 ![[ Home ]](../../images/logos/jd_logo_small.gif){kind=logo} |
|
 |
|---|---|---|
|
By Peter T. George Part III This article is reprinted with the kind permission of the folks at AAFO magazine reprints are available by contacting AAFO (800)441-3850
Figure 1- A) George Gauge assembled B) Component parts of George Gauge
Figure 3-Patient closing into upper incisor notch with midline indicator between central incisors. Figure 4-Mandible sides to anterior and posterior border positions.
Figure 5-Mandibular position observed on millimeter scale of George Gauge. Figure 6-Placing softened base plate wax and silicone putty on prongs of bite fork.
Figure 7-Patient closing into silicone putty to register construction bite. Figure 8-Trimming excess registration material to within one inch of occlusal surface. Figure 9-Top. Adjusting leg of clasp with narrow beak pliers. Bottom. Adjusting horizontal bar of clasp with three prong pliers. Figure 10-Marking oral breathing beak to reduce length. The purpose of the NAPA is to prevent the airway from constricting. This will help patients breathe more adequately and silently while sleeping. |
Patients suspect of OSA should be informed of this fact, and advised to see a physician. Let them know the seriousness of the condition. Do not tell the patient you have diagnosed OSA, or that you have cleared them of this sleep/breathing disorder. The Epworth Sleepiness Scale is only a screening instrument, and if not infallible. However, the protocol suggested in the last installment provides enough leeway to prevent any serious cases of OSA from slipping through the cracks. Although the NAPA has had excellent documentation in the prevention of OSA, never tell patients you are curing their OSA, or even their snoring. The purpose of the NAPA is to prevent the airway from constricting. This will help patients breathe more adequately and silently while sleeping. It will reduce or the stop the snoring and/ or OSA only while it is being used. In this sense it is very much like a crutch or eye glasses. It will not permanently alter any body structure or function, therefore, it is not therapy that will cure any future sleep/ breathing problem. Never place a NAPA in patients who refuse to sign the Informed Consent indicating you have advised them to see a physician. When dealing with minors make sure a parent or guardian signs this form. You cannot force your patients to see a physician, but it is your legal obligation to provide them with full disclosure. Follow the suggested protocol, and you can feel safe and comfortable in providing this very valuable and rewarding service to your patients. Also, I urge you to become more familiar with the pathological aspects of sleep/ breathing disorders. The best way of starting this education is by taking a full day course on the subject, and by joining the SDDS (Sleep Disorders Dental Society), 1167 Perry Highway, Building 1, Wexford, PA 15090, 412-935-0836. ORAL EXAMINATION If the NAPA patient has not come from your practice, you should, of course, perform a typical thorough new patient dental exam. Make sure the patient has at least one good posterior tooth in each quadrant. Since the NAPA requires strong clasping to prevent involuntary mouth opening during the night, it is essential that anchorage be available in each quadrant. Periodontal problems, per se, do not contraindicate the NAPA. This appliance grips each tooth, stabilizing the teeth, and distributes the occlusal forces throughout the dentition. However, if a tooth that is to be clasped is mobile, forces required in removing the appliance may be damaging to it. Obviously, in such a case, you, as a dentist, would initiate periodontal treatment or refer to a periodontist. Check to make sure all crown and bridge work is properly cemented. Inform the patient prior to taking records that properly cemented crown and bridge work should be able to withstand whatever force is required to routinely remove the NAPA. If a crown is unseated while removing the NAPA, it is and indication the crown needed to be re-cemented, or that a new crown is indicated. STUDY AND WORK MODELS Impressions for study and work models may be taken in alginate. Although study models are not essential in treatment for planning for the NAPA, as they are for functional orthodontic appliances, it is wise to take and store them. Patients will sometimes imagine that various preexisting conditions in their occlusion or dental structures occurred because of your treatment. In such cases it is handy to be able to show them that these conditions were there before treatment started. Impressions for work models should be poured up immediately in hard stone. It is essential that every tooth be included in the impressions, including third molars, if present. The NAPA requires full occlusal coverage to distribute the occlusal forces over the entire dentition, and to prevent super eruption of any teeth. BITE REGISTRATION RATIONALE The bite registration is critical in construction of the NAPA. An incorrect bite can result in a poor fitting appliance that is less effective and uncomfortable to wear. The basic requirements for the NAPA construction bite are 5mm between the incisors, 70% protrusion , and maintenance of the lateral relationship that exists in centric occlusion. Although you can take this bite with the traditional freehand method, which has been used for many years for functional orthodontic appliances, the George Gauge offers a simpler, more accurate method. You can be assured of a correct registration by presetting the gauge for the desired bite. You then have the patient simply bite simultaneously into the incisor notches and registration material. I also strongly recommend that anyone interested in becoming involved in anti-snore therapy view the video, “The Theory and Practice of Construction Bite Registration”, by this author. (Editor’s Note: Dr. George’s videotape is available through the following labs: Johns Dental, EOP, Great Lakes Orthodontics, and American Orthodontics.) This tape not only demonstrates how best to use the George Gauge, but displays the etiology of sleep/ breathing disorders in graphic form. General instructions on how to take construction bites for functional appliances, TMD splints and anti-snore devices comes with the George Gauge. The following information is specific for the NAPA Vertical: The George Gauge comes with two bite forks. One produces a 5mm vertical opening between the incisors and the other, 2mm. Always use the 5mm fork for the NAPA construction bite registration. Anti-snore devices are being made with inter-incisal space of from zero to over 20mm, however, I believe 5mm is the optimum opening for the NAPA. Dr. Alan Lowe and associates at the University of British Columbia, Department of Orthodontics did research on cats to learn more about the nature of tongue thrusting. What they found has great significance in the prevention of snoring and OSA. They cemented bit blocks to the lower dentition of these cats, and found that when the cats occluded on these blocks their genioglossus muscles would be activated. This would not only result in protrusion of the tongue, but would make it more resistant to any force tending to pull it back into the pharynx. What Dr. Lowe’s research tells us is that even an ordinary occlusal splint that tend to decrease snoring, and that the efficacy of the NAPA comes from more than its mandibular advancement. As a matter of fact, the efficacy of the NAPA comes from a number of other factors which we know of, and probably several others that we have not yet discovered. The thickness of the blocks in the feline experiments would translate into approximately 5mm between the incisors in a human. Whether a little more or less would be more effective is not certain. However, since the mandible rotates clockwise on opening, going much beyond 5mm increasingly moves the mandible posteriorly in addition to inferiorly. This, of course, tends to drive the tongue closer to the posterior pharyngeal wall. Opening the mandible less than 5mm between the incisors would leave insufficient room for the oral breathing beak.
Protrusive: The construction bite registration should produce a NAPA that holds the mandible in the most protruded unstrained position. Experience indicates this is approximately 70% of the protrusive range. To find and register this position it is necessary to 1. determine the length of the protrusive range, 2. determine where 70% of it would be, 3. have patient bite into registration material in that position. This can easily and accurately be done with the George Gauge. Some people have been advocating protruding the mandible to an end-to-end relationship for all mandibular repositioning anti-snore device bite registrations. This reasoning may be based on the erroneous assumption that a mandibular advancement device can only benefit snoring patients with retrognathic mandibles. They seem to assume these patients should be treated like Class II functional orthodontic cases. An end-to-end bite has varying degrees of validity in treatment of skeletal Class II malocclusions with functional orthodontic appliances. All Class II's have some over jet, or overjet can be developed as is often done in Class II, division 2 cases. A snore patient may or may not have an over jet. In fact, some snore patients have protrusive mandibles. The NAPA works just as well in Class III's as it does in Class II's. It is apparent then, an end-to-end bite, or any derivative of this incisor relationship, has no validity in a mandibular repositioning device for the prevention of snoring. Another reason the end-to-end bite is advocated is because some appliances do not have posterior anchorage; they become unstable when the bite protrudes the mandible beyond end-to-end. Repositioning the mandible accomplishes more than just moving the tongue away from the posterior wall of the pharynx. This was discovered when it was learned that mandibular advancement surgery did not improve the RDI (Respiratory Disturbance Index) when the advancement was less than 12mm. Surgeons at Stanford University found they had to move the mandible forward 15mm to be sure that the RDI would be reduced. Obviously, it is impossible to move a mandible that far forward with any appliance. What then does the mandibular advancement do in a NAPA? It develops a tension in the oral tissues that initiate certain reflexes, and inhibit others so that the tongue musculature can resist the suction of the airway. In other words, the NAPA not only creates an anatomical effect, but a physiological one. This will be discussed more fully later. The efficacy of the NAPA is not dependent on how big the over jet is, or how small the mandible. It is just as effective in skeletal Class III cases as in patients with retrognathic mandibles. Whether the patient is a Class II with micrognathia, advance the mandible 70% of its protrusive path to provide the optimum tension in the oral tissues. A bite registration with the lower incisors 7mm in front of the uppers may be correct for a patient who bites end-to-end in centric. THE GEORGE GAUGE The George Gauge is an adjustable instrument that can be preset to guide the mandible to any desired position along the range of the protrusive path. It also serves as a vehicle for the registration material (Figure 1). The gauge consists of three parts: the lower incisor clamp, the bite fork, and the body. The lower incisor clamp slides in and out of the body, forming the lingual wall of the lower incisor notch. It can be adjusted to fit over rotated incisors. The bite fork, which also slides in and out, contains the perforated prongs that hold the registration material, the upper incisor notch, and the shaft whose anterior end indicates mandibular position on the millimeter scale of the body. Bite forks are available in two incisor notch sizes, one producing a 2mm inter incisal distance and the other, 5mm. For the NAPA only the 5mm bite fork is used. BITE REGISTRATION TECHNIQUE To take a bite registration with the George Gauge, first center the lower incisor notch over the anterior teeth. Cinch up the lower incisor clamp to firmly grip these teeth, and tighten the lower turn screw to secure this position (Figure 2). Remove the instrument from the mouth. Insert the bite fork, into the body of the gauge, and slide it until the indicator end is at the 0 point on the millimeter scale. Lightly tighten the upper turn screw. Return the instrument to the mouth with the lower incisor notch centered over the lower midline. Instruct the patient to close into the upper incisor notch with the midline indicator between the central incisors (Figure 3). Modify the upper notch with an acrylic bur if the incisors are rotated or if the incisal edges are excessively thick. While the patiently is firmly biting into the notches instruct him/her to slide the jaw forward as far as possible. Make a mental note of the + reading on the millimeter scale (Figure 4 and 5). Then ask the patient to move the jaw back as far as he/she can. Note the position on the -end of the millimeter scale. Add these two numbers, the + and - signs. The total is the patient’s protrusive range. Multiply that sum by .7 (70%), and add it to the minus number (retrusive position). The result is the number at which you preset the George Gauge. Example: Your patient can protrude to the +6 mark on the millimeter scale, and can retrude to the -4. His protrusive range, therefore, is 10mm. Taking 70% of that range, which is 7mm, and adding it to the most retruded position, which is -4, gives you a setting of +3. Slide the marking end of the bite fork over the millimeter scale until its indicator end rests over the +3 mark, and tighten the upper turn screw. A simpler method of setting the George Gauge, which achieves approximately the same result, is to set its relative to the most protrusive position. You will find the vast majority of protrusive ranges will be larger than 7mm and smaller than 13mm. In these cases you may set the gauge at 3mm behind the most protrusive position. If the protrusive range is 7mm or less, set the gauge at 2mm behind the most protrusive position. If the range is 13mm or more the setting ca be at 4mm posterior to the most protrusive. Place registration material, wax or silicone putty, on the prongs of the bite fork (Figure 6). Cut base plate wax into 3" x 1.5" pieces, heat in water or over a flame, and wrap around each prong. Of the two registration materials, I believe silicone is simpler to use and provides a more accurate and durable record. Add hardener to the putty and knead in fingers until homogeneous. Roll the silicone into cigar shape, pinch in half, and impale on each prong. Return the George Gauge to the mouth with the lower notch centered over lower midline. Hand patient a mirror and instruct to close into upper incisor notch taking care to align incisors with midline indicator on bite fork (Figure 7). Maintain the same upper and lower midline relationship that exists in centric occlusion. Do not attempt to correct midline discrepancies with a NAPA. For greater accuracy or when working with poorly coordinated patients who have difficulty closing directly into the registration material, assist the patient to close into the correct position. Make any adjustments necessary before placing registration material on the bite fork. Then inject a material, such as polyvinyl-siloxane, between the teeth and bite fork to register the position. After registration material has sufficiently hardened, remove the instrument from the mouth. Trim excess registration material with a sharp blade to about a millimeter from occlusal surface (Figure 8). Separate the bite fork from the body of the George Gauge, and send the construction bite and bite fork, along with the patients models, to the laboratory. INITIAL INSERTION If your impressions and bite registration were accurate the appliance should fit comfortably with little or no adjustment. Test the fit of the NAPA on the upper arch first. If it does not seat completely, attempt to find the interference with indictor paste and remove. Then dislodge the appliance from the upper teeth. Check - and adjust, if necessary - the fit on the lower arch. Next reseat the NAPA on the upper arch, and have the patient bring the mandible up to engage the lower teeth in the appliance. I originally would hand the patient a mirror to guide him/her in locating the lower teeth into the clasps of the NAPA. I no longer do this. I now ask the patient to slowly bring the jaw up and forward, and gently feel around with the lower teeth to find the clasps. Most patients quickly find the correct position. The mirror seems to confuse rather than help most patients. If the NAPA fits well on lower and upper arch separately but not at the same time, the impressions and casts were accurate, but the bite registration is off. This occurrence has been practically eliminated in my practice since using the George Gauge with silicone putty. If the bite is off only slightly, use pressure indicator paste to find high spots, then grind them off. If the bite is off more than slightly, grind some of the acrylic in either the upper or lower arch (not both) then reline with cold cure acrylic. ADJUSTMENT The NAPA must securely grasp the teeth to prevent mandibular movement during sleep. This is important not only to prevent the NAPA from falling out of the mouth, but to prevent any movement of the mandible. Any play of the appliance in the mouth will tend to invoke and anti-tongue-biting reflex, which allows the tongue to fall back. This makes the NAPA less effective. Increasing the clasp retention is vital to increasing the efficacy of the NAPA. The retention can be increased by adjusting the Adams clasps. Grip the mesial and distal legs of the Adams clasps with a narrow beak pliers (e.g. #139) and bend in toward the tooth. Also squeezing the horizontal wire- with the center prong of a three prong pliers facing the tooth- will increase the retention (Figure 9). If you bend the wire too much, the NAPA won’t completely seat. In that case simply slightly reverse the bend until the appliance seats fully. A little practice will quickly teach you how much to bend. After the initial insertion ask the patient to open without the use of the hands, and see whether the upper or lower clasps release first. If the upper released first, increase the retention on that side until the lower side comes out first. Then increase the retention of the lower clasps until the upper comes out first. Repeat this process until the patient must exert a fairly strong effort to open. Assure the patient any discomfort resulting from the strong clasp retention is temporary. After the first few nights this firm retention results in a more comfortable as well as a more effective appliance. That is because when there is no play between the appliance and the teeth, the muscles can better relax. Also there is less excess salivation because of the less movement. Discomfort, if there is any, is more likely to result from the pressure of the acrylic rather than the wires. If the patient feels discomfort on any tooth, ask in which direction he/she feels the pressure (i.e. in toward the tongue, out toward the lips or cheeks, or up or down toward the roots), and relieve the acrylic accordingly. Inform the patient to expect a lot of salivation at first, but that it decreases with use. Some soreness of the teeth in the morning is not unusual, but should subside in several days. Aspirin (or other mild analgesic) at bedtime may be indicated for the first few nights. Let the patient know that his teeth will feel like they don’t come together properly in the morning. This is due to a temporary myostatic contracture (foreshortening) of the inferior lateral pterygoid muscles. This usually quickly subsides with normal function. To speed up this return to normal, the patient may clench his teeth in centric occlusion three repetitions of five seconds each after arising. This isometric effort of the closing muscles invokes and inverse stretch reflex that relaxes the protruding muscles, and returns them to their normal resting lengths. TMJ DISCOMFORT The vast majority of patients quickly adjust to the NAPA, but occasionally one will complain of TM discomfort. Assure the patient that the NAPA cannot harm the joint structure, and that the position it places the jaw is sometimes used therapeutically to relieve the pressure on the joint. Explain that what they are feeling is muscle tension, and that it should gradually subside. This explanation alone usually enables the patient to relax and the discomfort to dissipate. Tell the patient that if discomfort does not disappear by the next bedtime not to wear it that night. After there is no discomfort in the TM area, the patient should wear it again, but should remove it if the discomfort awakens him/her. This should be repeated until able to wear it entire night with no discomfort. Less than 1% of the patients have not been able to work through this discomfort. You may prescribe analgesics to take the morning after, but never under any circumstances prescribe sedatives, tranquilizers or muscles relaxants to take prior to bedtime for any patients who snore, whether they are wearing the NAPA or not. These drugs prolong apnea, and have a specific relaxant effect on the tongue that exacerbates OSA. ADJUSTING BEAK LENGTH The lab routinely makes the oral breathing beak of the NAPA longer than required in most cases. This is because lip thickness varies among patients. And it is important that the lips do not close over the opening of the beak. After the patient has tried the NAPA in the mouth, ask him to relax the lips, then with a china marking pen draw lines on the back at the edge of the upper and lower lips (Figure 10). Grind away excess beak material. FOLLOW-UP After the initial seating of the NAPA, check the patient in one week. At that point make sure the clasps are tight, and check for any discomfort. If any teeth are sore, relieve the acrylic around them. If all is well, reschedule the patient in three months. It is wise to let the patient know that these two follow up appointments are included in the original fee, and that subsequent annual checks or repair appointments will be on a fee per visit basis. Peter T. George, D.D.S. Phone: (808)947-3737 REFERENCES *Patents 4,715,368, D302,036, R33,442 **U.S. Patent No. 5,154,609, foreign patents pending 1. Lowe, A.A. Effects of posterior bite block therapy on genioglossus muscle activity. Pacific Coast Soc Orthod. Bull, 60; 1:41, 1988 2. Powell, N.B. Personal communication 3. George, P.T. “A New Instrument for Functional Appliance Bite Registration”, Journal of Clinical Orthodontics 26:721-723, 1992 |
