Access Opening of Premolars PDF

Access opening of premolars Preclinical Endodontics – Lecture 7  Introduction The pulp chamber of a premolar tooth is ribbon shaped, elongated bucco-lingually and usually located in the middle of the crown. The pulp horns extend bucco-lingually almost to the cusp tips. Since the...

Access opening of premolars Preclinical Endodontics – Lecture 7  Introduction The pulp chamber of a premolar tooth is ribbon shaped, elongated bucco-lingually and usually located in the middle of the crown. The pulp horns extend bucco-lingually almost to the cusp tips. Since the number of canals is variable, radiographs must be carefully examined to determine whether there appears to be one, two, or three canals. The facial (buccal) radiograph often superimposes the buccal and palatal or lingual roots and is not diagnostic for determining the number of root canals. An angulated off-angle radiograph, usually from the mesial, may be required to discern the number of root canals. Mandibular Premolar (Coronal access procedures): Draw the proposed outline of the access cavity on the occlusal surface and with#4 round bur prepare a “nest” in the enamel and 1-2 mm into the dentin. Access cavity is located between the central groove and buccal cusp tip. Then, with #2 round burs at high speed, penetrate from the floor of the “nest” into the pulp chamber. Direct the bur parallel to the lingual surface until it penetrates the pulp chamber. Clinically the radiograph shows the mesio-distal long axis of the tooth. Confirm penetration of the pulp chamber by probing with a DG-16 endodontic explorer. A, Mandibular first premolar and access starting location (X) (occlusal view). B, Mandibular first premolar and starting location (proximal view). C, Mandibular second premolar and access starting location (X) (occlusal view). D, Mandibular second premolar and starting location (proximal view). B, Buccal; DL, distolingual; L, lingual; ML, mesiolingual. A. The crown of a lower first premolar can be compared to that of a canine, given its highly developed cingulum. B. The pulp chamber lies almost entirely below the buccal cusp. C. In preparing the access cavity, the bur must be oriented buccally. D. The round diamond bur has accomplished the penetration phase. E. The round bur removes the residue of the chamber roof. F. The non-cutting diamond bur finishes and flares the cavity. G. Radiographic appearance of the completed access cavity. H. Occlusal view of the access cavity. J. The cavity has been created almost entirely at the expense of the buccal cusp. Procedural errors: A. Facial view. Bur appears to be at the correct depth; B. Proximal view shows improper angulation; C. Tooth inclined to the distal; D. Bifid canal seen on proximal view. Maxillary Premolars: The maxillary premolar teeth may have 1, 2, or 3 root canals. The clinical radiograph may not accurately show the number of root canals. Angulated radiographs will assist in determining the number of root canals. Coronal access procedures: Draw the proposed outline of the access cavity on the occlusal surface and with#4 round bur prepare a “nest” in the enamel and 1-2mm into the dentin. Determine the long axis of the root and penetrate into the pulp chamber. Bur should be directed parallel to the long axis of the root and parallel to the lingual surface. If the pulp chamber is large, the bur will “drop” into the pulp chamber. If not, measure the distance from the occlusal to the roof of the pulp chamber using diagnostic angled pre-operative radiograph. Place a #4 long shank round bur in a slow speed contra-angle under the overhanging roof of the pulp chamber and completely remove this dentin from the lingual and buccal using an outward stroking. This starts the “funneling” procedure. A, Starting location for access to the maxillary premolar (X). B, Initial outline form (dark area) and projected final outline form (dashed line). B, Buccal; L, lingual. 10 SLOBE Rule Radiograph for Maxillary Premolars: Angulated view: the horizontal central beam of the cone is at an off-angle either coming from mesial or distal. Cone Shift Technique: The technique used to identify the spatial relation of an object is called the cone shift technique. It is often referred to as the BUCCAL OBJECT RULE, or the SLOB (same lingual, opposite buccal) RULE. By shifting the central beam of the cone, the buccal root of a tooth is projected onto the sensor in a direction opposite from where it was taken. The beam coming from the mesial projects the buccal root to the distal. Another way to explain this concept is that the buccal root is projected in the same direction the beam is headed. Rapid (fast) break is the term used when there is a sudden discontinuity of the canal on the radiograph 12  A B (A): With the standard projection, the roots appear superimposed. (B): Angling the X-ray machine in a mesio-distal direction, the buccal root appears close to the second premolar, while the palatal root appears close to the canine. Clinical Data: 16 17 18 References 1. Torabinejad M, Fouad A, Shabahang S. Endodontics e-book: Principles and practice. Elsevier Health Sciences; 2020 Jun 25. Thank you 20