Читать книгу Bone and Soft Tissue Augmentation in Implantology - Группа авторов - Страница 63

The treatment of vertical bone defects is more complicated than that of horizontal bone atrophy because they are mostly 3D defects related to severe infections, traumata, or hypodontia. Advanced atrophy or severe bone defects cause not only a loss of alveolar bone height but also an alteration in the relation of the jaws to the antagonist dentition and the occlusion. Therefore, the planning of alveolar ridge reconstruction requires consideration of the altered anatomy and the desired prosthetic result.

In the presence of insufficient bone height of < 10 mm, the following procedures are recommended:

In the esthetic region, especially the anterior tooth area, the bone level of the neighboring teeth must be taken into consideration when planning. In principle, it is possible to augment the bone vertically only until the level of the bone covering the neighboring roots. In the situation where the bone of the neighboring teeth is partly missing, a decision must be taken with the patient about whether to accept pink ceramic in the definitive restoration or whether to remove the neighboring teeth with the missing alveolar bone before the bone grafting procedure. In cases where the neighboring teeth present sufficient bone that covers their roots, a 3D vertical bone grafting procedure following the SBB technique can be planned, since the vertical defects are normally 3D defects (horizontal and vertical). This 3D bone reconstruction can mostly be performed – up to missing vertical bone for six teeth in the anterior tooth area – with intraoral harvested bone blocks from the mandibular retromolar area. Bone grafts from extraoral sites, e.g. from the iliac crest, are used in cases where there is insufficient bone volume for the grafting procedure at the intraoral donor sites.

In the rare case of vertical bony defects where the remaining bone still has a wide platform of > 8 mm, independent of the region, sandwich grafting or distraction osteogenesis can be considered as an alternative to 3D bone reconstruction. For this purpose, a residual bone height of at least 6 mm is necessary so that the distractor can be sufficiently anchored in the local bone and a segment can be mobilized. Distraction osteogenesis is also suitable for the entire mandible under the same conditions. The patient acceptance for such a treatment is limited due to the 2- to 3-month disturbance caused by distraction devices.

In cases of vertical bony defects in the posterior mandible, the elongation of the teeth in the adjacent jaw and the available space for prosthetic reconstruction should be checked on the basis of the clinical situation and articulated models (Fig 2-22a to f). If a sufficient maxillomandibular distance is available for an absolute reconstruction of the alveolar crest for the future prosthetic construction, a choice exists between a 3D bone augmentation, a sandwich grafting or a distraction osteogenesis to restore the necessary bone volume. If the maxillomandibular distance is restricted and does not allow for any correction, e.g. reducing the volume of the antagonist teeth, then the method of nerve lateralization in connection with the implant placement could be considered.

In cases of vertical bony defects in the posterior maxilla, the maxillomandibular distance should be checked, as in the mandible. If there is sufficient maxillomandibular distance for a vertical bone augmentation, then a 3D augmentation with autogenous bone blocks with or without sinus floor elevation is recommended (Fig 2-23a to d). This is important so that the later crowns obtain a normal dimension, which also has not only esthetic but also hygienic significance in this region. Implants inserted in cases of important vertical bone loss in the posterior maxilla without vertical bone augmentation are very difficult to restore and to clean (Fig 2-23e and f). After a short time, this will lead to peri-implantitis. If the maxillomandibular distance is limited, implant placement is performed in conjunction with or after a sinus floor elevation.

Fig 2-22a Bone atrophy in the bilateral free-end situation.

Fig 2-22b The scope of the vertical defect is clearly visible in the articulator.

Fig 2-22c Simulation of the necessary grafting volume in wax.

Fig 2-22d Wax-up of correct tooth length in the left mandible.

Fig 2-22e Panoramic radiograph documenting a bilateral vertical bone augmentation in the right and left posterior mandible. The right bone graft is very close to the antagonist elongated second molar.

Fig 2-22f Panoramic radiograph documenting the implant insertion after reducing the graft volume. An endodontic treatment was also performed on the antagonist elongated tooth after reducing its volume.

Fig 2-23a Schematic illustration of a class C vertical bone defect according to Chiapasco et al.¹⁸

Fig 2-23b Simultaneous implantation with sinus floor elevation in class C, with the consequence of an unfavorable crown–implant ratio.

Fig 2-23c Schematic illustration of vertical grafting in a class E defect to create a physiologic course for the alveolar ridge.

Fig 2-23d Schematic illustration of implants placed after vertical reconstruction with a balanced crown–implant ratio.

Fig 2-23e Incorrect implant insertion in the posterior left maxilla.

Fig 2-23f Panoramic radiograph documenting the extreme apical position of the implants.

Fig 2-24a Clinical situation before treatment: closed bite and severe periodontal disease.

Fig 2-24b After periodontal treatment involving the extraction of the hopeless teeth and a fixed temporary restoration, vertical bone grafting in different areas of the maxilla with bone blocks from the mandibular left retromolar area. The external oblique was so pronounced that only one intraoral donor site was sufficient for the entire maxillary reconstruction.

Fig 2-24c Control radiograph 7 years postoperatively with a stable peri-implant bone level.

Fig 2-24d Clinical situation 7 years postoperatively.