Dentists' restorative decision-making and implications for an 'amalgamless' profession. Part 5: knowledge factors.

BACKGROUND: A phase-down of amalgam in Australia is possible given the Australian Government intends to ratify the Minamata Convention. There is little research as to the influence of a dentist's knowledge on decision-making, which may be of use when determining the impact of any change. METHODS: An online survey relating to aspects of and attitudes to use of direct restorative materials was distributed to all dentists who were members of the Australian Dental Association or Members or Fellows of the Royal Australasian College of Dental Surgeons. RESULTS: There were 408 respondents. Fifty-eight per cent agreed that there was consistency in undergraduate teaching. Fifty-two per cent stated that there was a difference between undergraduate teaching and the 'real world'. Postgraduate education was ranked the most important influence on decision-making. Ninety-six per cent stated that knowledge of the evidence base is important and 89% believed that they practised evidence-based dentistry. CONCLUSIONS: Dental schools need to maintain teachers' and students' understanding of the evolving technology of direct restorative materials. There is a perceived disconnect between undergraduate teaching and the 'real' world. The evidence base is viewed as confusing, contradictory and not readily understandable. The creation of clinical guidelines would be useful.

Dentists' restorative decision-making and implications for an 'amalgamless' profession. Part 4: clinical factor.

BACKGROUND: The Minamata Convention embodies a worldwide reduction in the production and use of mercury and mercury-containing products and processes, including a phase-down of dental amalgam. This will change the approach to the use of direct restorative materials in the near future. There is little research as to the influence of clinical factors on dentists' decision-making which may be of use when determining the impact of any change. METHODS: An online survey relating to aspects of and attitudes to the use of direct restorative materials was distributed to all dentists who were members of the Australian Dental Association and/or members or fellows of the Royal Australasian College of Dental Surgeons. Data were statistically analysed. RESULTS: There were 408 respondents to the survey. Eighty-seven per cent of respondents (strongly) disagreed that amalgam was a technically more difficult material to place compared with resin composite, 82% (strongly) disagreed that placement time for amalgam was longer than that for resin composite and 69% (strongly) disagreed that amalgam was more difficult to finish than resin composite. Eighty-three per cent of respondents stated they were confident in their ability to place amalgam restorations. Where physical properties were of importance, indirect restorations were preferred (e.g. parafunction) 54%. The factors considered most important when choosing a direct restorative material included moisture control and aesthetics; least important factors were cost and time to place. CONCLUSIONS: There is consensus that amalgam is not more technically difficult to use, place or finish than resin composite and vice versa. There is recognition that both amalgam and resin composite have limitations in terms of physical properties. When choosing a direct restorative material, clinical factors considered to be of greatest importance are moisture control, aesthetics and the need to apply minimally invasive approaches. There is little difference in the opinions of users and non-users of amalgam with respect to these findings.

Dentists' restorative decision-making and implications for an 'amalgamless' profession. Part 3: Dentists' attitudes.

BACKGROUND: The Minamata Convention has agreed to a worldwide reduction in the production and use of mercury-containing products and processes. This will change the approach to use of direct restorative materials in the future. There is little research exploring the attitudes of dentists to any change. METHODS: A survey relating to the use of direct restorative materials was distributed to dentists who were members of the Australian Dental Association or Members and Fellows of the Royal Australasian College of Dental Surgeons. Data were statistically analysed. RESULTS: There were 408 respondents. Responses to statements concerning attitudes toward a phase-down of amalgam depended on whether the respondent used amalgam, year of primary dental qualification and association with academia. Thirty per cent of respondents indicated they do not use amalgam. The mean use of amalgam for all direct restorative procedures was 18%. CONCLUSIONS: Dentists are concerned over potential implications of a phase-down of amalgam and much should be done to address these concerns. Many dentists are undecided as to what are the implications, which may reflect a lack of understanding of the issues. It is incumbent on policy-makers to produce and disseminate information relating to the issues identified by this research.

Dentists' restorative decision-making and implications for an 'amalgamless' profession. Part 1: a review.

The Minamata Convention has agreed to a worldwide reduction and ultimate elimination in the production and use of mercury containing products. This will have implications for the practice of dentistry. Australian organizations' pronouncements on the issue are limited and research examining the Australian context dated. The restoration of teeth with direct materials has changed significantly since the 1980s. Up to this time amalgam was the material of choice for direct posterior restorations. Its properties and guidelines for placement were, and remain, well established. Resin composite has replaced amalgam as the material of choice in many clinical situations. Despite inherent clinical disadvantages compared to amalgam, there continues to be a shift toward greater use of resin composite. There is consensus worldwide that the restoration of posterior teeth using resin composite now exceeds that of amalgam. The reasons for this are reviewed in this article along with current evidence and commentary relating to direct restorative and evidence-based decision-making, minimally invasive approaches, and approaches to education. The implications for these in an 'amalgamless' profession are identified.

Dentists' restorative decision-making and implications for an 'amalgamless' profession. Part 2: a qualitative study.

In some countries the use of amalgam has been restricted, and the dental profession may be forced into using alternatives to amalgam by a combination of public opinion and legislation, including the proposal that the material be 'phased-down'. The limited research that exists as to restorative decision-making is quantitative in nature and focuses on 'when' a restoration is placed. There is little qualitative research exploring 'why' a material is chosen. Purposive sampling of a representative group of dentists registered in Australia was carried out in two phases; initially six interviews followed by a focus group of six different participants who were audio-recorded. Qualitative data were analysed using computer aided qualitative data analysis software. The findings suggest that dentists' restorative decision-making is a complex interplay of factors. These may be categorized as 'clinical', 'knowledge', 'patient', 'practice type', 'biological' and 'environmental'. Use of amalgam is influenced by each of these to varying degrees. Quantitative analysis of the influences on restorative decision-making is recommended. While the potential future 'phase-down' of amalgam as a restorative material was of concern, there was a general sense of resignation or apathy to the matter. The implications for public health authorities, dental organizations and educators are noted.

Clinical investigation of G-Bond resin-based adhesive to non-carious cervical lesions over five years.

BACKGROUND: The aim of this study was to evaluate the clinical performance of G-Bond all-in-one adhesive with Gradia Direct resin composite placed in non-carious cervical lesions (NCCLs) over a five-year period. METHODS: Forty-seven restorations were placed in NCCLs in 10 subjects (age 45-75 years) after written informed consent was obtained. Institutional ethical approval for the trial was obtained before recruitment. Restorations were placed according to the manufacturer's instructions and using 50% phosphoric acid to etch uncut enamel margins. Patients were recalled annually for five years and restorations reviewed for presence and marginal staining. Photographic records were obtained prior to restoration, immediately after placement and at each recall. RESULTS: At five years, 6 of the original 10 subjects were available for recall, meaning 27 restoration sites could be evaluated. All restorations remained intact apart for one partial failure at four years. This resulted in a cumulative retention rate of 97.5% of restorations at five years. Marginal staining occurred around seven restorations during the study. Staining tended to be isolated to a few patients. CONCLUSIONS: It was concluded that G-Bond with Gradia Direct resin composite showed excellent results over the five years of the study. This material combination seems very suitable for the restoration of NCCLs.

Relationship between composite fracture toughness and bond strengths to enamel and dentine.

BACKGROUND: This study aimed to evaluate the association between the fracture toughness of two nanofilled-hybrid resin composites (Clearfil Majesty Esthetic [CME], Kuraray Medical, Japan; Estelite Σ [ES], Tokuyama, Japan) and their bond strengths to enamel and dentine mediated by a self-etching primer system (Clearfil SE Bond [CSE]; Kuraray). METHODS: Twenty-four permanent human molars were sectioned into enamel and dentine specimens and finished with 600-grit silicon carbide paper, bonded with CSE and either CME or ES, for µ-shear bond strength (µSBS) and µ-tensile bond strength (µTBS). The specimens were tested until failure at a cross-head speed of 1 mm/min, failure loads recorded, bond strengths calculated and results analysed using independent samples t-tests. Eight single-notched bar-shaped specimens, 30 mm × 5.2 mm × 2.2 mm, were prepared for each resin composite and fracture toughness measured using four-point bending at a cross-head speed of 0.5 mm/min. Results were analysed using independent samples t-tests. RESULTS: For µSBS and µTBS, there was no significant difference between the resin composites for enamel or dentine. The fracture toughness of CME was significantly higher than that of ES. CONCLUSIONS: For both enamel and dentine, resin composite fracture toughness affected neither µTBS nor µSBS to enamel or dentine.

Effect of tooth surface preparation on the bonding of self-etching primer adhesives.

The aim of this study was to determine the bonding effectiveness of four self-etching primer adhesives after various tooth preparation protocols. Enamel/dentin specimens were prepared from 84 permanent molars, divided into three enamel preparation groups (silicon carbide paper [SiC1; erbium, chromium:yttri-um, scandium, gallium, garnet [Er,Cr:YSGG] laser [EL] and diamond bur [DB]) and five dentin preparation groups (SiC, EL, DB, steel[SB], and ceramic burs [CBs]). In each group,specimens were equally divided into four sub-groups and were bonded using Clearfil SEBond (CSE, Kuraray), Xeno IV (XE, Dentsply),Tokuyama Bond Force (TK, Tokuyama) and Filtek Silorane System Adhesive (FS, 3MESPE), as well as a hybrid resin composite(Clearfil Majesty Esthetic, Kuraray) for CSE,XE, and TK, and Filtek Posterior Restorative(3M ESPE) for FS). After 24 hours of water storage at 370C, microshear bond strength(iSBS) testing was carried out. Data were analyzed using analysis of variance (ANOVA)-Tukey test at a=0.05 and bond failure modes assessed. Representative debonded specimens were prepared and examined under the scanning electron microscope (SEM). All adhesives exhibited no significant differences in 1SBS on enamel and dentin under the clinical cavity preparation protocols, except for TK on den-tin. SEM revealed areas of altered subsurface enamel/dentin following EL ablation.

Resin-dentine interfacial morphology following CPP-ACP treatment.

OBJECTIVES: To evaluate the quality of bonded resin-dentine interfaces produced by two self-etching primer adhesives after casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) treatment, in comparison to untreated dentine. METHODS: Thirty-four adult molar teeth were sectioned to obtain dentine with tubule orientations parallel/oblique or perpendicular to the surface. The specimens were divided into 'smear layer' (1A, 1B) and 'no smear layer' groups, after treatment with 15% EDTA (2A, 2B). The specimens were then left either untreated (1A, 2A) or treated (1B, 2B) with CPP-ACP paste (Tooth Mousse, GC Corp.) for 60 min x 7 days. Each treatment group was divided into three subgroups and specimens etched/conditioned (no conditioning; 30-40% phosphoric acid (H(3)PO(4)); 20% polyacrylic acid) and bonded with either a 2-step self-etching primer adhesive (Clearfil SE Bond, Kuraray Medical) or an 'all-in-one' adhesive (G-Bond, GC Corp.) and a hybrid resin composite. After 24-h water storage, the bonded specimens were sectioned, polished up to 4000-grit abrasive silicon carbide paper and 0.25-microm diamond paste, prepared for FE-SEM using the acid-base technique, critical point-dried, gold-coated and examined. Bonded and fractured dentine interfaces were also prepared and examined. RESULTS: The 2-step adhesive produced a similar appearance of bonded resin-dentine interface irrespective of smear layer group, treatment or etching/conditioning. After polyacrylic acid conditioning, the 'all-in-one' adhesive exhibited more areas with bond failures. The bond failures were within the hybrid layer and more pronounced following CPP-ACP treatment. CONCLUSION: The quality of the bonded resin-dentine interface produced after CPP-ACP treatment may depend on the adhesive system used.

An SEM evaluation of conditioned and bonded enamel following carbamide peroxide bleaching and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) treatment.

OBJECTIVES: The study aimed to evaluate, (a) the surface morphology of acid etched/conditioned enamel following carbamide peroxide bleaching with/without casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) (Tooth Mousse (MI Paste); GC Corp., Tokyo, Japan) treatment; and b) the nature of the bonded resin-enamel interfaces formed with a self-etching primer adhesive. METHODS: Twenty-four human adult molars were each sectioned into four, the specimens divided and treated according to four experimental groups: 1, no treatment; 2, 16% carbamide peroxide bleaching; 3, CPP-ACP paste; 4, bleaching and CPP-ACP paste. A self-etching primer adhesive (Clearfil SE Bond, CSE) was used. The specimens were further divided into four subgroups for etching/conditioning: A, CSE Primer only; B, 30-40% phosphoric acid and CSE primer; C, 15% EDTA and CSE primer; D, 20% polyacrylic acid and CSE primer. Bonded specimens were also prepared. The morphology of the etched/conditioned enamel surfaces and polished resin-enamel interfaces of the bonded specimens were observed by field-emission scanning electron microscopy (FE-SEM). RESULTS: Treatment with CPP-ACP did not inhibit phosphoric acid etching of enamel. Poorly defined enamel etch patterns were observed with the other conditioners in all the groups. The morphology of the bonded resin-enamel interfaces observed on FE-SEM for each acid etching/conditioning subgroup was similar in all the experimental groups, except after bleaching. Resin infiltration into enamel was observed with prior phosphoric acid etching and polyacrylic acid conditioning and was unaffected by experimental group treatments. CONCLUSIONS: The use of a CPP-ACP paste with or without prior bleaching did not inhibit enamel etching. Enamel etching/conditioning may help improve bonding efficiency of the self-etching primer adhesive after CPP-ACP treatment.

Mapping a non-carious cervical lesion using stereoimagery and dental casts incorporating optical texture.

OBJECTIVES: Recent advances in digital photogrammetry have enabled a new approach to high resolution mapping of tooth surfaces. The aim of this study was to assess the accuracy and the precision of a new system using automatic digital stereo-photogrammetry combined with an experimental casting material and to measure tooth surface loss in a non-carious cervical lesion. METHODS: A test object and tooth replicas incorporating optical texture obtained at baseline, one and 2 years were imaged with a pre-calibrated stereocamera. The stereoimagery was then processed with digital photogrammetric software to automatically generate digital surface models. Test object models were analysed for accuracy and precision and tooth surface models were aligned with point cloud analysis software and tooth surface loss determined. RESULTS: Replicas were mapped to an accuracy of (6+/-13)microm. The sensitivity of change detection on tooth replicas was 40 microm with change ranging from 40 to 70 microm per annum in a discrete part of the lesion. CONCLUSIONS: In the case examined, the change detection data were of sufficient accuracy and resolution to draw meaningful conclusions about the spatial distribution and quantum of tooth hard tissue loss. The results of this investigation suggest that annual change detection studies will provide a clearer picture of the pattern of tooth surface loss and, in combination with other analytical techniques, a more detailed explanation of the natural history of these lesions.

Dentine bonding after CPP-ACP paste treatment with and without conditioning.

OBJECTIVES: To evaluate microshear bond strength (MSBS) to dentine following application of a casein phosphopeptide amorphous calcium phosphate paste (Tooth Mousse (TM)), and the effect of smear layer removal before paste application and preconditioning. METHODS: Specimens of polished human dentine were divided into two groups: 1, smear layer retained; 2, smear layer removed using 15% EDTA for 90 s. In each group, half the specimens were left untreated and half treated with TM for 60 min daily x 7 days. Each subgroup was divided into three further subgroups for conditioning (Primer only; 30-40% phosphoric acid (PA)+primer; 20% polyacrylic acid (CC)+primer). Two self-etching/priming adhesives (Clearfil SE Bond (CSE) and G-Bond (GB)) were used for bonding resin composite to superficial/deep dentine and after 24h, stressed in shear until failure. Maximum loads at failure and bond failure modes were recorded. Group means were compared using one-way ANOVA and Tukey's post hoc test at alpha=0.05. RESULTS: TM did not significantly affect MSBS in group 1. In group 2, there was a statistically significant increase in MSBS for CSE on deep dentine (P=0.002) and a reduction for GB (P=0.013) on superficial dentine. PA conditioning did not significantly affect MSBS for CSE and GB while CC significantly reduced MSBS for GB. CONCLUSIONS: TM application did not reduce MSBS for CSE but significantly reduced MSBS for GB when the smear layer was removed before paste treatment. Preconditioning did not improve or worsen dentine MSBS for CSE or GB with/without TM, except when CC was used with GB.

A clinical trial comparing two all-in-one adhesive systems used to restore non-carious cervical lesions: results at one year.

BACKGROUND: Few data exist with respect to the clinical performance of all-in-one adhesive systems. However, their clinical use is increasing. The aim of this study was to evaluate the retention and marginal staining of resin composite restorations bonded with Clearfil S(3) Bond or G-Bond all-in-one systems placed in non-carious cervical lesions. MATERIALS AND METHODS: Sixty restorations were placed in 11 subjects, mean age 62.5 years. Approval for the clinical trial was obtained from the Human Ethics Committee of The University of Melbourne. Restorations were bonded and placed according to the manufacturers' instructions. No enamel etching was performed on the enamel margins prior to restoration placement. Patients were recalled at six months, and one year for evaluation of presence and marginal staining. Photographic records were obtained prior to restoration, immediately after and at recall. RESULTS: All patients could be recalled. All restorations were present at both recall periods. A 100 per cent retention rate was obtained. Slight marginal staining was observed on four restorations for S(3) and three restorations for G-Bond. CONCLUSIONS: The early results of this clinical evaluation showed good outcomes for both materials.

Bond strength test: role of operator skill.

BACKGROUND: Test method, substrate material and operator variability are factors known to affect bond strength test outcomes. The aim of this study was to determine if, with increasing experience, individual operator skill in material handling influenced microshear bond strength outcomes. METHODS: This retrospective study used data collected from six preliminary tests carried out successively on enamel microshear bond strength for two adhesives: Clearfil SE Bond (Kuraray) and Adper Single Bond 2 (3M ESPE) by one operator. Mean and median microshear bond strength values, standard deviations and coefficients of variation for each adhesive test group were calculated and assessed. RESULTS: A gradual increase in mean microshear bond strengths, a decrease in standard deviations and coefficients of variation over time for both adhesives and a progressively more uniform distribution of microshear bond strength results recorded in individual test sets was observed. The results suggest an improvement in bonding reliability as experience is gained. CONCLUSIONS: Operator skill in material handling appears to play a critical role in determining the outcome of bond strength testing. This same skill is probably relevant when using an adhesive for the first time clinically. It is important that clinicians become familiar with new adhesives in order to achieve optimal outcomes.

Local adverse effects of amalgam restorations.

Amalgam has been used for the restoration of teeth for well over 100 years, and is the most successful of the direct restorative materials with respect to longevity. Despite the increasing use of tooth-coloured materials, with advantages of aesthetics and adhesion, amalgam is one of the most widely used dental restorative materials. One of the principal disadvantages of amalgam, apart from aesthetics, is that it may have adverse biological effects, both locally and systemically. Locally, it can cause an erythematous lesion on the adjacent oral soft tissues (tongue and buccal mucosa), and systemically free mercury in the amalgam may give rise to a hypersensitivity reaction. The purpose of this paper is to review the literature concerning the local adverse reactions to dental amalgam. The focus will be on the reactions of the oral mucosa, and brief consideration will be given to laboratory cytotoxicity of dental amalgam and its components, and to the 'amalgam tattoo'.

Effects of conditioners on microshear bond strength to enamel after carbamide peroxide bleaching and/or casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) treatment.

OBJECTIVES: To evaluate (a) the enamel microshear bond strength (MSBS) of a universal adhesive and (b) the effects of conditioning with a self-etching primer adhesive with/without prior bleaching and/or casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) application. METHODS: Thirty-five molars were cut into four sections, assigned randomly to four groups (no treatment; 16% carbamide peroxide bleaching; CPP-ACP-containing paste (Tooth Mousse, TM); bleaching and TM) and treated accordingly. Specimens were divided into two for bonding with either a self-etching primer (Clearfil SE Bond, CSE) or a total-etch adhesive (Single Bond, SB). Specimens for CSE bonding were subdivided for one of four preconditioning treatments (no conditioning; 30-40% phosphoric acid (PA); 15% EDTA; 20% polyacrylic acid conditioner (Cavity conditioner, CC) and treated. The adhesives were applied and resin composite bonded to the enamel using microtubes (internal diameter 0.75mm). Bonds were stressed in shear until failure, mean MSBS calculated and data analysed using ANOVA with Tukey's HSD test (alpha=0.05). The modes of bond failure were assessed and classified. RESULTS: Two-way ANOVA revealed significant differences between treatments (P<0.0001), conditioners (P<0.0001) and a significant interaction between treatments and conditioners (P=0.001). One-way ANOVA revealed no significant differences in MSBS following any of the treatments for SB; following TM application for CSE without preconditioning; and significant differences in MSBS following bleaching with and without TM application for CSE. With preconditioning, applying PA before CSE post-bleaching and either PA or CC before CSE post-TM application, resulted in significant differences in MSBS (P<0.05). CONCLUSIONS: The use of conditioners prior to bonding with the self-etching primer adhesive system on treated enamel may significantly improve bond strengths.

Surface characteristics of aesthetic restorative materials - an SEM study.

To determine the degree of surface roughness of glass-ionomer cements (GICs) and polyacid-modified resin composite (PAMRC) after polishing and immersion in various foodstuffs. Three tooth-coloured restorative materials were used: a PAMRC (F2000), a conventional glass-ionomer cement (CGIC) (Fuji IX) and a resin-modified glass-ionomer cements (RM-GIC) (Fuji II LC). Disk-shaped specimens were prepared and tested with either a plastics matrix finish or after polishing with wet silicon carbide papers up to 2000-grit. All specimens were immersed in 37 degrees C-distilled water for 1 week, followed by three different foodstuffs (red wine, coffee or tea) for a further 2 weeks. Replicas of specimens were prepared by taking polyvinyl siloxane impressions, casting in epoxy resin, gold sputter-coating and examining using a Field-Emission Scanning Electron Microscope. The polished and matrix finish specimens of F2000 showed many microcracks at low magnification, and eroded surfaces with missing and protruding particles at high magnification in the polished specimens. The surface-polished specimens of Fuji II LC were considerably rougher than the matrix-finish specimens, with large voids and protruding filler particles. The effects of foodstuffs on Fuji II LC and F2000 were not noticeable. The CGIC became noticeably rougher after exposure to coffee and tea. All specimens had the smoothest surface when they were cured against a plastics matrix strip, and all materials had a rougher surface after polishing. None of the foodstuffs produced a perceptible increase in roughness on RM-GIC and PAMRC surfaces, whereas coffee and tea markedly increased the surface roughness of Fuji IX.

Recommendations for conducting controlled clinical studies of dental restorative materials.

About 35 years ago, Ryge provided a practical approach to evaluation of clinical performance of restorative materials. This systematic approach was soon universally accepted. While that methodology has served us well, a large number of scientific methodologies and more detailed questions have arisen that require more rigor. Current restorative materials have vastly improved clinical performance and any changes over time are not easily detected by the limited sensitivity of the Ryge criteria in short term clinical investigations. However, the clinical evaluation of restorations not only involves the restorative material per se but also different operative techniques. For instance, a composite resin may show good longevity data when applied in conventional cavities but not in modified operative approaches. Insensitivity, combined with the continually evolving and non-standard investigator modifications of the categories, scales, and reporting methods, has created a body of literature that is extremely difficult to meaningfully interpret. In many cases, the insensitivity of the original Ryge methods is misinterpreted as good clinical performance. While there are many good features of the original system, it is now time to move to a more contemporary one. The current review approaches this challenge in two ways: (1) a proposal for a modern clinical testing protocol for controlled clinical trials, and (2) an in-depth discussion of relevant clinical evaluation parameters, providing 84 references that are primarily related to issues or problems for clinical research trials. Together, these two parts offer a standard for the clinical testing of restorative materials/procedures and provide significant guidance for research teams in the design and conduct of contemporary clinical trials. Part 1 of the review considers the recruitment of subjects, restorations per subject, clinical events, validity versus bias, legal and regulatory aspects, rationales for clinical trial designs, guidelines for design, randomization, number of subjects, characteristics of participants, clinical assessment, standards and calibration, categories for assessment, criteria for evaluation, and supplemental documentation. Part 2 of the review considers categories of assessment for esthetic evaluation, functional assessment, biological responses to restorative materials, and statistical analysis of results. The overall review represents a considerable effort to include a range of clinical research interests over the past years. As part of the recognition of the importance of these suggestions, the review is being published simultaneously in identical form in both the "Journal of Adhesive Dentistry" and the "Clinical Oral Investigations." Additionally an extended abstract will be published in the "International Dental Journal" giving a link to the web full version. This should help to introduce these considerations more quickly to the scientific community.