Sim Clinic Standardised Measurements

Question 1

What are the dimensions required for an anterior PBM prep? What burs are used and margins produced?

• Incisal
• Labial:
• Proximal:
• Lingual:

Answer 1

Incisal:
-2.0mm (Technik 847)

Labial:

• Incisal 2/3: 1.5mm (Technik 847)
• Gingival 1/3: 1.0-1.3mm (Technik 847; shoulder margin)

Proximal:
-1.0mm (incisally) to 0.5mm (gingivally) (L10 or 169L then Komet 8877; transition from shoulder to fine chamfer margin)

Lingual:
-0.5mm (gingival cingulum wall) (Komet 8877, fine chamfer margin)
0.5-0.8mm (concave surface metal only)
1.0mm (concave surface metal + ceramic)
(Horico 239 or F40)

Question 2

What are the reductions and margins required for a posterior PBM prep? What burs are used?
Occlusal:
Buccal
Proximal

Answer 2

Occlusal:
Jet 330 parallel to long axis for depth cuts; Komet 8877/Tecknik 856/Horico 239 parallel to cusp inclines for reduction
-Metal veneered with ceramic: 2mm
-Metal alone (non functional cusp): 1mm
-Metal alone (functional cusp (1.5mm) 

Buccal (2 planes):
-Occlusal 2/3 (cusp): 1.5mm (856 or 8877)
-Gingival 1/3:
shoulder 1.0-1.3mm (847)
Heavy chamfer: 1.0mm (856 or 8877)
Bevelled shoulder: 1.0-1.3mm (847 and 8877
for bevelling)
(Bur aligned parallel to long axis of tooth,
which usually happens to be parallel to buccal
gingival third)

Proximal:
0.5mm gingivally to >1mm occlusally
6-10 degree taper
Initially L10 or 169L, then Komet 8877 (change from buccal margin to lingual light chamfer)

Lingual reduction (2 planes):

• Occlusal 2/3 (cusp): 1.5mm (856 or 8877)
• Gingival 1/3: 0.5mm to 0.8mm occlusally (Komet 8877 or Technik 856)
• Bur alignment is parallel to buccal gingival 1/3

(Note: in the actual order of procedure, occlusal and side of functional cusp done together as first step)
*Afterwards use Fiz10 to open buccal shoudler to 100 degrees to remove unsupported enamel

• IMPORTANT: If lower tooth, functional cusp reduction is the same as the buccal occlusal 2/3 reduction, there is NO NEED to do any further reductions beyond this. Proceed with lingual reductions as usual
• If upper tooth, extra functional cusp reduction 1.5mm needed on the palatal cusp IN ADDITION to the 1.5mm reduction on buccal-occlusal 2/3 aspect

Question 3

What are the reduction dimensions for an anterior PBZ crown? What margins are used?
Incisal
Proximal
Labial
Lingual

Answer 3

Margin: 1.3mm rounded shoulder (heavy chamfer) all the way around the tooth

• Prep must be smooth/rounded with no sharp points as scanning device can not accurately scan right angled surface
• Note that scanner also can not scan undercuts: important to avoid
• While prepping do not run the bur at full speed, control with foot pedal
• Keep in mind thickness of Zirconia coping around 0.6mm, prep must cater to this and around 0.4mm ceramic minimum

Incisal: 2.0mm

Labial:
Incisal 2/3: 1.5mm
Gingival 1/3: 1.0 to 1.5mm

Proximal: 1.0-1.5mm (1.3mm)
Lingual: 1.0-1.5mm (1.3mm)

Question 4

What are the reduction dimensions for a posterior PBZ crown?

Answer 4

Occlusal: 1.5 to 2.0mm
Functional cusp: 1.5 to 2.0mm
*Rounded shoulder/heavy chamfer 1.3mm all the way around tooth (proximal, buccal + lingual 1/3)
*Smooth flowing preparation with no sharp points

*If upper tooth, extra functional cusp reduction 1.5mm needed on the palatal cusp IN ADDITION to the 1.5mm reduction on buccal-occlusal 2/3 aspect