NEET MDS Lessons
Prosthodontics
LIMITING STRUCTURES
A) Labial, lingual & buccal frenum
- It is fibrous band extending from the labial aspect of the residual alveolar ridge to the lip containing a band of the fibrous connective tissue the that helps in attachment of the orbicularis oris muscle.
- It is quite sensitive hence the denture should have an appropriate labial notch.
- The fibers of buccinator are attached to the buccal frenum.
- Should be relieved to prevent displacement of the denture during function.
- The lingual frenum relief should be provided in the anterior portion of the lingual flange.
- This anterior portion of the lingual flange called sub-lingual crescent area.
- The lingual notch of the denture should be well adapted otherwise it will affect the denture stability.
B) Labial & buccal vestibule
- The labial sulcus runs from the labial frenum to the buccal frenum on each side.
- Mentalis muscle is quite active in this region.
- The buccal sulcus extends posteriorly from the buccal frenum to outside back corner of the retromolar region.
- Area maximization can be safely done here as because the fibers of the buccinator runs parallel to the border and hence displacing action due to buccinator during its contraction is slight.
- The impression is the widest in this region.
C) Alveololingual sulcus
- Between lingual frenum to retromylohyoid curtain.
- Overextension causes soreness and instability.
It can be divided into three parts:
i) Anterior part :
- From lingual frenum to mylohyoid ridge
- The shallowest portion(least height) of the lingual flange
ii) Middle region :
- From the premylohyoid fossa to the the distal end of the mylohyoid region
iii) Posterior portion :
- From the end of the mylohyoid ridge end to the retromylohyoid curtain
- Provides for a valuable undercut area so important retention
- Overextension causes soreness and instability
- Proper recording gives typical S –form of the lingual flange
D) Retromolar pad
- Pear-shaped triangular soft pad of tissue at the distal end of the lower ridge is referred to as the retromolar pad.
- It is an important structure, which forms the posterior seal of the mandibular denture.
- The denture base should extend up to 2/3rd of the retromolar pad triangle.
E) Pterygomandibular raphe
SUPPORTING STRUCTURES
A) Primary stress bearing area / Supporting area
1. Buccal shelf area
- Extends from buccal frenum to retromolar pad.
- Between external oblique ridge and crest of alveolar ridge.
Its boundaries are:
1. Medially the crest of the ridge
2. Laterally the external oblique ridge
3. Distally the retromolar pad
4. Mesially the buccal frenum
The width of this area increases as the alveolar resorption continues.
B) Secondary stress bearing area / Supporting area
1. Residual alveolar ridge
- Buccal and lingual slopes are secondary stress bearing areas.
RELIEF AREAS
A) Mylohyoid ridge
- Attachment for the mylohyoid muscle.
- Running along the lingual surface of the mandible.
- Anteriorly: the ridge lies close to the inferior border of the mandible.
- Posteriorly it lies close to the residual ridge.
- Covered by the thin mucosa which may be traumatized by denture base hence it should be relieved.
- The extension of the lingual flange is to be beyond the palpable position of the mylohyoid ridge but not in the undercut.
B) Mental foramen
- Lies on the external surface of the mandible in between the 1st and the 2nd premolar region.
- It should be relieved specially in case it lies close to the residual alveolar ridge due to ridge resorption to prevent parasthesia.
C) Genial tubercle
- Area of muscle attachment (Genioglossus and Geniohyoid).
- Lies away from the crest of the ridge.
- Prominent in resorbed ridges therefore adequate relief to be provided.
D) Torus mandibularis
- Abnormal bony prominence.
- Bilaterally on the lingual side near the premolar area.
- Covered by thin mucosa so it should be relieved
Bite Registration
- Thin medium, no tooth contact
- Use low-viscosity materials (e.g., waxes, elastomers) to record occlusal relationships without interference from tooth contact.
- Ensures accurate centric relation or maximum intercuspation records.
Gingival Management & Impression Protocols
- Impression after cord removal
- Take impressions only after bleeding has stopped to avoid voids and distortion.
- Gingival Sulcus Closure
- Sulcus begins to collapse 20–30 seconds post cord removal—timing is critical for accurate impressions.
- Electrosurgery
- Used to enlarge the sulcus and control bleeding during crown preparation or impression procedures.
- Offers precision and minimal trauma compared to mechanical retraction.
Pre-Operative Medication
- Methantheline Bromide
- Anticholinergic agent; 50 mg dose, administered 1 hour pre-op to reduce salivary flow.
- Enhances moisture control during procedures.
Moisture Control
- Rubber Dam
- Introduced by S.C. Barnum in 1864.
- Provides isolation, retraction, and accessibility—essential for adhesive procedures and endodontics.
Diagnostic Aids
- Explorer + Air
- Most effective for detecting small occlusal cavities—air drying reveals chalky enamel and explorer detects surface roughness.
- Lactobacillus
- Acidogenic and aciduric bacteria; thrive in low pH and contribute to caries progression.
- Saliva Buffering
- Saliva neutralizes acids produced by bacteria like Lactobacillus, protecting enamel from demineralization.
Surface Preparation
- McLaughlin Etching Technique
- Combination of Hydrochloric acid (HCl) and Sulfuric acid (H₂SO₄) with ultrasonic activation for 99 seconds.
- Used for enamel conditioning in orthodontics or bonding procedures.
| Muscle | Function | Clinical Relevance |
|---|---|---|
| Masseter | Elevates mandible (closes jaw) | Key in mastication; affects occlusal forces |
| Temporalis | Elevates and retracts mandible | Guides centric relation; helps in CR recording |
| Medial Pterygoid | Elevates and protrudes mandible | Assists in lateral movements |
| Lateral Pterygoid | Protrudes and depresses mandible | Controls orbitoaxial opening; guides condyle |
| Digastric | Depresses mandible; elevates hyoid | Important in opening jaw and swallowing |
| Mylohyoid & Geniohyoid | Floor of mouth support | Influence denture stability and border molding |
Retromolar Pad Composition
- Contents: Superior constrictor + Buccinator + Temporal tendon
- Clinical significance: Important for posterior denture extension
Border Anatomy
- Distobuccal border: Influenced by coronoid process
- Masseteric notch: Formed by masseter muscle over buccinator
- Buccal frenum muscle: Levator anguli oris
Midline Considerations
- Midline relief: Depends on resiliency of midline suture
- Individual variation: Varies with suture mobility
| Clasp Type | Key Features | Indications |
|---|---|---|
| Circumferential (Akers) | Cast, engages undercut from opposite side | Common in tooth-supported RPDs |
| Bar (Roach) | Approaches undercut from gingival direction | Used when esthetics are a concern |
| Ring Clasp | Encircles nearly the entire tooth | Useful for tipped molars |
| Combination Clasp | Wrought wire retentive arm + cast reciprocal arm | Offers flexibility and adaptability |
| Hairpin Clasp | U-shaped; engages deep undercuts | Rarely used; specific anatomical needs |
| Topic | Key Answer | Clinical Pearl |
|---|---|---|
| Retromolar pad | Superior constrictor + Buccinator + Temporal tendon | Posterior extension landmark |
| Distobuccal border | Coronoid process | Limits lateral extension |
| Food lodgement | Decreased flange length | Extend borders adequately |
| PPS function | Retention via partial vacuum | Seals against soft palate |
| Submucous fibrosis | Addition silicone | Best flow properties |
| Glossy wax | Intimate tissue contact | Quality indicator |
| Vibrating line | Soft palate location | PPS placement guide |
| Occlusal plane | Parallel to interpupillary/Camper's | Esthetic reference |
| Buccal frenum | Levator anguli oris | Border extension guide |
| Masseteric notch | Masseter over buccinator | Contouring landmark |
The mental attitude of patients towards complete dentures plays a significant role in the success of their treatment. Understanding these attitudes can help dental professionals tailor their approach to meet the needs and expectations of their patients. Here are the four primary mental attitudes that patients may exhibit:
1. Philosophical (Ideal Attitude)
- Characteristics:
- Accepts the dentist's judgment without question.
- Exhibits a rational, sensible, calm, and composed disposition.
- Open to discussing treatment options and understands the importance of oral health.
- Implications for Treatment:
- This type of patient is likely to follow the dentist's recommendations and cooperate throughout the treatment process.
- They are more likely to have realistic expectations and be satisfied with the outcomes.
2. Indifferent
- Characteristics:
- Shows little concern for their oral health.
- Seeks treatment primarily due to pressure from family or friends.
- Requires additional time and education to understand the importance of dental care.
- Their attitude can be discouraging to dentists, as they may not fully engage in the treatment process.
- Implications for Treatment:
- Dentists may need to invest extra effort in educating these patients about the benefits of complete dentures and the importance of oral health.
- Building rapport and trust is essential to encourage a more proactive attitude towards treatment.
3. Critical/Exacting
- Characteristics:
- Has previously had multiple sets of complete dentures and tends to find fault with everything.
- Often has high expectations and may be overly critical of the treatment process.
- May require medical consultation due to previous experiences or health concerns.
- Implications for Treatment:
- Dentists should be prepared to address specific concerns and provide detailed explanations about the treatment plan.
- It is important to manage expectations and ensure that the patient understands the limitations and possibilities of denture treatment.
4. Skeptical/Hysterical
- Characteristics:
- Has had negative experiences with previous treatments, leading to doubt and skepticism about the current treatment.
- Often presents with poor oral health, resorbed ridges, and other unfavorable conditions.
- May exhibit anxiety or hysteria regarding dental procedures.
- Implications for Treatment:
- Building trust and confidence is crucial for these patients. Dentists should take the time to listen to their concerns and provide reassurance.
- A gentle and empathetic approach is necessary to help alleviate fears and encourage cooperation.
- It may be beneficial to involve them in the decision-making process to empower them and reduce anxiety.