Recommendations to address respondent burden associated with patient-reported outcome assessment

Patient-reported outcomes (PROs) are increasingly used in healthcare research to provide evidence of the benefits and risks of interventions from the patient perspective and to inform regulatory decisions and health policy. The use of PROs in clinical practice can facilitate symptom monitoring, tailor care to individual needs, aid clinical decision-making and inform value-based healthcare initiatives. Despite their benefits, there are concerns that the potential burden on respondents may reduce their willingness to complete PROs, with potential impact on the completeness and quality of the data for decision-making. We therefore conducted an initial literature review to generate a list of candidate recommendations aimed at reducing respondent burden. This was followed by a two-stage Delphi survey by an international multi-stakeholder group. A consensus meeting was held to finalize the recommendations. The final consensus statement includes 19 recommendations to address PRO respondent burden in healthcare research and clinical practice. If implemented, these recommendations may reduce PRO respondent burden.

Management of neuronopathic Gaucher disease: revised recommendations

The original guidelines drawn up for the management of the neuronopathic forms of Gaucher disease were felt to be in need of revision; in particular, the role of high-dose enzyme replacement therapy (120 IU/kg of body weight every 2 weeks) in stabilizing neurological disease. The existing published evidence was analysed; it was concluded that it did not support the role of high-dose ERT, although this might be required to treat severe visceral disease.

Outcome of type III Gaucher disease on enzyme replacement therapy: review of 55 cases

The European Task Force for Neuronopathic Gaucher Disease (NGD) met in 2006 to review its 2001 guidelines. Fifty-five patients from five European countries were reviewed; 29 were male and 26 female. The majority of the patients were homozygous for the L444P mutation. All had been on enzyme replacement therapy (ERT). However, there was considerable variation in the dose of ERT, as well as an uneven distribution of risk factors. Thus, the oldest patients were on the lowest doses, and several had had a total splenectomy, while the youngest patients had a high proportion of compound heterozygosity and were on the highest doses, and very few had had a splenectomy. This heterogeneity rendered analysis very difficult. However, some observations were possible. The older patients appeared to remain relatively stable despite a low dose of ERT. In the younger patients, there was no clear effect of high-dose ERT. However, the period of follow-up was too short in many patients to draw valid conclusions. These data will be used to draw up revised guidelines.

A severity scoring tool to assess the neurological features of neuronopathic Gaucher disease

Type III Gaucher disease is one of the three recognized subtypes of Gaucher disease, an inherited deficiency of lysosomal glucocerebrosidase. Phenotypically there is a wide spectrum of visceral and neurological manifestations. Enzyme replacement is effective in managing the visceral disease; however, the neurological manifestations remain a more challenging obstacle. There is an unfulfilled need to reliably monitor neurological disease and its response to treatment. A severity scoring tool was developed through neurological domain identification, item generation and tool formation. Domain identification was established based on a retrospective single centre study (n = 15) and a systematic review of publications. Forty-seven patients with neuronopathic Gaucher disease were then assessed using the tool to establish the clinical and statistical reliability of each domain. Judgement quantification of the tool was established through a process of content validity involving five European experts. Content validity is considered to be most effective when undertaken systematically. Concurrent validity and feasibility of the tool was also highlighted. This process allowed a revised and validated version of the tool to be developed.

Clinical evaluation of ferric oxalate in relieving dentine hypersensitivity

Previous in vitro permeability and scanning electron microscopic (SEM) studies have demonstrated the effectiveness of the oxalate ion in dentine permeability reduction and effective tubule occlusion. The aim of this randomized double-blind, split mouth 4-week clinical study, therefore was to determine whether a 1-min application of ferric oxalate (Sensodyne Sealant) on exposed root dentine was effective in reducing dentine hypersensitivity (DH). Thirteen subjects [8F:5M, mean age 46.2 (s.d. 4.15) years] completed the study. The subjective response was evaluated by tactile, thermal and evaporative methods of assessment. Data were collected at baseline and post-application at +5 min and 4 weeks. Analysis was based on paired t-test (P=0.05) and Wilcoxon-Mann-Whitney tests. No statistically significant differences were noted between ferric oxalate and placebo preparations at +5 min and 4 weeks for any of the test stimuli. There was, however, a clear trend towards immediate reduction (+5 min) in DH reverting back to baseline values at 4 weeks with the exception of the Biomat Thermal Probe mean values, which maintained the reductions in DH compared with placebo. The results of the present study demonstrated that a 1-min application of ferric oxalate is both rapid and effective in reducing DH although its long-term effectiveness still needs to be determined.

The effects of reconditioning on the slot dimensions and static frictional resistance of stainless steel brackets

This study investigated the effects of reconditioning on the slot dimensions and the static frictional resistance of stainless steel brackets at 0, 5, and 10 degrees bracket/archwire angulation. A sample of 45 used, commercially reconditioned 0.018 x 0.030 inch stainless steel standard edgewise brackets was compared with a matched sample of 45 new brackets. The slot dimensions of 15 new and 15 reconditioned brackets were examined using a photomicroscope. With new brackets both the occluso-gingival slot width (mean = 0.0197 inch) and slot depth (mean = 0.0304 inch) exceeded the manufacturer's nominal dimensions of 0.018 x 0.030 inch. The reconditioning process resulted in a further increase in slot width (mean = 0.0205 inch), which was statistically significant (P = 0.028), and a reduction in slot depth (mean = 0.0291 inch), which was highly statistically significant (P = 0.002). This may be attributable to preferential metal removal by the electro-polishing phase of the reconditioning process. Friction testing of 30 new and 30 reconditioned brackets demonstrated that both showed an increase in binding effects as the bracket/archwire angulation was increased from 0 to 5-10 degrees. However, the changes in slot dimensions secondary to reconditioning did not result in a statistically significant difference in mean static frictional resistance when the two bracket types were compared. Although the brackets were altered physically by the reconditioning process, their performance during simulated sliding mechanics was not adversely affected. This implies that reconditioning may not result in clinically significant effects.

The crystal growth technique--a laboratory evaluation of bond strengths

An ex vivo study was carried out to determine differences in the bond strengths achieved with brackets placed using a crystal growth technique compared with a conventional acid-etch technique. A solution of 37 per cent phosphoric acid was used for acid-etching and a commercially available polyacrylic acid gel, Crystal-lok for crystal growth. A heavily-filled composite resin was used for all samples to bond brackets to healthy premolar teeth extracted for orthodontic purposes. Polycrystalline ceramic and stainless steel brackets were used and tested to both tensile and shear failure using an Instron Universal Testing machine. The tensile and shear bond strengths were recorded in kgF. In view of difficulties experienced with previous authors using different units to describe their findings, the data were subsequently converted to a range of units in order to facilitate direct comparison. The crystal growth technique produced significantly lower bond strengths than the acid-etch technique for ceramic and stainless steel brackets, both in tensile and shear mode. The tensile bond strength for stainless steel brackets with crystal growth was 2.2 kg compared with 6.01 kg for acid-etch, whilst with ceramic brackets the tensile bond strengths were 3.9 kg for crystal growth and 5.55 kg for acid-etch. The mean shear bond strength for stainless steel brackets with crystal growth was 12.61 kg compared with 21.55 kg for acid-etch, whilst with ceramic brackets the shear bond strengths were 7.93 kg with crystal growth compared with 16.55 kg for acid-tech. These bond strengths were below those previously suggested as clinically acceptable.

A comparison between the wear resistance of three types of denture resin to three different dentifrices

This study compares the abrasive effects of three dentifrices on three different denture base resins, a heat cured acrylic resin, a self cured acrylic resin and a light activated urethane dimethacrylate-based resin. Specimens of the resins were subjected to a regimen of mechanical brushing using measured amounts of paste on standard toothbrushes driven by a reciprocating device. The apparent wear of each specimen was assessed qualitatively using scanning electron microscopy and quantitatively using profilometry and reflex microscopy. The study showed that cleaning pastes play a significant role in the wear of conventional acrylic resins, the relative abrasivity of the dentifrices being substrate related. However, wear was less evident on the light activated urethane dimethacrylate resin. Brushing with water alone produced no detectable wear on any of the specimens.

A comparison of self-ligating and conventional orthodontic bracket systems

This ex-vivo study compared the static frictional resistance of three self-ligating brackets with a conventional steel-ligated Ultratrimm bracket. The effects of archwire size (0.020, 0.019 x 0.025 and 0.021 x 0.025-inch), bracket/archwire angulation (0, 5 and 10 degrees) and the presence of unstimulated human saliva were investigated. The study demonstrated that both increases in wire size and bracket/archwire angulation resulted in increased static frictional resistance for all bracket types tested, with the presence of saliva having an inconsistent effect. Mobil-Lock Variable-Slot had the least friction for all wires for 0 degree angulation. However, with the introduction of angulation, the values were comparable to those of the other brackets. Activa brackets had the second lowest frictional resistance, although high values were found with 0.019 x 0.025-inch wires. SPEED brackets demonstrated low forces with round wires, although with rectangular wires or in the presence of angulation, friction was greatly increased. Ultratrimm brackets produced large individual variation, confirming the difficulty in standardizing ligation force, although under certain conditions, significantly larger frictional forces were observed. In conclusion, self-ligating brackets showed reduced frictional resistance in comparison to steel ligated brackets only under certain conditions.

Adhesive composite resins for artificial teeth: a laboratory investigation of bond strength to a cobalt-chromium alloy

Adhesive resin systems are reported to improve the bond strength between resins and cast cobalt-chromium alloy. This investigation compares the behaviour of three resin systems. Cylinders and beams of cobalt-chromium, with 0.6-mm-diameter retention beads regularly cast onto the bonding surfaces, were air-abraded and ultrasonically cleaned. Resin veneers 4 mm deep on the cylinders and 2 mm on the bars were polymerized by heat and pressure or by light. Specimens were water-stored for 7 or 90 days, including thermocycling between 4, 37 and 60 degrees C, before testing in a Universal Testing Machine to examine the shear bond strength or the effect of the bonded resin spine on the flexural strength of the beams using a three-point bend test. Specimens were examined with an optical microscope to attempt to determine the nature of the failures that occurred. The investigation showed that, overall, the heat- and pressure-cured urethane dimethacrylate resin with and adhesive based upon methacrylic acid performed significantly less well than a conventional acrylic resin, or a hybrid composite resin with and adhesive monomer.

The bactericidal effects of dental ultrasound on Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. An in vitro investigation

This study investigated the possible bactericidal acoustic effects of the dental ultrasonic scaler. Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis suspensions, were subjected to the vibrations of a Cavitron P1 insert for 2.5 and 5.0 min in an acoustically-simulated pocket model and the survivors enumerated. The extent of any cavitation occurring within the pocket model to which the statistically significant bactericidal activity observed might be attributed, was determined by 'sonoluminescence', which was then investigated by photomultiplication techniques. However, these failed to detect any sonoluminescence within the pocket space and, moreover, the necessary deflection of the water coolant away from the insert tip, to avoid flooding of the experimental pocket, proved to result in temperatures of 47.6 degrees C and 52.3 degrees C at the respective time intervals, and thereby constituted an alternative possible bactericidal mechanism. Examination of the effects of such temperature changes on the target bacteria then revealed statistically significant differences in the viable counts of both microorganisms after 5.0-min periods, and as such were comparable to those previously detected in relation to the pocket model. Whilst it must be presumed that the bacteriolytic effect observed in the main investigation was due to the incidental temperature changes, in the absence of acoustic cavitation the influence of any associated acoustic microstreaming cannot be discounted. Further investigations to assess the bactericidal potential of acoustic phenomena using a modified experimental to exclude any hyperthermic effects are therefore necessary.

Method for enhancing the fluoride release of a glass-ionomer cement

The cariostatic action of the glass-ionomer cement has been attributed to its sustained release of fluoride. The fluoride in the set cement originates from the glass particles which are eroded, in part, during the setting reaction. In this study a water-activated glass-ionomer was mixed with sodium fluoride (NaF) solutions of different concentrations (0%, 2% and 4%). The different cements were used to prepare discs which were stored individually in demineralized water at 37 degrees C, the fluoride concentration of the storage solutions were measured, at intervals, until the specimens were 80 days old. The effect of the different mixing solutions on the working and setting times and compressive strength were also determined. It was found that the cement mixed with the 4% solution of NaF released significantly more fluoride than the water mixed control. The fluoride solution mixed materials had longer setting times than the control, but there was no significant difference in the compressive strengths. All the materials became progressively stronger on storage. Mixing the cement with a 4% solution of NaF increased the initial fluoride release of the glass-ionomer without seriously affecting other physical properties.

The effects of cross-infection control procedures on the tensile and flexural properties of superelastic nickel-titanium wires

The development of superelastic nickel-titanium archwires has simplified the alignment phase of orthodontic treatment by permitting the use of highly flexible, resilient archwires and avoiding the need for complex loops. The majority of these archwires appear undistorted when removed from the mouth after use. This feature, coupled with the disadvantage of relatively high cost has led to sterilization and recycling of these wires by some clinicians. This study was designed to examine the effects of currently used infection control procedures on the mechanical properties of superelastic nickel-titanium alloy (SENTA) archwires. One-hundred-and-forty lengths of a SENTA wire were subjected to various sterilization and disinfection procedures. These included cold disinfection in 2 per cent glutaraldehyde solution for 3- and 24-hour cycles, and steam autoclaving. Single and double cycles were used. The properties investigated were the 0.1 per cent yield strength, the ultimate tensile strength, and the flexural rigidity. No statistically significant differences were found between the groups or against an untreated control.

The ex vivo effect of ligation technique on the static frictional resistance of stainless steel brackets and archwires

This ex vivo investigation compared the effect of various orthodontic ligation techniques on the static frictional resistance of stainless steel brackets and archwires under both dry and wet conditions. The techniques studied were: elastomeric modules tied conventionally and in a 'figure of 8' pattern, stainless steel ligatures, and Teflon-coated ligatures. The first part of the investigation involved the construction of calibration curves for each of the materials, so an estimate of the normal force exerted by the ligatures could be ascertained. Secondly, a pair of ligature locking pliers were modified so that ligatures could be placed with a standardized force. Finally, the four methods of ligation were directly compared on a specially constructed testing apparatus. Results revealed that elastomeric modules tied in a 'figure of 8' pattern produced significantly more friction than any other method tested, under both dry and wet conditions. No significant differences in frictional resistance were found between conventionally tied elastomeric modules and stainless steel ligatures. Teflon-coated ligatures, however, were associated with the lowest frictional forces. The results of the calibration tests indicated that the normal forces exerted by all four methods of ligation may be higher than previously estimated.

Effects of cyclic stressing on attachment bond strength using glass ionomer cement and composite resin

Bonded orthodontic brackets were subjected to cyclic loading in order to simulate the effect of occlusal forces. The subsequent effect on bond strength was determined. Stainless steel, mesh-based brackets were bonded to extracted teeth with either composite resin or glass ionomer cement. A jig was designed to subject each bracket to a preselected loading level and the 24-hour shear/peel bond strength of both stressed and unstressed brackets was subsequently measured. Cyclic loading brought about a comparative decrease in bond strength when using both types of material. The potential implications of selecting these different types of bonding material for clinical use are discussed.

A study to compare the effects of simulated torquing forces on pre-adjusted orthodontic brackets

The transmission of torquing forces between three types of preadjusted bracket was investigated. 0.022-inch Roth prescription 'A'-Company (stainless steel), Silkon (reinforced polycarbonate), and Allure III (polycrystalline ceramic) brackets were used. A selection of stainless steel archwires were chosen, 0.018 x 0.025, 0.019 x 0.025, and 0.021 x 0.025 inch. The brackets were torqued with respect to the archwire and force v. angular deflection was recorded on an Instron machine. The dimension of angular change was in part dependent on the ability of the bracket to elastically or plastically deform. There were no significant differences between bracket types with the 0.018 x 0.025-inch archwire. 'A'-Company brackets demonstrated a significantly lower resistance to loading compared to Silkon brackets in the 0.019 x 0.025-inch group. The greatest amount of distortion was seen in Silkon brackets with an 0.021 x 0.025-inch archwire. Allure III brackets demonstrated the greatest resistance to loading in all groups. As no apparent distortion under loading is seen in Allure III brackets, it is assumed that the load is largely transmitted to the tooth. Full thickness stainless steel rectangular wires should be avoided with these brackets, in order to prevent overloading.

Properties of acrylic resins incorporating 4META for bonding to cobalt-chromium alloys

Polymer substitution into proprietary 4-methacryloxyethyltrimellitate anhydride (4META) resins creates tooth coloured veneers for cobalt-chromium overlay dentures. The elastic moduli and shear-bond strengths of proprietary resins (matched) and resins polymerised from 4META monomers and substituted polymers (unmatched) were determined. Bond strengths were similar for matched and unmatched heat curing resins (mean 14.1 (SD 1.6 MPa)) but differed for matched (6.9 (SD 1.3) MPa) and unmatched self-curing resins (5.7 (SD 0.9) MPa). Preparation of the alloy surface immediately before packing with resin dough provided significantly higher bond strengths. Structural examination in a scanning electron microscope suggested that bonds developed by unmatched resins may provide less satisfactory clinical performance.

A comparison of the frictional characteristics of five initial alignment wires and stainless steel brackets at three bracket to wire angulations--an in vitro study

The study investigated static planar frictional resistance between five initial alignment wires and stainless steel brackets at three bracket to wire angulations (0, 5 and 10 degrees). It was demonstrated that static frictional resistance increased significantly with increasing bracket to wire angulation due to binding within the system. Epoxy-coated steel had the highest static frictional resistance and coaxial stainless steel the lowest. Fibre-optic glass (Optiflex) had low frictional resistance. The coefficient of friction followed the trends of static frictional resistance in all respects.

The physical properties of a polyacetal denture resin

A polyacetal injection-moulded resin is being marketed for the construction of retentive and supportive components of removable partial dentures (RPDs). Specimens of poly(oxymethylene) cast by commercial laboratories were tested to examine the following physical characteristics: the modulus of elasticity in compression, extension and flexure, stress relaxation, the force displacement behaviour of clasp forms, impact strength and glass transition temperature. Results showed that the material has a flexural modulus lower than that of poly(methylmethacrylate) and is insufficiently rigid to be used as a supporting element for partial dentures. Resin clasps may be resilient enough to engage undercuts for the retention of RPDs but the low flexural modulus requires that the resin be used in greater cross-sectional area than metal alloys in order to gain useful retention. This greater bulk has implications for plaque accumulation and maintenance of periodontal health.

Preliminary study of factors affecting the fluoride release from glass-ionomer cements

A study has been made on the release of fluoride from three glass-ionomer cements. The effect of the maturity of cements at the time of immersion and powder/liquid ratio were examined. It was found that fluoride release from immature cements was dependent on cement and powder/liquid ratio and that the effect was permanent. The effect of cement type and powder/liquid ratio lessened as cements were allowed to mature prior to immersion. It appears that fluoride release was dependent on the strength and maturity of the cement matrix and not fluoride content. It was concluded that the rate of fluoride release would depend largely on clinical factors rather than cement type.

A retrospective study of 66 titanium cranioplasties

A review was undertaken to assess the outcome of treatment in 66 patients for whom a titanium prosthesis was provided for the repair of a calvarium defect. While many aspects were satisfactory, certain disappointing features led to a prospective pilot study which enabled the following problems to be identified: (a) poor communication between neurosurgeon and prosthetist; (b) difficulties in establishing the margins of the defect; (c) orientation of the prosthesis, and (d) marginal retention. All were overcome with an agreed protocol.

The influence of bracket material, ligation force and wear on frictional resistance of orthodontic brackets

Planar static frictional phenomena were investigated for two types of ceramic and one type of stainless steel orthodontic bracket against rectangular stainless steel archwire. The brackets studied were 'Starfire' (single crystal aluminium oxide), 'Allure III' (polycrystalline aluminium oxide), and 'Dentaurum' (stainless steel). The investigative parameters were: bracket material, force of ligation and whether the brackets were new or 'worn'. Without exception, both types of ceramic bracket produced greater frictional resistance than the stainless steel brackets throughout testing. At a ligation force of 500 g, the Starfire bracket gave the greatest frictional resistance. At ligation forces of 200 and 50 g, the greatest frictional resistance was seen with Allure III. After a period of simulated wear, frictional resistance of Starfire tended to increase at the greatest ligation load while that of both ceramics decreased slightly at the two lower ligation loads. The ceramic brackets caused abrasive wear of the archwire surfaces and the consequent wear debris may have contributed to the changes in frictional resistance seen with Starfire and Allure III. Dentaurum brackets produced minimal frictional resistance in any test and negligible change with wear.

Bone-derived growth factor release from poly(alpha-hydroxy acid) implants in vitro

Matrix proteins were extracted from bovine cortical bone and polymer implant discs (13 mm x 2 mm composed of 50:50 poly DL-lactide-co-glycolide; mol. wt. approximately 9000) prepared by compression moulding granules with lyophilized bone matrix extracts (BMX) 10.1 (w/w). BMX-containing polymers were cultured for 5 wk in either serum-free Dulbecco's modification of Eagle's medium (DMEM) or phosphate buffer, and growth factor activity released into the media assayed by its ability to stimulate the proliferation of murine fibroblast BALB/c/3T3 cells. Approximately 60-75% of the biological activity was released during the first week of culture; however, less than half of the growth factor units originally incorporated into the implants retained biological activity. Scanning electron microscopy revealed the development of significant internal porosity by week 2; the size of the channels, pores and surface openings suggested they were of the right order for bone ingrowth. These preliminary findings suggest that poly(alpha-hydroxy acid) polymers containing bone-derived growth factors could have potential for stimulating osseous regeneration in vivo.

Clinical efficacy of a low abrasive dentifrice for the relief of cervical dentinal hypersensitivity

2 strontium chloride hexahydrate-containing dentifrices (SCH), similar except for their respective abrasive systems, were compared in a 2-month randomised double-blind parallel clinical study to evaluate their comparative effectiveness in terms of cervical dentinal hypersensitivity. 2 groups of 20 subjects, each with cervical dentinal hypersensitivity, were evaluated for tactile sensitivity by Yeaple probe, air sensitivity using a dental air syringe and subjective perception of pain by means of a visual analogue scale. There was no difference between the dentifrices as regards reduction of cervical dentinal hypersensitivity at each time point. The response to both dentifrices was evident within 4 weeks of use and the degree of improvement increased throughout the 8-week study period. The results support the conclusion that changing the abrasive component of SCH dentifrices did not significantly increase or decrease the (desensitizing) activity of the original product.

In vitro bond strengths of three current dentin adhesives to primary and permanent teeth

The in vitro shear bond strengths of three chemically different dentin bonding agents were tested between both permanent and deciduous dentin and their respective anterior composite filling materials. The effect of the post-mortem age of the teeth on bond strength was evaluated by comparison of fresh (extracted within 24 h) and old (extracted within 10 d) teeth. The results indicated that these materials bonded more strongly to the dentin of permanent than to deciduous teeth (8.8 +/- 4.9 MN/m2 vs. 6.2 +/- 4.8 MN/m2). The intermaterial comparison indicated that the bonds to dentin were strongest for Scotchbond 2 (12.3 +/- 4.4 MN/m2) followed by Tenure (6.9 +/- 3.3 MN/m2) and then Gluma (3.3 +/- 1.7 MM/m2). Both the above findings were shown to be statistically significant. The effect of time lapse after extraction of the teeth was not statistically significant.

Dentifrice abrasivity and cervical dentinal hypersensitivity. Results 12 weeks following cessation of 8 weeks' supervised use

Following an 8-week controlled investigation of 2 strontium chloride hexahydrate dentifrices (SCH) of differing abrasivity, 2 groups of 20 subjects each, with cervical dentinal hypersensitivity, were re-examined at 20 weeks; that is, 12 weeks after the active period. The examination procedures were conducted in the same manner as in the main clinical trial. Sensitivity levels were assessed by 2 instrument methods: tactile (Yeaple probe), and cold air (dental air syringe), and by subjective perception of pain by means of a Visual Analogue Scale. The results from these methods of assessment demonstrated that 12 weeks following the cessation of 8 weeks' controlled use of standard and low abrasive SCH dentifrices, sensitivity levels reversed on slightly in both groups and, overall, sensitivity remained significantly lower than at baseline. The abrasivity of the dentifrice did not affect the desensitivity activity.

Domestic water treatment appliances and the fluoride ion

Specific ion metering of fluoride ion levels of water samples obtained after passage through water softeners and a conditioner showed no alteration in concentration when compared with controls. Similar comparison of water samples passed through water filters demonstrated that highly significant amounts of fluoride ion were removed. In one filter tested, 90% of the fluoride content was lost in the filtration process. The findings of this study suggest that, in a household using a filter, it may be necessary to increase the fluoride supplement or in some cases to initiate use of fluoride supplements as children are not receiving as much fluoride as was thought. New guidelines are required to take account of this surprising effect.

Marking width, calibration from tip and tine diameter of periodontal probes

The present study comprises an investigation of 7 different probe types, representing currently-marketed major designs (WHO-CPITN, Williams, Michigan), as well as available calibration systems (engraved, etched and painted markings). Width of markings, accuracy of calibration from probe tip, and tine diameter at the tip and at specified points along the tine were assessed, using a stereomicroscope at a magnification of x 40. Blind duplicate measurements of these probe tine characteristics were 100% reproducible to within 0.01 mm. There was an overall range in marking width from 0.00-1.13 mm. The best marking, in that it had no appreciable width and the highest accuracy, was the discrete transition between normal and engraved parts of probes with engraved bands. Mean inaccuracies of different probe sets varied from 0.06 to 0.22 mm. Probes from the same batch from the same production line could differ by more than 0.5 mm in calibration. Mean tip diameter ranged from 0.28 to 0.70 mm. It was concluded that probe tine diameter and calibration should be considered in addition to other variables of periodontal probing. Standardisation of tine characteristics and avoidance of the use of different types or batches in a single study should enhance the accuracy and reproducibility of periodontal probe-dependent measurements.

Assessment of ultrasonic debridement of calculus-associated periodontally-involved root surfaces by the limulus amoebocyte lysate assay. An in vitro study

This investigation assessed the effectiveness of an in vitro ultrasonic debridement regime on periodontally involved teeth with visually-detectable calculus deposits, using the LAL assay for lipopolysaccharides (LPS) as a marker of bacterial products. 34 single rooted teeth with extensive amounts of calcified accretions were selected, of which 10 served as uninstrumented controls for the estimation of existing LPS levels. The periodontally involved roots of the 24 experimental teeth were debrided with a Cavitron TF-10 tip for a limited time using light pressure and overlapping strokes which ensured complete surface instrumentation without reference to the presence of calculus. Marked reductions in root surface area coverage by calculus were nevertheless achieved as assessed planimetrically from photographic records of the teeth before and after debridement. The root surfaces of each tooth were then stripped away and the harvested material subjected to 'Westphal' extraction and LAL assay for LPS. The resulting LPS yields from the experimental teeth ranged from less than 0.08 to 22.387 ng compared to 1,900 to 29,200 ng from the uninstrumented controls. The extremely small residual LPS yields from the experimental teeth not only confirm the efficacy of ultrasonic debridement but, when coupled with the lack of a relationship with the widely varying amounts of the remaining calculus, support the contention that bacterial plaque rather than calculus has the greater pathogenic potential. These results reinforce the growing impression of the superficial location of bacterial toxic products associated with periodontally involved root surfaces.

The assessment of ultrasonic root surface debridement by determination of residual endotoxin levels

Recent demonstrations of the superficial nature and ease of removal of root-surface-associated cytotoxic materials suggest that extensive root-surface instrumentation is not warranted clinically. This in vitro investigation determined the detoxifying effects of a conservative regime of ultrasonic root debridement, using the Limulus amoebocyte lysate assay for lipopolysaccharide (LPS) as an indication of the presence or absence of cytotoxic materials. 20 extracted periodontally-involved single-rooted teeth, with no clinically detectable calculus deposits, were debrided with a Cavitron TF-10 tip. Light pressure, resulting from a force application of approximately 50 g, lasting for 0.8 s/mm2 of root surface was used and complete overlapping instrumentation ensured. The finding of LPS levels of less than 2.5 ng per root in 19 out of 20 teeth after such debridement was comparable to LPS levels found on healthy, uninvolved control teeth, and thus endorses the growing belief that root surface cleanliness can be readily achieved.

Materials for mouth protectors

A mixture containing 18% polyvinylacetate exhibits the optimum physical properties for mouth protection in contact sports.

The morphological characterization of dental amalgam alloy powders

Two commercially available amalgam alloy powders (one lathe-cut, the other spherical) were characterized in terms of density, surface area, particle size distribution and appearance under the scanning electron microscope. A third, experimental alloy powder, prepared by electrodeposition, was subjected to a similar analysis. It was found that particle size distribution can be a misleading indicator, in that when particles are porous, inordinately large amounts of mercury will be taken up on trituration, and the resulting amalgam will have wholly unsatisfactory mechanical properties. Surface area measured by BET (gas adsorption) may be the best single index of the morphological quality of an amalgam alloy powder.

Tensile and shear strength measurements on brazed "T" joints used in construction of intra- and intermaxillary hooks

Silver-brazed "T" joints, representing the first stage in the construction of intermaxillary hooks were fabricated under rigorously controlled conditions. Their tensile and shear strengths were then measured using specially developed test jigs. It was found that the braze joint itself was stronger than the component wires (under tensile load) while in shear mode, fracture occurred in one of a number of well-defined ways. The effect of prolonged heating was investigated using microhardness measurements and recommendations are made for the optimum brazing conditions.

The interaction between lining materials and composite resin restorative materials

The effects of four lining materials, Dycal, Procal, Cavitec and Poly F cement on Adaptic and Concise have been investigated in vitro. The parameters studied were surface roughness, hardness and colour both with and without an intermediate (or bonding) resin being present between the restorative material and the liner. The effects of the four liners on the composites varied both between the lining materials themselves and with the composite resin. Two materials, Procal and Dycal, had little interaction with the composites, provided an intermediate resin was used with the latter. Cavitec appeared to have an adverse reaction with the composites and Poly F, whilst having no effect on the colour of the composites, did increase surface roughness. The adverse effects of linig materials were ascribed to minor constituents, particularly methyl salicylate, present in the formulation.

Processing factors affecting the clarity of a rapid-curing clear acrylic resin

The difficulty in repeatedly producing unblemished, clear acrylic resin in the dental laboratory has hindered its wider use, despite its many advantages over coloured material. Recently, rapid-cure dental acrylics have been introduced, which are available in both clear and coloured forms. This investigation examined various factors which may influence the production of unblemished, rapid-curing, clear acrylic resin. Utilizing a quantitative assessment of clarity, the most important factor influencing the clarity of the resin is shown to be the choice of separating medium. Tin-foil produces extremely high clarity, but alginate mould separator causes surface blanching. However, this surface blanching can be removed by polishing. Porosity, caused by too rapid curing, and stone model dryness are of only secondary importance. Possible water contamination of the monomer liquid due to accidental exposure only affects clarity at very high levels of contamination.

A study of temperature changes during removal of amalgam restorations

Because tooth preparation is only one of several potent causes of trauma to the pulp during clinical procedures, the objective should be to increase the chance of pulp survival by reducing this trauma wheneve- possible. In case of tooth preparation, this study shows that there is far less potential for pulpal damage when water is used as a coolant.