Restorative angle of zirconia restorations cemented on non-original titanium bases influences the initial marginal bone loss: 5-year results of a prospective cohort study

Abstract

Aim: To assess radiographic, restorative, clinical and technical outcomes as well as patient satisfaction of directly veneered zirconia restorations cemented on non-original titanium bases over 5 years.

Material and methods: Twenty-four patients with a single missing tooth in the aesthetic zone were recruited. All patients received a two-piece implant with a screw-retained veneered zirconia restoration cemented extraorally on a titanium base abutment. Marginal bone levels (MBL), marginal bone changes, technical complications, patient satisfaction and clinical parameters including probing depth, bleeding on probing and plaque index were assessed at crown delivery (baseline), at 1 year (FU-1) and 5 years (FU-5) of follow-up. To investigate the relationship between restorative angle and MBL as well as marginal bone changes (bone loss/bone gain), correlation tests and linear regression models were carried out.

Results: Twenty-two patients were available for re-examination at 5 years. The mean MBL amounted to 0.54 ± 0.39 mm at baseline, and to 0.24 ± 0.35 at FU-5 (=bone gain) (p < .001). At FU-1, a positive correlation (r = .5) between the mesial restorative angle and mesial MBL was found (p = .012). Marginal bone changes between baseline and FU-1 at mesial sites were also positively correlated with the mesial restorative angle (r = .5; p = .037). Linear and logistic regression models confirmed that mesial marginal bone loss was significantly associated with the mesial restorative angle at FU-1 (p < .05). At 5 years, these significant associations at mesial sites disappeared (p > .05). At distal sites, no correlations or associations between the restorative angle and MBL or marginal bone changes were found regardless of the time point. During the 5-year follow-up, 5 technical complications occurred, mainly within the first year and mostly chippings. All patients were entirely satisfied with their implant-supported restoration at 5 years.

Conclusion: Within the limitations of the present study, the restorative angle of implant-supported crowns on non-original titanium bases might influence the initial marginal bone loss but without affecting their favourable long-term clinical performance. A restorative angle of <40° may limit the initial marginal bone loss at implant-supported crowns with titanium bases.

Keywords: CAD/CAM; dental implant-abutment design; dental implants; material testing; prosthodontics; titanium; zirconium.

FIGURE 1

Restorative angle measurements on radiographs

FIGURE 2

Distribution and location of the implants

FIGURE 3

Proportion (%) of implants displaying bone loss (mesial or distal) according to the restorative angle (≤40◦ or restorative angle >40º) at 1 year of follow‐up

Figure 4

Correlation analysis between the restorative angle and the marginal bone level at 1 year of follow up. (a) Positive correlation between mesial restorative angles and mesial marginal bone level (r = .5, p = .01). (b) Positive correlation between distal restorative angle and distal marginal bone level (r = .1, p = .64)

FIGURE 5

Proportion (%) of implants displaying bone loss at mesial or distal sites according to the restorative angle (≤40º or >40º) at five years follow‐up