Table of Contents 🔗
Stability Dip and AnyTime Loading Theory
Classic Total Stability & Stability Dip
In the previous post, we examined classic total stability and stability dip, noting the following points:
Primary Stability: The initial stability of the implant, which is primarily dependent on the mechanical engagement between the bone and the implant, decreases over time due to bone remodeling and bone resorption.
Secondary Stability: As the implant integrates with the bone, secondary stability increases due to the formation of new bone around the implant.
Taking into account the overall total stability, we observed that there is a stability dip. This dip occurs as the primary stability decreases before the secondary stability fully develops.
Reason of Bone Resorption
Bone resorption, which causes the decrease in primary stability, can occur due to several factors during implant placement:
Bone Trauma During Drilling: The process of drilling into the bone to prepare for the implant can cause micro-damage to the bone, leading to resorption as part of the natural healing response.
Overheating: Excessive heat generated during drilling can damage the bone cells, resulting in bone resorption as the body attempts to repair the affected area.
Overpressure: Applying too much pressure during implant placement can compress the bone excessively, potentially leading to resorption as the bone remodels itself in response to the stress.
Addressing these surgical challenges is crucial for successful dental implants. Overcoming them enables flexible restoration anytime, provided the soft tissue heals properly.
No Stability Dip & AnyTime Loading
To address this, Dr. Youngku Heo and Neobiotech introduced the ‘No Stability Dip' theory. This theory aims to eliminate the stability dip by maintaining primary stability through minimal bone resorption and the CMI Fixation concept.
Strategies to minimize bone trauma during surgery
To maintain primary stability by minimizing bone resorption, we will now explore the factors that contribute to bone resorption and examine strategies to reduce bone trauma during implant placement.
For successful implants, primary stability is very important. Primary stability depends on factors such as bone quantity and quality, implant design, and implant dimensions, but it also heavily relies on surgical technique like drilling protocol. When performing an implant osteotomy, necrotic bone can form around the area, with the extent of necrosis depending on the degree of bone trauma. While recent advancements have focused on implant design and surface treatments, it’s crucial to address the foundational aspects of surgical technique.
Key strategies to improve implant stability include:
Minimizing trauma during surgery
Utilizing an advanced thread design
For more details, refer to our other post about the CMI Implant(click!), where we discuss features like the magic thread, tapered body, and SLA surface that ensure strong primary stability and rapid osseointegration for AnyTime Loading.
These methods help shift the primary stability dip line to match Neobiotech’s optimized standards.
Then how to minimize trauma during surgery? We’ll focus on two critical factors: overheating and over-compression. Understanding and addressing these issues are key to improving surgery outcomes and maintaining primary stability.
Overheating
Understanding Bone Necrosis from Overheating: Case Insights
Thermal damage to bone is both time and temperature-dependent. Osteocytes, the cells within bone tissue, begin to die at temperatures around 50°C, while alkaline phosphatase, an enzyme crucial for bone formation, denatures at 56°C. Excessive bone heating can lead to hyperemia, protein degeneration, necrosis, osteocyte death, osteoclasts, and ultimately, bone necrosis. There are several case reports in the literature demonstrating instances of bone necrosis associated with implant placement.
One such case involves a young patient who had an implant placed in the premolar area. A few months later, the patient developed a periapical lesion that gradually increased in size, accompanied by pain. Despite antibiotic treatment, there was no improvement, and the implant eventually had to be removed. Histological analysis revealed bone necrosis. While various hypotheses were considered—such as pre-existing pathology, overloading, or infection— were consistent with the findings. The authors ultimately suggested that the periapical lesion was likely caused by overheating or the compression of bone chips in the apical area.
Factors Affecting Temperature Rise During Drilling
During dental implant procedures, managing the temperature generated during drilling is critical to preventing bone damage and ensuring successful outcomes. Several factors influence the temperature rise, including bone density, drill diameter, drilling speed and pressure, duration, cooling techniques, and drill design.
Bone Density and Cortical Thickness
Drilling in denser bone or bone with greater cortical thickness tends to cause a higher increase in temperature. Dense bone provides more resistance, leading to greater friction and heat generation during the drilling process.
Drilling Speed and Pressure
The speed and pressure applied during drilling also impact temperature. Increasing speed or pressure generally leads to a rise in temperature, but this relationship is not linear. Some studies suggest that beyond a certain speed, the temperature may stabilize or even decrease. Additionally, higher speed and pressure can reduce drilling time, which in turn minimizes the duration of heat exposure and helps control temperature.
Continuous vs. Intermittent Drilling
Intermittent drilling, which involves a pumping motion, is more effective in cooling the osteotomy site compared to continuous drilling. This technique allows better access for irrigation fluids and helps clear bone debris, reducing the risk of overheating.
Cooling Techniques
Effective cooling is crucial for temperature control during drilling. Both internal and external irrigation methods are used, with studies showing mixed results on which is more effective. However, the temperature of the irrigation fluid also matters. Cooling the saline solution before use, such as by refrigeration, has been shown to improve cooling efficiency. Additionally, the volume of irrigation fluid used is important; there is a threshold beyond which increasing the flow rate does not significantly enhance cooling and may even obstruct visibility.
Drill Diameter, Geometry and Design
The diameter and geometry of the drill to act a significant role in temperature increase. When drilling with a single bur, a larger diameter increases the surface area in contact with the bone, leading to higher temperatures. Also the drill design, including the shape and the number of flutes, influences temperature rise. Conical drills generally cause a smaller increase in temperature compared to other designs. Drills with more flutes can improve cutting efficiency and reduce heat generation, but they also risk clogging with bone particles, which can counteract these benefits and increase temperature.
Proper management of these elements helps ensure that the drilling process is safe and effective, reducing the risk of bone necrosis and improving implant success rates.
Over-compression(High Insertion Torque)
Low Torque, Reliable Results: Study-Based Evidence
Additionally, recent studies show that low torque values do not harm implant survival. In fact, low torque can achieve similar or even better outcomes by reducing bone stress and supporting long-term stability.
Study 1) The Influence of Insertion Torque on the Survival of Immediately Placed and Restored Single-Tooth Implants
This study followed 61 patients with immediately placed and restored single-tooth implants over a period ranging from 1.25 to 9.5 years (mean follow-up of 46 months). The implants were placed with a mean insertion torque of 22.5 N/cm. The results showed a high survival rate of 95.5%, with 78% of the cases showing no marginal bone loss (MBL). Only a small percentage of patients exhibited minimal bone loss. The study concluded that even a torque as low as 25 N/cm is sufficient to achieve favorable clinical outcomes, challenging the notion that higher torque is always necessary for implant stability.
Study 2) Influence of Low Insertion Torque Values on Survival Rate of Immediately Loaded Dental Implants: A Systematic Review and Meta-Analysis
This systematic review and meta-analysis investigated the survival rates of implants placed with low (<35 N/cm) and high (>35 N/cm) insertion torque. The review found that implants placed with low insertion torque had a mean survival rate of 96%, while those with higher torque had a survival rate of 92%. Importantly, the review highlighted that low insertion torque values did not significantly affect the survival rates of immediate loading implants over a mean follow-up of 24 months. This suggests that low torque can be just as effective as higher torque for implant success.
Study 3) Mechanical Stress During Implant Surgery and Its Effects on Marginal Bone: A Literature Review
This literature review explored the effects of mechanical stress during implant surgery, particularly focusing on how high insertion torque can impact marginal bone. The review emphasized that high insertion torque does not guarantee successful osseointegration and can actually lead to increased marginal bone loss due to excessive stress on the bone. The authors recommend that clinicians be cautious not to overstress the bone during surgery. Future implant systems should prioritize drill protocols and designs that derive stability from trabecular bone rather than relying on compressing the cortical layer.
Clinical Recommendation to achieve Optimal Bone-Implant Contact for AnyTime Loading
Minimizing bone trauma during implant placement is essential for maximizing bone-implant contact(BIC) and long-term stability. Following these techniques will secure successful implant outcomes and meet the criteria for AnyTime Loading.
Drilling Procedures:
Soft Bone: Active placement using undersized drilling, followed by self-compaction and self-tapping of the cortical portion.
Hard Bone: Passive placement using full-size drilling and pre-tapping the entire osteotomy. This approach stabilizes the implant against micro-motion, a common cause of failure in immediate or early-loaded implants.
Insertion Torque:
For insertion torques below 20N/cm, submerge the implant in soft tissue.
For insertion torques above 20N/cm, place a healing abutment.
If insertion torque is between 30 to 40N/cm, it satisfies one of the essential criteria for AnyTime Loading, allowing for immediate or early loading of the implant.
Do not exceed 40 N/cm to prevent excessive stress on the bone, which could compromise the stability of the implant.
Summary
In conclusion, it’s important to recognize that overheating can significantly reduce the bone’s regenerative capacity and weaken its mechanical properties. Additionally, using high insertion torque can lead to increased bone resorption and delayed healing. Therefore, clinicians should carefully consider bone quality and the intended loading protocol when determining the appropriate level of mechanical stability for successful implant outcomes.