NEET MDS Lessons
Conservative Dentistry
Instrument formula
First number : It indicates width of blade (or of primary cutting edge) in 1/10 th of a millimeter (i.e. no. 10 means 1 mm blade width).
Second number :
1) It indicates primary cutting edge angle.
2) It is measured form a line parallel to the long axis of the instrument handle in clockwise centigrade. Expressed as per cent of 360° (e.g. 85 means 85% of 360 = 306°).
3)The instrument is positioned so that this number always exceeds 50. If the edge is locally perpendicular to the blade, then this number is normally omitted resulting in a three number code.
Third number : It indicates blade length in millimeter.
Fourth number :
1)Indicates blade angle relative to long axis of handle in clockwise centigrade.
2) The instrument is positioned so that this number. is always 50 or less. It becomes third number in a three number code when
2nd number is omitted.
CPP-ACP, or casein phosphopeptide-amorphous calcium phosphate, is a significant compound in dentistry, particularly in the prevention and management of dental caries (tooth decay).
Role and applications in dentistry:
Composition and Mechanism
- Composition: CPP-ACP is derived from casein, a milk protein. It contains clusters of calcium and phosphate ions that are stabilized by casein phosphopeptides.
- Mechanism: The unique structure of CPP-ACP allows it to stabilize calcium and phosphate in a soluble form, which can be delivered to the tooth surface. When applied to the teeth, CPP-ACP can release these ions, promoting the remineralization of enamel and dentin, especially in early carious lesions.
Benefits in Dentistry
- Remineralization: CPP-ACP helps in the remineralization of demineralized enamel, making it an effective treatment for early carious lesions.
- Caries Prevention: Regular use of CPP-ACP can help prevent the development of caries by maintaining a higher concentration of calcium and phosphate in the oral environment.
- Reduction of Sensitivity: It can help reduce tooth sensitivity by occluding dentinal tubules and providing a protective layer over exposed dentin.
- pH Buffering: CPP-ACP can help buffer the pH in the oral cavity, reducing the risk of acid-induced demineralization.
- Compatibility with Fluoride: CPP-ACP can be used in conjunction with fluoride, enhancing the overall effectiveness of caries prevention strategies.
Applications
- Toothpaste: Some toothpaste formulations include CPP-ACP to enhance remineralization and provide additional protection against caries.
- Chewing Gum: Sucrose-free chewing gums containing CPP-ACP can be used to promote oral health, especially after meals.
- Dental Products: CPP-ACP is also found in various dental products, including varnishes and gels, used in professional dental treatments.
Considerations
- Lactose Allergy: Since CPP-ACP is derived from milk, it should be avoided by individuals with lactose intolerance or milk protein allergies.
- Clinical Use: Dentists may recommend CPP-ACP products for patients at high risk for caries, those with a history of dental decay, or individuals undergoing orthodontic treatment.
Implications for Dental Practice
A. Health and Safety Considerations
- Mercury Exposure: Understanding the amounts of mercury released during these procedures is crucial for assessing potential health risks to dental professionals and patients.
- Regulatory Guidelines: Dental practices should adhere to guidelines and regulations regarding mercury handling and exposure limits to ensure a safe working environment.
B. Best Practices
- Use of Wet Polishing: Whenever possible, wet polishing should be preferred over dry polishing to minimize mercury release.
- Proper Ventilation: Ensuring adequate ventilation in the dental operatory can help reduce the concentration of mercury vapor in the air.
- Personal Protective Equipment (PPE): Dental professionals should use appropriate PPE, such as masks and gloves, to minimize exposure during amalgam handling.
C. Patient Safety
- Informed Consent: Patients should be informed about the materials used in their restorations, including the presence of mercury in amalgam, and the associated risks.
- Monitoring: Regular monitoring of dental practices for mercury exposure levels can help maintain a safe environment for both staff and patients.
1. Noise Levels of Turbine Handpieces
Turbine Handpieces
- Ball Bearings: Turbine handpieces equipped with ball bearings can operate efficiently at air pressures of around 30 pounds.
- Noise Levels: At high frequencies, these handpieces may produce noise levels ranging from 70 to 94 dB.
- Hearing Damage Risk: Exposure to noise levels exceeding 75 dB, particularly in the frequency range of 1000 to 8000 cycles per second (cps), can pose a risk of hearing damage for dental professionals.
Implications for Practice
- Hearing Protection: Dental professionals should consider using hearing protection, especially during prolonged use of high-speed handpieces, to mitigate the risk of noise-induced hearing loss.
- Workplace Safety: Implementing noise-reduction strategies in the dental operatory can enhance the comfort and safety of both staff and patients.
2. Post-Carve Burnishing
Technique
- Post-Carve Burnishing: This technique involves lightly rubbing the carved surface of an amalgam restoration with a burnisher of suitable size and shape.
- Purpose: The goal is to improve the smoothness of the restoration and produce a satin finish rather than a shiny appearance.
Benefits
- Enhanced Aesthetics: A satin finish can improve the aesthetic integration of the restoration with the surrounding tooth structure.
- Surface Integrity: Burnishing can help to compact the surface of the amalgam, potentially enhancing its resistance to wear and marginal integrity.
3. Preparing Mandibular First Premolars for MOD Amalgam Restorations
Considerations for Tooth Preparation
- Conservation of Tooth Structure: When preparing a
mesio-occluso-distal (MOD) amalgam restoration for a mandibular first
premolar, it is important to conserve the support of the small lingual cusp.
- Occlusal Step Preparation: The occlusal step should be prepared more facially than lingually, which helps to maintain the integrity of the lingual cusp.
- Bur Positioning: The bur should be tilted slightly lingually to establish the correct direction for the pulpal wall.
Cusp Reduction
- Lingual Cusp Consideration: If the lingual margin of the occlusal step extends more than two-thirds the distance from the central fissure to the cuspal eminence, the lingual cusp may need to be reduced to ensure proper occlusal function and stability of the restoration.
4. Universal Matrix System
Overview
- Tofflemire Matrix System: Designed by B.R. Tofflemire, the Universal matrix system is a commonly used tool in restorative dentistry.
- Indications: This system is ideally indicated when three surfaces (mesial, occlusal, distal) of a posterior tooth have been prepared for restoration.
Benefits
- Retention and Contour: The matrix system helps in achieving proper contour and retention of the restorative material, ensuring a well-adapted restoration.
- Ease of Use: The design allows for easy placement and adjustment, facilitating efficient restorative procedures.
5. Angle Former Excavator
Functionality
- Angle Former: A special type of excavator used primarily for sharpening line angles and creating retentive features in dentin, particularly in preparations for gold restorations.
- Beveling Enamel Margins: The angle former can also be used to place a bevel on enamel margins, enhancing the retention of restorative materials.
Clinical Applications
- Preparation for Gold Restorations: The angle former is particularly useful in preparations where precise line angles and retention are critical for the success of gold restorations.
- Versatility: Its ability to create retentive features makes it a valuable tool in various restorative procedures.
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.
Turbid Dentin
- Turbid Dentin: This term refers to a zone of dentin
that has undergone significant degradation due to bacterial invasion. It is
characterized by:
- Widening and Distortion of Dentin Tubules: The dentinal tubules in this zone become enlarged and distorted as they fill with bacteria.
- Minimal Mineral Content: There is very little mineral present in turbid dentin, indicating a loss of structural integrity.
- Denatured Collagen: The collagen matrix in this zone is irreversibly denatured, which compromises its mechanical properties and ability to support the tooth structure.
Implications for Treatment
- Irreversible Damage: Dentin in the turbid zone cannot self-repair or remineralize. This means that any affected dentin must be removed before a restoration can be placed.
- Restorative Considerations: Proper identification and removal of turbid dentin are critical to ensure the success of restorative procedures. Failure to do so can lead to continued caries progression and restoration failure.
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.
Hybridization in Dental Bonding
Hybridization, as described by Nakabayashi in 1982, is a critical process in dental bonding that involves the formation of a hybrid layer. This hybrid layer plays a vital role in achieving micromechanical bonding between the tooth structure (dentin) and resin materials used in restorative dentistry.
1. Definition of Hybridization
Hybridization refers to the process of forming a hybrid layer at the interface between demineralized dentin and resin materials. This phenomenon is characterized by the interlocking of resin within the demineralized dentin surface, which enhances the bond strength between the tooth and the resin.
A. Formation of the Hybrid Layer
- Conditioning Dentin: When dentin is treated with a conditioner (usually an acid), it removes minerals from the dentin, exposing the collagen fibril network and creating inter-fibrillar microporosities.
- Application of Primer: A low-viscosity primer is then applied, which infiltrates these microporosities.
- Polymerization: After the primer is applied, the resin monomers polymerize, forming the hybrid layer.
2. Zones of the Hybrid Layer
The hybrid layer is composed of three distinct zones, each with unique characteristics:
A. Top Layer
- Composition: This layer consists of loosely arranged collagen fibrils and inter-fibrillar spaces that are filled with resin.
- Function: The presence of resin in this layer enhances the bonding strength and provides a flexible interface that can accommodate stress during functional loading.
B. Middle Layer
- Composition: In this zone, the hydroxyapatite crystals that were originally present in the dentin have been replaced by resin monomers due to the hybridization process.
- Function: This replacement contributes to the mechanical properties of the hybrid layer, providing a strong bond between the dentin and the resin.
C. Bottom Layer
- Composition: This layer consists of dentin that is almost unaffected, with a partly demineralized zone.
- Function: The presence of this layer helps maintain the integrity of the underlying dentin structure while still allowing for effective bonding.
3. Importance of the Hybrid Layer
The hybrid layer is crucial for the success of adhesive dentistry for several reasons:
- Micromechanical Bonding: The hybrid layer facilitates micromechanical bonding, which is essential for the retention of composite resins and other restorative materials.
- Stress Distribution: The hybrid layer helps distribute stress during functional loading, reducing the risk of debonding or failure of the restoration.
- Sealing Ability: A well-formed hybrid layer can help seal the dentin tubules, reducing sensitivity and protecting the pulp from potential irritants.