1) Traditional access cavity preparations using large round burs and Gates Glidden drills can remove excessive tooth structure and weaken teeth.
2) A more conservative access design called the "inverse funnel" or "blind funneling" is proposed to preserve the critical peri-cervical dentin through use of smaller tapered burs and partial de-roofing of the pulp chamber while still allowing for adequate debridement and obturation.
3) A study found that endodontically treated teeth with preservation of the peri-cervical dentin and pulp chamber "soffit" had greater fracture resistance compared to traditional access preparations due to reinforcement of remaining tooth structure.
This presentation is all about restoration of endodontically treated teeth, prefabricated post and core, cast post and core, direct and indirect technique.
Smear layer is a controversial topic in the field of operative dentistry and endodontics. This presentation includes composition, concepts, structure, advantages, disadvantages, and removal methods of smear layer.
This presentation is all about restoration of endodontically treated teeth, prefabricated post and core, cast post and core, direct and indirect technique.
Smear layer is a controversial topic in the field of operative dentistry and endodontics. This presentation includes composition, concepts, structure, advantages, disadvantages, and removal methods of smear layer.
An inlay may cap none, or may cap all but one cusp.
Sturdevant’s 4th ed. page579
Inlays may be used as single-tooth restorations for proximo-occlusal or gingival lesions with minimal to moderate extensions
Shillingburg page 1
An inlay may be defined as a restoration which has been constructed out of mouth from gold, porcelain, or other material & then cemented into the prepared cavity of a tooth.
William McGehee pg410
Design of a fixed Partial Denture (with Abutment Tooth Preparation)Taseef Hasan Farook
A simplified take on the steps to designing a Fixed partial denture. This presentation also includes an overview of abutment preparation, associated finishes and methods of impression taking prior to the designing of the prosthesis itself
An inlay may cap none, or may cap all but one cusp.
Sturdevant’s 4th ed. page579
Inlays may be used as single-tooth restorations for proximo-occlusal or gingival lesions with minimal to moderate extensions
Shillingburg page 1
An inlay may be defined as a restoration which has been constructed out of mouth from gold, porcelain, or other material & then cemented into the prepared cavity of a tooth.
William McGehee pg410
Design of a fixed Partial Denture (with Abutment Tooth Preparation)Taseef Hasan Farook
A simplified take on the steps to designing a Fixed partial denture. This presentation also includes an overview of abutment preparation, associated finishes and methods of impression taking prior to the designing of the prosthesis itself
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
Tooth preparation for cast metal restoration / endodontic courses by indian d...Indian dental academy
Welcome to Indian Dental Academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy has a unique training program & curriculum that provides students with exceptional clinical skills and enabling them to return to their office with high level confidence and start treating patients
State of the art comprehensive training-Faculty of world wide repute &Very affordable.
Gingival finish lines /certified fixed orthodontic courses by Indian dental ...Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
00919248678078
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
Vonlay; A paradigm shift in post endodontic restoration: A case report.komalicarol
Porcelain veneers have long been a popular restorative option that
have evolved into a well- accepted treatment that can be fabricated
in various ways. Onlays are another common treatment modality
used in contemporary dentistry to restore large areas of decay and
to replace old restorations. With the availability of newer highstrength materials such as lithium disilicate and processing technologies like CAD/CAM and heat pressing, dental professionals
are now able to produce highly esthetic, high-strength restorations
that blend seamlessly with the natural dentition while also withstanding posterior occlusal forces. A tooth more complex restoration is required after endodontic treatment when compared to normal tooth restoration, because of factors such as extensive caries,
post-treatment root canal dentin and even the economics condition
of the patient.One such design proposed by Dr.Ronald E Goldstein
is “Veenerlay”or “Vonlay”. Vonlay is a blend of an onlay with an
extended buccal veneer surface for use in premolar region, where
there is sufficient enamel present to bond. This restorative option
requires a much less invasive preparation than a full coverage
crown but provides the same structural benefits. Thus, the aim of
this case report is to present a case of Vonlay following endodontic
treatement of lower mandibular premol
Vonlay; A Paradigm Shift in Post Endodontic Restoration: A Case Reportsemualkaira
Porcelain veneers have long been a popular restorative option that
have evolved into a well- accepted treatment that can be fabricated
in various ways. Onlays are another common treatment modality
used in contemporary dentistry to restore large areas of decay and
to replace old restorations
The presentation shows the relation between the restorative dentistry and the periodontium , explaining the per-prothetic surgeries and the biological consideration including the biological width. Also, mention how to restore the open embrasures between teeth (the black triangle).
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
The Indian economy is classified into different sectors to simplify the analysis and understanding of economic activities. For Class 10, it's essential to grasp the sectors of the Indian economy, understand their characteristics, and recognize their importance. This guide will provide detailed notes on the Sectors of the Indian Economy Class 10, using specific long-tail keywords to enhance comprehension.
For more information, visit-www.vavaclasses.com
5. (A) The deroofing problem. Red arrow delineates the typical gouging.
(B) Blue arrow indicates the grossly excessive dentin removal of
pericervical dentin. Yellow arrow indicates the large canal flaring
with unacceptable dentin removal (blind funneling).
(C) Green circle highlights worsening lesion on mesial root ends.
6. Are endodontically treated teeth 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
7. Why do endodontically treated
teeth fail?
The degree of stress experienced by the tooth
under load.
The inherent biomechanical properties of the
remaining structure responsible for resisting
fracture.
9. Why are round burs so destructive?
Text after text shows the
same round bur technique
relying on tactile feedback
as the round bur drops
into the pulp chamber.
If the pulp chamber is
sufficiently large enough,
then a round bur can truly
“drop in” to the pulp
chamber
10. Much more representative of
the spectrum of cases typically
presenting for endodontic
treatment.
Clearly, trying to drop a round
bur into the scant or
nonexistent chamber is not
going to lead to the desired
outcome even for a skilled
clinician.
11. Why are Gates Glidden burs so problematic?
Since the introduction of rotary files, GG burs have
been used more aggressively and with more
reliance on larger sizes (4, 5, and 6) to reduce
binding and fracture of rotary files
GG burs have always been considered “safe”
because they do not end cut and are self-centering.
There is a significant problem here, which is
“cervical self-centering.”
Because the shank of the GG is so thin, it is difficult
to “steer” the GG bur away from high-risk
anatomy.
As the GG bur straightens the coronal, or “high-
curve,” it can shortcut across a fluting or furcation,
and weaken and/or create strip perforations.
Extensive coronal flaring results
in extrusion of obturation
material in the furcation. The
furcal strip perforation is a
perfect example of the dangers
of “Blind Funneling” with Gates
Glidden burs.
12.
13. Why is complete de-roofing so
dangerous?
Entire roof removed.
Tend to touch lateral walls leading to gouging which
is a serious problem.
Creates surface irregularities on lateral walls of
access cavity.
Ultimately leads to loss of dentin and compromises
integrity of PCD.
14. Round burs point cut, when
instead what is needed is
planing.
The new vision based
mental model is look,
groom, follow. The new
burs are all rounded-ended
tapers.
The tip size of these burs is
less than half as wide as the
corresponding round bur.
Round Bur
CK Bur (SS White)
15. The main cause of failure of root-filled teeth is the loss of tooth
structure. Traditional access cavity preparation is found to be
the second largest cause of failure of root canal treatment.
Thus, a reduced endodontic access design would reduce the
failure of root canal treatment.
Rezaei Dastjerdi M, Amirian Chaijan K, Tavanafar S. Fracture resistance of upper central
incisors restored with different posts and cores. Restor Dent Endod 2015;40:229-35.
Improved prognosis of root canal treated teeth is seen in
conservative endodontic cavity, or ultraconservative
‘‘endodontic cavity.
Belograd M. The Genious 2 is Coming. Available from:
http://www.dentinaltubules.com/videos/ninja-access-a-new-access-concept-in-
endodontics. [Last accessed on 2016 Sep18].
16. A NEW MODEL FOR ENDODONTIC ACCESS
5 catalyst forces that will change the future of
endodontic access and coronal shaping. They are:
1. Implant success rates
2.Operating microscopes and micro-endodontics
3.Biomimetic dentistry
4.Minimally invasive dentistry
5.Esthetic demands of patients
18. PCD
This critical zone, roughly 4 mm above the crestal
bone and extending 4 mm apical to the crestal bone.
Important for 3 reasons:
1. Ferrule
2. Fracturing
3. Dentin tubule orifice proximity from inside to out
The more dentin is kept, the longer the tooth is kept.
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
19. Glossary of Terms for Modern Endodontic Access
Glossary of Terms for Modern
Endodontic Access and Acronyms
Acronym
The endodontic-endorestorative-
prosthodontic continuum
EPPC
Three-Dimensional ferrule 3D Ferrule
The inverse funnel
Blind tunneling
Blind funneling
Partial de-roofing/Soffit
20. The endodontic-endorestorative-
prosthodontic (EERP) continuum
From tooth crown till apex, an outside reinforcement for
fracture resistance, and from inside to outside walls for
micro-leakage prevention is proposed.
Bio-mimetics and minimally invasive dentistry are the
basic principles of this treatment approach.
Each of these components must reinforce and not
compromise the others.
21. Three-dimensional Ferrule
Axial wall dentin covered by the axial wall of the crown or
bridge abutment.
Encompasses 3 components-
1. Vertical component/traditional ferrule/Dentin height: 1.5
mm to 2.5 mm.
2. Dentin girth (thickness): 1-2mm
3. Total occlusal convergence (TOC) or net taper: TOC is the
total draw of the 2 opposing axial walls of the prepared
tooth to receive a fixed crown: 10° - 20° /(3mm to 4mm)
22. Undermined Enamel vs Undermined Dentin
Undermined enamel has not been shown to be
strengthened by resin restorations: fracture
potential, poor C factor, physical and visual
obstruction.
Dentin acts as a trimodal composite.
The act of purposely undermining dentin for mechanical
retention of restorative materials or when using round
burs in endodontic access is no longer indicated.
23. Banking/Soffit/Roof Strut
(360°) (Stepped access)
Drs. Clark and Khademi have coined the term “soffit”,
which is a small piece of dentin roof around the entire pulp
chamber, to preserve the critical region of peri-cervical
dentin (PCD) without compromising debridement and
without inducing iatrogenic misadventure.
0.5 mm- 3.0 mm (strength and
anatomy)
Continuous ring of dentin (BRAZING
EFFECT).
24. 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.
Stiffness and resisting to bending are basic
engineering principles. The distance from the
“centroid” to the flange areas of both the tooth and
the I-beam determine resistance to bending.
Clark D, Khademi J, Herbranson E. Fracture resistant endodontic and restorative preparations.
Dent Today 2013.
25.
26.
27. CALALILY PREPARATION
Bevel of 45° on enamel margin to remove
undermined enamel
This modified preparation will now allow engagement
of nearly the entire occlusal surface.
Allows the entire enamel and dentin is involved in the
restoration improving overall resistance of a given
tooth.
29. Sacrifice vs Compromise
1. The dentist stopped
removing dentin because
the complete canal
system could not be
located and less than half
of the distal root was
filled.
2. Radiographically ugly but
clinically successful (20-
year) endodontic
treatment.
Residual PCD has buttressed this tooth to avoid fracture.
30. THE INVERSE FUNNEL
Undesirable endodontic access shape
The size of the access becomes wider as it
progresses deeper into the tooth.
Exacerbated when advanced magnification is not
used.
Common occurrence when constricted cavosurface
access opening size is paired with round bur use.
31. BLIND TUNNELING
Creates a parallel
sided access when
performed without
advanced
magnification,
relying on tactile
feedback rather than
on microscopic
visualization.
Typically performed
with round burs.
32.
33. BLIND FUNNELING
Obliterates significant tooth structure to
facilitate rapid and safe (avoidance of file
separation) machining of the roots with
rotary files.
Done with GG drills
Removes the PCD
35. Redesigned Access
The new vision-based mental model: Look, Groom, and
Follow.
The new instruments are all round-ended tapers (to
increase the radii of the gouges)
The flat sides help create smoother, flatter walls and
minimize the gouges and dings.
Small, cone-shaped, low-speed bur (such as the EG2 [SS
White ])
₹8071
36. Endo Guide Access Burs
Set of 8 uniquely
designed carbide burs.
Conical shaped, micro
diameter tip.
Variety of shank lengths,
head size, and shapes.
37.
38.
39.
40.
41. AIM: To evaluate the strength of an endodontically
treated tooth after preservation of peri-cervical
dentin and soffit.
42. Normal endodontic treatment was carried out with 2% flexible NiTi K-
files with 17% EDTA as chelating agent and 5.25% Sodium Hypochlorite
solution for irrigation. Obturation was carried out using the lateral
condensation technique with gutta- percha coated with sealer.
43. The pulp chamber was cleaned thoroughly with cotton
and all-in-one bonding agent was applied and scrubbed
with an applicator tip for 30 seconds.
Composite restoration was done as post-obturation
restoration.
Specimens were tested with a universal testing machine,
set to deliver an increasing load until failure.
Failure was defined as a 25% drop in the applied load. The
load was applied parallel to the long axis of the tooth.
44. R
E
S
U
L
T
S
The reason for
this would be
the banking of
tooth structure;
that is dentin
preserved at
both pericervical
region and the
soffit.
Gutmann JL et al also
showed that the mechanical
integrity provided by even a
small part of the roof of the
pulp chamber allows for
greater flexure of the tooth
during function.
45. The teeth after preservation of peri-cervical
dentin and soffit were found to be structurally
reinforced as compared to the teeth with
straight line access.
Clark-Khademi access preparation was found to
be more effective at dentin preservation and
strengthening the tooth when compared to
straight line access.
CONCLUSION
50. CT GUIDED ENDODONTIC
ACCESS OPENING
1. The canal system may partly or completely obliterate as a
consequence of physiological ageing and/or external injuries.
2. May eventually expose a root canal for further instrumentation
by preparing an access cavity parallel to the long axis of the
root.
3. Therefore, preoperative planning is highly recommended and
3D imaging may be a useful tool.
4. Templates can be produced by 3D-printing devices, based on
matched 3D surface scans with CBCT data (Kuhl et al. 2015).
51. Preoperative CBCT images are stored as
dicom files.
3D surface scans are performed using
intraoral 3D Surface scanner (eg. Itero,
align technology inc.
Data is then stored as STL (surface
tessellation language) files.
52. CBCT data were uploaded into a planning
software (co DiagnosticX).
The software allowed the creation of a virtual
image of a commercially available bur.
In addition, a virtual sleeve for guidance is
created for planning purposes.
53. The virtual bur was superimposed on each tooth
with the aim of creating a direct access to the
apical third of the root canal.
The surface scans were uploaded to the access
planning software.
Scans were matched with CBCT data by aligning
the crowns of the teeth.
54. Finally, a virtual template was designed by applying a tool of the software.
Information on sleeve‘s position was considered in the planning.
Exported stl-files allowed a 3D printer to produce the templates.
55. 1. Templates were attached to the
models, and their reproducible fitting
was checked. Marks were set
through the template sleeves to
indicate the region of access cavity.
2. Enamel should be removed in the
area using a diamond bur until
dentine is exposed. Then, the specific
bur is used to gain access to the root
canal.
3. The final position was reached when
the bur hit the mechanical stop of
the sleeve.
56. Disadvantages of CT-GEA
1. High price
2. More time required for access cavity preparation.
3. More exposure to radiation because of use full
mouth CBCT and optical surface scan.
57. The combined use of CBCT and optical scans for the
precise construction of a guide rail led to a drill path
with a precision below a risk threshold.
The present technique may be a valuable tool for the
negotiation of partial or complete pulp canal
obliteration.
Guided access cavity preparation using cone-beam computed tomography and
optical surface scans – an ex vivo study
J. Buchgreitz1, M. Buchgreitz1, D. Mortensen2 & L. Bjørndal2
1Private practice, Allerød; and 2Section of Cariology & Endodontics, Department of
Odontology, Faculty of Health and Medical Sciences, University of Copenhagen,
Copenhagen, Denmark
58. AIM: To evaluate in vitro the fracture strength of conservative versus traditional access cavity
design in molar teeth.
Forty two extracted human intact maxillary and mandibular molars were assigned to
Traditional Access Cavity (TAC), Conservative Access Cavity (CAC) and Sound Control groups
(SC) (n = 7/group/type).
59. 1. TAC groups were prepared with pulp chamber de-
roofing and straight line access.
2. For CAC a soffit and peri-cervical dentine were
maintained.
3. Working length was determined and canals were left
un-obturated and mounted in self-cured acrylic resin
molds of PVC for testing.
4. Specimens were then tested with a compression
testing machine and fracture force data were
recorded in Newton for analysis.
60.
61.
62.
63.
64. 1. Fracture strength of CAC was statistically significantly higher in mandibular
molars (P Value = 0.0367250) compared to TAC groups, without differing
significantly from the sound control groups.
2. There was no statistically significant difference in fracture strength
between CAC group and TAC group in maxillary molars.
3. Fracture strength of Maxillary Molars CAC group did not differ significantly
from that of the SC control group with a P Value of (0.3598322), whereas
that of the TAC group was statistically significantly lower than the control
group with a P value ( 0.0052701).
Root-canal treated teeth are more susceptible to fracture than sound
teeth essentially due to dentinal tooth structure removal during
endodontic therapy
65. Take Home Message
In keeping with this philosophy of minimal invasion of bulk dentin
structure, the use of round burs and Gates-Glidden burs is now
discouraged.
Gouging of the access and coronal canal space must be avoided
in order to preserve maximal resistance to structural flexure and
ultimate failure.
Try newer concepts of access cavity preparation: Truss access/X
access/Clark and Khademi access.
Use of EndoGuide Access Burs by CK
PRESERVE SOFFIT AND PCD.
66. CONCLUSION
The controversy should not be whether to completely de-roof
or partially de-roof a pulp chamber, or whether to cut a ninja-
type access cavity to any given orifice; rather, the answer to
this debate should be based on the reality of “do what you
can, with what you got, where you are.”
Ultimately, the size of the access cavity is most influenced by
anatomical knowledge, experience, and the technologies and
methods utilized to shape, 3D clean, and fill root canal
systems.
67. References
Clark D, Khademi JA. Case studies in modern molar endodontic access and directed dentin conservation.
Dent Clin North Am 2010;54:275-89.
Clark D, Khademi J. Modern molar endodontic access and directed dentin conservation. Dent Clin North
Am 2010;54:249-73.
Clark D, Khademi J, Herbranson E. Fracture resistant endodontic and restorative preparations. Dent
Today 2013;32:118.
Clark D, Khademi J, Herbranson E. The new science of strong endo teeth. Dent Today 2013;32:112.
Bürklein S, Schäfer E. Minimally invasive endodontics. Quintessence Int 2015;46:119-24.
Gutmann JL. The dentin–root complex: anatomic and biologic considerations in restoring endodontically
treated teeth. J Prosthet Dent 1992:67:458–467.
Ingle I. endodontic cavity preparation. In: J. I. Ingle, ed. Ingle's Endodontics 5th edn; 2002; pp.406-570.
BC Decker Inc
Clark D, Khademi J, Herbranson E. Fracture resistant endodontic and restorative preparations. Dentistry
today 2013; Available from: http://www.dentistrytoday.com/restorative/8666- fracture-resistant-
endodontic-and-restorative- preparations
Editor's Notes
Why do we need a newer concept when we already have a traditional concept of preparing access cavity?
So what are the problems we encounter while following a particular traditional way of preparing an access cavity and the rationale behind these newer concepts?
Let us discuss these unusual ways to the usual destination.
During patient treatment, the clinician needs to consider many factors that will affect the ultimate outcome. In simple terms, these factors can be grouped into 3 categories: the operator needs, the restoration needs, and the tooth needs.
The operator needs being conditions the clinician needs to treat the tooth. The restoration needs being the prep dimensions and tooth conditions for optimal strength and longevity. The tooth needs being the biologic and structural limitations for a treated tooth to remain predictably functional.
Traditional concepts Mostly concentrates on operator needs – funnel shaped prepn for SLA, deroofing for clear visibility and accessibilty, blind funneling where we enlarge coronal flaring to prevent instrument separation, SLA to root orifices.
Newer concepts aim to have a balance between these 3 factors so that the prognosis of the tooth improves by many fold.
Current trt protocols to extend life of RCT tooth upto 10-15 yrs – but what if a treated tooth can last for 20-40 years, this can be achieved when these 3 factors are met.
shows a lower first molar of a 20-year-old woman. These young teeth are dangerously hollow to begin with.
The following case is representative of a large percentage of endodontic accesses performed by general dentists and endodontists.
The general dentist created the first access using fissure burs and with the type of dentin removal that is the standard today (Fig. 2A). The tooth was then reaccessed by an internationally recognized endodontist (Fig. 2B, C). This model for generous removal of pericervical dentin is common in many specialty practices.
By the time that both of these well-meaning dentists had finished with the tooth, the molar was nearly worthless. The most important structures were so badly compromised that the tooth was permanently crippled.
Eighteen months later, the lesion on the mesial root continues to enlarge (Fig. 3). In the authors’ practices, such a tooth does not warrant endodontic retreatment. The wholesale loss of PCD has reduced the value of this tooth to the point that, when the tooth becomes symptomatic, extraction and replacement with an implant is a better option.
In Dr. Clark’s restorative practice and Dr. Khademi’s endodontic practice, such a tooth does not warrant endodontic retreatment. The wholesale loss of PCD has reduced the value of this tooth to the point that when the tooth becomes symptomatic, extraction and replacement with an implant is a better option.
In fairness to our patients, we must either change the process, or make implants a first option instead of the eventual option.
Large round burs remove enamel and dentin in the Pericervical area.
Pericervical dentin is located 4 mm above the crestal bone and extending 4 mm apical to the crestal bone.
It acts as the “neck” of the tooth. It is important for two reasons: for ferrule and to improve fracture resistance, whereas soffit is a small piece of roof around entire coronal portion of the pulp chamber. The soffit behaves like metal band surrounding barrel. It must be maintained to avoid the collateral damage that usually occurs, namely, the gouging of lateral walls.
The traditional way of initiating endodontic access is predicated on mental models that do not represent the day-to-day clinical reality presented to the clinician. Text after text shows the same round bur technique relying on tactile feedback as the round bur drops into the pulp chamber (Figure 7). These kinds of images, so frequently shown in dental school, textbooks and lectures are predicated on mental models based on occlusal decay in children.
If the pulp chamber is sufficiently large enough, then a round bur can truly “drop in” to the pulp chamber as shown here with a No. 6 round bur superimposed on the lower molar of this 11-year-old child (Figure 8).
The reality of day-to-day clinical practice is quite far removed from this, and these deeply ingrained mental models are a setup for occult iatrogenic trauma.
More realistically, the case shown in Figure 9 is much more representative of the spectrum of cases typically presenting for endodontic treatment. Clearly, trying to drop a round bur into the scant or nonexistent chamber is not going to lead to the desired outcome even for a skilled clinician.
Instead, the size of the burs relative to the chambers, the omnidirectional cutting blades (which side cut very aggressively), and chatter common with this bur design are much more likely to lead to the kinds of outcomes seen in Case 1 (refer again to Figures 2a to 3).
So while round burs are destructive because they contribute to, or exacerbate, these problems; it is really the tactile based mental models predicated on these kinds of drawings showing round burs dropping into the pulp are the ultimate problem. Care and magnification can compensate, but only to a degree
Since the introduction of rotary files, GG burs have been used more aggressively and with more reliance on larger sizes (4, 5, and 6) to reduce binding and fracture of rotary files. GG burs have always been considered “safe” because they do not end cut and are self-centering. There is a significant problem here, which is “cervical self-centering.” Because the shank of the GG is so thin, it is difficult to “steer” the GG bur away from high-risk anatomy. As the GG bur straightens the coronal, or “high-curve,” it can shortcut across a fluting or furcation, and weaken and/or create strip perforations (Figure 6).
Blue arrows indicate gouges. Red arrows indicate perforations. Essentially, all previ- ously accessed molars were gouged to some degree.
The first upper and lower molar cases show what many might consider acceptable access extension, and were obviously cut with round burs. Both are gouged.
The third upper and lower cases have frighteningly thin pulpal floors with blushing dentin. The upper fourth case is deceptive in that it is perforated, whereas the worse-looking lower case is not, but the pulpal floor is thin.
The last upper molar case (which has a class V resorption repair) shows what is possible with practice, microscope level magnification, an assistant, and the right instruments. The lower molar shows the type of access that should be routinely achievable with high-powered loupes and the right instruments.
(JK indicates that the case was done by John Khademi with adherence to the modern model of directed dentin conservation.)
Presuming one could drop into the pulp chamber in the way drawn and described above, the chamber roof would now be removed by scooping it up and away with a round carbide.
A 2-dimensional (2-D) drawing, with the relatively small size of the bur and chamber roof overhanging a large pulp chamber, makes this seem like a reasonable proposition.
The chamber walls are somehow always drawn flat even though they are cut by a round bur.
In reality, it is truly impossible to do: to cut flat walls in 3-D with a round instrument. What happens is that the chamber is unroofed in some areas leaving pulpal and necrotic debris, and the walls are overextended and gouged in other areas.
Furthermore, the internal radius of curvature at many of the pulpal line angles is simply too small for all but the smallest of round burs.
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.
round burs point cut in an endodontic access application, when instead what is needed is planing. What is needed is a new set of mental models based on vision, and a new set of instruments reflective of the task at hand and the desired shaping outcomes.
The new vision based mental model is look, groom, follow. The new burs are all rounded-ended tapers (Figure 11). It is an illustration comparing the CK Endodontic Access bur to the corresponding round bur. The tip size of these burs is less than half as wide as the corresponding round bur. One of the prototype CK Endodontic Access burs has had (right) is shown and contrasted with the corresponding surgical length round bur (left). These burs, designed by Drs. Clark and Khademi, will be available from SS White Burs.)
In both of our practices, our endodontic goals and armamentarium have been in a constant state of flux for nearly a decade as we have collaborated to bring the EERP continuum to maturity. The goal?
To satisfy the demands of the above mentioned “Big 5” forces for change. In so doing we have come to realize that, when preparing endodontic accesses, our previous needs as dentists were often in conflict with the needs of the tooth.
PCD is the dentin near the alveolar crest.
While the apex of the root can be amputated, and the coronal third of the clinical crown removed and replaced prosthetically, the dentin near the alveolar crest is irreplaceable. This critical zone, roughly 4 mm above the crestal bone and extending 4 mm apical to crestal bone, is sacred for 3 reasons: (1) ferrule, (2) fracturing, and (3) dentin tubule orifice proximity from inside to out. The research is unequivocal;
long-term retention of the tooth and resistance to fracturing are directly related to the amount of residual tooth structure.2,33
The more dentin we keep, the longer we keep the tooth.
The EERP is a restorative based concept with endodontics as simply a starting step to the restoration of the tooth, in conjugation with a complete incorporation of endodontics as part of an interconnected series of treatment strategy. From tooth crown till apex, an outside reinforcement for fracture resistance, and from inside to outside walls for micro-leakage prevention is proposed.
Biomimetics and minimally invasive dentistry are the basic principles of this treatment approach. Each of these components must reinforce and not compromise the others.
Biomimetics is a restorative approach that tends to retain as much natural tissue as practically possible, and to mimic the structures of the human body (Clark D J, 2010; Clark D J, 2007; Malterud M, 2013). This concept originated from the well accepted fact that endodontic treatment and restorative procedures lead to weakening of the remaining tooth structure compromising the restorative rehabilitation of the tooth.
The 3-dimensional (3-D) ferrule is the backbone of prosthetic dentistry. 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.
The clinician must remember that build-up material, although necessary, does not “count” toward the ferrule.
A more comprehensive view of ferrule is needed, and is embodied in the term 3-D ferrule. There are 3 components of the new ferrule, first is the vertical component, which is described above. The second component is dentin girth (thickness). The absolute minimum thickness is 1.0 mm; however 2.0 mm is obviously a safer number. The third component is total occlusal convergence (TOC), or net taper. That is the total draw of the 2 opposing axial walls of the prepared tooth to receive a fixed crown. A net taper or TOC of 10° requires 3.0 mm of vertical ferrule; a TOC of 20° requires 4.0 mm of vertical ferrule.
Deep chamfer marginal zones common with today’s porcelain crowns typically have a net taper of 50° or more, and therefore many of today’s aesthetic margins lose a millimeter or more of there original potential 3-D ferrule at the crown margin interface.
it can be of great value to the tooth whether the undermined dentin occurs naturally, such as the soffit, or from previous restor- ative/endodontic treatment. It is important to clarify that the act of purposely undermining dentin for mechanical retention of restorative materials or when using round burs in endodontic access is no longer indicated in contemporary restorative and endodontic dentistry. Enamel is essentially a crystalline structure and is therefore naturally supported 100% by dentin. Dentin, by contrast, is a multilevel composite that can stand alone and acts ideally as a semirigid pipe.
The idea that a round bur can be dropped below this soffit and drawn coronally to un roof the chamber is predicated on large pulp chambers and exceptional hand skills.
Clinically, it is impossible
Attempting to remove the pulp chamber roof does not accomplish any real endodontic objective, and invariably gouges the walls that are responsible for long-term survival of the tooth
The primary reason to maintain the soffit is to avoid the collateral damage that usually occurs, namely the gouging of the lateral walls
Drs. Clark and Khademi have coined the term “soffit”, which is a small piece of dentin roof around the entire pulp chamber, to preserve the critical region of peri-cervical dentin (PCD) that is 4mm above and below the crestal bone, without compromising debridement and without inducing iatrogenic misadventure.
It acts as the “neck” of the tooth. It is important for two reasons: for ferrule and to improve fracture resistance, whereas soffit is a small piece of roof around entire coronal portion of the pulp chamber. The soffit behaves like metal band surrounding barrel. It must be maintained to avoid the collateral damage that usually occurs, namely, the gouging of lateral walls.
Tiny “lip” or “cornice”
0.5 mm- 3.0 mm (strength and anatomy)
Continuous ring of dentin (BRAZING EFFECT).
Robust coronal dentin -maintained good distance away from the tooth’s centroid,(cervical) - tooth is stiffened, resists bending, and should resist fracturing.
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.
Stiffness and resisting to bending are basic engineering principles. The distance from the “centroid” to the flange areas of both the tooth and the I-beam determine resistance to bending.
We do not want our teeth to bend and flex at the cervical area, which for demonstration purposes is identified as the centroid of the tooth. It (the cervical) is the most common area of occurrence for fracture failures in endodontically treated teeth (endo teeth). When brittle items such as teeth start to bend, they easily break.
The myth of endodontic teeth being brittle may finally be explained in over-torqued dentin that slowly degrades until it finally fractures years (or decades) later.
The endo tooth doesn’t dry out, but a hollowed out endo tooth is constantly bending. When robust coronal dentin is maintained good distances away from the tooth’s centroid, the tooth is stiffened, resists bending, and should resist fracturing. An additional component of the soffit, aside from a second moment of area, is the strength that is inherent in a continuous ring of dentin that can act like a metal barrel ring around an oak barrel.
Clinical Recommendations Two questions invariably come up:
How do you get the pulp out of the soffit/pulp horn? The answer is a back action explorer, with a little patience.
Worst case, we have disassembled dozens of teeth where scraps of pulp were inadvertently left in chambers and it has not seemed to affect the tooth adversely, even after decades.
valuable future asset in the advent of unforeseen future trauma or disease, coupled with the reality that a tooth will need to last for decades and potentially be restored and then rerestored in the patient’s lifetime.
significant dentin was sacrificed to facilitate expedient and safe instrumentation, and yet the endodontic treatment was failing.
Contrast that case with the tooth seen in Figure 5. There was a significant compromise 20 years ago, when the dentist stopped removing dentin because the complete canal system could not be located and less than half of the distal root was filled. Despite this shortcoming, the “poor endodontic result” was successful, and the well-preserved PCD has buttressed the tooth making the overall case a smashing 20-year success.
Partial deroofing and maintenance of a robust amount of PCD is demonstrated. A soffit that includes pulp horns on mesial and distal is depicted.
A more appropriate access shape is overlayed.
The approach of banking of tooth structure in restorative dentistry dictates that whenever possible, more tooth structure should be preserved. It may involve a less expedient, but more conservative, approach. This banked tooth structure may serve as a valuable future asset in the advent of unforeseen future trauma or disease, coupled with the reality that a tooth will need to last for decades and potentially be restored and then rerestored in the patient’s lifetime. The primary reason to maintain the soffit is to avoid the collateral damage that usually occurs, by the gouging of the lateral walls.(4,5)
‘Soffit’ is totally a new concept in access cavity preparation and further research is required to be done on more number of samples to check the strength of the tooth. Research will certainly need to be done to validate other parameters like complete debridement, cleanliness, disinfection etc. with soffit preparation.
In conservative endodontic access cavity, the teeth are accessed at the central fossa and they are extended only as necessary to detect canal orifices. This helps in preserving the pericervical dentin and part of the chamber floor. The
pericervical dentin is the dentin that is located 4 mm above and 4 mm below the crestal bone and they serve in distribution of functional stresses in teeth. Thus it is necessary that we preserve this pericervical dentin in order to maintain the biomechanical response of the radicular dentin.4,5 The preservation of this dentin roof above the pulp chamber is known as the ‘soffit’.
Ninja endodontic access cavity
To obtain an access ‘ninja’ outline, the oblique projection is made towards the central fossa of the root orifices in an occlusal plane. As the endodontic access is parallel with the enamel cut of 900 or more to the occlusal plane, it is easier to locate the root canal orifices even from the different visual angulations.7
necessary to detect canal orifices. This helps in preserving the pericervical dentin and part of the chamber floor. The
pericervical dentin is the dentin that is
located 4 mm above and
4 mm below the crestal bone and they serve in distribution of functional stresses in teeth. Thus it is necessary that we preserve this pericervical dentin in order to maintain the biomechanical response of the radicular dentin.4,5 The preservation of this dentin roof above the pulp chamber is
known as the ‘soffit’.
The canal system may partly or completely obliterate as a consequence of physiological ageing and/or exter- nal injuries, such as attrition, caries, previous opera- tive procedures, as well as trauma
The clinician may eventually expose a root canal for further instrumentation by preparing an access cavity parallel to the long axis of the root with the aid of an operating microscope, long neck burs and/or ultra- sonic tips (da Cunha et al. 2009, Johnson 2009, Reis et al. 2009, McCabe & Dummer 2012). In some cases, the obliteration of the root canal is located apically, increasing the risk of jeopardizing the entire root, and if further attempts to reach the root canal are carried out, the use of additional radiographs, dye, or the so-called bubble tests with sodium hypochlorite have been advocated (McCabe & Dummer 2012). Apical surgery may eventually be indicated, but pulp rem- nants are still problematic in the residual calcified canal after root resection
the combined use of CBCT and optical scans of the region of interest may have the potential to improve the precision of guided dril- ling procedures using computerized numerically con- trolled (CNC) technology for guide rail production.
In these cases, preparing an adequate access and identifying the canal orifice can be challenging and may create a massive loss of tooth structure that is associated with a higher risk of fracture.
For this purpose, preoperative surface scans and cone-beam computed tomography scans are matched. After planning the position of the drill for root canal location, a virtual template is designed, and the data is exported as an STL file and sent to a 3D printer for template fabrication. The template is positioned on the teeth. A specific drill is used to penetrate through the oblit- erated part of the root canal so as to obtain minimally invasive access to the root canal. After miniaturization of the instruments, the technique was made accessible even for teeth with narrow roots such as mandibular incisors.
A recent study demonstrated that the (micro)guided endodontic access leads to a faster and more pre- dictable location of calcified root canals with signifi- cantly less substance loss compared to the traditional endodontic access using the operating microscope. Furthermore, in contrast to traditional access, the success of the guided approach is not influenced by the experi- ence of the operator.
Virtual design of the drill path
A CBCT scan (Orthophos XG 3D unit, Sirona Dental Systems, Bensheim, Germany) was made of each test specimen. Using specific software (Galaxis/Galileos Implant, Sirona Dental Systems), a drill path with a diameter of 1.2 mm was planned on a computer screen from an occlusal reference to the apical target point on each tooth and placed virtually in the bulk of dentine. The planned drill path was designed to reach the centre of the target point apically following specific alignment procedures (Fig. 2c). Superimposed on the drill path, a virtual sleeve was placed (inner diameter 1.2 mm, length 4 mm) for the guidance of the bur (Fig. 1b).
Apart from static guidance, dynamic navigation may be a new approach for the negotiation of calci- fied root canals. A stereo vision computer triangula- tion setup can be used to guide the bur during preparation of the access cavity. While the initial data is available on the accuracy of the method in the field of Implantology, future research has to demonstrate whether its implementation in Endodontics is feasible.
Fracture strength of CAC was statistically significantly higher in mandibular molars (P Value = 0.0367250) compared to TAC groups, without differing significantly from the sound control groups.
There was no statistically significant difference in fracture strength between CAC group and TAC group in maxillary molars with a P Value of (0.0951567).
Fracture strength of Maxillary Molars CAC group did not differ significantly from that of the SC control group with a P Value of (0.3598322), whereas that of the TAC group was statistically significantly lower than the control group with a Pvalue ( 0.0052701).
Root-canal treated teeth are more susceptible to fracture than sound teeth essentially due to dentinal tooth structure removal during endodontic therapy
The controversy should not be whether to completely de-roof or partially de-roof a pulp chamber, or whether to cut a ninja-type access cavity to any given orifice; rather, the answer to this debate should be based on the reality of “do what you can, with what you got, where you are.” Ultimately, the size of the access cavity is most influenced by anatomical knowledge, experience, and the technologies and methods utilized to shape, 3D clean, and fill root canal systems.
In keeping with this philosophy of minimal invasion of bulk dentin structure, the use of round burs and Gates-Glidden burs is now discouraged.
They are now recognised in endodontic treatment as instruments that commonly gouge the endodontic access and the coronal third of the root canal.
Gouging of the access and coronal canal space must be avoided in order to preserve maximal resistance to structural flexure and ultimate failure.
Thus you “bless the tooth” as you create endodontic ac- cess, as opposed to “cursing” the tooth with traditional burs and techniques.