Biomedical subjects

A Petschelt

Publications and source records attributed to A Petschelt.

At least 19 recordsLinked to original sources

PubMed2005

Calcium release and pH-characteristics of calcium hydroxide plus points.

AIM: To evaluate calcium ion release and pH-characteristics of calcium hydroxide plus points (CHPP), conventional calcium hydroxide points (CHP, both Coltène/Whaledent, Langenau, Germany) and aqueous calcium hydroxide suspension (CHS) (Calxyl, OCO, Dirmstein, Germany). METHODOLOGY: Ten CHPP or CHP of size 50 were immersed into 5 mL isotonic sodium chloride solution. Conventional Ca(OH)2-free gutta-percha points served as negative control. Calcium release was measured up to 44 days by means of complexometric titration. Time dependent pH behaviour of all points in comparison with CHS was determined immersing 30 points of size 50 into 2.3 mL 0.9% wt NaCl-solution at time intervals of 0.5-72 h by a microelectrode measuring chain and a pH-meter. The surface morphologies of new and used gutta-percha points were evaluated qualitatively under a scanning electron microscope. Statistical evaluation was carried out using Kolmogorov-Smirnov-tests, Mann-Whitney-tests and multifactorial anova. RESULTS: For CHPP, a threefold greater calcium release was measured compared with CHP. Both types of points as well as CHS showed a maximum pH of approximately 12. Differences between groups were statistically significant for calcium release and pH (multifactorial anova; P < 0.001). Both types of points showed porous surfaces after usage, with a rougher surface for CHPP. CONCLUSIONS: CHPP and CHP increased the pH of isotonic sodium chloride >11 within 3 min. CHPP had a greater release of Ca2+ compared with CHP.

Analysis of Variance↗

PubMed2005

Ceramic inserts do not generally improve resin composite margins.

summary Ceramic inserts are reported to possibly reduce polymerization shrinkage for posterior resin composite fillings. The aim of the present investigation was to evaluate the effect of different insert systems before and after thermomechanical loading. Sixty sound human third molars received occlusomesial Class II cavities, 40 with proximal margins 2 mm above and 20 with proximal margins 1 mm below the cementum-enamel junction. The specimens were randomly assigned to one of the six experimental groups (n = 10). The enamel-bordered cavities were restored with Syntac classic and Tetric Ceram (ST), Syntac classic, Tetric Ceram and beta-quartz inserts (TB), Syntac classic, Tetric Ceram and Cerana inserts (TC), Syntac classic, Tetric flow and SonicSys approx inserts (TS). The dentin-limited cavities were filled with Syntac classic and Tetic Ceram (DT), Syntac classic, Tetric flow and SonicSys approx inserts (DS). Before and after thermomechanical loading (100 000 x 50 N, 2500 x 5 degrees C/55 degrees C), replicas were made and both interfaces tooth/composite and insert/composite were examined under a scanning electron microscope at 200x. The Cerana and SonicSys insert groups showed significantly less gaps in enamel (P < 0.05). With beta-quartz inserts, no reduction of gaps was found (P > 0.05). Marginal integrity in dentine-bordered specimens could not be improved with SonicSys inserts (P > 0.05). The bonding performance insert/composite was promising for all IPS Empress inserts (Cerana, SonicSys enamel) but worse for beta-quartz inserts. Regarding gap formation between resin composite and tooth, Cerana and SonicSys inserts significantly reduced gaps. The use of SonicSys inserts in deep proximal cavities cannot be recommended.

Ceramics↗

PubMed2003

Effect of preparation mode on Class II resin composite repair.

Complete removal of failed posterior resin composite fillings is time-expensive and involves the risk of removing sound tooth substance. In any case of failure within the composite material, intra-oral repair would be favourable. This in vitro study was conducted to examine the effect of different preparation and bonding modes on integrity of repaired restorations. Forty-eight direct Class II resin composite restorations (Syntac Classic/Tetric Ceram) were placed in extracted human third molars. The specimens were stored for 365 days and then replaced partially by removing the central part of the proximal box with all margins located in composite. The partial repairs were placed with the same materials after pre-treatment with a silicon carbide bur and Syntac Classic (n = 8). Preparation modes have been (i) box-only parallel, (ii) box-only with undercuts, (iii) box with undercuts and additional occlusal retention. The repairs were performed either with (i) Tetric Ceram or with (ii) Tetric Flow as thin lining covered with Tetric Ceram. Before and after thermomechanical loading (100 000 cycles of 50 N and 2500 cycles between +5 and +55 degrees C in an artificial mouth), marginal quality between aged and freshly applied composite was evaluated by SEM at x200 magnification and microleakage was observed by light microscopy at x50 magnification. Box-only preparations exhibited a better fatigue resistance than preparations with additional occlusal retention. This observation was independent from the presence of undercuts (P < 0.05). An intermediary layer of flowable resin composite tended to result in better marginal quality, however, not being statistically significant.

Biocompatible Materials↗

PubMed2001

Effect of surface treatment on fatigue behaviour between Tetric Ceram inlays and Variolink luting composite.

The effect of pre-treatment of composite inlays on bonding performance between a resin composite inlay and a luting composite has not been fully studied. The aim of the present study was to evaluate the influence of three different pre-treatment modes on fatigue bond strength and marginal adaptation. One hundred twenty resin composite discs (Tetric Ceram) were made as simulated inlays and randomly assigned to four groups (n=30): Without treatment (WT), hydrofluoric acid etching for 15 s + silanating (HF), roughening with a silicon carbide bur (SC), and silica coating + silanating (CO). Luting composite cylinders (Variolink II low) were bonded to the discs using Heliobond, and after 24 h in water at 37 degrees C, quasistatic shear bond strengths (n=l) and fatigue bond strengths (n=20; 5,000 cycles) were measured. Thirty-two third molars received occlusomesial Class II cavities (n=8), and direct resin composite inlays were luted with identical methods and materials. Before and after thermomechanical loading (100,000x50 N, 2,500 x +5 degrees C/+55 degrees C), replicas were made and examined (SEM, x200). CO and SC exhibited significantly higher bond strengths and adhesive fatigue limits than HF and WT (P<0.05). After thermomechanical loading, CO (98% continuous margin) and SC (95% continuous margin) demonstrated that they provide significantly more fatigue resistance than HF (88%).

Acid Etching, Dental↗

PubMed2000

A new screening test for toxicity testing of dental materials.

OBJECTIVES: The development of a micro plate assay for cytotoxicity testing of dental materials based on a bioassay using brine shrimp larvae (artemia salina) as sensitive organisms. METHODS: Brine shrimp larvae are commonly used for cytotoxicity assays in pharmacology. These larvae are sensitive to toxic substances. The ratio between dead larvae (no motility) and living larvae (high motility) in comparison to a control without any toxic substances is used to estimate the toxicity of the test solutions. The test materials (Arabesk((R)), Solitaire((R)), Pertac((R)) II, Tetric((R)), Herculite((R)) and the compomer materials Dyract((R)), Hytac((R)), Compoglass((R))) were polymerized and consecutively milled. After incubation of 1g in 4ml distilled water at 37 degrees C for 48h, the solid materials were separated by centrifugation. The solutions were equibrilated with NaCl to a salt content of 25g/l. Aliquots of 200microl were distributed in eight micro wells and 50microl of a artemia salina containing (n=8-14) solution were added to each well. As controls eight wells with 250microl salt solution containing a comparable number of brine shrimp were used. At baseline, after 2, 5, 24 and 48h, the dead shrimp were counted using a stereo microscope. Finally all shrimps were sacrificed using Na-acid (5%) and counted to get the number of shrimps per well. RESULTS: All compomers and Solitaire caused 100% brine shrimp lethality after 24h and showed significantly (p<0.01, signed rank test) higher toxicities than the remaining composites. With the exception of Pertac II, all composites showed significantly higher toxic values than the control. Pertac II did not show any differences from the controls used. CONCLUSIONS: This new technique has some advantages for toxicity testing of restorative materials, because it can quickly be carried out at low costs. The disadvantage is the high quantity of material used and the low sensitivity.

Animals↗

PubMed1999

Fatigue behaviour of different dentin adhesives.

The aim of this in vitro study was to compare quasistatic and cyclic fatigue dentin bond strength of modern adhesive systems representing different generations. One hundred and fifty cavities were made in discs of freshly extracted human third molars and filled with direct resin composite restorations. Dentin adhesives of different generations (SY = Syntac Classic, multi-step system with self-etching primer; SE = Syntac Classic with additional phosphoric acid etching prior to application of the self-etching primer; SB = Scotchbond Multi-Purpose Plus, multi-step system with total etching; PE = Prime & Bond 2.1, single-step system with and without [PB] total etching) were used in combination with one hybrid composite. After 21 days of storage, 10 specimens for each adhesive system were subjected to thermocycling (1150 cycles) for 24 h and were afterwards debonded in a push-out test. Another 20 specimens were tested with cyclic fatigue according to the staircase method with 5000 cycles for each specimen. Static and cyclic push-out bond strengths, respectively, for each group were (MPa): SY 16.9 +/- 0.9 and 14.2 +/- 1.7, SE 17.5 +/- 1.8 and 14.8 +/- 3.4, SB 18.5 +/- 1.7 and 13.9 +/- 2.1, PB 14.6 +/- 2.2 and 7.2 +/- 2.4, PE 13.4 +/- 2.2 and 6.8 +/- 1.8. Both quasistatic and dynamic bond strengths revealed better values for the multi-step systems (P < 0.05). All adhesive systems tested revealed a significant fatigue behaviour which was more pronounced for the one-bottle system with a decrease of about 50% independent of additional dentin etching.

Adhesiveness↗

PubMed1999

Elution parameters and HPLC-detection of single components from resin composite.

The toxic effects of mercury derived from amalgam fillings have been a focus of controversy in Germany during the last 25 years. As alternatives to amalgam, composites are used widely to restore anterior and posterior permanent teeth. This study quantifies the amount of TEGDMA and methacrylic acid that can be derived from a polymerized commercial hybrid composite material. Different specimens were made with different curing methods with and without an oxygen inhibition layer. To simulate the removal of composite fillings, some samples were pulverized. The specimens were eluted in distilled water at 37 degrees C for different time intervals. To check the influence of acid conditions, pulverized material was incubated in 6 M HCl. The separation of the eluted chemical resin components was done by HPLC. A defined mixture of pure components was used as an external standard for the identification and quantification of the eluted components. The results focus on the release of triethylengly-coldimethacrylate (TEGDMA) and methacrylic acid. Concerning the different incubation methods, the results showed higher TEGDMA elution with oxygen inhibited surface layer and with the pulverized samples. Within acid conditions, the amount of TEGDMA found was low, but the amount of methacrylic acid increased. Small resin monomers like TEGDMA are primarily eluted from composite in aqueous solutions. Within acid conditions a hydrolytic disintegration of the ester bonding of the monomers could be observed. Methacrylic acid--a substance with allergenic potential--could be detected.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1999

Internal adaptation and overhang formation of direct Class II resin composite restorations.

The aim of the present in vitro study was to evaluate different restorative concepts for posterior resin composite fillings in terms of internal adaptation and overhang formation. Eighty standard occluso-distal cavities with and without a 1.5-mm bevel were restored in a phantom head using Syntac Classic and Tetric Ceram with and without Tetric Flow as thin lining or Solid Bond and Solitaire with and without FlowLine. The restorations were finished intraorally and afterwards subjected to thermal loading (1150 x +5 degrees C/+55 degrees C) for 24 h. The proximal margins of the original specimens were analyzed for overhangs under a stereo light microscope (100-fold magnification) before and after intraoral control with loupes, including additional polish. Afterwards the teeth were cut longitudinally, replicated, and their internal integrity analyzed under a SEM (200-fold magnification). The combination of flowable and viscous composites resulted in enhanced internal adaptation for both adhesive systems. However, Syntac Classic exhibited superior adaptation characteristics compared with Solid Bond. In terms of overhang formation, the use of flowable materials always led to higher percentages of marginal overhangs in beveled cavities. Higher viscous materials alone resulted in higher percentages of underfilled margins of beveled than box-shaped cavities. It was clear that the use of magnifying glasses during finishing was beneficial for reducing marginal overhangs up to 40%.

Composite Resins↗

PubMed1999

Crack formation of all-ceramic crowns dependent on different core build-up and luting materials.

OBJECTIVES: The aim of this in vitro study was to evaluate various core build-up and luting materials regarding their effect on crack formation of all-ceramic crowns. METHODS: Fifty-six freshly extracted sound human third molars were prepared according to a standardized procedure obtaining a circular shoulder of 1.5 mm with all margins located in dentin. Sixty percent of the dentin volume were removed and restored with totally bonded build-up composite resins or resin-modified glass ionomer cements (RMGIC) or compomers. Cast IPS-Empress caps were manufactured and luted with the different materials. For each material group, the volumes of the core build-ups and of the luting cements were determined. The caps were examined for cracks after 1, 3, 6, 9 and 12 months storage in 0.9% saline solution at 37 degrees C. RESULTS: The tested groups revealed no major differences in the percentage of the core build-ups and in the volume of the luting cements. After 12 months only the group with composite resin build-up and luting showed no crack formation. RMGIC/compomer build-up or RMGIC/compomer luting always resulted in cracking of the caps. CONCLUSIONS: Within the limits of this study it can be concluded that the hygroscopic expansion of RMGIC/compomer materials led to failure of all-ceramic crowns, when the materials are used for both core build-up or adhesive bonding.

Acrylates↗

PubMed1999

IPS Empress inlays and onlays after four years--a clinical study.

OBJECTIVE: Ceramic inlays are used as esthetic alternatives to amalgam and other metallic materials for the restoration of badly damaged teeth. However, only limited clinical data are available regarding adhesive inlays and onlays with proximal margins located in dentine. In a prospective, controlled clinical study, the performance of IPS Empress inlays and onlays with cuspal replacements and margins below the amelocemental junction was examined. MATERIALS AND METHODS: Ninety-six IPS Empress fillings were placed in 34 patients by six clinicians. The restorations were luted with four different composite systems. The dentin bonding system Syntac Classic was used in addition to the acid-etch-technique. At baseline and after 6 months, one, two and four years after placement the restorations were assessed by two calibrated investigators using modified USPHS codes and criteria. A representative sample of the restorations was investigated by scanning electron microscopy to evaluate wear. RESULTS: Seven of the 96 restorations investigated had to be replaced (failure rate 7%; Kaplan-Meier). Four inlays had suffered cohesive bulk fractures and three teeth required endodontic treatment. After four years in clinical service, significant deterioration (Friedman 2-way Anova; p < 0.05) was found to have occurred in the marginal adaptation of the remaining restorations. Seventy-nine percent of the surviving restorations exhibited marginal deficiencies, independent of the luting composite. Neither the absence of enamel margins, nor cuspal replacement significantly affected the adhesion or marginal quality of the restorations. CONCLUSION: After four years, extensive IPS Empress inlays and onlays bonded with the dentin bonding system Syntac Classic were found to have a 7% failure rate with 79% of the remaining restorations having marginal deficiencies.

Adult↗

PubMed1999

Direct posterior composite restorations with a new adhesive system: one-year results.

PURPOSE: Syntac Sprint is a new one-bottle adhesive based on the total-etch and total-bond technique. The aim of this study was to compare the new restorative system consisting of Syntac Sprint and the resin composite Tetric Ceram with the clinically proven combination of the dentin adhesive Syntac Classic and the resin composite Tetric. MATERIALS AND METHODS: In a controlled prospective clinical study, 47 cavities (36 premolars, 11 molars; 29 maxillary, 17 mandibular; 6 occlusal, 33 occluso-approximal, 7 MOD, 1 > 3 surfaces) in 33 patients (17 female, 16 male) were filled. Twenty-five fillings were placed with the combination Syntac Sprint/Tetric Ceram under total etching and total bonding conditions. In thirteen restorations, Syntac Sprint was precured prior to the application of the resin composite; in the other twelve cases, restoration and adhesive were cured simultaneously. The control group consisted of 22 cavities restored with Syntac Classic plus the composite Tetric. At baseline and after 6 and 12 months, two calibrated investigators examined the restorations with modified USPHS codes and criteria. RESULTS: The criteria marginal integrity and integrity of the tooth deteriorated significantly between the baseline and the 6- and 12-month investigations (Friedman 2-way ANOVA; p < 0.05). No differences were found in the criteria surface roughness, color matching, anatomic form, step formation, integrity of the filling, proximal contact, hypersensitivity, or satisfaction. After one year, all fillings were in good condition. There was no significant difference between the Syntac Sprint/Tetric Ceram and Syntac Classic/Tetric groups for any criterion (Kruskal-Wallis; p > 0.05). CONCLUSION: Within the limits of this study, Tetric Ceram fillings in combination with Syntac Sprint were clinically successful after one year.

Acrylates↗

PubMed1998

Evaluation of subsurface damage in CAD/CAM machined dental ceramics.

Commercial ceramics for dental computer aided design/computer aided manufacture (CAD/CAM) restorations suffer from surface chipping defects and microcracking. The influence of CAD/CAM machining of dental materials on the mechanical strength and extension of the damage zone was studied. Two different commercial dental ceramics, a feldspathic porcelain and a glass-ceramic, were CAD/CAM machined according to dental practice. The extension of the damage zone was analysed by a stepwise erosion of the surface, and the biaxial flexural strength was measured. To simulate the adhesive fixing of ceramic inlays, the specimens were sealed using a light-curing monomer. The different machining behaviour is dominated by the microstructure of the investigated materials. Owing to the high amount of glassy phase, the feldspathic porcelain shows extensive microcracking and chipping defects. The extent of the damage zone can be determined as 40-60 microm. Sealing of the surface did not affect the flexural strength of the machined samples. The dominating response to machining of the glass-ceramic is crushing and crumbling with a major contribution of plastic deformation on a microscopic scale. The extent of the damage zone is less than 20 microm. These cracks can be bridged by sealing of the surface, resulting in a substantial increase in strength.

Journal Article↗

PubMed1996

Comparison of two- and three-body wear of glass-ionomers and composites.

The two-body and three-body wear of glass-ionomers (GIC), visible light cured glass-ionomers (VLC-GIC), and composites were compared. The wear simulations were performed for the two-body wear in an artificial mouth and for the three-body wear with the so-called ACTA machine. The tested materials were different conventional glass-ionomers, light cured glass-ionomers, composites, and amalgam. The wear rates of 8 specimens of each material for the two-body and 16 for the three-body wear test were compared. After 10(5) cycles with each testing device, the wear shapes were measured. All measurements were related to the wear rate of amalgam. For the two-body wear method, the worn materials were qualitatively judged by scanning electron microscopy. The two different wear testing methods lead to similar results with slight differences in ranking. Amalgam showed the lowest wear rates with both methods. Photac Fil, a newly developed VLC-GIC, showed dramatically lower wear resistance than composites and conventional GIC with both methods. Further investigations are necessary to identify the material-specific parameters influencing the wear behaviour of a material in relation to different wear testing methods.

Acrylic Resins↗

PubMed1991

[High volume vs. activated root canal irrigation].

Irrigation of the root canal is carried out to remove the smear layer and the overlying pulp tissue remnants and dentin chips left by preparation. Our results show that even high volume irrigation is less effective in the apical section than towards cervical. A positive effect of activated continuous irrigation was demonstrated above all in the apical third of the root canal. Almost complete removal of both the smear layer and the overlying debris was achieved. Since high volume, continuous activated irrigation is superior to any other form of irrigation, particularly in the apical section, the results of our studies suggest that further efforts to develop such a root canal irrigation system to the state in which it can be clinically used are necessary.

Dental Cavity Preparation↗

PubMed1991

[Adverse side effects of amalgam? An interdisciplinary study].

In an interdisciplinary study starting 2.5 years ago patients with various symptoms, which they associate with amalgam fillings, were examined. According to the first results of this study with 50 patients, the Hg-concentration in urine does correlate with the amount of amalgam fillings before and after taking DMPS (2,3-Dimercapto-1-propane-sulfonic-acid), but with a maximum of 66.4 micrograms Hg (24 h urine) the amounts of mobilization measured were significantly below toxicologically critical limits. Only in 3 patients did the individual immunological values (CD4/8 ratio, antinuclear antibodies) by far exceed standard values. In one case an allergy to amalgam is suspected. 40% of the patients showed a pathological psychiatric status (neurosis, depression, etc.). Another quarter had psychological problems like alcoholism or drug abuse. There is no reason at the moment to reject amalgam as filling material either because of the measured Hg-concentrations or because of any immunological or allergological findings.

Adolescent↗

PubMed1990

[SEM study of radiogenic caries].

The present SEH study could show that radiogenic caries is accompanied by morphological changes at the dentine-enamel junction. These changes appear as lacunar defects of up to 300 microns in size. This kind of defect was found in 28 of 32 teeth which were exposed to radiation of more than 40 Gy. In a control group with caries of the smooth surfaces no comparable results could be obtained.

Dental Caries↗

PubMed1990

[Drying of root canals].

The dryness of root canals was checked using special paper points prepared with an indicator medium. In the presence of moisture these paper points promptly change from white to blue in color. In a two-step in vitro experiment, moisture was always demonstrated at the apical stop and in the apical third of the canal wall, although according to clinical criteria we believed the root canal to be dry. The results were not influenced by any previous manipulations of the prepared root canals. It may be recommended for routine root canal therapy to observe the following rules: 1. use alcohol for the last irrigation, 2. keep using larger paper points in between, 3. use 2 to 3 paper points more after you believe the root canal is dry, 4. remove the last paper point right before obturating the root canal.

Dental Cavity Preparation↗

PubMed1989

[Sequelae of unsecured elastic bands (the status after 7 years)].

The use of elastic bands without an adequate appliance mechanism to close a diastema represents a professional error on behalf of the dentist. Two case reports are presented showing both the consequences of such malpractice and the successful periodontal and orthodontic treatment over a period of seven years. The reasons for this successful treatment are discussed as well as points of special interest.

Child↗