| ObjectiveThe aim of this study is to evaluate advantages and disadvantages of two types of appliances both with the help of mini-screw for anchorage in upper molar distalization using the three-dimensional laser scanner technology and the two-dimensional cephalogram MethodsTotally,44 non-growing patients(male 4,female 40,average age 26.9±2.3years)meeting the inclusion criteria and exclusion criteria who needed upper molar distalization were selected in our study.They were divided into two groups to use two different molar distalization methods: Group1 used Invisalign appliances with the help of mini-screws for anchorage,group2 used straight wire appliances with the help of the mini-screws for anchorage.Dental casts and cephlograms of two groups were taken before(T0)and after molar distalization(T0).And the three-dimensional digital models were created from a 3_Shape laser scanner(Copenhagen,Denmark).We analysed and compared dental movement on three-dimension of both groups using Rapidform2006 software(INUS Technology,Seoul,Korea),and dental and skeletal changes on cephalograms of both groups also.Result1.In Invisalign group,from T0 to T1,SNA increased only by 0.56,while MP-SN,MP-FH had no change.the upper molar moved distally by 2.28±0.72 mm with distal tipping of 6.38°±4.6°and intrusion of 1.17mm±0.66mm;the upper second premolar had a mild mesial tipping of 0.72±5.22°at T1;the upper central incisor had a significant diference in labial movement and tipping(P<0.05)The upper first molar moved distally2.03±0.97 mm with a significant distal tipping,labial tipping and intrusive movement from T0 to T1 in Three dimensional model superimposition measurement;the second upper premolar had a mild mesial tipping,intrusion,crown buccal tipping at T1;the upper central incisor moved mesially by 1.10±0.82 mm and intruded by 0.77±0.89 mm.2.In the straight wire appliance group,the first upper molar has significant differences between T0 and T1 according to cephalometric mearurement.The first maxillary molar actually moved distally4.95±2.48 mm,with distal tipping of 8.32±7.60°,and intrusion of 2.42±1.94mm;the second upper premolar has significant differences between T0 and T1,including a minimal distalization 1.65±2.24 mm,distal tipping of 5.29±7.22°.The upper incisor has been intruded by 2.40±2.99 mm and OB has been induced by 3.32±1.5mm without remarkable buccal movement and labial toque.The upper first molar moved distally 3.99±1.17 mm with a significant distal tipping,labial tipping and intrusive movement from T0 to T1 in Three dimensional model superimposition measurement,the upper second premolar has a significant diference of the movement in vertical and labial direction;the maxillary incisor had been intruded 1.91±1.05 m with a mild crown lingual tipping8.45±9.76°,which has significant diference from T0 to T1.3.There was a statistically significant difference in the distance between the straight wire appliance group and the Invisalign appliance group(P<0.01).The diference between the two groups was 2.66±0.76 mm.The maxillary central incisor movement in the vertical,buccal,lingual direction between two groups had a significant diference.The straight wire appliance group had a more significant intrusive effect on the central incisors compared with the Invisalign appliance group of 1.9±0.69 mm,as well as OB of 2.93 ± 0.50 mm(P < 0.001).In the Invisalign appliance group,the loss of anchorage in incisor area resistance was significantly higher than that of the straight wire appliance group(P<0.001)The results of three-dimensional model measurement and analysis showed that The distance of the molar distalization,intrusion and distal tipping in the straight wire appliance group was significantly larger than that of the Invisalign appliance group.In the straight wire appliance group,the maxillary second premolar showed a small amount of distal movement while there was a small amount of mesial movement in the Invisalign appliance group.During the distal movement of the molars,the two groups of maxillary second premolars showed depression,buccal movement and tilt,but the changes in the straight wire appliance group were significantly greater than those in the Invisalign appliance group.In the straight wire appliance group,the incisor intrusion was significantly larger than that of the Invisalign appliance group.And the loss of the incisor anchorage was less than Invisalign group.The desired distance 3.99±1.17 mm were gained in 32.16±3.02 weeks by using straight wire appliances,and 2.03±0.97 mm were gained in 20.86±6.09 weeks by Invisalign.There is no significant differences of the velocity between the two groups.Conclusions1.Both the straight wire appliance and the Invisalign appliance can achieve effective molar distalization with the molars intruded,distal tipping,buccal toque to different degrees;the mandibular plane has no change;there is no significant difference of the velocity in molar distalization between two groups.2.The Invisalign can make less distal tipping,buccal toque during molar distalization;the premolars did not show obvious buccal movement and tipping,and the width of the middle arch did not increase significantly.However,the loss of anchorage in anterior arch is more serious than that of the straight wire appliance,suggesting that the way of molar-distalization and enhance the anchorage in anterior arch should be considered.3.The straight wire appliance with mini-screw anchorage can intrude incisor effectively during molar distalization,which is beneficial to patients with deep overbite.However the premolars showed obvious buccal movement and tipping,resulting in an increase in the width of the middle and posterior arches.The clinician should consider the indications,modify the shape of the archwire and control toque of posterior arch. |
