Pilot clinical study to evaluate the efficacy of a professionally delivered high fluoride varnish on erosive tooth wear in an in-situ model.

OBJECTIVES: The aim for this pilot study was to investigate the effect of a sodium fluoride varnish on step height measured by a profilometer from human enamel worn by healthy volunteers with a novel in situ/ex vivo erosion design. METHOD: Healthy volunteers aged 18-70 years wore a palatal splint containing 8 human enamel samples and underwent two 3-day treatment periods for 6 h a day with a varnish containing sodium fluoride at 22,600 ppm and the control with the same ingredients but without fluoride. Each splint contained 4 polished and 4 unpolished samples. The interventions were applied to the surface of the enamel samples in randomised order, removed after 6 h, then immersed ex-vivo in 1 %, pH 2.7 citric acid for 2 min, repeated 4 times a day, over 2 days. Measurements of enamel were assessed blindly by microhardness on day 2 and by non-contact laser profilometry on day 3 for the two treatments. RESULTS: 24 volunteers, 2 males and 22 females aged 27-54 years, were screened and recruited. The delta microhardness, from polished samples removed at the end of day 2, for the control and fluoride treatment was 95.7 (22.9) kgf/mm2 and 123.7 (28.9) kgf/mm2, respectively (p < .005). The mean (SD) step height for the control polished enamel surfaces was 3.67 (2.07) µm and for the fluoride varnish was 1.79 (1.01) µm (p < .0005). The control unpolished enamel surfaces had a mean 2.09 (1.53) µm and the fluoride varnish was 2.11 (1.53) µm but no statistical difference was detected. CONCLUSIONS: The results from this pilot study, utilizing an in-situ model where enamel was exposed to acid over the course of 2 days, demonstrated that a high fluoride varnish containing sodium fluoride at 22,600 ppm prevented erosive wear compared to a control on the polished enamel surfaces. CLINICAL SIGNIFICANCE: Intra-oral study demonstrated that a high fluoride varnish containing sodium fluoride at 22,600 ppm reduced erosive tooth wear.

The threshold of an intra oral scanner to measure lesion depth on natural unpolished teeth.

OBJECTIVES: To investigate the threshold and accuracy of intraoral scanning in measuring freeform human enamel surfaces. METHODS: Software softgauges, ranging between 20 and 160 µm depth, were used to compare four workflow analysis techniques to measure step height on a freeform surface; with or without reference areas and in combination with surface-subtraction to establish which combination produced the most accurate outcome. Having established the optimum combination, 1.5 mm diameter, individual depths ranging from 11 to 81 µm were created separately on 14 unpolished human enamel samples and then scanned with gold standard laboratory optical profilometry (NCLP, TaiCaan Technologies™, XYRIS2000CL, UK) and a clinical intraoral scanner (TrueDefinition™, Midmark Corp., USA). The sequence of surface registration and subtraction determined from the softgauges was used to measure step height on natural human enamel surfaces. Step heights (µm) were compared using two-way ANOVA with post-hoc Bonferroni (p < 0.05) and Bland-Altman analyses. RESULTS: Software differences were significantly reduced from - 29.7 to - 32.5% without, to - 2.4 to - 3.6% with reference areas (p < 0.0001) and the addition of surface-subtraction after registration reduced this further to 0.0 to - 0.3% (p < 0.0001). The intraoral scanner had a depth discrimination threshold of 73 µm on unpolished natural enamel and significant differences (p < 0.05) were observed compared to NCLP below this level. SIGNIFICANCE: The workflow of combining surface-registration and subtraction of surface profiles taken from intraoral scans of freeform unpolished enamel enabled confident measurement of step height above 73 µm. The limits of the scanner is related to data capture and these results provide opportunities for clinical measurement.

Progress and limitations of current surface registration methods when measuring natural enamel wear.

OBJECTIVES: Our ability to detect dental wear on sequential scans is improving. This experiment aimed to determine if widely used surface registration methods were sufficiently accurate to distinguish differences between intervention groups on early wear lesions. METHODS: Baseline measurements were taken on human molar buccal enamel samples (n = 96) with a confocal scanning profilometer (Taicaan, UK). Samples were randomly assigned to subgroups of brushing (30 linear strokes 300 g force) before or after an acid challenge (10 min citric acid 0.3% immersion) for four test dentifrices (medium abrasivity NaF, medium abrasivity SnF2, low abrasivity NaF and a water control). Post-experimental profilometry was repeated. 3D step height was analysed using WearCompare (www.leedsdigitaldentistry.co.uk/wearcompare, UK). Percentage Sa change was calculated using Boddies (Taicaan Technologies, Southampton, UK). Data were analysed in SPSS (IBM, USA). RESULTS: The mean 3D step height (SD) observed when samples were brushed before the erosive challenge was -2.33 µm (3.46) and after was -3.5 µm (5.6). No significant differences were observed between timing of toothbrushing or dentifrice used. The mean % Sa change for the low abrasivity group (water control and low abrasivity NaF) was -10.7% (16.8%) and +28.0% (42.0%) for the medium abrasivity group (medium abrasivity NaF and SnF2). CONCLUSIONS: Detectable wear scars were observed at early stages of wear progression. However standard deviations were high and the experiment was underpowered to detect significant changes. Brushing with a low abrasivity dentifrice or water control produced a smoother surface whereas brushing with a high abrasivity dentifrice produced a rougher surface. CLINICAL SIGNIFICANCE: The methodology currently used to align sequential scans of teeth and measure change is too imprecise to measure early wear on natural enamel surfaces unless a large sample size is used. Further improvements are required before we can fully assess early wear processes on natural teeth using profilometry.

The measurement threshold and limitations of an intra-oral scanner on polished human enamel.

OBJECTIVE: To investigate the measurement threshold of an intra-oral scanner (IOS) on polished human enamel. METHODS: The optical performance of an IOS was compared to a gold-standard non contacting laser profilometer (NCLP), on a painted microscope slide, compared to increasing particle size of silicon-carbide papers (21.8-269.0 µm) and separately on polished human enamel with increasing step-heights. The enamel samples were randomised (n = 80) and scanned using the IOS and NCLP at increasing step-height depths (µm) (1.87-86.46 µm) and quantified according to ISO:5436-1. The measurement threshold of the IOS was determined using a custom designed automated lesion localisation algorithm, corroborated by Gaussian skewness (Ssk) and kurtosis (Sku) analysis, to assess the minimum step-height measured on each enamel sample. RESULTS: The NCLP showed statistically increased Sq surface roughness for all silicon carbide particle sizes compared to the microscope slide, whereas, the IOS Sq roughness discriminated silicon-carbide particles above 68.0 µm compared to the glass slide (p ≤ 0.02). On polished enamel, the automated minimum detectable step-height measurable on each sample was 44 µm. No statistically significantly different step-height enamel lesion measurements were observed between NCLP and IOS above this threshold (p > 0.05). SIGNIFICANCE: This study revealed the fundamental optical metrological parameters for the IOS, was step-heights above 44 µm and this reflects the data acquisition of the system. These results highlight the limitations of IOS used in this study, mandating further research to optimise the performance of other IOS systems, for measuring wear of materials or tooth wear on human unpolished natural enamel surfaces.

Alternative practices of achieving anaesthesia for dental procedures: a review

Managing pain and anxiety in patients has always been an essential part of dentistry. To prevent pain, dentists administer local anaesthesia (LA) via a needle injection. Unfortunately, anxiety and fear that arise prior to and/or during injection remains a barrier for many children and adults from receiving dental treatment. There is a constant search for techniques to alleviate the invasive and painful nature of the needle injection. In recent years, researchers have developed alternative methods which enable dental anaesthesia to be less invasive and more patient-friendly. The aim of this review is to highlight the procedures and devices available which may replace the conventional needle-administered local anaesthesia. The most known alternative methods in providing anaesthesia in dentistry are: topical anaesthesia, electronic dental anaesthesia, jet-injectors, iontophoresis, and computerized control local anaesthesia delivery systems. Even though these procedures are well accepted by patients to date, it is the authors' opinion that the effectiveness practicality of such techniques in general dentistry is not without limitations.