Alveolar Width Distraction Osteogenesis for Early Implant Placement

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and increased alveolar width from 4 to 6 mm. Twenty implants successfully osteointegrated of 21 placed. Marginal bone resorption was not observed after 12 months’ follow-up. The advantages of horizontal distraction over block grafting include simultaneous expansion of soft tissue, high degree of dimensional stability, abbreviated overall treatment time, and no graft requirement.

The indications for alveolar ridge augmentation are acquired or congenital alveolar defects. Acquired al-veolar bone loss may be caused by post-extraction defects, traumatic avulsion, periodontal disease, and/or prolonged denture wear with subsequent disuse atro-phy. In most of these cases the most significant loss is in the horizontal dimension. Traumatic tooth avulsion with loss of the buccal bone plate is a typical example of a situation leading to a horizontal defect.1

Modalities to augment horizontal bone defects in-clude autogenous onlay bone graft,2,3 _{guided bone}

regeneration,4,5alloplastic augmentation,4,5and alve-olar split grafting.1 Each of these modalities has its advantages and disadvantages. Use of an autogenous bone graft has donor site morbidity6_{and graft}

resorp-tion is expected.7 While guided bone regeneration has been extensively documented,4,5it is often diffi-cult to provide optimal space for the regeneration of the desired bone volume and is therefore better suited for limited defects. Alloplastic materials4,5used

in quantity are not reliable for implant osseointegra-tion.

Alveolar widening by distraction osteogenesis (DO) is an alternative method for reconstructing alveolar atrophy8-11that is similar to alveolar split grafting but without the graft. The combination of vertical DO and osseointegration has produced a stable esthetic recon-struction of the alveolar bone and attached mucosa,12 but the use of distraction to gain alveolar width, first reported by Aparicio and Jensen,13has not been fully established clinically.14

Block et al15,16 confirmed isotropic augmentation by DO for alveolar bone in animal studies. But, clinical studies17,18have only established efficacy of alveolar distraction in the vertical dimension because there are few reports on the use of DO to gain width for dental implants.13,14,19-22 The purpose of this clinical study was to establish, in a consecutive series of horizontal alveolar distractions using the Laster Crest Widener (Surgetek Inc, Brussels, Belgium), that dental implant restoration could be consistently accomplished to an optimized alveolar width morphology.

Materials and Methods

During the development of alveolar width distrac-tion, 4 prototype devices were used on 9 patients aged 18 to 52-years-old who presented with moder-ately deficient alveolar bone in the horizontal dimen-sion.

The Laster Crest Widener consists of 4 sharp arms, 2 on each side connected with guide pins and an activating distraction screw. By rotating the activating

*Professor and Director, Department of Oral and Maxillofacial Surgery, Poriya Hospital, Poriya, Israel.

†Professor and Director, Department of Oral and Maxillofacial Surgery, Rambam Medical Center and the Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.

‡Private practice, Denver, CO.

Address correspondence and reprint requests to Dr Jensen: 303 Josephine St, Suite 303, Denver, CO 80206; e-mail: zvi@lasters.co.il ©2005 American Association of Oral and Maxillofacial Surgeons 0278-2391/05/6312-0005$30.00/0

doi:10.1016/j.joms.2005.09.001

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screw, the pair of arms move apart, thus engaging each side of the osteotomy site to spread it apart.

SURGICAL TECHNIQUE

Under local anesthesia, a crestal mucoperiosteal incision is made followed by buccal vertical muco-periosteal incisions placed anterior and posterior to the distraction zone (Fig 1). The crest itself is mini-mally exposed, otherwise there is no flap reflection. A round burr is used to make a small trough along the crest. Bone cuts are made through the trough, and through the anterior and posterior vertical incisions without stripping mucoperiostium using a sagittal micro saw, reciprocating scalpel saw, or piezoelectric ultrasonic bone cutter (Fig 2). An osteotome is intro-duced crestally and the buccal plate is “green-stick” fractured bucally (Fig 3). The distractor is tapped into place and the wound is approximated with sutures. A provisional prosthesis is then placed (Figs 4,5). Dis-traction begins 1 week later by turning the activating screw 2 and 1/2 turns per day (0.4 mm). This is done by the patient at home (Fig 6). After a 7- to 10-day retention period for early bone “consolidation,” the distraction device is removed and 1 week later im-plants are inserted percutaneously. In 1 case (no. 3) the periostium was stripped buccally to make a stop cut in the vestibule before out-fracturing the segment (Fig 7). Pressure or mastication on the distraction site by a temporary denture is avoided during distraction, consolidation, and osseointegration. The exposure of dental implants is performed 3 to 4 months after insertion, and prosthetic rehabilitation completed thereafter (Fig 8). Panoramic and periapical x-rays are taken following distraction, after implant placement,

Results

Nine patients underwent horizontal expansion of the alveolar process by DO followed by dental im-plant placement. The distraction was evident clini-cally and radiographiclini-cally. Alveolae increased in width between 4 and 6 mm (Table 1). The attached mucosa at the top of the alveolar crest increased simultaneous to increased bone mass.

No infections resulted from treatment. Of 23 threaded implants placed, 22 implants osseointe-grated. The post-distraction follow-up period was from 6 to 24 months. No significant marginal bone resorption was observed after implant placement, ex-cept in case no. 3, where reflection of a mucoperios-FIGURE 1. A crestal mucoperiosteal incision is made along the

desired area for widening, followed by vertical mucoperiosteal inci-sions anteriorly and posteriorly.

Laster, Rachmiel, and Jensen. Alveolar Width DO for Early Im-plant Placement. J Oral Maxillofac Surg 2005.

FIGURE 2.Bone cuts are made through the trough, and the anterior and posterior vertical incisionswithout stripping the mucoperiostium using a sagittal micro saw, a reciprocating scalpel saw, or piezoelec-tric bone cutter.

FIGURE 3. An osteotome is introduced and the buccal plate is

“green-stick”fractured bucally.

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Im-teal flap was performed. This resulted in loss of bone and exposed screw threads in 2 implants that were prosthetically rehabilitated.

One implant failed to integrate because of inade-quate primary stability but was successfully replaced 8 weeks later. All implants were loaded with dental prostheses.

Discussion

Reconstruction of the deficient alveolar process should address deficiency of both bone and attached mucosa. Experimental distraction studies23 have re-ported lamellar bone formation as well as histogenesis of soft tissue. This process has also been verified clinically.24,25

Because DO provides a simultaneous and general-ized histogenesis it eliminates the need for both bone and soft tissue grafting in implant cases.17,26,27 Hori-zontal distraction is especially useful in moderately narrow alveolar ridges which still have sufficient ver-tical height.

Nosaka et al20performed an experimental study on narrowed alveolar ridges in 6 beagle dogs, widening the alveolus by distraction. Twelve days after comple-tion of distraccomple-tion, during consolidacomple-tion, screw-type endosseous implants were placed into the distracted area. After 24 weeks the implants were found to be embedded in mature bone. Direct bone contact with the implant surface was observed without scar forma-FIGURE 4.The device is tapped into place and the wound is closed

primarily.

FIGURE 5.A provisional prosthesis is then placed.

FIGURE 6.The distraction begins 1 week later by turning the distrac-tion rod 2 ½ turns per day (0.4 mm.) This is done by the patient at home.

FIGURE 7.In 1 case (no. 3) the periostium was stripped buccally to make a stop cut in the vestibule before out-fracturing the segment.

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tion, admixture of dead bone, or evidence of vascular embarrassment as found in bone graft settings.

This study shows that horizontal alveolar ridge dis-traction is a reasonable adjunct for placement of im-plants in the moderately atrophic alveolus. Osseointe-gration is achieved despite implants being placed into regenerate during the early stage of consolidation. Providing there is primary implant stability, osseointe-gration occurs without significant disruption of the regenerative process. And, resorption of the superior aspect of the alveolar ridge was not observed when the flap procedure was minimal.

HORIZONTAL DISTRACTION OSTEOGENESIS PROTOCOL

Despite alteration of the distraction protocol during this clinical study, there was no significant difference in final outcome, with the exception of case no. 3. The following summarizes a proposed best technique for horizontal distraction:

STEP-BY-STEP PROCEDURE

1) Under local anesthesia, a crestal incision is made, followed by vertical incisions anteriorly and posteriorly. Flaps are not reflected, instead the crest is minimally exposed and by using a small round burr a trough is made mid-crestally. 2) A bone cut follows the trough to a depth of at least 10 mm using a reciprocating saw or piezo-electric knife. Bone cuts are made through the anterior and posterior vertical incisions using a sagittal micro saw (Figs 9,10).

3) A thin osteotome is used to out-fracture the buccal plate and then the wound is closed (Fig 11). 4) One week later the Laster Crest Widener is

tapped into place percutaneously (Fig 12). 5) A titanium safety wire is threaded through the

hole in the arm (this is best performed before the insertion of the device) (Fig 13).

6) Two counter-clockwise rotations are made with the activation screw to engage the device in bone and confirm mobilization of the transport. FIGURE 8.The exposure of dental implants was performed 3 to 4

months after their insertion, and the prosthetic rehabilitation completed thereafter.

Table 1. DEFICIENT ALVEOLAR BONE, PRIMARY DATA OF PATIENTS

Patient Age Area of Widening Length of Expansion (mm) No. of Implants

Z.I. (M) 45 34, 35, 36, 37 (Lt mandibular body) 5 4

G.Y. (M) 40 13, 14, 15, 16 (Rt maxilla) 6 4

M.O. (F) 33 46, 47 (Rt mandibular body) 4 2

G.S. (M) 50 46, 47 (Rt mandibular body) 5 2

P.D. (F) 52 32, 42 (Anterior mandible) 4 2

Z.Y. (F) 48 46, 47 (Rt mandibular body) 4 2

D.L. (M) 18 11, 12 (Anterior maxilla) 5 2

E.E. (M) 38 11, 12, 21 (Anterior maxilla) 4 3

T.Y. (F) 25 46, 47 (Rt mandibular body) 4 2

FIGURE 9.Anterior and posterior vertical incisions are made through the mucoperiostium.

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7) Activation begins immediately at a recom-mended rate of 0.4 mm per day (½ a turn twice a day.) The patient should be examined by the surgeon every 4 days.

8) Once sufficient width is achieved (10 to 14 days), activation is stopped. (Overdistraction of 1 to 2 mm is recommended.) The Laster Crest Widener is left in for a brief 7- to 10-day consol-idation. The device is then removed under local anesthesia without soft tissue closure (Fig 14). 9) Dental implantation is performed immediately

or 7 to 10 days after removal of the crest wid-ener despite incomplete mineralization (Fig 15). Implant placement is performed transgingivally (Fig 16).

Advantages of Distraction

Osteogenesis Over Bone Grafting

The advantage of DO is that there is little or no bone resorption as typically occurs in bone graft re-construction. Although relapse of the distraction may occur, it is likely within the regenerate (away from the buccal bone plate that establishes alveolar form and provides osseous coverage of the implant).

Another advantage of distraction is the concomi-tant proliferation of attached gingiva, obviating the need for soft tissue augmentation. Therefore, DO avoids donor site morbidity associated with both hard and soft tissue harvest.

There may also be less relapse with alveolar distrac-tion over other approaches. Rachmiel et al, in a 1-year FIGURE 10.Bone cuts are made through the facial plate using a

sagittal saw.

FIGURE 11. A thin osteotome is used to out-fracture the buccal plate.

FIGURE 12.One week later the Laster Crest Widener is tapped into place percutaneously.

FIGURE 13.A titanium safety wire is threaded through the hole in the arm.

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follow-up experimental study, found a 7% relapse after a 40-mm total maxillary advancement.25,26,28_The

relapse for small dimension horizontal distraction is negligible because the regenerate is quick to mature into lamellar bone.19,26 _{The process of bone graft}

incorporation and creeping substitution is completely avoided.

Another advantage to distraction is timing for im-plant placement. Early regenerate mineralization pro-ceeds by thickening of bony trabeculae. Implants placed during this relatively short time frame (4 to 8 weeks postoperative) heal in about half the time re-quired for a staged block graft.

Therefore, DO for width enhancement is relatively simple to perform, quicker to heal than bone grafts, minimally traumatic, and dimensionally stable.

One disadvantage, however, is the second proce-dure required for device removal, although it is easily performed without the need for an incision.

In general, the result of the distraction process for width enhancement resulted in an esthetic and func-tional prosthetic reconstruction, with a more favor-able axial implant placement and improved orthoal-veolar inter-arch relation.

Summary

A pilot study was performed using horizontal alve-olar distraction to treat edentulous sites with moder-ate horizontal atrophy. Sufficient generation of new bone allowed stable dental implant restorations. Soft tissue proliferation added to the hard tissue augmen-tation.

Alveolar distraction may be useful for augmenting the atrophic alveolus in select cases providing the advantage of less overall treatment time than standard staged bone grafting techniques as well as avoiding second site surgery.

Further study of the technique with long-term fol-low-up to confirm bone and implant stability as it relates to alveolar width is needed.

References

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4. Caplanis N, Sigurdsson TJ, Rohrer MD, et al: Effect of

alloge-FIGURE 14.The Laster Crest Widener is left for a brief 7- to 10-day consolidation period, then the device is removed under local anesthe-sia without soft tissue closure.

FIGURE 15.Dental implant placement is performed 7 to 10 days after device removal despite incomplete mineralization.

Laster, Rachmiel, and Jensen. Alveolar Width DO for Early

Im-FIGURE 16.Implant placement is performed percutaneously.

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human mandible by gradual distraction. Plast Reconstr Surg 89:1, 1992

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24. Oda T, Sawaki Y, Ueda M: Alveolar ridge augmentation by distraction osteogenesis using titanium implants: An experi-mental study. Int J Oral Maxillofac Surg 28:151, 1999 25. Rachmiel A, Jackson IT, Potparic Z, et al: Midface advancement

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