Effect of crown-to-implant ratio and crown height space on marginal bone stress: a finite element analysis

José Joaquim Da Rocha Ferreira,Luís Filipe Meira Machado,João Carlos Tomás Ramos,José Manuel Oliveira

doi:10.1186/s40729-021-00368-1

Abstract

BackgroundCrown-to-implant ratio and crown height space, associated with the use of short implants, have been related with marginal bone loss. However, it is unclear which of the two entities would play the most important role on the bone remodelling process. Using a finite element analysis, the present work aims to help clarifying how those two factors contribute for the stress generation at the marginal bone level. A numerical model (reference model), with a crown-to-implant ratio of 4, was double validated and submitted to a numerical calculation. Then, it was modified in two different ways: (a) by decreasing the prosthetic height obtaining crown-to-implant ratios of 3, 2.5 and 2 and (b) by increasing the implants length obtaining a crown-to-implant ratio of 2.08. The new models were also submitted to numerical calculations.ResultsThe reference model showed a marginal bone stress of 96.9 MPa. The increase in the implants’ length did not show statistically significant differences in the marginal bone stress (p-value = 0.2364). The decrease in the prosthetic height was accompanied with a statistically significant decrease in the marginal bone stresses (p-value = 2.2e− 16).ConclusionsThe results represent a paradigm change as the crown height space appears to be more responsible for marginal bone stress than the high crown-to-implant ratios or the implants’ length. New prosthetic designs should be attempted to decrease the stress generated at the marginal bone level.

Highlights

Crown-to-implant ratio and crown height space, associated with the use of short implants, have been related with marginal bone loss
* Correspondence: jose.j.r.ferreira.299@gmail.com 1Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI), Oporto, Portugal Full list of author information is available at the end of the article if the bone level is taken into account to measure the crown length, it is defined as a clinical crown-toimplant ratio (CIR) [7, 8]. The research on this concept is associated with the use of short implants, since their use frequently result in prosthetic rehabilitations with high crowns and, the creation of a potentially deleterious CIR
Electronic speckle pattern interferometry (ESPI) A qualitative analysis of the results showed that both, the numerical model and the tested samples, exhibited identical linear behaviour, with the resulting displacement being consistent with a rotation

Summary

Introduction

Crown-to-implant ratio and crown height space, associated with the use of short implants, have been related with marginal bone loss. A numerical model (reference model), with a crown-to-implant ratio of 4, was double validated and submitted to a numerical calculation. The crown-toimplant ratio (CIR) has been object of research It is defined as the relationship between the crown and the implant lengths. The rationale behind the concern with the CIR is related with the bending effect as a consequence of the horizontal components of mastication loads These offcentre forces generate bending stresses which maximum values are located at the implant-abutment connection and at the marginal bone area, with potentially deleterious consequences on implants and prosthetic connections, screws and marginal bone [9, 10]. The concern with the CIR results from the adoption of the tooth

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