Evaluation of a profilometrical method for monitoring erosive tooth wear

Impact of air-polishing with erythritol on exposed root dentin: A randomized clinical trial

INTRODUCTION

The effects of air-polishing on exposed root dentin surfaces are largely unknown, as there are only few studies which show heterogeneous results. Thus, this study was to investigate roughness changes of exposed dentin surfaces after air-polishing and the influence of subsequent polishing with cup and paste.

METHODS

Totally 54 teeth with exposed root dentin surfaces were treated using a split-mouth design by either air-polishing with erythritol and a rubber cup with polishing paste on the test side, or rubber cup and paste alone. Teeth were finally cleaned using a sonic tooth brush. Impressions were taken at relevant time points and replicated using epoxy resin. The resulting casts were profilometrically analysed to obtain the average surface roughness (sRa) and maximum peak-to-valley height (sRz), which are given as the mean ± standard deviation in μm.

RESULTS

After air-polishing, in comparison to the baseline, there was a slight but significant increase in sRa (0.168 ± 0.143, p < 0.001), but sRz did not change (-0.471 ± 4.857, p = 0.936). Subsequent polishing with cup and paste and cleaning with a sonic toothbrush did not reduce the surface roughness (sonic toothbrush-air-polishing, sRa -0.044 ± 0.081, p = 0.218; sRz -0.551 ± 3.563, p = 0.903).

CONCLUSION

The use of erythritol led to a slight increase in the roughness of the dentin surface, which was not reduced by polishing with a cup and paste. Polishing paste did not seem to conceal surface irregularities.

Effect of an experimental TiF4/NaF solution in preventing tooth erosion

OBJECTIVE

This was a randomized, double-blind, parallel, placebo-controlled in vivo study investigating the protective potential of a titanium tetrafluoride/ sodium fluoride (TiF4/NaF) solution compared to its respective positive and negative controls under an in vivo model, as well as the perception of participants regarding the use of this experimental solution.

METHODS

After the ethics approval and the selection procedures, 33 participants were divided into three treatments: TiF4/NaF solution (500 ppm F, pH 4.4); AmF/NaF/SnCl2-mouthwash (500 ppm F, pH 4.5) and water (pH 7.0) (n = 11). After professional cleaning, the participants rinsed with one of the solutions for one minute and waited two hours for the erosive challenge. The erosive solution (1 % citric acid, pH 2.5) was applied for 10 s on each central incisor (enamel area: 4 mm2) and collected for calcium analysis using III Arsenazo colorimetric method. The Ca2+ release data were compared using Kruskal-Wallis/ Dunn tests (p < 0.05).

RESULTS

Teeth treated with both fluoride solutions released less calcium into the acid (median and interquartile interval: TiF4/NaF - 0.45/0.19 mM and AmF/NaF/SnCl2 - 0.46/0.15 mM Ca2+, p = 0.99) compared to the negative control (1.12/0.42 mM Ca2+, 60 % reduction, p < 0.0006). For both F solutions, only one participant per group reported unpleasant taste. Four participants belonging to AmF/NaF/SnCl2-mouthwash reported burning sensation post-rinse, while only one participant described such feeling after TiF4/NaF rinsing.

CONCLUSION

The experimental TiF4/NaF solution was as effective as the commercial AmF/NaF/SnCl2-mouthwash in protecting enamel against erosive demineralization with a good acceptability by the participants.

Potential of different fluoride gels to prevent erosive tooth wear caused by gastroesophageal reflux

Background

This in-vitro-study aimed to evaluate the potential of different fluoride gels to prevent gastroesophageal reflux induced erosive tooth wear.

Methods

Surface baseline profiles of a total of 50 bovine enamel specimens [randomly assigned to five groups (G1–5)] were recorded. All specimens were positioned in a custom made artificial oral cavity and perfused with artificial saliva (0.5 ml/min). Reflux was simulated 11 times a day during 12 h by adding HCl (pH 3.0) for 30 s (flow rate 2 ml/min). During the remaining 12 h (overnight), specimens were stored in artificial saliva and brushed twice a day (morning and evening) with a toothbrush and toothpaste slurry (15 brushing strokes). While specimens in the control group (G1) did not receive any further treatment, specimens in G2–5 were coated with different fluoride gels [Elmex Gelée (G2); Paro Amin Fluor Gelée (G3); Paro Fluor Gelée Natriumfluorid (G4); Sensodyne ProSchmelz Fluorid Gelée (G5)] in the evening for 30 s. After 20 days, surface profiles were recorded again and enamel loss was determined by comparing them with the baseline profiles. The results were statistically analysed using one-way analysis of variance (ANOVA) followed by Tukey`s HSD post-hoc test.

Results

The overall highest mean wear of enamel (9.88 ± 1.73 µm) was observed in the control group (G1), where no fluoride gel was applied. It was significantly higher (p < 0.001) compared to all other groups. G2 (5.03 ± 1.43 µm), G3 (5.47 ± 0.63 µm, p = 0.918) and G4 (5.14 ± 0.82 µm, p > 0.999) showed the overall best protection from hydrochloric acid induced erosion. Enamel wear in G5 (6.64 ± 0.86 µm) was significantly higher compared to G2 (p = 0.028) and G4 (p = 0.047).

Conclusions

After 20 days of daily application, all investigated fluoride gels are able to significantly reduce gastroesophageal reflux induced loss of enamel.

Monitoring of Erosive Tooth Wear with Intraoral Scanners In vitro

Intraoral scanners (IOS) have been used to quantify tooth wear, but so far they have not been systematically validated for monitoring of tissue loss. The aim of this in vitro study was to investigate whether progression of tissue loss can be detected with an IOS and whether IOS values agree with those obtained with noncontacting profilometry (PRO) serving as a standard method. Model jaws were mounted in a phantom head positioned in a dental chair. Flattened areas were prepared on the non-load-bearing cusps of the first molars (model teeth; n = 16) in order to fix flat enamel samples with an experimental area and a reference area. After baseline PRO and IOS, the experimental enamel area was stepwise etched with 35% H3PO4 gel (4 × 30 s and 4 × 15 s). After each etching, PRO and IOS was performed and the vertical tissue loss between the reference and experimental areas was measured, each at the same 3 measurement points. Furthermore, cupped cusps were simulated by stepwise preparation of the load-bearing cusps of the model teeth with a spherical diamond bur, and the maximum vertical depth after each preparation step was measured only by IOS. Trios3 (3Shape, Denmark), Carestream CS3600 (Carestream, USA) and an optical profilometer (MicroProf, Fries, Germany) were used to measure the flat areas of the enamel samples, whereas only IOS were used to measure curved surfaces on the load-bearing cupped cusps of the model teeth. The IOS data were analyzed with an external software (GOM Inspect, Germany) and with the respective internal IOS software. PRO revealed a mean (±SD) tissue loss of 17.1 ± 4.7 µm after 30-s etching steps and 10.1 ± 5.1 µm after the 15-s etching steps. IOS and software types were able to detect the progression of tissue loss after each etching step (p ≤ 0.001 each); Bland-Altmann plots revealed good agreement with PRO regardless of the order of tissue loss, and no systematic difference was found. Increasing cupped lesion depths were detected by all IOS, with no significant differences between IOS and analysis methods. IOS were able to detect small amounts of tissue loss under simulated clinical conditions and seem to be a promising tool for monitoring even initial erosive tooth wear.

Novel methodology for measuring intraoral wear in enamel and dental restorative materials

Objectives

To test the hypotheses that (a) the chairside/handheld dental scanner combined with a metrology software will measure clinical wear in vivo in agreement with measurements from X‐ray computed microtomography and; (b) polished monolithic zirconia does not cause accelerated wear of opposing enamel.

Materials and methods

Thirty single crowns were randomized to receive a monolithic zirconia or metal‐ceramic crown. Two non‐restored opposing teeth in the same quadrants were identified to serve as enamel controls. After cementation, quadrants were scanned using an intraoral dental scanner. Patients were recalled at 6‐months and 1‐year for re‐scanning. Scanned images were compared using a metrology software to determine maximum vertical wear of teeth. The accuracy of the scanning measurements from this new method was compared with X‐ray computed microtomography (micro‐CT) measurements. Statistical analysis was performed using Mann–Whitney U test to determine significant differences between wear of enamel against zirconia, metal‐ceramic or enamel. Linear regression analysis determined agreement between measurements obtained using intraoral scanning and micro‐CT.

Results

Regression analysis demonstrated that there is a quantitative agreement between depth and volume measurements produced using intraoral scanning and the micro‐CT methodologies. There was no significant difference between the wear of enamel against polished monolithic zirconia crowns and enamel against enamel.

Conclusions

Intraoral scanning combined with a matching software can accurately quantify clinical wear to verify that monolithic zirconia exhibited comparable wear of enamel compared with metal‐ceramic crowns and control enamel. Agreement between the intraoral scanner and the micro‐CT was 99.8%. Clinical Trials.gov NCT02289781.

Analytical strategies for clinical studies on dental erosive wear

BACKGROUND

There is a need for analytical techniques for measuring Erosive Tooth Wear (ETW) on natural surfaces in clinical studies. The purpose was to investigate the use of two instruments aimed to assess initial to more advanced stages of ETW.

METHODS

Human premolar enamel samples (2x3mm) (n = 24), were polished flat and mounted in resin cylinders (4 cylinders, 6 samples in each). Part 1: Baseline analyses by White Light Interferometer (WLI), Surface Reflection Intensity (SRI: TableTop and OptiPen) and Surface Hardness (SH). Erosion (1% citric acid (pH 3.6) for 1, 2, 4, 6, 8, 10 min. SRI and SH analyses after every erosion episode and by WLI after 10 min. New indentations were made and enamel loss; was measured by change in indentation depths from toothbrush abrasion (200 g, 60 strokes, 30 s). Another series of 2 × 5 min erosion (totally15 min and 20 min) was analysed with SH and SRI after each erosion, and by WLI (on samples and impressions of samples) after 20 min. Part 2 investigated WLI performance in the interface where initial erosion increases in severity and substance loss occurs. The samples were repolished. Baseline analyses by WLI, SRI (TableTop and OptiPen) and SH. Four cylinders were etched for 1, 2, 4, 8 min respectively and analysed by SRI, SH on samples, and WLI on samples and impressions).

RESULTS

Part1: SRI decreased from baseline to ~ 6 min etch and increased slightly after abrasion, the two devices correlated well (ICC 0.98 p < 0.001, Spearmans rs 0.91 p < 0.001). SH decreased nearly linearly to 10 min etch, but increased distinctly after abrasion. Mean enamel loss from abrasion alone was 0.2 μm (change in indentation depths). After 10 min etch, it was 0.27 μm (WLI) and after 20 min etch, it was 2.2 μm measured on samples vs 2.4 μm on impressions of samples (7% higher). Part 2: From baseline to 8 min etch; SRI and SH decreased whereas WLI presented increasing etch depths.

CONCLUSIONS

With some adjustments, the use of SRI and WLI in combination seems to be a promising strategy for monitoring ETW in clinical studies.

The sensitivity of digital intraoral scanners at measuring early erosive wear

OBJECTIVES

To investigate the sensitivity of intraoral scanners to quantitatively detect early erosive tooth wear.

METHODS

Natural buccal enamel samples were mounted in acrylic and scanned at baseline with an intraoral scanner (3 M True Definition Scanner, 3 M, USA). Samples were then exposed to 0.3% citric acid pH 3.2 at intervals of 10 min up to a total of 120 min and scanned after each exposure resulting in analysis of 13 datapoints per sample. Each scan was aligned with the baseline and data points super-imposed using an iterative closest point (ICP) algorithm on the acrylic surfaces (Geomagic Control Software, 3Dsystems, Darmstadt, Germany). Wear was measured using maximum profile loss, average profile loss and volume change. Data were normally distributed and Pearson correlations between erosion time and wear measurements assessed.

RESULTS

After each 10-minute exposure until 120 min, maximum profile loss (μm) increased from 33.4 to 72.8 μm, average profile loss from 9.1 to 18.6 μm. Wear correlated with increasing acid exposure for both maximum profile loss wear (r = 0.877 p < 0.001) and average profile loss (r = 0.663 p = 0.019) respectively. Volume measurements were inconsistent at this level of wear.

CONCLUSIONS

Using scan data obtained from the intra oral scanners (IOS), increasing step height changes were observed with increasing exposures to acid. This study indicates there is potential of scans taken with an IOS to be used to detect early erosive tooth wear. However, precision was low suggesting limitations for minimal changes.

CLINICAL SIGNIFICANCE

Although sub-visual wear was detected by intra-oral scanners on natural enamel surfaces, the accuracy was not sufficient to reliably diagnose that wear had occurred and interpretation of measurements should be done with caution. However, these results may be promising for detecting wear at more advanced stages.

Wear measurement of dental tissues and materials in clinical studies: A systematic review

OBJECTIVES

This study aims to systematically review the different methods used for wear measurement of dental tissues and materials in clinical studies, their relevance and reliability in terms of accuracy and precision, and the performance of the different steps of the workflow taken independently.

METHODS

An exhaustive search of clinical studies related to wear of dental tissues and materials reporting a quantitative measurement method was conducted. MedLine, Embase, Scopus, Cochrane Library and Web of Science databases were used. Prospective studies, pilot studies and case series (>10 patients), as long as they contained a description of wear measurement methodology. Only studies published after 1995 were considered.

RESULTS

After duplicates' removal, 495 studies were identified, and 41 remained for quantitative analysis. Thirty-four described wear-measurement protocols, using digital profilometry and superimposition, whereas 7 used alternative protocols. A specific form was designed to analyze the risk of bias. The methods were described in terms of material analyzed; study design; device used for surface acquisition; matching software details and settings; type of analysis (vertical height-loss measurement vs volume loss measurement); type of area investigated (entire occlusal area or selective areas); and results.

SINIFICANCE

There is a need of standardization of clinical wear measurement. Current methods exhibit accuracy, which is not sufficient to monitor wear of restorative materials and tooth tissues. Their performance could be improved, notably limiting the use of replicas, using standardized calibration procedures and positive controls, optimizing the settings of scanners and matching softwares, and taking into account unusable data.

Accuracy and reproducibility of 3D digital tooth preparations made by gypsum materials of various colors

PURPOSE

The study aimed to identify the accuracy and reproducibility of preparations made by gypsum materials of various colors using quantitative and semi-quantitative three-dimensional (3D) approach.

MATERIALS AND METHODS

A titanium maxillary first molar preparation was created as reference dataset (REF). Silicone impressions were duplicated from REF and randomized into 6 groups (n=8). Gypsum preparations were formed and grouped according to the color of gypsum materials, and light-scanned to obtain prepared datasets (PRE). Then, in terms of accuracy, PRE were superimposed on REF using the best-fit-algorithm and PRE underwent intragroup pairwise best-fit alignment for assessing reproducibility. Root mean square deviation (RMSD) and degrees of similarity (DS) were computed and analyzed with SPSS 20.0 statistical software (α=.05).

RESULTS

In terms of accuracy, PREs in 3D directions were increased in the 6 color groups (from 19.38 to 20.88 µm), of which the marginal and internal variations ranged 51.36 - 58.26 µm and 18.33 - 20.04 µm, respectively. On the other hand, RMSD value and DS-scores did not show significant differences among groups. Regarding reproducibility, both RMSD and DS-scores showed statistically significant differences among groups, while RMSD values of the 6 color groups were less than 5 µm, of which blue color group was the smallest (3.27 ± 0.24 µm) and white color group was the largest (4.24 ± 0.36 µm). These results were consistent with the DS data.

CONCLUSION

The 3D volume of the PREs was predisposed towards an increase during digitalization, which was unaffected by gypsum color. Furthermore, the reproducibility of digitalizing scanning differed negligibly among different gypsum colors, especially in comparison to clinically observed discrepancies.

Dental wear estimation using a digital intra-oral optical scanner and an automated 3D computer vision method

The objective of this work was to propose an automated and direct process to grade tooth wear intra-orally. Eight extracted teeth were etched with acid for different times to produce wear and scanned with an intra-oral optical scanner. Computer vision algorithms were used for alignment and comparison among models. Wear volume was estimated and visual scoring was achieved to determine reliability. Results demonstrated that it is possible to directly detect submillimeter differences in teeth surfaces with an automated method with results similar to those obtained by direct visual inspection. The investigated method proved to be reliable for comparison of measurements over time.

Enamel erosion depths measured on impressions by a white light interferometer

OBJECTIVE

To investigate if measurements of the step heights on an impression of eroded enamel surfaces may give reliable values of the etching depths measured directly on the enamel.

MATERIALS AND METHODS

Twelve human enamel specimens, with one circular amalgam reference surface in each, were mounted on an epoxy block and ground flat. Baseline images were taken by a White Light Interferometer (WLI) followed by 12 min etch by 0.01 M HCl, pH 2.2. The mean etch depth on each specimen was calculated from three repeated measurements, both on the specimen surfaces and on the silicone polymer impressions of the surfaces. Paired samples t-test was used when comparing the precision of measurements on enamel vs on impression.

RESULTS

The mean lesion depths after 12 min etch measured on the 12 enamel surfaces and impressions were 9.9 µm and 10.6 µm, respectively. The direct and indirect measurements correlated well (r(2) = 0.95), with 7% higher mean etch depth measured on the impressions (p < 0.05). The reliability of three repeated measurements on enamel and impressions expressed by Intra Class Correlation (ICC) were 0.98 and 0.99, respectively. The average relative precisions of three repeated measurements on the 12 tooth and impression surfaces were (0.5 ± 0.1)% and (0.1 ± 0.02)%, respectively (p < 0.05). The accuracies were 0.4% and 7%, respectively.

CONCLUSION

WLI gave reliable but slightly higher etch depth measurements on impressions compared to enamel surfaces.

Clinical studies of dental erosion and erosive wear

We define erosion as a partial demineralisation of enamel or dentine by intrinsic or extrinsic acids and erosive tooth wear as the accelerated loss of dental hard tissue through the combined effect of erosion and mechanical wear (abrasion and attrition) on the tooth surface. Most experts believe that during the last decade there has been a significant increase in the prevalence and severity of erosive tooth wear, particularly in adolescents. Even when erosive wear occurs in its milder forms, this is a matter of concern, as it may compromise the integrity of an otherwise healthy dentition in later life. The erosive wear process is complicated and modified by many chemical, behavioural and associated processes in the mouth. If interventions are to be developed it is therefore important that in vivo methods are developed to assess the outcomes of the erosion and erosive wear processes and the effects of interventions upon them. This paper discusses potential methods of investigating erosion and erosive wear in vivo and the difficulties associated with clinical studies.

Erosion--diagnosis and risk factors

Dental erosion is a multifactorial condition: The interplay of chemical, biological and behavioural factors is crucial and helps explain why some individuals exhibit more erosion than others. The erosive potential of erosive agents like acidic drinks or foodstuffs depends on chemical factors, e.g. pH, titratable acidity, mineral content, clearance on tooth surface and on its calcium-chelation properties. Biological factors such as saliva, acquired pellicle, tooth structure and positioning in relation to soft tissues and tongue are related to the pathogenesis of dental erosion. Furthermore, behavioural factors like eating and drinking habits, regular exercise with dehydration and decrease of salivary flow, excessive oral hygiene and, on the other side, an unhealthy lifestyle, e.g. chronic alcoholism, are predisposing factors for dental erosion. There is some evidence that dental erosion is growing steadily. To prevent further progression, it is important to detect this condition as early as possible. Dentists have to know the clinical appearance and possible signs of progression of erosive lesions and their causes such that adequate preventive and, if necessary, therapeutic measures can be initiated. The clinical examination has to be done systematically, and a comprehensive case history should be undertaken such that all risk factors will be revealed.