Classifications of Residual Ridge Morphology for Complete Denture

Residual Alveolar Ridge is the absence of teeth after tooth extraction and after extraction of the teeth the bone starts to resorb which is called as Residual Ridge resorption. The Maxilla and Mandible resorb differently, with the Maxilla becoming narrower or decreasing in width and the mandible becomes wider.

What is a Residual Alveolar Ridge?

It is the portion of the alveolar ridge and its soft tissue covering which remains following the removal of or loss of teeth – GPT-8

Source: Zerodonto

Classification of Residual Ridge Morphology

Class I: The Residual Ridge Bone height is 21mm or greater measured at the least vertical height of the mandible. It has Class I maxillomandibular relationship.

The Class I morphology is the most suited and most apt morphology of Edentulous ridge for obtaining successful Prosthodontic treatment using Complete Denture prosthesis. We can get good Retention and resistance without much effort in this type of ridge morphology.

Class II: The Residual Ridge Bone height is 16 to 20 mm measured from the least vertical height of the mandible. It also comes with Class I maxillomandibular relationship. Residual Ridge morphology is such that it resists horizontal and vertical movement of the denture base.

This is not the most ideal for Complete denture but can be managed considerably well compared to the Class III and Class IV types. It represents the Residual ridge which has physical degradation of the Denture bearing structures and also seen are local soft tissue factors and patient management or lifestyle considerations.

Class III: The Residual Ridge bone height of 11 to 15mm measures at the least vertical height of the mandible is seen. It has any of the Class I, Class II or Class III maxillomandibular relationships. The resistance to horizontal and vertical movements of the denture base is minimal. Due to the decrease in height of the ridge and the location of the muscle attachments on the ridge lower border of the ridge might end up on the muscles attachments and lead to moderate influence on the denture base stability and retention

Due to the decrease in height of the ridge and the location of the muscle attachments on the ridge lower border of the ridge might end up on the muscles attachments and lead to a moderate influence on the denture base stability and retention.

This type of ridge needs surgical intervention before going for any prosthetic appliance, in case of implants and for obtaining proper Prosthodontic function related pre-prosthetic surgery is required.

Class IV: The bone height is minimal and similar to the least vertical height of the mandible. Because of the lack of bone height there is least resistance to horizontal or vertical movement with Class I, Class II and Class II maxillomandibular relationships. The location of the muscle attachments is such that, it plays a major role in affecting the stability and retention of the denture.

This type of Edentulous ridge always has any related medical condition, past dental history or financial consideration which has lead to the most debilitated edentulous condition of the alveolar ridge. Surgical reconstruction of the ridge is a must and even then no guarantee can be given regarding successful prognosis.

Reference: McGarry TJ, Nimmo A, Skiba JF, et al: The Classification system for complete edentulism.