离体牙上釉珠的观测与临床意义

本文从12379枚离体牙上观测了釉珠的发生率、发生部位、形态、直径大小。结果釉珠的发生率为2.49％,以上颌第三磨牙发生率最高,下颌第一磨牙次之。最常发生的部位是在冠颈部的根分叉处,上颌磨牙的釉珠多呈园形,下颌磨牙釉珠多呈梭形。釉珠最大直径为3.2mm,最小为0.5mm,平均为1.56mm。结合文献认为釉珠是一种牙齿形态发育异常,它对牙周病的发生、发展、治疗与预后有重要影响,口腔科医师对这种牙齿形态变异应予以重视。     

Fusion or gemination? An unusual mandibular second molar

Fusion and gemination is not an uncommon finding and affected most primary dentition and the permanent maxillary incisors. These changes can develop a series of complication. A 11-year-old male presented radiography finding: an unusual mandibular second molar. A well-documented case brings a challenge for radiologists classify between fusion and gemination. In conclusion, this alteration although common in other regions, there are no case in the literature involving “second and third” molar.     

Dentoskeletal changes following mini-implant molar intrusion in anterior open bite patients

Objective:To evaluate skeletal and dental changes after intrusion of the maxillary molars in subjects with anterior open bite.Materials and Methods:This retrospective cephalometric study evaluated skeletal and dental changes resulting from the use of maxillary orthodontic mini-implants in 31 consecutively treated patients. Radiographs were taken at the start and end of maxillary molar intrusion to evaluate the associated changes. Statistical analysis was performed using a one-sample t-test.Results:The mean treatment observation time was 1.31 years (SD  =  2.03). The maxillary first molars (P  =  0.0026) and second molars (P  =  0.039) were intruded. However, the mandibular first molars (P  =  0.0004) and second molars (P  =  0.003) erupted in adolescent patients. Both the maxillary and mandibular first molars inclined distally (P  =  0.025 and P  =  0.044, respectively). The mandibular plane angle decreased (P  =  0.036), lower facial height decreased (P  =  0.002), and the occlusal plane angle increased (P  =  0.009). The overbite increased (P < .0001). The ANB angle decreased (P < .0001). Mandibular dental and skeletal changes were more apparent in adolescents, while adults tended toward maxillary changes.Conclusions:Vertical traction from orthodontic mini-implants reduces the maxillary posterior dentoalveolar height, thereby assisting orthodontic closure of anterior open bite. However, simultaneous eruption or extrusion of the mandibular molars should be controlled. Adolescent patients tend to demonstrate more favorable effects of mandibular autorotation than do adults.     

Temporomandibular disorders with skeletal open bite treated with stabilization splint and zygomatic miniplate anchorage: A case report

This case report describes the treatment of a patient with temporomandibular disorder (TMD) and skeletal open bite. First, the patient was treated with a stabilization splint to stabilize the condyles in centric relation and to alleviate TMD signs and symptoms. After making a definitive diagnosis from postsplint records, orthodontic treatment was initiated. Titanium miniplates were placed at bilateral zygomatic buttresses and used as orthodontic anchorage for molar intrusion and distalization. The treatment was completed after 30 months. Satisfactory appearance and function were achieved for this patient.     

Nonsurgical and nonprosthetic camouflage treatment of skeletal Class II open bite with bilaterally missing lower first molars

This report illustrates the successful nonsurgical and nonprosthetic camouflage treatment of a skeletal Class II open bite malocclusion combined with missing mandibular first molars bilaterally. In the mandible, the second and third molars were uprighted and protracted, substituting for the missing first molars. In the maxilla, anterior bodily retraction and full-arch intrusion were achieved following premolar and second molar extraction, which also induced autorotation of the mandible. The treatment outcome and prognosis were confirmed with three-dimensional superimposition techniques, along with long-term stability.     

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.     

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.