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Biomedical subjects

Ulrich Salz

Publications and source records attributed to Ulrich Salz.

5 recordsLinked to original sources
PubMed2006

pKa value and buffering capacity of acidic monomers commonly used in self-etching primers.

PURPOSE: The aim of this investigation was to characterize acidic monomers used in self-etching primers/adhesives by determination of their pKa values and by calculation of their calcium dissolving capacity in comparison with phosphoric and hydrochloric acid. MATERIALS AND METHODS: The following acidic monomers were included in this study: 4-methacryloyloxyethyl trimellitate anhydride (4-META), 10-methacryloyloxydecyl dihydrogen phosphate (MDP), dimethacryloyloxyethyl hydrogen phosphate (di-HEMA-phosphate), ethyl 2-[4-(dihydroxyphosphoryl)-2-oxabutyl]acrylate (EAEPA), 2-[4-(dihydroxyphosphoryl)-2-ox-abutyl]acrylic acid (HAEPA), and 2,4,6 trimethylphenyl 2-[4-(dihydroxyphosphoryl)-2-oxabutyl]acrylate (MAEPA). The pKa values were obtained by titration with 0.1 mol/l NaOH in aqueous solution. The inflection points of the resulting potentiometric titration curve were determined as pKa values. In the case of the sparingly water-soluble acidic monomers MAEPA and 4-META, the co-solvent method using different water/ethanol ratios for MAEPA or water/acetone ratios for 4-META was used. The dissolving capacity of each acidic monomer is defined as the amount of hydroxyapatite (HA) dissolved by 1 g of acid. For each monomer, the HA dissolving capacity was calculated bythe corresponding pKa value and the molecular weight. To confirm the calculated dissolving capacities, increasing amounts of HA powder (100 mg portions) were slowly added to 15 mmol/l aqueous solutions of the monomers to determine how much HA could be dissolved in the acidic solutions. RESULTS: For all the investigated acidic monomers, pKal values between 1.7 to 2.5 were observed. The pKa2 values for the phosphate/phosphonate derivatives are between 7.0 and 7.3, and are comparable to phosphoric acid. For dicarboxylic acid derivatives, the pKa2 values are in the range of 4.2 to 4.5. Due to their comparable molecular weights and pKal values, the three tested acids di-HEMA phosphate, MDP and 4-META all possess comparable dissolving capacities for HA (ie, 0.26 to 0.28 g/g monomer). The same amount by weight of acidic monomer EAEPA dissolved more HA (ie, 0.35 g/g monomer). Due to their different molecular weights, phosphoric acid and hydrochloric acid dissolved three and ten times as much HA, respectively, as the first three acidic monomers. As a result, the ability of these acids to dissolve HA increases as their molecular weight decreases. CONCLUSION: There are no significant differences among the investigated acidic monomers in terms of their pKa values and HA dissolving capacities. Monomer selection criteria for new self-etching adhesives must include properties such as calcium salt stability, wetting of the substrate, and copolymerization behavior.

Acetone↗
PubMed2005

Chemical aspects of self-etching enamel-dentin adhesives: a systematic review.

OBJECTIVES: The paper gives an overview on the components and the polymer chemical aspects of currently used self-etching enamel-dentin primers/adhesives. In addition, the contribution of new adhesives monomers and cross-linkers exhibiting enhanced hydrolytic stability than methacrylates to improve the performance of single-bottle adhesives is discussed. SOURCES: Information from original scientific papers or reviews about enamel-dentin adhesives, the patent literature concerning dental adhesives and manufacturer information of commercial self-etching adhesives were included in this review. DATA: The most efficient self-etching enamel-dentin adhesives are based on strongly acidic adhesive monomers, containing dihydrogenphosphate, phosphonic acids or carboxylic acid groups. Serious problems of single-bottle water-based, strongly acidic self-etching enamel-dentin adhesives arise both from the hydrolytic instability of the methacrylate monomers used and the side reaction of the applied initiator components. CONCLUSIONS: The stability of the self-etching enamel-dentin adhesives can be improved by using new acrylic ether phosphonic acids or mono- or difunctional acrylamides, while more stable and compatible components have to be developed in the future.

Acrylamides↗
PubMed2005

Self-curing, self-etching adhesive cement systems.

PURPOSE: To investigate the influence of the acid-base reaction between acidic monomers and amines on the polymerization behavior of self-etching, self-curing adhesives, determine the effect of the application mode on the shear bond strength and morphology, and elucidate the adhesion performance of such systems by shear bond strength measurements. MATERIALS AND METHODS: The amine redox-initiator system N,N-di(2-hydroxyethyl)p-toluene (DEPT)/dibenzoyl peroxide (BPO) was selected to investigate the influence of the amine-base reaction on polymerization behavior. The PKa value of DEPT hydrochloride was measured by titration with NaOH. The influence of the pH value and DEPT concentration on the polymerization rate of methacrylates was investigated by exotherm time measurements. Three different application protocols of Multilink Primer (Ivoclar Vivadent) and Panavia 21 ED-Primer (Kuraray) were tested, 15 s passive vs 15 s agitation vs 60 s passive in combination with the corresponding resin luting material. The effects of these three application protocols were evaluated and monitored by both shear bond strength tests and SEM characterization of the surface morphology. The adhesion potential of these self-etching, self-curing luting systems was compared on enamel and dentin both directly after application and after 24 h. RESULTS: The pKa of DEPT-HCl is 4.45. The polymerization rate of the DEPT-containing, self-etching, self-curing adhesive system is highly influenced by both the amine concentration and the pH value. In the case of Multilink, agitation of the primer mixture for 15 s, especially on dentin, resulted in a higher bond strength and a more pronounced removal of the smear layer. Multilink resulted in statistically higher bond strengths (p < 0.05) than Panavia 21 for both the enamel and dentin directly after application and for the dentin after 24 h. CONCLUSION: Radical polymerization initiators used in self-curing systems are strongly adversely affected by acidic monomers incorporated in self-etching adhesives. However, if there is a good adjustment of these components and effects of adhesive application are taken in account, high bond strengths can be achieved.

Acid Etching, Dental↗
PubMed2005

Hydrolytic stability of self-etching adhesive systems.

PURPOSE: The aim of this investigation was to determine the hydrolytic stability of conventional methacrylates in comparison with a new acrylic ether phosphonic acid and a bis(acrylamide) cross-linking monomer under acidic aqueous conditions and to confirm the potential of these new monomers as components in a self-etching enamel-dentin primer, based on shear bond strength measurements. MATERIALS AND METHODS: Two new monomers were synthesized, an acrylic ether phosphonic acid and a bis(acrylamide). Characterization of the two monomers was carried out by 1H-NMR, and 13C-NMR spectroscopy and of the phosphonic acid by 31P-NMR spectroscopy. The hydrolytic stability of these monomers was evaluated by 1H-NMR spectroscopy or high performance liquid chromatography (HPLC), and was compared with the hydrolytic stability of conventional adhesive methacrylates, ie, MDP, 4-META, TEGDMA and GDMA. Shear bond strength to enamel and dentin was determined using the acrylic ether phosphonic acid and bis(acrylamide) formulated into what is now being marketed as a self-etching primer (AdheSE, Ivoclar Vivadent), and compared with the total-etch adhesives Prime & Bond NT (Dentsply) and Excite (Ivoclar Vivadent) and the self-etching systems One-Up Bond F (Tokuyama), Touch & Bond (Parkell), i-Bond (Heraeus Kulzer), Prompt-L-Pop (3M ESPE), and Clearfil SE Bond (Kuraray). Initial and 24-h bond strength values of AdheSE were compared with those after 16 weeks of storage at 42 degrees C. RESULTS: Stability studies have shown that conventional methacrylate monomers undergo rapid hydrolysis under acidic aqueous conditions (up to 90% degradation after 16 weeks at 42 degrees C). However, the newly formulated strongly acidic acrylic phosphonic acid and cross-linking bis(acrylamide) are stable under these conditions. Moreover, a self-etching enamel-dentin primer based on these new monomers showed high bond strength values. CONCLUSION: The shelf life of dental adhesives can be increased by using ether- or amide-linked polymerizable analogues instead of conventional, less stable ester derivatives. This should improve the performance of adhesive bonds made with these more hydrolytically stable comonomers.

Acid Etching, Dental↗