CROWN MODEL

How It Works:

Extracted human teeth are sorted and examined for areas with caries, white-spot lesions, abrasions, restorations, or any other damage to the tissue.  Acceptable specimens with sound enamel are selected and cleaned of soft tissue and other debris.  Prior to insertion into the crown slots, the sections are covered with an acid-resistant varnish on all cut surfaces so that only the natural outer surface is exposed to the oral environment. 

Individual sections are "sandwiched" and placed in a crown prior to each treatment period.  The crown is usually placed so that an approximating tooth is adjacent to the "sandwich" of sections.  This interproximal position helps in the natural plaque formation.

The intra-oral crown single-section model uses normal, healthy adults who are in need of a gold crown.  A slot is placed in the working crown which can hold 3 to 4 single sections.  A typical experiment would use an enamel lesion, root lesion, and sound root section which are characterized with polarized light microscopy and/or microradiography prior to insertion in the crown. 

After the experimental regimen (usually one month in duration), the sections are removed from the slot by removal of the cast crown, and soaked in methanol to remove the acid-resistant varnish.  The treated sections are then re-evaluated with polarized light microscopy and the lesions are re-characterized for any (unchanged, remineralized or demineralized) changes.

History: In 1980, Drs. James Wefel and Mark Jensen proposed a crown model.  The idea was to use a section of an extracted tooth, place it in a crown and temporarily seat the crown in a patient’s mouth.  Dr. Peter Hayes and Greg Maharry, students at the time, assisted in the development of the model as part of Dr. Hayes' thesis. 

The model has been used over the past 20+ years to evaluate mineral changes from the use of fluoride dentifrices and rinses, chewing gum, and food sequencing.  The advantages of the model are the before and after measurements on the same section, a natural plaque formation, interaction with saliva, and episodic demineralization /remineralization.  The model reduces the artificiality of the in situ study to a great extent and appears to be a useful predictor of demineralization/remineralization interactions.

This crown model has received nationwide attention in the dental research community, with conferences specifically given (funded by ADA, industry, NIDCR) about the intra-oral models to replace animal caries experiments.

For more information about the crown model, please e-mail Dr. James Wefel at James-Wefel@uiowa.edu or call the Office of Clinical Research at 319-335-6763.