I understand that a Class II Division 2 patient requires proper flaring of their upper anterior teeth, and when the mandible is advanced and positioned correctly, there is a tendency for teeth to meet edge-to-edge, so expansion of the uppers is necessary. I am curious to know whether expansion such as is necessary is always of the palatal sort, rather than dental--meaning it results from broadening of the palate by means of an expander (and is unstable in adults, requiring life-long retainer wear at night) as opposed to dental “expansion” which comes from the movement of teeth on the bone and/or tipping when necessary and if possible, the result of which can be stable.In a standard case (assuming one exists), how many millimetres does the upper arch need to spread in order to bite correctly? How much room can typically be created through movement and manipulation of the teeth alone, as opposed to palatal expansion?
I of course understand that each case is unique and some maxillae are considerably smaller and in need of expansion than others, but I’m wondering if there are some general figures you can give me. I’m really rather concerned about the need for life-long use of retainers, though I’m aware that a surgical alternative exists. Do you and other functional orthodontists generally approve of maxillary expansion surgery?
Also, a related question: when the uppers are properly flared and expanded to change a Division 2 into a Division 1, is there a limit to the size of overjet correctable though treatment by use of a functional appliance? I ask because I’ve read a 10mm overjet described as “severe”, and too great for non-surgical treatment, and by my own estimation, I’d imagine that to get the desirable Class I profile, at least 10mm of overjet will need to be created.
Sincere thanks for your help, Doc.
tooth975 - Skeletal expansion is always done because it keeps teeth properly surrounded by alveolar bone and oriented correctly vertically. Dental expansion is not really expansion at all but a tipping, as you have stated, and this is not desirable. Tipping will not allow teeth to distribute biting forces properly and this can cause teeth damage. Another problem is if teeth are moved facially enough dentally and not tipped to eliminate an edge to edge relationship, dehiscences may form because the teeth are moved beyond the confines of the jawbone (the buccal plate). Braces alone can effect limited dental expansion (1-2 mm) but this is almost always not enough. To eliminate an edge to edge bite, the upper posterior teeth must be moved at least a half a tooth (buccal-lingual width) and the smallest tooth would be the premolars so we are talking at least 3-4 mm and for molars it would be much more.
ReplyDeleteMaxillary surgical expansion is a viable alternative in adults and is stable and it is up to the patient whether he/she wants to go through the procedure. To determine how much expansion is needed for under developed jaws, there are several orthodontic analyses that can be used - the Schwarz Index or the Pont's Index. There is a correlation between the widths of the 4 maxillary incisors and palatal widths at the first premolar and first molar level.
It is true that a 10 mm overjet is considered severe but that is only an orthodontic classification term and NOT whether it can be corrected or not. Correction of overjets as high as 10mm are quite common. Any amount greater than that is usually done in 2 stages for adult patient comfort. Likewise, an overbite in which the upper front teeth completely overlaps the lower front teeth so that the lowers are not visible at all is classified as a severe overbite but yet easily correctable so do not let the term "severe" mislead you into thinking that it means untreatable; it is simply a term used to describe the severity of an orthodontic problem.