Case Report:Two Cases With Sever Crowding In Orthodontic Treatment With PASS Technique

Objective: To investigate the treatment of two cases with sever crowding by PASS Technique.Two cases were selected from the First Affiliated Hospital of Dalian Medical University,dated from January 2015 to January 2016.The cases consisted of one female case and one male case.The first case was an 18-year-old female patient,her permanent dentition included a class III molar relationship.The first molars had mesial inclination indicating that physiological anchorage is lost.Her ANB was 8.5 °,dentoskeletal frame classification was class II,hyperdivergent,severe crowding of the dentition,and anterior open bite with flat UOP and POP.The second case was a 16-year-old male patient,his permanent dentition including a class III molar relationship.His ANB was5°,dentoskeletal frame classification was class II,hyperdivergent,severe crowding of the dentition with deep overjet.His UOP was flat.The patient’s second molar eruption was significantly less than the height of the posterior teeth,so his POP was more steep.The data of these two patients were systematically analyzed and discussed.Two patients’ treatment plans are similar: First:Orthodontic-orthognathic surgical treatment,second,orthodontic treatment.Because the two patients and their families refused the surgical treatment,the two patients only chose the orthodontic treatment.Both patients removed four first premolars and the orthodontic treatment technique used was PASS Technique.The treatment was discussed by cephalometric analysis,“best-fit superimposition” and “Pitchfork analysis” before and after treatment.Result: The female patient received a total of 22 months of treatment,although ANB has not changed,and the skeletal problem has not been resolved,the effect is still significant.U1-NA decreased from 4mm to 0mm,U1-NA decreased from 28 ° to13°,U1-SN decreased from 110° to 94°,indicating that the maxillary incisors’ uprighting is obvious,L1-NB decreased From 10 mm to 9mm,L1-NB decreased from32° to 29°,indicating a slight lingual tipping of the lower incisors,Y-axis angle from 72 ° to 73 °,indicating a slight clockwise rotation of the mandible.EL-UL decreased from 3mm to 0mm,EL-LL decreased from 6.5mm to 4mm,Z angle measured value increased from 52° to 55°,indicating that patient’s facial profile improved significantly from the convex type into a straight type.Before the treatment,the UOP was 4 °,which is less than the normal 10° ± 3.58°,after treatment the UOP becomes 19 °,incisors’ uprighting can be found through the cephalometric measurements.Before treatment,the POP was 13 °,although in the normal range of14.9° ± 3.85 °,it can be found that the patient with maxillary first and second molar have varying degrees of physiological anchorage loss,after the treatment,POP was 16 °,within the normal range,at the same time,in the treating the POP,the first molar and the second molars’ distal inclination have created physiological anchorage.The male patient received a total of 9 months of treatment.Similar to the female patient,ANB didn’t change.U1-NA decreased from 8mm to 3mm,U1-NA decreased from 33° to 20°,U1-SN decreased from 114° to 100°.Incisors’ uprighting can be observed through the cephalometric measurements.L1-NB decreased From 9mm to8 mm,L1-NB decreased from 38° to 33°,indicating a slight uprighting mandibular incisors,Y-axis angle decreased from 72 ° to 70 °,Indicating a slight counter-clockwise rotation of the mandibular.EL-UL and EL-LL were not changed,but Z angle(°)measured value increased from 55° to 58°,indicating that the patient’s facial profile has changed from the convex type into a straight type.Before treatment,UOP was 11 °,within the normal range,after treatment UOP was 12 °,no significant change can be found.Before treatment POP was 24 °,which is steeper than normal,after treatment it was 17 °,which is a much improvement than before.The maxillary second premolar,first molar,second molar growth occurred forwards and downwards,and the second molar showed a more mesial inclination and a more forward and downward growth,significantly improving the previous steeper POP.Through the overlap of the cephalometric measurement we can see the improvement of previous steeper POP,the mandible also occurred in a more substantial forward-down growth,as POP was more flat than,the mandible showed a counter-clockwise rotation,showing significant improvement.Conclusion:(1)Case One:For this adult female patient,PASS Technique can solve the problem of anterior open bite and sever crowding rapidly,improve the facial profile significantly and maintain the POP within the normal range.(2)Case Two:For this male patient,PASS Technique can solve the problem of sever crowding rapidly and make the mandible a counter-clockwise rotation by improving the steeper POP.