NEET MDS Lessons
Prosthodontics
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.
Surveying
Surveying is the process of analyzing a dental cast to determine the optimal path of insertion and identify undercuts, guiding planes, and suitable abutments for RPD design.
Components of a Dental Surveyor
| Part | Function |
|---|---|
| Vertical Column | Holds the surveying arm |
| Surveying Arm | Moves horizontally to analyze contours |
| Tabletop | Rotates and tilts the cast |
| Analyzing Rod | Identifies height of contour |
| Undercut Gauge | Measures depth of undercuts for clasp design |
| Carbon Marker | Marks survey lines and guiding planes |
Key Surveying Objectives
-
Determine Path of Insertion
- Establish a direction that allows smooth placement and removal of the prosthesis.
-
Identify Height of Contour
- Line encircling the greatest bulge of a tooth; helps in clasp placement.
-
Locate Undercuts
- Areas below the height of contour used for retention via clasps.
-
Mark Guiding Planes
- Flat surfaces prepared on abutment teeth to guide insertion and enhance stability.
-
Evaluate Soft Tissue Undercuts
- Helps avoid interference and discomfort during prosthesis placement.
Applegate's Classification is a system used to categorize edentulous
(toothless) arches in preparation for denture construction. The classification
is based on the amount and quality of the remaining alveolar ridge, the
relationship of the ridge to the residual ridges, and the presence of undercuts.
The system is primarily used in the context of complete denture prosthodontics
to determine the best approach for achieving retention, stability, and support
for the dentures.
Applegate's Classification for edentulous arches:
1. Class I: The alveolar ridge has a favorable arch form and sufficient height
and width to provide adequate support for a complete denture without the need
for extensive modifications. This is the ideal scenario for denture
construction.
2. Class II: The alveolar ridge has a favorable arch form but lacks the
necessary height or width to provide adequate support. This may require the use
of denture modifications such as flanges to enhance retention and support.
3. Class III: The ridge lacks both height and width, and there may be undercuts
or excessive resorption. In this case, additional procedures such as ridge
augmentation or the use of implants might be necessary to improve the foundation
for the denture.
4. Class IV: The ridge has an unfavorable arch form, often with significant
resorption, and may require extensive surgical procedures or adjuncts like
implants to achieve a functional and stable denture.
5. Class V: This is the most severe classification where the patient has no
residual alveolar ridge, possibly due to severe resorption, trauma, or surgical
removal. In such cases, the creation of a functional and stable denture may be
highly challenging and might necessitate advanced surgical procedures and/or the
use of alternative prosthetic options like over-dentures with implant support.
It's important to note that this classification is a guide, and individual
patient cases may present with a combination of features from different classes
or may require customized treatment plans based on unique anatomical and
functional requirements.