A Comparative Study On Retromolar Space And Angulation Of Mandibular Third Molar In Different Vertical Skeletal Type

ObjectiveThe aim of this study is to evaluate the changes on mandibular third molar angulation and retromolar space with different ages and different vertical facial skeletal type in Angle I malocclusion patients.In order to providing correlated reference material to extract or remain mandibular third molar.Methods905Angle I malocclusion patients with mandibular third molar in both sides were chosen (405males and500females) with a range of12-28years old.All the patients divided into ten groups based on the age.12years group137cases;13years group134cases;14years group111cases;15years group113cases;16years group98cases;17years group77cases;18years group55cases;19years group46cases;20years group49cases;21years and above group85cases.Measure the SN-GoMe angle in order to divided patients into three different vertical facial skeletal types. All the different vertical facial skeletal types divided into four groups based on the age.12-14years group:high angle127cases, low angle group120cases,average angle135cases;15-17years group:high angle98cases, low angle group78cases, average angle112cases;18-20years group:high angle50cases, low angle group40cases,average angle60cases;21years and above group: high angle28cases, low angle group23cases,average angle34cases.All cephalometric radiographs were traced and analyzed by Auto CAD2007-Simplified Chinese software to evaluate the cephalometric characteristics of mandibular third molar angulation and retromolar space. Four measurements related to mandibular third molar were identified and all the results were analyzed by statistics.Results1. The measurements of left and right panoramic radiographs have no statistically difference in females and males.2. The males’third molar angulation were higher than females at14year.But the result transform the opposite at16-17year. The males’ retromolar space were smller than the famales at13year,but tend to be higher at16-19year.3. Compared with the near age group third molar angulation tend to be decreased in males at15-16,20-21year and female at14-15,18-19year.4. Compared with the near age group the third molar retromolar space tend to be increased in males at14-16year and female at12-14year.5. The males’third molar angulation were highest in high angle group during15-20year. For the female during12-14year the third molar angulation was lowest in the low angle group. There have no statistically difference in high angle group and average group.6. The males’retromolar space were lowest in high angle group during15-20year. For the female during12-17year the retromolar space was lowest in the high angle group. There have no statistically difference in low angle group and average group.Conclusions1. For males the third molar tend to be more upringht at15-16and20-21year,but for females the age were more earlier at14-15and18-19year.2. For males the retromolar space increased rapidly at14-16year.Famales increased rapidly at12-14year. The retromolar space increased gradually during12-21year both in males and females.3.The statistically difference among the different vertical facial skeletal type were during12-20year, there have no statistically difference at21year and above group. For males the statistically difference mainly appeared at15-20year, for females at12-17year.4.The low angle males have more upright third molar at15-20year and more sufficient retromolar space at15-20year than the high angle group. The low angle female have more upright third molar at12-14year and more sufficient retromolar space at12-17year than the high angle group.