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Cl Ι :- Pits and fissure caries- Upper anterior teeth palatal pits- Posterior teeth occlusalsurfaceCl ΙΙ:Posterior teeth proximal surfaceCl ΙΙΙ :Anterior teeth proximal surface ( not involving the incisal angle )Cl ΙV:Anterior teeth proximal surface involving the incisalangleCl V:All teeth cervical 1/3
Cavity preparation stages and steps:Initial stage steps:1. Out line form and initial depth2. Primary resistance form3. Primary retention form4. Convenience formFinal stage steps:5. Removal of infected dentin and old restoration6. Pulp protection7. Secondary resistance and retention form8. Finishing extrenaal walls9. Final cleaning,inspecting,varnishing and conditioning.
Step 1:( Out line form) - Mental image 1st → depth → rough out line → alter by seeing hidden problems.- Remove weakened enamel- Preserve cusp and marginal ridge strength - ↓ faciolingualextention- Connect two close cavities- ↓ dentin depth .2 - .8 mm- Care for D.C extension, esthetic, occlusion and cavosurface margin.
Step 2:( Primary resistance form) - Flat floor- ↓ extension - Rounding internal line angels- Cap weak cusps- Provide enough thickness for restorative material- Box shape- Preserve cusps and marginal ridge- Care for occlusion, remaining tooth structure amount and restorative material type.
Step 3: (Primary retention form) - Occlusaldove tail ( Cl ΙΙ) - Composite mechanical bond with tooth.- Amalgam:* ClΙΙ walls converge occlusally*ClΙΙΙ and Cl V retention grooves*Adhesive systems
Step 4: (Convenience form) - Observation- Accessibility- Ease prepare and restore
Step 7: ( Secondary resistance and retention form )- Cavity wall conditioning by etch enamel and dentin bonding agents- Mechanically:* Retention grooves and locks* Pins, slots and steps* Bevel enamel margins
Step 8: (Finishing extrenalwalls )- Create:* Good marginal seal between tooth and the filling material*Smooth marginal junction* Maximum strength to tooth and the filling material- Care for* Enamel rod direction and support ADJ and laterally.* Margin location* Filling material type → cavo surface angel:a. Amalgam: 90˚ → maximum strength of tooth and Amalgamb. Gold: bevel provide marginal metal ease burnishing and adaptation
Step 9: (Final cleaning,inspecting,varnishing and conditioning).Cleaning by remove debris and smear by citric or polycarboxilic acid
Box only preparation - Small D.C- Facial a lingual proximawallsocclusal convergence- Locks 0.5 mm depth in gingival point angels then decrease occlusally- ( ↓ retention )
Tunnel preparation- Proximal D.C- Marginal ridge intact - ↓ access and visibility
Slot preparation:- At root- Approach facial and lingual- High speed bur 2 , 4- Out line form : limited pulpal depth 0.75 – 1 mm gingivally and 1 – 1.25 mm occlusaly ( enamel )- In facial approach :* Lingual wall face facially as much as possible* Provide access, visibility and convenience* Help in Amalgam condensation- Remove remaining D.C by bur 2 , 4- External walls 90 ˚ cavosurface angel- Retention grooves by bur 1/4 in occlusal and gingival walls at axial line angels, with 0.25 mm depth
Sandwich technique:- G.I.C under composite- G.I.C bond to tooth and composite → ↑ retention and seal.- F → ↓ D.C
Bonded amalgam:- Same preparation- Retain ↑ weakened remaining tooth structure- Need special adhesive materials
Adjoining restorations:- Can repair or replace existing Amalgam filling defective part if the remaining Amalgam filling is good- Adjoining restoration on occlusal surface coz new restoration dove tail can be prepare without eliminating existing restoration dove tail- May prepare Amalgam filling in two or more phases ( eg. Cl ΙΙ lesion continued with Cl V , so 1st prepare and restore Cl ΙΙ before Cl V )
cavity preparation designs:- Conventional- Beveled conventional - Modified- Combination of the above three
Conventional :- Past design- Out line form :* Extend external walls to initial limited uniform dentin depth* External walls follow enamel rod direction* External walls on root meet root surface at right angel- Dentin retention grooves- For materials like ( Amalgam , silica , porcelain ) ( brittle and ↓ edge strength )- Not preferred for composite- For composite if lesion at root ( non enamel areas )
Beveled conventional :- Similar to conventional but with beveled enamel margins- To replace existing filling with conventional ( in enamel area )- For resin filling with ↑ thermal expansion coefficient ( acrylic resin , microfilledcomposite )- Filling bled esthetically with surrounding tooth color ( not like in conventional that a white line appear between tooth and filling " coz marginal enamel racture during fininshing )- Bevel :* By flame diamond bur ( 45˚to external tooth surface )* Rods are exposed → ↑ etched* ↑ etched surface area → ↑ enamel resin bond → ↑ retention and ↓ marginal leakage and discoloration* Width 0.25 – 0.5 mm
Modified :- No specific pulpal depth- No specific wall configuration- Only remove lesion conservatively- Rely on enamel etching for retention- For lesion ( initial , small , new , surrounded by enamel ) - Bevel enamel margin- Retention by grooves if large lesion
Resistance form:- Go around cusps- Don’t go deep pulpally- Depth 1.5 - 2 mm ( 1/2 – 2/3 bur cutting portion) ( 0.1 – 0.2 mm into dentin )- Don’t extend facial and lingual margins more than half way between cusp tip and central groove (1/4 distance between cusp tips )- Eliminate weak enamel wall by joining two cavities near each other less than 0.5 mm- Enameloblasty:* Conserve tooth*Remaining fissure not deeper than 1/4 – 1/3 enamel thickness*Eliminate developmental fault by open it by flame diamond side →smooth surface*Surface left meet cavity preparation with cavosurface angle not greater than 100˚ ( Amalgam margin not less than 80 ˚)* Remove Amalgam from enameloplasty area.- Bur no. 245* 3 mm length * 0.8 diameter *Pear shaped* Produce walls occlusal clearance* Produce rounded internal line angels*Long axis rarallel to tooth long axis* Bur no. 330 smaller size- If marginal ridge remaining thickness more than 1.6 mm → occlusal convergence to mesial and distal walls (if 1.6 mm occlusal divergence )- Isthmus width not more than bur diameter ( not more than 1.5 mm )
Retention form:Parallel or slight occlusal convergence of two or more opposing walls.
Removing remaining D.C:- Bur no. 245 →deepen floor ( maximum 2 mm )- Round bur ( slow speed )- Spoon scavator- Large instruments safe ( ↓ penetration )- Stop if feel hard firm ( as sound dentin ) before all stained discolored dentin removed
Pulp protection:- If ideal depth no need for liner or base- Two layers cavity varnish ( cotton pallet ) → D.T complete seal + ↓ microleakage ( ↓ tooth sensitivity and pulp inflammation )- Moderately deep lesion ( remaining dentin thickness 1 mm or more → place quick setting ZOE thin layer 0.5 mm ) ( don’t cover all pulp floor with ZOE because it is not strong senough to support Amalgam under ↑ occlusal forces )- Boded Amalgam to tooth * After acid etch by new dentin bonding agents contain 4-META*↓microleakage* ↑ Amalgam fracture resistance.- Extensive D.C* Distance between infected dentin and pulp less than 1 mm* ↓ D.C removal if pulp exposure expected ( by x-ray or by dentin pinkish hue )* If exposure occur decide direct pulp capping ( Ca(OH)2 )or R.C.T* Ca (OH)2 ( Dycal ) 0.5 mm base * Spherical Amalgam need ↓ condensational force
Cl Ι Composite: Conventional :- After old Amalgam filling removal- Flat floor- Dentin under cuts- 90˚ cavo surface angelBeveled conventional:- After old Amalgam filling removal- If large lesion- Use bur 245Modified:- For small pits and fissures
