Effect Of Different Premolar Extraction On The Angulation And Eruption Space Of The Third Molar In Adults

ObjectiveThe purpose of this study has been to evaluate the third molars with respect to what are the changes that occur in the position of the third molar during different premolar extration and nonextration orthodontic treatment in Angle I malocclusion patients; also provide some theoretical basis for the predicting of eruption of the third molar. In order to providing correlated reference material to extract or remain the third molar.Methods66Angle I malocclusion adult patients with the third molar were chosen(31males and35females) with a range of18-25years old; contained127maxillary third molars and124mandibular third molars. Cases were selected in which the third molars had not completed their root formation at the beginning of treatment and had nearly or fully completed their root development at the end of treatment. All the patients were nongrowing subjects who had a normal gonial angle and skeletal Class I at the beginning of the treatment. All the patients divided into third groups: nonextraction group(contained42maxillary third molars and39mandibular third molars),extracted the first premolar group(contained44maxillary third molars and42mandibular third molars)and extracted the second premolar group (contained41maxillary third molars and43mandibular third molars).All cephalometric radiographs were traced and analyzed by Auto CAD software to evaluate the cephalometric characteristics of the third molar angulation and eruption space. Statistical evaluation of the research data was made with SPSS19.0software.Results1.There were no significant difference in the change of the third molar impaction rate in Angle I malocculusion adult patients.2.There were no significant difference in the change in mandibular third molar angulation from pretreatment to posttreatment groups, but there were significant differences in the change in maxillary third molar angulation.3.There were significant differences in the change of the eruption space of the mandibular and maxillary third molar. Space change in5-extraction group was larger than that in4-extraction group.4.there are no significant differenced in the change in the third molar angulation and eruption space in nonextraction group.5. The eruption level of the maxillary third molar after orthodontic treatment was significantly higher in extraction groups, and the eruption level of the mandibular third molar was higher in5-extraction group than in non-extraction group and4-extraction group.Conelusions1.There were no correction in all groups within the third molar impaction and crowding in Angle I malocculusion adult patients.2.The angulation and the eruption space of the third molar had no change before and after orthodontic treatment in nonextraction group.3.For adult orthodontic patients, the maxillary third molar eruption space increased significant in the extraction groups compared with nonextraction group. Space change in5-extraction group was larger than in4-extraction group. The maxillary third molar angulation changed signicantly and the root became uprighting.4.For adult orthodontic patients, the third molar eruption space increased significant in the extraction groups compared with nonextraction group. Space change in5-extraction group was larger than in4-extraction group. But the mandibular third molar angulation changes regardless of the orthodontic treatment. The eruption level of the mandibular third moar only changed significantly in5-extraction group.