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Indian Journal of Dental Research, 23(3), 2012407

case report

Neutral zone and oral submucous fibrosis

Shaista Afroz, Sajjad Abdur Rahman1, Indresh Rajawat2, AK Verma2

Received : 06-05-11Review completed : 06-08-11Accepted : 20-01-12

ABSTRACTOral submucous fibrosis is a premalignant condition in which rigidity of the lip, tongue, and palate results in reduced mouth opening and tongue movement. Limited mouth opening, mucosal rigidity, and reduced salivary flow makes prosthodontic procedures difficult in these patients and affects the stability, retention, and the support of removable prostheses. The burning sensation in the mouth that these patients experience reduces the tolerance to prostheses. We report a case of oral submucous fibrosis where the conventional neutral zone technique with certain modifications was utilized to rehabilitate a completely edentulous patient with this condition.

Key words: Mucosal rigidity, neutral zone, oral submucous fibrosis

Department of Prosthodontics, 1Department of Oral and Maxillofacial Surgery, Dr Z A Dental College, AMU Aligarh, 2Department of Prosthodontics, Career Post-Graduate Institute of Dental Sciences, Lucknow, India

Address for correspondence: Dr Shaista Afroz E-mail: [email protected]

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DOI: 10.4103/0970-9290.102241

these patients. Mucosal rigidity and reduced salivary flow adversely affects the stability, retention, and the support of removable prosthesis and, in addition, the burning sensation in the mouth that these patients characteristically experience reduces the tolerance to the prosthesis.

CASE REPORT

A 55-year-old male presented with the chief complaint of ill-fitting maxillary and mandibular complete dentures and a burning sensation in the mouth. He gave history of betel nut chewing for 25 years. Thickened dense fibrous bands with blanching were observed on the buccal and labial mucosa, anterior lingual vestibule, and the hard and soft palate. Mouth opening was reduced and the inter-ridge space was 26 mm [Figure 1]. Based on these findings a clinical diagnosis of OSF was made.

Obtaining peripheral seal and placement of postpalatal seal was difficult because of the fibrosis and rigidity. There was reduction in the potential cubicle space of the mouth. The fibrous bands had resulted in a shallow vestibule and reduction in maxillary and mandibular denture-bearing areas. Decreased salivary flow resulted in poor retention and contributed to the intolerance to the prostheses.

The patient was advised to discontinue the habit of betel nut chewing; he was instructed in physiotherapy measures (e.g., opening and closing of mouth with maximum force); and he was prescribed multivitamin tablets and topical corticosteroids. An artificial salivary spray was also prescribed to reduce the discomfort. The patient was offered surgical correction of the fibrous bands but he refused. Fabrication of complete dentures using the neutral zone technique with some modifications was planned.

Oral submucous fibrosis (OSF) is an insidious-onset chronic disease that predominantly affects Indians and South-East Asians.[1] Consumption of chillies areca nut, nutritional deficiency, genetic susceptibility, altered salivary constituents, autoimmunity, and collagen disorders are the stated etiologic factors. Rigidity of lip, tongue, and palate, leading to reduced mouth opening and tongue movement, and intolerance to spicy food are the major complaints of these patients.[2] Discontinuation of the consumption of etiologic agents is an important preventive measure. Correction of nutritional deficiency is necessary. Local or systemic administration of immunomodulatory drugs like glucocorticoids help by preventing or suppressing inflammatory reactions, thus decreasing fibrosis by reducing fibroblastic proliferation and collagen deposition. Physiotherapy measures, such as opening and closing of mouth with maximum efforts and heat therapy, and surgical correction are the various strategies proposed for the management of reduced mouth opening seen in this disease.[3]

Limited mouth opening makes prosthodontic procedures – from the primary impression till insertion – difficult in

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408Indian Journal of Dental Research, 23(3), 2012

Neutral zone and oral submucous fibrosis Afroz, et al.

Technique• After making primary impressions in irreversible

hydrocolloid impression material (Zelgan 2002, Dentsply India Pvt. Limited), the final border molding was done conventionally, using low-fusing impression compound (DPI Pinnacle, Mumbai, India), and the final impression was made with metallic oxide impression paste (Septodont, Cidex, France). The posterior palatal seal was established at the final impression stage, using low-fusing impression compound.[4] The fluid wax technique can also be used.

• Maxillary bite rim was adjusted for lip support, phonetics, and esthetics and the occlusion plane was established.

• On mandibular trial denture base impression compound (Y-Dents, MDM Corporation, Delhi) was adapted in the shape of the residual ridge. It was softened uniformly in a warm water bath and inserted in the mouth. A cup of warm water was given to the patient to sip and he was instructed to sip and swallow several times. The procedure was repeated till the correct recording of the neutral zone was obtained [Figure 2].[5]

• The vertical dimension was recorded by reheating the mandibular bite rim.[6] The patient was guided in centric relation and instructed to swallow till both the rims touched lightly. This procedure resulted in the creation of an anterior stop. Excess material was trimmed. This tentative vertical dimension was evaluated by other techniques of recording vertical dimension, i.e., closest speaking space, vertical relation at rest, overall facial support, and the patient reported comfort. Centric relation was recorded using bite registration paste (3M, ESPE, Ramitec, Bangalore. India).

• The maxillary cast was mounted by a facebow transfer record, and the mandibular cast with the centric relation record.

• The addition-silicone putty (Aquasil, Dentsply, Germany) was used to make neutral zone index. One rope was molded into the tongue space and another one on the labial and buccal surface of the neutral zone record [Figure 3]. We ensured that it completely filled in the tongue space, level with the occlusal plane, and extended up to the posterior land area of the cast. After polymerization, the index was checked on the cast without record to ensure complete seating.[7]

• Semi-anatomic teeth (Lactodent, Pyrex Polychem, Roorkee, India) were selected for this patient. Maxillary and mandibular anterior teeth were arranged to satisfy the esthetics and phonetics, and the mandibular posterior teeth were arranged within the recorded neutral zone, touching the lingual index and at the level of recorded occlusal plane. The maxillary teeth were arranged in maximum intercuspation with the mandibular teeth.

• Metallic oxide paste was used to develop a polished surface contour [Figures 4 and 5]. Polyvinyl siloxane

light body can be used alternatively. To record the facial aspect of the maxillary trial denture, the patient was instructed to pucker his lips forward, smile broadly, open the mouth, and move the mandible side to side. The palatal surface was recorded by asking the patient to sip, swallow, and produce fricative and sibilant sounds.[7]

• Mandibular labial and buccal surfaces were recorded by asking the patient to pucker his lips and move the mandible side to side. Finally, the mandibular lingual surface was recorded by asking the patient to sip and swallow water several times, protrude the tongue and touch the anterior palate, move the tongue from side to side, and lick the upper and lower lips.

• Investment, processing, laboratory remounting, finishing, and polishing were done conventionally.

• The prosthesis was relined with permanent resilient denture liner (GC Lab Technologies Inc, USA). For this, 0.5 mm of the acrylic was removed from the tissue surface and the borders. A closed-mouth impression was taken with light body polyvinyl siloxane (Aquasil Ultra LV). The denture was invested and the impression material was replaced by permanent soft liner.

• After processing, finishing, and polishing, a clinical remount was performed by a new centric record and occlusal refining was done on the articulator.

• After insertion, the patient was recalled for postinsertion adjustment at 48 hours and then asked to come for periodic checkup, initially at 1-month intervals to look for any signs of intolerance to the prosthesis in the form of redness and ulceration and, later, at 6-month intervals for the maintenance of oral health.

DISCUSSION

In this case, the neutral zone technique as suggested by Schiesser and Beresin, with modifications, was utilized to fabricate the complete denture prostheses.[5] Since in oral SMF the rigidity of the tongue, lips, and cheeks occur due to progressive fibrosis of their muscles, the available space for denture teeth placement is altered; hence, utilization of the neutral zone concept to achieve the coordination of complete denture with the existing neuromuscular function was beneficial in this case.

The neutral zone is that area where the outward forces exerted by the tongue are neutralized by the inward forces exerted by the cheeks and lips during various functions such as chewing, swallowing, and speaking and while making various facial expressions.[5,8] These forces may vary in magnitude and direction in different areas of the oral cavity, in different individuals, and at different periods of the life. Different conditions may also alter this potential space, for example, oral cancer (resulting in mandibulectomy and glossectomy), oral SMF, trauma, burns, etc.[9,10]



Indian Journal of Dental Research, 23(3), 2012409


Figure 4: Polished surface of the maxillary denture recorded using metallic oxide paste.

Figure 5: Polished surface of the mandibular denture recorded using metallic oxide paste.

During the prosthodontic rehabilitation phase, the most difficult step is the insertion of the loaded impression tray and the final prostheses. Various modifications in the form of sectional impression trays with locking levers,[11] collapsible denture,[12] and sectional dentures[13] made in flexible denture material are reported in the literature. Most of these studies deal with fabrication of prostheses

for partially edentulous patients, where the presence of teeth poses an additional problem. In this patient, the inter-ridge space was reduced to 26 mm so the making of impression of individual arch was not a problem. The

Figure 2: Neutral zone record in impression compound.

Figure 3: Neutral zone index in putty on the mandibular cast

Figure 1: Inter-ridge distance at the reduced mouth opening.

Figure 6: Patient with the final prosthesis.



410Indian Journal of Dental Research, 23(3), 2012


only difficulty was when both the rims were to be inserted simultaneously. For that reason, the vertical dimension was recorded simultaneously with the neutral zone recording, with the mandibular bite rim made in softened impression compound. Also, the final vertical dimension was established at that reduced mouth opening so that the insertion of the final denture was not a problem.

Because of the fibrosis of the muscles, the vertical relation at rest and vertical relation at occlusion are expected to be altered. In one study it was found that neutral zone changed with change in vertical dimension, based on it decision was taken to record the neutral zone and the vertical dimension simultaneously.[14]

Since the harmony between the polished denture surface and the surrounding tissues during function is important, it was recorded using metallic oxide impression paste after the try-in.

Since the patient gave history of intolerance to prostheses, relining the prostheses with a permanent soft liner was done to provide a cushioning effect and thus increase patient acceptance [Figure 6]. A similar technique can be used for designing an implant-supported overdenture for better neuromuscular adaptation by the patient.

CONCLUSION

In this patient, the conventional complete denture was fabricated utilizing the neutral zone technique with modifications to meet with patient’s special requirements. The patient was recalled periodically to check the tissue response and the results have been satisfactory.

REFERENCES

1. Neville BW, Allen CM, Damm DD, Bouquot JE. Oral and maxillofacial pathology. Philadelphia: WB Saunders company; 1995.

2. Tilakaratne WM, Klinikowski MF, Saku T, Peters TJ, Warnakulasuriya S. Oral submucous fibrosis: Review on aetiology and pathogenesis. Oral Oncol 2006;42:561-8.

3. Rajendran R. Oral submucous fibrosis: Etiology, pathogenesis, and future research. Bull World Health Organ 1994;72:985-96.

4. Ansari IH. Establishing the posterior palatal seal during the final impression stage. J Prosthet Dent 1997;78:324-6.

5. Beresin VE, Schisser FJ. The neutral zone in complete denture. J Prosthet Dent 1976;36:357-67.

6. Alfano SG, Leupold RJ. Using the neutral zone to obtain maxillomandibular relationship records for complete denture patients. J Prosthet Dent 2001;85:621-3.

7. Cagna DR, Massad JJ, Schiesser FJ. The neutral zone revisited: From historical concepts to modern applications. J Prosthet Dent 2009;101:405-12.

8. The Glossary of Prosthodontic Terms 8th ed. J Prosthet Dent 2005;94:10-92

9. Wee AG, Cwynar RB, Cheng AC. Utilization of the neutral zone technique for a maxillofacial patients. J Prosthod 2000;9:2-7.

10. Ohkubo C, Hanatani S, Horoi T, Mizuno Y. Neutralzone approach for denture fabrictation for a partial glossectomy patient; a clinical report. J Prosthet Dent 2000;84:390-3.

11. Baker PS, Brandt RL, Boyajian G. Impression procedure for patients with severely limited mouth opening. J Prosthet Dent 2000;84:241-4.

12. Ohkubo C, Watanabe I, Tanaka Y, Hosoi T. Application of cast iron-platinum keeper to a collapsible denture for a patient with constricted oral opening: A clinical report. J Prosthet Dent 2003;90:6-9.

13. Al-Hadi LA. A simplified technique for prosthetic treatment of microstomia in a patient with scleroderma: A case report. Quintessence Int 1994;25:531-3.

14. Razek MK, Abdulla F. Two dimensional study of the neutral zone at different occlusal vertical heights. J Prosthet Dent 1981;46:484-9.

How to cite this article: Afroz S, Rahman SA, Rajawat I, Verma AK. Neutral zone and oral submucous fibrosis. Indian J Dent Res 2012;23:407-10.Source of Support: Nil, Conflict of Interest: None declared.



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