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PIN RETAINED RESTORATIONS

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PIN RETAINED RESTORATIONS

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  1. PIN RETAINED RESTORATIONS Dr Rakesh Kumar Yadav

  2. INTRODUCTION • Most of the teeth can be restored with amalgam and composite but if large crown portion lost due to caries or some other reasons, the remaining tooth structure is decrease and difficult to obtained resistance and retention form so prepare dentine lock and slot but when these retention features are insufficient to provide desired retention then pin supported restorations are used.

  3. TRETMENT OF BADLY BROKEN TOOTH • First-Evaluate biologically and mechanically • Status of pulp and periodontium should be evaluated. • Involvement of pulp or not • Restorative design planning if pulp is not involve-pin,inlay,onlay • Pulp involvement- pulpotomy ,pulpectomy, pin,full coverage- • Tooth anterior or posterior

  4. HISTORY In 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

  5. DEFINITION Defined as any restoration which requires the placement of one or more pins in dentin to provide to adequate resistance and retention form to the restoration. It has a greater retention than those using boxes or bonding system.

  6. INDICATIONS • Badly broken down or mutilated teeth. • Questionable prognosis-Controlled restoration in tooth with questionable pulp or periodontal prognosis • As a foundation under fixed restoration(core) • Economics • Age and health of the patient

  7. CONTRAINDICATIONS • Occlusal problems • Esthetics-Rarelly used in anterior teeth(Bonding Technique). • Access difficulties-In class V horizontal groove in the gingival & occlusal aspect etc.

  8. ADVANTAGES • Conservation of tooth structure • save time compared with cast restoration. • Greater resistance and retention form • Economics

  9. DISADVANTAGES • Dentinal micro fractures or crazing • Lowered fractured resistance • Strength of amalgam restoration is reduced • Micro leakage around pin • Perforations of pulp or ext. tooth structure. • Difficulty to achieve proper contours

  10. TYPES OF PINS • Cemented pins • Friction locked pins • Self threaded pins

  11. 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/locked the pins • Cause craze lines or cracks • Retain by resilience of dentin

  12. SELF THREADED PINS • Developed by Dr. Going in 1966 • Most popular type among all, the different types and most extensively used pin. • Made of stainless steel or gold plated titanium pins • Provide maximum retention among all types of pins • Cause craze lines • Used in vital teeth

  13. SELF THREADED PINS – THREAD MATE SYSTEM

  14. SELF THREADED PINS – THREAD MATE SYSTEM

  15. PIN DESIGNS

  16. ADVANTAGES OF TMS PINS • Versatile design • Wide range of pin sizes • Color coding allows ease of use • Gold plating eliminates corrosion • Good retention

  17. FACTORS AFFECTING THE RETENTION OFTHE PIN IN DENTIN AND AMALGAM • Orientation, number and diameter -Non-parallel pin - ↑ retention -Bending of pin – not desirable Interfere with condensation of amalgam Weaker pin, fractured dentin • ↑ no. of pin - ↑ retention ↑ crazing & fracture ↓ amount of dentin available ↓ amalgam strength

  18. PIN PLACEMENT • MECHANICAL ASPECTS • ANATOMICAL ASPECTS • MECHANO – ANATOMICAL ASPECTS

  19. MECHANICAL ASPECTS • A] STRESSING CAPABILITIES OF PINS • B] RETENTION OF PINS IN DENTIN • C] MICROCRACKING AND CRAZING

  20. MECHANICAL ASPECTS [PINS AND TOOTH STRUCTURE] A] Stressing capabilities of pins • Type of pins • Diameter of pins • Pin depth and dentinal engagement • Bulk of dentin • Type of dentin

  21. 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

  22. Drill – its use and function • Stresses induced during shortening pins • Retentive features • Inserting pins in stress concentration area of tooth

  23. 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

  24. 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

  25. C] MICROCRACKING AND CRAZING • Type of pin • Proximity of pin to DEJ • Induced stresses in involved dentin • Type of dentin

  26. ANATOMICAL ASPECTS • Knowledge of anatomy • Radiograph • Outer surface of tooth • Amount of dentin

  27. MECHANO ANATOMICAL ASPECTS FOR PIN PLACEMENT • Anatomical features • Tooth alignment • Cavity extent • Effect of age or relative age on the pulp chamber

  28. TECHNIQUES FOR INSERTING PINS • Pin channel preparations • Cemented pin technique • Threaded pin technique • Friction grip pin technique

  29. PIN CHANNEL PREPARATION • Twist drill-By using twist drill latch type or depth limiting drill at low speed ( 300-500) RPM • No. 1/4 round burs- first make pilote hole with round bur to localize position of the pin the complete the hole in one or two thrust( movement) • Apply intermittent pressure

  30. CEMENTED PIN TECHNIQUE INDICATIONS • Ideal technique • Only technique for endodontically treated tooth • Only technique to be used when avaliable location of the pin is close to DEJ

  31. Ideal technique for a sclerotized / tertiary / calcific barrier / highly demineralized / dehydrated dentin • For class IV restorations • When there is limited bulk of dentin

  32. 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 magnetisedtweezer or hemostat

  33. 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

  34. THREADED PIN TECHNIQUE INDICATIONS • 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

  35. 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

  36. FRICTION GRIP PIN TECHNIQUE INDICATIONS • For vital teeth • When bulk of dentin is present [min 4mm in all 3 dimensions] • Only in the accessible areas

  37. 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

  38. With the hammer light strokes are given until that colored mark • Remove all the holding devices • Check for cracks, chipped pieces or grossed fractures

  39. 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 supra-gingivally

  40. 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