Keen Family Dentistry
C. Mark Keen, DDS:
Practice Profile Page


Keen Family Dentistry
C. Mark Keen, DDS
Rancho Cucamonga, CA













A list of major dental treatments which I offer my patients:

Dental cleaning

White fillings


Inlays & onlays


Clear aligners

Sedation dentistry

Porcelain veneers

Teeth whitening

Dentures & partials

Root canal treatment

Tooth extraction

TMJ treatment

Sleep apnea therapy

Dental implants


Offers Even28 at-home™? No

Offers Even28 at-dentist™? No

Offers Invisalign®? Yes


Monday: 9:00 am to 5:00 pm

Tuesday: 9:00 am to 5:00 pm

Wednesday: 9:00 am to 5:00 pm

Thursday: 9:00 am to 5:00 pm

Friday: Closed

Saturday: Closed

Sunday: Closed





Check out what some of our happy patients are saying about us:

Samantha K. from San Francisco, CA (Source: Yelp)


I transferred our family over to this office after having been patients at another for over 20 years and I wish I’d made this decision 19 years ago!  The office staff is always friendly and helpful.  Dr. Keen makes even the most scared patient feel comfortable in his chair.  He always checks to make sure you’re feeling ok, skilled with his hands and is just generally a nice person!  Each hygienist has always done a great job with my sensitive teeth…my husband fell asleep getting his teeth cleaned!  So if you’re looking for a FANTASTIC dentist along with amazing support staff…Dr. Keen is your guy!

Mary E. Beatson (Source: Google)


Dr Mark Keen is the best dentist. We highly recommend him. He cares about the services that he provides, customers, and staff. Dr Keen and his staff are very nice, efficient, and provide an excellent service to the community. They make your teeth and smile look beautiful. Thank you Dr Mark Keen and staff. You are awesome

James L. from Fontana, CA (Source: Yelp)


Dr Keen’s office is hands down the best dentistry I have ever been to; and I have been to a lot of them! Each of the staff members is top notch and friendly and I am promptly greeted with a smile. My teeth have never been cleaned so well and honestly, I look forward to every cleaning. Dr Keen has done fillings and installed 2 crowns and my smile has never looked so good.  Keen Family Dentistry has truly raised the bar and I recommend them to everyone

Janice M. from Fontana, CA (Source: Yelp)


What can I say about Dr Keen?! UMMM HE’S A USC ALUMNI NEED I SAY MORE?! He is an amazing dentist! This is coming from a girl who much rather go through labor than see a dentist! He is so patient, so calm and so NICE like I can honestly see why people love him so much. My husband has been coming to him for years and while he’s a bit of a drive for us, he’s definitely worth it. The only downer at least for me is he doesn’t work Fridays and weekends but it’s ok I’m learning to work around it. Dr. Keen, thank you so much for taking care of me and my teeth, your patience really makes me feel more at ease coming to get dental work done

Gloria S. from Wrightwood, CA (Source: Yelp)


I don’t know why I haven’t written a review sooner. I have known Dr. Keen for many years. His bedside manner is awesome and he does some amazing quality work!! I know most people do not like going to see a dentist I am in fact one of those people. But once I step foot into those doors I forget why I am there. The warm smiles when you walk in from Monique and Dulce make you feel at home.  Not only are you there patient but they treat you like a family member. That is very hard to find these days and I can not say enough wonderful things about this fantastic practice. Thank you Dr. Keen and his wonderful team!!!

Kerri K. from Rialto, CA (Source: Yelp)


Dr. Keen is truly the best! I was referred to him by my orthodontist and could not be happier. I recently had some fillings redone and the entire procedure was painless. Dr. Keen and his staff ensured I was comfortable the entire time. I honestly did not feel a thing! Everyone at this dentistry is caring, professional, and welcoming. Dr. Keen and his staff always exceed my expectations. If you are looking for a great dentist who truly cares about his patients, look no further. I always have a positive experience here and I highly recommend Dr. Keen!

Chris V. from Upland, CA (Source: Yelp)


I am very surprised that I’m the first person to write a review for Dr. Keen. For some people it is very difficult to see the dentist.  The fears of root canals, more appointments, extractions, and pain are the worst.  Dr. Keen, removes ALL those fears.  I’ve moved around quite a bit in the last 12 years, and whenever I get a new dentist I use Dr. Keen as a reference to what a great dentist is.  After 3 dentists, I find myself commuting to Rancho Cucamonga, as he is the only dentist that makes me feel at ease. He is very professional and does great work as well. I hope this review helps

T. M. from Rancho Cucamonga, CA (Source: Yelp)


Dr Keen is an awesome dentist! I have been going to him for many many years. He really takes the time to make sure you are comfortable through out all procedures. He also put veneers on my front teeth a few years ago and I constantly get compliments from strangers about how perfect my teeth are. He really is the best!

Karen W. from Chino, CA (Source: Yelp)


This entire office makes going to the dentist comfortable. The office staff and hygienists are friendly and efficient. I’ve never had to wait more than 5 minutes to be seen. Dr Keen is friendly, warm, calm and will take time to explain things and answer your questions.  His standards are high. I had an implant incorrectly made by another lab. Dr Keen worked with the endodontist to see that it was remade correctly. I highly recommend DR Keen and staff. Dr Keen worked on two new crowns today in one visit. I’ve never had Novocain injections that didn’t hurt, but today I did!  Dr Keen is patient, understanding, and professional

Samantha A. from California (Source: Yelp)


Dr. Keen and his staff are always a pleasure to visit! My family has been receiving dental care here for years and we couldn’t imagine going anywhere else! I am a stay at home mother so my 18 mo daughter has to go with me to my appts but I never have to worry because I know that Dr. Keen will be patient and understanding with me as I deal with her when needed. I am thankful to have found a Dentist who is careful and gentle when taking care of my teeth and takes any necessary extra steps to ensure that I am comfortable and calm

Kaleena C. from Ontario, CA (Source: Yelp)


The best dentist ever…… I was traumatized by dentist when I was younger but he has give me faith that there really are good dentist out there. The staff was super friendly and amazing and so was Dr. Keen I am so glad I found him Thanks again..

Lisa R. from Upland, CA (Source: Yelp)


I just want to thank Dr.Keen and his staff. On Sunday my back tooth cracked in half and they fit me in their busy thanksgiving week schedule. Dr. Keen did an amazing job fixing my tooth until I go in next week for a crown. Thank you again!

Sarah J. from Rancho Cucamonga, CA (Source: Yelp)


Dr. Keen is awesome- everyone in the office is so friendly and helpful. I love that they text you a few days before your appointment to remind you as well. He really cares about how you’re doing from any work he does and wether or not it came out the way you wanted. Definitely recommend Dr. Keen

Mike T. from Rancho Cucamonga, CA (Source: Yelp)


Mark and all of his staff are amazing. My wife and I have been going to Mark for all of our dentistry work for years and have recommended the office to several friends and family members over the years. He is very gentle and attentive with all his patients, as well as the hygienists and support staff. We highly recommended them for all your future dentistry

Danielle E. from Rancho Cucamonga, CA (Source: Yelp)


I just have to say I’ve been to a lot of dentists and Dr. Keen is the best by far! He is so gentle with a needle and he walks you through everything he is doing with the procedure. He is also super sweet and very funny!! I would recommend my family and friends to go to him!! If you ever need the most amazing dentist around then Dr. Keen is your dental angel!!

Scott K. from Rancho Cucamonga, CA (Source:Yelp)


Fabulous dentist! I moved into the area from out of state and was concerned about finding a good dentist. A co-worker recommended Dr. Keen and he is great! The office staff is very kind and take care of all of my insurance claims very efficiently. He recently replaced some 40 year  old fillings for me and was so careful, gentle and concerned about me well-being during the two sessions needed to replace 7 fillings. My wife and I both go to Dr. Keen and recommend him to everyone

Steve G. from Brea, CA (Source:Yelp)


As usual, another excellent experience with Dr . Keen.  Been going to him for years with my various dental needs. I make the trip from Orange County to his Alta Loma/Rancho office and it is worth the drive.  No pain whatsoever with cavities, crowns and numbing injections. Every process has gone smoothly and quickly. Excellent staff and office.  It’s a great feeling to be confident that a dental visit will get done with minimal discomfort and no pain, and done with great care

Doug lowary (Source: Google)


Dr Keen and Staff are Awesome! Dr Keen is the best in the business! He is so smooth and fast! Dr Keen is very personable and cares about all his patients! I have have been his patient for over 20 years and have referred many family and friends. He will give you a full game plan for your mouth with high tech digital xrays and be able to tell you future issues before they happen, so you can plan year to year with insurance money.

Darlene B. from Chino, CA (Source: Yelp)


First time at Dr. Keens office and I would highly recommend anyone to his practice.  He is very gentle and thorough plus has a great personality.  His staff makes you feel very welcome – from the front desk to the back staff. Luis is very sweet.  A huge thank you to Monique for getting me in and keeping her painless promise.  Thank you again Dr.  Keen and team

Debi T. from Rancho Cucamonga, CA (Source: Yelp)


About 10 years ago my last dentist retired and my insurance required me to go to another dentist who was just terrible, I needed to find another dentist, even if I had to pay out of pocket.  I was referred to Dr. Keen’s office by our orthodontist.  Dr Keen and all of his staff are nothing short of outstanding!  They make me feel safe and really take care of this extremely nervous dental patient. I’ve had numerous procedures done and they really take the time to make you comfortable and the quality of work is terrific. I highly recommend!!

Christopher Michael Calver (Source: Facebook)


I came into the Keen Family Dentistry office after being referred. I was greeted by a friendly staff. I needed a lot of work done on my teeth and was discouraged by my past experiences with my previous dentist. Dr. Keen made me feel right at home. He was honest and explained every procedure thoroughly and had me fixed up in no time. I highly recommend this dentistry

Darla B. from Upland, CA (Source: Yelp)


I love this dentist office. Everyone is extremely nice and they take the time to get to know you. Every time i come in they ask how Im doing and ask about my family. They always make sure to answer any questions i may have. They also have new technology that allows them to show you pictures of your teeth so they can better explain any issues. They offer free coffee while you wait and have TVs in every station. I definitely reccomend them to anyone trying to find a dentist and they worked with our dental insurance so that we dont get over charged for any work

Timothy S. from Culver City, CA (Source: Yelp)


I’ve been waiting to get my teeth and my daughters teeth cleaned for sometime now. Was referred to this dental office by a friend. Extremely happy with the service and very friendly staff. Thank you again Bryce for your expertise and experience. See you in six months

Sylvia V. from Rancho Cucamonga, CA (Source: Yelp)


Dr. Keen and his staff are absolutely awesome! They are very friendly, caring, and highly professional. Dr. Keen was able to take away the fear that my 9 year old daughter had of the dentist. He is extremely gentle and made my daughter feel very comfortable during and after the procedure. I highly recommend Dr. Keen to anyone who is looking for an amazing dentist

Cate W. from Rancho Cucamonga, CA (Source: Yelp)


I have been a patient of Dr. keen for a long time. I have always received excellent care.  His attention to detail, whether repairing a broken tooth or fitting you for a night guard, is unsurpassed.  He will inform you of the latest technology available regarding your procedure so that you can make an informed decision.  If a filling is necessary I know he will make it as painless and quick as possible. I always feel as though I have chosen the best.  My children who started with Dr. Keen when they were young are still seeing him for their cleanings  and they are 29 and 30

Pamela B. from Rancho Cucamonga, CA (Source: Yelp)


Great dentist and wonderful, warm, competent staff.  My only wish would be that they were located a bit more off the beaten path: it’s not in the most modern of buildings and the parking lot is a bit of mess.  But I’d go to MUCH worse places to get this fantastic service

Mike R. from Glendora, CA (Source: Yelp)


Environment: super clean office, very well organized very pleasant. Staff: staff was very friendly and very accommodating to my concerns. Monique the front office manager assisted me through my the whole process of getting a treatment plan for my needs. Amber was my Hygienist and was very calm and helpful by explaining step by step of what the process of my cleaning was. She stopped multiple times during the process to make sure I was comfortable. Couldn’t of asked for a better experience especially for my first cleaning. Dr Keen is a great doctor who truly wants the best for his patients. He doesn’t treat you like a number rather a valued guest in his office. He did a filling for me and was very attentive during the process again making me feel comfortable and right at home. He’s very thorough in explaining everything he is doing. Overall very pleasant experience in this office great staff, great experience would highly recommend this practice

Sharon M. from Rancho Cucamonga, CA (Source: Yelp)


Dr. Keen deserves a great review.  I quit going to my last dentist when I just could not take the pain and long, long appointments.  Dr. Keen is not like that! I have been going to him for about five years.  During that time, he has had to fix some work that was done by my last dentist, and his work is far superior.  There is no comparison.  He works in a calm and careful manner, and lets me know exactly what he is doing.  I always feel comfortable

Bonnie K. from Rancho Cucamonga, CA (Source: Yelp)


I was so nervous to go to the dentist but Dr Keen explained everything and I felt so much more relaxed. He was awesome and I was very comfortable getting my procedure completed. I highly recommend his calming nature and detailed explanation

Frank C. from Rancho Cucamonga, CA (Source: Yelp)


I couldn’t be happier with Dr. Keen and his great team at Keen Family Dentistry.  I’ve have nothing but great service since first switching dentists 7 years ago.  I’ve had a positive experience with everyone at the office—Dr. Keen, Yolanda, Luis, Monique, and Dulce. Going to my old dentist’s office was like going to buy a new car. After finding what you wanted to buy you would have to see the finance manager to discuss how to finance the car for the next 5 years…Not at Dr. Keen’s office; his office is more concerned about your teeth and overall health and your positive family experience

Claudia M. from Alta Loma, CA (Source: Yelp)


I avoid dentists at all costs… It seems funny but, I am so scared that I simply do not remember when was the last time I had a consultation. I looked up a dentist closer to my house and met Dr. Keen last week. I was so impressed by his knowledge and professionalism (including all his staff) that right there, I’ve decided to give it a try. I am SO GLAD I did. I had to redo a filling on my tooth (No. 6) and believe me, I did not feel any pain or discomfort at all. I could not believe when he said he was done with the anesthesia. I did not feel a thing….. I am so impressed and DEFINITELY will go back over and over again. Congratulations Dr. Keen.  You have a patient for life!

Rosa A. from Rancho Cucamonga, CA (Source: Yelp)


I want to thank everyone at Dr Keens office, they all make you feel so comfortable, and relaxed. Had my 2nd appointment yesterday, went in very nervous and with anxiety about having my tooth drilled on. Everyone from Monique at the front desk to Luis that assisted Dr Keen to Dr Keen himself put me at ease. I had an awesome appointment, I wasn’t in pain during the procedure or after. They’re amazing, no pain today either. Never thought I would say I’m not afraid of going back. Would recommend Dr Keen and his staff to anyone that needs dental work done


Since we've opened our door for business, in 1995, we've been trusted by our patients to provide quality dental care for their families. We now enjoy 3 generations of happy, healthy patients who have helped build this practice into the "Family Dentistry" that it is today. Care Credit available. Dr. Keen was born and raised in Southern California, living in the Rancho Cucamonga area since 1990. He graduated with a biology degree in 1985 from USC, and graduated USC Dental School in 1989, following his passion for cosmetic dentistry. Dr. Keen's ultimate mission is to deliver the highest quality dentistry for his patients in a gentle, caring environment. He has been in his Alta Loma office for over 20 years, dedicating his efforts to helping patients achieve healthy, happy smiles. He is an active member in his community, often sponsoring his patient's sports teams. When he's not in the office, Dr. Keen takes pride in being a family man. He loves spending time with his wife, Diana, and their two sons Bryce and Blake. Together they enjoy golfing, motorcycle riding, camping and boating in Lake Havasu. Wanting to follow in their father's footsteps, Bryce will be entering USC Dental School in the fall of 2016 and Blake is a pre-dental student at the University of LaVerne.