牙齒大小的差異 Tooth-size discrepancy

The Bolton analysis has been designed following observation

that tooth size was important to ideal occlusion. (牙齒的大小與理想咬合有關係)

 

In order to obtain the proper interdigitation and arch coordination when the molars are in

a Class I relationship, the dimension of the lower teeth has to be proportional to the dimension

of the upper teeth. (下顎牙齒寬度與上顎牙齒寬度有一定的比例關係)

 

To present a normal overbite and overjet, the lower teeth must form a dental

arch that is smaller than the upper arch (正常下牙弓小於上牙弓)

 

Bolton calculated that a constant proportion between the upper and the lower

dentition was present when the occlusion was perfect. (正常上下牙弓之間有ㄧ定比例)

 

He determined that the sum of the mesio-distal dimension of the lower teeth must be equal

to 91% of the sum of the mesio-distal dimension of the upper teeth. (下牙弓牙寬之總和是上牙弓牙寬之總之 91%)

 

a satisfactory Class I canine occlusion was only possible if a specific proportion was present

between the upper and lower anterior teeth. (標準第一類犬齒咬合)

 

The sum of the size of the mesio-distal dimension of the lower anterior teeth in this instance

must be 77% of the sum of the size of the mesio-distal dimension of the upper anterior teeth.

The Bolton analysis is now mainly used for the anterior region (canine to canine).(下牙前牙牙寬之總和是上牙前牙牙寬之總和的 77%)

 

  • Bolton anterior ratio:

    •UA (Σ 13-23) =       mm

    •LA (Σ 33-43) =        mm

    •( 35.3 / 43.3 ) x 100 =     % (ideally 77%)

    (74.5 – 80.4 per cent)

 

Bolton overall ratio:

•UA (Σ 16-26) =       mm

•LA (Σ 36-46) =        mm

•( 73/ 80 ) x 100 =     % (ideally 91%)

(87.5 – 94.8 per cent)