Maxillary Molar Access Open:Step by Step Guide

Explore the step-by-step guide for maxillary first molar access with Dental EndoMaster. Enhance your endodontic training through realistic smartphone-based simulation designed for effective learning.
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Oct 21, 2024
Maxillary Molar Access Open:Step by Step Guide

This guide will explore the step-by-step process of access cavity preparation for the maxillary first molar.

Anatomy

1. External Anatomy

Occlusal Surface

The maxillary first molar has four cusps: two buccal cusps and two palatal cusps. When creating an access cavity, care must be taken not to invade the mesial marginal ridge or the oblique ridge.

The occlusal surface of the maxillary first molar

Root Inclination

The inclination of the roots within the dental arch is crucial when determining the direction for access cavity preparation. When viewed from the buccal side, the roots incline distally. From the front, they incline palatally. It is essential to consider the three-dimensional orientation of the roots when planning the access opening.

Root inclination: Buccal view(left), Frontal view(right)

2. Pulp Chamber Anatomy

Pulp Chamber Shape

The pulp chamber generally reflects the overall shape of the tooth, appearing as a large, wide, rectangular, or polygonal space. The maxillary first molar typically has four pulp horns, each extending towards the cusps. Over time, due to calcification with aging, the sharpness of the pulp horns may become less distinct.

Relationship Between Occlusal Surface and Pulp Chamber

From an occlusal view, the pulp horns form a square shape, while the canal orifices beneath them typically form a triangular arrangement.

The pulp horns form a square shape

Depth of the Pulp Chamber

According to the literature, the pulp chamber is generally located around the level of the CEJ (cementoenamel junction), with the distance from the cusp tips to the pulpal roof averaging 6.5 mm.

The pulp chamber is generally located around the level of the CEJ

3. Sectional Anatomy

Cross-Section of the Tooth

When a section is made near the CEJ, the pulp horns become visible, and during access cavity formation, the characteristic "sinking sensation" can be felt when reaching the pulp chamber.

Cross section at the level of CEJ.

Proceeding 1-2 mm deeper from this point will fully expose the pulp chamber and allow you to visualize the pulpal floor.

As you approach the canal orifices, you will observe the typical triangular arrangement of the root canal entrances. Familiarizing yourself with this standard configuration is critical for precise access cavity preparation.

Cross section at the canal orifice level

In calcification cases, observing the tooth's external structure can help locate the hidden canals. By following the natural shape of the tooth, the canals can still be found even if initially invisible due to calcification.

Simulation

Now, let's apply the knowledge you've learned in a practical simulation. Before practicing on actual teeth, we'll use the Dental EndoMaster app to familiarize yourself with the concepts. Once you're comfortable with the 3D anatomy and process, you'll be ready to practice on real teeth.

1. Penetration Cut

We're about to begin one of the most critical and nerve-wracking parts of root canal treatment—making the penetration cut to reach the pulp chamber. At this stage, you'll need to decide where to start, in what direction to proceed, and how deep to go. Remember not to invade the marginal ridge or the oblique ridge. Let's start at the central pit for this simulation.

The bur is located in the central pit of the occlusal surface.

Next, you need to determine the direction of your cut. Visualize the direction of the roots in your mind, as this is crucial in clinical practice. The Dental EndoMaster app will guide you by showing the direction you've chosen. In the Secondary View, you'll see that your current path is aligned toward the center of the pulp chamber. At first, use this tool to guide your decisions, but as you practice, you'll gradually be able to choose the correct direction without assistance.

The secondary view clearly identifies the direction of the bur.

Now, let's prepare the access cavity according to the direction you've chosen. When you press the Prep button, you'll hear a sound and feel a vibration indicating the formation of the cavity. As you approach the pulp chamber, you’ll experience a "sinking sensation" through the bur's speed, sound, and vibration.

Begin the penetration cut while displaying the depth information.

We’ve used a #8 bur to make the penetration cut. You've now reached the pulp chamber and can observe the pulpal floor map.

The penetration cut is finished at a depth of 5.7mm, revealing the pulpal floor map.

2. Canal orifice estimation

Using this information, let's predict where the canal orifices are located. This requires repetition, but once you understand the typical patterns of canal orifice positions, you can apply this knowledge to any tooth.

Pay close attention to the distance between the orifices as you predict the location of each canal orifice entrance. This spacing is key to accurately identifying the orifice positions.
You can check the results of your predictions in the Secondary View to see if they align with the actual canal orifice locations.

3. Access Cavity Outline Design

Now, it's time to widen the access cavity. Your goal is to make the cavity large enough to reveal all the canal orifices and include the pulp horns.

Design the shape of the access cavity so that instruments can easily reach the canals and no undercuts remain around the pulp horns.

How does your result look? Keep practicing until you achieve the ideal access cavity shape.

Rotate the formed access cavity to observe it from different angles. This will help you assess the shape and ensure it provides optimal access to the canals.

4. Evaluation

Finally, it's time to evaluate your work. The app provides a quantitative analysis of your access cavity preparation. Use this feedback to refine your understanding of canal anatomy and improve your cavity preparation technique. Keep practicing until you're satisfied with the result!

The relationship between the pulp horns, canal orifices, and the access cavity you've created is displayed in a 3D view. This lets you visually understand how the access cavity aligns with the internal structures, ensuring accurate preparation and easy canal access.
The depth relationship between each anatomical structure—pulp horns, canal orifices, and the access cavity—is now displayed. This 3D view highlights the varying depths, helping you understand how these structures are positioned relative to each other for precise treatment planning.

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