Jotikasthira Crown Angulation
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Jotikasthira Crown Angulation Document Transcript

  • 1. Dhirawat Jotikasthira, BSc, DDS, MDSc1 CROWN ANGULATION AND INCLINATIONPeter Sheffield, BSc, MS 2 OF NORTHERN THAIS WITH GOODAnmol Kalha, OSRE, BSc, BDS, MDS3 OCCLUSION When patients of differing ethnicities are treated with one bracketZameer Syed, BDS, MDS4 system, negative consequences for the occlusion can result. This study investigated the crown angulation and inclination on study casts of 60 Northern Thais (30 males and 30 females) with a good occlusion. In all study casts, each tooth (except the third molars) was evaluated with the orthodontic Torque Angulation Device (TAD) twice on the right side; this was also performed twice on the left side. The mean of the two evaluations was used for the statistical analysis. The means of the males and females were compared with the indepen- dent Student t test. The results were that the crown angulation of the mandibular first and second molars was significantly higher in females (P <.01) and that the crown inclination of all teeth did not dif- fer between the two sexes. World J Orthod 2010:71–74. Key words: crown inclination, crown angulation, Northern Thais, normal occlusion, Torque Angulation Device ccurate bracket positioning is of The or thodontic Torque Angulation A critical importance for biomechan- ics and the realization of the potential Device (TAD) is a device that measures crown angulation and inclination in a of preadjusted edgewise appliances. precise and objective fashion. Precise measurements of crown angu- lation and inclination are crucial for the construction of brackets for a specific MATERIALS AND METHODS1Associate population. Professor, Department of The advent of sophisticated appli- The materials comprised 60 plaster Orthodontics, Faculty of Dentistry, Chiang Mai University, Chiang Mai, ances and materials has helped raise casts and facial and intraoral pho- Thailand. the standard of orthodontic treatment. tographs of Northern Thais (30 males2Manager, TAD Concept & Dental As a result, achieving an ideal occlusion and 30 females) from the Department of Laboratory, Hexa Ceram, Chiang has become a realistic aim. The current Orthodontics, Faculty of Dentistry, Chi- Mai, Thailand.3Dean and Head, Department of concepts of ideal static occlusion are ang Mai University, Thailand. The age Orthodontics, Institute Of Dental based on Andrews’ keys of normal occlu- distribution by sex and the number of Studies and Technology, Dehli, sion, of which crown angulation and teeth are shown in Table 1. India. inclination are important features. 14Tutor, Department of Orthodontics, Andrews stated that if these key factors Inclusion criteria were: Govt. Dental College, J&K, India. are not achieved, there will be a spaceCORRESPONDENCE discrepancy in the dental arch or the • Excellent or good occlusion with nor-Dr Zameer Syed occlusion will be compromised.1 Crown mal overjet and overbiteFaculty of Dentistry angulation and inclination vary among • No or only slight incisor crowdingDepartment of Orthodontics populations. Only one study to date has • Pleasing profileGovernment Dental College and HospitalKaran Nagar described these parameters in Northern • No interproximal caries or extensiveSrinagar 190010 Thais. The measuring device used in this restorationsIndia investigation was a modified protractor.2 • No previous orthodontic intervention 71 © 2009 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
  • 2. Jotikasthira et al WORLD JOURNAL OF ORTHODONTICS Table 1 Mean age (y), standard deviation (SD), minimum, maximum, and sample size separately and combined for both sexes Total Age SD Minimum Maximum subjectsMales 20.18 1.60 16.30 25.90 30Females 19.19 2.62 15.60 28.80 30Combined 20.00 2.30 15.60 28.80 60Fig 1 (right) The orthodontic Torque Angulation Device (TAD). The blade was set tolie along to long axis of the clinical crown by adjusting the fine angulation knob.The crown angulation was read from a digital screen. Seven orthodontists evaluated all curvature of the blade fitted optimally therecords to exclude any subject with an vestibular surface of the tooth beingunacceptable occlusion or facial appear- measured. After this adjustment, theance. crown inclination was displayed. On all casts, all teeth (except the thirdmolars) on the right side were evaluatedtwice with the orthodontic Torque Angula- Statistical methodstion Device (TAD). The evaluation was alsoperformed twice on the left side. The The mean of the first and the secondstudy casts were fixated on an adjustable measurement was used for the statisticaltable with the horizontal occlusal line analysis. If the independent Student t test(HOL) parallel to the TAD platform (Fig 1). showed no significant difference betweenThe HOL is an imaginary line connecting the right and left side, the values fromthe right and left midcrown molar points both sides were combined. The indepen-and the average of the clinical midcrown dent Student t test was also used to com-points of both central incisors. pare the means of the males and The crown angulation was measured females. To test the reliability of the mea-according to Andrews1: The long axis of surements, the intraobserver differenceclinical crown (LACC) was drawn on the was calculated on six randomly selectedlabial surface of the clinical crown of models. Pearson correlation coefficient (r)every tooth (Fig 2). On the LACC of each was 0.978.tooth, the midpoint of the clinical crown(L A point) was marked. It was con-structed by bisecting the height of the RESULTSclinical crown (with 1.0 mm added for thegingival sulcus) on the LACC. Box plots of the crown angulation of all The model was then moved toward the teeth (right and left sides combined) ofblade of the TAD. At the same time, the ta - both sexes are shown in Fig 3. The crownble was adjusted in height. When the blade angulation of the mandibular first andwas running along the LACC, the crown second molars was significantly higherangulation could be read on the display. (P < .01) in females. The crown inclination was recorded by Box plots of the crown inclination of allmoving the model until the middle of the teeth (right and left sides combined) ofblade coincided with the LA point and the both sexes are shown in Fig 4. 72 © 2009 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
  • 3. VOLUME 11, NUMBER 1, 2010 Jotikasthira et al Male maxillary arch Female maxillary arch 1.88 (0.34) 2.79 (0.34) LACC 3.18 (0.48) 4.61 (0.42) A LACC 3.72 (0.54) 3.81 (0.52) 0.07 (0.44) 0.67 (0.50) I 0.42 (0,43) 1.57 (0.49) 0.96 (0,37) 0.74 (0.61) LA point Occlusal plane –1.89 (1.09) –5.17 (1.15) –30 –20 –10 0 10 20 20 10 0 –10 –20 –30Fig 2 Construction of the long axis of the Degrees Degreesclinical crown (LACC) and the midpoint ofthe clinical crown (LA point) to evaluate Central incisor Lateral incisor Canine First premolarcrown angulation (A) and inclination (I). Byconnecting the average of the LA-points of Second premolar First molar Second molarthe two central incisors with the mid-crown Degrees Degreesmolar points, the horizontal occlusal line –30 –20 –10 0 10 20 20 10 0 –10 –20 –30(HOL) is established as a reference line. 7.92 (0.81) 11.17 (0.74) 3.29 (0.52) 6.15 (0.52) 2.18 (0.59) 3.00 (0.52) 0.28 (0.52) 1.66 (0.57) 0.33 (0.52) –0.26 (0.56) 0.05 (0.48) –0.12 (0.49) 0.05 (0.40) –0.19 (0.45)Fig 3 Box plot graphs of the crown angula- Male mandibular arch Female mandibular archtion of all teeth in both sexes (right and leftsides combined). * = significant difference Outlying data P < .01(P < .01) between male and female. DISCUSSION CONCLUSION The values of crown inclination and angu- This study investigated the crown angula- lation measured in this study were simi- tions and inclination of Northern Thais with lar to those of a previous study.2 In the good occlusion. Measurements of each maxillary and mandibular arch, the crown tooth (except third molars) from the study angulations in the present study were casts of 60 subjects (30 males and 30 smaller than those of Andrews,1 except females) were performed twice by using for the first and second molars. the Orthodontic Torque Angulation Device The crown angulation of the central (TAD). The means of both measurements and lateral incisors in the present study were used for statistical analysis. The was greater than that of studies by Vardi- respective values of the two sexes were mon and Lambertz3 and Dellinger.4 compared with the independent Student 73 © 2009 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.
  • 4. Jotikasthira et al WORLD JOURNAL OF ORTHODONTICS Fig 4 Box plot graphs of the crown incli- Male maxillary arch Female maxillary arch 7.32 (0.51) 8.22(0.63) nation of all teeth in both sexes (right and left sides combined). 5.52 (0.61) 6.65 (0.64) –5.50 (0.67) –6.79 (0.65) –7.88 (0.67) –8.33 (0.76) –9.29 (0.62) –9.25 (0.71) –8.39 (0.70) –7.83 (0.72) –11.97 (0.86) –11.90 (0.77) –30 –20 –10 0 10 20 20 10 0 –10 –20 –30 Degrees Degrees Central incisor Lateral incisor Canine First premolar Second premolar First molar Second molar Degrees Degrees –30 –20 –10 0 10 20 20 10 0 –10 –20 –30 –29.15 (0.69) –28.88(0.71) –20.38 (0.95) –20.23 (0.94) –18.38 (0.84) –16.48 (1.04) –14.73 (0.89) –11.52 (0.88) –0.51 (0.85) –2.89 (0.70) 1.16 (0.82) 2.69(0.57) 4.32(0.82) 5.24 (0.66) Male mandibular arch Female mandibular arch Outlying datat test. The results were that females have a REFERENCESsignificantly higher (P < .01) crown angula-tion of the mandibular first and second 1. Andrew LF. The six keys to normal occlusion. Am J Orthod 1972;62:296–309.molars and that there is no significant dif- 2. Duangtaweeesub S, Jotikasthira D. Crownference of the crown inclination of all teeth inclination and crown angulation of northernbetween the two sexes. Thais with good occlusion. CM Dent J 2003; 24:61–67. 3. Vardimon AD, Lambertz W. Statistical evalua- tion of torque angles in reference to straight-ACKNOWLEDGMENTS wire appliance (SWA) theories. Am J Orthod 1986;89:55–66.The authors are grateful to Hexa Ceram, Chiang 4. Dellinger EL. A scientific assessment of theMai Province, Thailand, for providing the Torque straight-wire appliance. Am J Orthod 1978;Angulation Device (TAD). The authors are also 73:290–299.thankful to Dr Piyanart Chatiketu for her sugges-tions concerning statistical analysis. 74 © 2009 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.