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The purpose of this study was to compare skeletal and dentoalveolar shape and size differences in patients with maxillary impacted canines versus unaffected patients using landmarked CBCT images and geometric morphometrics.104 cone-beam computed tomography scans from patients presenting with palatal or buccal impacted maxillary canines and 40 control patients with no impacted dentition were landmarked. 146 landmarks were plotted in Stratovan Checkpoint. Cone-beam computed tomography images including the nasal cavity, palate, sinus, alveolar crest, maxillary lateral walls, and dentition were landmarked by five examiners. No patient had undergone any type of orthodontic treatment in the past. Landmarked CBCT images were evaluated for shape and symmetry using geometric morphometric analysis by performing Procrustes superimposition, principal component analysis, and canonical variates analysis. Shape differences were further investigated by using linear regression analyses. Size differences were then investigated by looking at centroid size based on ratios between dentition and the entire landmarked maxilla. To analyze shape differences, we utilized a principal components analysis and found impaction location of the canine contributed to the primary and secondary principal component of the variance in the shape. Removing the variance of tooth location, a principal component analysis was conduct on the asymmetric component. We found patients with maxillary canine impactions had a constriction of the arch on the side of the impaction as well as lowering of the sinus floor on the side of the maxillary canine impaction compared to the control. The shape differences found were not statistically significant and we found no difference in shape between palatal versus buccal impactions. Looking at size with differences of the dentition, the centroid size of the maxillary canine, central incisor and first molar were statistically different between the impacted and nonimpacted groups with a reduction in centroid size of the canine in the impacted versus nonimpacted groups. There were no statistically significant size differences between the impacted maxillary canine groups however there was a reduction in size in the palatal size versus the buccal side. The centroid sizes of the maxilla without teeth, arch width, and palate size in the impacted versus the nonimpacted group were all statistically different from the control group with the impacted group being smaller while there was no difference between the palatal versus buccal groups. When looking at the size of the maxilla between males versus females, it was found that males consistently had large centroid sizes in their overall maxilla compared to females. We isolating for gender, there was no statistically significant difference in maxilla size between maxillary impaction palatal or buccal impactions. Patients with impacted maxillary canines have both shape and size differences in the overall maxillary structure as well as the maxillary canine compared to patients without impacted maxillary canines. Amongst the dentition there was a general size reduction between the impacted versus nonimpacted tooth sizes. The impacted canines and first incisors and first molars on the side of the impaction had a statistically significant reduction in size compared to the nonimpacted canine patients. We also found a reduction in overall maxillary size in patients with impacted canines. There was also no statistically significant difference in centroid size of teeth or maxillary structures between palatal and buccal groups. These findings reflect that perhaps the etiology of canine impaction location is in line with the genetic theory rather than a lack of guidance from an undersized lateral incisor.

Abstract: OBJECTIVE: To analyze the relationship between the impacted maxillary canine and the root inclination of the adjacent maxillary incisors. While earlier literature relied on 2-dimensional radiographs, which display an overlapped representation of the maxillary incisors, this project had the advantage of using 3-dimensional imaging to measure each maxillary incisor root inclination independently. METHODS: CBCTs of 27 patients with palatally impacted maxillary canines (group P), 15 patients with buccally impacted canines (group B), and 30 patients with normally erupting maxillary canines (group C) were used in our analysis. Incisor root inclination with respect to the palatal plane was measured for each individual maxillary incisor, and an ANOVA was used to assess significant differences for each incisor between the 3 groups. Paired T-tests were conducted in groups P and B to evaluate whether or not lateral or central incisors on the side of the impacted canine showed significant differences in inclination from their contralateral counterparts. Factors such as distance away from the adjacent lateral incisor, vertical position of the canine crown, and impaction sector were recorded for each patient in groups P and B. These factors were included in Pearson correlation analyses also considering the adjacent lateral incisor’s root inclination. All three statistical analyses were repeated after patients with peg-shaped/small maxillary lateral incisors were removed from the groups (3 in group P, 2 in group B, 1 in group C). RESULTS: Compared to group C, lateral incisors on the side of the palatally impacted canine showed an average of approximately 10 degrees more buccal root inclination, and central incisors on the affected side averaged about 5 degrees more buccal root inclination. Group B showed significant differences in the ipsilateral lateral incisor alone, which averaged 12 more degrees of palatal root inclination when compared to group C. Within group P, the ipsilateral lateral incisor averaged 7.5 more degrees of buccal root inclination than its contralateral counterpart. In comparison, the central incisor on the affected side averaged 3 degrees more buccal root inclination than that of the contralateral side. In group B, the lateral incisor immediately adjacent to the buccally impacted canine displayed an average of approximately 10.5 degrees more palatal root inclination than the contralateral side. In group P, moderate correlations revealed that the closer and more coronally positioned the impacted canine is with respect to the lateral incisor, the more buccally inclined the lateral incisor’s root will be. A moderate correlation also showed that the more medially displaced the palatally impacted canine is situated (i.e., the higher the impaction sector), the more buccally inclined the adjacent lateral incisor’s root would be. In group B, a considerable correlation showed that the more medial the impacted canine was, the more palatally inclined the root of the lateral incisor would be, however this finding should be interpreted with caution since only two cases in group B had their canines situated in impaction sector 4-5. After peg-shaped/small laterals were removed, group P no longer showed significant differences in ipsilateral central incisor inclination compared to group C. Furthermore, the variable of impaction sector no longer shared a significant correlation with incisor root inclination in group P. Additionally, average root inclinations of all maxillary incisors demonstrated less buccal root inclination in group P and less palatal root inclination in group B. CONCLUSION: Patients with impacted maxillary canines do not show significant differences in the root position of all four maxillary incisors, but only in the incisors on the side of the impacted canine. While palatal impactions are associated with buccally positioned roots of both the ipsilateral lateral and central incisors (with different degrees of inclination), buccal impactions are only associated with palatally placed roots of the ipsilateral lateral incisors.

In the US, the state which has jurisdiction over a homicide can have significant impact on the criminal sanction an offender will receive. For example, a murderer who offended in Indiana can receive a death sentence. If the same crime were committed in Michigan, the harshest sentence the murderer would receive is life imprisonment. Indiana and Michigan, bordering states, have had opposing stances on capital punishment for over 150 years. Michigan was the first state to abolish capital punishment in 1846, and Indiana has used capital punishment since its founding in 1816. Historical institutional theory guides this study. It is posited that the media and the legal systems in these states have established differing discourse boundaries which constrain the state lawmaker's debates regarding the death penalty, and therefore, constrain the laws as originally enacted. The methodology of this study is a parallel comparative history of Indiana and Michigan. The primary sources of evidence include: Michigan and Indiana legal codes, state historical documents, legislative histories from the states, Indiana State Supreme Court case law, and newspaper archives. Discourse from these sources was analyzed at pivotal points in the history of the states when change to capital punishment laws might have been expected. Data analysis indicates that each state has established different discourse boundaries that hinder alterations in the states' stances on capital punishment. The primary finding is that Michigan gives more weight to arguments of a utilitarian nature and Indiana is more willing to accept arguments that capital punishment is appropriate retribution for some types of homicide. The differences in the states' discourse boundaries have constrained the debates of lawmakers and the choices they make regarding capital punishment; thus, continuing to constrain the states' original stance on the death penalty.