ARTICLE IN PRESS J Oral Maxillofac Surg xx:xxx, 2010
Immediate and Delayed Lateral Ridge Expansion Technique in the Atrophic Posterior Mandibular Ridge Dong-Seok Sohn, DDS, PhD,* Hyun-Jin Lee, DDS,† Jeung-Uk Heo, DDS, PhD,‡ Jee-Won Moon, DDS,§ In-Suk Park, DDS, PhD,储 and Georgios E. Romanos, DDS, Dr Med Dent, PhD¶ Purpose: The lateral ridge expansion technique is used to expand the narrow edentulous ridge for
implant placement. The staged approach can be used to split the mandibular ridge to decrease the risk of malfracture during osteotomy. The present study reports the clinical results of a surgical technique that expands a narrow mandibular ridge using an immediate and a delayed lateral expansion technique. Materials and Methods: A total of 32 patients with a narrow edentulous posterior mandibular ridge of 2 to 4 mm were included in the present study, and 84 implants were placed. Of the 32 patients, 23 were treated with an immediate lateral expansion technique and 9 with a delayed lateral expansion technique. Results: Of the 23 patients who underwent the immediate lateral expansion technique, a malfracture of the thin buccal cortical plate occurred during ridge splitting in 5 patients. All buccal segments of the 9 patients who underwent the delayed lateral expansion technique fractured as planned at the inferior horizontal corticotomy line favorably. After 4 to 5 months, all implants were stable and surrounded by bone, and ossification of the osteotomy line was obvious. Conclusions: The lateral ridge expansion technique is effective for horizontal augmentation in the severely atrophic posterior mandibular ridge. The delayed lateral ridge expansion technique can be used more safely and predictably in patients with high bone quality and thick cortex and a narrower ridge in the mandible. © 2010 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg xx:xxx, 2010 cluded onlay block bone grafting,1-3 guided bone regeneration,4-6 ridge split technique/ridge expansion,7-10 and distraction osteogenesis.11,12 The lateral ridge expansion technique is aimed at the creation of a new implant bed by longitudinal osteot-
The management of the atrophic posterior mandibular ridge is a common problem in implant dentistry. Numerous surgical techniques have been described for augmentation of the atrophic mandibular alveolar ridge. The strategies used to overcome this have in*Chairman and Professor, Department of Dentistry and Oral and Maxillofacial Surgery, Catholic University Hospital of Daegu, Daegu, Republic of Korea. †Clinical Instructor, Department of Dentistry and Oral and Maxillofacial Surgery, Catholic University of Daegu, Daegu, Republic of Korea. ‡Private Practice, GoodWill Dental Clinic, Busan, Republic of Korea. §Clinical Instructor, Department of Dentistry and Oral and Maxillofacial Surgery, Catholic University of Daegu, Daegu, Republic of Korea. 储Clinical Instructor, Department of Dentistry and Oral and Maxillofacial Surgery, Catholic University of Daegu, Daegu, Republic of Korea.
¶Professor, Division of Periodontology, Eastman Dental Center, University of Rochester, Rochester, NY. Address correspondence and reprint requests to Dr Sohn: Department of Oral and Maxillofacial Surgery, Catholic University Hospital of Daegu, 3056-6 Daemyung-4 Dong, Namgu, Daegu, Republic of Korea; e-mail:
[email protected] © 2010 American Association of Oral and Maxillofacial Surgeons
0278-2391/10/xx0x-0$36.00/0 doi:10.1016/j.joms.2010.04.009
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omy of the alveolar bone.13 The buccal cortex is repositioned laterally using a greenstick fracture, and the space between the buccal and lingual cortical plates is filled with autologous,14 allogenic,15 or alloplastic15,16 graft material or without any graft material.8,17 The lateral ridge expansion technique is usually performed simultaneously with implant placement and significantly shortens the treatment time. The lateral ridge expansion technique is more suitable to the maxilla than the mandible owing to the thinner cortical plates and softer medullary bone.18 In the mandible, the risk of malfracture of the osteomized buccal segment is greater because of the lower flexibility and thicker cortical plates.13,18 A staged approach to avoid malfracture in the mandible can also be used.13 The present study reports the clinical results of an immediate and a delayed lateral expansion technique used to expand a narrow mandibular ridge.
plate in depth. A small chisel was used to expand the buccal segmented bone, provoking a greenstick fracture. The chisel was carefully tapped with a mallet, and the buccal segmented plate was slowly dislocated in a buccal direction. After the preparation of the implant sites using twist drills, the implants were placed. Care was taken to avoid penetration of the sublingual plate. Each split area received 2 or 4 implants. Varying size bone grafts were grafted into the gap between the expanded plate and the lingual plate and varying resorbable barriers covered the augmented areas. They were used to coat the implants and fill the residual space created after replacement of the split window. Adjunctive material was not used in all cases. Tension-free soft tissue closure was performed over the implants using 4-0 or 5-0 nonresorbable sutures in all cases. After 4 to 5 months of healing, the implants were exposed.
Materials and Methods A total of 32 patients (5 men and 27 women, with a mean age of 48 years) with an edentulous atrophic posterior mandibular ridge were included in the present study, and 84 tapered screw type implants were placed. Of the 32 patients, 23 were treated with the immediate lateral expansion technique and 9 were treated with the delayed lateral expansion technique. These patients had a buccolingual ridge dimension ranging from 2 to 4 mm that was inadequate to allow the placement of dental implants but had adequate bone height. IMMEDIATE LATERAL EXPANSION TECHNIQUE
After administration of local anesthesia, 1 incision was made along the ridge crest slightly toward the lingual side and 2 vertical incisions were made (Figs 1A-F). A full-thickness mucoperiosteal flap was elevated to expose the buccal aspect of mandibular alveolar ridge. The lingual flap was minimally raised to maintain the blood supply to the bone. Rectangular corticotomies were made using the piezoelectric saw (SurgyBone, Silfradent, Sofia, Italy) or erbium:yttriumaluminum-garnet laser (Dual Laser; Lambda Scientifica, Altavilla Vicentina, Italy). The laser parameters were set at a power of 6 W, with a frequency of 20 Hz. A crestal horizontal corticotomy was started 1 to 2 mm away from the adjacent tooth. The length of the horizontal cut was determined, considering the number of implants and the space between the implants. Two vertical corticotomies were created on the buccal cortical plate, and the height of the vertical corticotomies was approximately one half length compared with the length of the implant to be placed. All corticotomies were performed to reach the lingual
DELAYED LATERAL EXPANSION TECHNIQUE
The delayed lateral expansion technique was applied to the ridges with a dense and thick cortex because the expansion could be caused by fracture of the expanded buccal segment. After administration of local anesthesia, an incision was made along the ridge crest slightly toward the lingual side, and 2 vertical incisions were made (Figs 2A-F). A full-thickness mucoperiosteal flap was elevated to expose the buccal aspect of the mandibular alveolar ridge. After completing the rectangular corticotomies with a piezoelectric saw or erbium:yttriumaluminum-garnet laser, greenstick fractures were created in the buccal segments. The greenstick fractured buccal segments were repositioned, and the mucoperiosteal flap was sutured. After the primary surgery, a 3- to 4-week healing period was allowed before performing delayed ridge expansion and implant placement as second-stage surgery. A crestal incision to expose the crestal cut was performed. The buccal flap had to be minimally reflected to preserve the blood supply for the buccal cortical plate. Also, a small chisel was used to carefully separate and mobilize the segmented bone, provoking a greenstick fracture. The blood supply on the buccal aspect of the displaced buccal plate was maintained. After preparation of the implant sites using twist drills and osteotomes, the implants were placed and bone graft augmentation was performed. Adjunctive material was not used in all cases. Tension-free soft tissue closure was achieved in all cases. After 3 to 4 months, the third phase of surgical exposure to change the cover screw to a healing abutment was performed.
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FIGURE 1. Immediate lateral expansion technique (from patient 19). A, B, Rectangular corticotomies were made using a piezoelectric saw. C, D, After expanding buccal segmented bone using a small chisel, 2 implants were placed on the split ridge, and the intercortical space was filled with mixed bone of allograft and xenograft. E(a), Preoperative cone-beam computed tomography scans. E(b), Postoperative cone-beam computed tomography scans. E(c), Follow-up cone-beam computed tomography scans after the 5-month healing period (implant corresponding to the left mandibular first molar). F(a), Preoperative cone-beam computed tomography scans. F(b), Postoperative cone-beam computed tomography scans. F(c), Follow-up cone-beam computed tomography scans after the 5-month healing period (implant corresponding to the left mandibular second premolar). G(a), Postoperative panoramic view. G(b), Follow-up panoramic view after 3 months of prosthetic loading. G(c), Follow-up panoramic view after 6 months of prosthetic loading. Sohn et al. Immediate and Delayed Lateral Ridge Expansion Technique. J Oral Maxillofac Surg 2010.
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FIGURE 2. Delayed lateral expansion technique (from patient 7). A, After reflecting buccal mucoperiosteal flap, rectangular corticotomies were made using a piezoelectric saw. The mucoperiosteal flap was repositioned and closed with nonresorbable sutures. B, Delayed lateral expansion was performed 3 weeks after corticotomies. The buccal flap was minimally reflected to preserve blood supply for buccal cortical plates. C, D, Two implants were placed, and the intercortical space was filled with particulate bone grafting material. E(a), Preoperative cone-beam computed tomography scans. E(b), Postoperative cone-beam computed tomography scans. E(c), Follow-up cone-beam computed tomography scans after 6-month healing period (implant corresponding to the right mandibular first molar). F(a), Preoperative cone-beam computed tomography scans. F(b), Postoperative cone-beam computed tomography scans. F(c), Follow-up cone-beam computed tomography scans after 6-month healing period (implant corresponding to the right mandibular second molar). G(a), Postoperative panoramic view. G(b), Follow-up panoramic view after 3 months of prosthetic loading. G(c), Follow-up panoramic view after 8 months of prosthetic loading. Sohn et al. Immediate and Delayed Lateral Ridge Expansion Technique. J Oral Maxillofac Surg 2010.
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Results A total of 32 patients with a narrow edentulous posterior mandibular ridge of 2 to 4 mm were included in the present study, and 84 implants were placed. Of the 84 implants, 63 were placed using the immediate lateral expansion technique and 21 were placed using the delayed lateral expansion technique. Of the 23 patients who underwent the immediate lateral expansion technique, malfracture of the thin buccal cortical plate occurred during ridge splitting in 5 patients. Of the 5 malfractured buccal plates, 1 was fixed with a microscrew and 4 were repositioned in place after placing the implants. All buccal segments of the 9 patients who underwent the delayed lateral expansion technique fractured as planned at the inferior horizontal corticotomy line favorably, leaving the buccal periosteum attached to the buccal segmented bone. The soft tissue healing was uneventful. None of the patients complained of paresthesia. The criteria of Buser et al19 were used to evaluate the osseointegration of the implants. The postoperative results were assessed using panoramic and periapical radiographs. After 4 to 5 months, all implants, except for 1 case, were stable and were surrounded by bone, and ossification of the osteotomy line was obvious. In 1 patient (patient 23) who underwent the immediate lateral ridge expansion technique, buccal bone resorption was found at the second procedure (Fig 3). The sec-
FIGURE 3. Buccal bone resorption found at second procedure in patient 23. Sohn et al. Immediate and Delayed Lateral Ridge Expansion Technique. J Oral Maxillofac Surg 2010.
ondary bone graft was performed. Fixed partial prostheses were successful in all cases. The adjacent implants were splinted. The average time to prosthetic loading was 17 months (Tables 1, 2).
Discussion The lateral ridge expansion technique is useful for managing the narrow edentulous ridge for implant placement. Careful expansion of the buccal plate is essential when the lateral expansion technique is used because abnormal bone healing can result from undue trauma to the plate. In 1992, Simion et al7 introduced a split-crest technique. The surgical technique involved splitting the alveolar ridge longitudinally in 2 parts, provoking a longitudinal greenstick fracture at the top of the bone to create a space-making defect. The created selfspacing anatomy prevented the membrane from collapsing into the defect and augmented the surface from which the osteogenic cells could be recruited. This technique was indicated when a standard osteotomy could not be created because of a crest width of 4 mm or less.7 In 1994, Scipioni et al8 presented the clinical results of an edentulous ridge expansion technique. They placed 329 implants in 170 patients. They had a success rate of 98.8%. Scipioni et al8 suggested that wherever dental implants are placed, a minimal thickness of 1 to 1.5 mm of bone should remain on both the buccal and the lingual/palatal aspects of the implants to ensure a successful outcome. This technique requires at least 3 to 4 mm of ridge width and can be extremely difficult or impossible to perform if the remaining bone is primarily cortical because of the risk of fracturing the expanding plates of bone and of being unable to stabilize the implant sufficiently to ensure predictable osseointegration.8,9 Sethi and Kaus10 reported the technique of maxillary expansion with simultaneous implant placement. They placed 449 implants in 150 patients in thin maxillary ridges of adequate height and comprising 2 separate cortical plates with intervening cancellous bone and observed them for a period of up to 93 months. A 97% implant survival rate after a 5-year observation period was found. In the ridge splitting procedure, the corticotomies can be performed using a No. 15 blade, Beaver blade, razor-sharp chisel, round bur, fissure bur, diamond disk, reciprocal saw, or piezoelectric device. On lowdensity bone such as the maxilla, the blade or razorsharp chisel can be efficient; however, on high-density bone such as the mandible, the rotary bur, diamond disk, piezoelectric device, or laser (erbium: yttrium-aluminum-garnet, erbium, chromium-doped: yttrium-scandium-gallium-garnet) is recommended.
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Table 1. IMMEDIATE LATERAL EXPANSION
Pt No.
Gender/Age (yr)
1
F/71
2
F/53
3
F/60
4 5
F/35 M/49
6
F/62
7
F/42
8 9
F/53 F/52
10
F/38
11
F/34
12
M/54
13
F/59
14
F/30
15
F/32
16 17
F/27 F/55
18
F/66
19
F/46
20
F/55
21
F/60
22 23
M/26 F/50
Site Left mandibular second premolar and first molar Left mandibular first premolar, second premolar, and first molar Left mandibular second premolar, first molar, and second molar Right mandibular first molar Left mandibular first molar and second molar Left mandibular first molar and second molar, right mandibular first premolar, first molar, and second molar Right mandibular first molar and second molar Left second premolar and first molar Left mandibular first premolar, first molar and second molar, right mandibular first molar, and second molar Left mandibular first molar and second molar Left mandibular second premolar and first molar, right mandibular first molar and second molar Right mandibular first molar and second molar Right mandibular second premolar, first molar, and second molar Right mandibular second premolar and first molar Right mandibular second premolar, first molar, and second molar Right mandibular first molar Left mandibular second premolar, first molar, and second molar Left mandibular second premolar and first molar Left mandibular second premolar and first molar Left mandibular first molar and second molar Left mandibular first premolar, first molar and second molar, right mandibular second premolar, first molar, and second molar Left mandibular first molar Left mandibular first molar and second molar
Mean Implant Diameter
Osteotomy Device
Prosthetic Loading (mo)
4.2
Piezoelectric saw
44
3.6
Piezoelectric saw
41
3.5
Piezoelectric saw
38
3.9 4.3
Piezoelectric saw Piezoelectric saw
34 26
3.97
Piezoelectric saw
26
4.3
Er:YAG laser
24
4.4 4.1
Er:YAG laser Piezoelectric saw
22 22
3.9
Piezoelectric saw
21
3.8
Piezoelectric saw
18
3.7
Piezoelectric saw
17
3.7
Er:YAG laser
15
4.8
Er:YAG laser
12
4.57
10
5.0 4.0
Er:YAG laser and piezoelectric saw Piezoelectric saw Piezoelectric saw
5.0
Er:YAG laser
8
4.0
Piezoelectric saw
6
4.0
Er:YAG laser and piezoelectric saw Er:YAG laser and piezoelectric saw
6
4.1
4.0 4.1
Piezoelectric saw Er:YAG laser and piezoelectric saw
10 8
6
5 4
Abbreviations: Pt No., patient number; F, female; M, male; Er:YAG, erbium:yttrium-aluminum-garnet. Sohn et al. Immediate and Delayed Lateral Ridge Expansion Technique. J Oral Maxillofac Surg 2010.
The piezoelectric saw is safer and more precise than the conventional rotary bur or reciprocal saw when performing osteotomies. In the present clinical report, a piezoelectric surgery system or erbium: yttrium-aluminum-garnet laser was used to create the vertical and horizontal corticotomies. Piezoelectric devices use ultrasonic microvibrations to create an osteotomy, and these microvibrations make selective
bone cuts possible without soft tissue damage.20-22 Moreover, more precise cuts can be performed and a severely narrow ridge of 2 to 3 mm can be osteotomized.22 The erbium:yttrium-aluminum-garnet laser allows increased hemostasis, improved visibility during surgery, a reduced incidence of infection, and reduced patient discomfort postoperatively when applied to soft and hard tissue.23
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Table 2. DELAYED LATERAL EXPANSION
Pt No.
Gender/Age (yr)
1
F/52
2 3
F/44 F/25
4
M/40
5
F/57
6 7
F/44 F/48
8
M/57
9
F/53
Site Left mandibular second premolar, first molar, and second molar Right mandibular first molar and second molar Left mandibular second premolar, first molar, and second molar Left mandibular first molar and second molar Right mandibular first molar Right mandibular and second molar Left mandibular second premolar, first molar, and second molar Left mandibular second premolar, first molar, and second molar
Mean Implant Diameter
Osteotomy Device
Prosthetic Loading (mo)
4.0
Piezoelectric saw
36
3.8 5.0
Piezoelectric saw Laser
36 11
4.47
Er:YAG laser and piezoelectric saw Er:YAG laser
10
4.0 4.0 4.5 4.0 3.77
Piezoelectric saw Er:YAG laser and piezoelectric saw Er:YAG laser and piezoelectric saw Er:YAG laser and piezoelectric saw
10 8 8 7 3
Abbreviations as in Table 1. Sohn et al. Immediate and Delayed Lateral Ridge Expansion Technique. J Oral Maxillofac Surg 2010.
The lateral ridge expansion technique with simultaneous immediate implant placement is usually performed because it shortens the total treatment time.7,10,24-26 However, in the mandible, the risk of malfracture of the osteomized segment is great because the mandibular bone has less flexibility and a thicker cortical plate. Ridge expansion with simultaneous implant placement has resulted in several complications such as a lack of initial stability for the implants, fracture of the buccal segmented bone, and compromised implant placement in the buccolingual and apicocoronal direction. Enislidis et al13 and Elian et al27 recommended a staged approach to avoid postoperative complications from malfracture of the buccal segment. Although a 2-stage approach increases the time, it also allows for subsequent evaluation of the expanded ridge and the avoidance of complications. With this approach, the location of the greenstick fracture is predetermined, and perfusion for the buccal segment remains intact. In the present study, bone grafts in the intercortical area were performed and resorbable collagen membranes were used to cover the graft, preventing soft tissue ingrowth into the graft site. Although some clinicians prefer to place particulate bone grafting materials around the implants and in the intercortical space,16,25-28 Scipioni et al8,17 have found that a bone graft is usually unnecessary. However, they used to create a partial thickness flap initially to prevent crestal bone resorption. Simion et al,7 when they introduced the split-crest technique in 1992, used guided tissue regeneration with expanded polytetrafluoroethylene membrane to cover the defect and create a space to allow bone tissue regeneration. In
contrast, Calvo Guirado et al25 believed that the periosteum is the best possible biologic membrane because it contains a rich supply of osteogenic cells. In the present clinical study, we used a tapered screwtype implant to increase the initial stability and prevent buccal bone segment fracture. Brunski29 reported that screw-shaped implants provided the strongest retention immediately after implant placement. Kan et al30 reported a notably greater implant survival rate for threaded implants (titanium 94.9%; HA-coated 96.0%) than for nonthreaded implants (HAcoated 75.4%). The lateral ridge expansion technique is very effective for horizontal augmentations in severely atrophic posterior mandibular ridges. In the mandibular ridge, which has low bone quality and a thin cortex, immediate lateral ridge expansion can be a useful procedure. Delayed lateral ridge expansion can be used more safely and predictably in patients with high bone quality and a thick cortex and narrower ridge in the mandible to avoid complete fracture of the buccal segments. In addition, delayed ridge expansion is recommended when the initial stability of the implants is poor.
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