Relationships Between the Physical Properties of Human Jawbone and the Initial Stability of Dental Implant, and Their Dependency on Anatomical Regions of Jawbone

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Abstract

Unstable implants tend to fail. Dental implants in the 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 regions 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.

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 custom made RF Analyzer (resonance frequency analyzer), Osstell™ (resonance frequency analysis) and Periotest® (mechanical tapping). 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. Bone implant contact percentage (BICP) and cortical bone thickness (CBT) were recorded from histomorphometric slides.

Both bone physical properties and initial implant stability differed between regions of maxilla and mandible. Generally, mandible had higher physical property measurements than maxilla. EM and H were higher in posterior regions than anterior however the reverse was true 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).

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