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Biomedical subjects

B K Berkovitz

Publications and source records attributed to B K Berkovitz.

At least 19 recordsLinked to original sources
PubMed1992

Ultrastructural quantification of collagen fibrils in the central region of the articular disc of the temporomandibular joint of the cat and the guinea pig.

This quantitative ultrastructural analysis was made on articular discs from four guinea pigs and four cats. Mean diameters of collagen fibrils were small (approximately 45 nm) and showed unimodal distributions. These features are consistent for connective tissues subjected to compressional forces. The relatively high percentage volume of the extracellular matrix occupied by collagen in the articular disc of the guinea pig (approximately 60 per cent) and the presence of crimping is, however, more typical of a connective tissue subjected to tension. Two differences were discernible between the collagen in the articular discs of the guinea pig and cat. First, the percentage volume occupied by collagen for the guinea pig disc was significantly higher than for the cat. Second, the frequency distribution of collagen fibril diameters for the cat, although unimodal, was skewed. These differences possibly reflect the different types of movement at the temporomandibular joints in the two species.

Actin Cytoskeleton↗
PubMed1991

Ultrastructural quantification of collagen fibrils in chordae tendineae of the sheep and rabbit.

Collagen fibril diameters and the volume occupied by collagen were quantified at the ultrastructural level in the chordae tendineae of the rabbit and the sheep. Collagen fibril diameter distribution was unimodal and significant differences were found between values on the left and right sides, those on the left being greater than those on the right. The differences are discussed in terms of mechanical loading and compared with results obtained from other tendinous structures subjected to continuous loading.

Animals↗
PubMed1991

An assessment of the control of matrix turnover by a quantitative ultrastructural analysis of fibroblasts of the periodontal ligament in rats.

A quantitative structural analysis of the synthetic and degradative organelles of fibroblasts of rat incisor and molar periodontal ligaments was conducted. The results showed that in these tissues which are reported to have significantly different rates of turnover of their functional matrix collagen the rate of synthetic activity was the same. However, there were differences in the pattern of degradation with the molar ligament having between 5 and 6 times more phagocytosed collagen than the incisor. It is suggested that post-synthesis processing may control collagen turnover rather than modulation of rates of synthesis.

Animals↗
PubMed1991

A quantitative study of the ultrastructure of fibroblasts within the enamel-related connective tissue of the rat incisor.

A quantitative ultrastructural study was made of the fibroblasts of the enamel-related connective tissue and periodontal ligament of the rat incisor. The two populations of fibroblasts were very similar in morphology, the only difference found in the parameters measured being the increased number of microtubules in the enamel-related connective tissue. The data do not lend support to the idea that the fibroblasts of the periodontal ligament generate the eruptive force by their motility or contractility.

Actin Cytoskeleton↗
PubMed1990

How teeth erupt.

The cause of delayed eruption is usually obvious and treatable (as with lack of space or impeding supernumerary teeth). However, in some cases there is no obvious cause. Treatment of these cases might be easier if we fully understood the mechanism of eruption itself. Unfortunately, the precise process of generating the eruptive force for teeth has not yet been fully elucidated. Various hypotheses have been put forward. In this article the author reviews current theories, and describes some of the experimental difficulties in testing them.

Humans↗
PubMed1990

The development of the periodontal ligament with special reference to collagen fibre ontogeny.

The development of the periodontal ligament was investigated from serial sections of the mandibles of ferrets ranging in age from 42 days to 66 days post partum. Both succedaneous and non-succedaneous teeth were studied and similarities were seen in both types of tooth. No significant amounts of alveolar bone were observed being deposited beneath the erupting root apices and periodontal collagen fibres were seen attached to the walls of the sockets just prior to emergence of the crown into the oral cavity. Compared with the condition a few days after eruption, the collagen fibres on, and just prior to, emergence were thinner, had a more limited area of attachment, and were more randomly orientated. The results indicate that alveolar bone deposition and collagen traction do not generate the eruptive force and that there are species differences in these structural features during the eruptive process.

Aging↗
PubMed1990

Effects of inflammatory periodontal disease ('broken mouth') on the mobility of the sheep incisor.

Loads directed linguolabially and between 0.01 N and 0.2 N were applied to a mandibular central incisor in each of 12 four-year-old ewes with evidence of inflammatory periodontal disease ('broken mouth'). For every incisor, tooth position was monitored continuously with an ultrasonic displacement transducer. Each load chosen was suddenly applied and then maintained for five minutes, producing a biphasic, viscoelastic-like response (a phase of rapid displacement being followed by a more gradual phase of creep). A similar biphasic recovery response was seen on suddenly removing the load. Comparing the findings with those obtained in a previous study for incisors in healthy dentitions, there was a considerable increase in mobility with inflammatory periodontal disease. Surprisingly, however, the patterns of the responses did not differ. The reason for the change in the amount of mobility may be related simply to the quantity of the tooth supporting tissues which is lost, although there is some evidence that qualitative changes occurring in these tissues may also be important.

Animals↗
PubMed1989

A comparison of the biomechanical properties of the periodontal ligaments of erupting and erupted teeth of non-continuous growth (ferret mandibular canines).

Extrusive loads of 0.01-0.2 N were applied to the permanent mandibular canine teeth of two groups of ferrets. In one group, aged approx. 7 weeks, the tooth had only recently emerged into the mouth. In the second group, comprising adult animals, the tooth had fully erupted and had been in function for a considerable time. Biphasic, viscoelastic-like responses followed both the application and removal of the load in both groups. However, there was significantly more mobility for all phases of the loading and recovery cycles in the erupting teeth. The data were compared with previous findings for continuously growing teeth. They highlight the marked periodontal changes which take place when tooth erupts into the mouth, provide some evidence against the generation of a tractional eruptive force, and show some differences in response between teeth of limited or continuous growth.

Animals↗
PubMed1989

Effects of inflammatory periodontal disease ('broken mouth') on the ultrastructure of collagen fibrils in the sheep incisor periodontium.

The ultrastructure of the matrix of the sheep central incisor periodontium showing clinical signs of severe periodontitis was analysed quantitatively. The distribution of collagen fibril diameters in the lower dental pad changed from a bimodal distribution seen in healthy periodontia to a unimodal distribution. Collagen fibrils with an abnormal morphology were seen in the connective tissue adjacent to the crest of the alveolar bone. These results suggest that the deepening periodontal pocket resulting from inflammation removes the major area of support for the tooth and abnormal loads are applied to fibres deeper within the tissue.

Animals↗
PubMed1988

Continuous monitoring of the movements of erupting and newly erupted teeth of limited growth (ferret mandibular canines) and their responses to hexamethonium.

The rates of these eruption-like movements were high and were consistent with reports that eruption is fastest at the time of emergence into the mouth. Once the tooth had attained its initial functional position, there was a significant reduction in the rates. Following administration of the hypotensive agent, hexamethonium, the emerging tooth showed a significant decrease in eruption rates. However, no change was observed for the tooth which had attained its initial functional position. These findings support the view that there are physiological differences at the eruptive and initial functional stages of eruption. The effects of hexamethonium on the erupting ferret canine differ from those reported for the erupting rabbit incisor. This may reflect differences in the eruptive processes for teeth of limited and continuous growth, although other evidence suggests similarities between these.

Animals↗
PubMed1988

A quantitative ultrastructural study of the extracellular matrix of the sheep incisor periodontium.

The ultrastructure of the matrix of the sheep central incisor periodontium was quantitatively analysed. Ewes with healthy mouths were selected. The distribution of collagen fibril diameters was bimodal in the lower dental pad with a population standard deviation significantly larger than the unimodal distribution of fibril diameters found in the periodontal ligament. The lower dental pad connective tissue also contained significantly more oxytalan fibres, some of which resembled mature elastin. These results are consistent with the view that the sheep central incisor is supported primarily by tension within the fibres of the lower dental pad.

Animals↗
PubMed1987

Fenestrated capillaries in the periodontal ligaments of the erupting and erupted rat molar.

Quantitative ultrastructural studies were conducted on eight rats (four aged 21 days and four aged 8 weeks) using the periodontal tissues around the mesial root of the mandibular first molar. The periodontal ligament of the erupting tooth contained significantly more capillary fenestrations than the erupted tooth, both in terms of the number per unit area of endothelium (2.2/microns2) and in terms of total number per cubic millimetre of tissue (30.5 X 10(6)/mm3). Differences were also discerned with respect to the percentage of capillaries in the tissue. Thus, the periodontal vasculature demonstrates marked morphological changes which may be related to the eruptive phase of the tooth.

Animals↗
PubMed1987

A laboratory method for studying tooth mobility of the mandibular central incisor of the sheep.

Linguolabially directed loads of 0.01 to 1.0 N were applied to a mandibular central incisor in each of 12 four-year-old ewes with healthy mouths. For each incisor, tooth position was monitored continuously with an ultrasonic displacement transducer. On suddenly applying a load and maintaining it for five minutes, a biphasic pattern of displacement was recorded, a phase of rapid displacement being followed by a more gradual one. A similar biphasic recovery response was seen on suddenly removing the load. These patterns are viscoelastic-like. The group mean displacements showed that for all phases the responses were force-dependent, though not linearly graded. For a given load, the group mean displacements were considerably larger than those reported previously for the teeth of other animals, supporting the impression that the sheep incisor is extremely mobile. These data will provide a baseline for studies on the mobility of the teeth of sheep with inflammatory periodontal disease ('broken mouth').

Animals↗
PubMed1985

The effects of preventing movement of the rat incisor on the structure of its periodontal ligament.

A quantitative, ultrastructural study was made on the periodontal ligaments of rat mandibular incisors immobilized for 18 days. Fibroblasts and their organelles (i.e. endoplasmic reticulum, mitochondria, microtubules, microfilament bundles, lysosomes, intracellular collagen profiles and intercellular contacts), oxytalan fibres, collagen fibrils and ground substance were quantified. There was re-orientation of tissue at the lateral borders of the ligament and an apparent increase in size of epithelial cell rests. Within the matrix, the mean collagen-fibril diameter decreased and the amount of ground substance increased. No change occurred in oxytalan fibres. Within the cells, effects were seen only in cell contacts and in the relative volume of intracellular collagen, lending no support to the view that fibroblast activity generates the force responsible for tooth eruption.

Animals↗
PubMed1985

Fenestrated capillaries in the connective tissues of the periodontal ligament.

A quantitative ultrastructural study was undertaken to assess the number and distribution of fenestrated capillaries in the periodontal ligaments of the rat dentition. Experiments were conducted on four animals using the right mandibular incisors and first molars. For the incisor, analysis was performed in three sites along the length of the periodontal ligament. Regardless of site, there was 0.1 fenestration per micron2 of endothelium. In the basal region, the incisor periodontal ligament contained 3.5 X 10(6) fenestrations per mm3 of tissue whereas more occlusally it contained 1 X 10(6) fenestrations per mm3 of tissue. For the molar, the capillaries showed more fenestrations, 0.4 fenestration per micron2 of endothelium. There were also more per unit volume of tissue, 12 X 10(6) fenestrations per mm3. Thus, the vasculatures of the rat incisor and molar periodontal ligaments exhibit significant numbers of fenestrations which, in the case of the incisor, are not distributed uniformly along its length.

Animals↗