Supernumerary teeth

Japanese: 過剰歯 - かじょうし（英語表記）Supernumerary teeth

What is the disease?

The tooth-forming primordium ( Tooth germ ( Last update ) When an excess of teeth are formed, or when one tooth germ divides, more than the normal number of teeth are produced. This is called a supernumerary tooth.

Some grow straight into the dentition, but others grow out of the dentition or fail to grow normally. Impacted teeth ( My clothes ) The shape of the teeth varies from nearly normal to incomplete due to degenerative tendencies (Figure 22).

What is the cause?

The cause is unclear, but various theories have been put forward, including that it is the sudden reappearance of teeth that were gradually lost during human evolution, genetic factors, or trauma causing the early tooth germ to split.

How symptoms manifest

Supernumerary teeth are rare in baby teeth. Supernumerary teeth in permanent teeth can appear in the area between the upper front teeth, between the upper and lower wisdom teeth ( Wisdom tooth ( Chishi )・Third University molar ( Kyushi ) It is said that supernumerary teeth tend to appear behind the upper jaw. Supernumerary teeth can easily cause a disruption in the alignment of the teeth, and if they appear in the front teeth area of the upper jaw, they can cause midline diastema (column). Furthermore, as supernumerary teeth grow in, they can press on the surrounding teeth, dissolving the tooth roots and making the teeth more mobile.

Treatment methods

Supernumerary teeth are generally extracted if they are likely to have a negative effect on the bite or surrounding teeth. In some cases, such as supernumerary teeth impacted deep in the bone, they may not be extracted if they are not causing any particular problems.

Keiji Moriyama

Fig. 22 Supernumerary tooth
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Fig. 22 Supernumerary tooth

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　歯を形作る原基（歯胚(しはい)）が過剰に形成されたり、1個の歯胚が分裂することで、歯が正常な数より多く作られる場合があります。これを過剰歯と呼びます。

　真っすぐ歯列内に生えてくる場合もありますが、歯列外に生えてくるものや正常に生えることができず埋伏歯(まいふくし)になるものもあります。歯の形は、正常に近いものから退化傾向により不完全な形を示すものまでさまざまです（図22）。

原因は何か

　原因ははっきりしていません。人間が進化する過程で徐々に失われてしまった歯が突然再び現れた結果であるという説や、遺伝的要素、外傷によって形成初期の歯胚が分割してしまうなど、さまざまな説があげられています。

症状の現れ方

　乳歯では過剰歯の発現はまれです。永久歯の過剰歯が現れる場所として、上あごの前歯の間、上下の親知らず（智歯(ちし)・第三大臼歯(きゅうし)）の後方などに出てくることが比較的多いといわれています。過剰歯があると歯列に乱れが生じやすく、とくに上あごの前歯部に出てくる場合は正中離開(せいちゅうりかい)（コラム）の原因になります。さらに過剰歯が生える過程で、周囲の歯を圧迫して歯の根を溶かしたり、歯の動揺を大きくしたりすることもあります。