Date of Graduation


Document Type


Degree Type



School of Dentistry



Committee Chair

Timothy Tremont

Committee Co-Chair

Richard Jurevic

Committee Member

Chris Martin


Background and Objectives: Diagnosing and treatment planning in contemporary orthodontics is based on comparing elements of craniofacial morphology to selected reference planes. Ideally, a valid reference plane should have good intra-individual reproducibility, low inter-individual variability, and good reliability. The aim of this study was to determine 1.) the reliability and reproducibility of FALL and Glabella Vertical as reference planes 2.) if Glabella Vertical can be used as a frontal reference plane and 3.) if NHO is affected by varying chin positions. Methods: Part 1) 3 judges measured 4 variables (F, FC, G, and GC) on 23 subjects at T1 and T2. Part 2) 105 lateral cephalograms were traced and measured to find the location of GALL to glabella. Part 3) 26 judges (13 orthodontists and 13 non-orthodontists) determined NHO in 3 chin positions (class I, class II, and class III). Results: Part 1) There were significant differences between mean levels of measurements between raters. The inter-rater reliability coefficient was moderate-good at T1 and T2 and the intra-rater reliability coefficient was good between T1 and T2. Part 2) GALL was not always located at glabella. Part 3) There were significant differences between angle means at class I, II and III. Tukey Kramer showed differences between class II and III but not between class I and II and class I and III. There were no differences in NHO between males and females or orthodontists vs non-orthodontists. Conclusion: FALL and Glabella Vertical are reliable and reproducible reference planes. Glabella Vertical can be used as a frontal plane for diagnosis and treatment planning. Judging NHO is under the influence of AP chin position; however, this influence is not clinically significant.