Flat Mandibular Ridge Impression Short Notes

 Neutral zone

In the absence of all-natural teeth, there exists a space called potential denture space bounded by the maxilla and soft palate above, mandible and floor of the mouth below, tongue medially, and lips and cheek laterally. Within the potential denture space is the area that is termed the neutral zone.

The neutral Zone or the neuromuscular approach (Sir Wilfred Fish, 1933)

Neutral zone Objectives:

1. Maximum comfort
2. Maximum efficiency
3. Esthetic appearance.

Flat Ridge Denture

Neutral Zone Factors Influencing Neutral Zone

1. Cheeks
   1. Masseter
      It affects the distodental border.
   2. Buccinator
      It helps to place food over the occlusal surface of the teeth in coordination with the tongue.
2. Lips
   1. Orbicularis oris
      It exerts force against teeth and the alveolar process which is counteracted by the tongue.
   2. Caninus
      Pulls lower lip. Helps in sucking and swallowing.
   3. Quadratus labii superioris
   4. Zygomaticus major
   5. Risorius
   6. Mentalis
   7. Triangularis
   8. Modiolus
      If a denture is not narrowed in the premolar area, it may unseat the lower denture.
3. Tongue
   Muscles of the tongue.
4. Denture surfaces
   • Impression surface
   • Occlusal surface
   • Polished surface
5. Denture shape
   It should be triangular in cross-section in the molar area. This triangular shape stabilizes the denture.

Flat Ridge Denture

Neutral zone Procedure

1. Preliminary impression:
   Modeling compound used.
2. Construction of acrylic tray:
   1. Modeling compound occlusal rims are made on the tray. Wire loops are made on the tray for the modeling compound to be attached as occlusal rims. Over extensions on the tray can be checked by disclosing wax.
   2. To serve as a tray for the final impression.
3. Location of the neutral zone:
   • The modeling compound rims are placed in the patient’s mouth and the patient is instructed to do various movements as pursing of lips, swallowing, and tongue movements for the lower arch and sucking fingers, swallowing for upper arch
   • Upper arch shape: Palatal surface sloping buccally and downward and buccal surface sloping lingually and downward.
   • Lower arch: Buccal surface inclined lingually with narrowing at the bicuspid area (modiolus function) and lingual surface inclined buccally.
4. Final impression:
   Zinc oxide eugenol with closed mouth technique, when a patient does all the needed movements.
5. Register the retruded jaw relation while the patient moves the cheeks, lips, and tongue through their full functional range
   • When recording the jaw relations in the patient’s mouth, the occlusal surface of the upper rim is trimmed parallel to the nasoauricular line, and positioned at a height so that the incisal edges of the patient’s artificial central incisors and the mesiopalatal cusps of the upper first molars will just touch it.
6. The resultant impression is poured with buccal and lingual registers or indices and after removing the acrylic base and impression material the resultant space is used to fabricate the denture.
7. The position of the teeth:
   • In the horizontal plane, the position of the teeth and the alveolar ridges which support them is determined by the interaction of the forces of the muscles surrounding them.
   • Lingually this force is provided by the tongue and buccally and labially by the cheeks and lips; thus the teeth are arranged in a zone of neutral muscular force.

Flat Ridge Denture

Balanced Articulation.

Balanced articulation is the arrangement of the teeth done in any jaw relationship and when as many teeth as possible are in occlusion and when changing from one position to another they move with a smooth, sliding motion, free from cuspal interference and maintaining even contact.

Complete dentures made with balanced articulation will have only minor occlusal corrections.

Balanced Articulation Factors In Balanced Articulation

These are the main four factors to achieve balanced articulation.

1. An adjustable articulator can be adjusted to copy the movements and reproduce the relationships of the jaws of the patient.
2. A method by which the recorded movements and relationships can be measured and transferred to the articulator.
3. An understanding of the factors related to Balanced occlusion, which influence the arrangement of the anterior and posterior teeth.
4. Anatomic tooth form to be used for Balanced occlusion. According to Hanau Balanced articulation is the change from one balanced occlusion to another while the masticatory surfaces remain in balanced contact.

Balanced Articulation Factors Affecting The Balanced Occlusion

1. Condylar guidance
2. Incisal guidance
3. Plane of occlusion
4. Compensating curve
5. Cuspal height.

Posterior palatal seal (pps).

Flat Ridge Denture

Posterior palatal seal Importance of apps

1. A positive contact is established posteriorly thereby preventing the final impression material from sliding down the pharynx.
2. For positioning the impression tray, accurately.
3. To create slight displacement of the soft palate
4. To determine if adequate retention and seal can be achieved in the potential denture border.
5. Adequate border seals resist horizontal forces and lateral torquing of the maxillary denture.
6. The function of the posterior palatal seal in the completed maxillary prosthesis is to maintain contact with the anterior portion of the soft palate during functional movements such as mastication, deglutition, and phonation.
7. To aid the denture to achieve better retention.
8. The posterior palatal seal will reduce patient awareness of the border of the denture hence reducing the gag reflex.

Posterior palatal seal Posterior Palatal Seal Area

• The post-palatal seal extends medially from one tuberosity to the other. Laterally, the pterygomaxillary seal extends through the pterygomaxillary notch (hamular notch) continuing for 3 to 4 mm anterolaterally approximating the mucogingival junction.
• The notch is covered by the pterygomandibular fold, which extends from the posterior aspect of the tuberosity posterior-inferiorly to insert into the retromolar pad which influences the posterior border seal if the mouth is in a wide open position during the final impression procedure.
• The exact position of the hamular process is to be located this will affect the length and direction of the pterygomaxillary seal. The hamular processes are covered by a thin layer of mucous membrane.
• There are two glandular openings fovea palatini, into which the ducts of other palatal mucus glands drain. They are located, on average, 1.31 mm anterior to the anterior vibrating line. The median palatal raphe overlies the medial palatal suture, contains little or no submucosa, and will tolerate little compression.

Posterior palatal seal Anterior And Posterior Vibrating Lines

• The anterior vibrating line is an imaginary line located at the junction of the attached tissues overlying the hard palate and the movable tissues of the immediately adjacent soft palate.
• One way to locate the anterior vibrating line is to have the patient perform the Valsalva maneuver, which requires that both nostrils be held firmly while the patient blows gently through the nose.
• Another method is for the patient to say “ah” with short vigorous bursts. Due to the projection of the posterior nasal spine, the anterior vibrating line is not a straight line between both hamular processes.
• The anterior vibrating line is always on soft palatal tissues. The posterior vibrating line is an imaginary line at the junction of the aponeurosis of the tensor veli palatine muscle and the muscular portion of the soft palate.
• It represents the demarcation between that part of the soft palate that has limited or shallow movement during function and the remainder of the soft palate that is displaced during functional movements.
• The posterior vibrating line is visualized by instructing the patient to say “ah” in short bursts in a normal, unexaggerated fashion.
• The posterior vibrating line marks the most distal extension of the denture base. The posterior palatal seal area lies between the anterior and posterior vibrating lines and is cupids bow-shaped.

Impression of flat ridges: resorbed residual alveolar ridge.

Flat Mandibular Ridge Impression

Flat Mandibular Ridge Impression Material Used

• Tissue-conditioning materials.
• A preliminary impression with overextended registration is made.
• An activated resin tray is made with an occlusal wax rim which simulates the height and position of the anterior and posterior teeth.
• The borders of the tray are adjusted so that the lingual flange and sublingual crescent area are in harmony with the resting and active phases of the floor of the mouth.
• The buccal and labial extension of the acrylic tray is adjusted to be short of the reflections of
  the cheek and lip. The retromolar pad is covered by the tray.

Flat Ridge Denture

Flat Mandibular Ridge Impression Technique

• Closed-mouth technique
• Open-mouth technique

Flat Mandibular Ridge Impression Closed-mouth technique

• Needs a well-fitting maxillary recording base
• An accurate occluding rims
• An acceptable vertical dimension.

Flat Mandibular Ridge Impression Open-Mouth Technique

Open-mouth technique in which the operator stabilizes the mandibular base directs the patient’s tongue to mold the lingual borders, and digitally manipulates the cheek and lip tissues.

Flat Mandibular Ridge Impression Technique

• Three applications of Coe product is required.
• Two applications of the more viscous pink Coe-Soft are made, each application is allowed to remain in the mouth for eight to ten minutes, removed, rinsed, and checked.
• Pressure areas were corrected at the time of the first application.
• The third and final wash is made with the white Coe-Comfort which is a light-bodied material and is the final corrective wash.
• The impression that is made will be very thick with conforming buccal borders and a relatively thick lingual and sublingual crescent area.
• Some conditioning materials are not compatible with dental stones. If such a material is used, then the third and final wash can be made with a light-bodied polysulfide material, such as Kerr Class III Pennlastic.

Flat Mandibular Ridge Impression Maxillary Resorbed Ridge

In making an impression for the maxillary resorbed ridge, the difference from the mandibular is that the peripheral borders are thicker. Since much less surface area is being used to retain the denture, the tissue contact area via the peripheral border is important to maintain a peripheral seal.

Denture adhesives.

The use of denture adhesives should be termed provisionally acceptable by the American Dental Association to be considered safe for use. Woelfel states that “all denture adhesives occupy space. Distribution of the adherent preparation into only a few limited regions where the denture does not fit alone is not possible to achieve.”

Denture adhesives Disadvantages

• More viscous adhesive pastes produce errors in the vertical dimension and denture positioning.
• If the use of adhesive encroaches upon the interarch distance then clicking of teeth and other speech defects occur.
• The magnitude of this discrepancy is related to the amount applied and to the adherent itself

Denture Adhesives Instruction To The Patient Regarding The Use

• If the dentist considers it necessary to temporarily enhance the retention of the denture, then an adhesive is recommended for a temporary period of time with instructions of how to use it.
• The adhesive powder is to be lightly sprinkled over the wetted tissue surface of the denture base. The excess powder should be shaken out of the denture before the patient inserts the prosthesis.
• Once properly seated, the patient should be instructed to close in the retruded jaw position to aid in the final positioning of the denture.
• When the patient wants to renew the adherent, the denture should be removed, thoroughly cleansed of all remaining denture adhesive used, and new adhesive reapplied as previously directed.

Denture adhesives are Available as:

Powder forms consist of natural gums such as tragacanth or karaya with cellulose added. Creams and liquids contain the same substances as in artificial saliva.

Denture adhesives Uses

• To hold the upper record block in position when securing intraoral records.
• To prolong the usefulness of an immediate upper denture for a short period of time.
• To enable a patient to wear an old, ill-fitting upper denture, while the used denture is being repaired.
• Public speakers, use adhesive to give them the assurance that the upper denture will not move while rendering speeches.

 Effects of decreased vertical dimension.
Answer:

Vertical dimension Definition

“It is the distance between two selected points, one on a fixed and one on a movable member.” GPT—6

It is maintained either by the occlusion of teeth or by the balanced tonic contraction of muscles of mandibular movements.

Vertical relations are classified as vertical dimensions of:

• Occlusion
• Rest and
• Other positions.

The vertical dimension of occlusion is established by the natural teeth when they are present and in occlusion.

• In the case of edentulous patients vertical dimension is established by the vertical height of the two dentures when the teeth are in contact. The vertical dimension of occlusion must be established for edentulous people so that their denture teeth will be properly related to each other.
• The vertical dimension of rest (or physiologic rest position of the mandible) is established by muscles and gravity. The interocclusal distance (formerly referred to as the “free-way space”) is the distance or gap existing between the occluding surfaces of maxillary and mandibular teeth when the mandible is in the physiologic rest position.
• The difference between the occlusal vertical dimension and the rest vertical dimension is the interocclusal distance. The interocclusal distance (formerly referred to as the “free-way space”) usually is 2 to 4 mm when observed at the position of the first premolars.
• It was observed that the clinically recorded rest position is not the same as the electromyographically determined one. A range of reduced muscle tension up to an interocclusal distance of about 10 mm has been noticed.

Vertical dimension Effects Of Decreased Vertical Dimension

1. Inefficiency: The pressure that is exerted with teeth in contact decreases considerably in overclosure because the attachment of muscles has been brought closer.
2. Cheek biting: When there is decreased vertical height the flabby cheek gets trapped between the teeth and gets bitten during mastication. Cheek biting often occurs because the buccal flange of the denture is too narrow and the cheek tends to fall.
3. Esthetics: Patients with decreased vertical height dentures look aged as the chin appears too close to the nose and forward. The lips lose their fullness and the vermilion borders are reduced to approximate a line. The corners of the mouth turn down as the orbicularis oris and its attachments are pushed too close to their origin.
4. Muscular action: The reduced vertical dimension of occlusion decreases the action of the muscles, with a resultant loss of muscle tone, giving the face an appearance of flabbiness instead of firmness.
5. Angular cheilitis or Perliche: Creases at corners of the mouth associated with Angular cheilitis.
6. Pain in the temporomandibular joint: Loss of posterior occlusion subjects the joint to greater load damaging the meniscus and resulting in clicking or crepitus which may be heard on movement.
   • As the posterior teeth contacts are missing the temporalis and masseter muscles can lead to a source of pain and discomfort.
   • The patients whose posterior tooth contact is absent tend to protrude the mandible in order to occlude resulting in pain in the lateral pterygoid muscle region which in turn is centered on or anterior to TMJ. In these patients, the vertical relation of occlusion should be gradually built up in successive dentures.
7. Impaired hearing: In case of decreased vertical dimension leading to less interarch space, the tongue will be pushed toward the throat region resulting in the closure of the eustachian tube opening leading to hearing problems.

 Effects of increased vertical dimension
Answer:

Effects Of Increased Vertical Dimension

1. Appearance: It will give the appearance of an elongated face with an expression of strain. There will be a slight parting of lips.
2. Discomfort: An increased vertical height affects the patients talking, eating, tongue movements causing discomfort.
3. Stability and retention: Stability and retention of the denture is decreased due to premature contact of the teeth.
4. Loss of freeway space: Affects the overall function of the denture in all aspects
5. Clicking teeth: At increased vertical height opposing cusps frequently meet each other producing clicking sounds.
6. Excessive bone resorption due to loss of freeway space.