@canine impaction(犬齒埋伏阻生)~1－崇愛牙醫診所(資料重建中,歡迎新舊朋友)

上顎犬齒阻生是臨床上常見的問題，在恆牙齒列中，犬齒是除了智齒之外，最容易發生阻生的牙齒，特别是上顎犬齒阻生的發生率尤甚，因此了解其特性，並知道如何正確治療，有其重要性。針對上顎犬齒阻生的發生率，好發部位，發生原因，可能併發症，診斷方法及臨床治療方式分别加以探討及說明。上顎犬齒阻生之治療，已發展出成熟且完整的診斷方法及治療程序，只要早期發現，並在最佳時機介入治療，往往能達到良好的治療效果。

(from:http://www.ceps.com.tw/ec/ecjnlarticleView.aspx?atliid=98713&issueiid=8362&jnliid=678)

●canine impaction可分為

1)palatal impaction

2)labial impaction

●The incidence (發生率)of maxillary canine impaction is between 0·9% to 2·0%

canine impaction was found to be 3.58%

Maxillary canine impaction is a well known dental. anomaly and the incidence is in the range 0.8–2.8%,(有些文獻講)The maxillary canine is second only to the third molar in frequency of impaction, with a prevalence of 0.8 to 3.3 %

canine impaction可以分為兩種理論"guidance theory” and “genetic theory"

●Dental features associated with palatal canine impaction are (顎側犬齒阻生的牙科所見為)

1)small size of upper lateral incisors (hypoplasia), (側門牙過小牙)

2)agenesis of upper lateral incisors, (上側門牙沒有形成)

3)agenesis of second premolars and (第二小臼齒沒有形成)

4)infraocclusion of primary molars.(乳臼齒的咬合下滯留)

●Diagnosis of canine impaction (診斷)is based on visual inspection, palpation and radiography. (視診,觸診,與x光)

In cases without arch length discrepancy, early deciduous canine extraction is a suitable way to prevent canine impaction. (早期拔除乳牙是一個避免犬齒阻生的較適合的方法)

Root resorptions of the lateral and central incisors often occur when palatal canine impaction is present.(側門牙與正門牙常會因為犬齒顎側阻生而導致牙根吸收)

Only computertomography accurately depicts root resorptions. Whenever surgical exposure of an impacted canine is needed the orthodontist should consider possible effects of different surgical techniques.

After surgical exposure, orthodontic traction is applied to the impacted tooth. Since Jacoby introduced the “ballista spring”, (jacoby使用ballista spring來誘導犬齒萌出)many cantilever mechanics for initial extrusion have been described.

THE LINGUAL BALLISTA SPRING

The purpose of this article is to review current diagnosis and treatment of maxillary canine impaction.

Canine impaction may be either labial or palatal and, in Europeans, palatal impaction is 2-3 times more frequent than labial impaction11.

The prevalence of palatine impaction with respect to labial impaction ranges from a ratio of 7:1, reported by Jacoby12, to a ratio of 2:1,

這個圖型代表以上顎兩中門齒的中間垂線,與埋伏犬齒的長軸中線的連線所構成的夾角,稱為beta角,角度在<25度以下,萌出機會較大,若是>45度以上,通常會考慮拔除為宜

Clinical examination revealed asymmetrybetween right and left cuspids; the 53 was overretained and not mobile whereas the 63 had exfoliated naturally allowing the 23 to erupt into the arch. The 13 was palatally impacted and required surgical exposure and orthodontic alignment.

surgical exposure+ortho. tx

significant overlap of the maxillary cuspid and the lateral incisor makes recovery of the impacted canine following extraction of the primary cuspid less likely.