| BackgroundOrthodontists often facing a tough choice by whether extraction or not for the patients coming with a slightly maxillary protrusion and(or) mild crowding,which also known as borderline cases. As the material continuous development, as well as the treatment paradigm, more and more orthodontists tend to non-extraction treatment for these cases. Firstly, because of its easy to use、reliable outcomes even less dependent on patient, no mention to its almost absolute anchorage,the micro-implant anchorage is more widely used in clinical work by orthodontist, especially in maxillary dentition distalization,which provides a guideline for borderline cases; Secondly, maxillary tuberosity is the back brim of maxillary arch, when the maxillary BMP meets the dental arch distal movement requirement, the whole dentition could move distalization,thus solve the front teeth protrusion and(or) congestion. Thirdly, the paradigm of remaining 28 teeth is mentioned again in the orthodontic clinic, also, many patients refuse extraction. Based on the above background, this study involved slightly protrusion and(or) mild crowding in borderline cases, and take maxillary dentition distalization with micro-implant anchorage as treatment methods. By analysis the cephalometric of each phase of the treatment, evaluate the treatment effect of this method, and explore the possibility of uncontrollable problems arise in the treatment process, lessons for clinical reference. ObjectiveIn this study, borderline cases, slightly protrusion and(or) mildly crowded, were treated by the maxillary dentition distalization with micro-implant anchorage. Cephalometric measurements were made and compared during three phases: T1: treatment began T2: aligning and leveling finished T3: treatment finished.the change of hard and soft tissue were observed and the movement of upper incisors and molars were analyzed to evaluate the clinical effect of maxillary distalization with micro-implant anchorage. Methods16 cases with slightly protrusion and(or) mildly crowded were selected,5 males and 11 females,aged range from 16.6 to 28.3 years old,with a means age of 22.4 years old. All cases were treated with MBT straight wire appliance,all designed with third maxillary molar extraction. Two mini-screws were implanted in zygomatic alveolar ridge area, 0.019×0.025 inch stainless steel archwires were used as the main arch wire. Power chain or Niti closing coil spring were applied from the neck of the mini-screws to the retraction hooks between the lateral incisors and the canines, each side 200 g forces for maxillary dentition distalization. Cephalometric from all the patients were collected by four stages: T1:treatment began,T2:aligning and leveling finished,T3:treatment finished. The cephalometric data were analyzed by SPSS21.0 for paired t-test.Results1.The stability of miniscrew anchorage: 16 patients were implanted with 32 miniscrew anchorage, including 3 off, the dropout rate was 9.38%. and therest of micro implant no loosening in the progress.2. Changes of incisors:From stage T1 to stage T2, U1-L1 on average decreased 2.09 °, U1-SN average increased 1.86 °, L1-MP increased by an average of 1.06 °, U1-FHP increased an average of 0.67 mm, U1-CFH average reduced by 0.88 mm, U1A-CFH average reduced by 1.52 mm, OB average reduced 2.71 mm, the above measurement changes were statistically significant(P<0.05);changes of U1-FHP and OJ were not statistically significant(P>0.05).From stage T2 to stage T3, U1-FHP on average decreased 3.72 mm, U1A-FHP reduce an average of 0.56 mm,OJ mean less of 3.32 mm, U1-L1 on average increased 5.45°, U1-SN average decreased 7.46 °, U1A-CFH increased an average of 0.99 mm, all the above changes were statistically significant(P<0.05);changes of OB、U1-CFH and L1-MP were not statistically significant(P>0.05). From stage T1 to stage T3, that is, before and after treatment were compared,U1-FHP on average decreased 3.05 mm, U1A-FHP reduce an average of 0.69 mm,U1-L1 on average increased 3.36°, U1-SN average decreased 5.60°, OJ average reduced 3.21 mm, L1-MP on average increased 1.0°, OB on average decreased 2.63 mm, U1A-CFH average decreased 0.53 mm, there were statistical significance in the differences(P<0.05); the change of U1-CFH was not statistically significant(P>0.05).3.Changes of molars:From stage T1 to stage T2, changes of U6A-CFH, U6-CFH, U6-FHP, U6A-FHP, U6-CFH(°) were not statistically significant(P>0.05). From stage T2 to stage T3,U6-CFH average decreased 1.31 mm, U6-FHP reduced an average of 3.20 mm, U6A-FHP reduced an average of 2.73 mm, U6-CFH(°) average increased 4.02 °, all the changes were statistically significant(P<0.05); the change of U6A-CFH was not statistically significant(P>0.05). From stage T1 to stage T3, that is, before and after treatment were compared, U6-FHP reduced an average of 3.11 mm, U6A-FHP reduced an average of 2.74 mm, U6-CFH average decreased 1.12 mm, U6-CFH(°) average increased 3.99 °, there were statistical significance in the differences(P<0.05); the change of U6A-CFH was not statistically significant(P>0.05). 4. Changes of hard tissues:From stage T1 to stage T2, the changes of SNA、SNB、ANB、A-CFH、A-FHP、SN-MP、SN-PP were not statistically significant(P> 0.05); SN-OP decreased by 2.20° on average, there was statistical significance in the differences(P<0.05). From stage T2 to stage T3, the changes of SNA、SNB、ANB、SN-PP、A-CFH、A-FHP were not statistically significant(P>0.05); SN-MP on average increased 0.72°, SN-OP average increased 3.60 °, the above measurement changes were statistically significant(P<0.05). From stage T1 to stage T3, that is, before and after treatment were compared, SNA,SNB, ANB, A-CFH, A-FHP, SN-PP,whose changes were not statistically significant(P>0.05). SN-MP on average increased 1.24 °while SN-OP increased on average 1.4 °, the differences of which were significant(P<0.05).5.Changes of soft tissues: From stage T1 to stage T2, NLA average decreased 1.44 °, Ls-E average increases 0.84 mm, Ls-FHP average increases 1.42 mm, changes of which were statistically significant(P<0.05); the change of Li-E was not statistically significant(P>0.05). From stage T2 to stage T3, NLA average increased 4.34 °, Ls-E reduces an average of 3.31 mm, Ls-FHP average decreased 3.84 mm, the above measurement changes were statistically significant(P<0.05); the change of Li-E was not statistically significant(P>0.05). From stage T1 to stage T3,that is, before and after treatment were compared, NLA average increased 4.33 °, Ls-E reduces an average of 2.46 mm, Ls-FHP average decreased 2.43 mm, the above measurement changes were statistically significant(P<0.05); the change of Li-E was not statistically significant(P>0.05). Conclusions1. For mild maxillary protrusion and(or) mild crowded borderline cases, the method of distalizing of maxillary dentition with miniscrew anchorage can achieve satisfactory treatment results.2.The distance of dentition distal movement is very significant by distalizing of maxillary dentition with miniscrew anchorage;incisors tends to tipping movement and molars moves approximate bodily movement;soft tissue changes greatly and patient-side appearance has significantly improved. |
PDF Full Text Request