Prosthetic rehabilitation of the gagging patient using acrylic training plates

The somatic gag reflex and the psychogenic gag reflex

The aetiology of the hyper-responsive gag reflex is complex and multifactorial. Kovats suggested that the gag reflex resembles a simple Pavlovian conditioned reflex in that gagging becomes so intimately associated with impression taking/denture insertion, eventually any procedure involving the oral cavity may trigger off the reflex.⁶ It was suggested that gagging can be understood as being somatogenic or psychogenic in origin.⁷ Somatically induced gagging is initiated by direct physical contact on trigger zones, such as the dorsum of the tongue or the pharyngeal mucosa. Psychogenic gagging can be provoked without any physical contact on a trigger zone. In severe patients, even the sight, smell or thought of dental treatment can be sufficient to induce gagging. Such patients are a particular challenge and may require referral for counselling/cognitive behavioural therapy before any form of dental treatment can be carried out.

Psychological factors which predispose a patient to gagging

The gag reflex is considered to have a strong psychosomatic component akin to that of atypical facial pain and burning mouth syndrome. However, there is no evidence of any significant differences between gagging and non-gagging patients in terms of neuroticism, extroversion, or psychoticism.^4,8 The influence of fear, anxiety and stress contribute significantly to the aetiology of the gag reflex in certain individuals.⁹ It has been reported that even the sight and the sound of the dental environment may trigger gagging, suggesting that visual and olfactory stimuli can significantly modulate the reflex.^10,11 Such patients may have had previous unpleasant experiences in the dental chair, which resulted in gagging. As such they may have learnt that similar future encounters with the dental profession may result in gagging.¹²

Iatrogenic factors which predispose a patient to gagging

Poorly executed dental treatment can produce the gag response on patients who previously had no history of gagging.³ Using oversized impression trays and overloading trays with impression material are able to stimulate triggers zones on the posterior tongue/pharyngeal mucosa and trigger gagging. Existing denture wearers may also gag as a result of faulty denture design. Incorrect design features include overextended lingual borders on mandibular dentures, overextended posterior pharyngeal borders on maxillary prostheses and loose/unretentive dentures. Such features may inadvertently stimulate gagging trigger zones and need to be corrected in the first instance.^6,11,13

Preparing a gagging patient for the primary impression

Systematic desensitization aims slowly to increase a patient's exposure to a stimulus that normally triggers gagging. Farrier et al suggested that gradually increasing some feature of the gagging stimulus (such as its size or the length of time it is in the mouth) will allow habituation and reduce the intensity of the gag reflex.²³ Various methods can be used as the desensitization stimulus, including dental mirrors and asking patients to massage their anterior soft palate with their own finger.

When confronted with an edentulous patient (with a moderate to severe gag reflex) requesting a maxillary denture, the patient could be provided with an edentulous stock tray to take home. Indeed, for some patients with a severe gag reflex, it may not be possible to take primary impressions at the first appointment. Patients are asked to keep the stock tray in their mouths for as long as possible when they are at home, but to remove the tray before they gag. Patients should be encouraged to keep the tray in their mouths for short, set periods of time and to remove the stimulus (even if patients do not feel that they may gag). Once patients are successful in keeping the tray in without gagging, they can gradually increase the length of time for which the tray is maintained in the oral cavity.²³

In accordance with Pavlov's studies, patients will start to develop a new conditioned reflex, where they will not gag, when they see or feel an impression tray in their mouths.²⁴

The primary impression appointment

Patients may need a few weeks or months of progressive desensitization with their stock trays at home before the primary impression can be made. We favour the use of a viscous, thixotropic impression material such as impression composition for the primary impression. Given the quick setting time of impression compound, the authors have recently been using the impression material to make the primary casts for a number of gagging patients. Figure 2 shows an impression of a patient who had all of her teeth extracted as she could not tolerate any form of operative dental treatment owing to the severity of her gag reflex.

Before taking the primary impression, a patient can be offered the opportunity to listen to music on his/her iPod or phone via earphones. This will minimize any auditory stimuli in the background (such as the impression material being prepared) that may have triggered a previous episode of gagging in the past. This will not only distract the patient but may also relax him/her. Patients can also be asked to close their eyes whilst the impression is being taken to minimize any exposure to visual dental stimuli that may trigger the gag reflex.^11,25 The clinician loads the impression material in the stock tray (without overloading it) and inserts it into the mouth. The head should be positioned forwards to prevent any impression material from flowing towards the oro-pharynx.

Once the impression is in the mouth, clinicians need to distract patients further by talking to them,²³ or even asking them to raise their leg during the impression-taking.¹³ Hoad-Reddick recommends that patients take inspirational breaths through their nose and expirational breaths via their mouth as the impression is taken. If patients feel a gagging attack coming on, they should slow down and deepen their breathing pattern, which will help to focus their attention on their breathing and reduce breath-holding.¹⁴

The clinician must make every attempt to record the entire denture-bearing anatomy of the edentulous maxillary arch with the primary impression whilst distracting the patient using the techniques described (Figure 2). Once the impression has been obtained, the patient should be congratulated for his/her efforts. If the original stock tray was used to make the primary impression, a new stock tray should be provided to continue using at home for desensitization.

The master impression appointment

Given the patient's hyperactive gag reflex, the use of a high viscosity material impression material, such as heavy bodied silicone/high viscosity alginate, is recommended for the master impression. A non-perforated, spaced special tray design is preferred as perforations within the tray will allow extrusion of the impression material and may precipitate gagging.²⁵

We have observed that patients who can tolerate a primary impression also tend to accommodate a master impression. The same techniques to distract the patient from a visual and auditory point of view can be used whilst taking the master impression. The extensions of the tray can be modified with thermoplastic green stick or pink isofunctional material. The authors build up the posterior aspect of the tray with a thermoplastic material (Figure 3a). This not only establishes a post dam, but will build up the palatal aspect of the tray and will prevent impression material from flowing down the oro-pharynx. For some patients with severe gagging problems, the authors may ask a patient to hold the tray in place to put him/her in control of the procedure (Figure 3b). The functional width of the sulci can be recorded with more thermoplastic material before applying adhesive to the special tray. A high viscosity impression material (like heavy-bodied silicone) can be introduced to the tray. The operator must ensure that the special tray is not overloaded. The tray is inserted intra-orally and the patient should be distracted, as described before, for the preliminary impression. The clinician must make every attempt to record the entire denture-bearing area (Figure 3c). This will optimize the retention of any prosthesis made on the master cast. Given the relatively long setting time of heavy-bodied silicone,²⁶ a severely gagging patient may not be able to tolerate the use of a silicone rubber. In such patients, a high viscosity alginate mix may have to be used as it will set more quickly. However, it should be cast relatively quickly.²⁶

Delivering the acrylic training plate

Once the master impression has been cast, the clinician should mark out the outline of the training base. The clinician should ensure that the plate extends to the full depth of the sulci, avoid any muscle attachments, engage any useful soft tissue undercuts and extend to the vibrating line and around both tuberosities. This will maximize the peripheral seal of the training appliance and will optimize its retention (Figure 4a). Some patients may not be able to tolerate a fully extended training plate to the vibrating line. The prosthesis may stimulate trigger zones in the oro-pharyngeal area and may induce gagging. As such, multiple post dams should be scribed into the master cast and incorporated into the definitive training plate (Figure 4b). The master cast (or a good quality duplicate of the model) should always be retained by the clinician, even after the plate has been delivered. Training plates could be constructed using pink or clear acrylic and it is advised to create a dull and matt surface finish by using a sandblasting technique.

At the fit appointment, clinicians need to educate patients and inform them that their palatal tissue and neuromuscular system may need time to tolerate the appliance fully. The patient should be given the plate and asked to insert it carefully in their mouths. If they gag significantly, the post dams should be sequentially removed from the most posterior region until a dam is reached which patients can tolerate.

The training base should be extended to the vibrating line to optimize the posterior seal. However, we have encountered numerous patients who could not tolerate such a wide base and therefore the appliance needed significant reduction to a more anteriorly positioned post dam. Surprisingly, a number of these patients were able to tolerate and retain (without adhesive) the adjusted plates, in spite of the fact that the plate was not positioned at the vibrating line. This has been noticed in a number of partially edentulous patients (Figure 5), completely edentulous patients (Figures 6a, b) and this is a finding that has been reported by other groups as well.²⁷ This suggests that some patients may retain their plates by controlling the polished surface of the appliances with their muscles of mastication.²⁸ A shortened dental arch approach could be used when constructing the prostheses (Figures 6c and d), as this is sufficient enough to maintain adequate oral function.²⁹

Bassi et al have recommended that patients should try and wear the plate once a day for 5 minutes, before steadily increasing the frequency of wear to twice a day for 5 minutes, three times a day for 5 minutes and so on.³ Patients should be asked to wear the plate when they are particularly busy, as the busy activity may distract them from the fact that they are wearing an appliance. However, the period of time patients can tolerate the plate will clearly depend on the severity of their gag reflex. Patients should be encouraged to keep a diary documenting the length of time for which they can retain the plate on a daily basis.

At subsequent review appointments, the diary can be analysed by the clinician and patients should be praised for their efforts. We have noted that severe gagging patients may need to wear their plates for a period of at least 3–6 months before they can tolerate wearing the plate throughout the day. However, this period of adaptation will clearly vary from patient to patient.

The definitive complete denture for the gagging patient

Once patients can tolerate their training bases without gagging, they should be provided with artificial teeth. A number of approaches can be employed. One option may be to retake the master impression of the maxillary edentulous and to have a wax rim constructed on it. However, some gagging patients are apprehensive about having a new impression taken.

An alternative approach would be to have a wax rim added to the patient's existing training plate. The wax rim should be carved to provide adequate lip support, incisal display, and should indicate to the technician the position of the teeth. An appropriate shade should be selected and a try-in appointment should be scheduled. The patient should evaluate the position and aesthetics of his/her new teeth at the trial appointment. Once satisfied, the teeth should be processed onto the plate. In the first instance, the addition of the anterior teeth (and even the premolar teeth if the patient has a broad smile) to the training plate should be considered. Once the patient has adapted to the anterior teeth, posterior teeth can also be added, if required. However, this approach requires processing new acrylic teeth onto a pre-existing, heat-cured acrylic resin training plate. If the training base is to be processed again to accommodate artificial teeth, there is a chance that the training plate may warp and distort.³⁰ An alternative approach may be to have the wax rim (on a rigid stable base) made on the patient's existing master cast. This rim can then be used to indicate the position of the artificial teeth before a new denture base is laid down and processed on the patient's master cast.

If the patient has an edentulous maxillary and mandibular arch, it is important for the clinician to bear in mind that the patient may request the provision of a mandibular denture in the future. As such, the clinician must ensure that he/she does not position the maxillary teeth at a level that will hinder the provision of a future mandibular prosthesis.