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Neutral zone technique Journal club presentation

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Dr Mujtaba Ashraf
Dr Mujtaba Ashraf

The document summarizes the neutral zone impression technique for constructing complete dentures. It describes the neutral zone as the area where the forces of the tongue pressing outwards are balanced by the forces of the cheeks and lips pressing inwards. The technique involves making an impression of the neutral zone using a tissue conditioner material while the patient performs functions like swallowing and talking to determine the optimal denture position and shape. This impression is then used by the dental technician to construct a wax denture try-in that precisely follows the contours of the neutral zone.

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The Neutral Zone Impression Revisited GAHAN MJ, WALMSLEY AD. BRITISH DENTAL JOURNAL 2005;198:269-72. Journal Club Presentation Presented by: Dr. Mujtaba Ashraf MDS II 6/9/2017 1
Introduction 6/9/2017 2
Neutral zone: the potential space between the lips and cheeks on one side and the tongue on the other; that area or position where the forces between the tongue and cheeks or lips are equal. – GPT-9 The neutral zone has been defined as the area in the mouth where during function, the forces of the tongue pressing outwards are neutralised by the forces of the cheeks and lips pressing inwards. -Beresin & Schiesser. 6/9/2017 3
The Neutral zone philosophy is based on the concept that for each individual patient there exists a specific area with in the denture 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. 6/9/2017 4
Sir Wilfred Fish first described the influence of the polished surfaces on retention and stability in 1931.He also described how dentures should be constructed in the ‘dead space’, which later became know as the neutral zone 6/9/2017 5
Beresin VE, Schiesser FJ. The neutral zone in complete dentures. St. Louis: C. V. Mosby Co; 1973.) A, cross section of molar area B, lateral view of incisor area Denture space 6/9/2017 6
Complete dentures are primarily mechanical devices, since they function in the oral cavity, they must be fashioned so that they are in harmony with normal neuromuscular function. All oral functions, such as speech, mastication, swallowing, smiling, and laughing, involve the synergistic actions of the tongue, lips, cheeks, and floor of the mouth which are very complex and highly individual. 6/9/2017 7
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. 6/9/2017 8
The neutral zone approach has been used for patients who have: • highly atrophic mandible • a partial glossectomy, • mandibular resections or motor nerve damage to the tongue — which have led to either atypical movement or an unfavourable denture bearing area. 6/9/2017 9
In the highly atrophic mandible, muscular control over the denture is the main retentive and stabilising factor during function. A denture shaped by the neutral zone (NZ) technique will ensure that the muscular forces are working more effectively and in harmony. The dentures will have other advantages: • Improved stability and retention • Posterior teeth will be correctly positioned allowing sufficient tongue space • Reduced food trapping adjacent to the molar teeth • Good aesthetics due to facial support. 6/9/2017 10
Functional Anatomy 6/9/2017 11
Oral functions involve the unique interplay of the oral structures and muscles. Any interference with their movements, by a denture, would result in denture instability. The main displacing forces acting on a lower complete denture are • the tongue • the lower lip • the modiolus. 6/9/2017 12
If the denture is placed in the zone that balances these displacing forces then the denture will be retained more effectively during function. If the denture strays outside the neutral zone it will be unstable during the activities of talking, swallowing and mastication. 6/9/2017 13
The major muscles involved are: • Modiolus • Buccinator • Orbicularis oris and mentalis • Muscles of tongue 6/9/2017 14
THE MODIOLUS. The modiolus is a strong knot of muscle that alters the position of the angle of the mouth. Free movement of this knot of muscle must be ensured if the lower denture is to be stable. 6/9/2017 15
The modiolus determines the position of the premolar teeth and the shape of the polished surface in that region. This produces a narrowing of the denture so that the polished surface does not hinder the movements of the modiolus during function. 6/9/2017 16
This muscle has a large role in determining the neutral zone. Extends anteriorly from the pterygomandibular raphe, from above the maxillary molars and below the mandibular molars to converge, with other muscles, at the modiolus. The role of the buccinator during function is to position food on the occlusal surfaces of the teeth. This action is coordinated with the tongue to maintain the food in this position. THE BUCCINATOR 6/9/2017 17
THE ORBICULARIS ORIS AND THE MENTALIS In the highly atrophic, mandible positioning of the anterior teeth can be problematic. The movement and interaction of the lip and the tongue determines the position of the lower anterior teeth. If they are positioned too far labially the contraction of the lip will displace the denture posteriorly. 6/9/2017 18
The ridge can also resorb to such an extent that the mentalis muscle displaces the neutral zone lingually and anterior tooth position becomes even more vital for the success of the denture. The NZ technique provides the correct tooth position to allow for the balancing of these muscular forces during function. 6/9/2017 19
THE TONGUE The tongue is a powerful group of muscles and it is in constant contact with the denture at rest and during function. During rest the two critical areas for the tongue are the anterior lingual flange and posterior to the molar teeth. The polished surfaces must be correctly shaped to allow for the tongue to lie unhindered in these areas. 6/9/2017 20
During function the position of the anterior and posterior teeth are critical. If the anterior or posterior teeth are set lingually the tongue will be cramped and the denture will be displaced during function. There must be sufficient tongue space to allow for movement. 6/9/2017 21
The occlusal plane is also important for stability. It should not be too high as to ‘wall in’ the tongue but should allow it to lie on the occlusal surface during rest. 6/9/2017 22
CLINICAL TECHNIQUE 6/9/2017 23
Stages of the neutral zone impression 1. Primary impressions 2. Secondary impressions 3. Assessing the base plates and recording the occlusion 4. Assessing upper wax try-in, the superstructure and OVD 5. Neutral zone impression 6. Wax try-ins 7. Finish and check record 8. Review 6/9/2017 24
Jaw registration The wax record rims are constructed on heat cured acrylic bases for increased stability, and assessed for extension, comfort and stability. Once the base plates have been assessed and modified, jaw registration can be carried out. The upper rim should be carved to provide support for the musculature labially and buccally. It is vitally important that the record rim is correctly trimmed to the full width of the sulcus; otherwise the correct width of the lower arch cannot be developed. 6/9/2017 25
After establishing the correct incisal level, occlusal planes and palatal contour — the lower rim is adjusted to the correct occlusal vertical dimension (OVD). The rims can now be registered in the retruded arc of closure. The laboratory can now articulate the rims on an average value articulator and construct the upper wax tryin and lower base plate. 6/9/2017 26
The wax is removed from the heat cured base plate and a superstructure is constructed. The superstructure has two functions: • to provide even occlusal stops at the correct OVD and • to provide support for the NZ impression material. Lower base plate construction 6/9/2017 27
Favoured designs include self-cured pillars in the premolar regions with a short vertical fin between them or a light cured vertical fin along the centre of the base plate. Whichever design is used it must be assessed in order that the structure does not deflect the cheeks, lip or tongue and that the desired OVD is maintained. 6/9/2017 28
The stops and fins can be modified with self-cured acrylic or greenstick tracing compound until the correct dimensions are produced. 6/9/2017 29
The neutral zone impression • Ensure the patient in sat upright with the head supported. This allows the actions of swallowing and speaking to be more natural. • Assess the base plate — checking that it is stable and does not hinder muscular function. • Ask patient to perform a series of actions designed to simulate physiological functioning. These actions will need to be rehearsed so that they are performed naturally and effectively. 6/9/2017 30
• Insert the upper wax try in - ensuring that the upper lip is supported, the incisal and occlusal planes are correct and the functional width of the sulcus is restored. • Reinsert the base plate and modify the occlusal stops so that the correct OVD is achieved. 6/9/2017 31
• With the base plate out of the mouth place the correct volume of a high viscosity mix of tissue conditioner on the superstructure. • Manipulate this to form an approximate rim and insert the plate into the mouth. The volume should be controlled so that the sulci are not distorted. 6/9/2017 32
• Instruct the patient to perform repeated actions: — Swallow and take frequent sips of water. — Talk aloud, pronouncing the vowels and count from 60 to 70. — Smile, grin, lick their lips and purse their lips. • These actions will mould the material by muscle activity. 6/9/2017 33
• After 10 minutes, when the impression has set, remove the plate and proceed to the laboratory stage. 6/9/2017 34
The Neutral Zone-laboratory Stages The technician will replace the NZ impression on the master model, cut locating grooves and place plaster or a silicone putty index around the impression. 6/9/2017 35
The Viscogel impression is then removed from the base plate and the index replaced. The index will have preserved the space of the neutral zone. Wax can then be poured into the space giving an exact representation of the neutral zone. 6/9/2017 36
Teeth can then be set up exactly following the index. During the setting up of the teeth their position can be checked by putting the index together around the wax try-in. The posterior teeth invariably have to be trimmed lingually in order that they are sufficiently narrow. 6/9/2017 37
Once the wax try-ins are deemed satisfactory the dentures may be processed and finished. Instructions must be given to the technician to polish the denture lightly so that the contours remain unaltered. On final insertion the dentures are fully inspected and a check record performed to eliminate any minor occlusal errors. Completion of the denture 6/9/2017 38
CONCLUSION 6/9/2017 39
Neutral zone is an alternative technique for the construction of lower complete dentures on highly atrophic ridges. It is especially useful in cases where dental implants are not possible and the copy technique would be inappropriate. The aim of the neutral zone is to construct a denture in muscle balance, as muscular control will be the main stabilising and retentive factor during function. The technique is relatively simple but there are increased chair time and laboratory costs. 6/9/2017 40
REFERENCES 6/9/2017 41
• Beresin V E, Schiesser F J. The neutral zone in complete and partial dentures p 15. C.V. Mosby Co., 1978. • Atwood D A. Post extraction changes in the adult mandible as illustrated by micrographs of midsagitall sections and serial cephalometric roentgenograms. J Prosthet Dent 1963; 13: 810– 824. • Ohkubo C, Hanatani S, Hosoi T, Mizuno Y. Neutral zone approach for denture fabrication for a partial glossectomy patient: A clinical report. J Prosthet Dent 2000; 84: 390–393. • Beresin V E, Schiesser F J. The neutral zone In complete dentures. J Prosthet Dent 1976; 36: 356–367. • Fahmi F M. The position of the neutral zone in relation to the alveolar ridge. J Prosthet Dent 1992; 67: 805–809. • Fahmi F M, Kharat D U. A study of the importance of the neutral zone in complete dentures. J Prosthet Dent 1990; 64: 459–462. 6/9/2017 42
6/9/2017 43

More Related Content

Neutral zone technique Journal club presentation

  • 1. The Neutral Zone Impression Revisited GAHAN MJ, WALMSLEY AD. BRITISH DENTAL JOURNAL 2005;198:269-72. Journal Club Presentation Presented by: Dr. Mujtaba Ashraf MDS II 6/9/2017 1
  • 3. Neutral zone: the potential space between the lips and cheeks on one side and the tongue on the other; that area or position where the forces between the tongue and cheeks or lips are equal. – GPT-9 The neutral zone has been defined as the area in the mouth where during function, the forces of the tongue pressing outwards are neutralised by the forces of the cheeks and lips pressing inwards. -Beresin & Schiesser. 6/9/2017 3
  • 4. The Neutral zone philosophy is based on the concept that for each individual patient there exists a specific area with in the denture 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. 6/9/2017 4
  • 5. Sir Wilfred Fish first described the influence of the polished surfaces on retention and stability in 1931.He also described how dentures should be constructed in the ‘dead space’, which later became know as the neutral zone 6/9/2017 5
  • 6. Beresin VE, Schiesser FJ. The neutral zone in complete dentures. St. Louis: C. V. Mosby Co; 1973.) A, cross section of molar area B, lateral view of incisor area Denture space 6/9/2017 6
  • 7. Complete dentures are primarily mechanical devices, since they function in the oral cavity, they must be fashioned so that they are in harmony with normal neuromuscular function. All oral functions, such as speech, mastication, swallowing, smiling, and laughing, involve the synergistic actions of the tongue, lips, cheeks, and floor of the mouth which are very complex and highly individual. 6/9/2017 7
  • 8. 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. 6/9/2017 8
  • 9. The neutral zone approach has been used for patients who have: • highly atrophic mandible • a partial glossectomy, • mandibular resections or motor nerve damage to the tongue — which have led to either atypical movement or an unfavourable denture bearing area. 6/9/2017 9
  • 10. In the highly atrophic mandible, muscular control over the denture is the main retentive and stabilising factor during function. A denture shaped by the neutral zone (NZ) technique will ensure that the muscular forces are working more effectively and in harmony. The dentures will have other advantages: • Improved stability and retention • Posterior teeth will be correctly positioned allowing sufficient tongue space • Reduced food trapping adjacent to the molar teeth • Good aesthetics due to facial support. 6/9/2017 10
  • 12. Oral functions involve the unique interplay of the oral structures and muscles. Any interference with their movements, by a denture, would result in denture instability. The main displacing forces acting on a lower complete denture are • the tongue • the lower lip • the modiolus. 6/9/2017 12
  • 13. If the denture is placed in the zone that balances these displacing forces then the denture will be retained more effectively during function. If the denture strays outside the neutral zone it will be unstable during the activities of talking, swallowing and mastication. 6/9/2017 13
  • 14. The major muscles involved are: • Modiolus • Buccinator • Orbicularis oris and mentalis • Muscles of tongue 6/9/2017 14
  • 15. THE MODIOLUS. The modiolus is a strong knot of muscle that alters the position of the angle of the mouth. Free movement of this knot of muscle must be ensured if the lower denture is to be stable. 6/9/2017 15
  • 16. The modiolus determines the position of the premolar teeth and the shape of the polished surface in that region. This produces a narrowing of the denture so that the polished surface does not hinder the movements of the modiolus during function. 6/9/2017 16
  • 17. This muscle has a large role in determining the neutral zone. Extends anteriorly from the pterygomandibular raphe, from above the maxillary molars and below the mandibular molars to converge, with other muscles, at the modiolus. The role of the buccinator during function is to position food on the occlusal surfaces of the teeth. This action is coordinated with the tongue to maintain the food in this position. THE BUCCINATOR 6/9/2017 17
  • 18. THE ORBICULARIS ORIS AND THE MENTALIS In the highly atrophic, mandible positioning of the anterior teeth can be problematic. The movement and interaction of the lip and the tongue determines the position of the lower anterior teeth. If they are positioned too far labially the contraction of the lip will displace the denture posteriorly. 6/9/2017 18
  • 19. The ridge can also resorb to such an extent that the mentalis muscle displaces the neutral zone lingually and anterior tooth position becomes even more vital for the success of the denture. The NZ technique provides the correct tooth position to allow for the balancing of these muscular forces during function. 6/9/2017 19
  • 20. THE TONGUE The tongue is a powerful group of muscles and it is in constant contact with the denture at rest and during function. During rest the two critical areas for the tongue are the anterior lingual flange and posterior to the molar teeth. The polished surfaces must be correctly shaped to allow for the tongue to lie unhindered in these areas. 6/9/2017 20
  • 21. During function the position of the anterior and posterior teeth are critical. If the anterior or posterior teeth are set lingually the tongue will be cramped and the denture will be displaced during function. There must be sufficient tongue space to allow for movement. 6/9/2017 21
  • 22. The occlusal plane is also important for stability. It should not be too high as to ‘wall in’ the tongue but should allow it to lie on the occlusal surface during rest. 6/9/2017 22
  • 24. Stages of the neutral zone impression 1. Primary impressions 2. Secondary impressions 3. Assessing the base plates and recording the occlusion 4. Assessing upper wax try-in, the superstructure and OVD 5. Neutral zone impression 6. Wax try-ins 7. Finish and check record 8. Review 6/9/2017 24
  • 25. Jaw registration The wax record rims are constructed on heat cured acrylic bases for increased stability, and assessed for extension, comfort and stability. Once the base plates have been assessed and modified, jaw registration can be carried out. The upper rim should be carved to provide support for the musculature labially and buccally. It is vitally important that the record rim is correctly trimmed to the full width of the sulcus; otherwise the correct width of the lower arch cannot be developed. 6/9/2017 25
  • 26. After establishing the correct incisal level, occlusal planes and palatal contour — the lower rim is adjusted to the correct occlusal vertical dimension (OVD). The rims can now be registered in the retruded arc of closure. The laboratory can now articulate the rims on an average value articulator and construct the upper wax tryin and lower base plate. 6/9/2017 26
  • 27. The wax is removed from the heat cured base plate and a superstructure is constructed. The superstructure has two functions: • to provide even occlusal stops at the correct OVD and • to provide support for the NZ impression material. Lower base plate construction 6/9/2017 27
  • 28. Favoured designs include self-cured pillars in the premolar regions with a short vertical fin between them or a light cured vertical fin along the centre of the base plate. Whichever design is used it must be assessed in order that the structure does not deflect the cheeks, lip or tongue and that the desired OVD is maintained. 6/9/2017 28
  • 29. The stops and fins can be modified with self-cured acrylic or greenstick tracing compound until the correct dimensions are produced. 6/9/2017 29
  • 30. The neutral zone impression • Ensure the patient in sat upright with the head supported. This allows the actions of swallowing and speaking to be more natural. • Assess the base plate — checking that it is stable and does not hinder muscular function. • Ask patient to perform a series of actions designed to simulate physiological functioning. These actions will need to be rehearsed so that they are performed naturally and effectively. 6/9/2017 30
  • 31. • Insert the upper wax try in - ensuring that the upper lip is supported, the incisal and occlusal planes are correct and the functional width of the sulcus is restored. • Reinsert the base plate and modify the occlusal stops so that the correct OVD is achieved. 6/9/2017 31
  • 32. • With the base plate out of the mouth place the correct volume of a high viscosity mix of tissue conditioner on the superstructure. • Manipulate this to form an approximate rim and insert the plate into the mouth. The volume should be controlled so that the sulci are not distorted. 6/9/2017 32
  • 33. • Instruct the patient to perform repeated actions: — Swallow and take frequent sips of water. — Talk aloud, pronouncing the vowels and count from 60 to 70. — Smile, grin, lick their lips and purse their lips. • These actions will mould the material by muscle activity. 6/9/2017 33
  • 34. • After 10 minutes, when the impression has set, remove the plate and proceed to the laboratory stage. 6/9/2017 34
  • 35. The Neutral Zone-laboratory Stages The technician will replace the NZ impression on the master model, cut locating grooves and place plaster or a silicone putty index around the impression. 6/9/2017 35
  • 36. The Viscogel impression is then removed from the base plate and the index replaced. The index will have preserved the space of the neutral zone. Wax can then be poured into the space giving an exact representation of the neutral zone. 6/9/2017 36
  • 37. Teeth can then be set up exactly following the index. During the setting up of the teeth their position can be checked by putting the index together around the wax try-in. The posterior teeth invariably have to be trimmed lingually in order that they are sufficiently narrow. 6/9/2017 37
  • 38. Once the wax try-ins are deemed satisfactory the dentures may be processed and finished. Instructions must be given to the technician to polish the denture lightly so that the contours remain unaltered. On final insertion the dentures are fully inspected and a check record performed to eliminate any minor occlusal errors. Completion of the denture 6/9/2017 38
  • 40. Neutral zone is an alternative technique for the construction of lower complete dentures on highly atrophic ridges. It is especially useful in cases where dental implants are not possible and the copy technique would be inappropriate. The aim of the neutral zone is to construct a denture in muscle balance, as muscular control will be the main stabilising and retentive factor during function. The technique is relatively simple but there are increased chair time and laboratory costs. 6/9/2017 40
  • 42. • Beresin V E, Schiesser F J. The neutral zone in complete and partial dentures p 15. C.V. Mosby Co., 1978. • Atwood D A. Post extraction changes in the adult mandible as illustrated by micrographs of midsagitall sections and serial cephalometric roentgenograms. J Prosthet Dent 1963; 13: 810– 824. • Ohkubo C, Hanatani S, Hosoi T, Mizuno Y. Neutral zone approach for denture fabrication for a partial glossectomy patient: A clinical report. J Prosthet Dent 2000; 84: 390–393. • Beresin V E, Schiesser F J. The neutral zone In complete dentures. J Prosthet Dent 1976; 36: 356–367. • Fahmi F M. The position of the neutral zone in relation to the alveolar ridge. J Prosthet Dent 1992; 67: 805–809. • Fahmi F M, Kharat D U. A study of the importance of the neutral zone in complete dentures. J Prosthet Dent 1990; 64: 459–462. 6/9/2017 42

Editor's Notes

  • #7: dead zone, stable zone, zone of minimal conflict, zone of equilibrium, zone of least interference, biometric denture space, denture space and potential denture space
  • #21: Extrinsic=the genioglossus, hyoglossus, styloglossus, and palatoglossus Intrinsic= superior longitudinal, inferior longitudinal, transverse, and vertical
  • #27: Centric occlusion/ most posterior border position/
  • #28: Numerous designs have been proposed and the final decision is one of clinical preference.
  • #31: —swallow, Smile, grin, lick and purse their lips.