Ultrasonic Bone Cut Part 2:
State-of-the-Art Specific Clinical Applications
Philippe Leclercq, DDS,* Charlotte Zenati, DDS†
and David M. Dohan, DDS, MS, PhD‡
The ultrasonic lancet makes it possible to realize, with extreme precision and safety, a great number of oral and maxillofacial surgeries. It is during 4 particular interventions, however, that this tool may have many advantages over conventional instrumentation, ie, nontraumatic removal of osseointegrated implants, chin and retromolar bone harvesting, and inferior alveolar nerve lateralization. This study presents these applications in detail and discusses their advantages and disadvantages compared with former techniques.
The use of the piezoelectric lancet considerably sim- plifies these surgical protocols as it has a nontrau- matic cut and a solid interface cleavage, under the effects of ultrasounds that facilitates the breaking of bone fragments.
The development of an appropriate instrumentation to any surgical situation is a determining element in the rationalization of the most complex interventions. This clinical and technologic research is able to transform some delicate surgeries into codified and reproducible acts.
In the field of bone graft, most available tools are more or less a lucky adaptation of the instrumentation used in dental or maxillofacial surgery. They are often little efficient, miniaturized applications of general-pur- pose instrumentation: oscillating saw, bone scissors and hammer, electrical motorized hand-piece, or bone drill.
Maxillomandibular bone grafts, however, cannot be as- similated to a true orthopedic surgery; bone grafts cor- respond more to the first stage of facial reshaping and
reconstruction. Therefore, they require instruments of appropriate precision.
Easy-to-use, precise, secure, and efficient for bone cut, the ultrasonic lancet is an effective tool for the surgeon in many clinical situations.1-6 However, in our opinion, for an experienced practitioner, the use of piezosurgery is truly required in only 4 particular interventions: the removal of osseointegrated im- plants, chin and retromolar bone harvesting, and in- ferior alveolar nerve lateralization. It is, indeed, during these 4 delicate operations that the properties of the ultrasonic lancet become a major advantage for suc- cessful treatment.
Ultrasonic Lancet and Removal of Osseointegrated Implants
An osseointegrated implant can resist in torsion to forces of greater than 90 N. Generally, above this threshold, the metal of the implant begins to lose its shape. The removal of such an ankylosed structure is therefore particularly delicate, and within a high risk of taking a part of the peri-implant bone with the implant. Fortunately, such operations are mostly real- ized on failed implants, ie, nonosseointegrated or with peri-implantitis. The removal, therefore, is easy because the implant is set in fibrous tissue.
It is sometimes necessary to eliminate some im- plants despite their perfect osseointegration. This is particularly the case with ectopic implants because they are judged as prosthetically unusable or because the position of the implant implies major esthetic damage. The removal of these implants has to be the least traumatic, to limit the decay of the implant site.
An osseointegrated implant is deeply connected to the bone that supports it, which implies great diffi- culties in breaking the bone/implant interface and high risk of fracture of the peri-implant osseous walls during the operation.
The ultrasonic lancet allows effective management of this type of situation because of solid interface cleavage under the effects of ultrasound vibrations and the realization, by microabrasion, of thin osseous trenches. In other words, it is sufficient to make 2
*Private Practice, Paris, France.
†Student, Biophysics Laboratory, Faculty of Dental Surgery, Paris V University, Odontology Service, AP-HP Hospital Albert Che- nevier, Créteil, France.
‡Assistant Professor, Department of Oral Surgery, AP-HP Hospital Albert Chenevier, Biophysics Laboratory, Faculty of Dental Surgery, Paris V University, Montrouge, France.
Address correspondence and reprint requests to Dr Dohan:
Biophysics Laboratory, Faculty of Dental Surgery, 1 Rue Maurice Arnoux, 92120 Montrouge, France; e-mail: drdohand@hotmail.com
©2008 American Association of Oral and Maxillofacial Surgeons 0278-2391/08/6601-0032$34.00/0
doi:10.1016/j.joms.2005.12.050
183
thin vestibular or lingual trenches, on each side of the implant, to give flexibility to the osseous wall, whereas the ultrasonic vibrations will favor the cleav- age of the solid bone/implant interface. The removal of the implant is then easy, with the knowledge of these procedures (Figs 1, 2). However, the risk of fracture of the peri-implant osseous walls remains important, particularly during the extraction phase itself, because this phase requires applying conse- quent twisting forces on the implant and on the alve- olar bone.
Ultrasonic Lancet and Chin Bone Harvesting
Chin bone harvesting may provide 1 or 2 big plates from a dense cortical bone with limited risk for the donor site. In many clinical situations, these 2 fragments are enough to realize moderate extent grafts, concerning either maxillary sinus lifts or apposition grafts to increase alveolar thickness or height.7This intraoral donor site is often recom- mended, as it allows avoiding extraoral osseous harvesting (from the parietal bone, iliac bone, etc), and general anesthesia. Light sedation and a local anesthetic are enough to perform a chin bone graft.
For a conscious patient, there is a particularly un- pleasant moment when the practitioner, after hav- ing cut the graft’s limits, uses the bone chisel to remove the bone fragment from the mandibular body. Every hammer blow echoes violently into the patient’s head, and after the intervention, this traumatic recollection can darken all the practitio-
ner’s efforts in decreasing the intraoperative suffer- ings.
The ultrasonic lancet offers an alternative to the bone chisel and hammer. Making the graft demarca- tion trench with the ultrasonic lancet creates a thin- ner section than the one obtained with the bone drill.8,9 This trench is also deeper than the one ob- tained with a cutting disc (eg, inserts allow work up to 10 or 12 mm of depth). Furthermore, the ultra- sound vibration transmission through the graft in- duces, little by little, a fracture of the solid interface between the cortical plate and the underlying med- ullar tissues. This cleavage of both structures of dif- ferent densities will allow easy collection of the osse- ous fragment, and sometimes it is not necessary to use a chisel and hammer. Even if the bone chisel is needed on occasion to finish the separation of the graft, the impacts that are made are very moderate (Fig 3).
The use of the ultrasound lancet provides secur- ity to the practitioner in regard to patient comfort and the prognosis of his intervention.10-12 By decreasing the number and the intensity of the chisel strokes needed for the cleavage of the cortical plate, the risk for fracture is reduced. To make grafts of quality, however, it is important to collect bone fragments of a determined dimension and shape to make a precise and meticulous reconstruction13; this is one of the keys to the functional and esthetic success for these grafts. The graft integrity is a crucial element.
Ultrasonic Lancet and Retromolar Bone Harvesting
Situated on the mandibular body in the mandib- ular branch continuation, the retromolar bone of-
FIGURE 1. For nontraumatic removal of an osseointegrated implant positioned in an ectopic place, make 2 thin trenches on each side of the implant to give a certain flexibility to the osseous wall while imposing ultrasonic vibrations to the bone/implant interface.
Leclercq, Zenati, and Dohan. Ultrasonic Bone Cut. J Oral Maxil- lofac Surg 2008.
FIGURE 2. Interface cleavage and the implant removal done with a minimum decay of the bone volume.
Leclercq, Zenati, and Dohan. Ultrasonic Bone Cut. J Oral Maxil- lofac Surg 2008.
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fers an alternative to chin bone harvesting. Al- though this zone is more difficult to access than the chin, it has the advantage of allowing the collection of longer and thicker fragments than in the chin zone. Furthermore, situated on the force conver- gence area of the mandible, the donor site will easily reconstitute itself under the influence of me- chanical stimuli that are applied.
The problem of retromolar harvesting is similar to chin harvesting: one must make the thinnest trenches and mobilize the graft least violently to avoid trau- matic shocks and graft breaking with a chisel and hammer.
It is important to make a sketch of the graft dimen- sions (for the receiving zone). The graft thickness is determined by a low, horizontal section. It can be made with a disc (mounted on an electrical motorized hand-piece) or with a specific insert of the ultrasonic lancet to trace the inferior limit of the osseous frag- ment. The use of the ultrasonic lancet is particularly reassuring, even more than for the chin zone, as it offers the certainty of avoiding damage to nearby tissues.14,15 With difficult surgical access and visual control of the retromolar angle, this security is of
great value and contributes to the surgical ease of the practitioner (Fig 4).
Ultrasonic Lancet and Inferior Alveolar Nerve Lateralization
The lateralization of the inferior alveolar nerve is a very delicate operation that is reserved for extreme clinical situations.16Its main difficulty remains in the initial release of the nerve: it is necessary to decorti- cate it, without any damage, up to the mental fora- men. This bone foramen must be eliminated to avoid risk of constriction of the nervous pedicle during the lateralization of the nerve.17,18
The use of the ultrasonic lancet is very interesting in this situation because it allows a secure bone cut and an easy access to and release of the nerve.19The ultrasonic vibrations make the cortical plate cleavage easier from the soft structures that are underneath.
This is the only true difficulty of the inferior alveolar nerve lateralization gesture, and it is raised as a matter of course with the ultrasonic lancet.
The release of the inferior alveolar nerve implies to meticulously introduce instruments through an osse-
FIGURE 3. Chin bone harvesting with an ultrasonic lancet. The graft outlines are made with a thin and diamond-coated insert (A) that allows the cleavage between the cortical plate and the mandibular mass with little use of chisel and hammer (B, C). The bone fragment has better chances to remain intact, and it is easier to control its thickness (D).
Leclercq, Zenati, and Dohan. Ultrasonic Bone Cut. J Oral Maxillofac Surg 2008.
ous wall of difficult access. The ultrasonic lancet has a cutting power only at the end of its insert; it can be used in inaccessible sectors without damaging the neighboring tissues (cheeks, tongue).
The risk for accidental damage of the nerve during the osseous section is reduced by the weak cutting power of the ultrasound lancet inserts. The micro- abrasive oscillations of these inserts will provide more
FIGURE 4. Retromolar harvesting using the ultrasonic lancet. On a bare mandibular body (A), the graft outlines are made using a thin insert, like a bone saw (B). The ultrasound vibrations facilitate the cleavage of the graft, which then only require a restricted use of the struck chisel (C). To control the thickness of the harvesting, it is important not to forget to draw the limits of the bone fragment on the lateral part of the mandibular body: an osseous fragment with perfectly calculated dimensions is obtained (D, E).
Leclercq, Zenati, and Dohan. Ultrasonic Bone Cut. J Oral Maxillofac Surg 2008.
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precise information to the surgeon about the hard- ness of the encountered tissues than a turbine or a hand-piece, and will reduce errors of the estimated cutting depth.12
The use of the ultrasonic lancet contributes to de- mystifying surgery of the inferior alveolar nerve. This procedure still remains delicate, but it is greatly se- cured and facilitated with this instrumentation (Fig 5).
Discussion
The main disadvantage for using the ultrasonic lan- cet in bone harvesting surgery is its inefficacy and fragility when facing very dense bone tissues.12,15 However, the major part of our harvesting comes from very cortical sectors, ie chin bone, retromolar bone, or parietal bone. Thus, in theory, the main indication of the ultrasonic lancet is more or less its main contraindication.
Clinically, however, it is easy to adapt to this lack of efficacy in front of hard bone tissues; by progressing
more slowly and without force, the most cortical bones always weaken. Note the accelerated wear of the inserts and a higher rate of parts fracture than with bones that are not as hard. These fractures do not have any consequences on the quality of cut- ting,11,13but they require a careful inventory control of spare inserts.
Despite this inadequacy, the ultrasonic lancet re- mains the best instrument available to realize bone harvesting, even for very dense cortical bones.10,13,20 The ultrasound vibrations favor the cleavage of the solid interfaces and facilitates the separation of the graft from the donor site. The harvesting of the bone plate will be even, often made without the help of a bone chisel and hammer, as the violent impacts would risk breaking the grafts in fragments that are difficult to use afterward. In deeply buried sites, the use of the ultrasonic lancet is extremely reassuring because it gives the certainty of not hurting soft or hard tissues.5,19 The cost of some broken inserts is widely rewarded by an ease and a surgical security
FIGURE 5. Release and lateralization before implantation of an inferior alveolar nerve with the use of the ultrasonic lancet. The osseous plate access is made with a diamond-coated insert (A). The bone hole of the mental foramen is eliminated and the nerve is released on all its length; it is a preliminary condition for the success of such an intervention without after effects (B).
Leclercq, Zenati, and Dohan. Ultrasonic Bone Cut. J Oral Maxillofac Surg 2008.
both for the practitioner and for the patient. This is a strong argument for an experienced practitioner; the bone chisel and hammer knocks are always the main postoperative painful recollections. For this reason only, the use of an ultrasonic lancet in the protocol of bone harvesting should be systematic.
In conclusion, the ultrasonic lancet belongs to the category of tools that transform delicate operations into easy and perfectly mastered procedures. How- ever, it is important to define the advantages, the inconveniences, and the reasonable application field to take advantage of its benefits without exceeding the limits.
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