Getting to the Margin of the Matter: Simple Solutions for Crown and Bridge Dentistry

Timothy M. Bizga, DDS, FAGD

www.2thLectures.com

ABOUT ME

• “It might well be said of me that I have merely made up a bunch of other men’s flowers, and brought nothing of my own but string that ties them together in a bunch, which I gladly offer to you”

• Michele Eyquem de Montaigme

Today’s Goals

• Improve Patient Care and the Experience

• Deliver applicable information

• Improve YOUR business results

• Have a great time

Overview

• ADA “ A Profession in Transition” August 2013

• 40% of dental revenues are crown and bridge, 80% of which are single unit

• On average, $900 per month lost in remakes

“Success in dentistry is mainly dependent on doing the basics well”

~Anonymous

“Success is not an accident!”~ Tony Robbins

If I Put My Dentist Hat On…

✓ Will it make my dentistry better?

✓ Can it make my job easier?

✓ Can it allow me to work faster?

✓ Will it hold-up better then what I already use?

✓ Is it less expensive?

My Thoughts on Efficiency in Dentistry

Working Quickly AND

Getting It Done Right the First Time

The Single Unit Crown Procedure

• Crown Preparation

• Provisional Impression

• Final Impression

• Provisional Crown

• Provisional Cementation

• Definitive Cementation

The Fundamental Aim of Tooth Preparation

...transform the tooth by a planned process

...to a uniformly reduced geometrical form

...with a closely defined finish line

...permitting sufficient space for the planned restoration

Crown Preparation-Reduction and Margin

SHOULDER-BEVEL SHOULDER CHAMFER

METAL CERAMIC CROWNS

FINISH LINES

Subsequent Results Of Shoulder-Bevel Crown Fit Before Cement

• No significant difference in marginal distortion from porcelain fusion (shoulder, shoulder-bevel, chamfer, chamfer-bevel)

Hamaguchi, 1982

• Finish line form did not affect the fit of metal ceramic crowns as a result of porcelain fusion

Richter-Snapp, 1988

Marginal Fit After Cementation

• No significant differences in marginal fit between metal shoulder-bevel, metal shoulder, and porcelain shoulders either before or after cementation

Belser, 1985

• Finish line form does not significantly affect the fit of cemented crowns

Byrne, 1992

Prep Design

My Single & Multi

Alternative Category to Traditional Mechanical Retraction: Paste/Putty

Chemical Retraction

• Additional overhead/consumables costs

• Performs adequately for hemostasis and fluid control but may underperform for retraction

• Some manufacturer’s instructions indicate product may work better in conjunction with cord

• Active compound in majority of products is Aluminum Chloride

• Will require dwell time, and requires aggressive water rinsing

Traxodent - Hemodent Paste Retraction System

Hemostatic Agent

Cord, Traxodent & Cap

Adapting the cap so that it contacts the soft tissue is imperative

Images courtesy of Abdi Sameni. DDS

Prep Sequence

1. Buccal/Lingual Reduction

2. Break Contact3. Reduce Occlusal4. Add secondary Retention

What Really Causes Crowns to Dislodge?

• Resistance to lateral forces and not retention is the determining factor in dislodgement

Wiskott, 1996

Location For Grooves

• Lateral Forces of masticatory cycle and parafunctional habits dislodge crowns

• Resistance to lateral forces is the determining factor in a crown’s resistance to dislodgement

Wiskott, 1996

• Proximal grooves provide complete resistance to FL forces whereas B or L grooves provide only partial resistance

Woolsey, 1978

5. Traxodent

6. Final Impression7. Temp

Model to Final

What About Today’s Modern Margins?

This is the guy who makes your crowns

• What is the average total revenue of a single unit?

– Full fee vs. Insurance

• Office Profitability

–Direct vs. Indirect?

• What does this mean to the office?

– Efficiency and Effectiveness

Fixed Prosthodontic Landscape

Tray Selection

“The Journey of a Thousand Miles Begins with a Single Step” -Lao-tzu

Tray Design and Viscosity Selection

Support for the material has to come from the tray or from the material itself!!!

The less supportive the tray is….the more stiff the material needs to be

Sources of impression distortion

• IF YOU ARE PREPPING THE MOST TERMINAL TOOTH IN THE ARCH, YOU CANNOT USE A TRIPLE TRAY!!! YOU MUST USE A FULL-ARCH OR QUARTER ARCH

Closed bite trays should only be used for 1-2 unit cases, with natural

occlusal stops

Is this a good scenario for triple tray?

Reality

Criteria for Closed-bite tray

INDICATIONS– 1-2 prepared teeth

– Tray will fit behind the tuberosity without impinging on the tissue

– Class I or II occlusion

– Prepared tooth has sound adjacent teeth on each side

– Natural occlusal stops

CONTRAINDICATIONS– More than 2 prepared

teeth

– Insufficient occlusalreduction

– Most distal tooth in the arch

– Class III occlusion

– Inadequate space for the tray posterior to the tuberosity

– No natural occlusal stops

It was reported that 89% of impressions had 1 or more

observable errors

Source: J Prosthet Dent 2005;94:112-7.

Confidential – FOR INTERNAL USE ONLY

Hemostasis must be achieved to record an impression with

accurate detail

Contaminants prevent the impression material from

capturing detail

Tray selection and seating are responsible for this example

Stock trays are not always the answer, tray size and proper

seating are critical

Movement during seating can cause drags in similar locations

Movement during seating can cause loss of marginal detail

Really?!?

Not enough tray material to support the wash material is the problem here, also cotton rolls should be removed from

impression for disinfection purposes & Tray Adhesive

Airwater…To Syringe or Not?

Freshest material on working side!

Intra-Oral Working Time is

Critically Dependent upon Temperature!!!

Working Time of Low Viscosity Impression Materials

Product(Manufacturer)

Per Manufacturers’

Instructions(seconds)

Per ADA Laboratory(seconds)

23°C 35°C 23°C 35°C

Affinis (Coltene/Whaledent, Inc.) NA† 60 80 30

Aquasil Ultra Smart Wetting (DENTSPLY Caulk) 150 NA 120 30

Correct Plus (Pentron Clinical Technologies, LLC)90 NA 40 <10

Examix NDS (GC America, Inc.) 135 NA 200 70

Flexitime (Heraeus-Kulzer) 150 NA 140 50

Genie Ultra Hydrophilic (Sultan Healthcare, Inc.) 135 NA 50 <10

Impregum Penta Soft Quick Step (3M ESPE) 60 NA 140 70

Imprint 3 (3M ESPE)120 NA 120 40

Take 1 (Kerr Corp.) 120 NA 120 40

VP Mix (Henry Schein, Inc.) 135 NA 120 30

Working Time Characteristics

PolyetherPolyvinyl Siloxane

Do not use expired materials

Check to make sure expiration dates have not passed

Materials Selection

• What are the next steps?

• Digital– Start simple

– Work with an incredible lab

– Do not mill chairside

– Do 25 single units before moving to multi

– Biggest hurdle is going back to old methods and old habits

Sure Ways Efficiently Prep forSuccess

1. 0.8mm circumferential margin

2. Use 847KR-016 type modified chamfer bur

3. Add mesial/distal boxes or slots for Resistance Form

4. Great tray selection!!!

5. Regular set might be best option for now

6. Digital is a commitment

Information v. Imparation

• Times are different

• Use dental assistants to full ability under the law

• Win in the first appointment

• Use an efficiency system

Contact Info

• Dr. Tim Bizga• Like Dr. Tim Bizga on Facebook

• @DrTimBizga

• 2thLectures.com

• Email: 2thLectures@gmail.com

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