Stress response in Escherichia coli following sublethal phenalene-1-one mediated antimicrobial photodynamic therapy: an RNA-Seq study.

Since the molecular mechanisms behind adaptation and the bacterial stress response toward antimicrobial photodynamic therapy (aPDT) are not entirely clear yet, the aim of the present study was to investigate the transcriptomic stress response in Escherichia coli after sublethal treatment with aPDT using RNA sequencing (RNA-Seq). Planktonic cultures of stationary phase E. coli were treated with aPDT using a sublethal dose of the photosensitizer SAPYR. After treatment, RNA was extracted, and RNA-Seq was performed on the Illumina NextSeq 500. Differentially expressed genes were analyzed and validated by qRT-PCR. Furthermore, expression of specific stress response proteins was investigated using Western blot analysis.The analysis of the differential gene expression following pathway enrichment analysis revealed a considerable number of genes and pathways significantly up- or down-regulated in E. coli after sublethal treatment with aPDT. Expression of 1018 genes was up-regulated and of 648 genes was down-regulated after sublethal treatment with aPDT as compared to irradiated controls. Analysis of differentially expressed genes and significantly de-regulated pathways showed regulation of genes involved in oxidative stress response and bacterial membrane damage. In conclusion, the results show a transcriptomic stress response in E. coli upon exposure to aPDT using SAPYR and give an insight into potential molecular mechanisms that may result in development of adaptation.

Shear Bond Strength of Adhesives Placed following Selective Removal of Red-Fluorescing Carious Dentine in vitro.

Red-fluorescing dentine indicates bacterial contamination [Caries Res 2002; 36: 315-319]. We investigated effect of removal of red fluorescent dentine caries on shear bond strength and fracture mode of 4 adhesive approaches. Sixty-five carious teeth and 50 noncarious controls were distributed into 4 groups: Clearfil™ self-etch (CSE), OptiBond™ FL total etch (OTE), Scotchbond™ Universal total etch (STE) and self-etch (SSE). Samples were excited at 405 nm and viewed through 530 nm filter. Carious samples were ground flat exposing strongly red-fluorescing (StrongRF) dentine, on which a composite cylinder was placed, using one of 4 adhesives. After 22 h in water, shear bond strength and fracture mode were analysed. StrongRF was removed; composite cylinders were placed on weakly red-fluorescing (WeakRF) dentine and tested as described above. Finally, red-fluorescing dentine was removed, and composite cylinders were placed on non-fluorescing (NonRF) dentine and tested. Composites were placed at 3 corresponding heights in controls. After 22 h in water, shear bond strength testing and fracture mode analysis were performed. Differences were tested using Mann-Whitney or Wilcoxon tests (p ≤0.05). Median (Q1, Q3) shear bond strength on StrongRF was SSE 14.4 (9.2, 18.2) MPa >CSE 10.2 (6.4, 17.3) MPa >STE 9.1 (6.9, 11.2) MPa >OTE 6.8 (4.0, 10.8) MPa. Shear bond strength increased statistically significantly for all adhesives on WeakRF: SSE 19.8 (13.6, 24.3) MPa >STE 19.5 (12.7, 23.1) MPa >CSE 17.5 (12.0, 22.5) MPa >OTE 15.8 (11.9, 20.9) MPa. Only STE 25.6 (22.4, 29.1) MPa and CSE 22.1 (17.6, 24.6) MPa were significantly different on NonRF compared to WeakRF. For controls tested at corresponding depths, superficial shear bond strength was OTE 18.7 (16.0, 22.1) MPa >STE 18.4 (12.0, 25.9) MPa >CSE 18.1 (12.7, 20.7) MPa >SSE 13.0 (9.6, 17.8) MPa. This was significantly higher compared to StrongRF except for SSE. Central shear bond strength was not significantly different to WeakRF, deep shear bond strength was significantly lower for SSE and CSE but higher for OTE compared to carious. Conclusion: StrongRF dentine should be removed for higher shear bond strength, but WeakRF dentine can often be preserved without compromising adhesive bond strength.

An in vitro coculture approach to study the interplay between dental pulp cells and Streptococcus mutans.

AIM: To develop a new coculture system that allows exposure of dental pulp cells (DPCs) to Streptococcus mutans and dentine matrix proteins (eDMP) to study cellular interactions in dentine caries. METHODOLOGY: Dental pulp cells and S. mutans were cocultured with or without eDMP for 72 h. Cell proliferation and viability were assessed by cell counting and MTT assays, while bacterial growth and viability were determined by CFU and LIVE/DEAD staining. Glucose catabolism and lactate excretion were measured photometrically as metabolic indicators. To evaluate the inflammatory response, the release of cytokines and growth factors (IL-6, IL-8, TGF-ß1, VEGF) was determined by ELISA. Non-parametric statistical analyses were performed to compare all groups and time points (Mann-Whitney U test or Kruskal-Wallis test; α = .05). RESULTS: While eDMP and especially S. mutans reduced the number and viability of DPCs (p ≤ .0462), neither DPCs nor eDMP affected the growth and viability of S. mutans during coculture (p > .0546). The growth of S. mutans followed a common curve, but the death phase was not reached within 72 h. S. mutans consumed medium glucose in only 30 h, whereas in the absence of S. mutans, cells were able to catabolize glucose throughout 72 h, resulting in the corresponding amount of l-lactate. No change in medium pH was observed. S. mutans induced IL-6 production in DPCs (p ≤ .0011), whereas eDMP had no discernible effect (p > .7509). No significant changes in IL-8 were observed (p > .198). TGF-ß1, available from eDMP supplementation, was reduced by DPCs over time. VEGF, on the other hand, was increased in all groups during coculture. CONCLUSIONS: The results show that the coculture of DPCs and S. mutans is possible without functional impairment. The bacterially induced stimulation of proinflammatory and regenerative cytokines provides a basis for future investigations and the elucidation of molecular biological relationships in pulp defence against caries.

Randomized controlled clinical trial on the efficacy of a novel antimicrobial chewing gum in reducing plaque and gingivitis in adolescent orthodontic patients.

OBJECTIVES: Chewing gums containing antiseptics or other antimicrobial substances may be effective in reducing plaque and gingivitis. Therefore, the aim of this randomized placebo-controlled clinical trial was to investigate the efficacy of a novel antimicrobial chewing gum containing essential oils (cinnamon, lemon, peppermint) and extracts on reduction of dental plaque and gingivitis as well as on oral health-related quality of life (OHRQoL) in adolescent orthodontic patients. MATERIALS: 52 patients (11-22 years of age) were randomly assigned to use a test chewing gum (COVIDGUM, Clevergum) or a commercially available control chewing gum over a period of 10 days. Approximal plaque index (API), papillary bleeding index (PBI) and an OHRQoL questionnaire for children (COHIP-G19) were assessed at baseline (BL), after 10 days (10d) and 30 days (30d). In addition, oral health and oral hygiene related questions of the COHIP-G19 questionnaire were evaluated separately in subscales at each timepoint. Data were analyzed using non-parametrical statistical procedures (α = 0.05). RESULTS: API and PBI decreased significantly over time from BL to 10d and from BL to 30d in both groups, without significant differences between the groups. In both groups, the COHIP-G19 score, oral health subscale and oral hygiene subscale decreased significantly over time. Regarding the oral hygiene subscale, the test group showed significantly better scores at 30d (p = 0.011). CONCLUSION: Both chewing gums performed similarly effective in terms of reducing plaque accumulation and gingival inflammation and improving OHRQoL. CLINICAL RELEVANCE: Chewing gums without antimicrobial ingredients may be sufficient to decrease plaque accumulation and gingival inflammation.

Fluorescence Spectroscopy Shows Porphyrins Produced by Cultured Oral Bacteria Differ Depending on Composition of Growth Media.

Red fluorophores synthesized by oral bacteria are important for fluorescence-based diagnosis and treatment because they are used as markers for bacterially infected tissue, mature plaque, or calculus. A range of porphyrins have been identified as the source of this fluorescence in carious tissue. It is not clear which of these porphyrins are produced by individual oral bacteria or whether this ability depends on other factors. This study examined and compared the fluorescence spectra produced by selected cultured oral bacteria when grown on agars containing different nutrients with spectra for protoporphyrin IX, Zn-protoporphyrin IX, haematoporphyrin, and haematin. Actinomyces israelii (Deutsche Sammlung von Mikroorganismen [DSM], 43320), Actinomyces naeslundii (DSM 43013), Fusobacterium nucleatum (DSM, 20482), Lactobacillus casei (DSM, 20011), Prevotella intermedia (DSM, 20706), Streptococcus mutans (DSM, 20523), Streptococcus oralis (DSM, 20627), Streptococcus salivarius (DSM, 20560) and Streptococcus sobrinus (DSM, 20742) were rehydrated and grown anaerobically on caso, caso blood (containing 5% sheep blood), and caso chlorophyll (containing 5% spinach extract) agar for 3 days at 37°C in the dark. Colonies were harvested, transferred to ethanol, and centrifuged. Fluorescence emission spectra were recorded from the supernatant at 405 nm excitation (Fluorolog 3-22, Jobin Yvon-Spex ISA, Edison, NJ, USA). All Streptococci, L. casei, and F. nucleatum produced red fluorescence when grown on caso and caso chlorophyll agar but not on caso blood agar. A. naeslundii and P. intermedia emitted intense red fluorescence when grown on caso or caso blood agar but not on caso chlorophyll agar. Fluorescence emission spectra of A. naeslundii and P. intermedia grown on caso blood agar correlated exactly with both fluorescence peaks for protoporphyrin-IX at 632 and 701 nm. Most peaks observed could be correlated with at least one of the emission peaks of protoporphyrin IX, Zn-protoporphyrin IX, or haematoporphyrin. Oral bacteria emitted red fluorescence matching known porphyrins, but this depended on nutrients available in the agar.

Preprocedural mouthwashes for infection control in dentistry-an update.

OBJECTIVES: Aerosols and splatter are routinely generated in dental practice and can be contaminated by potentially harmful bacteria or viruses such as SARS-CoV-2. Therefore, preprocedural mouthwashes containing antiseptic agents have been proposed as a potential measure for infection control in dental practice. This review article aims to summarize the clinical (and, if insufficient, preclinical) evidence on preprocedural mouthwashes containing antiseptic agents and to draw conclusions for dental practitioners. METHODS: Literature on preprocedural mouthwashes for reduction of bacterial or viral load in dental aerosols was searched and summarized. RESULTS: Preprocedural mouthwashes, particularly those containing chlorhexidine digluconate (CHX), cetylpyridinium chloride (CPC), or essential oils (EO), can significantly reduce the bacterial load in dental aerosols. With respect to viruses such as HSV-1, there are too little clinical data to draw any clear recommendations. On the other hand, clinical data is consolidating that CPC-containing mouthwashes can temporarily reduce the intraoral viral load and infectivity in SARS-CoV-2 positive individuals. Nevertheless, potential risks and side effects due to regular antiseptic use such as ecological effects or adaptation of bacteria need to be considered. CONCLUSIONS: The use of preprocedural mouthwashes containing antiseptics can be recommended according to currently available data, but further studies are needed, particularly on the effects on other viruses besides SARS-CoV-2. When selecting a specific antiseptic, the biggest data basis currently exists for CHX, CPC, EO, or combinations thereof. CLINICAL RELEVANCE: Preprocedural mouthwashes containing antiseptics can serve as part of a bundle of measures for protection of dental personnel despite some remaining ambiguities and in view of potential risks and side effects.

General diseases and medications in 687 patients reporting on adverse effects from dental materials.

OBJECTIVES: Examination of patients claiming adverse effects from dental materials can be very challenging. Particularly, systemic aspects must be considered besides dental and orofacial diseases and allergies. Therefore, the aim of this study was to investigate a cohort of 687 patients reporting on adverse effects from dental materials focusing on findings related to known general diseases or conditions or medication-related findings with relevance to their subjective complaints. METHODS: Six hundred eighty-seven patients visiting a specialized consultation on claimed adverse effects from dental materials were retrospectively investigated for their subjective complaints, findings related to known general diseases or conditions, medication-related findings, dental and orofacial findings, or allergies with relevance to their subjective complaints. RESULTS: The most frequent subjective complaints were burning mouth (44.1%), taste disorders (28.5%), and dry mouth (23.7%). In 58.4% of the patients, dental and orofacial findings relevant to their complaints could be found. Findings related to known general diseases or conditions or medication-related findings were found in 28.7% or 21.0% of the patients, respectively. Regarding medications, findings related to antihypertensives (10.0%) and psychotropic drugs (5.7%) were found most frequently. Relevant diagnosed allergies toward dental materials were found in 11.9%, hyposalivation in 9.6% of the patients. In 15.1% of the patients, no objectifiable causes for the expressed complaints could be found. CONCLUSIONS: For patients complaining of adverse effects from dental materials, findings related to known general diseases or conditions and medications should be given particular consideration, while still in some patients, no objectifiable causes for their complaints can be found. CLINICAL RELEVANCE: For patients complaining about adverse effects from dental materials, specialized consultations and close collaboration with experts from other medical fields are eligible.

Impact of access cavity cleaning on the seal of postendodontic composite restorations in vitro.

AIM: The aim of the study was to investigate the influence of cavity cleaning and conditioning on marginal integrity of directly placed post-endodontic composite class-I-restorations in vitro. METHODOLOGY: A total of 168 fully intact teeth without caries or fillings received pre-endodontic composite restorations (class-II) after their extraction. Occlusal endodontic access-cavities were prepared, and root canals were instrumented and filled with gutta-percha and an epoxy resin-based sealer. Prior to post-endodontic class-I-restoration, access cavities were completely contaminated with sealer, cleaned with alcohol and pre-treated as follows: cleaner only (alcohol), glycine-polishing, Al2 O3 sandblasting, carbide bur (immediate as well as delayed restoration). A positive control (not contaminated with sealer and adhesive used) and negative control (cleaner used but no adhesive) were established. Half of the teeth from each group were subjected to thermocycling and mechanical loading (TCML). Marginal integrity of post-endodontic restoration was evaluated in oro-vestibular or mesio-distal sections after AgNO3 dye penetration (DP) by standardized photomacroscopic imaging and expressed in per cent of margin length along all segments and separately for enamel, dentine and composite, respectively. Results were analysed non-parametrically (α = .05). RESULTS: No restorations or teeth fractured or debonded completely. Without TCML, the median DP of all segments was significantly higher for the negative control compared with all other groups in oro-vestibular cutting direction (53%; p = .002) and in mesio-distal cutting direction (51%; p ≤ .041). The other groups without TCML revealed 16%-24% DP (oro-vestibular) and 12%-24% DP (mesio-distal). With TCML, the median DP in oro-vestibular cutting direction for all segments ranged between 48% and 62% for all groups, a significant difference was only observed between glycine-polishing and carbide bur (p = .041). In mesio-distal cutting direction, the median DP in negative control was 69% with TCML and significantly higher compared with all other groups (p = .002). For all other groups, the median DP of all segments ranged between 28% and 40% with TCML without significant differences. Error rates method (k = 7) revealed a significant influence of TCML in general on penetration of all segments in both oro-vestibular and mesio-distal cutting directions. CONCLUSION: Additional access cavity pre-treatment after alcohol cleaning did not improve the marginal integrity of post-endodontic composite restorations. Thorough cleaning of the access cavity with alcohol seems to assure an acceptable marginal integrity to the tooth and restorative composite.

One-year results of a novel self-adhesive bulk-fill restorative and a conventional bulk-fill composite in class II cavities-a randomized clinical split-mouth study.

OBJECTIVES: In the context of the phase-down of amalgam, development of easily applicable, permanent restorative materials is of high clinical interest. Aim of this study was to evaluate the clinical performance of a novel, tooth-colored, self-adhesive bulk-fill restorative (SABF, 3M Oral Care) and a conventional bulk-fill composite (Filtek One, 3M Oral Care; FOBF) for restoring class II cavities. The null-hypothesis tested was that both materials perform similar regarding clinical performance. MATERIALS AND METHODS: In this randomized split-mouth study, 30 patients received one SABF and one FOBF restoration each. Scotchbond Universal (3M Oral Care) was used as adhesive for FOBF (self-etch mode), while SABF was applied directly without adhesive. Restorations were evaluated by two blinded examiners at baseline, 6 months and 12 months employing FDI criteria. Non-parametric statistical analyses and χ2-tests (α = 0.05) were applied. RESULTS: Thirty patients (60 restorations) were available for the 6- and 12-month recalls exhibiting 100% restoration survival. All restorations revealed clinically acceptable FDI scores at all time points and for all criteria. Only regarding esthetic properties, FOBF performed significantly better than SABF regarding surface lustre (A1) and color match and translucency (A3) at all time points and marginal staining (A2b) at 12 months. CONCLUSIONS: The null-hypothesis could not be rejected. Both materials performed similarly regarding clinical performance within the first year of clinical service. SABF exhibited slightly inferior, but clinically fully acceptable esthetic properties as compared to FOBF. CLINICAL RELEVANCE: Within the limitations of this study, the self-adhesive bulk-fill restorative showed promising results and may be recommended for clinical use.

Molecular Biological Comparison of Dental Pulp- and Apical Papilla-Derived Stem Cells.

Both the dental pulp and the apical papilla represent a promising source of mesenchymal stem cells for regenerative endodontic protocols. The aim of this study was to outline molecular biological conformities and differences between dental pulp stem cells (DPSC) and stem cells from the apical papilla (SCAP). Thus, cells were isolated from the pulp and the apical papilla of an extracted molar and analyzed for mesenchymal stem cell markers as well as multi-lineage differentiation. During induced osteogenic differentiation, viability, proliferation, and wound healing assays were performed, and secreted signaling molecules were quantified by enzyme-linked immunosorbent assays (ELISA). Transcriptome-wide gene expression was profiled by microarrays and validated by quantitative reverse transcription PCR (qRT-PCR). Gene regulation was evaluated in the context of culture parameters and functionality. Both cell types expressed mesenchymal stem cell markers and were able to enter various lineages. DPSC and SCAP showed no significant differences in cell viability, proliferation, or migration; however, variations were observed in the profile of secreted molecules. Transcriptome analysis revealed the most significant gene regulation during the differentiation period, and 13 biomarkers were identified whose regulation was essential for both cell types. DPSC and SCAP share many features and their differentiation follows similar patterns. From a molecular biological perspective, both seem to be equally suitable for dental pulp tissue engineering.

Colonization of Helicobacter pylori in the oral cavity - an endless controversy?

Helicobacter pylori is associated with chronic gastritis, gastric or duodenal ulcers, and gastric cancer. Since the oral cavity is the entry port and the first component of the gastrointestinal system, the oral cavity has been discussed as a potential reservoir of H. pylori. Accordingly, a potential oral-oral transmission route of H. pylori raises the question concerning whether close contact such as kissing or sharing a meal can cause the transmission of H. pylori. Therefore, this topic has been investigated in many studies, applying different techniques for detection of H. pylori from oral samples, i.e. molecular techniques, immunological or biochemical methods and traditional culture techniques. While molecular, immunological or biochemical methods usually yield high detection rates, there is no definitive evidence that H. pylori has ever been isolated from the oral cavity. The specificity of those methods may be limited due to potential cross-reactivity, especially with H. pylori-like microorganisms such as Campylobacter spp. Furthermore, the influence of gastroesophageal reflux has not been investigated so far. This review aims to summarize and critically discuss previous studies investigating the potential colonization of H. pylori in the oral cavity and suggest novel research directions for targeting this critical research question.

Limited antimicrobial efficacy of oral care antiseptics in microcosm biofilms and phenotypic adaptation of bacteria upon repeated exposure.

OBJECTIVES: The aims of this study were to investigate the antimicrobial efficacy of antiseptics in saliva-derived microcosm biofilms, and to examine phenotypic adaption of bacteria upon repeated exposure to sub-inhibitory antiseptic concentrations. METHODS: Saliva-derived biofilms were formed mimicking caries- or gingivitis-associated conditions, respectively. Microbial compositions were analyzed by semiconductor-based 16S rRNA sequencing. Biofilms were treated with CHX, CPC, BAC, ALX, and DQC for 1 or 10 min, and colony forming units (CFU) were evaluated. Phenotypic adaptation of six selected bacterial reference strains toward CHX, CPC, and BAC was assessed by measuring minimum inhibitory concentrations (MICs) over 10 passages of sub-inhibitory exposure. Protein expression profiles were investigated by SDS-PAGE. RESULTS: Both biofilms showed outgrowth of streptococci and Veillonella spp., while gingivitis biofilms also showed increased relative abundances of Actinomyces, Granulicatella, and Gemella spp. Antiseptic treatment for 1 min led to no relevant CFU-reductions despite for CPC. When treated for 10 min, CPC was most effective followed by BAC, ALX, CHX, and DQC. Stable adaptations with up to fourfold MIC increases were found in E. coli toward all tested antiseptics, in E. faecalis toward CHX and BAC, and in S. aureus toward CPC. Adapted E. coli strains showed different protein expression as compared with the wildtype strain. CONCLUSION: Antiseptics showed limited antimicrobial efficacy toward mature biofilms when applied for clinically relevant treatment periods. Bacteria showed phenotypic adaptation upon repeated sub-inhibitory exposure. CLINICAL RELEVANCE: Clinicians should be aware that wide-spread use of antiseptics may pose the risk of inducing resistances in oral bacteria.

Pathophysiological mechanisms of root resorption after dental trauma: a systematic scoping review.

BACKGROUND: The objective of this scoping review was to systematically explore the current knowledge of cellular and molecular processes that drive and control trauma-associated root resorption, to identify research gaps and to provide a basis for improved prevention and therapy. METHODS: Four major bibliographic databases were searched according to the research question up to February 2021 and supplemented manually. Reports on physiologic, histologic, anatomic and clinical aspects of root resorption following dental trauma were included. Duplicates were removed, the collected material was screened by title/abstract and assessed for eligibility based on the full text. Relevant aspects were extracted, organized and summarized. RESULTS: 846 papers were identified as relevant for a qualitative summary. Consideration of pathophysiological mechanisms concerning trauma-related root resorption in the literature is sparse. Whereas some forms of resorption have been explored thoroughly, the etiology of others, particularly invasive cervical resorption, is still under debate, resulting in inadequate diagnostics and heterogeneous clinical recommendations. Effective therapies for progressive replacement resorptions have not been established. Whereas the discovery of the RANKL/RANK/OPG system is essential to our understanding of resorptive processes, many questions regarding the functional regulation of osteo-/odontoclasts remain unanswered. CONCLUSIONS: This scoping review provides an overview of existing evidence, but also identifies knowledge gaps that need to be addressed by continued laboratory and clinical research.

Cetylpyridinium Chloride: Mechanism of Action, Antimicrobial Efficacy in Biofilms, and Potential Risks of Resistance.

Antimicrobial resistance is a serious issue for public health care all over the world. While resistance toward antibiotics has attracted strong interest among researchers and the general public over the last 2 decades, the directly related problem of resistance toward antiseptics and biocides has been somewhat left untended. In the field of dentistry, antiseptics are routinely used in professional care, but they are also included in lots of oral care products such as mouthwashes or dentifrices, which are easily available for consumers over-the-counter. Despite this fact, there is little awareness among the dental community about potential risks of the widespread, unreflected, and potentially even needless use of antiseptics in oral care. Cetylpyridinium chloride (CPC), a quaternary ammonium compound, which was first described in 1939, is one of the most commonly used antiseptics in oral care products and included in a wide range of over-the-counter products such as mouthwashes and dentifrices. The aim of the present review is to summarize the current literature on CPC, particularly focusing on its mechanism of action, its antimicrobial efficacy toward biofilms, and on potential risks of resistance toward this antiseptic as well as underlying mechanisms. Furthermore, this work aims to raise awareness among the dental community about the risk of resistance toward antiseptics in general.

Tooth survival and clinical outcomes up to 26 years after guided tissue regeneration therapy in deep intra-bony defects: Follow-up investigation of three randomized clinical trials.

AIM: To investigate tooth survival and clinical long-term outcomes up to 26 years following guided tissue regeneration (GTR) therapy in deep intra-bony defects. METHODS: Patients from three prospective clinical split-mouth studies, which investigated the outcomes of GTR therapy, were re-evaluated 21-26 years after surgery independent of the membrane type used, and tooth survival was assessed according to several site-specific and patient-related factors. RESULTS: About 50 patients contributing 102 defects were available for this long-term follow-up. After up to 26 years (median 23.3 years), 52.9% of the teeth were still in situ. The median survival of the extracted teeth was 13.8 years. Patients with diabetes mellitus and/or smoking history lost significantly more teeth in the long term. Compared to the 1-year situation, there was no new median CAL loss after up to 26 years in the teeth which were still in situ. CONCLUSIONS: Within the limitations of this study, our data show that more than 50% of the initially seriously diseased teeth were still in situ up to 26 years following GTR therapy despite an overall limited adherence to SPT. In the majority of these teeth, the CAL gain 1 year after GTR could be maintained over this long period.

Influence of selective caries excavation on marginal penetration of class II composite restorations in vitro.

Selective caries excavation may support pulp preservation. This in vitro study investigated the influence of selective removal of demineralized dentin on marginal integrity of composite restorations as determined by dye penetration. Dentinal caries-like lesions were produced in the approximal surfaces of 40 extracted human molars (ethylenediaminetetraacetate, 0.5 M, 96 h). The following test procedures were established: complete excavation, selective excavation, and caries-free control. Two class II cavities with enamel at the cervical margins were prepared per tooth and demineralization volume was determined by micro-computed tomography for the purpose of a stratified distribution to receive complete excavation or selective excavation. After complete or selective excavation (30 cavities each), adhesive composite restorations were placed. Cavities without demineralized dentin (20 cavities) served as control. The marginal integrity of restorations was evaluated by dye penetration with and without thermocycling or mechanical loading. Results were analyzed by non-parametrical statistical tests (Mann-Whitney U Test) with an α = 0.05 level of significance. Dye penetration did not differ significantly among completely excavated, selectively excavated, or undemineralized teeth, but was increased by thermocycling and mechanical loading in all experimental groups. Selective caries removal did not increase marginal penetration in class II restorations. The presence of remaining demineralized dentin surrounded by sound dentin did not impair marginal integrity of restorations with margins placed in sound enamel.

Longevity of posterior composite and compomer restorations in children placed under different types of anesthesia: a retrospective 5-year study.

OBJECTIVES: The aims of this study were (i) to assess cumulative survival rates of class II resin-based composite and compomer restorations in primary molars with a 5-year observation period and (ii) to analyze the influence of different types of anesthesia and different localizations of the restorations in the teeth. METHODS: Patient charts of a private practice for pediatric dentistry were screened for class II resin-based composite (Spectrum TPH3) and compomer (Dyract Posterior; both Dentsply DeTrey) restorations in primary molars with a 5-year observation period used with Adper Prompt L-Pop (3M-ESPE). One restoration per patient (age ≤ 6 years at placement) was randomly selected. RESULTS: Two hundred sixty restorations were included (43% resin-based composites, 57% compomers). After 5 years, cumulative survival rates were 43% for resin-based composite and 49% for compomer restorations with no statistically significant differences. There was a tendency for higher survival rates for restorations placed under N2O inhalation sedation or general anesthesia. Distal-occlusal compomer restorations showed significantly lower survival rates (p = 0.003) as compared to mesial-occlusal compomer restorations. CONCLUSION: Within the limitations of the study, we conclude that type of restorative material as well as the type of anesthesia do not influence restoration survival rates, although restorations placed in patients receiving N2O inhalation sedation or general anesthesia tend to perform better as compared with patients receiving no anesthesia or only local infiltration. CLINICAL RELEVANCE: Resin-based composite and compomer restorations show similar survival rates of more than 43% (annual failure rates less than 11.5%) after 5 years for restoration of primary molars.

A prospective clinical pilot study on the effects of a hydrogen peroxide mouthrinse on the intraoral viral load of SARS-CoV-2.

OBJECTIVES: SARS-CoV-2 is mainly transmitted by inhalation of droplets and aerosols. This puts healthcare professionals from specialties with close patient contact at high risk of nosocomial infections with SARS-CoV-2. In this context, preprocedural mouthrinses with hydrogen peroxide have been recommended before conducting intraoral procedures. Therefore, the aim of this study was to investigate the effects of a 1% hydrogen peroxide mouthrinse on reducing the intraoral SARS-CoV-2 load. METHODS: Twelve out of 98 initially screened hospitalized SARS-CoV-2-positive patients were included in this study. Intraoral viral load was determined by RT-PCR at baseline, whereupon patients had to gargle mouth and throat with 20 mL of 1% hydrogen peroxide for 30 s. After 30 min, a second examination of intraoral viral load was performed by RT-PCR. Furthermore, virus culture was performed for specimens exhibiting viral load of at least 103 RNA copies/mL at baseline. RESULTS: Ten out of the 12 initially included SARS-CoV-2-positive patients completed the study. The hydrogen peroxide mouthrinse led to no significant reduction of intraoral viral load. Replicating virus could only be determined from one baseline specimen. CONCLUSION: A 1% hydrogen peroxide mouthrinse does not reduce the intraoral viral load in SARS-CoV-2-positive subjects. However, virus culture did not yield any indication on the effects of the mouthrinse on the infectivity of the detected RNA copies. CLINICAL RELEVANCE: The recommendation of a preprocedural mouthrinse with hydrogen peroxide before intraoral procedures is questionable and thus should not be supported any longer, but strict infection prevention regimens are of paramount importance. TRIAL REGISTRATION: German Clinical Trials Register (ref. DRKS00022484).

Ca2+ release and buffering effects of synthetic hydroxyapatite following bacterial acid challenge.

BACKGROUND: Synthetic particulate hydroxyapatite (HAP; Ca5(PO4)3(OH)) is used as ingredient in oral care products but its effects on cariogenic biofilms are not clear yet. The primary mode of action of HAP may be acting as a calcium phosphate reservoir when deposited in oral biofilms and release Ca2+ and (hydrogen) phosphate ions upon bacterial acid challenge. The aim of this in vitro study was to test this hypothesis by investigating release of Ca2+ ions and potential buffering effects from HAP upon bacterial acid challenge in planktonic cultures and biofilms of Streptococcus mutans. METHODS: Planktonic cultures of S. mutans were grown in BHI broth with 1% sucrose or with additional 5% HAP or 5% silica for up to 48 h. Separately, biofilms of S. mutans were grown in BHI for 72 h in total. After 24 h of this biofilm culture, either BHI alone or BHI with additional 0.5% HAP or 0.5% silica was added. After 48 h, BHI with 1% sucrose was added to allow bacterial acid formation. Ca2+ release was determined colorimetrically and pH measurements were performed using a pH electrode. For statistical analysis, non-parametrical procedures were applied (n ≥ 10; Mann-Whitney U test; α = 0.05). RESULTS: Relevant release of Ca2+ was only evident in planktonic cultures or biofilms with HAP but not in both other groups (p ≤ 0.001). In suspended biofilms with HAP, median pH was 4.77 after 72 h and about 0.5 pH units higher as compared to both other groups (4.28 or 4.32, respectively; p ≤ 0.001). CONCLUSIONS: Under the tested conditions, synthetic HAP releases Ca2+ ions upon bacterial acid challenge and may also show some buffering capacity but further studies are needed to investigate whether the concentrations tested here can also be reached clinically in dental biofilms.

Antimicrobial photodynamic therapy - what we know and what we don't.

Considering increasing number of pathogens resistant towards commonly used antibiotics as well as antiseptics, there is a pressing need for antimicrobial approaches that are capable of inactivating pathogens efficiently without the risk of inducing resistances. In this regard, an alternative approach is the antimicrobial photodynamic therapy (aPDT). The antimicrobial effect of aPDT is based on the principle that visible light activates a per se non-toxic molecule, the so-called photosensitizer (PS), resulting in generation of reactive oxygen species that kill bacteria unselectively via an oxidative burst. During the last 10-20 years, there has been extensive in vitro research on novel PS as well as light sources, which is now to be translated into clinics. In this review, we aim to provide an overview about the history of aPDT, its fundamental photochemical and photophysical mechanisms as well as photosensitizers and light sources that are currently applied for aPDT in vitro. Furthermore, the potential of resistances towards aPDT is extensively discussed and implications for proper comparison of in vitro studies regarding aPDT as well as for potential application fields in clinical practice are given. Overall, this review shall provide an outlook on future research directions needed for successful translation of promising in vitro results in aPDT towards clinical practice.