Prof Kwangchul Choy on orthodontic jargon, inadvertent leveling and the 2nd edition of his extremely popular biomechanics book

Over the past two months, I have been reading a unique and profound book on orthodontic biomechanics which I absolutely enjoyed. It has expanded my understanding of complex mechanics and cleared up some grey areas in my knowledge. Previously, I already published two reviews on the book and today I would like to present my readers a short interview with one of the authors, Dr Kwangchul Choy. He is currently a clinical professor at Yonsei University as well as an adjunct professor at Ewha University. He runs a private practice in Seoul, South Korea and lectures on biomechanics around the world.

Hello Professor Choy! Let me first ask you about the most important person, the one the book was written for. How do you see your ideal reader? What are his/her qualities, aspirations, and attitude to orthodontics?

The biomechanics described in this book is ideal for both students and teachers who want to learn and understand the scientific principle underlying clinical orthodontics. This book will lead you to an adventurous journey that you have had never experienced during typical studies at a dental school. It is my hope that this book provides an exciting and refreshing foray into the world of biomechanics. I consider biomechanics a fun subject at its core. Therefore, we wanted this book to be an entertaining intellectual journey for both students and teachers.                   

Could you name orthodontic books which influenced you the most in the start of your own career?

The most influential experience was coming across Dr Burstone’s papers for the first time. I was instantly mesmerized by his crystal-clear scientific thinking. I had never been exposed to such approach during my dental school. However, only after going through many more orthodontic journals was I able to put jigsaw pieces together and answer some of the questions I initially had.                                                                      

When Dr Burstone and you first decided to write the book and what was the most challenging in the process?

I have been asking Dr Burstone to combine all his papers together and to compose an oeuvre of his life’s work for many years, but he was not interested in writing a book at first. Several years later, in 2012, he offered me an opportunity to write a book with him. The format of this book was adopted from the lectures on biomechanics that we gave at the University of Connecticut and Yonsei university for many years. These lectures and clinical cases on 35 mm slide films became the source for our book. While writing it, almost 2,000 emails were exchnged between us. These were the most challenging, but the most exciting and happiest moments of my life. Sadly, Dr Burstone could not see the publication.

What is the main difference of the book from all the other orthodontic textbooks on biomechanics? 

The orthodontist’s only tool is a mechanical force. Therefore, the orthodontist should study mechanical physics, a study of force. Unfortunately, even graduate courses of orthodontics in dental school lack an extensive curricula on mechanics. What makes it worse is that there are only a few textbooks that cover biomechanics systemically. Whenever I give a lecture on biomechanics, I find that many students approach me for recommendations on further readings on the subject. It is my hope this book will fill this void.

How the book should be read? One chapter after another, from cover to cover or it should be kept chairside to look things up when necessary?

The first few chapters should be easy for anyone with an engineering background. Other readers will familiarize themselves with both scientific and unscientific terminology used in orthodontics. Many orthodontists today are unfamiliar with terminology from classical mechanics. So it is my personal suggestion that the introduction chapters should not be skipped. Many orthodontists regard biomechanics as a tricky subject. If by following the sequence of this book the reader will be able to break that stereotype, I would consider this a great personal success of mine.

The idea that orthodontic language is not really a scientific one sounds very interesting to me. What are the orthodontic terms you find the most confusing and how you prefer to substitute them?

There are many words which are not scientific or misused, such as the terms ‘torque’ and ‘power arm’. They should be read ‘3rd order angulation’ and ‘extension or lever arm’. I tried to eliminate such orthodontic jargon in the book.

What are the most common mistakes in biomechanics orthodontists nowadays make? May there be a connection between such mistakes and popular marketing claims from the manufacturers?

One of the most common mistakes would be an inadvertent initial leveling which most orthodontists consider to be the easiest step of the treatment. If you get such leveling to be successful, it is just by luck, not by your excellence. Sometimes – not always though – inadvertent leveling leads to more serious problems such as open bite and canting of occlusal plane.

Commercialism also plays a role. The brand names of the brackets and wires with prefixes ‘intelligent’, ‘smart’, ‘frictionless, ‘bio’ perplex the orthodontists. Some marketing claims lead some orthodontists to believe that expensive braces produce better results with less adverse side effects. The course of the treatment should be driven by the orthodontist not an appliance.

What have been the feedback from your readers during the years?

After publishing the book, I received many questions from the readers by email. As I have been responding to these emails, I found that I am repeating same answers again and again. Sometimes my discussions with the readers seemed so valuable that I wished I could share them with others. Therefore, I decided to start a facebook discussion page ( On this webpage you will find the supplemental material of the book and also be able to raise questions which interest you.

Could you briefly tell the details on the 2nd edition? 

In the second edition I’ve tried to restructure the content but remain true to the mission of the first one. It is still the book of why (the concepts of orthodontics) rather than the book of how (the techniques of orthodontics). The biggest improvement would be video files that are added to supplement the concepts where still images are not enough demonstrative. You will be able to access the videos by scanning the following QR codes with your smart phones or tablets.

You can buy your copy of the book clicking this link. Please note: this is an affiliate Amazon link. Small bonuses I have from this helps me to support Orthodontic Grammar project, whereas you pay just a regular price and not a dime more.

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