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