Decision No. 3: Are You Designing Proper Access Cavities (Figures 2a to 2g)? Q: Is it possible to prepare straight-line access and preserve appropriate ferrule?
A: Straight-line access is conceptually simple.3 Endodontic files should not be impeded by enamel and/or dentin that can by easily removed. In anterior teeth, there are often essentially 2 triangles. The first triangle is referred to as Triangle No. 1, which is essentially made of enamel (Figure 2c). The second triangle is referred to as Triangle No. 2, which is essentially made of dentin (Figure 2d). The dentist performing anterior endodontics must decide to remove these 2 triangles before ever attempting to begin the rotary GlidePath. Failure to remove one or both of these obstructive triangles is the most common anterior access error that endodontists observe in endodontics as performed by restorative dentists. It is the leading cause for beginning the cascade of technical errors leading to failure in predictably producing the Endodontic Seal.
Straight-line dentinal triangular impediments exist in posterior teeth as well but are more subtle and often overlooked. Anatomically, they develop due to chamber calcification during natural aging and/or pulpal trauma. Evidence of posterior dentinal triangular removal is when the endodontic file’s reference point is the same cusp as the root canal that is being cleaned and shaped. For example, if you are cleaning and shaping the palatal canal of a maxillary premolar, the reference cusp should be the palatal cusp. In other words, the angle of access should be the same as the angle of incidence. The file should “stand straight and tall” coming out of the access versus an angle.
Guideline No. 3: Design all access cavities to achieve straight-line access without compromising ferrule integrity.
