A New Classification System to Determine Posterior Mandible Morphology for Implant Therapy

We studied the posterior mandibular morphology to develop a new alveolar ridge morphology classification system for implant therapy. Current classification systems do not adequately address essential parameters such as the influence of lingual undercut on implant placement. They do not fully consider clinically important factors such as the shape of the alveolar ridge, the depth and angle of the lingual concavity, and the position of the inferior alveolar canal (IAC). This study was based on an existing classification system and culminated in the development of a new CPD classification system, with a primary focus on lingual concavity.

One hundred and ninety-five patients aged above 19 to over 70 years were included in this cross-sectional study. Cone-beam computed tomography (CBCT) volumes of 90 males and 105 females were analyzed to determine the width of the alveolar bone at the crest (Wc), width of the alveolar bone at the base (Wb), alveolar ridge height (Vcb), alveolar bone height below the Point P (Vb), alveolar bone height above the Point P (Vc), and lingual concavity depth and angle. These parameters were selected to determine the ridge shape and the presence/absence of an undercut. These values were also analyzed in relation to age, gender, presence/absence of the first molar, and presence/absence of the lingual concavity.

The U-type (undercut) ridge was the most common (54.4% left; 52.1% right), followed by the P-type (parallel; 27.2% left; 33.5% right) and the C-type (convergent; 18.5% left; 14.4% right). Alveolar ridge height was correlated with age, gender, ridge type, presence of the first molar, and presence of an undercut. The width of the alveolar bone at the crest correlated with the presence of the first molar and ridge type. The lingual concavity depth correlated with the presence of the first molar, undercut, and ridge type.

We have developed and validated a new and comprehensive CPDU classification system for assessing the posterior mandible to enhance preoperative assessment for implant therapy by categorizing the alveolar ridge morphology into C-type, P-type, and D-type with or without undercut (U) based on the ridge shape, lingual concavity depth and angle, and IAC position.