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Dental Materials Research Restorative Dentistry Supporting Your Practice

What are the incidence rates, annual and 24-months, of defects and replacement on restorations?

Dental Bitewing X-raysThis summary is based on the study conducted by the National Dental Practice-Based Research Network on 24-month evaluation of amalgam and composite based restorations.




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Factors affecting early failure rates of dental restorations

  • Factors related to the patient factors: age, size of the lesion and location and type of tooth.
  • Material failure: longevity of amalgam compared to resin-based restorations vary depending on patient and tooth characteristics.
  • Factors related to the Clinician: age, gender, educational background.

Goal of the Study

Quantify the annual and two-year incidence rates of defects and replacement on restorations.

Results of the study

  • The study found a low failure rate of 6.2%.
  • Patient age was significantly associated with early failure of restorations.
  • The number of surfaces involved in the original restoration was significantly associated with higher failure rates.
  • Failure rates were significantly lower in practices that were either too busy or not busy enough.


  • The material of the restoration was not significantly associated with the longevity of the restoration.
  • Early failure restorations was most like to occur in older patients especially older than 65 years of age in restorations done in offices reporting balanced workloads compared to not busy and overly busy practices and in restorations that involve 4 or more surfaces in the initial treatment.
  • Four or more surfaces restorations had a success rate of 83% at 2 years. These restorations should be considered as viable options in restoring previously un-restored permanent teeth with multiple surfaces thereby saving tooth structure.


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