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About the Doctors

Dr. Adam Ostby

Dr. Adam Ostby is a fourth generation Montanan.  Like his wife Marlene, he has had an interest in orthodontics ever since he had braces as an adolescent.  He was amazed at how fast his orthodontist corrected his bite, and since then he has wanted to do the same for others.  Dr. Adam is board certified by the American Board of Orthodontics and has received extensive training in the most state-of-the-art technologies including three dimensional radiography and Temporary Anchorage Devices (TADs).

During dental school, Dr. Adam was inducted into the Omicron Kappa Upsilon Honor Society and was awarded the William S, Kramer Award of Excellence, which is given to the dental student who demonstrated the most scholarship, character, and potential promise to the field of dentistry.  Additionally, Dr. Adam’s research on orthodontic bonding materials has been published in several of the professions top orthodontic journals, including the American Journal of Orthodontics and Dentofacial Orthopedics, The Angle Orthodontist and Seminars in Orthodontics.


Dr. Adam is happily married to his wife, business partner and fellow orthodontist, Marlene. They both love living and working in Montana! They enjoy the great outdoors and spend most of their summers hiking, camping, golfing and biking. In the winter, they both enjoy alpine skiing. He also takes pleasure in coaching youth soccer and hockey.

When not spending time outdoors, Drs. Adam and Marlene love to spend time with their family and friends. They look forward to many more years enjoying Montana together.


Dr. Adam attended Montana State University where he received his degree (B.S.) in Cell Biology and Neuroscience, graduating with the highest honors in three years.  He then obtained his dental degree (D.D.S.) from the University of Iowa, and completed an additional two years of specialty training in orthodontics at the University of Minnesota where he earned an Orthodontic Certificate and Master’s degree (M.S.) in Dentistry.

Dr. Adam’s professional affiliations include: the American Dental Association; the Montana Dental Association; the American Association of Orthodontists; the American Board of Orthodontics; the Montana State Orthodontic Society and the Rocky Mountain Society of Orthodontists.

Dr. Marlene Ostby

Dr. Marlene Ostby is board certified by the American Board of Orthodontics, and she was the first board certified female orthodontist in the entire state of Montana!  She is thrilled to have the opportunity to offer quality orthodontic care for her patients, with a caring woman’s touch.

At the age of nine, Dr. Marlene experienced an early, limited phase of orthodontic treatment to correct a minor cross-bite. Her orthodontist was a cheery, hardworking, successful woman who enhanced the self-esteem of her patients by creating beautiful smiles. The future Dr. Marlene wanted to be just like her! Proving the value of hard work and perseverance, Dr. Marlene made her dream come true.

Dr. Marlene has had extensive training in the latest major advancements in orthodontics, including Temporary Anchorage Devices or TADs. TADs, also known as mini-anchors, have paved the way for many innovative treatments in orthodontics that were not previously possible.



Outside of work, Dr. Marlene cherishes the time she spends with her young family. During their leisure time together, they enjoy being active in the great outdoors and traveling to faraway places.


Dr. Marlene Ostby attended Southern Methodist University in Dallas, Texas earning her Bachelor of Science degree in Biology concurrently with a Bachelor of Arts in French. For her dental training, Dr. Marlene attended Baylor College of Dentistry, also in Dallas, earning her D.D.S. and graduating in 2003 with high honors. She then practiced general dentistry for two years in underserved areas of Dallas in addition to teaching in the Oral Diagnosis clinic at Baylor on a part-time basis.

When she decided to go back to school for her orthodontic training, Dr. Marlene was ready for a change in scenery and moved to the Midwest. After earning her Master of Science degree and a Certificate in Orthodontics in 2007 at the University of Iowa, she joined the Cleft Lip and Palate Team at the University of Iowa Hospitals and Clinics as the chief orthodontist. She was also able to simultaneously complete her requirements for board certification. Her practice in Iowa embraced everyone, from very complex craniofacial anomaly patients to routine crowded individuals. The experience was both professionally enhancing and personally rewarding.

Dr. Marlene’s professional affiliations include: the American Board of Orthodontics; the College of Diplomates of the ABO; the American Association of Orthodontists; the American Dental Association; the Rocky Mountain Society of Orthodontists; the Montana Dental Association; the Montana State Orthodontic Society; Rotary; the SMU Young Alumni Associates Board of Directors; the American Academy of Cosmetic Dentistry and the American Academy of Esthetic Dentistry.

Dr. Marvin C. Kastrop (Retired)

Dr. Marvin C. “Buddy” Kastrop has been in the specialty practice of orthodontics since 1973.  He attended undergraduate school at University of Texas.  He received his Dental degree (D.D.S.) from Baylor College of Dentistry and his Master’s degree (M.S.) from the University of Texas Dental Branch at Houston.  He has been board certified by the American Board of Orthodontics for over 29 years.

As an active member of the orthodontic community, Dr. Kastrop is affiliated with several professional associations: Director of the American Board of Orthodontics; Diplomate of the American Board of Orthodontics; American Association of Orthodontists; Past President and member of the Rocky Mountain Society of Orthodontists; Past President and member of the Montana State Society of Orthodontists; American Association of Orthodontics Foundation; American College of Dentists; Past President and member of the Ninth District Dental Society; American Dental Association; Montana State Dental Association.

In addition to his current activities, he served as an examiner for the North East Regional Specialty Board for 14 years. He has also served on numerous committees at various levels in the above mentioned organizations. Dr. Kastrop has received several awards throughout his dental career, including Baylor Odontological Honor Society, Clinical Excellence Award Montana State Dental Association, and Yellen-Schoverling Award for outstanding contributions to the art and science of orthodontics, presented by the University of Texas orthodontic alumni.

Dr. Kastrop has served on many committees and boards in Billings. He served on the Youth Court Conference Committee that serves as an alternative and diversionary procedure for first time juvenile offenders. He has long been active as an advisor for First Interstate Bank West Billings. He was a member of the Billings West End Rotary, and served as an advisor for Rocky Mountain College. Dr. Kastrop is a past president and member of Yellowstone Country Club. He is a past director for the Montana State Golf Association, and has served in various supportive roles for Shiloh Methodist Church.

Dr. Kastrop enjoys spending time with his family. His hobbies include golf, fly fishing, gardening, and teaching jewelry classes.

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