Pharmacology 4th Ed – Tara V Shanbhag, Smita Shenoy
PENICILLIN G
Author: Poojitha Surgi
DENTAL FACTS
- It takes 30 minutes after drinking soda for the acids in it to wear your enamel.
- Try to keep your toothbrush 6 feet from a toilet because bacteria after flushing can travel up to that distance.
- If you don’t floss, you miss 40% of your tooth surfaces.
- Tooth ‘prints’ just like fingerprints are individual to everyone.
- Bananas can help ease tooth sensitivity.
- Cheese is not only good for teeth because it has calcium, but also helps saliva to neutralize acids that cause plaque.
- Taste buds only have a life span of 10 days.
- There are more bacteria in your mouth than there are people on earth.
- The first toothbrush was invented in 1498.
- Tongue is the fastest healing part of body.
- Monkeys and apes take care of their teeth by picking them with twigs.
- 4 billion of people use a mobile phone. 3 billion of them use a toothbrush.
- Giraffes don’t have upper front teeth.
- Carrots contain vitamin A needed for healthy teeth.
- In the early 1600’s the job for dentist did not exist. Instead the job fell on barbers and blacksmiths to perform the majority of dental work.
- Tooth decay is the second most common disease.
🙂
ZINC PHOSPHATE CEMENT
Synonyms: Crown and bridge cement, Zinc oxyphosphate
APPLICATIONS:
Luting of restoration and orthodontic bands & brackets
Thermal insulation
Root canal restoration
High strength bases
Temporary restoration
CLASSIFICATION:
| PARTICLE SIZE | FILM THICKNESS | USE | |
| TYPE 1 | Fine | 25um | Luting |
| TYPE 2 | Medium | 40um | Luting, base |
SETTING OF THE CEMENT:
Phosphoric acid in the liquid dissolves zinc oxide and reacts with aluminium phosphate to form aluminium phosphate gel on the remaining undissolved zinc oxide particles.
SETTING TIME: 2.5 to 8 minutes
MANIPULATION:
It is an exothermic process.
Zinc oxide cement is dispensed on the glass slab and divided into 6 increments(1/16, 1/16, 1/8, 1/4, 1/4, 1/4). It is followed by dispensing of the liquid.
Mixing of the cement should be initiated by the smallest increment with a thin spatula. There should be brisk spatulation with large, wide circular motions to dissipate the heat.
When the spatula is drawn away from the mixture, a strand of 12-19 mm should be produced. Such cement is suitable for cementation.
MIXING TIME:
For each increment: 15-20 sec
Total mixing time: 1.5-2 min
PROPERTIES:
MECHANICAL PROPERTIES: Compressive strength = 104 MPa, Tensile strength = 5.5 MPa, Elastic modulus = 13 GPa
SOLUBILITY: Less soluble in water (0.06%). Soluble in lactic, acetic and citric acids (in-vivo)
ADHESION TO TOOTH: Mechanical bonding ( In case of application of a cavity liner before applying zinc phosphate, it does not bond well due to less retention as it will create smoother surface with less interlocking)
BIOLOGICAL PROPERTIES: Phosphoric acid is acidic and cytotoxic. Younger patients are more susceptible to it because of more open dentinal tubules. Older patients with sclerotic dentin have a tortuous path for the entry of acid.
Biological Considerations of Dental Materials
The biological considerations of dental materials cannot be isolated from their physical properties.
Biological requirements of Dental Materials
A dental material should:
- Be non-toxic to the body.
2. Be non-irritant to the oral or other tissues.
3. Not produce allergic reactions.
4. Not be mutagenic or carcinogenic.
Examples of hazards from chemicals in Dental Materials
✔Some dental cements are acidic and may cause pulp irritation.
✔Polymer based filling materials may contain irritating chemicals such as unreacted monomers, which can irritate the pulp.
✔Phosphoric acid is used as an etchant for enamel.
✔Mercury is used in dental amalgam, mercury vapor is toxic.
✔Dust from alginate impression materials may be inhaled, some products contain lead compounds.
✔Monomer in denture base materials is a potential irritant.
✔Some people are allergic to alloys containing nickel.
✔During grinding of beryllium containing casting alloys, inhalation of beryllium dust can cause berylliosis.
✔Some dental porcelain powders contain uranium.
✔Metallic compounds (e.g. of lead and tin) are used in elastomeric impression materials.
✔Eugenol in impression pastes can cause irritation and burning in some patients.
✔Laboratory materials have their hazards, such as: cyanide solution for electroplating, vapours from low fusing metal dies, siliceous particles in investment materials, fluxes containing fluorides, and asbestos.
✔Some periodontal dressing materials have contained asbestos fibres.
REFERENCES:
1.Textbook of Dental Materials – John J Manappallil
2.Images – Google
Finishing and Polishing: Goals & Benefits
🎯 GOALS…
- To obtain : ✔ Desired anatomy ✔ Proper occlusion ✔ Reduction of roughness, depth of gouges & scratches
- Polished surface should be smooth enough to be well tolerated by oral soft tissues and to resist bacterial adhesion & excessive plaque accumulation.
- When plaque deposits exist on restorative material surfaces, they should be easily removable by brushing & flossing.
⭐ BENEFITS ⭐
- BETTER GINGIVAL HEALTH:- A well contoured & polished restoration resists the accumulation of food debris and pathogenic bacteria. ✔ Food glides more freely over occlusal & embrasure surfaces during mastication.
- CHEWING EFFICIENCY:- Strength is improved especially in surfaces where more occlusal forces are applied.
- PATIENT COMFORT:- Patient can detect a surface roughness change of less than 1um ✔ Smooth restoration surfaces minimize wear rates on opposing & adjacent teeth.
- ESTHETICS:- Finishing and polishing aid in esthetics.
- TARNISH & CORROSION:- It can be reduced in metallic restoration.
- HYGIENE:- Smoother surfaces have less retention areas & are easier to maintain in a hygienic state when preventive oral care is practiced ( dental floss & toothbrush bristles )
REFERENCE:- STURDEVANTS – CONS. DENTISTRY
Impression techniques used in complete denture fabrication
BACTERIAL CELL WALL
The cell wall is a tough and rigid structure surrounding the bacterium like a shell. It weighs about 20-25% of the dry weight of the cell.
FUNCTIONS:
1.Shape
2. Protection against osmotic damage
3.Rigidity
4.Cell division
5.Possesses target site for antibiotics, lysozymes and bacteriophages. Carries bacterial antigens that are important in virulence and immunity.
The rigid part of the cell wall is a peptidoglycan which is a mucopeptide (murein) composed of N-acetyl muramic acid and N-acetyl glucosamine molecules alternating in chains, cross-linked by peptide sub-units.
DIFFERENCES BETWEEN GRAM POSITIVE AND GRAM NEGATIVE CELL WALL
| CHARACTER | GRAM POSITIVE | GRAM NEGATIVE |
| Thickness | 20-80nm | 10nm |
| Periplasmic space | Absent | Present |
| Lipids and Glycoproteins | Few(0.3%) | Many(58%) |
| Teichoic acid | Present | Absent |
| Peptidoglycan | <15% | 10-20% |
| Gram’s reaction | Violet | Pink |
| Outer membrane | Absent | Present |
| Lipopolysaccharides | Absent | Present |
DEMONSTRATION OF CELL WALL
1.Plasmolysis
2,Microdissection
3.Differential staining
4.Reaction with specific antibody
5.Electron microscopy
BACTERIA WITH DEFECTIVE CELL WALL
- MYCOBACTERIA: Naturally occurring bacteria without cell walls. They don’t require hypertonic environment for maintenance and are stable in culture medium.
- L-FORMS: Kleineberger-Nobel, while studying Streptobacillus moniliformis in the Lister Institute, London, observed abnormal forms of bacteria and named them L-forms after Lister Institute. L-forms developed either spontaneously or in the presence of penicillin or other agents that interfere with synthesis of cell wall.
- PROTOPLASTS: Derived from gram positive bacteria. Produced artificially lysozyme in a hypertonic medium.
- SPHEROPLASTS: Derived from gram negative bacteria. Produced in the presence of penicillin. They differ from protoplast in that some cell wall material is retained.
PLEOMORPHISM AND INVOLUTION FORMS
Certain species of bacteria exhibit great variation in shape and size of individual cells are called pleomorphic bacteria.
Some bacteria show swollen and aberrant forms in ageing laboratory cultures and are known as involution forms.
Defective cell wall synthesis is responsible for development of these two forms 🙂
SOURCE: MICROBIOLOGY – C.P BAVEJA
Dentowesome 