7 Years, Multicentre, Clinical Evaluation on 154 Permanent Restorations Made With a Glassionomer-based Restorative System

Objectives: The aim of this clinical study is to evaluate clinical performances, incidence of failures and mechanical resistance of a restorative system based on a high-viscosity, coated glassionomer cement, when used for permanent restorations.
Methods: Restorations of class I, II or V of Black were included in the study. Presence of antagonist teeth, occlusal contact and absence of bruxism were checked before inclusion of restoration in the study. The Equia™ restorative system (GC Corporation, Japan) was selected for this study and placed according to manufacturer's instructions. Follow-ups were planned at 3, 6, 12, and then every 12 months. Integrity of restorations and margins has been evaluated through visual observation with 4x magnification loupes and status of all restorations has been classified using Frencken’s evaluation criteria for glassionomer dental restorations.
Results: 154 restorations were performed in 124 patients. 5 restorations were lost as drop-outs during the study, for a total of 149 restorations evaluated at 7 years (42 Class I, 70 Class II, 37 Class V; 9 incisors, 11 canines, 50 premolars and 79 molars). At 7 years of follow-up 25 restorations reported chipping of margins (Criteria 1 or 2, successful); 33 restorations were lost or seriously damaged or lost (Criteria > 3, failures). This is equal to an overall general success rate, at 7 years, of 72,4%, and a general integrity rate (only Criteria =0) of 61,0%. The highest number of failures (code >3) has been reported in class II (21) in respect to Class I (no failures) and Class V (12). In molars, incidence of lost restorations seems to be influenced by numbers of walls involved by cavity preparation.
Conclusions: These results and the optimal performances for Class I (no failures over 42 restorations) suggest that a glassionomer-based restorative system can be a reliable choice for permanent dental restorations, even in load bearing tooth surfaces of molars and premolars. Retention and integrity of class V seems to be the worst in time. This leads to consider that evaluation of flexural forces during functional activity (e.g. through diagnosis of bruxism and severe tooth surface erosions/abrasions) might be crucial for preserving integrity of glassionomer restorative materials.