The effect of zirconia and titanium implant abutments on light reflection of the supporting soft tissues

Objectives: To determine the difference in light reflection of oral mucosa covering titanium (Ti) or zirconia (ZrO2) abutments as it relates to the thickness of the covering mucosa. Material and methods: Fifteen anterior implants (Astra Osseo speed (R)) in 11 patients were fitted with a Ti or a ZrO2 abutment (cross-over, within-subject comparison). Hyper-spectral images were taken with a camera fitted on a surgical microscope. High-resolution images with 70nm interval between 440 and 720 nm were obtained within 30 s (1392 x 1024 pixels). Black- and white-point reference was used for spatial and spectral normalization as well as correction for motion during exposure. Reflection spectra were extracted from the image on a line mid-buccal of the implant, starting 1mm above the soft tissue continuing up to 3mm apically. Results: Median soft tissue height is 2.3mm (min: 1.2mm and max: 3.1 mm). The buccal mucosa rapidly increases in the thickness, when moving apically. At 2.2mm, thickness is 3mm. No perceivable difference between the Ti and ZrO2 abutment can be observed when the thickness of the mucosa is 2 +/- 0.1mm (95% confidence interval) or more. Conclusion: It is expected that the difference in light reflection of soft tissue covering Ti or ZrO2 abutments is no longer noticeable for the human eye when the mucosa thickness exceeds 2mm. Haemoglobin peaks in the reflection spectrum can be observed and make hyper-spectral imaging a practical and useful tool for measuring soft tissue health.