Dental Burs

Dental burs are essential tools used in restorative dentistry for cutting, shaping, and finishing tooth structure. The design and characteristics of burs significantly influence their cutting efficiency, vibration, and overall performance. Below is a detailed overview of the key features and considerations related to dental burs.

1. Structure of Burs

A. Blades and Flutes

• Blades: The cutting edges on a bur are uniformly spaced, and the number of blades is always even.
• Flutes: The spaces between the blades are referred to as flutes. These flutes help in the removal of debris during cutting.

B. Cutting Action

• Number of Blades:
  • Excavating Burs: Typically have 6-10 blades. These burs are designed for efficient removal of tooth structure.
  • Finishing Burs: Have 12-40 blades, providing a smoother finish to the tooth surface.
• Cutting Efficiency:
  • A greater number of blades results in a smoother cutting action at low speeds.
  • However, as the number of blades increases, the space between subsequent blades decreases, which can reduce the overall cutting efficiency.

2. Vibration and RPM

A. Vibration

• Cycles per Second: Vibrations over 1,300 cycles/second are generally imperceptible to patients.
• Effect of Blade Number: Fewer blades on a bur tend to produce greater vibrations during use.
• RPM Impact: Higher RPM (revolutions per minute) results in less amplitude and greater frequency of vibration, contributing to a smoother cutting experience.

3. Rake Angle

A. Definition

• Rake Angle: The angle that the face of the blade makes with a radial line drawn from the center of the bur to the blade.

B. Cutting Efficiency

• Positive Rake Angle: Generally preferred for cutting efficiency.
• Radial Rake Angle: Intermediate efficiency.
• Negative Rake Angle: Less efficient for cutting.
• Clogging: Burs with a positive rake angle may experience clogging due to debris accumulation.

4. Clearance Angle

A. Definition

• Clearance Angle: This angle provides necessary clearance between the working edge and the cutting edge of the bur, allowing for effective cutting without binding.

5. Run-Out

A. Definition

• Run-Out: Refers to the eccentricity or maximum displacement of the bur head from its axis of rotation.
• Acceptable Value: The average clinically acceptable run-out is about 0.023 mm. Excessive run-out can lead to uneven cutting and discomfort for the patient.

6. Load Applied by Dentist

A. Load Ranges

• Low Speed: The load applied by the dentist typically ranges from 100 to 1500 grams.
• High Speed: The load is generally lower, ranging from 60 to 120 grams.

7. Diamond Stones

A. Characteristics

• Hardness: Diamond stones are the hardest and most efficient abrasive tools available for removing tooth enamel.
• Application: They are commonly used for cutting and finishing procedures due to their superior cutting ability and durability.

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

1. Remineralization: CPP-ACP helps in the remineralization of demineralized enamel, making it an effective treatment for early carious lesions.
2. 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.
3. Reduction of Sensitivity: It can help reduce tooth sensitivity by occluding dentinal tubules and providing a protective layer over exposed dentin.
4. pH Buffering: CPP-ACP can help buffer the pH in the oral cavity, reducing the risk of acid-induced demineralization.
5. 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.

 

Refractory materials are essential in the field of dentistry, particularly in the branch of conservative dentistry and prosthodontics, for the fabrication of various restorations and appliances. These materials are characterized by their ability to withstand high temperatures without undergoing significant deformation or chemical change. This is crucial for the longevity and stability of the dental work. The primary function of refractory materials is to provide a precise and durable mold or pattern for the casting of metal restorations, such as crowns, bridges, and inlays/onlays.

Refractory materials include:

- Plaster of Paris: The most commonly used refractory material in dentistry, plaster is composed of calcium sulfate hemihydrate. It is mixed with water to form a paste that is used to make study models and casts. It has a relatively low expansion coefficient and is easy to manipulate, making it suitable for various applications.

- Dental stone: A more precise alternative to plaster, dental stone is a type of gypsum product that offers higher strength and less dimensional change. It is commonly used for master models and die fabrication due to its excellent surface detail reproduction.

- Investment materials: Used in the casting process of fabricating indirect restorations, investment materials are refractory and encapsulate the wax pattern to create a mold. They can withstand the high temperatures required for metal casting without distortion.

- Zirconia: A newer refractory material gaining popularity, zirconia is a ceramic that is used for the fabrication of all-ceramic crowns and bridges. It is extremely durable and has a high resistance to wear and fracture.

- Refractory die materials: These are used in the production of metal-ceramic restorations. They are capable of withstanding the high temperatures involved in the ceramic firing process and provide a reliable foundation for the ceramic layers.

The selection of a refractory material is based on factors such as the intended use, the required accuracy, and the specific properties needed for the final restoration. The material must have a low thermal expansion coefficient to minimize the thermal stress during the casting process and maintain the integrity of the final product. Additionally, the material should be able to reproduce the fine details of the oral anatomy and have good physical and mechanical properties to ensure stability and longevity.

Refractory materials are typically used in the following procedures:

- Impression taking: Refractory materials are used to make models from the patient's impressions.
- Casting of metal restorations: A refractory mold is created from the model to cast the metal framework.
- Ceramic firing: Refractory die materials hold the ceramic in place while it is fired at high temperatures.
- Temporary restorations: Some refractory materials can be used to produce temporary restorations that are highly accurate and durable.

Refractory materials are critical for achieving the correct fit and function of dental restorations, as well as ensuring patient satisfaction with the aesthetics and comfort of the final product.

Mercury Release in Dental Procedures Involving Amalgam

Mercury is a key component of dental amalgam, and its release during various dental procedures has been a topic of concern due to potential health risks. Understanding the amounts of mercury released during different stages of amalgam handling is essential for dental professionals to implement safety measures and minimize exposure.

1. Mercury Release Quantification

A. Trituration

• Amount Released: 1-2 µg
• Description: Trituration is the process of mixing mercury with alloy particles to form a homogenous amalgam. During this process, small amounts of mercury can be released into the air, which can contribute to overall exposure.

B. Placement of Amalgam Restoration

• Amount Released: 6-8 µg
• Description: When placing an amalgam restoration, additional mercury may be released due to the manipulation of the material. This includes the handling and packing of the amalgam into the cavity preparation.

C. Dry Polishing

• Amount Released: 44 µg
• Description: Dry polishing of amalgam restorations generates the highest amount of mercury release among the listed procedures. The friction and heat generated during dry polishing can vaporize mercury, leading to increased exposure.

D. Wet Polishing

• Amount Released: 2-4 µg
• Description: Wet polishing, which involves the use of water to cool the restoration during polishing, results in significantly lower mercury release compared to dry polishing. The water helps to capture and reduce the amount of mercury vapor released into the air.

Nursing Bottle Caries

Nursing bottle caries, also known as early childhood caries (ECC), is a significant dental issue that affects infants and young children. Understanding the etiological agents involved in this condition is crucial for prevention and management. .

1. Pathogenic Microorganism

A. Streptococcus mutans

• Role: Streptococcus mutans is the primary microorganism responsible for the development of nursing bottle caries. It colonizes the teeth after they erupt into the oral cavity.
• Transmission: This bacterium is typically transmitted to the infant’s mouth from the mother, often through saliva.
• Virulence Factors:
  • Colonization: It effectively adheres to tooth surfaces, establishing a foothold for caries development.
  • Acid Production: S. mutans produces large amounts of acid as a byproduct of carbohydrate fermentation, leading to demineralization of tooth enamel.
  • Extracellular Polysaccharides: It synthesizes significant quantities of extracellular polysaccharides, which promote plaque formation and enhance bacterial adherence to teeth.

2. Substrate (Fermentable Carbohydrates)

A. Sources of Fermentable Carbohydrates

• Fermentable carbohydrates are utilized by S. mutans to form dextrans, which facilitate bacterial adhesion to tooth surfaces and contribute to acid production. Common sources include:
  • Bovine Milk or Milk Formulas: Often high in lactose, which can be fermented by bacteria.
  • Human Milk: Breastfeeding on demand can expose teeth to sugars.
  • Fruit Juices and Sweet Liquids: These are often high in sugars and can contribute to caries.
  • Sweet Syrups: Such as those found in vitamin preparations.
  • Pacifiers Dipped in Sugary Solutions: This practice can introduce sugars directly to the oral cavity.
  • Chocolates and Other Sweets: These can provide a continuous source of fermentable carbohydrates.

3. Host Factors

A. Tooth Structure

• Host for Microorganisms: The tooth itself serves as the host for S. mutans and other cariogenic bacteria.
• Susceptibility Factors:
  • Hypomineralization or Hypoplasia: Defects in enamel development can increase susceptibility to caries.
  • Thin Enamel and Developmental Grooves: These anatomical features can create areas that are more prone to plaque accumulation and caries.

4. Time

A. Duration of Exposure

• Sleeping with a Bottle: The longer a child sleeps with a bottle in their mouth, the higher the risk of developing caries. This is due to:
  • Decreased Salivary Flow: Saliva plays a crucial role in neutralizing acids and washing away food particles.
  • Prolonged Carbohydrate Accumulation: The swallowing reflex is diminished during sleep, allowing carbohydrates to remain in the mouth longer.

5. Other Predisposing Factors

• Parental Overindulgence: Excessive use of sugary foods and drinks can increase caries risk.
• Sleep Patterns: Children who sleep less may have increased exposure to cariogenic factors.
• Malnutrition: Nutritional deficiencies can affect oral health and increase susceptibility to caries.
• Crowded Living Conditions: These may limit access to dental care and hygiene practices.
• Decreased Salivary Function: Conditions such as iron deficiency and exposure to lead can impair salivary function, increasing caries susceptibility.

Clinical Features of Nursing Bottle Caries

• Intraoral Decay Pattern: The decay pattern associated with nursing bottle caries is characteristic and pathognomonic, often involving the maxillary incisors and molars.
• Progression of Lesions: Lesions typically progress rapidly, leading to extensive decay if not addressed promptly.

Management of Nursing Bottle Caries

First Visit

• Lesion Management: Excavation and restoration of carious lesions.
• Abscess Drainage: If present, abscesses should be drained.
• Radiographs: Obtain necessary imaging to assess the extent of caries.
• Diet Chart: Provide a diet chart for parents to record the child's diet for one week.
• Parent Counseling: Educate parents on oral hygiene and dietary practices.
• Topical Fluoride: Administer topical fluoride to strengthen enamel.

Second Visit

• Diet Analysis: Review the diet chart with the parents.
• Sugar Control: Identify and isolate sugar sources in the diet and provide instructions to control sugar exposure.
• Caries Activity Tests: Conduct tests to assess the activity of carious lesions.

Third Visit

• Endodontic Treatment: If necessary, perform root canal treatment on affected teeth.
• Extractions: Remove any non-restorable teeth, followed by space maintenance if needed.
• Crowns: Place crowns on teeth that require restoration.
• Recall Schedule: Schedule follow-up visits every three months to monitor progress and maintain oral health.

Glass ionomer cement is a tooth coloured material 
Material was based on reaction between silicate glass powder & polyacrylicacid.
They bond chemically to tooth structure & release fluoride for relatively long period

CLASSIFICATION 

Type I. For luting

Type II. For restoration 

Type II.1 Restorative esthetic 

Type II.2 Restorative reinforced

Type III. For liner & bases

Type IV. Fissure & sealent

Type V. As Orthodontic cement

Type VI. For core build up

Physical Properties

1. Low solubility
2. Coefficient of thermal expansion similar to dentin
3. Fluoride release and fluoride recharge
4. High compressive strengths
5. Bonds to tooth structure
6. Low flexural strength
7. Low shear strength
8. Dimensional change (slight expansion) (shrinks on setting, expands with water sorption)
9. Brittle
10.Lacks translucency
11.Rough surface texture

Indications for use of Type II glass ionomer cements 

1) non-stress bearing areas 

2) class III and V restorations in adults 

3) class I and II restorations in primary dentition 

4) temporary or “caries control” restorations 

5) crown margin repairs 

6) cement base under amalgam, resin, ceramics, direct and indirect gold 

7) core buildups when at least 3 walls of tooth are remaining (after crown preparation)

Contraindications 

1) high stress applications I. class IV and class II restorations II. cusp replacement III. core build-ups with less than 3 sound walls remaining

Composition

 

Factors affecting the rate or setting

1. Glass composition:Higher Alumina – Silica ratio, faster set and shorter working time.
2. Particle Size: finer the powder, faster the set.
3. Addition of Tartaric Acid:-Sharpens set without shortening the working time.
4. Relative proportions of the constituents: Greater the proportion of glass and lower the proportion of water, the faster the set.
5. Temperature

Setting Time

Type 1 - 4-5 min
type II - 7 min

PROPERTIES 

Adhesion :

- Glass ionomer cement bonds chemically to the tooth structure->reaction occur between carboxyl group of poly acid & calcium of hydroxyl apatite.
 
- Bonding with enamel is higher than that of dentin ,due to greater inorganic content. 

Esthetics :
-GIC is tooth coloured material & available in different shades.
Inferior to composites.
They lack translucency & rough surface texture.
Potential for discolouration & staining.

Biocompatibilty :

- Pulpal response to glass ionomer cement is favorable. 
- Pulpal response is mild due to 
- High buffering capacity of hydroxy apatite. 
- Large molecular weight of the polyacrylic acid ,which prevents entry into dentinal tubules. 

a) Pulp reaction – ZOE < Glass Ionomer < Zinc Phosphate 

b) Powder:liquid ratio influences acidity 

c) Solubility & Disintegration:-Initial solubility is high due to leaching of intermediate products.The complete setting reaction takes place in 24 hrs, cement should be protected from saliva during this period.

Anticariogenic properties :
- Fluoride is released from glass ionomer at the time of mixing & lies with in matrix.
Fluoride can be released out without affecting the physical properties of cement.

ADVANTAGE DISADVANTAGE