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2003 46th Ave Greeley, CO 80634 Phone: 970-330-4600
Pediatric Dentist

About Us

Keith A. Van Tassell, D.D.S.

Dr. Keith (as his patients know him) loves working with kids. He was born in California and grew up in some small towns in Utah and Idaho. He graduated from Weber State University in 2000 and entered dental school that same year at Virginia Commonwealth University School of Dentistry in Richmond, Virginia. Dr. Keith graduated Magna Cum Laude in 2004 and was elected into the OKU dental honor society which is reserved for the top 10% of graduating dentists in the nation. He was also awarded the Pierre Fauchard Academy Certificate of Merit for outstanding academic achievements. After dental school, Dr. Keith attended the University of Nevada School of Medicine for a two year pediatric dental residency where he served as chief resident his final year.

Dr Keith is a Board Certified Pediatric Dentist. He dedicates himself to providing the best dental care possible for his patients, insuring that they have a positive and fun experience while learning to care for their own oral health.

Dr. Keith enjoys spending time with his family, being outdoors, running, and playing just about any sport. He and his wife have five children (four daughters and a son). They moved to Ft. Collins in August 2006 to begin his practice. They love the community and are proud to call Northern Colorado home.

Memberships and Professional Associations:

  • Diplomate American Board of Pediatric Dentistry
  • American Academy of Pediatric Dentistry
  • Colorado Dental Association
  • Larimer County Dental Society
  • Harmony Surgery Center

Zachary Alleman, D.D.S.

Dr. Zach grew up in The Colony, Texas, a suburb north of Dallas. He earned his bachelor’s in Exercise Science from Brigham Young University and pursued his dental training at Baylor College of Dentistry.

After receiving his Doctorate of Dental Surgery, he decided to complete his residency at Baylor where he could take advantage of its strong Pediatric Dentistry program, which is affiliated with Children’s Health Dallas and Texas Scottish Rite Hospitals. Interacting with these incredible hospitals gave him extensive training with managing patients with special healthcare needs.

Pediatric dentistry is a perfect fit for Dr. Zach, who has always been surrounded by children. He is the fifth of eight children, father of two, and uncle to 25 nieces and nephews. He loves providing quality and fun treatment to ensure each child gets off to a terrific start with their oral health.

When Dr. Zach isn’t in the office, he likes to spend time outdoors with his family. He also enjoys cycling and playing basketball, tennis, and volleyball. He’s also an avid reader.

Dr. Zach and his family are excited to call Northern Colorado home.

Memberships and Professional Associations:

  • Diplomate American Board of Pediatric Dentistry
  • American Academy of Pediatric Dentistry
  • Colorado Dental Association
  • Larimer County Dental Society
  • Harmony Surgery Center

Rachel N. Ecker, D.M.D.

Dr. Rachel N. Ecker earned her Bachelor’s degree in psychology from Rhodes College in Memphis, TN and her Doctor of Medical Dentistry (DMD) from Midwestern University in Glendale, AZ. She completed her pediatric residency at Miami Children’s Hospital in Miami, FL and has been in private practice ever since. Dr. Ecker has special interests in cosmetic dentistry, sedation dentistry, and multidisciplinary craniofacial case management. She also finds great satisfaction in empowering children to take initiative in their own healthcare.

Dr. Ecker is a diplomate of the American Board of Pediatric Dentistry, and an active member of the American Dental Association, the American Academy of Pediatric Dentistry, the Colorado Dental Association.

Dr. Ecker is originally from Boulder, CO but now resides in Fort Collins, with her husband and their 2 children. Outside of the office, she enjoys running, biking, backpacking, hiking, skiing, and cheering on the Broncos!

Dr. Mark Crane

Dr. Mark Crane grew up in the San Joaquin Valley of Central California in the small town of Visalia. He completed his undergraduate work, attaining his Bachelor of Arts degree in 1996 from Brigham Young University. He attended UCLA School of Dentistry where he graduated Summa Cum Laude with a Doctorate of Dental Surgery in 2000. In July of 2000, he began his post-graduate residency in orthodontics at Virginia Commonwealth University in Richmond, Virginia. Dr. Crane completed his training in conjunction with receiving a Master of Science degree in June of 2002.

Dr. Crane’s careful selection of universities and residency training provided him with extensive knowledge of the latest technology in orthodontic procedures. Such techniques include digital imaging, digital diagnosis, as well as treatment planning, growth, and surgical predictions. In addition to his clinical accomplishments, Dr. Crane is also fluent in Portuguese.

He is a Diplomate of the American Board of Orthodontics. This board certification is a designation held by only 30% of orthodontists. He is also a member of the American Association of Orthodontists, Colorado Dental Association and the Invisalign® Study Club. He serves on the University of Colorado Health Cleft Palate Team. Dr. Crane was selected as a 5280 Top Dentist 2008-2017.

Dr. Crane married Cosette Renee Doxey in 1994. They have six children. In search of the perfect place to practice orthodontics, the Cranes fell in love with the Northern Colorado community. The Crane family enjoys outdoor activities and the natural setting of the community. In his free time, Dr. Crane likes golfing, playing basketball, mountain biking, and skiing. Dr. Crane and his family enjoy traveling for pleasure as well as service. Every two years he travels to Guatemala to do dental work.

Dr. Craig Seager

Dr. Craig Seager grew up in the towns of Houston, Texas and Denver, Colorado. He went to Brigham Young University where he completed his Bachelor of Science degree in 2003. He then attended the University of Texas Health Science Center in San Antonio where he received his Doctorate of Dental Surgery degree in 2007, graduating with Honors in Research. While at the University of Texas, he was elected for and served two years as the president of the Health Science Center’s Student Government Association.

In the summer of 2007, Dr. Seager began his residency in orthodontics at the University of Texas Health Science Center in Houston where he earned his Master of Science degree in Dentistry in 2009. During his residency, Dr. Seager received extensive training in both adolescent and adult orthodontic diagnosis and treatment. Other areas of his training have included Invisalign®, 3D imaging, growth analysis, and TMJ therapy. Dr. Seager is also fluent in Spanish, which aids in optimal communication with our Spanish-speaking patients.

Dr. Seager is a Diplomate of the American Board of Orthodontics This board certification is designation held by only 30% of orthodontists. He is also an active member of the American Association of Orthodontics and the Colorado Dental Association. He serves on the University of Colorado Health Cleft Palate Team. Dr. Seager was selected as a 5280 Top Dentist 2017.

In 2001, Dr. Seager married his wife, Melissa, and they now have three beautiful daughters. After enjoying his childhood growing up in the Denver area, Dr. Seager always knew that he wanted to live and practice in Colorado. As the Seager family searched for the best place to raise a family, Northern Colorado was the perfect fit with family-centered communities and outdoor recreation. Dr. Seager enjoys skiing, golf, running, fly-fishing, and camping with his wife and daughters.

Admin Team


I was born in Vail and grew up in Greeley. I love spending time with my husband, 2 kiddos and our 2 fur babies! We enjoy camping, boating and 4 wheeling. I love Colorado summers and lazy days at the lake!


I was born and raised in Northeast Colorado. I enjoy being outside walking, gardening and hiking with my husband in the beautiful Rocky Mountains. Spending time with my family means the world to me!!!!