Exact facial symmetry would mean that the face could be divided into identical left and right halves by a straight line through the midpoint of the nose, lips and chin, and the pupil lines on both sides would be perpendicular to this line and located at equal distances on both sides.Facial asymmetry usually refers to any shape and size imbalances of the left and right sides of the face. Kuijpers’s study confirmed that the asymmetry of soft tissue in the in the upper and middle part of the face was good in patients with skeletal class I, while the lower part of the face showed asymmetry, mainly in the chin.
Studies have shown that the facial soft tissue structure of patients with cleft lip and palate is different from that of normal peers, and can encompass a variety of facial asymmetric features[17–18]. There are many factors that affect the severity of the deformity, including the type of fissure, race, sex, the type and timing of the operation. [19–21]
Although the study of facial symmetry has been widely carried out in normal people and patients with cranio-maxillofacial deformities, there are few reports on the long-term effects of growth and development on facial symmetry. For cleft lip and palate patients with severe facial deformities, the changes associated with increasing age, growth and development, and interventions on facial symmetry remain unclear. Facial asymmetry is expected in normal people, which complicates analysis of facial asymmetry caused by cleft lip and palate. Therefore, the intent of this study was to carry out a cross-sectional study of the symmetry on both sides of the patient's face, reducing the impact of other influencing factors.
The average age of cleft lip and palate patients in the present study was 11.2 years, which corresponded to the early stage of puberty. The patients had not yet undergone alveolar process cleft bone grafting and had no previous orthodontic treatment. These inclusion requirements helped to minimize the effect of other treatment interventions on facial soft tissue morphology with the exception of cleft lip and palate repair during infancy. It weakened the effect of growth and development and functional factors on facial morphology.
The whole midfacial region of patients with cleft lip and palate is considered a “problem area”. As a result of both the defect and the operation, insufficient development in the midface can be observed. In these patients, the continuity of upper lip muscle, upper dental arch and palate is interrupted, which leads to the destruction of stress support. In addition, due to the imbalance of tension and traction between the muscles on both sides of the upper lip, growth stimulation of the maxilla on the fissure side is weakened and growth is inhibited.
The congenital structural abnormalities and secondary tooth deformities in patients with cleft lip and palate lead to differences in bilateral function, and these functional disparities further aggravate the craniofacial abnormalities. Surgical trauma and other factors can also cause severe craniofacial asymmetry, potentially involving both hard and soft tissue, especially in patients with unilateral cleft lip and palate. There is an important proportional relationship between the morphology of facial soft tissue and underlying hard tissue. Abnormalities of hard tissue will lead to morphological abnormalities of the corresponding soft tissue, and the soft tissue can only cover up and obscure the morphological abnormalities of hard tissue to a limited extent. But outcomes of hard tissue repair cannot always be expected to apply to adjacent soft tissue. Studies have reported asymmetry of lip muscle tension even following successful cleft lip repair in patients with unilateral cleft lip and palate. In fact, this may be one of the underlying reasons for the asymmetry of maxillofacial development.
The upper part of the face in both UCLA and UCLP groups was less affected by fissures and had better symmetry. In prior studies of UCLP patients, the nose has generally been asymmetric; the tip of the nose having been deformed, straightened and deviated towards the unaffected side. Bagante reported that alar wing length was shorter and flatter on the cleft side of the nose for patients with UCLP, which is consistent with the alar projection length (Ac-Prn) in the two patient groups in this study.
A number of studies have reported that the increase in nasal width is the most striking finding regarding the nose in patients with BCLP, and the increased ratio of nose width to lip width negatively affected cosmetic appearance[18, 25]. The alar base shape was even more flat due to insufficient bone support in the affected areas. Furthermore, nose width was increased and the columella was wider and shorter on the cleft side[27,16−17]. Bugaighis found that the UCLP group had a significantly shorter nasal bridge, broader anatomic and basal nasal widths, and a wider repaired nostril. Zreaqat also concluded that the width of the alar base was mainly related to the fissure side. In our study, nasal measurements showed that there were asymmetrical deformities in both horizontal and vertical directions, mainly in the nostrils and alae of the nose. The base width of the nostril (Sbal-Sni) was increased significantly on the fissure side in both UCLA and UCLP groups, mirroring the results of previous studies. This is a principal reason that affects the nasal symmetry of patients with cleft lip and palate. More attention should be paid to the correction of this in subsequent nasolabial repair in order to restore the beauty and symmetry of the nose.
There were statistically significant differences in lip measurements between UCLA and UCLP groups. The fissure side of these indices (Ch-Ac、Cph-Sbal、Sbal-Ch) was smaller than the non-fissure side. It has been postulated that this may be related to nasal collapse secondary to hypoplasia of the cleft jaw. The index of Cph-Sn suggested that the fissure side was larger than the non-fissure side, possibly related to asymmetry of the Christa philtri point on both sides. The Christa philtri point of the fissure side was lower than the non-fissure side, which was the cause of the morphological asymmetry of the upper lip and the philtrum. Previous studies have focused more on lip height with similar results. Bugaighis reported that the philtrum was wider, and a shorter upper lip length was found on the fissure side in the UCLP group.
In the present study, the depth of the midface of the fissure side was smaller than the non-fissure side in both groups. The growth and development of the middle part of the face on the fissure side was affected by the fissure, and was insufficient. The middle part of the face collapsed, the nose deviated to the fissure side, and the resultant appearance of the face was flat, in accordance with previous studies.
There is no consensus on soft tissue landmarks for three-dimensional facial image measurements in patients with cleft lip and palate. Different anthropometric points and indicators are used to evaluate the soft tissue of patients with cleft lip and palate[26–32]. The three-dimensional analysis and evaluation system of maxillofacial soft tissue in this study refers to the research of Alpagan and other scholars when selecting facial landmarks and measurement indices, and makes corresponding choices according to the facial soft tissue characteristics according to patient age. In the present study, the landmarks that were selected had strong characteristics that facilitated high repeatability, and measurement indicators that could reflect three-dimensional features to produce a comprehensive and systematic evaluation of maxillofacial soft tissue. To ensure the consistency and accuracy of soft tissue landmarks, the three-dimensional images were measured every two weeks, repeated three times, and the average of the three measurements was used as the final measurement.
Most studies on facial morphology of patients with cleft lip and palate are based on two-dimensional plane measurement, and the subjects are mostly adults. There are few studies on facial soft tissue morphology of preadolescent patients with cleft lip and palate. Previously used methods for the study of facial morphology included direct measurement, facial photography, X-rays, and Cone Beam CT. These measurement methods have limitations. Facial photos have low resolution and lack three-dimensional visualization. The soft tissue cannot be fully evaluated. Although the lateral cephalogram shows the whole craniofacial outline and is not hindered by the overlapping structure, the structure is limited to the midline plane and cannot be examined and evaluated in detail. CBCT can produce three-dimensional visualization and asymmetric evaluation, but it may require long exposures with the attendant radiation and necessitating considerable patient cooperation of patients. Repeated use for long-term follow-up or to record growth changes only compounds these risks and seems unreasonable. At present, three-dimensional technology can evaluate the therapeutic outcomes of cleft lip and palate more objectively, and three-dimensional photography is the optimal choice for soft tissue analysis[15, 33].
The reconstruction of deformities in patients with cleft lip and palate requires not only attention to soft tissue, but also the bone. But three-dimensional photography cannot image bone. Therefore, a combination of three-dimensional photography and CBCT can be instrumental in formulating the design of soft and hard tissue simulation surgery. The evaluation of soft tissue changes both before and following treatment seems more intuitive, and an even better plan to achieve successful outcomes would be facilitated with a combination of the two groups of data. In this study, we only used three-dimensional photography to measure and evaluate the soft tissue asymmetry of patients with cleft lip and palate, without use of CBCT to measure the bony tissue. The combination of these 2 modalities to fully characterize the soft and hard tissues will be the direction of our next research effort.
According to the deviation analysis chart in this study, patients with UCLA showed mild asymmetry, mainly in the ala, nostril and cheilion. Patients with UCLP showed severe asymmetry, covering the entire midface. The conclusion is consistent with the results of facial soft tissue morphology and symmetry analysis based on line distance measurement.
Once the data are captured, the deviation analysis chart has the advantages of simple operation and objective evaluation of the symmetry of facial soft tissue. It can qualitatively and quantitatively analyze the asymmetric distribution and degree of the face and provide a composite picture for orthodontists to achieve an understanding of the facial symmetry of these patients.
With the continuous progress of medical treatment, the orthodontic treatment of cleft lip and palate is also improving. Doctors and patients have higher aesthetic expectations for treatment. However, the treatment of patients with cleft lip and palate is often difficult to achieve a perfect result due to severe tissue defects and postoperative scar tissue. Many orthodontists are deterred from treating cleft lip and palate patients because of the difficulty of treatment, the complexity of the design of the treatment and the less-than-perfect therapeutic outcome. Therefore, accurate evaluation of facial soft tissue morphology in patients with cleft lip and palate becomes even more important. This will help orthodontists and plastic surgeons to obtain more comprehensive morphological information of maxillofacial soft tissue, so as to make a more accurate diagnosis and treatment design for these patients. It will also facilitate effective preoperative communication between doctors and patients’ family members.
In this study, a three-dimensional photography system was used to obtain the maxillofacial soft tissue morphological data of cleft lip and palate patients to construct a three-dimensional digital model of maxillofacial soft tissue. We compared and evaluated the facial soft tissue morphology and asymmetric deformities of cleft lip and palate patients using this technology, improved the three-dimensional detection method of maxillofacial soft tissue morphology, and explored the morphological rules of nasolabial deformities after cleft lip and palate surgery. We hope to provide a reference standard for the measurement and analysis of facial soft tissue morphology in patients with cleft lip and palate.