CHAPTER 8: CLINICAL TECHNIQUE FOR CLASS III-IV

main steps in tooth preparation for a Class III direct composite restoration

Access the defect (caries, fracture, etc.)

Remove faulty structures (caries, defective dentin/enamel, old restorations)

Create convenience form, often with a facial enamel bevel for esthetics

why lingual approach preferred for Class III restorations involving proximal surfaces

Conserves facial enamel for better esthetics

Less critical shade matching

Restoration discoloration/deterioration is less visible

indication of facial approach for Class III restorations

Lesion positioned facially to conserve tooth structure

Irregular tooth alignment making facial access more conservative

Extensive lesion extending onto facial surface

Replacement of a faulty facial restoration

instruments and techniques used for initial access in Class III preparation

Round carbide bur or diamond compatible with lesion size, entry perpendicular to enamel surface, light pressure, intermittent cutting (brush stroke), careful to avoid overextension

preparation shape and beveling in Class III restorations

Walls may diverge externally for a beveled marginal design; enamel bevels are usually applied at 45 degrees and 0.5-2 mm wide for esthetics and retention

considerations for gingival and root surface margins in Class III preparations

Gingival floor should have a 90-degree cavosurface margin, axial depth ≤ 0.75 mm, external walls perpendicular to root surface, and minimal extension to preserve enamel

when removal of old restorative material is necessary during Class III preparation

If old material is amalgam affecting color, caries beneath old material, symptomatic pulp, damaged restoration margins, deteriorated bonding, or to improve bonding surface

additional retention features be added in Class III restorations

If retention needs to be enhanced, grooves (gingival) or coves (incisal) may be added alongside bonding

treatment managed for adjacent or multiple Class III lesions

prepare and restore the larger lesion first for improved access, then the smaller lesion; reverse order for restorative insertion

isolation and matrix aids are used in Class III restorations

Rubber dam placement after anesthesia and shade selection

wedge inserted to depress dam and soft tissue for better gingival access

should be assessed before tooth preparation in Class III restorations

occlusal function and contacts

must be evaluated to design the preparation and adjust restoration for proper function.

importance of isolating the working field in Class III restorations

prevents contamination from saliva and moisture, which improves adhesive bonding effectiveness.

placing a wedge prior to restoration help in Class III

helps reestablish proper proximal contact and depress the rubber dam and soft tissues, improving access and adaptation.

purpose of maintaining a pulpal floor approximately 0.2 mm inside the DEJ

It creates a natural pulpal floor that rises occlusally when extended facially or lingually, preserving tooth strength.

unsupported enamel

intentionally left on the facial wall during Class III preparation

if the enamel is nonfriable and in a low-stress area

preserving it conserves tooth structure and improves esthetics

enamel bevels on Class III restorations prepared in relation to their width

bevel width ranges from 0.5 to 2 mm depending on preparation size, margin location, and esthetic requirements.

enamel bevel

this beveling is omitted especially near gingival or lingual margins

when enamel thickness is minimal or absent, or beveling would place the restoration margin in occlusal contact areas, bevels are omitted to maintain strength.

role of RMGI bases in deep Class III preparations

they seal the dentin, provide a protective barrier, and support bonding, especially when dentin thickness is <1.5 mm.

initial entry angle when starting the preparation with a rotary instrument

the bur should be held perpendicular to enamel but angled so the neck portion reaches as far as possible into the embrasure without touching the adjacent tooth.

effect of incorrect entry during preparation

may overextend the outline,

weaken the tooth structure unnecessarily,

complicate restoration.

divergent walls

this preparation walls not prepared to be perpendicular to enamel in Class III

instead, should diverge externally in small Class III restorations

as it results in a beveled margin that enhances bonding while conserving internal tooth structure

recommended margin design for gingival floor when the outline extends onto the root surface

a 90-degree cavosurface margin with external walls perpendicular to the root surface.

depth of gingivoaxial line angle

be limited to no more than 0.75 mm depth initially when the preparation extends gingivally

this is to preserve dentin and cementum integrity

direct pulp capping with calcium hydroxide or MTA

what is recommended if pulp exposure occurs during preparation?

management of calcium hydroxide or MTA liners after placement

always cover with a resin-modified glass ionomer (RMGI) base to seal and protect the liner.

advantage of preparing multiple adjacent lesions in one appointment

access from the larger preparation simplifies subsequent conservative restorations on adjacent teeth.

to enhance mechanical retention when bonding alone is insufficient.

why retention features like grooves or coves be added in some Class III preparations?

clinical sign indicates the need to remove an old restoration during Class III prep

Visible deterioration

recurrent caries under restoration

compromised bonding.

2 primary purposes of applying a matrix before restorative material insertion

to confine restorative material excess

To assist in developing appropriate axial tooth contours.

when matrix and wedge applied in relation to adhesive placement

before applying the adhesive, to contain adhesive components to the prepared tooth.

triangular wedges

a type of wedge used for deep sulcus margins

round wooden toothpick ends

a type of wedge used for margins coronal to gingival sulcus

purpose of trial opening and closing of the Mylar matrix before restoration

To ensure sufficient opening for insertion access

adequate closure for proper contour formation.

wedge placement facilitated when using a rubber dam

by stretching the rubber dam gingivally on the insertion side and using water-soluble lubricant on the wedge tip.

to prevent premature polymerization.

why light-cured composite be protected from ambient light before placement?

ways to remove excess composite before matrix closure

quickly removed with the blade of the insertion instrument or an explorer tine.

how the operator should handle the matrix strip during composite insertion and curing

Hold lingual side with index finger, reflect facial side with thumb; close lingual end over composite and hold, then pull matrix toward facial side to adapt composite; finally, close facial end and manually shift for proper contours before curing.

Yes, but avoid touching the matrix tip initially to prevent distortion of the restoration contour.

Can composite be light cured through the matrix?

ways to handle adjacent multiple restorations

restore the preparation with least access (usually second prepared) first, contour fully before restoring the other.

recommended instruments finishing and polishing convex and concave surfaces

for convex/flat — Flexible discs and finishing strips

for concave — oval finishing burs and polishing points

for both — polishing cups

speed and motion used with carbide finishing burs

Medium speed

light intermittent brush strokes with air coolant.

this is to remove excess composite on facial surfaces

abrasive discs

used in finishing

from coarse to fine grit, shifting motion to prevent flat spots, using various diameters to fit embrasure areas.

No. 12 surgical blade

used in finishing to remove excess composite from gingival proximal areas with precision, avoiding overreduction

finishing strips

used to contour proximal surfaces

Passed under contact or through embrasure

curved over tooth/restoration

pulled facially while avoiding gingival damage.

when occlusion be checked during the procedure

after rubber dam removal, by having the patient bite on articulating paper and adjusting as needed.

importance of preoperative occlusal assessment in Class IV direct composite restorations

It influences tooth preparation extension (placing margins in noncontact areas)

determines retention and resistance needs, especially in heavy occlusion.

challenges exist in shade selection for large Class IV restorations

Proper shade selection is more difficult; separate translucent and opaque composite shades are often necessary.

purpose of taking a preoperative impression for large Class IV restorations

to use as a template for developing restoration contours.

3 main goals of tooth preparation for Class IV direct composite restorations

Access to defective structure

Removal of faulty structures

Creation of convenience form for restoration.

difference of preparation for large incisoproximal Class IV defects from small ones

larger defects need more retention, possibly including groove retention, and wider enamel bevels for stronger bonding and esthetics.

recommended bevel angle and width for Class IV restorations

45-degree angle; 0.5 to 2 mm width depending on tooth structure missing and needed retention.

retention forms added when restoring large incisoproximal Class IV defects

groove-shaped or other undercuts

dovetail extensions

a gingival retention groove 0.2 mm inside DEJ, 0.25 mm deep extending along gingival floor and line angles

No, because incisal area is mostly enamel

Is retentive undercut usually necessary at the incisal area in Class IV restorations?

problems with Mylar matrices in Class IV restorations

Matrix flexibility can cause over- or undercontoured restorations and open contacts

excess composite extrusion incisally.

creasing the matrix at the lingual line angle

helps reduces undercontouring (rounding) at that area of the restoration.

preformed plastic or celluloid crown forms

not recommended as matrices for Class IV restorations bc they are usually too thick and hard to control.

fabrication of custom lingual matrix for large Class IV restorations

using polyvinyl siloxane or fast-set silicone impression putty or from a mockup restoration/waxed study model.

when adhesive be placed when using a lingual matrix

before seating the matrix.

difference of finishing and polishing of Class IV restorations from Class III

more difficult due to incisal edge and extended facial surface involvement; requires close assessment of incisal edge thickness and facial macro/microanatomy.

purpose of extending the enamel bevel in large Class IV restorations

to increase surface area for etching, enhancing bond strength and esthetic results.

how a custom lingual matrix be made if the existing restoration or tooth structure is missing preoperatively

using a quickly inserted mockup restoration or waxed study model.

recommended finishing and polishing instruments for Class IV restorations

aAccording to the surface shape — discs and strips for flat/convex, oval burs for concave, cups for polishing.

materials used to prepare a custom lingual matrix

Polyvinyl siloxane impression putty

fast-set silicone matrix materials.

recommended instruments for contouring the incisal edge in Class IV restorations

fine diamond burs and polishing points with careful control to preserve anatomy.