Abstract
Instead of the distal shoe appliance, we used the M type loop appliance to maintain the space of a mandibular second primary molar that had been lost before the eruption of the permanent first molar, on the most part in many cases it was recognized that the permanent first molar was able to be induced to an appropriate position.
Later, in the cases in which the M typeloop appliances were used, we observed how the un-erupted mandibular first permanent molar drift within the alveolar bone and gingiva with premature loss of the second primary molar until the first permanent molar erupted, and obtained the next following results.
1. Of the 40 cases in which the prognoses were able to make an identification,34 cases showed that the permanent first molar erupted along the M type loop appliance, and 6 cases showed that it erupted more mesially than the M type loop appliance.
2. In the cases in which the permanent first molar erupted along the M type loop appliance, using 15cases' study casts we were able to measure the distal edge of the pre-extraction second primary molar. In these cases, then, the position of the medial edge of the erupted permanent first molar was compared with the position of the distal edge of the pre-extraction second primary molar. As a result, the medial edge of the permanent first molar was found to be positioned medially at an average of 1.41 mm from the pre-extraction second primary molar distal edge.
3. As the positions of the M type loops were identified by using the Oblique Cephalogram, most of the under points of the loops were set up in the position that approximated the neighborhood of most of the under depressions of the opposite side second primary molar's distal side.
4. We observed that an un-erupted permanent first molar drifted within the alveolar bone and gingiva with premature loss of the second primary molar not only medially but also variously.
5. It was thought that the reason the permanent first molar erupted more medially than M type loop was that the setting of the M type loop was inadequate.
The results of this investigation suggest that if the setting of the loop is carried out prudently and the progress observation is carried out properly, the M type loop can be administered as a space maintainer with premature loss of the second primary molar.
