Wasserstein Atalia, Brezniak Naphtali, Shalish Miri, Heller Moshe, Rakocz Meir
Orthodontic Department, Israel Defence Forces, Tel-Hashomer, Israel.
Angle Orthod. 2004 Jun;74(3):332-6. doi: 10.1043/0003-3219(2004)074<0332:ACATRI>2.0.CO;2.
In the early developmental stage of the mandibular second premolar (MnP2), it is not unusual to find the tooth extremely angulated to the lower border of the mandible, as seen in the panoramic roentgenogram. On eruption, the tooth, in most cases, is close to being upright. However, impaction or other types of malocclusions due to its ectopic eruption are not rare. This study follows the angular changes of the MnP2 during development. Two hundred two panoramic roentgenograms of 101 patients were retrospectively analyzed. All patients had two sequential films with a minimal time interval of nine months. Each MnP2 was traced, and its developmental stage as well as its angulation to the lower border of the mandible was registered. We found that normally more MnP2 are distally (56.5%) than mesially (25%) inclined. There is a statistically significant difference in the inclination of the teeth during their development from stage D to stage F (D = 75.17 degrees +/- 15.25 degrees, E = 79.35 degrees +/- 12.18 degrees, F = 83.38 degrees +/- 10.79 degrees). The average amount of total angular change rate of the MnP2s from stage D to stage G is 0.09 +/- 0.25 degrees/mo, and the absolute angular change rate is 0.19 +/- 0.25 degrees/mo.
在下颌第二前磨牙（MnP2）的早期发育阶段，在全景X线片上可以看到该牙齿与下颌下缘呈极大角度，这种情况并不少见。在萌出时，大多数情况下该牙齿接近直立。然而，由于其异位萌出导致的阻生或其他类型的错牙合并不罕见。本研究追踪了MnP2在发育过程中的角度变化。对101例患者的202张全景X线片进行了回顾性分析。所有患者均有两张连续的片子，时间间隔最短为9个月。对每颗MnP2进行追踪，并记录其发育阶段以及与下颌下缘的角度。我们发现，正常情况下，更多的MnP2向远中倾斜（56.5%），而向近中倾斜的较少（25%）。在牙齿从D期发育到F期的过程中，倾斜度存在统计学上的显著差异（D期 = 75.17度±15.25度，E期 = 79.35度±12.18度，F期 = 83.38度±10.79度）。MnP2从D期到G期的总角度变化率平均为0.09±0.25度/月，绝对角度变化率为0.19±0.25度/月。
