4: Surgery of the partially edentulous maxilla

Surgery of the partially edentulous maxilla

imageAdditional illustrations can be found on the companion website at www.blockdentalimplantsurgery.com

Surgery of the anterior maxilla for the partially edentulous patient

Anterior maxilla multiunit restorations: Preoperative planning and assessment

Implant-supported therapy for a patient missing or who will be losing anterior maxillary teeth requires the same attention to general considerations as described in Chapter 3. The goals of the patient will usually be restoration of a functional occlusion in an esthetic manner.

Treatment planning includes collection of necessary radiographic information and knowledge of the final restoration’s requirements to meet the esthetic needs of the patient. A cone-beam scan is performed to gain insight into the available bone and general health of the rest of the mouth. The final restoration will need to be determined by fabrication of a new provisional, a mask over the current teeth, or a new removable prosthesis that identifies the form of the final crowns. From the final restoration, tissue deficiencies can be identified and then a thorough treatment plan developed.

A cone-beam radiograph and physical examination are sufficient to determine whether satisfactory bone bulk is present for the placement of implants into the maxilla. The cone-beam scan provides an accurate estimate of the amount of vertical bone available in the premolar and molar regions. If further information is needed, a mockup of the final restoration can be made with radiopaque material or duplicated and scanned in the patient’s mouth with the teeth slightly apart. Then computed tomography (CT) planning software can be used to finalize the needed information to initiate treatment.

For patients who smoke or drink alcohol heavily or who have uncontrolled diabetes or other systemic diseases that prevent bone grafting, the surgeon’s preferred option for placing implants is to use the available bone. Predictable grafting results vary according to the patient’s health and oral environment. After a discussion with the restorative dentist, the amount and location of available bone can be determined.

Placement of implants and onlay bone grafts for isolated defects

Patients with isolated bone defects caused by trauma or ablative tumor surgery who have retained a portion of the dentition often seek treatment for these defects. The missing bone results in a functional defect that is not amenable to placement of conventional removable prostheses. For these patients, the history of the problem and accurate treatment planning aid in the choice of a design that likely will include bone grafting and placement of implants to assist in prosthesis retention (Figure 4-1). Important information from the patient’s history includes smoking habits, radiation therapy, recurrent infection and scar formation, and malnutrition or other systemic factors that can affect wound healing.

Treatment planning must include accurate articulation of diagnostic casts, which are used to create a setup of the ideal restoration. This setup can be tried in the patient’s mouth for the individual’s approval of its esthetic characteristics and function. The setup is used to fabricate radiopaque stents for CT scanning and as the surgical guide stent for graft and implant placement. Based on diagnostic imaging of the available bone, a treatment plan with alternatives can be formulated and presented to the patient. Preoperative planning is crucial to these complex cases. If the treatment planning has been performed meticulously, the grafts will be placed in a position that allows for ideal implant positioning and thus a predictable prosthetic reconstruction.

Many patients who have had ablative tumor surgery or extensive trauma with resultant bone loss want a fixed restoration. However, the requirements for a fixed crown and bridge–type restoration include sufficient available bone and healthy, normal-appearing gingivae. Often the reconstruction of the anatomy does not lend itself to a good esthetic restoration based on a crown and bridge prosthesis; an implant-borne, fixed-removable restoration frequently results in a more esthetic restoration.

Augmentation of the anterior maxilla using particulate graft material combined with fibrin glue and resorbable membrane

The patient presented with a thin anterior ridge secondary to loss of teeth and bone from trauma. These patients often have sufficient vertical height but have lost most of the width of the alveolus. They require restoration of width sufficient for esthetic implant positioning and restoration of the esthetic ridge profile.

The patient had lost three anterior maxillary teeth. Diagnostic models showed that orthodontic treatment was indicated to realign the teeth that had been moved during healing of the patient’s complex alveolar fractures. After orthodontic realignment of the teeth, the extent of the necessary horizontal ridge augmentation was defined (see Figure 4-1). The treatment plan called for horizontal ridge augmentation and, after graft healing, the placement of implants for a three-unit, implant-borne restoration.

At the time of surgery, the arch wire was removed. A crestal incision was combined with sulcular incisions three teeth distal to the edentulous site. A full-thickness flap was elevated from the alveolus and teeth without tearing the facial gingiva. The subperiosteal release was extended to the piriform rim without damaging the nasal mucosa.

Bovine bone xenograft (Endobon, Biomet 3i, Palm Beach Gardens, FL) was used for this augmentation. Fibrin glue (Tisseel, Baxter, Deerfield, IL) was combined with the xenograft to form a composite, which was placed over the defect. Because scar tissue was present at the level of the nose, care was taken to avoid excessive pressure by tapering the augmentation in this region. The graft was placed 17 mm apical to the crest. This man had a significant distance from the crest to the floor of his nose. After the composite was placed over the concave defects and molded with the fingers, a collagen membrane was placed. The collagen membrane chosen (Osseoguard, Biomet 3i) has a half-life of barrier character of 6 months. Because of the extensive periosteal release, the flap was closed without tension. The arch wire then was replaced, with care taken to shorten the pontics to prevent pressure on the ridge. Swelling occurs after this procedure; therefore, judicious reduction of the apical portion of the pontics at the time of surgery is very important.

Postoperative instruction included a liquid diet and rinses using diluted mouthwash. Chlorhexidine was avoided for 10 days after the augmentation because of its fibrocyte toxicity. Antibiotics were prescribed for 2 weeks with staphylococci coverage. Sutures were removed after 2 weeks if they were still present.

Four months after the procedure, imaging was performed to confirm the augmentation. The orthodontic appliances were removed, and the final diagnostic setup was performed before implant placement.

After the augmentation form and position were confirmed, a new ideal tooth setup was done, identifying the final implant positions. A model had implant analogs placed into a diagnostic model, and small radiopaque markers were placed into a guide stent. A new CT scan was taken to confirm that the implants could be positioned into bone as planned, using the small pins to evaluate angulation of the implants. The position was confirmed, and a model-based CT guide stent was made. The implants were positioned with their entry into bone confirmed by a small palatal flap for direct visualization. Healing abutments were placed. After 4 months, the final restoration was made. The augmentation using bovine particulate under a resorbable membrane resulted in thick, healthy gingiva that was easily formed by the restoration, without recession (see Figure 4-1).

Horizontal grafting the thin ridge at the time of tooth removal for restoration of anterior six maxillary teeth

Several patients have long-span bridges in the anterior maxilla. Because of trauma from occlusion from lack of adequate posterior occlusal balance, the anterior bridges fail with accompanying tooth fractures. This patient (Figure 4-2) demonstrates the common dilemma of two canines in need of removal with the added need for mechanical bolstering from implant placement in the central incisor locations to avoid a similar problem from lack of a tripod mechanical situation.

The plan was to extract the canines and graft the extraction sockets and to perform a sintered xenograft augmentation using a long-lasting collagen membrane (Osseoguard, Biomet 3i, Palm Beach Gardens, FL) to maintain graft position.

Local anesthesia was infiltrated from molar to molar. A sulcular incision was made around the posterior teeth and a crestal incision across the edentulous space. A full-thickness flap was elevated superiorly to the piriform rim. A periosteal release was performed using a scissor and avoided entering the muscle. Mineralized cortical allograft was placed into the sockets and collagen membranes placed under the flap. Xenograft was placed under the collagen membranes. The incision was closed without tension using 4-0 chromic suture. The removable prosthesis was modified to remove the flange and to shorten the teeth to avoid trauma to the ridge.

After 4 months, the ridges looked ideal. A new cone-beam scan was made and a virtual tooth setup performed in the computer as a plan. The restorative dentist approved the placement of the teeth on the computer plan. A CT-generated surgical guide stent was fabricated for CT-guided implant placement.

This patient had soft bone, and thus a small palatal flap was elevated at the time of implant placement surgery even though the guided stent was available. The stent was placed and the initial pilot drills used to make the first set of holes for implant site development. These entry sites in the gingiva were connected with an incision and palatal vertical releases made. A palatal flap was carefully elevated. The pilot drill entry sites were confirmed and the implant sites preparation was finished. The implants were placed under direct visualization. Cover screws were placed rather than healing abutments because the removable provisional prosthesis was used.

After 4 months for implant integration, the implants were exposed and restored with a six-unit splinted restoration. Three-year follow-up shows excellent retention of form of the ridge and functional stability of the implant-supported restoration.

Surgery for the posterior maxilla

Single-premolar or single-molar restorations

Diagnosis and treatment planning indicate whether sufficient space and bone are available for implant placement. Periapical radiographs are necessary for single-tooth restorations to confirm that the roots of the adjacent teeth do not impinge on the space that will be used by the implant. If root angulation is a problem, preoperative orthodontics must be performed before implant placement, or a fixed bridge can be made rather than placement of an implant.

The periodontal status of the adjacent teeth must be controlled, and the teeth must show no evidence of recent active periodontal disease. If the patient’s oral hygiene is marginal in the remaining dentition, cross-contamination can occur from the teeth to the implant, resulting in failure of the implant secondary to infection during the early phases of healing. Important information about the patient’s dental history and ability to maintain the teeth can be gained from a consultation with the patient’s dentist.

If the patient’s teeth otherwise are healthy, radiographs are taken at the consultation visit. The surgeon should consult with the restorative dentist to confirm the treatment plan and the type of implant to be used. The procedure is discussed with the patient, and the patient reviews a consent form and receives answers to all questions. The office’s financial policy is discussed, with a complete understanding of the patient’s responsibilities.

At the surgical visit, a local anesthetic is administered. The incision is made slightly palatal to the crest, with vertical release incisions flaring into the vestibule to keep the base of the flap wider than the crestal incision width (Figure 4-3). Full-thickness, subperiosteal labial and palatal flaps are reflected to expose the crest and allow visualization of the vertical cortices of bone. The implant should be placed with its axis parallel to the occlusal forces, and the emergence of the implant should be angled to meet the buccal cusps of the mandibular teeth. A surgical guide stent can be used; however, if the neighboring dentition is in good repair and the mandibular dentition is well aligned, the fossae of the teeth can be used to direct implant placement.

A round bur is used to mark the planned implant location. The graduating-sized drilling sequence is used, and the implant is placed. If extremely soft maxillary bone is felt, osteotomes may be used to compact the bone in the implant site, although minimal scientific information validates the assumption that compaction of bone with osteotomes helps the integration rate. If encountered in the labial bone, dehiscences are treated in a manner similar to that discussed previously for anterior maxillary implants. After the implant has been placed, the periosteum is released as necessary, and the incision is closed (Figure 4-4).

After the appropriate healing period, which depends on the quality of the bone and the type of implant used, the implants are exposed. At the time of implant exposure, the keratinized gingiva (KG) is bisected so that it can be placed and transposed to the labial aspect of the implant as necessary. The KG is reflected, the cover screw is removed, and a temporary healing abutment is placed. After 2 weeks or longer for gingival healing, the depth of the sulcus is measured, and the restorative dentist places the abutment of the appropriate length. Comfort caps, which cover the sharp edges of the abutments, can be used until a provisional or permanent prosthesis can be delivered.

Multiple-teeth implant-borne restorations

The preoperative treatment planning for multiple teeth is similar to that for the single-tooth restoration. A surgical guide stent is necessary because fewer landmarks are available to guide the surgeon for ideal placement of the implants in relation to embrasure spaces and angulation to the buccal working cusps. These restorations typically involve the distal teeth. The final occlusion should be planned before implant placement to provide the patient with a long-lasting, functional restoration with physiologic balance.

Patients may have sufficient vertical bone but may be deficient in the width projection of the bone, which is common after extraction of the maxillary teeth. The bone loss occurs especially after trauma or long-term loss of the teeth, leaving the palatal bone intact but the alveolus thin and deficient. The patient shown in Figure 4-5 lost his anterior maxillary teeth while in his college years, and he now desires a fixed prosthesis to replace his irritating partial denture.

Patients may have sufficient bone for implant placement, but the bone may not be in an ideal location. If the bone is not ideally in position, then the use of grafting or osteotomy methods can be used to relocate and reconstruct the bone. Patients may not want extensive surgery. They may desire a simpler solution if function and esthetics can be met.

To assess the patient’s needs, a provisional restoration can be remade or modified. The patient shown in Figure 4-5 has a removable partial denture, which established his occlusion. It has a large flange. It can be used to provide a dual-scan prosthesis to plan the case treatment using virtual methods. The partial is duplicated in clear acrylic and fiduciary markers placed in the palatal portion. The cone-beam scan is taken with the duplicate in the patient’s mouth and by itself. The images are married on the software, and the implants can be placed on the computer demonstrating to the team the options available.

In this patient, implants can be placed. They will be angled. There is excessive space between the intaglio surfaces of the crowns to the bone. He will need pink restorative material in the final restoration. Hygiene access will need to be assessed. The prosthesis may need to be removed yearly for maintenance and evaluation. His smile lie was low with no gingival show.

A drill guide was made to guide the surgical placement of the implants, with the understanding that a screw-retained prosthesis will be necessary. After the implants were integrated, a provisional screw-retained provisional prosthesis was made and the flange adjusted until adequate hygiene was achieved. The final restoration was made with a thick framework for strength with all implants linked together for support. His 8-year follow-up indicates that the goals of a long-lasting functional restoration have been achieved.

Jan 5, 2015 | Posted by in Implantology | Comments Off on 4: Surgery of the partially edentulous maxilla
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