Stefan Kranz

Background: Our group previously reported on the high bactericidal potential of berry juices, particularly those derived from blackcurrant fruits. In the present study, we tested the efficiency of various juice fractions from blackcurrant fruits (all-fruit juice: AFJ, squeezed juice: SJ, non-dialyzable juice material: NDFM, alcoholic fraction from berry skins: AFBS, aqueous fraction from berry skins: AQFBS) in their efficiency to suppress various oral gram-positive and gram-negative bacteria. Methods: AFJ, SJ, NDFM, AFBS, and AQFBS were prepared from freshly harvested blackcurrant fruits. These fractions were used for direct contact tests with planktonic cultures of Fusobacterium nucleatum (F.n.), Aggregatibacter actinomycetemcomitans (A.a.), Porphyromonas gingivalis (P.g.), Streptococcus gordonii (S.g.), Streptococcus mutans (S.m.), Streptococcus sobrinus (S.s.), Actinomyces naeslundii (A.n.), and Enterococcus faecalis (E.f.). Results: AFJ was the most efficient fraction, causing complete suppression of F.n., P.g., and S.g., and inducing a major reduction in A.a., A.n., and E.f. colony count. Bactericidal efficiency of the juices presents as follows: AFJ> AFBS > SJ> AQFBS> NDFM. Gram-negative bacteria were more susceptible to blackcurrant extracts compared to gram-positive species. AFJ efficiency was similar to 0.2% chlorhexidine solution in suppressing F. n., P. g., and S. g. Conclusions: All-fruit juice from blackcurrant shows a strong bactericidal activity on F.n., A.a., P.g., S.g., and A.n. Further research should investigate the potential of blackcurrant fruit extracts in controlling oral biofilm formation.

The methodical work describes all the necessary steps for establishing a stable oral ex vivo biofilm using saliva and crevicular plaque samples from periodontal healthy donors. First, cover slips were preconditioned with saliva supernatants and subsequently inoculated with crevicular plaque suspensions. Ex vivo biofilm formation was characterized by confocal laser scanning microscopy (cLSM) after 1, 4, 24, 48 and 72 h of anaerobic cultivation. Exemplarily, the inhibitory characteristics of blackcurrant fruit extracts [all-fruit juice (AFJ); alcoholic fraction from berry skins (AFBS)] were observed on 1, 4 and 24 h-aged ex vivo biofilms. Chlorhexidine (CHX, 0.2%) served as positive control. After direct contact (3 min), biofilms were dispersed, plated onto agar and anaerobically cultivated for 24 h. Early ex vivo biofilms (1 h-biofilm) showed scattered microbial colonies. After 4 h of cultivation, a multilayered biofilm was formed. Biofilm mass gradually increased, displaying a complex polymicrobial structure after 24 h. At 72 h, the biofilms had a dense three-dimensional appearance. Treatment with AFJ and CHX was more efficient in inhibiting biofilm growth compared to AFBS. Early biofilms (1 h, 4 h) were more susceptible to AFJ and CHX compared to 24 h-biofilms. The introduced model can be recommended for testing the efficiency of plaque-controlling agents.

Background: In adhesive dentistry, debonding-on-demand is attractive for situations where no permanent attachment is required. Due to its destructive nature, ultraviolet (UV) light may be of interest for attenuating bond forces. The aim of this study was to investigate the impact of UV light on the shear bond strength (SBS) of etch-and-rinse (n = 4) and universal adhesives (n = 3). Methods: Glass-ceramic samples were bonded to bovine enamel surfaces (n = 10/adhesive) and subjected to shear bond testing before and after exposure to UV light (320–390 nm, 126 Jcm⁻²). Data was statistically analyzed by Mann–Whitney U test. Results: Initial photopolymerized etch-and-rinse adhesives showed superior SBS compared to universal adhesives. Highest values were recorded for iBOND^® Total etch (15.48 MPa) and Syntac classic© (17.60 MPa). Lowest SBS was obtained for Ecosite Bond^® (2.63 MPa). Additional UV exposure caused a significant decrease in SBS among iBOND Total etch (5.24 MPa, p = 0.009) and Solobond M© (3.65 MPa, p = 0.005), while for Syntac classic©, an increase (24.12 MPa, p = 0.047) was recorded. Among all other tested adhesives, no significant changes were observed. Conclusions: UV radiation impacted SBS of etch-and-rinse adhesives only (decrease: iBOND Total Etch, Solobond M; enhancement: Syntac classic©). Further research should focus on introducing sufficient light-triggered debonding mechanisms.

Background/Objectives: The effect of fusidic acid on oral bacteria, especially on Gram- negative periodontopathogenic species, has not yet been investigated. This in vitro study aimed to analyze the antibacterial effect of fusidic acid alone and as an active component in electrospun poly(L-lactide-co-D/L-lactide) fiber fleeces. Methods: Minimal inhibitory concentrations (MIC) of fusidic acid and metronidazole (control) were determined for various oral bacteria. Eluates were collected from electrospun poly(L-lactide-co-D/L-lactide) fiber fleeces loaded with 10 and 20 wt% fusidic acid over a period of 28 d. Antibacterial activity was analyzed by means of a microdilution assay. Cytotoxicity was observed toward human gingival fibroblasts (HGFs). Results: All tested Gram-positive and Gram-negative oral bacteria were susceptible to fusidic acid. The lowest MIC was observed for Porphyromonas gingivalis (MIC < 0.062 µg/mL). Compared to the antibacterial activity of metronidazole, that of Porphyromonas gingivalis was suppressed by significant lower fusidic acid concentrations (p < 0.01). The eluates obtained from electrospun poly(L-lactide-co-D/L-lactide) fiber fleeces inhibited the growth of P. gingivalis, S. aureus, A. viscosus, and A. neslundii over a course of 28 days. The largest inhibition zones were detected for Porphyromonas gingivalis in case of the 20 wt% concentrations. The eluates were not cytotoxic toward HGFs. Conclusions: It was shown that fusidic acid has significant antibacterial potential. The results of the present investigation suggest that fusidic acid alone or delivered by electrospun fiber fleeces might be attractive for controlling oral pathogenic bacteria.

Objective: The present in-vivo-study aimed on identifying periodontopathogenic key species in correlation to the current classification system. It was evaluated if there is an association in frequency to single periodontitis stages and grades. Materials and methods: The study included 100 patients that were assigned to 4 test groups (periodontitis stages I-IV) and one healthy control group, each n = 20. Samples were collected from the deepest pockets of each sextant and analyzed for: Fusobacterium nucleatum (F.n.), Aggregatibacter actinomycetemcomitans (A.a.), Porphyromonas gingivalis (P.g.), Tannerella forsythia (T.f.), Treponema denticola (T.d.) and Enterococcus faecalis (E.f.). Results: Among all samples, F.n. was most common (98%), followed by T.f. (73%), T.d. (66%), P.g. (45%), A.a. (12%) and E.f. (3%). Controls showed no P.g., A.a. and E.f.. In stage I T.f. (p < 0.001) and T.d. (p = 0.022) were significantly more frequent. In stages II and III, P.g., T.f. and T.d. were significant (p < 0,001). In stage IV, A.a. (p = 0.003), P.g., T.f. and T.d. (p < 0.001) occurred with significant higher frequency. Grade C was more common among stage III and IV (20%) as compared to stage I and II (2.5%). Patients diagnosed with stage IV and grade C, showed significant association to A.a. (p = 0.001) and P.g. (p = 0.021). Conclusions: The present investigation proved significant correlation between periodontopathogenic key species, disease severity and progression risk. A.a. and P.g were most frequently in stage IV and grade C. Clinical relevance: Microbial analysis provide additional information in regard to the classification of periodontitis.

The objective of this study was to compile the currently available evidence regarding the functional and morphologic outcomes of functional orthodontic therapy for mandibular condyle fracture. We performed searches in PubMed and Google Scholar as well as manually (IOK issues 2008–2019) using the keywords “trauma”, “TMJ”, “activator”, “condylar fracture”, “fracture”, “mandibular condylar fracture”, “occlusal splint” and “functional appliance”. Screening and analysis of study eligibility were performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The search strategy identified 198 studies published between 1971 and 2018, with 93 studies remaining after removing duplicate hits. Of the 93 studies, 19 were included in this study, considering the inclusion criteria. There were 12 follow-up, 4 prospective, and 3 purely retrospective studies. Some of the studies showed good functional results of mandibular condyle fracture treatment, in addition to subjective patient satisfaction. The incisal edge difference could be increased to physiological ranges of >35 mm by means of activator therapy. Partial mandibular deviations to the fractured side remained post-therapy, especially after unilateral fractures. Fractures without significant dislocation and luxation showed radiographic changes in shape, described as hypoplastic and ellipsoid, in addition to good morphologic results. One study found that collum length shortened twofold after a luxated fracture compared with fractures without significant dislocation, despite activator therapy. Straightening of the fragment occurred only in the low-dislocated fragments. Overall, children showed a higher remodeling potential than adult patients. Several studies observed an improved clinical outcome for functional therapy after mandibular condyle fracture. The outcome is essentially determined by fracture type, fracture height, and age. Further studies, especially prospective studies, are necessary to improve the evidence of functional orthodontic therapy for mandibular condyle fractures.

(1) Background: The in vitro study aimed to investigate mechanical characteristics of resin composites and their suitability in direct restauration of endodontically treated teeth (ETT). (2) Methods: 38 endodontically treated premolars with occlusal access cavities were directly restored using the following resin composites and adhesives: Tetric Evo Ceram^® + Syntac classic^® (n = 10), Venus Diamond^® + iBond Total-Etch^® (n = 10), Grandio^® + Solobond M^® (n = 9), Estelite^® Sigma Quick + Bond Force^® (n = 9). After thermocycling, the elastic modulus, shear-bond-strength, fracture load (Fmax) and fracture mode distribution were evaluated. Statistical analysis: one-way ANOVA, t-test, Kruskal–Wallis test; p < 0.05. (3) Results: Grandio^® showed the highest E-modulus (15,857.9 MPa) which was significant to Venus Diamond^® (13,058.83 MPa), Tetric Evo Ceram^® (8636.0 MPa) and Estelite^® Sigma Quick (7004.58 MPa). The highest shear-bond-strength was observed for Solobond M^® (17.28 MPa), followed by iBond^® (16.61 MPa), Syntac classic^® (16.41 MPa) and Bond Force^® (8.37 MPa, p < 0.05). The highest fracture load (Fmax) was estimated for ETT restored with Venus Diamond^® (1106.83 N), followed by Estelite^® Sigma Quick (1030.1 N), Tetric Evo Ceram^® (1029 N) and Grandio^® (921 N). Fracture-mode distribution did not show any significant differences. (4) Conclusions: The observed resin composites and adhesives show reliable mechanical characteristics and seem to be suitable for direct restoration of endodontically treated teeth.

Background: Material-dependent parameters have an important impact on the efficiency of light polymerization. The present in vitro study aimed to investigate the influence of the increment thickness and shade of nano- and nanohybrid resin composites on the transmission of curing light. Methods: Three contemporary resin composites were evaluated: Tetric EvoCeram^® (TEC); Venus Diamond^® (VD); and Filtek Supreme XTE^® (FS XTE). Light transmission (LT) was recorded in accordance with the sample thickness (0.5 to 2.7 mm) and the shade. Polymerized samples were irradiated for 10 s each using the high-power LED curing light Celalux 2 (1900 mW/cm²). LT was simultaneously recorded using the MARC Patient Simulator (MARC-PS). Results: LT was strongly influenced by the composite layer thickness. For 0.5 mm-thick samples, a mean power density of 735 mW/cm² was recorded at the bottom side. For the 2.7 mm samples, a mean power density of 107 mW/cm² was measured. Only LT was markedly reduced in the case of darker shades. From A1 to A4, LT decreased by 39.3% for FS XTE and 50.8% for TEC. Dentin shades of FS XTE and TEC (A2, A4) showed the lowest LT. Conclusions: The thickness and shade of resin composite increments strongly influences the transmission of curing light. More precise information about these parameters should be included in the manufacture manual.

Recently, our group showed that additional supplementation of Trolox™ (vitamin E analogue) can significantly enhance the antimicrobial photodynamic effect of the photosensitizer Indocyanine green (ICG). Up to now, the combined effect has not yet been investigated on Enterococcus faecalis in dental root canals. In the present in vitro study, eighty human root canals were inoculated with E. faecalis and subsequently subjected to antimicrobial Photodynamic Therapy (aPDT) using ICG (250, 500, 1000 µg/mL) and near-infrared laser light (NIR, 808 nm, 100 Jcm⁻²). Trolox™ at concentrations of 6 mM was additionally applied. As a positive control, irrigation with 3% NaOCl was used. After aPDT, root canals were manually enlarged and the collected dentin debris was subjected to microbial culture analysis. Bacterial invasion into the dentinal tubules was verified for a distance of 300 µm. aPDT caused significant suppression of E. faecalis up to a maximum of 2.9 log counts (ICG 250 µg/mL). Additional application of Trolox^TM resulted in increased antibacterial activity for aPDT with ICG 500 µg/mL. The efficiency of aPDT was comparable to NaOCl-irrigation inside the dentinal tubules. In conclusion, ICG significantly suppressed E. faecalis. Additional application of Trolox^TM showed only minor enhancement. Future studies should also address the effects of Trolox^TM on other photodynamic systems.

(1) Background: In the oral environment, sound enamel and dental restorative materials are immediately covered by a pellicle layer, which enables bacteria to attach. For the development of new materials with repellent surface functions, information on the formation and maturation of salivary pellicles is crucial. Therefore, the present in situ study aimed to investigate the proteomic profile of salivary pellicles formed on different dental composites. (2) Methods: Light-cured composite and bovine enamel samples (controls) were exposed to the oral cavity for 30, 90, and 120 min. All samples were subjected to optical and mechanical profilometry, as well as SEM surface evaluation. Acquired pellicles and unstimulated whole saliva samples were analyzed by SELDI–TOF–MS. The significance was determined by the generalized estimation equation and the post-hoc bonferroni adjustment. (3) Results: SEM revealed the formation of homogeneous pellicles on all test and control surfaces. Profilometry showed that composite surfaces tend to be of higher roughness compared to enamel. SELDI–TOF–MS detected up to 102 different proteins in the saliva samples and up to 46 proteins in the pellicle. Significant differences among 14 pellicle proteins were found between the composite materials and the controls. (4) Conclusions: Pellicle formation was material- and time-dependent. Proteins differed among the composites and to the control.