Secondary Alveolar Bone Grafting of the Cleft Alveolar Defect in Cleft Palate

Richard E. Kirschner

Michelle Scott

Matthew A. Hiersche

DEFINITION

Alveolar clefts are present in patients with orofacial clefts that involve the maxillary alveolar ridge.
- The defect can range from a simple alveolar notch to a complete cleft that involves the alveolus, maxilla, and inferior piriform rim.
Secondary alveolar bone grafting, as originally described by Boyne and Sands,¹ is the final step in closure of the orofacial cleft. This procedure closes the nasoalveolar fistula, unites the maxillary arch in preparation for definitive orthodontic treatment, creates support for the affected nasal structures, and provides alveolar bone for the support of the lateral incisor (if present), the canine, and surrounding dental structures.
Alveolar bone grafting is most often performed by utilizing autogenous bone from the iliac crest, which remains the standard.
- Other donor sites include the cranium, tibia, and mandibular symphysis.²^,³^,⁴
- The use of allogenic bone and bone morphogenetic protein (BMP) has also been reported.⁵^,⁶

ANATOMY

An alveolar cleft is a three-dimensional cleft in the maxilla most often extending from the piriform rim to the alveolar margin.
- The bony cleft is shaped as an inverted pyramid with its base at the piriform rim and its pinnacle at the alveolar margin (FIG 1).
Distal to the cleft, the alveolus may be hypoplastic, and the lateral maxillary segment may be displaced posteriorly and collapsed medially.

FIG 1 • A,B. Cone-beam CT demonstrating the pyramidal defect of the alveolar cleft.
The alveolus/piriform rim acts as the “foundation” for the overlying soft tissue of the lip and nasal tip.
- Alveolar clefting and displacement of the lateral maxillary segment may thus result in displacement and distortion of the lip, nasal sill, and alar base.
Dental anatomy adjacent to the cleft is often anomalous, demonstrating abnormalities in the position, shape, and presence of the canine and lateral incisor. Likewise, abnormalities in dental structure (eg, enamel hypoplasia, root abnormalities) and in dental eruption patterns are often noted.⁷

PATHOGENESIS

The face is formed through the fusion of five facial prominences that develop and fuse in weeks 6 to 8 of development. These facial prominences are the midline frontonasal prominence, the paired lateral nasal prominences, and the paired maxillary prominences.
The frontonasal prominence (median nasal prominence) forms the forehead, nasal bridge, nasal tip, columella, philtrum and central upper lip, septum, and premaxilla (primary palate).
The paired lateral nasal prominences form the alae of the nose.
The paired maxillary prominences form portions of the cheek, the lateral components of the upper lip, the maxilla, and the lateral palatal shelves (secondary palate).
In normal development, the primary palate, which receives its blood supply via the sphenopalatine artery from the septum, fuses with the bilateral palatal shelves to complete the development of the palate.
In clefts involving the alveolus, the primary palate and secondary palate fail to fuse at the alveolus, maintaining a connection between the oral and nasal cavities.
The etiology of cleft lip and palate is multifactorial with both genetic and environmental factors contributing to the development of orofacial clefts.
To be etiologic, environmental factors must affect the fetus between weeks 6 and 8 of development, as this is the critical time for development of the primary palate.
Medications that have been implicated in the development of a cleft lip and palate include anticonvulsants, folate antagonists, benzodiazepines, corticosteroids, and beta-blockers.
Certain maternal factors have been implicated in the development of cleft lip and palate, including smoking, excessive alcohol consumption, and obesity.
Maternal health conditions may also contribute, including diabetes and maternal fever.
Lastly, a family history of cleft lip and palate is one of the strongest risk factors for the development of a cleft lip or palate, implicating a complex genetic component.

NATURAL HISTORY

The need for repair of the alveolar cleft is generally accepted; however, timing of alveolar bone grafting remains controversial.
- Primary alveolar bone grafting is not practiced at most centers in light of evidence that it has a negative influence on maxillary growth.⁸^,⁹
- The remainder of this chapter is pertinent to secondary alveolar bone grafting.
In the absence of primary alveolar bone grafting or gingivoperiosteoplasty, the alveolar cleft remains as a persistent nasoalveolar fistula following closure of the lip and palate.
The persistent fistula allows regurgitation of oral contents into the nose and passage of nasal secretions into the oral cavity. Additionally, the cleft traps food products, reduces oral clearance, obstructs basic hygiene, and may contribute to periodontal disease and dental decay.
Without alveolar bone grafting, patients may maintain a flat, depressed lip, nasal sill, and alar base secondary to inadequate bony support of the soft tissues overlying the deficient piriform rim. Likewise, inadequate bone stock may lead to dental loss due to insufficient periodontal support.
The reconstructed alveolus and piriform rim support the overlying nasal structures.
Following closure of the alveolar cleft, orthodontic canine substitution may be employed to camouflage the defect resulting from an absent lateral incisor. Alternatively, the graft may be used to support replacement of the absent lateral incisor through implant placement.

PATIENT HISTORY AND PHYSICAL FINDINGS

Regurgitation of liquids or solids into the nose through a persistent nasoalveolar fistula may be reported.
Oral hygiene practices, regular dental evaluations, and current or prior orthodontic treatment must be documented and discussed in detail, as the proper coordination of dental and orthodontic care is important in ensuring optimal outcomes in secondary alveolar bone grafting.
It is important to solicit the patient’s surgical history as it pertains to any prior cleft lip or palate procedures, as well as prior surgical treatment of the alveolus, whether primary or secondary.
Additional treatment for or the presence of additional oronasal fistulae should be assessed.
On physical examination, the presence, location, stability, and morphology of the dentition adjacent to the cleft should be assessed, as well as noting overall oral hygiene, dental decay, and periodontal disease.
Overall, arch form should be assessed, as orthodontic preparation of the arch through expansion is often necessary to place the alveolar segments in an optimal position for bone grafting.
Evaluation for the presence of an additional oronasal fistula should be performed, noting the prior method of palate repair.

IMAGING

Panoramic and occlusal x-rays have been traditionally used to image the alveolar defect and to assess graft take postoperatively.
When available, a cone-beam CT scan offers improved three-dimensional evaluation of the cleft area and the adjacent dentition.
- It may be used to more accurately assess bone graft take by providing a high-resolution, three-dimensional image of the alveolus.

NONOPERATIVE MANAGEMENT

Patients who are not candidates for or who decline alveolar bone grafting may be offered prosthetic habilitation of the cleft site.
This can be achieved with a variety of fixed and removable devices for aesthetic replacement of the missing dentition and acrylic coverage of remaining fistulae.¹⁰^,¹¹

SURGICAL MANAGEMENT

Repair of the alveolar cleft is generally performed during the stage of mixed dentition, which ranges from 6 to 10 years of age.
- Graft placement should be performed before eruption of the permanent canine (or lateral incisor, when present) adjacent to the cleft.
- Imaging is performed to assess root formation of the canine or lateral incisor, and grafting is performed once approximately half of the root has developed.
- Performing the surgery at this stage provides bony support for the tooth as it erupts, and eruption of the tooth through the bone graft supports retention of graft volume.
- Delayed tooth eruption into the graft area may result in loss of alveolar height and bony support. Thus, the goal is to provide early bony support for tooth eruption while minimizing the time between grafting and eruption of the permanent canine or lateral incisor.
The main steps in the procedure are as follows:
- Development of soft tissue flaps to close the nasal floor, surface the buccal gingiva, and close any residual palatal fistulae
- Approximation of the nasal and palatal flaps to line the periosteal pocket for the bone graft
- Harvest of cancellous iliac crest bone graft
- Placement of the bone graft into the prepared pocket
- Approximation of the buccogingival flaps
- Placement of an intraoral splint, if necessary
- Closure of the iliac donor site in layers, including closure of the cartilaginous cap of the iliac crest
Indications for surgical management: patent alveolar fistula, dental arch collapse, deficiency of the piriform rim, support of adjacent teeth, and completion of dental habilitation (orthodontics and prosthodontics)
Contraindications to surgical management: noncompliance with preoperative orthodontic preparation and poor oral hygiene resulting in gingivitis or caries adjacent to the alveolar cleft