Physical Properties of Human Jawbone and Dental Implant Initial Stability

Objectives: Unstable implants tend to fail. Dental implants in posterior maxilla have the highest failure rate. Clinicians believe the posterior maxilla has poor bone quality. Little is known about whether or how bone physical properties vary between maxillary and mandibular resions and which physical properties might affect initial implant stability. This study measured initial implant stability and physical properties of different bone regions of human jaws to determine (1) relationships between bone physical properties and initial stability of dental implants, and (2) how physical properties and initial stability depend on anatomical regions of the jaws.

Methods: Four pairs of maxilla and mandible were retrieved from fresh human cadavers. Six implants were placed in different anatomical regions (maxillary anterior, right and left maxillary posterior, mandibular anterior, right and left mandibular posterior). Right after surgery, initial implant stability was measured with OsstellTM (resonance frequency analysis) and Periotest® (ultrasonic vibration). All implant surgeries and initial stability measurements were performed within 72 hours of death to simulate a clinical setting. Bone samples adjacent to implants were sectioned for physical property measurements. Bone elastic modulus(EM) and hardness(H) were measured using nano-indentation. Apparent density(AD) was measured using Archimedes principle. Cortical bone thickness and bone implant contact percentage were recorded from histomorphometric slides.

Results: Generally, mandible had higher physical properties than maxilla. EM and H were higher in posterior regions than anterior however it was reverse for AD. Mandibular implants had higher initial stability than maxillary implants. Posterior maxillary implants were least stable. Stability was less buccolingually than mesiodistally. Apparent density was highly correlated with initial implant stability (r = 0.82).

Conclusions: Both bone physical properties and initial implant stability differed between regions of maxilla and mandible. Non-invasive measurements of apparent density of bone might predict initial stability of dental implants.

(Partially supported by NIH/NIDCR R21-DE015410)