Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Drs. Lindsay E. Grosso, Morgan Rutledge, Donald J. Rinchuse, Doug Smith, and Thomas Zullo investigate buccolingual inclinations of patients with dolichofacial, brachyfacial, and mesofacial vertical facial growth patterns Abstract Objective: The purpose of this observational study was to investigate whether the buccolingual inclinations of pretreatment orthodontic patients’ occlusions vary for the maxillary and mandibular first molars in accordance with facial patterns (i.e., dolichofacial, brachyfacial, or mesofacial). Materials and Methods: Records of 30 pretreatment orthodontic patients were taken from a population of 523 and divided into three groups of 10 according to vertical facial patterns (dolichofacial, mesofacial, and brachyfacial) based on cephalometric analysis. Pre-existing CBCT images were used to take the following angle measurements relative to the occlusal plane: 1-2)long axis of the maxillary right first molar and maxillary left first molar 3-4)long axis of the mandibular right first molar and mandibular left first molar 5-6)buccal surface of the maxillary right first molar and maxillary left first molar 7-8)buccal surface of the mandibular right first molar and mandibular left first molar Lindsay E Grosso, DMD, MBA, is a graduate of Seton Hill University Center for Orthodontics, Greensburg, Pennsylvania. Morgan Rutledge, DMD, MS, is a graduate of Seton Hill University Center for Orthodontics, Greensburg, Pennsylvania. Donald J Rinchuse, DMD, MS, MDS, PhD, is Professor and Program Director, Seton Hill University Center for Orthodontics, Greensburg, Pennsylvania. Doug Smith, DMD, MDS, is Clinical faculty, Seton Hill University Center for Orthodontics, Greensburg, Pennsylvania. Thomas Zullo, PhD is Adjunct Professor, Seton Hill University Center for Orthodontics, Greensburg, Pennsylvania. Volume 5 Number 2 Educational aims and objectives The aim of this article is to discover whether the buccolingual inclinations of pretreatment orthodontic patients’ occlusions vary for the maxillary and mandibular first molars in accordance with facial patterns (i.e., dolichofacial, brachyfacial, or mesofacial). Expected outcomes Correctly answering the questions on page 49, worth 2 hours of CE, will demonstrate the reader can: • Review some of Andrews’ “The Six Keys to Normal Occlusion.” • Compare differences in buccolingual inclinations of maxillary and mandibular first molars in pretreatment patients with dolichofacial, brachyfacial, and mesofacial vertical facial growth patterns. • Recognize if orthodontists may need to implement bracket prescriptions for dolichofacial patients with greater mandibular buccal crown torque and, subsequently, greater maxillary buccal crown torque to keep cuspal heights of molars more even. • Realize the various concepts that are in use regarding tooth and arch parameters related to facial type. • Identify the American Board of Orthodontics’ measuring gauge that scores the buccolingual inclinations of maxillary and mandibular first molars. Three additional measurements were analyzed at a separate time: 1-2) the right angle of the mandible and the left angle of the mandible, and 3)the buccolingual cuspal height differences of the mandibular first molars. Results: Multivariate analysis of variance (MANOVA) indicated statistical significant differences (p = .019) between the buccolingual cuspal height differences of the mandibular first molars (known as buccolingual inclinations of the mandibular molars to the American Board of Orthodontics) relative to the occlusal plane. The pretreatment orthodontic patients with a dolichofacial vertical pattern showed greater lingual crown inclination with respect to the mandibular molars than brachyfacial and mesofacial types. Conclusions: If the American Board of Orthodontics (ABO) is correct in its assessment of the buccolingual inclination of molars, orthodontists may need to implement bracket prescriptions for dolichofacial patients with greater mandibular buccal crown torque and, subsequently, greater maxillary buccal crown torque to keep cuspal heights of molars more even. Introduction For years orthodontists have tried to mainstream clinical practice while maintaining the quality and long-term stability of treatment. One development that revolutionized orthodontics was the straight-wire appliance. In 1972, Dr. Lawrence Andrews published his classic article entitled “The Six Keys to Normal Occlusion,” in which he described the results of his static occlusion study of 120 non-orthodontic dental casts with “normal” untreated occlusion, juxtaposed with 1,150 posttreatment American Board of Orthodontics’ dental casts.1 His study was an effort to discern what characteristics were common among the 120 naturally occurring optimal occlusions (no orthodontic treatment), as compared to very successfully treated orthodontic case occlusions. Subsequently, Andrews’ “Six Keys” findings led to the development of the straight-wire appliance. Andrews’ third of his six keys discussed standards for crown inclination Orthodontic practice 43 CONTINUING EDUCATION Buccolingual inclinations of maxillary and mandibular first molars in relation to facial pattern CONTINUING EDUCATION Measurement Dolichofacial Brachyfacial Mesofacial FMA (MP-FH) (°) 22.9 - 31.8 2.4 - 14.1 19.2 - 28.9 Palatal-Mand Angle (PP-MP) (°) 25.4 - 40.8 7.5 - 23.8 26.1 - 36.6 Gonial/Jaw Angle (Ar-Go-Me) (°) 116.7 - 149.7 109.8 - 130.7 119.1 - 133.2 P-A Face Height (S-Go/N-Me) (%) 56.5 - 64.5 68.8 - 81.2 59.5 - 68.2 RH/LFH (ArGo/ANSMe) (%) 62.2 - 84.1 80.7 - 111.0 66.0 - 85.2 Table 1: Range of cephalometric values for the 10 patients in each facial pattern group Group Males Females Average Age Dolichofacial 6 4 13.76 Brachyfacial 6 4 15.79 Mesofacial 3 7 15.31 Table 2: Number of males and females, and average ages for each group in “optimal” occlusions, and as he noted, the maxillary and mandibular posterior crowns were lingually inclined, albeit to varying degrees.1 Recall, Andrews-judged inclination, or facial-lingual “slanting” of the teeth, from the crowns of the teeth, not the long axis through the roots of the teeth as can be gleaned from radiographic imaging. Lingual inclination of the maxillary posterior teeth from canine to molar was found to be relatively constant with slightly more inclination in the molars, while inclination of the mandibular molars progressively increased from the canine to second molar.1 A question in search of an answer is whether the same buccolingual inclination is appropriate for most patients, considering variation in facial/skeletal types and alveolar bone structure in a given patient population. More specifically, each bracket prescription is manufactured to position teeth with specified inclinations, assuming that brackets are bonded to ideal position on each tooth with little to no variability in facial surface contours for those teeth, and 44 Orthodontic practice that clinicians use full-size wires. Controversy has existed for years regarding tooth and arch parameters related to facial type. It is widely accepted that dolichofacial patients have narrower arches, higher-arched palates, and more tendency toward open bite and significantly smaller maximum biting force, while brachyfacial patients tend toward deep bites and have much stronger maximum biting force.2,3 Some authors have suggested that patients with long lower anterior face heights (i.e., dolichofacial) have molars that are more upright buccolingually, whereas patients with short lower anterior face heights (i.e., brachyfacial) have molars that are more lingually inclined.4,5 Janson, et al.,6 found that when dental casts from patients with different facial patterns were studied, “maxillary posterior teeth in subjects with vertical growth patterns (dolichofacial) [had] a statistically significantly greater buccal inclination as compared with those with horizontal growth patterns (brachyfacial).” They did not find any statistically significant differences in inclination of mandibular posterior teeth between the groups. Janson, et al.,6 takes this concept further and argues that because there tends to be greater palatal inclination in upper molars of brachyfacial patients, they can withstand more palatal expansion since a common collateral effect of rapid palatal expansion is buccal tipping of molars. This implies that greater expansion and potential buccal tipping could be carried out for brachyfacial patients without causing harm to the molars that have been tipped. However, the brachyfacial patients are typically the ones with wider arches who are less likely to need expansion. Conversely, Ross, et al.,7 found that there were no statistically different buccolingual inclinations of maxillary or mandibular molars between different vertical growth patterns when dental casts were used to evaluate crown inclinations. Furthermore, Tsunori4 argues that patients with long-face patterns have comparatively more narrow arches yet have tongue sizes similar to those patients with shortface patterns. The more narrowed arches allows the tongue to have a greater effect on the buccolingual inclination of the teeth by placing force on the molars and uprighting the teeth.4 Additionally, some conjecture that the weaker musculature of the dolichofacial pattern8,9,10 could prevent tipping of the molars or at least provide less resistance to the forces from the tongue.4 To this end, many “non-extractionists” believe that if the mandibular molars are lingually inclined, there is a need to upright these teeth and expand the dental arches, regardless of natural variations in inclination that may not yet be known.11 It should be mentioned that the final inclination of the posterior teeth is not solely dependent on prescription; final tooth position also depends on variables including appliance slot size, archwire size, anterior tooth inclination, arch width, Curve of Wilson, and so on. Nonetheless, further investigations are needed to determine whether certain aspects of treatment — such as inclination — can be standardized, while other aspects must continue to be prescribed for each individual patient. The purpose of this study was to investigate whether the buccolingual inclinations of maxillary and mandibular first molars in pretreatment orthodontic patients vary according to patients’ vertical facial patterns (i.e., brachyfacial, mesofacial, or dolichofacial). The null hypothesis was that there are no statistically significant Volume 5 Number 2 differences in the buccolingual inclinations of mandibular or maxillary first molars relative to vertical facial patterns. Materials and methods After receiving Institutional Review Board (IRB) approval, 30 patient records were selected by a single examiner (M.R.) from a total of 523 patients with pre-existing i-CAT® (Imaging Sciences International) cone beam computed tomography (CBCT) images available at a private practice in Pennsylvania. These 30 patient records were chosen because they highly characterized the three facial types, i.e., brachyfacial, mesofacial, or dolichofacial. The sample consisted of Caucasian patients with pretreatment CBCT images available, a fully erupted permanent dentition, no missing or impacted teeth with the exception of third molars, no significant molar rotations, no posterior crossbite and no previous orthodontic treatment. All pretreatment lateral cephalometric images were traced by one examiner (D.S.) using Dolphin Imaging 11.7 software (Dolphin Imaging & Management Solutions, a Patterson Technology). A separate cephalometric analysis was created in Dolphin Imaging to evaluate and categorize the vertical facial pattern of each patient and included FMA (MP-FH), palatal mandibular angle (PPMP), gonial/jaw Angle (Ar-Go-Me), P-A face height (S-Go/N-Me) expressed as a percentage and RH/LFH (ArGo/ANSMe) expressed as a percentage (Table 1). Volume 5 Number 2 Using these cephalometric measurements, 10 subjects out of the 523 who could be best characterized to represent each facial type (i.e., brachyfacial, mesofacial, or dolichofacial) were selected for a total of 30 subjects. When possible, those selected for the brachyfacial and dolichofacial groups had cephalometric measurements that were two standard deviations beyond the corresponding normal values (Table 1). The mesofacial group included subjects with values within the normal range for at least two measurements, and no values more than one standard deviation away from normal (Table 1). The subjects were between the ages of 11 and 20 years. The group consisted of 15 males and 15 females; six males and four females in the dolichofacial and brachyfacial groups, and three males and seven females in the mesofacial group (Table 2). Existing cone beam images were retrieved for each patient; extraneous portions of the images were removed; and a slice was taken to bisect the maxillary and mandibular first molars. The image was positioned with the occlusal plane perpendicular to the floor and rotated to view the first molars from the distal (Figure 1). The occlusal plane was established by drawing a line to connect the buccal cusp tips of the mandibular molars. CBCT images were used to take the following angle measurements relative to the occlusal plane (Figure 2,1-2) long axis of the maxillary right first molar and maxillary left first molar 3-4) long axis of the mandibular right first molar and mandibular left first molar 5-6) buccal surface of the maxillary right first molar and maxillary left first molar 7-8) buccal surface of the mandibular right first molar and mandibular left first molar The first four angles measured were the inner angles formed by the long axes of the four first molars (including crown and root). The other four measurements consisted of four inner angles formed between the occlusal surface and lines tangent to the buccal surface of the clinical crowns of each first molar. The CBCT images were also used to take three additional measurements relative to the occlusal plane that were analyzed at a separate time from the aforementioned measurements: (9-10) the right angle of the mandible and the left angle of the mandible, and 11) the buccolingual cuspal height differences of the mandibular first molars (Figure 3). The right and left angles of the mandible were measured by using the inside angle of a line drawn to bisect the mandible on both sides and the established occlusal plane. The buccolingual cuspal height differences of the mandibular first molars (known as buccolingual inclinations of the mandibular molars to the American Board of Orthodontics) was established for each subject by drawing a line from the buccal cusp of the left mandibular first molar to the buccal cusp of the right mandibular first Orthodontic practice 45 CONTINUING EDUCATION Figure 1: Sample CBCT of the angle measurement of the buccolingual cuspal height differences of the mandibular first molars. The measurement was established by drawing a line from the buccal cusp of the left mandibular first molar to the buccal cusp of the right mandibular first molar and a line from the lingual cusp of the left mandibular first molar to the lingual cusp of the right mandibular first molar, and then measuring the vertical distance between the two lines at the center Figure 2: Schematic of measurement taken on CBCT images. 1-2) Example of long axis of the maxillary right first molar and maxillary left first molar, 3-4) long axis of the mandibular right first molar and mandibular left first molar, 5-6) buccal surface of the maxillary right first molar and maxillary left first molar, 7-8) buccal surface of the mandibular right first molar and mandibular left first molar Figure 3: Schematic of measurement taken on CBCT images. 9-10) Example of angle measured from the occlusal plane to a line bisecting the mandible on right and left sides. 11) Milimeter measurement found by drawing a line from the buccal cusp of the left mandibular first molar to the buccal cusp of the right mandibular first molar and a line from the lingual cusp of the left mandibular first molar to the lingual cusp of the right mandibular first molar, and then measuring the vertical distance between the two lines at the center CONTINUING EDUCATION Facial Type UR6 UL6 B UR6 B UL6 LR6 LL6 B LR6 B LL6 N Mean Std. Deviation DOLICHOFACIAL 10 87.000 5.5638 BRACHYFACIAL 10 89.490 54.384 MESOFACIAL 10 88.990 5.4204 Total 30 88.493 5.3945 DOLICHOFACIAL 10 82.960 6.9451 BRACHYFACIAL 10 86.950 6.2179 MESOFACIAL 10 84.440 4.4410 Total 30 84.783 5.9912 DOLICHOFACIAL 10 89.350 4.9417 BRACHYFACIAL 10 94.600 10.9191 MESOFACIAL 10 96.250 8.8862 Total 30 90.203 12.7814 DOLICHOFACIAL 10 86.560 13.4257 BRACHYFACIAL 10 94.020 8.9674 MESOFACIAL 10 94.030 15.3190 Total 30 90.203 12.7814 DOLICHOFACIAL 10 105.420 6.2833 BRACHYFACIAL 10 102.900 2.7793 MESOFACIAL 10 102.570 2.8956 Total 30 103.630 4.3506 DOLICHOFACIAL 10 104.650 7.1581 BRACHYFACIAL 10 105.550 5.6086 MESIOFACIAL 10 105.550 5.6086 Total 30 104.247 5.4387 DOLICHOFACIAL 10 124.920 5.8719 BRACHYFACIAL 10 125.790 12.4512 MESOFACIAL 10 126.160 12.0418 Total 30 125.623 10.2027 DOLICHOFACIAL 10 130.090 13.7909 BRACHYFACIAL 10 131.010 7.9442 MESOFACIAL 10 131.330 10.4192 Total 30 130.810 10.6107 F Value Between Subjects 0.579 1.145 1.750 0.846 Results 1.312 0.796 0.036 0.034 Table 3: Descriptive Statistics for molar inclination measurements All findings were Insignificant. F = .933 for the MANOVA. Code: UR6 = Maxillary Right 1st Molar, UL6 = Maxillary Left 1st Molar, B UR6 = Buccal Surface of Maxillary Right 1st Molar, B UL6 = Buccal Surface of Maxillary Left 1st Molar, LR6 = Mandibular Right 1st Molar, LL6 = Mandibular Left 1st Molar, B LR6 = Buccal Surface of Mandibular Right 1st Molar, B LL6 = Buccal Surface of Mandibular Left 1st Molar 46 Orthodontic practice molar and a line from the lingual cusp of the left mandibular first molar to the lingual cusp of the right mandibular first molar, and then measuring the vertical distance between the two lines at the center. In total there were 11 measurements taken using the CBCT images. All measurements were taken by the same examiner (M.R.). Standard descriptive statistics were calculated for each measurement, which included the mean and standard deviation for each variable analyzed. A multivariate analysis of variance (MANOVA) was first used to test for differences in angles formed by the long axes and buccal surfaces of the teeth across the three facial types, as measured in the first eight measurements. A separate MANOVA was used to test for differences in angles for the right and left sides of the mandible, and the buccolingual cuspal height differences of mandibular molars. A Bonferroni (post hoc) test was also used done to account for multiple comparisons. The data were analyzed with IBM SPSS v.19 software. Regarding the first set of data, the largest mean angles measured for the long axis of the maxillary first molars were found in the brachyfacial type, with mean measurements of 89.490° for the maxillary right first molar (UR6) and 86.950° for the maxillary left first molar (UL6). The highest mean angles measured for the line tangent to the buccal surfaces of the maxillary first molars were found in the mesofacial group, with means of 96.250° (B UR6) and 94.030° (B UL6). For the long axis measurements of the mandibular arch, no facial type consistently had the largest or smallest angles, and it should be noted that there is very little difference among the mean values for the three facial types for these two measurements (Table 3). For the second set of data, the highest mean measured for the buccolingual cuspal height differences of the mandibular molars was found in the dolichofacial group, with a mean of 2.010 mm. The brachyfacial group again had the smallest measurement for buccolingual inclinations, with a mean of 1.030. Although the mesofacial group fell in the middle with a mean of 1.100, this measurement is very close to the mean brachyfacial measurement, and both are almost half of the dolichofacial group mean (Table 4). Volume 5 Number 2 Discussion The results of the present study demonstrated that in this particular population of pretreatment orthodontic patients, there was only a statistically significant difference with respect to buccolingual cuspal heights of the mandibular first molars among facial types. The dolichofacial group demonstrated more lingual crown inclination of mandibular molars leading to greater cuspal height differences as compared to the brachyfacial and mesofacial groups. The null hypothesis was therefore rejected. Isaacson, et al.,12 argued that patients with vertical facial patterns had narrower maxillae and were therefore more likely to be in posterior crossbite. This argument further supports the results of this study showing that buccolingual cuspal height differences should be greater for dolichofacial patients due to the narrow maxilla and other facial aspects that go along with the vertical pattern. Conversely, Janson et al.,6 found that when dental casts from patients with different facial patterns were measured, “maxillary posterior teeth in subjects with vertical growth patterns [had] a statistically significantly greater buccal inclination as compared with those with horizontal growth patterns.” They did not find any statistically significant differences in inclination of mandibular teeth between the groups. The results of the present study Volume 5 Number 2 Facial Type N Mean Std. Deviation DOLICHOFACIAL 10 111.62 5.1865 BRACHYFACIAL 10 106.13 4.8208 R Md ° 1.283 MESOFACIAL 10 108.04 11.4642 Total 30 108.597 7.8553 DOLICHOFACIAL 10 111.25 5.7504 BRACHYFACIAL 10 105.02 4.4758 MESIOFACIAL 10 108.26 6.5554 Total 30 108.117 6.0425 DOLICHOFACIAL 10 2.01 0.6740 BRACHYFACIAL 10 1.03 0.7646 MESIOFACIAL 10 1.100 0.6342 Total 30 1.380 0.8083 3.032 L Md° Cuspal 6.222* Height Diff. (mm) F Value Table 4: Descriptive Statistics for mandibular measurements Data revealed statistically significant differences among the facial types for the set of three variables for the MANOVA (F = 2.812, p = .019). Code: R Md° = Right mandibular angle, L Md° = Left mandibular angle, CHD of Md molars = Cuspal Height Difference of mandibular molars support Janson’s6 findings that there were no significant differences in the buccal inclinations of the maxillary teeth of any facial type. However, the present study demonstrates significant differences were found in the buccolingual cuspal height differences of the mandibular first molars among facial types, while Janson’s6 study did not study this particular variable. The findings of the present study are clinically relevant with respect to the American Board of Orthodontics grading system of clinical treatment outcomes for board certification. As previously mentioned, the buccolingual cuspal height differences of the mandibular first molars (known as the buccolingual inclination of the mandibular molars according to American Board of Orthodontics)13 were measured in the present study by drawing a line from the buccal cusp of the left mandibular first molar to the buccal cusp of the right mandibular first molar and a line from the lingual cusp of the left mandibular first molar to the lingual cusp of the right mandibular first molar, and then measuring the vertical distance between the two lines at the center. Currently, the American Board of Orthodontics utilizes a measuring gauge to score the buccolingual inclinations of maxillary and mandibular first molars.13 According to the model grading system, the gauge is placed on the occlusal surface of the right and left posterior teeth and should contact the buccal cusps of the mandibular first molars. With the gauge in place, the lingual cusp should be within 1 mm of the surface of the straight edge. If the mandibular lingual cusps are between 1 mm and 2 mm from the straight-edge surface, 1 point will be scored for that tooth; and if it is more than 2 mm from the straight edge surface, 2 points will be scored for that tooth. High scores on individual segments or combinations of segments can lead to a failure from the Board.13 The ABO states in the model grading system, “The buccolingual inclination is used to Orthodontic practice 47 CONTINUING EDUCATION Although some patterns were noted in the measurements of the first set of data, results of the MANOVA analysis revealed no statistically significant differences among the three facial types for any of the first eight angles measured (F = .933, p = .540) (Table 3). The MANOVA analysis for the second set of data revealed statistically significant differences among the facial types for the set of three variables (F = 2.812, p = .019) (Table 4). The tests of between subjects effects further revealed a statistically significant difference among the buccolingual cuspal height differences of the mandibular molar measurements for the three facial types. The Bonferroni (post hoc) test showed the buccolingual cuspal height differences of the dolichofacial group to be significantly larger, indicating more lingual crown torque of mandibular first molars, than the brachyfacial (p = .012) and mesofacial (p = .020) groups with no statistically significant differences between the brachyfacial and mesofacial groups. CONTINUING EDUCATION assess the buccolingual angulation of the posterior teeth. In order to establish proper occlusion in maximum intercuspation and avoid balancing interferences, there should not be a significant difference between the heights of the buccal and lingual cusps of maxillary and mandibular molars and premolars.”14 However, due to differing schools of thought on occlusal intercuspation and balancing interferences, the stance taken by the Board is equivocal and not supported by high quality evidence.15 If in fact the ABO is correct in its assessment of buccolingual inclination of molars, orthodontists may need to properly diagnose dolichofacial patients and implement bracket systems for these patients that would achieve more buccal crown torque. This would allow for less cuspal height differences of maxillary and mandibular molars, avoid balancing interferences due to plunging lingual cusps, and permit practitioners to achieve treatment results in line with standards set by the ABO. However, another thought could be that the ABO may need to look into revising the grading system with respect to the buccolingual inclinations of the mandibular first molars in patients with dolichofacial vertical patterns, since this view is not unequivocally supported by evidence. Currently in orthodontics, a straightwire appliance with one prescription for buccolingual inclination of maxillary and mandibular first molars is usually used, irrespective of vertical facial pattern. However, according to the present study’s findings, there were statistically significant differences in the initial buccolingual cuspal height differences of mandibular first molars for dolichofacial patterns. It can be argued that if only one prescription is being utilized, buccolingual cuspal height differences of mandibular molars in patients with true dolichofacial patterns may result in balancing interferences with maxillary molar cusps posttreatment unlike their brachyfacial and mesofacial counterparts. There were several limitations of this study. Ideally, a larger sample of subjects in each of the three facial types would have been preferred. However, the method in the present study allowed the researchers to select the best characterized 30 subjects from the total of 523 patients in a private practice office. While additional subjects could have been included in this study from the 523 study population, they would not have represented the facial type’s groupings as well. Next, researchers have been recently working to develop standards for evaluating and measuring CBCT.16,17 Thus far, no standards are universally accepted among the orthodontic community regarding orientation and reference planes for CBCT images. Nonetheless, even with the lack of subjects in each sample group, statistical significance was still found in the buccolingual cuspal height differences of mandibular molars among the three facial types. The dolichofacial group was found to be significantly larger than the brachyfacial and mesofacial groups. Future investigations are still needed to test additional angles and measurements in an effort to discern any existing relationships. Perhaps determination of a common method for selecting patients for facial pattern would increase reliability and validity. Conclusions The present study compared differences in buccolingual inclinations of maxillary and mandibular first molars in pretreatment patients with dolichofacial, brachyfacial, and mesofacial vertical facial growth patterns. The results indicate that there were statistically significant differences in the buccolingual cuspal height differences of the mandibular first molars (known as the buccolingual inclination of the molars according to the ABO) among the three facial types. The dolichofacial patients in a group of pretreatment orthodontic patients demonstrated greater cuspal height differences and more lingual crown inclination of mandibular, and subsequently maxillary molars than the mesofacial or brachyfacial patients. OP References 1. Andrews LF. The six keys to normal occlusion. Am J Orthod. 1972;62(3):296-309. 2. Pepicelli A, Woods M, Briggs C. The mandibular muscles and their importance in orthodontics: a contemporary review. Am J Orthod Dentofacial Orthop. 2005;128(6):774-780. 3. Proffit WR, Fields HW Jr. Contemporary Orthodontics. 2nd ed. Saint Louis: Mosby; 1992. 7. Ross VA, Isaacson RJ, Germane N, Rubenstein LK. Influence of vertical growth pattern on faciolingual inclinations and treatment mechanics. Am J Orthod Dentofacial Orthop. 1990;98(5):422-429. 8. Proffit WR, Fields HW. Occlusal forces in normal- and long-face children. J Dent Res. 1983;62(5):571-574. 9. Ingervall B, Helkimo E. Masticatory muscle force and facial morphology in man. Arch Oral Biol. 1978;23(3):203-206. 4. Tsunori M, Mashita M, Kasai K. Relationship between facial types and tooth and bone characteristics of the mandible obtained by CT scanning. Angle Orthod. 1998;68(6):557-562. 10. Proffit WR, Fields HW, Nixon WI. Occlusal forces in normal- and long-face adults. J Dent Res. 1983;62(5):566-570. 5. Okada N, Kasai K. Relationship between mandibular tooth inclination and maxillofacial morphology using CT scanning [in Japanese]. Nihon Univ J Oral Sci. 1996;22:381-392. 11. Rinchuse DJ, Kandasamy S. Implications of the inclination of the mandibular first molars in the extractionist versus expansionist debate. World J Orthod. 2008;9(4):383-390. 6. Janson G, Bombonatti R, Cruz KS, Hassunuma CY, Del Santo M Jr. Buccolingual inclinations of posterior teeth in subjects with different facial patterns. Am J Orthod Dentofacial Orthop. 2004;125(3):316-322. 12. Isaacson JR, Isaacson RJ, Speidel TM, Worms FW. Extreme variation in vertical facial growth and associated variation in skeletal and dental relations. Angle Orthod. 1971;41(3):219-229. 48 Orthodontic practice 13. American Board of Orthodontics. Grading System for Dental Casts and Panoramic Radiographs. St. Louis, MO; 2012. 14. Casko JS, Vaden JL, Kokich VG, Damone J, James RD, Cangialosi TJ, Riolo ML, Owens SE Jr, Bills ED. Objective Grading System for Dental Casts and Panoramic Radiographs. American Board of Orthodontics. Am J Orthod Dentofacial Orthop. 1998;114(5):589-599. 15. Rinchuse DJ, Kandasamy S, Sciote J. A contemporary and evidence-based view of canine protected occlusion. Am J Orthod Dentofacial Orthop.2007;132(1):90-102. 16. Tong H, Enciso R, Van Elslande D, Major PW, Sameshima GT. A new method to measure mesiodistal angulation and faciolingual inclination of each whole tooth with volumetric cone-beam computed tomography images. Am J Orthod Dentofacial Orthop. 2012;142(1):133-143. 17. Miner RM, Al Qabandi S, Rigali PH, Will LA. Conebeam computed tomography transverse analysis. Part 1: Normative data. Am J Orthod Dentofacial Orthop. 2012;142(3):300-307. Volume 5 Number 2