Dental materials research “icon” who developed bis-GMA resin dies
Those who knew Dr. Rafael “Ray” Bowen describe him as a “legend” who made significant contributions to dental materials research. Dr. Bowen, who retired in 2018 after 62 years at the American Dental Association, has died.
“Ray Bowen has been a fixture in restorative dental materials research for almost 60 years,” said Stephen Bayne, PhD, emeritus professor at the University of Michigan School of Dentistry, who first met Dr. Bowen as a graduate student and frequently connected with him over the years. “Ray shined in dental materials research in a way different from most.”
Dr. Bowen joined the ADA in 1956 after his first published research paper and presentation at an International Association for Dental Research meeting led to his encountering Dr. Robert Nelson of the ADA Research Unit, now part of the ADA Science & Research Institute.
While at the research unit located at the National Bureau of Standards, which later became the National Institute of Standards and Technology, Dr. Bowen developed bisphenol A-glycidyl methacrylate, a methacrylate monomer used in most modern composite resin restorative materials. He patented it in 1962, and it has been the most used resin in dental restoration for more than 50 years.
“Ray was one of the few icons in dental research who were well known not only in the United States but also globally, especially in Europe and Japan,” said Laurence Chow, PhD, former chief research scientist at the ADA Science & Research Institute, who joined the ADA Research Unit in 1969. “This invention revolutionized dental restoration techniques, replacing the silicate filling about 50 years ago and more recently the amalgam. Ray was also well known for his work in dentin bonding, from basic understanding of the adhesion science to formulating multistep dentin bonding techniques.”
In 1994, Dr. Bowen discussed his development process with the ADA News.
“I tried to make a hybrid material using a commercial epoxy resin as an adhesive binder to glue together powdered particles of silica glass or dental porcelain,” he said. “It occurred to me to replace the epoxy group on each end of this same kind of molecule with a methacrylate group. It was known that methacrylate groups polymerize rapidly under oral conditions. I hoped that the rest of the molecule would contribute many of the good properties of epoxies that made them so useful in many industrial applications.”
Dr. Bowen was well known for working on glass-ceramic tooth-colored restoratives, protective coatings for tooth and restoration surfaces, and methods for reducing shrinkage in composite materials, said Diane Bienek, PhD, ADA Science & Research Institute director of research operations.
He obtained many patents related to his research, Dr. Bayne said.
“Scientifically, Dr. Bowen is a legend. I used to tease him that he was the Elvis Presley of the dental world,” Dr. Bienek said. “Dr. Bowen’s scientific legacy will live on, as he inspired generations of scientists to take dental material development into uncharted territories.”
Dr. Bowen served as director of the Paffenbarger Research Center, a later iteration of the ADA Research Unit, from 1983 until 1994 and then became the ADA’s first distinguished scientist in 1994.
During his time as director, the center was successful in securing National Institute of Dental and Craniofacial Research funding, including a grant for 2 5-year periods that provided major funding for multiple interdisciplinary projects, Dr. Chow said.
For his contributions to dentistry, Dr. Bowen received numerous recognitions, including the ADA Distinguished Service Award in 1999 and the American Association for Dental Research Distinguished Scientist Award in 2014. A 1953 graduate of the University of Southern California School of Dentistry, he joined the ranks of the school’s hall of fame in 1997.
Despite all his career accomplishments, Dr. Bowen maintained an admirable work-life balance, enjoying activities from painting to skydiving to spending time with his wife, Dr. Bienek said.
“During all of that work, and beyond all of the chemistry persistence of Ray, surfaced the most important values of the man. He was charming, engaging, friendly, witty and always smiling,” Dr. Bayne said. “He treated everyone as an equal. He was always a team person. He made you feel important. That special grace is what we will always remember about our many special interactions with Ray.”
By Mary Beth Versaci, senior editor, ADA News
Early Childhood Caries Linked to Taxonomic Shifts in the Dental Mycobiome During Disease Progression, Study Reports
Early childhood caries is associated with strong taxonomic shifts in the dental mycobiome during disease progression, according to a study published online March 18 in Applied and Environmental Microbiology.
Researchers from Clemson University College of Science in Clemson, South Carolina, used amplicon sequencing to generate taxonomic profiles from 82 site-specific supragingival plaque samples obtained from 33 children. The children’s caries statuses differed and were categorized as caries free, caries active with enamel lesions, or caries active with dentinal lesions.
The researchers identified 139 fungal species in the plaque samples. Candida albicans was the most abundant followed by Candida dubliniensis.
The study findings showed that severely progressed plaque communities (that is, teeth with dentinal lesions) were significantly different from healthy plaque communities (that is, caries-free surfaces in caries-free children). C. albicans, C. dubliniensis, Nigrospora oryzae, and an unclassified Microdochium species were correlated with caries, while 12 other taxa were correlated with health.
The researchers also observed a steady increase in C. dubliniensis as caries progressed, suggesting that it may play an important role in caries pathogenicity. In contrast, 4 health-associated taxa identified in the plaque samples have the potential to antagonize Streptococcus mutans by means of xylitol production.
“This work provides valuable insight into the oral mycobiome and the role fungi play in the mouth as it relates to caries,” said corresponding author Vincent Richards, PhD, an assistant professor in the Department of Biological Sciences at Clemson University. “If we understand that better, then researchers can develop better [caries] prevention measures. For example, perhaps they can put beneficial fungal species into a probiotic treatment.”
The College of Dentistry at the University of Florida in Gainesville, Florida, provided the plaque samples for sequencing and analysis.
This research was funded, in part, by Clemson’s Biological Sciences Graduate Professional Development Grants in Aid of Research.
Salivary Microbial Colonization May be Lower in Patients with Clear Aligners than in those with Fixed Orthodontic Appliances, Study Finds
Orthodontic patients with clear aligners may have lower salivary microbial colonization than those with fixed orthodontic appliances, according to a study published online April 24 in PLoS One.
In this observational, prospective controlled study, researchers from the University of L’Aquila in L’Aquila, Italy; Vita-Salute San Raffaele University in Milan, Italy; and IRCCS San Raffaele Hospital in Milan evaluated salivary levels of Streptococcus mutans and lactobacilli, as well as other salivary indexes, in patients before the start of orthodontic treatment, at 3 months, and at 6 months.
The study sample was composed of 80 people (46 men, 34 women); 40 were treated with clear aligners, and 40 were treated with fixed appliances.
The study findings showed that patients in the clear aligner group had a plaque index score of 0 (range, 0-3) at all time points, whereas those in the fixed appliance group experienced a statistically significant increase in the plaque index score over time.
At 6 months, 15 of 40 participants (37.5%) in the fixed appliance group exhibited high salivary levels (> 105 colony-forming units per milliliter) of S. mutans (odds ratio [OR], 7.40; 95% confidence interval [CI], 1.94 to 28.25; χ2, 10.32; P = .001) and lactobacilli (OR, 23.40; 95% CI, 2.91 to 188.36; χ2, 15.31; P = .0001). In comparison, only 3 of 40 participants (8%) in the clear aligner group displayed high levels of S. mutans at 6 months, and 1 of 40 (2.5%) displayed high levels of lactobacilli.
After 6 months of orthodontic treatment, patients with clear aligners exhibited lower salivary microbial colonization than those with fixed appliances. Thus, additional strategies for plaque control are needed depending on the type of orthodontic appliance used, the researchers concluded.
HIV Screening in Dental Settings can be Beneficial, Researchers Report
Screening for HIV in the dental setting can be a good option for first-time testers and patients who have not seen a primary care provider in the past 12 months, according to a study published online April 16 in PLoS One.
In this demonstration project, the New York State Department of Health collaborated with the Northeast/Caribbean AIDS Education and Training Center and dental schools at the University at Buffalo State University of New York, Buffalo, New York; University of Rochester, Rochester, NY; and State University of New York at Stony Brook, Stony Brook, New York, to offer free HIV screening tests as part of routine dental care from February 2016 through March 2018.
Ten dental clinics in upstate New York and on Long Island participated in the study. Of the 14,887 dental patients offered HIV tests, 9,057 (60.8%) underwent screening by trained dentists, dental students, and hygienists. The rapid oral HIV screening test results for 1 patient (0.011%) were positive, and this patient was referred for medical care.
Multilevel generalized linear modeling analysis indicated that test acceptance was significantly associated with the patient’s age, race or ethnicity, sex, country of origin, primary payer status, previous primary care visits, previous HIV testing experiences, and the poverty level of the patient’s community.
Most of the participating dental care providers reported that HIV screening in the dental setting was successful largely because the at-home HIV tests were easy to administer, the results were obtained rapidly, and patient acceptance was high enough to warrant screening.
Funding for the HIV Screening in the Dental Chair ETE Demonstration Project was provided by the New York State Department of Health.
Compiled by Janice Snider.
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