Orthodontics

Notes

Index of Orthodontic Treatment Need

UK National Health Service funds orthodontic treatment for children where IOTN is equal or greater than DHC = 3 and AC = 6

Cephalometrics

Anterior cranial base → most stable craniofacial structure to be used for superimposition, it completes the majority of its growth before 7 y/o

Wits Analysis

Males : BO is 1mm ahead of AO

Females : BO = AO

Balancing extraction = same arch, opposite side → maintain symmetry and centreline relationships

Compensating extraction = same side, opposite arch → maintain inter-arch relationship

Serial extraction : C → D → 4

Thumb Sucking Features

• Upper incisor proclination
• Lower incisor retroclination
• Narrowing of upper arch
• Mandibular displacement and crossbite
• Anterior open bite (often asymmetrical)

First Permanent Molars of Poor Prognosis

In lower arch, good spontaneous alignment following extraction of lower 6 if → lower 7 development reached bifurcation, angulation between crypt 7 and 6 is <30°, 7 crypts overlap 6 roots

Scissors bite = lingual crossbite of lower posterior teeth

Removable Appliances

Signs of non wear:

• Missed appointments
• Broken appliances
• Poor speech with appliance in situ
• Poor fit
• Still active at each visit
• Non signs of wear on appliance / soft tissue
• Patient displays difficulty inserting or removing appliance

Incidence of Cleft Lip and Palate

Failure of fusion : maxillary process and median nasal process

1 in 700, more common in males

Unilateral clefts → left side

Isolated cleft palate → 1 : 2000, females

Veau Classification of CLP

Class I : SP

Class II : S / HP

Class III : unilateral CLP

Class IV : bilateral CLP

Commonly Impacted Tooth

Third molars → maxillary canines → maxillary central incisors

Delayed Eruption of Permanent Maxillary Incisor

• eruption of contralateral incisor occurred > 6 months earlier
• the maxillary incisors remain unerupted > 1 year after the eruption of mandibular incisors
• significant deviation from normal eruption sequence

Canines undergoing normal eruption should be palpable in buccal sulcus by 10 - 11 y/o

Optimal Force Levels for Various Tooth Movements

Intrusion                  : 10 - 20 g

Extrusion                 : 35 - 60 g

Rotation                   : 35 - 60 g

Tipping                    : 35 - 60 g

Root uprighting       : 50 - 100 g

Bodily movement    : 70 - 120 g