Rebecca Moazzez

Oral pH and drinking habit during ingestion of a carbonated drink in a group of adolescents with dental erosion

OBJECTIVES To investigate the relationship between dental erosion, oral pH and drinking habit in a group of adolescents. METHODS Oral pH was measured simultaneously at the surface of four teeth in 11 patients, aged 10-16 years, with erosion and in 10 controls subjects without erosion using antimony electrodes. Measurements were made before, during and after drinking 330 ml of a carbonated drink. The method and timing of drinking the beverage, reported dietary intake of acidic foods and flow rate and buffering capacity of saliva were recorded. RESULTS The erosion patients reported drinking more carbonated drinks (p<0.01) and drinking directly from a can more frequently than the controls (p<0.05). They also drank twice as quickly (p<0.05). The pH at the buccal surface of a molar remained lower for longer in the erosion patients than in the patients without erosion (p<0.01), whilst the labial surface of the upper central incisor had a longer exposure to low pH in the controls subjects (p<0.05). CONCLUSION The pattern of oral pH differed between subjects with and without erosion after drinking an acidic beverage. This may be related to observed differences in drinking habit, which could have influenced the pattern of erosion in these subjects.

An in situ study investigating dentine tubule occlusion of dentifrices following acid challenge

OBJECTIVES To investigate the dentine occlusion and acid resistance of dentifrices developed to treat dentine hypersensitivity. METHODS This was a single centre, single blind, randomised, split mouth, four treatments, two period crossover, in situ study in healthy subjects. Subjects wore buccal intra-oral appliances each fitted with four dentine samples over four consecutive days with one study product applied per appliance; 8% strontium acetate in silica base, 1040 ppm sodium fluoride (Sensodyne(®) Rapid Relief), 8% arginine, calcium carbonate, 1450 ppm sodium monofluorophosphate (Colgate Sensitive Pro-Relief(®)), 1450 ppm sodium fluoride (control paste) and water. On days 3 and 4, two agitated grapefruit juice challenges (ex vivo) occurred for 1 min. At the end of each treatment day 1 dentine sample was removed from each appliance for scanning electron microscopy (SEM). The extent of tubule occlusion was measured using an examiner-based visual scoring index (three trained examiners). RESULTS In total, 28 subjects ((12 males and 16 females with a mean age of 34.7 years (SD 8.41 years)) completed the study. On day 2, both test dentifrices demonstrated significantly better dentine tubule occlusion than water (p < 0.0001) and control paste (8% strontium p = 0.0003 and 8% arginine p = 0.0019). After 3 and 4 days of twice daily brushing with acid challenges on days 3 and 4 the strontium-based dentifrice demonstrated significantly better dentine occlusion than all other treatments (p < 0.0001). CONCLUSIONS Strontium acetate and arginine-based dentifrice result in statistically significant dentine tubular occlusion compared to controls, but the arginine-based dentifrice is more susceptible to acid challenge. CLINICAL SIGNIFICANCE Erosive beverages are an important aetiology in DH by exposing dentine tubules. Their consumption has increased significantly over the past decade in the UK. This 4-day in situ study investigated the properties of commercially available dentifrices designed to occlude dentine tubules and their resistance to an agitated acid challenge.

The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro

OBJECTIVES To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro. METHODS Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm x 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n=10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle=artificial saliva (2h, pH 7.0)+erosion (0.3% citric acid, pH 3.2, 5 min)+fluoride/control (5 min)+attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in mum was measured using optical profilometry. RESULTS When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences. CONCLUSIONS The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine.

The Effect of Chewing Sugar-free Gum on Gastro-esophageal Reflux

Regurgitated acid entering the mouth in gastro-esophageal reflux disease can cause dental erosion. Chewing gum could induce increased swallowing frequency, thus improving the clearance rate of reflux within the esophagus. The null hypothesis of this study was that chewing gum does not have any effect on the clearance of reflux from the distal esophagus. Thirty-one subjects presenting with symptoms of reflux were given a refluxogenic meal twice and were randomly selected to chew gum for half an hour after eating the meal. Esophageal pH was measured, and pH data were analyzed and compared during the postprandial periods for 2 hrs on the 2 occasions. The median (IQ range) values for the % time pH < 4 during the postprandial period without chewing gum were 5.7 (1.7–13.5) and, with chewing gum, 3.6 (0.3–7.3), respectively (p = 0.001). Chewing sugar-free gum for half an hour after a meal can reduce acidic postprandial esophageal reflux.

Trial of protective effect of fissure sealants, in vivo, on the palatal surfaces of anterior teeth, in patients suffering from erosion

OBJECTIVES Previous work has shown protection to eroded teeth offered by a resin-based adhesive lasted up to three months. The hypothesis investigated in this study was whether application of a fissure sealant would offer longer protection. METHODS Seventeen adult patients with palatal tooth wear were recruited and written consent obtained. Metal discs were cemented on the palatal surfaces of all upper anterior teeth following previously published techniques. Alternate teeth within each subject were randomly chosen and coated with a clear fissure sealant using previously published methods. The uncoated teeth were used as controls. Accurate impressions were taken in custom made trays and repeated at 3, 6, 9, 12 and 20 months and scanned using a non-contacting laser profilometer. RESULTS The mean (standard deviation) thickness of the fissure sealant was 290 μm (500) at the start and after 3 months a mean thickness of 120 μm (260) remained. At this point the control surfaces showed a mean 70 μm (113) of tooth wear. At 6 and 9 months the mean wear for control teeth was higher at 120 μm (114) and 110 μm (114) than sealed teeth at 50 μm (260) and 60 μm (440), respectively. A comparison of paired sites within subjects at their final visit indicated a statistically significant difference in wear between the sealed and control teeth (p=0.016). CONCLUSIONS The use of fissure sealant to protect palatal dentine surfaces may have a role in prevention of tooth wear for up to a period of nine months.

In Vitro Cultivation of 'Unculturable' Oral Bacteria, Facilitated by Community Culture and Media Supplementation with Siderophores.

Over a third of oral bacteria are as-yet-uncultivated in-vitro. Siderophores have been previously shown to enable in-vitro growth of previously uncultivated bacteria. The objective of this study was to cultivate novel oral bacteria in siderophore-supplemented culture media. Various compounds with siderophore activity, including pyoverdines-Fe-complex, desferricoprogen and salicylic acid, were found to stimulate the growth of difficult-to-culture strains Prevotella sp. HOT-376 and Fretibacterium fastidiosum. Furthermore, pyrosequencing analysis demonstrated increased proportions of the as-yet-uncultivated phylotypes Dialister sp. HOT-119 and Megasphaera sp. HOT-123 on mixed culture plates supplemented with siderophores. Therefore a culture model was developed, which incorporated 15 μg siderophore (pyoverdines-Fe-complex or desferricoprogen) or 150 μl neat subgingival-plaque suspension into a central well on agar plates that were inoculated with heavily-diluted subgingival-plaque samples from subjects with periodontitis. Colonies showing satellitism were passaged onto fresh plates in co-culture with selected helper strains. Five novel strains, representatives of three previously-uncultivated taxa (Anaerolineae bacterium HOT-439, the first oral taxon from the Chloroflexi phylum to have been cultivated; Bacteroidetes bacterium HOT-365; and Peptostreptococcaceae bacterium HOT-091) were successfully isolated. All novel isolates required helper strains for growth, implying dependence on a biofilm lifestyle. Their characterisation will further our understanding of the human oral microbiome.

The Association of Acidic Reflux above the Upper Oesophageal Sphincter with Palatal Tooth Wear

This case-controlled clinical study, conducted at a secondary care unit, compared pH measurement at 2 cm above the upper oesophageal sphincter (UOS) in 31 patients complaining of extra-oesophageal symptoms of reflux to 7 control subjects. Twenty-four-hour ambulatory pH measurements were recorded and analysed at 5 cm above the lower oesophageal sphincter (LOS) and 2 cm above the UOS. In reflux patients the proportion of supine time when pH at 5 cm above the LOS was <4 was significantly greater than in controls. The proportion of time when pH at 2 cm above the UOS was <5.5 was also significantly greater in patients than in controls. Palatal tooth wear observed in the patient group correlated with acid reflux at night. In this group of patients presenting with symptoms of reflux, gastric acid passed through the upper oesophageal sphincter and increased the potential for erosion.

A qualitative and quantitative investigation into the effect of fluoride formulations on enamel erosion and erosion–abrasion in vitro

OBJECTIVES To investigate the effect of a single application of highly concentrated SnF(2) and NaF solutions and a NaF/CaF(2) varnish on human enamel subjected to hydrochloric acid erosion and tooth brush abrasion. METHODS Forty enamel samples were prepared from human third molars and NaF (9500ppm, pH 8.0), SnF(2) (9500ppm, pH 2.6) solutions; Bifluorid10(®) varnish (42,500ppm, NaF 5%, CaF(2) 5%) and deionized water (control) was applied to the enamel. Following this three, six and nine cycles of erosion [1 cycle=erosion (0.01M HCl, pH 2.2, 2min)+artificial saliva (1h, pH 7.0)] and erosion-abrasion [1 cycle=erosion (0.01M HCl, pH 2.2, 2min)+artificial saliva (1h, pH 7.0)+abrasion (120 linear strokes in artificial saliva from Tepe medium soft brushes 200g loading)] were carried out. The fluoride treated enamel was analysed using Knoop microhardness, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). RESULTS For erosion alone, there was significantly less microhardness reduction in the Bifluorid10(®) group after three and six cycles of erosion (P<0.05), however no other groups showed statistically different hardness (P>0.05). The EDS analysis showed that only the Bifluorid10(®) group had any detectable fluorine following erosion and erosion-abrasion (0.1wt.% and 0.2wt.% fluorine respectively). The surface fluorine was found to have been removed after erosion and erosion-abrasion for all other surface treatments. Although precipitates were observed after application of the surface treatments, following erosion-abrasion, no visible surface effects from any fluoride preparation remained. CONCLUSIONS Enamel surface precipitates from application NaF, SnF(2) solutions appear to not be able to provide protection against gastric erosion and tooth brush abrasion. The NaF/CaF(2) varnish provided limited protection against erosion but the role for such varnishes in gastric erosion and tooth brush abrasion remains uncertain.

The relationship between incisal/occlusal wear, dentine hypersensitivity and time after the last acid exposure in vivo

OBJECTIVE The aim of this study was to investigate the relationship between tooth wear and dentine hypersensitivity on occlusal/incisal tooth surfaces and the time since dietary acid consumption. METHOD 350 subjects were recruited from hospital and general practice in SE England aged 19-34 years old. The severity of tooth wear and dentine hypersensitivity was calculated on occlusal/incisal tooth surfaces per subject using Basic Erosive Wear Examination (BEWE) and Cumulative Hypersensitivity Index (CHI) scores respectively at each appointment. The CHI score relied on evaporative stimuli applied to each occlusal/incisal tooth surface. The subjects were also asked about the time since their last acidic food or drink consumption. RESULT Tooth wear was recorded in 93% (n=327) of subjects and dentine hypersensitivity was recorded in 56% (n=196) of subjects. A positive statistically significant relationship existed between the severity of tooth wear and severity of dentine hypersensitivity recorded using BEWE and CHI on occlusal/incisal tooth surfaces (p<0.01). Dentine hypersensitivity and tooth wear were correlated with consumption of acidic beverages (p<0.01). The severity of dentine hypersensitivity on occlusal/incisal tooth surfaces was associated with the time since the subjects last acidic food consumption (p<0.01). Among those subjects who consumed an acidic beverage within 60min of their appointment, 87.2% (n=130) had dentine hypersensitivity. Among subjects who had consumed the acidic beverage more than 1h previously, the prevalence of dentine hypersensitivity was 12.8% (n=19). CONCLUSION The severity of tooth wear on occlusal/incisal tooth surfaces is associated with the dentine hypersensitivity severity. Subjects who consume dietary acidic beverages more recently are more likely to have dentine hypersensitivity. CLINICAL SIGNIFICANCE Occlusal tooth surfaces suffer erosive, attritive and abrasive tooth wear. Tooth wear is important in the aetiology of dentine hypersensitivity on these surfaces. Dentine hypersensitivity is more likely initiated if subjects consume acidic beverages more recently. This supports clinically the episodic nature of dentine hypersensitivity caused predominately by active erosive tooth wear.

Composition of Enamel Pellicle from Dental Erosion Patients

Oral health is dependent upon a thin mobile film of saliva on soft and hard tissues. Salivary proteins adhere to teeth to form the acquired enamel pellicle which is believed to protect teeth from acid erosion. This study investigated whether patients suffering diet-induced dental erosion had altered enamel pellicles. Thirty patients suffering erosion were compared to healthy age-matched controls. Subjects wore a maxillary splint holding hydroxyapatite and human enamel blocks for 1 h. The acquired enamel pellicle was removed from the blocks and compared to the natural incisor pellicle. Basic Erosive Wear Examination scores confirmed that dental erosion was present in erosion patients and absent from healthy age-matched controls. Erosion patients had half the amount of proteins (BCA assay) within the acquired pellicle forming on splint blocks compared to normal controls (p < 0.05). In particular, statherin, a calcium-binding protein, was 35% less abundant (p < 0.05). Calcium concentration within the acquired pellicle was also reduced by 50% in erosion patients (p < 0.001). In contrast, the natural pellicle on the incisor had similar amounts of total protein in erosion patients and healthy controls. In summary, the formation of new acquired pellicles on surfaces was reduced in erosion patients, which may explain their greater susceptibility to acid erosion of teeth.