Thesis
An investigation of palatal rugae patterns and torus palatinus in unaffected relatives of individuals with orofacial clefts
University of Iowa
Master of Science (MS), University of Iowa
Spring 2020
DOI: 10.17077/etd.005320
Abstract
Introduction: In order to explore genetic determinants in individuals with non-syndromic orofacial cleft (OFC), several studies have focused on capturing phenotypic abnormalities in relatives of these individuals, who are not affected by an overt cleft, yet may carry genetic risk. This study analyzed a large multiethnic sample of maxillary casts to determine if specific palatal features including palatal rugae, the presence of torus palatinus (TP) and features of the median raphe show differences in unaffected relatives of individuals with OFC compared with controls to identify potential risk factors that will help elucidate OFC etiology. Of these, palatal rugae are deemed stable structures, unique to each human individual, and are considered important signaling centers that express some of the same molecules that are essential for proper palatogenesis. Rugae features are complex and various classification schemes have been attempted to decipher their biological significance. Most studies have returned inconsistent results indicating that rugae patterns are not simple to assess and/or the classification schemes utilized are not reproducible. In this study we also designed and tested a simpler classification method that divides rugae into simple or complex and assessed their palatal location in the transverse dimension, in the hopes to facilitate rugae evaluation in large multiethnic samples.
Methods: A total of 1020 maxillary casts were rated from six different geographic locations, including 337 unaffected family members of non-syndromic cleft lip with or without palate, or cleft palate only subjects, 3 married-in relatives, and 680 unaffected non-relative controls. Digital maxillary casts were rated based on defined variables for rugae, torus palatinus and median palatal by three raters. After calibration a kappa score of 0.4, which indicated moderate agreement, was deemed acceptable for the variable to be used in further statistical analyses. Case-control differences were tested using Chi-squared tests of independence, Odds Ratio Estimates and Cochran-Mantel-Haenzel Odd Ratios to estimate the magnitude of the effects taking into account stratification by demographic variables when appropriate.
Results: Calibration results indicated that mid palatal raphe and 1 of 3 rugae categories had to be excluded from analyses because the Kappa scores were less than 0.4. When comparing unaffected relatives of OFC subjects to controls, there were no statistical significant differences in any rugae pattern variables between the two groups (P-values ranged from 0.2413- 0.9098) as well as between different overall family cleft types (P-values ranged from 0.0563 – 0.8184). We did find that sex and race had an effect on the presence of TP between case relatives and controls. The odds of a case relative having a TP was almost two times higher (P=0.0013121 Odds Ratio= 1.727 CI [1.243-2.400]) compared to controls regardless of sex. In addition, although a suggestive finding in the Asian racial group, case relatives had higher odds of having a TP (P=0.0926).
Conclusion: Rugae patterns did not show differences between unaffected relatives of non-syndromic cleft lip with or without palate and cleft palate only compared to controls. However it is difficult to determine if these results were due to the difficulty of classifying the rugae patterns or if there truly were no significant differences in rugae patterns. Since prior studies have seen overt cleft patients with significantly different rugae patterns it would be advantageous to conduct further studies of this sample group with a different classification scheme. Torus palatinus was found to be a potential phenotypic risk factor of OFC as it had significantly higher odds of occurrence in case relatives compared to controls. Also the Asian case group had a higher odds of having a TP than the Asian control group. Although only a suggestive finding, it is of interest as we know that Asian populations have the highest prevalence of CL/P. Further studies to help evaluate this phenotypic association as well as potential genetic determinants underlying this association would be beneficial.
Details
- Title: Subtitle
- An investigation of palatal rugae patterns and torus palatinus in unaffected relatives of individuals with orofacial clefts
- Creators
- Monica Obniski
- Contributors
- Lina M. Moreno Uribe (Advisor)Seth M. Weinberg (Committee Member)Shankar R. Venugopalan (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Orthodontics
- Date degree season
- Spring 2020
- DOI
- 10.17077/etd.005320
- Publisher
- University of Iowa
- Number of pages
- xii, 76 pages
- Copyright
- Copyright 2020 Monica Obniski
- Language
- English
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 73-76).
- Public Abstract (ETD)
Introduction: A way to explore how genetic risk influences cleft lip/palate (CL/P) anomalies is by evaluating both affected and unaffected members of families with clefts to search for common oral features since such close relatives may carry genetic risk for the condition. Particularly, anomalies in anatomical structures of the palate such as the rugae, median raphe or presence of tori found in the unaffected relatives but not in controls with no history of CL/P, will indicate that these anomalies are within the spectrum of symptoms of the CL/P condition.
Methods: This study defined, collected and statistically tested differences in a series of traits related to the rugae, median raphe and the presence of tori in 1020 digital upper arch casts of unaffected relatives and controls. Only rugae and palatal tori features achieved good reliability and were analyzed further.
Results: No differences were found in the palatal rugae between unaffected family members and controls. However, we found that unaffected relatives have almost twice the risk of presenting a palatal tori compared to controls. Further, unaffected family members of the Asian race group had higher odds of tori occurrence.
Conclusion: This study showed that palatal rugae are not related to cleft risk. However, the presence of tori is a potential risk factor for CL/P. Results in the Asian group indicating a higher odds of tori is interesting since it is known that CL/P is most common in this population. Results suggest that certain palatal features are markers of CL/P risk.
- Academic Unit
- Orthodontics; Craniofacial Anomalies Research Center
- Record Identifier
- 9983956197102771
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