Patients and methods

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口腔病理科 On-Line KMU Student Bulletin

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原文題目(出處)： Does the presence of mandibular third molars increase the risk of angle fracture and simultaneously decrease the risk of condylar fracture?

原文作者姓名： D. H. Duan1, Y. Zhang2

通訊作者學校： 1. Department of General Dentistry, Peking University School and Hospital of Stomatology, Beijing 100081, China

2. Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing 100081, China

報告者姓名(組別)： Int B. 李嘉翔 報告日期： 97.01.08 內文：

Abstract.

1. Previous studies Îmandibular third molars (M3s) increase the risk of mandibular angle fractures and decrease the risk of mandibular condylar fractures.

2. 700 patients with and without impacted M3s. Î The results showed that

a. patients with impacted M3s vs without impacted M3s Îby moderate trauma force Î lower risk , condylar fracture Î higher risk, angle fracture

b. not be identified by high trauma force.

3. Patients with impacted M3s vs. without impacted M3s Îno matter how they were injured (assault, fall, motor vehicle accident, other). Î higher risk , angle fracture 4. When injured by assault or in a motor vehicle accidentÎ impacted M3s Îless

likely to have a condylar fracture.

5. M3s Î dominant factorÎ angle fracture + preventing condylar fracture.

Introduction

1. Retrospective studiesÎwith M3s vs.without impacted M3s.Î more at risk of mandibular angle fractures

2. Risk of fracture was also dependent on M3 position

3. With impacted M3s vs. without impacted M3sÎ less condylar fracture

4.

Position of M3s, injury mechanism and injury cause,

Patients and methods

1. January 1991 to April 2005, 902 patients were treated for mandible fractures at Peking University School and Hospital of Stomatology, Department of Oral and Maxillofacial Surgery.

2. Data collected included age, sex, injury cause (motor vehicle accident, assault, fall, other), position of M3s and fractures sites.

3. 202 patients aged 16 years or younger Î Excluded 4. The magnitude of trauma force

low trauma force Î 1mandibular fracture site, moderate trauma force Î 2 mandibular fracture sites high trauma forceÎ 3 or more mandibular fracture sites.

5. To analyse the position Î

a. horizontal position(Class I, Class II and Class III) b. vertical position (Class A, Class B and Class C) c. absence of M3sÎ Class 0

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d. Class IA Î not impacted but fully erupted.

e. All remaining Îimpactions.

6. SPSS version 10.0 (means and standard deviation, x² test, Student’s t-test, Data were considered significant with P < 0.05.)

Results

1. 700 patients with 1280 mandibular fractures.

2. Motor vehicle accident (the most common)Î assaultÎfall Î other

3. The most common fracture Îbi-fracture Îmono-fracture Îmulti-fracture 4. Observed most frequently Îsymphysis Î condyle Îbody Î angle Î ramus 5. Mandibular angle fractures Î197 patients, 5 bilateral

6. Condylar fractures Î 300 patients, 112 bilateral 7. 22Î condylar*1 + angle fracture*1Î8 both same side.

8. 700 patients ,1400 mandibular halvesÎ 302 (22%) no M3s.

9. 1098 (78%) mandibular halves containing an M3,

a.horizontal position：Class I (525, 38%)Î Class II (322, 23%) Î Class III (251, 18%).

b.vertical position：Class A (656, 47%)ÎClass B (348, 25%) ÎClass C (94, 7%).

c.with impacted M3s Î younger , male

10. Without impacted M3s vs. with impacted M3s (P < 0.05). Î higher risk for condylar fractures,

11. With impacted M3s vs. without impacted M3s Î higher risk for angle fractures (P < 0.05).

12. Horizontal position of impacted M3s, highest incidence ,

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angle fracturesÎ Class II Î Class III Î Class I Î Class 0.

condylar fractures ÎClass 0 Î Class I Î Class III Î Class II 13. The highest incidence

angle fractures ÎClass B Î Class A Î Class CÎ Class 0 condylar fractures ÎClass 0 Î Class CÎ Class AÎ Class B

14. Impacted M3s Î lower risk of condylar fracture / higher risk of angle fracture 15. Without impacted M3s Îmoderate trauma force Îhigher risk of condylar

fractures Î lower risk of angle fractures

16. With impacted M3s vs. without impacted M3sÎ low trauma forceÎ higher risk of angle fracture

17. The difference was not statistically significant for condylar fracture

18. No matter how they were injured Î with impacted M3s Î higher risk of angle fracture than those without impacted M3s (P < 0.05).

19. Assault or motor vehicle accidentÎ with impacted M3s Îless condylar fracture than those without impacted M3s (P < 0.05)

Discussion

1. The resistance to angle fractures is decreased by the presence of impacted M3s The highest risk Î Class II and Class B

The lowest risk Î without M3s .

2. Angle fractures Îtension at the superior border Î compression at the inferior border.

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3. Impacted M3s disrupting the cortical bridge of the superior border cause an inherent weakness in the mandibular angle. Îwhy Class II and Class B positionsÎrather than Class III and Class C with the superior border intact.

4. KOBER et al. Î angle was weakened by incompletely erupted M3s,Îcondylar fracture would decreaseÎ forces would be dissipated by the angle fracture.

5. Angle was intact (with no M3s or fully erupted M3s )Îmore impact forces would transmit to the condyle Î fracture

6. The severity of injury was the primary factor resulting in multiple fractures, not the presence or absence of M3s.

7. A single fracture( low traumatic force)Î,impacted M3s increased the risk of angle fracture.

8. M3s Î in the mono-fracture group. Î no influence on condylar fractures 9. This could be explained by the low force of injury: a fracture would occur at the

condyle, due to its intrinsic weakness, rather than the angle with M3s.

10. Angle fracture Îmore affected by impacted M3s than that of condylar fracture.

題號題目

1 Which one is not the clinical features of exctodermal dysplasia?

(A) female predominance (B) Oligodintia

(C) Teeth maekedly reduced in number (D) The incisors usuallt appear tapered 答案(A ) 出處：Oral and Maxillofacila pathology p.644

male predominance is usually seen(X-linked inherance)

題號題目

2 Which one is not correct about Warthin tumor

(A) It’s the most common benign parotid gland tumor (B) It usually occurs metachronous

(C) It has been associated with cigarette smoking

(D) It is also named papillary cystandeoma lymphomatosum 答案( A) 出處：Oral and Maxillofacila pathology p.415

It’s the 2^nd common benign parotid gland tumor