At San Mateo Orthodontics our friendly, capable staff is extremely dedicated in the delivery of orthodontic care to our patients. We are here to help you, the patient and parents, have an enjoyable experience with your orthodontic treatment. We strive to be considerate of your time through efficient scheduling and the use of the latest technology in orthodontic appliances and materials.

Our Orthodontic Assistants are graduates from the College of San Mateo Dental Assisting Program with a combined 18 years of experience. They are Licensed Registered Dental Assistants.

Our Treatment Coordinators have extensive experience helping patients and parents with their insurance and financial matters. They will assist you in scheduling your orthodontic appointments so your treatment progresses as quickly and conveniently as possible.


Dr. EllerhorstTom Ellerhorst D.D.S., M.S.D.

Dr. Tom Ellerhorst, aka "Dr. Tom", grew up in San Mateo, attending Junipero Serra High School, where he was selected Valedictorian and Varsity Soccer Blanket Award winner. He studied at the University of San Francisco graduating with a Bachelor of Science degree in biology and chemistry. He earned his Dental and Masters degree at the University of the Pacific, in San Francisco.

Dr. Tom is a second-generation dentist following in the footsteps of both his mother (Dr. Ann Marie Silvestri) and father (Dr. Thomas Ellerhorst). He joined our team in June of 2004 and is a Diplomat of the American Board of Orthodontists (Board Certified), an active member of the American Association of Orthodontists, San Mateo County Dental Society, California Society of Orthodontists, American Dental Association, California Dental Association and Invisalign Premiere Provider.

Dr. Tom had the opportunity to aid in the repair and rehabilitation of over 175 children born with cleft lip and/or palate in Guatemala and found that volunteer mission to be the most humbling and rewarding experience of his life. He continues to help those in need, performing free dental screenings for the County of San Mateo. Continuing education is also a very important aspect of Tom's professional life, including the 2-week Tweed Course, widely considered one of the most intense orthodontic courses given today.

Family & Hobbies:
Dr. Tom married his high school sweetheart, Kacie, and currently lives in Redwood City, playing basketball whenever he gets the chance -- which is not as often as he'd like, as his children, Kaylee and Connor, keep him constantly on the run. He loves coaching soccer and T-ball and is an avid videogame player. He also loves going to the movies (almost anything with Adam Sandler) and spending time with his family and friends.


Katherine Kieu, D.D.S., M.S.D.   

Dr. Kieu was born and raised in Orange County. She earned her Bachelor of Science degree in Biology from the University of California, Los Angeles, where she graduated Magna Cum Laude. She then moved to Northern California to complete her dental training at the University of California, San Francisco.  Nominated by faculty during her senior year of dental school, Dr. Kieu was awarded the Craig Memorial Scholarship by the Rho Rho Chapter of Omicron Kappa Upsilon (OKU), National Dental Honor Society, for outstanding scholarship and ethical character.

After receiving her dental degree, Dr. Kieu worked as a general dentist in San Anselmo before starting her orthodontic residency at the University of the Pacific. Recognizing the importance of providing research-based treatment, she accepted a part-time faculty position to continue her work in the Craniofacial Research Instrumentation Laboratory (CRIL).

Dr. Kieu joined our team in January 2013 and is an active member of the American Association of Orthodontists, California Society of Orthodontists, and Pacific Coast Society of Orthodontists. She also serves on the alumni committee for the Pacific Orthodontic Chapter of the Arthur A. Dugoni School of Dentistry Alumni Association. Dedicated to excellence and patient-centered care, Dr. Kieu is a compassionate orthodontist who strives to ensure that patients enjoy high-quality results.

n her spare time, Dr. Kieu enjoys spending time with her family and friends. Being from Southern California, she is a diehard Lakers fan. In addition to watching and playing basketball, she enjoys trying new restaurants while traveling, as inspiration for her culinary creations in the kitchen. She also loves to read non-fiction and fiction literature and is an aspiring children’s book author. On weekends, she can usually be found with a book on the beach while her husband, Eddie, surfs.



Office Staff:


Maria Cooper -- Patient Care Coordinator

Maria has been in the dental field since November 2010. Her rigorous training and experience has guided her to strive in the specialty of orthodontics.  Her friendly, positive personality and compassionate attitude is the perfect addition to our team. In addition to traveling, listening to music, and anything Disney, Maria loves spending time with her family and friends.

Mari Medrano -- Patient Care Coordinator
Mari has been in the dental field since 2017, she graduated from San Francisco State University in 2019 with a bachelors in Sociology and minor in Criminal Justice and Labor Studies.  On her free time she loves to spend time with her family, especially with her 6 month old, Emilia.  She likes to binge watch shows on Netflix and go on walks with her daughter. 
Meghan Harvey, RDA -- Assistant

After graduating from Terra Nova High School, she joined our office in 2008. She is devoted to continuing education and thrives to make each patient experience memorable. Her outgoing personality and enthusiasm are a constant in the office. Meghan's compassionate nature is truly evident in the care she provides our patients. She and her husband love spending time and creating new memories with their new daughter, Samantha.  

Brandi, DA -- Assistant

Brandi was a former patient of our office who joined our orthodontic team in Sept 2014. Brandi enjoys working with kids, which is evident in the consistent care and compassionate interactions she shares with our patients. Brandi has an infectious laugh that makes our patients’ experiences more enjoyable and memorable—you can’t help but laugh with her. She enjoys traveling, going to country music concerts, and hanging out with friends and family.