Alveolar Bone Grafting in Cleft Patients from Bone Defect to Dental Implants

Abstract

Cleft lip and palate is the most common congenital deformity affecting craniofacial structures. Orofacial clefts have great impact on the quality of life which includes aesthetics, function, psychological impact, dental development and facial growth. Incomplete fusion of facial prominences during the fourth to tenth week of gestation is the main cause. Cleft gaps are closed with alveolar bone grafts in surgical procedure called osteoplasty. Autogenic bone is taken from the iliac crest as the gold standard. The time of grafting can be divided into two stages: primary and secondary. The alveolar defect is usually reconstructured between 7 and 11 years and is often related to the development of the maxillary canine root. After successful osteoplasty, cleft defect is closed but there is still a lack of tooth. The space closure with orthodontic treatment has 50-75% success. If the orthodontic treatment is not possible, in order to replace the missing tooth there are three possibilities: adhesive bridgework, tooth transplantation and implants. Dental implant has the role of holding dental prosthesis, prevents pronounced bone atrophy and loads the augmentation material in the cleft area. Despite the fact that autologous bone from iliac crest is the gold standard, it is not a perfect source for reconstruction of the alveolar cleft. Bone morphogenic protein (BMP) is appropriate as an alternative graft material. The purpose of this review is to explain morphology of cleft defects, historical perspective, surgical techniques and possibilities of implant and prosthodontic rehabilitation.

Introduction

Cleft lip and palate is the most common congenital deformity affecting craniofacial structures. Prevalence depends on population, therefore it is the highest in Indians and Native Americans where 3-4 children per 1000 births have cleft defect, whereas in Caucasians, cleft defect affects 1-2 newborns per 1000 births (1, 2). Males more often have cleft lip and palate, while isolated cleft palate occurs more frequently in females (3). Orofacial clefts have great impact on the quality of life which includes aesthetics, function, psychological impact, dental development and facial growth.

Incomplete fusion of facial prominences during the fourth to tenth week of gestation is the cause of clefts. Depending on which type of prominence is affected, there are clefts including primary and secondary palate. Cleft of the primary palate includes cleft of the lip, alveolus and small part of hard palate, while cleft of the secondary palate includes cleft of the rest of hard and soft palate from the incisal foramen (4). The etiology of deformity is multifactorial, associated with enviromental and genetic factors (5).

For many years one stage of surgical treatment for patients with orofacial clefts includes secondary alveolar bone grafting (6) with autologous bone (7). This type of bone graft provides essential osteogenic cells as well as osteoinductive factors needed for bone healing and regeneration. Donor site may be the patient’s iliac crest, mandibular symphysis, rib, tibia and calvarium (8). The gold standard is bone from iliac crest, taken by traditional approach or by minimally invasive surgery (9-11). The alveolar cleft is usually reconstructed between 7 and 11 years of age and is often related to the development of the maxillary canine root (12, 13). Precious (14) suggests a slightly younger age to improve the crown length and periodontal condition. There are several objectives and benefits of bone grafting: (1) to obtain maxillary arch continuity; (2) to maximize bone support for the dentition; (3) to stabilize the maxillary segments after orthodontic treatment, especially the removable primary palate of bilateral clefts; (4) to eliminate oronasal fistulae; (5) to provide nasal alar cartilage support; (6) to establish ideal alveolar morphology; and (7) to provide available bone with attached soft tissue for future endosteal implant placement in cases where there is a residual dental space (15-17).

The purpose of this review is to explain morphology of cleft defects, historical perspective, surgical techniques and possibilities of implant and prosthodontic rehabilitation.

Characteristics of facial morphology and growth in cleft patients

The treatment of clefts usually begins three months after birth, continuously throughout the whole developmental period and often ends in adulthood (18). The anatomical continuity of facial structures and normal functioning requires a cooperation of a maxillofacial surgeon, orthodontist, phoniatric specialist, otolaryngologist, speech therapist, pediatrician, oral surgeon and dentist (19-21).

Unilateral complete cleft involves cleft gap of the lip and alveolar process up to the incisor foramen and dividing maxilla and lip into two parts. The philtrum and the intermaxillary bone, as the larger part, are moved towards the contralateral side and upwards (22). The less developed part is moved backwards and the alveolar ridge has disturbed odontogenesis, which in most cases affects second incisors. Incisors and canines have abnormal shape and position.

In bilateral cleft, the medial part called prolabium is without muscle and shortened in the vertical dimension. This type of cleft has three parts: two lateral and one medial. Lateral parts are positioned backwards and upwards, while medial part is protruded anteriorly and mobile, formed by the hypoplastic intermaxillary bone. Vestibulo-nasal fistula is visible in large amount of cases and constitutes a pathological junction between the oral vestibule and nasal cavity.

Cleft gaps are closed with alveolar bone grafts in surgical procedure called osteoplasty. Autogenic bone is taken from the iliac crest as the gold standard. The time of grafting can be divided into two stages: primary and secondary. The difference is that primary grafting is made after lip repair but before repair of the palate (23, 24). Secondary grafting has been defined as early secondary at 2-5 years, early mixed dentition at 6-8 years, late mixed dentition at 9-12 years, and late secondary grafting if done after the age of 13 (25, 26).

History of surgical procedure

Lexer (1908) and Dratcher (1914) made first successful attempts of bone grafting in patients with clefts (27). After that, primary alveolar bone grafting was first mentioned by Schrudde and Stellmach, and in 1960’s reports of treatment results have shown great growth disturbances in the maxilla as a result of primary bone grafting (28). In 1962, Brauer et al. provided valuable insight into what surgeons and orthodontists were trying to achieve with primary alveolar bone grafting. They stated that in the unilateral cleft, the absence of bone and soft tissue, as well the pull of the repaired lip on the noncleft side, results in flattening and retrusion of the middle face (29). They believed that early repair of the unilateral alveolar cleft provided a bridge which would allow the retruded cleft-sided maxilla to grow normally and with less hypoplasia. In bilateral deformity some authors (30) stated that premaxillary segment was being bridged to stabilize premaxillary and maxillary components. This approach of early primary bone grafting continued throughout the 1970s in many parts of the developed world.

Secondary bone grafting was introduced by Boyne and Sands in 1972, and those results were presented by several authors (31-33). They found out that permanent stabilization of maxillary segments did not result from early bone grafting which causes malocclusion and growth restriction, which is similar to the findings of Millard (34). Secondary alveolar bone grafting has two benefits such as bony support for tooth eruption and stabilization of the maxilla. It is usually performed during the period of mixed dentition before eruption of the canine therefore it can erupt into solid bone and enhance stabilization of the maxilla (35, 36).

Surgical technique

Osteoplasty of alveolar cleft (Figure 1, 2) is performed with prophylactic antibiotics (amoxicillin/clavulanic acid) given intravenously to prevent infections and under general endotracheal anesthesia. Autogenic spongy bone is harvested from the anterior iliac crest. A skin incision is placed approximately 1 cm laterally to the iliac crest posterior to the anterior superior iliac spine and is about 2 cm long. The incision is made through all parts of the skin to the insertion of the oblique fascia on the crest, with special attention directed to the surrounding musculature. The underlying periosteum is sharply incised, exposing the segment of the iliac crest. An osteotome makes two perpendicular horizontal cuts to obtain a block of corticocancellous bone and to minimise risk of peritoneal penetration. Curettes are used to harvest the desired amount of cancellous bone (Figure 3). In children even a scalpel is sufficient to lift the part of iliac bone and the cancellous bone is exposed, which can be easily taken with cochlea. The surgical wound is irrigated, filled with microfibillar collagen (Surgicel, Ethicon Inc., USA) to achieve hemostasis and closed in a layered shape. No drain or pressure dressing is used.

Figure 1.

Panoramic radiograph before secondary alveolar cleft bone grafting of 11-year old patient with unilateral cleft lip and palate

Figure 2.

Intraoral image before osteoplasty

Figure 3.

A segment of iliac crest expose

The cleft area is infiltrated with 1% xylocaine with epinephrine on the palatal and buccal site of the anterior maxilla. Two full-thickness mucoperiosteal flaps are created by incising the anterior surface of the alveolar process, alongside the cleft ridge (Figure 4). The nasal mucosa is separated by an incision from the gingiva on the both sides of maxilla. Flaps are lifted cautiously with a periosteal elevator along the labial surface of alveolar process to the piriform aperture. The nasal mucosa is reflected into the nose and the periosteum out of the cleft so that new bone could be grafted. The autogenic bone fills the cleft fissure (Figure 5) and it is covered with lifted flaps. The incision of mucous flap for covering clefts can be moved from the lateral sides of the alveolar process (37). It is advised to place the bone graft in the region of the piriform aperture (Figure 6) to provide elevation and support for the base of ala nasi on the cleft. Bone graft could be taken in a block and fixed with screws (Figure 7, 8). The operation area is closed with a flap and secured with resorbable suture.

Figure 4.

Incision and flap elevation for secondary alveolar bone graft

Figure 5.

Cancellous bone harvested

Figure 6.

Graft placement during secondary alveolar bone grafting

Figure 7.

CT scan of patient with bilateral cleft lip and palate before osteoplasty

Figure 8.

Autologous bone graft fixed with screws in bilateral cleft

Medications are used to achieve postoperative analgesia and instructions for oral hygiene are given to patients and their parents.

Implant and prosthodontic rehabilitation

In cleft patients there is a higher incidence of dental anomalies than in the unaffected population. The cleft area creates many disturbances in the dentition such as impacted teeth, tooth agenesis, supernumerary teeth, delayed dental development and altered crown to root ratios (38-41). After a successful osteoplasty, cleft defect is closed but there is a lack of tooth. In most cases it is the lateral incisor. The space closure with orthodontic treatment has 50-75% success (42, 43). If orthodontic treatment is not possible, in order to replace the missing tooth there are three possibilities: adhesive bridgework, tooth transplantation and implants. Modern adhesive techniques and reduced caries rates are the main reasons for adhesive bridgework in the adolescent (44). The lower premolar is the most common tooth for transplantation and this has been demonstrated in grafted sites in cleft patients (45).

Positioned upright to create better osteoconductive conditions and to reduce resorption of the autologous graft, bone grafting is carried out with the use of Bio-Oss biomaterial (Geistlich Pharma North America Inc., USA) (46). It is a biological product with the same chemical and physical structure as a human bone, but prepared from the bovine. The crystalline structure of the matrix provides good stabilization and supports revascularization of the graft. Autogenic bone graft with platelet-rich plasma and bovine bioapatite has great use in implantology (47). In guided bone regeneration, in order to keep away connective tissue from bone gap, bioresorbable collagen barrier membranes (Bio Gide, Geistlich Pharma North America Inc., USA; Ossix, OraPharma Inc., USA) are used (48).

Dental implant (Figure 9) has the role of holding dental prosthesis, prevents pronounced bone atrophy and loads the augmentation material in the cleft area. Edentulous spaces may be small because of surgical and orthodontic pre-treatment accompanied by reduced bone in vertical and sagittal dimension. The soft tissue around cleft defect has a large amount of scar tissue therefore the peri-implant reconstruction is required in some cases.

Figure 9.

Dental implants positioned in cleft gaps

There are only a few articles in the literature focused on implantological treatment of the cleft. Landes (49) demonstrated in a study that the probability of success of implants in patients with cleft is very similar to prognosis of implants inserted after traumatic tooth loss. The oral-health-related quality of life of cleft patients is similar to that of non-cleft patients.

Matsui et al. (50) emphasized that sufficient bone availability is crucial for successful implant treatment in this group of patients, so re-augmentation (tertiary grafting) of the cleft jaw was undertaken with an autogenous iliac crest graft three or four months (51, 52) before the implants were positioned or simultaneously (53) with implant placement. Implant therapy offers a reliable option for patients but particular attention should be paid to bone volume, which can achieve primary implant stability. The complex treatment procedures require cooperation between maxillofacial surgeon and the implantologist (Figure 10).

Figure 10.

Final prosthodontic rehabilitation with implants and crowns

Future techniques

Despite the fact that autologous bone from iliac crest is gold standard in osteoplasty, it is not the perfect source for reconstruction of the alveolar cleft. There are many articles focused on bone fabricated by growth factor-aided tissue engineering, usable as an alternative graft material. One of these sources is bone morphogenic protein (BMP) delivered on a collagen sponge. Fallucco (54) had some success with the application of this product, but this product is expensive and its availability is limited. Institutions have not yet approved the use of this type of product.

The main reason for using these products is the avoidance of the second surgical site needed for the harvesting of autologous bone (55). Thanks to that we have absence of donor site morbidity, shorter operation time, shorter hospital stay and reduction of costs.