Abstract

Implant placement in vertically insufficient alveolar ridges of the posterior maxillae may require bone augmentation, such as sinus floor elevation, onlay grafting, and distraction osteogenesis. The purpose of this report is to evaluate the feasibility of vertical alveolar ridge expansion and simultaneous implant placement in the posterior maxilla using segmental osteotomy without sinus floor elevation, onlay grafting, and distraction osteogenesis. Two patients presenting with vertically insufficient alveolar ridges in the posterior maxillae were treated with the surgical procedure as follows. The edentulous ridge was split vertically using a segmental osteotomy before the preparation of an implant bed, and 1 implant body was placed simultaneously in the ridge with the vertical split. Three months later, abutments were connected and prosthetic loading of the implants was started. The follow-up was performed with the aid of dental and panoramic radiographs, evaluation of peri-implant probing depths, and Periotest values. In both patients, alveolar ridge expansion and implant placement were carried out without problems, good functional results were performed, and the clinical and radiologic findings were satisfactory. The outcome of the surgical procedure showed minimal invasion and good functional results.

Introduction

Implant placement in vertically insufficient alveolar ridges of the posterior maxillae is performed in conjunction with bone augmentation, such as sinus floor elevation, onlay grafting, and distraction osteogenesis.

Sinus floor elevation is commonly performed to ensure the reliable insertion of implants in vertically insufficient alveolar ridges, but it often violates the anatomic integrity and interferes with the physiologic mechanisms of the maxillary sinus, creating potential complications.1,7 Onlay bone grafting is prone to unpredictable resorption8,10 and increases morbidity.11,12 Distraction osteogenesis does not need bone grafting but needs postoperative placement of the distractors and distraction.13,18 

The author presents the experience in treating vertically insufficient alveolar ridges in the posterior maxillae by means of vertical expansion and simultaneous implant placement using segmental osteotomy without sinus floor elevation, onlay grafting, and distraction osteogenesis. In this report, the author provides a description of this technique and discusses the first clinical results.

Patients and Methods

Two patients presenting with vertically insufficient alveolar ridges in the posterior maxillae were treated with the surgical procedure. Both patients had severe alveolar deficiency caused by atrophy. Preoperative planning was carried out with the aid of dental and panoramic radiographs and plaster casts. In the two patients, the minimum vertical distance from the implant insertion plateau to the maxillary sinus floor was measured at 4 mm in the panoramic radiographs.

All surgical procedures were performed under local anesthesia. The procedure was started with incisions in the buccal vestibule of the planned insertion region of an implant. Careful subperiosteal dissection was performed to obtain adequate visibility of the underlying bone and to preserve as much as possible the palatal pedicle after the osteotomy was performed. The horizontal osteotomy was then carried out at a vertical distance of 3 to 4 mm from the implant insertion plateau with an oscillating saw, and the lateral osteotomies were carried out at a lateral distance of 3 mm from the planned insertion region of an implant with a reciprocating saw. The bone segment prepared using osteotomies was incompletely fractured down with a chisel, like a greenstick fracture. After the splint made of a set length of resin was placed into the vertical split between the bone segment and the basal bone (Figures 1 and 2), an implant bed was prepared with a drill in the ridge without penetration of the maxillary sinus floor. One hydroxyapatite-coated implant (AQB Implant System, Advance, Tokyo, Japan), in length of 8 mm, was inserted in the implant bed through the bone segment and the basal bone.

Figures 1–2. The splint made of a set length of resin that was placed into the vertical split between the bone segment and the basal bone in the preparation of an implant bed with a drill

Figures 1–2. The splint made of a set length of resin that was placed into the vertical split between the bone segment and the basal bone in the preparation of an implant bed with a drill

The splint was removed from the split before suture. The wound was closed with sutures after relaxation incisions on the periosteum in the mucoperiosteal flap.

Both patients received antibiotics and nonsteroidal analgesics after the operation. A soft diet for 2 weeks after surgery and appropriate oral hygiene with mouthwash were prescribed. After a 7-day waiting period for closure of the surgical wound, the sutures were removed. Three months later, abutments were connected after crestal and lateral incisions in the ridge and prosthetic loading of the implants were started.

In addition to the monthly clinical examinations, follow-up examination was performed with dental radiographs, panoramic radiographs, peri-implant probing, and evaluation of Periotest values (Simans, Bensheim, Germany) 3 months and 6 months after implant loading. At the time the Periotest values became negative and there was no resorption of the ridge bone around the inserted implant in both the dental and panoramic radiographs, the final prosthetic superstructure was set on the implant.

Results

In both patients, alveolar ridge expansion and implant placement were carried out without complication or problems, such as wound dehiscence. Three months after surgery, the splits between the bone segments and the basal bones were filled with new bone. There was no pathological loosening of the implants, and peri-implant conditions were good after implant loading. Good functional results were obtained, and the radiologic findings of both the dental and panoramic radiographs were satisfactory.

Report of Cases

Case 1

A 51-year-old woman with bilateral partially edentulous ridges in the maxilla and bilateral posterior partially edentulous ridge in the mandible was treated with the procedure only in the site of the missing maxillary right second premolar. In the sites of maxillary right canine, mandibular right second premolar and first molar, and mandibular left premolars, implant placement had been performed preoperatatively. The distance from the implant insertion plateau to the maxillary sinus floor was measured at 4 mm in panoramic radiographs (Figure 3). The horizontal osteotomy was carried out at a distance of 3 mm from the implant insertion plateau, and the ridge was vertically expanded to 4 mm. After implant placement, a bone fragment of 4 mm in width, harvested using osteotomies in the site of maxillary right first premolar, was put into the split in the ridge. This was in order that the bone segment would not be placed in its former site (Figure 4). Three months later, the split between the bone segment and the basal bone had disappeared completely (Figure 5). An abutment was connected and prosthetic loading of the implant was subsequently started. Radiologic follow-up showed no severe resorption in the peri-implant region. The radiopacity of the split in the bone was similar to that of the surrounding bone 3 months after loading. Seven months after the procedure, when the Periotest values became negative, the final prosthetic superstructure was set on the implant. The implant placed in the site of the missing maxillary right second premolar was connected with that in the site of maxillary right canine by 1 superstructure. Two years after surgery, the radiologic findings were satisfactory (Figure 6), the Periotest values were negative, and the peri-implant probing depth was 2 mm.

Figures 3–6. Figure 3 . The preoperative panoramic radiograph of patient 1, showing severe alveolar deficiency caused by atrophy in the right posterior maxilla. Figure 4 . After placement of an implant in the ridge with the vertical split into which a bone fragment was placed. Figure 5 . Three months after implant placement, the split between the bone segment and the basal bone had disappeared completely. Figure 6 . The panoramic radiograph 2 years after surgery

Figures 3–6. Figure 3 . The preoperative panoramic radiograph of patient 1, showing severe alveolar deficiency caused by atrophy in the right posterior maxilla. Figure 4 . After placement of an implant in the ridge with the vertical split into which a bone fragment was placed. Figure 5 . Three months after implant placement, the split between the bone segment and the basal bone had disappeared completely. Figure 6 . The panoramic radiograph 2 years after surgery

Case 2

A 72-year-old woman with bilateral partially edentulous ridges in the posterior maxilla was treated with the procedure in the site of the missing maxillary left first premolar. In the sites of the maxillary bilateral premolar and maxillary right first molar, implants had been placed preoperatively. The distance from the implant insertion plateau to the maxillary sinus floor was measured at 5 mm in panoramic radiographs (Figure 7). The horizontal osteotomy was carried out at a distance of 4 mm from the implant insertion plateau, and the ridge was vertically expanded to 2 mm. After implant placement, bone debris was filled into the split in the ridge in order that the bone segment would not be placed in its former site (Figure 8). Three months later, the split between the bone segment and the basal bone had partially disappeared (Figure 9). An abutment was connected and prosthetic loading of the implant was started subsequently. The radiologic follow-up showed no severe resorption in the peri-implant region. The radiopacity of the split in the bone was similar to that of the surrounding bone 3 months after loading. Seven months after the procedure, when the Periotest values had become negative, the final prosthetic superstructure was set on the implant. Two years after surgery, the radiologic findings were satisfactory (Figure 10), the Periotest values were negative, and the peri-implant probing depth was 2 mm.

Figures 7–10. Figure 7 . The preoperative panoramic radiograph of patient 2, showing severe alveolar deficiency caused by atrophy in the site of the missing maxillary left first premolar. Figure 8 . After placement of an implant in the ridge with the vertical split filled with bone debris. Figure 9 . Three months after implant placement, the split between the bone segment and the basal bone had partially disappeared. Figure 10 . The panoramic radiograph 2 years after surgery

Figures 7–10. Figure 7 . The preoperative panoramic radiograph of patient 2, showing severe alveolar deficiency caused by atrophy in the site of the missing maxillary left first premolar. Figure 8 . After placement of an implant in the ridge with the vertical split filled with bone debris. Figure 9 . Three months after implant placement, the split between the bone segment and the basal bone had partially disappeared. Figure 10 . The panoramic radiograph 2 years after surgery

Discussion

Placement of implants in the edentulous posterior maxilla introduces some unique anatomic considerations and limitations. In most patients, the residual resorbed ridge has inadequate bone volume, especially vertically, for placement of implants. When conventional methods of tooth replacement, such as a distal-extension removable partial denture or a fixed prosthesis are not desirable in the edentulous posterior maxilla, implant placement and vertical bone augmentation, such as sinus floor elevation, onlay bone grafting, and distraction osteogenesis, should be considered.

Sinus floor elevation is commonly performed to ensure the reliable insertion of implants in vertically insufficient alveolar ridges, but it has potential complications that can be specific or nonspecific. Some researchers have reported cases of acute sinusitis in up to 20% of patients after sinus floor elevation.1,7 One should be aware of the possible unique complications related to the maxillary sinus so that the patient can be properly informed.

Onlay bone grafting is prone to unpredictable resorption.8,9 Nyström et al10 reported that, in the 10-year follow-up of onlay bone grafting and implants in severely resorbed maxillae, the grafting bone loss was seen up to the third-year examination. When an implant is installed in the site of onlay bone grafting, implant placement needs to wait until the grafting bone loss is no longer seen. Moreover, onlay bone grafting increases morbidity because of the necessity of harvesting bone from intraoral or extraoral sites.11,12 

Distraction osteogenesis is a minimally invasive technique because it avoids the need to harvest bone transplants and avoids complications of donor sites. However, this method is applied only in sites that have sufficient bone height and width for accommodating the placement of distraction. In the literature, bone height of 5 mm is the minimum dimension necessary for distractor placement on the distracted site.13,18 In addition, it is also necessary to have an appropriate bone height for distractor placement on the basal site. Furthermore, after the surgical procedure, distraction must be performed on the distraction sites daily until the desired amount of distraction is obtained.

Here, a technique of alveolar ridge enlargement using immediate implant placement is described. Simion et al19 reported on a method for gaining bone width with a split-crest technique for patients with sufficient vertical bone height but insufficient bone width for implant placement. The technique was applied vertically in 2 reported cases using osteotomy without a membrane, and results were successful. The technique dispensed with membrane because sufficient bone regeneration was expected even without membrane. Santamaria et al20 reported no statistical significance in the density and residual volume of the newly formed tissue on the bone defect treated by primary closure after removal of a radicular cyst, with and without a membrane. Each split made using a segmental osteotomy in 2 reported cases was completely covered with the periosteum in the mucoperiosteal flap, dissimilar from the split-crest technique.

The planned augmentatative heights were achieved in this surgical procedure (2 mm, 4 mm). In both patients, good functional results were obtained on implant placement, and the clinical and radiologic findings were satisfactory. This surgical procedure was kept free from complications in maxillary sinus and morbidity by harvesting autogeneous grafting bone. It was not necessary to place the distractors and obtain distraction after surgery.

Successful implant placement was achieved in vertically insufficient alveolar ridges of the posterior maxillae using this surgical procedure with minimal invasion. However, long-term follow-up is necessary.

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Atsushi Fujita, DDS, is chief at the Horokanai Municipal Dental Treatment Center, Hokkaido, Japan and Oral and Maxillofacial Surgery, Department of Oral Pathobiologic Science, Graduate School of Dental Medicine, Hokkaido University, Hokkaido, Japan. Address correspondence to Dr Fujita at 6720 Horokanai, Horokanai-tyo, Uryu-gun, Hokkaido, Japan. (e-mail: plalaadsl0920@purple.plala.or.jp)