Minimally invasive

endodontics

Dr. Jagadeesh. K P.G 3rd year

Contents

• Definition

• Introduction

• Principles of access cavity preparation

• Minimally invasive access strategies

• A new model for endodontic access

• Endodontic working width

• PIPS

Definition

• The world congress of MID defines minimally

invasive dentistry as those techniques, which respect

health, function and esthetics of oral tissue by

preventing disease from occurring, or intercepting its

progress with minimal tissue loss (Nový and Fuller

2008)

Primary goals of endodontics ???

Tooth retention

Prevention/management of pulpal and periapical disease

PRESERVING STRUCTURAL INTEGRITY

Maintaining strength and stiffness that resists structural deformation becomes the recognized goal of all restorative procedures, especially in endodontics.

Endodontically treated teeth are more brittle and hence more vulnerable to fracture??

Only moisture loss of 9% after root treatment. The predominant reason that endodontically treated

teeth are more prone to fracture relates more than any other attribute to the structural loss of those root treated teeth requiring restoration.

Helfer A R, Melnick S, Schilder H. Determination of the moisture content of vital and pulp less teeth. Oral Surg Oral Med Oral Pathol 1972; 34: 661–670

Unfortunately, structural loss alone cannot answer every clinical question that relates to dentin failure.

• The relevance of fatigue as a main mechanism for

tooth fracture and the resistance of dental tissues

to both the initiation and propagation of cracks is

an important research area

• The resistance to propagation of fatigue cracks in

dentin decreases with increasing patient age and

the incremental rate of crack extension is up to

100 times greater in seniors.

Why endodontically treated teeth fail?

• When endodontically treated teeth fail under function,

that outcome is determined primarily by 2 aetiologies.

Those causes stated most simply are:

1) the degree of stress experienced by the tooth under load

2) the inherent biomechanical properties of the remaining

structure responsible for resisting fracture.

PRINCIPLES IN ACCESS PREPARATION

Do no harm.

Assessment of restorability.

SLA???

External root surface as guide

• Patterns in orifice location, size, colour, shape: 9

LAWS.

(Krasner P, Rankow HJ. Anatomy of the pulp chamber

floor; JOE 2004,30:5)

MINIMALLY INVASIVE ACCESS STRATEGIES

• Important factors that will affect the ultimate

outcome of treatment

• Operator needs,

• Restoration needs,

• Tooth needs.

• Traditional endodontic access has been

endodontic centric, primarily focused on operator

needs, and has been decoupled from the

restorative needs and tooth needs.

• Balance needs to be restored to these 3 needs,

which are almost always in conflict when

performing complete cusp-tip to root-tip

treatment.

SETTING THE STAGE FOR CONTEMPORARY

MOLAR ENDODONTIC ACCESS

• Directed dentin and enamel conservation is the

best and only proven method to buttress the

endodontically treated molar.

• No man-made material or technique can

compensate for tooth structure lost in key areas of

the PCD.

• The primary purpose of the redesigned access is

to avoid the fracturing potential of the

endodontically treated molar

A NEW MODEL FOR ENDODONTIC ACCESS

1. Implant success rates2.Operating microscopes and micro-

endodontics3. Biomimetic dentistry4. Minimally invasive dentistry5. Esthetic demands of patients.

Conservative and crafted preparations

Sofitt

3D Ferrule

Peri cervical dentin

Improved structural integrity

Three-Dimensional Ferrule

• It has historically been described as axial wall

dentin covered by the axial wall of the crown

(or bridge abutment restoration). The research

varies on the actual minimal vertical amount

required, but the range of absolute minimums

is from 1.5 to 2.5 mm

3 components of three dimensional ferrule

Net taper

thickness

Vertical component

Thickness of ferrule

• The absolute minimum thickness is 1 mm; however, 2

mm is obviously a safer number. Girth becomes more

important closer to the finish lines of the preparation.

• The thickness of the remaining dentin (the wall thickness)

between the external surface of the tooth at the finish line

and the endodontic access is more important apically.

• axially deep finish lines on root structure can be

extremely damaging to 3DF.

Total Occlusal Convergence (TOC) or net taper

3 mm ferrule needed

4 mm ferrule needed

Deep chamfer marginal zones common with today’s porcelain

crowns

Needed how much ferrule???

• Light axiomarginal reduction coupled with

apically placed finish lines and a nonzero-

degree emergence profile of the restoration can

provide high 3DF. The concept of 3DF

incorporates an interplay between these factors

that, in sum, indicate the true ferrule quality.

Pericervical dentin (PCD)

Defined as the dentin near the alveolar crest.

• Critical zone roughly 4 mm coronal to the crestal bone -4

mm apical to crestal bone. crucial -transferring load from

the occlusal table to the root,

• PCD is irreplaceable.

No man-made material or technique can compensate for

tooth structure lost in key areas of the PCD.

Clark D, Khademi J. Modern molar endodontic access and directed dentin conservation. Dent Clin North Am 2010

LOOK, GROOM, AND FOLLOW: SHAPING VERSUS MACHINING

Why are round burs so destructive?

Why is complete deroofing so dangerous?

• attempts at removing the soffit that are far

more damaging to the surrounding PCD.

• The primary reason to maintain the soffit is to

avoid the collateral damage that usually occurs,

namely the gouging of the lateral walls.

• This 360 soffit or roof-wall interface can also

be compared with the metal ring that stabilizes

a wooden barrel.

Banking/Soffit (360)(Stepped access)

Small border amount of the chamber roof near the point where it curves 90° and becomes the wall LEFT BEHIND

Tiny “lip” or “cornice” 0.5 mm- 3.0 mm (strength and anatomy). strength continuous ring of dentin (BRAZING EFFECT).

Dotted line shows the typical cut made to remove the entire pulp horn. Area between the lines should be maintained and is referred to as the soffit

Bend and flex at the cervical area - most common area of occurrence for fracture failures in endodontically treated teeth

Robust coronal dentin -maintained good distance away from the tooth’s centroid,(cervical) - tooth is stiffened, resists bending, and should resist fracturing.

Clark D, Khademi J, Herbranson E. Fracture resistant endodontic and restorative preparations. Dent Today 2013.

Preservation of the roof-wall interface (or soffit). the small shapes, and preservation of key dentin.

Redesigned Access• The new vision-based mental model is Look, Groom,

and Follow.

• The new instruments are all round-ended tapers

• The rounded ends are to increase the radii of the gouges

and nicks that can act as stress concentration points.

• The flat sides help create smoother, flatter walls and

minimize the gouges and dings that inevitably occur even

with the most careful technique

• Small, cone-shaped, low-speed bur (such as the EG2 [SS

White ])

CK burs or EndoGuide burs

Blind Tunneling

The enamel is cut back at 45 with the Cala Lilly shape. This modified preparation will now allow engagement of nearly theentire occlusal surface.

The Three Strikes Rule

(1) Excessive axial reduction (consistent with PFM or all-

porcelain restorations)

(2) Gouged endodontic access

(3) Large and arbitrarily round endodontic shape.

Undesirable access shapes

• The inverse funnel

• Blind tunneling

• Blind funneling

SHAPING THE ROOT CANAL SPACE

• Complex root canal anatomy should be considered one of

the most significant challenges in creating root canal

shapes that will support good obturation outcomes and

leave sufficient remaining strength in the root.

• After biomechanical instrumentation, the completed root

canal shapes need to withstand the internal compressive

forces of obturation; provide sufficient resistance form to

contain softened and compressible filling materials and

retain enough strength for mastication.

• Jou et al. coined the term ‘working width’ to alert

clinicians to the critical need to understand the horizontal

dimension of apical size and its clinical implication in

cleaning the apical terminus.

• Larger apical sizes -some literature credibility- bacterial

reduction

• “maintaining smaller sizes when possible (>20 ≤ 40)

desirable-preservation of radicular dentin methods of

canal cleaning and disinfection not at cost of losing

retained, sound tooth structure”

• James L Gutmann on MIE JCD 2013 (Guest editorial)

#30,#40 better than #20 - LARGER TAPER may compensate smaller sizes

Baumgartner et al; JOE 2004

• Root canal preparation instruments sometimes associated

with this strategy such as V‑Taper (SS White, Lakewood,

NJ, USA) and Endo-EZE AET (Ultradent, South Jordan

UT, USA) have not been shown to actually perform in a

superior way to traditional rotary instrumentation in the

laboratory

• Current Descriptions Of Horizontal Dimensions Of Root Canal

• Round(circular): Max IWW=Min IWW• Oval: Max IWW > Min IWW (2 times more)• Long oval: 2 or more times larger (upto 4)• Flattened(ribbon): 4 or more

Circumferential filing better for oval, long oval & ribbon shaped canals

Jou Y.et al; DCNA 2004

Traditional TechnologyStainless-Steel Hand Files

• Inexpensive, has a track record, usually safe, but…

• Time consuming

• Inflexible - difficulty negotiating curved canals

• Extrude debris periapically

• Pack debris into recesses

• Sequential irrigation

Issues with Rotary NiTi Files

• Peer-reviewed research has shown, so far, the following

consequences:

• Unpredictable File separation – even with advanced

metallurgy and reciprocation

• Excessive removal of dentin – especially with high-taper

systems

• Periapical debris extrusion – especially with reciprocation

• Packing of debris into recesses

• Efficiency of NaOCl is reduced when used with single-

file systems, due to shorter working time and non-

sequential work

• Formation of dentinal Micro-cracks, especially with

single-file systems

Cone beam CT presenting oval cross-sections of canals

• Achieve minimally-

invasive

• 3D root canal shaping,

cleaning

• and simultaneous Irrigation.

Abrasive surface

Compression

Gradual expansion by the SAF

1. Vertical vibration – 0.4 mm amplitude at 5,000 rpm

2. Slow low-torque rotation – at ~80 rpm

3. Clutch mechanism to avoid rotation while engaged with canal walls

4. Continuous irrigation

Hero Shaper ProTaper (complete fracture)

SAF

Dentinal micro-Crack Formation during Root Canal Preparations by Different NiTi Rotary Instruments and the Self-Adjusting File

Yoldas et al, J Endod 2012; 38:232-235

C-Shaped canals - Danger zone

Green - before preparation Red - after preparation

Solomonov et al, J Endod 2012; 38:209-214

SAF ProTaper

PIPS

conclusion

REFERENCES• Clark D, Khademi J. Modern molar endodontic access

and directed dentin conservation. Dent Clin North Am

2010

• Clark D, Khademi J, Herbranson E. Fracture resistant

endodontic and restorative preparations. Dent Today

2013

• Clark D, Khademi J, Herbranson E. The new science

of strong endo teeth. Dent Today 2013.

• Yi-Tai Jou et al Endodontic Working Width: current

concepts and techniques

• Helfer A R, Melnick S, Schilder H. Determination of the

moisture content of vital and pulp less teeth. Oral Surg Oral

Med Oral Pathol 1972; 34: 661–670

• Sedgley C M, Messer H H. Are endodontically treated teeth

more brittle? J Endod 1992; 18: 332–335.

• Krasner P, Rankow HJ. Anatomy of the pulp chamber floor;

JOE 2004,30:5

• Reeh E S, Messer H H, Douglas W H. Reduction in tooth

stiffness as a result of endodontic and restorative procedures.

J Endod 1989; 15: 512–516.

• Minimally invasive endodontics: challenging prevailing

paradigms A. H. Gluskin, C. I. Peters and O. A. Peters

• Pathways of pulp 10th ed. stephen cohen

Thank u