Changes in the dental arches as a factor in orthodontic diagnosis

Abstract

• 1.

  1. At birth there is no occlusion between the gum pads.

• 2.

  2. (a) There is a suggestion that poor occlusion is more prevalent when anterior space falls into Classes B, C, or D. However, in some instances, good occlusion may develop regardless of anterior space at birth. (b) A change of morphology of the anterior space from symmetric to asymmetric is associated with poor occlusion.

• 3.

  3. The mandible was posterior to the maxilla at birth in 161 infants. The distance A ranged from 0 to 8 mm. with a mean value of 2. 6 millimeters.

• 4.

  4. From the group of forty-eight children there were three (20 per cent) with good occlusion and twelve (80 per cent) with poor occlusion when the dimension A varied from 4 to 8 millimeters. This suggests that this range of dimension is more likely to be associated with poor occlusion.

• 5.

  5. Twenty-two children out of a group of thirty-eight have widths of the jaws at birth outside of the range of an established norm. Seven (31 per cent) developed into good occlusion, while fifteen (68 per cent) developed into poor occlusion. This suggests that poor occlusion may be foreshadowed at birth in many instances.

• 6.

  6. Smooth, rhythmic curves of the widths of the dental arches from birth onward are associated with good occlusion.

• 7.

  7. Irregular curves with lack of rhythm are associated with poor occlusion.

• 8.

  8. Among the sixteen children with good occlusion, only six (37. 5 per cent) show a decrease in width, whereas among the twenty-two children with poor occlusion, thirteen (51 per cent) show a decrease in width. This suggests that decrease in width is more likely to be associated with poor occlusion.

• 9.

  9. (a) Four out of the five infants with a difference of less than 3 mm. between the widths of the maxillary and mandibular arches developed poor occlusion. (b) Five out of the six children with a difference of over 7 mm. between the widths of the dental arches, as seen by the last casts, have poor occlusion. (c) Three out of four children with a difference under 4 mm. have poor occlusion. This suggests that dimensional differences within the limits mentioned are associated with poor occlusion.