J Oral Maxillofac Surg

47~469-474, 1989

Short-Term Experience With the Subperiosteal Tissue Expander in Reconstruction of the Mandibular

Alveolar Ridge

ALBERT R.M. WITTKAMPF, MD, DDS*

A review of 35 patients in whom a subperiosteal tissue expander was used before reconstruction of the alveolar ridge with hydroxylapatite granules is presented. The mean increase in mandibular height was 8.4 mm as mea- sured on true lateral cephalometric radiographs. Secondary preprosthetic surgery was necessary in two cases.

Introduction

During subperiosteal tunneling in moderately to extremely atrophic ridges (Kent class 3 and 4l), the unstretchable periosteum can tear, and loss of con- trol of the hydroxylapatite (HA) granules, as well as migration into the submucosal tissues, can occur. Such migration may result in complaints of pain due to pressure of the denture border on the granules, loss of granules and height of the augmentated al- veolar ridge, loss of depth of the vestibule, and pain and paresthesia due to mucosal perforation or pres- sure of the granules on the mental or inferior alve- olar nerves. To solve these problems, we have been using the subperiosteal tissue expander (STE). In the beginning, it was used only in extreme cases in which no reasonable alternative was available. Later, the applications for the use of the STE were extended because of the good short-term results in the previous cases. This article reports on the pre- liminary results in 35 patients.

Technique

While the patient is under local anesthesia, a IS- cm horizontal incision is made in the midline, 1 cm

* Senior staff member, Department of Oral and Maxillofacial Surgery, Academisch Ziekenhuis, Utrecht, The Netherlands.

Address correspondence and reprints to Dr Wittkampf: De- partment of Oral and Maxillofacial Surgery, Academisch Ziek- enhuis, Catharijnesingel 101 3511 GV Utrecht, The Netherlands.

0 1989 American Association of Oral and Maxillofacial Sur- geons

0278-2391/89/4705-0008$3.00/O

below the residual ridge, and the tissues superiorly are dissected subperiosteally until the alveolar crest is reached. Then a lingual tunnel is prepared in this region to create sufftcient space for the insertion of the expander on top of the alveolar ridge. The tun- nel is then continued toward the retromolar pad on the lingual side of the residual ridge to prevent dam- age to the inferior alveolar nerve. Once it is deter- mined that the nerve is not in the field, the muco- periosteum can be lifted buccally, avoiding injury to the nerve with the periosteal elevator. The tunnel must be slightly longer than the expander to create enough length on the lateral aspects of the mandible to insert the STE. It is mandatory to close small mucosal perforations that may have occurred dur- ing tunneling before the expander is inserted. By doing so, damage to the expander during suturing is avoided.

The U-shaped silicone 3.6 mL subperiosteal ex- pander (Cox-Uphoff Int, Santa Barbara, CA) has a self-sealing filling tube and a tab at both ends with a small perforation to facilitate insertion with the help of traction sutures. Sutures attached to the Teflon tabs at the end of the expander are passed through the tunnel using an awl kept in contact with the mandibular bone. After the awl perforates the mu- cosal tissue disto-buccally at the end of the tunnel, the sutures are grasped at the retromolar pad, and the awl is removed. To have control of the position of the expander during insertion, it is filled with approximately 1.5 mL of sterile saline. By pulling the sutures in a dorsal direction, the expander is easily inserted. The position on the mandible can easily be checked by a process of emptying and refilling the STE. When the expander has been

469

470 SUBPERIOSTEAL TISSUE EXPANDER

properly positioned, the self-sealing filling tube is placed in the lateral vestibule using an awl (Fig 1). The expander is then emptied, and the incision is closed in two layers.

Inflation of the expander is started the third week after insertion. Usually, four injections of saline are made over an eight-day period. The extent of inlla- tion is dictated by the blanching of the overlying mucosa and/or discomfort felt by the patient.

One month after insertion, the expander is re- moved under local anesthesia through the original horizontal incision. The silicone implant, as well as the expansion, induce the formation of a fibrous tissue capsule around the expander.* Bonomo,3 Lew et aL4 and Bock and Rose’ advise removal of this capsule between the expander and the mandible by curetting with a sharp instrument before the HA granules are inserted. However, in order to prevent damage to the nerve because of the extreme resorp- tion of the alveolar ridge and basilar bone in most of our patients, the capsule on top of the mandible was not removed. The presence of this layer did not interfere with stability of the augmentation. The nonporous HA granules are easily inserted into the tunnel with a normal applicator syringe and are

FIGURE 1. Use of the awl to bring thi lateral vestibule.

e fling tube

compressed by the piston. Migration of the granules does not occur with this compression. Nine and a half or 10 grams of nonporous HA granules are nec- essary to fill the tunnel created by the expander. After filling, the incision is closed in two layers.

A narrow-spectrum antibiotic is prescribed after insertion of the STE as well as after implantation of the granules. The dentures are made by the prosth- odontist 2 months after insertion of the HA gran- ules, based on the premise that in a 2-month period enough fibrous tissue has grown between the gran- ules to form a solid alveolar ridge.

Materials and Methods

Until now, 60 expanders have been inserted. The first group of 35 patients were analyzed for this re- port. The mean age was 50.5 years, with a range of 31 to 74 years. The study population was predomi- nantly female (66%). Thirty-one patients showed Kent class 4 and four patients class 3 alveolar ridge deficiencies. ’ One patient had had a sandwich-visor osteotomy and a vestibuloplasty and lowering of the floor of the mouth with split-thickness skin graft, and two patients had a vestibuloplasty with split- thickness skin graft previously. In one patient in whom a split-thickness skin graft was performed earlier, the graft was immobile and firmly attached to the mandible. Therefore, preparation of the tun- nel was very difficult. For this reason, an STE could not be inserted. This patient has not been included in this article.

The preoperative and postoperative sensibility of the lower lip was tested for touch with wisps of cotton, pain by pinpricks, and two-point discrimi- nation. The mandibular height was measured on true lateral cephalometric radiographs according to the method of Mercier6 preoperatively and immedi- ately postoperatively. In a Kent class 1 and 2 or Cawood class 4 knife-edged ridge,7 we used a com- bination of HA granules and fibrin glue to recontour the ridge.*

Results

The radiologic appearance in all the patients was consistently the same. A space between the hydrox- ylapatite and the mandible of variable thickness was seen initially, but it decreased during follow-up (Fig 2). This space between the granules and the mandi- ble did not interfere with the stability of the recon- structed alveolar ridge in any of the 35 patients. No migration or spilling of the granules took place ex- cept for a minor spill at the site of insertion in the anterior region (Figs 3 and 4). The mean preopera- tive mandibular height was 9.6 mm, and the mean initial augmentation was 8.5 mm. None of the pa-

ALBERT R.M. WI’I-IKAMPF 471

FIGURE 2. A, Radiograph immediately after insertion of HA granules. Note the space between the HA and the bone. B, Three months later there is diminished space seen.

tients had secondary corrections because of prob- lems caused by migrated granules. Complaints about painful mucosal areas caused by submucosal granules, or loss of granules during wearing of the denture, did not occur in any of the patients. Of the 35 patients with Kent class 3 and 4 ridges, vestibu- loplasties and lowering of the floor of the mouth were performed in only two.

COMPLICATIONS

Two patients had unilateral paresthesia of the lower lip after insertion of the expander. One re- covered within several weeks. After 6 months one patient still has a nondisturbing unilateral hypesthe- sia of a small part of the right lip. During the tunel- ing procedures, perforations occurred in four pa- tients. These were closed before the expander was inserted. Three, all in the second molar region, be- came dehiscent 1 week later. One of these patients had undergone preprosthetic surgery with a split- thickness skin graft performed earlier. It was de- cided to continue the expansion procedure. During expansion the dehiscence enlarged, as expected,

but after removal of the expander the dehiscence was easily closed and the tunnel filled with hydrox- ylapatite. However, this led to a somewhat short- ened alveolar ridge up to the first molar region. It had no measurably negative effect on stability of the lower denture.

Three patients showed dehiscence of the incision; all had undergone preprosthetic surgery earlier. Two dehiscenses occurred immediately after inser- tion of the STE and were easily closed after inser- tion of the granules. The other occurred after inser- tion of the granules. Repeated unsuccessful efforts were made to close this defect, but the previously grafted skin was resistant to therapy. However, the dehiscense eventually closed spontaneously after treatment of a local infection by incision and anti- biotic therapy.

A major complication was thinning of the overly- ing mucosa leading to a perforation. Thinned mu- cosa can rarely be closed. This type of perforation occurred in three patients. The final result was par- tial loss of the granules in the premolar region in two patients (classified as a partial failure), and granule leakage of up to two thirds of the inserted volume in the third patient (classified as a 100% failure). Even when a dehiscense or perforation oc- curred during the expander period, no infection was noticed.

Discussion

Several authors have described a vertical midline incision in the nonkeratinized mucosa for insertion of the expander.3F5 This type of incision has several disadvantages:

1.

2.

3

The incision is on top of the expander, and during closure a perforation of the expander may occur. Chance of dehiscense is more likely during wound healing or expansion (Lew et aJ4 two out of five patients; Bock and Rose,’ three out of live patients; this study, three out of 35 pa- tients.

d. The incision may give rise to vertical scar con- traction postoperatively, resulting in loss of depth of the vestibule.

A horizontal incision facilitates the tunneling on the lateral aspect of the mandible, and a better two- layer closure of the wound is possible because of the presence of muscular tissue on the inferior as- pect of the alveolar ridge. The horizontal incision also seems to be more reliable because of its dis- tance from the expander and expanded mucosa. De- hiscence of the incision was observed in only three

472

FIGURE 3. Immediate post- operative radiograph showing good containment of particles.

SUBPERIOSTEAL TISSUE EXPANDER

patients; all had preprosthetic surgery with a split- thickness skin graft performed earlier. In experi- ence with 60 patients in whom an STE was inserted there has been no need for an extensive open flap procedure as recently described by Lew et a1.9 Early filling of the expander, as described by Bonomo,3 Lew et aL4 and Bock and Rose,’ will not result in expansion of the potential denture-bearing region, but will only lift the tunnel and vestibule. Therefore, it is recommended to wait for at least 2 weeks before the first expansion takes place; an even longer waiting period is preferable.

As previously mentioned, the space between the granules and the mandible did not interfere with

stability of the reconstructed ridge. Biopsies of this interface taken immediately after removal of the ex- pander, 1 month after insertion, showed fibrous tis- sue with reactive bone formation (Fig 5). This in- terface decreases radiologically during follow-up (Fig 2). When using reconstructive methods with nonporous HA granules, bone formation is noticed only between the granules positioned on top of the mandible; the remaining granules are encapsulated in fibrous tissue.“,” Nevertheless, they form a functional and stable ridge. For this reason, the fi- brous tissue interface between the granules and the mandible may be left in place. It can also be as- sumed that the fibrous tissue between the granules

FIGURE 4. Occlusal radiograph immediately after augmentation using the STE technique (A) compared with a direct reconstruction method using HA granules (B). Note the migration of particles with the latter method.

ALBERT R.M. WITTKAMPF 473

A B C

FIGURE 6. Diagram illustrating subtypes of soft tissue man- dibular relationships. Type A, Potential broad denture-bearing area. Type B, Intermediate type. Type C, Almost no potential denture-bearing area.

FIGURE 5. Biopsy of the interface between the expander and the mandible 1 month after insertion. Note the fibrous tissue and reactive bone formation. (Hematoxylin and eosin. Original mag- nification, X75.)

and the mandible acts as a protective shield be- tween the granules and the mental and inferior al- veolar nerve. We have found no patient so far with sensibility disturbances due to pressure of the gran- ules. The unilateral paresthesia in two of the pa- tients was due to the tunneling procedure.

Intraorally, the postoperative retentive possibili- ties of the reconstructed ridges was variable but very predictable; they depended not only on the form and width of the mandible, but also on the relation of the mucosa in the cheek and floor of the mouth to the mandible. The relation of mucosal tis- sues in the cheek and floor of the mouth to the mandible in Kent’ class 1 and 2 or Cawood’ class 4 knife-edged ridges is of minor importance. How- ever, in Kent’ class 3 or 4 and Cawood’ class 5 or 6 ridges, the soft tissue-mandibular relationship sometimes has an even greater effect on the final result than the type of atrophy.

We make a distinction between three types of soft tissue-mandibular relationships independent of the type of mandibular atrophy. This classification can be used in combination with the classifications of Kent’ or Cawood.’ By doing so, the applications for the use of the STE and other reconstructive meth- ods are easily determined, and the chance that sec- ondary preprosthetic surgery is needed becomes predictable to a certain extent.

Type A shows a potential broad denture-bearing area. Type C, the unfavorable type, shows almost no potential denture-bearing area. Type B is the intermediate type (Fig 6). Although in all three types the radiologic result of the augmentation us- ing the STE was extremely satisfying, the protru- sion of the reconstructed ridge into the oral cavity showed variability from patient to patient. The in- traoral result depended on the preoperative type.

In type A, extremely good results can be

achieved using the STE technique. A very nice al- veolar ridge is formed with good retentive possibil- ities. Although it cannot be proved by measure- ment, the position of the vestibular sulcus and floor of the mouth is probably unchanged (Fig 7A). In cases such as type B, direct alveolar ridge augmen- tation methods may lead to loss of depth of the vestibule and floor of the mouth due to lifting of the mucosal tissues. For this reason, secondary pre- prosthetic surgery may be needed in most of these cases.

In the type B soft tissue-mandibular relationship, the STE may lead to expansion of the potential den- ture-bearing area, in most cases resulting in protru- sion of the reconstructed ridge into the oral cavity, even in the anterior region, and secondary prepros- thetic surgery may not be needed (Fig 7B).

Type C is the most difficult one. Here the STE, as well as other two-step procedures,‘2,‘3 or direct re- constructive methods, will not lead to the creation of an adequate denture-bearing area. The mucosal tissues are lifted, and intraorally the augmentation is very limited (Fig 7C). In this study, the type C cases needed extra preprosthetic surgery in order to get satisfying results. In the types A and B, the STE had a greater possibility of creating a good denture- bearing area, with hardly any risk of loss of depth of the vestibule and floor of the mouth. Using altema-

A B c FIGURE 7. Diagram showing when expander is used. Type A, Extremely good results by expansion of denture-bearing area. Type E, Good results by expansion of denture-bearing area using the STE. Type C, No gain in denture-beating area using the STE.

SUBPERIOSTEAL TISSUE EXPANDER

tive reconstructive methods, the risk of losing depth of the vestibule or floor of the mouth is very high in the type B patient.

Apart from the aspect of the soft tissue- mandibular relationship there are other advantages to using a two-step procedure. In direct reconstruc- tive procedures, care must be taken to prepare the subperiosteal tunnel just on top of the mandible in such a way that the HA granules will not migrate into the floor of the mouth or buccally. The surgeon is forced to make the tunnel in a labial direction toward the mental foramen or on top of the inferior alveolar nerve in extremely atrophic cases. In a two-stage procedure, like the STE technique, the mental foramen or the inferior alveolar nerve can be bypassed lingually because during the first stage only the expander is inserted and there is no con- cern about migration of the granules. Of the 120 mental nerves in 60 treated patients, only two showed paresthesia (temporary) due to the tunnel- ing procedure. All the other nerves showed normal reaction when tested as previously described.

The disadvantages of the STE technique are ob- vious. Two treatments under local anesthesia are necessary. One month delay, with regular atten- dance for inflation of the insert, is also necessary. However, this more than compensates for the lack of secondary preprosthetic procedures when pa- tients are selected on basis of already known clas- sifications as well as the classifications suggested in this article. The price of the expander is partly com- pensated for by the fact that only 9.5 or 10 g of nonporous HA are needed. The STE technique is never used for maxillary atrophy. A direct recon- structive method using HA granules and fibrin glue

combined with a submucosal vestibuloplasty re- mains the method of choice for that area.i4

References

1. Kent JN, Quinn JH, Zide MF, et al: Alveolar ridge augmen- tations using nonresorbable hydroxylapatite with and without autogenous cancellous bone. J Oral Maxillofac Surg 41:629, 1983

2. Van Rappard JHA: Controlled tissue expansion in recon- structed surgery. Thesis, State University Groningen, Ni- jmegen, S.S.N., 1988

3. Bonomo DJ: Subperiosteal Soft Tissue Expansion for Ridge Augmentation. Miniclinic Chicago Dent Sot Rev 1986, pp 34-39

4. Lew D, Clark R, Shahbazian T: Use of a soft tissue expander in alveolar ridge augmentation: A preliminary report. J Oral Maxillofac Sum 44516. 1986

5. Bock MJJ, Rose R: De; SubpeAostale Gewebe-Expander als Hilfsmittel bei der Alveolar Kamm Plastik. Dtsch Z Mund Kiefer Gesichtschir 11443, 1987

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8. Wittkampf ARM: Fibrine-glue as cement for HA-granules. Int J Craniomaxillofac Surg (submitted)

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10. Chang CS, Matukes VJ, Lemons JE: Histologic study of hydroxylapatite as implant for mandibular augmentation. J Oral Maxillofac Surg 41:729, 1983

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12. Kruger E: Alveolarkamaufbau im Unterkiefer mit Hydroxyl- apatit. Dtsch Z Mund Kiefer Gesichtschir 9194, 1985

13. Osbom JF, Kapovits M, Karl P: Die Zweizeitige Augmen- tation des atronhischen Kiefers mit Hydroxylapatit- keramik-Grant&t. Der Zahnarzt 3:149, 1986

14. Wittkampf ARM: Augmentation of the maxillary alveolar ridge with hydroxylapatite and fibrin glue. J Oral Maxil- lofac Surg 46:1019, 1988