Answers of lab cons


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Answers of lab cons

  1. 1. 1) What are the dental instrument parts? What are the advantages of contra angle? Most dental instruments are composed of three parts 1:handle 2:shank 3:blade or nib Advantage of conta angle To bring the cutting edge into near aligment with the long axis of handle to provide balance ,to facilitate control of instrument during application of force , and avoide twisting of the instrument . ………………… 2) Write the principles achieved by A: Parallel wall : to provide retention form ,opposing walls of occlusal restorations shoud be parallel to each other or should converge occlusally, enamel rod in most areas of the occlusal sur are directed roughly parallel to the long axis of the tooth . B: cavo-surface angle. To enhance their ability to resist fracture , so enamel margins should be prepared at 90 degree or more abtuse angle c) rounded angle to avois stress concentration and distribution of force c: removing undermined
  2. 2. the enamel at the margin of the preparation should be supported by sound dentin, any enamel that has been undermined should be removed wide opening and extension: Extending around the cusps to conserve tooth structure and prevent the internal line angles from approaching the pulp horns too closely. keeping the facial and lingual margin extension minimal as possible between the central groove the cusp tips. Minimally extending into the marginal ridges (only enough to include the defect) without removing dentinal support. …….. 6) Define Dental caries using mineral word and mention plaque classification? Dental caries is aprocess which may take place on any tooth surface in oral cavity where amicrobial film is allowed to develop for aperiod of time Classifications Class 1 :caries affecting pits and fissures Class 2:caries affecting the proximal sur of posterior teeth Class3 :caries affecting the proximal sur of anterior teeth Class4 :caries affecting approximal sur of anterior teeth and involving the incisal edge Class 5: caries affecting the cervical surface
  3. 3. 7) The main principles of cavity preparation in class 1 and define each one? 1:establish out line form , out line form is based primary on the location and extent f carious lesion,tooth fracture 2:obtain resistance form :resistance for the remaining tooth structure and to restoration ,so the restoration is resistance to displacement and both restoration and tooth structure are resistance to fracture the shape given to a prepared tooth to enable the restoration and remaining tooth structure to withstand masticatory stress 3:obtain retention form:prevention of dislodgment of restoration along the path of insertion,the provision made in a prepared tooth cavity to hold in place a restoration and to prevent its displacement. 4:obtain convenience form 111 ‫التكمله من الكتاب صفحه‬ 8) Mention 2 goals of amalgam burnishing? 1:shaping the occlusal surface of restoration 2:aiding in condensation 3:avoid marginal infiltration ………………………….. 9) Mention five elements in the amalgam capsule?
  4. 4. Mercury , silver . tin , copper,zinc , indium , palladium 10) Mention three advantages of contra angle shank. 1: To bring the cutting edge into near aligment with the long axis of handle to provide balance 2: ,to facilitate control of instrument during application of force 3: and avoide twisting of the instrument and prevent rotation and modified access ……………….. Caries 3, where this caries involve and what its clinical appearance? Class3 :caries affecting the proximal sur of anterior teeth Opaque chalky region (white spot ) 5) What are the benefits of thin layer of flowable composite under packable composite? Base and isolater