The Kennedy Classification is a very simple way of classifying partial dentures, however it is a relatively rigid classification that does not cater to majority of the patients that we see. As a result, Applegate developed 8 rules to help with utilising the Kennedy Classification – this post outlines these rules.

Why are Applegate’s rules helpful?

The Kennedy Classification divides partially dentate patients in the four classes. However, we rarely see patients that perfectly fit in to these four classes. As a result, Applegate developed 8 rules to help apply the Kennedy Classification to more realistic patient scenarios.

Applegate Rule 1

Classification should follow rather than precede any extractions of teeth that might alter the classification.

All extractions should be completed prior to determining the classification. This is important because the extractions may change the Kennedy Classification. For example, a patient may have a unilateral free-end saddle (Class II). If this patient then has posterior extractions on the opposite side of the same arch, then they may end up with bilateral free-end saddles and would be a Class I.

Applegate Rule 2

If a third molar is missing and is not to be replaced, it is not considered in the classification.

We very rarely would replace third molars and if patients do not have them, then we wouldn’t include these in the classification i.e. they don’t suddenly have free-end saddles.

Applegate Rule 3

If a third molar is present and is to be used as an abutment, it is considered in the classification.

This may be in a scenario where a patient is having their first and second molars replaced and so the denture utilises the third molar as an abutment. As a result, the saddle is a bounded saddle and not a free-end saddle.

Applegate Rule 4

If a second molar is missing and is not to be replaced, it is not considered in the classification.

This would be the usual cases if the opposing second molar is missing, then we wouldn’t classically replace the second molar as there would be nothing to occlude on.

Applegate Rule 5

The most posterior edentulous area (or areas) always determines the classification.

Ultimately, teeth missing in the most posterior areas will determine the classification. Edentulous spaces should first be assessed to see if they fall in to Kennedy Class I. Then Class II, followed by Class III and finally Class IV. This also links to Applegate’s Rule 1 where the class should be decided following extractions, as the extractions may be in the posterior regions.

Applegate Rule 6

Edentulous areas other than those that determine the classification are referred to as modifications and are designated by their number.

Patients will often have multiple edentulous areas, for example several ‘bounded saddles’. Under the classification system, Class III describes a single bounded saddle and therefore, we need space for modifications. This is demonstrated below where we have a unilateral bounded saddle and an anterior bounded saddle – this is the modification. So the dentition below would be a Kennedy Class III Modification 1.

Kennedy Class 3 Modification 1

Applegate Rule 7

The extent of the modification is not considered, only the number of additional edentulous areas.

It does not matter if there is one or several teeth in an edentulous space with regards to the modification – it is simply the number of spaces.

Applegate Rule 8

No modification areas can be included in Class IV arches.

If there are any other edentulous spaces, as the above rules dictate, the denture would fall in to one of the other classes.

Applegate’s Rules Summary

  • Applegate’s rules help to realistically apply the Kennedy Classification to partially dentate patients
  • There are 8 rules that should be followed when classifying

Useful Links & Recommended Reading

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BDS (Hons.) MFDS RCPS (Glasg.) Cert Med Ed Currently working as a Speciality Doctor in OMFS and as an Associate Dentist

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