The Clinical Use of Night Guards: Occlusal Objectives

Are you looking for ways to provide better service for your patients? Set yourself apart from the rest of the dentists in the area? Offer a service that is relatively easy to deliver, of value to your patients, and profitable for your practice? It is time that we, the dental community, re-engineer our practices to treat occlusal disease as effectively as we learned to treat bacterial disease.

Growing up in the 1950s, I learned from television commercials that if I brushed my teeth twice a day and visited the dentist twice a year, I could keep my teeth for a lifetime. In the 1970s dental school added daily flossing to the regimen but basically supported the concept that patients could also keep their teeth for their lifetime by following these basic preventive measures.

THE EVOLUTION OF PREVENTION

What about the year 2004? If I tell my patients the same thing as in the past, am I telling them all they need to know? Or, am I helping to perpetuate an old-fashioned concept that needs to be discarded?

Since 1950 dentistry has enjoyed unprecedented success in the ability to help our patients keep their teeth. Through the use of fluoride, sealants, and increased awareness of nutrition and dental hygiene, caries has been greatly reduced. Our understanding and treatment of periodontal disease has greatly prolonged tooth retention. On the medical side, our colleagues have increased life expectancy; people now live at least 20 years longer than they did in the 1950s. The result is that people are retaining more of their teeth and living longer. Men and women over the age of 80 now make up the fastest growing population segment in the United States!1

Figure 1. Patient in mid 30s showing effects of severe bruxism habit.

As practicing dentists, what do we need to know to help our patients keep their teeth healthy for this potentially longer life? Have you ever seen a patient who has little or no new decay, little or no active periodontal disease, and yet he or she is at risk of losing teeth due to the loss of enamel from occlusal disease? What if the patient brushes twice a day, flosses every day, and bruxes every night? See the patient in Figure 1. Not yet 40 years old, she shows no signs of caries or periodontal disease but is at great risk of occlusal disease.

It is incumbent on the proactive practitioner of the 21st century to be able to diagnose and treat occlusal disease with as much confidence as he or she has treated the bacterial diseases of caries and periodontal disease. This article is written to make you and your team more aware of what you can do to help your patients keep their teeth.

 

NIGHT GUARDS

Figure 2. Variety of occlusal appliances that have been advocated through the years.

A common definition of a night guard is an acrylic splint, either maxillary or mandibular, that assists the condyles in reaching their most anterior superior position in the fossa (centric relation).2 These types of appliances are also known as centric relation splints, occlusal appliances, and orthotics. As long as they accomplish the same objectives, they vary only in name, and I use the terms interchangeably. A variety of different appliances made from a variety of different materials have been used through the years (Figure 2).

 

OCCLUSAL OBJECTIVES

What are the desired objectives of a well-constructed night guard or occlusal appliance? Again, the goals are to allow the condyles to seat in their most anterior superior position (centric relation), to provide for anterior disclusion (cuspid guidance), and to have posterior point contact in centric occlusion and no posterior contact in any eccentric movement.3 If these are achieved, then the masseter muscles will become more relaxed and unable to exert the magnitude of harmful force when posterior interferences are present.4

Now that we understand the objectives of a night guard, let’s discuss some of its indications. All dentists are familiar with the indication of occlusal splint or night guard therapy for the treatment of temporomandibular joint dysfunction (TMD). It is not within the scope of this article to discuss TMD; entire textbooks are devoted to this topic alone.5 However, in addition to the traditional TMD patient, there are a host of other patients in our practices who can benefit from this treatment modality.

Figure 3. Lateral view of patient’s dentition where mandibular cuspid shows severe wear pattern from a parafunctional habit.

As we know (but may not be conveying to our patients), the greatest harm to the teeth and supporting structures occurs during parafunction, not during normal function. This becomes the first indication for treatment with a night guard: to protect the dentition during parafunctional habits (Figure 3). The 2 most commonly observed parafunctional habits are clenching and bruxism. One common misunderstanding appears to be how to diagnostically distinguish between the two. Clenching, or excessive vertical force, can be easily distinguished from bruxism, or “grazing” destructive forces, by looking closely at the lower second molars (or the most terminal lower tooth). Clenchers have an almost indistinguishable cupping on the occlusal table of the terminal tooth, an area hollowed out by the opposing lingual cusp. Bruxers are grazers who will wear the teeth flat, or in an early stage show wear facets and flat spots on posterior and/or anterior teeth. Either of these parafunctional habits can occur during daytime, nighttime, or both. 

Figure 4. Mandibular incisors that oppose porcelain crowns showing wear into the secondary dentin.

A second indication of the need to provide a night guard for a patient is the increasing use of porcelain in dental restorations. The posterior gold reconstruction we provided our patients 30 years ago wore with time; the porcelain reconstruction does not. Furthermore, we have all seen the destruction of natural enamel when it opposes traditional feldspathic porcelain. The patient in Figure 4 shows the destructive capacity of porcelain against enamel. Throughout my 24 years in private practice I have observed that temporomandibular joints and occlusion change with time, but porcelain does not. This alone is a cause for TMD.

Lastly, consider the brittle nature of porcelain and the concepts we know of fracture propagation. Normally, function does not seem to be of great concern to the long-term prognosis of all-ceramic crowns and veneers. However, parafunction can be of great harm to these types of restorations in particular. As a matter of routine, I provide a night guard to all of my patients with porcelain reconstructions. This helps me sleep better and keeps me from bruxing! The added safety net of a night guard can protect the ceramic restorations themselves when they oppose each other; it can also protect the natural dentition from the destruction that can occur when opposing porcelain. In addition, it can provide a degree of protection to the temporomandibular joints.

A third and often-overlooked indication for night guard therapy is to aid a patient with excessive tooth sensitivity to temperature. I have been very successful in treating these patients when I suspect nocturnal clenching to be the causative factor. Clues to look for include tooth mobility, the cupping of the lower occlusal terminal tooth, and the widening of the periodontal ligament space in teeth that are the recipients of excessive force. 

Figure 5. Facial abfractions due primarily to occlusal trauma.

Finally, we are all familiar with the recent use of the term “abfraction.” What we were taught in dental school as being toothbrush abrasion or erosion did not encompass what I have observed with others to be the more common condition now known as abfraction. This is the gingival V-shaped lesion that is caused by excessive occlusal trauma (Figure 5). The occlusal trauma causes tooth flexure, and it is at the point of flexure that microtrauma to the hydroxyapatite crystals occurs. It is most commonly observed on the facial aspect of the tooth, but can also occur lingually. Night guard therapy can help prevent further abfractions after traditional therapy of restoration and occlusal equilibration has been completed.

Although by no means an exhaustive list, the above are the most common indications for night guard therapy. Depending on the age of your patients and the types of restorations they have had, as many as 30% of your patients will fall into the category of those who would benefit from a night guard.6 With need this great, how can a night guard be easily and predictably done in the dental office?

NIGHT GUARD DELIVERY

Depending on state laws, the majority of the chairside procedures can be delegated to a competent chairside assistant. The assistant generally will enjoy providing this beneficial service, and it tends to be a welcome change from the routine of assisting the dentist. First, obtain an excellent set of alginate impressions. Take special precaution to snap removal of the impression from the mouth, as rocking causes distortion that leads to an ill-fitting appliance. Immediately pour the alginate impressions in a good quality stone or die stone. Second, take a facebow transfer for mounting on a semiadjustable articulator to minimize chairside adjustments at the delivery appointment. Again, this is a delegated task in my office. Many different articulator companies have simplified this procedure from dental school days so that this can be done in less than 5 minutes. 

Figure 6. Properly adjusted maxillary night guard showing point contact in the posterior areas with anterior guidance providing immediate posterior disclusion.

Another way to reduce delivery time is to take a centric relation bite record for use when mounting the models. Through the years, I have tried countless techniques and materials, and have personally found the easiest and most reliable to be the centric relation wax record technique that is taught at the Pankey Institute.7 As long as centric relation is obtained, any technique (power centric, leaf gauge, bimanual manipulation, etc) or material (wax, ZnOE paste, vinyl siloxane, etc) that you prefer will work. With these office procedures completed, I have found the laboratory can consistently produce a night guard that can be delivered to the patient in less than 15 minutes (with adjustments). Figure 6 illustrates a properly adjusted maxillary night guard with posterior point contact and anterior disclusion.

Another aid that has made the delivery appointment faster is the choice of material I instruct the laboratory to use. On the advice of my National Dentex laboratory (Smith Dental Prosthetics, Florida), I tried a new material called Thermo-Guard. Previously, I had used a hard, clear, heat-cured acrylic, which can be very unforgiving at the delivery appointment if there is any inaccuracy in the alginate impression (blebs, undercuts, etc). Even though it is heat-cured, Thermo-Guard remains ever so slightly resilient to provide for increased patient comfort. In addition, the night guard can be placed in warm water for a few minutes and then seated at the delivery appointment. Any small discrepancy is overcome by the softened material, so the appliance seats easily and then returns to its original state of hardness. Finally, Thermo-Guard has a milky white opacity after processing that gradually disappears, but can make it easier to read the articulating paper marks at the delivery appointment than it is to read the marks on a clear acrylic splint. 

Figure 7. Mounted study models indicating mandibular arch would be preferred for night guard due to uneven incisal edges.

A common question ap-pears to be which arch the night guard should be placed upon. An easy rule of thumb is to cover the more uneven anterior teeth. If the mandibular incisors are crowded, rotated, and of uneven height, a mandibular appliance will more easily achieve the desired objectives in most cases. On the other hand, if the maxillary incisors are the more uneven plane, a maxillary appliance is probably a better choice. The patient in Figure 7 would be best served with a mandibular appliance since that is the arch with the most uneven anterior teeth. If there is no difference, it is a matter of the operator’s choice; personally, I have found the maxillary appliance easier to fit and adjust and easier for the patients to accommodate to.

  

WIDESPREAD BENEFITS

Night guard therapy offers a number of benefits. The patient benefits by receiving a service that goes beyond the preventive dentistry concepts of the past to encompass the patient’s comprehensive needs of today. The dentist and staff benefit by offering a service that varies from the traditional drill-and-fill treatments that cause greater stress to the dental team. The entire office benefits from the additional sense of fulfillment that comes from helping patients to its maximum ability, and the business experiences financial benefits when providing this much-needed service efficiently and productively.

If we as a profession are to continue the advances we have offered to our patients in the past, our focus at the start of the new millennium should be on learning to treat occlusal disease as effectively as we have treated caries and periodontal disease. Success in the treatment of this third cause of tooth loss will benefit our patients by helping them keep their teeth as they live longer and healthier lives.


 

References

1. Peterson PG. Will America Grow Up Before It Grows Old? New York, NY: Random House; 1996:15-30.

2. Dawson PE. Evaluation, Diagnosis, and Treatment of Occlusal Problems. 2nd ed. St Louis, Mo: CV Mosby; 1989.

3. The L. D. Pankey Institute. Syllabus for Continuum One. Key Biscayne, Fla: The L. D. Pankey Institute; 1992; section V:1-7.

4. Williamson EH, Lundquist DO. Anterior guidance: its effect on electromyographic activity of the temporal and masseter muscles. J Prosthet Dent. 1983;49:816-823.

5. Okeson JP. Management of Temporomandibular Disorders and Occlusion. 3rd ed. St Louis, Mo: CV Mosby; 1993.

6. Christensen GJ. Abnormal occlusal conditions: a forgotten part of dentistry. J Am Dent Assoc. 1995;126:1667-1668.

7. The L. D. Pankey Institute. Syllabus for Continuum One. Key Biscayne, Fla: The L. D. Pankey Institute; 1992; section I:10.


Dr. Cowie is a 1976 graduate of Northwestern University Dental School and practices in Jacksonville, Fla. He has completed close to 2,000 hours of continuing education, including continuums at the Dawson Center for Advanced Dental Studies, the Society of Occlusal Studies, and The Pankey Institute. Dr. Cowie has lectured on occlusion and night guard therapy in more than 20 states in the last 2 years. He can be reached at (904) 771-0568, drcowie.com, or This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

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