Influence of geometric dimensions on early failures of adhesively retained composite resin core build-ups

To determine the influence of the geometric dimensions of core build-ups on early core build-up failure, that is, loss before definitive prosthesis cementation.

Adhesive core build-ups of exclusively vital teeth in 114 participants were evaluated (n materials: 40 Rebilda DC, 38 Multicore Flow, 36 Clearfil DC Core; n teeth: 8 incisors, 54 premolars, 52 molars). Impressions of the abutment teeth were made (1) after removal of insufficient restorations/caries and (2) after core build-up and preparation for a fixed prosthesis. Digitized model surfaces of both situations were aligned (Geomagic Design X) and core build-up volume (V_CBU ), remaining hard tissue volume (V_Abut ), and size of the adhesive surface (A_adh ) were assessed. The derived measure d_CBU  = V_CBU /A_adh can be interpreted as mean arithmetic core build-up thickness. Associations between participant or core build-up design characteristics and the occurrence of early failures were statistically evaluated (SPSS v27, α = 0.05).

A total of six (5.3%) core build-up failures were registered. Higher participant age, greater core build-up volume V_CBU and greater arithmetic uniform thickness d_CBU were associated with a greater incidence of failure in bivariate and univariate, however, not in multivariate statistics.

Core build-up volume and thickness were associated with early success or failure.

In the case of voluminous/thick core build-ups in relation to the adhesive surface, additional measures, such as the preparation of retentive elements to increase the bonding area, might be considered to reduce the risk of early core build-up failure.