The Tooth Cycle of Death
Category: Biomimetic Dentistry,
Traditional, nonbonded restorations do not adequately restore the strength and structural integrity of natural teeth, as discussed here.
Over the years, teeth restored with nonbonded restorations experience a series of failures and complications, ultimately leading to unrestorable failures and loss of teeth. This process is known as the “Tooth Cycle of Death”.
The process is ubiquitous. Every day, dentists around the world see these failures and complications occur. It has become a normal occurrence for restorations to fail, and for teeth to be lost and replaced for implants. Even patients have come to expect restorations to have a short useful life before requiring more invasive replacements.
Fortunately, this process can be avoided. In this post, we will review the steps in the cycle and how a biomimetic treatment approach could prevent the tooth cycle of death.
Summary of the Restorative Treatment Cycle
- Most teeth are initially treated with a filling.
- Traditional filling techniques require the removal of additional intact tooth structure. The filling does not restore the strength and stiffness of the tooth, and as a result, the weakened tooth is susceptible to cracks and fractures.
- As a result, fillings are routinely replaced for crowns, which require even more removal of intact tooth structure.
- On a long-term basis, crowned teeth require root canal treatment significantly more than those without them.
- The cumulative loss of tooth structure through filling, crown, and root canal often leaves inadequate tooth structure for retention without placing a post or post and core restoration.
- Ultimately, these restorations have altered the normal function and biomechanics drastically, leading to unrestorable failures and replacement procedures (implant, bridge, partial denture).
Tooth Cycle of Death – Detail
1. Natural Teeth
A healthy intact tooth has the ideal combination of properties. Enamel acts as a stiff outer shell and dentin as a compliant inner core. These two distinct layers are joined together through an extremely strong, biological bond via the dentin enamel junction (DEJ).
The resulting structure is able to withstand extremely heavy mechanical loads and transmit forces fluidly through the tooth without damaging stress concentrations that would lead to cracks and fractures.
While extremely resistant to mechanical forces, Enamel is highly susceptible to acid dissolution through the caries process, especially in early childhood when oral care is less than optimal. Once a cavity has formed, restorative intervention is indicated to treat the affected tooth structure and prevent further damage.
3. Amalgam Silver Filling
Traditionally, the tooth was restored with an amalgam restoration, requiring the removal of additional intact tooth structure to accommodate the restorative material and technique. The restorative technique for nonbonded amalgam restorations requires additional tooth preparation to provide mechanical retention, extension for prevention, and sufficient preparation depth to allow for the adequate thickness of the restoration. As a result, substantial intact tooth structure is removed.
This restoration treats the cavity and affected tooth structure, but nonbonded restorations do not restore the stiffness and structural integrity of intact teeth. As a result, the biomechanics of the tooth is significantly altered and damaging stress concentrations develop around the restoration, leading to cracks.
Over time, these cracks propagate and spread, often leading to symptoms and ultimately fractures. Sometimes the fractured tooth can be treated, however, sometimes the tooth is not restorable when there is a catastrophic fracture extending below the alveolar crest.
At this point, restoring the strength & stiffness of the fractured tooth becomes a priority. Traditionally, the tooth is restored with a build-up and crown (PFM, or Gold), requiring further removal of intact tooth structure. Over 75% of the coronal tooth structure is removed by this point in the process.
7. Root Canal Treatment
Teeth prepared for crowns face a significantly higher chance of complications and failures, often necessitating root canal treatment. As a consequence of the previous interventions, the remaining tooth structure is limited and mechanical retention is inadequate for a crown
8. Post and Core
A post and core must be placed now to allow for retention of a new crown. Posts do not strengthen teeth and they alter the natural biomechanics. The only purpose of the post and core is to provide retention for the crown due to the cumulative loss of tooth structure from previous treatments.
9. Unrestorable Failures
The altered biomechanics of the heavily restored tooth results in stress concentrations around the post and around the roots. These unnatural stress concentrations ultimately result in catastrophic root fractures. The tooth is no longer restorable at this point.
10. Replacement Implant
The tooth is extracted and the replacement of choice is a dental implant. Alternative options include no replacement, a fixed partial denture (bridge), or a removable partial denture.
The Biomimetic Approach Prevents the Tooth Cycle of Death
The Tooth Cycle of Death highlights the importance of preserving intact tooth structure and pulp vitality. These are the conditions that progressively increase failures, complications, and loss of teeth. Biomimetic restorations are bonded restorations that restore the structural integrity and strength of the tooth to the maximum extent possible. Additionally, tooth structure is conserved and biomimetic restorations are expected to have a long useful life, minimizing replacement and retreatment. In this way, biomimetic restorations address the conditions which result in the Tooth Cycle of Death.
The 3 Pillars of the Biomimetic Approach
- Mimic the properties and structure of natural teeth.
- Preserve tooth structure and pulp vitality.
- Restore the strength, stiffness, and structural integrity of teeth.
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