Fracture load and chewing simulation of zirconia and stainless-steel crowns for primary molars.

Aesthetic alternatives to stainless-steel crowns for restoring primary molars attain growing interest. We studied the mechanical properties of prefabricated zirconia crowns and conventional crowns. Three brands of prefabricated zirconia crowns were compared with computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crowns, preveneered stainless-steel crowns, and conventional stainless-steel crowns regarding: (i) fracture load under each of three conditions [no pretreatment, artificial aging in saliva for 12 wk, and after chewing simulation/thermocycling (1.68 × 106 cycles/5-55°C)]; and (ii) survival rate during chewing simulation, considering decementation, fracture, chipping, fatigue cracks, and occlusal holes. Without pretreatment, the prefabricated zirconia crowns showed mean fracture load values between 893 N and 1,582 N, while the corresponding values for CAD/CAM zirconia crowns and preveneered stainless-steel crowns were 2,444 N and 6,251 N. Preveneered stainless-steel crowns showed significantly lower fracture loads after artificial aging (5,348 N after saliva aging; 3,778 N after chewing simulation) than without artificial aging, whereas the fracture load of zirconia crowns was not influenced negatively. The survival rate of the different groups of zirconia crowns and preveneered stainless-steel crowns during chewing simulation was 100%, but only 41.7% for the stainless-steel crowns. These in-vitro data suggest that prefabricated zirconia crowns are aesthetically and durable alternatives to stainless-steel crowns for primary molars.

Sensitivity of caries pathogens to antimicrobial peptides related to caries risk.

OBJECTIVES: Antimicrobial peptides (AMPs) represent important facets of the immune system controlling infectious diseases. However, pathogens show varying susceptibilities to AMPs. This study investigates the susceptibilities of strains of Streptococcus mutans (SM), Actinomyces naeslundii (AN), and Lactobacillus spp. (LB) towards AMPs and if there are correlations between the appearance of such high-risk strains and clinical caries status. MATERIAL AND METHODS: Plaque samples were collected from patients along with clinical examinations. Bacterial strains were identified via selective media, matrix-assisted laser desorption/ionization analysis-time of flight (MALDI-TOF), and arbitrary-primed-PCR (AP-PCR). Each strain was tested for susceptibility to LL-37, HBD-2, HNP-1, and HNP-3 or phosphate-buffered saline as negative control in a biofilm model on hydroxylapatite discs. Survival rates and resulting risk classification for each strain were determined. Correlations were calculated between the number of high-risk strains (all/S. mutans) appearing in patients and their clinical caries status. RESULTS: Forty-seven patients were included with mean DMFT values of 11.4 ± 8.7. A total of 8 different SM, 30 LB, and 47 AN strains were detected. One-way ANOVA indicated that type/concentration of AMPs had major influence on reductions of Lactobacilli and Actinomyces. Seventeen strains of AN, 2 of SM, and 6 of LB had low susceptibilities to AMPs. The number of such strains in patients showed significant positive correlations to the DMFT values (all p = 0.001; r = 0.452; S. mutans p < 0.0001, r = 0.558). CONCLUSION: The occurrence of low susceptible strains to AMPs seems to correlate with the individual caries status. CLINICAL RELEVANCE: The results may lead to new ways to identify individuals with increased caries risk.

Differences in physical characteristics and sealing ability of three tricalcium silicate-based cements used as root-end-filling materials.

PURPOSE: To evaluate differences in physical characteristics and sealing ability of root-end-fillings made with these materials compared to the gold standard (ProRoot MTA). METHODS: The physical characteristics of ProRoot MTA, Medcem MTA and Biodentine were evaluated regarding setting time, flow, film thickness, solubility and radiopacity according to the German Institute for Standardization (EN-ISO 6878). To investigate their sealing ability as root-end-fillings, a glucose penetration model was used. 60 human extracted single-rooted teeth were endodontically treated, root-end resections performed and divided in three groups of 20 teeth, using either ProRoot MTA, Medcem MTA or Biodentine as root-end-filling material. After 30 days, glucose concentrations were determined photometrically, followed by statistical analysis (Kruskal-Wallis test, Mann-Whitney U-test). RESULTS: Biodentine showed the fastest setting time (< 12 minutes) and lowest film thickness (0.11± 0.01 mm), whereas Medcem MTA showed the best values regarding solubility (< 0.1%) and flow (9.5± 0.02 mm). ProRoot MTA revealed the highest radiopacity (7.58± 0.1 mm aluminum equivalent). The glucose leakage in the Medcem MTA group was significantly lower than in the ProRoot MTA group (P= 0.011). Biodentine showed lower leakage than ProRoot MTA (P= 0.031). CLINICAL SIGNIFICANCE: As Medcem MTA showed significantly lower leakage than the other materials tested, it may be an alternative for root-end-fillings with comparable physical characteristics to the current gold standard. With the exception of the high solubility, Biodentine performed well regarding leakage and setting time.

Comparison of ozone gas and sodium hypochlorite/chlorhexidine two-visit disinfection protocols in treating apical periodontitis: a randomized controlled clinical trial.

OBJECTIVES: In this single-blinded, prospective, randomized, controlled clinical trial, the effectiveness of an ozone gas or NaOCl/CHX disinfection protocol was compared within the root canal treatment of apical periodontitis. MATERIALS AND METHODS: Sixty permanent teeth were randomly allocated to one technique. The clinical/radiographic assessment criteria included clinical symptoms, periapical index (PAI), and size of the apical lesion. In both groups, the root canal was mechanically cleaned and irrigated with NaCl and EDTA. Ozone gas (32 g m-3) or NaOCl (3 %) was applied followed by a 1-week inter-appointment dressing (Ca(OH)2). As final disinfection, ozone gas (ozone group) or CHX 2 % (NaOCl group) was applied. Microbial samples were taken after preparing the access cavity, after chemo-mechanical treatment and after inter-appointment dressing by sterile paper points. Microbial identification was performed by mass spectroscopy (MALDI-TOF-MS) and 16S-rRNA gene sequencing. The treated teeth were blindly re-evaluated after 6/12 months. Success rates, the decrease in PAI, the size of apical lesions and bacterial reduction were compared between groups (Fischer's exact test, Mann-Whitney U test). RESULTS: There were no significant differences between the success rates (ozone group: 96.2/95.5 % after 6/12 months; NaOCl group: 95.5/95.2 % after 6/12 months). The differences in the decreases in PAI values and apical lesion sizes were also insignificant after 6 and 12 months. The bacterial reduction showed no significant differences between groups after chemo-mechanical treatment and after inter-appointment dressing. The most commonly found bacterial genera were Streptococcus spp., Parvimonas spp. and Prevotella spp. CONCLUSIONS: The here used ozone gas and NaOCl/CHX protocols showed no difference in bacterial reduction in the sampled areas of the root canals. CLINICAL RELEVANCE: Within the limitations of the study, ozone gas seems to be a possible alternative disinfection agent within the root canal treatment of apical periodontitis.

Comparison of chairside and laboratory CAD/CAM to conventional produced all-ceramic crowns regarding morphology, occlusion, and aesthetics.

OBJECTIVES: There are many ways to produce all-ceramic crowns. Computer-aided design and computer-aided manufacturing (CAD/CAM) procedures compete against conventional fabricated restorations. As different methods of production may produce variable results, this study aims to compare chairside and laboratory-based CAD/CAM systems to conventional crowns regarding their similarity to original tooth morphology, number of occlusal contacts, occlusal adjustment time, and subjective aesthetic perception. MATERIAL AND METHODS: Impressions of caries-free jaws were taken, and the resulting gypsum casts were scanned with a laboratory scanner. Preparations for all-ceramic full crowns were performed on first molars, and three different restorations were made: CEREC restorations (CER), laboratory-produced CAD/CAM crowns (LABCAD), and conventional waxed-up/pressed ceramic crowns (CONV). Time for occlusal adaptation and the number of occlusal contacts were noted. Two dentists performed aesthetic gradings of restorations. Statistical analysis included one-way ANOVA with least significant difference (LSD) post hoc test, t test, and Kruskal-Wallis test. RESULTS: Metrical deviations of the re-scanned crowns to the original, unprepared tooth surface were 220.55 ± 54.31 µm for CER, 265.94 ± 61.39 for LABCAD, and 252.44 ± 68.77 µm for CONV group. One-way ANOVA showed significant lower deviations for the CER group. LABCAD crowns showed significantly more occlusal contacts, whereas CONV crowns required the least time for occlusal adaptation and showed excellent aesthetic gradings. CONCLUSION: All three methods had pros and cons regarding different parameters. Further improvements of CAD/CAM software shall lead to restorations comparable to conventional restorations in all aspects, especially in aesthetics. CLINICAL RELEVANCE: All tested methods of production for all-ceramic crowns produced clinically acceptable results. Thus, in an individual case, the method chosen can be determined by the dentist's preference.

Antimicrobial effect of gaseous and aqueous ozone on caries pathogen microorganisms grown in biofilms.

PURPOSE: To evaluate the anti-microbial effect of gaseous and aqueous ozone on biofilms of caries pathogen microorganisms with regard to concentration and time dependency. METHODS: Biofilm cultures of Actinomyces naeslundii, Streptococcus mutans and Lactobacillus paracasei were grown on nitro-cellulose-membranes for 48 hours. The membranes were cut into equal-sized pieces and exposed to chlorhexidine digluconate (CHX) (positive control; 0.1-20%), gaseous (1-64 g m3) and aqueous ozone (1.25-20 microg ml(-1)) for 60 seconds. The influence of exposure time (30-120 seconds) was tested for exemplary concentrations of the three agents. Colony forming units of bacteria were counted. The bacteria survival rate was given as percentage of the negative control (PBS for CHX/aqueous ozone, ambient air for gaseous ozone). RESULTS: There was no difference in bacterial reduction of different species with general reduction close to zero for high concentrations of all agents. Univariate ANOVA with partial eta-squared (Eta2) statistics showed major effects for concentration/contact time of the agent on bacteria survival. High concentrated gaseous and aqueous ozone seem to be potential alternatives to CHX with equivalent antimicrobial activity.