Delayed Expansion of the Atrophic Mandible by Ultrasonic Surgery: A Clinical and Histologic Case Series Antonio Scarano, DDS, MD1/Adriano Piattelli, MD, DDS2/Giovanna Murmura, MD, DDS3/ Giovanna Iezzi, DDS, PhD3/Bartolomeo Assenza, MD4/Carlo Mancino, DDS5 Purpose: Ridge expansion is used to widen narrow ridges with adequate height for implant placement. This human case series presents the clinical and histologic results of delayed expansion of mandibles by ultrasonic surgery. Materials and Methods: Patients with residual alveolar ridge width between 2.3 and 4.1 mm in the coronal area of the posterior mandible were included in the study. First, four linear corticotomies were carried out by ultrasonic surgical device. Four weeks later, adequate bone expansion with a combination of scalpels, thin chisels, and threaded osteotomes that did not compromise cortical vascularization was performed, and two implants per ridge were inserted. Any gaps were filled with corticospongious porcine biomaterial. Three months after implant placement, healing caps were inserted, and bone cores were harvested from the regenerated areas for histologic analysis. Crestal width was recorded at each surgery. Results: The postoperative course was uneventful in all 32 patients (64 implants) who took part in the study, and the implant success rate was 96.88% at 3 months. The mean increase in ridge width was 5.17 ± 0.86 mm. The histologic specimens showed a mixture of new bone and particles of biomaterial, as well as newly formed bone. Histomorphometry demonstrated that 64% ± 3.1% of the specimen was composed of newly formed bone, 8% ± 0.8% was made up of marrow spaces, and 27% ± 2.6% comprised the residual grafted biomaterial. Conclusion: This study showed that mandibular ridge expansion using a delayed splitcrest technique by means of ultrasonic surgery and association with biomaterial led to good horizontal bone gain, with no fractures of the buccal plate, and a high implant success rate. The histologic specimens showed newly formed bone and good integration of the biomaterial. Int J Oral Maxillofac Implants 2015;30:144–149. doi: 10.11607/jomi.2753 Key words: alveolar bone loss, alveolar ridge augmentation, bone regeneration, bone resorption, piezosurgery
O
ne of the most common anatomical limitations in implant dentistry is atrophy of the alveolar bone.1,2 Patients with long-standing edentulous arches may have narrow, knife-edged ridge crests with changing angulations that make endosseous implant placement difficult and carry a risk of fenestrations or dehiscence of the cortical layers.1,2 Alterations in normal anatomical features may cause intraoperative and
1 Associate
Professor, Dental School, University of ChietiPescara, Chieti, Italy. 2Professor of Oral Pathology and Medicine, Dental School, University of Chieti-Pescara, Chieti, Italy. 3Researcher, Dental School, University of Chieti-Pescara, Chieti, Italy. 4Private Practice, Milano, Italy. 5Research Fellow, University of Chieti-Pescara, Chieti, Italy. Correspondence to: Dr Antonio Scarano, Via Dei Frentani 98/B, 66100 Chieti, Italy. Fax: +39-0871-3554099. Email: [email protected] ©2015 by Quintessence Publishing Co Inc.
postoperative difficulties, such as inadequate bone support on the lingual and buccal sides of an implant and therefore faulty implant placement.3,4 Bone expansion in oral surgery consists of expanding the atrophic bone crest to obtain sufficient bone width for proper dental implant placement.1 To achieve this, different regenerative surgical techniques have been developed: conventional onlay/inlay grafts, interpositional sandwich osteotomies, guided bone regeneration with semipermeable membranes, piezoelectric stimulation, and alveolar distraction osteogenesis. All these procedures can be used for alveolar ridge augmentation in the posterior mandible with autologous or homologous bone grafts, xenografts, or bone substitutes to allow implant placement in one or two surgical steps.5 One of the most predictable regenerative techniques to increase the volume of buccal bone is sagittal osteotomy of the ridge.6–8 This technique has been reported to have a very high success rate (98% to 100%) and to show minimal volumetric contraction in the long term, since the buccal bone is maintained
144 Volume 30, Number 1, 2015 © 2015 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
Scarano et al
Fig 1 Intraoral view before treatment. Note the osseous atrophy.
Fig 2 Computed tomographic image showing alveolar width deficit in the area of the right premolars and first molar.
Fig 3 Following a crestal incision with vestibular release incisions and elevation of a mucoperiosteal flap, the thin residual ridge could be clearly seen. A sagittal corticotomy in the coronal area of the alveolar crest with ultrasonic surgery was performed.
Fig 4 A distal vertical corticotomy was performed in the buccal wall.
in situ and provided with both endosteal and periosteal blood vessels, limiting secondary resorption. In the maxilla, slight separation of the ridge crest is performed as a hingelike separation of the buccal cortex. It is difficult to achieve the same hingelike separation in the posterior mandible because of its compact outer cortex and external oblique line.9 The aim of the present case series was to evaluate, clinically and histologically, delayed expansion of the mandible by ultrasonic surgery in humans.
premolar or molar areas with residual alveolar ridge width between 2.3 and 4.1 mm (Figs 1 and 2), as measured by an outside caliper (distance between the outer surfaces of the buccal and palatal bone walls, 1 mm apical to the alveolar crest).10 Those with severe illness, a history of head and neck radiation therapy, chemotherapy, uncontrolled diabetes, uncontrolled periodontal disease, and smoking were excluded from participation.
MATERIALS AND METHODS Study Design
All participating patients were scheduled for bone reconstruction procedures, including crest expansion and implant insertion. The protocol of the study was approved by the Ethics Committee of the University of Chieti-Pescara, Chieti, Italy, and all patients provided written informed consent. The inclusion criteria were: complete or partial edentulism in the mandibular
Surgical Procedures
Prior to surgery, the patients’ mouths were rinsed with chlorhexidine digluconate solution (0.2% for 2 minutes). Local anesthesia was obtained with articaine associated with epinephrine (1:100,000; Ubistesin 4%, Espe Dental). In the first surgery, four linear corticotomies were created with an ultrasonic surgical device (Surgysonic, Esacrom). A sagittal corticotomy was made in the coronal area (Fig 3) of the mandibular alveolar crest, two vertical corticotomies were made in the buccal wall (Fig 4) after a supracrestal incision and elevation of a buccal mucoperiosteal flap, and a The International Journal of Oral & Maxillofacial Implants 145
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Scarano et al
Fig 5 A sagittal corticotomy, lower (basally) in the buccal wall, was performed.
Fig 6 Second surgery 4 weeks later. The desired crest expansion was achieved by using a combination of scalpels, thin chisels, and threaded osteotomes without compromising cortical vascularization; it was possible to see the crest widening with the osteotomes.
sagittal corticotomy was made 2 to 3 mm above the mandibular canal (Fig 5). Bone expansion was not performed at this stage to prevent the possible loss of the blood supply to the osteotomized segment caused by the reflection of a full-thickness mucoperiosteal flap. The wound was closed with interrupted sutures (Vicryl 4.0, Ethicon FS-2). Four weeks later, a second surgery was carried out. This consisted of adequate bone expansion, which did not compromise cortical vascularization, with a combination of scalpels, thin chisels, and threaded osteotomes (Bone System) (Fig 6). Limited reflection of a soft tissue flap to maintain the blood supply to the buccal bone and a sequential introduction of osteotomes with increasing diameters were performed. The osteotomes were used to enable safe, controlled widening of the mandibular crest to permit implant placement. The ridge width was measured at baseline, before the first surgery, and after the second surgery. Two submerged implants (Bone System) for ridge were inserted in the premolar and molar areas (Fig 7) after the gaps were filled with corticospongious porcine biomaterial (OsteoBiol Gen-Os, Tecnoss). The implant osteotomies were created with an ultrasonic surgery device and a final conventional drill sequence appropriate to the size of the implant. Implants were inserted with a mechanical system initially, and insertion was completed with a manual wrench. Primary stability was evaluated manually, and all implants had insertion torque greater than 25 N/cm. The flaps were closed carefully with interrupted sutures (Vicryl 4.0, Ethicon FS-2). Periapical radiographs were taken after implant insertion to verify appropriate implant positioning. After surgery, amoxicillin (500 mg; one capsule every 8 hours for 7 days) and ibuprofen (600 mg as needed) were prescribed. Patients were not allowed to wear their removable dentures until implant uncovering (at
Fig 7 The implants have been placed, with the grafting material filling the gaps.
3 months). The postsurgical instructions included a soft diet for 2 weeks and appropriate oral hygiene, including twice-daily rinsing with 0.2% chlorhexidine digluconate mouthwash (Parodontax, GlaxoSmithKline). Clinical and radiographic follow-up was performed 1 month after surgery and again after 3 months, at which time healing screws were applied and bone cores were harvested from the augmented ridge.
Histologic Processing
A bone trephine with an internal diameter of 2 mm was used to retrieve bone samples from the regenerated area between the two implants. One specimen per patient was obtained. The specimens were then immediately stored in 10% buffered formalin and processed to obtain thin ground sections (Precise 1 Automated System, Assing).11 The specimens were dehydrated in a graded series of ethanol rinses and embedded in glycol methacrylate resin (Technovit 7200 VLC, Kulzer). After polymerization, the specimens were sectioned longitudinally with a high-precision diamond disk at approximately 150 µm and ground down to approximately 30 µm with a specially designed grinding machine (Precise 1 Automated System, Assing). Three slides were obtained from each specimen. These slides were stained with acid fuchsin and toluidine blue and examined under transmitted light (Leitz Laborlux). Histomorphometric analysis to determine the percentages of newly formed bone, grafted material, and marrow spaces was carried out using a light microscope (Laborlux S, Leitz) connected to a high-resolution video camera (3CCD, JVC KY-F55B, JVC) interfaced to a monitor and computer (Pentium III 1200 MMX, Intel). This optical system was associated with a digitizing pad (Matrix Vision) and a histometry software package with image-capturing capabilities (Image-Pro Plus 4.5, Media Cybernetics/Immagini & Computer).
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Scarano et al
Table 1 Characteristics of the Inserted Implants Implant diameter (mm)
Implant length (mm)
3.5
8.2
4.1
0
8
10
10
15
12
8
8
13.5
6
9
Total
24
40 Fig 8 Three months after implant placement, the intercortical bony gap is filled with new bone.
Table 2 Alveolar Bone Width Measurements in All Patients Patient no.
Presurgical width (mm)
Width at 3 mo after augmentation (mm) 7.1
Mean horizontal increase 4.8
1
2.3
2
3.1
7.5
4.4
3
2.3
7.1
4.8
4
3.1
7.5
4.4
5
3.9
8.2
4.3
6
3.5
8.2
4.7
7
3.7
8.9
5.2
8
2.6
9.2
6.6
9
2.3
9.1
6.8
10
3.1
7.5
4.4
11
3.9
8.2
4.3
12
3.5
10.2
6.7
13
3.5
8.9
5.4
14
2.6
9.2
6.6
15
2.3
7.1
4.8
16
3.1
7.5
4.4
17
3.3
8.2
4.9
18
3.5
9.2
5.7
19
3.7
8.9
5.2
20
2.6
9.2
6.6
21
2.3
7.1
4.8
22
3.1
7.5
4.4
23
4.1
8.2
4.1
24
3.5
8.2
4.7
25
3.7
8.9
5.2
26
2.6
9.2
6.6
27
2.3
7.1
4.8
28
3.1
8.5
5.4
29
3.9
8.2
4.3
30
3.5
8.2
4.7
31
3.7
8.9
5.2
32
2.8
Mean ± SD 3.14 ± 0.57
9.2 8.31 ± 0.83
6.4 5.17 ± 0.86
RESULTS Clinical Outcomes
Thirty-two patients (23 women and 9 men; mean age, 57 years; age range, 53 to 68 years) participated in the study and received 64 implants. The healing process was uneventful for all patients. No lesions to the inferior alveolar nerve were recorded. No dehiscence of the sutures, wound infections, or fracture of the buccal plate was observed in any of the patients. At implant placement, no dehiscence defects or perforations (either vestibularly or apically) occurred, and all implants showed good primary stability. The diameters and lengths of the inserted implants are described in Table 1. After the 3-month healing period, two implants had not osseointegrated (3.12%) and had to be removed; therefore, the implant success rate was 96.88%. Furthermore, ossification of the osteotomy was evidenced by increasing radiopacity on panoramic or periapical radiographs. Clinically, the intercortical bony gap seemed to be filled with newly formed bone (Fig 8). At re-entry, the healed augmented alveolar crest had a mean width of 8.31 ± 0.83 mm. The mean horizontal increase obtained was 5.17 ± 0.86 mm (range, 4.1 to 6.8 mm) (Table 2).
Histologic Findings
No chronic inflammatory cell infiltrate or multinucleated giant cells were seen around the graft or at the biomaterial-bone interface, and no evidence of foreignbody reaction was detected. At low magnification, the histologic specimens showed a mixture of new bone graft and particles of biomaterial, as well as new bone that formed bridges connecting the biomaterial particles (Fig 9). Marrow spaces were present, delimited by the newly formed bone and portions of the grafted material. In some areas, it was possible to observe the presence of detached particles at the periphery of the grafted biomaterial. At higher magnification, newly The International Journal of Oral & Maxillofacial Implants 147
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Scarano et al
Fig 9 Specimen at low magnification. Biomaterial particles are still present in the defect (acid fuchsin–toluidine blue; original magnification ×12).
formed bone was seen in close contact with the particles of biomaterials with no soft tissue interposition (Fig 10). The internal portion of most of the graft particles was infiltrated by biologic fluids and filled with a tissue with the staining characteristics of newly formed bone. In some fields, osteoblasts deposing osteoid matrix were observed. Histomorphometry demonstrated that 64% ± 3.1% of the specimen was composed of newly formed bone, 8% ± 0.8% was marrow spaces, and 27% ± 2.6% was made up of residual biomaterial.
DISCUSSION Narrow edentulous ridges require bone expansion before implant placement. Horizontal bone augmentation is possible using three different procedures: (1) lateral augmentation (eg, guided bone regeneration,12 cortical bone blocks13); (2) interpositional augmentation (crest splitting)14; or (3) distraction osteogenesis.15 The split-crest technique allows the clinician to place implants into anatomical situations with insufficient bone thickness by moving the external cortical plate of the mandible labially to gain an increase in width so that implants of a suitable diameter could be placed. Furthermore, bone augmentation should produce an appropriate bone contour, allowing for implant placement in a proper prosthetically directed position. Mandibular bone has a higher density than maxillary bone and therefore requires a different approach to ridge splitting. In the maxilla, an osteotomy of the crest could be achieved with chisels and without the assistance of surgical burs. A mallet could be used to expand the plates without vertical osteotomy. The posterior mandible is the most difficult region for reconstruction and early implant placement in cases of severe alveolar resorption. The atrophic ridge in this
Fig 10 A specimen at higher magnification. Most of the biomaterial particles are surrounded by newly formed bone in different stages of maturation. No inflammatory cell infiltrate is present (acid fuchsin– toluidine blue; original magnification ×100).
area is often made up of dense compact bone; therefore, the risk of fracture following mobilization of the vestibular flap by osteotomes is high.16 The bone expansion technique is a result of the evolution of the conventional split-crest technique, because a mandibular cortical plate, if not completely osteotomized, tends to fracture in an uncontrolled manner, creating serious obstacles to the success of the procedure. Specifically, the bone expansion technique presented in this study was designed to avoid fracture of the labial cortical plate. Indeed, this technique can be applied to edentulous ridges with no or little intervening cancellous bone between the cortical plates. By performing a basal longitudinal discharge osteotomy in addition to the vertical and longitudinal ones, the clinician can increase the elasticity of the vestibular bony flap, thereby minimizing any chance of bone fracture. This longitudinal osteotomy increases bone resilience and eases mobilization of the vestibular bone flap. During this phase, there is a risk of fracture with bone resorption.16 In cases of buccal plate fracture, the mobile plate may be retained with bone fixation screws.16 In the authors’ experience, with the bone expansion technique, a fracture of the labial cortical plate will be prevented. Basa et al16 applied a similar approach to 120 implants and achieved a 100% success rate after 4 months of loading. The strength of this technique is in the perfusion of the buccal segment. Because the procedure is performed in two stages, cortical resorption can be avoided, as the blood supply from the periosteum is not compromised. Revascularization of the cortical bone should be permitted before expansion to prevent resorption of the buccal plate. The displaced bone remains anchored to the basal bone by a bone pedicle (greenstick fracture), which facilitates stability of the fracture callus and osteoblastic rather than fibroblastic/chondroblastic differentiation of undifferentiated
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Scarano et al
mesenchymal cells. In fact, the expanded cortical bone is vascularized from the periosteum, not from the marrow spaces. Consequently, this technique should not be performed in a single stage if the expanded fragment is very thin or highly porous. In the present investigation, no clinical complications were recorded. The histologic observations supported the validity of the proposed technique. Newly formed bone was detected around the grafted biomaterial particles, with no signs of fibrous encapsulation. The osteotomized bone should be considered as an autogenous cortical graft, because perfusion and revascularization of osteotomized bone could be compromised. The predictability of the crestal expansion technique is supported by various reports on its medium-term clinical outcomes. Sethi and Kaus17 described a 5-year survival rate of 97% for 449 implants after ridge expansion in the maxilla. To separate the ridge gently, Chiapasco et al6 reported the use of a wedge-type device with two surgical steel arms hinged apically and with a transverse screw, which allowed progressive activation of the device. A fracture of the mandibular buccal plate occurred in one patient. In nine patients, the expansion was achieved gradually in 4 to 5 days by activating the device 1 mm per day. In the present study, no membrane was used to cover the split area, but a biomaterial was used to fill the gaps. Scipioni et al1 did not use any fillers or membranes over the bony gaps. Other investigators used a covering membrane in association with the crest-splitting technique.2 Mandibular ridge expansion using a split-crest technique with an ultrasonic device along with grafting of the implant sites seemed to be a viable therapeutic alternative for implant placement in this patient population. The split-crest technique should be considered a safe ridge expansion procedure in cases of crestal augmentation.
CONCLUSION The results of this study seem to support the hypothesis that delayed expansion of the compact mandibular bone crest with ultrasonic surgery associated with the use of biomaterials could be useful to prevent resorption and fracture of the buccal plate. Further long-term studies are certainly needed to validate these results.
REFERENCES 1. Scipioni A, Bruschi GB, Calesini G. The edentulous ridge expansion technique: A five-year study. Int J Periodontics Restorative Dent 1994;14:451–459. 2. Scipioni A, Bruschi GB, Giargia M, Berglundh T, Lindhe J. Healing at implants with and without primary bone contact. An experimental study in dogs. Clin Oral Implants Res 1997;8:39–47. 3. Nedir R, Bischof M, Briaux JM, Beyer S, Szmukler-Moncler S, Bernard JP. A 7-year life table analysis from a prospective study on ITI implants with special emphasis on the use of short implants. Results from a private practice. Clin Oral Implants Res 2004;15:150–157. 4. Jensen OT, Cullum DR, Baer D. Marginal bone stability using 3 different flap approaches for alveolar split expansion for dental implants: A 1-year clinical study. J Oral Maxillofac Surg 2009;67:1921–1930. 5. Scarano A, Carinci F, Assenza B, Piattelli M, Murmura G, Piattelli A. Vertical ridge augmentation of atrophic posterior mandible using an inlay technique with a xenograft without miniscrews and miniplates: Case series. Clin Oral Implants Res 2011;22:1125–1130. 6. Chiapasco M, Ferrini F, Casentini P, Accardi S, Zaniboni M. Dental implants placed in expanded narrow edentulous ridges with the Extension Crest device. A 1-3–year multicenter follow-up study. Clin Oral Implants Res 2006;17:265–272. 7. Blus C, Szmukler-Moncler S. Split-crest and immediate implant placement with ultra-sonic bone surgery: A 3-year life-table analysis with 230 treated sites. Clin Oral Implants Res 2006;17:700–707. 8. Demarosi F, Leghissa GC, Sardella A, Lodi G, Carrassi A. Localised maxillary ridge expansion with simultaneous implant placement: A case series. Br J Oral Maxillofac Surg 2009;47:535–540. 9. Selcuk B, Altan V, Neslihan T. Alternative bone expansion technique for immediate placement of implants in the edentulous posterior mandibular ridge: A clinical report. Int J Oral Maxillofac Implants 2004;19:554–558. 10. Scarano A, Murmura G, Sinjiari B, et al. Expansion of the alveolar bone crest with ultrasonic surgery device: Clinical study in mandible. J Immunopathol Pharmacol 2011;24:71–76. 11. Piattelli A, Scarano A, Quaranta M. High-precision, cost-effective cutting system for producing thin sections of oral tissues containing dental implants. Biomaterials 1997;8:577–579. 12. Buser D, Bragger U, Lang NP, Nyman S. Regeneration and enlargement of jaw bone using guided tissue regeneration. Clin Oral Implants Res 1990;1:22–32. 13. Pikos MA. Block autografts for localized ridge augmentation. Part II. The posterior mandible. Implant Dent 2000;9:67–75. 14. Ferrigno N, Laureti M. Surgical advantages with ITI TE implants placement in conjunction with split crest technique: 18-month results of an ongoing prospective study. Clin Oral Implants Res 2005;16:147–155. 15. Takahashi T, Funaki K, Shintani H, Haruoka T. Use of horizontal alveolar distraction osteogenesis for implant placement in a narrow alveolar ridge: A case report. Int J Oral Maxillofac Implants 2004;19:291–294. 16. Basa S, Varol A, Turker N. Alternative bone expansion technique for immediate placement of implants in the edentulous posterior mandibular ridge: A clinical report. Int J Oral Maxillofac Implants 2004;19:554–558. 17. Sethi A, Kaus T. Maxillary ridge expansion with simultaneous implant placement: 5-year results of an ongoing clinical study. Int J Oral Maxillofac Implants 2000;15:491–499.
ACKNOWLEDGMENTS This study was supported by the Ministry of Education, University and Research (M.I.U.R.), Rome, Italy. The authors reported no conflicts of interest related to this study.
The International Journal of Oral & Maxillofacial Implants 149 © 2015 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
O
ne of the most common anatomical limitations in implant dentistry is atrophy of the alveolar bone.1,2 Patients with long-standing edentulous arches may have narrow, knife-edged ridge crests with changing angulations that make endosseous implant placement difficult and carry a risk of fenestrations or dehiscence of the cortical layers.1,2 Alterations in normal anatomical features may cause intraoperative and
1 Associate
Professor, Dental School, University of ChietiPescara, Chieti, Italy. 2Professor of Oral Pathology and Medicine, Dental School, University of Chieti-Pescara, Chieti, Italy. 3Researcher, Dental School, University of Chieti-Pescara, Chieti, Italy. 4Private Practice, Milano, Italy. 5Research Fellow, University of Chieti-Pescara, Chieti, Italy. Correspondence to: Dr Antonio Scarano, Via Dei Frentani 98/B, 66100 Chieti, Italy. Fax: +39-0871-3554099. Email: [email protected] ©2015 by Quintessence Publishing Co Inc.
postoperative difficulties, such as inadequate bone support on the lingual and buccal sides of an implant and therefore faulty implant placement.3,4 Bone expansion in oral surgery consists of expanding the atrophic bone crest to obtain sufficient bone width for proper dental implant placement.1 To achieve this, different regenerative surgical techniques have been developed: conventional onlay/inlay grafts, interpositional sandwich osteotomies, guided bone regeneration with semipermeable membranes, piezoelectric stimulation, and alveolar distraction osteogenesis. All these procedures can be used for alveolar ridge augmentation in the posterior mandible with autologous or homologous bone grafts, xenografts, or bone substitutes to allow implant placement in one or two surgical steps.5 One of the most predictable regenerative techniques to increase the volume of buccal bone is sagittal osteotomy of the ridge.6–8 This technique has been reported to have a very high success rate (98% to 100%) and to show minimal volumetric contraction in the long term, since the buccal bone is maintained
144 Volume 30, Number 1, 2015 © 2015 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
Scarano et al
Fig 1 Intraoral view before treatment. Note the osseous atrophy.
Fig 2 Computed tomographic image showing alveolar width deficit in the area of the right premolars and first molar.
Fig 3 Following a crestal incision with vestibular release incisions and elevation of a mucoperiosteal flap, the thin residual ridge could be clearly seen. A sagittal corticotomy in the coronal area of the alveolar crest with ultrasonic surgery was performed.
Fig 4 A distal vertical corticotomy was performed in the buccal wall.
in situ and provided with both endosteal and periosteal blood vessels, limiting secondary resorption. In the maxilla, slight separation of the ridge crest is performed as a hingelike separation of the buccal cortex. It is difficult to achieve the same hingelike separation in the posterior mandible because of its compact outer cortex and external oblique line.9 The aim of the present case series was to evaluate, clinically and histologically, delayed expansion of the mandible by ultrasonic surgery in humans.
premolar or molar areas with residual alveolar ridge width between 2.3 and 4.1 mm (Figs 1 and 2), as measured by an outside caliper (distance between the outer surfaces of the buccal and palatal bone walls, 1 mm apical to the alveolar crest).10 Those with severe illness, a history of head and neck radiation therapy, chemotherapy, uncontrolled diabetes, uncontrolled periodontal disease, and smoking were excluded from participation.
MATERIALS AND METHODS Study Design
All participating patients were scheduled for bone reconstruction procedures, including crest expansion and implant insertion. The protocol of the study was approved by the Ethics Committee of the University of Chieti-Pescara, Chieti, Italy, and all patients provided written informed consent. The inclusion criteria were: complete or partial edentulism in the mandibular
Surgical Procedures
Prior to surgery, the patients’ mouths were rinsed with chlorhexidine digluconate solution (0.2% for 2 minutes). Local anesthesia was obtained with articaine associated with epinephrine (1:100,000; Ubistesin 4%, Espe Dental). In the first surgery, four linear corticotomies were created with an ultrasonic surgical device (Surgysonic, Esacrom). A sagittal corticotomy was made in the coronal area (Fig 3) of the mandibular alveolar crest, two vertical corticotomies were made in the buccal wall (Fig 4) after a supracrestal incision and elevation of a buccal mucoperiosteal flap, and a The International Journal of Oral & Maxillofacial Implants 145
© 2015 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
Scarano et al
Fig 5 A sagittal corticotomy, lower (basally) in the buccal wall, was performed.
Fig 6 Second surgery 4 weeks later. The desired crest expansion was achieved by using a combination of scalpels, thin chisels, and threaded osteotomes without compromising cortical vascularization; it was possible to see the crest widening with the osteotomes.
sagittal corticotomy was made 2 to 3 mm above the mandibular canal (Fig 5). Bone expansion was not performed at this stage to prevent the possible loss of the blood supply to the osteotomized segment caused by the reflection of a full-thickness mucoperiosteal flap. The wound was closed with interrupted sutures (Vicryl 4.0, Ethicon FS-2). Four weeks later, a second surgery was carried out. This consisted of adequate bone expansion, which did not compromise cortical vascularization, with a combination of scalpels, thin chisels, and threaded osteotomes (Bone System) (Fig 6). Limited reflection of a soft tissue flap to maintain the blood supply to the buccal bone and a sequential introduction of osteotomes with increasing diameters were performed. The osteotomes were used to enable safe, controlled widening of the mandibular crest to permit implant placement. The ridge width was measured at baseline, before the first surgery, and after the second surgery. Two submerged implants (Bone System) for ridge were inserted in the premolar and molar areas (Fig 7) after the gaps were filled with corticospongious porcine biomaterial (OsteoBiol Gen-Os, Tecnoss). The implant osteotomies were created with an ultrasonic surgery device and a final conventional drill sequence appropriate to the size of the implant. Implants were inserted with a mechanical system initially, and insertion was completed with a manual wrench. Primary stability was evaluated manually, and all implants had insertion torque greater than 25 N/cm. The flaps were closed carefully with interrupted sutures (Vicryl 4.0, Ethicon FS-2). Periapical radiographs were taken after implant insertion to verify appropriate implant positioning. After surgery, amoxicillin (500 mg; one capsule every 8 hours for 7 days) and ibuprofen (600 mg as needed) were prescribed. Patients were not allowed to wear their removable dentures until implant uncovering (at
Fig 7 The implants have been placed, with the grafting material filling the gaps.
3 months). The postsurgical instructions included a soft diet for 2 weeks and appropriate oral hygiene, including twice-daily rinsing with 0.2% chlorhexidine digluconate mouthwash (Parodontax, GlaxoSmithKline). Clinical and radiographic follow-up was performed 1 month after surgery and again after 3 months, at which time healing screws were applied and bone cores were harvested from the augmented ridge.
Histologic Processing
A bone trephine with an internal diameter of 2 mm was used to retrieve bone samples from the regenerated area between the two implants. One specimen per patient was obtained. The specimens were then immediately stored in 10% buffered formalin and processed to obtain thin ground sections (Precise 1 Automated System, Assing).11 The specimens were dehydrated in a graded series of ethanol rinses and embedded in glycol methacrylate resin (Technovit 7200 VLC, Kulzer). After polymerization, the specimens were sectioned longitudinally with a high-precision diamond disk at approximately 150 µm and ground down to approximately 30 µm with a specially designed grinding machine (Precise 1 Automated System, Assing). Three slides were obtained from each specimen. These slides were stained with acid fuchsin and toluidine blue and examined under transmitted light (Leitz Laborlux). Histomorphometric analysis to determine the percentages of newly formed bone, grafted material, and marrow spaces was carried out using a light microscope (Laborlux S, Leitz) connected to a high-resolution video camera (3CCD, JVC KY-F55B, JVC) interfaced to a monitor and computer (Pentium III 1200 MMX, Intel). This optical system was associated with a digitizing pad (Matrix Vision) and a histometry software package with image-capturing capabilities (Image-Pro Plus 4.5, Media Cybernetics/Immagini & Computer).
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Table 1 Characteristics of the Inserted Implants Implant diameter (mm)
Implant length (mm)
3.5
8.2
4.1
0
8
10
10
15
12
8
8
13.5
6
9
Total
24
40 Fig 8 Three months after implant placement, the intercortical bony gap is filled with new bone.
Table 2 Alveolar Bone Width Measurements in All Patients Patient no.
Presurgical width (mm)
Width at 3 mo after augmentation (mm) 7.1
Mean horizontal increase 4.8
1
2.3
2
3.1
7.5
4.4
3
2.3
7.1
4.8
4
3.1
7.5
4.4
5
3.9
8.2
4.3
6
3.5
8.2
4.7
7
3.7
8.9
5.2
8
2.6
9.2
6.6
9
2.3
9.1
6.8
10
3.1
7.5
4.4
11
3.9
8.2
4.3
12
3.5
10.2
6.7
13
3.5
8.9
5.4
14
2.6
9.2
6.6
15
2.3
7.1
4.8
16
3.1
7.5
4.4
17
3.3
8.2
4.9
18
3.5
9.2
5.7
19
3.7
8.9
5.2
20
2.6
9.2
6.6
21
2.3
7.1
4.8
22
3.1
7.5
4.4
23
4.1
8.2
4.1
24
3.5
8.2
4.7
25
3.7
8.9
5.2
26
2.6
9.2
6.6
27
2.3
7.1
4.8
28
3.1
8.5
5.4
29
3.9
8.2
4.3
30
3.5
8.2
4.7
31
3.7
8.9
5.2
32
2.8
Mean ± SD 3.14 ± 0.57
9.2 8.31 ± 0.83
6.4 5.17 ± 0.86
RESULTS Clinical Outcomes
Thirty-two patients (23 women and 9 men; mean age, 57 years; age range, 53 to 68 years) participated in the study and received 64 implants. The healing process was uneventful for all patients. No lesions to the inferior alveolar nerve were recorded. No dehiscence of the sutures, wound infections, or fracture of the buccal plate was observed in any of the patients. At implant placement, no dehiscence defects or perforations (either vestibularly or apically) occurred, and all implants showed good primary stability. The diameters and lengths of the inserted implants are described in Table 1. After the 3-month healing period, two implants had not osseointegrated (3.12%) and had to be removed; therefore, the implant success rate was 96.88%. Furthermore, ossification of the osteotomy was evidenced by increasing radiopacity on panoramic or periapical radiographs. Clinically, the intercortical bony gap seemed to be filled with newly formed bone (Fig 8). At re-entry, the healed augmented alveolar crest had a mean width of 8.31 ± 0.83 mm. The mean horizontal increase obtained was 5.17 ± 0.86 mm (range, 4.1 to 6.8 mm) (Table 2).
Histologic Findings
No chronic inflammatory cell infiltrate or multinucleated giant cells were seen around the graft or at the biomaterial-bone interface, and no evidence of foreignbody reaction was detected. At low magnification, the histologic specimens showed a mixture of new bone graft and particles of biomaterial, as well as new bone that formed bridges connecting the biomaterial particles (Fig 9). Marrow spaces were present, delimited by the newly formed bone and portions of the grafted material. In some areas, it was possible to observe the presence of detached particles at the periphery of the grafted biomaterial. At higher magnification, newly The International Journal of Oral & Maxillofacial Implants 147
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Fig 9 Specimen at low magnification. Biomaterial particles are still present in the defect (acid fuchsin–toluidine blue; original magnification ×12).
formed bone was seen in close contact with the particles of biomaterials with no soft tissue interposition (Fig 10). The internal portion of most of the graft particles was infiltrated by biologic fluids and filled with a tissue with the staining characteristics of newly formed bone. In some fields, osteoblasts deposing osteoid matrix were observed. Histomorphometry demonstrated that 64% ± 3.1% of the specimen was composed of newly formed bone, 8% ± 0.8% was marrow spaces, and 27% ± 2.6% was made up of residual biomaterial.
DISCUSSION Narrow edentulous ridges require bone expansion before implant placement. Horizontal bone augmentation is possible using three different procedures: (1) lateral augmentation (eg, guided bone regeneration,12 cortical bone blocks13); (2) interpositional augmentation (crest splitting)14; or (3) distraction osteogenesis.15 The split-crest technique allows the clinician to place implants into anatomical situations with insufficient bone thickness by moving the external cortical plate of the mandible labially to gain an increase in width so that implants of a suitable diameter could be placed. Furthermore, bone augmentation should produce an appropriate bone contour, allowing for implant placement in a proper prosthetically directed position. Mandibular bone has a higher density than maxillary bone and therefore requires a different approach to ridge splitting. In the maxilla, an osteotomy of the crest could be achieved with chisels and without the assistance of surgical burs. A mallet could be used to expand the plates without vertical osteotomy. The posterior mandible is the most difficult region for reconstruction and early implant placement in cases of severe alveolar resorption. The atrophic ridge in this
Fig 10 A specimen at higher magnification. Most of the biomaterial particles are surrounded by newly formed bone in different stages of maturation. No inflammatory cell infiltrate is present (acid fuchsin– toluidine blue; original magnification ×100).
area is often made up of dense compact bone; therefore, the risk of fracture following mobilization of the vestibular flap by osteotomes is high.16 The bone expansion technique is a result of the evolution of the conventional split-crest technique, because a mandibular cortical plate, if not completely osteotomized, tends to fracture in an uncontrolled manner, creating serious obstacles to the success of the procedure. Specifically, the bone expansion technique presented in this study was designed to avoid fracture of the labial cortical plate. Indeed, this technique can be applied to edentulous ridges with no or little intervening cancellous bone between the cortical plates. By performing a basal longitudinal discharge osteotomy in addition to the vertical and longitudinal ones, the clinician can increase the elasticity of the vestibular bony flap, thereby minimizing any chance of bone fracture. This longitudinal osteotomy increases bone resilience and eases mobilization of the vestibular bone flap. During this phase, there is a risk of fracture with bone resorption.16 In cases of buccal plate fracture, the mobile plate may be retained with bone fixation screws.16 In the authors’ experience, with the bone expansion technique, a fracture of the labial cortical plate will be prevented. Basa et al16 applied a similar approach to 120 implants and achieved a 100% success rate after 4 months of loading. The strength of this technique is in the perfusion of the buccal segment. Because the procedure is performed in two stages, cortical resorption can be avoided, as the blood supply from the periosteum is not compromised. Revascularization of the cortical bone should be permitted before expansion to prevent resorption of the buccal plate. The displaced bone remains anchored to the basal bone by a bone pedicle (greenstick fracture), which facilitates stability of the fracture callus and osteoblastic rather than fibroblastic/chondroblastic differentiation of undifferentiated
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mesenchymal cells. In fact, the expanded cortical bone is vascularized from the periosteum, not from the marrow spaces. Consequently, this technique should not be performed in a single stage if the expanded fragment is very thin or highly porous. In the present investigation, no clinical complications were recorded. The histologic observations supported the validity of the proposed technique. Newly formed bone was detected around the grafted biomaterial particles, with no signs of fibrous encapsulation. The osteotomized bone should be considered as an autogenous cortical graft, because perfusion and revascularization of osteotomized bone could be compromised. The predictability of the crestal expansion technique is supported by various reports on its medium-term clinical outcomes. Sethi and Kaus17 described a 5-year survival rate of 97% for 449 implants after ridge expansion in the maxilla. To separate the ridge gently, Chiapasco et al6 reported the use of a wedge-type device with two surgical steel arms hinged apically and with a transverse screw, which allowed progressive activation of the device. A fracture of the mandibular buccal plate occurred in one patient. In nine patients, the expansion was achieved gradually in 4 to 5 days by activating the device 1 mm per day. In the present study, no membrane was used to cover the split area, but a biomaterial was used to fill the gaps. Scipioni et al1 did not use any fillers or membranes over the bony gaps. Other investigators used a covering membrane in association with the crest-splitting technique.2 Mandibular ridge expansion using a split-crest technique with an ultrasonic device along with grafting of the implant sites seemed to be a viable therapeutic alternative for implant placement in this patient population. The split-crest technique should be considered a safe ridge expansion procedure in cases of crestal augmentation.
CONCLUSION The results of this study seem to support the hypothesis that delayed expansion of the compact mandibular bone crest with ultrasonic surgery associated with the use of biomaterials could be useful to prevent resorption and fracture of the buccal plate. Further long-term studies are certainly needed to validate these results.
REFERENCES 1. Scipioni A, Bruschi GB, Calesini G. The edentulous ridge expansion technique: A five-year study. Int J Periodontics Restorative Dent 1994;14:451–459. 2. Scipioni A, Bruschi GB, Giargia M, Berglundh T, Lindhe J. Healing at implants with and without primary bone contact. An experimental study in dogs. Clin Oral Implants Res 1997;8:39–47. 3. Nedir R, Bischof M, Briaux JM, Beyer S, Szmukler-Moncler S, Bernard JP. A 7-year life table analysis from a prospective study on ITI implants with special emphasis on the use of short implants. Results from a private practice. Clin Oral Implants Res 2004;15:150–157. 4. Jensen OT, Cullum DR, Baer D. Marginal bone stability using 3 different flap approaches for alveolar split expansion for dental implants: A 1-year clinical study. J Oral Maxillofac Surg 2009;67:1921–1930. 5. Scarano A, Carinci F, Assenza B, Piattelli M, Murmura G, Piattelli A. Vertical ridge augmentation of atrophic posterior mandible using an inlay technique with a xenograft without miniscrews and miniplates: Case series. Clin Oral Implants Res 2011;22:1125–1130. 6. Chiapasco M, Ferrini F, Casentini P, Accardi S, Zaniboni M. Dental implants placed in expanded narrow edentulous ridges with the Extension Crest device. A 1-3–year multicenter follow-up study. Clin Oral Implants Res 2006;17:265–272. 7. Blus C, Szmukler-Moncler S. Split-crest and immediate implant placement with ultra-sonic bone surgery: A 3-year life-table analysis with 230 treated sites. Clin Oral Implants Res 2006;17:700–707. 8. Demarosi F, Leghissa GC, Sardella A, Lodi G, Carrassi A. Localised maxillary ridge expansion with simultaneous implant placement: A case series. Br J Oral Maxillofac Surg 2009;47:535–540. 9. Selcuk B, Altan V, Neslihan T. Alternative bone expansion technique for immediate placement of implants in the edentulous posterior mandibular ridge: A clinical report. Int J Oral Maxillofac Implants 2004;19:554–558. 10. Scarano A, Murmura G, Sinjiari B, et al. Expansion of the alveolar bone crest with ultrasonic surgery device: Clinical study in mandible. J Immunopathol Pharmacol 2011;24:71–76. 11. Piattelli A, Scarano A, Quaranta M. High-precision, cost-effective cutting system for producing thin sections of oral tissues containing dental implants. Biomaterials 1997;8:577–579. 12. Buser D, Bragger U, Lang NP, Nyman S. Regeneration and enlargement of jaw bone using guided tissue regeneration. Clin Oral Implants Res 1990;1:22–32. 13. Pikos MA. Block autografts for localized ridge augmentation. Part II. The posterior mandible. Implant Dent 2000;9:67–75. 14. Ferrigno N, Laureti M. Surgical advantages with ITI TE implants placement in conjunction with split crest technique: 18-month results of an ongoing prospective study. Clin Oral Implants Res 2005;16:147–155. 15. Takahashi T, Funaki K, Shintani H, Haruoka T. Use of horizontal alveolar distraction osteogenesis for implant placement in a narrow alveolar ridge: A case report. Int J Oral Maxillofac Implants 2004;19:291–294. 16. Basa S, Varol A, Turker N. Alternative bone expansion technique for immediate placement of implants in the edentulous posterior mandibular ridge: A clinical report. Int J Oral Maxillofac Implants 2004;19:554–558. 17. Sethi A, Kaus T. Maxillary ridge expansion with simultaneous implant placement: 5-year results of an ongoing clinical study. Int J Oral Maxillofac Implants 2000;15:491–499.
ACKNOWLEDGMENTS This study was supported by the Ministry of Education, University and Research (M.I.U.R.), Rome, Italy. The authors reported no conflicts of interest related to this study.
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