م.د. محمد عبدالمنعم عبداللطيف

• Sterilization: Sterilization involves any process, physical or chemical that will destroy all forms of life, including bacterial, fungi, spores and viruses. • Disinfection: It is the process of using an agent that destroys germs or other harmful microbes or inactivates them. • Antisepsis: It is the destruction of pathogenic micro-organisms existing on the living tissue. Center for disease control and prevention (CDC) classified the instrument into critical, semicritical and noncritical depending on the potential risk of infection during the use of these instruments.

Instruments are used to examine, clean, cut, and help to restore teeth. The main types of cutting instruments are either hand-held or rotary instruments driven in a handpiece. Other equipment includes fibreoptic lights for illumination, light-curing systems used for polymerization of resinbased materials (such as; composite materials), new instruments for tooth-cutting/ caries removal, and ultrasonic scalers. These instruments may be reused after suitable decontamination and sterilization procedures, or else are disposable, single-use items.............

Dental caries is a multifactorial disease that causes destruction to the hard tooth structures due to acids released by bacteria. There are sveral factors combine to cause dental caries at which they are: 1. Host (tooth and saliva). 2. Diet (carbohydrates). 3. Dental plaque (bacteria). 4. Time............

Dental pulp is the soft tissue of the tooth. The pulp occupies the internal cavities or spaces of the tooth which include the pulp chamber and the pulp canal (root canal). The shape of the pulp cavities correspond to the external outline form of the tooth (the shape of the pulp chamber corresponds to the shape of the crown whereas the shape of the pulp canal corresponds to the shape of the root). The size of the pulp cavity depends on the age of the tooth and history of trauma.

The development of the crown and the root of the tooth take place within the bone in the jaw. The tooth passes through stages named according to their shapes.......

It is usually described as four-cusped, two placed buccally and two lingually. It has been reported that five-cusp forms were more commonly present in dentitions of mongoloid origin. It supplements mandibular first molar in function.........

The mandibular first molar is the largest tooth in the mandibular arch. It is usually the first permanent tooth to erupt at age of 6 year. It has five well developed cusps: two buccal, two lingual, and one distal. It has two well-developed roots, one mesial and one distal, which are very broad buccolingually. These roots are widely separated at the apices. The distal root is smaller and usually more rounded than the mesial root........

The maxillary second molar is a smaller replica of the first molar with similar root and canal morphology. It is the seventh tooth from the midline of the maxillary arch and supplements the maxillary first molar in function. It is also known as “teenager tooth” because of its age of eruption. No fifth cusp is evident.......

The maxillary molars differ in design from any of the teeth previously described. These teeth assist the mandibular molars in performing the mastication (grinding the food), also they support the muscles of mastication. They are the largest and strongest maxillary teeth. They have large crowns with four well-formed cusps; two buccal cusps and two lingual cusps. Also, they have three roots; two buccal and one lingual, the lingual root is the largest. The outlines and curvatures of all the maxillary molars are nearly similar.

The mandibular second premolar most commonly has three cusps but can have two as well. The three-cusp variety has one large cusp on the buccal with two smaller lingual cusps. The mesiolingual cusp is twice the size of the distolingual cusp. The three-cusp type, is UNIQUE since it is the only premolar that has three triangular ridges (one per cusp), and these ridges do NOT join to form a transverse ridge.......