2. Palatal Rugae Patternfor Personal Identification following Orthodontic Treatment
Palatal rugae are often used as an identification tool in forensic dentistry as the tissue is resistant to decomposition due to the protection rendered by the buccal pad of fat and teeth. Also, similar to the fingerprint, the palatal rugae pattern is unique for every individual and allows identification. The age changes in the palatal rugae pattern are minimal and hence could aid as an adjunct tool in forensic dentistry, especially in edentulous patients. However, significant changes in the rugae pattern could occur as a result of surgery, orthodontic treatment (which could range from minor corrections in the alignment of teeth to complicated procedures such as arch expansion, use of headgears, functional appliances, and orthognathic surgery), or extraction of teeth. Considerable published literature is available that has assessed and reported the palatal rugae pattern before and after orthodontic treatment. With the available information, the present systematic review with meta-analysis was formulated to assess the reliability of palatal rugae for personal identification following orthodontic treatment.
The nature of orthodontic treatment in the included articles ranged from rapid maxillary
[8][9], retraction of maxillary anterior teeth with straight wire with or without extraction
[10][11][12][13][14][15], use of headgears and functional appliances including fixed orthodontic appliances
[16][17], and pre-adjusted edgewise therapy
[18]. The diagnostic modalities used for the assessment of palatal rugae patterns varied among the included studies, leading to heterogeneity. However, Taneva, E.D. et al. had compared two different techniques for the assessment of the rugae pattern and reported no significant differences in the two techniques
[19]. Hence it may be potentially inferred that the variations in the palatal rugae pattern reported by the included study due to the differences in the diagnostic modalities could be minimal.
Most of the included studies demonstrated no significant changes in morphologic alterations in the rugae pattern following orthodontic treatment and thus concluded that palatal rugae could be considered a reliable tool in forensic dentistry. Also, few studies had reported that the third palatal rugae were the most reliable landmark for forensic identification
[20][10][8][12][13][16]. Considering the stability of medial and lateral points of the palatal rugae in rendering accurate forensic information, contradictory results were reported in the published data included in the present review. While Jang, I. et al. and Almeida, M.A. et al. reported the medial points of the third palatal rugae to be most stable, Bailey, L.J. et al. reported that both medial and lateral points of the third palatal rugae were stable anatomic reference points
[10][12][16]. These differences could be attributed to the type of orthodontic treatment rendered to the study participants and the sample size employed in the studies.
On the contrary, few studies have reported changes in the palatal rugae pattern following orthodontic treatment. Kapoor, P. and Miglani, R. reported that the 3rd rugae underwent maximum changes in the transverse pattern
[8]. Deepak, V. et al. and Mustafa, A.G. et al. questioned the reliability of these palatine rugae as forensic markers
[18][21]. This highlights the importance of maintaining dental records and cast models before and after orthodontic treatment, which could later render forensic information despite minor changes in the pattern. However, both the studies had a moderate risk of bias and did not report details of the selected study participants. The quantitative changes in the palatal rugae pattern before and after orthodontic treatment were assessed in only six out of the eighteen studies included. The remaining twelve studies had assessed only morphological alterations. However, only in three
[10][11][13] out of six studies with quantitative data, the type of orthodontic treatment was similar and the age of the study participants was above 18 years. Age was a major factor as in participants below 18 years, the influence of the growth spurt on the rugae pattern could have been a potential confounder. A meta-analysis of the three studies revealed a significant transverse bilateral change in the lateral first rugae (
p = 0.02) and anteroposterior change in the 2–3 lateral rugae of the left side (
p = 0.04), respectively. There were no significant changes in the other rugae points assessed. The significant quantitative change in the transverse dimension of the lateral first rugae and the anteroposterior dimension of the second to third lateral rugae could be attributed to the fact that in all three studies, retraction of maxillary anterior teeth was carried out along with the extraction of premolars. Considering the role of tooth extraction on the palatal rugae pattern, very few studies had compared the changes in rugae pattern and reported no significant difference in the morphological pattern, while a few studies had only assessed the rugae pattern with orthodontic treatment and extraction
[10][11][12][13][14][15]. However, in the present meta-analysis, we observed quantitative change in a transverse direction. Hence, the results must be viewed with caution owing to the heterogeneity of data and sample size. Further studies have to be carried out to assess the exact role of extraction on palatal rugae patterns
[10][11][13].
Shukla, D. et al., Aziz, H.M.A., and Sabet, N.E. assessed the quantitative changes in right and left palatal rugae in the anteroposterior direction
[11][13]. Comparison of quantitative changes in the anteroposterior direction of palatal rugae in various types of orthodontic treatment including extraction, non-extraction, head-gear, and functional appliance was reported by Bailey, L.J. et al. and Almeida, M.A. et al.
[10][16]. However, the third rugae were found to be more stable in comparison with the first and second, which is concurrent with the previously reported literature on the stability in the morphologic pattern of the third rugae. Despite significant overall dimensional changes, observers were able to make a highly accurate (>90%) matching between the pre- and post-treatment casts using the morphological pattern of the rugae. This can be explained by the observations of the individual studies wherein the morphological pattern of the rugae was reported to be unchanged
[22][11][23][24][17][9] despite the orthodontic treatment. Palatal rugae can thus be a reliable tool for personal identification by a combination of objective assessment of the morphologic pattern of palatal rugae and quantitative dimensional assessment, thereby reducing intraobserver and interobserver bias. Also, the findings of the present review must be viewed with caution, considering the moderate risk of bias in 11 of the included studies. Future studies assessing the changes in palatal rugae patterns following orthodontic treatment must focus on minimizing the confounding factors. Studies on the duration of stability of palatal rugae with changes in body weight also have to be conducted to determine the reliability of palatal rugae patterns as forensic tools.