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Biomedical subjects

A J Laws

Publications and source records attributed to A J Laws.

At least 19 recordsLinked to original sources
PubMed1993

The heritability of gingival crevice depths in sheep.

The gingival crevices of the four central incisor teeth of 396 sheep with known sires were measured at the mid-labial, mid-mesial and distal (interproximal), and mid-lingual aspects to test the hypothesis that gingival crevice depths were heritable. In total, 6336 gingival crevices were examined. Mean crevicular depths were 1.50 mm (labial), 3.16 mm (interproximal) and 6.52 mm (lingual). Within breedstrain genetic variation was examined and paternal half-sib heritability estimates were found to be high for the interproximal crevice depth (0.66 +/- 0.20) and the lingual crevice depth (0.69 +/- 0.21), but lower, and non-significant, for the labial crevice depth (0.24 +/- 0.17).

Animals↗
PubMed1989

Environmental influences on the progression of clinical and microbiological parameters of sheep periodontal disease.

The responses of some clinical and microbiological parameters of periodontal disease (PD) in sheep were examined subsequent to transferring animals between PD-affected and PD-free farms. Previously healthy animals showed transient deterioration in some clinical, but not microbiological parameters, which suggests either that a different microbiota to the one studied may be more important in the initiation of the disease, or that sampling did not intercept periods of destructive disease activity in the early lesions. In sheep with established disease, those parameters indicative of periodontitis which included pocket depth and bleeding on probing as well as the proportions of black-pigmented Bacteroides species were not significantly altered by environmental changes. This observation suggests that once the disease is established on PD-affected farms, the hand, some clinical signs of the disease including lengthening and mobility of incisor teeth increased in sheep on the PD-affected farm relative to the PD-free farm. This suggests that the disease may have a complex aetiology.

Animals↗
PubMed1988

A study of periodontal disease in sheep over a twelve month period.

Sheep affected by broken mouth periodontal disease (P.D.) were examined over a twelve month period for different clinical parameters. It is suggested that P.D. in sheep is an episodic phenomenon similar to human P.D., and that only a few animals with signs of P.D. may undergo clinically significant destruction over a yearly period. No single parameter could reliably predict future deterioration in other parameters.

Journal Article↗
PubMed1988

Dental configuration among different breeds of sheep.

Three breeds of sheep, Southdown, Suffolk and Romney, and two mixed breeds, Border Leicester over Romney and Coopworth over Romney, managed identically on a research station, where they were free from culling and allowed to live their natural life, had their dental configuration examined. The sheep were divided into age groups with 10 sheep in each. The least variation was found in the relation of the upper dental pad to the lower jaw. The most statistically significant differences were found in the first age group: one year six months. The Suffolk breed was noticeably different from the others. Deepened gingival sulci, as well as the inconsistency of bleeding after probing associated with labial gingivitis highlighted the problems of using these latter criteria as indicators of health or disease among sheep on the basis of a single examination.

Age Factors↗
PubMed1987

Suspected periodontopathic microorganisms and their oral habitats in young children.

Samples of subgingival plaque from 67 children, 5-7 years of age, were examined for the presence of certain suspected periodontal pathogenic species using the conventional technique of anaerobic sonification, dilution and spiral plating. When this technique was compared with a direct plating procedure which involved no preliminary dispersion and dilution of plaque specimens, it was found that the direct method resulted in double the frequency of children in whom black-pigmented Bacteroides (BPB) were detected and a 10-times increase in the number of subjects harbouring Actinobacillus actinomycetemcomitans. Samples from the tongue, tonsils and saliva were also plated using the direct technique. BPB were detected less commonly in the plaque specimens (61.3% of children) than in saliva (89.5%), or on the tongue (86.6%) and tonsils (97.1%). Expressed as percentages of a pooled sample of the total BPB population, the most frequently detected species in plaque were Bacteroides intermedius (44.4%) and Bacteroides melaninogenicus (48.0%). The most prevalent isolate in all other oral sites was B. melaninogenicus. Expressed as percentages of children in whom BPB were detected, the most frequently isolated species from plaque using the conventional dilution technique was B. intermedius (21.3%), whereas other BPB species were present in fewer than 5% of children. Fusobacterium nucleatum and Capnocytophaga species were isolated most frequently from plaque but were also commonly detected in the various other oral sites.

Aggregatibacter actinomycetemcomitans↗
PubMed1985

A clinical study of periodontal disease in sheep.

Detailed examinations were made of the central permanent incisors and periodontia of 30 or 40 ewes on each of one control farm and three periodontal disease (P.D.) farms. The study confirmed that incisor crown lengthening, protrusion and loosening were significant features of P.D. Periodontitis (assessed by increased sulcus depth and bleeding after probing) about the lingual sulcus was a significant feature of P.D. Labial gingivitis and labial periodontitis were not significant features. A relatively long lower jaw did not appear to be a feature of P.D. 87.

Journal Article↗
PubMed1981

The relationship between crown size and the incidence of bifid root canals in mandibular incisor teeth.

From an initial sample of 729 extracted mandibular incisor teeth a final sample of 286 (172 central and 114 lateral incisors) was used to determine if any relationship existed between crown size, expressed as the M-D/F-L index, and the presence of bifid canals within the root of the tooth. The M-D/F-L index was calculated for each tooth and was matched against the presence of bifid canals as determined from radiographs of the lateral aspect of the teeth. The results indicate that bifid canals occur more frequently in teeth with the smaller M-D/F-L index and from regression equations, which had a high coefficient of correlation, the indications are that the incidence of bifid canals among the teeth with the lowest M-D/F-L index could be as high as 70 percent.

Dental Pulp Cavity↗