INTRODUCTION:
One of the complex and distinctive structure within the human body is cranium that provides primary interface for interaction and communication, The soft palate is also one such crutial structure in the human body.
Development of palate:
Embryonic palate - human hard palate develops between embryonic stages 15 and 18. Between 17 and 18 stage, fusion in the human embryo from an epithelial seam to the mesenchymal bridge. Fetal palate - Secondary palate fusion in human embryo occurs at week 9. This process requires growth of palatal shelves, elevation and fusion.
Embryological background:
The face is formed by fusion of number of embryonic processes that for around primitive oral cavity or stomodeum. At 4th week of intra uterine life , at the site of future neck 5 branchial arches develop. The mandidular arch which is the 1st arch plays an important role in the development of naso maxillary complex. The mesoderm covering the stomodeum grows, proliferates and overhands the stomodeum. The dorsal end of the mandibular arch on either side of the stomodeum gives off a bud called the maxillary process. As there is formation of nasal pits, the fronto nasal process divides into medial nasal process and two lateral nasal process. As the fusion occurs between maxillary process with median and lateral nasal process it results in the formation of upper lip and primary palate. The fusion of upper lip and primary palate starts by 6th week of gestation. The palate is formed by contribution of fronto nasal process and maxillary process. The maxillary process gives of palatal shelves that grow medially. The union of two palatal shelves is initially prevented by the presence of the tongue. Thus the palatal shelves grow vertically down. At 7th week of intrauterine life, the tongue present between the palatal shelves descends down and as a result the palatal shelves becomes more horizontal, Approximately around 8 ½ weeks two palatal shelves are in close approximation to each other. Closure of secondary palate by elevation of palatal shelves follows that of primary palate by nearly 2 weeks. Initially during 6th week of development Soft palate- The exact mechanism of closure of soft palate is not fully determined but several theories being put forward. A recent study [1] on embryos from late embryonic to early fetal period has identified the timing of soft palate closure- Late embryonic , epithelial seam present throughout the soft palate-57 days and Early fetal (9 week), only epithelium persists in the most posterior regions of soft palate-64 days.
The soft palate is the fibro muscular portion in the posterior part of the palate that is attached to the posterior edge of the hard palate. It is formed by the fusion of 3 components, namely 2 palatal processes and the primitive palate which is formed by fronto nasal process [2]. The intramembranous ossification does not occur in the posterior region while ossification occurs in the mesoderm of the soft palate to form hard palate in the anterior region [3][4]. Soft palate participates in most of the oral functions especially velopharyngeal closure which is related to normal functions of sucking , swallowing and pronunciation[5][6].
The soft palate has been classified into 6 morphological types [7][8] [ Type 1-Leaf shaped / lanceolate shaped, Type 2 - rat tail shaped, Type 3 - Butt like shaped, Type 4 - straight line shaped, Type 5- S shaped / distorted soft palate, Type 6 - Crooked shaped]. Unlike the evaluation of abnormalities , diversity in radiographic appearance of the soft palate morphology remains unrecognised.
The purpose of the present study was to investigate the variation of soft palate morphology among patients seeking orthodontic treatment.
MATERIALS AND METHODS:
A retrospective study was carried out in the Department of Oral Medicine and Radiology, Saveetha Dental College by analysing 100 lateral cephalometric radiographs of patients seeking orthodontic treatment from the period of October 2016 to December 2016.
Radiographs of good quality and visibility of patients seeking orthodontic treatment were included while radiographs with poor quality and take for other purposes were excluded. All lateral cephalograms were taken using Planmeca, Promax. The morphological variants of soft palate was assessed on Digital lateral Cephalometric radiograph and were allocated to one of the six patterns as described by You et al [8].
Type 1 Leaf shaped or lanceolate shaped-soft palate is elevated in the middle portion on both nasal and oral side (Figure 1)
Type 2 Rat tail shaped - Anterior portion of soft palate is inflated and free margin shows coarctation (Figure 2)
Type 3 Butt like shaped – soft palate appears shorter and there is no distinct difference in the width from anterior to free margin (Figure 3)
Type 4 Straight line shaped (Figure 4)
Type 5 S shaped / distorted soft palate (Figure 5),
Type 6 Crooked shaped - Posterior portion of soft palate crooks anterosuperiorly (Figure 6).
All the radiographs were examined, traced and categorised and obtained data is analysed statistically.
RESULTS:
The distribution and proportion of various types of soft palate of our study population are shown in table 1 and 2
Table 1- Distribution of various shapes of soft palate
|
Type |
1 |
2 |
3 |
4 |
5 |
6 |
|
n= |
26 |
47 |
2 |
14 |
5 |
6 |
Table2-Types of soft palate and gender variation
|
Type |
Female |
Male |
Total |
p-value |
|
1 |
10 |
16 |
26 |
0.184 |
|
2 |
24 |
23 |
47 |
|
|
3 |
1 |
1 |
2 |
|
|
4 |
9 |
5 |
14 |
|
|
5 |
5 |
0 |
5 |
|
|
6 |
3 |
3 |
6 |
In our study, the frequency of rat tail shaped (type 2) soft palate (47%) was seen in highest proportion while butt like (type 3) soft palate (2%) was least in both the genders. Around 26% of the cases (male-16, female-10) showed type 1 variety of soft palate, 14% (male -5,female-9) had type 4 while 6%(male3,female-3) showed type 6 pattern.
Figure1: Type 1- leaf shaped - - middle portion of soft palate is elevated on both nasal and oral side
Figure 2:Type 2 -Rat tail shaped- Anterior portion of soft palate is inflated and free margin shows coarctation
Figure3: Butt like- soft palate appears shorter with no distinct difference in the width from anterior to free margin
Figure 4: straight line shaped
 |
Figure 5:Distorted/S shaped
Figure 6: Crooked shaped- Posterior portion of soft palate crooks antero superiorly
|
Chi square test |
|||
|
|
GENDER |
Soft palate TYPE |
|
|
GENDER |
Pearson Chi square |
1 |
0.184 |
|
Sig. (2-tailed) |
|
0.067 |
|
|
N |
100 |
100 |
|
|
TYPE |
Pearson Chi square |
0.184 |
1 |
|
Sig. (2-tailed) |
0.067 |
|
|
|
N |
100 |
100 |
|
Chi square test was done to evaluate the relation between gender and type of soft palate and there was no significant difference in soft palate shapes between male and female (p=0.184)..
DISCUSSION:
Soft palate is present in the posterior border of the hard palate, it is a mobile flap slopes downward and backward between nasal and oral parts of pharynx. It is a thick mucosal fold consisting muscular tissue, aponeurosis, mucous glands, vessles, nerves, lymphoid tissue. Soft palate has important oral functions like velopharyngeal closure which is essential for normal functioning of swallowing, sucking, blowing, pronounciation and phonation. Functions of soft palate are usually disturbed in patients with cleft lip and palate, enlarged adenoids, obstructive sleep apnoea syndrome (OSAS), skeletal craniofacial malocclusion, snoring, poorly retained maxillary denture [9].
Palate is formed by fusion of two palatal processes and the primitive palate which is formed by fronto nasal process. Intra membraneous ossification takes place in mesoderm to form hard palate while soft palate is formed in the posterior region where ossification does not occur. For velopharyngeal closure (VPC) the important muscle of action is levator veli palatine (LVP). Apart from evaluation of soft palate abnormalities , diversity in the radiographic appearance of soft palate morphology especially in patients seeking orthodontic treatment remains unrecognised.
The six patterns of soft palate morphology as described by You et al [8].
Type 1: Leaf shaped soft palate - middle portion of soft palate is elevated on both nasal and oral side.
Type 2: Rat tail shaped - Anterior portion of soft palate is inflated and free margin shows coarctation
Type 3: Butt like – soft palate appears shorter with no distinct difference in the width from anterior to free margin
Type 4: straight line shaped
Type 5: S shaped/distorted soft palate
Type 6: Crooked shaped- Posterior portion of soft palate crooks antero superiorly.
The lateral cephalogram is the most common diagnostic radiograph used in orthodontics. Also cephalometric analysis is a commonly accepted technique for evaluation of soft palate because of its easy availability, cost effectiveness and relatively good assessment of soft tissue [10–12]. It is a likely hypothesis that velopharyngeal adequacy depends on the coordination of the anatomic parts of the soft palate. So it is essential to understand the morphology of soft palate especially in patients seeking orthodontic treatment.
Radiological evaluation of soft palate morphology greatly helps to diagnose various inflammatory, neurologic, neoplastic disorders of soft palate in adults. Also soft palate dimension with its surrounding structures especially velar length and width has been discussed in various studies [3,13], nevertheless the variation of velar morphology which is the most logic cause of different dimensions of soft palate [2,6,10]. In patients with cleft or soft tissue defects in the soft palate, normal function of the soft palate is not frequently achieved and velopharyngeal insuffiency (VPI) with hypernasal speech is seen in 30% or more of patients even after closure. One of the several reasons for this surgically successful yet functionally compromised after repair of the defect may be due to the difference in the morphology of soft palate and associated structures in these patients. Therefore, a pre surgical evaluation of the soft palate morphology is essential which will aid in success of surgery.
In our study, Type II shaped soft palate ( rat tail shaped) was the most frequently observed type (47%) while in a previous study by You M et al [14] leaf shaped soft palate type was described as classic type of soft palate morphology. This variation in our study may be due to the fact that all of our study cases had malocclusion requiring orthodontic treatment.
Obstructive sleep apnoea (OSA) is characterised by the recurrent occlusion of the upper airways resulting from the inspiratory collapse of the pharyngeal wall during sleep [13,15]. The etiological or predisposing factors for obstructive sleep apnoea syndrome (OSAS) is still not fully established. There is an increased incidence of Obstructive sleep apnoea in middle aged adults [16]. It was found that pharyngeal morphology remains unchanged during childhood and adolescence, and changes throughout adult life [15,17]. There is an increased tendency toward longer and thicker soft palate and narrower oropharynx during adulthood, which may explain the possible increased incidence of Obstructive sleep apnea and related disorders occurring later in life [10,16,18]. It has been found that ‘hooked’’ shaped soft palate (type 6) patients are at high risk for developing Obstructive sleep apnea syndrome (OSAS) [3,4,19]. You et al. described this hooked appearance as S shaped soft palate [18]. Velopharyngeal closure is obtained by normal apposition of the soft palate with the posterior and lateral pharyngeal walls, there by separating the nasal cavity from oral cavity during speech and swallowing. When the lateral and posterior pharyngeal wall and velum fails to separate the oral cavity from nasal cavity, velopharyngeal incompetence (VPI) occurs.
Also studies reveal that there is an increase in thickness, length and sagittal area of soft palate with age in both the genders but increase in soft palate area was significantly more in males [20–22]. In the present study, there was no significant difference in the types of soft palate between males and females. However there are limitations in our study, the stability of particular type of soft palate with age could not be assessed. Further research can be carried out on larger population to evaluate changes in velar morphology and its correlation with age.
CONCLUSION:
Understanding the morphological variants of the soft palate helps us to get a better understanding of velopharyngeal closure (VPC), structural and functional repair in cases of cleft palate and in the etiological study of obstructive sleep apnoea and snoring. Knowledge of varied spectrum of velar morphology may help in successful functional and structural repair of soft palate and may also be used in future research into the cause of Obstructive sleep apnoea (OSA) and related disorders.
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Received on 25.02.2018 Modified on 18.03.2018
Accepted on 26.04.2018 © RJPT All right reserved
Research J. Pharm. and Tech 2018; 11(12): 5233-5237.
DOI: 10.5958/0974-360X.2018.00954.X