Young-Jin Park, DDS,* and Sung-Am Cho, DDS, MS, PhD

Transcription

1 J Oral Maxillofac Surg 68: , 2010 Retrospective Chart Analysis on Survival Rate of Fixtures Installed at the Tuberosity Bone for Cases With Missing Unilateral Upper Molars: A Study of 7 Cases Young-Jin Park, DDS,* and Sung-Am Cho, DDS, MS, PhD Purpose: To evaluate the survival rate of implants placed in the maxillary tuberosity region using the fixed prosthesis in partially edentulous cases. Materials and Methods: Of implant-treated patients who visited Kyung Pook National University Hospital, 7 partially edentulous patients (2 male and 5 female; mean age, 52.3 years; range, approximately 43 to 65) were selected according to the following criteria: 1) less than 3-mm thickness alveolar bone reaming at the first molar area and 2) 1 to 2 fixture premolars, with the additional implant at the maxillary tuberosity region. For the control group, patients who had nontuberosity areas were selected. After 1 to 7 years, marginal bone level, fixture mobility, and radiolucency of tuberosity fixtures of the fixed prostheses were evaluated by digital panorama (Starpacs, Infinitt, Seoul, Korea). Results: None of the fixtures of the tuberosity-installed implants for 1 to 7 years failed. The marginal bone level around the implants of the maxillary tuberosity 1 to 6 years (average 3.4 years) after the final prostheses was approximately 0.6 to 1.3 mm, with an average of 0.94 mm. Conclusion: The fixture installation at the maxillary tuberosity using the unilateral partially edentulous implant-fixed prosthesis would be a clinically acceptable treatment module American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 68: , 2010 The absence of upper molars is problematic for dental implantation if there is severe alveolar bone resorption. 1 Bone grafting using the iliac crest has been the most common procedure for increasing bone volume. 1 Grafting with a Le Fort I, inlay bone grafting for sinus lift, and zygoma implants also have been suggested. 2 These can be expensive, time-consuming procedures. 3 The most posterior part of the maxillary arch is the tuberosity, which is often well developed, but the bone quality is too spongy to provide predictable Received from the Department of Prosthodontics, School of Dentistry, Kyung Pook National University, Dae-Gu, South Korea. *Resident. Professor. Address correspondence and reprint request to Dr Cho: Department of Prosthodontics, Kyung Pook National University, School of Dentistry, Sam Dukdong 2 ga, Jung-Gu, DaeGu, South Korea ; sungamcho@gmail.com 2010 American Association of Oral and Maxillofacial Surgeons /10/ $36.00/0 doi: /j.joms osseointegration. However, the maxillary tuberosity rests against an extremely dense mass of bone formed by the pterygoid process. 4 Pterygoid plate implants were introduced by Tulasne 4 and later reported by Krogh, 5 Graves, 6 and Kyayaht and Nadar 7 using the cortical bone in the pterygoid plate with tuberosity (Table 1). Many investigators have reported varying rates of implant success at the tuberosity area: Bahat 8 reported a 93% success in 1992, and Balshi et al 9,10 reported success rates of 88% in 1992 and 86.3% in Krogh 5 explained that using the tuberosity met with uniform failure because the operators attempted to place the fixtures perpendicular to the occlusal plane; however, if a fixture was angled posteriorly, the pterygoid plate could be engaged with good initial and long-term results. Graves 6 reported 67% implant success at the pterygoid plate with tuberosity. Khayat and Nader 7 reported a 95% success rate with 4 years of observation. Bahat 8 stated that the real posterior structure of the maxillary tuberosity is the pyramidal process of palatine bone. He reported a 93% success rate. 11 Recently, 1338

2 PARK AND CHO 1339 Table 1. SUCCESS RATE OF TUBEROSITY REGION IMPLANTS BY LITERATURE REVIEW Year Reference Fixture Location Success Rate/Survival Rate Period (yrs) Number of Tuberosity Fixtures/Patients Fully or Partially Edentulous Arch 1991 Krogh 5 T P 8 Not clear F P 1992 Tulsane 4 T P /97% /34 F P 1992 Bahat 8 T /93% / F P 1994 Graves 6 T P 67% 4 64/49 F P 1994 Khayat and Nader 7 T P 95% 4 65/51 Not clear 1995 Balshi et al 9 T P 86.3% /44 F P 1999 Balshi et al 10 T P 88.2% /189 F P 2000 Bahat 11 T 93.4% /202 F P 2000 Krekmanov et al 13 T 98% /22 F 2001 Aparico et al 14 T 95.2/100% Not clear F P 2009 Ridell et al 3 T 100% /21 F P Abbreviations: F, fully edentulous missing case; F P, fully and partially edentulous missing case; P, partially edentulous missing case; T, tuberosity bone (usually tuberosity of maxillary bone); T P, fixture head at the tuberosity and fixture apex at the pyramidal process of the palate and pterygoid process of the sphenoid bone. Ridell et al 3 reported using the maxillary tuberosity bone located just behind the maxillary sinus, which, although composed of only soft bone, could provide enough volume for at least 1 or 2 fixtures without any failure. The aim of this 1- to 7-year retrospective follow-up study of clinical cases was to evaluate the survival rate of implants placed in the tuberosity using screw-retained fixed bridge installation. Materials and Methods PATIENT SELECTION Data for this study were obtained from charts of patients treated at the University of Kyung-Pook National University Hospital from January 2001 to December These charts were consecutively evaluated for subjects who met the following inclusion criteria: 1) 1 implant installed at the maxillary tuberosity region, 2) additional 1 to 2 fixtures installed at the premolar area, 3) grade 4 titanium implant with length of 11.5 to 15 mm and diameter of 3.75 mm (CSM, Daegu, South Korea), 4) unilateral upper molar as the edentulous space, and 5) subsequent anchorage of the fixed bridge made 6 months after installation. Seventeen molar fixtures in 7 patients (7 tuberosity implants) were selected. Recorded clinical and radiographic data were interpreted by a single investigator to form an assessment outcome. Implants were classified as survival if radiographic (digital panorama) and recorded clinical data demonstrated that the implant was present in the mouth and functional at the time of recall without definite signs of absolute failure, such as peri-implant radiolucency or implant mobility, even with subsequent post-treatment intervention or adjunctive procedures. Failure was assumed if the implant was removed or planned for removal. SURGICAL CONSIDERATIONS The site was prepared with care to minimize drilling mistakes. Drilling was started with a 2.0-mm round drill at 1,000 rpm to penetrate the cortical bone. Next, a 2.0-mm twist drill at 500 rpm was used to obtain the desired depth of drilling. All fixtures were inserted at 15 rpm with 25 to 40 N-cm without any countersinking and tapping. In all cases, sufficient amounts of bone were found at the posterior of the maxillary sinus, and the density was sufficient to receive the insertion torque of 25 to 40 N-cm. Firm primary stability was achieved for all implants; hence, the cover screw was firmly attached without any rotation of fixtures. All fixtures installed in the tuberosity region were 3.75 to 4 mm in diameter and 11.5 to 15 mm in length. Implants were placed close to and parallel to the posterior sinus walls and were tilted posteriorly approximately 15 to 35. PROSTHETIC CONSIDERATIONS All implants were surgically placed and restored by the same prosthodontic faculty staff. The procedure consisted of a 2-stage treatment only. At an average of 6 months after installation, each fixture was connected with the healing abutment. Two to 4 weeks later, fixture-level impressions were made to make a porcelain fused Ni Cr alloy fixed bridge using the University of California Los Angeles type abutment, which was used to splint the tuberosity implant with a nontuberosity implant in the maxilla.

3 1340 TUBEROSITY BONE FIXTURE SURVIVAL MEASUREMENT OF MOBILITY OF FIXTURE The mobility of all tuberosity implants except that in patient 5, who had a commentated fixed bridge with a natural second premolar crown, was measured on manipulation by removing the implant bridge during the same visit as the final panoramic x-ray. MEASUREMENT OF MARGINAL BONE LEVEL OF FIXTURE The marginal bone level of the fixtures for the tuberosity-installed area was evaluated after prosthesis by digital panorama with a distance measuring program (Starpacs, Infinitt, Seoul, Korea) using the panoramic view (Figs 1, 2); panoramic radiography was used because the length and angulation of the tuberosity implant did not permit use of the standardized periapical method. Marginal bone levels in relation to the fixture abutment junction were measured during the final panoramic x-ray. SURVIVAL RATE Kaplan-Meier analysis was performed to determine the cumulative implant survival rate at the current stage of the study. FIGURE 2. Two implants were placed in the right posterior maxilla, one in the tuberosity region and the other in the first molar region, and splinted with a ceramometal fixed bridge. Results In total, 17 implants were placed in the posterior maxillary area of 7 patients (5 female and 2 male) 43 to 65 years of age (average years), for whom 7 prostheses were fabricated. Of these, 7 implants were placed in the pterygomaxillary site, and the fixed bridges were connected after an undisturbed healing period of about 6 months. The bone-anchored prostheses were fabricated using porcelain fused to Ni Cr alloy. The mean number of implants per restoration was 2.7 (range, 2 to 3). All prostheses were free-standing except 1, which was connected to a natural tooth (patient 5). No fixtures in the tuberosity installed group failed during the 1 to 7 years after installation (Table 2). The marginal bone level around the implants on the maxillary tuberosity at 1 to 6 years after the final prosthesis loading was 0.6 to 1.18 mm. The mean value of the marginal bone level of the tuberosity installed group was 0.93 mm. For the tuberosity implants, no radiolucency of the periapical and peri-implant regions was found (Table 3). REPORTS OF 7 TUBEROSITY IMPLANT CASES FIGURE 1. A, Two implants were placed in the left posterior maxilla, one in the tuberosity region and the other in the area of the first molar. B, The 2 fixtures were splinted with ceramometal restoration. Patient 1 Three implants were placed in the right posterior maxilla, with 1 in the tuberosity region, another in the autogenous bone grafted area of the second molar area, and a third in the second premolar area. Implants were splinted by a temporary resin bridge for 6 years. These right-side tuberosity implants were not included in the chart analysis because the second fixture was involved in the grafted bone. Two implants were placed in the left posterior maxilla. The first implant was in the pterygomaxillary region and had a diameter (d) of 3.75 mm and a length (l) of 15 mm. The second implant was in the area of the first molar (d 3.75 mm, l 10 mm). The insertion torque of the tuberosity implant was 40

4 PARK AND CHO 1341 Table 2. MARGINAL BONE LOSS OF TUBEROSITY IMPLANTS Marginal Bone Level 1-6 yrs After Final Prostheses (mm) Time Passed Since Prosthesis (yrs) Time Passed Since Installation (yrs) Date of Measurement Time Passed Since Prosthesis to Panorama (yrs) Date of Final Panorama Date Prosthesis Placed Date of Installation Number of Fixtures Placed in Tuberosity Area Number of Fixtures Placed in Nontuberosity Area Number of Implants Age/ Gender Number N1 46/F April 2001 October 2001 May September N2 43/F August 2003 February 2004 January September N3 65/F May 2004 November 2004 October September N4 49/F June 2004 December 2004 August September N5 63/M September 2004 March 2005 February September N6 57/M September 2005 March 2006 April September N7 43/F March 2007 October 2007 February September Total Average N-cm without any tapping or countersinking (Fig 1A). In 2007, the 2 fixtures were splinted with a ceramometal restoration. Just mesial of the second fixture, a fixture was found that migrated into the sinus, but there were no symptoms (Fig 1B). Patient 2 Two implants were placed in the right posterior maxilla, 1 in the tuberosity region (d 4 mm, l 13 mm) and the other in the first molar region (d 4 mm, l 13 mm), and splinted with the ceramometal fixed bridge. The insertion torque of tuberosity implant was 30 N-cm without any tapping or countersinking (Fig 2). Patient 3 Three implants were placed in the right posterior maxilla, with 1 in the tuberosity region (d 3.75 mm, l 11.5 mm). The second implant was in the first molar region (d 3.75 mm, l 11.5 mm). The third implant was in the second premolar region (d 3.75 mm, l 11.5 mm), and splinted with a ceramometal fixed bridge. The insertion torque of tuberosity implant was 35 N-cm without any tapping or countersinking (Fig 3). Patient 4 Two implants were placed in the left maxilla, 1 in the tuberosity region (d 3.75 mm, l 13 mm) and the other in the first molar region (d 3.75 mm, l 10 mm), and splinted with a ceramometal fixed bridge. The insertion torque of the tuberosity implant was 30 N-cm without any tapping or countersinking (Fig 4). Patient 5 Two implants were placed in the left posterior maxilla, 1 in the tuberosity region (d 3.75 mm, l 11.5 mm) and the other in the first molar region (d 3.75 mm, l 11.5 mm), and splinted with the second premolar natural tooth by a ceramometal 5-unit fixed bridge. The insertion torque of the tuberosity implant was 35 N-cm without any tapping or countersinking (Fig 5A). After splinting with a ceramometal fixed bridge, which was connected to the natural tooth, 3 years 9 months later, only the first screw level of marginal bone loss (0.6 mm) was detected (Fig 5B). Patient 6 Three implants were placed in the right posterior maxilla, with 1 in the tuberosity region (d 4 mm, l 11.5 mm) and the other 2 implants in the first molar region at the distal side (d 4 mm, l 15 mm) and the mesial side (d 4 mm, l 13 mm), and splinted with a ceramometal fixed bridge, which had mesial cantilevered pontics. The left tuberosity implant was kept, and a lower implant supported over

5 1342 TUBEROSITY BONE FIXTURE SURVIVAL Table 3. FIXTURE MOBILITY, IMPLANT LENGTH, DIAMETER, AND CHARACTERISTICS OF RADIOGRAPHY AND PROSTHESIS MOBILITY FOR TUBEROSITY-INSTALLED IMPLANT Number Age/Gender Fixture Mobility Implant Diameter Implant Length Radiolucency Around Fixture Radiolucency at Apex Fixture Prosthesis Mobility N1 46/F No No No No N2 43/F No 4 13 No No No N3 65/F No No No No N4 49/F No No No No N5 63/M No No No No N6 57/M No No No No N7 43/F No No No No Total 7 Average the denture was placed. The insertion torque of the tuberosity implant was 40 N-cm without any tapping or countersinking (Fig 6). Patient 7 Three implants were placed in the left maxilla, with 1 in the tuberosity region (d 3.75 mm, l 13 mm), the second in the first molar region (d 3.75 mm, l 8 mm), and the third in the second premolar region (d 3.75 mm, l 13 mm), and splinted with a ceramometal fixed bridge. The anterior bridge was removed for screw-loosening check. The insertion torque of the tuberosity implant was 25 N-cm without any tapping or countersinking (Fig 7). Discussion Many investigators have reported varying rates of implant success at the tuberosity area (Table 1). Reiser, 11 using cadaver dissection, investigated whether specific structures that might support implants in the pterygomaxillary region were the tuberosity of maxillary bone, the pyramidal process of the palate, and the pterygoid process of the sphenoid bone. Depending on the tuberosity dimension and quality, if it is adequate, an implant can be placed completely within the tuberosity; if not, implants can be angled and the apex made to engage the pyramidal process of the palate and/or pterygoid process of the sphenoid bone. 12 Bahat, 8,11 Balshi et al, 9 Krekmanov et al, 13 and Aparicio et al 14 reported success rates of 93%, 93.4%, 98%, and 100%, respectively, using tuberosity of the maxillary bone; however, it was not clear if the apices of those implants were located at the cortical bone of pterygoid process of the sphenoid bone or pyramidal process of the palate. Ridell et al 3 reported good survival rate for tuberosity implant using soft bone. This case study confirmed several prerequisites for a high success rate. 1. Firm primary stability should be obtained using a smaller drill and no pretapping Enough healing time for maturation of host bone (6 to 8 months). 3,14 FIGURE 3. Three implants were placed in the right posterior maxilla, one in the tuberosity region and the others in the first molar and second premolar regions, and splinted with a ceramometal fixed bridge. FIGURE 4. Two implants were placed in the left maxilla, one in the tuberosity region and the other in the first molar region, and splinted with a ceramometal fixed bridge.

6 PARK AND CHO 1343 FIGURE 7. Three implants were placed in the left maxilla, one in the tuberosity region, the other 2 were in the first molar and second premolar regions, and splinted with a ceramometal fixed bridge. The anterior bridge was removed for screw-loosening check. FIGURE 5. A, Two implants were placed in the left posterior maxilla, one in the tuberosity region, the other in the first molar region, and splinted with the second natural premolar with a ceramometal 5-unit fixed bridge. B, After splinting with the ceramometal fixed bridge, which was connected to a natural tooth, 3 years 9 months later, only the first screw level of marginal bone loss (0.6 mm) was detected. 3. An implant diameter larger than 4 mm and length longer than 13 mm is recommended The nearby natural tooth should be free of any pathogens especially including periodontal lesions. FIGURE 6. Three implants were placed in the right posterior maxilla, one in the tuberosity region, the other 2 implants in the first molar region, and splinted with a ceramometal fixed bridge. The left tuberosity implant was kept and a lower implant supported over the denture was placed. The limitation of this study is that these case reports consist of only the unilateral partially edentulous cases, which have a short span. It is necessary to compare these with the long span of fully edentulous cases using tuberosity implants, especially bilaterally. The span of a splinted bridge could influence the success rate of tuberosity implantation, although many investigators have reported a high success rate. 3,8 References 1. Keller EE, van Roekel NB, Desjardins RP, et al: Prosthetic-surgical reconstruction of the severely resorbed maxilla with iliac bone grafting and tissue-integrated prostheses. Int J Oral Maxillofac Implants 2:155, Kahnberg KE, Nilsson P, Rasmusson L: Le Fort I osteotomy with interpositional bone grafts and implants for rehabilitation of the severely resorbed maxilla: A 2-stage procedure. Int J Oral Maxillofac Implants 14:571, Ridell A, Gröndahl K, Sennerby L: Placement of Brånemark implants in the maxillary tuber region: Anatomical considerations, surgical technique and long-term results. Clin Oral Implants Res 20:94, Tulasne JF: Osseointegrated fixtures in the pterygoid region, in Worthington P, Brånemark P-I (eds): Advanced Osseointegration Surgery: Applications in the Maxillofacial Region. Chicago, Quintessence, 1992, p Krogh PHJ: Anatomic and surgical considerations in the use of osseointegrated implants in the posterior maxilla. Oral Maxillofac Surg Clin North Am 3:853, Graves S: The pterygoid plate implant: A solution for restoring the posterior maxilla. Int J Periodontics Restorative Dent 14: 513, Khayat P, Nader N: The use of osseointegrated implants in the maxillary tuberosity. Pract Periodontics Aesthet Dent 6:53, Bahat O: Osseointegrated implants in the maxillary tuberosity: Report of 45 consecutive patients. Int J Oral Maxillofac Implants 7:459, Balshi TJ, Lee HY, Hernandez R: The use of pterygomaxillary implants in the partially edentulous patient: A preliminary report. Int J Oral Maxillofac Implants 10:89, 1995

7 1344 TUBEROSITY BONE FIXTURE SURVIVAL 10. Balshi TJ, Wolfinger GJ, Balshi SF: Analysis of 356 pterygomaxillary implants in edentulous arches for fixed prosthesis anchorage. Int J Oral Maxillofac Implants 14:398, Bahat O: Brånemark system implants in the posterior maxilla: Clinical study of 660 implants followed for 5 to 12 years. Int J Oral Maxillofac Implants 15:646, Reiser GM: Implant use in the tuberosity, pterygoid, and palatine region: Anatomic and surgical considerations, in Nevins M, Mellonig JT (eds): Implant Therapy: Clinical Approaches and Evidence of Success. Vol 2. Chicago, Quintessence, 1998, p Krekmanov L, Kahn M, Rangert B, et al: Tilting of posterior mandibular and maxillary implants for improved prosthesis support. Int J Oral Maxillofac Implants 15:405, Aparicio C, Perales P, Rangert B: Tilted implants as an alternative to maxillary sinus grafting: A clinical, radiologic, and Periotest study. Clin Implant Dent Relat Res 3:39, Langer B, Langer L, Harman I, et al: The wide fixture: A solution for special bone situations and a rescue for the compromised implant. Int J Oral Maxillofac Implants 8:400, 1993