In vivo validation of the historical in vitro thermocycling temperature range for dental materials testing

In dental research, restorative materials have been regularly subjected to alternating in vitro thermal stress in investigations since the 1950s, in order to simulate in vivo alternating temperature stress and to artificially stress them in vitro. The provocation temperature is mostly 5°C for cold provocation, and 55°C for hot provocation. These temperatures are determined quite arbitrarily based on very few examinations in vivo. Extensive temperature data for the approximal space of teeth, which is decisive for the success of fillings adhesively attached to dentin, has so far not been addressed. The objective of this study was to examine the interproximal temperature characteristics created in the space of all teeth in vivo with thermal alternating stress, and therefore to validate the in vitro standardized thermal alternating stress of 5–55°C. Fifteen study participants with healthy teeth were used to determine the temperature in each inter-dental space, resulting from hot/cold provocation in the upper and lower jaw, from the central incisor to the second molars. This was performed by a thermal element (cable sensor GTF 300, Greisinger Electronic GmbH, Regenstauf, Germany). The temperature sensor was attached with dental floss into the interproximal space and the temperature was recorded by the computer. The participants in the pilot test had to state when they were able to sip an 85°C hot drink. That particular temperature value was taken for hot provocation as maximum temperature reference. Cold ice water (0°C) was used for cold provocation as minimum temperature reference. The respective recordings with a total of 14 measurements for each individual were performed simultaneously in the upper and lower jaw. The study participants were to start with hot provocation, followed by cold provocation. This cycle was repeated at least once with an individual dwell time. The highest recorded approximal space temperature was 52.8°C in the lower jaw, between the first and the second premolar. The lowest temperature of 13.7°C was recorded in two participants in the upper jaw, between the 1st and 2nd incisor, and between the two central incisors. The mean of the maximum temperatures was 43.8±3.7°C, and the mean of the minimum temperatures 24.2±4.6°C. The mean initial temperature was 35.2±1.3°C. None of the recordings reached either the upper threshold (55°C) or the lower threshold (5°C). This study showed that the actual thermal stress in the interproximal space of teeth is slightly lower than the one used in in vitro examinations. For class II cavities, most of the alternating temperature stress limits selected at 5–55°C cover the actually occurring temperature interval quite well.     

个体化钛支架在构筑颌骨三维形态中的应用

目的　在运用快速成型技术制作的颌骨模型上作成个体化钛支架 ,以构筑颌骨三维形态。方法　 18例颌骨缺损患者进行个体化钛支架联合游离组织瓣修复重建。其中 10例上颌骨缺损以钛网支架重建上颌骨前壁、外侧及底壁 ,如内侧壁缺损则一并恢复 ,其口鼻创面以前臂皮瓣或串联腓骨肌瓣修复 ;8例下颌骨缺损以钛板支架塑形 ,联合游离腓骨 ,精确恢复下颌骨外形及髁突生理位置。结果　所有的病例随访 6～ 12个月 ,除 1例于术后9个月眶外侧壁复发外 ,其余未见肿瘤复发。皮瓣除 2例因术后放疗部分坏死外全部成活。所有患者面部外形均非常满意 ,张口度 2 .5～ 4cm ,正常进食。上颌骨重建病人无口鼻瘘 ,语音较为清晰 ,下颌髁突均在正常解剖生理位置 ,面部软组织亦很对称。结论　个体化钛支架应用于颌骨重建 ,能够较为精确地恢复颌骨外形 ,有利于术中引导移植骨准确对位 ,可避免术后的继发功能障碍 ,有效节省手术时间 ,其在复杂颅颌面疾病诊治中的应用前景非常乐观。     

Effects on dental health of spacing of teeth in anterior segments

Abstract The purpose of the study was to examine the relationship between spacing and dental health in 15-year-old adolecents. The whole sample consisted of 156 subjects. Out of them, 74 females and 73 males with 6 anterior teeth made up the study group for examination of the upper jaw. 75 females and 75 males had 6 anterior teeth in the lower jaw and made up the study group for examination of the lower jaw. The Plaque Index (PII) and the Gingival Index (GI) were recorded. Probing depths (PD) were measured as explained by Glavind & Løe. Filled surfaces (FS) were taken from the individual ease sheets and controlled clinically. The spacing of the individuals was assessed by counting the number of proximal surfaces without visible contact with the adjacent proximal surfaces, on model casts. The sum of proximal surfaces without contact made up the Space Index (SpI) of the individual jaw. Parametric and non-parametric statistical methods were used to analyze the data. In both sexes and both jaws proximal surfaces without interdental contact had a more favourable periodontal condition than surfaces with contact. In the upper jaw of both sexes, proximal surfaces without interdental contact had a reduced number of filled surfaces compared to surfaces with contact. The linear relationship between SpI and FS was significant, i.e., an increased number of surfaces without contact was accompanied by a reduced number of filled surfaces. In the lower jaw, the differences between the SpI groups and the linear relationship between SpI and FS did not reach significance. In both sexes and both jaws, proximal surfaces without fillings had a more favourable periodontal state compared to surfaces with fillings. Indications are that the summation effect of the presence of interdental contact and the presence of fillings contributed to the differences in periodontal condition between surfaces with and without interdental contact.     

Occlusion as the cause of undiagnosed pain

The teeth provide precise skeleto-motor influences for the stomatognathic system. This unique guidance mechanism characterizes each individual's chewing pattern. It controls the activity of jaw muscles to ensure that appropriate tooth contacts within the limits of existing tooth relationships occur at the end of each chewing cycle. This acts as a means of re-setting the neuromuscular system in anticipation of the next jaw opening movement. The absence of stable centric occlusion at the end point of each chewing cycle alters neuromuscular co-ordination and predisposes to muscle dysfunction. Tooth and jaw or craniomandibular relationships are associated with craniocervical relationships and especially tongue posture. This is also directly influenced by the need for airway maintenance as the predominant influence on tongue-muscle function. The susceptibility to pain and dysfunction is further influenced by individual stereognathic sensitivity or the variable awareness of tooth contour and tooth contacts. These special features are present within the framework of the psycho-physiological and psycho-social significance of the face and mouth, which directly bears on the individual response to and appreciation of pain and dysfunction. Tooth guidance also influences condyle-disc function. Anterior and posterior teeth provide primary and secondary lateral guidance in function, directing the jaw into centric occlusion. If this guidance tends to direct the jaw posteriorly along distal, rather than mesial tooth inclines, it restricts the antero-posterior 'function' of jaw movement at tooth contact. This predisposes to condyle-disc dysfunction and the development of internal derangements, by increasing the likelihood of the posterior thick band of the disc being displaced anteriorly and the condyle posteriorly.(ABSTRACT TRUNCATED AT 250 WORDS)     

Wire-free fixation of jaw fractures

Stainless steel wire is often used in the management of jaw fractures to provide intraoperative or postoperative intermaxillary fixation (IMF). Wiring of the jaws is time-consuming, a second procedure is needed to remove it, and needlestick injuries occur during placement.We report on 151 consecutive patients who had wire-free fixation of jaw fractures, and outline the value of a system of plastic anchorage points applied to individual teeth in both jaws that allows for wire-free IMF when they are linked by elastics (Rapid IMF™, Synthes, PA, USA).A total of 150 successive patients had wire-free fixation of 146 mandibular and 5 maxillary fractures. Ninety-eight were hand-held in occlusion, and 52 were treated using Rapid IMF™. There were few complications.     

The influence of tonic muscle activation on human jaw displacement tremor

Jaw displacement tremor was investigated. Both tremor amplitude and tremor frequency were found to increase with increasing muscle activation. Co-contraction of jaw elevator and jaw depressor muscles was employed in order to vary muscle activation levels without the teeth being in occlusion. Reproducibility of tremor changes was statistically significant for each individual investigated. The relationship between tremor frequency and tremor amplitude, over the range of muscle activation investigated, varied per individual. It is hypothesized that the physiological basis for this inter-individual variation is differences in the development of jaw stiffness with increasing muscle activation between subjects. This explanation may be the basis, at least in part, for the clinical presence of objective jaw stiffness in one subject and its absence in another.     

Diagnostics and planning of orthodontic treatment of patients with crowded teeth position with the use of elastomeric correcting splints

3D scanning of plaster jaw models and further processing of the received data in editing program for three dimensional models Rapid Form 2006 Basis is one of the used methods of diagnostics of patients with crowded teeth position (measurement of anthropometric parameters of jaw models, dental arches symmetry, sizes and forms of dentitions). On 3D jaw models with crowded teeth position there were planned trajectories of gradual single tooth displacement in such a way that to move them in new correct position. Prescribing determined step with which the tooth would be moved there was made a series of individual plastic jaw models corresponding to each stage of treatment by stereolithographic method. On the received models there was made a series of elastomeric correcting splints producing some pressure upon teeth and making for their displacement.     

Bilateral variation of the masseteric myotatic reflex and the silent period in young humans

Increased bilateral differences in jaw reflexes have been considered as pathological findings. The aim of this study was to investigate the normal variation between sides in the jaw jerk and the silent period and determine the range of its boundaries, using the present experimental set-up. Electromyographic data were simultaneously recorded from the right and left masseter muscles by surface electrodes, using a computerized recording and analysis system. The reflexes were elicited by chin taps during mandibular rest and at moderate intercuspal clenching in 20 healthy dentate adults (10 males and 10 females) with a mean age of 26 years. The reflexes were always elicited bilaterally and no overall significant differences were observed between sides for occurrence, latency, duration and amplitude of the jaw jerk and for the latency and duration of the silent period (P > 0.05). However, in the individual analysis significant bilateral variation was occasionally recorded, particularly for the jaw jerk at rest and mainly in the amplitude measurements. On the other hand, in the silent period duration measurements individual variation was very limited. Bilateral individual latency differences for the jaw jerk did not exceed 1 ms at rest (x = 0.3 +/- 0.3 ms) and 0.7 ms at clench (x = 0.3 +/- 0.2 ms), while latency differences for the silent period did not exceed 0.8 ms for the early type (x = 0.4 +/- 0.2 ms) and 4.8 ms for the late phase of depression (x= 1.9 +/- 1.7 ms). Bilateral differences for the silent period duration did not exceed 7.1 ms (x = 2.2 +/- 2.3 ms) in the early type (simple + early phase of combined types) and 3.3 ms (x = 1.5 +/- 0.9 ms) in the total duration of the combined types.     

双膦酸盐相关性颌骨坏死16例临床分析

目的　探讨双膦酸盐相关性颌骨坏死的临床特点及治疗效果。方法　选取2018年6月至2019年3月于中国医科大学附属口腔医院口腔颌面外科就诊的双膦酸盐相关性颌骨坏死患者16例,回顾性分析所有患者的临床和影像学资料。结果　所有患者早期仅表现为牙龈不适,后期表现为颌骨疼痛、牙龈组织肿胀溢脓,其中有6例患者颊部肿胀并有瘘管形成,10例患者死骨裸露,4例患者张口受限,3例患者下唇麻木,1例患者发生颌面部多间隙蜂窝织炎。CT显示11例患者发生溶骨性骨质破坏,5例患者出现骨小梁增粗、结构紊乱,5例患者有死骨形成并与周围骨组织分离。患者进行手术综合治疗6例,保守治疗10例。治疗3个月后,手术综合治疗患者疗效评分明显高于保守治疗患者。结论　双膦酸盐相关性颌骨坏死主要临床特点为颌骨疼痛,多数病例可见死骨裸露,CT显示很可能发生溶骨性骨质破坏,手术综合治疗能够取得良好效果。     

Influence of maximum bite force on jaw movement during gummy jelly mastication

It is known that maximum bite force has various influences on chewing function; however, there have not been studies in which the relationships between maximum bite force and masticatory jaw movement have been clarified. The aim of this study was to investigate the effect of maximum bite force on masticatory jaw movement in subjects with normal occlusion. Thirty young adults (22 men and 8 women; mean age, 22·6 years) with good occlusion were divided into two groups based on whether they had a relatively high or low maximum bite force according to the median. The maximum bite force was determined according to the Dental Prescale System using pressure‐sensitive sheets. Jaw movement during mastication of hard gummy jelly (each 5·5 g) on the preferred chewing side was recorded using a six degrees of freedom jaw movement recording system. The motion of the lower incisal point of the mandible was computed, and the mean values of 10 cycles (cycles 2–11) were calculated. A masticatory performance test was conducted using gummy jelly. Subjects with a lower maximum bite force showed increased maximum lateral amplitude, closing distance, width and closing angle; wider masticatory jaw movement; and significantly lower masticatory performance. However, no differences in the maximum vertical or maximum anteroposterior amplitudes were observed between the groups. Although other factors, such as individual morphology, may influence masticatory jaw movement, our results suggest that subjects with a lower maximum bite force show increased lateral jaw motion during mastication.     

The influence of jaw innervation on the dental maturation pattern in the mandible

OBJECTIVES: To explore the relationship between mandibular dental maturation and the pattern of jaw innervation. SETTING AND SAMPLE POPULATION: The sample included 365 panoramic radiographs taken in the period 1965-1969 in a Danish municipality. DESIGN: For assessing dental maturity, the seven left mandibular teeth (M2, M1, P2, P1, C, I2, I1) were given a dental maturity score according to a method introduced by Demirjian. Spearman correlation coefficients between the maturity score of an index tooth (one of each teeth) and the maturity score of the 6 other teeth was calculated and illustrated. RESULTS: All the correlation coefficients were larger than 0.5 indicating a rather high level of association between the development of mandibular teeth in the same individual. Thus, associations between the pattern of dental maturation and jaw innervation were not obvious. CONCLUSION: When the correlation between the dental maturity stages was analysed, no significant relation was found between dental maturation and jaw innervation in the mandible. This is interesting considering the results presented in a recent study, which showed that the clinical observed tooth eruption was closely related to the pattern of jaw innervation. Those authors suggested that the factors influencing the eruption might be associated with jaw innervation. In our study, the stepwise dental maturation process, however, is not equally associated with jaw innervation.     

个性化牙颌组织三维有限元模型库的建立

目的 探讨建立牙颌组织个体化有限元模型库的方法。方法：以正常上下颌骨及全牙列三组有限元模型为基础，利用Ansys5．5分析软件，分割、修整或重建非正常情况的牙颌组织模型。结果：分类建成3类常用的模型库．包括牙槽骨吸收牙、松动牙、以及缺牙区牙槽骨降低3类情况，308个单元体。结论：模型具有良好的几何形态，有限元力学模型用于个体化病例，更符合临床和科研需要：     

The relationship between the isotonic mechanical power in jaw-opening and jaw-closing muscles in man

The relationship between isotonic jaw-opening and jaw-closing muscle function was studied using a newly developed apparatus which enables load and velocity to be detected simultaneously. The following results were obtained from 17 male adults (age range 22-32 years) without any occlusal dysfunction. (i) The force-velocity relationship in jaw-opening and jaw-closing muscles was represented by a hyperbolic curve, which fitted well with Hill's equation. (ii) The theoretical maximum force obtained by extrapolation from regression was 32.55 +/- 4.98 kg for jaw opening and 35.74 +/- 4.52 kg for jaw closing. (iii) The theoretical maximum velocity obtained by extrapolation from regression was 456.70 +/- 183.27 mm s-1 for jaw opening and 372.77 +/- 141.67 mm s-1 for jaw closing. (iv) The maximum mechanical power (Pmax) calculated from the product of the force and velocity was 772.20 +/- 182.65 kg.mm s-1 for jaw opening and 708.68 +/- 128.14 kg.mm s-1 for jaw closing. (v) The Pmax exerted by individual subjects was approximately 12-34% of the maximum possible force (Fmax) calculated from the force and velocity, in both jaw opening and jaw closing. There were no statistically significant differences between jaw opening and jaw closing with regard to any isotonic muscle functions. In other words, the results of this study strongly indicated a substantial balance between isotonic jaw-opening and jaw-closing muscle function in the subjects who were investigated.     

Atrophy of the residual alveolar ridge following tooth loss in an historical population

Oral Diseases (2010) 17 , 33–44 Objectives: To study the natural aetiopathology of jaw atrophy after tooth loss, unaltered by prosthetic procedures, an historical population without modern dental treatment was examined. Methods: Based on the hypothesis that there are predictable changes in shape during jaw‐atrophy, frequency and degree of atrophy as well as clinical aspects of bone quality and resorption were determined in the skeletal remains of 263 individuals. The potential association between age and frequency/severity of atrophy was analysed. Results: Atrophy in at least one jaw segment was present in 45.2% of the analysed jaw specimens. The residual ridge underwent a series of changes in shape and height following the pattern of resorption described for modern populations. The severity of these alterations was associated with the age of the individual and the region within the jaw. Atrophy was frequently related to structural degradation of the covering cortical layer. Conclusions: These findings prove that atrophy of the jaw evidently does occur, displaying similar patterns of resorption in a population without modern prosthetics, where the negative effect of ill‐fitting dentures is excluded. The basic information about alterations of shape and the cortical layer covering the residual crest might help to provide a deeper insight into aetiopathological mechanisms of this common oral disease.     

Fiber-type composition of the human jaw muscles--(part 1) origin and functional significance of fiber-type diversity

This is the first of two articles on the fiber-type composition of the human jaw muscles. The present article discusses the origin of fiber-type composition and its consequences. This discussion is presented in the context of the requirements for functional performance and adaptation that are imposed upon the jaw muscles. The human masticatory system must perform a much larger variety of motor tasks than the average limb or trunk motor system. An important advantage of fiber-type diversity, as observed in the jaw muscles, is that it optimizes the required function while minimizing energy use. The capacity for adaptation is reflected by the large variability in fiber-type composition among muscle groups, individual muscles, and muscle regions. Adaptive changes are related, for example, to the amount of daily activation and/or stretch of fibers. Generally, the number of slow, fatigue-resistant fibers is relatively large in muscles and muscle regions that are subjected to considerable activity and/or stretch.     

开窗减压术治疗颌骨囊肿54例临床研究

目的：探讨开窗减压术在颌骨囊肿治疗中的效果及应用价值。方法：对54例颌骨囊肿病例行开窗减压术治疗,术后随访9～ 36个月,观察囊腔周围骨质变化情况并测量囊肿大小。结果：54例颌骨囊肿经减压术后3～ 6月,囊肿体积开始缩小,未完全消失者12～24个月后行刮治术,无复发。结论：颌骨囊肿开窗减压术具有操作简单,能最大程度保留颌骨及牙列的完整性,术后复发率低及并发症少。     

Frequency of awake bruxism behaviours in the natural environment. A 7‐day,multiple‐point observation of real‐time report in healthy young adults

The aim of this study was to assess awake bruxism (AB) behaviours in a sample of healthy young adults using a smartphone‐based application for a real‐time report (ie, ecological momentary assessment [EMA], also called experience sampling method [ESM]). Forty‐six dental students used a smartphone application that sent 15 alerts at random intervals during the day for 1 week to collect AB self‐reports. They had to answer on time by tapping on the display icon that refers to their current condition of jaw muscles: relaxed; teeth contact; teeth clenching; teeth grinding; jaw clenching without teeth contact (ie, bracing). The average frequency of relaxed jaw muscles, as a percentage of answers over the 7 days, was 71.7%. Teeth contact (14.5%) and jaw clenching (10.0%) were the most frequent AB behaviours. No significant gender differences were detected. Interindividual differences were quite relevant, but the overall frequency was in general only moderately variable from day‐to‐day. Coefficient of variation (CV) was low for the condition “relaxed jaw muscles” (0.44). At the individual level, teeth contact was the most prevalent behaviour, with a 39.1%‐52.2% proportion of subjects reporting it at least once a day. During a 7‐day observation period, the frequency of real‐time report of AB behaviours in a sample of healthy young adults was 28.3%. The low daily variability in the average frequency value for the relaxed jaw muscles condition suggests that EMA may be a reliable strategy to get deeper into the epidemiology of oral behaviours. This investigation introduced EMA principles to the study of AB and provided data on the frequency of AB behaviours in young adults that could be compared to populations with risk/associated factors and possible clinical consequences.     

Characteristics of mastication in the anodontic mouse

Teeth and periodontal mechanoreceptors play important roles in regulating jaw movements during mastication. However, little is known concerning how jaw movements develop without tooth eruption. To answer this question, we studied masticatory behavior in the osteopetrotic mouse, where tooth eruption does not occur and periodontal mechanoreceptors are missing. A masticatory sequence of the osteopetrotic mouse was divided into two stages: incision and chewing. Incision is characterized by small amplitude and rapid (7 Hz) open-close jaw movements, while slow (5 Hz) and large amplitude open-close jaw movements characterize chewing. The frequency and properties of jaw movements were comparable with those in the normal mouse, though the osteopetrotic mouse had a higher cycle number during incision than did the normal mouse. These results indicate that conversion from sucking to mastication occurs in the anodontic mouse, and the central pattern generator producing the masticatory rhythm develops almost normally without tooth eruption.     

Mandibular metastasis from carcinoma of the bladder.

A case of metastasis to the jaw from carcinoma of the bladder is reported. Only one other case has been reported in the past 90 years. The case is also unusual in that the symptoms of the jaw were the first indication that metastasis had occurred.     

Jaw muscle fatigue and pains induced by experimental tooth clenching: a review

Maximal voluntary isometric contractions of the elevator jaw muscles, with the mandible in the position of maximal intercuspation of the natural teeth, can induce fatigue and weak as well as severe pains in the jaw muscles of children and adults. A subjective sensation of muscle fatigue appears after about 0.5 min of clenching, and it seems as if the psychological parameter of fatigue onset to a large, but unknown, extent is determined by the physiological parameter of the amount of isometric contractile activity, and perhaps also the original strength of the muscle; however, also individual psychological factors seem to play a role. Pains in the elevator jaw muscles appear after about 1 min of clenching. Although isometric contractions are necessary to cause onset of jaw muscle pains, it is conceivable that the perception of the moment of onset of pains to a large, but unknown, extent depends on psychological factors, perhaps the intensity of pains; however, also physiological factors may play a role. The severe muscle pains and gradually increasing subjective exhaustion of the elevator jaw muscles can be endured for about 2 min of maximal voluntary tooth clenching. It is suggested that the psychological parameter of muscle endurance to a large, but unknown, extent depends on the physiological parameter of isometric contractile activity, but also individual psychological factors seem to play a role.