C axis; a growth vector for maxilla
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The document discusses the c-axis and g-axis as growth vectors for the maxilla and mandible respectively, emphasizing their importance in cephalometric analysis for understanding malocclusion. It details the methodology, results, and conclusions from studies of maxillary and mandibular growth, demonstrating significant growth patterns in males and females during adolescence. The findings indicate that while both axes allow for quantification of complex craniofacial growth, growth dynamics differ based on gender and age, with specific growth rates reported for each gender.
C axis; a growth vector for maxilla
- 1. C- Axis : A growth vector for the Maxilla. Stanley Braun : Angle Orthod : 1999 www.indiandentalacademy.com
- 2. Introduction •Cephalometric analysis is important in orthodontics because it helps the clinician to understand the factors that may contribute to malocclusion . •Downward & forward migration often used in describing maxillary growth but imprecisely used. Nanda & Merill proposed “M” point constructed point representing the centre of largest circle that is tangent to the superior anterior & palatal surfaces of the maxilla in sagittal plane. www.indiandentalacademy.com
- 3. • “M” point - A geometrically defined point within the maxillary complex, would permit a description of the natural loci of this complex in relation to craniofacial structures during growth & development. www.indiandentalacademy.com
- 4. C axis : > A linear line from sella to M point. > The purpose of this investigation was to study the natural changes in position of M point in relation to anterior cranial base (S-N) using polar coordinates in combination with the palatal plane. Objective : It provides a quantitative description of the anterior & downward migration of the maxilla associated with growth. www.indiandentalacademy.com
- 6. Materials and Methods : • Lateral ceph 19 males & 20 females, • Age group 7.4 to 18.75 years from Mooseheart growth study, Chicago, illinois • no history of orthodontic intervention • “M” point determined on transparent template containing a no of circle whose diameter increased in 1mm increments. • The best fit circle was selected. www.indiandentalacademy.com
- 8. Discussion : Chronological growth along the C axis Based on slope of linear regression formula. upto age 14. C Axis in males increased at a rate of 1.14 mm /year. C axis in females increased at rate of 1.13mm/year Regression formula suggest growth along C axis tends to cease at age 16 years in females. In males increased through out the age of selected age group. www.indiandentalacademy.com
- 10. Increases for both males and females throughout the age studied. It is relatively small. For males - 3.980 Females - 2.250 Linear regression formula suggests no statistically significant difference in growth axis angle. Growth axis angle (C axis - SN) V/s Chronological age. www.indiandentalacademy.com
- 11. Conclusion •C axis permits the quantification of complex maxillary growth in Cephalometric terms relative to various craniofacial structures in the sagittal plane. C axis angle is independent of gender within the chronological age studied. > www.indiandentalacademy.com
- 12. • C axis however are related to gender up to age 14 in males and females display average yearly growth increments of 1.14mm and 1.13 mm per year respectively . • After age 14 growth increments in females tends to diminish and cease at the age of 16 years. • In males growth along the C axis continues linearly throughout the age range studied. www.indiandentalacademy.com
- 14. ∝ angle = θ - Ǿ www.indiandentalacademy.com
- 15. • Single point “M” cannot by itself summarized the growth of the dento maxillary in the sagittal plane • However when associated with the palatal plane the downward and forward migration is more accurately described than previously possible. www.indiandentalacademy.com
- 17. ∀∝ angle tends to flatten the palatal plane with respect to the C axis during growth and development. www.indiandentalacademy.com
- 18. • The C-axis incremental growth change & its vector offer a means of quantifying complex maxillary growth in the sagittal plane via cephalometric measurements relative to & co-ordinated with other craniofacial structures www.indiandentalacademy.com
- 19. The G axis ; A growth vector for the mandible: Stanley Braun et al. Angle Orthod : 2004 www.indiandentalacademy.com
- 20. Growth of the mandible : > Expressed through the resorption & deposition at periosteal & endosteal surfaces. > Cartilage replacement by bone at the condyle & dental eruption accompanied by growth of alveolar bone. > Net result for this is the downward & forward displacement of the mandible. > This displacement quantified to a degree through the description of the Y-Axis (S-GN) Introduction : www.indiandentalacademy.com
- 21. It is noted that usefulness of the Y-axis has been questioned because of extensive remodeling of the external symphyseal area. > This study was undertaken to establish an improved descriptive growth axis for the mandible. > Length of the axis is determined by sella to G point > G point is defined as a point representing the center of the largest circle that is tangent to the internal inferior, anterior & posterior surfaces of the mandibular symphyseal region. www.indiandentalacademy.com
- 23. • G Axis vector (Direction) is defined by the angle α which G axis establishes relative to the sella-nasion. ∀ θ angle: It is the angle between the mandibular plane to the S-G point. • Use of the three dimensions ∝, θ, & length of the G axis provides a quantitative description of the anterior & downward migration of the mandible related to growth & maturation. www.indiandentalacademy.com
- 24. Methods & Materials : > Serial lateral ceph of 24 males & 24 females. > Age group 6 to 19.25 years without orthodontic intervention. > ANB angle – 1 to 5o . > Ratio of N-ANS to ANS to GN 0.80 to 0.09 for males & 0.82 to0.09 for females. > G-point was established using specially designed transparent template containing a number of circles whose diameter increased in 1mm increments. > The best fit circle is selected www.indiandentalacademy.com
- 26. • G axis length increases in males 2.3mm / year. • G Axis length increases in females 1.6mm/year. • Growth velocities of G- axis length are determined by the slope of the mean linear regression formula. • Mean velocity of G - axis length increase for both genders is relatively constant within the age range studied. Discussion : www.indiandentalacademy.com
- 28. • The low correlation coefficients of growth vector axis angle for age range studied shows little change in magnitude • Slope of both graphs are relatively shallow. www.indiandentalacademy.com
- 30. • Angular relationship of mandibular plane to the “G” axis. • Mean value increases 0.4º/year for males. 0.3º/year for females. www.indiandentalacademy.com
- 31. From a clinical viewpoint, the mandibular plane angle is commonly measured relative to S-N. This angle, herein referred to as the angle ǿ, bears a geometric relationship to the angles α and θ. It is ǿ =(α – θ) www.indiandentalacademy.com
- 32. Conclusion : “G” Axis (S-G point) allows quantification of the complex mandibular growth process in relation to various craniofacial structures in Sagittal plane. www.indiandentalacademy.com