The oral microbiota is a reservoir for antimicrobial resistance: resistome and phenotypic resistance characteristics of oral biofilm in health, caries, and periodontitis.

BACKGROUND: Antimicrobial resistance (AMR) is an ever-growing threat to modern medicine and, according to the latest reports, it causes nearly twice as many deaths globally as AIDS or malaria. Elucidating reservoirs and dissemination routes of antimicrobial resistance genes (ARGs) are essential in fighting AMR. Human commensals represent an important reservoir, which is underexplored for the oral microbiota. Here, we set out to investigate the resistome and phenotypic resistance of oral biofilm microbiota from 179 orally healthy (H), caries active (C), and periodontally diseased (P) individuals (TRN: DRKS00013119, Registration date: 22.10.2022). The samples were analysed using shotgun metagenomic sequencing combined, for the first time, with culture technique. A selection of 997 isolates was tested for resistance to relevant antibiotics. RESULTS: The shotgun metagenomics sequencing resulted in 2,069,295,923 reads classified into 4856 species-level OTUs. PERMANOVA analysis of beta-diversity revealed significant differences between the groups regarding their microbiota composition and their ARG profile. The samples were clustered into three ecotypes based on their microbial composition. The bacterial composition of H and C samples greatly overlapped and was based on ecotypes 1 and 2 whereas ecotype 3 was only detected in periodontitis. We found 64 ARGs conveying resistance to 36 antibiotics, particularly to tetracycline, macrolide-lincosamide-streptogramin, and beta-lactam antibiotics, and a correspondingly high prevalence of phenotypic resistance. Based on the microbiota composition, these ARGs cluster in different resistotypes, and a higher prevalence is found in healthy and caries active than in periodontally diseased individuals. There was a significant association between the resistotypes and the ecotypes. Although numerous associations were found between specific antibiotic resistance and bacterial taxa, only a few taxa showed matching associations with both genotypic and phenotypic analyses. CONCLUSIONS: Our findings show the importance of the oral microbiota from different niches within the oral cavity as a reservoir for antibiotic resistance. Additionally, the present study showed the need for using more than one method to reveal antibiotic resistance within the total oral biofilm, as a clear mismatch between the shotgun metagenomics method and the phenotypic resistance characterization was shown.

Influence of the long-term use of oral hygiene products containing stannous ions on the salivary microbiome - a randomized controlled trial.

Oral hygiene products containing tin are suitable to prevent erosive tooth wear, yet effects on the oral microbiota are not known yet. Therefore, this study determined the salivary microbiome of 16 participants using products with stannous ions for three years (TG) compared with a control group (CG) to assess their influence on the microbiota. Participants were included in a randomized controlled clinical trial (RCT) with biannual visits. Illumina Miseq sequencing revealed as most abundant genera: Streptococcus (TG 14.3%; CG 13.0%), Veillonella (TG 11.3%; CG 10.9%), Prevotella (TG 7.0%; CG 9.8%), Haemophilus (TG 6.6%; CG 7.2%), Porphyromonas (TG 5.9%, CG 5.1%), Leptotrichia (TG 5.8%; CG 4.9%), Actinomyces (TG 4.0%; CG 4.6%) and Neisseria (TG 5.4%; CG 4.2%). Beta-Diversity was not significantly different between groups at both time points, although significant differences between groups were found for certain taxa after three years. The genus Prevotella was found in higher abundance in CG whereas Neisseria and Granulicatella, health-associated taxa, were found more abundantly in TG. Salivary microbiota after three years reflected a composition associated with oral health, hence continual use as a preventive measure for dental erosion can be considered safe and benefitting oral health for patients with a high risk of erosion.

Underlying Resin Infiltration and Direct Composite Veneers for the Treatment of Severe White Color Alterations of the Enamel: Case Report and 13-Month Follow-Up.

Pronounced white color alterations due to structural anomalies of the enamel are often insufficiently masked by bleaching techniques or resin infiltration procedures alone. This frequently leads to the choice of more invasive prosthetic restorations in order to correct tooth color and form. This article describes a minimally invasive treatment option for esthetic and functional rehabilitation in the case of a 13-year-old female patient with suspected severe fluorosis and misalignment of the anterior teeth. The restorations were performed using underlying resin infiltration to homogenize the tooth shade. In a second step, direct composite veneers were applied on top to attain a natural tooth color and adjust tooth alignment and form. By joining the two minimally and noninvasive techniques, this treatment option combines the directive for preservation of hard tooth structure while treating adolescents with the benefits of easy adaptation and repair when the occlusion is still in adjustment.

Clinical effect of stannous fluoride and amine fluoride containing oral hygiene products: A 4-year randomized controlled pilot study.

This 4-year randomized controlled trial (RCT) aimed at investigating whether routine home use of both a SnCl2/AmF/NaF-containing mouth rinse and toothpaste has a preventive effect on oral health. Fifty-four test subjects were examined in biannual intervals. The primary endpoint "dental erosion" was determined by the Basic Erosive Wear Examination (BEWE). The secondary endpoints were "saliva pH", "dentin hypersensitivity" generated by Visual Analogue Scale (VAS), and "discoloration" measured by the Lobene Stain Index (LSI). A mixed model for repeated measures (MMRM) was used to analyze the primary endpoint "dental erosion". Primary analysis showed a significant intervention effect of the SnCl2/AmF/NaF-containing test product (p1 = 0.0242). This result was confirmed by two additional MMRM-based sensitivity analyses. Comparison of all models showed "dental erosion" values of the intervention group  below values of the control group. Discoloration of the teeth was significantly higher in the intervention than in the control group at all time points. Saliva pH and dentin hypersensitivity were not significantly different between groups over four years. In summary, this RCT is the first to indicate a possible preventive effect of SnCl2/AmF/NaF-containing oral hygiene products on dental erosion over a follow-up period of four years.

Diagnostic Value of the Basic Erosive Wear Examination for the Assessment of Dental Erosion on Patients, Dental Photographs, and Dental Casts.

OBJECTIVES: The aim of this trial was to investigate the diagnostic value of the basic erosive wear examination (BEWE) in clinical use, on dental photographs, and on dental casts over a two-year follow-up period (2013-2015). According to the main hypothesis for longitudinal monitoring of dental erosion, the BEWE is equally reproducible by the three assessment methods. METHODS AND MATERIALS: The clinical assessment included intraoral photographic documentation, dental impressions, oral examination, and assessment of BEWE. Clinical assessment of BEWE was done by one blinded examiner, whereas assessment on photographs and dental casts was performed by three calibrated examiners and repeated after 14 days. The three assessment methods were analyzed separately by longitudinal agreement and inter- and intrarater reliability (intraclass correlation coefficient) alongside 95% confidence intervals (CIs). RESULTS: Comparing the longitudinal data of the years 2013-2015, clinical use and photographs showed no significant difference (p=0.0681-0.9963), whereas the statistical analysis showed a significant difference for dental casts by comparing data from 2013 vs 2014 (p=0.0266) as well as data from 2013 vs 2015 (p=0.0001). Statistical evaluation of overall BEWE showed an intrarater reliability of 0.79-0.91 for photographs and 0.60-0.87 for dental casts. The interrater reliability was 0.77 (95% CI=[0.69; 0.84]) for photographs and 0.63 (95% CI=[0.52; 0.72]) for dental casts. CONCLUSION: This investigation showed that in longitudinal clinical monitoring, the assessment of the BEWE on patients and dental photographs yielded comparable results. In addition, based on these findings, the assessment of the BEWE on dental casts showed moderate reproducibility. Therefore, dental casts may be better used for laboratory assessment techniques.

Clinical management and prevention of dental caries in athletes: A four-year randomized controlled clinical trial.

The aims of this four-year randomized controlled clinical trial were to gain insights into management and prevention of dental caries and the effect of stannous fluoride products in athletes. Fifty-four participants were randomized into test and control groups. The test group used special stannous fluoride products. The primary endpoint dental caries was assessed by the ICDAS-II-System and analyzed both by a linear mixed model for repeated measures and a generalized linear mixed model. During the observation period an increase in caries-free surfaces from 64.91 ± 6.42 at baseline to 73.22 ± 4.43 was observed. In surfaces with caries superficialis and caries media, a decrease from 13.94 ± 5.70 and 2.96 ± 2.55 surfaces at baseline to 7.89 ± 3.18 and 0.46 ± 0.78 after 2.5 years was noted, respectively. The analysis showed no effect of stannous fluoride products, but a significant difference for the time of examination (p < 0.0001). In addition, it could be shown that at any time of examination, the odds of developing caries media on a new surface was significantly lower than at baseline (up to 25-times). Due to biannual dental examinations, professional tooth cleaning and restorative treatment the number of caries-free surfaces increased and the odds of a new surface to be afflicted with caries media decreased 25-fold.

Psychosocial impact, perceived stress and learning effect in undergraduate dental students during transition from pre-clinical to clinical education.

INTRODUCTION: This study aimed to develop a suitable instrument for a comprehensive quantitative and qualitative assessment of perceived psychosocial impact, levels of stress and learning effect in undergraduate dental students during the transition from pre-clinical to clinical education. These findings might improve curricular structures and didactic organisation during this period. MATERIALS AND METHODS: At the beginning of their first clinical year, undergraduate dental students were asked to complete an anonymous forty-item questionnaire. Two hundred and seventy-six undergraduate dental students were willing to participate and completed the questionnaire and participated during the years 2011-2016. RESULTS: The response rate was between 45% and 96%. Correlational analysis (Spearman-Rho) in the field of psychosocial impact showed the dental teacher to be the most important multiplier of students' feelings. If the students feel that their teacher acts cooperatively, positive items increase and negative items decrease significantly (P < .0001). Also, students who report high levels of stress are affected significantly in their psychosocial interaction (P < .0001). Wilcoxon test yielded highest levels of stress in endodontology during the first weeks (P < .0001). During the same period, the greatest learning increment was seen for diagnostics and caries excavation. CONCLUSION: In conclusion, teaching of undergraduate dental students during the transition period from pre-clinical to clinical education can be positively influenced by a supportive learning environment and by specific chronological modifications in the curriculum. Students should start their clinical training with diagnostics, preventive dentistry and initial periodontal treatment. Due to high levels of perceived stress, endodontology should be introduced later in the clinical curriculum.

Novel Microscalpels for Removing Proximal Composite Resin Overhangs on Class II Restorations.

INTRODUCTION: Limited access to interdental spaces complicates removal of excess material when placing class II composite resin restorations. Evidence-based recommendations on interproximal finishing are rare. We present novel microscalpels for this indication. The aim of the study was to test their fracture strength and cutting ability and to compare microscalpels with the use of a scaler, oscillating devices (G5-ProShape, G5-Proxocare), finishing strips and scalpels of sizes 12, 15, and 21 in a standardized in vitro model. METHODS AND MATERIALS: Fracture strength (LOAD) and cutting forces (CUT) of microscalpels were evaluated at different angles (15, 30, 60, and 75 degrees; n=30 each) in a universal testing machine. Devices were compared in vitro using standardized composite overhangs. Marginal quality (QUAL; n=30) and quantity of excess/deficit (QUAN; n=30) were evaluated using scanning electron microscopy (SEM) for each device (explorative data analysis, Student t-test or analysis of variance; post hoc Scheffé). RESULTS: Microscalpels showed the highest LOAD (95.8 [5.0] N) (mean [standard deviation]) and easiest cutting (CUT) (7.6 [1.5]) at 15 degrees. At all angles, LOAD was significantly higher than CUT (p<0.001). Perfect margins were seen most often with scalpel size 12 (QUAL: 37% relative frequency), while most excess (73.4%) was observed with finishing strips. QUAN was lowest with microscalpels (19.3 [4.4] µm) and highest with finishing strips (116.0 [18.8]). Use of scalers led to fractures and crack formation. CONCLUSION: Microscalpels are able to cut composite at a lower force than necessary to fracture the blades at all angles. Small and/or curved scalpels yield the best-quality margins.

Effect of endurance training on dental erosion, caries, and saliva.

The aim of this investigation was to give insights into the impact of endurance training on oral health, with regard to tooth erosion, caries, and salivary parameters. The study included 35 triathletes and 35 non-exercising controls. The clinical investigation comprised oral examination, assessment of oral status with special regard to caries and erosion, saliva testing during inactivity, and a self-administered questionnaire about eating, drinking, and oral hygiene behavior. In addition, athletes were asked about their training habits and intake of beverages and sports nutrition. For saliva assessment during exercise, a subsample of n = 15 athletes volunteered in an incremental running field test (IRFT). Athletes showed an increased risk for dental erosion (P = 0.001). No differences were observed with regard to caries prevalence and salivary parameters measured during inactivity between athletes and controls. Among athletes, a significant correlation was found between caries prevalence and the cumulative weekly training time (r = 0.347, P = 0.04). In athletes after IRFT and at maximum workload, saliva flow rates decreased (P = 0.001 stimulated; P = 0.01 unstimulated) and saliva pH increased significantly (P = 0.003). Higher risk for dental erosions, exercise-dependent caries risk, and load-dependent changes in saliva parameters point out the need for risk-adapted preventive dental concepts in the field of sports dentistry.

Proximal box elevation with resin composite and the dogma of biological width: clinical R2-technique and critical review.

Provided that moisture control is possible, today's resin composite materials can be applied successfully in the restorative treatment of extensively decayed teeth. This suggests that restorative margins will be increasingly located below the cementoenamel junction, probably invading biological width. The recently introduced technique of proximal box elevation (PBE) offers the possibility of performing a stepwise elevation of deep proximal cavities to create more favorable preparation margins for direct or indirect restorations. Clinical instructions for the restoration of extensively damaged teeth are given through this presentation. A two-step R2-technique will be shown, and a critical review of the dogma of biological width will be presented.

Bacterial biofilm composition in caries and caries-free subjects.

BACKGROUND: Certain major pathogens such as Streptococcus mutans, Lactobacillus spp. and others have been reported to be involved in caries initiation and progression. Yet, in addition to those leading pathogens, microbial communities seem to be much more diverse and individually differing. The aim of this study, therefore, was to analyze the bacterial composition of carious dentin and the plaque of caries-free patients by using a custom-made, real-time quantitative polymerase chain reaction assay (RQ-PCR). METHODS: The study included 26 patients with caries and 28 caries-free controls. Decayed tooth substance and plaque samples were harvested. Bacterial DNA was extracted and tested for the presence of 43 bacterial species or species groups using RQ-PCR. RESULTS: Relative quantification revealed that Propionibacterium acidifaciens was significantly more abundant in caries samples than were other microorganisms (fold change 169.12, p = 0.023). In the caries-free samples, typical health-associated species were significantly more prevalent. Unsupervised hierarchical cluster analysis showed a high abundance of P. acidifaciens in caries subjects and distinct but individually differing bacterial clusters in the caries-free subjects. The distribution of 11 bacteria allowed full discrimination between caries and caries-free subjects. CONCLUSION: Within the investigated cohort, P. acidifaciens was the only pathogen significantly more abundant in caries subjects. Cluster analysis yielded a diverse flora in caries-free subjects, whereas it was narrowed down to a small range of a few outcompeting members in caries subjects.

Intermingled skin grafts with in vitro cultured keratinocytes--experiments with rats.

In vitro cultured autogenic keratinocytes were used instead of autogenic skin islets in intermingled skin grafts on rats. According to the observations made with the original method, the allogenic epidermis is being rejected. The cultured keratinocytes start to grow out in circles, eventually covering the remaining allodermis in the form of a multilayered, well-differentiated epidermis. The prospects of these findings for possible future clinical applications are discussed.