Evaluation of the three-dimensional soft tissue changes after anterior segmental maxillary osteotomy

Abstract

The aim of this study was to assess the three-dimensional soft tissue changes following anterior segmental maxillary osteotomy, in terms of magnitude and direction in correlation to hard tissue changes, using cone beam computed tomography (CBCT). The study included 6 patients (age range 17–35 years) suffering from dental maxillary protrusion that required surgical correction by anterior segmental maxillary osteotomy. For each patient, preoperative and postoperative CBCT, photographs, and orthodontic casts were taken before and 6 months after operation to analyse soft tissue changes, in terms of magnitude and direction in correlation to hard tissue changes, using linear and angular measurements. Hard and soft tissue changes were only observed in the maxillary region, upper lip area and nasal tip. Soft tissue mean change included 53% backward displacement of the labrale superius in relation to bone displacement and 18.7% mean increase in the naso-labial angle. The highest correlation coefficient was obtained between the hard and soft tissue changes in the upper lip region. Anterior segmental maxillary osteotomy might be recommended as the treatment modality of choice in patients with maxillary or dento-alveolar protrusion, the technique is simple, safe, and postoperative complications are minimal.

Orthognathic surgery is considered to be the principal tool for correcting severe dentofacial skeletal discrepancies. Although the main goal of this surgery is to achieve functional occlusion, it is also important to improve the patient’s profile, which improves the patient’s quality of life. It is important to be able to predict the postsurgical profile accurately in the planning process before treatment.

Two premolar extraction to retract the anterior teeth was one of the treatment choices of typical orthodontics. It is more complicated in adult patients because of the difficulty in achieving physiologic tooth movement, longer treatment time, relatively worse periodontal status, and increasingly strict social conditions. Considering these inherent limitations, surgery with extraction of premolars and surgical retraction of anterior segment using the subapical osteotomy technique is gaining acceptance as a better treatment modality than orthodontics alone.

The first report of anterior segmental maxillary osteotomy (ASMO) was published by C ohn-Stock in 1921 . After transverse incision in the palatal mucosa, he made a wedge shaped ostectomy palatal to the anterior teeth. A greenstick fracture was created at the ostectomy site, and the anterior maxilla was retracted. The anterior segment relapsed within 4 weeks. Since then the method has been developed and refined .

ASMO is indicated primarily for correction of dento-alveolar protrusion. It is also useful for correcting anterior open bite, closing dental spaces between segments, and it can be combined with other osteotomies to achieve optimal correction of dentofacial aesthetics and occlusion. Currently, three technical variations of ASMO are used: the Wassmund, Wunderer, and downfracture methods. When the Wassmund method is used, the anterior maxillary segment derives its blood supply from both facial and palatal gingivae, as no flaps are raised . The planned osteotomy sites are reached by tunnelling under mucoperiosteum . The Wunderer method involves a palatal flap raised by means of a transverse incision of the palate. The anterior osteotomy is made after tunnelling, leaving the buccal blood supply intact . In the downfracture method, a buccal flap is raised, and the palatal osteotomy is made after tunnelling, leaving the palatal blood supply intact .

W assmund advocated complete tunnelling mucoperiosteum both labial and palatally through two labial vertical incisions. The palatal bone was sectioned transversely from the vertical osteotomy site to the contralateral side. The transverse palatal bone incision was facilitated by a mid-palatal sagittal mucosal incision immediately distal to the incisive foramen. This technique is performed in a relatively blind fashion with difficulty in gaining access to the superior and palatal aspects of anterior maxilla.

W underer proposed reflecting a palatal flap. He made the transverse osteotomy line across the palate, completed all other osteotomies, and then swung the mobilized block anteriorly to gain access to the septum posteriorly through the palatal wound. With this technique, vascularity was maintained by the undermined but intact mucosa on the labio-buccal aspect of the mobilized segment .

In 1955, C upar described a down fracture technique using a circumvestibular incision. A vertical osteotomy cut was made on the buccal side, subapical cut, extraction, and alveolar ostectomy, were followed by transpalatal ostectomy. This was found to be best for superior repositioning of the anterior maxillary segment.

There have been many reports in the literature of hard and soft tissue changes after orthognathic surgery, but few about the anterior segmental surgery of the maxilla and mandible. Studies of the frontal view of the face, as compared with profile studies, are scarce, but changes in the frontal view are of substantial clinical importance and are often one of the key criteria by which patients judge the success of the treatment. The main objective of the present study is to assess the three-dimensional soft tissue changes in terms of magnitude and direction in correlation to hard tissue changes after ASMO using cone beam computed tomography (CBCT).

Materials and methods

This study was conducted on 6 adult female patients, aged 17–35 years. They were selected because their main problem was an excess of the anterior part of the maxilla and dental protrusion with a class I occlusal relation which required surgical correction by ASMO. The preoperative and postoperative records consisted of oriented photography, orthodontic casts and CBCT; the postoperative records were taken 6 months after surgery.

The maxillary excess in all cases was treated by ASMO using the modified downfracture approach (Epker modification ). After extraction of the upper first premolar from both sides, a circumvestibular incision was made from the premolar area of one side to the premolar area of the contralateral side. The mucoperiosteum was reflected and the inferior aspect of the piriform aperture was exposed. Careful dissection of the nasal mucoperiosteum from the anterior nasal floor and piriform rims was accomplished without tearing the nasal mucoperiosteum for haemostasis ( Fig. 1 ).

Fig. 1
Vestibular incision and reflection of nasal mucosa.

A nasal septal osteotome was used to separate the nasal septum from the anterior maxilla. The osteotome was malleted posteriorly only to the area of the planned transverse palatal osteotomy. Subapical osteotomy was performed 5 mm above the apices from the infero-lateral angle of the piriform aperture to the extraction site using a fissure bur. A vertical osteotomy cut was made on the buccal side opposite to the extraction socket; this was completed by tunnelling in the buccal mucoperiosteum. Transpalatal osteotomy cuts were also completed through tunnelling of the palatal mucoperiosteum using muco-periosteal elevator. Bur and osteotome were used to connect the two buccal osteotomy sites ( Fig. 2 ).

Fig. 2
Subapical osteotomy extending horizontally from the piriform aperture to the extraction site bilaterally.

The segment was then down fractured by applying digital pressure, manipulated and placed in its predetermined position guided by mock osteotomy on the casts. Any further intrusion of the anterior part of the maxilla was helped by bone removal from superior and lateral aspects of the osteotomized segment. Upper and lower teeth were put into occlusion by arch bars and wire (temporary maxillomandibular fixation), and the osteotomized segment was fixed in the desired position using two L-shaped 2.0 titanium miniplates ( Fig. 3 ). Using 3.0 black silk sutures V-Y closure of the horizontal vestibular incision line and closure of the flap to overcome problems of short upper lip were carried out. This problem was corrected to some extent by excision of the anterior nasal spine.

Fig. 3
Anterior segment secured in the new position (miniplate fixation).

Postoperative care included administration of antibiotics, steroidal anti-inflammatory drug and analgesics, a soft and semi-solid diet for 4 week, and resuming the normal diet thereafter.

Preoperative and postoperative CBCT were traced for each patient. Hard and soft tissue landmarks were located in all tracings with respect to stable reference planes. The reference planes constructed for measurements were the Frankfort horizontal plane (H line) and the nasion vertical plane, which is perpendicular to the Frankfort horizontal plane (V line). The net movement of each point was determined. The following landmarks were used ( Fig. 4 ): soft-tissue nasion (N′), The deepest point on the concavity overlying the area of the frontonasal suture; pronasale (Prn), the most prominent or anterior point of the nose tip; columella point (Cm), the most anterior point on the columella of the nose; subnasale (Sn), a point located at the junction between the lower border of the nose and the beginning of the upper lip at the mid-sagittal plane; labrale superius (Ls), the most prominent point on the vermilion border of the upper lip in the mid-sagittal plane; incision anterius (IA), the most prominent point on the maxillary incisor as determined by a tangent to the incisor passing through the subspinale.

Fig. 4
CBCT, profile view, soft and hard tissue predetermined cephalometric points.

In the lateral aspect, 5 linear and 2 angular measurements were evaluated: upper lip and incisor protrusions, nasolabial angle, and the nasal tip inclination. Upper lip protrusion, Ls to V line (the most prominent point on the vermilion border of the upper lip in the mid-sagittal plane to the line perpendicular to the Frankfort horizontal plane). Ls to H line, the most prominent point on the vermilion border of the upper lip in the mid-sagittal plane to Frankfort horizontal plane. Upper incisor protrusion, IA to V line, the most prominent point on the maxillary incisor as determined by a tangent to the incisor passing through the subspinale to the line perpendicular to the Frankfort horizontal plane. IA to H line, the most prominent point on the maxillary incisor as determined by a tangent to the incisor passing through the subspinale to the Frankfort horizontal plane. Nasolabial angle, the angle formed between columella point, subnasale, and labrale superius (Cm–Sn–Ls). Nasal tip inclination, the angle formed between the soft tissue nasion to pronasale and Frankfort horizontal plane (N′–Prn to H line). Lip thickness, Ls to IA, the most prominent point on the vermilion border to the most prominent point on the maxillary incisor.

In the frontal aspect, 3 linear measurements were evaluated: nasal width, lip width, and philtrum length ( Fig. 5 ): nasal width, the distance alar to alar; lip width, commissure to commissure; philtrum length, subnasale to stomion.

Fig. 5
Linear measurements from CBCT, frontal aspect.

Data were presented as mean and standard deviation (SD) values. Paired t -test was used to study the changes after treatment. Pearson’s correlation coefficient was used to determine significant correlations between different variables. The significance level was set at P ≤ 0.05. Statistical analysis was performed with SPSS 16.0 (Statistical Package for Scientific Studies) for Windows.

Results

In this study, complications of ASMO were relatively rare. Neither sloughing nor non-union of setback segment developed in any of the treated cases. No periodontal involvement of the teeth adjacent to, or included in, the osteotomy segment was observed. The incisional wounds healed uneventfully.

Blood loss was minimal and did not necessitate replacement during or after surgery. Post-surgical oedema was minimal and subsided completely within 1 week. Postoperative pain and discomfort were controlled satisfactorily by non-steroidal anti-inflammatory analgesics.

Clinically there was a significant change in soft and hard tissue parameters as observed in the front, profile, and occlusal photographs and the upper lip area ( Figs. 6–13 ).

Fig. 6
Preoperative lateral occlusal photograph.

Fig. 7
Postoperative lateral occlusal photograph of the patient in Fig. 6 .

Fig. 8
Preoperative photograph (front view).

Fig. 9
Postoperative photograph (front view) of the patient in Fig. 8 .

Fig. 10
Preoperative photograph of the upper lip area.

Fig. 11
Postoperative photograph of the upper lip area of the patient in Fig. 10 .

Fig. 12
Preoperative photograph (profile view).

Fig. 13
Postoperative photograph (profile view) of the patient in Fig. 12 .

Analysis of the preoperative and postoperative tracing is shown in Tables 1 and 2 .The mean of the skeletal changes (IA to V line) was a maxillary setback of 6.2 mm. The ratio of mean upper lip retraction (Ls to V line mean change) to maxillary incisor retraction (IA to V line mean change) was 0.53:1 ( Table 1 ). There was no statistically significant change in mean Ls to H line and IA to H line measurement after treatment ( Table 2 ).

Table 1
The means, standard deviation (SD) values and results of paired t -test for the changes in soft tissue measurements in lateral aspect.
Measurement Treatment Mean change P -value
Before treatment After treatment
Mean SD Mean SD
Upper lip protrusion (Ls to V line) 31.8 4.6 28.6 5.6 3.3 0.017 *
Upper incisor protrusion (IA to V line) 29.4 6.5 23.2 6.8 6.2 0.001 *
Ls to H line 29 2.6 28.4 1.4 0.6 0.640
IA to H line 41.4 2.7 41.1 2.5 0.3 0.830
Nasolabial angle (Cm–Sn–Ls) 83.7 14.3 102.4 13.5 18.7 0.010 *
Nasal tip inclination (N′–Prn to H line) 49.4 6.4 53.6 10.4 4.2 0.391
Lip thickness 8.6 1.2 11.1 1.2 2.5 0.001 *
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Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Evaluation of the three-dimensional soft tissue changes after anterior segmental maxillary osteotomy
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