Surgery of the Edentulous and Partially Edentulous Maxilla

Chapter 3 Surgery of the Edentulous and Partially Edentulous Maxilla

Chapter Outline

Surgery for the posterior maxilla

Multiple-teeth implant-borne restorations

CT-guided surgery: complications associated with scanning, processing, surgery, and prosthetics

Surgery of the Anterior Maxilla

Preoperative Planning and Assessment

Implant-supported therapy for the patient with an edentulous maxilla depends on several treatment planning issues. The following factors determine the treatment of choice:

Treatment planning usually is initiated at the restorative dentist’s office. It involves establishing the patient’s goals regarding what the patient wants at the completion of implant therapy. Once these goals have been established, the surgeon is consulted, and an assessment of bone availability is performed.

A panoramic radiograph and physical examination often are sufficient to determine whether satisfactory bone bulk is present for the placement of implants into the maxilla. The panoramic radiograph allows an estimate of the amount of vertical bone available in the premolar and molar regions. A good-quality panoramic radiograph can confirm the presence of adequate anterior maxillary bone for the placement of implants at least 10 mm long. Occasionally, a reformatted computed tomography (CT) scan or complex motion tomogram is obtained to confirm the presence of bone before implant placement. If cross-sectional radiography is planned, a radiopaque stent significantly increases the amount of information gathered. The radiopaque material, typically 20% to 30% barium sulfate combined with a clear acrylic, causes the teeth in the patient’s prosthesis to become radiopaque in the cross-sectional image. This image provides information concerning the relationship of the bone to the desired teeth.

The amount of bone in the anterior and posterior maxillae should be determined. The anterior maxilla consists of the area anterior to the lateral walls of the nose or the anterior border of the sinus. The posterior maxilla consists of the regions of the second premolars and molars. The following four conditions are considered:

A prosthetic plan is completed, with the aid of the restorative dentist, after the amount of bone has been determined. Parel’s classification of the edentulous maxilla is useful for conceptualizing the prosthetic plan (Box 3-1).

BOX 3-1 Parel’s Classification of the Edentulous Maxilla

Class I Only maxillary teeth are missing, but patient has retained alveolar bone almost to its original level.
Class II Teeth and some alveolar bone have been lost.
Class III Teeth and most alveolar bone have been lost to the basal level.

For the Class I maxilla, a fixed, implant-borne restoration can be fabricated, because the patient has adequate alveolar bone to support the soft tissues and is missing only the teeth. Usually greater than 10 mm of bone height is present in both the anterior maxilla and the posterior maxilla. For a fixed crown and bridge restoration, implants need to be placed within the confines of the teeth of the planned restoration. In addition, implant placement should avoid excessive angulation to ensure that the implants can draw as a single unit. Placement should avoid the embrasure regions to promote an esthetic outcome and oral hygiene. Finally, the implants should be placed 3 mm apical to the gingival margin of the planned restoration to allow the restorative dentist to develop a natural emergence of the crowns from the gingiva. A well-made, detailed surgical template is essential for a fixed crown and bridge restoration. The template should have full palatal coverage with anatomic retention at the hamular notches (posterior maxilla), enabling the stent to be placed in a repeatable, stable, and accurate position that allows the surgeon to follow its prescription when placed into the mouth.

If the patient with a Class I edentulous maxilla desires a tissue-borne overdenture on four implants because of financial constraints, the overdenture bar must avoid an excessive space-occupying design, because the patient is missing only teeth and not alveolar bone.

The Class II maxilla rarely can be managed esthetically with a fixed crown and bridge prosthesis, because this class requires the labial flange of the maxillary prosthesis to support the nasolabial soft tissues. A useful technique for determining the need for acrylic to support the soft tissues is to duplicate the patient’s maxillary dentures and remove the labial flange, leaving only the teeth. The resultant soft tissue profile with the modified duplicated maxillary denture can help the implant team and the patient decide on the treatment plan. In addition, a deficiency of alveolar bone necessitates the placement of implants more apical than is ideal, resulting in excessively long teeth, teeth with pink acrylic, a removable lip “plumper,” or a type of hybrid prosthesis with space between the prosthesis and implants.

A fixed crown and bridge prosthesis, a fixed-removable (e.g., spark erosion or milled) prosthesis, or a type of removable overdenture prosthesis may be prescribed. The fixed implant-borne and fixed-removable prostheses require at least six (preferably eight) endosseous implants to support a maxillary implant-borne prosthesis adequately. Zygomatic implants are the exception (see later discussion). These traditional fixed or fixed-removable prostheses require posterior maxillary vertical bone height for implants placed in the first molar region. The removable tissue-borne prosthesis requires four implants placed into the anterior maxilla to support a bar, which has retentive vertical stress-breaking attachments. All the edentulous maxillary prostheses usually are fabricated with cross-arch stabilization of the left and right implants.

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

Placement of Four Implants into the Anterior Maxilla

For the patient with adequate anterior vertical bone height and a treatment plan for anterior implants to provide overdenture support, four implants can be placed. Placement of at least four implants is recommended for an implant-supported overdenture in the maxilla, because fewer than four maxillary implants will not predictably resist the forces placed on them (Figure 3-1, A-B, and DVD Figure 3-1, A-F). Two implants are contraindicated to retain a maxillary overdenture.

Preoperative radiographs and a physical examination can reveal the height and thickness of the alveolar ridge. Four implants in the anterior maxilla, often combined with vertical stress-broken attachments placed at the distal aspects, are used to support a rigid bar. The anterior maxillary implants should be placed within the confines of the borders of the planned prosthesis and not labial to the borders of the teeth. The implants should be placed to avoid impingement of the teeth in the overdenture and to allow space for fabrication of the bar. Careful attention to the position of the incisal edges of the lower teeth provides important information and prevents conflicts of space between the lower teeth and the palatal portion of the overdenture and the underlying bar.

At surgery, the surgeon should understand the prosthetic plan and recognize the ideal locations of the implants. Often these implants can be placed slightly palatal to the crest to engage more of the palatal bone, providing a thicker width of labial bone (Figure 3-2, A-E). A local anesthetic is infiltrated into the labial and palatal regions of the anterior maxilla. Incisions for implants placed into the anterior maxilla usually are placed over or slightly palatal to the crest. Vestibular incisions are avoided in the anterior maxilla, because they can shorten the vestibule and increase the patient’s postoperative discomfort.

The incision is made along the crest, moving labially around the incisive papilla to avoid transecting its contents, and carried to bone through the periosteum. A full-thickness mucoperiosteal flap is raised, with care taken to prevent trauma to the flap. If necessary, vertical release incisions can be made distal to the planned implant locations to help raise the flap superiorly and thus expose the facial aspect of the maxillary bone. An anterior midline release is not used; it would increase postoperative morbidity because of the disturbance in the anterior lip musculature.

A full-thickness palatal reflection is then accomplished. The contents of the incisive canal are preserved and not incised. The palatal reflection should allow visualization of the slope of the vertical palatal bone to ensure that the surgeon can visualize the insertion of the implants without violating either the labial or the palatal cortical bone, thereby keeping the implant body within bone. The visualization also allows determination of the probable need for osteotomes, either round or flat, to widen the ridge during implant placement.

After the labial and palatal tissues have been reflected, the surgeon should have a good view of the crestal bone thickness and the contours of the palatal and facial cortical bone. The dissection often must be extended superiorly to identify the piriform rim, especially for the more atrophic maxilla. The thickness of bone is confirmed, and the surgical stent is placed. The areas of planned implant placement are examined.

Often the crest of the maxilla is narrow and widens within a few millimeters of the crest. Specific sites may be wider than others, indicating a site that is more ideal for the implant when bone bulk is considered. However, before placing the implant in a site slightly different from that prescribed by the surgical stent, the surgeon should ensure that the prosthetic plan will not be adversely affected.

Because the maxillary crest usually has sharp edges and slopes, the first step is the creation of a depression in the ridge that allows accurate engagement of the drills. The implant sites are scored with either rongeur forceps or a round bur, creating a divot into the bone. The round bur is used to initiate the osteotomy site and to determine the specific location of the implant in the middle of the crest. Accurate placement of this round bur hole is important, because subsequent drills will start in this round hole; changing the position may be difficult once the drilling process has started. If the first drill needs adjustment in position (e.g., the hole is too far labial or palatal), the round bur is used to relocate the hole slightly palatal, labial, distal, or mesial, guided by the need to place the implants into adequate bone and in the correct location. The surgeon must always critically examine the implant sites; the implants must be placed accurately to ensure successful prosthetic treatment.

Subsequent graduating-sized drills initiate and expand the implant site until the final drills are used. If the ridge is excessively narrow, round or flat osteotomes can be used to expand it, or the ridge may require grafting before implant placement. Usually the ridge has sufficient width for placement of the implants. If the ridge width is deficient, the surgeon should consider whether osteotomes can be effective or whether onlay grafting is indicated. If the ridge width is 3 mm, osteotomes can be used to expand it in most cases. However, if the ridge is thin and does not expand as the bone is examined superiorly, the use of osteotomes or ridge splitting in a ridge less than 3 mm is not predictable. For these cases, onlay grafting is indicated and should be discussed with the patient. (See Chapter 4 for examples of onlay grafting of the anterior maxilla with symphyseal bone.)

Implants for overdentures typically are placed with their centers slightly palatal to the crest to avoid dehiscence and thin bone over the facial aspect of the implants. The incisive canal should be avoided as a site for implant placement. Implants should be placed to prevent dehiscence of the implant within the incisive canal. Specifically, implants for overdentures are placed in the canine and premolar locations, depending on the availability of bone. An implant can be placed in the lateral incisor position if necessary. However, implants placed in the central incisor locations complicate the prosthetic rehabilitation, because the presence of the abutments and bar near the midline may result in excessive palatal bulk in the denture; this outcome may be bothersome to the patient.

If a dehiscence of bone occurs in the midportion of the implant because of concavity of the ridge, particles of dense, nonresorbable hydroxylapatite (HA) are placed to obliterate the defect. Use of a membrane depends on the surgeon’s clinical judgment. In general, a membrane is not necessary for small dehiscences.

After the implants and the implant cover screws have been placed into the implant bodies, the incision is closed. Occasionally the periosteum must be released to allow tension-free closure. If no graft has been placed, the type of suture depends on the clinician’s preference. If a graft has been placed, nonresorbable sutures are indicated.

The patient’s current prosthesis should be left out of the mouth for 7 to 10 days after implant surgery. However, if the patient cannot accept this recommendation, the surgeon or restorative dentist should remove the labial flange to the gingival margin of the denture teeth and relieve the crest region. This extremely relieved maxillary prosthesis then can be glued in with denture adhesive on the palate without adhesive on the incision sites. Patients can wear the modified prosthesis for esthetic reasons, but they must consume a liquid, pureed diet for 2 weeks.

Placement of Eight Implants without a Graft

If the patient’s goal is to have a denture that accommodates a palateless prosthesis, enabling the patient to chew all textured foods without the prosthesis, a sufficient number of implants (depending on the tissues for support) is required to resist the forces of mastication. For these patients, six to eight implants for a fixed implant-supported or removable prosthesis is recommended, with an adequate number of implants located posteriorly to support the molars.

The edentulous patient with a Class I maxilla requires only the placement of implants to replace the missing teeth (Figure 3-3, A-G). In most patients with a Class I maxilla, who have lost their teeth with minimal bone loss, the labial bone has an irregular contour. These patients may benefit from augmentation of the labial bone to smooth the bone contour and enhance the final restoration, especially for those with high smile lines (Figure 3-4, A-I).

Patients with a Class II maxilla, who have lost their teeth but have a moderate amount of bone, must have an esthetic evaluation. These patients may require the labial flange of a removable prosthesis to provide nasolabial support. They may have sufficient bone for the placement of implants, but without additional lip support, the result may be compromised (Figure 3-5, A-F). The patient’s denture can be duplicated in clear acrylic, and the flange can be completely removed. If the modified denture is placed into the mouth and the lip support is adequate, a fixed restoration can be used. However, the locations of the implants and the need for removable prosthetics to aid in the maintenance of effective oral hygiene also are important considerations.

Patients with a Class III maxilla, who have lost their teeth and most of the alveolar bone to the basal level, benefit from a fixed-removable restoration (Figure 3-6, A-E).

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May 3, 2016 | Posted by in Implantology | Comments Off on Surgery of the Edentulous and Partially Edentulous Maxilla
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