Biomedical subjects

Matthias Zehnder

Publications and source records attributed to Matthias Zehnder.

At least 19 recordsLinked to original sources

PubMed2007

Enterococcus faecalis type strain leakage through root canals filled with Gutta-Percha/AH plus or Resilon/Epiphany.

The aim of this in vitro study was to compare leakage of Enterococcus faecalis ATCC 29212 through root canals of single-rooted extracted human mandibular premolars filled with either gutta-percha/AH Plus or Resilon/Epiphany using the continuous wave of condensation technique. Test and control teeth were suspended in an experimental bacterial leakage setup for 50 days. Kaplan-Meyer curves showed a tendency of the gutta-percha/AH Plus root fillings to prevent leakage better than Resilon/Epiphany counterparts. This tendency, however, was not statistically significant (log-rank test, p = 0.141). The estimated mean time for turbidity to occur in the broth below the suspended root was 35 days (SD = 5 days) in the gutta-percha/AH Plus and 33 days (SD = 4 days) in the Resilon/Epiphany group. It was concluded that within the limitations of this study, there was no apparent advantage of using Resilon/Epiphany over gutta-percha/AH Plus.

Dental Leakage↗

PubMed2006

Root canal irrigants.

Local wound debridement in the diseased pulp space is the main step in root canal treatment to prevent the tooth from being a source of infection. In this review article, the specifics of the pulpal microenvironment and the resulting requirements for irrigating solutions are spelled out. Sodium hypochlorite solutions are recommended as the main irrigants. This is because of their broad antimicrobial spectrum as well as their unique capacity to dissolve necrotic tissue remnants. Chemical and toxicological concerns related to their use are discussed, including different approaches to enhance local efficacy without increasing the caustic potential. In addition, chelating solutions are recommended as adjunct irrigants to prevent the formation of a smear layer and/or remove it before filling the root canal system. Based on the actions and interactions of currently available solutions, a clinical irrigating regimen is proposed. Furthermore, some technical aspects of irrigating the root canal system are discussed, and recent trends are critically inspected.

Anti-Infective Agents, Local↗

PubMed2006

Bone powder enhances the effectiveness of bioactive glass S53P4 against strains of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans in suspension.

OBJECTIVE: To assess whether bone powder in suspension enhances the antimicrobial efficacy of bioactive glass S53P4 against Gram-negative microbiota commonly associated with peri-implant disease. METHODS: Standardized suspensions of Porphyromonas gingivalis ATCC 33277 and YH 3, as well as Actinobacillus actinomycetemcomitans ATCC 29523 and KK 2 were added to 24-h suspensions of bioactive glass S53P4 with ground bovine bone powder, decalcified bone, or hydroxylapatite powder. Recovery of viable bacteria was assessed using anaerobic culture methods. As a reference, the antibacterial effect of an inert borosilicate powder with a particle size corresponding to that of the bioactive glass was tested. Counts of bacteria suspended in a pure unbuffered saline solution served as controls. RESULTS: A significant drop in viable microorganisms was observed in suspensions of bioactive glass and bone powder compared to counterparts of pure bioactive glass. In contrast, neither the presence of hydroxylapatite powder nor the presence of decalcified bone in suspension caused any increase in bioactive glass killing efficacy on the microorganisms under investigation. Inert borosilicate glass showed no antibacterial effects per se or in combination with bone powder. CONCLUSION: The antimicrobial effect of a combined bioactive glass-ground bone powder suspension was an in vitro observation which should be confirmed using adequate in vivo models.

Aggregatibacter actinomycetemcomitans↗

PubMed2005

Dentin enhances the effectiveness of bioactive glass S53P4 against a strain of Enterococcus faecalis.

OBJECTIVE: The aim of the current study was to test the impact of dentin powder on the antimicrobial efficacy of bioactive glass S53P4 (BAG). STUDY DESIGN: BAG was suspended (preincubated) in saline at 37 degrees C for different time periods with or without human dentin powder, hydroxylapatite, or decalcified dentin. Subsequently, Enterococcus faecalis ATCC 29212 cells were added to these suspensions and bacterial recovery measured with and without the use of gentle sonication. Furthermore, survival of bacteria in test and control suspensions was assessed over time. Supernatants of suspensions were analyzed for their element contents using atomic absorption spectrophotometry. The effects of pH, silica, and osmolarity on E faecalis viability were assessed using specifically prepared solutions. RESULTS: BAG preincubated with dentin powder caused a significant (P < .05) decrease in viability compared to pure BAG suspensions. This was not based on adherence of bacteria to solid particles or agglutination of the cells, because sonication did not increase bacterial yields. Hydroxylapatite and decalcified dentin did not increase BAG killing efficacy. The additive effect of BAG + dentin powder was dose dependent, occurred only with solids in suspension, and increased with suspension time. An augmented dissolution of glass components, especially silicon, was measured in BAG + dentin powder compared to pure BAG suspensions or counterparts containing hydroxylapatite or decalcified dentin. High osmolarity per se did not affect E faecalis viability, whereas high pH and silica levels did. CONCLUSION: The observed phenomenon was related to an increased BAG dissolution triggered by dentin powder, causing elevated local pH and silica levels.

Anti-Infective Agents, Local↗

PubMed2005

Sealing smooth enamel surfaces with a newly devised adhesive patch: a radiochemical in vitro analysis.

OBJECTIVES: To assess the enamel-protective potential of a newly devised adhesive patch when used as a smooth surface sealant. METHODS: Eighty enamel discs were prepared from bovine lower central incisors and then irradiated. Twenty specimens were treated with one of three sealing options: enamel bond in a two-step application, the prototype of an adhesive patch, or a flowable resin. Unsealed enamel served as positive controls. Loss of apatite was determined using a radiochemical liquid scintillation method after immersion of the samples in saliva or lactic acid (n=10 per treatment group) each for up to 21 days, during which this experimental and control enamel surfaces were exposed to ten toothbrush strokes per day. Quantitative liquid scintillation data were verified by polarized light microscopy. RESULTS: With lactic acid exposure, a double layer of enamel bonding showed better enamel protection than untreated controls, but was significantly less effective than the adhesive patch or filled composite (P<0.05). No significant differences were noted between the latter two treatments. SIGNIFICANCE: It was concluded that the adhesive patch under investigation merits further studies to assess its potential as an inter-proximal sealant.

Acrylates↗

PubMed2005

Factors affecting the outcome of orthograde root canal therapy in a general dentistry hospital practice.

OBJECTIVE: The goal of this study was to weigh the impact of patient-related, tooth-related, and treatment-related factors on therapy outcome in a series of consecutive patients. STUDY DESIGN: Eighty-four patients were included. Of these, 66 (79%) were available for recall after > or = 30 months (mean = 46 months). Root canal treatments were performed using a standard protocol. At recall, teeth were scored by means of the periapical index (PAI), which was the dependent variable (dichotomized to sound/ unsound). Explanatory variables were patient age, integrity of the nonspecific immune system, smoking status, dichotomized PAI score before treatment, initial treatment versus retreatment, prior exposition of the root canal to saliva, stainless-steel hand versus NiTi rotary instrumentation, and quality of root filling. Unit of observation was the patient-individual. Data were analyzed using univariate tests and backward stepwise logistic regression analysis. RESULTS: After 5 steps with elimination of the least significant independent variable, status of the immune system (P = .05), initial PAI (P = .04), and root filling quality (P = .01) were found to be the indispensable predictors for treatment outcome. Using these 3 explanatory variables, the logistic regression model had a predictive value of 87%, compared to 91% with all 8 variables. Success rate at recall (PAI < or = 2 without symptoms) was 88% (95% CI = 78, 94). CONCLUSION: The integrity of a patient's nonspecific immune system, which has been neglected in earlier investigations, is a significant predictor for endodontic treatment outcome, and should receive more attention in future studies.

Adolescent↗

PubMed2005

Interface evaluation after manual and ultrasonic insertion of standardized class I inlays using composite resin materials of different viscosity.

OBJECTIVE: The aim of the present study was to investigate the effect of manual and ultrasonic insertion of standardized class I inlays (Cerana) using three composite resin materials of different viscosity (Tetric Flow, Tetric, and Tetric Ceram) on time to seat inlays, film thickness, and filler distribution within the materials. METHODS: In a preliminary test, mean loads for manual and ultrasonic insertion were measured using the high viscosity composite resin material (Tetric Ceram). These loads were then applied with all composite resin materials to evaluate the times required to seat the inlays. In addition, film thickness was assessed using scanning electron microscopy, and filler distribution (wt% silicon, barium, ytterbium) was monitored using energy-dispersive spectroscopy. RESULTS: Ultrasonic insertion significantly reduced mean load applied to seat inlays (6.4+/-1.4 N; mean+/-SD) as compared to manual insertion (18.9+/-3.1 N; p < 0.001). Using an ultrasonic device, times for insertion values were significantly lower in the high and medium viscosity composite resin material groups compared to manual insertion (p < 0.05). The widest film thickness was recorded for the high viscosity composite resin material in combination with manual insertion (p < 0.05). However, when ultrasound was applied, there was no difference in film thickness between the three materials at any levels. Furthermore, the analysis of filler distribution revealed no significant differences between groups. CONCLUSION: Highly filled viscous composite resin materials may be used in combination with the ultrasonic insertion technique without untoward effects on film thickness or filler distribution.

Barium↗

PubMed2005

Reducing surface tension in endodontic chelator solutions has no effect on their ability to remove calcium from instrumented root canals.

The aim of this study was to evaluate the effect of reducing surface tension in endodontic chelator solutions on their ability to remove calcium from instrumented root canals. Aqueous solutions containing 15.5% EDTA, 10% citric acid, or 18% 1- hydroxyethylidene-1, 1-bisphosphonate (HEBP) were prepared with and without 1% (wt/wt) polysorbate (Tween) 80 and 9% propylene glycol. Surface tension in these solutions was measured using the Wilhelmy method. Sixty-four extracted, single-rooted human teeth of similar length were instrumented and irrigated with a 1% sodium hypochlorite solution and then randomly assigned (n = 8 per group) to receive a final one-minute rinse with 5 ml of test solutions, water, or the pure aqueous Tween/propylene glycol solution. Calcium concentration in eluates was measured using atomic absorption spectrometry. Incorporation of wetting agents resulted in a reduction of surface tension values by approximately 50% in all tested solutions. However, none of the solutions with reduced surface tension chelated more calcium from canals than their pure counterparts (p > 0.05).

Analysis of Variance↗

PubMed2005

The effects of temperature on sodium hypochlorite short-term stability, pulp dissolution capacity, and antimicrobial efficacy.

The purpose of this study was to test some effects of preheating NaOCl solutions using a commercially available syringe heating device. Irrigating solution temperatures in 10-ml syringes were measured. Stability of 5.25, 2.62, and 1% NaOCl solutions for 60 min at 20, 45, and 60 degrees C was assessed using iodine/thiosulfate titration. Human pulp tissue dissolution capacity of a 1% NaOCl solution was gauged at the latter temperatures, and compared to corresponding values with a 5.25% solution at 20 degrees C. Killing efficacy of diluted NaOCl solutions against 48-h incubations of Enterococcus feacalis ATCC 29212 was compared at 45 degrees C and 20 degrees C. Using the heating device, a 20 degrees C solution reached 45 degrees C and 60 degrees C in 7 and 20 min, respectively. Solutions remained stable during the observation period. The 1% NaOCl solution at 45 degrees C dissolved pulp tissues as effectively as the 5.25% solution at 20 degrees C, while the 60 degrees C/1% solution was significantly more effective (p < 0.05). A 100-fold increase in killing efficacy was observed between corresponding NaOCl solutions at 20 degrees C and 45 degrees C.

Analysis of Variance↗

PubMed2005

Chelation in root canal therapy reconsidered.

The aim of this study was to assess interactions of EDTA and citric acid (CA) with sodium hypochlorite (NaOCl), the indispensable endodontic irrigant. Other chelators were simultaneously evaluated as possible alternatives: sodium triphosphate (STP), amino tris methylenephosphonic acid (ATMA), and 1- hydroxyethylidene-1, 1-bisphosphonate (HEBP). Available chlorine was titrated in chelator-NaOCl solutions. All chelators other than HEBP and STP caused an almost complete, immediate loss of available chlorine in solution. Atomic absorbtion spectrometry and SEM evaluation of root canal walls of instrumented teeth indicated that NaOCl had no negative effect on calcium-complexing ability of chelators. STP was too weak a complexing agent to warrant further studies. Finally, CA-, EDTA-, and HEBP-NaOCl mixtures were evaluated for their antimicrobial capacity. Again, EDTA and CA negatively interfered with NaOCl, while HEBP did not.

Anti-Infective Agents, Local↗

PubMed2004

Preliminary evaluation of bioactive glass S53P4 as an endodontic medication in vitro.

Calcium hydroxide is the "gold standard" endodontic medication, but it may fail to eliminate certain facultative bacteria and yeasts found in root canal systems. In this study, standardized bovine dentin blocks infected with Enterococcus faecalis were treated with an aqueous calcium hydroxide or bioactive glass S53P4 (BAG) powder suspension. While calcium hydroxide was ineffective, the BAG suspension eliminated the infection in the sampled dentin layers after 5 days. In a direct exposure test, preincubation with human dentin boosted the BAG-killing efficacy against E. faecalis ATCC29212, Candida albicans CCUG19915, Pseudomonas aeruginosa ATCC9027, Streptococcus sanguis ATCC10556, and S. mutans ATCC25175. BAG placed in the root canals of extracted teeth did not alter root-dentin pH. Consequently, the conditions under which the microbiota were killed were not pH-mediated. Further studies are ongoing to help clarify the antimicrobial BAG effect in the presence of dentin.

Animals↗

PubMed2004

Soft tissue dissolution capacity of currently used and potential endodontic irrigants.

Necrotic soft-tissue remnants in root canals may provide a source of nutrition for surviving microbiota after root-canal therapy. This study assessed the necrotic tissue dissolution capacity of some popular and some potential root-canal irrigants: 1% (wt/vol) sodium hypochlorite (NaOCl), 10% chlorhexidine, 3% and 30% hydrogen peroxide, 10% peracetic acid, 5% dichloroisocyanurate (NaDCC), and 10% citric acid. Standardized necrotic tissue samples obtained from pig palates were incubated in these solutions, and their weight loss was measured over time. None of the test solutions except sodium hypochlorite had any substantial tissue dissolution capacity. It was concluded that this might be important when considering the use of irrigants other than NaOCl.

Animals↗

PubMed2004

[Uses of MTA, a review. Part 2: Clinical applications].

Mineral trioxide aggregate (MTA) has been used in dentistry for the last five to eight years. Because of its high biocompatibility, its good sealing ability, and the fact that cemental tissues grow on this material, it has a relatively wide range of applications in endodontics. MTA may be used to cap exposed vital pulps, to seal open apices or perforations, or as a retro-filling material in apical surgery. These applications are presented in the current article, and discussed based on case reports.

Aluminum Compounds↗

PubMed2004

Glutaraldehyde in bonding systems disinfects dentin in vitro.

PURPOSE: To study the dentin disinfecting capacity of glutaraldehyde-containing bonding agents. MATERIALS AND METHODS: Uniformly sized bovine dentin blocks infected with Enterococcus faecalis ATCC 29212 were treated according to manufacturer's instructions with a three-step bonding system (Syntac Classic), its single components, or Gluma Primer. Bacterial growth from dentinal filings obtained immediately after application of the bonding agents was assessed at different dentin depths. Minimal inhibitory concentration and minimal bactericidal concentration of glutaraldehyde against E. faecalis were determined. RESULTS: Both Gluma Primer and Syntac Adhesive disinfected dentin, while the other components failed to do so. This was explained by the high antibacterial efficacy of glutaraldehyde even at low concentrations. Applied in consecutive order, the Syntac bonding system disinfected dentin blocks equally well with or without previous application of Gluma Primer. CONCLUSION: Under the conditions of the current study, bonding agents containing glutaraldehyde appear to be good dentin disinfectants compatible with bonding systems. However, their effect on pulp tissue awaits further clarification.

Animals↗

PubMed2004

[Indications for use of MTA, a review. Part 1: Chemical, physical and biological properties of MTA].

Mineral trioxide aggregate is a recently introduced dental material. It may be used to seal perforations, make retrograde fillings in root-end resections, seal open apices, or cap vital pulps. In this review of the literature, physical, chemical, and biologic properties of MTA are discussed. Studies have suggested that MTA provides a better seal than formerly used materials such as IRM, amalgam, and Super-EBA. Further, MTA has low cytotoxicity and excellent biocompatibility. In vivo studies demonstrated a beneficial effect of MTA on pulpal and periodontal regeneration. Although controlled randomized clinical trials are still missing, MTA appears to be a suitable material to tightly seal dental hard tissues from the periodontium, or to cap the exposed pulp.

Aluminum Compounds↗

PubMed2004

Penetration of a bonding agent into De- and remineralized enamel in vitro.

PURPOSE: To evaluate bonding penetration into different enamel substrates. MATERIALS AND METHODS: Ten extracted human molars were mesiodistally sectioned. Buccal and lingual enamel surfaces were divided into four equal areas using sticky wax. The central two areas of each tooth (n = 20) were demineralized for 12 weeks using an acidic gel (pH 4.8). The lateral areas served as controls. After demineralization, ten specimens were remineralized in a saliva substitute for three weeks. An amine fluoride solution (Elmex Fluid) was applied on one half of each specimen before acid etching. After etching for 120 s, an enamel-bonding agent (Heliobond) containing 0.1% rhodamine was applied onto test and control areas, and was light cured for 60 s. Subsequently, the specimens were sectioned and tag length was determined using a confocal laser scanning microscope (CLSM). Results were statistically compared with ANOVA followed by Scheffe's and Bonferroni/Dunn post hoc tests. RESULTS: With a mean penetration depth of 68 +/- 22 microm, tags in demineralized enamel were significantly longer than in other groups (p < or = 0.01). Penetration decreased significantly in remineralized areas or when fluoride was used (p < or = 0.01), but was still significantly deeper than in control sites (p < or = 0.01). CONCLUSION: Penetration of an unfilled resin into enamel was considerably influenced by the degree of dental hard tissue mineralization. Penetration was increased in demineralized enamel; however, remineralized enamel also allowed good penetration of the bonding agent.

Acid Etching, Dental↗

PubMed2004

Glass-fiber frameworks for fixed partial dentures: laser-interferometrical in vitro analysis.

OBJECTIVES: Laboratory tests confirmed superior physical properties of fiber-reinforced resin composites; however, clinical failures continue to be observed. This in vitro study introduces a new method to measure strain and fracture resistance in glass fiber-reinforced pontics. METHOD AND MATERIALS: Thirty standardized pontics in five groups were fabricated. Pontics were reinforced with: glass fiber (group 1); glass-fiber bundle surrounded by glass-fiber mesh (group 2); glass fiber with glass-fiber mesh parallel to the pontic's occlusal surface (group 3); or glass-fiber mesh parallel to glass-fiber bundle (group 4). Unreinforced resin composite pontics served as controls (group 5). A laser interferometer measured inner strains (microm/mm) in sectioned pontics, occlusally loaded with 250 N and 450 N, with a universal testing machine. Inner strains were measured on three levels (1, 2, and 3). Specimens were then loaded to crack onset, and loads were recorded. Comparisons were made using analysis of variance. Kruskal-Wallis and Fisher's exact tests were used, respectively, for nonparametric and categorical data. RESULTS: Group 3 showed significantly lower mean strain values than controls. No significant differences in maximal inner strain values or crack onset loads were recorded. The framework of Group 3 inhibited crack propagation significantly better than that in groups 2 and 5. CONCLUSION: Within the limitations of this study, speckle interferometry proved to be a promising method for analyzing strains of pontics under load. The tested framework designs in this study had only limited influence on load-to-crack onset. When strategically placed, a glass-fiber mesh prevented crack propagation.

Analysis of Variance↗

PubMed2003

Cytokine gene expression--part of host defence in pulpitis.

Analyses of cytokines mediating inflammatory reactions are key to understanding the etiopathology of various diseases. This study investigated differences in cytokine gene expression between pulps from healthy virgin teeth and from symptomatic vital teeth with severe caries lesions in a group of young, healthy individuals. The mRNA levels of IL-1alpha, IL-1beta, IL-6, IL-8, and IL-18 were measured concomitantly by quantitative real-time RT-PCR. IL-1alpha and IL-1beta were not expressed at significantly higher levels in symptomatic versus clinically healthy pulps, while the difference was significant for the other cytokines (log-rank test, P<0.05). A concordance test for independence revealed significant correlation between IL-1alpha and IL-1beta, and between IL-6, IL-8, and IL-18 mRNA levels (P<0.05). The cytokine-specific differences revealed a differential significance of gene expression in cytokine regulation. The hypothesis that increase of cytokine mRNA expression is part of host reaction in pulpitis was corroborated by our observation.

Adolescent↗