NEET MDS Lessons
Conservative Dentistry
Various dyes have been tried to detect carious enamel, each having some Advantages and Disadvantages:
‘Procion’ dyes stain enamel lesions but the staining becomes irreversible because the dye reacts with nitrogen and hydroxyl groups of enamel and acts as a fixative.
‘Calcein’ dye makes a complex with calcium and remains bound to the lesion.
‘Fluorescent dye’ like Zyglo ZL-22 has been used in vitro which is not suitable in vivo. The dye is made visible by ultraviolet illumination.
‘Brilliant blue’ has also been used to enhance the diagnostic quality of fiberoptic transillumination.
Continuous Retention Groove Preparation
Purpose and Technique
- Retention Groove: A continuous retention groove is prepared in the internal portion of the external walls of a cavity preparation to enhance the retention of restorative materials, particularly when maximum retention is anticipated.
- Bur Selection: A No. ¼ round bur is used for this procedure.
- Location and Depth:
- The groove is located 0.25 mm (half the diameter of the No. ¼ round bur) from the root surface.
- It is prepared to a depth of 0.25 mm, ensuring that it does not compromise the integrity of the tooth structure.
- Direction: The groove should be directed as the bisector of the angle formed by the junction of the axial wall and the external wall. This orientation maximizes the surface area for bonding and retention.
Clinical Implications
- Enhanced Retention: The continuous groove provides additional mechanical retention, which is particularly beneficial in cases where the cavity preparation is large or when the restorative material has a tendency to dislodge.
- Consideration of Tooth Structure: Care must be taken to avoid excessive removal of tooth structure, which could compromise the tooth's strength.
Surface Preparation for Mechanical Bonding
Methods for Producing Surface Roughness
- Grinding and Etching: The common methods for creating
surface roughness to enhance mechanical bonding include grinding or etching
the surface.
- Grinding: This method produces gross mechanical roughness but leaves a smear layer of hydroxyapatite crystals and denatured collagen approximately 1 to 3 µm thick.
- Etching: Etching can remove the smear layer and create a more favorable surface for bonding.
Importance of Surface Preparation
- Proper surface preparation is critical for achieving effective mechanical bonding between dental materials, ensuring the longevity and success of restorations.
Wedging Techniques
Various wedging methods are employed to achieve optimal results, especially in cases involving gingival recession or wide proximal boxes. Below are descriptions of different wedging techniques, including "piggy back" wedging, double wedging, and wedge wedging.
1. Piggy Back Wedging
A. Description
- Technique: In piggy back wedging, a second smaller wedge is placed on top of the first wedge.
- Indication: This technique is particularly useful in patients with gingival recession, where there is a risk of overhanging restoration margins that could irritate the gingiva.
B. Purpose
- Prevention of Gingival Overhang: The additional wedge helps to ensure that the restoration does not extend beyond the tooth surface into the gingival area, thereby preventing potential irritation and maintaining periodontal health.
2. Double Wedging
A. Description
- Technique: In double wedging, wedges are placed from both the lingual and facial surfaces of the tooth.
- Indication: This method is beneficial in cases where the proximal box is wide, providing better adaptation of the matrix band and ensuring a tighter seal.
B. Purpose
- Enhanced Stability: By using wedges from both sides, the matrix band is held securely in place, reducing the risk of material leakage and improving the overall quality of the restoration.
3. Wedge Wedging
A. Description
- Technique: In wedge wedging, a second wedge is inserted between the first wedge and the matrix band, particularly in specific anatomical situations.
- Indication: This technique is commonly used in the maxillary first premolar, where a mesial concavity may complicate the placement of the matrix band.
B. Purpose
- Improved Adaptation: The additional wedge helps to fill the space created by the mesial concavity, ensuring that the matrix band conforms closely to the tooth surface and providing a better seal for the restorative material.
Condensers/pluggers are instruments used to deliver the forces of compaction to the underlying restorative material. There are
several methods for the application of these forces:
1.
Hand pressure: use of this method alone is contraindicated except in a few situations like adapting the first piece of gold tothe convenience or point angles and where the line of force will not permit use of other methods. Powdered golds are also
known to be better condensed with hand pressure. Small condenser points of 0.5 mm in diameter are generally
recommended as they do not require very high forces for their manipulation.
2.
Hand malleting: Condensation by hand malleting is a team work in which the operator directs the condenser and moves itover the surface, while the assistant provides rhythmic blows from the mallet. Long handled condensers and leather faced
mallets (50 gms in weight) are used for this purpose. The technique allows greater control and the condensers can be
changed rapidly when required. However, with the introduction of mechanical malleting, use of this method has decreased
considerably.
3.
Automatic hand malleting: This method utilizes a spring loaded instrument that delivers the desired force once the spiralspring is released. (Disadvantage is that the blow descends very rapidly even before full pressure has been exerted on the
condenser point.
4.
Electric malleting (McShirley electromallet): This instrument accommodates various shapes of con-denser points and has amallet in the handle itself which remains dormant until wished by the operator to function. The intensity or amplitude
generated can vary from 0.2 ounces to 15 pounds and the frequency can range from 360-3600 cycles/minute.
5.
Pneumatic malleting (Hollenback condenser): This is the most recent and satisfactory method first developed byDr. George M. Hollenback. Pneumatic mallets consist of vibrating nit condensers and detachable tips run by
compressed air. The air is carried through a thin rubber tubing attached to the hand piece. Controlling the air
pressure by a rheostat nit allows adjusting the frequency and amplitude of condensation strokes. The construction
of the handpiece is such that the blow does not fall until pressure is placed on the condenser point. This continues
until released. Pneumatic mallets are available with both straight and angled for handpieces.
Gingival Seat in Class II Restorations
The gingival seat is a critical component of Class II restorations, particularly in ensuring proper adaptation and retention of the restorative material. This guide outlines the key considerations for the gingival seat in Class II restorations, including its extension, clearance, beveling, and wall placement.
1. Extension of the Gingival Seat
A. Apical Extension
- Apical to Proximal Contact or Caries: The gingival seat should extend apically to the proximal contact point or the extent of caries, whichever is greater. This ensures that all carious tissue is removed and that the restoration has adequate retention.
2. Clearance from Adjacent Tooth
A. Clearance Requirement
- Adjacent Tooth Clearance: The gingival seat should clear the adjacent tooth by approximately 0.5 mm. This clearance is essential to prevent damage to the adjacent tooth and to allow for proper adaptation of the restorative material.
3. Beveling of the Gingival Margin
A. Bevel Angles
-
Amalgam Restorations: For amalgam restorations, the gingival margin is typically beveled at an angle of 15-20 degrees. This bevel helps to improve the adaptation of the amalgam and reduce the risk of marginal failure.
-
Cast Restorations: For cast restorations, the gingival margin is beveled at a steeper angle of 30-40 degrees. This angle enhances the strength of the margin and provides better retention for the cast material.
B. Contraindications for Beveling
- Root Surface Location: If the gingival seat is located on the root surface, beveling is contraindicated. This is to maintain the integrity of the root surface and avoid compromising the periodontal attachment.
4. Wall Placement
A. Facial and Lingual Walls
- Extension of Walls: The facial and lingual walls of the proximal box should be extended such that they clear the adjacent tooth by 0.2-0.3 mm. This clearance helps to ensure that the restoration does not impinge on the adjacent tooth and allows for proper contouring of the restoration.
B. Embrasure Placement
- Placement in Embrasures: The facial and lingual walls should be positioned in their respective embrasures. This placement helps to optimize the aesthetics and function of the restoration while providing adequate support.
Cariogram: A Visual Tool for Understanding Caries Risk
The Cariogram is a graphical representation developed by Brathall et al. in 1999 to illustrate the interaction of various factors contributing to the development of dental caries. This tool helps dental professionals and patients understand the multifactorial nature of caries and assess individual risk levels.
1. Overview of the Cariogram
- Purpose: The Cariogram visually represents the interplay between different factors that influence caries development, allowing for a comprehensive assessment of an individual's caries risk.
- Structure: The Cariogram is depicted as a pie chart divided into five distinct sectors, each representing a specific contributing factor.
2. Sectors of the Cariogram
A. Green Sector: Chance to Avoid Caries
- Description: This sector estimates the likelihood of avoiding caries based on the individual's overall risk profile.
- Significance: A larger green area indicates a higher chance of avoiding caries, reflecting effective preventive measures and good oral hygiene practices.
B. Dark Blue Sector: Diet
- Description: This sector assesses dietary factors, including the content and frequency of sugar consumption.
- Components: It considers both the types of foods consumed (e.g., sugary snacks, acidic beverages) and how often they are eaten.
- Significance: A smaller dark blue area suggests a diet that is less conducive to caries development, while a larger area indicates a higher risk due to frequent sugar intake.
C. Red Sector: Bacteria
- Description: This sector evaluates the bacterial load in the mouth, particularly focusing on the amount of plaque and the presence of Streptococcus mutans.
- Components: It takes into account the quantity of plaque accumulation and the specific types of bacteria present.
- Significance: A larger red area indicates a higher bacterial presence, which correlates with an increased risk of caries.
D. Light Blue Sector: Susceptibility
- Description: This sector reflects the individual's susceptibility to caries, influenced by factors such as fluoride exposure, saliva secretion, and saliva buffering capacity.
- Components: It considers the effectiveness of fluoride programs, the volume of saliva produced, and the saliva's ability to neutralize acids.
- Significance: A larger light blue area suggests greater susceptibility to caries, while a smaller area indicates protective factors are in place.
E. Yellow Sector: Circumstances
- Description: This sector encompasses the individual's past caries experience and any related health conditions that may affect caries risk.
- Components: It includes the history of previous caries, dental treatments, and systemic diseases that may influence oral health.
- Significance: A larger yellow area indicates a higher risk based on past experiences and health conditions, while a smaller area suggests a more favorable history.
3. Clinical Implications of the Cariogram
A. Personalized Risk Assessment
- The Cariogram provides a visual and intuitive way to assess an individual's caries risk, allowing for tailored preventive strategies based on specific factors.
B. Patient Education
- By using the Cariogram, dental professionals can effectively communicate the multifactorial nature of caries to patients, helping them understand how their diet, oral hygiene, and other factors contribute to their risk.
C. Targeted Interventions
- The information derived from the Cariogram can guide dental professionals in developing targeted interventions, such as dietary counseling, fluoride treatments, and improved oral hygiene practices.
D. Monitoring Progress
- The Cariogram can be used over time to monitor changes in an individual's caries risk profile, allowing for adjustments in preventive strategies as needed.