Mouth Preparation In Complete Dentures

Impression And Mouth Preparation Definitions

Impression And Mouth Preparation Important Notes

1. Types Of Impression:

1. Muco compressive – records tissue in functional and displaced form
2. Mucostatic records tissue in a relaxed form
3. Selective pressure – records tissue without interfering with the limiting structures at function and rest

Read And Learn More: Prosthodontics Question And Answers

2. Objectives Of Impression:

• Retention: It is the resistance to displacement away from the tissue surface. It is a mucosa-borne phenomenon.
• Support: It is the resistance to the occlusal forces in the vertical direction. It is a bone-borne phenomenon.
• Stability: It is resistant to lateral shifting.
• Preservation of remaining structures.

3. Factors Affecting Retention:

• Anatomical factors- Size of denture bearing area, quality of denture bearing area
• Physiological factor – Saliva Physical factor-adhesion, cohesion, capillary attraction, interfacial surface tension, atmospheric pressure
• Mechanical factors- Undercuts, retentive springs, magnetic forces, denture adhesives
• Muscular factors

4. Primary Stress-Bearing Areas:

5. Secondary Stress-Bearing Areas:

6. Relief Areas:


7. Anterior Vibrating Line:

• Anterior Vibrating Line is an imaginary line at the junction of the attached tissues overlying the hard palate and movable tissues of the soft palate
• The Anterior Vibrating Line is always on soft palatal tissue
• The Anterior Vibrating Line is visualized by asking the patient to say “ah” with a short vigorous burst

8. Posterior Vibrating Line:

• Posterior Vibrating Line is an imaginary line at the junction of the aponeurosis of the tensor veli palatine and muscular portion of the soft palate
• Posterior Vibrating Line represents the demarcation between the parts of the soft palate showing limited movements and those with marked movements
• Posterior Vibrating Line is the most distal extension of the denture

9. Alveolar Lingual Sulcus:

• Extends from the lingual frenum to the retro mylohyoid curtain
• It is divided into three parts

10. Posterior Palatal Seal:

• Lies between anterior and posterior vibrating line
• Functions
  • Retention of the maxillary denture
  • Maintain contact with the anterior portion of the soft palate during functional movements
  • Slightly displaces the soft tissue at the distal end of the denture to ensure a complete seal that helps in the retention of the denture.
  • Prevents ingress of food and saliva beneath denture base.
  • Prevents excess impression material from running down the patient’s throat.

11. Buccal Frenum:

• The buccal frenum of maxilla contains Caninus or levator anguli oris.
• The buccal frenum of mandible contains Triangularis or depressor anguli oris.

12. Pterygomandibular Raphe:

• Pterygomandibular Raphe is the tendinous insertion of superior constrictors and buccinators
• Pterygomandibular Raphe arises from the hamular process of the medial pterygoid
• Gets attached to the mylohyoid ridge

13. Fovea Palatine:

• The fovea palatine are indentations near the midline of the palate formed by the coalescence of several mucous gland ducts.
• Fovea palatine is always on the soft palate 2mm behind the vibrating line.

14. Retromylohyoid Fossa Is Bounded By:

• Anterior – Retro mylohyoid curtain
• Posterolateral – Superior constrictor of the pharynx
• Posteromedial – Palatoglossus and lateral surface of the tongue
• Inferior- Submandibular gland

15. Buccal Frenum Has The Following Muscle Attachments:

• Levator anguli oris
• Orbicularis oris
• Buccinator

16. Buccal Shelf Area Is Bounded By:

• Medially crest of the ridge
• Distally-retromolar pad
• Laterally external oblique ridge

17. Retromolar Pad:

• Contains glandular tissue and fibers of temporalis, buccinators, superior constrictor, and pterygomandibular raphe
• All these prevent the placement of extra pressure
• Functions
  • Provides peripheral seal to mandibular denture
  • Marks distal extension
  • Provides retention, stability, and support to the denture

18. Frena Present:

19. Border Molding:

• Border molding is the procedure by which the entire periphery of the tray is refined
• Polyether impression material is the material of choice
• Ideal requisites
  • Should have sufficient viscosity
  • Should not be sticky
  • Should have setting time 3-5 min
  • Should not displace tissues
  • Should be easily trimmed
  • Should retain its flow properties

20. Advantages Of ZOE Paste Include:

• Accurate borders are formed since the material is more plastic in nature.
• Does not absorb the mucous secretion produced in the palate and thus accurately records the palatal part of the impression.
• Does not require a separating medium.

21. Modiolus Is A Point Where Eight Muscles Meet At The Angle Mouth:

• Depressor anguli oris (or) tringularis
• Levator anguli oris or canines
• Risorius
• Orbicularis oris
• Buccinators
• Zygomaticus major
• Quadratus labii superioris
• Quadratus labii inferioris

22. Snow Shoe Effect:

• The denture base should cover as much denture-bearing area as possible
• It results in the distribution of forces over a wider area
• Leading to the reduction of force per unit area
• Called snowshoe effect

Impression And Mouth Preparation Short Essays

Question 1. Pre-prosthetic surgical management in complete denture
(or)
Pre-prosthetic surgery
Answer:

Question 2. Mucostatic impression.
Answer:

Mucostatic Impression:

• Mucostatic impression is an impression technique used in complete denture patients based on the theory of impression-making.
• By Richardson
• The impression is made with the oral mucous membrane & the jaws in a normal relaxed condition
• The material Of Choice is impression plaster
• Border molding is not done here
• Tray Used: Oversized tray
• Retention: Due to interfacial surface tension

Significance Of Mucostatic Impression:

• Closely adapted denture
• Good stability of the denture

Disadvantages Of Mucostatic Impression:

• Poor peripheral seal
• Poor retention
  • Mucostatic Synonym: Passive impression as the impression is made in the rest position of oral tissues

Question 3. Posterior palatal seal area
Or
Definition and functions of the posterior palatal seal.
Answer:

Posterior Palatal Seal Definition:

The soft tissues at or along the junction of the hard & soft palates on which pressure within the physiological limits of the tissues can be applied by a denture to aid in the retention of the denture

• Functions Of Posterior Palatal Seal:
  • Aids in retention
  • Maintain constant contact with soft palate during functions
  • Reduces gag reflex
  • Prevents formation of a gap between denture and pal- ate during the function
  • Prevents food accumulation
  • Compensate for polymerization shrinkage
• Parts Of Posterior Palatal Seal:
  • Pterygomaxillary seal
  • Postpalatal seal

Methods To Record It:

• Conventional approach
• Fluid wax technique
• Arbitrary scraping of the master cast
• Extended palatal technique

Question 4. Methods of recording posterior palatal seal
Answer:

1. Conventional Method

Fabricate trial base using shellac base plate or self-cure resin

• The posterior palatal area is wiped with gauze
• T burnisher is used to locate the hamular notch by palpating posteriorly to the maxillary tuberosity on both sides
• The full extent of the hamular notch is marked with a delible pencil
• The posterior vibrating line is marked
• The line marked in the hamular notch is connected with a posterior vibrating line
• The trial base is inserted into the patient’s mouth
• Markings are transferred to the trial base is seated on the master cast
• This transfers the markings to the cast
• The trial base is trimmed to the posterior border Anterior vibrating line is marked in the patient’s mouth
• These markings are transferred to the cast The area between the anterior and posterior vibrating line is scrapped

2. Fluid Wax technique:

• Wash impression is made
• Anterior and posterior vibratory lines are marked in the patient’s mouth
• The impression is re-inserted in the patient’s mouth
• Markings are transferred into impression The impression is painted with wax in the area of markings
• The impression tray is inserted in the patient’s mouth and the patient is asked to make rotational movements
• The impression is removed after 4-6 minutes and examined
• In contrast to the green stick compound, glossy areas show tissue contact
• The procedure is repeated till even tissue contact is achieved
• Wax in the region of the anterior vibrating line should have a knife-edge margin

3. Arbitrary Scrapping Of Master Cast:

• In this technique, anterior and posterior vibratory lines are visualized in the patient’s mouth and ap- proximately marked overcast
• Technician scrapes 0.5-1 mm of stone in posterior palatal seal area and fabricates the denture