[Diagnostic method for assessment of possible distalization of the first upper molars]

The therapeutic method of distalization of the first upper molars by external traction has been considerably extended in recent years. Some failures are, however, encountered. The cause is lack of space. The author elaborated a method which helps to assess the future spatial possibilities in the molar region. The distance between the distal margin of the first upper molar from the normal from the posterior margin of the maxilla on the bispinal plane is assesed: +6:M. Point "M" is the most posterior point on the anterior border of the fissura pterygopalatina. At the same time the breadth of the second and third molar is taken into account where considerable individual differences exist. The growth of the maxilla in the molar region was investigated in a group of 146 probands. Growth increments, on average 1 mm per year, were recorded up to the age of 18 years. Based on this information the author elaborated a formula for assessment of possible distalization of the molars: M2 + M3 + PP = + 6:M + (age 18-of the patient). The sum of the width of the crowns of the second molar (M2) and third molar (M3) and the planned distal shift of the first molar (PP) equals distance + 6 from the normal from point M on the bispinal plane (+6:M) plus the difference between 18 and the patient's age.