Mandibular Ridge Expansion Using a Horizontal Bone-Splitting Technique and Synthetic Bone Substitute: An Alternative to Bone Block Grafting? Bruno Ella, DDS, PhD1/Mathieu Laurentjoye, MD2/Cyril Sedarat, DDS, PhD1/ Jean-Christophe Coutant, DDS, PhD3/Emmanuel Masson, DDS4/André Rouas, DDS, PhD5 Purpose: Inadequate bone width in atrophic edentulous jaws is a challenge for successful oral rehabilitation with endosseous dental implants. The aim of this clinical study was to evaluate the effectiveness of a new method for ridge expansion with sagittal splitting using a new surgical device (Crest-Control Bone Splitting System, Meisinger) and to determine whether it is necessary to fill the expansion area with bone substitute to maintain the expanded bone volume. Materials and Methods: During a 3-year period, a prospective study was performed in 32 patients (59% women, 41% men). All participants needed implants in the horizontally atrophied edentulous mandible and were treated in a private practice and a hospital. The only inclusion criteria were a mandibular ridge width between 3 and 4 mm and ridge height of at least 11 mm. Expansion with horizontal splitting of the ridge was performed simultaneously with implant placement. In 17 of the 32 arches, selected alternately, the expanded ridges were filled with a biphasic calcium phosphate (hydroxyapatite 60% and beta-tricalcium phosphate 40%) synthetic bone substitute (SBS 60/40). The other 15 expanded arches were left unfilled. All areas were covered with a resorbable collagen membrane (Bio-Gide, Geistlich). Results were analyzed with the Mann-Whitney and Kruskal-Wallis tests (α = .05). Results: There was a significant difference (α = .02) between the patients who received SBS 60/40 (17 cases) and those who did not (15 cases). The ridges that received SBS 60/40 after expansion showed no bone resorption. Conclusion: Horizontal expansion of the ridge is easily reproducible. In this study, in very narrow ridges, a lack of bone substitute resulted in significant resorption of 3- to 4-mm-wide crests (5%), even after expansion. A bone substitute should be placed to maintain the alveolar bone walls after expansion. Int J Oral Maxillofac Implants 2014;29:135–140. doi: 10.11607/jomi.2201 Key words: bone expansion, bone grafting, narrow ridge, synthetic bone
A
trophic edentulous jaws can represent a significant challenge to the successful use of endosseous im-
1 Assistant
Professor and Researcher, Department of Odontology and Buccal Health, University Hospital Center, Bordeaux, France. 2Hospital Practitioner and Researcher, Department of Maxillofacial Surgery, University Hospital Center, Bordeaux, France. 3Hospital Practitioner and Researcher, Department of Odontology and Buccal Health, University Hospital Center, Bordeaux, France. 4Medical Resident, Department of Odontology and Buccal Health, University Hospital Center, Bordeaux, France. 5Professor, Department of Odontology and Buccal Health, University Hospital Center, Bordeaux, France. Correspondence to: Prof Bruno Ella, Odontology and Buccal Health, University Hospital Center, 10-20 Cours de la Marne, Bordeaux 33082, France. Email: [email protected] ©2014 by Quintessence Publishing Co Inc.
plants for prosthetic reconstruction of the edentulous mandible. Although ridge augmentation can help to restore ridge volume, grafting procedures can significantly increase patient morbidity, costs, and treatment time before dental implants can be placed.1,2 Inadequate bone width in the ridge is a common limitation for dental rehabilitation in oral implant therapy. An implant must be surrounded by at least 1 mm of cortical bone on both sides; if the alveolar ridge is narrower than 5 mm, it is difficult to insert an implant to replace a molar or a premolar.3,4 The autogenous bone onlay graft is considered the gold standard for grafting; however, intraoral donor sites do not always provide sufficient graft volume.5–7 In addition, intraoral grafting methods present several drawbacks: the invasiveness of the surgery with its increased risk of morbidity, the risk of exposure and/ or infection of the bone graft and/or membrane, and an increased number of operations, which reduces patient comfort and lengthens treatment time.8–11 The International Journal of Oral & Maxillofacial Implants 135
© 2014 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.
Ella et al
Horizontal bone expansion has been used since the 1980s to create sufficient width in narrow ridges with simultaneous implant placement.12 This technique has continued to evolve, and new protocols have been developed, some of which include filling of the expanded ridge.13–15 A new surgical device (Crest-Control Bone Splitting System, Meisinger) has been proposed to expand narrow ridges in the mandible in association with sagittal osteotomy.16 The Crest-Control Bone Splitting System consists of two surgical steel arms hinged apically and a transverse screw, which allows the device to be activated progressively. After ridge expansion is complete, the expansion devices are removed and implants are placed following standard procedures. The use of this device should allow progressive, controlled widening of a horizontally atrophied crestal ridge with a reduced risk of alveolar plate fracture. Some authors reported implant placement after alveolar bone expansion, without filling of the residual defects around implants,17 while others reported crestal resorption after this approach.18 The aims of this study were, therefore: (1) to present the preliminary results obtained with the aforementioned ridge-splitting tool for crestal expansion of horizontally atrophied mandibular crestal ridges in conjunction with implant placement, and (2) to determine whether it is necessary to pack the expansion area with a bone substitute to maintain the expanded bone volume.
Material and methods Study population
The study was carried out over a 3-year period in patients who attended a private practice for implant therapy of the edentulous mandible. Inclusion criteria were: no general or other pathology, an average width of the edentulous ridge of 3 to 4 mm, and a minimum of 11 mm of bone height, including at least 1 mm of cancellous bone (Fig 1a). Two sectors of the mandible were considered: the anterior sector (ie, incisors and canines) and the lateral sectors (premolar and molar areas). Patients were treated for prosthetic rehabilitation of implants in only one edentulous sector of the mandible, and the considered edentulous sectors corresponded, on average, to the replacement of two or three teeth. Thus, each patient received two implants per sector. In addition, the patients had to agree to participate in a postoperative checkup program. Each patient signed an appropriate consent form. On the ridges that were treated, there needed to be a minimum of 11 mm of bone between the top of the ridge and the inferior alveolar nerve. Patients were excluded from participation if they had systemic conditions contraindicating oral surgery,
a drug allergy, a smoking habit, alcohol or drug abuse, periodontal disease, or poor oral hygiene.
Surgical Protocol
It was decided to use a ridge expansion technique and to insert the implants simultaneously. In some cases, the spaces between the implants were filled with a synthetic bone substitute (type SBS 60/40 biphasic calcium phosphate, MBCP, Expanscience).19 Under local anesthesia, a crestal incision was made and a full-thickness flap was raised to obtain adequate visibility of the crestal bone; the incision was completed with a partial-thickness flap apical to the crest. The initial osteotomy was performed on midcrestal bone, with a rotating saw used to separate the buccal plate from the palatal plate, and was limited to 1 mm from the adjacent teeth. The Crest-Control Bone Splitting System was placed through the crestal osteotomy. The Crest-Control Bone Splitting System consists of two surgical steel arms hinged apically and a transverse screw, which allows the device to be progressively activated (Fig 1b). After ridge expansion was completed, the expansion devices were removed, and implants were placed following standard procedures. Speedy Groovy implants (Nobel Biocare) were used in all patients; diameters were 3.3 or 4 mm (Fig 1c). Implant placement was submerged. All areas were covered with a resorbable collagen membrane (Bio-Gide, Geistlich)20,21 (Fig 1d). The flaps were sutured without tension and were made watertight to protect the area (Fig 1e). All patients received antibiotic therapy (amoxicillin 2 g per day), which started the day before surgery and continued for 6 days; an analgesic (acetaminophen 3 g per day for 5 days); and a 0.12% chlorhexidine mouthwash (twice a day for 3 weeks). All sites were checked at follow-up visits, and any nonabsorbable sutures were removed 15 days after surgery. After 6 months of healing, stage-two surgery was carried out. Prostheses were placed per the usual protocol in patients with no bone resorption around the implants (Fig 1f ). However, in all cases where there was bone resorption, bone rehabilitation was performed using the same substitute material as was used for the bone expansion before prosthetic treatment.22,23
Measurements
Bone resorption was quantified as 1 or 2 mm, and horizontal fractures were noted (0 = no fractures, 1 = at least one fracture). The postsurgical width of the edentulous ridge was measured after the expansion and simultaneous placement of implants. At 6 months, the expanded sector was opened to measure the width of the expanded bone and its contact with the implants and to place healing abutments (Fig 1g). The increase
136 Volume 29, Number 1, 2014 © 2014 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.
Ella et al
Fig 1a Computed tomographic scan of the mandibular ridge.
Fig 1b Horizontal expansion (two expanders placed).
Fig 1c Implants placed in the expanded ridge.
Fig 1d Resorbable membrane placed after ridge filling (SBS).
Fig 1e Sutures.
Fig 1f The expanded ridge 6 months after surgery; bone gain and bone resorption were measured (horizontal expansion).
Fig 1g Prosthetic abutments placed.
in width and the bone levels around the implants were assessed using a periodontal probe (PCP UNC 15, Hu-Friedy) and recorded to the nearest millimeter. Measurements around the implants were made from the base of the resorption to the implant platform.24,25
Statistical Analyses
The Mann-Whitney test (α = .05) was performed to compare groups for bone resorption and fracture data: “women versus men,” “anterior versus lateral sector,” “3 mm versus 4 mm of crest width,” and “with SBS versus without SBS.” If the groups were significantly different, the Kruskal-Wallis test was performed (α = .05).
Results Thirty-two patients were treated with two implants each in the atrophied mandible; 41% were men and 59% were women. With regard to the treated area, 56% of treated areas were in the lateral mandible (premolars or molar) and 44% were in the anterior mandible (incisors or canines). Of the implants placed, 53% were 3.3 mm wide and 47% were 4 mm wide. Seventeen patients received SBS and 15 did not. After 6 months, all expanded sectors, with or without bone substitute, had healed. One year after ridge expansion, no implants had been lost or showed mobility. The International Journal of Oral & Maxillofacial Implants 137
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100 90 80 70 60 50 40 30 20 10 0
% of patients
% of patients
Ella et al
Men
Women
*
100 90 80 70 60 50 40 30 20 10 0
3 mm
4 mm
100 90 80 70 60 50 40 30 20 10 0
*
% of patients
% of patients
Fig 2 Frequency of bone fracture following alveolar expansion with respect to (left) gender and (right) original alveolar ridge width. *α = .04, Mann-Whitney test; α = .05, Kruskal-Wallis test.
No biomaterial
With biomaterial
100 90 80 70 60 50 40 30 20 10 0
No SBS With SBS
0 1 2 0 1 2 3 mm
0 1 2 0 1 2 4 mm
Fig 3 Frequency and amount of bone resorption 6 months after ridge expansion with respect to the use of SBS.
Fractures
With respect to fracture frequency, men and women were significantly different (Mann-Whitney test, α = .07), but no significant difference was confirmed with the Kruskal-Wallis test (Fig 2). “Anterior sector” and “lateral sector” were not significantly different with the Mann-Whitney test. “With SBS” and “without SBS” groups were not significantly different with the Mann-Whitney test, but the “3-mm-wide crest” and “4-mm-wide crest” groups were significantly different (α = .04). In addition, a significant effect of crest width on fracture in the SBS group was obtained with the Kruskal-Wallis test (α = .05) (Fig 2).
Bone Resorption
With respect to bone resorption, women and men were significantly different with the Mann-Whitney test (α = .0082), but no significant difference was seen with the Kruskal-Wallis test. “Anterior sector” and “lateral sector” were not significantly different with the MannWhitney test. The “with SBS” and “without SBS” groups were significantly different with the Mann-Whitney test (α = .00); SBS had a significant effect on resorption of 3-mm-wide crests (5%) and on resorption of 4-mm-wide crests (5%) according to the Kruskal-Wallis test (α = .02%).
Discussion Bone Resorption
The location of the intervention (anterior versus lateral sector) had no effect on bone resorption. Filling with SBS, however, did have an effect on bone resorption, regardless of the original crest width, and resulted in a strong preservation of crestal width gain.
Fracture Risk
There was a gender-related difference in fracture risk, which was higher in women. The location of the intervention (anterior or lateral sector) had no effect on fracture risk. A narrow initial crest width increased the risk of fracture. Filling with SBS increased the fracture risk when the initial crest was narrow. Analysis of the present sample can show not only whether this horizontal ridge expansion technique is easily reproducible, but also whether filling with bone substitute is necessary to maintain the bone walls after expansion. Almost 53% of the expanded sectors were filled with SBS 60/40, while about 47% were not, regardless of preoperative ridge width. It should be noted that 94% of ridges that received SBS 60/40 after expansion showed no resorption, regardless of the preoperative
138 Volume 29, Number 1, 2014 © 2014 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.
Ella et al
a Fig 4a A very narrow ridge (3 mm).
b
c
Figs 4b and 4c (b) Horizontal expansion with one expander placed in a very narrow ridge; (c) horizontal fracture during expansion.
width (α = .02). On the other hand, almost 47% of all ridges showed resorption around the implants. The majority of resorption was seen in the expanded ridges that had not been filled with SBS 60/40, with a higher resorption rate (25%) in the narrowest ridges (3 mm) (Fig 3). Ridges of 3 or 4 mm in patients who had received SBS 60/40 were significantly different (5%) from ridges that had not been filled with SBS 60/40. Indeed, bone resorption was noted around the implants in most patients where the expanded area had not been filled with SBS 60/40. Resorption would therefore appear to be all the more significant when the expanded ridge had not been filled with SBS 60/40 (α = .02). Comparison of the expanded sectors with and without SBS 60/40, all parameters combined, revealed a significant difference, with a 5% risk (α = .05), which could suggest that filling a horizontally expanded site with a bone substitute has the effect of reducing resorption in the bone walls around the implant.26–28 This particular bone substitute material therefore appears to have maintained bone volume. This effect was even more marked around implants when the bone walls were very thin (3 mm). Despite the expansion of the ridge, the bone walls in direct contact with the implant probably exert pressure, however minimal, on the implant surface. This pressure could thus affect bone vascularization and cause resorption that is ischemic in origin. It is possible that this pressure is reduced by the SBS material occupying the space between the two bone walls. Contact between the bone walls and the surface of the implants would then be passive after expansion. Another drawback when ridges are too narrow (Fig 4a) is the risk of fracture during horizontal expansion (Figs 4b and 4c). In fact, in this sample, 43% of the ridges presented a fracture, with one or both of the bone walls becoming disconnected. The narrowest ridges (3 mm wide, 40% of the sample) accounted for almost all of the fractures. When the 3-mm ridges were compared with the 4-mm ridges, all parameters combined, there was a 5% risk (α = .05) that ridge width would affect the risk of fracture in the bone walls
during horizontal expansion. However, this characteristic showed no direct link between the fracture of the ridge and its eventual resorption. The expansion of ridges of less than 4 mm wide seemed to present more constraints than those that were already 4 mm wide. These constraints manifested themselves in several ways in the present study. Bone resorption around the implants and fractures was clearly evident in the narrowest ridges (3 mm).29 Bone fractures could be the result of several factors, one of which could be that there was not a minimum amount (1 mm) of spongy bone interposed between the two cortical plates of the ridge.30
Conclusion Horizontal expansion using the Crest-Control device is certainly reproducible and can be a good alternative to bone block grafting in a narrow ridge.31–33 However, the ridge bone must have a minimum width, and there must be a minimum amount of cancellous bone between the cortical plates to prevent fracture during surgery and the very probable risk of postoperative resorption in the short or medium term. This technique prevents the need for donor site bone and must be compared with the technique of osteoperiosteal flap. The risk of fracture during surgery did not lead to failure during the healing process; on the other hand, whether the expanded area was filled with a bone substitute material had a considerable influence on the expected gain in bone volume. It therefore appears necessary, especially in the case of the narrowest ridges (3 mm), to maintain the expanded ridge with a grafting material, which may be based on an entirely synthetic bone substitute, as was done in this study.34 Today, a wide range of surgical procedures are available; however, it is difficult to demonstrate that any one of these can offer better outcomes than another. Every surgical procedure presents advantages and disadvantages, so priority should be given to those that are simpler, less invasive, and less risky.35 The International Journal of Oral & Maxillofacial Implants 139
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Ella et al
acknowledgments The authors reported no conflicts of interest related to this study.
References 1. Santagata M, Guariniello L, D’Andrea A, Tartaro G. A modified crestal ridge expansion technique for immediate placement of implants: A report of three cases. J Oral Implantol 2008;34(6):319–324. 2. Laster Z, Rachmiel A, Jensen OT. Alveolar width distraction osteogenesis for early implant placement. J Oral Maxillofac Surg 2005; 63(12):1724–1730. 3. 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(7):535–540. 4. Mecall RA, Rosenfeld AL. The influence of residual ridge resorption patterns on fixture placement and tooth position. Part I. Int J Periodontics Restorative Dent 1991;11(1):9–23. 5. Barone A, Covani U. Maxillary alveolar ridge reconstruction with nonvascularized autogenous block bone: Clinical results. J Oral Maxillofac Surg 2007;65(10):2039–2046. 6. Misch CM. Implant site development using ridge splitting techniques. Oral Maxillofac Surg Clin North Am 2004;16(1):65–74. 7. Lizuka T, Smolka W, Hallermann W, Mericske-Stern R. Extensive augmentation of the alveolar ridge using autogenous calvarial split bone grafts for dental rehabilitation. Clin Oral Implants Res 2004;15(5): 607–615. 8. Wallace S, Gellin R. Clinical evaluation of freeze-dried cancellous block allografts for ridge augmentation and implant placement in the maxilla. Implant Dent 2010;19(4):272–279. 9. Koo S, Dibart S, Weber HP. Ridge-splitting technique with simultaneous implant placement. Compend Contin Educ Dent 2008;29(2): 106–110. 10. Machtei EE. The effect of membrane exposure on the outcome of regenerative procedures in humans: A meta-analysis. J Periodontol 2001;72(4):512–516. 11. Silva FM, Cortez AL, Moreira RW, Mazzonetto R. Complications of intraoral donor site for bone grafting prior to implant placement. Implant Dent 2006;15(4):420–426. 12. 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(6):700–707. 13. Nishioka RS, Souza FA. Bone spreader technique: A preliminary 3-year study. J Oral Implantol 2009;35(6):289–299. 14. Piccinini M. Mandibular bone expansion technique in conjunction with root form implants: A case report. J Oral Maxillofac Surg 2009; 67(9):1931–1936. 15. Dene L, Condos S. Ridge expansion and immediate implant placement in the esthetic zone. N Y State Dent J 2010;76(2):28–31. 16. Enislidis G, Wittwer G, Ewers R. Preliminary report on a staged ridge splitting technique for implant placement in the mandible: A technical note. Int J Oral Maxillofac Implants 2006;21(3):445–449. 17. Scipioni A, Bruschi GB, Calesini G, Bruschi E, De Martino C. Bone regeneration in the edentulous ridge expansion technique: Histologic and ultrastructural study of 20 clinical cases. Int J Periodontics Restorative Dent 1999;19(3):269–277.
18. Coatoam GW, Mariotti A. The segmental ridge-split procedure. J Periodontol 2003;74(5):757–770. 19. Boix D, Weiss P, Gauthier O, et al. Injectable bone substitute to preserve alveolar ridge resorption after tooth extraction: A study in dog. J Mater Sci Mater Med 2006;17(11):1145–1152. 20. Agis H, Magdalenko M, Stögerer K, Watzek G, Gruber R. Collagen barrier membranes decrease osteoclastogenesis in murine bone marrow cultures. Clin Oral Implants Res 2010;21(6):656–661. 21. Zwahlen RA, Cheung LK, Zheng LW, et al. Comparison of two resorbable membrane systems in bone regeneration after removal of wisdom teeth: A randomized-controlled clinical pilot study. Clin Oral Implants Res 2009;20(10):1084–1091. 22. Zitzmann NU, Schärer P, Marinello CP. Long-term results of implants treated with guided bone regeneration: A 5-year prospective study. Int J Oral Maxillofac Implants 2001;16(3):355–366. 23. Calvo Guirado JL, Pardo Zamora G, Saez Yuguero MR. Ridge splitting technique in atrophic anterior maxilla with immediate implants, bone regeneration and immediate temporisation: A case report. J Ir Dent Assoc 2007;53(4):187–190. 24. De Assis DS, Ribeiro PD Jr, Duarte MA, Gonçales ES. Evaluation of the mesio-buccal gingival sulcus depth of the upper central incisors in patients submitted to surgically assisted maxillary expansion. Oral Maxillofac Surg 2010;15(2):79–84. 25. Lee KH, Kim BO, Jang HS. Clinical evaluation of a collagen matrix to enhance the width of keratinized gingiva around dental implants. J Periodontal Implant Sci 2010;40(2):96–101. 26. Norton MR, Odell EW, Thompson ID, Cook RJ. Efficacity of bovine bone mineral for alveolar augmentation: A human histologic study. Clin Oral Implants Res 2003;14:775–783. 27. Zitzmann NU, Schärer P, Marinello CP, Schüpbach P, Berglundh T. Alveolar ridge augmentation with Bio-Oss: A histologic study in humans. Int J Periodontics Restorative Dent 2001;21:288–295. 28. Hellem S, Astrand P, Stenström B, Engquist B, Bengtsson M, Dahlgren S. Implant treatment in combination with lateral augmentation of the alveolar process: A 3-year prospective study. Clin Implant Dent Relat Res 2003;5:233–240. 29. Strietzel FP, Nowak M, Küchler I, Friedmann A. Peri-implant alveolar bone loss with respect to bone quality after use of the osteotome technique: Results of a retrospective study. Clin Oral Implants Res 2002;13:508–513. 30. 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(9):1921–1930. 31. Chiapasco M, Casentini P, Zaniboni M. Bone augmentation procedures in implant dentistry. Int J Oral Maxillofac Implants 2009; 24(suppl):237–259. 32. 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. 33. Funaki K, Takahashi T, Yamuchi K. Horizontal alveolar ridge augmentation using distraction osteogenesis: Comparison with a bonesplitting method in a dog model. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;107(3):350–358. 34. Cortes AR, Cortes DN. Nontraumatic bone expansion for immediate dental implant placement: An analysis of 21 cases. Implant Dent. 2010;19(2):92–97. 35. 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.
140 Volume 29, Number 1, 2014 © 2014 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.
A
trophic edentulous jaws can represent a significant challenge to the successful use of endosseous im-
1 Assistant
Professor and Researcher, Department of Odontology and Buccal Health, University Hospital Center, Bordeaux, France. 2Hospital Practitioner and Researcher, Department of Maxillofacial Surgery, University Hospital Center, Bordeaux, France. 3Hospital Practitioner and Researcher, Department of Odontology and Buccal Health, University Hospital Center, Bordeaux, France. 4Medical Resident, Department of Odontology and Buccal Health, University Hospital Center, Bordeaux, France. 5Professor, Department of Odontology and Buccal Health, University Hospital Center, Bordeaux, France. Correspondence to: Prof Bruno Ella, Odontology and Buccal Health, University Hospital Center, 10-20 Cours de la Marne, Bordeaux 33082, France. Email: [email protected] ©2014 by Quintessence Publishing Co Inc.
plants for prosthetic reconstruction of the edentulous mandible. Although ridge augmentation can help to restore ridge volume, grafting procedures can significantly increase patient morbidity, costs, and treatment time before dental implants can be placed.1,2 Inadequate bone width in the ridge is a common limitation for dental rehabilitation in oral implant therapy. An implant must be surrounded by at least 1 mm of cortical bone on both sides; if the alveolar ridge is narrower than 5 mm, it is difficult to insert an implant to replace a molar or a premolar.3,4 The autogenous bone onlay graft is considered the gold standard for grafting; however, intraoral donor sites do not always provide sufficient graft volume.5–7 In addition, intraoral grafting methods present several drawbacks: the invasiveness of the surgery with its increased risk of morbidity, the risk of exposure and/ or infection of the bone graft and/or membrane, and an increased number of operations, which reduces patient comfort and lengthens treatment time.8–11 The International Journal of Oral & Maxillofacial Implants 135
© 2014 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.
Ella et al
Horizontal bone expansion has been used since the 1980s to create sufficient width in narrow ridges with simultaneous implant placement.12 This technique has continued to evolve, and new protocols have been developed, some of which include filling of the expanded ridge.13–15 A new surgical device (Crest-Control Bone Splitting System, Meisinger) has been proposed to expand narrow ridges in the mandible in association with sagittal osteotomy.16 The Crest-Control Bone Splitting System consists of two surgical steel arms hinged apically and a transverse screw, which allows the device to be activated progressively. After ridge expansion is complete, the expansion devices are removed and implants are placed following standard procedures. The use of this device should allow progressive, controlled widening of a horizontally atrophied crestal ridge with a reduced risk of alveolar plate fracture. Some authors reported implant placement after alveolar bone expansion, without filling of the residual defects around implants,17 while others reported crestal resorption after this approach.18 The aims of this study were, therefore: (1) to present the preliminary results obtained with the aforementioned ridge-splitting tool for crestal expansion of horizontally atrophied mandibular crestal ridges in conjunction with implant placement, and (2) to determine whether it is necessary to pack the expansion area with a bone substitute to maintain the expanded bone volume.
Material and methods Study population
The study was carried out over a 3-year period in patients who attended a private practice for implant therapy of the edentulous mandible. Inclusion criteria were: no general or other pathology, an average width of the edentulous ridge of 3 to 4 mm, and a minimum of 11 mm of bone height, including at least 1 mm of cancellous bone (Fig 1a). Two sectors of the mandible were considered: the anterior sector (ie, incisors and canines) and the lateral sectors (premolar and molar areas). Patients were treated for prosthetic rehabilitation of implants in only one edentulous sector of the mandible, and the considered edentulous sectors corresponded, on average, to the replacement of two or three teeth. Thus, each patient received two implants per sector. In addition, the patients had to agree to participate in a postoperative checkup program. Each patient signed an appropriate consent form. On the ridges that were treated, there needed to be a minimum of 11 mm of bone between the top of the ridge and the inferior alveolar nerve. Patients were excluded from participation if they had systemic conditions contraindicating oral surgery,
a drug allergy, a smoking habit, alcohol or drug abuse, periodontal disease, or poor oral hygiene.
Surgical Protocol
It was decided to use a ridge expansion technique and to insert the implants simultaneously. In some cases, the spaces between the implants were filled with a synthetic bone substitute (type SBS 60/40 biphasic calcium phosphate, MBCP, Expanscience).19 Under local anesthesia, a crestal incision was made and a full-thickness flap was raised to obtain adequate visibility of the crestal bone; the incision was completed with a partial-thickness flap apical to the crest. The initial osteotomy was performed on midcrestal bone, with a rotating saw used to separate the buccal plate from the palatal plate, and was limited to 1 mm from the adjacent teeth. The Crest-Control Bone Splitting System was placed through the crestal osteotomy. The Crest-Control Bone Splitting System consists of two surgical steel arms hinged apically and a transverse screw, which allows the device to be progressively activated (Fig 1b). After ridge expansion was completed, the expansion devices were removed, and implants were placed following standard procedures. Speedy Groovy implants (Nobel Biocare) were used in all patients; diameters were 3.3 or 4 mm (Fig 1c). Implant placement was submerged. All areas were covered with a resorbable collagen membrane (Bio-Gide, Geistlich)20,21 (Fig 1d). The flaps were sutured without tension and were made watertight to protect the area (Fig 1e). All patients received antibiotic therapy (amoxicillin 2 g per day), which started the day before surgery and continued for 6 days; an analgesic (acetaminophen 3 g per day for 5 days); and a 0.12% chlorhexidine mouthwash (twice a day for 3 weeks). All sites were checked at follow-up visits, and any nonabsorbable sutures were removed 15 days after surgery. After 6 months of healing, stage-two surgery was carried out. Prostheses were placed per the usual protocol in patients with no bone resorption around the implants (Fig 1f ). However, in all cases where there was bone resorption, bone rehabilitation was performed using the same substitute material as was used for the bone expansion before prosthetic treatment.22,23
Measurements
Bone resorption was quantified as 1 or 2 mm, and horizontal fractures were noted (0 = no fractures, 1 = at least one fracture). The postsurgical width of the edentulous ridge was measured after the expansion and simultaneous placement of implants. At 6 months, the expanded sector was opened to measure the width of the expanded bone and its contact with the implants and to place healing abutments (Fig 1g). The increase
136 Volume 29, Number 1, 2014 © 2014 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.
Ella et al
Fig 1a Computed tomographic scan of the mandibular ridge.
Fig 1b Horizontal expansion (two expanders placed).
Fig 1c Implants placed in the expanded ridge.
Fig 1d Resorbable membrane placed after ridge filling (SBS).
Fig 1e Sutures.
Fig 1f The expanded ridge 6 months after surgery; bone gain and bone resorption were measured (horizontal expansion).
Fig 1g Prosthetic abutments placed.
in width and the bone levels around the implants were assessed using a periodontal probe (PCP UNC 15, Hu-Friedy) and recorded to the nearest millimeter. Measurements around the implants were made from the base of the resorption to the implant platform.24,25
Statistical Analyses
The Mann-Whitney test (α = .05) was performed to compare groups for bone resorption and fracture data: “women versus men,” “anterior versus lateral sector,” “3 mm versus 4 mm of crest width,” and “with SBS versus without SBS.” If the groups were significantly different, the Kruskal-Wallis test was performed (α = .05).
Results Thirty-two patients were treated with two implants each in the atrophied mandible; 41% were men and 59% were women. With regard to the treated area, 56% of treated areas were in the lateral mandible (premolars or molar) and 44% were in the anterior mandible (incisors or canines). Of the implants placed, 53% were 3.3 mm wide and 47% were 4 mm wide. Seventeen patients received SBS and 15 did not. After 6 months, all expanded sectors, with or without bone substitute, had healed. One year after ridge expansion, no implants had been lost or showed mobility. The International Journal of Oral & Maxillofacial Implants 137
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100 90 80 70 60 50 40 30 20 10 0
% of patients
% of patients
Ella et al
Men
Women
*
100 90 80 70 60 50 40 30 20 10 0
3 mm
4 mm
100 90 80 70 60 50 40 30 20 10 0
*
% of patients
% of patients
Fig 2 Frequency of bone fracture following alveolar expansion with respect to (left) gender and (right) original alveolar ridge width. *α = .04, Mann-Whitney test; α = .05, Kruskal-Wallis test.
No biomaterial
With biomaterial
100 90 80 70 60 50 40 30 20 10 0
No SBS With SBS
0 1 2 0 1 2 3 mm
0 1 2 0 1 2 4 mm
Fig 3 Frequency and amount of bone resorption 6 months after ridge expansion with respect to the use of SBS.
Fractures
With respect to fracture frequency, men and women were significantly different (Mann-Whitney test, α = .07), but no significant difference was confirmed with the Kruskal-Wallis test (Fig 2). “Anterior sector” and “lateral sector” were not significantly different with the Mann-Whitney test. “With SBS” and “without SBS” groups were not significantly different with the Mann-Whitney test, but the “3-mm-wide crest” and “4-mm-wide crest” groups were significantly different (α = .04). In addition, a significant effect of crest width on fracture in the SBS group was obtained with the Kruskal-Wallis test (α = .05) (Fig 2).
Bone Resorption
With respect to bone resorption, women and men were significantly different with the Mann-Whitney test (α = .0082), but no significant difference was seen with the Kruskal-Wallis test. “Anterior sector” and “lateral sector” were not significantly different with the MannWhitney test. The “with SBS” and “without SBS” groups were significantly different with the Mann-Whitney test (α = .00); SBS had a significant effect on resorption of 3-mm-wide crests (5%) and on resorption of 4-mm-wide crests (5%) according to the Kruskal-Wallis test (α = .02%).
Discussion Bone Resorption
The location of the intervention (anterior versus lateral sector) had no effect on bone resorption. Filling with SBS, however, did have an effect on bone resorption, regardless of the original crest width, and resulted in a strong preservation of crestal width gain.
Fracture Risk
There was a gender-related difference in fracture risk, which was higher in women. The location of the intervention (anterior or lateral sector) had no effect on fracture risk. A narrow initial crest width increased the risk of fracture. Filling with SBS increased the fracture risk when the initial crest was narrow. Analysis of the present sample can show not only whether this horizontal ridge expansion technique is easily reproducible, but also whether filling with bone substitute is necessary to maintain the bone walls after expansion. Almost 53% of the expanded sectors were filled with SBS 60/40, while about 47% were not, regardless of preoperative ridge width. It should be noted that 94% of ridges that received SBS 60/40 after expansion showed no resorption, regardless of the preoperative
138 Volume 29, Number 1, 2014 © 2014 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.
Ella et al
a Fig 4a A very narrow ridge (3 mm).
b
c
Figs 4b and 4c (b) Horizontal expansion with one expander placed in a very narrow ridge; (c) horizontal fracture during expansion.
width (α = .02). On the other hand, almost 47% of all ridges showed resorption around the implants. The majority of resorption was seen in the expanded ridges that had not been filled with SBS 60/40, with a higher resorption rate (25%) in the narrowest ridges (3 mm) (Fig 3). Ridges of 3 or 4 mm in patients who had received SBS 60/40 were significantly different (5%) from ridges that had not been filled with SBS 60/40. Indeed, bone resorption was noted around the implants in most patients where the expanded area had not been filled with SBS 60/40. Resorption would therefore appear to be all the more significant when the expanded ridge had not been filled with SBS 60/40 (α = .02). Comparison of the expanded sectors with and without SBS 60/40, all parameters combined, revealed a significant difference, with a 5% risk (α = .05), which could suggest that filling a horizontally expanded site with a bone substitute has the effect of reducing resorption in the bone walls around the implant.26–28 This particular bone substitute material therefore appears to have maintained bone volume. This effect was even more marked around implants when the bone walls were very thin (3 mm). Despite the expansion of the ridge, the bone walls in direct contact with the implant probably exert pressure, however minimal, on the implant surface. This pressure could thus affect bone vascularization and cause resorption that is ischemic in origin. It is possible that this pressure is reduced by the SBS material occupying the space between the two bone walls. Contact between the bone walls and the surface of the implants would then be passive after expansion. Another drawback when ridges are too narrow (Fig 4a) is the risk of fracture during horizontal expansion (Figs 4b and 4c). In fact, in this sample, 43% of the ridges presented a fracture, with one or both of the bone walls becoming disconnected. The narrowest ridges (3 mm wide, 40% of the sample) accounted for almost all of the fractures. When the 3-mm ridges were compared with the 4-mm ridges, all parameters combined, there was a 5% risk (α = .05) that ridge width would affect the risk of fracture in the bone walls
during horizontal expansion. However, this characteristic showed no direct link between the fracture of the ridge and its eventual resorption. The expansion of ridges of less than 4 mm wide seemed to present more constraints than those that were already 4 mm wide. These constraints manifested themselves in several ways in the present study. Bone resorption around the implants and fractures was clearly evident in the narrowest ridges (3 mm).29 Bone fractures could be the result of several factors, one of which could be that there was not a minimum amount (1 mm) of spongy bone interposed between the two cortical plates of the ridge.30
Conclusion Horizontal expansion using the Crest-Control device is certainly reproducible and can be a good alternative to bone block grafting in a narrow ridge.31–33 However, the ridge bone must have a minimum width, and there must be a minimum amount of cancellous bone between the cortical plates to prevent fracture during surgery and the very probable risk of postoperative resorption in the short or medium term. This technique prevents the need for donor site bone and must be compared with the technique of osteoperiosteal flap. The risk of fracture during surgery did not lead to failure during the healing process; on the other hand, whether the expanded area was filled with a bone substitute material had a considerable influence on the expected gain in bone volume. It therefore appears necessary, especially in the case of the narrowest ridges (3 mm), to maintain the expanded ridge with a grafting material, which may be based on an entirely synthetic bone substitute, as was done in this study.34 Today, a wide range of surgical procedures are available; however, it is difficult to demonstrate that any one of these can offer better outcomes than another. Every surgical procedure presents advantages and disadvantages, so priority should be given to those that are simpler, less invasive, and less risky.35 The International Journal of Oral & Maxillofacial Implants 139
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acknowledgments The authors reported no conflicts of interest related to this study.
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