01 October 2022

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Pilot study: 24 months in vivo wear of enamel antagonists to lithium disilicate implant crowns

Lara Figini

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Clinical monitoring of wear of implant crowns is of therapeutic and scientific interest, and traditional indirect methods are still the gold standard to carry it out. Using digital technology, clinicians can detect the wear of the teeth using intraoral scanners. 

The digital impressions can be produced by intraoral scanning and then directly superimposed with a special 3D program that measures the dental wear. The advantages of this method are the simplified clinical procedure, with no intermediate steps prone to errors, saving time, increased comfort for the patient and the reproducibility of the impressions. 

Material and methods 

In a study published Sept. 1 in the Journal of Dentistry, the authors investigated whether there is a significant difference between the wear ratio of implant-borne lithium disilicate crowns and their enamel antagonists and the wear between enamel / enamel antagonists in adjacent teeth. 

The authors performed intraoral scans of the occlusal surfaces of 41 patients in whom an implant was placed at time 0 (baseline) and after 12 and 24 months. From the initial cohort study, 11 pairs of lithium disilicate crowns on implant / enamel antagonists and nine pairs of enamel / enamel antagonists were analyzed after 12 months.  

After 24 months, 10 implant crown / enamel pairs were reviewed in eight patients. This was possible due to decementation of an implant crown. A specially developed semi-automatic iterative algorithm was used to overlay the scan surfaces at the baseline time with the scans obtained at the two follow-ups to measure the maximum height loss of each identified wear side. The mean maximum wear of the teeth and the standard deviation were calculated per unit. The wear ratio of the enamel / enamel antagonist teeth and the wear ratio of the lithium disilicate implant crowns to the enamel antagonist teeth were evaluated. Tooth movements and rotations were also analyzed using a separate measurement procedure. 

Results 

After 12 months, the wear ratio between the pairs of enamel antagonists was found to be 0.95 ± 0.27 µm and the lithium disilicate / enamel ratio was 0.73 ± 0.49 µm. After 24 months, the enamel / enamel wear ratio was found to be 1.04 ± 0.28 µm and the lithium disilicate / enamel wear ratio was 0.73 ± 0.51 µm. The reports did not differ significantly from each other. 

Conclusions 

From the data of this study, it can be concluded that the wear at two years between the lithium disilicate implant crowns on the natural enamel of the antagonist teeth was comparable to that which occurs between two natural teeth, antagonists with enamel / enamel surfaces in contact. 

Clinical implications 

Intraoral scanning and computer analysis could be a useful method for detecting long-term wear between natural teeth and between natural teeth and antagonistic restorations. 

Digital monitoring of prosthetic restorations should be integrated into the clinical workflow to identify potential factors affecting longevity and to identify the multidirectional movements of the natural antagonistic teeth and of the natural teeth antagonistic to the individual implant superstructures. 

"Twenty-four months in vivo wear of enamel antagonists to lithium disilicate implant crowns - a pilot study." Annabelle von der Stuck, Stefan Raith, Sven Reich. Jdent.2022.104215