I would like to acknowledge my wife Marty, my children Sverre, Autumn, and Trygve, and my grandchildren as the underlying inspiration and drive for any success I might have outside the home.
I especially want to thank those who contributed so greatly to making this book possible: my publisher Tomoko Tsuchiya for taking a chance on me once again, Lisa Bywaters for her extreme patience and expert guidance, Bryn Goates for her positive and concise editing, Sue Robinson on an artistic layout and design, and Peter Jurek for his outstanding renderings.
I also want to express special thanks to Karen Shoop, my implant coordinator and brain away from home, Kristen Stifflear, who gave birth to a child this year and still provided many of the photos and essential content organization for the book, and my fantastic surgical assistants Cindy Formanek and Jennifer Patrick.
Dr Jared Cottam contributed as a research assistant; special thanks to him. Without my staff and associates, this decade-long process could not have been completed.
To see what is in front of one’s nose requires constant struggle.
—George Orwell
In the early evolutionary years of oral and maxillofacial surgery, pulpal response to alveolar osteotomies was a central question to be answered. Relatively few surgeons, however, were interested in this fundamental question. At the annual association meetings of the American Association of Oral and Maxillofacial Surgeons or the International Association for Dental Research, it was not unusual to see only five or six surgeons in attendance in the research sessions debating the question of what constitutes a viable tooth.
It had been recognized for some time that teeth contained within a repositioned dento-osseous segment did not respond positively to electrical stimulation immediately after surgery. This aberrant testing was usually transient and results returned to normal after 3 to 8 months. A small, dedicated cadre of investigators1–6 often debated as to whether pulpal vascularity were more important than neuronal continuity.
In time, preservation of pulpal circulation was generally considered to be necessary if normal pulpal anatomy were to be preserved following dentoalveolar surgery. Neuronal, blood flow, and histologic studies gradually confirmed these findings and created enormous interest in the surgical repositioning of all maxillary and mandibular teeth by dentoalveolar surgery and orthodontics. These studies opened the gate to the possibility of simultaneous repositioning of all or a part of the maxilla and maxillary teeth independently as small dento-osseous segments.
Recent studies have used laser Doppler flowmetry to assess tooth vitality after Le Fort I osteotomy.7,8 These studies have clearly demonstrated that teeth without normal innervation can have an intact blood supply and be vital.
Fig 1-1a Anterior maxillary osteotomy performed after reflection of the labial and buccal mucoperiosteum. (Reprinted from Bell et al23 with permission.)
Biology of Wound HealingMaxillary deformities have been recognized and described for centuries, but the challenge to correct them through surgery in the anterior maxilla was not met until the turn of the century. Bold attempts to move the anterior maxilla were first made by Cohn-Stock,9 Wassmund,10 and Spanier,11 who were unaware of the biologic basis for the healing of such surgically created wounds. Analysis of Cohn-Stock’s initial attempt to retroposition the anterior maxilla surgically indicates that he feared the consequences of such a procedure and attempted to avoid them by creating a greenstick fracture of the anterior maxilla through a transverse palatal incision; the retropo-sitioned maxilla subsequently relapsed.
When maxillary surgical procedures were introduced to the United States,12–15 the rationale for use of the various surgical techniques for correcting dentofacial deformities was empirical.16 Basic questions concerning the healing of surgical wounds produced by maxillary osteotomies had not been investigated. Many surgeons believed that the maxilla healed by fibrous union. Others believed absolute stability was necessary. Devitalization of teeth and bone in the mobilized segments had been re-ported. Varying degrees of relapse subsequent to posterior maxillary osteotomy9 and total maxillary osteotomy were reported. The possibility that the maxilla could be successfully repositioned superiorly or inferiorly through surgery was doubted by many clinicians and scientists. The blood vessels necessary to maintain circulation to the mobilized bony segments and teeth had not been studied. Consequently, both one-stage and two-stage procedures (of empirical duration ranging between 2 and 8 weeks) were devised to prevent impairment of the vascular supply to the mobilized dentoalveolar segments.17
Fig 1-1b Midpalatal sagittal incision for palatal osteotomies. (Reprinted from Bell et al23 with permission.)
In 1962, animal and clinical investigations were initiated to delineate the biology of maxillary osteotomy wound healing. Since then, rabbits, dogs, monkeys, and baboons have been used as experimental models to investigate the revascularization and bone healing associated with various maxillary techniques.12,16,18,19 Macaca mulatta was usually selected as the experimental animal of choice because of its anatomic, physiologic, and dental similarities to the human. Because maxillary osteotomies are usually performed in adults, large male rhesus monkeys from 8 to 14 years of age and weighing an average of 9 kg, were chosen for study.
From 1962 to 1965, revascularization and bone healing were studied on animal models after clinical simulations of three variations of anterior maxillary osteotomy techniques10,14,20 (Fig 1-1) were performed via various flap designs to validate vascularity to the repositioned osseous segments.12,13,22 The animals were killed 1, 3, 6, and 24 weeks after surgery for microangiographic and histologic investigation.
Fig 1-2 Horizontal microangiogram demonstrating the vascular pattern of a control animal. A reticulated network of periodontal plexus encircles each tooth, composed of anastomosing blood vessels from the labial (facial), gingival, intra-alveolar, and apical vessels. (Reprinted from Bell et al21 with permission.)
Serial 1-mm transverse, sagittal, and horizontal tissue slices were cut from the specimens for microangiographic study, which were in turn cut into seven microscopic slices for histologic study. Microangiographic and histologic techniques demonstrated that intraosseous and intrapulpal circulation to the anterior maxillary segment was maintained when soft tissue was kept intact.12,22 Osteonecrosis was minimal and vascular ischemia was only transient when the anterior maxillary bone segment was pedicled to the labiobuccal mucoperiosteum, palatal mucoperiosteum (Figs 1-2 and 1-3), or a combination of both. Osseous union between most of the sectioned segments occurred within 6 weeks without immobilization of the mandible.
Circulation to the dental pulp was maintained when the bone cuts were made away from the apices of the teeth (5 mm when feasible, which was thought intuitively to be “safe”). In some of the early animals, before we became familiar with the anatomy of the monkey (very long, curvilinear canines), we inadvertently sectioned some of the tooth-root apices.20,23,24 When this occurred, pulpal circulation terminated and pulpal necrosis was observed.
Six weeks after the osteotomies, there was no detectable intraosseous or intrapulpal ischemia. The repar-ative response in the endosteal vascular bed appeared more intense than it did in the periosteal vascular bed. Histologically, the proximal and distal bony segments were united with cancellous bone.
Fig 1-3 Microangiogram of the premolar region of an experimental animal, 6 weeks after single-tooth repositioning, demonstrating the generalized distribution of barium sulfate in the soft tissues, bone, and pulp canals of the tooth. (Reprinted from Bell et al21 with permission.)
Twenty-four weeks after maxillary osteotomies, the periosteal and endosteal circulatory beds had been virtually reconstituted to their normal vascular architecture. The endosteal-periosteal anastomosis through cortical bone had been restored. Histologic examination of the osteotomy wounds revealed healing of the cortical bone and remodeling of the spongiosa.
Each of the three different single-stage anterior maxillary osteotomy techniques maintained blood supply to the bone and soft tissue. When the labial mucoperiosteum was completely reflected from the anterior alveolar region, collateral circulation from the palatal vessels was sufficient to replace the interrupted circulation (Fig 1-4a). When anterior maxillary osteotomy was performed through a palatal mucosal flap in combination with buccal vertical flaps in the premolar regions, the anterior maxillary bone fragment and teeth received their blood supply from an intact labial pedicle through the vascular plexuses of the gingiva and the nasal floor (Fig 1-4b).
The possibility that the anterior maxillary bone segment was a free dental osseous segment that rapidly revascularized was not supported by these studies. When the mucoperiosteum was completely reflected from the bone, intraosseous necrosis, gross vascular ischemia, and nonunion resulted.25 Nonpedicled, free anterior maxillary dental osseous segments did not revascularize, became necrotic within a week, and did not heal with the proximal bone fragment. It is clear that the viability of transposed dental osseous segments was preserved through continuous circulation supplied by attached mucoperiosteum.
Fig 1-4a Incisions of soft tissue and bone for correction of anterior vertical maxillary excess via the Cupar technique of anterior maxillary osteotomy. (Reprinted from Bell et al21 with permission.)
Some of the clinical techniques for anterior maxillary osteotomy are difficult because the palatal bone cuts are made blindly. A transverse palatal incision26,27 affords excellent access to the hard palate for this operation14 but severs palatal blood vessels. The operation may alter the circulation to both bone and teeth and reduce the viability of the mobilized segment.14
Overall, these findings suggested that analogous clinical pedicled segmental surgeries should maintain vitality through use of osteoperiosteal flaps. Selection of the individualized surgical technique that will best avoid damage to the blood supply would be dependent on the clinical objective of the surgeon.
In 1971, Bell and Levy25 reported on the biology of wound healing in posterior maxillary osteotomies (Fig 1-5). Their microangiographic and histologic study of single-stage posterior maxillary osteotomies in adult rhesus monkeys revealed minimal osteonecrosis, transient vascular ischemia, and osseous union between most of the osteotomized segments. When the bone cuts were made away from the apices of the teeth, pulpal circulation was preserved. Within 4 weeks after the palatal surgery, the palatal mucoperiosteum was reattached to the underlying bone, as evidenced by the revascularization of the raised buccal and palatal soft tissue flaps to the underlying bone.
Fig 1-4b Incisions of soft tissue and bone for correction of anterior-posterior maxillary excess via the Wunderer technique of anterior maxillary osteotomy. (Reprinted from Bell et al21 with permission.)
The results of these clinically analogous animal studies indicated that single-stage posterior maxillary osteotomies are biologically sound. The single-stage posterior maxillary osteotomy will become one of the most commonly used surgical procedures for correction of posterior maxillary vertical hyperplasia. A single simple subapical ostectomy or osteotomy may greatly facilitate predictable and rapid superior repositioning of the posterior maxilla through compression osteogenesis or immediate repositioning. The repositioned osseous segment may include one or more dental implants28 (Fig 1-6).
Thus, wound healing in rhesus monkeys has shown that both anterior and posterior maxillary osteotomies are a biologically sound clinical procedures when the circulation to the mobilized bone segment is maintained by attached mucoperiosteum (Fig 1-7).12,13,25 The collateral circulation occurs between osseous and soft tissue elements; intraosseous collateral circulation and vascular anastomoses are found among the periodontal, gingival, floor of the nose, and palatal plexuses (Fig 1-8). Therefore, bone and soft tissue incisions can be designed and made selectively without significantly altering the blood supply to the bone or teeth in the mobilized segment.
Figs 1-5a and 1-5b Incisions of soft tissue and bone used for posterior maxillary osteotomy in experimental animals. (Reprinted from Bell et al21 with permission.)
Fig 1-5c Intraoperative view of single-stage pos- terior maxillary osteotomy.
Fig 1-6 Correction of anterior open bite by posterior maxillary osteotomy (Kufner technique). (a) The soft tissue incision is retracted inferiorly to expose the interdental osteotomy site; the superior portion of the interproximal osteotomy is accomplished. (b) The medial wall of the maxillary sinus is sectioned between the palatal roots and the nasal floor with a curved osteotome. The palatal mucosa is preserved by carefully malleting an osteotome against the surgeon’s finger positioned at the horizontal-vertical juncture of the palate. The dentoaveolar segment pedicled to palatal mucosa and buccal gingiva is downfractured. Ostectomy of the superior, medial, and posterior aspects of the segment is accomplished. (c) Repositioned posterior segment is fixed to the zygomatic buttress with a suspension wire, which is ligated to an orthodontic arch wire fixed to a stable part of maxilla. (Reprinted from Bell et al21 with permission.)
Successful transposition of the maxillary dento-osseous segments by Le Fort I osteotomy depends on preserving the viability of the repositioned segment by proper design of the soft tissue and bony incisions (Figs 1-9 to 1-11). The collateral circulation within the maxilla and its enveloping soft tissues and the many vascular anastomoses in the maxilla permit numerous technical modifications of the Le Fort I osteotomy.
Vascular anastomoses between the maxilla and its enveloping soft tissues are crucial in providing compensatory blood supply to dento-osseous segments after the nutrient medullary vascular system is transsected. The normal blood supply of the maxilla originates centrifugally from the alveolar medullary arterial system29–31 (see Fig 1-8). The mucoperiosteal arterial system also gives off many branches that penetrate the cortical bone and supply blood to the maxilla (Fig 1-12). The system consists not only of capillaries but also arteries and veins, which are arranged in varied configurations.32 The multiple sources of blood supply to the maxilla and the abundant vascular communications between the hard and soft tissues constitute the biologic foundation of maintaining dento-osseous viability despite transsection of the medullary blood supply after osteotomies.32
Fig 1-7a Histology showing necrosis of nonpedicled segment at 1 week. A blood clot (far right) demarcated from the proliferating mesenchymal tissue and capillaries (young granulation tissue [G]). Spicules of necrotic bone are already adjacent to bone cut (NB) (original magnification ×180).
Fig 1-8 Blood supply to the anterior maxilla. The vascular architecture, consisting of freely anastomosing gingival plexus, palatal plexus, periodontal plexus, labial artery, intra-alveolar vessels, apical vessels, and pulp vessels, permits anterior maxillary osteotomies to be performed without compromising circulation to the anterior maxilla and teeth. (Reprinted from Bell et al21 with permission.)
Fig 1-9 (a) Intraoperative view of pedicled four-segment Le Fort I osteotomy in adult Rhesus monkey showing 10-mm maxillary advancement; maxilla stabilized with interosseous wires. (b) Clinically analogous pedicled downfractured four-segment Le Fort I osteotomy technique.
Fig 1-7b Pedicled segmental osteotomies will quickly revascularize with osseous union occurring at 5 to 6 weeks, wheras nonpedicled osteotomy segments undergo osteonecrosis.
Fig 1-10a Microangiogram of the canine–first premolar region of an experimental animal immediately after total maxillary osteotomy, revealing ischemia (I) in the bone encasing the canine (C) and an avascular zone (A) below the buccal and nasal mucosal flaps (F). T—vascularized premolar; Pa—palate; OS—osteotomy site; EM—extravasated injection medium. (Reprinted from Bell et al21 with permission.)
Fig 1-10b Microangiogram of the molar region of experimental animal 2 days after surgery, revealing generalized distribution of the injection medium in soft tissues, bone, and pulp canals of the molar (T) as well as an avascular space (A) between superior surface of the maxilla (M) and detached nasal mucosa (NM). Pa—palate; NC—nasal cavity. (Reprinted from Bell et al21 with permission.)
Fig 1-10c Microangiogram of molar region of experimental animal 1 week after Le Fort I osteotomy demonstrates increased filling of periosteal (P) vascular beds and (E) endeosteal circulatory bed in the margins of the osteomized bone. OS—osteotomy; Pa—palate; NC—nasal cavity; M—maxilla.
Fig 1-10d Microangiogram of the molar region of an experimental animal 4 weeks after surgery, revealing reconstitution of the circulation between osteotomized segments by proliferating vessels. (arrow) osteotomy site; MS—maxillary sinus; T—vascularized pulp canal of the molar. (Reprinted from Bell et al21 with permission.)
Fig 1-10e Histologic appearance of the osteotomy site 4 weeks after surgery. Bone segments are united by viable vascularized osteophytic new bone, osteoid, and mature fibrous connective tissue (hematoxylin-eosin stain; original magnification ×130). (Reprinted from Bell et al21 with permission.)
Fig 1-11 Experimental animal. Wound dehiscence, infection, osteonecrosis, and loosening of teeth have manifested 12 days after nonpedicled total maxillary osteotomy surgery. Similar wound healing is observed in smaller nonpedicled maxillary and mandibular dento-osseous segments. (Reprinted from Bell et al21 with permission.)
In an attempt to identify the effects of soft tissue flap design, segmentation of the maxilla, stretching of the vascular pedicle during healing, and transsection of the descending palatine vessels, clinically analogous four-piece maxillary osteotomies were performed using the Le Fort I osteotomy technique in 14 adult rhesus monkeys. The revascularization and bone healing associated with the operation were studied at various time intervals by microangiographic and histologic techniques.32 Transient vascular ischemia, minimal osteonecrosis in the margins of the osteotomized segments, and small variations in the timing of osseous union of the segments were observed in the experimental animals. Within the period of postoperative study, osseous union of the bone segments was observed.
Fig 1-12 Circulation and freely anastomosing vascular plexuses of the gingiva, palate, nose, maxillary sinus, and periodontium permit the surgeon to make many technical modifications without jeopardizing the blood supply to the maxillary dentoalveolar segments.
Results of this qualitative study indicated that palatal mucosa and the labiobuccal gingival mucosa provide an adequate nutrient pedicle for single-stage Le Fort I maxillary osteotomies. Segmentation, stretching of the vascular pedicle, and transsection of the descending palatine vessels have no long-term discernible effect on revascularization or bone healing associated with the technique 13,20,30,31 (see Fig 1-10).
Preservation of the integrity of the descending palatine vessels has not been found to be essential to maintaining maxillary viability.29,32 Experimental blood flow studies have shown that the immediately postoperative volume of blood flow after Le Fort I osteotomy was much lower in the maxilla with a transsected and ligated descending palatine vessel than it was in the maxilla in which the integrity of the vessel was preserved.30,31,33 However, You and colleagues31 showed that transsection of the descending palatine vessels had no discernible effect on bone or soft tissue healing. The combination of angiography and histology provides a means of qualitatively studying the effects of surgery on the intact blood supply of the osseous and dental pulp cells.
Fig 1-13 (a to c) Small dentoalveolar segments can be repositioned to move single-tooth or two-tooth sites into occlusion. (d) Freely anastomosing vascular plexuses of the gingiva, palate, periodontium, and pulp.
After the development of predictable, biologically based techniques for immediate repositioning of the anterior and posterior maxillary dentoalveolar segments, which usually contained between three and six teeth, the challenge remained as to whether single-tooth dento-osseous segments could be repositioned similarly. Because pedi-cling the segment to a relatively small amount of soft tissue could presumably imperil circulation to the mobilized dento-osseous segment, many surgeons have avoided such procedures. The biology of healing associated with the surgical repositioning of single-tooth dento-osseous segments was studied in two different surgical techniques performed in adult mongrel dogs.34
The adult mongrel dog serves as an excellent experimental model for studying biologic and surgical principles involved in the immediate repositioning of single-tooth dento-osseous segments. The interdental spacing (approximately 1 to 2 mm) is comparable to many clinical situations in which immediate repositioning of small dento-osseous segments by vertical interdental and subapical osteotomies is currently considered feasible.34
Microangiographic and histologic studies of both one-stage and two-stage techniques for immediate surgical repositioning of single-tooth dento-osseous segments—analogous to segmental osteotomies of edentulous sites for dental implants—revealed early but transient vascular ischemia, minimal osteonecrosis, and osseous union between the osteotomized segments33 (Figs 1-13a to 1-13d). The attached soft tissue provided an adequate nutrient pedicle for immediate repositioning of single-tooth dento-osseous segments by interdental and subapical osteotomies. With these experimental surgeries, there were no advantages to the use of the two-stage procedure from a biologic point of view. The results supported the clinical use of techniques that maximize the attachment of the mucogingiva to the mobilized dento-osseous segment.34 Clinical trial and application of both of these techniques for immediate repositioning of single-tooth dento-osseous segments is justified.
Fig 1-13 (e to g) This procedure was a forerunner to small single-tooth segmental osteotomies later treated with dental implants.
Successful transposition of dento-osseous segments depends on preservation of viability by proper design of the soft tissue and bony incisions. The collateral circulation within the maxilla and its enveloping soft tissues and the numerous vascular anastomoses in the maxilla permit many technical modifications of the two techniques used in the investigation. These early studies further add credibility to the use of small segmental osteotomy fragments of edentulous bone as long as the vascularized pedicle remains intact (Figs 1-13e to 1-13g).
Clinical Application of the Le Fort I OsteotomyFrom the initial description of the downfracture technique for segmentation of the maxilla until the present time, approximately two thirds of Le Fort I osteotomies have been segmental operations.29–33 The descending palatine vessels were either intentionally or inadvertently transsected in approximately one-third of these cases, without discernible clinical consequences. In all probability, however, the vessels were unknowingly transsected in even more cases. A reasonable effort is routinely made to preserve the integrity of these vessels whenever feasible; there is, however, no reluctance to clamp them with a vascular clip or cauterize them to gain accessibility or enhance visualization. Superior or posterior repositioning of the posterior portion of the maxilla is a movement in which transsection of the vessels may most frequently be indicated in order to visualize and gain access to the tuberosity–pterygoid plate junction and to reposition the maxilla.
In principle, surgical repositioning of small dentoalveolar segments by the downfracture technique is biologically and clinically sound. In clinical practice, to improve the tooth alignment or move edentulous segments, one or multiple interdental osteotomies can be planned to move segments that are one or more teeth in length.17,34–41
The Le Fort I osteotomy may be designed to reposition small anterior and posterior maxillary dento-osseous segments simultaneously37 (Figs 1-14 to 1-18). Maximal palatal or labiobuccal soft tissue attachment must be maintained. Without proper planning and precise technique, mobilized dentoalveolar segments may become so small that any movement may devascularize and devitalize them. In each case, the design of the bony and soft tissue incisions should be individualized to maintain the largest possible dento-osseous segment to preserve the largest possible soft tissue pedicle; the larger the osseous segment, the greater the amount of palatal mucosa. In this way, a single-tooth dento-osseous segment can still retain an adequate soft tissue pedicle.
Fig 1-14a Sectioning. The anterior maxilla is partially divided into two segments before the lateral osteotomies are accomplished. (left) The mucosa is retracted to visualize the labial osteotomy site. The interdental osteotomy, incompletely accomplished with a fissure bur, extends from the anterior aspect of the nasal floor inferiorly to the crest of the alveolar ridge. (right) Superiorly, the interdental osteotomy is deepened into the spongiosa; more inferiorly, a corticotomy is made. (Reprinted from Bell and Guerrero37 with permission.)
Fig 1-14b Interincisal osteotomy is accomplished with the reciprocating saw blade placed superiorly into the piriform aperture. The skin hook is placed inferiorly to facilitate visualization and prevent injury of the attached gingiva. (Reprinted from Bell and Guerrero37 with permission.)
Fig 1-14c Sectioning. (left) A finger is positioned on the palate to feel the blade transect bone. (right) An osteotome is sequentially malleted into the interradicular area, proceeding inferosu-periorly until it partially transects the palatal bone and its tip makes contact with the nasal floor immediately lateral to the anterior nasal spine. (center) Subperiosteal tunneling dissection of the anterior maxilla, infraorbital nerve, and anterior nasal septum, and lateral nasal walls superiorly to the base of the inferior turbinate. Given that the anterior-inferior margin of the piriform rim is usually elevated above the nasal floor, care must be taken to remain in a subperiosteal plane by dissecting inferiorly and posteriorly from the inferior piriform rim. The dissection is carried to the posterior aspect of the hard palate, onto the base of the nasal septum approximately 5 mm above the nasal floor, and then to the base of the inferior turbinate on the lateral nasal wall. (Reprinted from Bell and Guerrero37 with permission.)
Fig 1-14d Mobilization. The osteotome is malleted into the interseptal area between the central incisors to fracture the crestal alveolar bone. Digital pressure on the palate indicates when the osteotome has transected the palatal cortex. This is important to prevent damage to the palatal mucoperiosteum, which is the principal blood supply. Incomplete splitting of the anterior maxilla is facilitated by malleting (1) and manipulating a sharp osteotome into the center of the stable maxilla. The two segments are made partially mobile by careful torquing (2) and lateral manipulations of an osteotome. (Reprinted from Bell and Guerrero37 with permission.)
Almost any combination of one-, two-, three-, four-, five-, or six-tooth segments may be simultaneously mobilized and selectively repositioned to achieve the desired alignment by a combination of interdental or subapical corticotomies and/or osteotomies (see Fig 1-14a). Corticotomies are used for sectioning, perforating, or mechanically altering the cortical bone to the depth of the medullary bone, which remains intact; they are used to facilitate repositioning of teeth predominantly by tipping movements.42,43 Osteotomies are for sectioning both the cortical and medullary bone to create a bone segment; interdental osteotomies may be used for selective bodily movement of dentoalveolar segments by distraction osteogenesis. 17,40–44
Fig 1-15 A high-level Le Fort I osteotomy is customized to achieve variable repositioning of the maxilla (arrows). This is frequently accomplished without bone grafting. (Reprinted from Bell and Guerrero37 with permission.)
Fig 1-16 With the maxilla downfractured, the posterior maxilla is widened by a midpalatal sagittal osteotomy accomplished with a straight reciprocating saw blade. A finger is positioned on the palate to feel the blade when it partially transects the cortical plates. The bone is then completely sectioned and mobilized with an osteotome malleted along the intended line of osteotomy. (Reprinted from Bell and Guerrero37 with permission.)
Fig 1-17a The maxilla has been repositioned laterally to create a 10-mm gap between the incisors. (Reprinted from Bell and Guerrero37 with permission.)
Fig 1-17b The segments are maintained in the planned position by a rapid palatal expander as the incisors close the distraction gap spontaneously (without active orthodontics). (Reprinted from Bell and Guerrero37 with permission.)
Simultaneous tipping and retraction of proclined and prominent maxillary anterior teeth or uprighting and advancement of retroclined anterior teeth can be accomplished by segmental Le Fort I osteotomy. Arch length can be increased by this procedure, greatly improving treatment efficiency and avoiding the need for maxillary and mandibular extractions in selected cases.
Periodontal and periapical problems associated with interdental osteotomies are minimized if the Le Fort I downfracture technique is used to gain simultaneous access to and direct visualization of labiobuccal and palatal aspects of the areas where they are planned. Meticulous and precise surgical technique, prudent selection of osteotomy sites, good lighting of the surgical field, careful use of thin sharp osteotomes, the use of ultrasonic osteotomy (piezoelectric surgery),45 with its soft tissue–sparing effect, and the use of directly bonded orthodontic appliances are vital adjuncts to safe and successful interdental and subapical osteotomies.
Fig 1-18 Surgically facilitated prosthetic and orthodontic reconstruction of the maxilla using the versatility of the Le Fort technique. Palatally inclined (Pa) teeth repositioned by interdental and subapical corticotomies. Bucally inclined (Bu) teeth repositioned by interdental and subapical osteotomies.
Fig 1-19a Histologic appearance of pulp (P) of a control maxillary third molar crown; odontoblastic layer (O) and adjacent pulpal tissues; dentin (D); and blood vessel (BV) (hematoxylin and eosin and Bodian stains; original magnification ×10). (From Di et al.50 Reprinted with permission.)
Fig 1-19c Bone-impacted maxillary third molar buds (arrows) before surgery. (From Di et al.50 Reprinted with permission.)
Segmentation of the anterior maxilla to improve the axial inclination of the anterior teeth without ostectomy or extractions may be the treatment of choice in selected cases; the desired anteroposterior position is achieved by Le Fort I osteotomy.
There have been relatively few reports of the loss of small or large maxillary dento-osseous segments after Le Fort I osteotomies. A study of the circumstances involved when segments are lost generally reveals that the operat-ing surgeon has violated a basic biologic or surgical principle. Most frequently, the vascular pedicle has not been maintained by proper soft tissue flap design, or circulation to the mobilized segment has not been preserved by way of attached palatal mucoperiosteum. Excessively long and traumatic surgery, imprudent selection of interdental osteotomy sites, strangulation of the circulation by improperly positioned suspension wires or imprudent use of palatal splints, poor visualization of the surgical site because of insufficient blood pressure control, and excessive stretching of the palatal mucosal pedicle are other causes of compromised wound healing.
Fig 1-19b Histologic appearance of the pulp of a maxillary third molar crown 50 months after surgery. The tooth demonstrates an intact and well-aligned odontoblastic layer (O) and normal adjacent pulpal architecture; D—dentin; N—nerve; P—dental pulp (hematoxylin and eosin and Bodian stains; original magnification ×10).
Fig 1-19d Same teeth fully developed and erupted (arrows) at follow-up, 28 months after Le Fort I surgery. (From Di et al.50 Reprinted with permission.)
Devascularization and devitalization of a repositioned segment may be caused by excessive stretching or detachment of the soft tissue pedicle or by inappropriately designed palatal soft tissue incisions. Such complications can be avoided by the use of precise three-dimensional cone-beam computed tomography studies to determine the three-dimensional positional changes of the segments, careful three-dimensional anatomic cast surgery, and/or or virtual imaging and meticulous surgical technique during the operation.
Preoperative assessment of arch length and interdental spacing is vital for precise treatment planning. This is achieved by dentoalveolar imaging.
Inadvertent injury of the cementum in the midroot portion of a tooth (usually secondary to interdental osteotomy with a bur or saw) is not a frequent clinical problem because of the propensity of cementum to repair itself. Excessive removal of crestal alveolar bone, however, can compromise the periodontium. Inadvertent transsection of a root apex43 by interdental or subapical osteotomy may initiate progressive pulpal atrophy and fibrous degeneration. In such cases, devitalization of a tooth may gradually occur despite pulpal and osseous evascularization. Careful clinical follow-up is mandatory in such cases.
Transient pulpal vascular ischemia and direct injury to the apices of the teeth have been implicated as the causes of degenerative and atrophic pulpal changes in experimental animals after Le Fort I osteotomy, despite the presence of collateral circulation.31,38,46–52 A study of the incompletely developed extracted maxillary third molars following Le Fort I osteotomy explored the long-term biologic effects on the pulp and the development of teeth. Histologic examination revealed an intact pulpal circulation and minimal pathologic changes in the pulpal tissue (Figs 1-19a and 1-19b).50 Clinical and radiographic studies showed that the growing teeth developed normally after surgery (Figs 1-19c and 1-19d). The Le Fort I downfracture procedure had minimal long-term effect on the pulp and on the development of human third molars.
SummaryThe biologic basis of total jaw and segmental tooth-borne osteotomies, scientific vascular studies, and long clinical experience worldwide now establish a framework for use of pedicled edentulous bone fragments or dento-osseous segments in alveolar reconstructive schemes for dental implant restorations. Several questions remain:
It appears that the biologic basis of interdental osteotomies is sound, proven by a long track record of animal and clinical studies. It is the task of the upcoming generation of maxillofacial surgeons to discover the limits and vitality of vascularized bone fragments in the ongoing effort to treat dentofacial deformities and ablative alveolar atrophy.
References