Efficiency of molar distalization associated with second and third molar eruption stage

Objective:To evaluate the efficiency of molar distalization associated with the second and third molar eruption stage.Materials and Methods:A systematic computerized database search was conducted using several databases. Adaptations of the terms molar distalization and distalizing appliances were used. The reference lists of all the selected articles were also searched for any potential articles that might have been missed in the electronic search. The data provided in the selected publications were grouped and analyzed in terms of molar distalization with respect to various eruption stages of maxillary second and third molars.Results:Out of the 13 initially identified articles only four fulfilled the final selection criteria. Three of the four studies showed no statistical significance in linear molar distalization based on the eruptive stage of the second and/or third molars, while one study found that the amount of distal movement of the first molars was significantly greater in the group with unerupted second molars. Only one study found that the amount of molar tipping that occurred as a result of distalization was related to the eruption stage of the maxillary molars. Similarly, three of the four studies found that molar distalization time was not significantly affected by eruption of the second or third molars.Conclusion:The effect of maxillary second and third molar eruption stage on molar distalization—both linear and angular distalization—appears to be minimal. This conclusion is only based on low–level of evidence clinical trials. The large variability in the outcomes should be considered clinically.     

Comparison of two implant-supported molar distalization systems

Objective:To examine skeletal, dental, and soft tissue effects of the Miniscrew Implant Supported Distalization System (MISDS) and the Bone-Anchored Pendulum Appliance (BAPA).Materials and Methods:Among 28 patients displaying Angle Class II malocclusion, 14 patients with a mean age of 14.8 ± 3.6 years treated with MISDS were included in the first group, and 14 patients with a mean age of 14.5 ± 1.5 years treated with BAPA were included in the second group. The pretreatment and posttreatment lateral cephalograms were analyzed. Statistical evaluation was carried out using the paired Shapiro-Wilk test, the paired-sample t-test, and the unpaired t-test.Results:Upper posterior teeth were distalized successfully in both groups. Nearly bodily distalization was seen in the MISDS group, whereas significant distal tipping of the upper first molars was observed in the BAPA group (P < .001). There were no statistically significant changes in the sagittal position of the maxilla and mandible and in the position of the upper incisors as a result of treatment in either group.Conclusions:Both methods provided absolute anchorage for distalization of posterior teeth; however, almost translatory distal movement was encountered in the MISDS group, and substantial distal tipping of the maxillary molars accompanied distalization in the BAPA group.     

Characterisation of developmentally hypomineralised human enamel

Objectives

To investigate and clarify physical and chemical properties of enamel affected by molar incisor hypomineralisation (MIH).

Methods

A series of in vitro studies were performed on extracted molars affected by MIH and sound teeth for controls. Tooth sections underwent Vickers microhardness testing before lapping and subsequent transverse microradiographic analysis and examination under polarised light microscopy. Carbonate content was determined by CO₂ release from acid digestion. Unprepared and fractured surfaces were examined under scanning electron microscopy.

Results

MIH-affected molars demonstrated a severe degree of hypomineralisation with an average mineral content of only 58.8% vol% mineral. Vickers microhardness was significantly reduced in MIH compared with controls (1.8 ± 1.1 v 4.4 ± 1.0 GPa, p < 0.05) and polarised light microscopy revealed the bulk of MIH lesions had a porosity of ≤5% but also substantial areas of ≥10% and smaller areas exceeding 25% porosity. A surface layer was frequently observed on both intact and broken-down lesions and cervical regions of MIH teeth were typically spared. Carbonate content of MIH enamel was higher than control samples (6.6 ± 2.1 v 4.4 ± 1.1 wt%, p < 0.05). Scanning electron microscopy showed that both the enamel rod and surface ultrastructure were defective. Clinical characteristics did not consistently correlate with all properties.

Conclusions

The properties of MIH-affected enamel significantly differ from those of normal enamel and were highly variable, however some common characteristics were observed. Implications for aetiology and clinical management are discussed.     

高角拔牙病例治疗前后牙齿位移与软组织颏部改变的相关性研究

目的 分析高角拔牙病例正畸治疗前后牙齿位移与软组织颏部位置及曲线形态改变的相关性.方法 对60例高角拔牙病例(Ⅰ或Ⅱ类骨面型)正畸治疗前后的头颅定位侧位片进行7项牙性指标,3项骨性指标及2项软组织指标的定点测量分析,再通过Pearson简单直线相关分析,偏相关分析以及多元线性回归分析研究软硬组织变化的相关性.结果 Pearson简单直线相关分析证实,7项牙性指标中与软组织指标面角的改变相关的指标为U6-PP距与L6-MP距之和及U1-PP距;与软组织指标颏沟倾角的改变相关的为U6-PP距与L6-MP距之和、L1-NB距、U1-PP距及L1-MP距.偏相关分析显示U6-PP距与L6-MP距改变之和与面角和颏沟倾角的改变为强相关,且为间接相关.多元线性回归分析筛选出对面角和颏沟倾角的改变影响力较大的牙性指标:对面角影响大的只有U6-PP距与L6-MP距之和;对颏沟倾角影响大的有2项牙性指标,并按影响力大小排序:U6-PP距与L6-MP距之和的影响力大于L1-NB距.结论 在高角拔牙病例的正畸治疗中磨牙高度的改变与颏部位置及曲线形态的改变密切相关.     

微种植体与J钩内收上前牙后的切牙位置变化比较

目的 比较微种植体支抗和头帽J钩内收上前牙后上颌切牙及支抗磨牙位置变化的差异.方法 选择24例安氏Ⅱ1上颌前突患者,随机分为微种植体组和J钩组各12例,微种植体组在上颌第二前磨牙和第一磨牙牙根间植入微种植体支抗,内收上前牙,J钩组使用头帽J钩内收上前牙,比较两种支抗方式矫治前后X线头影测量的变化.结果 矫治后,两组上中切牙切缘至RL距离以及上中切牙角均减小,微种植体组减少更明显,上切牙内收且直立,差异具有统计学意义(P<0.05);两组上中切牙切缘至腭平面距离均减小,上切牙被压低,J钩组压低更显著,两组间比较差异具有统计学意义(P<0.05);J钩组上磨牙至RL距离、腭平面距离明显增大,上磨牙近中移动、伸长,微种植体组增大不明显,两组间比较差异具有统计学意义(P<0.05).结论 微种植体支抗内收上颌切牙效果显著,支抗磨牙前移较少,是稳定有效的骨性支抗,但植入在牙槽骨后段的微种植体压低上前牙的作用却不及头帽J钩,严重的深覆深覆盖应考虑两种支抗方式的联合应用.     

Prevalence of odontogenic cysts and tumors associated with impacted third molars: A systematic review and meta-analysis

PurposeThis systematic review aimed to investigate the prevalence of odontogenic cysts and tumors associated with impacted third molars (ITM).MethodsOnly studies that performed histopathological diagnosis of lesions were eligible for inclusion. Five main electronic and three grey literature databases were searched. Risk of bias (RoB) of included articles was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Studies Reporting Prevalence Data.ResultsFrom 1,300 studies identified, 16 met the inclusion criteria. Seven studies were classified as high, seven as moderate, and two as low RoB. The prevalence of odontogenic cysts and tumors associated with ITM was 5.3% (95%CI: 3.1%–8.1%) of ITM. Odontogenic cysts in particular were found in 4.4% (95%CI: 2.5–6.8%) of the extracted ITM, whilst odontogenic tumors in 0.5% (95%CI: 0.2–0.9%). The dentigerous cyst was mentioned in eleven studies with a pooled prevalence of 2.1% (95%CI: 1.4–3.1%). The odontogenic keratocyst was cited by nine studies and had a prevalence of 0.5% (95%CI: 0.2–0.7%). The radicular cyst was mentioned only in three articles and the pooled prevalence was 4.7% (95%CI: 0.0–19.4%)ConclusionOdontogenic cysts and tumors were found in 5.3% of ITM extracted. The most common lesions were the radicular cyst, dentigerous cyst, and odontogenic keratocyst.     

血红蛋白最佳聚合工艺匹配条件的研究

目的 探讨以戊二醛为交联剂的血红蛋白类氧载体（HBOCs）的聚合工艺匹配条件的优化研究,进一步降低终产品的平均分子质量和超大分子含量,提高聚合血红蛋白的有效转化率.方法 在前期对人胎盘血红蛋白与戊二醛交联的单因素影响水平的研究基础上,选取戊二醛的加样速度、血红蛋白的质量浓度和戊二醛与血红蛋白的摩尔比3个因素做正交试验以优化血红蛋白聚合工艺的匹配条件.结果 戊二醛与血红蛋白的摩尔比对聚合血红蛋白分子质量分布的影响最大,其次是血红蛋白的质量浓度,最后为戊二醛的加样速度.对平均分子质量的影响分析,不同的戊二醛与血红蛋白摩尔比条件下的平均分子质量间的差异均具有统计学意义（P＜0.05）,而不同的血红蛋白质量浓度和戊二醛的加样速度条件下的平均分子质量间的差异均无统计学意义（P＞0.05）;对有效转化率的影响分析,不同的戊二醛与血红蛋白摩尔比和不同的血红蛋白质量浓度条件下的有效转化率间的差异均具有统计学意义（P＜0.05）,不同的戊二醛加样速度条件下的有效转化率间的差异均无统计学意义（P＞0.05）;对超大分子含量的影响分析,不同的戊二醛与血红蛋白摩尔比条件下的超大分子含量间的差异均具有统计学意义（P＜0.05）,不同血红蛋白的质量浓度和戊二醛的加样速度条件下超大分子含量间的差异均无统计学意义（P＞0.05）.结论 通过以上实验分析,优化确定了血红蛋白聚合工艺的最佳匹配条件.     

钟摆矫治器联合颊侧推簧远移磨牙的疗效分析

目的：评价钟摆矫治器联合颊侧推簧远移磨牙的疗效.方法：选择40例牙性安氏Ⅱ类错（牙合）畸形的患者,随机均分为两组：钟摆矫治器联合颊侧推簧远移磨牙组（组1）和头帽口外弓远移磨牙组（组2）,在治疗开始前（T0）和远移磨牙完成时（T1）分别拍摄侧位头影定位片进行头影测量,t检验分析组内和组间的差异.结果：组1和组2远移磨牙的平均距离分别是（4.48±1.63） mm、（2.68±1.71） mm;组1和组2磨牙远中倾斜的平均角度分别是5.46°±3.23°、1.02°±2.16°;组1上颌中切牙未发生明显的唇倾和唇向移位,而组2上颌中切牙发生了较为明显的腭侧移位.结论：钟摆矫治器联合颊侧推簧远移磨牙可有效防止前牙支抗的丧失、控制磨牙的近中颊侧旋转.     

微种植钉近中移动下颌第二磨牙关闭第一磨牙拔牙间隙

目的探讨微种植钉近中移动下颌第二磨牙关闭第一磨牙缺隙的正畸治疗效果。方法对5例第一磨牙缺失患者使用微种植钉近中移动下颌第二磨牙关闭其间隙。结果矫治后尖牙、磨牙中性关系,前牙覆盖、覆袷正常,后牙袷关系良好,下颌第一磨牙拔牙间隙关闭,第二磨牙近中移动量为11．7mm。疗程为18．5～31．0个月,平均为26．1个月。结论在下颌第一、第二双尖牙间采用微种植钉近中移动第二磨牙,能有效地关闭第一磨牙拔牙间隙。