1. 牙科放射線學(1) Buccal Object Rule 從X光片辨識物體位置 陳玉昆教授: 高雄醫學大學 口腔病理科
~2755 1

2. 學 習 目 標 Introduction Understand buccal object rule
Assessment of the impacted maxillary canine tooth position
2. Eric Whaites: Essentials of dental radiography & radiology, 3rd edition,
p.7, 8, 113,
1. White & Pharoah: Oral radiology: principle & interpretation, 5th edition,
Chapter 5, p
References:
Introduction
Conclusions

3. Introduction
* Clark [1909, ref. 1] reported a radiographic procedure for
the localization of impacted teeth.
* Buccal Object Rule (BOR) is a method for determining the relative location of objects hidden in the oral region.
* Initial concepts of the procedure were reported in 1952 &
1953 [refs. 2, 3] & since that time the procedure has been
developed to its present state of refinement & usefulness.
[1] CLARK C A. A method of ascertaining the relative position of unerupted teeth by means of film
radiographs. Royal Society of Medicine Transactions 3:87-90,
[2] RICHARDS AG. Roentgenographic localization of the mandibular canal. Journal of Oral Surgery
10: , 1952.
[3] RICHARDS AG. The Buccal object rule. Journal of the Tennessee State Dental Association 33:263-
268, 1953.

4. Understand buccal object rule
Lingual
Mesial shift
同方向移動
Tube shift technique
Buccal object rule
Clake’s rule (1910)
Direct
orientation
Zygomatic
process
X-ray beam
Buccal
Mesial shift
相反方向移動
Distal shift
Zygomatic process
往mesial方向移動
(與X-ray beam相反方向移動)
X-ray beam
Ref. 1

5. Assessment of the impacted maxillary canine tooth position
Parallax in the horizontal plane
Parallax in the vertical plane
A vertex occlusal
A true PA and lateral skull views
(two views at right angles)
*Impacted maxillary canine teeth occur in about 2% of the population.

6. 1. Parallax in the horizontal plane
Principle of parallax: The apparent displacement of
an object due to different positions of the observer
Front
Right
Left
Object moves in different direction
Same Lingual
Opposite Buccal
SLOB
(遠方)
(近方)
Ref. 2

7. 1. Parallax in the horizontal plane
Position 1-
centrally
oriented
Position 2-
distal shift
Position 1
Position 2
Same Lingual
(遠方-palatal side) 11 12
Ref. 2

8. 1. Parallax in the horizontal plane12 22 21 22 21 12 11
Choices
(1) Same Lingual
(2) Opposite Buccal
(遠方)
(近方)
Ref. 2

9. 1. Parallax in the horizontal plane
Choices
(1) Same Lingual
(2) Opposite Buccal
(遠方)
(近方)
Apex
Crown
Ref. 2

10. 2. Parallax in the vertical plane
Panorex
Upper occlusal
Unerupted
mesiodens
Crown portion
(遠方-palatal side)
(近方-labial side)
SLOB
(1) Same Lingual
(2) Opposite Buccal
Apex portion
Ref. 2

11. 3. A vertex occlusal Vertex occlusal Not recommended
due to high radiation
dose
Vertex occlusal
Ref. 2

12. Mass of head in a different position & different shape
4. A true PA and lateral skull views
(two views at right angles)
Mass of head in a different
position & different shape
Similar images
PA view
Lateral view
Similar images
Radiodense object
Ref. 2

13. Conclusion (1)

14. Conclusion (2)

15. Conclusion (3)

16. Summaries Knowing : Understand Clake’s rule
Assessment of the impacted maxillary canine tooth position

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