A threshold gap size for in situ secondary caries lesion development

Area of Science:

• Dental Materials Science
• Cariology
• Restorative Dentistry

Background:

• Secondary caries (SC) is a primary cause of dental restoration failure.
• The role of microgaps between restorations and tooth structure in SC development is not fully understood.
• Understanding the critical gap size is crucial for improving restoration longevity.

Purpose of the Study:

• To investigate the influence of very small gaps on secondary caries development.
• To determine the threshold gap size associated with secondary caries.
• To correlate gap size with caries activity levels in volunteers.

Main Methods:

• An in situ study using modified occlusal splints worn by 15 volunteers for 21 days.
• Dentin-composite samples with varying interfaces (bonded, no-bonded, intentional gaps of 30, 60, 90 μm) were used.
• Samples were exposed to a sucrose solution, and lesion depth/mineral loss were quantified using transversal wavelength independent microradiography (T-WIM).

Main Results:

• No wall lesion formation occurred in bonded (B) or no-bonded (NB) groups without intentional gaps.
• Intentional gaps, particularly those 30 μm or wider, led to secondary caries lesion progression.
• A trend for deeper lesions was observed with larger gaps in the high caries activity group.

Conclusions:

• A gap size of 30 μm or more appears to be a threshold for secondary caries development, irrespective of patient caries activity.
• Individual factors may play a significant role in secondary caries wall lesion progression, even in a controlled in situ environment.