Caseanalysis Of Application Of J Hook With Straight Wire In Adult With Bimaxillary Protrusion

Objective: J hooks with straight wire appliance treatment to treat a adult withbimaxillary protrusion，by contracting tooth position and changes in hard and soft tissuebefore and after treatment，to investigate the J hooks to control maxillary anterior teethin sagittal direction and the vertical direction and the improvement of extractiontreatment to soft tissue profile.Methods: A female patient with bimaxillary protrusion was selected fromShenyang Stomatological Hospital in November2011，who was18yeas old. SkeletalClass I malocclusion， maxilla and mandible normal development， bimaxillarydentoalveolar protrusion，lip eversion.Lower lip covered the upper incisors excessively，lower lip protruding significantly (Figure1). When closed lip chin muscle tension，chin dimple nest apparent，mentolabial ditch elevation，soft tissue profile convex；canineand molar are class I relationship，normal overjet and overbite，no crowded. Accordingto model measurements and X-ray measurement data analysis，combining patient’srequest in initial treatment， we decided to adopt the straight wire appliance andextraction treatment which needed extracting the four first premolars. When weprepared closing the extraction space，we asked the patient to use J hook headgear traction to tract canine moving distad to protect molar anchorage，and then verticaldown and moving the maxillary anterior teeth backward to make lips moving backwardand improved soft tissue profile. The case was adopted3M Unitek orthodontic nonmetalbrackets (0.022*0.025in). When pulling canine moving distad，the direction is parallelwith the occlusal plane and the force is200g；When vertical down and moving themaxillary anterior teeth backward，the direction is with the occlusal plane of30°and theforce is100~150g. Wearing time is more than12hours a day. To compare the modelmeasurements and X-ray measurement data analysis before and after treatment，weanalyzed the changes in the patient as well as hard and soft tissues and the teeth position.In addition， compared with a case of adult with bimaxillary protrusion usingmicro-implant anchorage.Results: Treatment course is total24months. After the end of treatment，patient’steeth are alignment；bilateral first molars and canines relationship is neutral，normaloverjet and overbite，normal midline，all the teeth achieved good occlusion. Soft tissueprofile has great improvement and the patient is very satisfied with the treatmentoutcome. To compare the X-ray measurement data analysis before and after treatment：(1)Sagittal changes，SNAdecreased0.5°，the maxillary have a small alteration with thebackword of the anterior teeth；U1-SN decreased12.5°，U1-NA decreased11°，L1-MPdecreased8°，L1-NB decreased8°，U1-L1increased22°，demonstrating inclination ofthe upper and lower front teeth is decreased as well as protrusion is reduced；U6-RLincreased2.2mm，U1E-RL decreased4.8mm，demonstrating J hook protected the molaranchorage leading to the anterior teeth moved more than the posterior teeth. Patient’ssagittal anchorage was well controlled.(2)Vertical changes：U6-PP has no change，which demonstrating posterior teeth did not elongate in the treatment process；U1E-PPdecreased2.5mm， U1A-PP decreased1.5mm， LL-U1decreased1mm， whichdemonstrating mandibular and occlusal plane get a small amount of anticlockwiserotation，the vertical was controlled.(3)Soft tissue changes：Z angle decreased8°，UL-EP decreased1.4mm，LL-EP decreased4.9mm，ULP decreased0.7mm，LLPdecreased4.9mm，which demonstrating the lips moved forward along with incisor teeth；NLA increased5°，which demonstrating nasolabial became shallow. Upper lipthickness increases1.4mm，the thickness of the lower lip basically unchanged；the lowerlip length increases2.0mm，the thickness of the upper lip length basically unchanged.The additional case：(1)Sagittal changes： U6-PP increased0.7mm， U1E-RLdecreased5.7mm，which demonstrating micro-implant anchorage can be significantlyenhanced anchorage.(2)Vertical changes： U1A-PP decreased0.5mm whichdemonstrating micro-implant can slightly down U1；U1E-PP increase1.5mm，OP-FHdecreased1°，which demonstrating pendulum effect along with moving backword U1a long distance，the occlusal plane would occur clockwise rotation.Conclusion:(1)J hook headgear traction can move forward anterior teeth andprotect anchorage in the sagittal，soft tissue profile has significant improvement.(2)Jhook headgear traction can overall down anterior teeth and counteract pendulum effectwhen moving forward. At the same time J hook can prevent clockwise rotation of themandible of the patients with high-angle.(3)The distance of lips moved backward alongwith incisor teeth related with a variety of factors.(4)In the sagittal，J hooks andmicro-implant can enhance the anchorage，but J hooks is better than micro-implant inthe control of the vertical.