The Hidden Dangers and Pitfalls in Full Arch Dentistry: Ensuring Precision for Long-Term Success
Introduction
In the intricate world of full arch dentistry, achieving a passive fit for implant-supported restorations is crucial for the long-term success of the prosthesis and the overall satisfaction of your patients. However, several factors can significantly impact the accuracy of your work, leading to potential complications and failures.
Consider the fact that full-arch dentists have a margin of only 100 - 150 microns to achieve passivity. That's about the size of a human hair! Unfortunately, each stage of the prosthetic process can introduce small errors, which "stack up" and may lead to a poor fit.
Even a discrepancy of just a few microns can affect the passivity of a full-arch restoration. Misfits can lead to complications that result in costly remakes and ultimately impact patient satisfaction.
This white paper explores several "hidden enemies of passive fit" and the dangers they present in the success of your full-arch cases. These are widely accepted and understood principles in manufacturing—but are largely unknown in the dental industry. Unfortunately, each "hidden enemy" will have a significant impact on the fabrication of your final full-arch prosthesis. Being aware of these principals will help ensure a passive fit that minimizes stress and increases the likelihood of long-term success for your cases.
Topics explored:
  • Mandibular flexure
  • Thermal expansion
  • Error propagation
  • Tolerance stacking
  • Heat transfer to scanbodies
Chapter 1: Understanding Mandibular Flexure
What is Mandibular Flexure?
One often overlooked factor that can significantly impact the accuracy of a case is mandibular flexure. Mandibular flexure refers to the deformation of the jaw in at least three directions due to non-masticatory physiological movements. This deformation can range from a few microns to 1 mm, with an average value of approximately 0.073 mm. In some cases, patients can experience more than 4 mm of elastic displacement of the mandibular condyles during mandibular movement.
The complex biomechanical behavior of the mandible is influenced by several factors, including the attachment of masticatory muscles, the patient's age, bone density, and individual anatomical variations. During wide opening, protrusion, and lateral excursion movements, the mandible undergoes both mediolateral compression and dorsoventral shear, resulting in a three-dimensional deformation that can significantly impact the accuracy of impressions and the fit of prosthetic restorations.
Clinical Significance in Full Arch Implant Cases
In full arch implant cases, mandibular flexure becomes particularly problematic because dental implants are rigidly anchored to bone, unlike natural teeth which have a periodontal ligament that allows for minor movement. This rigid connection means that any flexure in the mandible will transfer stress directly to the implant-prosthesis interface, potentially compromising the integrity of the restoration and the health of the surrounding bone.
Research studies have demonstrated that the greatest amount of mandibular flexure occurs during maximum opening of the mouth, precisely when impressions are typically taken. This timing creates a significant challenge for achieving accurate impressions and subsequently passive-fitting prostheses.
Real-World Dangers of Mandibular Flexure
Misalignment of Restorations
Mandibular flexure can cause misalignments in the final restoration, leading to a poor fit and increased stress on the implant abutments. When impressions are taken with the mouth widely open, the mandible is in a deformed state. As the mouth closes, the mandible returns to its resting position, creating a discrepancy between the impression and the actual position of the implants. This discrepancy can be as small as 100 microns, but even this minute difference can prevent passive seating of the prosthesis.
Bone Resorption
The deformation of the jaw can lead to peri-implant bone resorption, which compromises the stability and longevity of the implant. When a non-passive prosthesis is attached to implants, the resulting strain can trigger a biological response in the bone. This response includes increased osteoclastic activity, leading to bone resorption around the implants. Long-term studies have shown that this bone loss can progress over time, eventually resulting in implant failure if left unaddressed.
Prosthetic Complications
Mandibular flexure can cause distortion of impressions, improper fit of prostheses, and even fracture of implant screws or porcelain crowns. This can lead to increased rates of remakes and adjustments, adding to the time and cost of treatment. Studies have reported screw loosening in up to 45% of cases with non-passive frameworks, compared to only 5-10% in cases with passive fit. Additionally, porcelain fractures occur at nearly twice the rate in restorations with fit discrepancies related to mandibular flexure.
Patient Discomfort and Dissatisfaction
Beyond the technical complications, patients may experience discomfort, pain, or a sensation that "something doesn't feel right" with their restoration. This discomfort can manifest as soreness around implant sites, difficulty in speaking or chewing, or even temporomandibular joint (TMJ) pain due to altered biomechanics. Patient dissatisfaction can lead to complaints, requests for adjustments, or even legal issues, all of which impact the practice's reputation and profitability.
Long-term Implant Failure
The cumulative effect of continued stress from mandibular flexure can lead to late implant failure, even years after initial successful integration. The micromovements and resulting microgaps between the implant components create environments for bacterial colonization, leading to peri-implantitis. Additionally, the repeated loading and unloading cycles caused by mandibular flexure can lead to metal fatigue and eventual implant or component fracture.
Increased Strains and Stress at the Implant Prosthetic Complex
Mandibular flexure can increase the biological and biomechanical complications affecting the overall implant and prosthetic success. This can lead to loosening and fracture of the implant or prosthetic screws, chipping of the veneering material, and bone resorption around the implant.
Occlusal Interference and Pain
When the denture is worn to perform functions, the teeth and restorations are susceptible to undesirable stress, causing occlusal interference, pain, and discomfort.
Bone Resorption and Gingivitis
The stress caused by mandibular flexure can lead to bone resorption and gingivitis, compromising the stability and longevity of the implant.
Complications in Fixed Dental Prostheses (FDP)
Mandibular flexure may cause complications and failures in both conventional and implant-supported fixed dental prostheses, especially when a long-span prosthesis is planned to connect the anterior to the posterior region of the mandible.
Increased Stresses in Prosthesis and Abutment
Median Mandibular Flexure (MMF) can lead to challenging problems with both conventional and implant-supported prostheses by increasing the stresses in the prosthesis and abutment.
Absence of Prostheses Passivity
Bilateral rigid connection with distal extension in conventional prostheses can result in muscle pain, limited mouth opening, and absence of prostheses passivity, among other complications.
Strategies to Mitigate Mandibular Flexure Issues
Understanding mandibular flexure is only the first step. Implementing strategies to mitigate its effects is crucial for long-term success in full arch implant cases. These strategies include:
  • Taking impressions with the mouth only partially open to minimize flexure
  • Using sectional impressions for cases spanning both sides of the arch
  • Incorporating stress-breaking elements in the prosthetic design
  • Utilizing digital workflows that can compensate for predicted flexure through software algorithms
  • Allowing for passive fit through precision milling techniques with appropriate tolerances
Conclusion
Mandibular flexure is a critical factor that can significantly impact the success of full arch restorations. By understanding and addressing the real-world dangers associated with mandibular flexure, dentists can ensure better patient outcomes, reduce complications, and enhance the longevity of implant-supported prostheses. Choosing the right photogrammetry system is essential for achieving precision and reliability in full arch dentistry.
Visual Representation Ideas:
Metaphor: Rubber Band
Imagine stretching a rubber band in different directions. The deformation of the rubber band represents the deformation of the jaw due to mandibular flexure. This illustrates how small movements can lead to significant changes in the overall structure.
When multiple implants are placed along this "rubber band," they remain fixed in their positions. As the rubber band flexes and returns to its original shape, these fixed points experience stress at their attachment points. Over time, this repeated stress can weaken the bond between the implant and the surrounding material (bone), much like how repeatedly stretching a rubber band around fixed objects eventually causes the rubber band to tear or lose elasticity at those points of contact.
  1. Jaw Movement Diagram:
  • Illustration: Create a diagram showing the jaw in different positions (closed, partially open, fully open). Highlight the areas where mandibular flexure occurs and the extent of deformation.
  • Impact: Demonstrates how mandibular flexure varies with jaw movement and its potential impact on implant placement and restorations.
  1. Cross-Arch Restoration Impact:
  • Illustration: Show a cross-arch restoration with and without considering mandibular flexure. Highlight the misalignments and stress points in the restoration when mandibular flexure is not accounted for.
  • Impact: Emphasizes the importance of considering mandibular flexure in treatment planning to avoid complications.
  1. Muscle and Ligament Forces:
  • Illustration: Create a diagram showing the muscles, ligaments, and tendons attached to the mandible. Indicate the forces exerted by these structures during jaw movements and how they contribute to mandibular flexure.
  • Impact: Provides a clear understanding of the anatomical factors contributing to mandibular flexure.
  1. Clinical Consequences:
  • Illustration: Use a series of images to show the clinical consequences of mandibular flexure, such as peri-implant bone resorption, impression distortion, and prosthetic failures.
  • Impact: Highlights the real-world dangers and potential complications associated with mandibular flexure.
Key Findings on Thermal Expansion
When different materials are heated from room temperature (20°C) to body temperature (37°C), they expand at varying rates, creating critical challenges for full arch restorations.
Zirconium: Most Stable (0.8 μm)
Zirconium is the most thermally stable material, with a coefficient of just 5.7 μm/(m·K) and only 0.8 μm of expansion. Its minimal dimensional change under temperature fluctuations.
Titanium & Steel: Minimal Expansion
Titanium and steel have minimal thermal expansion, with 1.2 μm and 1.8 μm of expansion, respectively. Titanium's modest expansion, combined with its excellent biocompatibility, explains why it is the preferred choice in full-arch dentistry.
Aluminum: Highest Metal Expansion (3.1 μm)
Aluminum has the highest coefficient of linear thermal expansion at 23.1 μm/(m·K), leading to a 3.1 μm expansion over the 17°C temperature change. This significant expansion explains why aluminum components used in impression copings or healing abutments can introduce errors when moving from room temperature to oral temperature.
When designing surgical guides or provisional restorations with aluminum components, clinicians must account for this expansion to prevent fit discrepancies that could compromise implant positioning or prosthetic outcomes.
PEEK/TECAPEEK/Plastic: Extreme Expansion (6.8 μm)
Plastics and PEEK polymer have the highest thermal expansion at 50 μm/(m·K), leading to a 6.8 μm increase in size. This significant expansion rate makes plastic materials particularly susceptible to temperature-induced dimensional changes.
Temporary abutments or scan bodies made from PEEK can introduce substantial errors.While PEEK offers advantages like shock absorption and weight reduction, its high thermal sensitivity presents dire consequences for precision applications.
Clinical Implications
The thermal expansion properties of different materials directly impact clinical outcomes in implant dentistry. When designing full arch restorations, the cumulative effect of thermal expansion across multiple components can significantly influence passive fit. Materials with higher expansion coefficients may require digital compensation in the design software or alternative clinical protocols. Understanding these material properties allows clinicians to make informed decisions about component selection and anticipate potential fit issues before they manifest clinically. The most successful full arch cases often incorporate strategic material choices that minimize thermal expansion variations.
Even micron-level expansions can compound across a full arch, potentially creating misalignments that compromise the passive fit of the final restoration. For full arch cases, where precision is measured in microns, these expansion characteristics must be considered to ensure accurate final restorations that are free from complications.
Chapter 3: The Dangers of Error Propagation
What is Error Propagation?
Error propagation refers to how uncertainty in the measurement process affects the result of calculations. Small measurement errors can accumulate and lead to significant deviations in the final product. In full arch dentistry, where precision is measured in microns, these propagated errors can be the difference between a successful restoration and clinical failure.
Error propagation follows mathematical principles where errors compound through each step of the process. For example, a small deviation in the impression stage combines with minor inaccuracies in the scanning process, which further combine with manufacturing tolerances. The result is a cascade of errors that amplifies throughout the workflow.
Sources of Errors in Full Arch Dentistry
Errors can originate from various sources throughout the digital and conventional workflow:
  • Impression technique errors (conventional or digital)
  • Model fabrication inaccuracies
  • Scan body positioning issues
  • Scanner calibration problems
  • CAD software approximations
  • Milling/3D printing tolerances
  • Material shrinkage during processing
Real-World Dangers of Error Propagation
1
Cumulative Errors
Small errors in each step of the measurement process can accumulate, leading to significant deviations in the final restoration. This can result in a poor fit, increased stress on the implant abutments, and potential implant failure. A deviation of just 30 microns at the impression stage can multiply to over 100 microns by the time the final prosthesis is delivered.
Full arch cases are particularly vulnerable because errors multiply across the span of the arch. An error of 50 microns in the anterior region might result in a 200-micron discrepancy in the posterior, creating a "rocking" restoration that places uneven forces on implants.
2
Unpredictable Outcomes
Error propagation can result in less predictable outcomes, compromising the overall accuracy and reliability of the restoration. This can lead to patient dissatisfaction and the need for additional corrective procedures. The unpredictability increases with the complexity of the case and number of implants involved.
Even with meticulous attention to detail, propagated errors can manifest as complications that aren't immediately evident. These may include screw loosening, framework fracture, or bone loss around implants due to uneven force distribution.
3
Increased Treatment Time and Costs
Addressing the consequences of error propagation often requires additional appointments, remakes, or adjustments. This extends treatment timelines and increases costs for both the practice and the patient. Studies have shown that error-related complications can increase the total treatment cost by up to 30%.
The financial impact extends beyond direct costs to include opportunity costs of chair time that could be dedicated to other patients, as well as potential damage to the practice's reputation if complications become recurring issues.
4
Biological Complications
Beyond mechanical failures, error propagation can lead to biological complications. Ill-fitting prostheses create areas that are difficult to clean, leading to peri-implantitis and tissue inflammation. Furthermore, prostheses with poor passive fit can transmit harmful forces to the bone-implant interface, potentially accelerating bone loss.
Research has demonstrated that framework misfit exceeding 150 microns significantly increases the risk of biological complications, with a 35% higher incidence of peri-implantitis in cases with propagated errors.
Preventing Error Propagation
Mitigating error propagation requires a systematic approach:
  • Verification jigs: Utilize verification jigs at critical stages to confirm accurate transfer of implant positions
  • Consistent temperature control: Maintain consistent temperatures during impression making and scanning
  • Regular calibration: Ensure all scanners and milling machines are regularly calibrated
  • Staged verification: Implement verification protocols at each stage of the workflow
  • Master technician oversight: Have experienced technicians review critical measurements
Visual Representation
Illustration: Domino Effect
Visualize error propagation as a line of dominos. If the first domino is slightly misaligned, it can cause a chain reaction of errors, leading to a collapse of the entire sequence. This illustrates how an initial error can propagate and disrupt the entire process.
In full arch implant restorations, this domino effect is particularly problematic because each implant position affects the others. A single misaligned implant can compromise the entire prosthesis, much like how a single misaligned domino can topple the entire arrangement.
Mathematical Representation
Mathematically, error propagation follows the principle that when independent measurements with individual uncertainties are combined, the overall uncertainty increases according to specific formulas. For a full arch restoration with multiple measurements, this can be represented as:
Total Error = √(Error₁² + Error₂² + Error₃² + ... + Errorₙ²)
This formula demonstrates why full arch cases are particularly vulnerable to error propagation - the more measurements involved, the greater the potential for significant combined error.
Chapter 4: The Pitfalls of Tolerance Stacking
What is Tolerance Stacking?
Tolerance stacking refers to the accumulation of individual tolerances within an assembly, resulting in an overall error in the final product.
Real-World Dangers of Tolerance Stacking
1
Overall Error
Individual tolerances can "stack" together, leading to a significant overall error in the final restoration. This can result in misalignments, poor fit, and increased stress on the implant abutments.
2
Prosthetic Failures
Tolerance stacking can cause prosthetic failures, such as fractures of implant screws or porcelain crowns, leading to increased rates of remakes and adjustments.
Visual Representation
Illustration: Building Blocks
Imagine constructing a tower with building blocks. If each block is slightly uneven, the tower becomes unstable and may topple over. This analogy shows how cumulative errors can lead to instability and failure.
Chapter 5: The Impact of Heat Transfer to ScanBodies
What is Heat Transfer?
Heat transfer refers to the movement of thermal energy from one object to another. When ScanBodies are subjected to temperature changes, they undergo thermal expansion, which can affect the precision of the measurements.
Real-World Dangers of Heat Transfer
1
Misalignment
Heat transfer can cause ScanBodies to expand or contract, leading to misalignments in the final restoration. This can result in a poor fit and increased stress on the implant abutments.
2
Inaccurate Measurements
Different materials expand at different rates, which can lead to inaccuracies in the measurements. This can compromise the overall accuracy of the restoration and lead to increased rates of remakes and adjustments.
Visual Representation
Metaphor: Road Trip
Visualize heat transfer as a road trip with multiple stops. If each stop is slightly off course, the overall journey will deviate significantly from the planned route. This illustration shows how small deviations at each step can lead to a large overall error.
Chapter 6: Why ICam is the Best Choice for Full Arch Dentists
Superior Accuracy and Reliability
ICam's precision measurements provide the most predictable and reliable results on the market, giving dentists the best chance at achieving a passive-fit restoration. Here are some key reasons why ICam stands out:
1
Superior Accuracy
ICam's measurements are both precise and true, ensuring that each restoration fits perfectly with minimal stress on the implant abutments.
2
Reduced Error Propagation
ICam minimizes the impact of error propagation, leading to more reliable and consistent outcomes.
3
Minimized Tolerance Stacking
ICam effectively addresses tolerance stacking, helping achieve passivity in restorations.
4
Enhanced Process Reliability
With ICam, manufacturers can identify and mitigate variability, reduce defect rates, and enhance process reliability.

Chapter 7: Investigating Other Photogrammetry Systems

When comparing ICam to other photogrammetry systems, several key differences become apparent. Systems like MicronMapper, Tupel, PIC, Shining 3D Aoral Elite, and IOS methods have been investigated, and the results highlight significant shortcomings: MicronMapper, PIC and Tupel These systems often struggle with achieving the same level of precision and trueness as ICam. The lack of four moving cameras results in less accurate measurements, leading to potential misfits and increased stress on implant abutments. Their plastic scanbodies are prone to expansion in the body and deformation when torqued or autoclaved. Shining 3D Aoral Elite Unvetted and preliminary data shows not as reliable—especially in the presence of blood, saliva, and other intraoral challenges. This can lead to higher rates of remakes and adjustments. IOS Methods Intraoral scanners (IOS) are generally less accurate than dedicated photogrammetry systems like ICam. This method is highly-technique sensitive, not scalable and prone to error propagation and tolerance stacking, resulting in less predictable outcomes.

Visual Representations and Analogies
1. Comparison Chart: Create a side-by-side comparison chart that highlights the key differences between ICam and other photogrammetry systems (e.g., MicronMapper, Tupel, PIC, Shining 3D Aoral Elite, and IOS methods). This chart can include metrics such as accuracy, precision, error propagation, and tolerance stacking.
2. Accuracy and Precision Diagrams: Use diagrams to visually explain the concepts of accuracy, trueness, and precision. For example, you can show a series of target diagrams where the dots represent measurements. This will help illustrate the differences between precise but not true, true but not precise, and both precise and true measurements.
3. Error Propagation Illustration: Create an illustration that shows how error propagation affects the final outcome. This can be a flowchart or a series of images that depict how small measurement errors can accumulate and lead to significant deviations in the final product.
4. Tolerance Stacking Visualization: Use a visual representation to explain tolerance stacking. This can be a diagram that shows how individual tolerances add up within an assembly, resulting in an overall error in the final product. Highlight how ICam minimizes this effect compared to other systems.
5. Thermal Expansion Metaphor: Use a metaphor like a "brick wall" to explain thermal expansion. Imagine building a brick wall where each brick represents a measurement or component. If each brick is slightly off in size due to thermal expansion, the errors accumulate as you stack them, resulting in a crooked wall. This illustrates how small inaccuracies in individual measurements can add up to a significant overall error.
6. Mandibular Flexure Metaphor: Use a metaphor like a "rubber band" to explain mandibular flexure. Imagine stretching a rubber band in different directions. The deformation of the rubber band represents the deformation of the jaw due to mandibular flexure. This illustrates how small movements can lead to significant changes in the overall structure.
7. Case Study Infographic: Create an infographic that presents a case study comparing the outcomes of using ICam versus other photogrammetry systems. Include data on success rates, patient satisfaction, and the number of remakes or adjustments required.
8. Before and After Images: Show before and after images of implant-supported restorations achieved with ICam versus other systems. This visual evidence can be very compelling in demonstrating the superior results of ICam.
9. Patient Testimonials: Incorporate quotes or testimonials from patients and dentists who have experienced the benefits of using ICam. Pair these with images of happy patients and successful restorations.
Conclusion
For full arch dentists, choosing the right photogrammetry solution is crucial for the success of implant-supported restorations. ICam's superior predictability, precision, and reliability make it the best choice for achieving passivity and ensuring long-term success. By leveraging the principles of Six Sigma and maintaining maximum accuracy at each stage of the restorative process, ICam provides dentists with the confidence and peace of mind they need to deliver exceptional results for their patients.
Eliminate Hidden Dangers
ICam helps dentists avoid the hidden pitfalls of mandibular flexure, thermal expansion, error propagation, tolerance stacking, and heat transfer issues that can compromise long-term outcomes.
Ensure Precision
With superior accuracy and reliability, ICam delivers consistently predictable results that lead to perfectly fitting restorations and satisfied patients.
Cost-Effective Long-Term
Though initial investment may be higher, the reduction in remakes, adjustments, and failures makes ICam the most cost-effective solution over time.
Final Note
With only 100 microns of allowable error, precision is essential requirement for full-arch dentistry. The hidden dangers we've discussed can have profound effects on long-term outcomes. By carefully choosing your method for capturing implant positions, you're ensuring a foundation of accuracy that will prevent costly failures and complications down the road.
Saving a few dollars on inferior methods for capturing implant position can lead to significant long-term costs in failures and complications. The precision of ICam isn't just a luxury—it's an investment in your practice's reputation and your patients' satisfaction.