Anatomical Variation At The Sites Of Autogenous, Mandibular Graft Harvest

Objectives: Intra-oral bone grafting is an important component of implant treatment. The relationships between the bone surface and the underlying nerves and vessels at the two most commonly-employed intra-oral (retro-molar and symphyseal) sites for bone-harvesting were characterised.
Methods: Data was collected by direct measurement from patients (n=103) undergoing CT scanning prior to implant treatment (50 retro-molar: 53 symphyseal). Measurement included the distance between the bone-surface and the underlying ID/incisive canal, and the thickness of the bone available for harvesting (incisive and retro-mandibular regions). Linear regression was performed to study the relationship of these anatomical variables to patient demographics.
Results: The retro-molar analysis comprised 33 female and 17 male patients. Data recorded included: maximum thickness of the mandible across the inferior dental canal (IDC) (mean 13.79mm; range 10.2–18.2mm), distance from the IDC to the outer buccal cortex (mean 3.2mm; range 1.0–7.9mm); distance from the most buccal point of the lower second-molar root to the outer buccal cortex (mean 3.3mm; range 1.0-6.5mm). Symphyseal analysis included 26 female and 27 male patients. Data recorded included: maximal width of mandible between the lower central incisor root tips (mean 13.4mm; range 8.91-16.39mm); tip of canine to the mandibular incisive nerve (mean 4.30mm; range 1.2–8.9mm), canine root tip to the outer labial cortex (mean 3.96mm; range 1.85–7.30mm), mid-line distance from the incisive nerve to the outer labial cortex (mean 2.97mm; range 1.02–6.86mm). Linear regression indicates that mandibular thickness decreases with age in women (p=0.032). Whilst the thickness of bone buccally to the IDC remains relatively constant in females (p=0.43), it decreases with age in men (p=0.075).

Conclusions: This study demonstrated that, although bone grafts are common, the proximity of underlying vital structures may be overlooked in routine examination of implant patients and may be related to patient characteristics.