How To Increase the vertical dimension by molar eruption
Dr. Michel Champagne, BA, DMD, MAGD, IBO, CDE,
The lack of vertical molar eruption is more often seen with the lower molars in case of hypodivergency and is relatively easy to treat if a proper diagnosis is made. The earlier the better and the option of treating the patient during growth is the best one but not always possible. At a young age, the clinician will probably opt for a passive molar eruption by posterior disarticulation, more often in the mandible and by using a removable appliance with anterior bite plane or even with the use of composite lingual to the upper incisors (mini-molds). You must make sure that the tongue is kept away from the occlusal surfaces of the teeth you want to extrude.
How do we manage the lack of vertical dimension in patient wearing full braces when the treatment is well on its way and we need molar eruption to improve the skeletal and dental deep bite resulting in better lower face height. Are we better off by rebracketing or what other options are available. In any case, the extrusion of the lower posterior teeth will necessitate a desarticulation of the teeth involved and also a planification of the anchorage unit(s).
What are our options:
- In mixed dentition, as said earlier, we will take the approach of passive eruption with a minimum of appliances with options like the lingual upper incisors mini-molds, a Hawley appliance with an anterior bite ramp, a Rickinator, etc. The tongue must behave or be managed to assure good results (Images 1 and 2).
- In the permanent dentition with full fixed braces we do have some options but remember to manage the tongue if appropriate:
- Desarticulation is a must in all cases.
- Proper anchorage design, normally on a heavy SS wire with consolidation of a group of teeth, a trans-palatal bar, mini-screw(s) or even by extra-oral anchorage are all options. The choice of anchorage is a personal to each clinician but it has to be sufficient and these days a mini-screw facilitates our task (Image 3).
- Eruption of the concerned group using the rebound memory of a CuNiti wire is also an option. The wire is curved during engagement because an excessive curve of Spee is normally present and the memory of the wire wants to go back to it’s initial straight shape pulling on the teeth with an eruption force. This will occur only and if the teeth have been disarticulated. The clinician can assist and support this rebound wire effect with the use of weak 2 ounces elastics (Image 4). Some clinicians will suggest a misbracketing on purpose. Personally, I do not like this concept because often we will have to rebracket the case at one point and that will cost us a few months of treatment. The same rebound effect can occur without misbracketing.
- Eruption of the concerned group of teeth towards the end of treatment when we have a big SS or TMA wire, like a 19 x 25. The wire is sectioned directly in the mouth mesial and distal to the group of teeth you want to erupt. The full arch wire now becomes a multi section wire and all the sections are be kept securely in place (cinch the segments to avoid emergencies). Vertical elastics will be placed between the anchored upper teeth and the lower teeth on the sectioned wire, the teeth you want to erupt. The elastics can be buccal and/or lingual depending on the case. The anterior and posterior vertical sections of the elastics should, most of the time, be oriented to continue the initial correction i.e. in a Class 2 direction for Class II cases or Class 3 direction for a Class III malocclusion (Image 5).
Continue to improve your techniques and stay safe.
Figure 1. Passive eruption with mini-molds.
Figure 2. Passive eruption with a Rickinator.
Figure 3. Using a mini-screw. for anchorage
Figure 4. Using an elastic to help the rebound effect of the wire
Figure 5. Box elastics.