Oral implant rehabilitation in atrophic jaws represents a common procedure nowadays. In those cases where immediate implant placement is not achievable due to the advanced vertical or horizontal bony deficiency, a regenerative procedure may be indicated. Depending upon the quantity, quality and location of the bony defect, the surgeon can choose one of the several techniques that have been described in literature, including guided bone regeneration, onlay and inlay bone grafting, distraction osteogenesis and ridge splitting. Among them, autologous bone grafting is considered the gold standard to treat vertical and horizontal bony defects, due to its biological properties that allow for osteogenic, osteoinductive and osteoconductive processes.
Autologous bone grafting is a consolidated procedure that has been employed in all those surgical fields which manage hard tissues.
Current concepts of jaws regeneration with autologous bone grafts promote local intraoral harvesting procedures against farther donor site (such as the iliac crest or the calvaria), which have demonstrated problematic donor site morbidities, as well as higher surgical invasiveness. Intraoral bone grafts can be harvested from the mandibular ramus, symphysis and tuberosity or all of them. They have the advantages to avoid cutaneous scars, to improve the cost/effective ratio – due to the possibility to perform the entire procedure under local anesthesia – and to provide grafts with a similar micro-architecture to that of the receiving site. However, some disadvantages need to be mentioned. A careful preoperative assessment and planning must be carried out to perform an accurate case selection: intraoral grafts provide only a limited amount of autologous bone, so that it might not be the best procedure when large regenerations are required. Moreover, one of the most advocated complications of this procedure is the risk for inferior alveolar and incisor nerve injury. It represents the major anatomical limitation to intraoral bone harvesting from the mandibular ramus and chin so that other techniques and used associated materials have been developed during the last years. Nevertheless, today’s the digital approach allow for a careful and utmost precise diagnosis and presurgical digital planning, so that adverse events related to technical errors and related morbidities could be minimized.
In this article we introduce a case of a posterior mandibular bidimensional defect treated with computer guided autologous bone regeneration and implant supported rehabilitation.
Fig.1
Initial OPT examination.
Fig.2
The initial clinical view of the case in a frontal vision shows several problems at the dental-restorative level with an important deep-bite. In the 3rd quadrant, a marked atrophy at the premolar and molar level is evident, which generates a negativity of the marginal boney crest, insufficient to receive a prosthetically guided implant treatment. In these cases, the strength for a correct surgical-prosthetic approach lies, preliminarily, in determining a reorganisation of the natural position of the jaw aimed at restoring the correct DVO. All this is categorically decisive for the purpose of quantifying the reconstruction space of the hard tissue to be regenerated.
Fig.3
Lateral view of the defect showing evident alteration of the normal occlusal relationships.
Fig.4
Incisal jig to deprogram the occlusion and establish a new OVD (occlusal vertical dimension) from which to start a wax-up to guide the reconstruction of the dental elements and the new occlusal plane.
Fig.5
Only after establishing these parameters will it be possible to quantify the interarch space and therefore correctly decide the extent of the bone augmentation, both in vertical and horizontal direction.
Fig.6
An occlusal vision of the site of the defect shows its extent and the quality of soft tissues where a small band of keratinized tissue is well represented. This last element is extremely important for the primary closure of the wound following reconstructive surgery. Another consideration is the depth of the fornix and the mobility of the free mucosa. After these evaluations, a targeted evaluation of the underlying hard tissues can be made to establish the size of the boney structure to be restored, the choice of method and the most suitable technique.
Fig.7
Then, a CBCT evaluates the extent of the defect, and the relationships with the nervous vessel bundle.
The choice of technique was oriented on an autologous bone block graft harvested from the homolateral mandibular branch. This was done for several reasons, first of all a single surgical site (donor site and receiving site); the possibility of obtaining a more than satisfactory bone quota for a 3D reconstruction and also the possibility of performing the sample, digitally, matching the DICOM files of the CBCT and IOS 3Shape with EXOCAD 1.6.11. This allows us to design a bone harvested stent, in total safety against the lower alveolar.
Fig.8
Surgical stent project to harvest bone block graft in safety from the mandibular ramus.
Fig.9
Osteotomy lines just performed with the aid of a piezosurgery instrument, following the indications of the surgical guide.
Fig.10
Bone graft just separated from the donor site by means of a lever.
Fig.11
This is how the donor site appears immediately after the harvest. It is possible to clearly distinguish the cortical bone from the medullary bone.
Fig.12
Cortico-cancellous bone block just harvested with its classic shape.
Fig.13
The harvested bone was first divided into two parts, after which the two portions were thinned using a scraper and fixed with osteosynthesis screws to delimit the extent of the reconstruction. The bone harvested with the scraper was placed as filler material inside the box.
Fig.14
Lateral view of the healing of the site 4 months after surgery.
Fig.15
Occlusal view of the healing of the site 4 months after surgery.
Fig.16
A new CBCT was performed together with a new intraoral scan of the healing site in order to plan the prosthetically guided placement of three implants in positions 3.5, 3.6, 3.7.
Fig.17
Surgical re-entry, immediately after the flap was elevated to access the regenerated area. Excellent healing and the osteosynthesis screws to be removed are clearly evident.
Fig.18
Using guided surgery, the three implants were placed at crestal level, and MUA abutments were simultaneously screwed onto them. Finally, a connective tissue graft was inserted along the entire length of the wound on the buccal side to improve the quality and thickness of the peri-implant tissues.
Fig.19
The case finalized six months after re-opening. Splinted monolithic zirconia crowns were screwed onto the implants. Single monolithic zirconia crowns were placed on elements 3.4, 2.4, 2.5, 2.6 and 2.7, and composite resin restorations on the anterior sectors.
Fig.20
Final OPT examination.
Fig.21
A final frontal view of the rehabilitation.
Conclusions
A multidisciplinary approach in the resolution of complex cases where the presence of severe atrophies are not the only aspect to be considered.
The need to create ideal conditions before formulating a correct implant diagnosis is a fundamental and mandatory aspect. The execution of a technique is easy to apply if the prerequisites are created. Therefore, in this case, the restoration of the natural mandibular position and the new DVO gave a different evaluative input in dimensional and positional terms in relation to the type of reconstruction required and the correct prosthetically guided positioning of the implants. From this stems the choice of technique, although questionable from the point of view of operational difficulties, but certainly codified if addressed with basic knowledge and with the appropriate clinical and instrumental devices. Finally, the management of these cases may require an economic commitment on the part of the patient for which it may be inaccessible to many of them. For this reason, the choice and knowledge of materials for regenerative and restoration can make the appearance less questionable while maintaining a more than acceptable aesthetic, biological, biomechanical and functional performance.
Bibliography
- Tonetti MS, Hämmerle, CH. Advances in bone augmentation to enable dental implant placement: Consensus Report of the Sixth European Workshop on Periodontology. J Clin Periodontol 2008;35:168-72.
- Elnayef B, Monje, A, Gargallo-Albiol, J, et al. Vertical Ridge Augmentation in the Atrophic Mandible: A Systematic Review and Meta-Analysis. Int J Oral Maxillofac Implants 2017;32:291-312.
- Dorosz N, Dominiak, M. Mandibular ridge reconstruction: A review of contemporary methods. Adv Clin Exp Med 2018;27:1159-68.
- Khan SN, Cammisa, FP, Jr., Sandhu, HS, et al. The biology of bone grafting. J Am Acad Orthop Surg 2005;13:77-86.
- Hernigou P. Bone transplantation and tissue engineering, part I. Mythology, miracles and fantasy: from Chimera to the Miracle of the Black Leg of Saints Cosmas and Damian and the cock of John Hunter. Int Orthop 2014;38:2631-8.
- Hernigou P. Bone transplantation and tissue engineering. Part II: bone graft and osteogenesis in the seventeenth, eighteenth and nineteenth centuries (Duhamel, Haller, Ollier and MacEwen). Int Orthop 2015;39:193-204.
- Chiapasco M, Zaniboni, M, Boisco, M. Augmentation procedures for the rehabilitation of deficient edentulous ridges with oral implants. Clin Oral Implants Res 2006;17 Suppl 2:136-59.
- Scheerlinck LM, Muradin, MS, van der Bilt, A, et al. Donor site complications in bone grafting: comparison of iliac crest, calvarial, and mandibular ramus bone. Int J Oral Maxillofac Implants 2013;28:222-7.
- Jensen SS, Terheyden, H. Bone augmentation procedures in localized defects in the alveolar ridge: clinical results with different bone grafts and bone-substitute materials. Int J Oral Maxillofac Implants 2009;24 Suppl:218-36.
- Reininger D, Cobo-Vázquez, C, Monteserín-Matesanz, M, et al. Complications in the use of the mandibular body, ramus and symphysis as donor sites in bone graft surgery. A systematic review. Med Oral Patol Oral Cir Bucal 2016;21:e241-9.
- Khoury F. Bone augmentation in oral implantology. London: Quintessence; 2006.
- De Stavola L, Fincato A, Bressan E, Gobbato L. Results of Computer-Guided Bone Block Harvesting from the Mandible: A Case Series. Int J Periodontics Restorative Dent. 2017 Jan/Feb;37(1):e111-e119.
- Fistarol F, De Stavola L, Fincato A, Bressan E. Mandibular Canal Position in Posterior Mandible: Anatomical Study and Surgical Considerations in Relation to Bone Harvesting Procedures. Int J Periodontics Restorative Dent. 2019 Nov/Dec;39(6):e211-e218.
- Sivolella S, Brunello G, Fincato A, De Stavola L. Computer-guided bone lid osteotomy with piezosurgery. Annali di Stomatologia. 2018;9(2):84-90.
