Who We Are

Who We Are


We are a team of experienced dentists and healthcare operators who are committed to improving people’s lives through better oral health.

We know that a healthy mouth contributes to a healthier, more confident and happier person. And we also know that dentists can’t achieve that goal alone. That’s where D4 delivers a new dimension in dentistry. We bring the dental office to you- at your office- to make it easier and more convenient to get the care you need when you need it. We help you identify and manage oral health risk factors and take protective steps to prevent and treat dental disease.

We help companies improve the quality of life and work experience for their teams by establishing customized dental offices on site.


Dr. Mark E. Doherty


CEO, Co-Founder


Hi, I’m Dr. Mark E. Doherty, I grew up in southeast Massachusetts and earned my dental degree from the University of Pennsylvania and my post-doctoral training in Endodontics at Boston University. As a 6th generation dentist, my interest in dentistry started at an early age. In fact, I distinctly recall being only 6 years old when I knew I would one day become a dentist. As a kid, I watched my father, Mark J.(Sr.), improve access to oral healthcare for people who didn’t have many options for seeing a dentist. One way he did this was by creating a groundbreaking program that brought dentists to kids across the state. That practice continues to serve hundreds of locations to this day, 40 years later!

I remember thinking even as a kid that it would be great to offer the same convenience to the parents of those children, adults who have limited time or flexibility to take hours off from work to go see their own dentist. Fast forward to today and that idea is now being carried out by D4.

I am passionate about health, wellness and dentistry, and I like to help people achieve their personal oral and overall health goals. At D4, we are doing just that.

    Alex Spiegel


    President, Co-Founder


    Hi, I’m Alex, I’ve lived in Massachusetts for over 20 years, and I attended Middlebury College in Vermont. I have spent my career in healthcare services, much of it building and running businesses that have shared a commitment to breaking down barriers to care and an obsession over customer satisfaction. With help from Mark J. and Mark E. I previously ran a company that brought dental and other clinical services to patients who had few other options for receiving care. My role was all about enabling our team and ensuring that customer needs were met promptly and completely and even anticipated whenever possible.

    I like finding the win for all stakeholders. At D4, that starts with the person we’re treating, but it also includes our client companies, our doctors and other team members. When people have healthy mouths, they’re also more likely to have healthy bodies and minds, and when we have healthier people, we have a happier and more productive team.

    Dr. Mark J. Doherty


    Senior Advisor, Co-Founder


    Hi, I’m Dr. Mark J. Doherty, and I’m Mark E.’s father, so that must make me a 5th generation dentist! I am a General Dentist by training and I attended dental school at the University of Pennsylvania. Over the years, I have served as Dental Director for multiple oral health centers and have treated people in both private practices and community health centers. I am particularly proud of the work we have done at Commonwealth Oral Health Services since its founding in 1979. Together, we have been providing oral health services to disadvantaged children and adolescents who have historically had trouble accessing dental care. I have also been very fortunate to work with an excellent team of dentists, clinicians and practice management experts at the DentaQuest Institute where we have positively impacted over 500 safety net dental programs across the country.

    I am passionate about removing barriers to and improving the quality of oral healthcare. D4 continues that charge for the many working people who find it difficult to see the dentist. At D4, our team partners with employers and patients to make oral healthcare accessible, convenient, and relevant.

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