The Controversy Continues

Periodontal diseases have been associated with occlusal stresses for more than 100 years. In 1901, Karolyi reported that teeth undergoing excessive occlusal forces seemed to have greater periodontal destruction than those that were not under excessive occlusal stress.¹ Stillman reported 20 years later that occlusion was the primary cause of periodontitis and that the occlusion must be balanced for successful treatment.² Since this time, a large number of studies have been performed in an attempt to clarify the role of occlusion in periodontal disease. Despite all of the research, the role of occlusion in the progression and treatment of periodontal diseases remains controversial.

Two series of important animal studies were performed during the 1970s and ’80s in an attempt to clarify the relationship between inflammation and occlusal forces in the progression of periodontal diseases. A group of researchers in Rochester, NY, studied periodontal inflammation in an occlusal trauma model in the squirrel monkey and a group of researchers from Gotenberg, Sweden, performed similar studies using beagle dogs.^3,4 While marked differences existed between the study designs used by the two groups, their results were very similar. Both showed that in animals, occlusal forces caused increased mobility of the teeth and a decrease in bone volume, but occlusal forces did not routinely cause attachment loss and increased pocket depths. Only in beagle dogs where the bone level was surgically altered and inflammation was artificially induced was there any loss of attachment. Both study groups concluded that controlling inflammation, rather than balancing the occlusion, was paramount to the control of periodontal destruction.

HUMAN STUDIES

Many of the studies that looked at the relationship of occlusion in the progression of periodontal diseases have evaluated human autopsy material. These include frequently quoted studies by Weinmann, Glickman, and Waerhaug.^5-7 One of the problems inherent in evaluating post-mortem specimens is the difficulty in determining the occlusal pattern that the subject possessed while alive. The only indication of occlusal relationships that can be detected after death is the wear patterns on the teeth. Wear patterns may indicate the position where the patient bruxed his or her teeth during parafunctional movements but the actual occlusal relationship (centric relation/centric occlusion) cannot be determined after death. As a result, the findings of post-mortem studies are subjective and their clinical relevance must be questioned.

Several human studies have clinically evaluated occlusal relationships and compared them to periodontal conditions. McGuire and Nunn studied changes in prognosis and the number of teeth lost in patients with periodontal diseases who had parafunctional habits such as bruxing.^8,9 In patients with parafunctional habits that had not been treated with an occlusal appliance, no improvement in periodontal prognosis was noted despite nonsurgical and surgical periodontal therapy. Additionally, more teeth were lost in the group that did not have an occlusal guard than in the group that received occlusal guard therapy. Burgett performed a controlled clinical trial on patients who underwent both non-surgical and surgical periodontal treatment. In half of the patients, all occlusal discrepancies were corrected by occlusal adjustment by reshaping the biting surfaces of the teeth with rotary instruments. Half did not receive any occlusal treatment. Following both surgical and nonsurgical therapy, the group that received occlusal adjustment had a statistically significant improvement in attachment levels when compared with the group that did not have occlusal adjustment.¹⁰

Harrel and Nunn performed a large retrospective study on patients with severe periodontal destruction who were referred to a periodontal office for therapy.^11-13 Unlike other studies, these looked at the status of individual teeth rather than the patient means used in most studies on occlusion. Patient means average all of a patient’s pocket depths and express a single average pocket depth. Often a patient will have many relatively healthy teeth with only isolated areas of periodontal destruction. When a patient mean is used, the measurements from the healthy teeth tend to statistically wash out the deeper readings on teeth with periodontitis. The results showed that teeth with occlusal discrepancies had pockets that were approximately 1 mm deeper than teeth without occlusal discrepancies. Further, it was noted that teeth with untreated occlusal discrepancies did not respond as well to periodontal therapy as did teeth with treated occlusal discrepancies. These data indicated that an occlusal discrepancy was an independent risk factor for the progression of periodontal destruction in patients with an active periodontal disease.

OCCLUSAL DISCREPANCIES AS A RISK FACTOR

For the past 50 years, the periodontal literature has consistently reported that occlusal forces do not initiate periodontitis. Therefore, there is no indication for occlusal treatment to prevent periodontal destruction in the periodontally healthy individual. However, there is strong evidence that occlusal forces are a significant risk factor for accelerated periodontal destruction in the presence of existing chronic periodontitis.

Periodontal diseases are multifactorial diseases in which inflammation is stimulated by bacterial plaque and tissue destruction is caused by the patient’s defensive immune response. However, this process works in concert with multiple other risk factors. For example, smoking is a risk factor for periodontal diseases. However, there are patients who are heavy smokers who do not have appreciable periodontal destruction and there are also patients who have never smoked with severe active periodontal destruction. This indicates that the act of smoking is not the cause of periodontal destruction. However, a patient who is susceptible to periodontitis and who also smokes has a greater risk of significant periodontal destruction. Therefore, smoking is not a causative agent of periodontal diseases but is a risk factor for the diseases.

The Harrell/Nunn studies suggest that occlusal discrepancies, like smoking, function as a risk factor for periodontal degeneration. Periodontal treatment consists of removing all controllable factors contributing to the disease processes. Just as oral hygiene, scaling, root planing, and periodontal surgery are aimed at controlling periodontal inflammation, other risk factors, such as smoking and occlusal discrepancies, should be included in the treatment of periodontal diseases as well. As a controllable risk factor, occlusal therapy should be a routine part of the treatment of periodontal diseases.

THE HYGIENIST’S ROLE

The dental hygienist is in a unique position to evaluate and record evidence of occlusal stress on the teeth of periodontal patients. Occlusal stress is illustrated by parafunctional habits such as grinding/clenching or may occur as a result of either skeletal or positional misalignment of the teeth. Each periodontal patient should be evaluated for signs of occlusal stress and the findings should be recorded.

The prominent clinical feature of parafunctional habits (grinding/clenching) is the presence of wear on the teeth. The presence of flat spots or wear facets on the teeth is an indication of parafunctional habits that have occurred in the past and may be continuing. Obvious wear facets with a shiny surface usually indicate that the patient is presently grinding his or her teeth. Wear facets with a dull surface may indicate that the periodontal patient has been a bruxer in the past but is not currently, or it may mean that the patient is an intermittent bruxer. In either case, the findings should be recorded and the possibility of clenching/grinding should be discussed with the patient. Many patients who routinely clench their teeth are not aware of the habit and may deny that they either grind or clench their teeth. The first step in educating patients is to show them the wear patterns on their teeth. Often if you ask the patient to grind his or her teeth you can show that the wear facets on the upper fit into the wear patterns on the lower. The presence of this type of wear facet is almost never due to natural wear from chewing but results from parafunctional habits. The rare exception may be a patient who works in a very abrasive environment with dust or sand in the air or a patient who consumes an abrasive diet. However, in such patients, occlusal wear is typically more generalized than what is observed in patients with parafunctional habits.

If periodontal patients are unsure or deny that they are bruxers, a series of signs that will help them self-diagnose their parafunctional habit should be given. These signs include: waking in the middle of the night or in the morning with their teeth clamped together, waking up in the morning with a sense of tiredness of the muscles of the face and jaws, having “tired teeth” in the morning as if they have been chewing gum all night, or waking up with tenderness or pain in front of the ear (TMJ). Any of these signs is an indication the patient is grinding/clenching his or her teeth during sleep and that some type of occlusal appliance/nightguard is indicated.

OCCLUSAL APPLIANCES

There are many types of occlusal appliances but some are not suitable for patients with periodontitis, especially if there has been a significant loss of bony support. A mandibular appliance is contraindicated for periodontal patients because it tends to act as a wedging orthodontic appliance and can cause the maxillary teeth to flare toward the facial or buccal. This is especially true for a commercially available premade appliance that fits over the mandibular anterior teeth. While these devices may be helpful in the short term treatment of patients with joint pain, long-term use may cause flaring of the maxillary anterior teeth and may also allow the super-eruption of the posterior teeth. Soft night guards, similar to athletic guards, for the maxilla or mandible are also contraindicated for most periodontal patients. Typically patients will chew on these soft appliances, which may increase tooth mobility. The preferred nightguard for periodontal patients is thin and is made of hard acrylic and fits over the maxillary teeth. When a patient bruxes with this design of nightguard in place, the teeth will slide on the hard plastic of the nightguard without causing tooth mobility. The nightguard will also act as an orthodontic retainer to keep the periodontally involved teeth in position.

The dental hygienist plays an invaluable part in discussing the possible need for appliance therapy with the periodontal patient. The underlying factors and signs of parafunctional habits and the options for treating the habits should be discussed with the patient during routine treatment. Once the diagnosis is confirmed and depending on state regulations, the hygienist may be permitted to make the necessary impressions and assist in delivering the nightguard.

The presence of skeletal and positional malocclusion requires a more detailed analysis of the patient’s occlusal contact pattern. In most cases, it is necessary to gently manipulate the patients jaw into a retruded position (centric relation) and then ask the patient to slowly close. If the initial contact is not simultaneous on most of the teeth and there is a slide to maximum tooth contact (centric occlusion), then a misalignment of the teeth or jaws exists. Misalignments also may exist in side to side (lateral) movements or in forward (protrusive) movements. The accurate analysis of occlusion requires practice but once learned can usually be performed easily and quickly. The findings should be routinely recorded in the chart as part of the evaluation of the periodontal patient.

If misalignments of tooth contacts are present, they are usually best treated by reshaping the occlusal surfaces of the teeth with a rotary instrument, such as a diamond bur, to change the contacts. Typically, the contacts in various movements are confirmed with inked occlusal ribbons and then the biting surfaces of the teeth are reshaped to change the way in which the teeth contact. Many dentists are not comfortable performing definitive occlusal adjustments. It may be necessary to refer the patient to a dental professional with advanced training in this area such as a periodontist or prosthodontist.

Dentists and dental hygienists often overlook occlusally-related pathology in the periodontal patient, possibly because they have not been taught to look for it. Occlusal problems are considered one of the most underdiagnosed and undertreated problems in dentistry. Most dental hygienists are in an ideal position to evaluate periodontal patients for signs of occlusal trauma. Hygienists can also educate patients about the potential effects of occlusal discrepancies on the health of their dentition and discuss available treatments options.

REFERENCES

1. Karolyi M. Beobachtungen über pyorrhea alveolaris. Öst. Ung. Vierteeljschr Zahnheilk. 1901; 17: 279.
2. Stillman PR. The management of pyorrhea. Dent Cosmos. 1917;59:405-414.
3. Polson AM, Kennedy JE, Zander HA. Trauma and progression of periodontitis in squirrel monkeys. I. Co-destructive factors of periodontitis and thermally-produced injury. J Periodontal Res. 1974;9:100-107.
4. Lindhe J, Svanberg G. Influence of trauma from occlusion on the progression of experimental periodontitis in the beagle dog. J Clin Periodontol. 1974;1:3-14.
5. Weinman J. Progress of gingival inflammation into the supporting structure of the teeth. J. Periodontol. 1941;12:71-76.
6. Glickman I, Smulow JB. Alterations in the pathway of gingival inflammation into the underlying tissues induced by excessive occlusal forces. J Periodontol. 1962;33:7-13.
7. Waerhaug J. The angular bone defect and its relationship to trauma from occlusion and downgrowth of subgingival plaque. J Clin. Periodontol. 1979;6:61-82.
8. McGuire MK, Nunn ME. Prognosis versus actual outcome. III. The effectiveness of clinical parameters in accurately predicting tooth survival. J Periodontol. 1996;67;666-674.
9. McGuire MK, Nunn ME. Prognosis versus actual outcome. II. The effectiveness of clinical parameters in developing an accurate prognosis. J Periodontol. 1996;67;658-665.
10. Burgett FG, Ramfjord SP, Nissle RR, Morrison EC, Charbeneau TD, Caffesse RG. A randomized trial of occlusal adjustment in the treatment of periodontitis patients. J Clin Periodontol. 1992;19:381-387.
11. Nunn ME, Harrel SK. The effect of occlusal discrepancies on treated and untreated periodontitis. I. Relationship of initial occlusal discrepancies to initial clinical parameters. J Periodontol. 2001;72:485-494.
12. Harrel SK, Nunn M. The effect of occlusal discrepancies on periodontitis. II. Relationship of occlusal treatment to the progression of periodontal disease. J Periodontol. 2001;72:495-505.
13. Harrel SK, Nunn ME. The effect of occlusal discrepancies on gingival width. J Periodontol. 2004;75:98-105.

From Dimensions of Dental Hygiene. May 2006;4(5): 16-18.