Predictable 3D Bone Reconstruction and Implant Restoration with Full Digital Workflow in Aesthetic Zone

Introduction

Implant restorations have become the preferred choice of treatment for restoring a single or multiple teeth as compared to fixed partial dentures [1]. Loss of teeth due to trauma or pathology is accompanied by significant bone loss within the first three years and can be aggravated in presence of pre-existing endodontic or periodontal infection. Bone resorption is a biological phenomenon and cannot be prevented by the immediate implant placement [2, 3] alone. These clinical situations require additional bone augmentation to create bone volume to be able to place dental implants in an ideal position for an esthetic outcome. The most described techniques in the dental literature are: Guided Bone Regeneration (GBR), Distraction osteogenesis, Ridge splitting and inter-positional inlay grafting technique [4, 5, 6]. GBR which is a commonly advised procedure, entails the use of a barrier membrane to isolate bone defects and thus allows bone regeneration without interference from surrounding tissues. However, the uncertain resorption rate of collagen membrane often leads to a compromised clinical result [7, 8, 9, 10]. Khoury [11] in 2007 advocated a technique for grafting the alveolar ridge using thin cortical plates harvested from the ramus. Although this method has shown great success, the technique has disadvantages due to the need for a second surgical site, donor site morbidity, and being technique sensitive [11, 12, 13, 14, 15]. In the present case report a failing maxillary central incisor, with endodontic pathology, is rehabilitated with GBR- (a combination of the autogenous bone plate with Xeno bone particles & barrier membrane), followed by a full digital implant restoration workflow.

Case Presentation

A 30-year-old young male presented with pain and mobility in a root canal treated maxillary left central incisor. Patient was unhappy with the re-cession of the anterior gingiva and presented a concern about it and wanted to explore the possibilities of fixed restoration using a dental implant. His medical history revealed no known drug allergies nor any medical health conditions. His expectations were reasonable, social history indicated that he was a non-smoker. Esthetic risk analysis revealed overall high- risk profile [16]. CBCT scan exhibited periapical pathology with inadequate bone availability for implant placement in the desired position (Figure 1). These findings suggested poor prognosis of the tooth and extraction was advised. Rehabilitation with implant supported prosthesis was agreed upon. Pre-implant surgery to augment the area with ramus cortical bone plate in combination with Xeno- bone particles and membrane was planned as phase 1of treatment. Tooth supported bonded provisional restoration was planned during this phase [15, 16, 17]. After 4-6 months of healing period guided implant placement and immediate CAD-CAM provisional was planned [18, 19, 20].

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Preoperative CBCT of the mandible revealed inferior alveolar nerve canal at 7-10 mm from the buccal cortex indicating safe site for harvesting a bone plate from ramus. The surgical procedure was carried out under local anaesthesia (lignocaine with Adrenaline1:80,000) and antibiotic cover (amoxicillin plus clavulanic acid 625 mg) starting 1 hour before surgery. A mucoperiosteal flap exposing the underlying bone was raised by making sulcular incision from Right central incisor to left lateral incisor, followed by two vertical releasing incisions preserving the adjacent papilla (Figure 2a). The vertical and horizontal bone defect demonstrated Seibert class 3 situation (Figure 2b) [21].

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Figure 2a: Sulcular incision design with vertical release on adjacent teeth.

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Figure 2b: Full thickness flap elevation showing Siebert class 3 bone defect.

Discussion

Guided Bone Regeneration (GBR) is a method of enhancing bone growth by preventing soft-tissue ingress using a resorbable or non-resorbable barrier membrane thereby achieving bone regeneration. Several techniques have been advocated in literature, however many of them remain unpredictable especially for larger and vertical bone defects [8, 9, 10, 11]. Vertical augmentation procedures are challenging in the aspect of 3D reconstruction of the defect and securing the transplant for stable integration. Non-resorbable membrane in combination with bone substitute material is a commonly described procedure in literature, however a common complication is the exposure of membrane and the need for its removal which has a detrimental effect on the outcome [9]. Alternatively Autogenous bone plates with fixation screws provided good stability of the transplant ensuring integration and lesser tissue irritation compared to GBR techniques using membrane [11, 14]. The augmentation technique used in the case report may be easily altered according to the morphological bone defect. Clinical study by Khoury Fouad and Thomas H demonstrated that 97.89% of patients presented with low or moderate pain perception with low complication rate during the process of bone harvesting suggesting higher reproducibility and predictability of the procedure [15].

Guided implant surgery allows a minimal invasive procedure without the necessity to elevate a flap, thereby maintaining vascularization over the grafted bone. This allows soft tissue to be in immediate contact with its natural surface thereby assisting faster healing and a stable reattachment of the tissue with the underlying surface [18].

Furthermore, frequent removal and insertion of the healing abutment is associated with increased crestal bone loss [19, 24]. Romanos, et al. suggested placement of the final abutment immediately after the surgical implant placement (“one-abutment at one-time” protocol) to significantly reduce crestal bone loss [20]. José Eduardo Maté also reported that the use of Bio-HPP abutment in combination with guided surgery and immediate restoration provides softer loading of the implant resulting in stable crestal bone and peri- implant tissue [23, 24, 25]. In clinical comparison to the results perceived in the present case report for three-dimensional reconstruction and implant rehabilitation in the esthetic zone, a similar result could be achieved with various other techniques described in the literature, However, the proposed protocol seems to be associated with fewer complications such as marginal bone loss, dehiscence, infection and allows a significant reduction in treatment time.

Summary

This retrospective case observation exhibited predictable results for the management of challenging implant restorative cases with horizontal and vertical bone defects in esthetic zones while maintaining healthy peri-implant tissue. Autogenous bone augmentation and a full digital implant workflow aided in overall reduction of treatment time, improved esthetic and stable peri-implant tissue; thus the author advocates the treatment workflow for management of such complex cases in esthetic zone.