Assessment of Dimensional Changes in Arch Width and Palatal Rugae Pattern in Pre and Post Orthodontic Treatment

Introduction

Orthodontic diagnosis and treatment planning involves consideration of the probable three-dimensional changes that occur in the dentition and in the dento-facial complex. Dimensional changes of the dental arch gained attention because of their possible influence on smile esthetics and long-term stability.^1,2 Tooth movement occurring naturally in three planes of space leads to increased arch dimensions. Several studies have shown that changes in arch dimensions occur both during orthodontic treatment after the tooth extraction and also during non-extraction therapy.^3,4

Palatal rugae are ridges or striations in the anterior part of hard palate behind the incisive papilla. These ridges are distributed on both sides of the median palatal raphe. Palatal rugae are also referred as ‘plicae palatinae’.^5,6 Palatal rugae are formed during third month of intrauterine life and undergo few morphological changes in their anatomical pattern, in length, as a result of normal palatal growth. Transverse palatine folds or palatal rugae are asymmetrical and irregular elevations of the mucosa in the anterior third of the palate, arranged in a transverse direction from the palatine raphe located in the mid-sagittal plane.⁷

The structure of palatine rugae is important in the stability of orthodontic treatment. Palatal rugae is unique in every patient; hence this characteristic feature provides us reasonable stability to serve as suitable reference point.^8,9 These rugae provide us a reference plane necessary for longitudinal cast analysis, and the structural stability for the orthodontic treatment has correlation with amount of distortion of the palatal surface.¹⁰ Palatal rugae is not so reliable in measuring intermolar width^11, and molar distalization.¹² 

Susana Braga et.al ¹³ 2015 studies determined that the initial right rugae had a discernible size difference before and after the treatment. Panagiotis Christou et.al ¹⁴ 2008 concluded that third palatal rugae are more stable. Janalt Damstra et.al ¹⁵ 2009 concluded that medial aspects of the third rugae cannot be considered a stable reference. Insan Jang et.al ¹⁶ 2009 concluded that medial points of the third palatal rugae are stable in 3-dimensional tooth movement. Shukla et.al ¹⁷ 2011 studies determined that third palatal rugae are most immutable in human life. Pateria et.al¹⁸ 2011 concluded that third palatal rugae are stable in pre and post-treatment. Shetty et.al ¹⁹ 2013 studied the assessment of palatal rugae pattern and their reproducibility for application in forensic analysis and determined that palatal rugae are unique to every individual. Kulkarni et.al ²⁰ 2013 studied palatal rugae and concluded palatal rugae are stable. Nienkemper et.al ²¹ 2013 studied implant stability in the midpalatal area and found to be stable at third palatal rugae. Hourfar et.al ²² found the medial of the third palatal rugae to be stable for implant placement. Deepak et.al ²³ found the palatal rugae to be stable in forensic studies. Mustafa et.al ²⁴ studied morphometric changes in rugae and found to be stable.

Aim of the study

To evaluate the changes in arch width and quantify the dimensions, positional variations and area of the rugae in extraction and non-extraction orthodontic cases.

Objectives of the study

1. The evaluate the dimensional changes of arch width in extraction and non - extraction cases.
2. To assess the positional variations of palatal rugae pattern in extraction and non-extraction cases.

Materials and Methods

Source of the data

This study was conducted on pre and post treatment models collected from the Department of Orthodontics and Dentofacial Orthopedics, AME’s Dental College, Hospital and Research Center, Raichur, Karnataka, for assessing the arch width and rugae patterns.

Materials used

1) Pre and post treatment models

2) Digital caliper

3) Matte acetate sheets

4) Graph sheet

5) Lead pencil 0.3 mm

6) Image analyzer software

Inclusion criteria

1) Age range: 14 to 27 years

2) Cases involving extraction of first premolar or second premolar

3) Non-extraction cases

4) Cases presenting with all permanent teeth with or without third molar

Exclusion criteria

1) Previously treated orthodontic cases

2) Missing premolars

3) Extraction because of supernumerary teeth or decay

4) Palatal deformity 

Methodology

The study included a sample of 52 sets of pre and post models of orthodontically treated patients. The sample was collected from the Department of Orthodontics and Dentofacial Orthopaedics. The sample of 52 sets of models included 26 extraction cases and 26 non-extraction cases.

Using digital calipers, inter canine and inter premolar distances were measured in pre and post orthodontic treatment models and palatal rugae were carefully highlighted using 0.3 mm lead pencil. The traced palatal rugae were observed and measured for size, shape, direction and pattern. A median palatal plane was constructed as a reference plane. The highlighted palatal rugae were traced using matte acetate tracing sheet and graph sheet overlapped and measurements were carried out.

The followings measurements were recorded:

1. Inter canine measurements (Figure 1)

2. Inter premolar measurement (Figure 2)

3. Bilateral transverse width measurement of rugae pattern (Figure 3)

4. Antero posterior measurements of rugae pattern (Figure 4)

5. Measurement of surface area of palatal rugae pattern (Figure 5)

Statistical analysis

A sample size of 52 subjects (26 in each group) would yield 80% power to detect significant differences, with effect size of 0.8 and significance level at 0.05. Data were entered in the Excel spread sheet. Descriptive statistics like mean, standard deviation and percentages were calculated. Inferential statistics like Chi square test for proportions, independent sample t test was used to compute the significant difference between the groups. Paired sample t test was used to find the statistical distinction between pre-and post cast measurements using SPSS version 20. (IBM SPASS statistics [IBM corp. released 2011]. Any other necessary tests were dealt at the time of analysis based on data distribution.

Results

Significant difference was observed in anterio posterior measurements of 2-3rd lateral rugae right, 2-3rd medial rugae right, 1-2nd lateral rugae left, 1-2nd medial rugae left and 2-3rd medial rugae left in extraction group when compared with non-extraction group (Table 3).

No significant difference was found in the surface area of pattern of palatal rugae in extraction group. However, significant difference was found in 2nd palatal rugae left and 1st palatal rugae right in non-extraction group (Table 4).

Discussion

This study demonstrated increase in dimensions, i.e., inter canine (p <0.026) and inter premolar widths (p <0.021) between pre and post orthodontic treatment in extraction cases. No changes were observed in bilateral transverse dimensions in palatal rugae pattern in both extraction and non-extraction groups. There were changes noted in antero posterior dimensions of 2-3rd lateral rugae right, 2-3rd medial rugae right, 1-2nd lateral rugae left, 1-2nd medial rugae left, 2-3rd medial rugae left in extraction group. Significant changes in surface area dimensions of 2nd palatal rugae left, 2nd palatal rugae right were observed in extraction group.

Claudio Herzog et al., (2017) studied arch-width changes in extraction vs non-extraction treatments. They found that extraction group showed increase in maxillary and mandibular inter canine widths and decrease in mandibular inter molar width and maxillary and mandibular perimeters. The non-extraction group showed increase in all four arch-width measurements, while the maxillary and mandibular perimeters were maintained.¹

Maria Saadeh et al., (2017) studied the instability of palatal rugae following rapid maxillary expansion. Several criteria were noted, including individual rugae, transverse and antero-posterior linear and angular measures, palatal dimensions, and dental characteristics. The palatal rugae were found to be strongly impacted by Rapid Maxillary Expansion (RME) in all dimensions, including angular and linear, almost equally on the right and left sides, with average linear changes of roughly 1 mm.⁵

Susana Braga et al., (2015) conducted a study to evaluate the palatal rugae patterns following orthodontic treatment and found that initial right side changes between the rugae before and after the therapy were noticeable, suggesting that, in females, palatal rugae morphology is a better marker than palatal rugae length.¹³

Conclusion

Inter canine width increased in extraction group when compared to non- extraction group. The antero posterior dimension of palatal rugae showed significant increase in dimension and increase in the surface area of palatal rugae pattern in non-extraction group.

Conflicts of Interest

Nil