Composites: Composition

Composites are tooth coloured restorative materials that are usually recommended for class III, IV and class I cavities with less or no occlusal stress and esthetics are important. Specially designed composites are used in almost 50% of class II restorations, although less durable in comparison to dental amalgam. Composites can be classified as microfilled, nanofilled, flowable, packable, all purpose and laboratory. Composites are used for provisional restorations and core build-ups and in fibre-reinforced posts.

Composites: Properties

You have read about the composition of dental composites in earlier class notes This article will speak about the properties. 

Properties of Composites

The important properties of the composites are as follows:

1. Polymerisation shrinkage - should be low
2. Water sorption - should be low
3. Coefficient of thermal expansion - should be same as tooth
4. Fracture resistance - should be high
5. Wear resistance - should be high
6. Radiopacity- should be high
7. Bond strength to enamel & dentin - should be high
8. Colour match to tooth structure - should be excellent
9. Manipulation - should be easy
10. Finishing and polishing - should be easy

Few of the above mentioned properties may be important for anterior than posteriors restorations and vice versa. The properties of 

microfilled and nanofilled composites are same while the microhybrid's differ from both of them.

Direct Esthetic Restorative Materials

There are four types of direct esthetic restorative materials currently in use. They are:

1. Composites
2. Compomers
3. Hybrid Ionomers
4. Glass Ionomers

Composites are dominating the materials used for direct esthetic restorations. Glass ionomers are primarily used for restorations of cervical eroded areas. Hybrid ionomers provide better esthetics than glass ionomers. Compomers provide improved handling and fluoride release when compared with composites.

Polysulfide Impression Materials

Permlastic is a polysulfide, condensation-cured, elastomeric impression material in three viscosities

Polysulfide impression materials are flexible but do not have the major changes in dimensions during storage like agar and alginate. Furthermore, the polysulfide impression is much stronger and more resistant to tearing than agar or alginate. It can be electroformed and therefore metal dies or models, in addition to gypsum models, can be prepared. 

Non-carious loss of tooth structure

 

Types, clinical features, Causes prevention & treatment

Non-carious loss of tooth structure is a problem that is often found in senior citizens and is a cause of many complaints. It is not a new entity but has acquired more attention in recent time.

Types of tooth wear

1. Abrasion
2. Attrition
3. Erosion
4. Demastication
5. Abfraction

NEET 2022-23 Exam Dates Declared by NBE for NEET-MDS UG and PG

National Board of Examinations in Medical Sciences have declared the dates for NEET MDS, NEET PG & other exams. Candidates can check the exam dates below.

1. NEET-MDS 2023: January 8, 2023
2. DNB/DrNB Final Practical Examination – June 2022: October/November 2022
3. Foreign Medical Graduate Examination (FMGE) December 2022, Foreign Dental Screening Test (FDST) 2022: December 4, 2022
4. Formative Assessment Test (FAT) 2022: December 10, 2022
5. DNB/DrNB Final Theory Examination – December 2022: December 21, 22, 23 and 24, 2022
6. Fellowship Entrance Test (FET) 2022: January 20, 2023
7. FNB Exit Examination 2022: February/March 2023
8. DNB/DrNB Final Practical Examination – December 2022: Feb/March/April 2023
9. NEET-PG 2023: March 5, 2023

Distribution of subject wise questions in NEET MDS examination.

The candidates are being advised to check the details and the updated information at the NBE website - https://natboard.edu.in/ as the dates mentioned are tentative and subject to approval and confirmation.

Harmful Effects of Excessive Radiation

The harmful effects of the excessive dose of the ionizing radiation can be divided into two types. These are as follows:  

1. Deterministic effects and   
2. Stochastic effects  

 We shall discuss them one by one in detail. 

Radiography: Radiation Safety

In earlier articles on radiography, you studied the effects of ionizing radiation on biological tissues. These effects can be divided into two types- Deterministic and Stochastic. Therefore, the radiation safety becomes of paramount importance white taking a radiograph.