Marianne Federlin

Influence of Root Canal Disinfectants on Growth Factor Release from Dentin

INTRODUCTION During dentinogenesis, growth factors become entrapped in the dentin matrix that can later be released by demineralization. Their effect on pulpal stem cell migration, proliferation, and differentiation could be beneficial for regenerative endodontic therapies. However, precondition for success, as for conventional root canal treatment, will be sufficient disinfection of the root canal system. Various irrigation solutions and intracanal dressings are available for clinical use. The aim of this study was 2-fold: to identify a demineralizing solution suitable for growth factor release directly from dentin and to evaluate whether commonly used disinfectants for endodontic treatment will compromise this effect. METHODS Dentin disks were prepared from extracted human teeth and treated with EDTA or citric acid at different concentrations or pH for different exposure periods. The amount of transforming growth factor-β1 (TGF-β1), fibroblast growth factor 2, and vascular endothelial growth factor were quantified via enzyme-linked immunosorbent assay and visualized by gold labeling. Subsequently, different irrigation solutions (5.25% sodium hypochloride, 0.12% chlorhexidine digluconate) and intracanal dressings (corticoid-antibiotic paste, calcium hydroxide: water-based and oil-based, triple antibiotic paste, chlorhexidine gel) were tested, and the release of TGF-β1 was measured after a subsequent conditioning step with EDTA. RESULTS Conditioning with 10% EDTA at pH 7 rendered the highest amounts of TGF-β1 among all test solutions. Fibroblast growth factor 2 and vascular endothelial growth factor were detected after EDTA conditioning at minute concentrations. Irrigation with chlorhexidine before EDTA conditioning increased TGF-β1 release; sodium hypochloride had the opposite effect. All tested intracanal dressings interfered with TGF-β1 release except water-based calcium hydroxide. CONCLUSIONS Growth factors can be released directly from dentin via EDTA conditioning. The use of disinfecting solutions or medicaments can amplify or attenuate this effect.

Retrospective clinical investigation and survival analysis on ceramic inlays and partial ceramic crowns: results up to 7 years

Abstract This study retrospectively evaluated the clinical performance of 287 all-ceramic restorations placed during routine patient care in the University setting in the past 7 years. All patients (n = 106) with ceramic inlays or partial ceramic crowns (PCC), placed during 1988–1994 (n = 327) by five experienced dentists were asked to take part in a clinical investigation, and 92 patients with 287 restorations (232 inlays, 55 PCC) agreed to do so. The following ceramics were used: 44 (15.3%) Dicor (Dentsply), 126 (43.9%) IPS-Empress (Ivoclar), 82 (28.7%) Mirage II, 33 (11.5%) Cerec-Vita-Mark I (Vita), and 2 (0.7%) Duceram LFC (Ducera) restorations. The restorations were placed using the following luting composites: 73 (25.4%) Dual Cure Luting Cement (Optec), 81 (28.3%) Variolink high viscosity (Ivoclar), 32 (11.1%) Microfill Pontic C (Kulzer), 51 (17.8%) Dual Zement (Ivoclar), 40 (13.9%) Dicor Light Activated Cement (Dentsply), and 10 (3.5%) Vita Cerec Duo Cement (Vita). Restorations were evaluated according to the modified USPHS criteria. Kaplan-Meier analysis was used to calculate the probability of survival. Of the 287 restorations 270 (94.2%) were still in function without any need of intervention. Fourteen restorations (4.8%) had failed before starting the clinical investigation, and in three a fracture was found during the investigation. These 17 failed restorations consisted of 14 PCC and 3 ceramic inlays. The results of the clinical investigation revealed 59.2% Alpha-ratings for marginal adaptation. Only one restored tooth showed recurrent caries. The probability of survival (95% confidence interval) for 7 years was 98% (97.99–98.01%) for ceramic inlays and 56% (46–66%) for PCC. Our findings show that ceramic inlays can be regarded as an acceptable alternative to cast gold restorations within the methodological limitations of the present study. For PCC further experience with more recent ceramics is warranted.

Effect of dimension of luting space and luting composite on marginal adaptation of a class II ceramic inlay.

This study evaluated the in vitro marginal quality at the interproximal cervical margin of class II Cerec restorations. Marginal quality was evaluated separately by (1) SEM analysis before and after simultaneous thermocycling and mechanical loading for the integrity of the restoration surface and (2) dye penetration after thermocycling and mechanical loading to evaluate the strength of the bond within the depth of the cavity. The results reveal that marginal integrity is influenced by the width of the luting space and the luting composite. With a luting space of 100 microns, marginal quality with as little as 3% to 14% loss of adhesion can be obtained. Luting spaces greater than 100 microns can partially be compensated by the luting composite. For Cerec inlays, highly filled luting composites with a high viscosity are recommended.

Mutagenicity of the root canal sealer AHPlus in the Ames test

Abstract The mutagenic activity of the root canal sealing cement, AHPlus, was tested in a bacterial gene mutation assay (Ames test). The material was mixed according to the manufacturers instruction and tested immediately after mixing and after a setting time of 24 h at 37°C in a humidified chamber. The set material was powdered and both the freshly mixed and the powdered material were eluted in dimethyl sulfoxide (DMSO) and physiological saline (0.1 g/2 ml) for 24 h at 37°C. Aliquots of serially diluted eluates were then used in the standard plate incorporation assay. The Salmonella typhimurium tester strains TA98 and TA100 were employed to detect the induction of frameshift mutations and base pair substitutions both in the presence and in the absence of a metabolically active microsomal fraction from rat liver (S9 fraction). No mutagenic and no toxic effects were found with physiological saline eluates of the freshly mixed material and of mixed material which was set for 24 h. However, DMSO eluates of the freshly mixed AHPlus were mutagenic in tester strain TA100 in a dose-related manner in the absence of S9. A four- to fivefold increase of the mutation frequencies was induced by 2.5 mg AHPlus per plate compared with the number of spontaneous mutants. The mutagenic effect was completely abolished in the presence of a metabolically active S9 fraction. Also, no mutagenic effects were observed with DMSO eluates of AHPlus set for 24 h. However, the set material was more toxic towards bacteria than the freshly mixed sealer. This difference was indicated by a tenfold lower amount of material necessary to cause complete absence of the background lawn in both S. typhimurium tester strains. Therefore, we conclude that at least two different compounds of AHPlus are biologically active in DMSO eluates to cause mutagenic and toxic effects in S. typhimurium TA100 and TA98.

Partial ceramic crowns: influence of ceramic thickness, preparation design and luting material on fracture resistance and marginal integrity in vitro.

This in vitro study tested the effects of two different ceramic thicknesses, two preparation designs and two different luting agents on the marginal integrity and fracture resistance of partial ceramic crowns (PCC). Eighty extracted human molars were prepared according to the following preparation designs: a) Coverage of functional cusps/butt joint (n=40), b) Horizontal reduction of functional cusps (n=40). PCC (Vita Mark II, Cerec3 System) were fabricated and the ceramic thickness of the functional cusps was adjusted to (1): 0.5-1.0 mm and (2): 1.5-2.0 mm. PCC were adhesively luted to the cavities with either Excite/VariolinkII (VL) or RelyX Unicem (RX). The specimens were exposed to thermocycling and central mechanical loading (5000 x 5 degrees C-55 degrees C; 30 second/cycle; 50,0000 x 72.5N, 1.6Hz). Marginal integrity was assessed by evaluating dye penetration (fuchsine) on multiple sections in the bucco-oral direction by relating the actual penetration distance to the maximal length of the corresponding cavity wall (100%). Restoration/luting agent (RL)--and tooth/luting agent (TL) interfaces were evaluated separately. The data were statistically analyzed with the Mann Whitney U-test and the Error Rates Method (ERM), and the fracture rates were analyzed with the chi2-test. Dye penetration data indicated that ceramic thickness and luting agent had a statistically significant influence upon marginal integrity in general, irrespective of all other parameters (ERM): RX showed significantly lower microleakage along the RL interface than VL. VL revealed significantly lower microleakage at the TL interface than RX. Fifteen PCC of group 1 (0.5-1.0 mm) and two PCC of group 2 (1.5-2.0 mm) were fractured after thermocycling and central mechanical loading, with the difference being statistically significant. PCC fabricated from industrially sintered feldspathic ceramic should have at least a thickness of 1.5-2.0 mm in stress-bearing areas.

Partial ceramic crowns. Influence of preparation design and luting material on margin integrity—a scanning electron microscopic study

This in vitro study examines the effects of three preparation designs and different luting agents on the marginal integrity of partial ceramic crowns. One hundred forty-four extracted human molars were prepared according to the following preparation designs: A. Coverage of functional cusps, B. Horizontal reduction of functional cusps and C. Complete reduction of functional cusps. Partial ceramic crowns (Vita Mark II, Cerec 3 System) were bonded to the cavities with: Variolink II/Excite (Vivadent), Panavia F/ED primer (Kuraray), Dyract/Prime and Bond NT (Detrey/Dentsply), and Fuji Plus/GC cavity conditioner (GC). The specimens were exposed to thermocycling and mechanical loading. Marginal adaptation was assessed on replicas using quantitative margin analysis in the scanning electron microscope (SEM). Significant differences were observed between the preparation designs in general. Coverage of functional cusps with preparation of butt joints and use of Variolink as luting material showed a tendency toward the lowest values for compromised adhesion, especially within the dentin. Significant differences could be determined between luting systems: resin-modified glass ionomer cement (RMGIC) caused fracture of the restorations and revealed higher values than all other luting materials for compromised adhesion at ceramic-luting agent and tooth-luting agent interfaces. The dentin-luting material interface, in general, showed higher percentages of compromised adhesion (38–100%) than enamel- and ceramic-luting material interfaces (0–30%). In conclusion, the SEM data indicate that, with adhesively bonded partial ceramic crowns, retentive preparation is not contraindicated and the choice of luting material is more relevant than the preparation design. Margins below the cemento-enamel junction reveal significant loss of adhesion in spite of adhesive luting techniques. The RMGIC cannot be recommended as a luting material for feldspathic partial ceramic crowns.

Marginal Integrity of Partial Ceramic Crowns Within Dentin With Different Luting Techniques and Materials

This in vitro study evaluated the marginal integrity of partial ceramic crowns (PCCs) luted with or without a resin-coating and compared the results with the marginal sealing of a recently introduced self-adhesive universal resin cement. PCC preparations were performed on 84 extracted human molars, with proximal margins placed 1 mm below the cemento-enamel junction. The PCCs were fabricated from Vita Mark II ceramic (Vita) using the Cerec-3 Unit (Sirona). The prepared teeth were assigned to three groups: (1) conventional luting technique (n=36), (2) resin-coating luting technique (n=36) or (3) recently introduced self-adhesive universal resin cement (n=12). Within these three groups, the following materials were applied: (1) Excite/Variolink II (EVC), ED-Primer/Panavia-F2.0 (PAC), Syntac Classic/ Variolink II (SYC); (2) Excite/Variolink II with Excite/Tetric Flow resin-coating (EVR), ED-Primer/Panavia-F2.0 with Clearfil SE-Bond/ Protect-Liner F resin-coating (PAR), Excite/ Variolink II with Syntac Classic/Tetric Flow resin-coating (SYR); (3) RelyX Unicem (REX). After thermocycling and mechanical loading (TC: 5000 cycles at 5 degrees C/55 degrees C; 30 seconds/cycle; ML:500000 cycles at 72.5 N, 1.6 Hz), microleakage was assessed by evaluating silver staining (%) on multiple tooth sections. Ceramic/composite-, resin-coating/composite- (where applicable) and dentin/composite-interfaces were evaluated separately. The data were statistically analyzed with the Mann-Whitney-U-test and the Error Rates Method. In Groups 1 and 2, the evaluation of microleakage at dentin showed better marginal integrity when the resin-coating technique was applied (EVR, PAR, SYR: 18-53%) than within the conventional luting technique group (EVC, PAC, SYC: 58-67%). However, the lowest microleakage values were found for RelyX Unicem (REX: 15%). In conclusion, resin-coating may improve the marginal sealing within dentin, depending on the materials used. Luting with a self-adhesive universal resin cement showed the best marginal sealing of all groups.

Ceramic inlays and partial ceramic crowns: influence of remaining cusp wall thickness on the marginal integrity and enamel crack formation in vitro.

No information is currently available about what the critical cavity wall thickness is and its influence upon 1) the marginal integrity of ceramic inlays (CI) and partial ceramic crowns (PCC) and 2) the crack formation of dental tissues. This in vitro study of CI and PCC tested the effects of different remaining cusp wall thicknesses on marginal integrity and enamel crack formation. CI (n = 25) and PCC (n = 26) preparations were performed in extracted human molars. Functional cusps of CI and PCC were adjusted to a 2.5 mm thickness; for PCC, the functional cusps were reduced to a thickness of 2.0 mm. Non-functional cusps were adjusted to wall thicknesses of 1) 1.0 mm and 2) 2.0 mm. Ceramic restorations (Vita Mark II, Cerec3 System) were fabricated and adhesively luted to the cavities with Excite/Variolink II. The specimens were exposed to thermocycling and central mechanical loading (TCML: 5000 x 5 degrees C-55 degrees C; 30 seconds/cycle; 500000 x 72.5N, 1.6Hz). Marginal integrity was assessed by evaluating a) dye penetration (fuchsin) on multiple sections after TCML and by using b) quantitative margin analysis in the scanning electron microscope (SEM) before and after TCML. Ceramic- and tooth-luting agent interfaces (LA) were evaluated separately. Enamel cracks were documented under a reflective light microscope. The data were statistically analyzed with the Mann Whitney U-test (alpha = 0.05) and the Error Rates Method (ERM). Crack formation was analyzed with the Chi-Square-test (alpha = 0.05) and ERM. In general, the remaining cusp wall thickness, interface, cavity design and TCML had no statistically significant influence on marginal integrity for both CI and PCC (ERM). Single pairwise comparisons showed that the CI and PCC of Group 2 had a tendency towards less microleakage along the dentin/LA interface than Group 1. Cavity design and location had no statistically significant influence on crack formation, but the specimens with 1.0 mm of remaining wall thickness had statistically significantly more crack formation after TCML than the group with 2.0 mm of remaining cusp wall thickness for CI. The remaining cusp wall thickness of non-functional cusps of adhesively bonded restorations (especially for CI) should have a thickness of at least 2.0 mm to avoid cracks and marginal deficiency at the dentin/LA interface.

SEM analysis of marginal expansion and gap formation in Class II composite restorations

OBJECTIVES Morphological changes in terms of marginal expansion have been observed at the dentin-composite interface of resin composite restorations with the scanning electron microscope (SEM), which could not be described with the criteria conventionally used for quantitative marginal analysis. The purpose of the present study was to elucidate the influence of marginal expansion upon marginal integrity and clarify the cause of these morphological changes. METHODS A total of 22 extracted human molars were restored with Class II resin composite restorations, with and without the use of a dentin bonding agent. The cervical restoration margin was located below the cemento-enamel-junction (CEJ). The marginal adaptation at the dentin- and enamel-composite interfaces was evaluated and measured on replicas using quantitative SEM analysis after different storage periods. The chemical composition of the marginal expansion was determined qualitatively by EDX (Energy Dispersive X-Ray) analysis using original tooth samples. The results obtained from quantitative SEM analysis were statistically analyzed by applying the Mann-Whitney U-test and the error rates method. RESULTS Significantly less marginal expansion occurred at the enamel interface than at the dentin-composite interface (p < or = 0.01). Within the dentin, less marginal expansion was observed with the use of a dentin bonding agent than without a dentin bonding agent (p < or = 0.05). At 1 y, a significant (p < or = 0.05) decrease in marginal expansion was observed in both groups. EDX analysis revealed that the chemical composition of the marginal expansion is comparable to the resin composite, since peaks for silicon, barium and ytterbium could be found at these sites. SIGNIFICANCE In Class II resin composite restorations below the CEJ, partial disruption of the adhesive bond may occur initially when curing the restoration. Water sorption causes gap reduction by hygroscopic expansion, seen in the SEM as a volume increase. Thus, the observed morphological changes can be regarded as an early sign of insufficient adhesion between composite and dentin at sites where disruption of the bond occurred initially, whether or not a dentin bonding agent was used.

Clinical evaluation of heat-pressed glass-ceramic inlays in vivo: 2-year results

Abstract In the present study, the 2-year clinical and scanning electron microscope (SEM) results for heat-pressed ceramic inlays are reported. In a selected patient population, 51 cavities were restored with all-ceramic inlays. All margins were located within the enamel. The inlays were luted to the cavities with a high-viscosity, dual-cure luting composite. After 2 days, 1 year, and 2 years, the restorations were evaluated clinically, using the modified USPHS criteria. Quantitative margin analysis was performed in the SEM on the replicas fabricated at the recall times. The data were tested for significant differences, using the chi-square test for the clinical evaluation and the Mann-Whitney U-test for the margin analysis. After 2 years, the clinical evaluation of the margin adaptation revealed Bravo ratings for 14 restorations (27.5%); 37 restorations (72.5%) were rated Alfa. Compared to the baseline data, this difference was statistically significant (p≤0.5). SEM analysis revealed that the ceramic-composite interface exhibited significantly (p≤0.01) more gap formation than the enamel-composite interface at all times of evaluation. Wear of the luting composite could be determined along 50% of the restoration interface during the first year, 53% during the second year. The inlay restorations controlled in this study perform well after a period of 2 years.