Resumo

BRANDAO FILHO, Rivail Almeida; BITTENCOURT, Marcos Alan Vieira  e  CAMPOS, Paulo Sérgio Flores. Relationship between the mandibular ramus height/posterior alveolar bone height index and the mandibular plane angle. Rev. Dent. Press Ortodon. Ortop. Facial [online]. 2008, vol.13, n.6, pp. 89-97. ISSN 1415-5419.  http://dx.doi.org/10.1590/S1415-54192008000600011.

AIM: This study evaluated the relationship between two cephalometric variables: the mandibular ramus height/posterior alveolar bone height index (MRH/ABH) and the mandibular plane angle (MP). METHODS: Two examiners assessed 81 lateral cephalometric radiographs of at least 18 years old patients, retrieved from the archives of the Orthodontic Department from Federal University of Bahia (Salvador, BA, Brazil). The data input from the cephalogram was accomplished by using Radiocef Studio 1.0 software. The mandibular plane angle was used to assess the vertical growth pattern, in order to divide the sample into three groups: the normal face group (NG, 22º - 28°), the short face group (SG, less than 22°) and the long face group (LG, more than 28°). The palatal plane angle was evaluated as a criterion to exclude radiographs that presented values below -2.5° and above 3.5°. Thus, the final sample consisted of 46 lateral cephalometric radiographs. RESULTS: The ramus height differed between the SG and LG groups; however, there was no significant statistical difference for the posterior alveolar bone height among the three groups. No strong correlation between the mandibular ramus height (MRH) and the posterior alveolar bone height (ABH) was found; nevertheless, the correlation between the mandibular ramus height/posterior alveolar bone height index (MRH/ABH) and the mandibular plane angle (MP) was statistically significant and negative. CONCLUSION: Therefore, we concluded that this index (MRH/ABH) should be considered by orthodontists when evaluating the mandibular plane angle of patients with vertical dysplasias.

Palavras-chave : Mandible; Radiography; Alveolar process.