TOOTH PREPARATION FOR CLASS II AMALGAM RESTORATION

the detail description about the topic is given

1. Dental materials TOPIC : Tooth preparation for class ii AMALGAM RESTORATION Done by : Divya Darsini .S Second year BDS

2. SYNOPSIS : INTRODUCTION INITIAL CLINICAL PROCEDURES TOOTH PREPARATION FOR CLASS II AMALGAM RESTORATION THAT INVOLVE ONLY ONE PROXIMAL SURFACE INITIAL TOOTH PREPARATION OCCLUSAL OUTLINE FORM PROXIMAL OUTLINE FORM PRIMARY RESISTANCE FORM PRIMARY RETENTION FORM FINAL TOOTH PREPARATION REMOVAL OF ANY REMAINING DEFECTIVE ENAMEL AND INFECTION CARIOUS DENTIN PULP PROTECTION SECONDARY RESISTANCE AND RETENTION FORM FININISHING THE PROXIMAL WALLS VARIATION OF PROXIMAL SURFACE TOOTH PREPARATION MANDIBULAR FIRST PREMOLAR MAXILLARY FIRST MOLAR MAXILLARY FIRST PREMOLAR BOX ONLY PREPARATION TOOTH PREPARATION FOR CLASS II AMALGAM RESTORATION INVOLVE TWO PROXIMAL SURFACE OCCLUSAL EXTENSION PROXIMAL EXTENSION

3. EXAMPLES OF MODERATE CLASS II AMALGAM RESTORATION MAXILLARY FIRST MOLAR MANDIBULAR FIRST MOLAR MANDIBULAR FIRST PREMOLAR MANDIBULAR SECOND PREMOLAR MODIFICATIONS IN THE TOOTH PREPARATION OF PROXIMAL SURFACE SLOT PREPARATION FOR ROOT CARIES ROTATED TEETH ADJOINING RESTORATION UNUSUAL OUTLINE FORM RESTORATIVE TECHNIQUE FOR CLASS II AMALGAM PREPARATION DESENSITIZER PLACEMENT MATRIX PLACEMENT UNIVERSAL MATRIX BURNISHING THE MATRIX BAND PREPARING THE RETAINER TO RECEIVE THE BAND PLACING THE BAND WITH RETAINER ON THE PREPARED TOOTH WEDGING TECHNIQUE ROUND VERSUS TRIANGULAR WEDGE RIGID MATERIAL SUPPORTED SECTIONAL MATRIX PRE-COUNTED SECTIONAL MATRIX STRIPS CONDENSATION AND CARVING OF AMALGAM REMOVAL OF THE MATRIX BAND AND CARVING COMPLETION FINISHING AND POLISHING OF THE AMALGAM QUADRANT DENTISTRY

4. introduction Class II restoration restore the defects that affect one or both of the proximal surface of the posterior teeth AMALGAM RESTORATION THAT PROVIDE YEARS OF SERVICE WHEN : THE OPERATING FIELD IS ISOLATED THE TOOTH PREPARATION IS CORRECT THE MATRIX IS SUITABLE THE RESTORATIVE MATERIAL IS MANIPULATED PROPERLY INITIAL CLINICAL PROCEDURE : Occlusal contacts should be marked with articulating paper before tooth preparation . Any opposing ‘plunging cusp’ need to be re-contoured to reduce risk of fracture of new restoration Class to amalgam in premolar and molar

5. TOOTH PREPARATION FOR CLASS II AMALGAM RESTORATION THAT INVOLVE ONLY ONE PROXIMAL SURFACE Bur used in class II tooth preparation 245 BUR

6. INITIAL TOOTH PREPARATION OCCLUSAL OUTLINE FORM : STEP I : PUNCH CUT Enter the pit nearest to the involved proximal surface with a punch cut using a no.245 bur Viewed from the proximal and lingual aspects , the long axis of the bur should be parallel to the long axis of tooth crown during cutting Proper depth of the initial entry cut is 1.5-2 mm . The pulpal depth is usually 0.1-0.2 mm into the dentin . This introduces the principles and technique of class II tooth preparation for an amalgam restoration involving caries lesion on one proximal surface. Pre-operative placement of a wedge[pre-wedging] in the space adjacent to the proximal surface with caries lesion will create space between adjacent teeth PUNCH CUT ENTRY;PROXIMAL VIEW

7. STEP II : OCCLUSAL EXTENTION Proper depth of the initial entry cut is 1.5-2 mm .the pulpal depth is usually 0.1-0.2 mm into the dentin . While maintaining the same depth and orientation , bur is moved to extend the outline to include the central fissure and opposite pit ,if necessary Include all the carious occlusal pits and fissures in such a manner that sharp angles in the marginal outline are avoided The isthmus width should be as narrow as possible , ideally should be ¼th of the intercuspal distance Distal wall can be made occlusally divergent by tilting the bur, if the extension of distal margin would reduce the dentinal support of marginal ridge

8. Step III : OCCLUSAL DOVETAIL Dovetail prevents the proximal displacement of the restoration . It is not required in outline form of single step proximal box ,unless a fissure is radiating from the occlusal pit Enameloplasty should be used where indicated to conserve tooth structure Completed occlusal step Step IV : PROXIMAL EXTENTION Before extending into the involved proximal marginal ridge , the final location of the facial and lingual walls of the proximal box relative to the contact area should be visualized , to prevent over extention of the occlusal outline form [i.e., occlusal step] where it joins the proximal outline form [i.e., proximal box] While maintaining the established pulpal depth and with bur parallel to the long axis of the crown , the preparation is extended mesially , stopping approximately 0.8 mm short of cutting through the marginal ridge into the contact area

9. The occlusal step in this region is made slightly wider labiolingually than in the class I cavity preparation because additional width is necessary for the proximal box The extension include part of mesial marginal ridge DEJ . The location of the DEJ is an important guide in the developed of the proximal preparation REVERSE CURVE PROXIMAL MARGIN

10. PROXIMAL OUTLINE FORM : Again visualize the desired final location of the facial and lingual walls of the proximal box relative to the contact area THE OBJECTIVES FOR EXTENTION OF PROXIMAL MARGINS ARE : Include all caries ,faults ,or existing restorative materials Create 90 degree Cavo surface margins [butt joint margins] E stablish not more than 0.5 mm clearance with the adjacent proximal surface facially, lingually and gingivally. P rimary flare is the flare given from isthmus to the proximal Cavo surface margin . This is done to bring the facial and proximal walls to the facial and lingual embrasures

11. STEP I : PROXIMAL DITCH CUT The initial procedure in preparation of outline form is the isolation of the proximal enamel by giving the proximal ditch cut Allow the end of the bur to cut a ditch gingivally along the exposed DEJ . Two third at the expense of dentin and one third at the expense of enamel . The 0.8 mm diameter bur end will cut approximately 0.5 to 0.6 mm into enamel Proximal Ditch cut STEP II : GINGIVAL EXTENTION OF PROXIMAL WALL The ditch extended gingivally just beyond the caries or the proximal contact , whichever it is greater . Ideally the extension of facial and lingual margins of proximal box should be such that , it provides clearance of 0.2 – 0.3 mm from the adjacent tooth But the clearance greater than 0.5 mm is excessive unless indicated to include caries , undermined enamel , or existing restorative material

12. Ideally the gingival margin should clear the adjacent tooth by only 0.5 mm , which may be measured with the slide of explorer Gingival extension of proximal wall The faciolingual dimension of the proximal ditch is greater at the lingual level than at the occlusal level to provide occlusal convergence of the facial and lingual proximal box walls

13. STEP III : PREPARATION OF AXIAL WALL It is an prepared wall that is parallel to the long axis of the tooth and it is always placed in dentin to obtain resistance and elasticity of dentin bulk of the restoration placement of retentive locks Length of the axial wall : 0.4 – 0.6 mm from the axiopulpal line angle to axiogingival line angle The axial wall should be straight or convex but it should never be concave It should follow the contour of proximal surface PREPARATION OF GINGIVAL SEAT It is an external cavity wall that is perpendicular to the long axis of the tooth It is extended beyond the contact area up to the proximal lesion whichever is more . This also help in providing a contact clearance gingivally It is made flat so that the masticatory force are distributed equally The width of gingival seat : 0.6 – 0.8 mm [premolars] 0.8 – 1.0 mm [molars] It consists of 2/3 of dentin ,1/3 of enamel

14. STEP IV : PROXIMAL EXTENTION OF PROXIMAL BOX In completing the proximal extensions , next make two cuts , one starting at the facial limit of the proximal ditch and the other starting at the lingual limit , extending toward and perpendicular to the proximal surface [until the bur is nearly through the enamel at contact level] The side of the bur may emerge slightly through the surface at the level of the gingival floor

15. ISOLATION OF PROXIMAL ENAMEL

16. STEP V : BREAKING THE PROXIMAL WALL A matrix band may be used around the adjacent tooth to prevent marring its proximal surface The isolated enamel , if still in place , may be fractured out with a spoon excavator or by additional movement of the bur To protect the gingiva and the rubber dam when extending wall gingivally , a wooden wedge should already be in place in the gingival embrasure to depress the soft tissue and rubber dam

17. With the enamel hatchet , the bin angle chisel , or both , cleave away any remaining undermined proximal enamel , establishing the proper direction to the mesiolingual and mesiofacial wall Proximal margins having cavosurface angles of 90 degree are indicated

18. PRIMARY RESISTANCE FORM : Pulpal and gingival walls being flat and perpendicular to the forces and perpendicular to the forces directed to the long axis of the tooth Restrict the extension of the walls to allow strong cusps and ridges to remain with sufficient dentin support Restricting the occlusal outline form to areas receiving minimal occlusal contact Reverse curve optimizing the strength of both the amalgam and tooth structure at the junction of the occlusal step and proximal box Rounding off the internal line angles Providing the enough thickness of the restorative material PRIMARY RETENTION FORM : Occlusal convergence of facial and lingual walls Dovetail design of occlusal step [when present]

19. FINAL TOOTH PREPARATION REMOVAL OF ANY REMAINING DEFECTIVE ENAMEL AND INFECTION CARIOUS DENTIN Accomplished in the same manner as in the class I Preparation Infected carious dentin is removed with a slowly revolving round bur of appropriate size or a discoid type spoon excavator or both

20. The presence of infected dentin carious dentin on a portion of either the pulpal wall [floor] or axial wall does not indicate deepening the entire wall Infected carious dentin on axial wall does not call for preparing axial wall towards the pulp as shown by dotted lines . It should be removed with round bur

21. A partial extension of a facial or lingual wall is permissible if: The entire wall is not weakened the extension remains accessible and visible sufficient gingival seats remain to support the restoration a but joint fit at the amalgam and enamel margin [90 degree amalgam angle and 90 degree Cavo surface angle] is possible PULP PROTECTION : It is desirable to have approx. 2 mm bulk beneath the pulp and metallic restoration which may be dentin , liner or a base Liner / base – mechanical ,chemical ,thermal pulp protection and act as a barrier that protects the dentin

22. Remaining dentin thickness 0.5 – 1 mm zinc phosphate cement , glass monomer cement base is used followed by calcium hydroxide liner The base insulates the pulp from thermal changes , bonds to the dentin, releases fluoride and is strong enough to resist the forces of condensation

23. SECONDARY RESISTANCE AND RETENTION FORM Using the gingival margin trimmer to bevel or round the axiopulpal line angle PROXIMAL RETENSION LOCKS Placed on axiofacial and axiolingual line angles Terminate at axiopulpal point angle Prepared with no.169L bur There are four characteristics or determinants of proximal locks : 1.position 2.translation 3.depth 4.occlusogingival orientation

24. Proximal retention locks

25. POSITION : Refers to the axiofacial and axiolingual line angles of initial tooth preparation it is important to note that retention locks should be placed 0.2 mm inside the DEJ , regardless of the depth of the axial wall and axial line angles TRANSLATION : refers to the direction of movement of the axis of the bur i.e., parallel to DEJ DEPTH : Refers to the extent of translation [i.e., 0.5 mm at gingival floor level] OCCLUSOGINGIVAL ORIENTATION : Refers to the tilt of the no.169L Bur, which dictates the occlusal height of the lock ,given a constant depth PROXIMAL RETENTION LOCKS

26. RETENTION GROOVES : Placed on axiofacial and axiolingual line angles Extend from the gingival floor to the occlusal surface Prepared with no.1/4 round bur with head diameter of 0.5 mm or no.1/8 bur with head diameter of 0.4mm In preparation with deep proximal box grooves should be in the proximal walls just inside the DEJ and not in the corners of the box

27. FOUR CHARACTERISTICS OF RETENSION GROOVES

28. FININISHING THE PROXIMAL WALLS : There should be no unsupported enamel and marginal irregularities present There should but joint relation between the tooth and amalgam Cavo surface [20 degree] at the gingival margin can be given by G.M.T to remove the unsupported enamel rods When the gingival margin is positioned gingival to the cementoenamel junction [CEJ] on the tooth root , the bevel is not indicated

29. VARIATION OF PROXIMAL SURFACE TOOTH PREPARATION MANDIBULAR 1 ST PREMOLAR The support of the small lingual cusp may be conserved by preparing the occlusal step more at the expense of tooth structure facial to the central groove than lingual The lingual cusp may need to be reduced for capping if the lingual margin of the occlusal step extends more than two thirds the distance from the centre fissure to the cuspal eminence SLOPING PULPAL FLOOR : This preparation is done in the mandibular 1 st premolar because of a short lingual cusp and also due to the lingual inclination of the tooth This preparation coincides with the occlusal morphology of the tooth For the preparation that will not cross the transverse ridge, prepare the proximal box before the occlusal portion to prevent removing the tooth structure that will form the isthumus The bur axis is parallel to the tooth crown which is tilted slightly lingually, pulpal Wall is facially inclined

30. MAXILLARY FIRST MOLAR : Extension into the enamel oblique ridge is avoided whenever possible to maintain possible to maintain the cross-splinting strength is provided to the tooth It may require extending through the oblique ridge to unite the proximal preparation with the occlusal step Cutting through the oblique ridge is indicated only if : The ridge is undermined with caries It is crossed by a deep fissure Occlusion portion of the separate MO and DO outline forms leave less than 0.5 mm of the tooth structure between them

31. MAXILLARY FIRST PREMOLAR A class II preparation involving the mesial surface requires attention because the mesiofacial embrasure is esthetically prominent The occlusogingival preparation of the facial wall of the mesial box should be parallel to the long axis of the tooth instead of converging occlusally to minimize in the faciogingival corner of the restoration The facial extension of the mesiofacial proximal wall should be minimal and margins may be placed lingual to the facial contact

32. BOX ONLY PREPARATION A proximal box that is prepared without occlusal step When restoring a small,cavitated , proximal lesion in a teeth with neither occlusal fissures nor a previously inserted occlusal restoration , a proximal box preparation without an occlusal step has been recommended This preparation should be limited to A proximal surface with a narrow proximal contact and When the involved marginal ridge has no occlusal contact To minimize retention ,the box only preparation should have following characteristics Facial and lingual walls that almost oppose each other should recommended Facial and lingual proximal walls converge occlusally Retention grooves are mandatory in box only preparation

33. TOOTH PREPARATION FOR CLASS II AMALGAM RESTORATION INVOLVE TWO PROXIMAL SURFACE This section describes factors to consider when amalgam is used in moderate and large class II restoration . OCCLUSAL EXTENSION Requires extending grooves that are fissured .capping cusps that are underlined , or extending the outline form up the cuspal inclines Grooves extension occurs at the same initial pulpal floor depth [i.e.,1.5mm] but follows the DEJ as the groove is extended in a facial or lingual direction This extension will usually require some alteration in the orientation of the bur : a slight lingual tilt when extending in a facial direction , a slight facial tilt when extending in a lingual direction .

34. PROXIMAL EXTENSION Larger class II restoration will often require larger proximal box preparation Extensive proximal boxes are usually prepared the same as a more conservative proximal box , but may require modification . The increased dimensions of a large proximal box usually require the use of retention locks or other secondary retention form features If the proximal box is extended onto the root surface , the axial wall depth is no longer dictated by the DEJ . Axial wall depth of approximately 0.8 mm.

35. EXAMPLES OF MODERATE CLASS II AMALGAM RESTORATION MAXILLARY FIRST MOLAR The mesioocclusodistal tooth preparation of the maxillary first molar may require extending through oblique ridge to unite the proximal preparation with the occlusal text Extend is indicated only if The ridge is undermined by the caries lesion It is crossed by the deep fissure MANDIBULAR FIRST MOLAR The distal cusp on the mandibular first molar may be weakened when positioning the distofacial wall and margin Facial extension of the distofacial margin to clear the distal contact often places the occlusal outline in the centre of the cusp ; this indicates relocation of the margin to provide a sound enamel wall an 90 degree amalgam that is not on a cuspal eminence

36. MANDIBULAR FIRST PREMOLAR When the mesioocclusodistal amalgam tooth preparation need for first premolar, the support of small lingual cusp may be conserved by preparing the occlusal step more at the expense of the tooth structure facial to the central groove than lingual The bur is slightly tilted lingual to establish correct pulpal wall direction MANDIBULAR SECOND PREMOLAR A moderate mesioocclusodistal preparation on the mandibular second premolar that had a moderately sized MOD carious lesion

37. MODIFICATIONS IN THE TOOTH PREPARATION OF PROXIMAL SURFACE SLOT PREPARATION FOR ROOT CARIES : When caries is present in the proximal aspect without involving the marginal ridge Indicated in cases of gingival recession having root surface caries gingival to the proximal aspect When the adjacent tooth is missing Preparation for class II restoration with facial or lingual access are sometimes referred to as KEY HOLE PREPARATION The tooth preparation is usually approached from the facial and has the form of a slot Prepare retention groove with no.1/4 ,bur into the occlusoaxial and gingivoaxial line angles, 0.2 mm inside the DEJ or 0.3 to 0.5 mm inside the cemental cavosurface margin The depth of these grooves is one half the diameter of the bur head and the bur is directed to bisect the angle formed by the junction of occlusal and axial walls

38. SLOT PREPARATION FOR ROOT CARIES

39. ROTATED TEETH Tooth preparation for rotated teeth follows the same principles as for normally aligned teeth When the tooth is rotated 90 degrees and the proximal lesion is on the facial or lingual surface or orthodontic correction is declined or ruled out , the preparation may require an isthmus that includes the cuspal eminence If the lesion is small , consideration should be given to the slot preparation

40. ADJOINING RESTORATION It is permissible to repair or replace a defective portion of an existing amalgam restoration if the remaining portion of the original restoration retains adequate resistance and retention form Where the two restoration adjoin , care should be taken that the outline of the second restoration does not weaken the amalgam margin of first UNUSUAL OUTLINE FORM Usually seen in mandibular third molars having unusual groove pattern

41. RESTORATIVE TECHNIQUE FOR CLASS II AMALGAM PREPARATION DESENSITIZER PLACEMENT A dentin desensitizer is placed on the prepared tooth structure per manufacturer instruction . Excess moisture is removed without desiccating the dentin MATRIX PLACEMENT The primary function of the matrix is to enable proper restoration of anatomical contours and contact areas The qualities of matrix are : Rigidity Establishment of proper anatomic contour Restoration of correct proximal contact relation Prevention of the gingival excess Convenient application Ease of removal

42. UNIVERSAL MATRIX The universal matrix system is ideally indicated when three surface that is [mesial ,occlusal ,distal ] of the posterior tooth have been prepared This system is commonly used in two surface restoration The advantage of tofflemire retainer is that it may be positioned on the facial or lingual aspect of the tooth

43. TYPES OF BAND : UNCONTOURED BANDS : The conventional flat universal matrix band must be shaped [burnished] to reproduce natural contour and resultant proximal contact Two thickness bands are 0.05 mm 0.038 mm PRE-CONTOURED BANDS : Pre-contoured bands for the universal retainer are commercially available and need no adjustment before being placed in retainer or after being positioned around teeth

44. BURNISHING THE MATRIX BAND : This means that the metal band is intentionally deformed occlusolingually with the with suitable hand instrument to produce a rounded or convex surface that produces restorative that is in contour with the adjacent proximal surface The nos .26-28 is generally recommended for burnishing the band

45. PREPARING THE RETAINER TO RECEIVE THE BAND : STEP 1 : The larger of the knurled nuts is turned contour until the locking vice is positioned adjacent to the guide channel on the end of the retainer STEP 2 : Next , while holding the large nut the dentist turns the smaller knurled nut counter clock wise until the pointed spindle is free STEP 3 : The band is folded to form a loop and to be positioned in the retainer [occlusal edge of band first ] STEP 4 : The spindle is tightened against the band in the locking wise

46. PLACING THE BAND WITH RETAINER ON THE PREPARED TOOTH : STEP 1 : If the proximal wedges are used during the tooth preparation , the wedges are removed at this point and matrix band is fitted around the tooth STEP 2 : Once the matrix band is placed , the larger knurled nut is rotated clockwise to tighten the band slightly . Ideally the band should be positioned 1mm apical to the gingival margin or deep enough to be engaged by the wedge and 1-2mm above the adjacent marginal ridge to allow for adequate condensation of amalgam in the marginal ridge areas

47. WEDGING TECHNIQUE : After the matrix contour and extension are evacuated a wedge is placed in the gingival embrasure. The length of the wedge should approx. 1 to 2 cm SINGLE WEDGING TECHNIQUE Place matrix retainer in place Take a wedge and place the pointed edge from lingual or buccal embrasure whichever is bigger Wedge the band tightly against the tooth

48. PIGGYBACK WEDGING : In this technique two wedges are used One larger wedge is inserted as used normally , while another small wedge is inserted above the larger one It is indicated in cases of shallow proximal box with gingival recession This is a technique provides closer adaptation and contour of the matrix band DOUBLE WEDGING : Two wedges are used One is inserted from buccal embrasure and another from lingual embrasure This technique is used in Spacing between adjacent teeth where the single wedge is not sufficient Widening the proximal box in buccolingual dimension

49. WEDGE WEDGING : In this technique two wedges are used One wedge is inserted from the lingual embrasure area while another is inserted from the wedge and matrix band at right angle to first wedge They are primarily indicated while the treating of mesial aspect of first premolar

50. ROUND VERSUS TRIANGULAR WEDGE : Some situation required a triangular wedge that is modified to conform to the approximating tooth contours The rounded toothpick wedge is usually the wedge of choice with conservative proximal boxes, because its action is more occlusal than triangular wedge The triangular wedge is recommended for a preparation of deep gingival margin

51. MODIFIED TRIANGULAR WEDGE

52. RIGID MATERIAL SUPPORTED SECTIONAL MATRIX The alternative to the universal matrix band is the use of a properly contoured sectional matrix that is rigid enough to resist condensation pressure Examples : light cured , thermoplastic , quick setting rigid PVS materials

53. PRE-COUNTED SECTIONAL MATRIX STRIPS : Commercially available sectional matrix strips are pre contoured and ready for application in tooth These have limited applications when used for amalgam because of their rounded contour

54. CONDENSATION AND CARVING OF AMALGAM Proper condensation of amalgam results in close material adaptation to the preparation walls and minimal inclusion of internal voids STEP 1 :Condensation should occur in the proximal boxes first by enough amalgam with the amalgam carrier to fill the gingival portion about 1 mm STEP 2 :Additional amalgam is carefully condensed against the proximal margins of the preparation and into proximal retention grooves STEP 3 : The procedure of adding and condensing continues until the amalgam reaches the level of pulpal wall STEP 4 : The occlusal margins are covered by at least 1 mm using a large condenser ,ensuring that the marginal ridges are well condensed ,especially in the marginal ridge

55. REMOVAL OF THE MATRIX BAND AND CARVING COMPLETION : STEP 1 : The retainer is removed from the band after turning the small knurled nut contour counter clock wise to retract the pointed spindle STEP 2 : the end of the index finger may be placed on the occlusal surface of the tooth to stabilize the band as the retainer is removed STEP 3 : The number 110 pliers are used to tease the band free from one contact area at the time pushing or pulling the band in linguo occlusal direction STEP 4 : The wedge may be left in place to provide separating of the tooth while the matrix band is removed , and then finally wedge is removed

56. FINISHING AND POLISHING OF THE AMALGAM Finishing and polishing of the occlusal surface of the class II amalgam should follow the approach presented in the general concepts 0f guiding restoration with amalgam restoration Finishing and polishing of the proximal surface may be indicated where the proximal amalgam is accessible The area usually includes the facial , lingual margins and occlusal contact areas

57. QUADRANT DENTISTRY When several teeth is involved in a quadrant have caries lesions the experienced dentist usually treats them all at the same appointment rather than individually Quadrant dentistry increases efficiency and reduces chair time for the patient Use of rubber dam is particularly important in the quadrant dentistry For maximal efficiency , when a quadrant of amalgam tooth preparation is planned , each rotatory or hand instrument should be used on every tooth where it is needed before being exchanged

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