Current Concepts in Access Cavity Preparation
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Current Concepts in Access Cavity Preparation
- 2. Current Concepts in Access Cavity Preparations By: Dr. Urvashi Tanwar MDS II UNUSUAL WAYS, USUAL DESTINATION
- 4. CASE REPORT Preoperative view of tooth #36 in a 20-year-old woman.
- 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.
- 8. Problems Associated With Traditional Access Use of large round burs Use of gates glidden drill De-roofing
- 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.
- 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
- 17. Hierarchy Of Needs To Maintain Optimal Strength, Fracture Resistance
- 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.
- 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.
- 28. 45° Bob Margeas/Infinity Edge Margin
- 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.
- 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
- 34. A more appropriate access shape is overlayed.
- 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.
- 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
- 47. X ENTRY ACCESS
- 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.
- 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
Hinweis der Redaktion
- 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.