Journal of Forensic and Legal Medicine 31 (2015) 19e22
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Journal of Forensic and Legal Medicine j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j fl m
Morphological changes in palatal rugae patterns following orthodontic treatment Ayman G. Mustafa a, *, Mohammed Z. Allouh a, Rawan M. Alshehab b a b
Department of Anatomy, Faculty of Medicine, Jordan University of Science and Technology, Irbid, 22110, Jordan Department of Forensic Medicine, Faculty of Medicine, Jordan University of Science and Technology, Irbid, Jordan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 October 2014 Received in revised form 12 December 2014 Accepted 9 January 2015 Available online 16 January 2015
This study investigated the morphometric changes that occur in palatal rugae during orthodontic treatment. The potential impact of these changes on the individuality of the palatal rugae patterns and on the use of palatal rugae patterns in human identiﬁcation was also explored. Fifty pairs of pre- and post-orthodontic treatment dental casts were used. The palatal rugae patterns were compared between each pre-treatment cast and its post-treatment counterpart to reveal any morphometric changes. In addition, the individuality of the pre- and post-treatment sets of the casts was evaluated. Finally, a matching test of the palatal rugae patterns was performed in which the ability to match each posttreatment cast with its duplicate was compared with the ability to match that post-treatment cast with its pre-treatment counterpart. Statistical analysis of the results revealed the incidence of several morphometric changes, including segmentation (22%); uniﬁcation (20%); changes in orientation (6%), shape (6%), and length (28%); anteroposterior displacement of the medial (54%) and lateral (60%) end of the ruga; and mediolateral displacement of the medial end of ruga (20%). The individuality of the palatal rugae patterns was conﬁrmed in both pre- and post-treatment sets of casts. Finally, the mean percentage of correct matches was found to be signiﬁcantly higher when the post-treatment casts were matched with their duplicates compared to when they were matched with their pre-treatment counterparts. The study revealed that Orthodontic treatment induces various morphometric changes in the palatal rugae patterns. These changes may potentially complicate palatal rugae-based human identiﬁcation. © 2015 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.
Keywords: Forensic science Forensic dentistry Morphology Orthodontic Palatal rugae Palate
1. Introduction Palatal rugae are ridges or wrinkles situated in the anterior part of the hard palate behind the incisive papilla. These ridges are distributed on both sides of the median palatal raphe. Palatal rugae are also referred to as “plicae palatinae”, “transverse palatal folds”, or “rugae palatina”.1,2 Palatal rugae are formed by the 12the14th week of prenatal life as a connective tissue core embedded deeply between the submucosal fatty tissue and the stratum reticulum of the palate.3,4 Several groups have characterized the morphometric patterns of palatal rugae in various populations to reveal that palatal rugae patterns are highly variable among different genders and ethnicities.5e7 Palatal rugae patterns have gained more attention from researchers due to their clinical signiﬁcance. The size and morphology of palatal rugae are relevant to dental practice in terms of inﬂuencing prosthodontic treatment plans for edentulous * Corresponding author. Tel.: þ962 2 7201000x23836; fax: þ962 2 7201064. E-mail address: [email protected]
patients.2,8,9 Palatal rugae are utilized as reference points to measure teeth migration during orthodontic therapy.2,8,9 They can also be used to diagnose and detect submucosal clefts in the palate because certain morphometric patterns of palatal rugae can be indicative of the presence of submucosal clefts.10,11 Several reports have suggested that palatal rugae patterns are unique.5,12e14 The proposed individuality of palatal rugae patterns may facilitate their use in postmortem identiﬁcation.9,13,14 This is reinforced by the fact that palatal rugae can resist postmortem decomposition changes for up to 7 days after death and can withstand massive thermal insults like third degree burns.15,16 Palatal rugae can also resist other forms of massive trauma because their location is protected by the tongue, dentition, and cheeks. However, several studies have questioned whether palatal rugae patterns can remain stable and constant during orthodontic treatment,9,17e20 leading to conﬂicting reports on the stability of palatal rugae. This study was designed to further investigate the stability of palatal rugae patterns during orthodontic treatment. The study aims to document the incidence of any morphological change in the palatal
http://dx.doi.org/10.1016/j.jﬂm.2015.01.002 1752-928X/© 2015 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.
A.G. Mustafa et al. / Journal of Forensic and Legal Medicine 31 (2015) 19e22
rugae patterns following orthodontic treatment. It also aims to investigate the impact of these changes (if any) on the individuality of palatal rugae and their potential use in human identiﬁcation. 2. Materials and methods 2.1. Morphometric changes in the palatal rugae The assessment of palatal rugae was carried out on dental casts replicating the upper jaw and the palate. The study was approved by the Institutional Review Board (IRB) at Jordan University of Science and Technology. Fifty pairs of pre- and post-treatment dental casts were collected from private orthodontic clinics in Jordan. Each cast was given a serial number and marked with the gender and age of the patient (for whom the cast was made). The palatal rugae and the median palatal raphe in each cast were outlined with a pencil and a vernier caliper was used to measure the length of each ruga. The palatal rugae were then categorized according to the classiﬁcation provided by Thomas et al. (1987) and described in detail by Mustafa et al. (2013).5 Subsequently, each pair of the casts was examined for evidence of the following morphometric changes: a. Changes in number: These could result from segmentation, where one or more rugae in the pre-treatment cast split into two or more in the post-treatment cast; and/or uniﬁcation, where two or more rugae in the pre-treatment cast combine to become one in the post-treatment cast. b. Changes in orientation: These occur when the rugae orientation changes, e.g., posterior rugae become horizontal rugae. c. Changes in shape: These occur when the rugae shape changes, e.g., circular rugae become crescent. d. Changes in length: These occur when the rugae undergo elongation or shortening. e. Displacement of lateral end in the mediolateral direction: Movement of the lateral end of one or more rugae closer to or farther from the median palatal raphe. f. Displacement of medial end in the mediolateral direction: Movement of the medial end of one or more rugae closer to or farther from the median palatal raphe. g. Displacement of medial end in the anteroposterior direction: Movement of the medial end of one or more rugae closer to or farther from the incisive papillae. h. Displacement of lateral end in the anteroposterior direction: Movement of the lateral end of one or more rugae closer to or farther from the incisive papillae.
2.2. Testing the individuality of the palatal rugae patterns The individuality of the palatal rugae was examined by performing pair-wise qualitative comparisons within each set of the 50 casts (pre-treatment casts and post-treatment casts). Each cast was compared with the other 49 casts resulting in 1225 qualitative pairwise comparisons. Each comparison was based on examining the palatal rugae patterns in the compared casts to reveal identical patterns (if any). 2.3. Matching test of the palatal rugae patterns The post-treatment set of casts was duplicated, and the teeth in each cast were covered with tape, basing the matching test only on the palatal rugae patterns. Random samples of 10 casts were selected from the post-treatment casts. In the ﬁrst part of the matching test, each examiner was asked to match the selected 10 casts with their duplicates of post-treatment casts. While in the
second part of the matching test, each examiner was asked to match the selected casts with their pre-treatment counterparts. Each examiner repeated the matching test three times using three different samples of selected casts. The results for each examiner were averaged, and the mean percentage of correct matches for all examiners was compared between the two parts of the matching test. 2.4. Statistical analysis All the data were manually transferred into a computer. The frequencies and percentages of the morphometric changes were calculated and reported without further analysis. The results of the matching test were analyzed using paired student's t-test. 3. Results 3.1. Changes in the number of palatal rugae Changes in the number were represented either by an increase or decrease in the palatal rugae number, resulting from segmentation or uniﬁcation, respectively. Segmentation was detected in 11 (22%) palatal rugae patterns, whereas uniﬁcation was detected in 10 (20%) palatal rugae patterns (Table 1). 3.2. Changes in the orientation of palatal rugae Changes in orientation occurred on a limited scale and were detected only in three palatal rugae patterns (6%; Table 1). 3.3. Changes in the shape of palatal rugae Only three casts showed changes in shape (6%; Table 1). 3.4. Changes in the length of palatal rugae Changes in the length of rugae were evident in 14 casts (28%), as shown in Table 1. The changes involved either elongation or shortening of the palatal rugae. 3.5. Changes related to the displacement of lateral ends of palatal rugae Displacement of the lateral ends of the palatal rugae occurred on a larger scale compared to the previous changes. Thus, 60% of the casts showed anteroposterior displacement while 28% of the posttreatment casts showed mediolateral displacement (Table 1).
Table 1 Frequencies and percentages of morphometric changes of palatal rugae after orthodontic treatment. Morphological change
Segmentation Uniﬁcation Orientation Shape Length DLat: A-P DLat: M-L DMed: A-P DMed: M-L
11 10 03 03 14 30 28 27 10
22 20 06 06 28 60 56 54 20
DLat: A-P, displacement of the lateral end in anteroposterior direction. DLat: M-L, displacement of the lateral end in mediolateral direction. DMed: A-P, displacement of the medial end in anteroposterior direction. DMed: M-L, displacement of the medial end in mediolateral direction.
A.G. Mustafa et al. / Journal of Forensic and Legal Medicine 31 (2015) 19e22
3.6. Changes related to the displacement of medial ends of palatal rugae Displacement of the medial ends of the palatal rugae in the anteroposterior and mediolateral directions occurred in 54% and 20% of the post-treatment casts, respectively (Table 1). 3.7. Individuality of the palatal rugae patterns The palatal rugae patterns were highly individualized as we did not detect any identical pattern in our samples of the pre-treatment casts. Furthermore, we could not detect identical palatal rugae patterns even within the samples of the post-treatment casts (Table 2). 3.8. Matching test The mean percentage of correct matches (mean score) when matching the post-treatment casts with their duplicates (PostePost) and with their pre-treatment counterparts (Post-Pre) was 99% and 90%, respectively, and the difference in the mean scores was statistically signiﬁcant (P < 0.05). 4. Discussion It is proposed that the morphological patterns of palatal rugae can be used in human identiﬁcation as an alternative to ﬁngerprints, by virtue of their stability and individuality.3,21,22 However, it is unclear whether palatal rugae patterns can maintain these characteristics after orthodontic treatment. Several studies have investigated the effect of orthodontic treatment on the stability and individuality of the morphological patterns of palatal rugae, only to yield conﬂicting reports.19,23 In this study, we demonstrate that orthodontic treatment induces changes in the number of palatal rugae, in terms of segmentation and uniﬁcation (22% and 20% of the casts, respectively). This ﬁnding contradicts previous reports, which suggest that palatal rugae remain fairly stable in number.23,24 It is possible that orthodontic treatment strategies involve certain procedures that may increase or decrease the width of the palate25 by exerting compressive and/or stretching forces on the palatal soft tissues, leading to movements in the palatal rugae. These movements may cause splitting of a palatal ruga or approximation of two rugae so that they appear as one ruga.19 It is likely that the samples tested in the previous reports were not subjected to these invasive strategies. With respect to the changes in the length of palatal rugae, our study concurs with previous reports.1,23 Indeed, certain types of orthodontic treatment strategies such as rapid maxillary expansion, maxillary constriction, or retraction of anterior segment are expected to induce changes in the length of palatal rugae.9,26 Only 6% of the casts showed changes in orientation and/or shape, indicating that these two characteristics are the most stable morphological aspects of palatal rugae. This notion is supported by previous reports that have repudiated the presence of any
Table 2 Testing the individuality of palatal rugae patterns within the pr-treatment and the post-treatment set of casts revealed no identical palatal rugae patterns in either set of casts. Group of comparison
No. of comparisons
Percent of identical rugae patterns
Pre-treatment set Post-treatment set
signiﬁcant change in the shape or orientation of palatal rugae following orthodontic treatment.1,27 Our results are in agreement with a previous report documenting a limited degree of changes in the orientation of palatal rugae following orthodontic treatment.28 More than half of our samples exhibited displacement in the lateral end of palatal rugae in both anteroposterior and mediolateral directions. This ﬁnding concurs with several reports in the literature suggesting that the lateral ends of rugae are unstable.2,17,20 However, other studies have reported that the lateral points of the third rugae are the most stable. Thus, the identiﬁcation of the most stable end of a ruga is still open to debate.2,18 Interestingly, we found that the medial ends of the rugae are not stable as they move in the anteroposterior (54%) and mediolateral (20%) directions. This ﬁnding contradicts many reports that have suggested that the medial ends of rugae are stable and can thus be used as reference points to measure teeth migration during orthodontic treatment.17 On the other hand, Damstra et al. (2009) have suggested that adding rapid maxillary expansion to ﬁxed appliance therapy causes changes in transverse measurements of the medial ends of rugae but has no effect on the anteroposterior measurements.19 The conﬂicting reports on the stability of palatal rugae may be related to the time frame in which the post-treatment cast is made. This is based on the theory that during treatment, palatal soft tissues undergo stretching and changes in dimensions. After some time, relapse occurs and the palatal rugae resume their normal, pre-treatment position.19 This conﬂict can be resolved by designing a prospective study in which the type of orthodontic treatment as well as the time of generating the post-operative casts is controlled. Our study supports the individualistic nature of palatal rugae patterns. Even after orthodontic treatment, the palatal rugae patterns remained individualized. This result corroborates with several reports suggesting the individuality of palatal rugae patterns and their potential use in forensic identiﬁcation.5,7,29 Moreover, our study ﬁndings show that the morphometric changes induced by orthodontic treatment do not signiﬁcantly hamper the matching of pre-treatment casts with the post-treatment casts. In our study, the mean percent of correct matches between the posttreatment and duplicated post-treatment casts was 99% whereas matching between the pre- and post-treatment casts yielded 90% correct matches. Although this difference in the mean percentage of correct matches was statistically signiﬁcant, it may be greatly reduced if the matching is done by a trained forensic specialist. Other studies in which matching tests were performed between pre- and post-treatment casts revealed comparable results to our study.9,22,23 Orthodontic treatment induces various morphometric changes in the palatal rugae patterns. Although these changes do not seem to affect the individuality of the palatal rugae patterns, they may potentially complicate palatal rugae-based human identiﬁcation. Thus, it is essential to maintain and update dental records, especially after orthodontic treatment, if palatal rugae are to be used in human identiﬁcation. Conﬂict of interest statement None declared by the authors. Funding Funding was provided by the Deanship of research at Jordan University of Science and Technology. Ethical approval The study was approved by the Institutional Review Board (IRB) at Jordan University of Science and Technology.
A.G. Mustafa et al. / Journal of Forensic and Legal Medicine 31 (2015) 19e22
Acknowledgments The authors would like to thank the Deanship of research at Jordan University of Science and Technology for providing the ﬁnancial support for this work. Grant number: 2014/27. References 1. Kapali S, Townsend G, Richards L, Parish T. Palatal rugae patterns in Australian Aborigines and Caucasians. Aust Dent J 1997;42(2):129e33. 2. Almedia MA, Phlilips C, Kula K, Tulloch C. Stability of the palatal rugae as landmarks for analysis of dental casts. Angle Orthod 1995;65(1):43e8. 3. Patil MS, Patil SB, Acharya AB. Palatine rugae and their signiﬁcance in clinical dentistry: a review of the literature. J Am Dent Assoc 2008;139(11):1471e8. 4. Jibi PM, Gautam KK, Basappa N, Raju OS. Morphological pattern of palatal rugae in children of Davangere. J Forensic Sci 2011;56(5):1192e7. 5. Mustafa AG, Allouh MZ, Tarawneh IA, Alrabata RH. Morphometric analysis of palatal rugae among Jordanians: further evidence of worldwide palatal rugae individuality. Aust J Forensic Sci 2014;46(1):53e63. 6. Kotrashetti VS, Hollikatti K, Mallapur MD, Hallikeremath SR, Kale AD. Determination of palatal rugae patterns among two ethnic populations of India by logistic regression analysis. J Forensic Leg Med 2011;18(8):360e5. 7. Shetty SK, Kalia S, Patil K, Mahima VG. Palatal rugae pattern in Mysorean and Tibetan populations. Indian J Dent Res 2005;16(2):51e5. 8. Hemanth M, Vidya M, Shetty N, Karkera BV. Identiﬁcation of individuals using palatal rugae: computerized method. J Forensic Dent Sci 2010;2(2):86e90. 9. Bansode SC, Kulkarni MM. Importance of palatal rugae in individual identiﬁcation. J Forensic Dent Sci 2009;1(2):77e81. 10. Kratzsch H, Opitz C. Investigations on the palatal rugae pattern in cleft patients. Part I: a morphological analysis. J Orofac Orthop 2000;61(5):305e17. 11. Park S, Eguti T, Kato K, Nitta N, Kitano I. The pattern of palatal rugae in submucous cleft palates and isolated cleft palates. Br J Plast Surg 1994;47(6): 395e9. 12. De Angelis D, Riboli F, Gibelli D, Cappella A, Cattaneo C. Palatal rugae as an individualising marker: reliability for forensic odontology and personal identiﬁcation. Sci Justice 2012;52(3):181e4. 13. Saraf A, Bedia S, Indurkar A, Degwekar S, Bhowate R. Rugae patterns as an adjunct to sex differentiation in forensic identiﬁcation. J Forensic Odontostomatol 2011;29(1):14e9.
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