Dong-Hoon Shin, H. Ralph Rawls

Dental Materials, August 2009 (Vol. 25, Issue 8, Pages 1030-1038)

Objectives: This study investigated p-octyloxy-phenyl-phenyl iodonium hexafluoroantimonate (OPPI) as a photoinitiator, in combination with camphorquinone/amine photoinitiation systems, for use with di(meth)acrylate-based composite resins. The investigation determined if the inclusion of OPPI improved degree and rate of conversion, initial color and color stability of a representative composite resin dental material.

Methods: Camphorquinone (CQ) and OPPI were combined in various proportions with the amine co-initiator 2-dimethylaminoethyl methacrylate (DMAEMA) and used at two levels in which CQ+OPPI+DMAEMA=1wt.% or 3wt.% to photoinitiate a BisGMA/BisEMA/TEGDMA (37.5:37.5:25wt.%) monomer blend. Monomer mixture (GTE) was made by mixing 37.5wt.% BISGMA (lot # 568-21-07, ESSTECH, Essington, PA), 37.5wt.% BISEMA (lot # 474-32-02, ESSTECH), and 25wt.% TEGDMA (lot # 597-23-02, ESSTECH). A total of eight groups (four groups for each level of total photoinitiator, 1% and 3%) were tested according to the following proportion of components in the photoinitiator system: Each monomer was polymerized using a quartz-halogen curing unit (Demetron 400, Demetron Research Corp., Danbury, CT) with an intensity of 400mW/cm2 for 5s, 20s, 40s, 60s, 300s and their conversion levels (DC) were determined at each exposure time using a Fourier transform infrared spectrophotometer (FTIR). To examine color stability, experimental composite resins were made by mixing 3.2% silanated barium glass (78wt.%, average filler size; 1μm) with each monomer system, except both CQ only group and 1% CO group, which were found to cure insufficiently to be able to prepare useful specimens. Disk-shaped samples (10mm in diameter and 1.5mm in thickness) were made and stored under the conditions of dry or saline solution at room temperature (25°C) or 60°C water bath. Each CIELAB scale was determined with a colorimeter (CHROMA METER CR-400) at the time of baseline (day after curing), 1 week, 2 weeks, and 4 weeks later.

Results: The high level (3%) photoinitiated groups exhibited greater DC than the low level (1%) groups. In the 3% group, the COA group showed the fastest and the highest DC, while in the 1% group the CA and COA groups showed the greatest DC. In the color stability test, both CA groups were darker and more yellow than the CO and COA groups. Color was more stable in composite resins containing OPPI than those containing only the CQ and amine components. The least color change (greatest color stability) was found using 25°C saline solution aging, and the most change (least color stability) occurred using 60°C dry air aging.

Significance: This study suggests that OPPI can be used to replace the amine in a given CQ/amine photoinitiator system to accelerate cure rate, increase conversion, reduce initial color and increase color stability.

Link: http://www.demajournal.com/article/S0109-5641%2809%2900139-0/abstract

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K.J. Anusavice, N.-Z. Zhang and C. Shen

J DENT RES 2006; 85; 950

ABSTRACT
Chlorhexidine salts are available in various formulations for dental applications. This study tested the hypothesis that the release of chlorhexidine from a urethane dimethacrylate and triethylene glycol dimethacrylate resin system can be effectively controlled by the chlorhexidine diacetate content and pH. The filler concentrations were 9.1, 23.1, or 33.3 wt%, and the filled resins were exposed to pH 4 and pH 6 acetate buffers. The results showed that Fickian diffusion was the dominant release mechanism. The rates of release were significantly higher in pH 4 buffer, which was attributed to the increase of chlorhexidine diacetate solubility at lower pH. The higher level of filler loading reduced the degree of polymerization, leading to a greater loss of organic components and higher chlorhexidine release rates.

Link:  http://jdr.sagepub.com/cgi/content/abstract/85/10/950

It is possible that high doses of bisphenol A during pregnancy and/or lactation can reduce survival, birth weight, and growth of offspring early in life.  BPA has also been shown to have estrogenic effects. *

According to internal analysis, Esstech’s bisGMA, Product Code X-950-0000, has one of the lowest BPA concentrations in the industry.

EASE OF FORMULATION

To simplify formulations, X-950-0000 is available in pre-mixed solutions with Triethyleneglycol Dimethacrylate (TEGDMA).

• 50% bisGMA in TEGDMA is X-951-0050

• 80% bisGMA in TEGDMA is X-951-0080

BPA-FREE ALTERNATIVES

Esstech is constantly striving to provide customers with the most up-to-date and novel materials.  The f0llowing are resin “alternatives” that do not contain BPA.

X-850-0000, Urethane Dimethacrylate

• Cures to create a hard glassy surface
• Low color values
• Excellent compatibility with light cure systems

X-726-0000, Extended UDMA

• Increased flexibility
• Enhanced fracture toughness

Esstech is constantly striving to provide customers with the most up-to-date and novel materials.  Contact us if you would like to discuss a certain material or to hear what we have in development.

^{* NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of Bisphenol A.  National Toxicology Program, U.S. Department of Health and Human Services.  NIH Publication No. 08-5994, September 2008.}

Carmem S. Pfeifer, Laura R. Silva, Yoshio Kawano, Roberto R. Braga

Dental Materials Volume 25, Issue 9, Pages 1136-1141 (September 2009)

Looking forward to seeing everyone.  Contact us for a face-to-face appointment, techsupport@esstechinc.com.

This blog presents topics of interest to dentists, material scientists and PhD students. Feel free to browse around and leave comments.  Recent Posts include:

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Dental Materials Blog is coordinated by the Santini Miletic Research Group.  Providing research focused on Recent research has focused on dental resin based composites and adhesives using Raman Spectroscopy, High performance liquid chromatography, Scanning and Transmission Electron Microscopy and Atomic Force Microscopy.  You can contact the Santini Miletic Research Group at: info@santinimiletic.com

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