22 April 2021

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Zirconia Implants Vs. Titanium implants: radiographic and histometric crestal bone response

Giulia Palandrani

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Titanium implants    have been successfully used for the replacement of teeth for over 40 years, mechanical and biological stability and excellent long-term results make titanium  the gold standard as an implant material. Demand for metal-free implant materials has recently increased, partially due to more or less founded criticism towards titanium  and the potential of optimal esthetic outcomes of white ceramic materials.

Clinical studies show promising survival rates for periods of up to 5 years for currently commercially available zirconia implants. Most implant failures occur in the first year with a survival rate of 95.6%; then, failure incidence decreases to 0.05% per year with almost constant survival curves. 

The purpose of this study was to evaluate the influence of loading time and implant material on crestal bone levels around a two-piece zirconia  (test) and well-documented titanium  (control) implant under functional loading.

Material and Methods
Implants were placed in healed edentulous ridges 12 weeks after extraction of all mandibular premolars and first molars in five male, laboratory-bred hound dogs with mean age of 18 months.

The test material was a novel two- piece zirconia implant , with an endosseous diameter of 4.1 mm and endosseous length of 8 mm, featuring a machined collar of 4.8 mm diameter and 1.8 mm height.

The control was a commercially available implant with similar endosseous and collar dimensions as the test.
Three test and 3 control implants were inserted in an alternating pattern bilaterally in the healed edentulous ridge, yielding a total of 6 implants per side. Full ceramic, single-tooth restorations were cemented after 6 weeks of transmucosal healing, allowing for full functional loading of the implants. The crowns all had an identical outer shape and appropriate inner shape for the respective abutment type, i.e.,zirconia  or titanium  .

Periapical radiographs (PAs) and the measurement of the distance between implant shoulder and bone crest (DIB) were taken immediately after implant placement, after restoration, and at harvesting. The impact of the implant material (zirconia/titanium) on the main outcome DIB was assessed. Additionally histometric distance between implant shoulder and most coronal bone-to-implant contact (IS-cBIC) was compared with DIB. 

Results
All 60 implants and 60 restorations were still in function after 4 and 16 weeks of loading in both test and control groups. No implant loss, no implant or abutment fracture, and no chipping at the restorations could be detected. 

The mean DIB increased for zirconia  from placement (1.47 mm) to 16 weeks of loading (2.25 mm) and from 1.33 to 1.95 mm for Titanium   . 

Histometric (IS-cBIC) values differed from radiographic (DIB) values at both harvesting times (P < 0.0001) after 4 weeks and after 16 weeks. The overall IS- cBIC was 2.31 mm, whereas the overall DIB reached 1.92 mm. 

When comparing PAs to histometry at zirconia implants   , the discrepancy between DIB and IC-cBIC depended on the loading period : the highest discrepancy was found after 4 weeks (1.66 mm vs. 2.18 mm, respectively) and the lowest at 16 weeks (2.25 mm vs. 2.48 mm). For Titanium the difference between PAs and histometry was more similar between the two time points.

Discussion and Conclusions
Zirconia  implants showed a more pronounced crestal bone loss than titanium implants between 4 and 16 weeks after loading, following initial bone gain. PAs overestimated the bone level around dental implants on average by 0.39 mm. Underestimation of bone loss was considerable at 4 weeks for zirconia  implants , whereas DIB matched histometry at 16 weeks after further tissue maturation around the same implant. The overestimation of crestal bone level was more linear over time at Titanium implants .

For additional information: Crestal bone response to loaded zirconia and titanium implants: a radiographic and histometric analysis in canines.