# Insights on Closing Lower Premolar Space

# Question:

Hi everyone! Need help with this case; will submit it to clearly reviews if the patient is willing but the patient was not sure to do the treatment so i wanted to see what you would do in a case like this to inform her better before going further. Would you extract 18-28-38 and keep 48? Is it predictable to close the Space of 85? The patient doesn’t want to pay to replace it.. <https://shub.invisalign.com/cc-cloud/latest/index.html?locale=en_US&user=user&ccModIntegrity=false&configUrl=%2Fconfig%2Fscsl_cc_cloud&ccId=547192>


# Answer:

[https://www.loom.com/share/2b94acaac2774f7d9a6ba7daa443e1b5?sid=181baff4-05d9-480d-9e4d-2ae9be1deccf](https://www.loom.com/share/2b94acaac2774f7d9a6ba7daa443e1b5?sid=181baff4-05d9-480d-9e4d-2ae9be1deccf)


## Orthodontic Considerations for Space Closure in Lower Second Premolar Cases

### Introduction

This case study explores the feasibility of closing the space of a lower second premolar by mesializing the third molar (8), second molar (7), and first molar (6). Several biomechanical and occlusal considerations must be taken into account to determine the best course of action.

### Occlusal Considerations

The patient presents with a significant overjet and space loss in the premolar region due to the position of the lower second primary molar. If space were to be opened for a premolar, placing a spring between the lower first premolar and first molar would push the anterior teeth forward and the posterior teeth backward. While this would contribute to a Class II correction, it would not fully resolve the skeletal Class II discrepancy.

### Anchorage and Root Considerations

To move all lower molars forward, anchorage from the anterior teeth would be required. However, this poses a challenge because the anterior teeth would be susceptible to retraction into the space, potentially causing a significant midline shift toward the missing tooth. The discrepancy in root numbers between anterior and posterior teeth further complicates anchorage; there are six posterior roots compared to four anterior roots, making it more likely for the anterior teeth to move rather than the posterior teeth.

### Mechanical Space Closure

A key factor in space closure is root positioning rather than simply moving crowns. In cases where root divergence is minimal, space closure is more predictable. However, when roots are widely spaced, moving them into alignment requires significant effort.

One approach is to create space between the premolar and first molar to allow aligners to fully grip the teeth. Additionally, over-treatment of root tip positioning can help achieve better outcomes. The use of attachments on both the buccal and lingual aspects facilitates controlled mesial root tipping. Forces applied in opposing directions help create rotational movements necessary for root alignment.

### Treatment Progression

Treatment typically involves successive refinements. Initial adjustments focus on root positioning before space closure is attempted. As the process continues, overcorrection may occur, requiring further refinements. At the final stage, additional measures such as bite settling with temporary retainers and interproximal reduction (IPR) may be used to optimize occlusion.

### Class II Considerations and Midline Shifts

As space closure progresses, some retraction of anterior teeth occurs, potentially exacerbating the Class II relationship. In unilateral cases, significant midline shifts are expected, making space closure a less favorable option. Additionally, if the lower third molar is only partially erupted, its involvement in the movement process must be carefully assessed.

### Alternative Treatment Options

When a unilateral missing tooth is present, an implant may be a more viable solution than space closure. However, temporary anchorage devices (TADs) could be used to drag molars forward. While this is a viable option, it is complex and outside the scope of this discussion.

### Conclusion

Closing space in a lower second premolar case through molar mesialization is possible but presents significant challenges. Root positioning, anchorage control, and Class II considerations all play a critical role in treatment planning. In many cases, alternative solutions such as implants may provide a more predictable outcome.