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Biomedical subjects

Marleen Peumans

Publications and source records attributed to Marleen Peumans.

10 recordsLinked to original sources
PubMed2006

How to simulate wear? Overview of existing methods.

OBJECTIVES: The aim of the overview is to critically analyse the contributing factors to the biological wear process and to screen the wear simulators in dentistry for their capacity to mimic the wear conditions. An overview of the types of wear, grouped as biotribocorrosion, combined with a description of the different wear simulating devices will allow us to better understand the multifactorial nature of wear. METHODS: A search on keywords highlights the most common in-vitro wear simulators and their use in the laboratories for various simulation applications. RESULTS: Wear is a complex process that can hardly be simulated while controlling all variables. Especially the extrapolation of the in-vitro wear results to the in-vivo situation is difficult because there is a lot of interplay with biological factors that are difficult to mimic. SIGNIFICANCE: It is not the degree of sophistication, but the right mix of controllable variables that will make a wear simulator predictive.

Dental Materials↗
PubMed2005

Micro-tensile bond strength of adhesives bonded to Class-I cavity-bottom dentin after thermo-cycling.

UNLABELLED: A widely used artificial aging methodology is thermo-cycling. The ISO TR 11450 standard (1994) recommends 500 cycles in water between 5 and 55 degrees C. Recent literature revealed that more cycles are needed to mimic long-term bonding effectiveness. Furthermore, the artificial aging effect induced by thermo-cycling is not clearly established. Two underlying mechanisms can be advanced: (1) hot water may accelerate hydrolysis and elution of interface components and (2) repetitive contraction/expansion stress can be generated. OBJECTIVES: The purpose of this study was to evaluate the relative contribution of both chemical (hydrolysis and elution of interface components) and mechanical (repetitive contraction/expansion stress) degradation pathways on the thermo-cycling-induced artificial aging of dentin-adhesive interfaces at the bottom of class-I cavities. METHODS: The micro-tensile bond strength (muTBS) of contemporary adhesives (a three-step etch and rinse, a two-step and a one-step self-etch adhesive) bonded to class-I cavity-bottom dentin was determined after 20,000 cycles as well as after 20 days of water storage (control). Restored class-I cavities (repetitive contraction/expansion stress) as well as prepared micro-specimens (diffusion-dependent hydrolysis and elution) were subjected to the thermo-cycling regimen. RESULTS: Thermo-cycling did not enhance chemical or mechanical degradation of the bonds produced by a two-step self-etch and a three-step etch and rinse adhesive to dentin. The one-step self-etch adhesive tested was, however, not able to withstand polymerization shrinkage stress, nor thermo-cycling, when applied in class-I cavities. SIGNIFICANCE: Thermo-cycling results in combined contraction/expansion stress and accelerated chemical degradation. However, the relative contribution of each is strongly dependent on the specific test set-up and the adhesive used.

Analysis of Variance↗
PubMed2005

A randomized controlled study evaluating the effectiveness of a two-step self-etch adhesive with and without selective phosphoric-acid etching of enamel.

OBJECTIVES: The purpose of this randomized controlled clinical trial was to test the hypothesis that a two-step self-etch approach is equally effective to restore cervical class-V lesions as a self-etch approach with beforehand selective etching of enamel using phosphoric acid. METHODS: Twenty-nine patients received two or four restorations randomly following two experimental protocols ('paired-tooth' study design): (1) A 'mild' self-etch adhesive (Clearfil SE, Kuraray) was applied following a self-etch approach on both enamel and dentin (C-SE non-etch); (2) Similar application of Clearfil SE, but including beforehand selective acid-etching of the enamel cavity margins with 40% phosphoric acid (C-SE etch). Clearfil AP-X (Kuraray) was used as restorative composite for all 100 restorations. The clinical effectiveness was recorded in terms of retention, marginal integrity and clinical micro-leakage after 2 years of clinical service. RESULTS: No restoration losses were recorded. Clinical micro-leakage was slight and only rarely observed. No significant differences were found between both groups for the diverse parameters evaluated except for the number of small incisal marginal defects, which was significantly higher in the C-SE non-etch group (McNemar: p = 0.0391). SIGNIFICANCE: The clinical effectiveness of the mild two-step self-etch adhesive Clearfil SE was excellent after 2 years of clinical service. Although in general no difference in clinical performance was recorded when Clearfil SE was applied following either of the experimental protocols, more marginal defects at the enamel side were noticed when enamel was not beforehand etched with phosphoric acid. However, these defects were small and of clinically negligible relevance.

Acid Etching, Dental↗
PubMed2005

Fatigue resistance of dentin/composite interfaces with an additional intermediate elastic layer.

According to the "elastic bonding" concept, a thick intermediate layer of flexible resin has been suggested to absorb part of the polymerization shrinkage stress and to absorb shocks during function. In this study, the effect of an additional intermediate layer of a low-viscosity resin on the microrotary fatigue resistance (microRFR) of a hybrid composite bonded to dentin was evaluated. The hypotheses tested were that an intermediate layer of a low-viscosity resin (i) increases the microRFR to dentin, but (ii) has no effect on the static bond strength. Microtensile bond strength (microTBS) samples were loaded until failure or inserted in a microrotary fatigue testing device. Specimens were tested at 4 Hz until failure or until 10(5) cycles were reached. An additional intermediate elastic layer had no effect on the static microTBS, but significantly lowered the median microRFR from 28.4 MPa to 21.6 MPa. However, the application of an intermediate flexible layer had, no effect on the static microTBS. In conclusion, an additional elastic intermediate layer did decrease significantly the microRFR (rejection of hypothesis i), but did not alter the microTBS (acceptance of hypothesis ii). The decrease in microRFR most likely may be explained by the lower mechanical properties of the intermediary layer.

Composite Resins↗
PubMed2005

Three-year clinical effectiveness of a two-step self-etch adhesive in cervical lesions.

A 3-yr randomized, controlled prospective study evaluated the clinical effectiveness of a mild two-step self-etch adhesive, Clearfil SE, in Class-V non-carious lesions. The hypothesis tested was that prior selective etching of enamel with phosphoric acid does not affect the 3-yr clinical performance of this adhesive. A total of 100 lesions in 29 patients were randomly restored in one or two pairs, according to two experimental protocols: (i) application of Clearfil SE according to the instructions of the manufacturer (C-SE non-etch); and (ii) similar application of Clearfil SE with prior etching of enamel cavity margins with phosphoric acid (C-SE etch). Clearfil AP-X was used as a restorative material. At 3 yr, 90% of the restorations were examined for retention, marginal integrity, marginal discoloration, caries recurrence, postoperative sensitivity, and preservation of tooth vitality. An excellent retention rate (100%) was noted after 3 yr of clinical functioning. Only one restoration of the C-SE etch group was clinically unacceptable owing to the presence of a severe cervical marginal defect. A pairwise comparison between both groups showed a significant difference only in the number of small marginal defects at the enamel side, which was higher in the C-SE non-etch group. These incisal defects were small and clinically irrelevant. Superficial marginal discoloration increased slightly in the C-SE non-etch group and was related to the higher frequency of small incisal marginal defects. In this latter group, localized marginal discoloration was observed significantly more in smokers. In conclusion, the clinical performance of the mild two-step self-etch adhesive, Clearfil SE, remained excellent after 3 yr of clinical functioning. Additional etching of the enamel cavity margins was not critical for its clinical performance.

Acid Etching, Dental↗
PubMed2005

Technique-sensitivity of contemporary adhesives.

Besides micro-mechanical interlocking through hybrid-layer formation, self-etch adhesives may benefit from additional chemical interaction between the functional monomer and residual hydroxyapatite. One-step adhesives are commonly associated with lower bonding effectiveness, which must be attributed in part to the dissolution of hydrophilic and hydrophobic monomers in a relatively highly concentrated solvent. In this 'difficult' mixture, also water is essential as ionization medium to enable self-etching activity. Due to the high hydrophilicity, one-step self-etch adhesives have been reported to behave as semi-permeable membranes, allowing fluids to pass through and seriously jeopardizing bond durability. Recent research has also revealed that HEMA-free one-step adhesives are prone to phase-separation, which may also account for their lower bonding effectiveness. Employing an appropriate air-drying technique may, however, improve the bonding effectiveness of such phase-separating adhesives by getting rid of substantially more interfacial water than HEMA-containing adhesives, of which water might be more difficult to remove from.

Acid Etching, Dental↗
PubMed2004

A prospective ten-year clinical trial of porcelain veneers.

PURPOSE: The aim of this in vivo study was to evaluate the clinical performance of porcelain veneers after 5 and 10 years of clinical service. MATERIALS AND METHODS: A single operator placed porcelain laminates on 87 maxillary anterior teeth in 25 patients. All restorations were recalled at 5 years and 93% of the restorations at 10 years. Clinical performance was assessed in terms of esthetics, marginal integrity, retention, clinical microleakage, caries recurrence, fracture, vitality, and patient satisfaction. Failures were recorded either as "clinically unacceptable but repairable" or as "clinically unacceptable with replacement needed". RESULTS: Porcelain veneers maintained their esthetic appearance after 10 years of clinical service. None of the veneers were lost. The percentage of restorations that remained "clinically acceptable" (without need for intervention) significantly decreased from an average of 92% (95 CI: 90% to 94%) at 5 years to 64% (95 CI: 51% to 77%) at 10 years. Fractures of porcelain (11%) and large marginal defects (20%) were the main reason for failure. Marginal defects were especially noticed at locations where the veneer ended in an existing composite filling. At such vulnerable locations, severe marginal discoloration (19%) and caries recurrence (10%) were frequently observed. Most of the restorations that present one or more "clinically unacceptable" problems (28%) were repairable. Only 4% of the restorations needed to be replaced at the 10-year recall. CONCLUSION: It was concluded that labial porcelain veneers represent a reliable, effective procedure for conservative treatment of unesthetic anterior teeth. Occlusion, preparation design, presence of composite fillings, and the adhesive used to bond veneers to tooth substrate are covariables that contribute to the clinical outcome of these restorations in the long-term.

Adult↗
PubMed2003

Two-year clinical effectiveness of a resin-modified glass-ionomer adhesive.

PURPOSE: To evaluate the clinical effectiveness of a resin-modified glass-ionomer adhesive FujiBond LC (GC) in non-carious Class V cervical lesions. METHODS: 28 patients and 52 abrasion-erosion lesions were restored using FujiBond LC and a microfilled resin composite in a cavity design with the adjacent enamel margins beveled. Clinical parameters as retention, marginal integrity, clinical microleakage, caries recurrence, esthetics, gingival response, tooth vitality and post-operative sensitivity were evaluated at 6 months, 1 and 2 years. RESULTS: A 100% retention rate was recorded after 2 years of clinical service. However, only 15% of the restorations showed a perfect marginal adaptation. All marginal defects were small, either located at the incisal or at the cervical margin. The percentage of small marginal defects was obviously higher at the incisal enamel margin than at the cervical dentin margin. At the 2-year recall, half of the restorations exhibited a superficial, localized discoloration at the restoration margin, however none of the restorations showed deep, generalized discoloration. Remaining criteria of clinical effectiveness were rated as excellent.

Adult↗
PubMedDate not supplied

A randomized, controlled trial evaluating the three-year clinical effectiveness of two etch & rinse adhesives in cervical lesions.

A three-year randomized, controlled prospective study evaluated the clinical performance of two three-step etch & rinse adhesives (OptiBond FL, Kerr: O-FL; PermaQuick, Ultradent: PMQ) in Class V cervical erosion-abrasion lesions. The latter adhesive was also tested with two restorative composites with contrasting stiffness in order to evaluate the effect composite stiffness might have on the clinical longevity of cervical restorations. A total of 150 lesions were randomly restored in pairs of the three adhesive/composite combinations (PMQ combined with Amelogen Hybrid: PMQ/A-Hy, Ultradent; PMQ combined with Amelogen Microfill: PMQ/A-Mi, Ultradent; O-FL combined with Prodigy: O-FLJPro, Kerr) per patient and evaluated at baseline, after six months, one year, two years and three years of clinical service. After three years, the retention rate was 100% for O-FL/Pro and 98% for both PMQ/A-Hy and PMQ/A-Mi, thereby, satisfying the "full acceptance" guidelines specified by the American Dental Association. A pairwise comparison showed no significant difference in adhesive performance between restorations made using the microfilled and hybrid composite for any evaluation criteria (p>0.05).

Chi-Square Distribution↗