Patient presented with removable appliance, relatively pleased with the aesthetics
Clinical examination of the patient was performed and initial presentation showed four maxillary as well as three mandibular implants which appeared to be failing (Fig. 17.4). All implants showed significant bone loss with thread exposure. The tissue support around implants showed inflammation and superficial infection. The soft tissue supporting the denture was very inflamed and irritated. The initial radiographic examination confirmed significant bone loss around all existing implants and improper angulation. Facial evaluation showed a pleasing smile with appropriate teeth showing in repose and smiling, and there appeared to be sufficient lip support from the over-denture flange. The removal of the denture showed significant lack of lip support by the existing bony structures of the maxilla. The edentulous ridge was not visible during smiling with the denture removed.
Radiographic evaluation showed all implants in the maxilla and mandible to exhibit significant bone loss circumferentially. Restorative space measured on a cephalometric film obtained from CT scan was measured at 42 mm (Fig. 17.5). Panoramic and cross-sectional images of the maxilla and mandible were obtained and showed significant atrophy of the both arches. The maxilla exhibited large pneumatized sinuses occupying majority of the maxilla. There was significant atrophy of the premaxilla with 7–8 mm of alveolus remaining below the floor of nose. There was minimal bone remaining in the molar and premolar regions, zones 2 and 3 (Fig. 17.6). The mandible showed moderate amount of resorption with 10 mm of bone above the inferior alveolar nerve and with sufficient width throughout.
17.1.1 Surgical Treatment Plan (Patient 1)
Patient is a healthy 73-year-old with no absolute contraindications for oral surgery procedures. Mild sedation with profound local anaesthesia was utilized to perform the procedure in a safe and comfortable manner.
Space: The patient has undergone moderate alveolar atrophy with perhaps alveoloplasty at the time of the existing implant placement. 41 mm of inter-arch space was measured clinically. The patient was treatment planned for an acrylic resin titanium prosthesis. There was sufficient space for the proposed restoration. No further space creation via bone reduction was necessary. It was determined that due to severe atrophy of the maxilla and superior position of the implants an appropriate contour to the prosthesis can be achieved to provide lip support without a horizontal shelf formation; therefore no further bone reduction is necessary to place implants.
Spread: The challenge in this case is the lack of bone in all three zones of maxilla. The removal of the existing implants will complicate the reconstruction. The implant removal defects will limit the options in positions available for placement. Pre-planning of implant placement showed that an angled implant configuration such as All-on-4™ would not be possible due to the extensive anterior extension of the maxillary sinuses. Both posterior implants would not be in maxillary bone if the platform was kept in the bicuspid regions or zone 2 and the implants were angled no more than 45°. Furthermore, the lack of anterior bone volume under the floor of the nose did not allow axial implant placement (Fig. 17.7). An alternative placement scheme was devised with posterior support provided by bilateral zygomatic implants and the anterior support by bilateral angled implants in the pyriform rim or lateral nasal wall. The mandible would be treated with removal of the existing implants and alveoloplasty to create a flat platform for implant placement. Two implants would be placed just anterior of the mental foramen and two axial implants in the anterior midline of the mandible (Fig. 17.8).
Stability: The zygoma is an extremely dense bone structure that will provide excellent stability to the zygomatic implants. There is sufficient ridge to allow for anchorage of the crestal portion of the zygomatic implants. The anterior implants would be placed with the apical portion in the very dense lateral nasal wall—pyriform rim of the maxilla.
17.1.2 Prosthetic Evaluation
This patient presented having recently undergone dental implant therapy but was unhappy with the removable implant and tissue-supported over-dentures that were provided. The patient requested a fixed prosthesis and was unwilling to go through grafting procedures.
On clinical examination the dentures lacked retention and stability. The palatal tissues were inflamed. There was an absence of keratinized mucosa. The existing implants demonstrated bone loss and were in unfavourable locations (Figs. 17.9 and 17.10)
From a diagnostic perspective the following factors were evaluated:
Incisal edge position—The patient was relatively pleased with the aesthetics of the existing dentures. The incisal edge position appeared to be satisfactory. A diagnostic denture set-up was to be done to evaluate any modifications in aesthetics (Fig. 17.11).
Restorative space—Due to the severe bone resorption, restorative space would be available for any material combination. Due to financial constraints, acrylic resin titanium prosthesis was selected.
Lip support—The patient had a severe lack of lip support and a concave facial profile when the dentures were removed. This is one of the factors that would pose a challenge in providing the patient with a fixed restoration. Due to the fact that the patient was unwilling to go through additional grafting procedures alternative clinical strategies would need to be evaluated such as alveolectomy and tilting of the anterior implants so the contour of the restoration could be developed so that it was maintainable (Figs. 17.12 and 17.13).
Smile line—With the dentures removed, the alveolar ridge was not visible so hiding the transition zone would not pose a problem.
Contours and emergence—The horizontal discrepancy between the implant position and where the patient desired the teeth aesthetically posed a significant challenge. Using shorter implants, tilting the anterior implants and starting the emergence profile higher up would help create some space for contour development.
Tissue contact—The existing tissues must be made healthy prior to any surgical procedures. Soft relining of the patient’s existing denture is to be carried out to achieve this. Due to the extensive resorption and available space shaping the restorative contours for a convex undersurface is attainable. This will allow the patient to maintain the prosthesis.
Occlusion—Occlusion must be addressed in the immediate load provisional to protect the implants in the weakest quality bone from excessive loads. In the definitive restoration occlusion must be organized to distribute the loads over a wide an area as possible.
17.1.3 Surgical Procedure
The patient was anaesthetized with a mild sedative combination of fentanyl, midazolam, diazepam and morphine sulfate. Antibiotic medication consisting of 1 g of cefazolin was administered intravenously at the beginning of the procedure. After titration of the sedatives, infiltration and block injections of local anaesthesia were completed to provide a profound local anaesthesia. 10 min of time was allowed for the local anaesthesia to take full affect. Crestal incision was made in the maxilla with bilateral vertical releasing incisions in the tuberosity region. The maxilla was completely exposed. The existing implants were removed utilizing retrieval tools. Trephine drills were not necessary. The nasal cavities were identified and exposed allowing for visualization of the lateral walls. Openings into bilateral sinus cavities were created along the buttress of the zygomatic bone using large round burs. The Schneiderian membranes were lifted off the interior of the sinus extending to the roof of the sinus and exposing the medial aspect of the zygomatic process. Using the zygomatic 2.9 mm drill the initial osteotomy was made through the maxillary alveolus at the second bicuspid region. The long drill was extended through the maxillary sinus to engage the zygomatic bone at its thickest portion and exiting at the prominence of the zygoma (Fig. 17.14). Appropriate length implants were selected and placed. Next, two 13 mm NobelSpeedy implants were placed in the approximate position of lateral incisors and angled to engage the lateral nasal wall. The placement of the angled implants in the anterior maxilla allowed for placement of longer implants engaging the very dense areas of bone in lateral nasal wall (Fig. 17.15). A 10 mm NobelSpeedy implant was placed in the midline maxilla. Multi-unit abutments were placed on the zygomatic implants. The midline anterior implant also received a straight multi-unit abutment. The angulation of the two lateral implants was corrected by placement of 17° multi-unit abutments. In the mandible the previous implants were removed. Bilateral mental nerves were identified. Alveoloplasty was performed to create a level platform for implant placement. Posterior implants were placed by positioning the platforms superior to the foramen and the axis of the implants was tilted up to 45° to avoid injury to the nerve. Two more NobelSpeedy implants were placed between the implant defects created by the removal of the previous fixtures. All implants were long enough to engage the very dense cortical plates of inferior border of the mandible (Fig. 17.16). All maxillary and mandibular implants were found to be very stable. Multi-unit abutments were placed on the posterior implants to correct the angulation of the implants and straight abutments were placed on the anterior two implants (Figs. 17.17 and 17.18). All surgical sites were irrigated and closed utilizing chromic gut sutures. Patient tolerated the procedure well and was turned over to the prosthodontic team for fabrication of the provisional prosthesis.