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Biomedical subjects

B G Smith

Publications and source records attributed to B G Smith.

At least 37 records · Page 2Linked to original sources
PubMed1997

A New Mechanism for the Regulation of Stomatal Aperture Size in Intact Leaves (Accumulation of Mesophyll-Derived Sucrose in the Guard-Cell Wall of Vicia faba).

At various times after pulse-labeling broad bean (Vicia faba L.) leaflets with 14CO2, whole-leaf pieces and rinsed epidermal peels were harvested and subsequently processed for histochemical analysis. Cells dissected from whole leaf retained apoplastic contents, whereas those from rinsed peels contained only symplastic contents. Sucrose (Suc)-specific radioactivity peaked (111 GBq mol-1) in palisade cells at 20 min. In contrast, the 14C content and Sucspecific radioactivity were very low in guard cells for 20 min, implying little CO2 incorporation; both then peaked at 40 min. The guard-cell apoplast had a high maximum Suc-specific radioactivity (204 GBq mol-1) and a high Suc influx rate (0.05 pmol stoma-1 min-1). These and other comparisons implied the presence of (a) multiple Suc pools in mesophyll cells, (b) a localized mesophyll-apoplast region that exchanges with phloem and stomata, and (c) mesophyll-derived Suc in guard-cell walls sufficient to diminish stomatal opening by approximately 3 [mu]m. Factors expected to enhance Suc accumulation in guard-cell walls are (a) high transpiration rate, which closes stomata, and (b) high apoplastic Suc concentration, which is elevated when mesophyll Suc efflux exceeds translocation. Therefore, multiple physiological factors are integrated in the attenuation of stomatal aperture size by this previously unrecognized mechanism.

Journal Article↗
PubMed1996

A study of the association between gastro-oesophageal reflux and palatal dental erosion.

Thirty-six patients aged 15-74 with palatal dental erosion where the aetiology was unclear were investigated for gastro-oesophageal reflux. Ten subjects without symptoms of reflux or palatal erosion acted as controls. Distal and proximal oesophageal reflux were measured over 24 hours by dual channel antimony electrodes. Oral pH was measured simultaneously over the same period by a radio-telemetry capsule held palatally in a vacuum formed splint. Data were logged onto two portable digitable recorders. Twenty-three patients (64%) with palatal erosion had pathological gastro-oesophageal reflux compared with standard criteria. More than 4% of the total percentage time that the pH is less than 4 in the distal oesophagus is internationally recognised by gastroenterologists as representing a pathological level of reflux. The median percentage time < pH 4 in the distal oesophagus for these patients was 5.7%, in the proximal oesophagus, pH 4 was 0.5% and pH < 5 was 3.1%. In the mouth, the results for the percentage time that the pH < 5.5 was 0.3% and < 6 was 4.4%. A relationship was observed between the pH < 4 in the distal oesophagus and the mouth pH < 5.5 (r = 0.47, P = 0.002) and pH < 6 (r = 0.34, p = 0.02). There was a relationship between oral acid exposure time pH < 6 and the tooth wear index (r = 0.37, P = 0.01). These results show that gastro-oesophageal reflux is strongly associated with palatal erosion and that some patients presenting with palatal dental erosion should be assessed for gastro-oesophageal reflux as a possible cause, even in the absence of clinical symptoms of reflux.

Adolescent↗
PubMed1996

A personal, historical view of the management of tooth wear.

The management of caries, periodontal disease and tooth wear has followed similar patterns over the last 30 years but at different rates. The reduced emphasis on surgery in the treatment of periodontal disease has now caught up with minimum interventive treatment of caries. Tooth wear is still, in my opinion, often over-treated and it is time that the management of tooth wear followed the same pattern.

Humans↗
PubMed1996

The prevalence of toothwear in 1007 dental patients.

The dental profession is becoming increasingly concerned about unacceptable levels of toothwear and there is an impression that the condition is becoming more prevalent. There is, as yet, little epidemiological evidence to illuminate the question and so this study is therefore intended to provide baseline data on the prevalence of toothwear in a sample of the dental attending population of South East England. A degree of toothwear is normal and progresses throughout life. Toothwear which is acceptable in an older age group would not be so with younger patients. It is therefore necessary to designate threshold values of acceptable levels of toothwear for different age groups to reach realistic conclusions about the prevalence of unacceptable levels of toothwear. Of the 1007 patients examined only nine had completely unworn dentitions. More than 93,500 tooth surfaces were examined and of these 5.1% had wear which exceeded the threshold values. Despite increasing the threshold values for the older age groups from those proposed in an earlier study by Smith & Knight (1984), these patients still had higher levels of unacceptable toothwear. There was a slight tendency for men to have more wear than women, but there was no clinically significant relationship between the number of missing posterior teeth and wear of the anterior teeth.

Adult↗
PubMed1996

The relationship between gastro-oesophageal reflux disease and dental erosion.

It is well known that acid regurgitated from the stomach into the mouth will erode teeth. Conditions such as anorexia and bulimia nervosa, chronic alcoholism and gastric disturbances cause palatal dental erosion. The common factor in these conditions is the role played by the stomach and oesophagus in the acid movement. Acid moving through the lower oesophageal sphincter into the oesophagus is described as gastro-oesophageal reflux (GOR). In some patients the acid movement becomes chronic, painful and requires treatment and is termed gastro-oesophageal reflux disease (GORD). It is felt by many gastroenterologists that GORD is a failure of the anti-reflux mechanism, which is predominantly controlled by the lower oesophageal sphincter (LOS). Regurgitation is the reflux of gastric juice through the upper oesophageal sphincter and into the oral cavity. Once the acid has reached the mouth the potential exists for damage to the teeth. This paper reviews the role of GOR, GORD and regurgitation in the aetiology of dental erosion.

Esophagogastric Junction↗
PubMed1996

[Study on experimental cervical defect of human tooth by SEM].

Experimental cervical defects on 12 pairs of premolar caused by cross-brushing, erosion and occlusal force separately or together were observed under SEM Changes on the surface of cervical defects suggested that the defects were induced by the above three factors combined. It was interesting that various kinds of microcracks were noticed on sections of enamel and dentin at the cervical defect areas made by mimicking occlusal force combined with other factors. The results seemed to indicate that the occlusal force would play an important role on formation of the cervical wedge-shaped defect and that accumulation of the stress caused the hard tissue injured and microcracked.

Adolescent↗
PubMed1995

Reinforcement of weakened cusps by adhesive restorative materials: an in-vitro study.

Pairs of extracted premolar teeth were prepared with MOD cavities reducing the lingual cusp at its base to one of five widths: 1.25-2.25 mm. One of each pair was then restored with one of five adhesive restorative techniques and the weakened cusp of both teeth fractured by a force applied to the cusp at an angle of 30 degrees to the long axis of the tooth. At all cusp widths a layered restorative technique in which the cavities were filled to the enamel-dentine junction with glass-ionomer cement and the enamel replaced by composite, reinforced the weakened cusp more than the other restorative materials tested. This combination of materials to reinforce weakened cusps is worth considering as a cost effective alternative to removing the cusp entirely and making a crown or protecting the cusp with a cuspal coverage gold inlay.

Adhesives↗
PubMed1995

The distribution of erosion in the dentitions of patients with eating disorders.

Anorexia and bulimia nervosa (the eating disorders) are potentially life threatening and are becoming more prevalent. This paper reviews the effects of these disorders on dental erosion and reports a study to assess the effects of the eating disorders on the erosion of teeth relating the severity of erosion to factors such as the frequency of self-induced vomiting (SIV). One hundred and twenty-two eating disorder patients and an equal number of age, sex, and social class matched controls were studied. The study population was divided into subgroups according to the eating disorder. All the subgroups had significantly more abnormal toothwear than the controls (P < 0.005), with the differences being most marked in the SIV groups. Further analysis did not find any consistent relationships to the frequency or duration of SIV.

Anorexia↗
PubMed1995

Polysaccharide composition of unlignified cell walls of pineapple [Ananas comosus (L.) Merr.] fruit.

The polysaccharides of cell walls isolated from the fleshy, edible part of the fruit of the monocotyledon pineapple [Ananas comosus (L.) Merr.] (family Bromeliaceae) were analyzed chemically. These cell walls were derived mostly from parenchyma cells and were shown histochemically to be unlignified, but they contained ester-linked ferulic acid. The analyses indicated that the noncellulosic polysaccharide composition of the cell walls was intermediate between that of unlignified cell walls of species of the monocotyledon family Poaceae (grasses and cereals) and that of unlignified cell walls of dicotyledons. Glucuronoarabinoxylans were the major non-cellulosic polysaccharides in the pineapple cell walls. Xyloglucans were also present, together with small amounts of pectic polysaccharides and glucomannans (or galactoglucomannans). The large amounts of glucuronoarabinoxylans and small amounts of pectic polysaccharides resemble the noncellulosic polysaccharide composition of the unlignified cell walls of the Poaceae. However, the absence of (1-->3,1-->4)-beta-glucans, the presence of relatively large amounts of xyloglucans, and the possible structure of the xyloglucans resemble the noncellulosic polysaccharide composition of the unlignified cell walls of dicotyledons.

Carbohydrate Sequence↗
PubMed1995

Clinical and radiographic diagnosis of occlusal caries: a study in vitro.

Various methods of diagnosing occlusal caries have been described, but only visual, clinical examination and radiographic examination are commonly used in dental practice. This laboratory study investigated the ability of 12 examiners to detect the presence or absence of occlusal caries in 48 extracted molar teeth using these two techniques. The presence or absence of caries was subsequently verified by sectioning the teeth. Diagnosis from visual examination was poor, only 48.7% of lesions in dentine being detected. Radiographic diagnosis was better with 62.2% of dentine lesions being found. However, this increase in sensitivity of the diagnosis was accompanied by a decrease in specificity with the number of false positive diagnoses increasing when the radiograph was used. Therefore, although the bite-wing radiograph may be regarded as a safety net for the diagnosis of occlusal caries, it must be interpreted with caution bearing in mind the possibility of false positive diagnoses.

Dental Caries↗
PubMed1995

[The effect of occlusal force on the formation of experimental cervical wedge-shaped defects on human teeth].

Nine pairs of premolar from 7 patients were divided into three groups according to different occlusal forces. Every tooth was tested with pH5 or pH7 water bath by an electric toothbrushing machine and an electric occlusal force fatigue machine alternatively. Only the buccal surface of every tooth suffered from brushing test. There were 600 000 strokes of occlusal force fatigue test and/or 800 000 cycles of cross-brushing test for every tooth throughout the experiment with 4 intervals. During every interval, the depth at the profile of the cervical defect on each replica of tested tooth was measured and the shape of every defect was recorded with a computerized Seescan image analysis system. The findings suggested that the occlusal force played an important role in the formation of experimental cervical wedge-shaped defects. Occlusal force alone could produce cervical tooth defect in very slow rate. When the occlusal force associated with acid erosion and tooth-brushing abrasion, the depth of cervical defect increased significantly and the wedge-shaped defects were formed.

Acid Etching, Dental↗
PubMed1994

Comparison of the effect of fluoride and non-fluoride toothpaste on tooth wear in vitro and the influence of enamel fluoride concentration and hardness of enamel.

The effect of the presence of fluoride in toothpaste on tooth wear was investigated in extracted human premolar teeth collected from two geographic areas with different fluoride concentrations in the public water supply. Nine teeth from each area were divided bucco-lingually into matched pairs and subjected to a wear regime in vitro. The regime consisted of 5 minutes immersion in 6% citric acid buffered at pH 3.5, followed by 200 cycles of linear tooth-brushing in a slurry of either a fluoride or a non-fluoride toothpaste, the whole process repeated 720 times. Teeth collected from subjects in Birmingham (public water supply fluoridated at 1 ppm) had a higher fluoride concentration in the surface enamel (P < 0.01) and greater hardness (P < 0.001) than teeth collected from subjects in London (non-fluoridated water supply). The results showed that less wear was produced in the presence of the fluoride toothpaste than in the presence of the non-fluoride toothpaste with an otherwise identical formulation (P < 0.001), and that the amount of tooth wear in vitro was not significantly affected by differences in fluoride concentration and hardness of enamel.

Dental Enamel↗
PubMed1994

The effect of restorative materials on the wear of human enamel.

The wear of human dental enamel against amalgam, Concise composite, SR-Isosit Inlay/Onlay composite, Vitadur-N glazed porcelain, unglazed IPS Empress ceramic, and enamel (control) was investigated by use of a modified stress cycling machine. Testing was carried out in water and in citric acid (pH 4) and the enamel-material couples were subjected to 25,000 cycles of wear with a maximum load of 40 N. Tooth profile reduction was measured at baseline and at 5000 cyclic intervals with a computer image analysis program. The depth of the wear scars on material specimens was analyzed with a profilometer. All materials produced increased enamel wear in acid. Vitadur-N glazed porcelain was found to be the most destructive to human dental enamel, and this was closely followed by Empress and enamel.

Acrylic Resins↗
PubMed1994

Replacement of missing cusps: an in vitro study.

One of the commonest methods of replacing a missing cusp, a pinned amalgam restoration, was compared with three adhesive restorative techniques, two of them with additional pin retention. All the teeth were subjected to occlusal/lateral forces and loaded to fracture in an Instron testing machine. A layered restoration of glass ionomer cement replacing the dentine, and resin composite replacing the enamel, without pins required more force to fracture than any of the other techniques including the pinned amalgam restoration. A composite restoration with dentine bonding agent and additional pin retention was second best and significantly better than the pinned amalgam restoration. A cermet restoration with additional pin retention required slightly less force to fracture than pin-retained amalgam restorations, but not significantly so.

Bicuspid↗
PubMed1994

The dental impact of eating disorders.

Our self-perceptions are all influenced to some extent by the media. The increase in sales of diet plans immediately after Christmas only serves to highlight the fact that many people (consciously or subconsciously) are aware of the effect that advertisements have on our lives. The weight of most people is controlled by a combination of diet and homoeostatic control and remains relatively constant, but weight loss has a more profound and sinister effect for others. Unexplained dental erosion can occasionally be found during dental examinations and, despite careful questioning, a definitive diagnosis may prove elusive. In these patients, once the more common causes of dental erosion have been eliminated, the eating disorders should be considered. In this paper, the effects of psychological conditions affecting the diet on the dentition will be discussed.

Anorexia Nervosa↗
PubMed1994

Audit in restorative dentistry.

Auditing activity requires patient data to be collected and analysed to allow comparisons to be made and conclusions drawn. Within the General Dental Services the Dental Practice Board regularly collects practitioner specific clinical data and distributes this to allow dentists to compare their own clinical activity with local and national means. In hospital dentistry, a software package has been developed to enable orthodontic audit to be performed in hospital practice. The package is now being piloted in several centres. A similar software package is required for auditing restorative dentistry activity in units where consultant services are provided. Hospital patient administration systems provide demographic data and appointment systems predominantly with little opportunity for patient specific clinical analysis. Carefully designed software will allow appropriate clinical data and analysis. To ensure compliance and accurate recording both by clinical and support staff it is essential that any software system should be easy to use.

Dental Service, Hospital↗