Less is More, more or less
Change is the only constant in life. Thermomechanically treated NiTi's, digital radiographs, CBCT's, electronic apex locators, microscopes, bioceramic materials, and active irrigation are a mere smattering of the myriad of transformative developments that differentiate twenty-first-century endodontics from that of yore. Contemporary literature is replete with evidence that the sum mass of coronal dentine is central to the survivability of endodontically treated teeth. Hence, the rules for access preparation have evolved, with conservation of tooth structure taking precedence over the once venerated straight-line access. Conservative 'ninja' accesses are en vogue and are broadcast with boundless ardour in dental journals and social media websites. Is a heroically conservative access a worthwhile endeavour if a crown or an extensive restoration is in situ? Indubitably, as the mass of coronal dentine is already compromised. Preservation efforts in these teeth will be more impactful than in a lightly restored tooth that has an abundance of coronal dentine to rely on for fracture resistance.
Unroofing a chamber, in its entirety, to gain straight-line access to each orifice is a quirky rule best left to the annals of debunked historical endodontic doctrine. The new credo is to preserve sections of the roof and the dentine coronal to it. Some have mistakenly referred to these lips or cornices as the soffit of the tooth. However, eave is a more accurate term as an eave is the part of a roof that projects beyond the wall. See the diagrams above for more details. The benefits to preserving sections of the chamber roof and the dentine coronal to it are:
The need for straight-line access to each orifice is obsolete in modern endodontics. Magnification, illumination, and angulation of the hand mirror enable visualisation of all canal orifices, even those under an eave of dentine. Thermomechanically treated NiTi rotary files can safely prepare a canal with angled access to the orifice. Nor do modern active irrigation devices require unhindered vertical access to a canal.??
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Pericervical dentine (PCD) extends from 4mm coronal to 6mm apical to the crestal bone level. This is the tooth's strategically important ‘neck’, where occlusal forces are transferred to the root. A well-preserved PCD makes for a stronger tooth with an optimised fracture resistance form. Gouging of chamber walls and floors, excess orifice enlargement, or severe coronal flaring in the canals will compromise the integrity of the PCD and inadvertently weaken teeth.?
Preoperatively, both of the teeth above were heavily restored. The amount of coronal dentine remaining was compromised, yet the canal orifices were obliterated by restorative materials or camouflaged by stained secondary and tertiary dentine. To add insult to injury, as a chamber calcifies the orifices become increasingly indiscernible and migrate both coronally and centrally. An endodontic failure is probable if dentine is preserved and an orifice remains undiscovered. Yet endodontic success at the expense of preservation of coronal dentine is a quixotic misstep. Modern endodontic techniques and equipment enable one to better balance the necessity of gaining access to all the canals and the juxtaposed goal of preserving coronal dentine. The ideal access is an elusive beast, as less is more but not too much less as that would be less than ideal, more or less.?