20 quick facts about the treatment of Class II malocclusion

I am a subscriber to Dr Kevin O’Brien‘s blog. He is a professor at the University of Manchester, UK. He has been a clinical orthodontist and a researcher for about 30 years. He directed several research projects on the result of orthodontic treatments by using the method of randomized clinical trials, including the treatment of Class II malocclusion and more particularly on the effects of the Twin Block removable functional appliance.

My attention was brought to one of his blogs on facts about the treatment of Class II malocclusion. I reproduce below its contents with my personal annotations.

20 quick facts

1. Treatment should be considered if the overjet is greater than 6 mm. This is also the IOTN (index of treatment need) criteria.

2. There is an increased risk of trauma to the upper incisors particularly if the lips are incompetent (when the teeth are prominent and the lower lip rests under the upper teeth). However, most trauma has occurred before orthodontic treatment can be started.

3. No one ever had any problems because their molars are half a unit (2-3 mm) Class II!

4. Early treatment (phase 1) as part of a two-phase treatment to correct Class II malocclusion is rarely indicated as it is not effective and incurs greater cost than one course of treatment with fixed appliances provided when the child is in adolescence.

5. Early treatment costs more money (in reference to a two-phase treatment to correct Class II malocclusion).

6. When children have early treatment there is a 40% less chance of trauma to their upper incisors.

7. Early treatment does increase the attractiveness of the facial profile and increase self-esteem. But… this effect ‘washes out’ by adolescence. In other words, the effect does not last since another treatment is required in adolescence. In other words, the effect does not last since another treatment is required in adolescence.

8. Functional appliances are very effective at correcting Class II incisal relationships.

9. Functional appliances do not change the skeletal pattern to a meaningful degree.

10. In adolescent treatment there is nothing wrong with extracting upper first premolars and reducing the overjet. This treatment is practiced all over the world in countries where functional appliances are not so extensively used.

11. There are no differences in the treatment result of fixed and removable functional appliances.

12. There is greater patient co-operation with fixed functionals than removables.

13. The Twin Block is the most popular removable functional appliance in the UK.

14. There is no point in putting on or leaving off the labial bow on a Twin Block.

15. If headgear is used to “drive Class II molars distally” the average length of the “drive” is 1.6 mm.

16. When a fixed functional breaks it is more hassle to repair than a Twin Block. Personal comment: With the new fixed functional appliances, breakages are not as problematic. Indeed, even if it is true that a fixed appliance that breaks is more hassle to repair than a Twin Block that breaks, this problem is largely compensated by the fact that a fixed functional appliance is smaller and easier to adapt to than a Twin Block.

17. We should trial removable functional appliance treatment against fixed appliance treatment.

18. The major aetiological feature of Class II malocclusion is a retrusive mandible (retrognathia).

19. The major aetiology is genetic (hereditary) with a small environmental component (allergy, respiratory function, atypical swallowing, chronic mouth breathing or nonnutritive sucking behavior).

20. No orthodontist or dentist can grow a mandible!