A dental implant serves as a secure foundation in the jawbone, to which a visible tooth replacement (crown) is attached. This attachment is secured by a small titanium screw that connects the implant body to the abutment and crown. When this screw fractures, a fragment remains lodged inside the implant fixture, causing the crown to become loose or unstable. Although stressful, a broken screw is a recognized and manageable complication. The primary goal of treatment is to safely remove the remaining fragment without compromising the underlying implant fixture, allowing a new restoration to be placed.
Understanding Why Implant Screws Break
Implant screws are designed to withstand normal chewing forces, but they can fail due to factors that place excessive or repeated stress on the material. The most frequent reason for fracture is material fatigue, a gradual weakening that occurs over time under repeated loading. This wear and tear is often accelerated by excessive bite forces placed on the implant.
Occlusal discrepancies, or problems with how the upper and lower teeth meet, can direct abnormal, non-axial forces onto the implant system, increasing the risk of breakage. Parafunctional habits, such as teeth grinding (bruxism) or clenching, subject the screw to high-magnitude forces that lead to fracture. Additionally, a screw not tightened to the manufacturer’s recommended torque value can loosen over time. This movement increases stress on the screw, potentially leading to its eventual fracture.
Component misfit, where the manufactured pieces do not perfectly align, can also concentrate stress on the screw, contributing to failure. The screw often acts as a safety mechanism, failing before the more permanent implant fixture itself is damaged. Understanding the underlying cause is crucial, as simply replacing the screw without addressing the root problem, such as bruxism or an uneven bite, will likely lead to a recurrence.
Initial Assessment and Diagnosis
When a patient presents with a loose crown, the clinician first performs a thorough examination to determine if the issue is a loose screw, a loose abutment, or a fractured screw. The crown is typically removed to access the implant’s internal connection and visualize the screw head. If the screw head is missing or clearly broken, the diagnosis of a fractured screw is confirmed.
Diagnostic imaging follows the visual check to assess the fragment’s exact position and the condition of surrounding structures. Standard two-dimensional X-rays, such as periapical radiographs, confirm the fragment’s location and depth within the fixture. Because X-rays can obscure three-dimensional detail, a Cone-Beam Computed Tomography (CBCT) scan may be necessary. This 3D imaging provides a detailed view of the fragment’s angle and proximity to the internal threads, which is crucial for planning the safest removal strategy.
Conceptual Overview of Removal Techniques
The primary goal of removing a fractured screw is to retrieve the fragment while preserving the delicate internal threads of the implant fixture. Techniques are generally approached in a conservative-to-aggressive sequence, starting with the least invasive methods. If the fractured piece is slightly loose or superficial, a specialized, non-rotary instrument, such as a sharp explorer or fine dental probe, may be used. The clinician gently engages the fragment’s edge and rotates it counter-clockwise, using friction to unscrew the piece.
If the fragment is more tightly bound, controlled vibration is used to loosen the piece. An ultrasonic scaler, applied carefully in a non-cutting mode, transmits micro-vibrations that help break the friction or debris locking the fragment in place. This method is often performed with high magnification to ensure the instrument only contacts the broken screw and avoids the implant walls. Once slightly dislodged, the clinician may return to non-rotary instruments to complete the removal.
For deeply embedded or tightly wedged fragments, more advanced, specialized instruments are required. Many implant manufacturers offer specific screw removal kits featuring reverse-tapping drills. These drills create a small purchase point within the center of the broken screw. Once engaged, the instrument is rotated slowly in reverse (counter-clockwise), aiming to grip the fragment and rotate it out of the implant.
Creating a Slot
If the fragment’s top surface is damaged, a small, round bur may be used to carefully cut a slot into the head of the broken piece. This slot acts as a purchase point for a modified screwdriver or slot driver, allowing the clinician to manually unscrew the fragment.
Troughing
The most aggressive technique, often used as a last resort, involves creating a tiny channel, or “troughing,” around the fragment with a fine, high-speed bur. This aims to relieve any binding between the fragment and the implant wall. However, this technique carries the highest risk of damaging the implant’s internal threads, potentially rendering the entire fixture unrestorable.
Patient Recovery and Long-Term Management
Recovery following broken screw removal is typically straightforward, especially if the implant fixture’s internal threads remained undamaged. Since the procedure is confined to the crown and abutment area, immediate downtime is minimal, and any slight sensitivity resolves quickly. A temporary restoration may be placed to protect the site while a new, custom-fabricated abutment and crown are being made.
Fabricating the new components can take several weeks, allowing the dental lab time to ensure a passive and precise fit to prevent recurrence. Once ready, the replacement screw is tightened to the precise torque value specified by the manufacturer. Long-term management focuses on preventing the initial cause of the fracture. If bruxism was a contributing factor, the patient will be advised to wear a custom-fitted night guard to protect the implant from excessive nocturnal forces. Regular follow-up appointments are important to check bite alignment and ensure the new screw remains tight, addressing issues before they escalate to another fracture.