Search PubMed⌕ Search

Biomedical subjects

S M Higham

Publications and source records attributed to S M Higham.

At least 55 records · Page 3Linked to original sources
PubMed1999

Fluoride recharge of aesthetic dental materials.

The objective of the study was to compare the potential for fluoride recharge of two glass-ionomer cements, a resin-modified glass-ionomer cement, a compomer and a fluoride-containing composite in artificial saliva. Disc samples of each of the materials were placed into artificial saliva. The fluoride content of the artificial saliva was determined at various intervals up to 57 days. The discs were subjected to a 2 min exposure of NaF (500 parts/106). This recharge procedure was repeated at 64 and 120 days. The fluoride release was measured before and after recharge. The fluoride release for all of the materials increased after each exposure to NaF; however, the amount for the composite was very low. The resin-modified glass-ionomer cement displayed the greatest potential for fluoride recharge at 57 and 64 days (P<0.05). By 120 days, the amount of fluoride released in the 24 h post-recharge interval had decreased in all the materials. All the materials showed a potential for fluoride recharge. This effect, however, was minimal in the fluoride-containing composite.

Acrylic Resins↗
PubMed1999

An in situ caries model to study demineralisation during fixed orthodontics.

OBJECTIVES: To investigate de/remineralization of enamel during the early stages of orthodontic treatment using the in situ caries model. DESIGN: A prospective, longitudinal study, using the in situ caries model. SETTING AND SAMPLE POPULATION: The Department of Orthodontics at the University of Liverpool School of Dentistry. Fifteen orthodontic patients undergoing fixed appliance treatment with extraction of premolar teeth. EXPERIMENTAL VARIABLE: Two enamel samples with pre-formed caries-like lesions were placed bilaterally, in specially constructed holders, on an orthodontic fixed appliance. One sample was bonded with a small bracket base. OUTCOME MEASURE: The parameters of the pre-formed carious lesion, expressed as mineral loss (delta Z), lesion depth (ld), lesion width (lw) and ratio (delta Z/ld) were compared between the bracketed, the non-bracketed and a control sample that had not been placed in the mouth. The difference between brackets place on the dominant (toothbrush hand) side and non-dominant side were also investigated. The correlation between mineral loss and length of time the sample was in the mouth was also analysed. RESULTS: There was considerable individual variation; however, a one-factor repeated analysis of variance showed a significant difference in ratio values between the three groups (p = 0.006). A pairwise comparison showed a significant reduction in ratio value for the non-bracketed sample compared with the control, but not the bracketed sample. There was no significant difference in mineral loss between the dominant and non-dominant sides. There was no linear correlation between the length of time the sample was in the mouth. CONCLUSION: An enamel sample with a pre-formed carious lesion, when placed in the mouth of an orthodontic patient, showed reduced remineralization in the presence of a simulated orthodontic bracket. Consistently effective preventive regimes to prevent demineralization in patients with fixed orthodontic appliances need to be developed. The technique described will be a valuable tool in this process.

Analysis of Variance↗
PubMed1999

Thickness of acquired salivary pellicle as a determinant of the sites of dental erosion.

Dental erosion shows a typical distribution pattern within the dental arches. Tooth protection from erosion by salivary pellicle has been shown in vitro, but the hypothesis that pellicle may differ quantitatively at sites of erosion has not been investigated. This study aimed to determine the thickness of acquired salivary pellicle within the dental arches, investigate the possible relationship of this thickness to the distribution and severity of erosion within the arches, and confirm the protective effect of pellicle against dental erosion. Eight enamel blocks were produced from each of 5 bovine incisors assigned to five volunteers. Each block was further cut into 2 slabs, producing control and experimental slabs. Pellicle developed on experimental slabs located on 8 intra-oral sites after 1 hr of exposure was stained by "sheep anti-human IgGAM-FITC". Slabs were then visualized, and pellicle thickness measured, by confocal laser scanning microscopy. Eroded enamel lesions were produced in experimental and control slabs by means of pure orange juice. The degree of erosion was quantified by transverse microradiography. Pellicle thickness varied significantly within the dental arches and among individuals. An inverse relationship (r = -0.96, p<0.001) was observed between the degree of erosion and pellicle thickness. Significant differences in erosion were observed between slabs with and those without pellicle. This study has shown that the thickness of acquired salivary pellicle varies within the dental arches, which may be responsible for the site-specificity of dental erosion, and that pellicle does protect the teeth from erosion.

Analysis of Variance↗
PubMed1999

Caries inhibiting and remineralizing effect of xylitol in vitro.

This study aimed to determine the effect of xylitol on the development and remineralization of caries in vitro, and to compare this effect with that of fluoride alone and in combination. Two experiments were devised. In experiment 1, bovine incisors were each sectioned into 4 portions which were randomly assigned to 4 demineralizing agents: A) acidic buffer (x), B) x + 0.5 ppm fluoride, C) x + 20% xylitol, and D) x + 20% xylitol + 0.5 ppm fluoride. Caries-like lesions were produced in specimens. In experiment 2, carious lesions were produced in teeth. Five lesion-bearing slabs were cut from each tooth. While one was reserved as control (UN), others were randomly assigned to 4 remineralizing agents: 1) artificial saliva (y), 2) y + 0.05 ppm fluoride, (3) y + 20% xylitol, and 4) y + 20% xylitol + 0.05 ppm fluoride. Mineral loss (delta Z) and lesion depth (ld) were quantified after 4-week remineralization. In experiment 1, numerical values of delta Z and ld observed can be ranked as A > C > B > D. These differences were significant only in B and D when compared with A for delta Z, but not between any group for ld. In experiment 2, the numerical values of delta Z and ld for control UN (unremineralized) and remineralized groups (1-4) ranked as UN > 3 > 4 > 1 > 2. Compared with UN, this difference was significant in all groups with ld, but not in any group with delta Z. We concluded that tolerable levels of xylitol alone may not show a significant caries inhibiting and remineralizing effect, but may act as a caries inhibitor additively with fluoride.

Animals↗
PubMed1998

The influence of xylitol and fluoride on dental erosion in vitro.

The aim was to determine the effect of xylitol, fluoride and xylitol/fluoride combined on the erosion of dental enamel by pure orange juice in vitro. Freshly extracted bovine incisors were sectioned vertically into four equal portions. Each portion was then coated with an acid-resistant nail varnish except for an enamel window on the labial surface of the tooth. These were then divided into four groups with each group containing one portion of each tooth selected randomly. Four erosive agents were prepared as follows: (A) pure orange juice only; pure orange juice plus either (B) xylitol (25% w/v) or (C) fluoride (0.5 parts/10(6)) or D) xylitol/fluoride (25% and 0.5 parts/10(6) respectively). Each group was assigned to one of the erosive agents and immersed six times daily for a period of 5 min on each occasion and stored in artificial saliva between exposures and for 12 hr overnight, for 24 days making a total of 12 hr of exposure to the assigned erosive agent. Sections were cut from each enamel specimen ground to a thickness of 80 microns and microradiographed. Mineral loss was quantified by a two-step image analysis. Mineral loss was significantly lower (p < 0.05) in group D (xylitol/fluoride) only when compared with group A (pure orange juice only). The numerical values of mineral loss could be ranked as follows: group D < group C < group B < group A. It was concluded that xylitol and fluoride have an additive effect in the reduction of dental erosion by pure orange juice in vitro.

Animals↗
PubMed1998

Factors affecting the development of carious lesions in bovine teeth in vitro.

This study aimed to determine the effect of temperature, duration of exposure, position on enamel surface, and type of demineralization solution on the production of caries-like lesions in bovine enamel in vitro, and to establish the conditions for the formation of artificial caries in bovine enamel. Caries-like lesions were produced in incisal, middle and cervical sites on enamel samples, with either an acidified hydroxyethylcellulose gel system or a partially saturated acidic buffer solution at either 20 degrees C or 37 degrees C for 3, 4, or 5 days. Lesion variables (mineral loss/lesion depth) were quantified. Regular subsurface lesions were produced in all specimens in acidic buffer solution within 3 days at either temperature. In gel, caries-like lesions were produced in 62% of the specimens at 37 degrees C and in 49% at 20 degrees C, while the remaining specimens were either eroded or softened. Mineral loss and lesion depth were significantly greater with buffer than with gel, and with increased length of exposure in either solution. There were no significant differences in either variable with position or temperature in either solutions, though numerically both variables were greater at the cervical site, and at 37 degrees C in either solution. It was concluded that caries-like lesions can be consistently produced in bovine enamel with a partially saturated acidic buffer solution at 20 degrees C or 37 degrees C within 3 days.

Analysis of Variance↗
PubMed1998

Morphometric assessment of enamel demineralisation from photographs.

OBJECTIVES: To investigate the validity and reproducibility of a method of morphometric assessment of enamel demineralisation. METHODS: An in vitro investigation was carried out on 22 human teeth. One investigator coated the crowns of the teeth with an acid-resistant varnish, leaving a small window on the buccal surface. This was incrementally occluded by varnish over a 14-day period, during which the teeth were placed in a demineralising gel at pH 4.5. After varnish removal, a second investigator blindly quantitated the demineralised area by three methods of examination; direct visual, microscopic and from photographs. The microscopic and photographic measurements were carried out using a morphometric assessment with a 121-dot array. Photographs and assessments were repeated after 1 week. The readings were analysed using the kappa statistic, the limits of agreement and the coefficient of repeatability. RESULTS: Photographic assessments demonstrated excellent agreement for grid positioning (kappa > 0.81) and substantial agreement for reading reproducibility (kappa = 0.61-0.80). The coefficients of repeatability were found to be the same for repeat readings of the same slide and the repeated slides (5.0 mm2). They were higher for the microscopic technique (6.8 mm2) and for the direct visual technique (7.8 mm2). The limits of agreement are presented graphically. CONCLUSIONS: The photographic technique used was a reproducible method of measuring artificial enamel demineralisation. Measurement from photographs was more reproducible than direct measurement with the naked eye. Subjectiveness of the index leads to most variation and more objective means of assessing enamel demineralisation need to be found.

Humans↗
PubMed1998

Use of transverse microradiography to quantify mineral loss by erosion in bovine enamel.

The aim of the present study was to develop transverse microradiography (TMR) in order to quantitatively assess the influence of artificial saliva and orange juice on the erosion of bovine enamel. Bovine incisors were sectioned sagittally into two equal halves. Each half was coated with acid-resistant nail varnish except for a rectangular enamel window on the labial surface of the tooth. While both halves of each tooth were immersed in pure orange juice 6 times daily for a period of 5 min at each occasion making a total of 30 min per day, one half was stored in artificial saliva and the other half in deionized distilled water between exposures to orange juice and for the remaining 12 h overnight, for 24 days making a total of 12 h of exposure to orange juice. Sections bearing intact and eroded enamel surfaces were cut from each specimen and ground to 80 microm thickness, and TMR of the sections was made. Mineral loss was quantified from the microradiographs using two-step image analysis. Mineral loss was significantly greater in those specimens cycled in orange juice and de-ionized distilled water. TMR was used successfully to quantify the mineral loss by erosion in vitro, and it is envisaged that it will be useful for specimens used in intra-oral appliances during in situ trials. Artificial saliva saturated with respect to calcium and phosphate salts can possibly remineralize an erosive lesion and may reduce the degree of erosion.

Analysis of Variance↗
PubMed1998

Efficacy of sterilisation methods and their effect on enamel demineralisation.

The aim of this project was to determine the effectiveness of sterilisation methods for dental enamel for use in intra-oral cariogenicity tests, and their possible effect on the degree of demineralisation of enamel. Bovine incisors were cut vertically into five portions and each assigned to one of five groups. Group 1 was used as a control while the other four groups were subjected, respectively, to gamma irradiation ( congruent with 25kGy), steam autoclaving (121 degrees C for 15 min), sodium hypochlorite (12% w/v for 24h) and povidone-iodine (7.5% w/v for 24h). Total viable counts of microorganisms remaining following sterilisation of the specimens were performed following incubation of the specimens for 24h at 37 degrees C. Caries-like lesions were produced in each specimen using an acidic buffer solution (pH4.5). Sections were cut from each specimen, ground to 80-microgram thickness, and microradiographed. Mineral loss and lesion depth were quantified using transverse microradiography. Statistical analysis was by ANOVA. Dunnett's and Tukey's tests. Microbial growth (Staphylococcus aureus and bacilli) was observed only in control specimens in both brain heart infusion broth and on blood agar plates. The sterilisation methods affected the enamel surface as follows: gamma irradiation (cream discolouration), NaOCl (bleaching), and povidone-iodine (white spot-like lesion). Compared with the control, there was no significant difference in mineral loss and lesion depth with any of the groups, but the numerical values of mineral loss and lesion depth in groups can be ranked as follows: gamma irradiation <povidone-iodine <control <autoclave <NaOCl. In conclusion, the four sterilisation methods were all effective to sterilise enamel, but gamma irradiation proved the most acceptable method for enamel to be used in cariogenicity tests having the least adverse effect.

Acids↗
PubMed1997

The establishment of a xerostomia clinic: a prospective study.

The study investigated the aetiological factors and management of patients who have xerostomia. The subjects were 100 consecutive patients referred to the Oral Medicine Unit for investigation of oral dryness. A detailed case history was recorded and patients underwent a systematic examination together with sialometry, haematological, biochemical and immunological investigations. Suspected cases of Sjögren's syndrome (SS) were referred for assessment by a rheumatologist and ophthalmologist. Objective evidence of salivary gland hypofunction was found in 39 patients. A definite diagnosis of primary and secondary SS was made in 24 and 15 patients respectively, a further five cases had possible primary SS. Other causes of xerostomia were: undiagnosed diabetes (3); drug-induced (11); therapeutic radiation (3); alcohol-related (3); psychogenic (15) and idiopathic (21). Patients complaining of a dry mouth should be questioned about non-oral symptoms. In total, 40% of patients attending the dry mouth clinic had a diagnosis of SS.

Adult↗
PubMed1997

Signs and symptoms in patients with salivary gland hypofunction.

Salivary gland hypofunction can have a devastating effect on oral health and may be an indicator of systemic disease such as Sjögren's syndrome. This prospective study investigates the oral and non-oral signs and symptoms in 120 patients with objective evidence of salivary gland hypofunction (ie, an unstimulated whole salivary flow of < 0.2 ml/min). Patients were questioned about symptoms associated with decreased oral function; non-oral symptoms were also noted. The underlying cause of salivary gland hypofunction was established on the basis of clinical and laboratory findings and further investigations. Eighty-five per cent of patients reported symptoms of decreased oral function in addition to oral dryness. Non-oral signs and symptoms were reported by 106 patients. Fifty-three per cent of patients were diagnosed as having Sjögren's syndrome. The prevalence of the following non-oral signs and symptoms were significantly higher in patients with Sjögren's syndrome, than in those without; a history of dry/irritated eyes, salivary gland swelling, dry skin and reduced lacrimal flow. Salivary gland hypofunction is associated with a wide range of oral and non-oral signs and symptoms. Several of these are of potential value as triggers for the clinician to identify patients with Sjögren's syndrome, and should serve to prompt referral for specialist investigation.

Adult↗
PubMed1997

Visualization of root caries lesions by means of a diazonium dye.

A diazonium dye was used to visualize caries lesions in root tissue. Root caries lesions were created in vitro according to a variety of protocols based on methylcellulose gel (6% w/v) and/or lactic acid buffer (0.05 M, pH 4.5). Teeth containing lesions were soaked overnight in an alkaline solution of 2% (w/v) 2-naphthol or resorcinol, rinsed with distilled water, and immersed in a diazonium solution (prepared by titration of aniline with sodium nitrite in 1 M HCl at 5 degrees C) for up to 10 min, prior to being thoroughly rinsed with distilled water. The area of the caries lesion on the anatomical surface was clearly marked with a red/orange color following 5 minutes' incubation in the diazonium solution. The diazonium complex formed with 2-naphthol was found to be more resistant to leaching during rinsing and sectioning than that formed with resorcinol. Microscopic examination of sections taken in the apicalcoronal plane showed that the depth of area of the lesion was also marked by the red/orange coloration. Chemical changes in root mineral monitored during lesion formation showed some degree of correlation between lesion area and mineral dissolution. Visualization of coronal caries by this technique is currently under investigation. The visualization technique provides a simple means of determining the extent and severity of root caries lesions and may be a useful first step in their classification.

Calcium↗
PubMed1996

Acidogenic potential and total salivary carbohydrate content of expectorants following the consumption of some cereal-based foods and fruits.

The acidogenic potential of a group of popular cereal-based foods and fruits and total carbohydrate content of salivary expectorants following their consumption were assessed using an indwelling electrode with telemetry and the anthrone method. Paired t tests indicated that sorbitol did not cause the plaque pH to fall as low as any of the test foods (p <0.05) but there was no significant difference between sucrose and the test foods. Only the fruits produced less acid than sucrose. The breakfast cereals tended to yield the highest levels of total carbohydrate in the salivary expectorants although a greater percentage of original carbohydrate was retained after rice and bread. These results suggest the important effect of carbohydrate retention on plaque pH response.

Acids↗
PubMed1995

Effects of lactate dehydrogenase and nicotinamide adenine dinucleotide on human dental plaque pH and acid anion concentrations.

The effect of sucrose rinses supplemented with L-LDH and NAD was investigated. When LDH or NAD were added to the sucrose rinse, the pH fall was less marked than with rinsing with sucrose alone. Significant differences (p < 0.05) in mean minimum pH and cH areas were observed when sucrose rinses were supplemented with LDH, NAD or with a combination of LDH and NAD, when compared with sucrose alone. Plaque fluid concentrations of lactate and acetate significantly decreased with all rinses when compared with sucrose alone. Phosphate levels also decreased, although not significantly, when NAD was the sole supplement. No significant decreases were observed in succinate, formate or propionate concentrations. The results confirm the beneficial effect of LDH in reducing the accumulation of lactate in plaque following a sucrose rinse. The inclusion of NAD in the rinse demonstrated the role of extracellular hydrogen acceptors in the reaction. Further work is required to identify endogenous hydrogen receptors and to clarify the fate of pyruvate resulting from the oxidation of lactate before the potential role of LDH as a cariostatic agent can be fully understood.

Acetates↗
PubMed1995

Salivary gland hypofunction in elderly patients attending a xerostomia clinic.

OBJECTIVES: To investigate the aetiological factors and the prevalence of salivary gland hypofunction (SGH) in patients complaining of xerostomia. DESIGN: Prospective, clinical study. SETTING: Xerostomia clinic in the Department of Oral Medicine at Liverpool University Dental Hospital. SUBJECTS: 100 consecutive patients, aged 60 years or older, referred for investigation of xerostomia. INTERVENTIONS: Patients were asked specific questions concerning their complaint of oral dryness and associated orofacial symptoms. A detailed medical history was recorded and patients underwent a systematic examination of the head, neck and oral structures. All patients underwent haematological, biochemical, immunological investigations, urinalysis and sialometry. Further investigations and referrals to other specialists were undertaken when appropriate. MAIN OUTCOME MEASURES: The causes of xerostomia were established on the basis of clinical and laboratory findings and SGH was defined as an unstimulated whole salivary flow rate of < 0.2ml/min, RESULTS: The causes of xerostomia were identified as: Sjögren's Syndrome (40), iatrogenic (22), psychogenic (14), idiopathic (19), diabetes (1), candidosis (3) and alcohol (1). Sixty five percent of the patients studied had SGH. CONCLUSIONS: This study has shown that 65% of patients whose presenting complaint was xerostomia had objective evidence of SGH. Several aetiological factors were identified, the most common of which was Sjögren's Syndrome. The possibility of associated systemic diseases should be considered when establishing the aetiology of SGH.

Aged↗
PubMed1995

Role of saliva in caries models.

The crucial role played by the actions of saliva in controlling the equilibrium between de- and remineralization in a cariogenic environment is demonstrated by the effects on caries incidence of salivary dysfunction and by the distribution of sites of caries predilection to those were salivary effects are restricted. However, of the several properties of saliva which may confer protective effects, it is not certain which are most important. A distinction can be made between static protective effects, which act continuously, and dynamic effects, which act during the time-course of the Stephan curve. Evidence implicates salivary buffering and sugar clearance as important dynamic effects of saliva to prevent demineralization; of these, the buffering of plaque acids may predominate. Enhanced remineralization of white spot lesions may also be regarded as dynamic protective effects of saliva. Fluoride in saliva (from dentifrices, ingesta, etc.) may promote remineralization and (especially fluoride in plaque) inhibit demineralization. The design of experiments using caries models must take into account the static and dynamic effects of saliva. Some models admit a full expression of these effects, while others may exclude them, restricting the range of investigations possible. The possibility is raised that protective effects of saliva and therapeutic agents may act cooperatively.

Animals↗
PubMed1994

Saliva stimulation and caries prevention.

The protective role of saliva is demonstrated by the rampant caries seen in human subjects with marked salivary hypofunction, and in desalivated animals. In normal cases, however, the relationship between saliva flow and coronal or root caries experience is doubtful, and to examine the concept that stimulation of saliva might have protective effects against caries, one must look beyond a simple correlation between caries and flow rate. Protective properties of saliva which increase on stimulation include salivary clearance, buffering power, and degree of saturation with respect to tooth mineral. These benefits are maximized when saliva is stimulated after the consumption of fermentable carbohydrates, by reducing the fall in plaque pH leading to demineralization and by increasing the potential for remineralization. Plaque acid production is neutralized, and experimental lesions in enamel are remineralized, when gum is chewed to stimulate saliva after a carbohydrate intake. The pH-raising effects are more easily explained by the buffering action of the stimulated saliva than by clearance of carbohydrates. The remineralization action depends upon the presence of fluoride. These findings suggest that the protective actions of saliva can be mobilized by appropriate salivary stimulation, and that in addition to established procedures such as tooth cleaning and fluoride regimens, eating patterns which lead to saliva stimulation to increase the potential for saliva protection might be included in recommendations for caries prevention. Confirmation of this concept in clinical tests is required.

Dental Caries↗