Lethal and sub-lethal responses of the biogenic reef forming polychaete Sabellaria alveolata to aqueous chlorine and temperature.

Sabellaria alveolata, a reef-forming marine polychaete, was exposed to aqueous chlorine which is routinely used as an anti-fouling agent in power station cooling water. Worms were treated to a range of chlorination levels (0, 0.02, 0.1 and 0.5 mg l(-1) Total Residual Oxidant referred to as control, low, intermediate and high TRO) at mean and maximum summer temperatures (18 and 23 °C respectively). Overall mortality was relatively low, however a combination of high temperature and intermediate and high TRO resulted in a significant increase in mortality compared to the control and low TRO treatments. In contrast the extension of dwelling tubes was reduced at high TRO, but increased at low and intermediate TRO levels relative to the controls independent of temperature. Finally, tube strength was found to decrease with increasing TRO, again independent of temperature. On the basis of these findings, S. alveolata can be considered tolerant of one month exposures to low TRO at water temperatures up to and including the summer maxima for southern UK waters. However, at higher TRO levels and during warm weather, high mortality would be predicted.

Basic science knowledge of dental students on conventional and problem-based learning (PBL) courses at Liverpool.

This cross-sectional study investigated performances of two consecutive cohorts of second year dental students on completion of a conventional didactic course and two succeeding cohorts of second year dental students on a recently introduced problem-based learning (PBL) course at The University of Liverpool School of Dentistry. A 40 part true/false questionnaire tested recall of factual knowledge in anatomy, biochemistry, oral biology and physiology. The results showed no significant difference in the total scores when negatively marked between the conventional and PBL course groups but higher total scores in the PBL groups when positively marked. Performances in anatomy, oral biology and physiology did not differ between the groups when negatively marked but the scores of the conventional course groups in biochemistry were significantly lower than the others. With positive marking biochemistry scores were not significantly different but all other subjects were significantly higher in the PBL course groups. The PBL course groups offered fewer blank responses than the conventional course groups but the ratio of correct to incorrect responses, for both definite and intelligent guess responses, were similar in these groups. The compositional profile of the study groups was similar with respect to educational background but the PBL course groups included more females and more older students. The results of this study show that the overall knowledge recall in the basic sciences by dental students on PBL or conventional didactic courses does not differ and may be helpful to those considering the introduction of PBL into the curriculum.

The value of a questionnaire in assessing the acquisition and retention of basic science knowledge by dental students.

This cross-sectional study aimed to assess and compare, by performances in a questionnaire, the level of knowledge of basic medical sciences in 6th-form school pupils studying science subjects as entrance requirements to University and in 2nd, 3rd and 4th-year undergraduate dental students. A 40-part multiple response, true/false questionnaire, testing recall of factual knowledge in anatomy, biochemistry, physiology and oral biology, was used as the method of assessment. The results suggested that this simple format was an acceptable and useful method of assessment of the knowledge level of the study groups. The difference in scores of knowledge, expected to be higher in 2nd-year students compared to 6th form groups, was greatest in anatomy and oral biology, less in biochemistry and, unexpectedly, was not apparent in physiology. A difference in performance on the knowledge questionnaire was observed between 4th and 2nd year dental students, attributable primarily to decreased scores for 4th year dental students in biochemistry and, to a lesser extent, anatomy. The results obtained with this standardised test of factual knowledge recall may be of value to teachers compiling medical sciences courses for dental undergraduates and to those planning and evaluating new curricula with a less didactic approach.

Effects on tooth movement of force delivery from nickel-titanium archwires.

The aim of this project was to determine the in vivo effects of tooth movement with nickel-titanium archwires on the periodontium during the early stages of orthodontic treatment. The extent of tooth movement, severity of gingival inflammation, pocket probing depth, gingival crevicular fluid (GCF) flow, and the amount of the chondroitin sulphate (CS) glycosaminoglycan (GAG) component of the GCF of one maxillary canine in each of 33 patients treated with a pre-adjusted appliance were measured before and at four stages during the first 22 weeks of treatment. The methods involved the use of a reflex metrograph to determine the type of tooth movement and electrophoresis to quantitate the CS in the GCF. It was found that GCF flow increased after 4 weeks of tooth movement whereas the increase in the amount of CS in the GCF, which is taken to be indicative of periodontal tissue turnover, occurred at the later stage of 10 weeks. Teeth which showed the greatest amount of tooth movement continued to express large amounts of CS in large volumes of GCF until 22 weeks, whilst the CS levels in those teeth moving to a smaller extent declined. These data suggest that nickel-titanium archwires may produce a super-elastic plateau effect in vivo on canine teeth, which are initially displaced from the arch such that large amounts of tooth movement occur in the first 22 weeks of treatment.

The clinical assessment of a ceramic-coated transmucosal dental implant collar.

This study compared the superficial tissue responses to titanium and ceramic surfaces of transmucosal elements of established IMZ implants. In a splitmouth study on 14 patients with two mandibular implants and a bar-retained complete mandibular denture, a conventional titanium and a newly developed ceramic-coated transmucosal element were placed. A range of clinical parameters were recorded before transmucosal-element replacement and at 1, 4, and 12 weeks postplacement. A comparison of the recorded soft tissue responses revealed no significant differences between a group of implants fitted with ceramic-coated transmucosal elements and a group of contralateral implants fitted with titanium transmucosal elements. Further analysis suggested that the peri-implant soft tissues adjacent to titanium and ceramic surfaces may differ in features that are not apparent when routine clinical parameters are used. The plaque accumulation scores for ceramic-coated transmucosal elements were significantly lower than those recorded in titanium transmucosal elements. These results suggest that the further development of a ceramic implant transmucosal collar may assist plaque control at the soft tissue-implant interface and may favourably influence the tissues in this region. This investigation should be considered a pilot study in view of the duration of the observations and number of patients involved.

Monitoring of IMZ titanium endosseous dental implants by glycosaminoglycan analysis of peri-implant sulcus fluid.

Determination of glycosaminoglycans (GAGs) in peri-implant sulcus fluid (PISF) may monitor tissue changes around implants. This study investigated osseointegrated IMZ titanium implants at five stages from initial exposure to occlusal loading from prostheses. Two peri-implant sulcus fluid glycosaminoglycans (PISF GAGs), hyaluronic acid (HA) and chondroitin-4 sulfate (CS), were determined by cellulose acetate electrophoresis and densitometric scanning. Compared to longer-serving implants, CS contents at early stages was higher and with full occlusal loading was three times greater, without significant changes in HA contents. These observations appeared to reflect predominantly responses in the supporting bone, particularly when compared to our previous studies on ceramic implants and teeth affected by periodontal disease. This study supports the potential of PISF GAG analysis to detect adverse tissue responses, notably bone resorption.

The monitoring of orthodontic tooth movement over a 2-year period by analysis of gingival crevicular fluid.

Gingival crevicular fluid (GCF) was collected from around canine teeth before orthodontic treatment, during retraction, and in retention. The aim was to investigate the changes in the flow of GCF and its glycosaminoglycan (GAG) components at these three stages of orthodontic treatment, and relate them to tooth movement, gingival inflammation, and other clinical parameters recorded at the time of GCF sampling. GAG in GCF samples, collected for a 15-minute period into microcapillary tubes, were separated and identified electrophoretically, stained with Alcian blue and quantitated using a laser densitometer. The increase in GCF volume during orthodontic tooth movement and the decrease during retention are only partly due to changes in the severity of gingival inflammation. Levels of the GAG component chondroitin sulphate found in GCF samples taken during retention appear to be related to the duration of retention, particularly the length of time that the fixed appliance is passive before debonding. GCF analysis may assist the clinician to conduct this phase of orthodontic retention more reliably.

The effects of orthodontic tooth movement on the glycosaminoglycan components of gingival crevicular fluid.

In this study, gingival crevicular fluid (GCF) was collected from around a canine tooth, in children, before and during orthodontic tooth movement. The aim was to identify and quantify the glycosaminoglycan (GAG) components of GCF and relate them to tooth movement, gingival inflammation, plaque accumulation, pocket probing depth and GCF volume recorded at the site of sampling. GAG in GCF samples, collected for a 15-min period into microcapillary tubes, were separated electrophoretically, stained with Alcian blue and quantified using a laser densitometer. 2 GAG components of hyaluronic acid (HA) and chondroitin sulphate (CS) were identified. The increase in GCF volume during orthodontic tooth movement was only partly due to increased gingival inflammation. GAG levels varied with different types of orthodontic tooth movement. In GCF, levels of CS, in particular, may reflect the changes in the deeper periodontal tissues which could be monitored during orthodontic tooth movements.

Monitoring of Tübingen endosseous dental implants by glycosaminoglycans analysis of gingival crevicular fluid.

Glycosaminoglycans (GAG) in gingival crevicular fluid (GCF) samples were determined by cellulose acetate electrophoresis and densitometric scanning. Two GAG bands, hyaluronic acid and chondroitin-4-sulphate (C4S), were detected in GCF from implants, similar to the profile from teeth. High GCF volumes and GAG contents, notably C4S, may reflect postoperative alveolar bone responses, particularly resorption, at different stages of healing and function of successful implants. They may also indicate adverse tissue changes in failing implants. A comparison of crowned implants and matched teeth suggests that the periodontal ligament contributes to the GCF GAG profile. This may be a useful laboratory method of monitoring implants to detect adverse tissue responses at an early stage.

Glycosaminoglycans of human alveolar bone.

Bone proteoglycan was extracted and the glycosaminoglycan (GAG) components identified. Chondroitin-4-sulphate was the major GAG detected and represented 93.8% of the total GAG extracted. In addition, hyaluronic acid (1.3%), dermatan sulphate (3.1%) and heparan sulphate (1.8%) were identified as minor constituents.

The glycosaminoglycan constituents of alveolar and basal bone of the rabbit.

Proteoglycan was extracted from alveolar and basal bone of New Zealand White rabbits using a sequential extraction procedure. Proteoglycans not associated with the bone mineral represented 1% of the total organic matrix whereas proteoglycans associated with the mineral represented 20% of the alveolar organic matrix and 12% of the basal organic matrix. Chondroitin-4-sulphate and keratan sulphate were identified in both alveolar and basal bone following protease treatment of the proteoglycan extracts and enzymic digestion with chondroitinase AC, ABC and keratanase. Differences were observed in the percentage of each glycosaminoglycan (GAG) in the total organic matrix. In alveolar bone samples, keratan sulphate and chondroitin-4-sulphate is present in equal proportions. In basal bone chondroitin-4-sulphate represents approximately half the value found in alveolar bone and keratan sulphate about a quarter. The extracts were examined by gel filtration on Sepharose 4B under associative conditions. The 280 nm absorbance profiles of proteoglycan from alveolar and basal bone were essentially similar with three main peaks evident, including molecular weight material in excess of 2 X 10(6). The bulk of the bone GAG appeared in the medium molecular weight range with trace amounts in lower molecular weight fractions.

Glycosaminoglycans in human gingival crevicular fluid during orthodontic movement.

Glycosaminoglycans (GAG) in gingival crevicular fluid (GCF) were investigated by cellulose acetate electrophoresis of simultaneously collected samples from the mesial and distal surfaces of teeth in 3 groups of young persons. In a control group, which had not undergone orthodontic treatment, a major band of hyaluronic acid (HA) and a minor band of chondroitin sulphate (CS) were present. No differences in the mean content of either GAG between the mesial and distal surfaces were detected. From teeth undergoing movement by fixed appliances (active group), a raised mean level of CS was present in GCF from the surface towards which movement was directed. Teeth held passively by an appliance following cessation of active movement (retention group) showed raised levels of CS at mesial and distal surfaces. A heparan sulphate-like GAG was commonly present in this group only. No significant increase in the levels of HA were detected at the mesial and distal surfaces of either the active or the retention groups, despite increased GCF flow rates unassociated with more severe gingival inflammation. The GAG composition of GCF, particularly CS, appears to reflect changes occurring in the deeper periodontal tissues of alveolar bone and periodontal ligament during orthodontic treatment.

Hyaluronic acid and hyaluronidase activity in gingival exudate from sites of acute ulcerative gingivitis in man.

Gingival exudates from sites of acute ulcerative gingivitis (AUG) and chronic gingivitis (CG) in adults were investigated by cellulose-acetate electrophoresis for the hyaluronic acid (HA) content and assayed for the levels of HA-degrading enzymes. HA was the only glycosaminoglycan (GAG) in gingival exudate from CG sites. HA was not detected at untreated AUG sites but was evident, at increasing levels, after two and seven days of effective antibacterial treatment. In AUG exudates, the total HA-degrading enzyme activity, of bacterial origin, decreased to approx. 30 and 10 per cent of the high initial levels after two and seven days of treatment respectively, to that level found at sites of CG. The specific activity of HA-degrading enzyme of lysosomal origin was low initially and increased with treatment to a level comparable to CG. The notable absence of HA from gingival exudate from sites of untreated AUG thus appears to result from the increased levels of bacterial hyaluronidase. Electrophoresis of gingival exudate may be an indirect method of monitoring the rate of response of AUG to different antibacterial treatments.

Glycosaminoglycans in human gingival crevicular fluid as indicators of active periodontal disease.

The glycosaminoglycans (GAG) in gingival crevicular fluid (GCF) were investigated by cellulose-acetate electrophoresis of samples from individual sites of defined conditions variously affecting the tissues of the periodontium. The non-sulphated GAG, hyaluronic acid, was present in all samples and was the only major band from sites of chronic gingivitis. An additional sulphated GAG band identified by enzymic digestions as chondroitin-4-sulphate, was detected in GCF from sites of untreated-advanced periodontitis. Initial samples from sites of early periodontitis and juvenile periodontitis yielded a similar additional band which was not detected, however, in samples collected after either surgery to eliminate deep pockets or daily subgingival irrigation with a chlorhexidine solution. Sulphated GAG was also present in fluid from the control situations, i.e. of teeth either undergoing orthodontic movement or showing evidence of trauma from occlusion, and from healing tooth-extraction wounds. Thus the presence of such a component in GCF correlates with those clinical conditions in which degradative changes are occurring in the deeper-periodontal tissues. The electrophoretic profile of GAG in a sample of GCF may be a sensitive laboratory method of indicating active phases of destructive periodontal disease at individual sites.

Evidence against the incorporation into protein of amino acids directly from the membrane transport system in rat heart.

The possibility suggested recently [Hider, R.C., Fern, E.B. and London, D.R. (1969) Biochem. J. 114, 171-178; Hider, R.C., Fern, E.B. and London, D.R. (1971) Biochem. J. 121, 817-827; van Venrooij, W.J., Poort, C., Kramer, M.F. and Jansen, M.T. (1972) Eur. J. Biochem. 30, 427-433; and Adamson, L.F., Herington, A.C. and Bornstein, J. (1972) Biochim. Biophys. Acta 282, 352-365] that protein synthesis takes place using amino acids directly from the membrane transport system and not from an intracellular pool has been investigated in rat heart. The tissue was perfused first for 30 min with either [14C]glycine or [14C]leucine and then for a further 30 min with identical medium containing [3H]glycine or [3H]leucine, respectively. After an initial lag, [14C]glycine was incorporated into protein at a linear rate up to 60 min. The [3H]glycine was accumulated into tissue water and incorporated just as readily as the [14C]glycine had been. The rate of total protein synthesis agrees with literature values only if intracellular and not extracellular specific activity values are used in the calculation. Some glycine was converted to serine or threonine. Leucine influx and efflux were very rapid in contrast to the relatively slow exchange reported for incubated tissues [Hider, R.C., Fern, E.B. and London, D.R. (1969) Biochem. J. 114, 171-178; Hider, R.C., Fern, E.B. and London, D.R. (1971) Biochem. J. 121, 817-827; van Venrooij, W.J., Poort, C., Kramer, M.F. and Jansen, M.T. (1972) Eur. J. Biochem. 30, 427-433]. The results are consistent with the existence of an intracellular precursor pool for glycine. Some possible reasons for the discrepancies between this and the other studies are discussed.