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Resumen
Background: Contour augmentation around early-placed implants (Type 2 placement) using autogenous bone chips combined with deproteinized bovine bone mineral (DBBM) and a collagen barrier membrane has been documented to predictably provide esthetically satisfactory clinical outcomes. In addition, recent data from cone beam computed tomography studies have shown the augmented volume to be stable long-term. However, no human histologic data are available to document the tissue reactions to this bone augmentation procedure.
Methods: Over an 8-year period, 12 biopsies were harvested 14 to 80 months after implant placement with simultaneous contour augmentation in 10 patients. The biopsies were subjected to histologic and histomorphometric analysis.
Results: The biopsies consisted of 32.0% ± 9.6% DBBM particles and 40.6% ± 14.6% mature bone. 70.3% ± 14.5% of the DBBM particle surfaces were covered with bone. On the remaining surface, multinucleated giant cells with varying intensity of tartrate-resistant acid phosphatase staining were regularly present. No signs of inflammation were visible, and no tendency toward a decreasing volume fraction of DBBM over time was observed.
Conclusions: The present study confirms previous findings that osseointegrated DBBM particles do not tend to undergo substitution over time. This low substitution rate may be the reason behind the clinically and radiographically documented long-term stability of contour augmentation using a combination of autogenous bone chips, DBBM particles, and a collagen membrane.
Implant treatment in the esthetic zone is, in general, considered advanced or complex in the straightforward, advanced, complex (SAC) classification.1 Even small deviations from the ideal three-dimensional implant position may lead to significantly compromised esthetic outcomes.2 A key issue in predictably attaining good esthetic results is to preserve or to regain a symmetric level of the mucosal margin at the implant reconstruction and the contralateral tooth.3 An intact facial bone wall is a prerequisite to reach this goal.4 However, the facial bone wall in the anterior maxilla is frequently thin or non-existent,5,6 especially in cases where teeth are lost due to luxation injuries or periodontal or endodontic lesions.
Experimental and clinical studies document that the bundle bone (the part of the alveolar bone nourished by the periodontal ligament) will resorb within 8 weeks after tooth extraction.7,8 In case of a thin facial bone wall (<1 mm), a median vertical bone loss of 7.5 mm has been observed in a recent cone beam computed tomography (CBCT) study in the anterior maxillae of 39 patients.9 Therefore, resorption of the bundle bone requires contour augmentation with implant placement to avoid an esthetically compromised result on the facial aspect of the implant.4 Immediate implant placement (Type 1 placement)10 has been recommended to prevent alveolar bone resorption.11 However, as a tooth-related anatomic structure, the bundle bone will disappear whether an implant is placed or not12 and whether a flap is raised or not.13 Immediate implant placement may be combined with a simultaneous bone augmentation procedure to compensate for the physiologic bone resorption. However, if bone augmentation is performed during a flapless procedure, it can be performed only within the confines of the previous extraction socket and thus cannot compensate for the facial bone resorption. If a flap is raised and a bone augmentation procedure is performed on the facial aspect, the flap needs to be coronally advanced to ensure undisturbed primary wound healing. In consequence, a displacement of the mucogingival junction has to be expected, compromising the esthetic outcome.14 Therefore, it has been recommended to postpone implant placement until complete soft tissue healing has taken place, after 6 to 8 weeks,15 referred to as early implant placement or Type 2 placement.10 When the implant is placed, a simultaneous contour augmentation of the facial bone is performed, and undisturbed primary wound healing with minimal advancement of the flap is obtained.15 This contour augmentation technique uses a combination of locally harvested autogenous bone chips, a superficial layer of deproteinized bovine bone mineral (DBBM), and coverage by a non-cross-linked collagen membrane. This surgical technique has been reported to bear little risk of recession of the facial mucosa and to sustain long-term stability of the augmented volume as documented clinically as well as radiographically with CBCT16-19 compared with Type 1 placement.4 DBBM has been documented to undergo minimal long-term resorption during bone remodeling in experimental bone defects20 as well as in humans when used for sinus floor elevation.21 To the knowledge of the authors, no histologic data have been reported on the stability of DBBM used for contour augmentation in humans. Therefore, the aim of the present study is to analyze the long-term stability of contour augmentation based on human biopsies harvested from the esthetic zone.
