Early secondary closure of alveolar clefts with mandibular symphyseal bone grafts and β-tri calcium phosphate (β-TCP)

Abstract

Alveolar reconstruction of bony defects in cleft lip and palate patients is a widely accepted treatment regimen for which multiple donor sites can be used. For 25 years, autogeneous bicortical mandibular symphyseal bone grafts have been used at the authors’ centre. In cases in which the alveolar defect was too large to match the volume of the mandibular symphyseal bone transplant, β-TCP granules were packed against the bone transplant to fill the defect completely. In a retrospective study, 18 patients, who were treated with mandibular symphyseal bone wrapped in β-TCP granules, were compared with 29 patients, who were treated with mandibular symphyseal bone only. To assess alveolar height, occlusal radiographs were taken directly postoperatively and 1 year later. Mean alveolar bone loss was calculated and compared between groups using Student’s t -test and linear regression analysis. No statistically significant difference in alveolar height was found between the two groups. It was concluded that mandibular symphyseal bone grafts enriched with β-TCP granules can be used successfully in cases in which the alveolar cleft is too large to be grafted with mandibular symphyseal bone alone.

Secondary bone grafting of the residual alveolar cleft in patients with cleft lip and palate has become a well-established procedure. Successful grafting allows eruption of teeth into the former cleft area and the achievement of orthodontic movement of teeth adjacent to the cleft site, to obtain non-prosthodontic rehabilitation. Secondary alveolar bone grafting (SABG) is ideally carried out between 9 and 11 years of age, before eruption of the maxillary canine, to allow the canine to erupt through the grafted site. A slight reduction in anterior vertical maxillary growth has been found after SABG. This effect is partially compensated by the capacity of the erupting canine to generate alveolar bone.

After bridging the alveolar cleft with bone, functional loading either by resumption of eruption of the canine or by orthodontic guidance into the new bone will help to maintain the bone graft. At present, autologous bone is the preferred material for closure of the osseous defect in the alveolar process. Iliac crest particulate cancellous bone is most commonly used for this purpose. Reports advocating the use of mandibular symphyseal bone, rib bone, calvarial bone and bone harvested from the tibia have been published.

Harvesting an autologous bone graft has several disadvantages. Donor site surgery requires prolonged operating time and may cause morbidity. Serious side effects of taking iliac crest bone transplants, such as hypersensitivity, pelvic instability, infection, and paraesthesia affect 10–30% of patients. The mandibular symphysis has been advocated as an alternative donor site , although it is associated with minor complications such as paraesthesia and apical root damage.

In the authors’ hospital, the SABG-procedure has been performed using a mandibular symphyseal bone transplant for 25 years. In most cases, the volume of the harvested bone was sufficient to fill the cleft region, but sometimes there was a shortage of bone. In those cases, the use of an alternative donor site was considered. To avoid the disadvantages mentioned above alloplastic materials are also an option.

In cases where a discrepancy was found between the volumes of the chin bone transplant and the alveolar defect, β-TCP granules were positioned at the buccal side of the graft and the remaining minor spaces, in such a way that the central part of the cleft region was always filled by autogenous bone, forming a bony bridge between the adjacent parts of the maxilla.

The aim of this study was to compare alveolar height and canine eruption between clefts grafted either with chin bone or with chin bone and β-TCP.

Material and methods

Patients

From April 1998 to December 2005, 182 patients with a cleft lip and palate underwent surgery for early secondary reconstruction of the alveolar process using a symphyseal bone graft. All patients were operated on by one surgeon. SABG was performed when one-quarter to one-half of the final root length of the adjacent canine was formed, as indicated by the radiographic appearance of a root length equal to that of the crown. In all cases the canine crown was still completely covered by bone.

β-TCP as an adjunct to autologous symphyseal bone was used in 31 patients (17%) of whom 18 patients, who had complete records, were included in this study. A control group of 29 patients, grafted with symphyseal bone only was taken at random from the remaining 151 patients. In case of a bilateral cleft, the clefts were scored as two solitary clefts. The inclusion criteria for the study were based on the presence of sufficient and accurate radiographs preoperatively, directly postoperatively and 1 year postoperatively. Exclusion criteria were radiographs of insufficient quality and inability to conform to the 1 year postoperative follow up.

Cleft surgery

All operations were performed under general anaesthesia. At induction, a prophylactic antibiotic regimen with cefazolin and metronidazol was given. Surgery began by infiltration of local anaesthetic with adrenaline 1:200,000 (Ultracain DS Forte ® ) into the anterior vestibulum of both the lower and upper jaw and into the palatal foramen region of the maxilla. The cleft area was exposed subperiosteally by making vertical incisions along the edges of the cleft. On the buccal side the vestibular gingival sulcus incision was extended distally along the attached mucosa of the adjacent teeth to the second molar area. In this region, a buccal relieving incision with an additional periosteal relieving incision was performed. A mucoperiosteal transposition flap was created that covered the alveolar cleft and bone transplant in a tension free manner. At the cleft site, first the nasal mucoperiosteum was separated from the oral mucoperiosteal lining, then elevated and freed from the cleft site extending posterior along the nasal floor. The soft tissue nasal floor was reconstructed using 5–0 vicryl sutures. No tissue glue was used.

Grafting procedure

To harvest the mandibular symphyseal bone transplant, a marginal incision into the gingival sulcus along the lower incisors with two vertical relieving incisions in the canine region was made ( Fig. 1 ). After deflecting the mucoperiosteum, the chin region was exposed. Keeping a minimal distance of 5 mm from the apices of the lower incisors to prevent damage, a rectangle was outlined in the symphyseal region between the developing canine teeth. By drilling a ‘through and through’ hole using a 2 mm round bur, a starting point was created. Then, using an oscillating saw with a small blade, a rectangular bone transplant was created leaving the lower border of the symphysis intact. The bicortical mandibular symphyseal bone graft was elevated and then delivered by freeing it from the lingualy attaching muscles. Bone wax or a gelatin sponge were applied for haemostasis routinely. The mucoperiosteum was replaced and sutured with interdental interrupted stitches (3–0 Vicryl). No drains were used.

Fig. 1
Donor site procedure. (a) A complete thickness hole was created with a drill. (b) Using an oscillating saw a rectangular bone transplant was harvested. (c) The bicortical mandibular symphyseal bone graft was elevated, leaving (d) the lower border intact.

Grafting of the cleft

The mandibular symphyseal bone graft was reshaped and wedged into the alveolar cleft in such a way that the buccal cortex of the chin graft functioned as the buccal cortex of the reconstructed alveolus. In the control group the cleft was totally filled up. In the bucco-palatal direction the reconstructed area was the same or broader than the original alveolar width. In case this bucco-palatal dimension could not be achieved, additional bone substitute granules were applied to cover the positioned mandibular symphysis bone graft to prevent resorption. A prerequisite was that at least a bony bridge was created between the two original alveolar bone segments ( Figs. 2 and 3 ).

Fig. 2
Symphyseal bone graft (a) with β-TCP granules (black arrow). Space discrepancies were filled with the β-TCP granules. At the buccal side of the bone transplant the granules function as barrier (a).

Fig. 3
β-TCP granules were positioned at the buccal side of the graft and remaining minor spaces, in such a way that the central part of the cleft region was always filled by autogenous bone forming a bony bridge between the adjacent parts of the maxilla.

As bone substitute, β-TCP 1000–2000 μm particles (Cerasorb ® Curasan AG, Germany) were used mixed with fresh locally derived autogenous blood to create a paste-like substance. If primary closure was impossible, palatal incisions were made from the anterior teeth posteriorly, parallel to the course of the greater palatine artery. Palatal flaps were created, mobilized and sutured together to close the palatal cleft. An extra oral submental elastic dressing was applied to create pressure over the chin region and removed after 5 days.

Follow up

Occlusal radiographs were taken preoperatively, and 1 week and 1 year postsurgically. Alveolar bone height was assessed on the two postsurgical radiographs ( Fig. 4 ). The height of the alveolar bone in the cleft region was expressed as a percentage of the length of the root of the incisor adjacent to the former cleft. Taking the length of the root of the incisor as a reference, differences in magnification ratio and inclination of the ‘immediate’ postoperative and ‘late’ postoperative radiographs were corrected. By comparing the two radiographs the percentage of alveolar bone height loss could be determined.

Fig. 4
(a) Direct postoperative occlusal radiograph. (b) 1 year postoperative occlusal radiograph. Root length of the incisor adjacent to the former cleft (A). Alveolar height (B). Comparing A with B gives the ratio of the alveolar height to the length of the incisor. Percentage loss of alveolar height after 1 year can be determined by comparing A with B.

To describe the postoperative status of the canine at the cleft side, its eruption was categorized as completely erupted, surgically assisted forced eruption or in eruption. All measurements were performed by two independent observers who were blinded for the treatment. In both groups medical charts were searched for postoperative complications.

Statistical analysis

From the measurements, the average alveolar bone height was calculated at the two ages for each group. Comparisons between the two groups were made using Student’s t -test to detect any statistically significant differences. The postoperative complication rate and the status of canine eruption were analysed. Fisher’s Exact Test was used to test if the type of grafting material had a significant influence on the eruption of the canine. P -values <0.05 were considered to be statistically significant. All statistical analyses were performed using SPSS version 16.0.1 software (SPSS Inc., Chicago, IL, USA, 2007).

Results

Patient characteristics of the two groups are given in Table 1 . In all patients the maxillary dental arch was expanded orthodontically prior to bone grafting.

Table 1
Distribution of patients and patient characteristics.
Patient data Autogenous symphyseal bone Autogenous symphyseal bone and β-TCP granules
N (clefts) 29 (31) 18 (22)
Mean age (year and month) 10.4 (range 8.9–13.5) 10.2 (range 9.3–11.7)
Male to female ratio 12–17 12–6
Uni-bilateral ratio 18–11 * 14–4
Left-right ratio (clefts) 16–15 10–12

* In 9 patients only one site could be included due to overlap, which made tracing of the radiographs impossible.

All operations were uneventful. In the control group, 3 cases with minor complications were found: one minor dehiscence and two small bony sequestrations. In the experimental group, 3 patients experienced leakage of not more than five β-TCP granules out of the nose during the first postoperative days.

The duplicate measurement error appeared to be 5%. In order to minimize the inter-observer variability, the mean scores of the two observers were used for the statistical analyses. The mean percentage of the immediate postoperative bone levels of the control group was 64% (SD 0.23; range 26–95%) and 66% (SD 0.18; range 33–95%) for the group of patients treated with β-TCP. No significant difference between groups was found for preoperative bone height ( P = 0.650) using Student’s t -test. It was not necessary to correct for confounding by indication.

In order to explore the effect of β-TCP on alveolar height after 1 year, Student’s t -test was carried out. As result of the remodelling process, bone resorption and bone apposition were seen, resulting in an average of 1% bone resorption (SD 0.20; range −43% to +51%) for the control group compared with an average of 3% bone apposition (SD 0.25; range–32% to +36%) in the group of patients treated with a symphyseal bone transplant and β-TCP. No significant difference was found between the two groups ( P = 0.306).

A Student’s t -test was performed to explore the effect of other variables on the percentage of bone resorption after 1 year. The derived P values for each of the variables were as follows: gender ( P = 0.695), unilateral or bilateral cleft ( P = 0.792) and side of cleft ( P = 0.518).

Table 2 shows the fate of the canine at the cleft side. In order to investigate a trend in probabilities of an eruption disturbance across the two groups, Fischer’s exact test was applied. No significant association between eruption disturbance and grafting material was found ( P = 0.574).

Feb 8, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Early secondary closure of alveolar clefts with mandibular symphyseal bone grafts and β-tri calcium phosphate (β-TCP)
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