A prospective population based study of gender differential in mortality from cardiovascular disease and "all causes" in asymptomatic hyperglycaemics.

There have been few prospective epidemiological studies of asymptomatic hyperglycaemia as a risk factor for cardiovascular disease and all causes mortality in women. Gender-specific all causes, cardiovascular disease (CVD), ischaemic heart disease (IHD) and stroke mortality rates and relative risks for asymptomatic hyperglycaemics (top 5%) have been compared to normoglycaemics (bottom 95%) during a mean follow-up of 11.6 years (range 10-14) among 4696 men and 5714 women aged 45-64 at entry in the west of Scotland. Univariate analysis showed that asymptomatic hyperglycaemia was associated with increased risk of all causes, CVD, IHD and stroke mortality in both genders. The degree of this association was greater in women than in men. Using multiple logistic regression (MLR) analysis to take into account differences in age, systolic (SBP) and diastolic blood pressure (DBP), serum cholesterol, body mass index (BMI), and cigarette smoking, high causal blood glucose level was still a significant risk factor for CVD mortality in both genders. It was also a significant risk factor for all causes, IHD and stroke mortality in women but not in men. This study shows that to a lesser degree asymptomatic hyperglycaemia shows the same gender differentials in risk of mortality as have been demonstrated amongst known diabetics.

Gender differential in all-cause and cardiovascular disease mortality.

The gender differential in mortality from all causes, cardiovascular disease (CVD), ischaemic heart disease (IHD) and stroke during the mean follow-up of 11.6 years (range 10-14) was examined among 4696 men and 5714 women aged 45-64 at entry in West of Scotland. Overall mortality was 19.4/1000 person-years of observation among men and 10.8/1000 person-years among women. A multiple logistic regression model was used to control the influence of gender, along with seven other cardiovascular risk factors simultaneously. The risk factors considered were age, systolic (SBP) and diastolic blood pressure (DBP), serum cholesterol, causal blood glucose, body mass index (BMI) and cigarette smoking. Both the prevalence of risk factors and relative mortality risk associated with them differed by gender. Adjustment slightly reduced the gender differential in overall mortality from 2 to 1.9 and from 1.5 to 1.4 for stroke deaths. Multiple logistic regression increased minimally the gender differential for mortality from 2.4 to 2.8 for CVD and from 2.8 to 3.4 for IHD, suggesting that these cardiovascular risk factors do not account for the overall gender difference in mortality rates. Age, SBP, DBP, blood glucose and cigarette smoking were significant predictors of mortality for both genders. Serum cholesterol was a statistically significant predictor of CVD death only for men.

The effect of chewing gum use on in situ enamel lesion remineralization.

Two independent cross-over studies investigated the possibility of enhanced early enamel lesion remineralization with the use of chewing gum. The first study involved a sorbitol-containing chewing gum, and the second, which had an identical protocol, tested a sucrose-containing chewing gum. In each study, 12 volunteers wore in situ appliances on which were mounted enamel sections containing artificial caries lesions. Subjects brushed twice daily for two min with a 1100-ppm-F (NaF) dentifrice (control and test) and in the test phase chewed five sticks of gum per day for 20 min after meals and snacks. Microradiographs of the enamel lesions were made at baseline and at the end of the seven-week experimental period. In the sugar-free gum study, the weighted mean total mineral loss (delta z) difference [(wk7-wk0) x (-1)] was 788 vol.% min. x micron for the gum, corresponding to remineralization of 18.2%, vs. the control value of 526 vol.% min. x micron, 12.1% remineralization (p = 0.07). There were no significant differences for the surface-zone (p = 0.20) and lesion-body (p = 0.28) values. In the sucrose-containing gum study, the delta z difference was 743 vol.% min. x micron for the gum, corresponding to a remineralization of 18.3%, vs. the control value of 438 vol.% min. x micron, 10.8% remineralization (p = 0.08). The surface-zone values were not significantly different (p = 0.55). For the lesion body, however, the sucrose-containing gum value of 6.11 vol.% min. was significantly different (p = 0.01) from that of the control (2.81 vol.% min.).

Comparison of various predictive formulae for the estimation of resting energy expenditure.

The accuracy of the Harris-Benedict (HB), Kleiber and Robertson-Reid predictive formulae and the Fleisch tables in estimating resting energy expenditure (REE) has been assessed in 114 cancer patients and 54 patients with nonmalignant illness. The effects of weight status and disease on the predictive ability of the formulae were assessed by comparison of the estimated REE value with that measured by indirect calorimetry. Underestimation of measured REE by greater than 10% occurred in 6-62% of patients, depending on the formula used. Weight loss did not affect predictive ability, whereas the presence of cancer resulted in inaccurate prediction of REE in female patients. Using a multiple comparison procedure, the Fleisch tables were the most accurate in all groups, while the HB formula was least accurate in male patients, irrespective of weight status or disease status. The use of predictive formulae and tables are inappropriate for the accurate estimation of REE in individual patients.

Impact of prenatal screening and diagnosis on the epidemiology of structural congenital anomalies.

OBJECTIVE: To assess the impact of prenatal screening on the birth prevalence of three categories of structural congenital anomaly: abdominal wall defects (omphalocele and gastroschisis), renal agenesis/dysgenesis, and limb reduction defects. SETTING: Glasgow, Scotland, United Kingdom. METHODS: Data on the selected defects were obtained retrospectively from the population based Glasgow Register of Congenital Anomalies for the period 1980-91 inclusive. The register records all clinical or laboratory diagnoses of congenital anomaly in live births, stillbirths, and induced abortions occurring in women resident within the boundaries of the Greater Glasgow Health Board. The secular trends in the proportions of the defects diagnosed prenatally and terminated after screening, and in their prevalence at birth and during pregnancy, were examined. A total of 154,845 births were surveyed: 309 cases were identified in the selected anomaly categories. RESULTS: 83 cases of omphalocele/gastroschisis (5.4/10,000 births), 92 cases of renal agenesis/dysgenesis (5.9/10,000 births), and 134 cases of limb reduction defects (8.7/10,000 births) were found. Marked increases occurred over the study period in the proportions of cases diagnosed prenatally but not in the proportions terminated. The greatest difference between the prevalence at birth and during pregnancy was found for omphalocele. There were no significant secular trends in the prevalence of the selected defects. CONCLUSIONS: Prenatal screening has made a limited epidemiological impact on the prevalence of these defects. It has been moderately (but inconsistently) effective in the avoidance of births of infants with omphalocele/gastroschisis and renal agenesis/dysgenesis but not of limb reduction defects. Future efforts should be directed towards improving the technical aspects of the ultrasonographic detection of fetal abnormalities and exploring in detail, locally, the reasons for the varying pattern of decision making about termination of pregnancy among prospective parents.

Tailored written invitations for second round breast cancer screening: a randomised controlled trial.

OBJECTIVES: Firstly, to determine if attendance for second round mammography screening in those sent a tailored letter (that is, making reference to their screening history) is increased compared with those sent a standard letter; secondly, to investigate the acceptability of tailored letters. SETTING: North West Glasgow Breast Screening Centre. METHODS: A randomised controlled trial. RESULTS: Overall attendance was unrelated to whether the women were sent a tailored or standard letter; 60% of those sent the standard letter attended (922/1531) compared with 62% of those sent the tailored letter (956/1552) (chi 2 = 0.61, P = 0.4) (difference 2%; 95% confidence interval -2% to 5%). There were no significant differences in percentage attendance within each of the study subgroups: women who attended previously and received an all clear result, women who attended previously and received a false positive result, women who were invited previously and failed to attend, and women who were previously too young to be invited for screening. However, there was a statistically significant difference in percentage attendance between these four groups, independent of letter type (chi 2 = 510, P < 0.00001). Although women found the letters acceptable and understandable, they did not seem to pay close attention to the content. CONCLUSIONS: Tailoring invitation letters does not have a significant effect on uptake rates for breast screening and does not justify the additional workload required.

Demographic characteristics of general practitioners attending educational meetings.

There are many factors which influence general practitioners' behaviour with regard to attendance at education meetings. The demographic characteristics of general practitioners in the west of Scotland attending educational meetings were studied over a two year period. A total of 1672 doctors had attended sufficient sessions to claim their postgraduate education allowance and of these 1551 (93%) responded to the questionnaire. Overall attendance at meetings did not vary between age groups, but older doctors (those born before 1935) attended the highest mean number of education sessions on disease management and the lowest mean number on service management and health promotion. Doctors in rural areas attended fewer meetings than those in urban areas with the largest difference in the disease management category. Doctors from smaller practices attended significantly fewer sessions on service management than those from larger practices. There was no difference between sexes regarding the mean total number of education sessions attended but men attended significantly more sessions on service management and women attended more on health promotion. Full-time doctors attended more service management sessions than part-time doctors. Those who were widowed or divorced attended fewer sessions in total, the differences being greatest in service management and health promotion. Multiple regression analysis showed that location of practice, whether working full time or part time and marital status had a small but statistically significant bearing on overall attendance at meetings. Although the differences are small, these factors should be noted by education providers, negotiators and government.

Formation of interdental soft tissue defects after surgical treatment of periodontitis.

This study monitored the development and repair of interdental soft tissue defects following surgical treatment of periodontitis in 21 patients. Open flap curettage was performed at 100 interdental areas with follow-up examinations 1, 3, and 6 months later. Interdental gingival contours were assessed both clinically and indirectly with silicone elastomer impressions from which stone models were obtained; defect depths were then calculated using the Reflex Microscope. Two types of defect were identified at the 1-month follow-up: 13 interdental clefts (mean depth, 1.8 mm); and 30 craters, (mean depth, 1.6 mm). Although clefts tended to persist, craters showed a strong tendency to repair. Thus, at the 6-month follow-up, the depths of clefts and craters were 1.3 mm and 0.7 mm respectively. The development of soft tissue defects did not appear to be related to the use of a periodontal dressing nor did the existence of an underlying bone defect appear to be of etiological importance. Pre-operative probing depths, however, were positively associated with the occurrence of soft tissue craters (P = 0.02). Pre-operatively, the overall mean probing depth and frequency of bleeding on probing were 5.3 mm and 100% respectively. At 6 months, these values were reduced to 2.0 mm and 22%. When clefts, craters, and interdental areas with no soft tissue defect were compared, no significant differences in probing depth reduction or frequency of bleeding were observed at any time point.(ABSTRACT TRUNCATED AT 250 WORDS)

Caries prevalence in the permanent dentition of a mediaeval population from the south-west of Scotland.

The prevalence, distribution and location of dental caries were studied in the permanent dentition of skeletons from a large mediaeval cemetery, where successive phases of use could be distinguished. The main phases dated from 1240 AD to 1440 AD. During this 200-year period, caries prevalence showed a statistically significant linear trend to increase. There was an increase in caries prevalence with increasing age from age band 20-25 through 26-35 to 36-45, and this trend was statistically significant in all phase groups but one. The teeth attacked by caries were chiefly molars, followed by premolars, with a low rate of attack in incisors and canines. The differences in caries prevalence between these major tooth classes were significant. Juveniles and adults presented different patterns of carious attack on tooth surfaces, occlusal surfaces being most frequently affected in juveniles, and approximal surfaces in adults. The overall caries prevalence in the mediaeval population of Whithorn was 6.4% of the teeth present, a figure similar to those published for other Scottish mediaeval groups, but lower than the caries prevalence in an English mediaeval group.

Caries prevalence in the deciduous dentition of a mediaeval population from the south-west of Scotland.

The prevalence, distribution and location of dental caries were studied in the deciduous dentition of 185 skeletons aged between 6 months and 13 years from a large, mostly mediaeval, cemetery, where successive phases of use could be distinguished. The main phases dated from 1240 to 1440 AD. During this period, no consistent trend or pattern of caries was identified, but there was a significantly higher caries prevalence in the age band 6-12.9 years than in the age band 0.1-5.9 years. The caries prevalence in the juveniles from the earlier Northumbrian, or Anglo-Saxon, phase of the cemetery was higher than in any mediaeval phase group, with mostly approximal surfaces affected. In the mediaeval population, first deciduous molars generally showed lower caries prevalence than second deciduous molars, significantly lower for the older age band, and maxillary molars consistently showed lower levels than mandibular molars. The highest caries rate, shown by mandibular second molars in the older age band, was 7.9%. In deciduous molars, the occlusal surface was most frequently affected by caries, whereas in the permanent molars of the same population the approximal surfaces had shown the highest level of attack. The overall caries prevalence in deciduous teeth in the mediaeval population of Whithorn was 2.3% of the teeth present, lower than the levels found in previous Scottish and English population groups, including a small assemblage of children from the Scottish sites of Elcho, Southwick and Kirkhill.

Effect of fluoridated salt intake in infancy: a blind caries and fluorosis study in 8th grade Hungarian pupils.

UNLABELLED: Salt fluoridation is effective at inhibiting caries, but fluorosis prevalence data are deficient. OBJECTIVES: The purpose was to undertake a blind study of caries and tooth mottling in 8th grade school pupils from south-east Hungary who had resided (test) or not resided (control), until November 1985, in a 350 ppm F-/kg domestic salt-fluoridated area during their early years of life. METHODS: In Szeged, blind clinical caries and anterior tooth mottling scoring (+10% repeats) of 49 previously salt-fluoridated (mean age 14.14 years) and 59 non-salt-fluoridated subjects (mean age 14.08 years) were undertaken by one examiner, in June 1997. In addition, radiographic and photographic recordings were taken. In Glasgow, four dental and two lay staff scored the projected 35 mm colour transparencies (+10% repeats) of each pupil's six upper anterior teeth, for tooth mottling. All clinical, radiographic and photographic data were then analysed. RESULTS: Mean DMFS scores were 9.18 (SD=10.72) for test users and 4.51 (SD=6.24) for control users (P<0.01) and, based on repeat observations, clinical reliability=0.99; X-ray reliability=0.95. Clinically, three test children had fluorosis of 10 teeth, with eight teeth in two controls. Photographic scoring by the clinical examiner gave a 97.2% clinical match, while photographic agreements for all four dentist pairs were 92.5%-97.2%, with lay observers' agreements at 89.8%. For both groups, 10% repeats produced 98.5% agreements. In a sole test case "fluorosis" photographic unanimity was obtained, and non-unanimous "possible fluorosis" was recorded by two to four panel members for only three other test and two control subjects. CONCLUSIONS: No evidence was found that significant anterior tooth fluorosis resulted in subjects exposed previously to 350 ppm F-/kg domestic salt from birth to 2.3-4.8 years of age. However, no caries benefit was demonstrated after the 11.5-year salt fluoridation gap. Caries differences seemed social class-related, city-based controls having less disease than rural test subjects, in spite of an identical F- tablet regimen in all schools from 1987, until subjects were 10 years old. These data emphasise (a) the superiority of sustained community-delivered fluoridation and (b) the need to maintain constant fluoride delivery to tooth surfaces, certainly well beyond 10 years of age.

Fluoride release from orthodontic band cements-a comparison of two in vitro models.

OBJECTIVES: To compare, in vitro, the fluoride release from a conventional glass ionomer cement (Ketac-Cem), a resin-modified glass ionomer cement (3M-Multicure) and a polyacid modified composite (Ultra Band-Lok) using a banded tooth model and a disc model with the same mean cement weight. METHODS: Forty pairs of caries-free third molars were collected and divided into two groups, each of 20 teeth. One tooth from each pair was banded with Ketac-Cem and the other with Ultra Band-Lok or 3M-Multicure; the average band size for each cement group was the same. Two coats of nail varnish were painted on each tooth to within 1mm of the band margin. Five discs (4.5mm diameter and 2mm depth) were prepared for each cement, these dimensions having been calculated so that the mean cement weight of the banded tooth model matched that of the disc model for each cement. The fluoride released into 2ml of deionised water, from each banded tooth or disc, was measured at regular intervals over 30 days using an Orion ion-selective electrode connected to an ion analyser. RESULTS: At 30 days, for both banded tooth and disc models, the mean cumulative fluoride release was greatest from 3M-Multicure followed by Ketac-Cem, which in turn released more fluoride than Ultra Band-Lok. These differences were all significant (p<0.05). Despite having the same mean cement weight, the banded tooth model for Ketac-Cem and 3M-Multicure released approximately 3-4 times more cumulative fluoride than the disc model after 30 days (p<001). For Ultra Band-Lok, both models released comparable levels of fluoride (p>0.05). CONCLUSIONS: Cement type, specimen geometry and surface area appear to influence significantly fluoride release characteristics.

Fluoride release from orthodontic bonding agents: a comparison of three in vitro models.

The aim of this in vitro study was to compare fluoride release from two cement disc models (partially varnished and unvarnished) of three orthodontic bonding materials with fluoride release from the same materials when used to bond an orthodontic bracket onto a tooth surface. A resin-modified glass ionomer cement (Vitremer) and a compomer material (Dyract Ortho) were compared with a conventional resin adhesive (Right-On). Ten discs (3.0 mm diameter and 1.5 mm thick) of each material were manufactured in a silicone mould and ten premolar teeth were bonded with orthodontic brackets using each material. All the premolar teeth were covered with nail varnish up to the bracket periphery and five of the discs for each material were coated with nail varnish on both upper and lower surfaces which halved the surface area. The fluoride released into 2 ml of deionised water, from each tooth or disc, was measured at regular intervals over 60 days. At 60 days, cumulative fluoride release was highest from the unvarnished discs, less for the varnished discs and least from the tooth-bracket model for both test materials. Despite having twice the surface area, the unvarnished disc model released only 1.2 to 1.5 times more fluoride than the varnished disc model. Compared with the tooth-bracket model, the unvarnished discs released 3.0 to 4.5 times more fluoride, whereas the varnished discs released only 2.2 to 3.7 times more fluoride. For the materials tested in this study, halving the surface of the discs did not reduce the cumulative fluoride release by half. The tooth/bracket model with minimal bonding material demonstrated substantial cumulative fluoride release. The pattern of fluoride release was similar for all models tested.

Investigation of human enamel wear against four dental ceramics and gold.

OBJECTIVES: This in vitro study compared the wear of enamel against aluminous porcelin, bonded porcelain, low fusing hydrothermal ceramic, feldspathic machinable ceramic, and cast gold. METHODS: Fifty pairs of tooth-material specimens were tested in a dental wear machine, under a standard load (40 N), rate (80 cycles min-1) and for 25,000 cycles in distilled water. The amount of wear was determined by measuring the height loss of the tooth, and the depth of wear track of the restorative materials. RESULTS: There was a significant difference in wear among the groups for both enamel and materials (p < 0.001). Follow-up comparisons (95% CI significance level) showed that gold caused significantly less enamel wear than all ceramics tested. The amount of enamel wear in the aluminous and bonded porcelain groups was significantly higher than with the hydrothermal and machinable ceramic groups. There was no significant difference between the amount of enamel wear produced by the aluminous and bonded porcelains nor between that produced by the hydrothermal and machinable ceramics. Furthermore, the wear of the aluminous and bonded porcelains was significantly greater than that of the hydrothermal ceramic, the machinable ceramics and gold. No significant difference in wear was found between aluminous and bonded porcelains, hydrothermal and machinable ceramics, or between machinable ceramic and gold. However, the hydrothermal ceramic had significantly greater wear than gold. CONCLUSIONS: It was concluded that the hydrothermal and the machinable ceramics were significantly less abrasive and more resistant to wear than the conventional aluminous and bonded porcelains. Gold was the least abrasive material and most resistant to wear, although the difference in wear between the machinable ceramic and gold was not statistically significant.

The effect of a resin-modified glass ionomer restorative material on artificially demineralised dentine caries in vitro.

OBJECTIVES: Recurrent caries is one of the most common reasons for the replacement of restorations. One method of reducing the frequency of this problem may be by using fluoride-releasing restorative materials. The aim of this in vitro study was to evaluate the progression of artificial lesions around resin-modified glass ionomer (Vitremer) restorations placed in root surfaces. Class V cavities were prepared on the mesial and distal surfaces of 28 human premolar teeth. Artificial carious wall lesions were created in all cavities. The root of each tooth was then hemisected through the middle of the two cavities, before being restored with either the glass ionomer or amalgam, while the opposing cavities on the same root portion were varnished as negative controls. Forty-eight specimens were pH-cycled in remineralising and demineralising solutions for 20 h and 4 h, respectively, each day for 4 weeks, whilst in a smaller control group of eight specimens, the demineralising solution was replaced with deionised water. Mineral changes in the carious lesions were evaluated using contact microradiography. RESULTS: Results showed that varying degrees of subsurface demineralisation and remineralisation were evident, with a laminated appearance in lesions adjacent to the glass ionomer. There was higher remineralisation in the glass ionomer-filled cavities compared with the amalgam-filled cavities. In the water-cycled group, glass ionomer showed an increase in mineral content (p < 0.05), while no changes were observed in the amalgam-filled cavities. CONCLUSIONS: This model has shown that glass ionomer has a greater potential than amalgam for remineralisation of artificially created wall lesions within an acidic environment.

Fluoride release and cariostatic ability of a compomer and a resin-modified glass ionomer cement used for orthodontic bonding.

OBJECTIVES: The aims of this study were to compare the local and systemic uptake of fluoride released from a compomer material (Dyract Ortho) and a resin-modified glass ionomer cement (Vitremer) with that of a conventional resin adhesive (Right-On) and to compare the cariostatic ability of each of the test materials with that of the resin control. METHODS: Twenty six patients were randomly allocated to have a bracket bonded to a premolar on one side of the arch with one of the test materials and on the opposite side with the control material. Premolars destined for extraction as part of an orthodontic treatment plan were selected for bonding. A non-fluoride toothpaste was used by all participants for 4 weeks prior to bracket bonding and throughout the 4 week trial period. Fluoride release was measured in saliva, plaque and urine samples taken pre-bonding and 4 weeks post-bonding. Enamel demineralisation was assessed by scoring the buccal surface of each extracted tooth using a caries index. RESULTS: Neither Vitremer nor Dyract Ortho altered salivary or urinary fluoride concentration significantly 4 weeks post-bonding but plaque fluoride concentration increased significantly around premolars bonded with Vitremer. The test materials as a combined group were associated with significantly less demineralisation than the control material but there was no significant difference in cariostatic ability detected between either Dyract Ortho or Vitremer when each group was compared separately with the control. CONCLUSIONS: Fluoride released from Dyract Ortho or Vitremer is likely to exert a local and not a systemic effect. In a 4-week clinical study, the cariostatic ability of the fluoride-releasing cements, as a combined group, was superior to that of the non-fluoride releasing control but there was no significant difference in cariostatic ability between the two test materials when each test group was compared separately with the control.

Daily exposure to fluoride mouthrinse produces sustained fluoride release from orthodontic adhesives in vitro.

OBJECTIVES: To determine firstly, if sustained fluoride release can be achieved from five orthodontic adhesives: Ketac-Cem, Fuji ORTHO LC, Sequence, Transbond and Right-On, with daily exposure to fluoride mouthrinse in vitro, and secondly, if sustained fluoride release can be re-established from the same specimens, after an interruption in mouthrinse exposure. METHODS: Ten brackets were bonded to bovine incisors using each adhesive. Each adhesive group was divided equally into a test and a control sub-group. In phase 1 (42 days), the test sub-groups were exposed for 1min daily to fluoride mouthrinse (225 ppm), followed by immersion in de-ionised water for 42 days to deplete their fluoride reserves. Mouthrinse exposure was then resumed in phase 2 (28 days). Mean cumulative fluoride release (MCFR) was calculated for days 0-21 of phase 1 and for the plateau portion of the fluoride release curves in phase 1 (days 21-42) and phase 2 (days 7-28). RESULTS: During phase 1, the MCFR for each test sub-group was significantly greater than its control (p<0.05). There was no significant difference in MCFR between the curve plateau portion of phases 1 and 2 for all adhesives except Transbond, for which MCFR was less in phase 2 (p<0. 05). CONCLUSIONS: Sustained fluoride release occurred for each adhesive exposed daily to fluoride mouthrinse, at a level significantly greater than its control. After fluoride exhaustion, re-exposure to daily fluoride mouthrinse produced sustained fluoride release levels comparable to those prior to exhaustion, for all adhesives except Transbond.

A clinical study of pulsed Nd: YAG laser-induced pulpal analgesia.

The pulsed Nd: YAG laser is advocated as an alternative means of providing analgesia during routine dental procedures. Since the evidence to support this claim is mainly anecdotal, a clinical trial was carried out using an electric pulp tester (EPT) to measure the extent and duration of any analgesic effect induced by pulsed Nd: YAG laser treatment. A double-blind crossover experiment involving laser and sham treatments was used on 21 subjects. A small (3.6 arbitrary units) but statistically significant increase was observed in the mean responses measured 5 min after laser treatment with 113 mJ pulses at 15 pulses s-1 (pps) for 3 min. The pain thresholds returned to baseline values after 60 min. No statistically significant changes in threshold were found with the sham treatment. The order in which laser and sham treatment was received made no difference to the results.

Fluoride release from orthodontic cements-effect of specimen surface area and depth.

OBJECTIVE: The aims of this in vitro study were firstly to compare fluoride release from a disc model of two orthodontic cements with various surfaces varnished, reducing the surface area by 25, 50 and 75%; secondly, to measure the fluoride release from previously exhausted discs of the same cements following removal of various depths of surface material. METHODS: Forty discs of each cement, Fuji Ortho LC and Ultra Band-Lok, (6mm diameter by 3mm) were divided into two groups of 20 discs each. For each material, the first group was divided further into four groups of five discs, one group acting as control, while the other three groups were varnished reducing the surface area by 25, 50 and 75%, respectively. The second group was exhausted initially over a 60 day pre-experimental period and was subsequently divided into four groups of five discs, one group acting as control. The other three groups had material ground from one of the flat surfaces, to depths of 10, 100 or 1000 microm, to reveal a fresh surface. In both studies, the discs were immersed either daily (up to day 20) or twice weekly (up to day 60) in fresh 2ml aliquots of deionised water. The fluoride concentration in the deionised water was measured at the end of the experimental period. RESULTS: For each cement, the relationship between the cumulative fluoride release and the percentage of the surface covered was clearly non linear at both 5 and 60 days. Fuji Ortho LC proved to release significantly greater amounts of fluoride at both 5 days and 60 days compared with Ultra Band-Lok. The results for Ultra Band-Lok were also significant when compared to the control group, but significantly less fluoride was released when compared with Fuji Ortho LC. When comparing the 25 and 50% covered discs, the amount of fluoride released was not significantly different for both cements. Furthermore, the relationship between fluoride release and depth was clearly non linear for both cements. CONCLUSIONS: For the materials tested in this study, reducing the surface area of the discs did not reduce the cumulative fluoride release in a linear fashion. In addition, the previously exhausted discs began to release fluoride again, but this fell to concentrations similar to the control discs after the initial 5-day period for both cements. This suggests that further traces of previously unreleased fluoride had become available from the subsurface of these cements. The pattern of fluoride release was similar for all models tested.

Fluoride release, microbial inhibition and microleakage pattern of two orthodontic band cements.

OBJECTIVES: To compare, in vitro, the fluoride release, microbial inhibition and microleakage pattern of a conventional glass ionomer cement (Ketac-Cem) and an acid-modified composite (Ultra Band-Lok) for band cementation. METHODS: Fluoride release was measured from cement discs (3.0 mm diameter and 1.5 mm thick) at regular intervals over 40 days using a potentiometric method. Microbial inhibition was determined for each cement using an agar diffusion test against one of four different strains of Streptococcus mutans. Thirty pairs of banded third molars (15 banded pairs for each cement) were thermocycled and microleakage determined by a dye penetration method. The depth of microleakage was assessed by an index applied by two examiners independently to photographic records taken of the mid-buccal aspect of each tooth. RESULTS: The cumulative and daily fluoride release for days 5, 15 and 40 were significantly greater for Ketac-Cem than for Ultra Band-Lok (all p < 0.05). After the initial set, the anti-microbial activity was significantly greater for Ketac-Cem than for Ultra Band-Lok over the following 24 h period for all four strains of S. mutans (all p < 0.05). There was no significant difference between the two cement groups for microleakage at the cement/enamel interface (p = 0.66) but a borderline significance was detected for microleakage at the cement/band interface (p = 0.051). CONCLUSIONS: The fluoride release and anti-microbial activity of Ketac-Cem were greater than that of Ultra Band-Lok. There was no significant difference in microleakage between the cements at the cement/enamel interface but a borderline difference existed between the cements at the cement/band interface.