BACKGROUND: Tooth intrusion easily leads to root resorption. Previous studies regarding orthodontic treatment-caused tooth root resorption or retrospective clinical studies based on X-ray films have great errors in outcome evaluation because of intrusion force which cannot be precisely controlled. OBJECTIVE: This study established dog models of mini-implant anchorage for incisor intrusion to observe the histological changes of tooth root and periodontal tissue and to evaluate the feasibility and safety of mini-implant anchorage for incisor intrusion. METHODS: Nine dogs were assigned to one control group (n = 1) and four experimental groups per time to sacrifice (1, 2, 4 and 12 weeks; n = 2 dogs for each experimental group). No force was added to the control group. In the experimental groups, mini-implant as an anchorage was placed in the buccal alveoli between maxillary second and third incisors on each side. A traction force of 100 g was imposed to each side to intrude the maxillary first and second incisors on each side. At 1, 2, 3, and 4 weeks (traction force was imposed for 4 weeks and after withdrawal of extraction force, mini-implant was retained in place for 8 weeks), dogs were sacrificed. The first and second incisors together with gingival and alveolar bone were completely resected to prepare histological specimens. Following hematoxylin-eosin staining, histological changes of tooth root and periodontal tissue were observed. RESULTS AND CONCLUSION: Compared with the control group, in the 1-week group, histological changes were primarily at the root tip and alveolar ridge crest, alveolar bone and cementum were absorbed and peridental membrane presented glassy degeneration in local region; in the 2-week group, bone resorption degree and range were obviously enlarged, and bone resorption developed from root tip, root middle part to cervical part; in the 4-week group, bone resorption was still active and the glassy degeneration of peridental membrane disappeared; in the 12-week group, significant improvement in alveolar bone and cemental surface was observed, bone lacuna had deposition of newly formed bone, and peridental membrane was orderly arranged. These findings reveal that in the mini-implant anchorage for dog incisor intrusion, early histological changes primarily appear in the root tip and alveolar ridge crest, presenting as alveolar bone and cemental resorption and the glassy degeneration of the peridental membrane. Bone resorption extent and range expand with the persistence of traction force. After withdrawal of traction force, tooth root and periodontal tissue were gradually repaired

BACKGROUND:Large bone defect caused by various reasons has been a difficult problem in clinical practice. To establish a standard experimental animal model of critical bone defects has vital significance for evaluating the efficacy of bone osteogenesis using various materials and techniques.
OBJECTIVE:To establish the rabbit model of parietal critical bone defects and to determine the diameter of the critical defects of parietal bone in limited time.
METHODS:10 New Zealand white rabbits were selected. The skul seam was treated as the boundary. Four ful-thickness round defects of bone in the parietal bone were made, with diameters of 4, 5, 6 and 7 mm, so as to establish rabbit models of parietal critical bone defects. Gross anatomical observation, X-ray and cone beam CT were used to determine the bone density in the new bone defect area. The healing of bone defects was evaluated by histological examination.
RESULTS AND CONCLUSION:After 12 weeks, the 4 mm group showed high bone healing capacity significantly, and part of the bone bridge had been connected completely. Quantitative analysis of bone mineral density revealed that gray value at defect site and trabecular bone area at the same magnification and the same vision in the 4 mm group were significantly higher than the other three groups (P<0.001). Only a smal amount of new bone in the periphery of bone defects appeared in the 5, 6 and 7 mm groups. The center of defect site was mainly fil ed by fibrous connective tissue. The results confirmed that this study successful y established rabbit models of parietal critical bone defects. During the 12 weeks of observation, bone defects with a diameter of ≥ 5 mm could not be self-healed, which was conformed to the criteria of critical defects of bone, and could be used as a reference value for critical parietal bone defects of a rabbit.

Primary failure of eruption(PFE) is an unusual dental disease.Clinically,it is difficult to distinguish PFE from Mechanical failure of eruption (MFE),and the diagnosis is especially challenging since misdiagnosis and mistreatment always take place.The present paper reports the treatment experience of a case of PFE.

An adult patient with skeletal crossbite and mandibular deviation was treated by mandibular molar distalization using micro-im-plant and intermaxillary traction.After treatment,the facial contour of the patient was improved,the Class Ⅰ molar and cuspid relationship was achieved.

BACKGROUND:Studies have shown that simvastatin can promote bone formation, but there is stil controversial on the osteogenic mechanism and osteogenic effect.
OBJECTIVE:To explore the osteogenesis effect of the composite of simvastatin and Bio-Oss versus simple Bio-Oss material on the repair of rabbit mandibular defects.
METHODS:Twelve New Zealand white rabbits were selected to establish alveolar bilateral mandibular defects models. The composite of simvastatin and Bio-Oss was implanted randomly in one side of defect region;Bio-Oss was simply implanted in the other side of defect region. Both sides were covered with Bio-Gide bilayer col agen membrane. Four rabbits in each group were sacrificed at 4, 8 and 12 weeks after implantation, and the general observation X-ray film, oral cone-beam CT imaging observation and histopathologic study and quantitatively were conducted to quantitatively and qualitatively comparative analyze the alveolar bone formation in the graft region.
RESULTS AND CONCLUSION:At 4, 8 and 12 weeks after implantation, new bone formation was found and increased with time prolonging. With the gradual degeneration of high resistance fire Bio-Oss bone meal, the bone mineral density at different time points of the simvastatin composite Bio-Oss group was lower than that of the simple Bio-Oss group (P<0.05). The percentage of bone formation in the simvastatin composite Bio-Oss group was significantly higher than that in the simple Bio-Oss group (P<0.05). Simvastatin could accelerate Bio-Oss degradation and promote new bone formation in bone defects repairing.

BACKGROUND:Studies have found that the platelet-rich plasma (PRP) can promote bone and soft tissue injury repair, but its effect on the process of bone healing is stil controversial.
OBJECTIVE:To contrastively observe the osteogenesis effect of PRP/Bio-Oss/Bio-Gide in the repair process of alveolar bone defect in rabbits, so as to explore the role of PRP in bone healing.
METHODSixteen New Zealand white rabbits were used to establish animal models of critical-size alveolar bone defect. One side was damaged randomly and repaired by PRP/Bio-Oss/Bio-Gide as experimental side, and the other side repaired by Bio-Oss/Bio-Gide as control side. Four animals were executed at each time-point, postoperative weeks 2, 4, 8, 12. Through general observation, X-ray radiograph, Cone Beam CT assessment, histological examination, the osteogenesis effect in the defect region was qualitatively and quantitatively analyzed.
RESULTS AND CONCLUSION:It could be know from each observation index that as time went on, the experimental and control sides had a different degree of new bone formation and the degradation-absorption of bone graft material. At 12 weeks, continuous cortical bone formation was seen on the surface of the experimental side, new bone formed and tended to be mature, obvious degradation of the bone graft was found, but those in the control side were not as good. At each time-point of 2, 4, 8, 12 weeks, the bone mineral density of the experimental side were lower than that of the control side (P<0.05), but the percentage of new bone area was larger than in the experimental side than the control side (P<0.05). These findings indicate that the PRP/Bio-Oss/Bio-Gide has a better osteogenesis effect than the Bio-Oss/Bio-Gide in the repair process of alveolar bone defect in rabbits, and PRP can promote new bone formation and degradation-absorption of Bio-Oss.

An adolescent patient,in the peak of growth and development,with severe skeletal Class Ⅲ malocclusion and maxillary impacted canines was treated by removable and fixed appliances in the upper and lower dental arches.After treatment,the crossbite was relieved,the facial contour was improved,the integrity of the denture was kept and the Class Ⅰ molar relationship was achieved.

Objective To compare the osteogenesis effect of platelet-rich fibrin (PRF) and platelet-rich plasma (PRP) and investigate the methods of repairing bone defect with PRF.Methods Four defects measuring 7 mm in diameter were made in the parietal bone of 16 New Zealand white rabbits.The defects named A,B,C,and D and were filled with PRF,PRF-mixed Bio-Oss (BO),PRP-mixed BO,and PRP separately.Every four rabbits were sacrificed at postoperative 2,4,8,and 12 weeks and defects were examined grossly,radiographically,and histologically.Besides,bone mineral density and bone trabecular area were determined and expressed as gray-scale values.Results Newly regenerated bone appeared at all defect areas at postoperative 2 weeks.Thereafter,more bone formations were observed over time and area B demonstrated the best bone healing followed by area C,A,and D in succession.Bone trabecular area in areas A,B,C,and D was 10.95 ± 0.58,15.45 ± 0.79,10.22 ± 0.43,and 6.58 ± 0.64 at postoperative 2 weeks with significant differences in pair comparison (F =22.869,P ＜0.01),followed by some increase at postoperative 4 and 8 weeks.Whereas,bone trabecular area in areas A,B,C,and D increased largely at postoperative 12 weeks (35.09 ± 0.58,59.44 ± 0.60,50.75 ± 1.56,and 30.94 ± 1.19) and showed significant difference when compared in a pair (F =1 002.904,P ＜ O.01).Conclusion PRF is superior to PRP in promoting bone formation,but a much better effect of PRF/BO composite is observed in bone repair.

Objective:To compare the clinical effects of rapid maxillary expansion between tooth-borne and hybrid-borne expanders.Methods:PubMed,Cochrane Library,EMbase,CBM,CNKI,VIP and WanFang Data were searched from the date of their establishment to October 31,2015,to find clinical trials about comparison of rapid maxillary expansion by tooth tissue-borne versus hybrid-borne expanders.The quality of the included studies was evaluated by 2 independent reviewers,and Meta-analysis was performed by using RevMan 5.3 software.Results:8 articles with 206 cases were included.The results of Meta-analysis showed that:there were significant differences between the 2 groups in the changes of the right first molar dental inclination [MD =-1.62,95 ％ CI (-3.18,-0.07)],inter first premolar width [SMD =-0.86,95％ CI(-1.47,0.25)] and molar alveolar inclination [SMD =-0.86,95％ CI(-1.10,-0.20)].There was no significant difference between the 2 groups in the changes of inter first molar ~dth [SMD =-0.08,95％ CI (-0.6l,0.45)],the left first molar dental inclination [MD =-1.12,95％ CI(-2.57,0.33)],maxillary width [SMD =-0.30,95％ CI(-1.08,0.47)].Conclusion:The effect between tooth-borne and hybrid-borne expanders in the expansion of maxillary dental arch is similar.However,tooth-borne expanders may cause greater inclination of first molar and alveolar process.

UNLABELLEDTo construct a three-dimensional finite element model comparing between one-step and two-step methods in torque control of anterior teeth during space closure.

METHODSDicom image data including maxilla and upper teeth were obtained though cone-beam CT. A three-dimensional model was set up and the maxilla, upper teeth and periodontium were separated using Mimics software. The models were instantiated using Pro/Engineer software, and Abaqus finite element analysis software was used to simulate the sliding mechanics by loading 1.47 Nforce on traction hooks with different heights (2, 4, 6, 8, 10, 12 and 14 mm, respectively) in order to compare the initial displacement between six maxillary anterior teeth (one-step method) and four maxillary anterior teeth (two-step method).

RESULTSWhen moving anterior teeth bodily, initial displacements of central incisors in two-step method and in one-step method were 29.26 × 10⁻⁶ mm and 15.75 × 10⁻⁶ mm, respectively. The initial displacements of lateral incisors in two-step method and in one-step method were 46.76 × 10(-6) mm and 23.18 × 10(-6) mm, respectively. Under the same amount of light force, the initial displacement of anterior teeth in two-step method was doubled compared with that in one-step method. The root and crown of the canine couldn't obtain the same amount of displacement in one-step method.

CONCLUSIONSTwo-step method could produce more initial displacement than one-step method. Therefore, two-step method was easier to achieve torque control of the anterior teeth during space closure.

Cone-Beam Computed Tomography ; Finite Element Analysis ; Humans ; Incisor ; Maxilla ; diagnostic imaging ; Periodontium ; diagnostic imaging ; Software ; Tooth Crown ; diagnostic imaging ; Tooth Movement Techniques ; methods ; Tooth Root ; diagnostic imaging ; Torque