CLINICAL
Classification of the Alveolar Ridge Width: Implant-Driven Treatment Considerations for the Horizontally Deficient Alveolar Ridges Len Tolstunov, DDS, DMD1 Among many techniques advocated for the horizontally deficient alveolar ridges, ridge-split has many advantages. Here, treatment management strategies of the horizontally collapsed ridges, especially the ridgesplit approach, are discussed and a clinically relevant implant-driven classification of the alveolar ridge width is proposed, with the goal to assist an operator in choosing the proper bone augmentation technique. Comparison and advantages of two commonly used techniques, ridge-split and block bone graft, are presented. Key Words: ridge-split, block bone graft, alveolar ridge
INTRODUCTION
I
t has been shown that although bone collapse after tooth loss is usually three dimensional (3D), the horizontal deficiency or width loss develops to a larger extent.1,2 Alveolar width deficiency can represent loss of buccal (labial) cortical or medullary bone, or both. Deficiency of the buccal cortex (cortical plate) after tooth extraction can present significant difficulty in implant reconstruction.3,4 The buccal cortical plate with a thickness ,2 mm next to an implant appears to have a higher risk of subsequent resorption.5 A variety of implant-driven bone augmentation techniques for the deficient alveolar bone have been proposed.6–8 Four of these techniques are frequently performed: (1) guided bone regeneration (GBR)/particulate bone grafting;9,10 (2) onlay (veneer) block bone grafting with intraoral sources, such as chin, ramus, posterior mandible, zygomatic buttress, and maxillary tuberosity;11–13 (3) ridgesplit/bone graft procedure;14–16 and (4) alveolar distraction osteogenesis.17–19 Most of these tech-
1
Private practice, Oral and Maxillofacial Surgery, San Francisco, Calif, and Departments of Oral and Maxillofacial Surgery, University of the Pacific, Arthur A. Dugoni School of Dentistry and University of California San Francisco, San Francisco, Calif. Corresponding author, e-mail: [email protected] DOI: 10.1563/AAID-JOI-D-14-00023
niques are designed to improve horizontal bone loss before or simultaneously with dental implant placement. DIAGNOSIS
AND
TREATMENT PLANNING
It is important to establish a proper diagnosis based on the alveolar ridge assessment before initiation of the treatment plan. Initial clinical evaluation supplemented by radiographic images helps in most cases to distinguish two-dimensional (2D) versus 3D alveolar bone deficiency. Although minimal bone loss and patient’s lack of desire to go through grafting surgical procedure(s) can be circumvented with restorative means, extensive bone atrophy usually requires surgical correction for a proper implant placement. Alveolar bone should be initially assessed clinically (visually) for a rough width and height analysis and interarch-occlusal relationships. In some cases, although 7–8 mm of bone width is present, it could be lingually (palatally) positioned and therefore might require an additional buccal bone grafting for a proper restoratively driven implant insertion. Alveolar width can be measured with different calipers on top of the thin mucosa or by ridge Journal of Oral Implantology
365
Classification of the Alveolar Ridge Width
FIGURES 1 AND 2. FIGURE 1. Cone beam computerized tomography scan of the horizontally deficient edentulous maxillary alveolar ridge. Alveolar bone width and height, as well as thickness of the buccal and palatal cortical and medullary bone are demonstrated. This alveolar ridge is a class III ridge according to the classification presented in the article. FIGURE 2. Axial cone beam computerized tomography scan of the horizontally collapsed edentulous right maxillary alveolar ridge showing varied thickness of the alveolar ridge.
TABLE 1 Classification of alveolar ridge width Alveolar ridge width (mm), based on CBCT* scan Alveolar ridge deficiency
.10
8–10
6–8
4–6
No deficiency
Minimal
Mild
Moderate
Class
0
I
II
III
Schematic diagram Comments
Immediate insertion
Hard tissue surgery is Hard tissue surgery is rarely indicated. not indicated. Occasionally, Occasionally, alveolar width can alveolar width be improved by (buccal convexity) particulate bone can be improved for graft or palatal soft esthetic reasons tissue graft for with a soft tissue esthetic and graft. prosthetic reasons. Yes Yes
Operator experience
Basic
Indications for surgery
*CBCT, cone beam computerized tomography. ÀGBR, guided bone regeneration.
366
Vol. XL /Special Issue / 2014
Basic
An ideal width for the Particulate (GBR) ridge-split grafting or ridgeprocedure that can split is often needed be done in a singleto improve labial or two-stage bone projection and approach (see proper occlusal Figure 3). Block implant position. graft or GBR can also be done. Yes/no, depends on presence of apical bone for primary implant stability Basic
Yes/no, depends on presence of apical bone for primary implant stability (see Figure 4) Basic to advanced
Tolstunov
FIGURES 3 AND 4. FIGURE 3. Intraoperative photograph of the ridge-split procedure demonstrating the mobilization and repositioning of the buccal muco-osteo-periosteal flap. FIGURE 4. Intraoperative photograph of the ridge-split procedure that is done simultaneously with the implant insertion.
mapping (with local anesthesia) through it. Panoramic and other 2D radiographic images are often sufficient in some implant cases, although an implant-driven bone analysis often implies need for a 3D or volumetric bone evaluation with cone
beam computerized tomography (CBCT) scans. CBCT improves the ability for precise measurement of the ridge on all levels as well as evaluation of both cortical and medullary portion of the bone for primary implant stability (Figures 1 and 2).
TABLE 1 Extended 2–4
,2
6–10/2–4
2–4/6–10
Severe
Extreme
‘‘Bottleneck’’
IV
V
‘‘Hourglass’’ (undercut) (buccal or lingual) VI
VII
GBRÀ at the mid ridge level can be done
Ridge reshaping or GBR at the top of the ridge can be done
Ridge-split or block bone graft is a graft of choice (surgeon’s experience).
Large extraoral block graft is a preferable surgical choice. Alternative is multiple and sequential augmentation procedures.
Not recommended
No
Yes/no, depends on the severity of the undercut
Usually yes, can depend on the morphology of the top portion of the ridge
Advanced
Advanced
Basic
Basic
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367
Classification of the Alveolar Ridge Width TABLE 2 Ten-point comparison of ridge-split and monocortical block bone graft techniques Comparison
Monocortical Block Grafting (Intraoral)
Ridge-split Procedure
Onlay: external, ‘‘cortex to cortex’’; donor cortical graft is added to the collapsed recipient buccal cortical bone, resulting in the grafted bone that has cortical environment on one side and periosteum on the other side Free (devascularized) graft; the grafted bone may contain a substantial amount of nonvital bone that did not survive detachment, devascularization, and transportation; an increased risk of postoperative graft resorption27; slow and incomplete neovascularization rate28 Yes: pain, swelling, IAN* injury (posterior mandible, ramus), ‘‘wooden teeth sensation’’ (chin), sinus perforation (zygomatic buttress), others Soft tissue dehiscence and graft exposure, loose fixation screws and graft mobility; graft loss Primary wound closure is mandatory
Inlay: internal (like an ‘‘open book’’); cortical envelope is preserved and expanded and a particulate grafting is done ‘‘from within,’’ resulting in a bilateral proximity of the grafted bone to both cortices (similar to a 4wall defect of extraction socket) Vascular bone flap (muco-osteoperiosteal flap) (see Figure 3), vascularization is preserved at all times; ‘‘cancellous bone grafts are more rapidly and completely revascularize than cortical grafts’’29 Decreased risk of postoperative graft resorption16 No
1
Type of grafting
2
Graft resorption
3
Donor site morbidity
4
Recipient site morbidity
5
Wound closure
6
Buccal soft tissue flap
7
Wound healing
8
Immediate implant insertion
Traditionally not done
9
Delayed implant insertion
10
Environmental factors and long-term stability of a graft
Implants are placed into the cortical bone interface 4 to 6 months later More subject to a postoperative injury (‘‘external’’ grafting); less long-term stability and more long-term resorption28
Buccal flap is lifted and often stretched; tension-free primary closure is important, but can be challenging By plasmatic imbibition from the host (recipient) tissue
Soft tissue dehiscence and graft exposure, buccal plate malfracture; inadequate split Closure by secondary intention is preferred Buccal flap is not compromised; it is not lifted and left attached to the buccal periosteum Internal ‘‘coagulum’’ is easily converted in the woven bone due to protection and excellent vascularization from both cortices throughout the whole process Can be done in some cases (see Figure 4) Implants are placed into the cancellous bone interface 4 to 6 months later Less subject to a postoperative injury during mastication; it is more protected (‘‘internal’’ or interpositional grafting); less longterm resorption and more long-term stability30,31
*IAN, inferior alveolar nerve.
CLASSIFICATION
OF THE
ALVEOLAR RIDGE WIDTH
In 1988, Cawood and Howell20 suggested an anatomic classification of the edentulous jaws for the preprosthetic surgery. It proposed six classes and detailed the changes that the edentulous alveolar process in anterior and posterior maxilla and mandible undergo after teeth extraction (the pattern of resorption). In 1989, Jensen21 proposed 368
Vol. XL /Special Issue / 2014
an implant-driven site classification by bone quality and quantity and proximity to vital structures. In 2002, Wang and Al-Shammari22 described a practical (therapeutically oriented) classification of alveolar ridge defects, that is, horizontal, vertical, and combination defects, proposing the edentulous ridge expansion approach (ridge-split) for the horizontal and combination defects of the alveolar ridge.
Tolstunov
Here, a clinically relevant implant-driven classification of the alveolar ridge width based on precise measurement of the alveolar width with computerized tomography/CBCT scans is recommended; it is presented in the Table 1. The classification attempts to match the specific ridge (its width and topography) with the appropriate surgical technique (GBR, ridge-split, or block graft) that can be used in the particular case of horizontal bone atrophy. Although each operator’s experience ultimately determines the chosen surgical technique, it is important to compare benefits and drawbacks of different surgical procedures for certain ridges to improve the selection process.
CONCLUSION
Knowledge of 3D bone anatomy with CBCT scan helps to establish a proper ridge diagnosis before initiation of implant treatment. The recommended ridge width classification for the horizontally deficient alveolar ridges is designed to be a clinically relevant implant-driven anatomic guide for choosing an appropriate surgical modality for the specific collapsed alveolar ridge. Operator experience and surgical comfort ultimately determines the choice of the technique. The ridge-split approach tends to have many advantages, including lack of donor site morbidity and a graft stability over time.
ABBREVIATIONS COMPARISON
OF THE
RIDGE-SPLIT AND BLOCK BONE GRAFTING TECHNIQUES
A literature review showed few similarities and many differences between autogenous intraoral monocortical (veneer) block graft and ridge-split/ bone graft techniques. Both procedures require a skilled surgical practitioner equipped with knowledge of regional anatomy and vascularization and prepared for risks and complications of the procedure. Both the ridge-split and block grafting techniques are used mainly for a 2D horizontal alveolar ridge augmentation (alveolar bone widening; some height gain can also be achieved with both techniques). Autogenous block bone grafting demonstrates high osteogenic potential and effective in severe anterior alveolar atrophy in maxilla and mandible.23–25 Two main disadvantages of monocortical block grafts are donor site morbidity and late-term graft resorption.26 The monocortical block bone resorption has been reported to have up to 5% early bone loss and up to 40% late bone loss of the entire graft volume due to remodeling and inadequate consolidation.27 Table 2 shows differences (10-point comparison) between the ridge-split procedure and autogenous intraoral monocortical block bone grafting. Factors that are presented include donor- and recipient site morbidity, type of wound closure, buccal flap integrity and vascularity, specifics of wound healing, type of bone interface, and possibility of an immediate implant placement.
CBCT: cone beam computerized tomography GBR: guided bone regeneration REFERENCES 1. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft tissue contour changes following single tooth extraction: a clinical and radiographic 12-month prosthetic study. Int J Periodont Restor Dent. 2003;23:313–323. 2. Botticelli D, Berglundh T, Lindhe J. Hard tissue alterations following immediate implant placement in extraction sites. J Clin Periodontol. 2004;31:820–828. 3. Cardaropoli G, Arau´jo M, Lindhe J. Dynamics of bone tissue formation in tooth extraction sites. An experimental study in dogs. J Clin Periodontol. 2003;30:809–818. 4. Arau´jo M, Lindhe J. Dimensional ridge alterations following tooth extraction. An experimental study in the dog. J Clin Periodontol. 2005;32:212–218. 5. Qahash M, Susin C, Polimeni G, Hall J, Wikesjo¨ UM. Bone healing dynamics at buccal peri-implant sites. Clin Oral Implants Res. 2008;19:166–172. 6. Aghaloo TL, Moy PK. Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants. 2007;22(suppl): 49–70. 7. McAllister BS, Haghighat K. Bone augmentation techniques. J Periodontol. 2007;78:377–396. 8. Chiapasco M, Zaniboni M, Boisco M. Augmentation procedures for the rehabilitation of deficient edentulous ridges with oral implants. Clin Oral Implants Res. 2006;1(suppl 2):136–159. 9. Buser D, Bra¨gger U, Lang NP, Nyman S. Regeneration and enlargement of jaw bone using guided tissue regeneration. Clin Oral Implants Res. 1990;1:22–32. 10. Annibali S, Bignozzi I, Sammartino G, La Monaca G, Cristalli MP. Horizontal and vertical ridge augmentation in localized alveolar deficient sites: a retrospective case series. Implant Dent. 2012;21: 175–185. 11. Bedrossian E, Tawfilis A, Alijanian A. Veneer grafting: a technique for augmentation of the resorbed alveolus prior to implant placement. A clinical report. Int J Oral Maxillofac Implants. 2000;15:853–858.
Journal of Oral Implantology
369
Classification of the Alveolar Ridge Width 12. Pikos MA. Mandibular block autografts for alveolar ridge augmentation. Atlas Oral Maxillofac Clin North Am. 2005;13:91–107. 13. Tolstunov L. Maxillary tuberosity block bone graft: innovative technique and case report. J Oral Maxillofac Surg. 2009;67:1723–1729. 14. Simion M, Baldoni M, Zaffe D. Jawbone enlargement using immediate implant placement associated with a split-crest technique and guided tissue regeneration. Int J Periodontics Restorative Dent. 1992;12:462–473. 15. Scipioni A, Bruschi GB, Calesini G. The edentulous ridge expansion technique: a five-year study. Int J Periodontics Restor Dent. 1994;14:451–459. 16. 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. 17. McCarthy JG. The role of distraction osteogenesis in the reconstruction of the mandible in unilateral craniofacial microsomia. Clin Plast Surg. 1994;21:625–631. 18. Chin M, Toth BA. Distraction osteogenesis in maxillofacial surgery using internal devises: review of five cases. J Oral Maxillofac Surg. 1996;54:45–53. 19. Laster Z, Reem Y, Nagler R. Horizontal alveolar ridge distraction in an edentulous patient. J Oral Maxillofac Surg. 2011;69: 502–506. 20. Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg. 1988;17:232–236. 21. Jensen O. Site classification for the osseointegrated implant. J Prosthet Dent. 1989;61:228–234. 22. Wang HL, Al-Shammari K. HVC ridge deficiency classification: a therapeutic oriented classification. Int J Periodontics Restor Dent. 2002;22:335–343. 23. Barone A, Covani U. Maxillary alveolar ridge reconstruction
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with nonvascularized autogenous block bone: clinical results. J Oral Maxillofac Surg. 2007;65:2039–2046. 24. Cordaro L, Amade´ DS, Cordaro M. Clinical results of alveolar ridge augmentation with mandibular block bone graft in partially edentulous patients prior to implant placement. Clin Oral Implants Res. 2002;13:103–111. 25. Adeyemo WL, Reuther T, Bloch W, et al. Influence of host periosteum and recipient bed perforation on the healing of onlay mandibular bone graft: an experimental pilot study in the sheep. Oral Maxillofac Surg. 2008;12:19–28. 26. Casap N, Brand M, Mogyros R, et al. Island osteoperiosteal flaps with interpositional bone grafting in rabbit tibia: preliminary study for development of new bone augmentation technique. J Oral Maxillofac Surg. 2011;69:3045–3051. 27. Romero-Olid Mde N, Vallencillo-Capilla M. A pilot study in the development of indices for predicting the clinical outcomes of oral bone grafts. Int J Oral Maxillofac Implants. 2005;20:595–604. 28. Acocella A, Bertolai R, Calafranceschi M, Sacco R. Clinical, histological and histomorphometric evaluation of the healing of mandibular ramus bone block grafts for the alveolar ridge augmentation before implant placement. J Craniomaxillofac Surg. 2010;38:222–230. 29. Oppenheimer AJ, Tong L, Buchman SR. Craniofacial bone grafting: Wolff’s law revisited. Craniomaxillofac Trauma Reconstr. 2008;1:49–61. 30. Gonzalez-Garcia R, Monje F, Moreno C. Alveolar split osteotomy for the treatment of the severe narrow ridge maxillary atrophy: a modified technique. Int J Oral Maxillofac Surg. 2011;40: 57–64. 31. de Wijs FL, Cune MS. Immediate labial contour restoration for improved esthetics: a radiographic study on bone splitting in anterior single-tooth replacement. Int J Oral Maxillofac Implants. 1997;12:686–696.
Classification of the Alveolar Ridge Width: Implant-Driven Treatment Considerations for the Horizontally Deficient Alveolar Ridges Len Tolstunov, DDS, DMD1 Among many techniques advocated for the horizontally deficient alveolar ridges, ridge-split has many advantages. Here, treatment management strategies of the horizontally collapsed ridges, especially the ridgesplit approach, are discussed and a clinically relevant implant-driven classification of the alveolar ridge width is proposed, with the goal to assist an operator in choosing the proper bone augmentation technique. Comparison and advantages of two commonly used techniques, ridge-split and block bone graft, are presented. Key Words: ridge-split, block bone graft, alveolar ridge
INTRODUCTION
I
t has been shown that although bone collapse after tooth loss is usually three dimensional (3D), the horizontal deficiency or width loss develops to a larger extent.1,2 Alveolar width deficiency can represent loss of buccal (labial) cortical or medullary bone, or both. Deficiency of the buccal cortex (cortical plate) after tooth extraction can present significant difficulty in implant reconstruction.3,4 The buccal cortical plate with a thickness ,2 mm next to an implant appears to have a higher risk of subsequent resorption.5 A variety of implant-driven bone augmentation techniques for the deficient alveolar bone have been proposed.6–8 Four of these techniques are frequently performed: (1) guided bone regeneration (GBR)/particulate bone grafting;9,10 (2) onlay (veneer) block bone grafting with intraoral sources, such as chin, ramus, posterior mandible, zygomatic buttress, and maxillary tuberosity;11–13 (3) ridgesplit/bone graft procedure;14–16 and (4) alveolar distraction osteogenesis.17–19 Most of these tech-
1
Private practice, Oral and Maxillofacial Surgery, San Francisco, Calif, and Departments of Oral and Maxillofacial Surgery, University of the Pacific, Arthur A. Dugoni School of Dentistry and University of California San Francisco, San Francisco, Calif. Corresponding author, e-mail: [email protected] DOI: 10.1563/AAID-JOI-D-14-00023
niques are designed to improve horizontal bone loss before or simultaneously with dental implant placement. DIAGNOSIS
AND
TREATMENT PLANNING
It is important to establish a proper diagnosis based on the alveolar ridge assessment before initiation of the treatment plan. Initial clinical evaluation supplemented by radiographic images helps in most cases to distinguish two-dimensional (2D) versus 3D alveolar bone deficiency. Although minimal bone loss and patient’s lack of desire to go through grafting surgical procedure(s) can be circumvented with restorative means, extensive bone atrophy usually requires surgical correction for a proper implant placement. Alveolar bone should be initially assessed clinically (visually) for a rough width and height analysis and interarch-occlusal relationships. In some cases, although 7–8 mm of bone width is present, it could be lingually (palatally) positioned and therefore might require an additional buccal bone grafting for a proper restoratively driven implant insertion. Alveolar width can be measured with different calipers on top of the thin mucosa or by ridge Journal of Oral Implantology
365
Classification of the Alveolar Ridge Width
FIGURES 1 AND 2. FIGURE 1. Cone beam computerized tomography scan of the horizontally deficient edentulous maxillary alveolar ridge. Alveolar bone width and height, as well as thickness of the buccal and palatal cortical and medullary bone are demonstrated. This alveolar ridge is a class III ridge according to the classification presented in the article. FIGURE 2. Axial cone beam computerized tomography scan of the horizontally collapsed edentulous right maxillary alveolar ridge showing varied thickness of the alveolar ridge.
TABLE 1 Classification of alveolar ridge width Alveolar ridge width (mm), based on CBCT* scan Alveolar ridge deficiency
.10
8–10
6–8
4–6
No deficiency
Minimal
Mild
Moderate
Class
0
I
II
III
Schematic diagram Comments
Immediate insertion
Hard tissue surgery is Hard tissue surgery is rarely indicated. not indicated. Occasionally, Occasionally, alveolar width can alveolar width be improved by (buccal convexity) particulate bone can be improved for graft or palatal soft esthetic reasons tissue graft for with a soft tissue esthetic and graft. prosthetic reasons. Yes Yes
Operator experience
Basic
Indications for surgery
*CBCT, cone beam computerized tomography. ÀGBR, guided bone regeneration.
366
Vol. XL /Special Issue / 2014
Basic
An ideal width for the Particulate (GBR) ridge-split grafting or ridgeprocedure that can split is often needed be done in a singleto improve labial or two-stage bone projection and approach (see proper occlusal Figure 3). Block implant position. graft or GBR can also be done. Yes/no, depends on presence of apical bone for primary implant stability Basic
Yes/no, depends on presence of apical bone for primary implant stability (see Figure 4) Basic to advanced
Tolstunov
FIGURES 3 AND 4. FIGURE 3. Intraoperative photograph of the ridge-split procedure demonstrating the mobilization and repositioning of the buccal muco-osteo-periosteal flap. FIGURE 4. Intraoperative photograph of the ridge-split procedure that is done simultaneously with the implant insertion.
mapping (with local anesthesia) through it. Panoramic and other 2D radiographic images are often sufficient in some implant cases, although an implant-driven bone analysis often implies need for a 3D or volumetric bone evaluation with cone
beam computerized tomography (CBCT) scans. CBCT improves the ability for precise measurement of the ridge on all levels as well as evaluation of both cortical and medullary portion of the bone for primary implant stability (Figures 1 and 2).
TABLE 1 Extended 2–4
,2
6–10/2–4
2–4/6–10
Severe
Extreme
‘‘Bottleneck’’
IV
V
‘‘Hourglass’’ (undercut) (buccal or lingual) VI
VII
GBRÀ at the mid ridge level can be done
Ridge reshaping or GBR at the top of the ridge can be done
Ridge-split or block bone graft is a graft of choice (surgeon’s experience).
Large extraoral block graft is a preferable surgical choice. Alternative is multiple and sequential augmentation procedures.
Not recommended
No
Yes/no, depends on the severity of the undercut
Usually yes, can depend on the morphology of the top portion of the ridge
Advanced
Advanced
Basic
Basic
Journal of Oral Implantology
367
Classification of the Alveolar Ridge Width TABLE 2 Ten-point comparison of ridge-split and monocortical block bone graft techniques Comparison
Monocortical Block Grafting (Intraoral)
Ridge-split Procedure
Onlay: external, ‘‘cortex to cortex’’; donor cortical graft is added to the collapsed recipient buccal cortical bone, resulting in the grafted bone that has cortical environment on one side and periosteum on the other side Free (devascularized) graft; the grafted bone may contain a substantial amount of nonvital bone that did not survive detachment, devascularization, and transportation; an increased risk of postoperative graft resorption27; slow and incomplete neovascularization rate28 Yes: pain, swelling, IAN* injury (posterior mandible, ramus), ‘‘wooden teeth sensation’’ (chin), sinus perforation (zygomatic buttress), others Soft tissue dehiscence and graft exposure, loose fixation screws and graft mobility; graft loss Primary wound closure is mandatory
Inlay: internal (like an ‘‘open book’’); cortical envelope is preserved and expanded and a particulate grafting is done ‘‘from within,’’ resulting in a bilateral proximity of the grafted bone to both cortices (similar to a 4wall defect of extraction socket) Vascular bone flap (muco-osteoperiosteal flap) (see Figure 3), vascularization is preserved at all times; ‘‘cancellous bone grafts are more rapidly and completely revascularize than cortical grafts’’29 Decreased risk of postoperative graft resorption16 No
1
Type of grafting
2
Graft resorption
3
Donor site morbidity
4
Recipient site morbidity
5
Wound closure
6
Buccal soft tissue flap
7
Wound healing
8
Immediate implant insertion
Traditionally not done
9
Delayed implant insertion
10
Environmental factors and long-term stability of a graft
Implants are placed into the cortical bone interface 4 to 6 months later More subject to a postoperative injury (‘‘external’’ grafting); less long-term stability and more long-term resorption28
Buccal flap is lifted and often stretched; tension-free primary closure is important, but can be challenging By plasmatic imbibition from the host (recipient) tissue
Soft tissue dehiscence and graft exposure, buccal plate malfracture; inadequate split Closure by secondary intention is preferred Buccal flap is not compromised; it is not lifted and left attached to the buccal periosteum Internal ‘‘coagulum’’ is easily converted in the woven bone due to protection and excellent vascularization from both cortices throughout the whole process Can be done in some cases (see Figure 4) Implants are placed into the cancellous bone interface 4 to 6 months later Less subject to a postoperative injury during mastication; it is more protected (‘‘internal’’ or interpositional grafting); less longterm resorption and more long-term stability30,31
*IAN, inferior alveolar nerve.
CLASSIFICATION
OF THE
ALVEOLAR RIDGE WIDTH
In 1988, Cawood and Howell20 suggested an anatomic classification of the edentulous jaws for the preprosthetic surgery. It proposed six classes and detailed the changes that the edentulous alveolar process in anterior and posterior maxilla and mandible undergo after teeth extraction (the pattern of resorption). In 1989, Jensen21 proposed 368
Vol. XL /Special Issue / 2014
an implant-driven site classification by bone quality and quantity and proximity to vital structures. In 2002, Wang and Al-Shammari22 described a practical (therapeutically oriented) classification of alveolar ridge defects, that is, horizontal, vertical, and combination defects, proposing the edentulous ridge expansion approach (ridge-split) for the horizontal and combination defects of the alveolar ridge.
Tolstunov
Here, a clinically relevant implant-driven classification of the alveolar ridge width based on precise measurement of the alveolar width with computerized tomography/CBCT scans is recommended; it is presented in the Table 1. The classification attempts to match the specific ridge (its width and topography) with the appropriate surgical technique (GBR, ridge-split, or block graft) that can be used in the particular case of horizontal bone atrophy. Although each operator’s experience ultimately determines the chosen surgical technique, it is important to compare benefits and drawbacks of different surgical procedures for certain ridges to improve the selection process.
CONCLUSION
Knowledge of 3D bone anatomy with CBCT scan helps to establish a proper ridge diagnosis before initiation of implant treatment. The recommended ridge width classification for the horizontally deficient alveolar ridges is designed to be a clinically relevant implant-driven anatomic guide for choosing an appropriate surgical modality for the specific collapsed alveolar ridge. Operator experience and surgical comfort ultimately determines the choice of the technique. The ridge-split approach tends to have many advantages, including lack of donor site morbidity and a graft stability over time.
ABBREVIATIONS COMPARISON
OF THE
RIDGE-SPLIT AND BLOCK BONE GRAFTING TECHNIQUES
A literature review showed few similarities and many differences between autogenous intraoral monocortical (veneer) block graft and ridge-split/ bone graft techniques. Both procedures require a skilled surgical practitioner equipped with knowledge of regional anatomy and vascularization and prepared for risks and complications of the procedure. Both the ridge-split and block grafting techniques are used mainly for a 2D horizontal alveolar ridge augmentation (alveolar bone widening; some height gain can also be achieved with both techniques). Autogenous block bone grafting demonstrates high osteogenic potential and effective in severe anterior alveolar atrophy in maxilla and mandible.23–25 Two main disadvantages of monocortical block grafts are donor site morbidity and late-term graft resorption.26 The monocortical block bone resorption has been reported to have up to 5% early bone loss and up to 40% late bone loss of the entire graft volume due to remodeling and inadequate consolidation.27 Table 2 shows differences (10-point comparison) between the ridge-split procedure and autogenous intraoral monocortical block bone grafting. Factors that are presented include donor- and recipient site morbidity, type of wound closure, buccal flap integrity and vascularity, specifics of wound healing, type of bone interface, and possibility of an immediate implant placement.
CBCT: cone beam computerized tomography GBR: guided bone regeneration REFERENCES 1. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft tissue contour changes following single tooth extraction: a clinical and radiographic 12-month prosthetic study. Int J Periodont Restor Dent. 2003;23:313–323. 2. Botticelli D, Berglundh T, Lindhe J. Hard tissue alterations following immediate implant placement in extraction sites. J Clin Periodontol. 2004;31:820–828. 3. Cardaropoli G, Arau´jo M, Lindhe J. Dynamics of bone tissue formation in tooth extraction sites. An experimental study in dogs. J Clin Periodontol. 2003;30:809–818. 4. Arau´jo M, Lindhe J. Dimensional ridge alterations following tooth extraction. An experimental study in the dog. J Clin Periodontol. 2005;32:212–218. 5. Qahash M, Susin C, Polimeni G, Hall J, Wikesjo¨ UM. Bone healing dynamics at buccal peri-implant sites. Clin Oral Implants Res. 2008;19:166–172. 6. Aghaloo TL, Moy PK. Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants. 2007;22(suppl): 49–70. 7. McAllister BS, Haghighat K. Bone augmentation techniques. J Periodontol. 2007;78:377–396. 8. Chiapasco M, Zaniboni M, Boisco M. Augmentation procedures for the rehabilitation of deficient edentulous ridges with oral implants. Clin Oral Implants Res. 2006;1(suppl 2):136–159. 9. Buser D, Bra¨gger U, Lang NP, Nyman S. Regeneration and enlargement of jaw bone using guided tissue regeneration. Clin Oral Implants Res. 1990;1:22–32. 10. Annibali S, Bignozzi I, Sammartino G, La Monaca G, Cristalli MP. Horizontal and vertical ridge augmentation in localized alveolar deficient sites: a retrospective case series. Implant Dent. 2012;21: 175–185. 11. Bedrossian E, Tawfilis A, Alijanian A. Veneer grafting: a technique for augmentation of the resorbed alveolus prior to implant placement. A clinical report. Int J Oral Maxillofac Implants. 2000;15:853–858.
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