PubMed Health⌕ Search

Biomedical subjects

Roland Frankenberger

Publications and source records attributed to Roland Frankenberger.

At least 19 recordsLinked to original sources

Compomers in restorative therapy of children: a literature review.

OBJECTIVE: The restoration of carious primary teeth plays an underestimated role in paediatric dentistry. This is astonishing for many reasons, not least because many new materials have been introduced in recent years. New or modified techniques and materials, with better aesthetics and flexural properties, allow minimally invasive treatment. A transfer of techniques between different dentitions, however, may be problematic because of both micromorphological differences and compliance. Therefore, this paper deals with options for restoring primary teeth and the early stages of the mixed dentition using polyacid-modified composites, the so-called compomers. METHODS: Medline and Embase were scanned from 1990 through 2006. Furthermore, a hand-search of nonlisted but peer-reviewed papers was performed. The search items were compomer*, dent*, primary* and deciduous*, which identified 109 relevant publications. CONCLUSIONS: Based on high clinical success rates, compomers are now an effective alternative to other materials for restorative therapy in the anterior and posterior primary teeth. A minimum amount of compliance is still mandatory in order to allow for a few minutes of adhesive pretreatment and layering without contamination. If this is not the case, compomers make no sense. Stainless steel crowns are still the most effective from of restoration for severely decayed primary molars.

Child↗

Influence of moisture on the apical seal of root canal fillings with five different types of sealer.

The aim of this study was to evaluate the influence of moisture on apical leakage using five different types of sealer. There were 120 single-rooted teeth instrumented to .02/#60 and randomly assigned to 10 experimental groups, one control group (AH Plus, lateral condensation) (n = 10) or positive/negative controls (n = 5). Before obturation teeth were dried thoroughly, followed by recontamination with moisture in a wet chamber (moist groups; 37 degrees C for 7 days). The teeth of the experimental groups (a, dry; b, moist) were obturated with sealer (groups 1, AH Plus; 2, Apexit; 3, Ketac-Endo; 4, RoekoSeal; 5, Tubli-Seal) and a single gutta-percha cone .02/#55. Teeth were centrifuged (30 x g for 3 minutes) in 5% methylene blue. Linear dye penetration was measured under a stereomicroscope. Moisture led to less microleakage for Apexit, RoekoSeal, and Tubli-Seal and higher values for AH Plus and Ketac-Endo. Multifactorial ANOVA displayed a significant dependence of leakage on sealer (p < 0.001) and the combination sealer or moisture (p < 0.01). It depends on the sealer type in which way moisture affects the apical seal.

Analysis of Variance↗

Evaluation of two different teaching concepts in dentistry using computer technology.

The common teaching goal of two different phantom head courses was to enable the students to provide an all-ceramic restoration by the means of computer technology. The aim of this study was to compare these two courses with regard to the different educational methods using identical computer software. Undergraduate dental students from a single year were randomly assigned to two different courses. One course was a conventional teacher-centred course [TRAD]. The other course contained problem-based learning (PBL) oriented structured modules [HYBRID]. The students completed an evaluation based on a 25 item seven-point Likert scale. Two independent evaluators assessed the practical work. Differences between TRAD and HYBRID were tested for significance using the Mann-Whitney U-test (at p < or = 0.05). Both courses were rated as demanding. The HYBRID group rated those items significantly better, which focused on course atmosphere and student-teacher relationship. The TRAD group felt that their course was more satisfying. Practical results of the two groups did not differ significantly. Within the limits of the study it was revealed, that the HYBRID group was less satisfied with the own success although the learning conditions were rated better. This could be interpreted in two ways: (1) the PBL oriented course lead the students to more self skepticism to their own work or (2) due to increased intellectual demands and the lack of detailed guidelines the course was felt as more burdening.

Attitude of Health Personnel↗

Reinforcement effect of adhesively luted fiber reinforced composite versus titanium posts.

OBJECTIVE: The aim of the present study was to investigate the influence of the rigidity of different post materials (titanium versus glass fiber reinforced composite [FRC]) on the fracture resistance of endodontically treated teeth (ETT). METHOD: Forty-eight caries-free maxillary central incisors were randomly assigned to six groups (n=8). After endodontic treatment, teeth of four groups were flattened 2mm above and two groups at the cemento-enamel junction (CEJ). As control, specimens of one group received neither composite build-up nor post, and teeth were left empty (E). In another group only a resin composite build-up was placed (C). In two groups, both titanium and FRC posts were inserted. One group with titanium (2/T) and FRC (2/FRC) post received a 2mm deep ferrule preparation. For one group with titanium (0/T) and FRC (0/FRC) post no ferrule design was provided. All-ceramic crowns were adhesively luted on all specimens. Specimens were exposed to thermomechanical loading and finally statically loaded until failure. RESULTS: The median fracture load values (min-max) were: E=317 (242-404); C=387 (335-475); 0/FRC=352 (0-440); 2/FRC=502 (326-561); 0/T=420 (0-548), 2/T=517 (416-653). Statistically significant differences were computed between E, C, 2/FRC, 0/T and 2/T; between C, 2/FRC and 2/T; between 0/FRC, 2/FRC and 2/T; between 0/T and 2/T regarding maximum fracture load. SIGNIFICANCE: Fracture resistance of ETT is not influenced by the rigidity of the post material. The combination of ferrule preparation and endodontic post results in higher load resistance after TML than any other build-up design.

Composite Resins↗

Strength and fatigue performance versus filler fraction of different types of direct dental restoratives.

The aim of this study was to evaluate the mechanical properties, such as Young's moduli, fracture strengths (FS), and flexural fatigue limits of todays resin composite dental restoratives. All materials have been subdivided into flowable, aesthetic hybrid and nano-filled hybrid composites as marketed by dental manufacturers and analyzed in terms of the actual filler configurations. Specimen bars have been manufactured in reference to ISO 4049 standard, light-cured for 20 s, and stored in distilled water before testing. The elastic moduli (EM), FS, and flexural fatigue limits (FFL) were measured after 14 days storage by using the four-point bending test. The FFL was determined for 10(4) cycles. The fatigue data were analyzed by using the "staircase" approach and statistically treated by ANOVA analysis. Flowable materials with a reduced filler content exhibited the lowest Young's moduli, compared with those measured for higher filled materials. A linear relationship has been found between elastic moduli and filler loading (r(2) = 0.798). Correlations of FS and fatigue data to different filler fractions could not be proved. FS ranged between 61.3 and 124.9 MPa. After 10(4) cycles of fatigue loading, the FS suffered from a decrease between 45.2 and 61.7%. However, materials providing high initial strengths do not obviously reveal the best fatigue resistance. A marketing-based grouping of direct restorative materials has no meaning toward laboratory testing of mechanical properties.

Dental Restoration, Permanent↗

Clinical performance of posterior compomer restorations over 4 years.

PURPOSE: To clinically evaluate two polyacid-modified resin composites (Hytac and Dyract AP) for the restoration of posterior teeth over a 4-year period and to investigate accessible margins by light microscopy. METHODS: In a controlled prospective clinical study, 71 cavities (21 occlusal, 41 MO/OD, 9 MOD) in 30 patients were restored with compomers by three dentists. Thirty-eight restorations were placed with the combination OSB/Hytac, the same patients received 33 restorations with Prime&Bond 2.1/Dyract AP. Enamel margins of the cavities were etched with phosphoric acid. At baseline, after 12, 24, and 48 months, the restorations were examined by two independent investigators according to modified USPHS-criteria. Focusing on the 40 restorations available at all recalls, a semi-quantitative margin analysis was carried out at each recall using replicas and light microscopy at x130 magnification. RESULTS: Twenty restorations were not investigated at the 4-year recall (drop-out). After 48 months, 11 restorations (Hytac: n = 8, Dyract AP: n = 3) had to be replaced due to tooth fracture (n = 4), gap formation (n = 5), and adhesive failure (n = 2). Forty restorations were still in function after 4 years (overall failure rate 16%; Hytac: 21%; Dyract: 9%). Between the recalls, statistically significant differences were detected for the criteria marginal integrity (Alpha dropping from 76% at baseline to 32% after 4 years), restoration integrity (Alpha ratings at baseline 99% vs. 40% after 4 years), and occlusion (100% vs. 24%). For the criteria surface roughness (from the 6-month recall) and anatomical shape (after 4 years), a significant difference between the materials was evident in favor of Dyract AP. Except gap-free margins, the predominant criterion in the microscopic analysis at baseline was marginal overhang (24%) and 30% negative step formation after 4 years.

Acetone↗

Ceramic inlays bonded with two adhesives after 4 years.

OBJECTIVE: The aim of the present study was to clinically evaluate the effect of two different adhesive/resin composite combinations for luting of IPS Empress inlays. METHODS: Ninety-four IPS Empress restorations were placed in 31 patients in a controlled prospective clinical split-mouth study. The restorations were luted with EBS Multi/Compolute (3M Espe) or with Syntac/Variolink II low (Ivoclar Vivadent) without lining. At baseline and after 0.5, 1, 2, and 4 years, the ceramic restorations were examined according to modified USPHS codes and criteria. RESULTS: Two patients including four restorations missed the 4 years recall (drop out). After 4 years of clinical service, four restorations in two patients (three luted with Compolute, one with Variolink II) had to be replaced due to hypersensitivities, 90 inlays and onlays were acceptable (failure rate 4%; Kaplan-Meier survival analysis). Between the five recalls, a statistically significant deterioration was found for the criteria marginal adaptation and inlay fracture (Friedman 2-way ANOVA; p < 0.05). Between the adhesives no statistical difference was found. At baseline, 95% of the restorations revealed luting composite overhangs. After 4 years, 55% of cases had overhangs and 38% showed marginal ditching. No differences were found for surface roughness, color matching, integrity tooth, proximal contact, hypersensitivity, and satisfaction (p > 0.05). CONCLUSION: For luting of ceramic inlays, no difference between the two luting systems was detectable. The overall failure rate after 4 years was 4%.

Adult↗

Effect of surface treatment on the shear bond strength of three resin cements to a machinable feldspatic ceramic.

The aim of this study was to evaluate the shear bond strength of three resin cements to Vita Mark II ceramics under different pretreatments of the ceramic surface and to examine whether simplified pretreatment procedures would result in satisfying results compared to the state of the art. RelyX Unicem (RXU), Calibra (CAL), and Variolink II (VAR) were used as resin cements and bonded to machine milled feldspatic disks, pretreated in five different ways. (1) no pretreatment of the ceramic surface; (2) surface etched with hydrofluoric acid (HF); (3) ceramic surface silanized; (4) ceramic surface etched (HF) and silanized, (5) ceramic surface etched (HF), silanized, and covered with Heliobond. The shear bond strengths were measured initially, after 5000 and 10,000 thermocycles (TC). After 10,000 TC for CAL only procedure 5 resulted in a reliable adhesion median value of 10.7 MPa. VAR showed median values of 24.6, 17.2, and 18.1 MPa for pretreatments 5, 3, and 4, respectively. RXU performed 25.9, 22.0, and 11.0 MPa for procedures 5, 4, and 3, respectively. For procedure 2, RXU revealed the significantly highest value with 15.4 MPa (U-test, p = 0.05). Only RXU-luted specimens of procedure 1 survived the 10,000 thermocycles. The results revealed that a simplification of the ceramic pretreatment for VAR and RXU might be possible.

Adhesives↗

A challenge to the conventional wisdom that simultaneous etching and resin infiltration always occurs in self-etch adhesives.

This study provided morphological evidence that discrepancies between the depth of demineralisation and the depth of resin infiltration can occur in some mild self-etch adhesives. Sound dentine specimens derived from extracted human third molars were bonded with 5 one-step and 5 two-step self-etch adhesives. One millimeter thick slabs containing the resin-dentine interfaces were immersed in 50 wt% aqueous ammoniacal silver nitrate and processed for TEM examination. A zone of partially etched but uninfiltrated dentine was identified beneath the hybrid layers in the milder versions of both one-step and two-step self-etch adhesives. This zone was characterised by the occurrence of silver deposits along the interfibrillar spaces of mineralised collagen fibrils. The silver infiltrated interfibrillar spaces were clearly identified from the one-step self-etch adhesives Xeno III, iBond, Brush&Bond and the experimental adhesive, and were thinner and only occasionally observed in the two-step self-etch adhesives Clearfil SE Bond and Clearfil Protect Bond. The more aggressive one-step and two-step adhesives that exhibit more abrupt transitions from completely demineralised to mineralised dentin were devoid of these silver-infiltrated interfibrillar spaces beneath the hybrid layers. Incomplete resin infiltration observed in some self-etch adhesives may be caused by the reduced etching potential of the acidic monomers toward the base of hybrid layers, or the presence of acidic but non-polymerisable hydrolytic adhesive components, creating potential sites for the degradation of the bonded created by these self-etch adhesives.

Acid Etching, Dental↗

Characterisation of resin-dentine interfaces by compressive cyclic loading.

The aims of this in vitro study were to evaluate the ultra-morphological changes in resin-dentine interfaces after different amounts of thermomechanical load (TML), and to determine the corresponding microtensile bond strengths (microTBS). Enamel/dentine discs with a thickness of 2 mm were cut from 24 human third molars and bonded with four adhesives involving different adhesion approaches: Syntac (Ivoclar Vivadent; used as multi-step etch-and-rinse adhesive), Clearfil SE Bond (Kuraray; two-step self-etch adhesive), Xeno III (Dentsply DeTrey; mixed all-in-one self-etch primer adhesive system), and iBond (Heraeus Kulzer; non-mixed all-in-one self-etch adhesive). The resin-dentine discs were cut into beams (width 2 mm; 2 mm dentine, 2 mm resin composite) and subsequently subjected to cyclic TML using ascending amounts of mechanical/thermal cycles (20 N at 0.5 Hz of mechanical load and 5-55 degrees C of thermal cycles: for 0/0, 100/3, 1,000/25, 10,000/250, 100,000/2,500 cycles). Loaded specimens were either cut perpendicularly in order to measure microTBS (n=20; crosshead speed: 1 mm/min) or were immersed in an aqueous tracer solution consisting of 50 wt% ammoniacal silver nitrate and processed for ultra-morphological nanoleakage examination using transmission electron microscopy (TEM). microTBS were significantly decreased by increasing amounts of TML for all adhesives (p<0.05). Bond strengths after 0 vs. 100,000 thermomechanical cycles were: Syntac: 41.3/30.1 MPa; Clearfil SE Bond 44.8/32.5 MPa; Xeno III 27.5/13.7 MPa; iBond 27.0/6.2 MPa. Relatively early, a certain amount of nanoleakage was observed in all groups by TEM, which was more pronounced for Xeno III and iBond. The incidence of nanoleakage remained stable or was even reduced with increasing load cycles for all adhesives except iBond, where exact failure origins were detected within the adhesive and at the top of the hybrid layer.

Adhesiveness↗

Clinical performance of bonded leucite-reinforced glass ceramic inlays and onlays after eight years.

OBJECTIVE: Ceramic inlays and onlays are a tooth colored alternative to metallic restorations. Clinical long-term data are scarce though, especially about inlays and onlays having proximal margins in dentin. The present prospective controlled clinical study evaluated the clinical performance of IPS Empress inlays and onlays with cuspal replacements and proximal margins below the cementoenamel junction over eight years. METHODS: Ninety six ceramic restorations were placed in 34 patients by six dentists. The restorations were bonded with an enamel/dentin bonding system (Syntac Classic) and four different resin composite systems. The restorations were assessed after placement by two calibrated investigators using modified USPHS codes and criteria at the following time periods: baseline, 1,2,4,6 and 8 years. RESULTS: Eight of the 96 restorations investigated had to be replaced (failure rate 8%; Kaplan-Meier): Six inlays suffered cohesive bulk fractures, two teeth required endodontic treatment. After eight years of clinical service, significant deterioration (Friedman 2-way ANOVA; P < 0.05) was found for marginal adaptation of the remaining restorations. 98% of the surviving restorations exhibited marginal deficiencies, independent of the luting composite. CONCLUSIONS: IPS Empress inlays and onlays demonstrated to be successful even in large defects. Neither the absence of enamel margins, nor cuspal replacement significantly affected the quality of the restorations.

Adult↗

Self-etch vs etch-and-rinse adhesives: effect of thermo-mechanical fatigue loading on marginal quality of bonded resin composite restorations.

OBJECTIVE: This study evaluated the marginal integrity of dentine adhesives bonded to enamel and dentine, before and after thermo-mechanical loading (TML). METHODS: MO cavities with proximal boxes beneath the CEJ were prepared in extracted human third molars. Direct resin composite restorations (Tetric Ceram) were bonded with 3-step etch-and-rinse (Syntac Classic, Solobond Plus, OptiBond FL), 2-step etch-and-rinse (Admira Bond, Single Bond), 2-step self-etch (AdheSE, Clearfil SE Bond), and 1-step self-etch (all-in-one) adhesives (Adper Prompt, Xeno III, iBond). Marginal gaps were analyzed using SEM of epoxy resin replicas. Bonded interfaces before TML were examined with TEM to identify pre-existing attributes for subsequent marginal disintegration. RESULTS: In enamel, high percentages of gap-free margins were initially identified for all adhesives. After TML, etch-and-rinse adhesives exhibited significantly higher percentages of gap-free margins (approximately 90%) compared with two-step self-etch (approximately 75%) and all-in-one (approximately 55%) adhesives (p<0.05). iBond did not completely etch through the enamel smear layer. In dentine, 89-100% gap-free margins were initially observed. After TML, there were no statistical differences among etch-and-rinse (62-70%) and two-step self-etch (62-63%) adhesives (p>0.05). The all-in-one adhesives exhibited significantly less gap-free margins (<40%) in dentine (p<0.05), with iBond showing the worst marginal integrity (15%). The presence of pre-existing water channels within the adhesives probably expedited water sorption when restorations were under functional stresses. CONCLUSION: Enamel bonding was more effective with phosphoric acid-etching. Etch-and-rinse and 2-step self-etch adhesives showed promising marginal adaptation to dentine and may have a better clinical prognosis than the all-in-one bonding approach.

Acid Etching, Dental↗

Evaluation of resin composite materials. Part I: in vitro investigations.

PURPOSE: To evaluate different resin-based composites using a variety of in vitro investigation methods to predict their clinical behavior. METHODS: Materials selected for this study were Heliomolar radiopaque (microfilled), Tetric Ceram, Pertac II (minifilled hybrids), Ariston pHc (ion releasing hybrid), and Solitaire I (hybrid with porous fillers). The evaluated in vitro criteria were three-body wear according to the ACTA method, microtensile bond strengths to enamel and dentin, flexural strength (four-point bending strength), flexural fatigue behavior (flexural fatigue limit), and calcium ion release (for Ariston pHc). RESULTS: Concerning wear resistance, Ariston pHc (20.5 microm after 200,000 cycles) was inferior to the other materials (13.7-15.9 microm). Microtensile bond strengths to dentin were similar for Heliomolar (32.0 MPa), Tetric Ceram (30.4 MPa; both bonded with Syntac Classic), and Pertac II (30.8 MPa; bonded with EBS Multi) being above Solitaire I (22.5 MPa; bonded with Solidbond) being above Ariston pHc (13.2 MPa; bonded with Ariston Liner). Enamel bond strengths for Heliomolar (40.0 MPa), Tetric Ceram (36.5 MPa), and Pertac II (38.9 MPa) were significantly higher than for Solitaire I (26.6 MPa) which was above Ariston pHc (7.2 MPa). Heliomolar, Tetric Ceram, and Pertac II revealed higher micro-TBS to enamel than to dentin, Ariston showed the contrary, and Solitare exhibited no difference between enamel and dentin micro-TBS. Solitaire I exhibited a lower initial flexural strength than the other materials, the computed fatigue strength of the material even dropped to the level of glass ionomer cements (17.9 MPa). Long-term calcium release data for Ariston exhibited a continuously high calcium release becoming lower at the end of the observation beyond 21 months.

Acrylic Resins↗

Pit and fissure sealing. Bonding of bulk-cured, low-filled, light-curing resins to bacteria-contaminated uncut enamel in high c-factor cavities.

PURPOSE: To examine the ultrastructure of bonding to occlusal enamel fissures using phosphoric acid etching in combination with a pit and fissure sealant (Clinpro Sealant), a total-etch single-bottle adhesive (One-Step) followed by the fissure sealant, and two single-step self-etch adhesives (Adper Prompt and Xeno III) followed by the fissure sealant. METHODS: Sections of bonded enamel fissures retrieved from specimens bonded in vivo were polished, and rinsed with phosphoric acid to bring surfaces into relief. They were examined, first under non-dehydrated conditions with field emission-environmental SEM, to evaluate the marginal integrity of the bonds. The same specimens were then re-examined under dehydrated conditions with conventional SEM to capture more detailed ultrastructural features. Extent of resin penetration into etched enamel was further evaluated by TEM examination of sections taken from undemineralized unstained bonded specimens. These sections were further examined after HCl demineralization and staining. RESULTS: All occlusal fissure walls examined were lined with remnant aprismatic enamel. Full penetration of resins into the bottom of the fissures, and gap-free interfaces were not observed in any of the specimens, irrespective of whether total-etch or self-etch adhesives were used with the sealant. Phosphoric acid did not penetrate well into the fissures and although hybridization of the etched aprismatic enamel was observed with or without the use of the total-etch adhesive, etching was inconsistent and gaps were frequently observed. Entrapment of bacteria within the fissure walls was frequently seen. The more aggressive self-etch adhesive Adper Prompt created etching in aprismatic enamel that approached that of phosphoric acid etching. The moderately aggressive self-etch adhesive Xeno III produced 1 mm thick hybrid layers in the aprismatic enamel fissure wall.

Acid Etching, Dental↗

Evaluation of resin composite materials. Part II: in vivo investigations.

PURPOSE: To clinically evaluate two different resin-based composites (Solitaire I and Ariston pHc) in order to determine the minimum clinical evaluation time needed to detect critical signs of failure. METHODS: In a controlled prospective clinical study, 99 cavities (30 Class I, 69 Class II) in 31 patients were restored (50 Ariston pHc without enamel etching and rubber dam, 49 Solitaire I restorations with total etching and rubber dam) and clinically investigated at baseline, after 6, 12, and 24 months. RESULTS: After 2 years of clinical service, 49 restorations (Ariston pHc: n = 38, Solitaire: n = 11) had to be replaced. The majority of failures occurred after more than 1.5 years. The reasons for replacement were differently distributed in both groups (Ariston pHc: 28 tooth fractures, 3 gap formations, 5 hypersensitivities, 1 bulk fracture, 1 marginal fracture. Solitaire: 5 gap formations, 1 hypersensitivity, 3 bulk fractures, 1 wear of the restorative material, 1 void in the restoration). Forty-four restorations were still in function after 2 years (overall failure rate after 2 years: 14%; Ariston pHc: 17%; Solitaire: 7%; survival analysis algorithm according to Kaplan/Meier). Comparing the materials, no statistical differences were evident except for the criteria "integrity tooth" (= tooth fracture or cracks) and "hypersensitivity" (from the 12-month recall; Mann-Whitney U-test; P< 0.05). In both cases of significant difference, Ariston pHc exhibited inferior results. After 2 years, only three teeth restored with Ariston pHc did not show considerably cracked enamel. The additional marginal analysis showed statistically significant differences for both materials regarding the criteria "perfect margin" (decrease), "gap formation" (increase), and "negative step formation" (increase; P< 0.05; Friedman 2-way ANOVA) between the four recalls. Therefore, a 2-year in vivo evaluation should be recommended prior to marketing a dental restorative material.

Acid Etching, Dental↗

The effect of six years of water storage on resin composite bonding to human dentin.

The aim of this in vitro study was to evaluate dentin bond strength and marginal adaptation of direct resin composite fillings after different storage times. Three hundred sixty cavities were prepared in discs of freshly extracted human third molars and filled with resin composites. Multistep self-etching adhesives (Syntac Classic, A.R.T. Bond, both with and without total etching), three-step etch-and-rinse adhesives (Scotchbond Multi-Purpose Plus, EBS), and two-step etch-and-rinse adhesives (Prime and Bond 2.0, Syntac Single-Component) were used for bonding. After 1, 90, and 2190 days of water storage and 24 h thermocycling (1150 cycles), push-out testing was performed. From the 6-year group, replicas were made after 1 day, 90 days, and 1, 2, 3, 4, 5, and 6 years, and examined regarding marginal adaptation under an SEM (x 200 magnification). In all groups under investigation, push-out bond strengths remained stable after 90 days; however, the strengths significantly decreased after 6 years of water storage. The two-step systems exhibited lower bond strengths than three-step systems after 6 years. Marginal analysis revealed a significant loss regarding the percentage of perfect margins having been stable after 2 years for the three-step etch-and-rinse systems. Overall, the older three-step systems proved to be more effective than the simplified adhesives Syntac Single-Component and Prime and Bond 2.0 with regard to bond strength and marginal adaptation.

Adhesives↗

Mechanical properties and three-body wear of veneering composites and their matrices.

Fatigue as one of the major factors affecting three-body wear of resin composites is influenced by mechanical properties of the resin matrix. The aim of this in vitro study was to determine three-body wear (ACTA methodology), fracture strength, and Young's modulus of four veneering composites (Artglass old and new formula, Vita Zeta LC Composite, Targis) and one direct restorative composite (Z 100). Furthermore, three-body wear of the pure matrices of the materials was tested. The wear results were compared to Amalgam as reference material. It should be computed whether there exists a correlation between the wear results of resin composite and matrix alone. Wear of the veneering composites was significantly higher than of Z100 (13 microm) and Amalgam (14 microm; p < 0.01, Mann-Whitney U-test). Mean fracture strengths of indirect composites ranged from 127.5 MPa (Targis) to 71.6 MPa (Vita Zeta LC). The elastic moduli of the composites were between 2.9 and 12.8 GPa. The matrix wear rates did not differ significantly. Three-body wear results of complex resin composites are highly influenced by their filler content, filler particle size distribution, kind of filler particles, shape, and their silanization to the matrix. Due to this fact, three-body wear testing is an essential testing method and cannot be replaced by testing single material components.

Composite Resins↗

Toughening of dental glass ionomer cements with reactive glass fibres.

A fibre reinforced glass ionomer cement (FRGIC) for dental applications was loaded with 20 vol% short fibres (430 microm) with a glass composition in the system SiO(2)-Al(2)O(3)-CaF(2)-Na(3)AlF(6). The fracture toughness and the total energy release rate were examined. A 20% anisotropic fibre alignment was observed, perpendicular to the loading direction. An increase of fracture toughness of 140% and of total energy release rate of 440% was achieved compared to the unreinforced glass ionomer cement. Matrix-fibre interface reaction is supposed to exert the major influence on mechanical behaviour of FRGIC by controlling fibre pull-out and thus the total energy release rate.

Anisotropy↗