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Pin retained restorations


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  • 2. CONTENTS1. Introduction2. Definition3. Indications and contraindications4. Advantages and disadvantages5. Pins – types and designs6. Pin placement – factors7. Techniques for inserting pins8. Cavity preparations9. Complications and failures
  • 3. INTRODUCTION Most of the teeth can be restored with amalgam and composite but when the tooth preparation is extensive due to caries or other reason the remaining tooth structure is very less, it becomes difficult to achieve optimal resistance and retention form. In such cases dentin lock and slots are prepared in dentin
  • 4.  But when these retention features are insufficient to provide desired retention then pin supported restorations are used In these cases pins support the restorative materials and resist their dislodgment in severely damaged tooth
  • 5. HISTORYIn 1958, Dr. Miles Markley introduced a practical instrumentation for the use of a stainless steel cemented pin that resulted in the extensive use of cemented pins in dentistry
  • 6. DEFINITIONPin retained restoration is defined as any restoration which requires the placement of pin/pins in dentin in order to provide retention and/or resistance form to the restoration
  • 7. INDICATIONS Extensive tooth loss Questionable prognosis As a foundation Economics Age and health of the patient
  • 8. CONTRAINDICATIONS Occlusal problems Esthetics Access difficulties
  • 9. ADVANTAGES Conservation of tooth structure Appointment time Resistance and retention form Economics
  • 10. DISADVANTAGES Dentinal micro fractures Lowered fractured resistance Strength of amalgam restoration is reduced Micro leakage Perforations Difficulty to achieve proper contours
  • 11. TYPES OF PINS1. Cemented pins2. Friction locked pins3. Self threaded pins
  • 12. CEMENTED PINS Developed by Dr. Markley to retain large amalgam restorations Made of Stainless Steel They are used to build foundation after endodontic treatment as they produce the least amount of stress Offer less resistance than the other pins
  • 13. FRICTION LOCKED PINS Developed by Dr. Goldstein in 1966 Made of stainless steel More retentive than cemented pins Used in vital teeth with good access and ease of tapping the pins Cause craze lines or cracks
  • 14. SELF THREADED PINS Developed by Dr. Going in 1966 Most popular type among all the different type of pins and extensively used Made of stainless steel or titanium pins Provide maximum retention among all types of pins Cause craze lines Used in vital teeth
  • 15. CEMENTED PINS FRICTION LOCKED PINS SELF THREADED PINSStainless steel with Stainless steel with Stainlessthreads or serrations threads steel/Titanium with gold platingPin channel [0.020” Pin channel is 0.001” Pin channel is 0.015”to 0.32”] larger than smaller than pin size to 0.004” smallerpin size [0.018” to than pin size0.30”]Luted with standard Taped into place with Placed by handluting agents mallet wrench or contra angle hand pieceEase of placement Pin placement is Pin placement is difficult easy
  • 16. CEMENTED PINS FRICTION LOCKED PINS SELF THREADED PINSLess internal Increased internal Increased internalstresses stress stressesLeast retentive 2-3 times more 5-6 times more retentive than retentive than friction cemented pins locked pins
  • 19. REGULAR MINIM MINIKIN MINUTA•Largest •Next smaller •Diameter is •SMALLESTdiameter pins diameter pins lesser than SIZE of pins•Causes •Lesser stress minim pins •They are toomaximal are created •Very less risk small tostress •Lesser of dentinal provide•Causes dentinal crazing adequatemaximum crazing •Good retentiondentinal •Good retention •Not widelycrazing retention •MINIM AND used•Rarely used MINIKIN ARE COMMONLY USED SIZES OF TMS SYSTEM
  • 21. Standard •7mm longdesign •They have flattened heads to fit into the hand wrench or handpiece chuck •After placement the pin is reversed 1/4th turn to reduce stresses on dentin •Pin height can be adjusted appropriatelySelf •Avaliable in varying lengthsshearing •They have flattened heads to fit into the hand wrench ordesign handpiece chuck •During pin placement when the pin reaches the bottom of the pin hole, the head automatically shears off, leaving a portion projecting from dentinTwo in one •It consists of 2 pins connected by means of a joint which servesdesign as a shear line for peripheral pin •Total length is 9mm and 2 pins are about 4mm each •They have flattened heads to fit into the hand wrench or handpiece chuck •The handpiece need not be reloaded during insertion of more than 1 pin
  • 22. Link series •They have a plastic sleeve that fits into the latch typedesign contra angle handpiece or a special plastic hand wrench •Self shearing •Pin engages the dentin and the plastic sleeve can be discarded •Can align well into pin channelsLink plus •Similar to link series designdesign •Self shearing •Avaliable as single or 2 in 1 pins •The major difference in this pin design is that pins have sharper threads and a tapered tip to decrease dentinal stresses while seating
  • 23. ADVANTAGES OF TMS PINS Versatile design Wide range of pin sizes Color coding allows ease of use Gold plating eliminates corrosion Good retention
  • 25. MECHANICALASPECTS[PINS AND TOOTH STRUCTURE]A] Stressing capabilities of pins Type of pins
  • 26.  Diameter of pins Pin depth and dentinal engagement Bulk of dentin Type of dentin
  • 27.  Shape of pin channels Loose pins Irregularly shaped dentinal end of pins Ratio of dentinal engagement : pin protrusion [ideal 2:1] Number of pins in one tooth
  • 28.  Drill – its use and function Stresses induced during shortening pins Retentive features Inserting pins in stress concentration area of tooth
  • 29. B] RETENTION OF PINS IN DENTIN Type of pin Pin depth and dentinal engagement Pin channel circumferential shape relative to that of pin Inter pin distance
  • 30.  Type of cement Ratio of dentinal engagement : pin protrusion [ideal 2:1] Type of involved dentin Surface roughness of the pins Mode of shortening of pins after insertion of pins Bulk of dentin around the pin
  • 31. C] MICROCRACKING AND CRAZING Type of pin Proximity of pin to DEJ Induced stresses in involved dentin Type of dentin
  • 32. MECHANICAL ASPECTS[PINS AND RESTORATIVE MATERIALS]A] Effect of pins on the strength of amalgam and composite restorations Compressive strength Tensile strength
  • 33. B] RETENTION OF PINS TO RESTORATIVE MATERIALS Type of pin Pin diameter Inter pin distance Pin length in restorative material Proximity of restorative material with the pin surface Surface material of pins
  • 34. ANATOMICAL ASPECTS Knowledge of anatomy Radiograph Outer surface of tooth Amount of dentin
  • 35.  Anatomical features Tooth alignment Cavity extent Effect of age or relative age on the pulp chamber
  • 37. TECHNIQUES FOR INSERTINGPINS Pin channel preparations Cemented pin technique Threaded pin technique Friction grip pin technique
  • 38. PIN CHANNEL PREPARATION Twist drill No. 1,2,3 round burs Measuring probes or depth guage
  • 39. CEMENTED PIN TECHNIQUEINDICATIONS Ideal technique Only technique for endodontically treated tooth Only technique to be used when avaliable location of the pin is close to DEJ
  • 40.  Ideal technique for a sclerotized / tertiary / calcific barrier / highly demineralized / dehydrated dentin For class IV restorations When there is limited bulk of dentin
  • 41. PROCEDURE Preparation of pin channel Checking the surface irregularities of pins Slow setting phosphate / polycarboxylate introduced by perio explorer tip or lenticulo spiral at slow speed Placement of pin using lock in or magnetised tweezer or hemostat
  • 42.  Large amalgam plugger is needed to check the complete seating of the pin In case of class IV restorations, bending of the pins is to be done before cementation of the pin channel
  • 43. THREADED PIN TECHNIQUEINDICATIONS Vital teeth Dentin to engage the pin is either primary or secondary Minimum avaliable location is 1.5mm from DEJ If minimum pins are needed for the restoration
  • 44. PROCEDURE Preparation of pin channel Pin is engaged to a driving device and pin is continuously threaded into the pin channel until it offer resistance initiated by the pin channel floor Desired length of the pin can be cut using small bur and high speed handpiece in the direction of threading and with light intermittent touches Surface irregularities are corrected No bending should be performed
  • 45. FRICTION GRIP PIN TECHNIQUEINDICATIONS For vital teeth When bulk of dentin is present [min 4mm in all 3 dimensions] Only in the accessible areas
  • 46. PROCEDURE Pin channel is prepared Checking the surface irregularities of pins Put a colored mark on the pin to indicate the exact depth of the pin channel using a measuring probe Pin is held in its place at the entrance of the cavity Concave headed seater is placed on the pin
  • 47.  With the hammer light strokes are given until that colored mark Remove all the holding devices Check for cracks, chipped pieces or grossed fractures
  • 48. CAVITY PREPARATION Remove all carious and weakened tooth structure Initial cavity is prepared with dovetails, boxes, grooves etc Facial and lingual walls are kept parallel wherever possible Margins are placed supragingivally
  • 49.  Areas to receive pins should be flat and perpendicular to long axis of the tooth. There must be enough dentin for pin placement Weakened cusps should be reduced and occlusal contour should follow the normal contour of the unreduced tooth PULP PROTECTION
  • 50. CLASS II DESIGN Pins should be put in apically deepest and most peripheral parts of the cavity Pin should not be placed below the cusp Decreasing the stress concentration on the pin Use of minimum number of pins with less diameter Placement of the pin should be such that theres enough restorative material around it
  • 51. CLASS III AND CLASS IVDESIGNCLASS III Pronounced gingival floor in 2 dimensions must be made One pin per gingival floor is sufficient
  • 52. CLASS IV For unilateral class IV, L shaped cemented pin is sufficient For bilateral class IV, U shaped cemented pin is used
  • 53. CLASS V DESIGN Pins are placed axially parallel to the adjacent proximal surface Pin protrusion should be minimal Deep retentive grooves are placed Pins should be placed midway in the preparation but as close to gingival wall as possible
  • 55. COMPLICATIONS Drill breakage Pin breakage Loose pins Heat generation Dentinal cracks Perforation into pulpal space or external tooth surface
  • 56. FAILURES
  • 57. EFFECT OF PINS ON PULP Generally it responds positively and accepts its presence without any adverse effects Histologic evaluation reveals inflammatory response, necrotic tissue encapsulation, fibrous tissue regeneration and formation of pre dentin by odontoblasts Inflammatory reactions have been observed under all kinds of pins
  • 58. CONCLUSION The prognosis of the involved tooth and its role in overall treatment plan helps to decide the restoration to be placed If amalgam is selected as the restorative material to be placed, pins placed in dentin improve the retention of the restoration Pins have been extensively used in the past to restore such badly broken
  • 59. REFERENCES1. Principles and practices of Operative Dentistry – Gerald T Charbeneau2. Text book of Operative Dentistry – Nisha Garg3. Text book of Operative Dentistry – Vimal K Sikri4. Operative Dentistry – Modern theory and practice – M A Marzouk5. Sturdevents’ Art and Science of Operative Dentistry6. Clinical Operative Dentistry Principles and
  • 60. THANK YOU