Australasian Dentist Issue 89

Category AustrAlAsiAn Dentist 53 the anchorage requirements. For those patients that are edge to edge or half cusp Class 2 in the molars, there can be unfavourable space loss in the upper arch, which then would move the molar to a full Class ii relationship. these patients would benefit from the provision of an upper nance space maintainer during the driftodontics phase after first premolars have been extracted. this can prevent the unfavourable mesial drift of the upper first permanent molar. A major advantage of the serial extraction procedure is that the crowded permanent canines are not displaced buccally from the line of the arch. in many late premolar extraction cases, the crowded canines are displaced to the buccal such that they erupt with minimal attached gingiva. this gingival retreat remains after the fixed appliance treatment. By contrast, the serial extraction cases have the canines erupt into attached gingiva which is a significant advantage. Another advantage to serial extraction is a reduction in the Phase ii treatment time. When studies that compare similar treatment outcomes for serial extraction and late premolar extraction are done, we find that the serial extraction cases have a treatment time reduction of anywhere from 4 to 12 months, depending on the study. Also, the serial extraction cases tend to have a lower PAr index compared to late premolar extraction cases, as a result of the driftodontics. some claim that the improved alignment of the incisors secondary to serial extraction results in improved stability. the study by little shows that this is not the case. However, there may be a difference in stability between those serial extraction cases that show good alignment of incisors compared to those that do not show good incisor alignment after serial extraction. this supposition is based on Haruki’s study which showed that Phase i treatment involving incisor alignment did result in greater long term stability of the lower incisors. it may therefore be that serial extraction cases that exhibit good incisor alignment after extraction alone may have greater stability, but this supposition needs to be tested with appropriate research. extractions have been criticized as being detrimental to the face. However, in a comparison of serial extraction cases with and without treatment to late premolar extraction cases, there is no difference in facial profile outcome. Most facial flattening occurs from normal growth. When you consider that the extraction is done to resolve crowding of 8mm or more per arch, it makes sense that most of the tooth movement is taken roll in towards the lingual. the Curve of spee deepens after serial extraction and frequently the lower incisors tip back 5° _after lower premolar extraction. there can also be a two-step occlusal plane with 6 anterior teeth (canine-to-canine) at one level and the posterior dentition at a separate different level. During active treatment, the levelling of the Curve of spee usually returns the lower incisors to their pre-extraction position. Often during active orthodontic treatment, it is the lower arch treatment which takes the greatest amount of treatment time both because of the levelling and also the need to upright tilted teeth adjacent to the lower extraction site. Another modification in serial extraction results from consideration of premolars, results in less intervention. (Figure 2 serial extraction approach with removal of deciduous first molars and enucleation of first premolars ) When done under sedation or general anaesthesia, the child often does not associate the extractions with a negative dental experience. the major change is the improvement in alignment secondary to serial extraction. there is tilting of teeth adjacent to the lower extraction sites but not adjacent to the upper extraction sites. specifically, the lower canine tips back into the lower extraction site, requiring future uprighting. in addition to this, the Curve of Wilson in the lower arch becomes more accentuated. not only do the lower molars tip forwards, but also Figure 2a Serial extraction approach with removal of deciduous canines at about age 7.5 years Figure 2b Serial extraction approach with removal of deciduous first molars and enucleation of first premolars at about age 9.5 years Figure 3 a patient who should have undergone serial extraction but refused Figure 3a Patient with severe upper and lower crowding figure 3b 2 years later after declining serial extraction approach Figure 3c occlussal view 2years later after declining serial extraction lInICal