Failure of eruption of first permanent molar teeth: a diagnostic challenge

Ankylosis, mechanical and primary failure of eruption of molar teeth are rare and often difficult to distinguish between. All may have significant repercussions on the occlusion and successful management may involve invasive procedures. We present a case where an initial presentation characteristic of mechanical failure of eruption (ankylosis) of a first permanent molar tooth was excluded following a period of monitoring. Subsequent relief of crowding using a removable and then sectional fixed orthodontic appliance allowed spontaneous eruption of the tooth obviating the need for surgical intervention. This case highlights the utilisation of conservative treatment options until a diagnosis was confirmed to minimise the risk of iatrogenic damage and unnecessary treatment.     

Intrapartum fetal surveillance: a physiological approach

Continuous utero-placental circulation, and patent umbilical blood vessels ensure an uninterrupted transfer of oxygen and nutrients to the fetus as well as clearance of metabolic waste products. The onset of labour characterized by progressive and strong uterine contractions poses a threat to fetal oxygenation as a result of collapsing the spiral arterioles traversing the myometrium to supply the placental bed, and repetitive compression of the blood vessels within the umbilical cord. Human fetuses are equipped with compensatory mechanisms to cope with transient interruptions of blood supply during labour. The ability to compensate may be blunted in cases of poor fetal reserves, increased metabolic demand (macrosomia or maternal fever), and due to non-hypoxic pathways (e.g. chorioamniontis or fetal hypovolumia-hypotension syndrome). Intrapartum fetal surveillance involves prompt recognition of the features that signal the onset of fetal decompensation on the cardiotocograph (CTG) to ensure a timely intervention to avoid hypoxic-ischaemic encephalopathy (HIE) or perinatal deaths. This article summarises a ‘physiological approach’ to the interpretation of the CTG which, in places, conflicts with other current UK guidance.     

锥形束CT测量牙龈厚度准确性的初步研究

目的评价锥形束CT(CBCT)法测量牙龈厚度的可信度及准确性。方法选择20例牙龈健康者的120颗上颌前牙,采用CBCT法和牙龈穿刺法测量唇侧中央龈缘下2mm处牙龈厚度,比较两组差异并用Kappa系数评价两种方法的一致性;应用Kappa系数评价不同检查者用CBCT法测量牙龈厚度的一致性,以及组内相关系数ICC评价同一检查者重复测量数据的可信度。结果CBCT法测量牙龈厚度为(1.23±0.27)mm,牙龈穿刺法测量结果为(1.24±0.26)mm,差异无统计学意义(P>0.05),两组之间一致率为83.33%(Kappa=0.547)。不同的检查者CBCT法测量牙龈厚度的一致性检验Kappa系数为0.814,可信度良好(ICC=0.795),同一检查者CBCT法重复测量数据之间一致性检验Kappa系数为0.864,可信度良好(ICC=0.893);CBCT法对厚牙龈生物型具有高的灵敏度(92.05%)和低的特异度(59.38%)。结论CBCT测量牙龈厚度的结果与牙龈穿刺法的结果较一致,具有良好的可信度。     

Observations on fluid flow from exposed dentine in primary teeth: An in vitro study

ObjectiveTo investigate fluid flow through dentine in primary teeth in vitro using the replica technique, and to compare the results with those obtained from permanent dentine.DesignThe experiments were carried out on 22 extracted, mandibular, primary, incisor teeth. The incisal edge was removed to 1 mm below the dentino-enamel junction and half the exposed surface etched with phosphoric acid. The exposed dentine was blotted dry and the pressure in the pulp cavity held at 0, 15, 30 or 45 cm H₂O above atmospheric for 30 s. Fluid that accumulated on the dentine surface was recorded with impression material and a replica made with epoxy resin which was examined in a scanning electron microscope.ResultsStructures resembling fluid droplets were present in the replicas of unetched dentine in all 22 teeth, and at all the pulpal pressures tested. The droplets formed at 45 cm H₂O were significantly larger (median diam., 5.14 mm; interquartile range, 3.26 mm; Friedman repeated measures analysis of variance on ranks (RMAVR) and Tukey test) than those formed at other pressures. There was no evidence of droplets in the replicas of etched dentine with any of the pulpal pressures.ConclusionsThese results demonstrate that fluid will tend to flow from dentine in deciduous teeth when it is exposed. They are similar to those obtained in a previous study in this laboratory on permanent teeth. The fact that fluid droplets were absent from etched dentine suggests that, after being blotted, the etched dentine matrix absorbed fluid that tended to flow out through the dentinal tubules.     

Sleep duration and remaining teeth among older people

BackgroundNo studies have examined the associations between the numbers of teeth and sleep disturbance. Therefore, we examined the associations between the number of teeth and sleep duration in older people, considering the evidence linking fewer teeth and sleep apnoea through changes in jaw position.MethodsFor this study we used information from a sample of 23,444 cohort participants, randomly selected from the Japan Gerontological Evaluation Study 2010 (N = 169,215). The outcome variable was self-reported sleep duration (h/day), and the explanatory variable was self-reported number of teeth (0, 1–9, 10–19, ≥20). We treated age, sex, body mass index, educational attainment, annual equalized household income, depressive symptoms, physical activity, activities of daily living, presence of diabetes, and smoking status as covariates. Multinomial logistic regression was used among the 20,548 eligible participants with all necessary information.ResultsThe mean age was 73.7 (standard deviation = 6.13) years. Most participants (28.1%) reported sleep duration of 7 h, while a small proportion of the participants reported short (≤4 h, 2.7%) or long (≥10 h, 4.7%) sleep duration. The proportion of edentulous participants was 14.7%. Taking the 7-h sleep duration as the reference category, edentulous participants (relative risk ratio (RRR) = 1.43, 95% confidence interval (CI) = 1.07–1.90) or one to nine teeth (RRR = 1.29, 95% CI = 1.02–1.63) had a significantly higher relative risk ratio for short sleep, independent of covariates. Furthermore, they had a higher relative risk ratio for long sleep duration (RRR = 1.75, 95% CI = 1.40–2.19; RRR = 1.48, 95% CI = 1.21–1.81, respectively).ConclusionsCompared to people with 20 or more teeth, older adults with fewer than 10 teeth have higher risks for short and long sleep durations.     

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??Abstract??Objective To obtain the data of dental measurements in healthy Bai teenagers. Methods Normal dentognathic models were obtained in 97 teenagers. The width of the tooth crown and the size of the dental arch were measured with a venier. The measurments were statistically analysed. Results The tooth crown in boys was wider than that in girls except first premolar and second premolar;the dental arch width and length in boys were wider than those in girls.There was no significant difference in Bolton index and Pont index between boys and girls. Conclusion The norms of teeth??denal arch and dentition index on normal occlusion in Bai teenagers have been established?? and they have a certain reference value to guide clinical orthodontics.     

Evaluation of avulsed primary incisor in 3-year-old girl with hypophosphatasia who received enzyme replacement therapy

Hypophosphatasia (HPP) is an inherited skeletal disease with features of hypomineralization of bone and early exfoliation of primary teeth due to disturbed cementum formation. Recent introduction of enzyme replacement therapy has reduced mortality in severe cases, though the effects of that treatment on dental manifestations remain unknown. We examined an avulsed primary incisor in a 3-year-old female diagnosed with perinatal HPP who underwent enzyme replacement therapy from 1 day after birth and report our findings.     

前牙压低技术在深覆(牙合)患者矫治中的应用进展

深覆(牙合)的治疗是口腔正畸矫治的难点之一.对于伴有垂直生长型、长面型或上唇过短、露龈笑的患者,就更需要医生进行细致诊断,合理选择矫治方法和器械.通过单纯地压低前牙能较为有效地治疗该类患者的深覆(牙合)畸形.目前,临床常用的压低前牙的方法主要有三段式片段弓技术、多用途弓技术、J钩联合高位牵引技术和微种植支抗技术等.本文...