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Biomedical subjects

A H Brook

Publications and source records attributed to A H Brook.

At least 37 records · Page 2Linked to original sources
PubMed2001

A quantitative study of the effect of pumicing and etching on the remineralisation of enamel opacities.

AIMS: The aim of this study was to investigate the effects of pumicing and acid etching on the remineralisation of enamel opacities using quantitative measurement methods. METHODS: Teeth with diffuse opacities were subjected to a treatment sequence of: (a) pumicing for 30-35 seconds (b) etch with 37.5% phosphoric acid for 2 minutes, (c) pumicing for 30-35 seconds and (d) etch for 1 minute, or served as controls. Both groups were then placed in a remineralising solution containing 1.5 mmol/L Ca2+ for 3 weeks. Mineral content changes were measured using contact microradiography and x-ray microtomography. In addition, the reflectivity of the opacities was monitored with infrared reflectance. RESULT: The treatment sequence removed 34 +/- 4 microns of the surface enamel but no mineral loss was observed in the subsurface layer. The treatment sequence enhanced the formation of a new remineralised surface layer with a mean thickness of 22 +/- 3 microns. This new surface layer was less reflective. CONCLUSION: Pumicing and acid etching can be used as a simple technique for the conservative treatment of enamel opacities.

Acid Etching, Dental↗
PubMed2000

Detection of a novel mutation in X-linked amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a heterogeneous group of inherited disorders of defective enamel formation. The major protein involved in enamel formation, amelogenin, is encoded by a gene located at Xp22.1-Xp22.3. This study investigated the molecular defect producing a combined phenotype of hypoplasia and hypomineralization in a family with the clinical features and inheritance pattern of X-linked amelogenesis imperfecta (XAI). Genomic DNA was prepared from buccal cells sampled from family members. The DNA was subjected to the polymerase chain-reaction (PCR) in the presence of a series of oligonucleotide primers designed to amplify all 7 exons of the amelogenin gene. Cloning and sequencing of the purified amplification products identified a cytosine deletion in exon VI at codon 119. The deletion resulted in a frameshift mutation, introducing a premature stop signal at codon 126, producing a truncated protein lacking the terminal 18 amino acids. Identifying mutations assists our understanding of the important functional domains within the gene, and finding another novel mutation emphasizes the need for family-specific diagnosis of amelogenesis imperfecta.

Amelogenesis Imperfecta↗
PubMed1998

The aetiology of developmental defects of enamel: a prevalence and family study in East London, U.K.

The aim of this study was to investigate genetic and environmental factors associated with hypoplastic defects of enamel in a detailed family study combined with an overall prevalence study. 68 percent of 1,518 children with a "complete" permanent dentition had enamel defects, 14.6 percent having hypoplasia. The Family Study consisted of 101 Index Cases from the Prevalence Study having 2 or more teeth with hypoplasia and their first degree relatives: they were compared with 101 matched controls and their relatives. The clinical examinations were supplemented with structured interviews to obtain social, medical and dental histories. Three Index Cases had amelogenesis imperfecta and 18 had "chronological hypoplasia". Bilateral hypoplasia of lower central incisors had a multifactorial aetiology (heritability 70 percent +/- 38 percent), while hypoplasia of pre-molars was associated with familial occurrence of defects. There was evidence suggesting a predisposition in some families to developmental defects of enamel.

Adolescent↗
PubMed1997

Environmental causes of enamel defects.

A large number of causes of enamel defects, both environmental and genetic, have been described. However, many of these are derived from case histories and studies of individual conditions. What is needed now is a systematic investigation of the problem. The first requirement in exploring the aetiology further is the standardization of both the clinical diagnosis and the descriptive terminology. This has been provided by the Fédération Dentaire Internationale Developmental Defects of Enamel Index. Comparing studies using standardized methods, including this index, has highlighted areas for closer investigation. The total prevalence of enamel defects in a population needs to be established as a baseline for studies on aetiology. Sixty-eight per cent of 1518 school children in London have enamel defects in the permanent dentition, with 10.5% having 10 or more teeth affected and 14.6% having hypoplasia, i.e. missing enamel. These findings are in contrast to the 37% with hypoplasia found in a group of third to fifth century Romano-Britons from Dorset, England, suggesting further consideration of possible environmental and genetic differences between the two populations. An overall long-term study of dental development in low birth weight children has shown significantly more (P < 0.001) enamel defects related to major health problems during the neonatal period. By using standardized, reproducible criteria in prevalence studies to gain an overview of the problem and then studying specific groups or conditions, it is possible to identify general and specific factors in the aetiology of enamel defects and investigate further the varying role of genetic and environmental effects.

Adolescent↗
PubMed1997

Planning future general anaesthetic services in paediatric dentistry on the basis of evidence: an analysis of children treated in the Day Stay Centre at the Royal Hospitals NHS Trust, London, between 1985-95.

This study aimed to provide evidence for future planning of general anaesthetic services in Paediatric Dentistry. An audit was carried out on children (< or = 17 years) with special needs who were treated under general anaesthesia in the Day Stay Centre at The Royal Hospitals NHS Trust, London, between 1985-95. During these years, 586 child patients were treated, of which 350 had medical complications and/or mental disabilities. Although the number of peri-operative admissions were low (11 planned and 9 emergency), it highlighted the necessity for these patients to be treated in a hospital. Comprehensive dental treatments were carried out which included 1630 deciduous and 596 permanent tooth restorations, and 1382 deciduous and 261 permanent tooth extractions. These patients had follow-up preventive support in the Dental Institute and the readmission rate for further dental treatment under general anaesthesia was low (14 per cent). Comparing the results between 1985-87, 1988-91 and 1992-95 periods, there was a trend for more patients, travelling longer distances, to be treated in the latter periods. It is suggested that more centres with appropriate equipment and trained staff need to be established to meet the increased demand.

Adolescent↗
PubMed1997

DNA diagnosis of X-linked amelogenesis imperfecta (AIH1).

Mutations in the amelogenin gene, AMGX, are known to cause X-linked amelogenesis imperfecta (AIH1). We have used DNA single-strand conformational polymorphism analysis and DNA sequencing to diagnose this disorder unequivocally in two related boys aged 3 and 7 years, respectively, from a family in which an existing mutation in the amelogenin gene is segregating.

Alleles↗
PubMed1993

Small primary tooth-crown size in low birthweight children.

As part of a longitudinal study of dental development in a group of low birthweight children (LBW), study models of 72 children at age 7 years were measured to determine the tooth-crown size of primary molars and canines and to compare the findings with equivalent measurements in 60 normal birthweight (NBW) controls. Mesiodistal (length) and buccolingual (width) dimensions were measured manually, using dial calipers. Primary canines and molars were smaller in the LBW than the controls, with significance values ranging from P < 0.001 for the mesiodistal dimension of maxillary and mandibular canine (> 4% difference) to a non-significant difference P < 0.2 for the buccolingual dimension mandibular first primary molar (1.8% difference). Within the LBW group there was a positive correlation between birthweight and mesiodistal tooth size. Small primary tooth size in LBW children may be influenced by both genetic and environmental factors. The shorter prenatal growth period and poor perinatal and early postnatal development may influence the developing deciduous dentition. Small primary tooth-crown size, associated with LBW, should be considered in all population studies of tooth size.

Child↗
PubMed1990

Enamel defects in the primary dentition of children born weighing less than 2000 g.

The findings for enamel defects in the primary dentition of a group of low birthweight (LBW) children were related to their perinatal medical histories. Examination of 110 LBW children and 93 control children aged 5 years showed that significantly more of the LBW children (71%) had hypoplasia than controls (15%), but there was no difference in opacities alone (LBW 25%, control 26%). In the LBW group, defects were seen more often in children classified as ill during the perinatal period, who received ventilator support or intravenous alimentation and in those children born at less than 32 weeks gestation, compared to the LBW children without these perinatal problems. It is speculated that the high incidence and the cause of enamel defects in sick preterm infants may be due to oxygen deprivation and mineral substitute depletion.

Analysis of Variance↗
PubMed1987

Vasopressin release in sheep following various degrees of rehydration.

Restriction of the water intake of sheep to 0.5 1/day for 7-9 days increases plasma arginine vasopressin (pAVP), and voluntary rehydration causes a rapid fall in pAVP with no change in plasma osmolality. The extent of that inhibition of AVP release was assessed by comparing the decline of pAVP after drinking with pAVP disappearance curves obtained in the same sheep after stopping a constant infusion of AVP at 0.5 micrograms/h, which increased pAVP to the dehydration level. The fall in pAVP after drinking was almost identical with the disappearance curve showing that AVP release was almost completely inhibited during the 2-3 min taken for the sheep to drink 3-5 liters to satiate themselves. The response seemed, therefore, to be cued before the intake reached the satiating volume. When dehydrated sheep drank only 0.5 or 1.0 liter, in 30 s or less, pAVP again fell rapidly but only to a minimum approximately 15 min after drinking. The pAVP was unaltered in dehydrated sheep presented with water but denied access to it. Thus satiation was not necessary for rapid inhibition of AVP release after drinking, but satiation was necessary for this inhibition to be maintained. The initial inhibition was associated with falls in hematocrit and plasma total protein but not plasma osmolality. This isosmolar dilution occurred even in sheep that saw but were denied access to the water and suggests a shift of fluid from the extravascular space.

Animals↗
PubMed1986

An image analysis system for the determination of tooth dimensions from study casts: comparison with manual measurements of mesio-distal diameter.

A first comparison of an image analysis method with classical hand measurement was made using the mesio-distal diameter data derived by the simplest image analysis method, the jawview mode. Fifty casts of male Hong Kong Chinese dental students, mean age 20.4 years, were examined by both methods. The two techniques gave comparable overall results, the correlation coefficients generally being greater than 0.9. A combination of the buccal and occlusal image analysis views gave the best correlation with hand measurement with a comparable variability for different tooth types. For certain teeth, particularly posteriors, reproducibility was better using hand measurement. Optimal weighting of the data from these two different image analysis views can give an "estimated hand measurement" value. Further development of the method to deal with differing orientations of teeth is possible.

Adult↗
PubMed1985

Haemophilic pseudotumours of the mandible: report of a case in a one-year-old child.

Pseudotumours of bone are an uncommon complication of severe haemophilia and only seven cases occurring in the mandible have been reported previously in the English literature. If treated early the condition appears to have a better prognosis and so it should be included in the differential diagnosis of any slowly progressive swelling of hard and soft tissues occurring in a patient with severe haemophilia. However aspiration and biopsy should be avoided if possible. Previous authors have advocated a variety of invasive procedures for this condition. A further case is described which is unique in the age at which the bilateral lesions developed, in the successful outcome of conservative management and in the dental observations.

Diagnosis, Differential↗
PubMed1985

Acute reduction of plasma vasopressin levels by rehydration in sheep.

Sheep were depleted of water by restricting water intake to 500 ml/day for 7-9 days and were then rehydrated by three treatments: voluntary intake of water, administration of water by tube into the stomach, or voluntary intake of 0.9% NaCl solution (saline). The volumes of fluids drunk within 2-3 min, or administered by tube, were approximately equal to the animal's weight loss. Plasma vasopressin rose from 4.4 +/- 0.6 to 16.8 +/- 1.0 pg/ml during water restriction. After drinking water plasma vasopressin fell from 19.0 +/- 1.9 to 7.5 +/- 0.4 pg/ml (P less than 0.001) in 15 min and gradually fell to 3.2 +/- 0.4 pg/ml over 6 h. Plasma osmolality fell from 302.4 +/- 0.9 to 301.0 +/- 1.1 mosmol/kg (NS) 15 min after water drinking and then gradually fell to subnormal levels. Sheep given water by stomach tube showed a similar decline in plasma osmolality, but the fall in plasma vasopressin was attenuated. The fall in plasma vasopressin in the first 30 min after drinking saline was almost identical with the fall after drinking water, but plasma osmolality was unaltered. Plasma vasopressin fell so rapidly after drinking water or saline as to suggest that the act of drinking caused almost complete inhibition of vasopressin release without a change in plasma osmolality. The results are consistent with earlier evidence that oropharyngeal receptors initiate the inhibition of vasopressin release after drinking.

Animals↗
PubMed1984

A unifying aetiological explanation for anomalies of human tooth number and size.

Genetic and environmental factors are implicated in the aetiology of supernumerary teeth, hypodontia, megadontia and microdontia ; these anomalies tend to be associated. 1115 school children aged 11-14 years examined clinically and radiographically provided prevalence data. A further 703 children with dental anomalies were studied. 153 of these became probands for a family study and 327 of their first-degree relatives were examined. There were much higher frequencies (p less than 0.001) of all anomalies among the relatives of probands than in the general population. Males more often had supernumerary teeth and megadontia and females more frequently had hypodontia (p less than 0.05) and microdontia . For hypodontia, the proportion of relatives affected varied with the severity of the condition in the proband (p less than 0.05). In the prevalence study, there was an association between hypodontia and microdontia (p less than 0.001). These findings may be explained by a multifactorial model having a continuous scale, related to tooth number and size, with thresholds. Position on the scale usually depends upon the combination of numerous genetic and environmental factors, each with a small effect, but occasionally a chromosomal anomaly, a major single gene or a major environmental insult may have a large effect. The finding that the estimated difference between the means of the sexes was the same for each anomaly, within the limits of experimental error, supports the validity of the model.

Adolescent↗