Richard L. Gregory, PhD

Richard L. Gregory, PhD
Richard L. Gregory, PhD
Associate Dean for Graduate Education
Professor of Biomedical and Applied Sciences and Pathology and Laboratory Medicine
Adjunct Professor of Preventive and Community Dentistry
Director, PhD. Dental Science Program
School of Dentistry

Contact Info

Phone  (317) 274-9949
Fax       (317) 278-1411

Office Address

Indiana University School of Dentistry
Department of Biomedical and Applied Sciences
Oral Health Research Institute
415 Lansing St., Room 123
Indianapolis, Indiana  46202


Allam, E., W. Zhang, C. Zheng, R.L. Gregory, and L.J. Windsor.  2011.  Smoking and oral health.  In: Cigarette Smoke Toxicity - Linking Individual Chemicals to Human Diseases.  D. Bernhard (ed.).  Wiley-VCH Verlag GmbH & Co. KGaA  (pub.)  pp. 257-280. 

Huang, R., M. Li and R.L. Gregory.  2011.  Bacterial interactions in dental biofilm.  Virulence 2:435-444.  PubMed PMID: 21778817.  Impact Factor 2.787. 

Gregson, K.S., H. Shih and R.L. Gregory.  2011.  The impact of three strains of oral bacteria on the surface and mechanical properties of a dental resin material.  Clin. Oral Invest. 16:1095-1103.  

Nassar, H., M. Li and R.L Gregory.  2012.  Effect of honey on Streptococcus mutans growth and biofilm formation.  Appl. Environ. Microbiol. 78:536-540.  PubMed PMID 22038512. 

Levitt, I.A. and R.L. Gregory.  2012.  Antibiotics and dental biofilms.  Dimensions of Dental Hygiene.  January 2012 issue, pp. 54-57. 

Huang, R., M. Li and R.L. Gregory.  2012.  Effect of nicotine on growth and metabolism of Streptococcus mutans.  Eur. J. Oral Sciences 120:319-325 and Indiana Branch of the American Society for Microbiology Newsletter (Feb. 2013). 

Wahaidi, V.Y., G.J. Eckert, R.L. Gregory, M.J. Kowolik and D.M. Galli.  2013.  The in-vitro response of human peripheral blood neutrophils to Fusobacterium nucleatum.  Int. J. Clin. Dent. 6:59-66. 

McCarlie, V.W., J.K. Hartsfield, Jr., J.S. Blum, C. González-Cabezas, J.R. Chin, G.J. Eckert, L.A. Morford, M.D. Pescovitz, H. Rodriguez, M. Fontana and R.L. Gregory.  2013.  Total IgA and IgA reactivity to antigen I/II epitopes in HLA-DRB1*04 positive subjects.  Open J. Immunol. 3:82-92. 

Sabrah, A.H.A., G.H. Yassen and R.L. Gregory.  2013.  Effectiveness of antibiotic medicaments against biofilm formation of Enterococcus faecalis and Porphyromonas gingivalis.  J. Endo. 39:1385-1389. 

Bottino, M.C., K. Kamocki, G. Yassen, J.A. Platt, M.M. Vail, Y. Ehrlich, K.J. Spolnik and R.L. Gregory.  2013.  Bioactive nanofibrous scaffolds for regenerative endodontics.  J. Dent. Res. 92:963-969. 

Li, M., R. Huang, X. Zhou and R.L. Gregory.  2013.  Role of sortase in Streptococcus mutans under the effect of nicotine.  Int. J. Oral Sci. 5:206-211. 

Twigg III, H.L., D.E. Nelson, R.B. Day, R.L. Gregory, Q. Dong, R. Rong, K. Knox, K. Crothers, E. Sodergren, G. Weinstock.  2014.  Comparison of whole and acellular bronchoalveolar lavage to oral wash microbiomes:  Should acellular bronchoalveolar lavage be the standard?  Annals of the American Thoracic Society. 11:S72-73. 

Li, M., R. Huang, X. Zhou, K. Zhang, X. Zheng and R.L. Gregory.  2014.  Effect of nicotine on dual species biofilms of Streptococcus mutans and Streptococcus sanguinis.  FEMS Microbiology Letters 350:125-132. 

Bottino, M.C., R.A. Arthur, R.A. Waeiss, K. Kamocki, K.S. Gregson, and R.L. Gregory.  2014.  Biodegradable nanofibrous drug delivery systems:  Effects of metronidazole and ciprofloxacin on periodontopathogens and commensal bacteria.  Clin. Oral Invest. Clin. Oral Investig. 18:2151-2158. 

Whatley, J.D., K.J. Spolnik, M.M. Vail, B.H. Adams, R. Huang, R.L. Gregory and Y. Ehrlich.  2014.  Susceptibility of methacrylate-based root canal filling to degradation by bacteria found in endodontic infections.  Quintessence International 45:647-652. 

Palasuk, J., K. Kamocki, L. Hippenmeyer, J.A. Platt, K.J. Spolnik, R.L. Gregory and M.C. Bottino.  2014.  Bi-mix antimicrobial scaffolds for regenerative endodontics.  J. Endo.  40:1879-1884. 

Feitosa, S.A., J. Palasuk, K. Kamocki, S. Geraldeli, R.L. Gregory, J.A. Platt, L.J. Windsor and M.C. Bottino.  2014.  Doxycycline-encapsulated nanotube modified dentin adhesives.  J. Dent. Res. 93:1270-1276. 

Huang, R., M. Li, M. Ye, K. Yang, X. Xin and R.L. Gregory.  2014.  Effect of nicotine on Streptococcus gordonii growth, biofilm formation and cell aggregation.  Appl. Environ. Microbiol. 80:7212-7218. 

Allison, L., L.A. Walker, B.J. Sanders, Z. Yang, G. Eckert and R.L. Gregory.  2015.  Effect of human milk and it’s components on Streptococcus mutans biofilm formation.  J. Clin. Ped. Dent. 39:255-261. 

Hamilton, M.F., A.D. Otte, R.L. Gregory, R. Pinal, A. Ferreira-Zandona and M.C. Bottino.  2015.  Physico-mechanical and antibacterial properties of experimental resin-based dental sealants modified with nylon-6 and chitosan nanofibers.  J. Biomed. Mater. Res. B Appl. Biomater. (in press). 

Sabrah, A.H.A., G.H. Yassen, W.C. Liu, W.S. Goebel, R.L. Gregory and J.A. Platt.  2015.  The effect of diluted triple and double antibiotic pastes on dental pulp stem cells and established Enterococcus faecalis biofilm.  Clin. Oral Investig. (in press). 

DuBois, A.E., Z.C. Bennett, U. Khalid, A. Khalid, R.A. Meece, G.J. DiFiore and R.L. Gregory.  2015.  Oral microorganism growth as affected by nicotine.  Fine Focus (Undergraduate Microbiology Journal) 1:63-75. 

Sabrah, A.H.A., G.H. Yassen, K.J. Spolnik, A.T. Hara,  J.A. Platt and R.L. Gregory.  2015.  Evaluation of residual antibacterial effect of human radicular dentin treated with triple and double antibiotic pastes.  J. Endodon. (in press). 

Huang, R., J. Zhang, F.X. Yang and R.L. Gregory.  2015.  PCR-based multiple species cell counting for in vitro mixed culture.  PLoS ONE 10(5): e0126628. doi:10.1371/journal.pone.0126628. 

Huang, R., M. Li and R.L. Gregory.  2015.  Nicotine promotes Streptococcus mutans extracellular polysaccharide synthesis, cell aggregation and overall lactate dehydrogenase activity.  Archs. Oral Biol. 60:1083-1090. 

Algarni, A.A., G.H. Yassen and R.L. Gregory.  2015.  Inhibitory effect of gels loaded with a low concentration of antibiotics against biofilm formation by Enterococcus faecalis and Porphyromonas gingivalis.  J. Oral Sci. 57:213-218. 

Shirley, K.P., L.J. Windsor, G.J. Eckert and R.L. Gregory.  2015.  In vitro effect of Plantago major extract, aucubin and baicalein on Candida albicans biofilm formation, metabolic activity and cell surface hydrophobicity.  J. Prosthodontics (in press). 

Münchow, E.A., M.T.P. Albuquerque, B. Zero, K. Kamocki, E.Piva, R.L. Gregory and M.C. Bottino.  2015.  Development and characterization of novel ZnO-loaded electrospun membranes for periodontal regeneration. Dent. Mat. (in press). 

Albuquerque, M.T.P., S.J. Ryan, E.A. Münchow, M.M. Kamocka, R.L. Gregory, M.C. Valera and M.C. Bottino.  2015.  Antimicrobial effects of novel TAP-mimic scaffolds on A. naeslundii biofilm.  J. Endo. (in press). 

Albuquerque, M.T.P., J.D. Evans, R.L. Gregory, M.C. Valera and M.C. Bottino.  2015.  Antibacterial TAP-mimic electrospun polymer scaffold –effects on P. gingivalis-infected dentin biofilm.  Clin. Oral Invest.  (in press). 

Tagelsir, A., G.H. Yassen, G.F. Gomez and R.L. Gregory.  2015.  Effect of antimicrobials used in regenerative endodontic procedures on three-week old Enterococcus faecalis biofilm.  J. Endo. (in press). 

Clark, S.A., G. Eckert and R.L. Gregory.  2015.  Effect of commonly prescribed liquid medications on Streptococcus mutans biofilm development. J. Clin. Ped. Dent. (in press). 

Hinds, L.M., E. Moser, G. Eckert, and R.L. Gregory.  2015.  Effect of infant formula on Streptococcus mutans biofilm formation. J. Clin. Ped. Dent. (in press).



Research Interests

Dr. Gregory's research has been funded by grants from the National Institute of Dental and Craniofacial Research, National Institute of Heart and Lung, Smokeless Tobacco Research Council and numerous industrial projects.  Current efforts are focused on mucosal biofilm biology with specific interests in oral bacteria, particularly Streptococcus mutans, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum and Aggregatibacter actinomycetemcomitans.  To help understand the complex biofilm interactions in Streptococcus mutans-induced caries formation, we are defining the role bacterial cell surface proteins play in colonization and bacterial atherosclerosis/endocarditis. Mechanisms that may diminish colonization of S. mutans cells to enamel surfaces and cardiac tissue are being explored. The effect of tobacco on S. mutans virulence is a major focus.  Inhibitory factors being investigated include botanical agents, mucosal vaccines and neutralization of receptor sites.  A sensitive and specific in vitro biofilm caries model system has been developed in this laboratory and is being used to assess the ability of various anti-microbial agents and antibodies in prevention of S. mutans colonization of enamel surfaces and caries formation. In addition, the model is used to determine the relative cariogenicity of oral microorganisms.  His work is currently supported by a NIH U01 grant.