A randomized controlled clinical trial on press and block lithium disilicate partial crowns: a pilot study

Aim Lithium disilicate is available in two formulations: press and block. The first requires an analog workflow, the latter a full digital workflow. The aim of this study was to evaluate clinical performance of two lithium disilicate systems by means of the novel Functional Index for Teeth (FIT) after one year of clinical service.

Materials and methods Partial adhesive crowns on posterior teeth were made on 60 patients, who were randomly divided into two groups: Group 1 Initial LiSi Press and Group 2 Initial LiSi Block (GC Co., Tokyo, Japan), which therefore followed full analog and digital workflows respectively. The restorations were followed-up for 1 year, and the FIT evaluation was performed at baseline and at last recall. The FIT includes 7 variables: Interproximal, Occlusion, Design, Mucosa, Bone, Biology and Margins, that are investigated using an intraoral radiograph and occlusal and buccal pictures and evaluated using a 0-1-2 score as follows. The presence or not of major, minor or no discrepancy (€˜Interproximal€™, €˜Occlusion€™ and €˜Design€™), presence or not of keratinized and attached gingiva (€˜Mucosa€™), presence of bone loss >1.5 mm, <1.5 mm or not detectable (€˜Bone€™), presence or not of Bleeding on Probing and or Plaque Index (€˜Biology€™), presence of detectable gap and marginal stain or not (€˜Margins€™). The Mann-Whitney €˜U€™ test was used and a level of significance at p<0.05. Also, "success" of the crowns (restoration in place without any biological or technical complication) and "survival" (restoration still in place with biological or technical complication) were evaluated.

Results All FIT parameters had high scores, between 1.85 and 2, and no statistically significant differences between the two groups were found (p>0.05). No statistically significant difference was found between baseline and recall scores. All FIT scores were compatible with the clinical success and not one restoration was replaced or repaired. The success rate at 1 year was 100%.

Conclusions The FIT can be a viable standardized evaluation of the quality of prosthodontic therapy. The two materials showed similar results at 1 year. Longer observation times are needed to confirm these preliminary results.