Cleaning lateral morphological features of the root canal: the role of streaming and cavitation.

AIM: To investigate the effects of ultrasonic activation file type, lateral canal location and irrigant on the removal of a biofilm-mimicking hydrogel from a fabricated lateral canal. Additionally, the amount of cavitation and streaming was quantified for these parameters. METHODOLOGY: An intracanal sonochemical dosimetry method was used to quantify the cavitation generated by an IrriSafe 25 mm length, size 25 file inside a root canal model filled with filtered degassed/saturated water or three different concentrations of NaOCl. Removal of a hydrogel, demonstrated previously to be an appropriate biofilm mimic, was recorded to measure the lateral canal cleaning rate from two different instruments (IrriSafe 25 mm length, size 25 and K 21 mm length, size 15) activated with a P5 Suprasson (Satelec) at power P8.5 in degassed/saturated water or NaOCl. Removal rates were compared for significant differences using nonparametric Kruskal-Wallis and/or Mann-Whitney U-tests. Streaming was measured using high-speed particle imaging velocimetry at 250 kfps, analysing both the oscillatory and steady flow inside the lateral canals. RESULTS: There was no significant difference in amount of cavitation between tap water and oversaturated water (P = 0.538), although more cavitation was observed than in degassed water. The highest cavitation signal was generated with NaOCl solutions (1.0%, 4.5%, 9.0%) (P < 0.007) and increased with concentration (P < 0.014). The IrriSafe file outperformed significantly the K-file in removing hydrogel (P < 0.05). Up to 64% of the total hydrogel volume was removed after 20 s. The IrriSafe file typically outperformed the K-file in generating streaming. The oscillatory velocities were higher inside the lateral canal 3 mm compared to 6 mm from WL and were higher for NaOCl than for saturated water, which in turn was higher than for degassed water. CONCLUSIONS: Measurements of cavitation and acoustic streaming have provided insight into their contribution to cleaning. Significant differences in cleaning, cavitation and streaming were found depending on the file type and size, lateral canal location and irrigant used. In general, the IrriSafe file outperformed the K-file, and NaOCl performed better than the other irrigants tested. The cavitation and streaming measurements revealed that both contributed to hydrogel removal and both play a significant role in root canal cleaning.

Impact of scientific and technological advances.

Advancements in research and technology are transforming our world. The dental profession is changing too, in the light of scientific discoveries that are advancing biological technology-from new biomaterials to unravelling the genetic make-up of the human being. As health professionals, we embrace a model of continuous quality improvement and lifelong learning. Our pedagogical approach to incorporating the plethora of scientific-technological advancements calls for us to shift our paradigm from emphasis on skill acquisition to knowledge application. The 2017 ADEE/ADEA workshop provided a forum to explore and discuss strategies to ensure faculty, students and, ultimately, patients are best positioned to exploit the opportunities that arise from integrating new technological advances and research outcomes. Participants discussed methods of incorporating the impact of new technologies and research findings into the education of our dental students. This report serves as a signpost of the way forward and how to promote incorporation of research and technology advances and lifelong learning into the dental education curriculum.

The Graduating European Dentist: A New Undergraduate Curriculum Framework.

With "The Graduating European Dentist", ADEE provides a new approach that reflects best academic practice for European undergraduate dental education. The new suite of documents sees increased emphasis on important curriculum components such as patient safety, working as a team and patient-centred care. There is also an increased emphasis on teaching excellence, student satisfaction and student preparedness and support. Guidance relating to methods of teaching and learning, and assessment (educational measurement), is also provided. It is anticipated that this new format will further increase accessibility and utility for educators, institutions, societies and regulators, across the sector.

The Graduating European Dentist: Contemporaneous Methods of Teaching, Learning and Assessment in Dental Undergraduate Education.

It is often the case that good teachers just "intuitively" know how to teach. Whilst that may be true, there is now a greater need to understand the various processes that underpin both the ways in which a curriculum is delivered, and the way in which the students engage with learning; curricula need to be designed to meet the changing needs of our new graduates, providing new, and robust learning opportunities, and be communicated effectively to both staff and students. The aim of this document is to draw together robust and contemporaneous methods of teaching, learning and assessment that help to overcome some of the more traditional barriers within dental undergraduate programmes. The methods have been chosen to map specifically to The Graduating European Dentist, and should be considered in parallel with the benchmarking process that educators and institutions employ locally.

A novel methodology providing insights into removal of biofilm-mimicking hydrogel from lateral morphological features of the root canal during irrigation procedures.

AIM: To introduce and characterize a reproducible hydrogel as a suitable biofilm mimic in endodontic research. To monitor and visualize the removal of hydrogel from a simulated lateral canal and isthmus for the following: I) Ultrasonic-Activated Irrigation (UAI) with water, ii) UAI with NaOCl and iii) NaOCl without UAI. METHODOLOGY: A rheometer was used to characterize the viscoelastic properties and cohesive strength of the hydrogel for suitability as a biofilm mimic. The removal rate of the hydrogel from a simulated lateral canal or isthmus was measured by high-speed imaging operating at frame rates from 50 to 30,000 fps. RESULTS: The hydrogel demonstrated viscoelastic behaviour with mechanical properties comparable to real biofilms. UAI enhanced the cleaning effect of NaOCl in isthmi (P < 0.001) and both NaOCl and water in lateral canals (P < 0.001). A greater depth of cleaning was achieved from an isthmus (P = 0.009) than from a lateral canal with UAI and also at a faster rate for the first 20 s. NaOCl without UAI resulted in a greater depth of hydrogel removal from a lateral canal than an isthmus (P < 0.001). The effect of UAI was reduced when stable bubbles were formed and trapped in the lateral canal. Different removal characteristics were observed in the isthmus and the lateral canal, with initial highly unstable behaviour followed by slower viscous removal inside the isthmus. CONCLUSIONS: The biofilm-mimicking hydrogel is reproducible, homogenous and can be easily applied and modified. Visualization of its removal from lateral canal anatomy provides insights into the cleaning mechanisms of UAI for a biofilm-like material. Initial results showed that UAI improves hydrogel removal from the accessory canal anatomy, but the creation of stable bubbles on the hydrogel-liquid interface may reduce the cleaning rate.

Core continuing professional development (CPD) topics for the European dentist.

INTRODUCTION: In the context of free movement, EU-citizens need assurance that dental practitioners providing their care have a degree/license to practice that meets EU-standards and that they maintain their knowledge and skills through ongoing education. AIM: One aim of the 'DentCPD' project (HYPERLINK 'http://www.dentcpd.org' www.dentcpd.org) was to identify and agree essential CPD requirements for EU dentists. This paper reports the consensus process and outcomes. METHODS: Agreement on core components of CPD was achieved through a three stage process: an online survey of dental educators' (n = 143) views on compulsory topics; a paper-based questionnaire to practitioners (n = 411); leading to a proposal discussed at the Association for Dental Education (ADEE) 2011 Lifelong Learning special interest group (SIG). RESULTS: From the online survey and practitioner questionnaire, high levels of agreement were achieved for medical emergencies (89%), infection control (79%) and the medically compromised patient (71%). The SIG (34 attendees from 16 countries) concluded that these three CPD topics plus radiation protection should be core-compulsory and three CPD topics should be core-recommended (health and safety, pain management, and safeguarding children & vulnerable adults). They also agreed that the teaching of all topics should be underpinned by evidence-based dentistry. CONCLUSION: Building four core topics into CPD requirements and making quality-approved education and training available will ensure that all dentists have up-to-date knowledge and skills in topic areas of direct relevance to patient safety. In turn, this will contribute to patients having access to comparably high standards of oral health care across Europe.

Core continuing professional development (CPD) topics for the European dentist.

INTRODUCTION: In the context of free movement, EU-citizens need assurance that dental practitioners providing their care have a degree/license to practice that meets EU-standards and that they maintain their knowledge and skills through ongoing education. AIM: One aim of the 'DentCPD' project (HYPERLINK 'http://www.dentcpd.org' www.dentcpd.org) was to identify and agree essential CPD requirements for EU dentists. This paper reports the consensus process and outcomes. METHODS: Agreement on core components of CPD was achieved through a three stage process: an online survey of dental educators' (n = 143) views on compulsory topics; a paper-based questionnaire to practitioners (n = 411); leading to a proposal discussed at the Association for Dental Education (ADEE) 2011 Lifelong Learning special interest group (SIG). RESULTS: From the online survey and practitioner questionnaire, high levels of agreement were achieved for medical emergencies (89%), infection control (79%) and the medically compromised patient (71%). The SIG (34 attendees from 16 countries) concluded that these three CPD topics plus radiation protection should be core-compulsory and three CPD topics should be core-recommended (health and safety, pain management, and safeguarding children & vulnerable adults). They also agreed that the teaching of all topics should be underpinned by evidence-based dentistry. CONCLUSION: Building four core topics into CPD requirements and making quality-approved education and training available will ensure that all dentists have up-to-date knowledge and skills in topic areas of direct relevance to patient safety. In turn, this will contribute to patients having access to comparably high standards of oral health care across Europe.

Continuing professional development systems and requirements for graduate dentists in the EU: survey results from the DentCPD project.

INTRODUCTION: By maintaining skills and keeping dentists up-to-date, continuing professional development (CPD) supports safe clinical practice. However, CPD for dentists across Europe is not harmonised. AIM: One aim of the 'DentCPD' project (www.dentcpd.org) was to identify and agree essential CPD requirements for EU dentists. As part of the process, data were collected on existing approaches to CPD for EU dentists. This paper reports those findings. METHODS: Informed by a review of the literature and internet search, the CPD for Graduate Dentists questionnaire gathered data from dental educators on CPD systems, requirements, provision and accreditation in Europe. It sought opinion on mandatory CPD and e-learning. RESULTS: Responses were received from 143 individuals from 30 EU countries. About half the countries had a compulsory CPD system which typically included mandatory core topics. Elsewhere CPD was optional or based on recommended hours. University dental schools and professional dental associations were the most common CPD providers. National regulatory bodies were the most common accrediting body. Only 41% of respondents thought they knew the criteria for successful accreditation of CPD. Eighty-one percent agreed that 'CPD should be obligatory for all dentists'. CONCLUSION: These results present an overview of the status of CPD for EU dentists. Despite a notable trend towards regulated CPD systems, current requirements for dentists to engage in CPD show variation. The harmonisation of requirements would enhance both dentist mobility and safe clinical practice.

Continuing professional development systems and requirements for graduate dentists in the EU: survey results from the DentCPD project.

INTRODUCTION: By maintaining skills and keeping dentists up-to-date, continuing professional development (CPD) supports safe clinical practice. However, CPD for dentists across Europe is not harmonised. AIM: One aim of the 'DentCPD' project (www.dentcpd.org) was to identify and agree essential CPD requirements for EU dentists. As part of the process, data were collected on existing approaches to CPD for EU dentists. This paper reports those findings. METHODS: Informed by a review of the literature and internet search, the CPD for Graduate Dentists questionnaire gathered data from dental educators on CPD systems, requirements, provision and accreditation in Europe. It sought opinion on mandatory CPD and e-learning. RESULTS: Responses were received from 143 individuals from 30 EU countries. About half the countries had a compulsory CPD system which typically included mandatory core topics. Elsewhere CPD was optional or based on recommended hours. University dental schools and professional dental associations were the most common CPD providers. National regulatory bodies were the most common accrediting body. Only 41% of respondents thought they knew the criteria for successful accreditation of CPD. Eighty-one percent agreed that 'CPD should be obligatory for all dentists'. CONCLUSION: These results present an overview of the status of CPD for EU dentists. Despite a notable trend towards regulated CPD systems, current requirements for dentists to engage in CPD show variation. The harmonisation of requirements would enhance both dentist mobility and safe clinical practice.

Effect of plastic-covered ultrasonic scalers on titanium implant surfaces.

OBJECTIVES: Maintaining oral health around titanium implants is essential. The formation of a biofilm on the titanium surface will influence the continuing success of the implant. These concerns have led to modified ultrasonic scaler instruments that look to reduce implant damage while maximising the cleaning effect. This study aimed to assess the effect of instrumentation, with traditional and modified ultrasonic scalers, on titanium implant surfaces and to correlate this with the oscillations of the instruments. MATERIALS AND METHODS: Two ultrasonic insert designs (metallic TFI-10 and a plastic-tipped implant insert) were selected. Each scaler probe was scanned using a scanning laser vibrometer, under loaded and unloaded conditions, to determine their oscillation characteristics. Loads were applied against a titanium implant (100g and 200 g) for 10 s. The resulting implant surfaces were then scanned using laser profilometry and scanning electron microscopy (SEM). RESULTS: Insert probes oscillated with an elliptical motion with the maximum amplitude at the probe tip. Laser profilometry detected defects in the titanium surface only for the metallic scaler insert. Defect widths at 200 g high power were significantly larger than all other load/power conditions (P<0.02). Using SEM, it was observed that modifications to the implant surface had occurred following instrumentation with the plastic-tipped insert. Debris was also visible around the defects. CONCLUSIONS: Metal scalers produce defects in titanium implant surfaces and load and power are important factors in the damage caused. Plastic-coated scaler probes cause minimal damage to implant surfaces and have a polishing action but can leave plastic deposits behind on the implant surface.

Online discussion boards in dental education: potential and challenges.

BACKGROUND: Online discussion boards may enhance critical analysis and reflection, and promote the acquisition of knowledge. AIMS: To assess the effectiveness of online discussion board as a pedagogical tool in augmenting face-to-face teaching in dental education. METHOD: Data were collected from a discussion archive offered through the E-course website of the School of Dentistry, University of Birmingham, UK in 2008. A multi-component metric included; participation, social learning, cognitive processing, role of instructors, and quality of discussion. Messages were coded for 14 variables to evaluate these dimensions. Data were analyzed using content analysis methodology and a complete message was uses as the unit of analysis. RESULTS: There were no significant difference in participation between students and instructors (P<0.05). Social interaction with peers appeared only through students posting messages with open questions (27/135 messages). The discussion board was mainly used by students to understand concepts (27/102 messages) and apply procedural knowledge (17/102 messages). Instructors were mainly replying to students' messages with (49/120 messages) or without (54/120 messages) proposing another action. CONCLUSIONS: Online discussion boards were found to be successful pedagogical tools in dental education. Further development of instructor-led discussion approach is needed to promote higher level learning and collaborative thinking.

Improved biofilm removal using cavitation from a dental ultrasonic scaler vibrating in carbonated water.

The use of cavitation for improving biofilm cleaning is of great interest. There is no system at present that removes the biofilm from medical implants effectively and specifically from dental implants. Cavitation generated by a vibrating dental ultrasonic scaler tip can clean biomaterials such as dental implants. However, the cleaning process must be significantly accelerated for clinical applications. In this study we investigated whether the cavitation could be increased, by operating the scaler in carbonated water with different CO2 concentrations. The cavitation around an ultrasonic scaler tip was recorded with high speed imaging. Image analysis was used to calculate the area of cavitation. Bacterial biofilm was grown on surfaces and its removal was imaged with a high speed camera using the ultrasonic scaler in still and carbonated water. Cavitation increases significantly with increasing carbonation. Cavitation also started earlier around the tips when they were in carbonated water compared to non-carbonated water. Significantly more biofilm was removed when the scaler was operated in carbonated water. Our results suggest that using carbonated water could significantly increase and accelerate cavitation around ultrasonic scalers in a clinical situation and thus improve biofilm removal from dental implants and other biomaterials.

Innovative educational methods and technologies applicable to continuing professional development in periodontology.

Continuous professional development (CPD) in Periodontology refers to the overall framework of opportunities that facilitate a life-long learning practice, driven by the learner-practitioner and supported by a variety of institutions and individuals. CPD must address different needs for a great diversity of practitioners. It is clear that no particular methodology or technology is able to successfully accommodate the entire spectrum of CPD in Periodontology. Course designers must choose from and combine a wide array of methodologies and technologies, depending upon the needs of the learners and the objectives of the intended education. Research suggests that 'interactivity', 'flexibility', 'continuity' and 'relevance to learners' practice' are major characteristics of successful CPD. Various methods of mentoring, peer-learning environments and work-based learning have been combined with reflective practice and self-study to form the methodological backbone of CPD courses. Blended learning encompasses a wide array of technologies and methodologies and has been successfully used in CPD courses. Internet-based content learning management systems, portable Internet devices, powerful databases and search engines, together with initiatives such as 'open access' and 'open courseware' provide an array of effective instructional and communication tools. Assessment remains a key issue in CPD, providing learners with valuable feedback and it ensures the credibility and effectiveness of the learning process. Assessment is a multi-level process using different methods for different learning outcomes, as directed by current evidence and best practices. Finally, quality assurance of the education provided must follow CPD courses at all times through a structured and credible process.

Profile and competences for the graduating European dentist - update 2009.

This paper presents the profile and competences for the European Dentist as approved by the General Assembly of the Association for Dental Education in Europe at its annual meeting held in Helsinki in August 2009. A new taskforce was convened to update the previous document published in 2005. The updated document was then sent to all European Dental Schools, ministries of health, national dental associations and dental specialty associations or societies in Europe. The feedback received was used to improve the document. European dental schools are expected to adhere to the profile and the 17 major competences but the supporting competences may vary in detail between schools. The document will be reviewed once again in 5 years time. Feedback to the newly published document is welcomed and all dental educators are encouraged to draw upon the content of the paper to assist them in harmonising the curriculum throughout Europe with the aim of improving the quality of the dental curriculum.

The effect of standoff distance and surface roughness on biofilm disruption using cavitation.

Effective biofilm removal from surfaces in the mouth is a clinical challenge. Cavitation bubbles generated around a dental ultrasonic scaler are being investigated as a method to remove biofilms effectively. It is not known how parameters such as surface roughness and instrument distance from biofilm affect the removal. We grew Strepotococcus sanguinis biofilms on coverslips and titanium discs with varying surface roughness (between 0.02-3.15 µm). Experimental studies were carried out for the biofilm removal using high speed imaging and image analysis to calculate the area of biofilm removed at varying ultrasonic scaler standoff distances from the biofilm. We found that surface roughness up to 2 µm does not adversely affect biofilm removal but a surface roughness of 3 µm caused less biofilm removal. The standoff distance also has different effects depending on the surface roughness but overall a distance of 1 mm is just as effective as a distance of 0.5 mm. The results show significant biofilm removal due to an ultrasonic scaler tip operating for only 2s versus 15-60s in previous studies. The technique developed for high speed imaging and image analysis of biofilm removal can be used to investigate physical biofilm disruption from biomaterial surfaces in other fields.

How does ultrasonic cavitation remove dental bacterial biofilm?

Bacterial biofilm accumulation is problematic in many areas, leading to biofouling in the marine environment and the food industry, and infections in healthcare. Physical disruption of biofilms has become an important area of research. In dentistry, biofilm removal is essential to maintain health. The aim of this study is to observe biofilm disruption due to cavitation generated by a dental ultrasonic scaler (P5XS, Acteon) using a high speed camera and determine how this is achieved. Streptococcus sanguinis biofilm was grown on Thermanox™ coverslips (Nunc, USA) for 4 days. After fixing and staining with crystal violet, biofilm removal was imaged using a high speed camera (AX200, Photron). An ultrasonic scaler tip (tip 10P) was held 2 mm away from the biofilm and operated for 2 s. Bubble oscillations were observed from high speed image sequences and image analysis was used to track bubble motion and calculate changes in bubble radius and velocity on the surface. The results demonstrate that most of the biofilm disruption occurs through cavitation bubbles contacting the surface within 2 s, whether individually or in cavitation clouds. Cleaning occurs through shape oscillating microbubbles on the surface as well as through fluid flow.

Numerical investigation of cavitation generated by an ultrasonic dental scaler tip vibrating in a compressible liquid.

Bacterial biofilm accumulation around dental implants is a significant problem leading to peri-implant diseases and implant failure. Cavitation occurring in the cooling water around ultrasonic scaler tips can be used as a novel solution to remove debris without any surface damage. However, current clinically available instruments provide insufficient cavitation around the activated tip surface. To solve this problem a critical understanding of the vibro-acoustic behaviour of the scaler tip and the associated cavitation dynamics is necessary. In this research, we carried out a numerical study for an ultrasound dental scaler with a curved shape tip vibrating in water, using ABAQUS based on the finite element method. We simulated the three-dimensional, nonlinear and transient interaction between the vibration and deformation of the scaler tip, the water flow around the scaler and the cavitation formation and dynamics. The numerical model was well validated with the experiments and there was excellent agreement for displacement at the free end of the scaler. A systematic parametric study has been carried out for the cavitation volume around the scaler tip in terms of the frequency, amplitude and power of the tip vibration. The numerical results indicate that the amount of cavitation around the scaler tip increases with the frequency and amplitude of the vibration. However, if the frequency is far from the natural frequency, the cavitation volume around the free end decreases due to reduced free end vibration amplitude.

Students' attitudes towards an on-line orthodontic learning resource.

AIM: The purpose of this study was to develop an online undergraduate orthodontic e-course and assess its success as a learning resource from the students' perspective. METHODOLOGY: The orthodontic e-course was composed of six main components; modules, photo gallery, clinical consultations, glossary, reading lists and resources. Four undergraduate orthodontic lectures were converted into a web-based format using text, photographs, PowerPoint presentations and animations. The sample was comprised of sixty-four third year undergraduate dental students at Birmingham Dental School, UK. Their average age was 20.7 years (age range: from 20-25 years). A questionnaire was developed to assess; course design, course delivery, course outcome and the potential use of the e-course as a teaching method. RESULTS: There were no significant difference between genders (P < 0.05). Overall, student responded very positive to positive for course design, course delivery and course outcome. The orthodontic e-course was still seen by most subjects (86%) as an adjunct and not a replacement of the traditional teaching methods. 34.4% of subjects felt that it should be as an optional supplement and 51.6% felt that it should be integrated with the undergraduate orthodontic curriculum. The significance of the program as a learning resource was reported to be the best aspect of the program. CONCLUSION: Delivery of web-based material in the undergraduate orthodontic curriculum was seen by students as a significant learning resource which supplements traditional learning methods.

The use of the OSCE in postgraduate education.

BACKGROUND: The Objective Structured Clinical Examination (OSCE) is a method of assessing the clinical skills of undergraduates in medicine, dentistry and other health sciences and is employed increasingly in postgraduate education. AIM: To describe the application of the OSCE to the development of Lifelong Learning and Continuing Professional Development (CPD) for General Dental Practitioners (GDPs). METHODS: A postgraduate course was designed as an OSCE for GDPs. The OSCE comprised 12 stations covering different aspects of general dentistry. After an introductory seminar outlining the aim of the course, the participants spent 7 min at each station. Each question or task required 10 answers and was designed to highlight areas of weakness or interest and to stimulate further study of the presenting topic. Solutions and answers were provided at each station for self-assessment along with a list of locally presented courses related to that subject. Participants were invited to leave contact details and to make suggestions for future postgraduate courses. The final session consisted of a group discussion and participants were invited to complete an evaluation form to express opinions on the course. RESULTS: The evaluation demonstrated that most candidates found participation in the OSCE stimulated their interest in CPD. The OSCE also highlighted areas of weakness in knowledge of certain clinical procedures. Group discussion confirmed that practitioners found the hands-on component valuable and that they were likely to participate in further OSCEs to enhance their CPD. Suggestions received during the discussion were used to modify the course. CONCLUSIONS: The OSCE course fulfilled its aim of assisting practitioners to organise their CPD. The reflective nature of the course was helpful in evaluating clinical knowledge and the unique multidisciplinary style fulfilled its objective in promoting thoughts regarding future study.

Cuspal deflection and microleakage in premolar teeth restored with resin-based composites with and without an intermediary flowable layer.

OBJECTIVES: To assess cuspal deflection and cervical enamel microleakage with and without an intermediary flowable RBC layer for the incremental restoration of mesio-occluso-distal (MOD) cavities with two resin-based composites (RBCs). METHODS: Forty sound upper premolar teeth had standardised MOD cavities prepared. Restoration of the teeth involved the placement of the RBCs (Filtek P60 or Filtek Supreme) in eight increments with the appropriate bonding system with and without an intermediary flowable RBC layer (Filtek Flow). Buccal and palatal cusp deflections were recorded post-irradiation using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in a 0.2% basic fuchsin dye for 24h, sagittally sectioned and examined for cervical enamel microleakage. RESULTS: A significant reduction in cuspal deflection was evident when both RBC materials were used to restore the cavity by employing an intermediary flowable (P<0.001) compared with when no intermediary flowable was utilised. No statistically significant differences were identified in microleakage between the teeth restored with Filtek P60 or Filtek Supreme when an intermediary flowable (Filtek Flow) was employed. CONCLUSIONS: The results of the current study suggest that there was a benefit to the operator in terms of a reduction in cuspal deflection but not from the maintenance of the synergism of the adhesive bond, namely microleakage at the cervical enamel cavosurface margin, when an intermediate layer of a flowable RBC was used under higher elastic modulus RBCs.