Our Mission Statement


To provide a warm, comfortable, and stress-free environment for our patients’ dental care and to deliver uncompromising dentistry.

Meet our Doctors

Long H. Nguyen, DDS

After graduating from Wesleyan University in Connecticut with a Master of Science degree in Molecular Biology and Biochemistry, Dr. Long Nguyen decided to pursue a career in dentistry. After graduating from Columbia University in New York City, Dr. Nguyen joined the United States Public Health Service (USPHS) to provide his services to areas where oral health professionals are lacking. He then packed his bags and headed west to serve as a commissioned officer on a Navajo Reservation in Kayenta, Arizona. He is grateful for such a wonderful experience; both professionally and spiritually.


After serving for two years with the UPHS, he moved back to the East coast in order to realize his dream of opening a private practice. Having practiced dentistry since 2003, he has established his practice in Gainesville, VA. Since improving patient care is of huge importance to Dr. Nguyen, he continues to attend a multitude of continuing education classes in order to keep up with constant changes in the field of dentistry.


Dr. Nguyen lives with his wife, daughter, and son in Gainesville, VA. During his free time, he enjoys golf, volleyball, and spending time with his family.

Mary A. Speicher, DMD

Dr. Speicher joined Lake Manassas Dental Center in July 2013 after relocating to Northern Virginia from Pennsylvania, where she had been in private practice since 1989. Dr. Speicher graduated from the University of Scranton with a Bachelor of Science in Biophysics. She then earned her dental degree from Temple University School of Dentistry.


Dr. Speicher has 2 daughters: Kelsea, a graduate of the University of Southern California and Taylor, a junior at Moravian College in Bethlehem, PA. Dr. Speicher enjoys playing golf and traveling in her spare time.

Meet our Team

Jennifer Miller, RDH

Jennifer Miller is our treasured Dental Hygienist at Lake Manassas Dental since 2010.  Jennifer was born and raised in Northern Virginia, and currently resides in Fairfax County with her son.  She enjoys traveling and outdoor activities in her spare time.

Taneilya Williams

Taneilya has been a dental assistant for 13 years.  Taneilya first worked with Dr. Nguyen in an office in Herndon, VA prior to joining him at Lake Manassas Dental Center in 2008.  Since then, she has gotten married and has 2 beautiful children.  She loves spending time with her family and traveling with her husband.

Crystal Lee

Crystal was born in Fairfax, Virginia and is currently living in Haymarket for the last 9 years.  She has been in the dental industry since 2013 but has been in the medical field for 10 years prior.  She has been married for 5 years and together they have an amazing son.  Crystal loves to travel with her family whenever opportunities arise.

Amanda Embrey

Amanda joined Lake Manassas Dental Center in 2014.  Prior to joining, she spent 7 years in the medical field.  She is newly married.  She loves animals and spending time at the beach.

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