020 – Crooked teeth

Case Report


Class II Division I malocclusion, Excessive overjet & Deep Bite with a Congenital Missing Lower Incisor Treated Non-Extraction Orthodontic Treatment.

History & Aetiology

A 15 years old female presented with compromised facial & dental aesthetics, associated with malocclusion.  Her chief complaints were crooked teeth and proclined incisors. The patient hopes to resolve her problem with orthodontic treatment. The patient had no known contributing habit, medical, dental or family history, so the aetiology the malocclusion appeared to be an hereditary factors. Clinical examination revealed congenital missing of lower incisor causing asymmetry facial and lower midline deviated.


Skeletal :

  1. Class II skeletal profile (Maxilla Prognathism)
  2. Positive Ricketts’s Esthetic line with upper lip 3mm, lower lip 5mm


  1. Angle Class II molar relationship on Right Side
  2. Angle Class II division I incisor relationship
  3. Overjet 5mm (Incisors Protruding)
  4. High canine of tooth #13
  5. Crossbite 25 (Wrong biting position of upper & lower teeth)
  6. Missing 1 lower incisor
  7. Deep bite 4mm




Treatment plan

Non extraction treatment with a full fixed passive self-ligating bracket system (Damon Q) is planned to align the dentition, level the arches & reduce the excessive overjet & overbite. Interproximal enamel reduction performed in anterior segments of upper arches to correct Bolton ratio discrepancy. Anterior bite turbo on both upper central incisor to correct deep bite.

Results achieved

Treatment was completed in 24 months with significant  improvement in overbite(4mm reduce to 2mm ), overjet(5mm reduce to 2mm), facial profile(reduce upper lip 3mm to 0.5mm  & lower lip 5mm to 3mm  to E line). Upper and lower dentition aligned. Class I molar relationship maintained.  Class 1 incisor relationship achieved.





Clear overlay retainer were delivered for both arches. The patient was instructed to wear the overlay retainer full time for 1st 3 months and nights only thereafter.


A congenital missing lower incisor is a significant compromise for most patients. The aetiology is multifactorial and usually is a hereditary trait. Mandibular incisors were the most commonly missing teeth in Asian population. Congenital missing incisor is often associated with excessive overjet, deepbite, and asymmetry occlusion and midline deviation.    Orthodontic treatment plan is depends on clinical assessment on skeletal pattern in the sagittal, transverse and skeletal dimensions. Bolton ratio is use to indicate for extraction or non-extraction orthodontic treatment. The decision to open or close space is depends on factor aesthetics, periodontal health and function in long term. For the presented case, patient with class I molar relationship, missing single mandible incisor, mild convex profile, space closure is preferable.



Prepared by

Dr Khor Su Yean

Dental Surgeon (Alma Branch)