Primary Stability: The Biomechanics Behind Successful Implant Integration

The literature defines primary stability as the absence of micromotion of a dental implant immediately after its placement, highlighting its role as a vital prerequisite for osseointegration and long-term implant survival.

Primary stability allows us to bridge the critical gap until secondary stability takes over, reducing micromotion and supporting healing. However, there are biomechanical determinants, clinical measurement methods, and strategies for primary stability that we need to review to optimize our results. 

Understanding Primary Stability

Mechanical vs. Biological Stability

Primary stability tangles the mechanical anchorage achieved at placement, while secondary stability comes from bone healing and remodeling around the implant surface, also known as osseointegration. As professionals, we must ensure a strong primary stability to prevent micromotions during the healing window, particularly during the first few weeks post-placement.

Measuring Primary Stability

The main clinical method used to assess primary stability values is using insertion torque values (ITV) and resonance frequency analysis (RFA) to obtain Implant Stability Quotient (ISQ) readings.

• Insertion torque value (ITV): It indicates the resistance to rotational forces.
• Resonance frequency analysis (RFA): It reflects stiffness at the bone-implant interface and resistance to bending.

Biomechanical Determinants of Primary Stability

Bone Quality and Density

Adequate bone density strongly correlates with initial stability. Dense bone, usually type I-II, provides better mechanical purchase, whereas soft bone (type IV) can represent a clinical challenge for the professional.

Bone Quantity and Morphology

Cortical thickness and cancellous bone structure influence implant anchorage in every dental implant scenario. This is also true for ridge width and angulation. Although clinical evidence in this matter is more limited, we know that adequate bone volume and proper morphology improve both ITV and ISQ. 

Implant Design

Certain macrodesign features directly affect primary, such as:

• Tapered or cylindrical shape
• Tread pitch
• Depth
• Shape

A recent study showed that implant stability is significantly higher in healed ridges with cylindrical, shallow-threaded designs compared to deep-treated tapered ones, producing superior ITV and RFA values. 

Surface Treatments

Modifications in implant surface topography at micro and nano levels considerably enhance osseointegration potential. For the last decades, multiple surface modifications have been proposed and studied to promote osseointegration and, simultaneously, act as a resistance barrier against bacterial contamination.

Most of these modifications, like SLA and RBM, are capable of modulating intra- and extracellular responses, aiding in healing on the implant surface at the healing site.

       

Surgical Technique

Under-preparation, with an undersized osteotomy, in low-density bone, increases friction and ITV values. A 2024 in vitro study demonstrated that under-milling, using up to 0.8 mm smaller than the implant diameter, significantly increases ITV. However, clinicians must balance increased torque with the risk of bone compression and implant deformation.

Biological and Healing Considerations

Transition from Primary to Secondary Stability

Over time, primary stability gradually turns into secondary stability due to bone remodeling and healing. The critical window that should have all our attention as dental professionals are the first 3–6 weeks after placement, when stability dips before new bone formation increases anchorage.

Early vs. Conventional Loading

Immediate or early loading protocols require high primary stability. Literature supports these protocols when ITV > 20–35 Ncm or ISQ ≥ 60–65. However, clinicians must be cautious in soft bone or compromised healing conditions to guarantee predictable results.

Host Factors

Certain patient-specific factors, like systemic conditions or smoking history, can impair bone quality and healing. Due to regional variations in these factors’ prevalence, it is essential to plan and address every case individually and according to its population. 

Clinical Strategies to Enhance Primary Stability

Site Preparation Modifications

Consider implementing undersized osteotomies or bone condensation techniques in softer bone to boost mechanical interlocking. Also, avoid excessive drilling and overheating with plenty of irrigation.

Implant Selection

Preferably, choose implant macrodesign according to site conditions. Keep in mind that soft bone offers better fixation with aggressive threading or tapered shape designs.

Adjunctive Approaches

Bone grafting and using biologic techniques, such as growth factors or PRF, can augment ridge dimensions and bone quality, significantly increasing the prognosis of a stronger initial fixation. While these strategies address volume and healing capacity, their direct effect on initial mechanical stability must be addressed on a case-by-case basis.

Evidence-Based Clinical Thresholds

Torque and ISQ Practice Guidelines

Multiple studies suggest ITV between 20-45 Ncm or ISQ ≥ 60 is commonly associated with successful osseointegration and acceptable for immediate loading protocols. Other research recommends ITV ≥ 35 Ncm for safe loading and ISQ values between 55 and 85 across various implant systems. 

Long-Term Outcomes

Achieving high primary stability correlates with better implant survival and fewer complications. However, excessively high torque may compress bone or damage implant threads and other components. Therefore, keeping a balanced approach is key to providing sufficient mechanical engagement without over-compression while preserving bone structure and implant integrity.

Practical Suggestions for Clinicians

Pre-operative Planning and Evaluation

No treatment is possible without a comprehensive evaluation and corresponding treatment plan. Clinicians must assess bone quality, volume, and type through CBCT, radiographic, and clinical evaluation.

Patient-related factors must be a significant consideration while selecting implant design, loading protocols, and adjunctive therapies.

Surgical Protocol

The literature suggests using an under-prepared osteotomy and monitoring for appropriate insertion torque in soft bone. The main objective is to preserve cortical bone whenever possible, making the most out of digital workflow while avoiding overheating at all costs.

Implant Selection

Favor macrodesign, whether threaded or tapered, that enhances mechanical engagement. GDT implant systems offer a variety in geometry and surface treatment, providing multiple combinations that adapt to your needs.

Monitoring Stability

Monitoring values during the procedure is essential to guarantee a controlled procedure within the appropriate thresholds. Use insertion torque and RFA measurement at placement and track stability progression, particularly during weeks 1–4 when ISQ dips.

Loading Timing

Empirical thresholds might require base loading (ITV ≥ 35 Ncm and ISQ ≥ 60), adjusting for patient factors and bone quality.

Individualized Approach

Every case involves customization, but patients with a high prevalence of osteoporosis or metabolic bone disease require tailored techniques and protocols, like the use of biologics.

Challenges in Clinical Practice for Primary Stability

Even with the most careful planning, achieving optimal primary stability can be a challenge in certain cases. Every day practice involves facing anatomical, biological, and procedural factors that create obstacles that we must anticipate.

Posterior Maxilla

The posterior maxilla represents the greatest difficulty due to its low bone density, typically Type III–IV, and thin cortical layer. These factors make us face significant limitations in bone quality, ridge height, and width. Additionally, sinus pneumatization, present in many patients, further reduces available bone height, making stability even harder to achieve.

In these cases, the literature suggests combining tapered implants with undersized osteotomies or sinus augmentation procedures combined with biologics to provide a secure anchorage.

Immediate Implant Placement

Post-extraction sockets can limit cortical engagement, especially if the socket walls are thin or compromised by infection. While some cases may require grafting[SP1] , biologics, or ridge augmentation, others may also need careful site preparation, often with angled implant positioning to engage native bone beyond the socket apex.

Patients With Systemic Conditions

Osteoporosis, uncontrolled diabetes, and smoking are our biggest enemies. They negatively impact bone quality and hinder healing capacity, reducing the window of tolerance for micromotion. As a result, both primary stability and careful post-operative management become critical.

Clinicians must also consider delayed loading, especially for severely compromised cases.

Technical Errors

Over-drilling, overheating, or poor irrigation during osteotomy preparation can irreversibly damage bone, directly impairing implant stability. Similarly, aiming for excessively high insertion torque may risk bone necrosis, implant deformation, or microfractures.

Avoiding these common mistakes requires:

• Careful preparation and implant selection, integrating digital workflow, surgical guides, and 3D planning.
• Monitoring ISQ before, during, and after the procedure.

Conclusion

Primary stability is the cornerstone of implant success. It secures mechanical engagement during the critical, initial healing phase and sets the stage for biological integration.

For clinicians, optimizing primary stability involves a strategic blend of careful site assessment, implant selection, and technique refinement. During the procedure, specialists must look for detailed implant handling, torque supervision, and overheating prevention to balance mechanical thresholds with biological sensitivity.

By leveraging GDT’s design-focused implant systems, you can deliver consistently successful outcomes for your dental practice.

References 

1. Javed, F., Ahmed, H. B., Crespi, R., & Romanos, G. E. (2013). Role of primary stability for successful osseointegration of dental implants: Factors of influence and evaluation. Interventional medicine & applied science, 5(4), 162–167. https://doi.org/10.1556/IMAS.5.2013.4.3

2. do Vale Souza, J. P., de Moraes Melo Neto, C. L., Piacenza, L. T., Freitas da Silva, E. V., de Melo Moreno, A. L., Penitente, P. A., Brunetto, J. L., Dos Santos, D. M., & Goiato, M. C. (2021). Relation Between Insertion Torque and Implant Stability Quotient: A Clinical Study. European journal of dentistry, 15(4), 618–623. https://doi.org/10.1055/s-0041-1725575

3. Esposito M, Coulthard P, Thomsen P, Worthington HV. The role of implant surface modifications, shape and material on the success of osseointegrated dental implants. A Cochrane systematic review. Eur J Prosthodont Restor Dent. 2005 Mar;13(1):15-31. PMID: 15819145.

4. Javed, F., Ahmed, H. B., Crespi, R., & Romanos, G. E. (2013). Role of primary stability for successful osseointegration of dental implants: Factors of influence and evaluation. Interventional medicine & applied science, 5(4), 162–167. https://doi.org/10.1556/IMAS.5.2013.4.3

5. Rosas-Díaz, J., Guerrero, M. E., Córdova-Limaylla, N., Galindo-Gómez, M., García-Luna, M., & Cayo-Rojas, C. (2024). The Influence of the Degree of Dental Implant Insertion Compression on Primary Stability Measured by Resonance Frequency and Progressive Insertion Torque: In Vitro Study. Biomedicines, 12(12), 2878. https://doi.org/10.3390/biomedicines12122878