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ePaper created 2018-03-13, 09:28:55 | version 1.38.0
research | result, and the patient’s compliance are just a few of the variables that should be considered. Numerous case reports have been published showing how treatment time can be reduced when patients are treated with cor- ticotomy. Case reports, however, have limited scientific validity. The predictability and quantification of treatment time reduction are still not scientifically possible. The addi- tional expenses and morbidity associated with the use of alveolar corticotomy should always be carefully evaluated to determine whether they are worth the saving of few months. A shorter orthodontic treatment is desirable, but certainly not at the expense of a high- quality end result. Regarding OTM, numerous studies have shown that its speed is influenced by bone turnover and the individual response to mechanical forces and it is not related to the level of the forces.12–15 Clinical experience confirms this: there are slow movers and fast movers, but we are still far from recognising them. In addition to this variability, there is the temporary effect of alveolar corticotomy, which we will discuss under the third key. A faster treatment may be a secondary advantage and may be obtained in a sub- stantial way only in those “simple” orthodontic cases that require a naturally short treatment. In conclusion, alveolar decortication should not be combined with orthodontic treatment with the only objec- tive of accelerating OTM and reducing treatment time: the risk of not obtaining either as desired may be high. Despite this scientific evidence against its major claims, alveolar corticotomy has its place in orthodontic therapy. Let us consider the surgical insult and the associated RAP reaction produced at a biomechanical level: the increased metabolism, the transient reduced regional density (osteopenia) created by the increased osteoclas- tic activity, the reduced undermining resorption and hya- linisation (we still do not know exactly what happens in humans) facilitate OTM. The decorticated tooth is less resistant to orthodontic forces and will be easier to move and will require less anchorage. Spena et al. in two studies conducted on a total of 12 adult patients with Class II malocclusions treated with distalisation of the maxillary molars showed how maxil- lary molars could be bodily distalised with simple buccal mechanics and no anterior anchorage.16, 17 Corticotomy was performed only on the teeth to be moved, thus reducing the anchorage needs and their resistance to distal forces. The term “Periodontally Facilitated Orthodontics”, instead of “Periodontally Accelerated Osteogenic Ortho- dontics”, is used to describe a procedure that has the pri- mary goal of simplifying, enhancing and improving OTMs that are difficult or risky, from a biomechanical and biolog- ical point of view. The surgical procedure and the asso- ciated orthodontic treatment and biomechanics depend on the initial problems and the goals of every single spe- cific treatment. This is in agreement with Oliveira et al.: corticotomies should be used to “…facilitate the imple- mentation of mechanically challenging orthodontic movements and enhance the correction of moderate to severe skeletal malocclusions”.18 2. Alveolar corticotomy has limited effect in time Since the early studies of Frost on the biology of frac- ture healing, it is known that the altered metabolism of bone after a traumatic (or surgical) event has lim- ited duration: it is the natural search for equilibrium or homeostasis. The burst of hard- and soft-tissue remodelling starts a few days after the insult, peaks at the first or second month, and returns to a normal pace after a maximum of four to six months. This RAP reaction, when applied to the alveolar bone, causes an accelerated/facilitated movement of the teeth subjected to applied orthodontic forces. The effect lasts for as long as there is this reac- tion, so for a limited part of an orthodontic therapy. This has been confirmed by experimental studies on animals and by clinical studies on patients.19 Clinically, this tem- porary phenomenon leads to the need to perform the alveolar corticotomy when the RAP is necessary. Timing is fundamental. Alveolar corticotomy may be repeated during the treatment with the objective of prolonging the effect.20 The effective benefit, cost and risks must be taken into account. Sanjideh et al. in a split-mouth study on fox- hounds found that a second corticotomy performed after 28 days in the mandible produced a higher rate of tooth movement and a greater total tooth movement.21 How- ever, they concluded that proper timing for a second cor- ticotomy needed to be better determined. Wilcko,22–24 Dibart25 and Murphy26, 27 claimed that con- tinuously activated orthodontic forces applied after decortication may maintain a constant mechanical stim- ulation, and allow a prolonged osteopenic state during which teeth can be moved rapidly. In order to achieve this effect, they recommended seeing patients frequently (every two weeks) and con- tinuing the activation of the applied orthodontic forces. If not, remineralisation would complete the healing process and bring the bone metabolism to a normal level. It must be said that these claims have never been demonstrated either clinically or histologically. ortho 1 2018 21