Comparison of movement rate with different initial moment-to-force ratios.

INTRODUCTION: The objective of this clinical prospective study was to evaluate the effect of the 2 treatment strategies, translation or controlled tipping, followed by root correction on canine retraction efficiency, specifically canine movement rate. METHODS: Twenty-one patients who needed bilateral maxillary canine retraction to close extraction space as part of their treatment plan were selected for this study. Segmental T-loops designed for controlled tipping or for translation were applied randomly to each side. Two digital maxillary dental casts (taken before and after treatment) were used to measure the tooth displacements of each patient. The coordinate system located at the center of canine crown on the pretreatment model with the 3 axes defined in the mesial-distal (M-D), buccal-lingual, and occlusal-gingival directions was used to express the 6 tooth displacement components. The movement rates on the occlusal plane and in the M-D direction were computed. Movement rates were calculated by dividing the M-D displacements or the resultant displacement on the occlusal plane with the corresponding treatment time. RESULTS: T-Loops for controlled tipping moved canines faster (33.3% on occlusal plane and 38.5% in the M-D direction) than T-loops for translation. The differences were statistically significant (P = 0.041 on the occlusal plane and 0.020 in the M-D direction). CONCLUSIONS: Moment-to-force ratio (M/F) affects the canine movement rate in a maxillary canine retraction treatment with the use of a segmented T-loop mechanism. Within the neighborhood of the ratio for translation, lower M/F moves the canine faster than higher M/F both on the occlusal plane and in the M-D direction.

Three-dimensional evaluation of labial alveolar bone overlying the maxillary and mandibular incisors in different skeletal classifications of malocclusion.

OBJECTIVES: The purpose of this study was to investigate differences in the thickness of the labial bone overlying the maxillary and mandibular incisors in class I, II, and III skeletal classifications using three-dimensional cone-beam computed tomographs (CBCT) technology. METHODS: Pretreatment CBCTs of 54 Caucasian subjects (44 males, 10 females) were collected from the archives of a graduate orthodontic clinic. The subjects were divided into three groups based on their skeletal classification. CBCT scans were oriented to the long axis of each maxillary and mandibular incisor from the root apex to incisal tip and the axial inclination of each incisor was measured and recorded. Labial bone thickness was measured at the apex (A) and at the midpoint (MP) on each maxillary and mandibular incisor. A linear measurement, perpendicular to the long axis, was recorded from the labial bone surface to the most anterior root surface at two points. The effects of skeletal classification, jaw, incisor position, and side on A, MP, and Inclination were evaluated using mixed-model ANOVA. A 5% significance level was used for all tests. RESULTS: Significantly greater bone thickness at the apex and midpoint was reported in class III individuals than class I or II. Central incisors had significantly greater bone thickness at both the root apex and midpoint. Significantly greater bone thickness was noted in the mandible at the level of the apex. At the level of the midpoint, significantly greater thickness was reported in the maxilla. There was a positive correlation between thickness and angle within each jaw-incisor combination for class I patients and for central incisors in class III patients. CONCLUSION: The thickness of labial alveolar bone over the incisors varies based on the underlying skeletal discrepancy in each patient. Skeletal discrepancy influences the inclination of the maxillary and mandibular incisors.

Retrospective CBCT analysis of airway volume changes after bone-borne vs tooth-borne rapid maxillary expansion.

OBJECTIVES: To compare changes in upper airway volume after maxillary expansion with bone- and tooth-borne appliances in adolescents and to evaluate the dentoskeletal effects of each expansion modality. MATERIALS AND METHODS: This retrospective study included 36 adolescents who had bilateral maxillary crossbite and received bone-borne maxillary expansion (average age: 14.7 years) or tooth-borne maxillary expansion (average age: 14.4 years). Subjects had two cone beam computed tomography images acquired, one before expansion (T1) and a second after a 3-month retention period (T2). Images were oriented, and three-dimensional airway volume and dentoskeletal expansion were measured. Analysis of variance was used to test for differences between the two expansion methods for pretreatment, posttreatment, and prepost changes. Paired t-tests were used to test for significance of prepost changes within each method. RESULTS: Both groups showed significant increase only in nasal cavity and nasopharynx volume (P < .05), but not oropharynx and maxillary sinus volumes. Intermolar and maxillary width increased significantly in both groups (P < .05); however, the buccal inclination of maxillary molars increased significantly only in the tooth-borne group (P < .05). There was no significant difference between tooth- and bone-borne expansion groups, except for the significantly larger increase in buccal inclination of the maxillary right first molar after tooth-borne expansion. CONCLUSIONS: In adolescents, both tooth- and bone-borne RME resulted in an increase in nasal cavity and nasopharynx volume, as well as expansion in maxillary intermolar and skeletal widths. However, only tooth-borne expanders caused significant buccal tipping of maxillary molars.

Enamel Hypomineralization in Children With Clefts and the Relationship to Treatment: A Cross-sectional Retrospective Study.

OBJECTIVE: The aim of this study was to determine whether molar incisor hypomineralization (MIH) is greater in patients with cleft lip and palate (CLP) who underwent primary alveolar grafting (PAG) as compared with CLP waiting for secondary alveolar grafting (SAG) and with controls. DESIGN: A retrospective analysis of intraoral photographs of 13 CLP patients who underwent a PAG, 28 CLP prior to SAG, and 60 controls without CLP was performed. Mantel-Haenszel χ tests were used to compare the 3 groups for differences in MIH scores, and Wilcoxon rank sum tests were used to compare the groups for differences in average MIH scores. A 5% significance level was used for all tests. RESULTS: Molar incisor hypomineralization scores were significantly higher for the PAG and SAG groups compared with the control group (P < 0.001). The PAG group had significantly higher incisor MIH (P = 0.016) compared with the SAG group. Molar incisor hypomineralization average scores were significantly higher for the 2 graft groups compared with the controls (P < 0.0001). The PAG group had significantly higher average MIH score and average MIH score for incisors compared with the SAG group (P = 0.03). CONCLUSIONS: Cleft lip and palate patients have significantly greater MIH compared with controls, and CLP patients with PAGs have significantly greater MIH in the incisor region compared with CLP patients with SAGs, indicating that subjects with PAGs have more severely affected dentition.

The Relationship Between Hard Tissue and Soft Tissue Dimensions of the Nose in Children: A 3D Cone Beam Computed Tomography Study.

This study using three-dimensional cone beam computed tomography (CBCT) images of children determined relationships between nasal skeletal and soft tissue measurements and assessed the association with sex, age, and skeletal maturation stage. Following reliability studies, skeletal and soft tissue parameters were measured on coded CBCTs of 73 children (28M:45F;6-13 yoa). Pearson and Mantel correlations were used to analyze associations between skeletal and soft tissues. Partial Mantel correlations were used to study the associations between skeletal and soft tissue, adjusting for sex, age, and skeletal maturation. Linear regression analyses were used to predict soft tissues sizes. Logistic regression was used to study the relationships between soft and skeletal tissue symmetry. Except for nasal aperture width and interalar width, skeletal landmarks best predicted corresponding soft tissue landmarks. Significant positive associations existed between skeletal and soft tissues after adjusting for sex, skeletal maturation, and age. Children's nasal skeletal tissues predicted nasal soft tissue reasonably well.

Three-dimensional evaluation of airway volume changes in two expansion activation protocols.

The purpose of this study was to evaluate the airway volume changes associated with rapid maxillary expansion (RME) protocols using different activation rates. A sample of forty RME treated cases was classified into two groups according to the rate of RME activation (Group A: 0.8mm per day and Group B: 0.5mm per day). Three-dimensional images were obtained for each case before and three months after expansion. Dolphin imaging software was used to identify landmarks and calculate airway volumes. Intraclass correlation coefficient was used to confirm reliability and Wilcoxon signed rank tests were used for comparison between the initial and final measurements within each group and between groups. Significant increase in the nasal cavity volume for both groups was observed (P<0.0001 and P=0.001 for groups A and B respectively). The increase in nasopharynx volume was significant in the group with a more rapid activation rate (P=0.0006). Significant differences between the two groups in post-treatment changes were detected in the nasal cavity volume (P<0.0001), nasopharynx volume (P=0.0035), and soft palate area (P=0.0081). A more rapid activation rate results in a higher volume increase for the nasal cavity and nasopharynx than a slower activation rate.

Two-dimensional vs 3-dimensional comparison of alveolar bone over maxillary incisors with A-point as a reference.

INTRODUCTION: Our objectives were to compare, relative to A-point, (1) bone thickness over the most forward maxillary incisor (MFMI) in 2 dimensions vs 3 dimensions, and (2) bone thickness and inclination of each maxillary incisor in 3 dimensions. METHODS: Thirty-four cone-beam computed tomography (CBCT) images were coded, and 2-dimensional (2D) cephalograms were derived from each image using Dolphin software (Dolphin Imaging and Management Solutions, Chatsworth, Calif). A-point and the MFMI crown were located. After reliability tests, alveolar bone buccal to 3 points on the MFMI root, bone to reference line Frankfort horizontal (FH)-A-point, and incisor inclination were measured. This procedure was repeated on the 3-dimensional (3D) CBCT images comparing MFMI with all maxillary incisors. The 2D and 3D measurements were compared using paired t tests, and 3D measurements were compared with analysis of variance. A 5% significance level was used for all tests. RESULTS: The MFMI's buccal bone thickness at the root apices and the distance between buccal bone and FH-A-point line at 2 root points were significantly greater in 2 dimensions than in 3 dimensions. In 3 dimensions, bone thickness at MFMI's root apex and the distance from FH-A-point line at all root points were significantly greater than those of the lateral incisors. Bone buccal to MFMI was significantly smaller than at the lateral incisors 3 mm from the cementoenamel junction. CONCLUSIONS: Evaluation of 2D CBCT derivations can result in overestimation of alveolar bone buccal to the maxillary incisor root apices compared with 3D evaluations. The anterior nasal spine obscures bone measurements over the maxillary incisors in 2 dimensions.

Root resorptions associated with canine retraction treatment.

INTRODUCTION: The hypothesis of this study was that multiple factors are dominant in causing external apical root resorption (EARR). The objective of this investigation was to better understand the clinical factors that may lead to EARR. METHODS: Maxillary cone-beam computed tomography scans of 18 subjects who were treated with bilateral canine retractions during orthodontics were used to calculate EARR. The subjects were treated using well-calibrated segmental T-loops for delivering a 124-cN retraction force and the moment-to-force ratio suitable for moving the canine under either translation or controlled tipping. The subjects' age, sex, treatment duration, and genotype were collected. RESULTS: Six subjects of the 18 showed definite EARR, meaning that load was not the only causing factor. All 5 subjects with the genotype identified had GG genotype of IL-1ß rs11143634, indicating that people with this genotype may be at high risk. Longer treatment duration, female sex, and older age may also contribute to EARR, although the findings were not statistically significant. CONCLUSIONS: EARR appears to be related to multiple factors. The orthodontic load and the genotype should be the focuses for future studies.

Three-dimensional evaluation of molar buccolingual inclinations after orthodontic treatment using edgewise mechanics.

OBJECTIVES: The purpose of this study was to measure changes in buccolingual inclination and in thickness of maxillary and mandibular buccal and lingual bone of maxillary and mandibular molars following orthodontic treatment using edgewise mechanics. MATERIALS AND METHODS: Cone-beam computed tomography scans of 48 patients taken before and after completion of comprehensive orthodontic treatment were collected for this retrospective study. Buccolingual molar inclinations were reported as angular measurements using the long axis of the teeth and inferior border of the nasal floor and inferior border of the mandible, respectively. Distances between the buccal and lingual cusps of maxillary and mandibular molars, respectively, were measured to the occlusal plane to assess the change in buccolingual inclination after orthodontic treatment. The amount of buccal and lingual bone at the level of the root apex of each molar was also evaluated before and after orthodontic treatment. RESULTS AND CONCLUSION: Orthodontic edgewise mechanics caused significant increases in mandibular first molars' inclination angle, lingual bone, and mandibular second molars' buccal bone and inclination angle. Significant decreases were noted in mandibular first molars' buccal bone, inclination distance and mandibular second molars' lingual bone and inclination distance. Maxillary teeth had fewer significant changes than the mandibular teeth. Significant decreases were found for maxillary first molars' buccal bone, inclination distance, and maxillary second molar buccal bone.

Effects of Primary Alveolar Grafting on Alveolar Bone Thickness in Patients With Cleft Lip and Palate.

The purpose of this study was to compare alveolar bone thickness around the teeth adjacent to the cleft using cone beam computed tomography (CBCT) in patients with cleft lip and palate (CLP) who underwent primary alveolar grafting (PAG) as compared with CLP waiting for secondary alveolar grafting (SAG) and to determine the associations with other factors such as the patient's age, sex, and type of cleft. CBCTs of 39 CLP patients were divided into either group 1 (PAG, N = 11) or group 2 (SAG, N = 28). Measurements of bone thickness around the closest tooth to the cleft were performed on the axial sections on each subject's CBCT at 3, 6, and 9 mm apical to the cementoenamel junction along the root length. Intraclass correlation coefficients and Bland-Altman plots were used to evaluate intrarater reliability. Bone measurements with 95% confidence intervals for the mean were estimated using analysis of variance models with a random patient effect to account for correlation among multiple measurements within a patient. Similar models were used to test the associations of age, sex, and type of the graft with the bone measurements. No statistically significant associations of the factors were found with mesial or distal bone measurements. Buccal bone thickness was significantly greater only at 9 mm in the primary bone graft subjects compared with secondary bone graft subjects (P = 0.009). Unilateral cleft subjects showed significantly greater buccal bone thickness at the level of 9 mm compared with bilateral cleft subjects (P = 0.046) and lingual bone thickness at the level of 6 mm (P = 0.0026) and 9 mm (P = 0.0096). In conclusion, PAG does not add benefits to the bone width on the cleft sides of the closest teeth to the cleft as compared with children with CLP who have not undergone alveolar grafts yet.

Three dimensional evaluation of alveolar bone changes in response to different rapid palatal expansion activation rates.

INTRODUCTION: The aim of this multi-center retrospective study was to quantify the changes in alveolar bone height and thickness after using two different rapid palatal expansion (RPE) activation protocols, and to determine whether a more rapid rate of expansion is likely to cause more adverse effects, such as alveolar tipping, dental tipping, fenestration and dehiscence of anchorage teeth. METHODS: The sample consisted of pre- and post-expansion records from 40 subjects (age 8-15 years) who underwent RPE using a 4-banded Hyrax appliance as part of their orthodontic treatment to correct posterior buccal crossbites. Subjects were divided into two groups according to their RPE activation rates (0.5 mm/day and 0.8 mm/day; n = 20 each group). Three-dimensional images for all included subjects were evaluated using Dolphin Imaging Software 11.7 Premium. Maxillary base width, buccal and palatal cortical bone thickness, alveolar bone height, and root angulation and length were measured. Significance of the changes in the measurements was evaluated using Wilcoxon signed-rank test and comparisons between groups were done using ANOVA. Significance was defined at p ≤ 0.05. RESULTS: RPE activation rates of 0.5 mm per day (Group 1) and 0.8 mm per day (Group 2) caused significant increase in arch width following treatment; however, Group 2 showed greater increases compared to Group 1 (p < 0.01). Buccal alveolar height and width decreased significantly in both groups. Both treatment protocols resulted in significant increases in buccal-lingual angulation of teeth; however, Group 2 showed greater increases compared to Group 1 (p < 0.01). CONCLUSION: Both activation rates are associated with significant increase in intra-arch widths. However, 0.8 mm/day resulted in greater increases. The 0.8 mm/day activation rate also resulted in more increased dental tipping and decreased buccal alveolar bone thickness over 0.5 mm/day.

Validity and reliability of three-dimensional palatal superimposition of digital dental models.

OBJECTIVE: To evaluate the validity and reliability of three-dimensional (3D) landmark-based palatal superimposition of digital dental models using Ortho Mechanics Sequential Analyzer (OMSA). METHODS: The sample consisted of pre- and post-treatment digital maxillary dental models of 20 orthodontic cases. For each case, the pre- and post-treatment digital models were superimposed using surface-based methods utilizing 3dMD Vultus and Invivo 5 software as well as a landmark-based method utilizing OMSA. The same set of parameters were measured on the superimposed 3D data by the three softwares for comparison. Agreement in the superimposition outcomes among the three superimposition methods was evaluated with intraclass correlation coefficients (ICCs), Bland-Altman plots, and repeated measures ANOVA. A P value of ≤ 0.05 was considered statistically significant. RESULTS: Repeatability was acceptable for all methods based on the ICCs. Agreement as measured by the ICCs and repeated measures ANOVA was high among the three methods. CONCLUSION: The results indicate that OMSA offers a valid and reliable tool for 3D landmark-based digital dental models superimposition using 3 points marked along the midpalatal raphe as reference.

Three dimensional evaluation of alveolar bone changes in response to different rapid palatal expansion activation rates

ABSTRACT Introduction: The aim of this multi-center retrospective study was to quantify the changes in alveolar bone height and thickness after using two different rapid palatal expansion (RPE) activation protocols, and to determine whether a more rapid rate of expansion is likely to cause more adverse effects, such as alveolar tipping, dental tipping, fenestration and dehiscence of anchorage teeth. Methods: The sample consisted of pre- and post-expansion records from 40 subjects (age 8-15 years) who underwent RPE using a 4-banded Hyrax appliance as part of their orthodontic treatment to correct posterior buccal crossbites. Subjects were divided into two groups according to their RPE activation rates (0.5 mm/day and 0.8 mm/day; n = 20 each group). Three-dimensional images for all included subjects were evaluated using Dolphin Imaging Software 11.7 Premium. Maxillary base width, buccal and palatal cortical bone thickness, alveolar bone height, and root angulation and length were measured. Significance of the changes in the measurements was evaluated using Wilcoxon signed-rank test and comparisons between groups were done using ANOVA. Significance was defined at p ≤ 0.05. Results: RPE activation rates of 0.5 mm per day (Group 1) and 0.8 mm per day (Group 2) caused significant increase in arch width following treatment; however, Group 2 showed greater increases compared to Group 1 (p < 0.01). Buccal alveolar height and width decreased significantly in both groups. Both treatment protocols resulted in significant increases in buccal-lingual angulation of teeth; however, Group 2 showed greater increases compared to Group 1 (p < 0.01). Conclusion: Both activation rates are associated with significant increase in intra-arch widths. However, 0.8 mm/day resulted in greater increases. The 0.8 mm/day activation rate also resulted in more increased dental tipping and decreased buccal alveolar bone thickness over 0.5 mm/day.

RESUMO Introdução: o objetivo do presente estudo retrospectivo multicêntrico foi quantificar as alterações na altura e na espessura do osso alveolar após o uso de dois diferentes protocolos de ativação na expansão rápida da maxila (ERM), bem como determinar se uma taxa de expansão mais rápida tem maior probabilidade de causar mais efeitos adversos, tais como inclinação dos dentes e do processo alveolar, fenestração e deiscência dos dentes de ancoragem. Métodos: a amostra consistiu de registros pré- e pós-expansão de 40 indivíduos (com idades entre 8 e 15 anos) que se submeteram à expansão rápida da maxila usando o aparelho Hyrax com quatro bandas como parte de seu tratamento ortodôntico para correção da mordida cruzada posterior. Os indivíduos foram divididos em dois grupos, de acordo com a taxa de ativação na expansão rápida da maxila (0,5 mm/dia e 0,8 mm/dia; n = 20 cada grupo). Imagens tridimensionais de todos os indivíduos da amostra foram avaliadas com o uso do software Dolphin Imaging v. 11.7 Premium. Foram analisadas as seguintes medidas: largura da base da maxila, espessura das corticais ósseas vestibular e lingual, altura do osso alveolar, angulação e comprimento das raízes. A significância das alterações nessas medidas foi avaliada com o teste não paramétrico de Wilcoxon e as comparações entre os grupos foram feitas usando a ANOVA. A significância foi definida como p ≤ 0,05. Resultados: as taxas de ativação na ERM de 0,5mm/dia (Grupo 1) e 0,8mm/dia (Grupo 2) causaram aumento significativo na largura da arcada após o tratamento. Porém, o Grupo 2 apresentou maior aumento, se comparado ao Grupo 1 (p < 0,01). A altura e a largura do osso alveolar vestibular diminuíram significativamente em ambos os grupos. Ambos os protocolos de tratamento resultaram em aumento significativo na inclinação vestibulolingual dos dentes. Porém, o Grupo 2 apresentou maior aumento, em comparação ao Grupo 1 (p < 0,01). Conclusão: ambas as taxas de ativação estão associadas a um aumento significativo nas larguras intra-arcada; entretanto, a taxa de 0,8mm/dia resultou em maior aumento. Essa mesma taxa de ativação também resultou em maior inclinação dos dentes e em redução mais acentuada da espessura do osso alveolar vestibular.

Influence of prenatal EGCG treatment and Dyrk1a dosage reduction on craniofacial features associated with Down syndrome.

Trisomy 21 (Ts21) affects craniofacial precursors in individuals with Down syndrome (DS). The resultant craniofacial features in all individuals with Ts21 may significantly affect breathing, eating and speaking. Using mouse models of DS, we have traced the origin of DS-associated craniofacial abnormalities to deficiencies in neural crest cell (NCC) craniofacial precursors early in development. Hypothetically, three copies of Dyrk1a (dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A), a trisomic gene found in most humans with DS and mouse models of DS, may significantly affect craniofacial structure. We hypothesized that we could improve DS-related craniofacial abnormalities in mouse models using a Dyrk1a inhibitor or by normalizing Dyrk1a gene dosage. In vitro and in vivo treatment with Epigallocatechin-3-gallate (EGCG), a Dyrk1a inhibitor, modulated trisomic NCC deficiencies at embryonic time points. Furthermore, prenatal EGCG treatment normalized some craniofacial phenotypes, including cranial vault in adult Ts65Dn mice. Normalization of Dyrk1a copy number in an otherwise trisomic Ts65Dn mice normalized many dimensions of the cranial vault, but did not correct all craniofacial anatomy. These data underscore the complexity of the gene­phenotype relationship in trisomy and suggest that changes in Dyrk1a expression play an important role in morphogenesis and growth of the cranial vault. These results suggest that a temporally specific prenatal therapy may be an effective way to ameliorate some craniofacial anatomical changes associated with DS.

Cone-Beam Computed Tomography Analysis of Mucosal Thickening in Unilateral Cleft Lip and Palate Maxillary Sinuses.

OBJECTIVE: To compare maxillary mucosal thickening and sinus volumes of unilateral cleft lip and palate subjects (UCLP) with noncleft (nonCLP) controls. DESIGN: Randomized, retrospective study of cone-beam computed tomographs (CBCT). SETTING: University. PATIENTS: Fifteen UCLP subjects and 15 sex- and age-matched non-CLP controls, aged 8 to 14 years. MAIN OUTCOME MEASURE: Following institutional review board approval and reliability tests, Dolphin three-dimensional imaging software was used to segment and slice maxillary sinuses on randomly selected CBCTs. The surface area (SA) of bony sinus and airspace on all sinus slices was determined using Dolphin and multiplied by slice thickness (0.4 mm) to calculate volume. Mucosal thickening was the difference between bony sinus and airspace volumes. The number of slices with bony sinus and airspace outlines was totaled. Right and left sinus values for each group were pooled (t tests, P > .05; n = 30 each group). All measures were compared (principal components analysis, multivariate analysis of variance, analysis of variance) by group and age (P ≤ .016 was considered significant). RESULTS: Principal components analysis axis 1 and 2 explained 89.6% of sample variance. Principal components analysis showed complete separation based on the sample on axis 1 only. Age groups showed some separation on axis 2. Unilateral cleft lip and palate subjects had significantly smaller bony sinus and airspace volumes, fewer bony and airspace slices, and greater mucosal thickening and percentage mucosal thickening when compared with controls. Older subjects had significantly greater bony sinus and airspace volumes than younger subjects. CONCLUSIONS: Children with UCLP have significantly more maxillary sinus mucosal thickening and smaller sinuses than controls.

Estimating the location of the center of resistance of canines.

OBJECTIVE: To develop a method to quickly estimate the location of center of resistance (CR) in mesial-distal (MD) and buccal-lingual (BL) directions from the tooth's image. MATERIALS AND METHODS: The maxillary cone-beam computed tomography (CBCT) scans of 18 patients were used. Finite element (FE) models of the canines and their surrounding tissues were built based on their CBCT scans to calculate the locations of CR. Root length, centroid of the contact surface (CCS), and centroid of projection of the contact surface (CPCS) were also obtained from the images. The CCS and CPCS locations were projected on the tooth's long axis, which were represented as percentages of the root length measured from the root's apex. RESULTS: Using the FE results as the standards, the errors of using CCS or CPCS to estimate CR were calculated. The average location of CR calculated using the FE method was 60.2% measured from the root's apex in the MD direction and 58.4% in the BL direction. The location of the CCS was 60.9%. The difference in CR was 0.7% in the MD direction and 2.5% in the BL direction. The location of CPCS was 60.2% in the MD direction and 59.1% in the BL direction, which resulted in a 0.1% and 0.8% difference with the reference CR, respectively. The average difference of CR in the MD and BL directions was small but statistically significant (P < .05). CONCLUSION: The locations of the CR of a human canine in the MD and BL directions can be estimated by finding the CPCSs in those directions.

The association of malocclusion and trumpet performance.

OBJECTIVE: To determine whether trumpet performance skills are associated with malocclusion. MATERIALS AND METHODS: Following institutional review board approval, 70 university trumpet students (54 male, 16 female; aged 20-38.9 years) were consented. After completing a survey, the students were evaluated while playing a scripted performance skills test (flexibility, articulation, range, and endurance exercises) on their instrument in a soundproof music practice room. One investigator (trumpet teacher) used a computerized metronome and a decibel meter during evaluation. A three-dimensional (3D) cone-beam computerized tomography scan (CBCT) was taken of each student the same day as the skills test. Following reliability studies, multiple dental parameters were measured on the 3D CBCT. Nonparametric correlations (Spearman), accepting P < .05 as significant, were used to determine if there were significant associations between dental parameters and the performance skills. RESULTS: Intrarater reliability was excellent (intraclass correlations; all r values > .94). Although associations were weak to moderate, significant negative associations (r ≤ -.32) were found between Little's irregularity index, interincisal inclination, maxillary central incisor rotation, and various flexibility and articulation performance skills, whereas significant positive associations (r ≤ .49) were found between arch widths and various skills. CONCLUSIONS: Specific malocclusions are associated with trumpet performance of experienced young musicians.