- Email: [email protected]
non-vertical growers using CBCT
International Orthodontics 2019; 17: 123–129
Skeletal and dental relationships in vertical/non-vertical growers using CBCT
Original Article
Websites: www.em-consulte.com www.sciencedirect.com
Kacey Tung, Manuel O. Lagravère
Available online: 13 February 2019
Department of Dentistry, University of Alberta, ECHA 5-524, 11405 - 87th avenue, Edmonton, T6G 1C9 Alberta, Canada
Correspondence: Manuel O. Lagravère, School of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, ECHA 5-524, 11405 - 87th avenue, Edmonton, T6G 1C9 Alberta, Canada. [email protected]
Mots clés Croissance verticale Imagerie volumétrique par faisceau conique Orthodontie
Summary The purpose of this study was to determine if there were any common skeletal and dental structural characteristics obtained from CBCTs of patients with different growth patterns (Vertical or Non-Vertical). Sixty-three patients were previously categorized as vertical or not vertical grower using clinical examination and 2D cephalometric created images. Twenty-three landmarks were selected to examine CBCT images and used to calculate linear and angle measurements using geometric and trigonometric equations. Statistical analysis was done using SPSS statistical package and ICC values showed excellent reliability. The calculated linear and angular measurements were not statistically or clinically different between vertical and non-vertical growers. This indicates that other methods may need to be used to determine if a patient is a vertical or non-vertical grower.
Résumé Analyse tomographique CBCT des relations dentaires et squelettiques dans les cas de croissance verticale et non verticale Le but de cette étude était de déterminer s'il existait des caractéristiques dentaires et osseuses structurelles communes d'après les images Cone-Beam Computed Tomography (CBCT) de patients avec différentes typologies de croissance (hyperdivergente ou non). Soixante-trois patients ont préalablement été classés, grâce à l'examen clinique et aux images céphalométriques 2D, en deux catégories selon leur croissance verticale. Vingt-trois repères ont été choisis pour étudier les images du CBCT et calculer les mesures linéaires et angulaires à l'aide d'équations géométriques et trigonométriques. L'analyse statistique a été effectuée à l'aide du logiciel statistique SPSS et les valeurs du coefficient de corrélation intra-classes (ICC) ont montré une excellente fiabilité. Les mesures linéaires et angulaires calculées n'ont pas été statistiquement ou cliniquement différentes entre les patients avec et sans croissance verticale. Cela indique que d'autres méthodes sont souhaitables pour déterminer si un patient a une croissance verticale ou non.
tome 17 > n81 > March 2019 https://doi.org/10.1016/j.ortho.2019.01.007 © 2019 CEO. Published by Elsevier Masson SAS. All rights reserved.
123
Keywords Vertical growth CBCT imaging Orthodontics
124
Original Article
K. Tung, M.O. Lagravère
Introduction Facial growth can be categorized based on the rotation of the mandible. When the mandible presents in a clockwise rotation, it results in excessive vertical growth (in relation to the horizontal plane) and causes reduction of vertical overbite resulting in a hyperdivergent profile, vertical grower [1]. When it presents in a counter clockwise rotation, it results in a deficiency of vertical growth (in relation to the horizontal plane) and causes an increase of vertical overbite resulting in a hypodivergent profile, horizontal grower [1]. Facial growth affects the aesthetics and function of the maxillofacial complex and orthodontists must assess these growth patterns to determine the ideal treatment. The diagnosis and determination of the type of facial growth is in its majority determined using radiographic imaging. Imaging has proven to be very beneficial for dentistry as an adjunct to the clinical exam; it is very helpful in orthodontics regarding diagnosis and treatment planning. Lateral cephalograms, a type of two-dimensional (2D) radiographic view, helps to evaluate the spatial relationships between dental, cranial, and soft tissue features. These features are analysed prior to, during, and after orthodontic treatment for monitoring and to determine effectiveness of the treatment. Landmarks are in these radiographs and with the use of angles and distances between them, have helped categorize common spatial arrangements seen in patients. Unfortunately, these 2D images present limitations due to the complexity of replicating the complex three-dimensional (3D) maxillofacial skeleton. Common issues seen are superimposition of overlying structures and the loss of 3D spatial information, both resulting in less accurate anatomy replications [2]. CBCT (cone-beam computed tomography) uses a cone-shaped x-ray machine and produces 3D images based on the 2D images it gathers as it rotates around the object [2]. CBCT produces high spatial resolution images of the cranial and dental structures for less radiation and cost as opposed to medical CT (computed tomography) [2]. CBCT is proving to be very useful in orthodontics to assess facial growth. Growth patterns have been categorized using angles measured in 2D lateral cephalograms, specifically the angles formed by the mandibular plane (Gonion-Menton) and the cranial base (SellaNasion) have been found to be characteristic in differentiating the different growth patterns [1]. Nevertheless, this categorization cannot be applied to 3D images since it has been made for 2D use. CBCT is advantageous in analysing the spatial relationships. However, there is little research on the specific angles and characteristics of growth patterns using CBCT. There are studies that assessed the correlation of landmarks and angles between conventional and CBCT cephalograms [3]. Park et al. found a linear correlation except for the ANB difference, facial convexity, and the gonial angle, of which is shown to be important in assessing growth patterns [3]. The purpose of this study is to determine common skeletal and dental characteristics of
patients that can help orthodontists determine their growth pattern using CBCTs.
Material and methods CBCT images from sixty-three patients (males and females aged between 11–17 years old) were obtained from the University of Alberta Graduate Orthodontic Program database, which were taken as a standard record for orthodontic diagnosis and treatment planning. Patients were categorized as vertical or nonvertical growers using clinical examination and 2D cephalometric created images from the CBCTs. The parameters used to take the CBCT images include images obtained by iCAT machine (Imaging Sciences International, Hatfield, PA) with a collimation height scan of 13 centimetres, scan time of 8.9 seconds and resolution of 0.3 millimetre voxel size. Twenty-three landmarks were selected (based on traditional and newly suggested landmarks) to examine CBCT images using the AVIZO software (FEI Visualization Sciences Group, Berlin). Figure 1 presents the landmarks and definitions used for the CBCT analysis and figure 2 presents the calculations performed to obtain the specified distances and angles. Reliability and measurement error were determined by analysing ten images three times using intraclass correlation coefficient (ICC). All CBCT images were then analysed and the landmark coordinates were used to calculate linear and angle measurements using geometric and trigonometric equations. Statistical analysis was done using SPSS statistical package (IBM, Armonk, NY).
Results ICC values showed excellent reliability as all twenty-three landmarks had an ICC above 0.97 in all axes. The lowest ICC value was found in the Left Anterior Concavity point, 0.990 (CI 95% 0.970– 0.997). The largest measurement error was 1.62 mm 0.68 found in the y-axis for the Right Anterior Concavity point. The ANOVA test showed that all linear and angular measurements did not present a statistically significant difference between both growth groups (P > 0.05). The Left Anterior Facial Height (A point – B point) showed the greatest difference between the groups; the vertical group was 39.0 mm 3.9 while the non-vertical group was 35.2 mm 4.4 (figure 3). The symphysis thickness (POG–Z point) also showed one of the largest differences; the vertical group was 23.3 mm 3.2 while the non-vertical group was 21.2 mm 2.9. The smallest differences between groups were the Right Posterior Facial Height (S–Right Go) 85.3 mm 4.5 and 86.0 mm 5.6, vertical and non-vertical respectively and the Left Notch Perpendicular distance (1.5 mm 0.8 and 1.3 mm 0.7, vertical and non-vertical respectively) (figure 4). Figures 5–9 illustrate some dimensions measured comparing an example in a vertical grower and a non-vertical grower.
tome 17 > n81 > March 2019
Original Article
Skeletal and dental relationships in vertical/non-vertical growers using CBCT
Figure 1 Landmark and definitions used for the CBCT analysis
The direction of growth of the mandible can significantly affect a person's occlusion and therefore function and aesthetics. Growth is usually defined as vertical resulting in a hyperdivergent profile or horizontal resulting in a hypodivergent profile. Being able to predict a patient's growth pattern is very useful for orthodontists, as interventions can be made earlier to correct skeletal discrepancies at critical time periods to avoid or decrease the amount of surgery or orthodontic treatment needed. Currently, there are multiple indexes used to determine growth patterns using 2D lateral cephalograms including the SnGoGn (mandibular plane) according to Riedel [4] and Ricketts et al.'s VERT index [5]. Lateral cephalograms have also been used to measure certain characteristics, such as symphysis
tome 17 > n81 > March 2019
morphology [6], which contribute to the ability to predict growth patterns. While 2D imaging has proven beneficial, there are some limitations; objects of interests are superimposed by overlying structures and the conversion of a 3D object to a 2D image results in a loss of spatial information [2]. CBCT, 3D imaging, performs one rotation around an object to produce a series of 2D images, which are reconstructed in 3D providing high spatial resolution of bone and teeth. CBCT has less effective radiation compared to conventional CT and is less expensive. CBCT has more radiation than lateral cephalograms, however CBCT provides 3D images from both sides of the face in one scan. With 3D imaging, the goal is if the historical 2D landmarks could be translated to 3D imaging to create diagnostic definitions. Park
125
Discussion
Original Article
K. Tung, M.O. Lagravère
Figure 2 Calculations performed for the CBCT analysis
126
et al. [3] found that linear measurements between the two imaging modalities were not statistically different except for U1 (upper incisor) to facial plane and that the differences in the gonial angle, ANB difference, and facial convexity were clinically significant. The lack of correlation to CBCT for the gonial angle and A and B points, landmarks that were traditionally used to determine growth with lateral cephalograms and used in the current study with CBCT, may have affected the findings with the current study. In the present study, the ICC was high indicating that the landmarks are reliable to locate in CBCT's. However, overall, the differences between the vertical and non-vertical group were statistically and clinically not significant. Lagravère et al. found that landmarks without clearly defined borders resulted in greater measurement errors [7]; the current study had set definitions however between patients, the differences in anatomy and the increase in spatial information from CBCT
may have made choosing the same landmarks on each patient more difficult. For example, the Right Anterior concavity point showed the largest measurement error. Like the current study, Aki et al. [6] found that symphysis morphology, using lateral cephalograms was an accurate predictor of growth which in the current study, the symphysis thickness had one of the greatest differences between the groups. Additionally, the antegonial notch was one of the measurements between the groups resulting in the greatest differences which was similar to Singer et al. [8] who found that the depth of the mandible in lateral cephalograms, when dividing the groups into deep (>3 mm) and shallow (<1 mm) notch groups, could be used as an indicator of mandibular growth potential as they noted a significant difference in facial characteristics between the two groups. In the current study, the vertical group's right and left notch perpendicular distances
tome 17 > n81 > March 2019
Original Article
Skeletal and dental relationships in vertical/non-vertical growers using CBCT
Figure 3 Left anterior facial height (A and B)
Figure 4 Left notch perpendicular distance
tome 17 > n81 > March 2019
measurements used to determine growth were based on populations of extremes and that in a non-extreme population, which orthodontists will see mostly, there were no significant correlations. Kolodziej et al. [9] measured non-ortho treated
127
were respectively, 1.58 1.00 mm and 1.47 0.80 mm. The non-vertical group's right and left notch perpendicular distances were respectively, 1.28 0.83 mm and 1.32 0.70 mm. However, Kolodziej et al. [9] found that previous anatomical
Original Article
K. Tung, M.O. Lagravère
Figures 5˘9 Images to illustrate some dimensions measured comparing an example in a vertical grower and a non-vertical grower
128
subjects at multiple time points (8.5 years, 12 years, and > 17 years) and found the antegonial notch distance did not change much throughout growth and distances ranged from 1.7 0.7 mm–2.0 1.1 mm. The values obtained in the current study were similar to Kolodziej et al. [9] potentially due to the similarity of the age of the subjects, status (no previous orthodontic treatment), and by determining growth patterns with no extreme characteristics.
A limitation in the current study was the inability to create a grid scheme for the CBCTs. There may have been interclass discrepancies as multiple landmarks did not have clearly defined borders. It was difficult and impossible to calculate many of the angles traditionally used in 2D cephalograms due to the 3D nature. Additionally, with the increase in information from CBCT, no one landmark can be used to predict growth potential and multiple factors and definitions will have to be utilized to make a
tome 17 > n81 > March 2019
clinical diagnosis. Due to the increased radiation of CBCT and the principles of ALARA, it was more difficult to obtain normative values for subjects to use as a comparison, which means that all the scans used usually have some sort of malocclusion [10].
Conclusion Growth patterns have traditionally been categorized based on clinical and 2D lateral cephalogram analysis. There have
been some correlations between 2D and 3D landmarks; however, the current study did not find a statistical difference between the vertical and non-vertical group using CBCT landmarks and thus alternate landmarks or methods may need to be utilized.
Original Article
Skeletal and dental relationships in vertical/non-vertical growers using CBCT
Disclosure of interest: the authors declare that they have no competing interest.
References
[2]
[3]
[4]
Schudy FF. The rotation of the mandible resulting from growth: its implications in orthodontic treatment. Angle Orthod 1965;35:36–50. Shah N, Bansal N, Logani A. Recent advances in imaging technologies in dentistry. World J Radiol 2014;6:794–807. Park CS, Park JK, Kim H, Han SS, Jeong HG, Park H. Comparison of conventional lateral cephalograms with corresponding CBCT radiographs. Imaging Sci Dent 2012;42:201–5. Riedel RA. The relation of maxillary structures to cranium in malocclusion and in normal occlusion. Angle Orthod 1952;22:142–5.
tome 17 > n81 > March 2019
[5]
[6]
[7]
Ricketts RM, Roth RH, Chaconas SJ, Schulhof RJ, Engel GA. Bioprogressive technique of Ricketts. Buenos Aires: Panamericana; 1983. Aki T, Nanda RS, Currier GF, Nanda SK. Assessment of symphysis morphology as a predictor of the direction of mandibular growth. Am J Orthod Dentofacial Orthop 1994;106:60–9. Lagravère MO, Low C, Flores-Mir C, et al. Intraexaminer and interexaminer reliabilities of landmark identification on digitized lateral cephalograms and formatted 3-dimensional cone-beam computerized tomography images. Am J Orthod Dentofacial Orthop 2010;137:598–604.
Singer CP, Mamandras AH, Hunter WS. The depth of the mandibular antegonial notch as an indicator of mandibular growth potential. Am J Orthod Dentofacial Orthop 1987;9:117– 24. [9] Kolodziej RP, Southard TE, Southard KA, Casko JS, Jakobsen JR. Evaluation of antegonial notch depth for growth prediction. Am J Orthod Dentofacial Orthop 2002;12:357–63. [10] Gribel BF, Gribel MN, Manzi FR, Brooks SL, McNamara Jr JA. From 2D to 3D: an algorithm to derive normal values for 3-dimensional computerized assessment. Angle Orthod 2011;8:3–10.
[8]
129
[1]
Skeletal and dental relationships in vertical/non-vertical growers using CBCT
Original Article
Websites: www.em-consulte.com www.sciencedirect.com
Kacey Tung, Manuel O. Lagravère
Available online: 13 February 2019
Department of Dentistry, University of Alberta, ECHA 5-524, 11405 - 87th avenue, Edmonton, T6G 1C9 Alberta, Canada
Correspondence: Manuel O. Lagravère, School of Dentistry, Faculty of Medicine and Dentistry, University of Alberta, ECHA 5-524, 11405 - 87th avenue, Edmonton, T6G 1C9 Alberta, Canada. [email protected]
Mots clés Croissance verticale Imagerie volumétrique par faisceau conique Orthodontie
Summary The purpose of this study was to determine if there were any common skeletal and dental structural characteristics obtained from CBCTs of patients with different growth patterns (Vertical or Non-Vertical). Sixty-three patients were previously categorized as vertical or not vertical grower using clinical examination and 2D cephalometric created images. Twenty-three landmarks were selected to examine CBCT images and used to calculate linear and angle measurements using geometric and trigonometric equations. Statistical analysis was done using SPSS statistical package and ICC values showed excellent reliability. The calculated linear and angular measurements were not statistically or clinically different between vertical and non-vertical growers. This indicates that other methods may need to be used to determine if a patient is a vertical or non-vertical grower.
Résumé Analyse tomographique CBCT des relations dentaires et squelettiques dans les cas de croissance verticale et non verticale Le but de cette étude était de déterminer s'il existait des caractéristiques dentaires et osseuses structurelles communes d'après les images Cone-Beam Computed Tomography (CBCT) de patients avec différentes typologies de croissance (hyperdivergente ou non). Soixante-trois patients ont préalablement été classés, grâce à l'examen clinique et aux images céphalométriques 2D, en deux catégories selon leur croissance verticale. Vingt-trois repères ont été choisis pour étudier les images du CBCT et calculer les mesures linéaires et angulaires à l'aide d'équations géométriques et trigonométriques. L'analyse statistique a été effectuée à l'aide du logiciel statistique SPSS et les valeurs du coefficient de corrélation intra-classes (ICC) ont montré une excellente fiabilité. Les mesures linéaires et angulaires calculées n'ont pas été statistiquement ou cliniquement différentes entre les patients avec et sans croissance verticale. Cela indique que d'autres méthodes sont souhaitables pour déterminer si un patient a une croissance verticale ou non.
tome 17 > n81 > March 2019 https://doi.org/10.1016/j.ortho.2019.01.007 © 2019 CEO. Published by Elsevier Masson SAS. All rights reserved.
123
Keywords Vertical growth CBCT imaging Orthodontics
124
Original Article
K. Tung, M.O. Lagravère
Introduction Facial growth can be categorized based on the rotation of the mandible. When the mandible presents in a clockwise rotation, it results in excessive vertical growth (in relation to the horizontal plane) and causes reduction of vertical overbite resulting in a hyperdivergent profile, vertical grower [1]. When it presents in a counter clockwise rotation, it results in a deficiency of vertical growth (in relation to the horizontal plane) and causes an increase of vertical overbite resulting in a hypodivergent profile, horizontal grower [1]. Facial growth affects the aesthetics and function of the maxillofacial complex and orthodontists must assess these growth patterns to determine the ideal treatment. The diagnosis and determination of the type of facial growth is in its majority determined using radiographic imaging. Imaging has proven to be very beneficial for dentistry as an adjunct to the clinical exam; it is very helpful in orthodontics regarding diagnosis and treatment planning. Lateral cephalograms, a type of two-dimensional (2D) radiographic view, helps to evaluate the spatial relationships between dental, cranial, and soft tissue features. These features are analysed prior to, during, and after orthodontic treatment for monitoring and to determine effectiveness of the treatment. Landmarks are in these radiographs and with the use of angles and distances between them, have helped categorize common spatial arrangements seen in patients. Unfortunately, these 2D images present limitations due to the complexity of replicating the complex three-dimensional (3D) maxillofacial skeleton. Common issues seen are superimposition of overlying structures and the loss of 3D spatial information, both resulting in less accurate anatomy replications [2]. CBCT (cone-beam computed tomography) uses a cone-shaped x-ray machine and produces 3D images based on the 2D images it gathers as it rotates around the object [2]. CBCT produces high spatial resolution images of the cranial and dental structures for less radiation and cost as opposed to medical CT (computed tomography) [2]. CBCT is proving to be very useful in orthodontics to assess facial growth. Growth patterns have been categorized using angles measured in 2D lateral cephalograms, specifically the angles formed by the mandibular plane (Gonion-Menton) and the cranial base (SellaNasion) have been found to be characteristic in differentiating the different growth patterns [1]. Nevertheless, this categorization cannot be applied to 3D images since it has been made for 2D use. CBCT is advantageous in analysing the spatial relationships. However, there is little research on the specific angles and characteristics of growth patterns using CBCT. There are studies that assessed the correlation of landmarks and angles between conventional and CBCT cephalograms [3]. Park et al. found a linear correlation except for the ANB difference, facial convexity, and the gonial angle, of which is shown to be important in assessing growth patterns [3]. The purpose of this study is to determine common skeletal and dental characteristics of
patients that can help orthodontists determine their growth pattern using CBCTs.
Material and methods CBCT images from sixty-three patients (males and females aged between 11–17 years old) were obtained from the University of Alberta Graduate Orthodontic Program database, which were taken as a standard record for orthodontic diagnosis and treatment planning. Patients were categorized as vertical or nonvertical growers using clinical examination and 2D cephalometric created images from the CBCTs. The parameters used to take the CBCT images include images obtained by iCAT machine (Imaging Sciences International, Hatfield, PA) with a collimation height scan of 13 centimetres, scan time of 8.9 seconds and resolution of 0.3 millimetre voxel size. Twenty-three landmarks were selected (based on traditional and newly suggested landmarks) to examine CBCT images using the AVIZO software (FEI Visualization Sciences Group, Berlin). Figure 1 presents the landmarks and definitions used for the CBCT analysis and figure 2 presents the calculations performed to obtain the specified distances and angles. Reliability and measurement error were determined by analysing ten images three times using intraclass correlation coefficient (ICC). All CBCT images were then analysed and the landmark coordinates were used to calculate linear and angle measurements using geometric and trigonometric equations. Statistical analysis was done using SPSS statistical package (IBM, Armonk, NY).
Results ICC values showed excellent reliability as all twenty-three landmarks had an ICC above 0.97 in all axes. The lowest ICC value was found in the Left Anterior Concavity point, 0.990 (CI 95% 0.970– 0.997). The largest measurement error was 1.62 mm 0.68 found in the y-axis for the Right Anterior Concavity point. The ANOVA test showed that all linear and angular measurements did not present a statistically significant difference between both growth groups (P > 0.05). The Left Anterior Facial Height (A point – B point) showed the greatest difference between the groups; the vertical group was 39.0 mm 3.9 while the non-vertical group was 35.2 mm 4.4 (figure 3). The symphysis thickness (POG–Z point) also showed one of the largest differences; the vertical group was 23.3 mm 3.2 while the non-vertical group was 21.2 mm 2.9. The smallest differences between groups were the Right Posterior Facial Height (S–Right Go) 85.3 mm 4.5 and 86.0 mm 5.6, vertical and non-vertical respectively and the Left Notch Perpendicular distance (1.5 mm 0.8 and 1.3 mm 0.7, vertical and non-vertical respectively) (figure 4). Figures 5–9 illustrate some dimensions measured comparing an example in a vertical grower and a non-vertical grower.
tome 17 > n81 > March 2019
Original Article
Skeletal and dental relationships in vertical/non-vertical growers using CBCT
Figure 1 Landmark and definitions used for the CBCT analysis
The direction of growth of the mandible can significantly affect a person's occlusion and therefore function and aesthetics. Growth is usually defined as vertical resulting in a hyperdivergent profile or horizontal resulting in a hypodivergent profile. Being able to predict a patient's growth pattern is very useful for orthodontists, as interventions can be made earlier to correct skeletal discrepancies at critical time periods to avoid or decrease the amount of surgery or orthodontic treatment needed. Currently, there are multiple indexes used to determine growth patterns using 2D lateral cephalograms including the SnGoGn (mandibular plane) according to Riedel [4] and Ricketts et al.'s VERT index [5]. Lateral cephalograms have also been used to measure certain characteristics, such as symphysis
tome 17 > n81 > March 2019
morphology [6], which contribute to the ability to predict growth patterns. While 2D imaging has proven beneficial, there are some limitations; objects of interests are superimposed by overlying structures and the conversion of a 3D object to a 2D image results in a loss of spatial information [2]. CBCT, 3D imaging, performs one rotation around an object to produce a series of 2D images, which are reconstructed in 3D providing high spatial resolution of bone and teeth. CBCT has less effective radiation compared to conventional CT and is less expensive. CBCT has more radiation than lateral cephalograms, however CBCT provides 3D images from both sides of the face in one scan. With 3D imaging, the goal is if the historical 2D landmarks could be translated to 3D imaging to create diagnostic definitions. Park
125
Discussion
Original Article
K. Tung, M.O. Lagravère
Figure 2 Calculations performed for the CBCT analysis
126
et al. [3] found that linear measurements between the two imaging modalities were not statistically different except for U1 (upper incisor) to facial plane and that the differences in the gonial angle, ANB difference, and facial convexity were clinically significant. The lack of correlation to CBCT for the gonial angle and A and B points, landmarks that were traditionally used to determine growth with lateral cephalograms and used in the current study with CBCT, may have affected the findings with the current study. In the present study, the ICC was high indicating that the landmarks are reliable to locate in CBCT's. However, overall, the differences between the vertical and non-vertical group were statistically and clinically not significant. Lagravère et al. found that landmarks without clearly defined borders resulted in greater measurement errors [7]; the current study had set definitions however between patients, the differences in anatomy and the increase in spatial information from CBCT
may have made choosing the same landmarks on each patient more difficult. For example, the Right Anterior concavity point showed the largest measurement error. Like the current study, Aki et al. [6] found that symphysis morphology, using lateral cephalograms was an accurate predictor of growth which in the current study, the symphysis thickness had one of the greatest differences between the groups. Additionally, the antegonial notch was one of the measurements between the groups resulting in the greatest differences which was similar to Singer et al. [8] who found that the depth of the mandible in lateral cephalograms, when dividing the groups into deep (>3 mm) and shallow (<1 mm) notch groups, could be used as an indicator of mandibular growth potential as they noted a significant difference in facial characteristics between the two groups. In the current study, the vertical group's right and left notch perpendicular distances
tome 17 > n81 > March 2019
Original Article
Skeletal and dental relationships in vertical/non-vertical growers using CBCT
Figure 3 Left anterior facial height (A and B)
Figure 4 Left notch perpendicular distance
tome 17 > n81 > March 2019
measurements used to determine growth were based on populations of extremes and that in a non-extreme population, which orthodontists will see mostly, there were no significant correlations. Kolodziej et al. [9] measured non-ortho treated
127
were respectively, 1.58 1.00 mm and 1.47 0.80 mm. The non-vertical group's right and left notch perpendicular distances were respectively, 1.28 0.83 mm and 1.32 0.70 mm. However, Kolodziej et al. [9] found that previous anatomical
Original Article
K. Tung, M.O. Lagravère
Figures 5˘9 Images to illustrate some dimensions measured comparing an example in a vertical grower and a non-vertical grower
128
subjects at multiple time points (8.5 years, 12 years, and > 17 years) and found the antegonial notch distance did not change much throughout growth and distances ranged from 1.7 0.7 mm–2.0 1.1 mm. The values obtained in the current study were similar to Kolodziej et al. [9] potentially due to the similarity of the age of the subjects, status (no previous orthodontic treatment), and by determining growth patterns with no extreme characteristics.
A limitation in the current study was the inability to create a grid scheme for the CBCTs. There may have been interclass discrepancies as multiple landmarks did not have clearly defined borders. It was difficult and impossible to calculate many of the angles traditionally used in 2D cephalograms due to the 3D nature. Additionally, with the increase in information from CBCT, no one landmark can be used to predict growth potential and multiple factors and definitions will have to be utilized to make a
tome 17 > n81 > March 2019
clinical diagnosis. Due to the increased radiation of CBCT and the principles of ALARA, it was more difficult to obtain normative values for subjects to use as a comparison, which means that all the scans used usually have some sort of malocclusion [10].
Conclusion Growth patterns have traditionally been categorized based on clinical and 2D lateral cephalogram analysis. There have
been some correlations between 2D and 3D landmarks; however, the current study did not find a statistical difference between the vertical and non-vertical group using CBCT landmarks and thus alternate landmarks or methods may need to be utilized.
Original Article
Skeletal and dental relationships in vertical/non-vertical growers using CBCT
Disclosure of interest: the authors declare that they have no competing interest.
References
[2]
[3]
[4]
Schudy FF. The rotation of the mandible resulting from growth: its implications in orthodontic treatment. Angle Orthod 1965;35:36–50. Shah N, Bansal N, Logani A. Recent advances in imaging technologies in dentistry. World J Radiol 2014;6:794–807. Park CS, Park JK, Kim H, Han SS, Jeong HG, Park H. Comparison of conventional lateral cephalograms with corresponding CBCT radiographs. Imaging Sci Dent 2012;42:201–5. Riedel RA. The relation of maxillary structures to cranium in malocclusion and in normal occlusion. Angle Orthod 1952;22:142–5.
tome 17 > n81 > March 2019
[5]
[6]
[7]
Ricketts RM, Roth RH, Chaconas SJ, Schulhof RJ, Engel GA. Bioprogressive technique of Ricketts. Buenos Aires: Panamericana; 1983. Aki T, Nanda RS, Currier GF, Nanda SK. Assessment of symphysis morphology as a predictor of the direction of mandibular growth. Am J Orthod Dentofacial Orthop 1994;106:60–9. Lagravère MO, Low C, Flores-Mir C, et al. Intraexaminer and interexaminer reliabilities of landmark identification on digitized lateral cephalograms and formatted 3-dimensional cone-beam computerized tomography images. Am J Orthod Dentofacial Orthop 2010;137:598–604.
Singer CP, Mamandras AH, Hunter WS. The depth of the mandibular antegonial notch as an indicator of mandibular growth potential. Am J Orthod Dentofacial Orthop 1987;9:117– 24. [9] Kolodziej RP, Southard TE, Southard KA, Casko JS, Jakobsen JR. Evaluation of antegonial notch depth for growth prediction. Am J Orthod Dentofacial Orthop 2002;12:357–63. [10] Gribel BF, Gribel MN, Manzi FR, Brooks SL, McNamara Jr JA. From 2D to 3D: an algorithm to derive normal values for 3-dimensional computerized assessment. Angle Orthod 2011;8:3–10.
[8]
129
[1]