Access Cavity Dr. Ahmed Jawad Alashaw

Adequate access is essential for successful endodontic treatment. Knowledge of pulp chamber morphology, along with an examination of preoperative radiographs, should be integrated when designing the access cavity to a tooth for root canal treatment. Access is the most important phase of root canal treatment.

OBJECTIVES of ACCESS CAVITY PREPRATION To achieve straight- or direct-line access to the apical foramen or to the initial curvature of the canal. To locate all root canal orifices. To conserve sound tooth structure.

Endodontic Coronal Cavity Preparation I. Outline Form II. Removal of the Remaining Carious Dentin and Defective Restorations III. Convenience Form IV. Cleansing of the Cavity

I. Outline Form The outline form of the endodontic cavity must be correctly shaped and positioned to establish complete access for instrumentation, from cavosurface margin to apical foramen. The outline of an access depends on the shape of the pulp chamber of the involved tooth

II. Removal of the Remaining Carious Dentin and Defective Restorations Caries and defective restorations remaining in an endodontic cavity preparation must be removed for three reasons: 1. To mechanically eliminate as many bacteria as possible from the interior of the tooth 2. To eliminate the discolored tooth structure that may ultimately lead to staining of the crown 3. To reduce the risk of bacterial contamination of the prepared cavity resulted from leakage of an old restoration

III. Convenience Form Unobstructed access to the canal orifice, Direct access to the apical foramen, Cavity expansion to accommodate filling techniques, and Complete authority over the enlarging instrument

IV. Cleansing of the Cavity All of the caries, debris, and necrotic material must be removed from the chamber before the radicular instrumentation is begun. This should be done without the use of an air syringe to prevent emphysema. Sodium hypochlorite (NaOCl) should also be used during the access preparation for its added benefits of disinfection, removal of hemorrhagic or purulent fluids, and flushing action of debris and dentin chips.

Guidelines Of Access Prep Visualization of the Likely Internal Anatomy Diagnostic radiographs help the clinician to estimate: The position of the pulp chamber. The degree of chamber calcification. The number of roots and canals. The approximate canal length. The extent of the pathology. Palpation along the attached gingiva aids the determination of root location and direction.

Preparation of the Access Cavity through the Lingual and Occlusal Surfaces

Removal of All Defective Restorations and Caries before Entry into the Pulp Chamber Removal of unsupported tooth structure. Creation of access cavity walls that do not restrict straight- or direct-line passage of instruments to the apical foramen or initial canal curvature.

Location, Flaring, and Exploration of All Root Canal Orifices: A sharp endodontic explorer is used to locate canal orifices and to determine their angle of departure from the pulp chamber.

Divergence of cavity walls: Access cavity should be wider occlusaly for the following reasons: To prevent Occlusal forces from pushing the temporary restoration into the cavity and disrupt the seal. Allow better space for vision Provide a slope in the wall that terminate in the canal orifice Remove any coronal interference for the passage of instrument to the most apical part of the canal

Maxillary Central Incisor All upper anterior teeth have one root and one canal. Central incisor are large and on an average length of 23 mm. The canal form is usually Type I. The pulp in young patients normally has 3 pulp horns.

Maxillary Lateral Incisor Average length of 21- 22 mm. The canal form is usually Type I. In young patients have only two pulp horns and is wider in labiopalatal dimension. The canal is tapered and the apex is often curved generally in distal direction.

Maxillary Canine It is the longest tooth (26.5 mm) Seldom has more than one canal The pulp chamber is quite narrow M- D, and there is one pulp horn pointed to the incisal angle. The pulp space is much wider labiopalatally and the pulp space follows this outline. Oval Type I root canal. The root apex is often tapered and very thin. The canal is usually straight but may show a distal apical curvature.

Endodontic Preparation of Maxillary Anterior Teeth Location: middle middle 1/3 Shape: follow the shape of the crown

Maxillary Anterior Teeth ERRORS in Cavity Preparation Coronal perforation Weakening of tooth structure due to wrong angulation Weakening of tooth structure due to wrong position Incomplete removal of lingual shoulder resulting in un- instrumented areas in the canal Incomplete removal of pulp horn resulting in tooth discoloration Ledge formation. Root perforation.

Maxillary Anterior Teeth ERRORS in Cavity Preparation

Mandibular Central and Lateral Incisors Average length is 21 mm, but the central incisor may be shorter than the lateral. Type I canal form is most prevalent, Types II and III are less prevalent. The pulp chamber is smaller replica of the upper incisors. When the tooth has a single root canal it is normally straight but may curve to the distal. CENTRAL LATERAL

Mandibular Canine Smaller than the maxillary canine. The average length is 22.5 mm. Type I canal form is most prevalent. Rarely has 2 roots, but fewer of mandibular canine display the Type IV canal form with 2 separates apical formina.

Endodontic Preparation of Mandibular Anterior Teeth Location: between the middle and incisal 1/3 Shape: follow the shape of the crown

Mandibular Anterior Teeth ERRORS in Cavity Preparation Weakening of tooth structure due to wrong position (A, B and C) Small access opening could left a canal un detected (D) Access cavity located more near the cingulum resulting in incomplete removal of pulp chamber and un-instrumented area (E) Access cavity through proximal surface results in instrumentation of only one side of the canal.

Mandibular Anterior Teeth ERRORS in Cavity Preparation

Maxillary First Premolar Generally has 2 root with 2 canals, but in the case of 1 root has 2 canals which open in a common apical foramen. Many types of canal configurations. Average length 21.5 mm. The pulp chamber is wide B-P with 2 distinct pulp horn. M-D, the pulp chamber is much narrower.

Maxillary Second Premolar The typical second premolar has one root and one canal and sometimes has an apical distal curvature. The Type I canal form is prevalent with a frequency of 48%, approximately the same as types II and IV-VII combined. The pulp chamber is wider B-P and narrower M- D and has 2 well defined pulp horns. The canal orifice is directly in the centre of the tooth. Average length: 21 mm.

Endodontic Preparation of Maxillary Premolar Teeth Location: between the buccal and palatal cusp tips Shape: oval

Maxillary Premolar Teeth ERRORS in Cavity Preparation Insuficient access Weakening of tooth structure due to large access Wrong angulation Wrong position

Maxillary Premolar Teeth ERRORS in Cavity Preparation

Mandibular Premolars As a rule, both teeth have a single canal. Usually has a single delicate root with a mesial concavity, but occasionally present a division of the root in the apical half. As a rule, both teeth have a single canal. The coronal pulp is wide B-L with a large buccal horn and a small lingual horn. The shape of the canal is similar in first and second premolars. Average Length: 22mm

Endodontic Preparation of Mandibular Premolar Teeth Location: at the center of the occlusal surface Shape: oval

Mandibular Premolar Teeth ERRORS in Cavity Preparation

Maxillary First Molars Generally three rooted with 3 canals. Additional canal is located in the MB root. It has 3 or 4 pulp horns, the MB is the longest. The floor of the pulp chamber is normally just apical to the cervix. The MB canal opening is closer to the buccal wall than is the DB orifice. The DB canal is closer to the middle of the tooth than to the distal wall, and is the shorter and finest of the 3 canals. Average Length: MB: 20mm DB: 19.5mm P : 20.5mm

Endodontic Preparation of Maxillary Molar Teeth Location: between the mesial marginal ridge and the oblique ridge Shape: triangular with the base toward the buccal aspect and the apex toward the palate

Maxillary Molar Teeth ERRORS in Cavity Preparation

Mandibular First Molar Usually has 2 roots one mesial and one distal. The Distal root is smaller and vertical. Distal curvature of the mesial root (84% of the time) which has two canals. The distal canal is larger and more oval. The MB is the most difficult canal to instrument because its tortuous path. Average Length: 21 mm

Endodontic Preparation of Mandibular Molar Teeth Location: on the mesial half of the tooth Shape: trapezoid, the base toward the mesial surface and the apex toward the distal

Mandibular Molar Teeth ERRORS in Cavity Preparation