Volume 18, Issue 1
Prosthodontics

Neutral Zone Technique for an Atrophic Mandibular Ridge

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CHTIOUI Hajer - DDS
Assistant Professor; Removable Prosthetics Department, ABCDF laboratory, Faculty of Dental Medicine, University of Monastir Tunisia - hajer.chtioui@gmail.com

BEKRI Sana - DDS
Associate Professor; Removable Prosthetics Department, ABCDF laboratory, Faculty of Dental Medicine, University of Monastir Tunisia - sanabekri2015@gmail.com

OUNI Imed - DDS
Associate Professor; Removable Prosthetics Department, ABCDF laboratory, Faculty of Dental Medicine, University of Monastir Tunisia - imed_o@yahoo.fr

MANSOUR Lamia - DDS
Professor; Removable Prosthetics Department, ABCDF laboratory, Faculty of Dental Medicine, University of Monastir Tunisia - mansourlamia64@yahoo.fr


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CHTIOUI Hajer, BEKRI Sana, OUNI Imed, MANSOUR Lamia. Neutral Zone Technique for an Atrophic Mandibular Ridge. Smile Dental Journal. 2023;18(1):04-07.

 

ABSTRACT

Conventional mandibular complete denture for patient with severe ridge resorption is challenging. The dental implant therapy may be a fascinating option for improving retention and stability however the neutral zone approach is an important alternative when implant therapy is impossible.

Hence, residual ridge resorption becomes a challenging scenario for a clinician during fabrication of complete dentures. The neutral zone concept plays a significant role in overcoming these challenges.

The neutral zone philosophy is based on the concept that for each individual patient there exists within the denture space a specific area where the function of the musculature will not unseat the denture and at the same time, where the forces generated by the tongue are neutralized by the forces generated by the lips and cheeks. Furthermore, denture stability is as much or more influenced by tooth position and flange contour as by any other factors.

The modified neutral zone technique enhanced the stability of the partial denture. A marked improvement in esthetics, function and psychology was noticed.

KEYWORDS

Neutral zone technique, Prosthetic rehabilitation, stability, atrophic mandibular ridge.

INTRODUCTION

The unstable mandibular complete denture is a fundamental yet challenging scenario for dentist. Residual ridge resorption is a chronic, progressive, irreversible, and disabling disease, probably of multifactorial origin (an inevitable and natural physiologic process).1

Implant placements have been proved to be a good alternative but, in many cases, this procedure is not possible due to financial issues. Maximum stability of the partial denture base may be accomplished by a functional impression procedure and by eliminating lateral and horizontal forces caused by the functional movements of the lips, cheeks and tongue.2

 

The goal of this technique is to place the teeth such that the forces exerted by the tongue and the cheek muscles are nullified, and the teeth remain in a safe. It is also known as dead zone,3 stable zone, zone of minimal conflict, zone of equilibrium, zone of least interference.4

Unfortunately, it isn’t a widely practiced procedure; this may be attributed to a lack of knowledge and experience of clinicians to this technique.

In this clinical case, we go to describe step by step this approach.

CASE REPORT

A healthy 64-year-old male was referred to the removable partial dentures department-Dental Clinic, Monastir-Tunisia for prosthetic rehabilitation. His main chief complaint was functional, He complained about his old denture unstable to mastication and phonation.

The clinical examination revealed a partial maxillary edentulous and a thin resorbed mandibular ridge. (Fig. 1)

A preliminary impression of the partially edentulous maxillary was made with irreversible hydrocolloid impression material, a lead wire was adjusted on the mandibular ridge, it served as a support for the impression material (permaplastic), the wire was filled with impression material and inserted in the mouth, the impression was checked and each time we did the relining until the perfect registration of all the mandibular ridge. (Fig.2)

The impressions were immediately cast in dental plaster, and primary casts were prepared.

The secondary impressions of upper and lower arches were performed using the conventional method. (Fig. 3)

THE PIEZOGRAPHIC BASE

The base were carefully examined and adjusted in the patient mouth to reduce any over extension or interference from tongue movement and lip. Any under extended border should be corrected.

It should be stable during speaking, swallowing and mouth opening.

MATERIAL

The ideal material must meet the criteria stability and fidelity. It must have an enough slow plasticity time to allow the various manipulations. We used auto polymerized resin.

The phonation was chosen as vector of the piezographic approach by making the patient pronounce certain phonemes by the repetition of a standard sequence (sis, sis, so, te, pe, de) until the setting reaction of the material is completed. The patient was then asked to speak, swallow to remove excess material and release the play of the various muscles concerned. (Fig. 4a,b)

Two silicone keys were made to determine the prosthetic corridor where the space between the lips and cheeks on one side, and the tongue on the other; that area where the forces are equal. (Fig. 4c)

Then, the recording base and occlusion rim base were fabricated; they were made of auto polymerized resin. (Fig. 5a)

The upper recording base with wax rim was inserted.

The occlusal plane, phonetics and lip support were checked.

The lower recording base was then inserted to verify the vertical dimension of occlusion. The wax adjusted to ensure it is in contact with the upper at centric relationship in proper VDO. The maxillary and mandibular occlusal rims were articulated. (Fig. 5b)

The artificial teeth were positioned in the neutral zone; the mandibular denture was again evaluated with silicone key prior to denture insertion. (Fig. 5c)

Vertical dimension, centric relation, esthetics and phonetics were rechecked during denture try-in. (Fig. 6b)

After processing, finishing and polishing, the dentures were delivered to the patient and tested for stability, retention, intercuspal relation, esthetics and phonetics. (Fig. 6c)

The new dentures successfully improved stability comfort and function for the patient.

 

DISCUSSION

In the field of oral rehabilitation, particularly in geriatric prosthodontics, many factors contribute to the overall performance of complete dentures. It’s a general experience that the lower denture is relatively less stable than the upper one with increasing life expectancy, agerelated reduction in adaptability, and progressive severe mandibular resorption. One of the philosophies being introduced to overcome the challenge of unstable dentures in clinics is the concept of the neutral zone.1

The neutral zone technique described in this article is simplified to record the physiological dynamic of oral and perioral muscle function.

The principle of the neutral zone concept remains the same since it had been described.

However, the neutral zone impression technique has various modification, not only in terms of impression material used but also in terms of the functional.3,5,6,7

Various material have been recommended by different authors for recording neutral zone as: soft wax, silicone, polyether.2,7,8,9

Different functional movement have also been reported by different prosthodontist.5,9,10

Some clinicians recorded the neutral zone with the maxillary denture or recording base,2,3 however, some others recorded the neutral zone without inserting any thing in the upper arches.

To achieve optimum success in complete denture prosthesis, the dentures should be both retentive and stable. The retention of a denture is mainly dependent on the accuracy of the impression and fit of the denture base to the tissues.10

 

CONCLUSION

The neutral zone philosophy is based on the concept that for each individual patient there exists within, the denture space, a specific area where the function of the musculature will not unseat the denture and, at the same time, where the forces generated by the tongue are neutralized by the forces generated by the lips and cheeks.11

In other words, we should not be dogmatic and insist that the teeth should always be placed over the crest of the ridge, or lingual to the ridge or buccal to the ridge. Placement of the teeth should be dictated by the musculature and will vary for different patients.

 

Functional and aesthetic dental treatments for patients with atrophic ridges are an inestimable service provided by a prosthodontist. The technique has proved to be efficient for patients who are not satisfied with mandibular dentures. Complete and partial denture failures are often related to noncompliance with neutral zone factors.

REFERENCES

  1. Prathibha Saravanakumar, Saravanan Thirumalai Thangarajan, Umamaheswari Mani, Anand Kumar V. Improvised Neutral Zone Technique in a Completely Edentulous Patient with an Atrophic Mandibular Ridge and Neuromuscular Incoordination: A Clinical Tip. Cureus. 2017; 9(4):1189. DOI 10.7759/cureus.1189
  2. Shuchi Tripathi, Vibha Singh, Saumyendra V Singh, Deeksha Arya. Modified Neutral Zone Technique for the Partial Mandibulectomy. Patient International Journal of Prosthodontics and Restorative Dentistry. 2012;2(4):146-9.
  3. Christopher D Lynch, P Finbarr Allen. Overcoming the unstable mandibular complete denture: the neutral zone impression technique. Dent Update. 2006;33(1):21-2, 24-6.
  4. Raybin NH. The polished surface of complete dentures, J. Pros. Den. 1963;13(2):236-9.
  5. V E Beresin, F J Schiesser. The neutral zone in complete denture. J Prosthet Dent. 1976;36(4):356-67.
  6. David R Cagna, Joseph J Massad, Frank J Schiesser. The neutral zone revisited: from historical concepts to modern application. J Prosthet Dent. 2009;101(6):405-12.
  7. Yi-Lin Yeh, Yu Hwa Pan, Ya-Yi Chen. Neutral zone approach to denture fabrication for a severe mandibular ridge resorption patient: Systematic review and modern technique. Journal of Dental Sciences. 2013;8(4); 432-8.
  8. Berrenas L, Odman P. Myodynamic and conventional construction of complete dentures: a comparative study of comfort and function. J Oral Rehabilitation. 1989;16(5); 457-65.
  9. F Lott, B Levin. Flange technique: an anatomic and physiologic approach to increased retention, function, comfort, and appearance of dentures. J Prosthet Dent. 1966;16(3):394-413.
  10. Gahan MJ, Walmsley AD. The neutral zone impression revisited. Br Dent J. 2005;198(5):269-72.
  11. Virag Srivastava, NK Gupta, Amrit Tandan, Laxman Singh Kaira, Devendra Chopra. The Neutral Zone: Concept and Technique. The Neutral Zone: Concept and Technique. Journal of Orofacial Research. 2012;2(1):42-7.

 

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