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BASIC PRINCIPLES OF RESTORATIVE DENTISTRY

BASIC PRINCIPLES OF RESTORATIVE DENTISTRY. UNCLASSIFIED//REL TO NATO/ISAF. Overview. The completion of a restorative procedure for a patient is only one part of patient care.

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BASIC PRINCIPLES OF RESTORATIVE DENTISTRY

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  1. BASIC PRINCIPLES OF RESTORATIVE DENTISTRY UNCLASSIFIED//REL TO NATO/ISAF

  2. Overview • The completion of a restorative procedure for a patient is only one part of patient care. • It is a highly technical service that involves dental surgery (the cutting and manipulation of affected dental tissues) and reconstruction using special materials and instruments. AFAMS Dental Advisor Team

  3. Overview • The basic principles of restorative dentistry will differ with different restorative materials. The principles discussed in this unit pertain to silver amalgam restorations. AFAMS Dental Advisor Team

  4. Overview • The basic principles discussed in this unit will be important in many units that follow, so it is imperative that you have a good understanding of these principles. AFAMS Dental Advisor Team

  5. Holding Instruments • There are different ways to hold instruments – 2 techniques • Pen Grasp • Palm-thump Grasp CFHSTC Clin Perio Crse 0013

  6. Pen Grasp • The pen grasp is not actually the way a pen is held for writing. • The instrument is held between the index finger and thumb, and the middle finger is placed atop the handle or shank, nearer the working end of the instrument, to provide more force, or thrust, directed toward the working end of the instrument. AFAMS Dental Advisor Team

  7. Pen Grasp AFAMS Dental Advisor Team

  8. Pen Grasp • The pen grasp is used in a chopping (downward) motion. • The ring finger is resting on the incisal edges of the anterior teeth. During the use of any instrument in the mouth (with the exception of the mirror), a firm rest must be achieved on teeth or attached gingival tissue. AFAMS Dental Advisor Team

  9. Pen Grasp AFAMS Dental Advisor Team

  10. Pen Grasp • The pen grasp is shown here as the instrument is used more posteriorly and with a side-to-side or scraping motion. • The small finger and ring finger are resting on the facial and occlusal surfaces, respectively. AFAMS Dental Advisor Team

  11. Pen Grasp AFAMS Dental Advisor Team

  12. Pen Grasp • The importance of a finger rest during all operative procedures cannot be overemphasized. AFAMS Dental Advisor Team

  13. Palm-Thumb Grasp • In this grasp, the thumb serves as a brace. • The thumb controls side-to-side, rotation, or thrusting movements of the instrument by the wrist and fingers, which is firmly in contact with the teeth. • This grasp is used mostly when working on the maxillary anterior teeth. AFAMS Dental Advisor Team

  14. Palm-Thumb Grasp AFAMS Dental Advisor Team

  15. Palm-Thumb Grasp • The instrument is grasped much nearer to its end than in the pen grasp, so that the thumb can be braced against the teeth to provide control during movement of the instrument. AFAMS Dental Advisor Team

  16. STEPS IN CAVITY PREPARATION • Cavity preparations should be related to the: • tooth’s anatomy and position in relation to the other teeth • extent of the carious lesion • replacement material’s physical properties AFAMS Dental Advisor Team

  17. STEPS IN CAVITY PREPARATION • The following sequence of steps must be followed during cavity preparation: • Gain access to the lesion • Remove caries in a lateral direction only • Confirm appropriate treatment (according to clinical situation) • Plan cavity preparation (re: external outline form) • Complete cavity preparation (re: internal outline form) • Remove remaining unsupported enamel and place additional retentive features if necessary • Remove caries pulpally and axially • Wash, dry and assess AFAMS Dental Advisor Team

  18. STEPS IN CAVITY PREPARATION 1. Gain Access to the Lesion • Initial access is achieved with the first cutting of the tooth surface. This occurs at a prominent pit or area of decay to an initial depth of 2.0 mm. • This will put the bur at 0.5 mm into dentin. AFAMS Dental Advisor Team

  19. STEPS IN CAVITY PREPARATION Gain Access to the Lesion • The angle of the bur for initial penetration into the carious lesion at the central pit of a premolar or molar should be perpendicular to a plane: •  through the tips of the buccal and lingual cusps •  across the mesial and distal marginal ridges. AFAMS Dental Advisor Team

  20. STEPS IN CAVITY PREPARATION Gain Access to the Lesion • For anterior teeth and the buccal surface of posterior teeth, the angle of the bur is also perpendicular to a point on the tooth’s surface where the lesion is. • Access is perpendicular to a line drawn at that point. AFAMS Dental Advisor Team

  21. STEPS IN CAVITY PREPARATION Gain Access to the Lesion • Why is access to the lesion always perpendicular to the surface of the tooth? • Enamel rods are perpendicular to the surface and we want 90 degrees to eliminate unsupported rods. Therefore, if penetration is perpendicular to the surface we are penetrating parallel to enamel rods and this ensures that no enamel rods are left unsupported by dentin. AFAMS Dental Advisor Team

  22. STEPS IN CAVITY PREPARATION 2.Confirm Appropriate Treatment • Once the size of the preparation has been determined, the restorative material initially chosen when the treatment plan was made, is confirmed as the best choice before further preparation is done. AFAMS Dental Advisor Team

  23. STEPS IN CAVITY PREPARATION 3. Plan Cavity Preparation (External Outline) • External outline of the cavity preparation is related to the: • elimination of undermined enamel (accomplished in second step) • extent of the carious lesion (determined in the seconf step) AFAMS Dental Advisor Team

  24. STEPS IN CAVITY PREPARATION Plan Cavity Preparation Cavity preparations should not be cut to stereotypical forms: • The external outline must also allow adequate access for vision, removal of decay, and instrumentation: • The outline of the cavity preparation may have to be extended to provide this vision and access to complete the cavity preparation or to allow for proper insertion of the restorative material. AFAMS Dental Advisor Team

  25. STEPS IN CAVITY PREPARATION Factors, which reduce the amount of tooth removal required to complete the restoration with convenience, are: • proper lighting • use of a rubber dam to enhance vision and provide gingival retraction • selection of smaller instruments • application of restorative materials that require minimal reduction of tooth material for purposes of retention and fracture-resistance • restorative material's ability to be placed in areas of the tooth that will resist dislodgement AFAMS Dental Advisor Team

  26. STEPS IN CAVITY PREPARATION Extension for Prevention or Restriction with Conviction • Today, with smaller instruments and improved restorative materials, it is not always necessary to remove healthy tooth structure. Conservative cavity preparation removes only carious areas, not caries susceptible areas. AFAMS Dental Advisor Team

  27. STEPS IN CAVITY PREPARATION Attain smooth flowing curves – no sharp edges. AFAMS Dental Advisor Team

  28. STEPS IN CAVITY PREPARATION Extension for Prevention or Restriction with Conviction: • Occlusalcavosurface margins of posterior cavity preparations should not end directly on contacting areas with the opposing arch. • They end in grooves or on inclines of cusps or marginal ridges. AFAMS Dental Advisor Team

  29. STEPS IN CAVITY PREPARATION Extension for Prevention or Restriction with Conviction: • Proximal CSMs are extended to areas that are self-cleansing especially in posterior teeth. • In other words, contact with the adjacent teeth is broken slightly. A hand instrument or explorer can be used to determine the proper extension of facial, lingual and gingival margins by measuring the space between the cavity preparation margins and the adjacent tooth. Where recurrent caries is not anticipated the thickness of an enamel hatchet or the tine of an explorer (.5 mm) is considered adequate. AFAMS Dental Advisor Team

  30. STEPS IN CAVITY PREPARATION Extension for Prevention or Restriction with Conviction: • Join cavity preparations which are within 1.0 mm of each other to avoid leaving weak tooth structure. AFAMS Dental Advisor Team

  31. STEPS IN CAVITY PREPARATION Complete Cavity Preparation • Using appropriate instruments and techniques, a suitable cavity preparation is completed. • It is important to plan fracture-resistance of the tooth-restoration unit. • The cavity preparation should not contribute to the breakage of the restorative material, which will fill it, or the remaining tooth structure it is meant to save. AFAMS Dental Advisor Team

  32. STEPS IN CAVITY PREPARATION Complete Cavity Preparation • The surface area of the restoration exposed to chewing forces should be kept as small as possible. • Keep isthmus as narrow as possible – ¼ to ⅓ the intercuspal distance Correct extension faciolingual cross-section AFAMS Dental Advisor Team

  33. STEPS IN CAVITY PREPARATION Complete Cavity Preparation • Avoid extending the cavity preparation outline too far and weakening cusps or marginal ridges Incorrect extension mesiodistal cross-section Correct extension mesiodistal cross-section AFAMS Dental Advisor Team

  34. STEPS IN CAVITY PREPARATION Complete Cavity Preparation • A faciolingual cross-section through the isthmus area of a cavity preparation for dental amalgam should display internal line angles that are rounded but defined. INCORRECT CORRECT AFAMS Dental Advisor Team

  35. STEPS IN CAVITY PREPARATION Complete Cavity Preparation • Sharp line angles concentrate stresses and promote cusp fracture during mastication. • Rounded internal angles distribute stress. CORRECT INCORRECT AFAMS Dental Advisor Team

  36. STEPS IN CAVITY PREPARATION Complete Cavity Preparation • Cavity preparation floors and seats must be strong, flat, smooth, and perpendicular to the occlusal forces to distribute the forces of mastication and resist harmful movement of the restoration. Resistance forms must consider resistance of tooth to fracture from forces exerted on restoration. Flat floor (A) will prevent restoration movement, whereas rounded pulpal floor (B) is conducive to restoration rocking action producing a wedging force, resulting in shearing tooth structure. AFAMS Dental Advisor Team

  37. STEPS IN CAVITY PREPARATION • Finish Enamel (remove unsupported enamel rods) and place additional retentive features if required. •  The occlusal enamel walls may have to be planed smooth with fissure burs at slow speeds. Proximal enamel walls are planed with sharp hand instruments such as hatchets and chisels. •  The enamel walls are refined to leave full-length enamel rods extending from the DEJ to the cavosurface. AFAMS Dental Advisor Team

  38. STEPS IN CAVITY PREPARATION Buccal pit preparation of a molar that is cut perpendicular to the external facial,lingual, or approximal surface would not have occlusal walls oriented with the occlusal direction of the enamel rods. Coronal section through inter- proximal box cavityprep- aration. Use of a rotary bur, which may leave the proximal wall with an acute enamel angle and indermined enamel, requires careful planning. Marginal defect, resulting from improper cavity wall prep- aration, leads to eventual loss of enamel at the restoration interface. AFAMS Dental Advisor Team

  39. STEPS IN CAVITY PREPARATION • This is a most delicate and important phase of cavity preparation because it prevents the future fracture of unsupported enamel rods and creates a smooth surface that permits better adaptation and finishing of the restoration at the cavosurface. weak amalgam edge weak enamel rods Want 90o CSMs AFAMS Dental Advisor Team

  40. STEPS IN CAVITY PREPARATION An acute cavosurface margin of enamel has the potential for fracture; a 90-degree enamel margin on the occlusal surface will withstand occlusion. The left margin exhibits an acute “fin” of amalgam, which has a greater propensity for fracture, depending on the load applied to it during mastication. The right marginal configuration allows nearly a 90-degree angle for amalgam, imparting greater strength AFAMS Dental Advisor Team

  41. STEPS IN CAVITY PREPARATION • Frictional retention results from the parallel cavity preparation walls and/or the intimate contact of the restorative material or dental adhesive with the cavity preparation walls. AFAMS Dental Advisor Team

  42. STEPS IN CAVITY PREPARATION Mechanical retention results from: • undercuts including (a) retentive grooves, (b) retentive points, and (c) walls converging towards the tooth surface AFAMS Dental Advisor Team

  43. STEPS IN CAVITY PREPARATION dovetails which are widened, fanned-out portions of cavity preparations, are established to assist large Class 2 or 3 restorations and resist lateral displacement Class 2 Cavity Preparation showing retentive slot Occlusal Outline Form showing occlusal dovetail Proximal View showing slightly converging B & L proximal walls AFAMS Dental Advisor Team

  44. STEPS IN CAVITY PREPARATION Remove caries AFAMS Dental Advisor Team

  45. STEPS IN CAVITY PREPARATION Wash, Dry and Assess Cavity Preparation (final cleansing) • Prior to final clinical inspection of the cavity preparation, it must be cleaned. Water from the dental unit syringe and HVE are used to clear the majority of the debris from the operating field. • Do not desiccate dentin with prolonged use of air. • Apply air only until visible moisture is eliminated. AFAMS Dental Advisor Team

  46. STEPS IN CAVITY PREPARATION Teeth which have restorations are prone to recurrent caries. • Faulty planning, completion and final assessment of cavity preparations increase the risk of recurrent caries. AFAMS Dental Advisor Team

  47. Common Sites of Dental Caries • Around existing restorations: AFAMS Dental Advisor Team

  48. STEPS IN CAVITY PREPARATION Teeth which have restorations are prone to recurrent caries. Recurrent caries is usually the result of failure to:  • remove all infected and weakened tooth structure • extend the cavity preparation margins to caries resistant areas • remove all unsupported enamel. AFAMS Dental Advisor Team

  49. STEPS IN CAVITY PREPARATION Final assessment of the cavity preparation must assure that it has the proper characteristics that will ensure a successful restoration. The cavity preparation should not contribute to: •  further injury of the dentin/pulp complex, •  fracture of the tooth-restoration unit, •  loss of the restoration, •  recurrent caries. AFAMS Dental Advisor Team

  50. سوالات؟ Questions? UNCLASSIFIED//REL TO NATO/ISAF

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