9 11.Cl5 Amal.principles.09

7/31/2019 9 11.Cl5 Amal.principles.09

1/69


2/69

CLASS V AMALGAM

Design Principles


3/69

CLASS V


4/69

DISTAL

WALL

GINGIVAL WALL

OCCLUSAL WALL

MESAL

WALL

DC

DBC

MBC

DBC

MBC


5/69

AXIAL WALL


6/69

OUTLINE FORMPRINCIPLE

rounded trapezoid in

gingival third G & O outline

straight & parallel to

occlusal table

RATIONALE

conforms to usual

lesion location provides retention


7/69

EXTENSION

a balance between

conservation oftooth structure and

the need for access

and to remove

defective tooth

structure


8/69

EXTENSIONPRINCIPLE

encompasses carioustissue

eliminates unsupportedenamel

encompasses contiguousrestorations

RATIONALE

eliminates infected tissue

eliminates weakenedtooth structure

maximizes restoration

lifespan


9/69

OCCLUSO-GINGIVAL EXTENSION

PRINCIPLE

occlusally to height of

contour or extent oflesion

gingivally to extent of

lesion (frequentlysubgingival)

RATIONALE

provides access

(convenience form)


10/69

MESIO-DISTAL EXTENSIONPRINCIPLE

to line angles of tooth or

extent of lesion

RATIONALE

provides access

(convenience form)


11/69

AXIAL DEPTH

PRINCIPLE

depth 0.5mm into

dentin (1-1.25mmgingivally, 1.5-

1.75mm occlusally)

RATIONALE

suf ficient bulk of

amalgam to preventfracture

suf ficient O & G walllength for retention

1-1.25mm

1.5-1.75mm


12/69

AXIAL WALL

PRINCIPLE

smooth

curved M-D

straight O-G

parallels surface

RATIONALE

optimize adapatation of

amalgam to wall uniform bulk of amalgam to

prevent fracture

maximum pulpal protection

A

B

B

A

A-A

B-B


13/69

MESIAL & DISTAL WALLS

PRINCIPLE

smooth

diverge creating 90

cavosurface angle

RATIONALE

optimize adaptation

of amalgam to walls optimizes strength of

both amalgam and

enamel at margin

B

B

B-B


14/69

OPTIMUM CAVOSURFACE

ANGLE FOR AMALGAM

cross-section ofamalgam restoration

margin

amalgam enamel

90 butt joint

weak amalgam margin weak enamel margin

surface of tooth


15/69

OPTIMUM CAVOSURFACE

ANGLE FOR AMALGAM

cross-section ofamalgam restoration

margin

amalgam enamel

90 butt joint

weak amalgam margin weak enamel margin

surface of tooth


16/69

OCCLUSAL WALL

PRINCIPLE

smooth

straight mesio-distally

90 cavosurface angle

RATIONALE

optimize adaptation of

amalgam to walls easier to visualize &

carve followingcondensation

optimizes strength ofboth amalgam andenamel at margin

opposes G-wall(retention)


17/69

OCCLUSAL RETENTION

PRINCIPLE

retention groove 0.5mm

deep placed in occlusalwall 0.5mm deep to DEJ

RATIONALE

only required when

preparation is over-extended occlusallybecause occlusal &gingival walls will be

divergent


18/69

GINGIVAL WALL

PRINCIPLE

smooth

straight mesio-distally

70 axio-gingival angle

plane enamel at cavo-

surface margin to 90

RATIONALE

optimize adaptation ofamalgam to walls

easier to visualize &carve followingcondensation

helps lock restoration in

tooth (retention)

elimination of weak toothstructure

70

90


19/69

70

angles of

gingival wall

90

gingival wall

cavosurface angle

axio-gingival angle

axial wall


20/69

plane enamel at cavo-

surface margin to 90

90


21/69

CAVITY REFINEMENT

PRINCIPLE

internal line angles well-

defined but not sharp

RATIONALE

maximizes amalgam

resistance todislodgement

reduces stressconcentration & risk

of subsequent toothfracture


22/69


23/69


24/69


25/69


26/69

CAVITY REFINEMENT

PRINCIPLE

angles between O, M, G,

& D walls rounded

RATIONALE

reduces stressconcentration & riskof subsequent toothfracture

dif ficult to condense

viscous amalgam intosharp external angles


27/69


28/69

CAVITY REFINEMENT

PRINCIPLE

cavosurface margins

regular, well-defined,well-supported

RATIONALE

easier to visualize & carvefollowing condensation

optimize adaptation ofamalgam to margins

eliminates weak toothstructure

maximizes marginalintegrity


29/69

CLEANLINESSPRINCIPLE cavity is free of debris

& moisture

RATIONALE

facilitates adaptation

of amalgam to thecavity

improves physical

properties of therestoration by

elimination of voids

& foreign material


30/69

CLASS V AMALGAM

Preparation Technique


31/69

CEJ


32/69


33/69


34/69


35/69


36/69


37/69


38/69

#245

rounded straight fissure bur

3.5mm head length

t t h O li


39/69

create trench near O-line

i t i d th


40/69

maintain even depth

just shy of bur head length (3mm)

as trench follows curvature of surfacefrom M to D

k b di l t f


41/69

keep bur perpendicular to surface

as it curves from M to D

this creates a flat

occlusal wall and a

curved axial wall


42/69

i h f 3


43/69

starting shy of 3 mm

allows room for refining

the axial wall later

create a second trench near the G-line


44/69

create a second trench near the G-line

this one is less than 2mm deep

(1/2 length of bur head)

t ti t h


45/69

cut connecting trenches

with matching depths

remove intervening plaster


46/69

remove intervening plaster

rough out axial wall


47/69

rough out axial wall

maintain curvature

& O-G depth change

begin M & D walls just shy of pencil line


48/69

begin M & D walls just shy of pencil line

keep bur perpendicular to surface of tooth

M & D walls should be divergent


49/69

M & D walls should be divergent

axial wall should curve from M to D


50/69

the target axial depth is

3mm occlusally

2mm gingivally

being slightly shy of thesemeasures is preferable at

this point to allow room

for smoothing

finishing with the primary & secondary cutting edges of a hatchet


51/69

finishing with the primary cutting edges of a chisel


52/69

finishing with the primary cutting edges of a chisel

plane gingivo-axial angle to 70 with gingival margin trimmer


53/69

plane gingivo axial angle to 70 with gingival margin trimmer

plane the gingival cavosurface margin enamel


54/69

finished walls should just reach the pencil line


55/69

j p

self-evaluate beforeseeking instructor evaluation

accomplished: 30-O Class I cavity preparation for amalgam


56/69

planned: 30-F Class V cavity preparation for amalgam

p y p p g

imagine there is a Class V caries lesion


57/69

draw outline with gingival line at FGM


58/69

bench instructor approval recommended

Bow


59/69

Double-Bowed

212 Retainer

For

gingivalretraction

Li beak

Fa beak

Bow

To increase g ing iva l re t rac t ion fac ia l ly , bend l ingual beak inc isa l ly


60/69

212 retainer used to retract the gingiva


61/69

begin 1.5mm deep (


62/69

extend mesially & distally


63/69

axial wall depth approx. 1.5mm--

l ll l i i ll


64/69

more occlusally, less gingivally

extend walls to pencil lines


65/69

may need to remove 212

to create divergent M & D walls

finish walls with

chisel 111 hoe or


66/69

chisel, 111 hoe, or

hatchet

Wedelstaedt chisel

111 hoe

set gingival wall to 70 with gingival margin trimmer


67/69

self-evaluate before

seeking instructor evaluation


68/69

seeking instructor evaluation


69/69

Documents

9 11.Cl5 Amal.principles.09