Knowledge and Awareness among Dental Students on the use of Neutral Zone Technique for Fabrication of Complete Dentures

Priyanka Shenoy B, Vinoth Kumar Sengottaiyan

Department of Prosthodontics, Saveetha Dental College, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, India.

*Corresponding Author E-mail: doctor.vinoth.kumar@gmail.com

Abstract:

AIM: The aim of this study is to evaluate the knowledge and awareness among dental students on the use of neutral zone technique for fabrication of complete dentures. BACKGROUND: The stability of complete dentures is influenced by the surrounding neuromuscular system in the oral cavity. The retention and stability of complete denture become unfavorable when ridge resorption gets more severe, especially in the mandible. The neutral zone technique is an alternative approach for the construction of lower complete dentures. It is most effective where there is a highly atrophic ridge and a history of denture instability. The technique aims to construct a denture that is shaped by muscle function and is in harmony with the surrounding oral structures. The technique is by no means new but is a valuable one. METHODOLOGY: A self administered questionnaire containing 10 questions will be prepared and circulated among 100 dental students belonging to two different colleges. Data collection and analysis will be done based on frequencies and percentage values. REASON: The neutral zone technique is most effective for patients who have had numerous unstable, unretentive lower complete dentures. This study aims at assessing the knowledge and awareness among dental students on the use of neutral zone technique for fabrication of complete dentures. From the results obtained in this survey, the knowledge and awareness about the neutral zone technique seems to be just above average and hence there is reduced incidence of practice of this technique. Thus, there is still in need for continued education about the technique and a need for motivation to adopt it in practice.

KEY WORDS:

INTRODUCTION:

The ultimate goal of dentistry is to keep all the teeth of an individual healthy and in comfort throughout his life. If however teeth are lost despite all efforts to save them, the prosthesis should be fabricated in such a manner so as to function efficiently and comfortably [1].

The Complete loss of the tooth leads to the disability, impairment and handicap. Thus the Restoration of the dentition leads to an improvement in the oral health related quality of life. Complete dentures are used to restore the oral cavity into its original condition [2]. These complete dentures are nothing but primarily mechanical appliances, but since they function in the oral cavity, they must be designed in such a way that they are in harmony with the normal neuromuscular system. [3] The primary and the main objectives of complete denture prosthesis is to construct dentures that will satisfy the three requirements that are basic to the edentulous patient: maximum comfort, efficiency and the aesthetics. This objective can be achieved only if the dentures are both stable and retentive.[4] The major goals of providing complete denture prosthesis to an edentulous patient include the provision of functionally aesthetic substitutes and the replacement of associated structures within the oral cavity [5].

The stability of complete dentures is influenced by the surrounding neuromuscular system in the oral cavity. Functions of the oral cavity, such as swallowing, mastication, smiling, speech, and laughing, involve the synergistic actions of the cheeks , lips, tongue, and floor of the mouth that are very complex and highly individual [6]. The key for the stability of dentures is the neuromuscular control. Size and position of denture teeth and the contours of polished surface play a crucial role in denture’s stability as they are subjected to destabilizing forces from the tongue, lips, and cheeks if they interfere with the function of oral structures [7].

General dental practitioners and prosthodontists alike usually encounter problems when making complete dentures for patients with atropic residual ridges [8]. This problem is commonly encountered in mandible [9] and it is difficult to achieve retention and stability in mandibular dentures as compared to the maxillary ones. Unstability in mandibular complete dentures may be present due to a number of reasons. The common ones, as described by Jagger & Harrison [10] are:

a) Inappropriate extensions of buccal and lingual flanges of a denture;

b) Poorly adapting denture fitting surface;

c) Severely atropic mandibular alveolar ridge;

d) Poorly contoured polished surfaces of a denture;

e) Abnormal denture teeth positions, inappropriate orientation and high level of the occlusal plane and presence of occlusal errors.

The retention and stability of complete denture become unfavorable when ridge resorption gets more severe, especially in the mandible [11]. In these cases, the Stability of mandibular complete denture is a difficult treatment aim to achieve because of the continuous reduction of residual ridge size and its proximity to limiting structures [12]. Dental implants or overdentures could stabilize the mandibular complete dentures in the case of atrophic mandible. But there may be some situations when it is not possible to provide implants. They may be medical, surgical or cost factors. The neutral zone technique can be used as an alternative approach for these type of complex cases. This neutral zone technique is not new but is one that is valuable and yet not practised often [13].

The neutral zone is more effective for patients who have had numerous unstable, unretentive lower complete dentures [14]. It is not only a treatment of choice in atrophied mandible but also in patients with partial glossectomy, mandibular resection or motor nerve damage to the tongue which have led to either atypical movement or an unfavourable denture bearing area [15].

The Glossary of Prosthodontic Terms [16] define the denture space as “the portion of the oral cavity that is or may be occupied by the maxillary and/or mandib- ular denture(s) or the space between and around the residual ridges that is accessible for dentures”. The neutral zone is also known as zone of minimal conflict. It exists between the lingual and buccal musculature within which the polished surfaces of a denture should be placed ideally [17], [18]. Neutral zone is defined as that region in the oral cavity where forces produced by the tongue directed outward are balanced by inward forces originating from the lips and cheeks during normal neuromuscular function [7].

Various terminologies has been given to this concept such as dead zone, stable zone, zone of minimal conflict, zone of equilibrium, zone of least interference, biometric denture space, denture space and potential denture space [19]. The neutral zone technique is an alternative solution for such cases. The musculature surrounding the neutral zone is divided into two groups. First being those muscles which dislocate the denture primarily during activity. The Second one being the muscles that fix the denture on its secondary supporting surfaces by muscular pressures [20]. Dislocating muscles are i. Vestibular: masseter, mentalis, incisivuslabiiinferioris. ii. Lingual: internal pterygoid, palatoglossus, styloglossus, mylohyoid. Fixing muscles are i. Vestibular: buccinator, orbicularisoris. ii. Lingual: genioglossus, lingual longitudinal, lingual vertical, lingual transverse. [19]

The central thesis of this neutral zone technique lies in identifying the location in the edentulous oral cavity where the teeth should be positioned so that the muscle forces will tend to stabilize the denture rather than to loosen it [21]. Hence, this study aims to access knowledge and awareness among dental Students on the use of neutral zone technique for fabrication of complete dentures.

MATERIALS AND METHODS:

A cross-sectional study was conducted in Saveetha Dental College, Chennai. A total of 100 dental students were selected randomly. All the participants were distributed a self structured questionnaire and were assured of their anonymity. The study participants voluntarily completed the questionnaire which consisted of 10 questions. The questionnaire included questions which would assess their knowledge and awareness about the neutral zone technique for the fabrication of complete dentures. The data obtained was subjected to statistical analysis using SPSS software.

The questionnaire consisted of following questions:

1) Do you think neutral zone technique is not an important technique in compete denture fabrication?

A. Yes

B. No

C. Not sure

2) Do you or any of your colleagues practice neutral zone technique?

A. Yes

B. No

C. Not sure

3) Do you think neutral zone technique is an added advantage in a compromised and resorbed Ridge?

A. Yes

B. No

C. Not sure

4) where is a neutral zone present?

A. Between upper and lower teeth

B. Between teeth present on each side of the same arch

C. Between tongue and cheek

5) Can neutral zone technique be employed for maxillofacial prostheses fabrication?

A. Yes

B. No

C. Not sure

6) Do you think carving, festooning and contouring of polished surfaces are essential for a compete denture fabricated using neutral zone technique?

A. Yes

B. No

C. Not sure

7) Do you arrange teeth exactly over the crest of the Ridge in neutral zone technique?

A. Yes

B. No

C. Not sure

8) Neutral zone techniques does not improve

A. Retention

B. Stability

C. Fractures resistance of the denture

9) Do you think neutral zone technique is difficult to learn and practice?

A. Yes

B. No

C. Not sure

10) Are you being or had you been ever taught about neutral zone technique in your under graduate period?

A. Yes

B. No

C. Not sure

RESULTS:

Graph 1 – Response to question 1

Graph 1 represents the importance of neutral zone technique for the fabrication of complete dentures. Among 100 participants, 13% think that neutral zone is not important for the fabrication of complete dentures, 52% think that that it is important for the complete denture fabrication whereas 35% are not sure about its importance in fabrication.

Graph 2 –Response to question 2

Graph 2 represents the practice of neutral zone technique. Among 100 participants, 10% practice the neutral zone fabrication technique for the complete denture, 75% don’t practice this technique whereas 15% are not sure.

Graph 3 – Responds to question 3

Graph 3 indicates the knowledge of the dental students about the advantage of neutral zone technique. Among 100 participants, 50% feel that the neutral zone technique is an advantage in compromised and resorbed ridge, 15% feel that it is not an advantage whereas 35% were not sure about the advantage.

Graph 4 – Responds to question 4

Graph 4 indicates the knowledge about the location of neutral zone. Among 100 participants, 37% of the dental students think that neutral zone is present between the upper and the lower teeth, 20% think that it is present between the teeth present on each side of the same arch, 43% think that it is present between tongue and cheek.

Graph 5 – Respond to question 5

Graph 5 indicates the knowledge about whether the neutral zone technique be employed for maxillofacial prosthesis fabrication. Among 100 dental students that participated, 62% think that this neutral zone technique can be employed for maxillofacial prosthesis fabrication, 13 % feel that it cannot be employed for the fabrication of maxillofacial prosthesis whereas 25% of them were not sure.

Graph 6 – Responds to question 6

Graph 6 indicates the the knowledge about arrangement of teeth in the neutral zone technique. Among 100 participants, 32% that the arrangement the teeth should be exactly over the crest in neutral zone technique, 25 % don’t think that the teeth is not arranged exactly over the crest whereas 43% of the participants were not sure about the arrangement.

Graph 7 – Response to question 7

Graph 7 indicates the knowledge about the need of carving, festooning and contouring for the complete dentures fabricated using this neutral zone technique. Among 100 participants, 30% think that it is essential to carve, festoon and contour the complete dentures fabricated using this neutral zone technique, 20% think that is not essential to carve, festoon and contour whereas 50% were not sure.

Graph 8 – Response to question 8

Graph 8 indicates the knowledge about the dental students about the factors that the neutral zone technique does not improve. Among 100 dental students that participated, 33% think that the neutral zone technique does not improve retention, 30 % think that the neutral zone fabrication technique does not improve stability, 37% think that the neutral zone technique does not improve fracture resistance of the denture.

Graph 9 – response to question 9

Graph 9 represents the difficulty of the neutral zone technique to learn and practice. Among 100 participants, 53% think that this technique is difficult to learn and practice, 10% feel that neutral zone technique is not difficult to learn and practice, where as 37% were not sure.

Graph 10 – response to question 10

Graph 10 indicates that among 100 dental students that participated, 57% are being taught or had been taught about the neutral zone technique in the undergraduate period, 16% think that it has not been taught in the undergraduate period and 27% were not sure about this.

DISCUSSION:

Provision of the complete denture in mandible is often difficult when compared to a a maxillary complete denture and it becomes even more difficult when powerful activity of oral musculature exists. Dental implants are a good alternative option for treatment in such scenarios however; they may be contraindicated in patients due to a variety of reasons which may be economic, clinical, and medical contraindications of the patient. Fabrication of dentures using neutral zone technique may help in overcoming these difficulties [5].

The concept of neutral zone plays an important role in complete denture fabrication.The need for neutral zone was stressed as early as 1931 by Fish [22,23]and 1954 by Earl Pound [24].The aim of the neutral zone is to construct a denture in muscle balance. That is a denture which is in harmony with its surroundings to provide optimum stability, retention and comfort [13]. Thus, a denture fabricated using the neutral zone technique will have better retention, stability and aesthetics due to good facial support.[5]

When the ridge is severely resorbed, gaining retention and stability in a denture becomes a challenge. The Positioning of the artificial teeth and connection of the polished surfaces with the surrounding tissues are the two major factors that determine success in complete denture therapy. When artificial teeth are arranged within the neutral zone, the prosthetic teeth do not interfere with the normal oral function. This technique typically helps to locate posterior denture teeth in a slight facial position rather than their arrangement over the crest of alveolar ridge [25].

Denture fabricated over a severely resorbed mandibular ridge by neutral zone impression technique will insure that the muscular forces aid in the retention and stabilization of the denture rather than dislodging it during function. The dentures will also have other advantages such as reduced food lodgment, good esthetics due to facial support, proper positioning of the posterior teeth which allows sufficient tongue space [12].

Clinical studies have shed light on the advantages of using the neutral zone technique. Stromberg and Hickey in 1965 found better patient adaptability to physiologically formed denture bases when compared with conventional ones [26].

In another clinical study, Fahmy and Kharat reported greater comfort and improved speech clarity with dentures fabricated using the neutral zone technique compared with their conventionally prepared dentures [27] . The neutral zone denture functionally contours all the polishing surfaces of the denture and this may be an important contributing factor to better speech and comfort [28].Barrenas and Odman found less postinsertion problems and better patient acceptance in neutral zone dentures when compared with conventional ones [29] These studies suggest that the neutral zone concept for denture fabrication may be helpful in certain edentulous situations.

Sharif in his study of a comparison of complete patient satisfaction levels between a group where the neutral zone technique and another group where the conventional technique was used reported significant differences between the two groups. Patients for whom the modified neutral zone technique was used had significantly greater satisfaction levels in comparison to the group where the conventional technique was employed.[2]

CONCLUSION:

From the results obtained in this survey, the knowledge and awareness about the neutral zone technique seems to be just above average and hence there is reduced incidence of practice of this technique. Thus, there is still in need for continued education about the technique and a need for motivation to adopt it in practice.

The neutral zone technique for denture fabrication has an advantage that it stabilizes the denture with the surrounding soft tissues, instead of being dislodged by them. Retention and stability of dentures are greatly improved, especially in the severely atrophic ridges. This approach can be also be easily used for limited oral opening cases as it offers an alternative technique for patients with partially resected mandible for whom the insertion of conventional impression trays is impossible. The aim of the neutral zone is to design a denture in the balance of muscles, as muscular control will be the main retentive and stabilising factor during function.The disadvantage of this neutral zone technique involves the laboratory aspect. Increased time and in the laboratory and cost are necessary, and the laboratory technician must be trained to support this clinical procedure.

Considering the benefits of this technique, it is recommended that clinicians should incorporate it in their routine prosthodontic management of edentulous patients.

REFERENCES:

1. Bhorgonde D, Nandakumar K, Khurana PR, Kumari VS, Reddy MS, Siddique S. An evaluation of the position of the neutral zone in relation to the crest of mandibular alveolar ridge-An In-vivo study. Journal of international oral health: JIOH. 2014 Apr;6(2):45.

2. Tasleem R, Saeed MH, Javed MU. ComparisionOf complete Denture fabricated by two different bordermoldingmateriald, in terms of patient satisfaction. Journal of Ayub Medical College Abbottabad. 2013 Jul 1; 25(3-4):78-80.

3. Zarb GA, Hobkirk J, Eckert S, Jacob R. Prosthodontic treatment for edentulous patients, 8th ed. St. Louis;CV Mosby Co.; 1975. p. 436-43.

4. Boucher CO. Complete denture prosthodontics - The state of art. J Prosthet Dent 1975; 34:372-82.

5. Arora V, Nagpal V, Setia P, Mittal N. Complete Denture in Neutral Zone: Case Report.

6. Yeh YL, Pan YH, Chen YY. Neutral zone approach to denture fabrication for a severe mandibular ridge resorption patient: Systematic review and modern technique. Journal of dental sciences. 2013 Dec 1;8(4):432-8.

7. Beresin VE, Schiesser FJ. The Neutral Zone in Complete and Partial Dentures. St. Louis: C.V. Mosby Co., 1978.

8. Pinar K, Nilgun A, Calikkocaoglu S. Using Tissue Conditioner Material IN NEUTRAL ZONE TECHNIQUE. NY State Dent J. 2007; 73: 40-42.

9. Lynch CD, Allen PF. Overcoming the mandibular unstable denture: The neutral zone impression technique. Dent Update. 2006; 33: 21-26.

10. Jagger D, Harrison A. Complete Dentures- problem solving. London; BDJ Books. 1999.

11. Adell R, Lekholm U, Rockler B, Bra ̊nemark PI. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981; 10:387e416.

12. Anand KR, prasad KB. Neutral zone impression technique for mandibular compromised ridges:A case report. Int J Dent Med Res 2014:1(4):79-82.

13. Gahan MJ, Walmsley AD. The neutral zone impression revisited. British dental journal. 2005 Mar 12; 198(5):269.

14. kaur A, Padikaraneer N et.al. Neutral Zone Technique for Rehabilitation of Reseorbed Mandibular Ridge. J Mahatma Gandhi Univ Med Sci Tech 2016; 1(1): 35-38.

15. Victor E Beresin. The neutral zone in complete dentures. J prosthet dent 2006; 95:93-100.

16. Academy of prosthodontics. The glossary of Prosthodontics terms. 8th ed. J Prosthet Dent 2005; 94:22. 46,60.

17. Fish EW. Principles of full denture prosthesis. 1st ed. London; Staples press.1933.

18. Basker RM, Davenport JC. Prosthetic treatment of edentulous patient. 4th ed. Oxford; Blackwell Munksgaard, 2002.

19. Revathy Gounder et.al. Prosthodontic Management Of Severely Atrophied Maxillary And Mandibular Ridges - A Clinical Report. Indian Journal of Dental Sciences. October 2015 Supplementary Issue, Issue: 4, Vol.:7.

20. N.Brill, G.Tryde and R.Cantor. The dynamic nature of the lower denture. J. Prosthet. Dent.1965; may-june, vol15, no.3, 401-418.

21. Beressin VE, Schiesser FJ. Neutral zone in complet denture. J Prosthet Dent 1976; 36:356-67.

22. Fish EW. Tongue space in full denture construction.Br Dent 1947; 83:137-42.

23. Fish EW. Principles of full denture prosthesis, 5th ed. London: Staples Press Ltd.; 1964.

24. Pound E. Lost fine art in the fallacy of ridges. J Prosthet Dent 1954; 4:6-16.

25. Boucher CO. Complete denture prosthodontics – The state of the art. J Prosthet Dent 1975; 34:372-383.

26. Stromberg WR, Hickey JC. Comparison of physiologically and manually formed denture bases. J Prosthet Dent 1965; 15: 213e26.

27. Fahmy FM, Kharat DU. A study of the importance of the neutral zone in complete dentures. J Prosthet Dent 1990; 64:459e62.

28. Şebnem Begüm Türker, Ender Kazazoğlu et al. Using a Modified Neutral Zone Technique to Obtain Maxillary and Mandibular Impressions in 1 Stage for Construction of a Denture for a Mandibular Defect Patient: A Technical Report. Balk J Stom, 2008; 12:107-111.

29. Barrenas L, Odman P. Myodynamic and conventional construction of complete dentures: a comparative study of com- fort and function. J Oral Rehabil 1989; 16:457e65.

Received on 12.08.2018 Modified on 29.09.2018

Research J. Science and Tech. 2018; 10(4):261-269.

DOI: 10.5958/2349-2988.2018.00037.2