Management of traumatically injured pulps in immature teeth using MTA

Maintaining pulpal health during tooth development is an important goal in managing traumatic injuries in the immature dentition. The introduction of mineral trioxide aggregate has offered an improved method for pulp protection in such cases. This article describes a technique using MTA for vital pulp therapy on teeth with crown fractures that have resulted in pulp exposure.     

兔下颌骨骨压缩动物实验的初步研究

目的:使用自制的骨压缩器缩短兔的下颌骨,建立骨压缩动物模型.方法:使用自行制作的骨压缩器,植入兔右侧下颌骨体部.以0.56mm/d、1次/d的速度与频率缩短骨压缩器;3周后在左侧实行同样手术.观察下颌骨长度的变化及下颌骨的组织学变化.结果:①骨压缩器缩短3mm,下颌骨缩短了3mm.②实验前上下颌中线基本一致;右侧骨压缩后,下颌明显右偏;右侧停止骨压缩,而左侧骨压缩后,上下颌中线又基本一致,同时前牙覆盖增大.③X线片测量显示骨压缩器中间固位钉间距离在实验后减少了2.8mm;下颌切迹到下颌中切牙间距离减少了6.5mm.结论:使用压缩力可以将下颌骨缩短,本实验建立了兔的下颌骨骨压缩模型.     

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.     

Ceramic augmentation of the lower jaw.

Atrophy of the lower jaw is essentially a manifestation of vertical bone resorption and must be treated in a compensatory manner. Animal experiments have shown the value of the bioactive glass ceramic Ceravital as a bone replacement material. After box-shaped or step-shaped osteotomies, we perform interpositional plastic operations with glass ceramic in order to augment the atrophied human lower jaw. Results, advantages and dangers of the method are shown in 12 patients.     

The influence of food material properties on jaw kinematics in the primate, Cebus

ObjectiveTo quantify the impact of food material properties on temporal and spatial variables of chewing kinematics at the level of the feeding sequence, gape cycle, and gape cycle phases.DesignThree-dimensional kinematics were quantified from two adult, male capuchin monkeys (genus Cebus) while chewing on foods grouped by material properties into two categories, foods of high toughness and foods of low toughness.ResultsTotal sequence duration and the total number of chews in a sequence are significantly influenced by food material properties, with foods of high toughness having shorter sequence durations and lower total chew numbers per sequence. Mean cycle duration is not impacted by food material properties at the level of the sequence, but food group differences are found when each cycle is compared independently by food group. Prior to chew fifteen, foods of low toughness elicit significantly lower gape cycle durations and significantly lower vertical displacements of M₁. At the level of the chew phase, variance in slow close explains the majority of variance in chew cycle duration prior to chew thirteen, with foods of low toughness eliciting shorter slow close durations and smaller vertical displacements of M₁. The vertical displacement of M₁ throughout the chewing sequence is the primary spatial determinant of variance in the duration of slow close.ConclusionsThese data reveal that chewing behaviour in Cebus is temporally stereotyped at the level of the gape cycle, but temporally and spatially flexible within the cycle, at least partly due to central mechanisms of motor control.     

Rocking moments in extraction of teeth in the lower jaw

The purpose of this study was to observe, by means of strain gauges attached to forcep handles, the rocking moments needed during the extraction of lower jaw teeth. Great variation was found between the values for rocking moments and their acting times in different tooth groups. There were also great individual differences in the attachment of teeth. The mean value of the highest lingual rocking moments (2.80 J) was recorded during the extraction of first and second molars, and the highest labial moments (4.78J) during the extraction of canines. The mean value of the total rocking moments was highest during the extraction of canines (1.98 J) and lowest (1.19 J) during the extraction of premolars. The mean value of total rocking moments for incisors and canines was significantly lower (P less than 0.01) and for molars almost significantly lower (P less than 0.05) for the group aged 40 and over when compared to corresponding values for the group under 40 years of age. The lowest mean value of all extraction times was observed for incisors in all age groups.