Effect of low pull headgear on head position

Objective

To evaluate changes in head position following the use of low pull headgear (LHG) and compare these changes with an untreated control group.

Subjects and methods

The test group comprised pre-treatment and post-treatment lateral cephalograms of 30 males, aged 11 ± 1.5 years, who were receiving LHG therapy for correction of Class II malocclusion. Pre-observation and post-observation lateral cephalograms of 25 untreated male subjects, aged 11 ± 1.6 years, served as controls. The average treatment time for the treatment group was 12 ± 2.02 months and the average observation period for the control group was 11 ± 1.03 months. Four postural variables (NSL/CVT, NSL/OPT, CVT/HOR, OPT/HOR) were measured to evaluate the head position in all subjects pre- and post-observations.

Results

There was no significant difference in all the measurements concerning the head position within each group (p > 0.05). The mean differences of pre- and post-observations of 4 postural variables in the LHG group were 1.43, 0.9, −1.13, and −1.08, while those of the control group were 1.56, −0.32, −0.24, and 0.04, respectively. There was no significant difference between the headgear and control groups for any of the postural variables measured (p = 0.924, 0.338, 0.448, and 0.398, respectively).

Conclusions

Although postural variables showed considerable variability in both groups, head position exhibited no significant changes over a period of 11–12 months either in the control or headgear group.     

Relationships of sagittal skeletal discrepancy,natural head position,and craniocervical posture in young Chinese children

Objective: The aim of this study was to investigate the relationships of sagittal skeletal discrepancy, natural head position (NHP), and craniocervical posture in young Chinese children with average vertical facial pattern.

Methods: Ninety patients with average Frankfort mandibular plane angle (FH/ML) were classified into skeletal class I, II, and III relationships according to their ANB angle. Cephalometric radiographs in NHP were taken. Variables representing sagittal and vertical craniofacial morphology, head posture, and craniocervical posture were measured and compared.

Results: Subjects in the skeletal class II group showed the largest craniovertical angles and craniocervical angles, while subjects in the skeletal class III group exhibited the smallest craniovertical angles and craniocervical angles, though not all the measurements showed significant differences. The angle formed by the nasion-sella line and the tangent to the posterior border of the mandibular ramus (NSL/RL) was largest in the skeletal class II group and smallest in the skeletal class III group (p?=?0.05).

Discussion: Significant differences exist in NHP and craniocervical posture among skeletal class I, II, and III relationships in young Chinese children. Subjects with skeletal class II relationship tended to exhibit more extended head, and children with skeletal class III relationship often exhibited flexed head.     

Relationships of vertical facial pattern,natural head position and craniocervical posture in young Chinese children

Objective: To investigate relationships of vertical facial patterns, natural head position (NHP), and craniocervical posture in young Chinese children with skeletal Class I relationship.

Methods: Ninety-four patients with skeletal Class I relationship were classified into low, average, and high angle groups according to their mandibular plane angle (NSL/ML). Cephalometric radiographs in NHP were taken. Variables representing vertical and sagittal craniofacial morphology, head posture, and craniocervical posture were measured and compared.

Results: Inclinations of the mandible to the true vertical and cervical column were smallest in the high angle group and largest in the low angle group. Other variables representing head posture and craniocervical posture were largest in the high angle group, smallest in the low angle group. Inclinations of ramus to cervical column were largest in the high angle group and smallest in the low angle group.

Discussion: Subjects with large NSL/ML angles showed extended head and craniocervical posture, while subjects with small NSL/ML angles exhibited flexed head and craniocervical posture.     

The influence of size,specific gravity,and head position on the swallowing of solid preparations

AimTo clarify the influence of size and specific gravity of solid preparations, and the position of healthy volunteers when swallowing, for the purpose of practical use in patient consultation regarding the taking of medicines.Materials and methodsThe paper reports three studies. Volunteers were asked to swallow four different capsules (A, large and heavy; B, large and light; C, small and heavy; D, small and light) in Study 1, two preparations with different positions (upright, horizontal, and chin-down) in Study 2, and two preparations before and after anesthetization of the bilateral lingual and inferior alveolar nerve in Study 3. The oral transit time (OTT) and pharyngeal transit time (PTT) were evaluated with videofluoroscopy.ResultsThe mean OTT became longer in the order of C, D, B, A. The mean PTT showed no statistically significant differences. The swallowing preference of the four preparations ranked by the subjects showed that difference in size but not the difference in specific gravity is a significant factor. In the chin-down position, OTT was shorter for two preparations, compared with the other two positions. The mean OTT for both the A and B preparations was significantly longer after the bilateral lingual and inferior alveolar nerves were anesthetized.ConclusionWhen swallowing solid preparations, a consideration of size and the position will enable ease of swallowing of medicines. This would especially be the case when delivery of the medicines to be taken by the aged suffering from oral hypoesthesia caused by an underlying disease.     

The difference between registered natural head position and estimated natural head position in three dimensions

This study determined the intra-rater and inter-rater reliability of re-orientating three-dimensional (3D) facial images into the estimated natural head position. Three-dimensional facial images of 15 pre-surgical class III orthognathic patients were obtained and automatically re-orientated into natural head position (RNHP) using a 3D stereophotogrammetry system and in-house software. Six clinicians were asked to estimate the NHP of these patients (ENHP); they re-estimated five randomly selected 3D images after a 2-week interval. The differences in yaw, roll, pitch, and chin position between RNHP and ENHP were measured. For intra-rater reliability, the intra-class correlation coefficient (ICC) values ranged from 0.55 to 0.77, representing moderate reliability for roll, yaw, pitch, and chin position, while for inter-rater reliability, the ICC values ranged from 0.38 to 0.58, indicating poor to moderate reliability. The median difference between ENHP and RNHP was small for roll and yaw, but larger for pitch. There was a tendency for the clinicians to estimate NHP with the chin tipped more posteriorly (6.3 ± 5.2 mm) compared to RNHP, reducing the severity of the skeletal deformity in the anterior–posterior direction.     

Influence of forward head posture on condylar position

There are several reports suggesting that forward head posture is associated with temporomandibular disorders and restraint of mandibular growth, possibly due to mandibular displacement posteriorly. However, there have been few reports in which the condylar position was examined in forward head posture. The purpose of this study was to test the hypothesis that the condyle moves posteriorly in the forward head posture. The condylar position and electromyography from the masseter, temporal and digastric muscles were recorded on 15 healthy male adults at mandibular rest position in the natural head posture and deliberate forward head posture. The condylar position in the deliberate forward head posture was significantly more posterior than that in the natural head posture. The activity of the masseter and digastric muscles in the deliberate forward head posture was slightly increased. These results suggest that the condyle moves posteriorly in subjects with forward head posture.     

头位左倾和右倾变化对咀嚼肌肌电的影响

目的：研究不同的头位变化对咀嚼肌肌电活动的影响。方法：以30例健康正常[牙合]受试者为研究对象，通过肌电图仪（EMG）测试下颌姿势位和牙尖交错位最大紧咬时，5种头位姿势的颞肌前束（TA）、颞肌后束（TP）、咬肌（MM）、二腹肌前腹（DA）的肌电幅值，并对结果进行统计学分析。结果：下颌姿势位和紧咬位时，与正中头位相比，头左倾和右倾状态时咀嚼肌的肌电值变化无显著性差异（P〉0．05）。结论：咀嚼肌在头位左倾和右倾变化过程中所受影响不大。     

肌位牙合板对颅颌功能紊乱者髁突位置及盘突关系异常影响的研究

目的　研究颅颌功能紊乱（ Ｃ Ｍ Ｄ） 者牙尖交错位（ Ｉ Ｃ Ｐ） 的髁位及戴入肌位牙合板后的改变, 对戴入肌位牙合板后颞颌关节（ Ｔ Ｍ Ｊ） 弹响消失者, 观察盘突关系的变化。方法　对１０２ 例 Ｃ Ｍ Ｄ 者在 Ｉ Ｃ Ｐ 及戴入肌位牙合板后咬合接触时, 在断层深度不变的情况, 分别进行双侧 Ｔ Ｍ Ｊ侧位中层摄影, 对其中９ 例戴板后弹响立即消失者行戴板前、即刻戴入牙合板后及治疗后, Ｔ Ｍ Ｊ上腔造影的断层摄影。结果　１０２ 例 Ｃ Ｍ Ｄ 者 Ｉ Ｃ Ｐ 时, 髁突一侧后位或双侧后位４３ 例, 中位４６ 例, 一中一前６ 例, 双侧前位７ 例。戴入牙合板后, 后位者３０ 例双侧居中, 中位者３６ 例前下移,而髁位异常在戴板后持不变者５ 例。９ 例盘突关系异常者, 戴入牙合板后全部恢复正常, 但３ ～６ 月后去板, 仅１ 例盘突关系正常,８ 例仍异常。结论　肌位牙合板可使后位的髁突居中, 居中者前下调位并纠正不对称的髁位, 而对盘突关系异常的调整作用有限。     

Both head extension and mouth opening impair the ability to swallow in the supine position

Head position and mouth opening in the supine position may impair the ability to swallow. If this does occur, it would lead to retention of intra‐oral fluids during dental treatment, which would lead to stimulation of the cough reflex. This study was conducted to investigate how head position and mouth opening affect swallowing ability. The water swallowing test was performed in 13 healthy adult subjects in the supine position. The subjects were asked to swallow 10 mL of water that was injected into the mouth in a single attempt. After swallowing, the residual intra‐oral water was suctioned and its volume was measured. An electromyogram (EMG) of the suprahyoid (SH) muscles was also recorded during the test. The duration of SH muscle activity and peak amplitude of SH EMG were examined. The water swallowing test was performed under three head positions (neutral, extended and flexed) and four mouth opening patterns (interincisal distances of 0, 20, 30 and 40 mm). The wider the subject opened the mouth, the more the water remained in the mouth after swallowing. The residual volume of water was more in the extended position compared with that in the neutral and flexed positions. Peak amplitude of SH EMG decreased with mouth opening. Duration of SH muscle activity was longer in the extended position than in the neutral and flexed positions. Head extension and mouth opening can induce difficulty in swallowing in the supine position by extending the duration of SH muscle activity while reducing its intensity.     

正中关系位-正中[牙合]位垂直向不调患者戴用Roth诊断[牙合]垫前后头影测量比较

目的比较髁突位置垂直向异常患者传统的最大牙尖交错位（centricocclusion,CO）头颅侧位片与戴用骀垫后获得的正中关系位（centricrelation,CR）头颅侧位片头影测量结果差异,揭示患者真实的咬合关系,了解不同下颌位置的头影测量分析存在的差异可能为临床诊断带来的影响,为临床提供参考。方法选取髁突位置垂直向异常患者14例,拍摄传统CO位头颅侧位片和戴用殆垫后获得的CR位头颅侧位片,比较两组头影测量21项指标结果差异。结果CR位头影测量值ANB角、关节角、Y轴角、覆盖明显大于CO位头影测量值（P〈0．05）,而SNB角、面轴角明显小于CO位头影测量值（P〈0．05）。结论髁突位置垂直向异常患者CO位和CR位头影测量各项目差异说明,髁突从CO位退到CR位时下颌位置在矢状和垂直向发生改变,对这类患者的临床诊断和治疗设计可能会产生影响。     

托槽在数字化牙颌模型上位置与间接粘结转移后实际位置的一致性研究

目的 本研究比较托槽在数字化牙颌模型上的位置与转移至初始石膏模型上的位置的差异,以期为数字化托槽间接粘结位置的一致性提供实验依据.方法 选取在含牙根的数字化牙颌模型上进行托槽定位的15个数字化模型,通过间接粘结转移托盘将托槽转移至初始石膏模型上,用OrthoRx软件工具测量每个托槽在数字化牙颌模型上的位置与初始石膏模型上位置的线距差.结果 所有牙位托槽在数字化牙颌模型上的位置与初始石膏模型上位置的线距差值均小于检验值0.20 mm,与检验值差异有统计学意义(P<0.05).结论 托槽在数字化牙颌模型上的位置与初始石膏模型上位置具有一致性.     

双颌前突中国成人拔牙正畸治疗后唇组织变化预测方法初探

目的：探索并建立双颌前突中国成人拔除4个第一前磨牙正畸治疗后的唇组织改变的预测方法。方法：筛选满足纳入标准的32位双颌前突中国成人患者,在计算机辅助下对其治疗前后头颅侧位片行头影测量分析并行配对t检验,软组织变化的相关分析及逐步多重回归分析。结果：治疗前后水平向唇组织改变有统计学意义而垂直向改变无统计学差异。上唇水平向的位置变化（H—LS）与上切牙颈部的位置变化（H—Pro）正相关,下唇水平向的位置变化（H—Li）与上切牙突点（H—UIP）的位置变化正相关。结论：双颌前突中国成人拔除4个第一前磨牙后正畸治疗的患者,可以通过切牙回收量较好地预测其唇组织水平向的改变。     

Update on melanoma: the present position

Cutaneous melanoma is becoming increasingly common among people with fair skins, and this has been blamed on exposure to ultraviolet radiation from sunbathing, the use of sun beds, and holidays abroad. The key to controlling the epidemic of melanoma is prevention, but also important are the organisation of the skin cancer service, surgical advances, and the development of neoadjuvant treatments. Because there are many of these tumours in the head and neck region, head and neck surgeons are increasingly involved in the management of such patients. We review the current philosophy in the management of melanoma.     

New way to achieve frontal facial photographs of the head in its natural position

Frontal photographs of the head in its natural position are not as easy to achieve as lateral ones. We describe a new way to obtain standard 2-dimensional images of its natural position in full-face frontal view using a customised photographic system, which may provide supplementary information for traditional lateral facial imaging, and be helpful for standard assessment of 3-dimensional facial images.     

青少年错患者正畸治疗后牙尖交错位接触特征变化初探

目的探讨经正畸治疗获得正常牙列形态的青少年错患者主动矫治结束后12个月内牙尖交错位接触的变化规律。方法选择20例正畸主动矫治结束后戴用标准霍利保持器的青少年错患者,使用T-ScanⅡ咬合分析系统分别于矫治结束即刻（T1）和矫治结束12个月时（T2）记录其牙尖交错位接触并进行比较。结果 20例患者T1至T2前牙接触面积及前牙力占总力的百分比有所减小,后牙接触面积及后牙力占总力百分比有所增加,但所有测量项目两时间点的差异均无统计学意义（P〉0.05）。结论戴用标准霍利保持器12个月后,患者牙尖交错位接触状况仅有轻微改善,主动矫治结束前的咬合检查及精细调整是必不可少的。     

无牙颌位至最大开口位下颌运动规律的初步探讨

目的：探讨从无牙颌位至最大开口位时下颌颏部及髁突顶部的运动轨迹的规律，分析在无牙颌患者牙尖交错位建He与此运动轨迹的关系。方法：分别对22例无牙颌患者行无牙颌位、牙尖交错位和最大开口位时的头颅侧位X线片拍摄，测定在二三个位置时颏前点、髁突顶点以及相应的面角的改变。结果：颏前部从无牙颌位至牙尖交错位及最大开口位发生向下向后的移位，髁突顶发生向下向前的移位，SNPg角逐渐减小。结论：颏部及髁突从无牙颌位到最大开口位下颌的位置出现旋转性的位移，颏前部及髁突顶部可出现不同的旋转曲线，在此轨迹上有助于帮助确定牙尖交错位建He点。     

Simple technique to achieve a natural head position for cephalography

The cephalometric measurement of the face in terms of aesthetics can be difficult and misleading due to the variability of the intra-cranial reference lines according to diversity of head posture. Natural head position (NHP) has been proposed as a preferred reference position for assessing facial morphology. Even though natural head position is more proper and valid, it is still abandoned by reasons of time-consumption and additional and necessary complex equipment. Hence, we developed a modified level laser approach to acquire the natural head position. This method was a simple and straightforward technique which may be of value as and adjunct to routine orthognathic planning.     

中国人正常(牙合)牙齿舌侧形态和位置的特征研究

目的 测量正常He牙齿舌侧面各项指标的参考值范围，为舌侧正畸托槽的国产化、改良设计与应用提供基础数据。方法 应用YM-2115型三维测量仪，对普查所得的50副正常He模型的牙齿舌侧面进行定点测量，开发相应的软件进行数据处理。结果 得出正常He牙齿舌侧的转矩角、轴倾角、磨牙补偿角、冠凸距4项指标的参考值。结论 ①中国人牙齿舌侧面的各项指标与国外数据相比，有很多差异；②正常He牙齿舌侧面各项指标的变异程度很大，舌侧托槽的正确安放依赖于精确的技工室程序。     

前牙反(牙合)对牙齿位置的影响及与牙齿形态的相关联系

目的 :研究前牙反牙合对牙齿位置的影响及与牙齿形态的相关联系。方法 :选取 81例青少年恒牙列2 1|122 1|12 反牙合者作为研究组 ,95例青少年恒牙列2 1|122 1|12 非反牙合者作为对照组 ,比较两者在牙齿位置与形态方面的差别。结果 :⑴前牙反牙合组上颌牙错位率为 14 .0 % ,前牙非反牙合组为 8.8% ,两者差异显著 (P <0 .0 5 ) ;⑵前者错位比例高于后者的牙位 (P <0 .0 5 )为 :唇向低位的上颌尖牙 ,腭向错位的上颌侧切牙及腭向错位或阻生的上颌第二前磨牙 ;⑶前牙反牙合组下颌牙排列基本正常 ,错位率为 0 .9% ,前牙非反牙合组为3 .5 % ;⑷前牙反牙合者较前牙非反牙合者更容易出现锥形侧切牙这种异常发育的牙齿 (P <0 .0 5 )。结论 :前牙反牙合使得上颌牙齿的错位及发育异常明显增加。因此 ,前牙反牙合不仅对上颌骨的发育有影响 ,而且对上颌牙的位置与形态可能也存在影响 ,对该类患者建议尽早开始全面、综合性的矫治