Analysis of Average Horizontal and Vertical Mandibular Growth Components Relative to the Horizontal Plane as Determined from Cross-sectional Cephalometric Normal Standards

Research Article

J Dent App. 2014;1(4): 55-60.

Analysis of Average Horizontal and Vertical Mandibular Growth Components Relative to the Horizontal Plane as Determined from Cross-sectional Cephalometric Normal Standards

Richard G. Standerwick*

Associate Clinical Professor, UBC Faculty of Dentistry, Dept. of Orthodontics, Vancouver, BC, Canada

*Corresponding author: Dr. Richard G. Standerwick, 20159 88th Ave, Suite E207, Langley, BC, Canada V1M

Received: June 26, 2014; Accepted: September 02, 2014; Published: September 04, 2014


Objective: To provide some insight into annual horizontal and vertical components of mandibular growth.

Material and Methods: The averaged growth data for the ages of 8 to 16 were garnered from an Atlas of craniofacial growth: Cephalometric standards from the university school growth study, the University of Michigan and organized into horizontal and vertical growth components utilizing trigonometry.

Results: Considering the limitations of the data, during puberty it would seem the average horizontal growth vector of the mandible is approximately 1.5mm per year for females and 2mm/yr for males. The average vertical component of growth during puberty is approximately 2.8mm/yr for males and 1.5 mm/yr for females.

Conclusion: The amount of horizontal growth may be overestimated and vertical growth underestimated with current use of growth along anatomic planes rather than relative to the horizontal or Frankfort plane.


Diagnosis and treatment often rely on the amount of craniofacial growth available, however it is difficult to find a description of annual horizontal (ventral) and vertical (caudad) components of normal mandibular growth relative to the Frankfort horizontal (FH) on a search of orthodontic literature. Mandibular growth in length is often described utilizing the distance between condyle associated landmarks and mandibular symphysis associated landmarks eg condylion-gnathion (Co-GN), condylion-pogonion (Co-Pg), articulare-pogonion (Ar-Pg), and articulare-gnathion (Ar-Gn) [1-4]; however these measured changes are angled relative to the Frankfort Horizontal /horizontal plane. For this reason, the measured change does not adequately reflect clinically observed facial development [5] nor the ventral change resulting in decreased facial convexity.

According to Proffit [6,7] mandibular ramus height growth (condylion-gonion) is 1 to 2 mm per year and mandibular body (gonion-pogonion) growth is 2 to 3 mm per year based on the growth standards utilized in this study [8], and Ricketts reported 1.5mm/yr of mandibular growth measured from Co to symphysis [9]. Burstone and Marcotte [10] observed Ar-Pg annual growth and growth increments for female ages 10 to 14 which displayed annual growth increments of 2mm, 3.5mm, 1.9mm and 1.4mm, and for male ages 12 to 16 which displayed annual growth increments of 2.2mm, 2.8mm, 4.7mm and 2.3mm. Female mandibular length as Ar-Pg has been observed to display 4.29mm of growth for 18months prior to menarche and then a subsequent decrease in growth rate to 2.84mm for 18 months post-menarche [3], which is approximately 2.4mm a year over the 36 months of pubertal growth. Mandibular length measured as Co-Gn displayed growth of 4.31mm per year measured over a 5 to 24 month observation period [1], 2.5mm/year over 5 years from 91/2 years of age to 14½ [2], and approximately 2mm per year for an untreated control group [11,12]. Mandibular length measured as Ar-Gn displayed a 3.26 ± 1.47mm/yr for males and 2.90 ± 1.32 mm/yr of incremental growth [4] and 1.33mm/yr as observe for an untreated control group [12]. Bjork described 2-5mm of condylar growth per year [13], and Buschang [14] described incremental condylar growth with an approximate average of 2.8mm/yr for males and 2.2mm/yr for females, however this may not directly translate into the desired growth direction at pogonion [15].

Growth vector analysis has been previously described utilizing a constructed reference of a perpendicular line to the sella turcica-nasion line (SN), SN-7 or FH which originates from sella, however growth periods presented often do not allow an annual assessment of growth without additional assumption [5,15-18].

The purpose of this study was to provide an estimate for the average amount of horizontal and vertical circumpubertal mandibular growth using cross-sectional data from normal growth standards relative to the horizontal plane approximating the Frankfort horizontal (FH) [8]. Potential application includes orthodontic diagnosis and treatment planning when considering normal growth and the potential for orthopedic or dento-alveolar modification.

Material and Methods

The sample for this study was obtained from an Atlas of Craniofacial Growth: Cephalometric Standards from the University School Growth Study, the University of Michigan and consisted of 83 Caucasian individuals (47 male, 36 female). Growth standard measurements for condylion-gonion (Co-Go), condylion-gnathion (Co-Gn), gonion-gnathion (Go-Gn), and sella-nasion-gonion-gnathion (SN-GoGn) (Table 1) were obtained for the ages of 8 to 16 years of age and were chosen as they were the only available landmark measurements which would relate the condyle, gonion and mandibular symphysis; Co, Go, Gn. 6A measurement for the gonial angle was not available; therefore, the cosine rule was used to establish the angle of Co-Go-Gn (θCo-Gn) (Figure 1). The Law of Sines was then used to calculate the remaining angles θGo-Gn and θCo-Go (Figure 1).