CLASS II AMALGAM. Design Principles

Transcription

1 CLASS II AMALGAM Design Principles

2 CLASS II

3 Class II cavitated caries lesions

4 Class II cavitated caries lesions opaque white haloes identify areas of enamel undermining and decalcification from within

5 radiographic appearance of the Class II caries lesion

6 A E1 lesion confined to outer half of enamel

7 E2 lesion reaches into inner half of enamel B

8 cavitated lesion spreading radiolucency at DEJ C

9 Primary Caries E2 D1

10 Primary Caries D2 D1 D3

11 Accepted Terminology extending into proximal extending gingivally preparing a proximal box Jargon dropping a box deepening cervically

12 The Class II cavity prepared to receive amalgam has two parts

13 the occlusal portion design principles are the same as for the Class I cavity

14 the proximal portion or proximal box design principles will be presented now

15 names of walls for the the occlusal portion of the Class II cavity are similar to the Class I Class II Class I

16 BUCCAL WALL MESIAL WALL DISTAL WALL Class II BUCCAL WALL LINGUAL WALL Class I DISTAL WALL LINGUAL WALL

17 PULPAL FLOOR Class II Class I PULPAL FLOOR

18 names of walls for proximal portion of Class II cavity

19 DISTAL WALL BUCCAL WALL LINGUAL WALL GINGIVAL SEAT

20 BUCCAL WALL LINGUAL WALL

21 BUCCAL OCCLUSAL WALL LINGUAL OCCLUSAL WALL BUCCAL PROXIMAL WALL LINGUAL PROXIMAL WALL

22 AXIAL WALL

23 names of line angles for proximal portion of Class II cavity AXIO-PULPAL LINE ANGLE AXIO-BUCCAL LINE ANGLE AXIO-LINGUAL LINE ANGLE BUCCO-GINGIVAL LINE ANGLE AXIO-GINGIVAL LINE ANGLE LINGUO-GINGIVAL LINE ANGLE

24 names of cavosurface margins for proximal portion of Class II cavity BUCCAL PROXIMAL CAVOSURFACE MARGIN LINGUAL PROXIMAL CAVOSURFACE MARGIN GINGIVAL CAVOSURFACE MARGIN

25 names of point angles for proximal portion of Class II cavity AXIO- BUCCO- GINGIVAL POINT ANGLE BUCCO- GINGIVO- CAVOSURFACE POINT ANGLE AXIO- LINGUO- GINGIVAL POINT ANGLE LINGUO- GINGIVO- CAVOSURFACE POINT ANGLE

26 PROXIMAL OUTLINE FORM PRINCIPLE straight B & L outlines near parallel to long axis of tooth gingival outline perpendicular to long axis of tooth RATIONALE conservative of tooth structure resists forces of occlusion

27 EXTENSION a balance between conservation of tooth structure and the need for access and to remove defective tooth structure

28 PROXIMAL EXTENSION PRINCIPLE encompasses carious tissue eliminates unsupported enamel encompasses contiguous fissures encompasses contiguous restorations RATIONALE eliminates infected tissue eliminates weakened tooth structure reduces risk of secondary caries maximizes restoration lifespan

29 PROXIMAL EXTENSION PRINCIPLE clears adjacent tooth by 0.5mm ( mm) RATIONALE access for matrix band allows inspection of restoration margin access for finishing

30 PROXIMAL DEPTH proximal depth is M-D dimension of proximal box

31 PROXIMAL DEPTH proximal depth is M-D dimension of proximal box Syn: axial depth NOT pulpal depth

32 PROXIMAL DEPTH PRINCIPLE 0.5mm into dentin mm measured at level of gingival seat RATIONALE sufficient bulk of amalgam to prevent fracture maximum thickness of dentin protecting pulp

33 AXIAL WALL PRINCIPLE smooth straight O-G, parallel to long axis of tooth parallels curvature of tooth surface B-L RATIONALE optimize adapatation of amalgam to wall uniform bulk of amalgam to prevent fracture maximum pulpal protection

34 AXIO-PULPAL LINE ANGEL PRINCIPLE rounded or beveled RATIONALE reduces risk of amalgam fracture

35 GINGIVAL SEAT PRINCIPLE smooth, flat, straight perpendicular to long axis of tooth M-D & B-L enamel planed at margin RATIONALE optimize adaptation of amalgam to walls resists forces of occlusion elimination of friable enamel plane margin enamel A A-A A

36 BUCCAL & LINGUAL WALLS PRINCIPLE smooth, straight G-O wall nearest functional cusp convergent 6 G-O wall nearest nonfunctional cusp parallels long axis of tooth RATIONALE optimize adaptation of amalgam to walls helps lock restoration in tooth (retention) preserves strength of cusps (resistance form) FC NFC

37 tangent

38 BUCCAL & LINGUAL WALLS PRINCIPLE angle with proximal cavosurface (measured to tangent) tangent 90 RATIONALE optimizes strength of both amalgam and enamel at margin 110 tangent

39 the cavosurface angle is defined as the angle in metal at the margin of a restoration 90 70

40 BUCCAL & LINGUAL WALLS PRINCIPLE proximal cavosurface angle is (measured to tangent) RATIONALE optimizes strength of both amalgam and enamel at margin

41 PROXIMAL RETENTION GROOVES PRINCIPLE placed in B&L proximal walls 0.5mm deep to DEJ directed laterally, not pulpally extending from G seat to A-P line angle 0.5mm deep gingivally, fading away occlusally rounded cross-section RATIONALE provides mechanical lock against displacement proximally prevents encroachment on pulp prevents undermining enamel maximizes retention while minimizing weakening of tooth

42 CAVITY REFINEMENT PRINCIPLE internal line angles welldefined but not sharp RATIONALE maximizes amalgam resistance to dislodgement reduces stress concentration & risk of subsequent tooth fracture

43 cusp fracture

44 CAVITY REFINEMENT PRINCIPLE B-G and L-G line angles have slight radius RATIONALE reduces stress concentration & risk of subsequent tooth fracture difficult to condense thick amalgam into sharp point angles

45 CAVITY REFINEMENT PRINCIPLE cavosurface margins well-defined & wellsupported RATIONALE easier to visualize & carve following condensation optimize adaptation of amalgam to margins eliminates weak tooth structure maximizes marginal integrity

46 CAVOSURFACE MARGINS unsupported, rough cavosurface margin tooth surface enamel poorly defined

47 CAVOSURFACE MARGINS unsupported, rough cavosurface margin tooth surface poorly defined amalgam enamel

48 ditching

49 CLEANLINESS PRINCIPLE cavity is free of debris & moisture RATIONALE facilitates adaptation of amalgam to the cavity improves physical properties of the restoration by elimination of voids & foreign material

50 TISSUE PRESERVATION PRINCIPLE rubber dam intact adjacent tooth undamaged gingival soft tissues not unduly traumatized RATIONALE isolation important to quality of result prevention of postoperative sensitivity, inflammation, & nidus for further caries attack