The Story of Occlusion

Occlusion is a subject that represents the mastication system, yet as clinicians, we are confused. Occlusion in dentistry has a unique portfolio; it is the most crucial subject in dental reconstruction and the most controversial.1 Many regard occlusion as highly complex and troublesome and not demonstrating a scientifically based relationship to any disease process.2 Others cite that the literature is mainly empirical and not evidence-based. Christensen once described the dental profession’s understanding of occlusion as chaotic.3The American Dental Association sponsored 3 conferences to identify occlusion’s fundamental principles and suggested, without success, that recommendations be introduced into the curriculum at dental schools.4 The principles of occlusion raise several questions. The first is (1) if occlusion is considered an understanding of the mastication system, and because it is, (2) why are there no rules? This commentary aims to discuss the circumstances that have created what is known as occlusion confusion.The story begins early in the 19th century when dentists faced the age-old problem of bruxism or grinding one’s teeth. Little was known about its etiology then, and assuming a proactive approach, its management became the immediate concern.The first idea or concept was to disperse bruxism’s parafunctional forces over the occlusal surfaces of the bicuspids and molars by equilibration; it was termed “group function.” Later, D’Amico, based on his studies of attrition, reduced these forces by directing them forward to the cuspid, resulting in “functional occlusion.”5Because this concept was somewhat effective, a paradigm began to develop that the way teeth touched in function had an essential relationship to the well-being of the mastication system. However, this paradigm was not functional. Teeth rarely touch during functional activities (chewing, swallowing, and speech) and only lightly if they do so; this was classic dysfunction. Nevertheless, the new goal became “optimum functional occlusion.” Reflecting on what happened here is essential because it sets the stage for decades of confusion.The goal of optimum functional occlusion was a red herring or distraction to focusing on the system itself. Successful management of any biological system depends on diagnosing and treating diseases or malfunctions. The 2 main malfunctions affecting the mastication system are (1) horizontal parafunction (bruxism) and (2) vertical parafunction (clenching or dental compression syndrome [DCS]).6 Because of D’Amico’s influence, the dental profession created occlusal schemes by equilibration to manage bruxism while disregarding DCS. This focus on modifying the occlusal surfaces of teeth to address bruxism has led to a narrow perspective on the mastication system, neglecting other crucial aspects, such as DCS. DCS is twice as potent,7 lasts twice as long,7 has a unique set of markers,6 focuses explicitly on the temporomandibular joint (TMJ), and has a long list of etiological factors.Clenching doesn’t seem to bother most people as it works within one’s subconscious. Therefore, when problems occur, such as TMJ disorders, damaged dentition, and alveolar bone loss, the focus is on the target, not the source. This makes it critical for the practitioner to recognize its signs.6 Unlike bruxism’s flattened dentition, DCS has a unique set of footprints; its signs and symptoms that qualify it as a syndrome were not identified and associated with compression until the early 1980s.8,9 Management is important. Unlike bruxism, with which a guard will suffice while sleeping, DCS occurs while awake, so patients must monitor themselves. However, the practitioner must thoroughly explain the many etiological factors, such as medications, stress, exercise, and lifestyle.Using “occlusion” to refer to the mastication system has been troublesome and confusing. It is a significant oversimplification and can be considered a misdirection in understanding the complexity of this biological system.Optimal functional occlusion is an enigma; the term itself is contradictory. Instead of asking how teeth should touch each other in function, we should inquire about the optimal functional relationship in which teeth have minimal contact. Christensen asked if occlusion can be implemented into a general practice.10 Occlusion is not a treatment, concept, or procedure for which we must charge the patient; it’s just a word that means closure.Gunnar Carlsson opined that a patient with ideal occlusion functions well, is physiologically acceptable, and does not need intervention.11 Is this perfect occlusion or, perhaps, a patient not affected by parafunction? There is also the idea in the literature that a physiological occlusion can be synonymous with a good occlusion, that is, functioning without problems, stable, and does not change: doesn’t this describe a patient unaffected by parafunction?To address the dilemma of occlusion confusion, the dental community needs to adopt a more holistic view of the mastication system. It needs to recognize the limitations of the term “occlusion,” which has been overused, confused, and extended beyond its meaning, and to develop a more comprehensive understanding of all the contributing factors to mastication disorders.