Synthesis of phosphate monomers and bonding to dentin: Esterification methods and use of phosphorus pentoxide

Ogliari, Fabrício Aulo; da Silva, Eduardo de Oliveira; Lima, Giana da Silveira; Madruga, Francine Cardozo; Henn, Sandrina; Bueno, Márcia; Ceschi, Marco Antônio; Petzhold, Cesar Liberato; Piva, Evandro

doi:10.1016/j.jdent.2007.11.003

« Previous Next »Journal of Dentistry
Volume 36, Issue 3 , Pages 171-177, March 2008

Synthesis of phosphate monomers and bonding to dentin: Esterification methods and use of phosphorus pentoxide

Fabrício Aulo Ogliari
- Operative Dentistry Department, School of Dentistry, Federal University of Pelotas, RS, Brazil
Eduardo de Oliveira da Silva
- Organic Chemistry Department, Chemistry Institute, Federal University of Rio Grande do Sul, RS, Brazil
Giana da Silveira Lima
- Operative Dentistry Department, School of Dentistry, Federal University of Pelotas, RS, Brazil
Francine Cardozo Madruga
- Operative Dentistry Department, School of Dentistry, Federal University of Pelotas, RS, Brazil
Sandrina Henn
- Operative Dentistry Department, School of Dentistry, Federal University of Pelotas, RS, Brazil
Márcia Bueno
- Operative Dentistry Department, School of Dentistry, Federal University of Pelotas, RS, Brazil
Marco Antônio Ceschi
- Organic Chemistry Department, Chemistry Institute, Federal University of Rio Grande do Sul, RS, Brazil
Cesar Liberato Petzhold
- Organic Chemistry Department, Chemistry Institute, Federal University of Rio Grande do Sul, RS, Brazil
Evandro Piva
- Operative Dentistry Department, School of Dentistry, Federal University of Pelotas, RS, Brazil
- Corresponding author at: CDC-Bio, School of Dentistry, Federal University of Pelotas, Rua Gonçalves Chaves 457, CEP 96015-560, Pelotas, RS, Brazil. Tel.: +55 53 3222 6690; fax: +55 53 3222 6690.

Received 31 July 2007; received in revised form 24 October 2007; accepted 3 November 2007.

Abstract

Objectives

The aim of this study was to synthesize an acidic monomer using an alternative synthetic pathway and to evaluate the influence of the acidic monomer concentration on the microtensile bond strength to dentin.

Methods

The intermediary 5-hydroxypentyl methacrylate (HPMA) was synthesized through methacrylic acid esterification with 1,5-pentanediol, catalyzed by p-toluenesulfonic acid. To displace the reaction balance, the water generated by esterification was removed by three different methods: anhydrous sodium sulfate; molecular sieves or azeotropic distillation. In the next step, a phosphorus pentoxide (4.82mmol) slurry was formed in cold acetone and 29mmol of HPMA was slowly added by funnel addition. After the reaction ended, solvent was evaporated and the product was characterized by ¹HNMR and FTIR. The phosphate monomer was introduced in a self-etch primer at concentrations of 0, 15, 30, 50, 70 and 100wt%. Clearfil SE Bond was used as commercial reference. Microtensile bond strength to dentin was evaluated 24h after the bonding procedures, followed by fracture analysis (n=20). Data was submitted to ANOVA and Tukey's post hoc test.

Results

The highest yield was obtained (62%) when azeotropic distillation was used, while the reaction with molecular sieves was not feasible. The phosphoric moiety attachment to the monomer was successfully performed with a quantitative yield that reached around 100%. The acidic monomer concentration significantly affected the bond strength and the highest mean (55.1±12.8MPa) was obtained when 50% of acidic monomer was used.