Maxillary third molar position in Class II malocclusions: the effect of treatment with and without maxillary premolar extractions

Abstract

The present study compared the number of erupted and functioning maxillary third molars and their mesio-distal angulation in patients with Class II malocclusions orthodontically treated with and without extraction of two maxillary premolars and fixed appliances. For that purpose, the records of 55 patients were selected, which were divided into two groups. Group 1 was treated without extractions and comprised 28 patient records (19 males and 9 females), with a mean age of 19.03 years [standard deviation (SD) = 2.33], treatment time of 2.59 years (SD = 1.08), and follow-up time of 6.48 years (SD = 2.42). Group 2 was treated with extractions and comprised 27 patient records (14 males and 13 females), with a mean age of 19.94 years (SD = 2.87), treatment time of 2.95 years (SD = 1.17), and follow-up time of 5.88 years (SD = 2.96). Analysis of the erupted and functioning maxillary third molars was conducted on the maxillary and mandibular dental casts. The mesio-distal angulations of the maxillary third molars were assessed on panoramic radiographs with the presence of both maxillary third molars. The results demonstrated that the number of erupted and functioning maxillary third molars was statistically greater (P = 0.01) in Class II subjects treated with extraction of maxillary premolars, when compared with those treated without extractions. The patients treated with two maxillary premolar extractions presented significantly smaller third molar mesio-distal angulations, that are more favourable to eruption, than those treated non-extraction.

Influence of unilateral maxillary first molar extraction treatment on second and third molar inclination in Class II subdivision patients

“…16 On the other hand, Class II individuals treated with two maxillary first premolar extractions demonstrated a double increase in the mesial inclination of maxillary third molars compared with those treated with via the nonextraction route. 6 In extraction treatment planning (premolars or molars), differences in the intra-arch location of the extraction site and in the amount of tooth mass removed should be considered. 6 The closer the position of the extracted tooth to the maxillary third molar, the more influential will be the extraction on the M3 development.…”

“…6 In extraction treatment planning (premolars or molars), differences in the intra-arch location of the extraction site and in the amount of tooth mass removed should be considered. 6 The closer the position of the extracted tooth to the maxillary third molar, the more influential will be the extraction on the M3 development. 17 In this context, molar extraction protocols may produce more favorable conditions for M3 uprighting than do premolar extractions.…”

“…In our study, we selected instead two horizontal references planes based on skeletal structures, of which the repeatability had been validated by previous research. 6 Despite the high correlation between the measurements defined by the two planes, we decided to use both types to increase measurement validity.…”

“…The landmarks, reference planes, and angular measurements 6 used for the study are displayed in Figure 1. Molar inclination was estimated using the following angles: M2/IOP, the angle between the M2 long axis and the interorbital plane (IOP); M3/IOP, the angle between the M3 long axis and the IOP; M2/ITP, the angle between the M2 long axis and the intertuberosity plane (ITP); M3/ITP, the angle between the M3 long axis and the ITP (Figure 1).…”

“…5 In theory, extraction of posterior teeth followed by orthodontic mesialization of the buccal segments may enhance the mesioangular inclination, and therefore the eruption status, of M3s. Orthodontic treatment involving extraction of two maxillary first premolars, 6 four first premolars, 7 or four first molars 8 resulted in significant improvement in the developing M3 position compared to nonextraction therapy. Other researchers observed no significant differences on the final M3 angulation between subjects orthodontically treated with either first premolar extraction and nonextraction 1,9 or first premolar and second molar (M2) extractions.…”