Our Team

Dr. Letter

Dr. Mark Letter is a native of Brookfield, Wisconsin. After graduating from Brookfield East High School, he earned a degree in Psychology from Marquette University. He then spent the next three years employed with St. Mary’s Psychiatric Hospital as a Counselor of Adolescent Patients; working with patients ranging in age from six to eighteen. It was during this time at St. Mary’s that Dr. Letter chose to pursue a dental career and enrolled in the Marquette University School of Dentistry. He continued to work at St. Mary’s Hospital while attending dental school until he graduated in 1987. Upon dental school graduation, Dr. Letter began his dental career as an associate dentist in the Green Bay area while also working as a Clinical Instructor in a Hygiene Clinic.

In 1993, Dr. Letter relocated to Kewaunee and purchased a practice from Dr. Grady. Dr. Letter continues to operate his practice in Kewaunee, providing the best quality dental care possible. Over the years he has built long-lasting relationships with his patients and values the time he spends with each of them. Dr. Letter believes in the importance of continuing education and remains active in organized dental associations and study groups. His affiliations include: WDA (Wisconsin Dental Association), ADA (American Dental Academy) and the local BDKDS (Brown Door Kewaunee Dental Society.)

Dr. Letter met his wife, Laura, during his early years as a dentist in Green Bay. He and Laura have four children. Dr. Letter enjoys volunteering as a coach for his children’s various sports teams. He also spent 5 years as a Chairperson on a Board of Trustees for the Green Bay Diocese.

Dr. Sperber

Dr. Brian Sperber is from Green Bay, Wisconsin. Growing up he took an early interest in dentistry which was attributable mostly to his relationship with Dr. Letter. While in high school Dr. Sperber spent time shadowing Dr. Letter to gain a better insight into dentistry. Dr. Sperber attended UWGB where he earned a Bachelor of Science degree in Human Biology. While attending UWGB, Dr. Sperber volunteered his service at the Tri-County Community Dental Clinic in Appleton, Wisconsin where he assisted dental students from Marquette University School of Dentistry. After completing his degree at UWGB, Dr. Sperber attended Marquette University School of Dentistry where he graduated Magna Cum Laude. During his time at Marquette, Dr. Sperber volunteered in programs such as Give a Kid a Smile and working with developmentally disabled individuals at the Southern Wisconsin Center.

After graduation from Marquette University, Dr. Sperber joined up with Dr. Letter to provide caring and quality dental treatment to their patients. Dr. Sperber enjoys working with his patients to bring their dental dreams to reality and maintaining healthy smiles. An integral part of his practice is staying on the leading edge of technology and attending numerous continuing education courses. Dr. Sperber is an active member in organized dentistry being affiliated with the WDA (Wisconsin Dental Association), ADA (American Dental Association), and BDKDS (Brown Door Kewaunee Dental Society).

Dr. Sperber and his wife, Alaina, met while attending a course at UWGB. They have three children; Oliver, Vera and Edison. When away from the dental clinic Dr. Sperber enjoys spending time in the outdoors hunting and fishing, cooking, and spending time with family and friends.


Patti is our Office Manager. She has been with the practice since 1989. Her role is focused on keeping our practice running smoothly and providing a positive experience for patients. You will often see her friendly face, as she works closely with patients by completing treatment plans, providing insurance estimates and assisting with financial arrangements. “I love working with our patients, helping them with their dental needs and seeing them smile,” she says!

Patti is a native of the Kewaunee area and graduated from NWTC. Patti and her husband Rick have a grown son Luke, but its their big black lab who keeps the house active! In her free time Patti loves to read, walk, scrapbook, craft and spend time with her family and pets.


Tracy has been with us since 1992 as a Registered Dental Hygienist. In her role, you will find Tracy providing preventative dental care to patients, including teeth cleanings; radio-graphs and other digital imaging of the mouth and teeth; placing sealants; providing fluoride treatments; assessing and treating periodontal disease; and performing oral cancer screenings. She also administers anesthesia and educates on oral hygiene instruction. Tracy always knew she wanted to work in a health profession where she could help people – and make them smile! Tracy’s goal is to provide a comfortable and stress free dental experience for patients. This means she takes care to communicate with and listen to her patients, ensuring they fully understand their dental care.

Tracy grew up in Kewaunee and graduated from NWTC with a degree in Dental Hygiene. Tracy is mom to daughter Morgan and two sons, Nolan and Donovan. She truly enjoys watching and supporting her children in the many activities they are involved in. Tracy is an avid outdoor fan, enjoying outdoor activities at any time of year. A few of her favorites include biking, hiking, camping, skiing and snowmobiling.


Ashlee is a Registered Dental Hygienist and has been with us since 2003. She always knew she wanted to go into healthcare and is so glad she chose dentistry! A large part of her role as Hygienist is delivering preventative care to patients such as x-rays, fluoride treatments and cleanings. Ashlee also provides treatment and maintenance of periodontal disease. Ashlee strives to provide a high quality of care for her patients while keeping you comfortable and making your visits a positive experience.

Ashlee grew up in Kewaunee and graduated from NWTC with an Associate Degree in Dental Hygiene. She is married to Chris and together have two sons, one daughter and two dogs. They are excited to be back in the Kewaunee area (after living in Green Bay) to raise their family “in the country.” Ashlee looks forward to spending time with her family at their cabin, boating, and simply enjoying time outdoors relaxing with friends and family.


Rachel has been a Dental Assistant at our practice since June of 2001. Rachel is eager to get to know our patients. You will often hear Rachels laugh throughout the office joking with them to try and lighten the fact they are having dental work done and trying to make each patient feel comfortable. Helping them improve their oral health is her top priority. She assists Dr. Letter and Dr. Sperber in providing gentle, caring dental care.

Rachel was born and raised in Algoma and now resides in Kewaunee with her husband, their two young sons and new puppy Chloe. She attended and graduated from NWTC in the Dental Assisting program in 2001. Rachel loves to cheer on the Wisconsin teams at Packer, Badger, Buck and Brewer games.

In her free time, you will find Rachel playing softball and volleyball, coaching her boys in various sports and relaxing with family and friends.


Wendy, a Dental Assistant since 2002, joined the LetterSperber team in 2015. You will find Wendy assisting both Dr. Letter and Dr. Sperber during dental procedures. She is passionate about helping patients feel comfortable and informed about their dental procedures. Wendy guarantees to do her best to help patients achieve the smile they want!

A Career Day during her years at Kewaunee High School is what originally drove Wendy’s interest in dentistry. After high school, Wendy went on to graduate from the Dental Assistant Program at NWTC. Outside of work, Wendy’s interests include spending time with her nieces, nephews, brothers and sisters. She also enjoys staying active by running, biking and working out.


Cassandra is a Registered Dental Hygienist and has been a great addition to our team. She grew up in Kewaunee, graduated from Kewaunee High School and then graduated from NWTC with her Associates Degree in Dental Hygiene. Cassandra’s caring attitude makes appointments with her an enjoyable experience. She loves to share her knowledge about oral hygiene and will give you the highest quality of care.

Cassandra now lives the apartment life with a beautiful view of Lake Michigan and of downtown Kewaunee. She enjoys spending time with family, friends and especially her dog, Archie.


Bridgett graduated from NWTC in 2002 and has been with us since 2018. As a hygienist for many years, she has learned a lot along the way. She specializes in ” all things hygiene” with an emphasis on patient comfort. Her passion is building a strong rapport with each patient giving them their very best dental experience. You’ll often hear laughter coming from her room, having fun while at work is an extra bonus.

Bridgett is from the Luxemburg area where she still resides. She is married to Greg and they have 4 very active children. Aleece, Myles, Calvin and Elsie with ages from high school down to elementary school. Her spare time consists of chauffeuring her children to their activities, volunteering for many booster clubs and raising puppies. When it’s time to relax, her family enjoys spending time at their cottage up north.

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