Permanent maxillary canines – Review of eruption pattern and local etiological factors leading to impaction. J Investig Clin Dent 2015;6:1-7

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口腔病理科 On-Line KMU Student Bulletin

原文題目(出處)：

Sajnani AK 原文作者姓名：

KIMS Qatar Medical Center, Wakra, Qatar 通訊作者學校：

報告者姓名(組別)：甘岱平 (Intern K 組) 104/06/09

報告日期：

Introduction

The Function of Canine

• Fighting with enemies or rivals.

• In modern human

Support the facial muscle Mastication

Guide the mandible into centric position Congenital Missing

• Consideration:

The number of missing teeth Overall alignment and occlusion Patient’s and parents’ preference

• Option:

Extraction

Orthodontic alignment

Retain the primary canine and Replace with prosthesis

Impaction

• Delay eruption time

• Not expected to erupt complete based on clinical and radiographic assessments.

• Maxillary canine is the most frequently impacted tooth in childhood.

Surgical approach to remove or perform orthodontic movement Etiology of Impaction

• Generalized

• Hypopituitarism

• Hypothyroidism

• Cleidocranial dysostosis

• Down syndrome

• Achondroplasia

• Hypovitaminosis (A or D)

• Amelogenesis imperfect

• Osteoporosis

• Localized

• Tooth size/ arch length discrepancy.

• Prolonged retention or early loss

• Abnormal tooth bud position

• Long path of eruption

• Alveolar cleft

• Ankylosis

• Follicular Disturbance

• Cyst or neoplasm

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• Dilaceration

• Trauma

• Crowding Path of Eruption

• 4-12 months

• Calcification

• 2.5 years

• Lying above the first premolar tooth germ

• 6-7 years

• Crown complete

• 5-15 years

• Travel almost 22 mm

• Move down the distal aspect of the lateral incisor.

• Displacement from the normal path cause impaction

• Crowding cause buccal impaction

• A number of causes attributed the palatal impaction

• Guidance theory

• Genetic theory Guidance Theory

 Miller and Bass:

Congenitally missing lateral incisors associated with palatally impacted canines

 Becker et al.

Two phase of development of canine displacement.

1. Canine deviates from the physiologic eruption path in the palatal direction.

2. Corrective movements

 Palatally displacement canines are found adjacent to normally development lateral incisors

Genetic Theory

Palatal displacement rarely occurs as an isolated symptom 1. Autosomal gene ex: MSX1/MSX2 homeodomain gene

Bilateral occurrence Gender related Families history

2. Disturbance in an ontogenetically critical zone Sequential Hypothesis

4-5 months old

• The tooth germ of the maxillary permanent canine starts to develop

• High in the anterior wall of the maxillary sinus, under the floor of the orbit 3 years old

• Inferior to the orbit, superior to the floor of the nasal cavity, and between the nasal cavity and the maxillary sinus.

• The crown of the tooth is directed mesially and lingually with respect to the primary canine and to the developing first premolar

• With the development of the first premolar, the developing permanent canine and first premolar and the first primary molar are all positioned one above each other

• Meanwhile, the developmental position of the lateral incisor is palatal in relation to both the permanent central incisor and the permanent canine.

5 years old

• The disto-incisal corner of the maxillary central permanent incisor is in

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contact with the mesial surface of the roots of the adjacent primary lateral incisor.

• The maxillary canine begins to lose its potential to move in the vertical plane and would eventually become impacted

• Normally erupting canine would travel approximately 22 mm, a canine that would eventually remain impacted would travel less than 3.5 mm in the next 7 years of its development

• Lateral incisors would be positioned away from the permanent canine at this age, could substantially influence the eruption of the permanent canine

• Genetic factors regulate the ectopic position of the canine.

6 years old

• Canine crown tip is at the level of the nasal floor, palatal to the primary canine root and directed mesially.

• Both buccally and palatally impacted canines, microdontia was exhibited by the lateral incisors almost twice and thrice times respectively of that reported

• Corrective movements may occur after this stage and the canine may move into a more favorable position in the arch. In patients with microdontia of the lateral incisor, this self-correcting movement will be prevented by the meanwhile completely developed roots of the maxillary lateral incisors.

8 to 9 years old

• The maxillary canine gains guidance from the developing root of the adjacent lateral incisor and begins to change from a mesial inclination to a more vertical direction

• The increased risk of palatal canine displacement with aplasia, or impaction of other teeth

Conclusions

• Impaction of a maxillary canine is a frequent occurrence and requires a multidisciplinary approach for proper management

• Awareness of the eruption patterns and etiology of impaction allow for early recognition and implementation of interceptive treatment

題目

The most frequently impact teeth are mandibular 3^rd molar, and the followed are?

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(A) Maxillary central incisor (B) Maxillary 2^nd premolar

(C) Mandibular canine

(D) Maxillary 3^rd molar and maxillary canine

出處：Oral and Maxillofacial PATHOLOGY,3rd edition , Neville, et al.

P.74 答案(D)

題目

2 Which is not the strategy of treatment for impaction?

(A) Long-term observation

(B) Orthodontically assisted eruption

(C) Surgical remove

(D) None of the above

出處：Oral and Maxillofacial PATHOLOGY,3rd edition , Neville, et al.

P.74 答案(D)

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