Current Strategies to Control Recurrent and Residual Caries with Resin Composite Restorations: Operator- and Material-Related Factors.

This review addresses the rationale of recurrent and/or residual caries associated with resin composite restorations alongside current strategies and evidence-based recommendations to arrest residual caries and restrain recurrent caries. The PubMed and MEDLINE databases were searched for composite-associated recurrent/residual caries focusing on predisposing factors related to materials and operator's skills; patient-related factors were out of scope. Recurrent caries and fractures are the main reasons for the failure of resin composites. Recurrent and residual caries are evaluated differently with no exact distinguishment, especially for wall lesions. Recurrent caries correlates to patient factors, the operator's skills of cavity preparation, and material selection and insertion. Material-related factors are significant. Strong evidence validates the minimally invasive management of deep caries, with concerns regarding residual infected dentin. Promising technologies promote resin composites with antibacterial and remineralizing potentials. Insertion techniques influence adaptation, marginal seal, and proximal contact tightness. A reliable diagnostic method for recurrent or residual caries is urgently required. Ongoing endeavors cannot eliminate recurrent caries or precisely validate residual caries. The operator's responsibility to precisely diagnose original caries and remaining tooth structure, consider oral environmental conditions, accurately prepare cavities, and select and apply restorative materials are integral aspects. Recurrent caries around composites requires a triad of attention where the operator's skills are cornerstones.

Verification of lateral flow antigen tests for SARS-CoV-2 by qPCR directly from the test device.

OBJECTIVE: Fast and reliable detection of infection is a key to control the SARS-CoV-2 pandemic. Lateral flow antigen tests (LFATs) are inexpensive, easy to use, but have to be verified, as they are rather unspecific and can produce both, false positive and false negative results. Our objective was to combine the speed of LFAT for SARS-CoV-2 with the reliability of qPCR tests. METHODS: A serial dilution of a patient sample positive for SARS-CoV-2 was prepared and added to LFAT wells from two manufacturers. After evaluation, the devices were opened, the strips removed and extracted in a solution. Amplification was performed using point of care PCR systems (cobas® Liat®, ID NOW™) or on a LightCycler after extraction by MagNAPure 96. RESULTS: The nucleic acid amplification systems yielded higher sensitivity to LFAT. Thus, all samples determined positive by LFAT from the serial dilution were also positive in the subsequent amplification reactions. Sensitivity using extracted eluates was 10-100 times higher. SIGNIFICANCE: The usage of LFAT is highly recommended for single samples in emergency dental or emergency clinical settings, for smaller cohorts, or even for larger population screening, as it is inexpensive and fast. Positive results can be conveniently verified directly from the test devices using either point of care test equipment or more complex laboratory equipment thus making a major impact on efficient management of infections and isolations.

Direct and indirect eluates from bulk fill resin-based-composites.

OBJECTIVES: To compare elutable substances directly released from bulk-fill (BF) resin-based composites (RBCs) with indirect elution from teeth restored with a BF composite. In addition to (co)monomers, the analytical focus was on other potentially toxic ingredients or impurities. Furthermore, the barrier function of the residual dentin/adhesive layer was studied. METHODS: Six BF-RBC materials were studied. For each material subgroup, ten human third molar teeth with standard Class-I occlusal cavities were prepared and provided with a three-step adhesive system and the respective composite restoration (tooth groups). Same sized control specimens of the restorative material were prepared ('direct BF-RBC' groups). Each specimen was placed in an elution chamber such that the elution media (ethanol/water, 3:1) only contacted the tooth root or ¾ height of each specimen. They were incubated at 37 °C for up to 7 d. Samples of eluate were taken after 1, 2, 4 and 7 d and were analysed by high-temperature gas chromatography/mass spectrometry. RESULTS: (Co)monomers such as Bisphenol A ethoxylate dimethacrylate (bisEMA) or tetraethylene glycol dimethacrylate (TEEGDMA) were mostly found in the eluates of the 'direct BF-RBC' groups in statistically significantly greater amounts than in the eluates of the 'tooth groups'. The residual dentin and/or adhesive layers acted as a diffusion barrier for most of the substances except for triethylene glycol dimethacrylate (TEGDMA) or diethylene glycol dimethacrylate (DEGDMA). For TEGDMA up to 3 orders of magnitude more were found in the 'tooth groups' compared to the 'direct BF-RBC' groups, evidently released by the adhesive system. Substances of Very High Concern (SVHC) including TINUVIN® 328 and BPA were found mainly in the eluates of 'direct BF-RBC' groups. SIGNIFICANCE: For estimation of biocompatibility, a total system, specifically BF-RBC + adhesive, should always be investigated since individual considerations, such as only elution from a BF-RBC, do not correctly reflect the total clinical situation. The focus of elution tests should not only be on the co(monomers), but also on other ingredients or impurities that may be released.

Special Teaching Formats during the COVID-19 Pandemic-A Survey with Implications for a Crisis-Proof Education.

Modern teaching formats have not been considered necessary during the COVID-19 pandemic with uncertain acceptance by students. The study's aim was to describe and evaluate all measures undertaken for theoretical and practical knowledge/skill transfer, which included objective structured practical examinations (OSPEs) covering a communication skills training. The students' performance in the OSPE as well as the theoretical knowledge level were assessed, of which the latter was compared with previous terms. In conservative dentistry and periodontology (4th and 5th year courses), theoretical teaching formats were provided online and completed by a multiple-choice test. Practical education continued without patients in small groups using the phantom-head, 3D printed teeth, and objective structured practical examinations (OSPEs) including communication skills training. Formats were evaluated by a questionnaire. The organization was rated as very good/good (88.6%), besides poor Internet connection (22.8%) and Zoom® (14.2%) causing problems. Lectures with audio were best approved (1.48), followed by practical videos (1.54), live stream lectures (1.81), treatment checklists (1.81), and virtual problem-based learning (2.1). Lectures such as .pdf files without audio, articles, or scripts were rated worse (2.15-2.30). Phantom-heads were considered the best substitute for patient treatment (59.5%), while additional methodical efforts for more realistic settings led to increased appraisal. However, students performed significantly worse in the multiple-choice test compared to the previous terms (p < 0.0001) and the OSPEs revealed deficits in the students' communication skills. In the future, permanent available lectures with audio and efforts toward realistic treatment settings in the case of suspended patient treatment will be pursued.

SARS-CoV-2 and regular patient treatment - from the use of rapid antigen testing up to treatment specific precaution measures.

INTRODUCTION: The COVID-19 pandemic poses a continued challenge for all parties involved especially for the dentist as routine operation must be resumed. Rapid Antigen Tests (RATs) are actually recommended to identify and minimize infectious risks. However, there is still no guideline on the implementation of RATs in a dental or medical setting. METHODS: Based on data and an extensive literature research regarding rapid antigen testing and reflecting the recommendations given by the various professional societies a task force was formed to determine a specific testing and treatment strategy. RESULTS: A comprehensive test and treatment strategy and risk analysis was developed with practical suggestions for a wide range of typical activities in dental and medical offices. The transmission of SARS-CoV-2 and its variants via aerosols and droplets as well as the difficulties to maintain the minimum distance form special challenges to the dental routine. RATs might in addition to optimal and necessary hygienic standards in combination with the use of adequate personal protection equipment be an important instrument in managing the challenges. CONCLUSIONS: The present work gives recommendations for dental routine operation (dental practices, outpatient clinics) to provide the necessary dental care for the population while protecting the doctor, practice team and patient at the same time.

Direct and indirect monomer elution from an RBC product family.

OBJECTIVE: To develop a model for quantitative comparison of elutable substances by direct elution from resin-bonded composite (RBC) test specimens versus indirect elutability of substances from RBC-restored teeth. Furthermore, it was to be investigated whether the different composites of the Tetric® RBC product family release different types and amounts of substances. METHODS: Four different composite materials from the Tetric® product family were studied. For each material subgroup ten human third molar teeth were prepared with standard Class-I occlusal cavities. These 'tooth group' specimens were provided with a three-step adhesive system (incorporating TEGDMA) and the respective composite restoration. Same sized control specimens, of each RBC restorative material, were prepared ('direct RBC' groups). All specimens were placed in individual elution chambers such that the elution media (ethanol/water, 3:1) only came into contact with either the tooth root or ¾ height of the 'direct RBC' materials. They were incubated at 37 °C for up to 7 d. Samples of the eluant were taken after 1, 2, 4 and 7 d and were analysed by high-temperature gas chromatography/mass spectrometry. RESULTS: Bisphenol A ethoxylate dimethacrylate (bisEMA), bisphenol A glycidyldimethacrylate (bisGMA), tetraethylene glycol dimethacrylate (TEEGDMA), decan-1,10-diol dimethacrylate (DDDMA) were mostly found in the eluates of the 'direct RBC' groups in statistically significantly greater amounts than in the eluates of the 'tooth groups'. Such quantitative differences were also the case with eluates containing bisphenol A (BPA), dicyclohexyl phthalate (DCHP) and drometrizole, which are common in the environment. In contrast to the behavior found with all the other monomers, up to 3 orders of magnitude more triethylene glycol dimethacrylate (TEGDMA) was found in the 'tooth groups' compared to the 'direct RBC' groups, evidently released by the adhesive system. SIGNIFICANCE: The release of most of the substances was clearly delayed in the 'tooth groups' indicative of their chronic, rather than acute, elution to the oral environment. A barrier function of the residual dentin layer and the adhesion layer can be inferred. The different release patterns of substances from the various composites of the RBC product family is a manifestation of their different and indication-specific compositions. Consideration of an overall restorative care (RBC plus adhesive) system, when assessing the total amount of released substances, is emphasized.

An alternate methodology for studying diffusion and elution kinetics of dimethacrylate monomers through dentinal tubules.

OBJECTIVE: Ethoxylated bisphenol A dimethacrylate (bisEMA) is a base monomer in several dental resin composites. It was the main aim of the present study to determine if bisEMA can reach the dental pulp by generally passive diffusion through the coronal dentinal tubules stimulated via eluent liquids surrounding the root structures only. METHODS: In 20 human third molar teeth, standard Class-I occlusal cavities were prepared and provided either with an adhesive system alone or additionally with a composite restoration, according to the instructions of the manufacturer. The teeth were placed in an elution chamber such that the elution media only came into contact with the tooth root/tooth base where they were incubated at 37 °C for up to 7 d. Samples were taken after 1, 2, 4 and 7 d. Gas chromatography/mass spectrometry was used to identify bisEMA and other monomers in ethanol/water (3:1) and aqueous eluates. RESULTS: bisEMA was only found in ethanol/water eluates, where the teeth had received a composite restoration. Traces of bisEMA with up to three ethylene oxide units could be detected in these eluates. Depending on the dentin thickness, different elution kinetics of bisEMA were determined. Regardless of the treatment of teeth, triethylene glycol dimethacrylate (TEGDMA) and tetraethylene glycol dimethacrylate (TEEGDMA) were found in ethanolic/aqueous eluates in equal amounts. Most TEGDMA and TEEGDMA diffused through the dentin within the first 24 h. SIGNIFICANCE: Depending on the dentin layer thickness, bisEMA was released for varied time periods, resulting in varied concentrations and exposure times for the different cells of the dental pulp. The concentrations of TEGDMA and TEEGDMA were greatest for cells of the dental pulp within the first 24 h.

Effectiveness of dentifrices with new formulations for the treatment of dentin hypersensitivity - A meta-analysis.

PURPOSE: This meta-analysis was conducted to evaluate if strontium-acetate- and arginine-containing dentifrices can significantly reduce dentin hypersensitivity (DH). METHODS: A systematic literature search was performed. The investigation period was from 2006 to 2015 with the search term "dentin hypersensitivity". Nine original articles were relevant. A network meta-analysis of combined z scores was performed. Pooled results from random effects models with their 95% confidence intervals are reported. RESULTS: The results from the random effects network meta-analysis show a significant improvement for the agents strontium acetate, arginine, and arginine with whitener, at all times for all stimuli, in comparison with the placebo. Strontium chloride is equivalent to the placebo. None of the dentifrices had a negative effect on DH. This meta-analysis showed that strontium-acetate- and arginine-containing dentifrices can significantly reduce DH. Calcium sodium silicate and potassium nitrate formulas show a tendency for pain relief. Because of the limited power of the available studies, a randomized study with several agents is recommended. CLINICAL SIGNIFICANCE: The aim of the treatment of dentin hypersensitivity (DH) is pain relief. Dentifrices with formulations of strontium acetate, of arginine or of arginine with whitener seem to have a good impact in the therapy of DH and can be recommended for daily use.

The prevalence of tooth hypersensitivity following periodontal therapy with special reference to root scaling. A systematic review of the literature.

PURPOSE: To provide a current status of the art, answering the question whether a certain procedure of periodontal treatment is more reliable than another and where innovative developments could improve on the incidence of hypersensitivity by a systematic literature review. METHODS: Pubmed, Embase and Cochrane library were considered for the study. 2,656 articles of the PubMed search were found, from the beginning of 1945 until April 2011. 99 articles from PubMed were evaluated for this review. From Embase, 60 articles were selected and one was included in this review. From the Cochrane library, 182 were found, of which two contributed to the review. Included were all studies dealing with periodontal treatment followed by hypersensitivity and all studies dealing with the loss of attachment, followed by hypersensitivity. Excluded were any treatments of tooth hypersensitivity with pathogenesis not related to dentin exposure, genetically caused disorders, and fractures. Ultimately, 102 papers were evaluated, included and referred to in the review. RESULTS: The term "tooth hypersensitivity" is most often used. Common causes of loss of hard substance are listed and updated. Mechanical loss of hard tissue formed one group of etiological factors; gingival recession and loss of attachment another. Surgical interventions, scaling and root planing were considered and in most cases performed as combined procedures. The different methods were evaluated and critically discussed. There were no properly randomized studies in the literature. The weak point of all epidemiological studies is the lack of any objective measurement. With respect to periodontal therapy, further research and developmental work on medical devices is needed, as well as ongoing applied research with laser technologies, continuing education and training programs for professionals.

The bone-to-cement interface improvement by Ca-phosphate ceramics.

BACKGROUND: Polymethylmethacrylate used in surgery is one of the first biomaterials. Conventional histology dissolves the resin; one of the reasons that only few complete histology is published. OBJECTIVES AND PURPOSE: The question is, whether a complete histology changes the understanding, influences the application and opens approaches for improvements. The dos and don'ts of the processing technology are presented in reproducible manner. MATERIAL AND METHODS: Ten femurs of giant rabbits were taken from running experiments of femur-canal filling with bone cement. Different stages were considered for high-resolution histology and electron microscopy: 4-weeks-stage (bone healing), 12-weeks-stage (remodelling) and one and two years. A human-cadaver specimen with a follow up of two years was processed. All animals were perfusion-fixated and the complete vasculature micro-casted. Serial cuts were performed with a stone saw, followed by a wet grinding processing. The fluorescence documentation in the High Intensity Incident Fluorescent Light (HIIFL) and Orthoplan Leitz Ploemopak(®) was applied and high resolution microradiography used the Siemens Kristalloflex(®) . The Scanning Electron Microscopy (SEM) was performed applying deep-freezing technology for the PSEM-500. The human specimen was embedded after sectioning using epoxy-resin. RESULTS: All cement implants showed osseointegration and remodelling with a tangential adherence of bone onto the ceramic/PMMA surfaces. Intact cancellous structures after one and two years did not show any signs of heat necrosis. The human specimen confirmed the results from the animal experiments. CONCLUSION: The complete bone-to-cement histology changed the understanding of the bone cements function, influenced its application and opened new ways for improvement.

Osseointegration of hydroxyapatite and remodeling-resorption of tricalciumphosphate ceramics.

BACKGROUND: Cancellous bone defects surrounded by still intact bone structures never heal. Ceramics offer a solution providing osteoconductive scaffolds. PURPOSE: The purpose of the study is to evaluate whether structured ß-TCP and HA implants can reconstruct cancellous bone defects, which role micro- and macro-porosity, stiffness and surface area play; finally the indication for both materials based on its resorbability. MATERIAL & METHODS: 10 German Shepard dogs were operated on both tibial heads implanting shell-like fully interconnected ceramic cylinders, using a wet grinding hollow drill coated with diamonds. ß-TCP was compared with HA. A polychromatic sequential labelling with 4 different fluorochromes controlled bone formation dynamics. Non-decalcifying histology after perfusion fixation and vessel casting was performed. µ-CT was combined with high resolution microradiography and histology on thin ground crossections. The stages after 6 weeks, 2, 3, 4 months and 15 months were evaluated. RESULTS: In spite of osseointegration of HA and ß-TCP, the osseointegration of both materials was completely different. Both shell-like bone void fillers were osseointegrated in a sandwich-like manner. HA yielded primarily a reinforcement of the recipient's cancellous-bone bed and full osseointegration after 4 months, whereas ß-TCP-implants were fully osseointegrated after 6 weeks. HA did not show signs of resorption. The resorption of the ß-TCP resulted during remodelling. The final stage showed restitution "ad integrum" of the ß-TCP defects with a physiological architecture, whereas HA was integrated in the cancellous bone construction providing 600 µm measuring macropores showing osteoinductive properties.

ε-Caprolactone in micro-chambered ceramic beads--a new carrier for gentamicin.

PURPOSE: The purpose of this preliminary and descriptive study was to evaluate a biodegradable drug delivery system in combination with an innovative ceramic implant. METHODS: The delivery of gentamicin of standardized samples was measured in the laboratory using ultra-high-performance liquid chromatography. Biocompatibility and biodegradation of the materials was investigated in an animal experiment in sheep up to 14 months. As carrier ε-caprolactone, 1:1 mixed with gentamicin, intruded into micro-chambered ß-tricalcium-phosphate beads (MCB®) was studied. RESULTS AND DISCUSSION: Gentamicin was released in calculable concentrations during the first 30 days. The release from ε-caprolactone was higher than that from polymethylmethacrylate and more predictable. The caprolactone carrier was reabsorbed by osteoclasts.

Correlation of the degree of conversion with the amount of elutable substances in nano-hybrid dental composites.

OBJECTIVES: This study's purpose was to measure and compare the degree of conversion (DC) and the amount of elutable substances from modern resin-based composites (RBCs) as function of polymerization time. One nano-hybrid RBC based on tricyclodecane-(TCD)-urethane (Venus(®) Diamond) and two conventionally formulated RBCs (TetricEvo Ceram(®), Filtek™ Supreme XTE) were considered. METHOD: DC (n=5) was investigated in real time for 5min by Fourier transform infrared spectroscopy (ATR-FTIR) in a filling depth of 2mm at varied irradiation times (5, 10, 20, 40s). After storing the specimens in ethanol/water for 7 d at 37°C the eluates were analyzed by gas chromatography/mass spectrometry. Results were statistically analyzed using a multivariate analysis (α=0.05) an independent t-test (p<0.05) and a Pearson correlation analysis. RESULTS: In all groups increasing curing time resulted in a significant increase in DC. For TetricEvo Ceram(®) a high significant inverse correlation was found between DC and the amount of eluted camphorquinone (CQ, Pearson correlation coefficient=-0.88), ethylene glycol dimethacrylate (EGDMA, -0.73), 4-N,N-dimethylaminobenzoic acid ethylester (DMABEE, -0.87), triethylene glycol dimethacrylate (TEGDMA, -0.68), Tinuvin P (-0.71) and bisphenol-A-polyetheylene glycol dimethacrylate (BisEMA, -0.84). Unexpectedly DC and the amount of eluted methyl acrylate (MAA) correlated directly (0.72). In the specimens of Venus(®) Diamond a significant inverse correlation was found between DC and the amount of eluted CQ (-0.69) and TEGDMA (-0.50), whereas in the specimen of Filtek™ Supreme XTE DC correlated with CQ (-0.96), EGDMA (-0.70), DMABEE (-0.87), TEGDMA (-0.92) and MAA (-0.92). SIGNIFICANCE: This study demonstrated a strong inverse correlation between DC and elutable substances in RBCs. Both evaluation methods emphasis the importance of an adequate polymerization (20, 40s), since short curing-times (5, 10s) resulted in lower DC and higher amount of eluted substances with toxic potential.

Value and limits of µ-CT for nondemineralized bone tissue processing.

An experimental approach was performed on 20 giant rabbits to establish the possibilities and limitations of µ-CT for routine processing of nondemineralized bone tissue. Hydroxyapatite (HA) or ß-tricalciumphosphate (ß-TCP) bead implants or a melange of both, microchambered and solid, were implanted into a standardized and precise defect in the patellar groove. The bone-healing phase was chosen for the histology considering 1 or 2 days, and 2, 3, and 6 weeks. Normal X-ray and µ-CT were applied on all specimens; five specimens in the 6-week stage were additionally processed according to the full range of conventional nondemineralized bone processing methods. µ-CT increased the possibilities of nondemineralized histology with respect to bone morphometry and a complete sequence of sections, thus providing a complete analysis of the bone response. µ-CT was limited in differentiating bone quality, cell analyses, and mineralization stages. The investigation based on normal X-rays is limited to defining integration and excluding the fibrous and bony encapsulation of loose implants. µ-CT allows a 3D evaluation of newly formed bone which is clearly marked against the ceramic implant. It does not allow, however, for the differentiation between woven and lamellar bone, the presentation of the canalicular lacunar system, or on the cell level, revealing canaliculi or details of the mineralization process which can be documented by high-resolution microradiography. Titer dynamics of bone formation remains the domain of polychromatic sequential labeling. The complete sequence of µ-CT slices enhances the possibilities for routine histology, tremendously allowing to the focus on detail histology to topographically well-defined cuts, thus providing more precise conclusions which take into consideration the whole implant.

Safety and efficiency of novel sonic scaler tips in vitro.

BACKGROUND: The aim of the study was to evaluate a novel sonic scaler tip for subgingival root surface instrumentation combining high efficiency in calculus removal with minimized risk of root damage through subgingival debridement. METHODS: A metal sonic scaler tip with a paddle-like working end covered with spheroid convexities of 0.8 mm diameter and 0.3 mm height was designed from the aspect of optimized adaptation to the root anatomy (tip-end dimension: 3.0 x 1.5 x 0.6 mm). Using a customary sonic scaler tip as control, instrument efficiency was quantified by measuring the time needed to completely remove calculus on extracted teeth (n=52) under standardized conditions. To quantify the amount of calculus removed, the mean calculus area per tooth was measured on photographs taken before instrumentation. The tips safety was evaluated instrumenting calculus-free root surfaces in vitro (n=18, lateral forces 0.5, 1, 2 N, 20 s instrumentation time, tip angulation 0 degrees ) with subsequent laser-optical determination of resulting root substance loss. RESULTS: Debridement efficiency was significantly higher for the novel tip (0.78+/-0.81 mm2/s completely debrided) than for the conventional tip (0.42+/-0.33 mm2) (Mann-Whitney test, p<0.05). Concerning instrument safety, the novel tip caused significantly less root substance loss than the conventional tip. CONCLUSION: The novel scaler tip appears to be significantly more efficient in calculus removal and less damaging to the root surface than the assessed conventional tip.