Porosity evaluation and pore size distribution of a novel directly placed ceramic restorative material

The aim of this in vitro study was to compare porosity, i.e. voids or pores due to placement, of a new directly placed ceramic restorative material (DoxaDent, Doxa Certex AB, Uppsala, Sweden) to a glass ionomer (Fuji IX, GC Corporation, Tokyo, Japan), a hybrid composite control (Filtek Z250, 3M ESPE St Paul, MN, USA) and an amalgam control (Tytin, Kerr Orange, CA, USA). Pore distribution and size were determined for each material tested.

Standardized MOD preparations (one operator) on 20 extracted human molars had gingival margins located above and below the CEJ. Restored teeth (5 teeth/material) were sectioned in mesio-distal directions (two sections/tooth; n=10/group). Sections were polished through 1 microm Al2O3 abrasive. Porosity levels and size distributions were measured using SEM. Effects of different gingival extensions of inter-proximal boxes on porosity levels and distributions were investigated (mesial, occlusal, and distal regions).

No MOD region was free of pores. Porosity in mesial, occlusal and distal boxes, respectively, for each restorative material were (vol%): Tytin: 1.3(0.9), 2.9(2.1), and 2.9(1.4); Filtek Z250: 2.6(1.0), 2.9(1.0), and 2.6(0.8); Fuji IX: 8.8(1.9), 7.9(1.7), and 7.7(1.8); Doxadent: 13.0(1.8), 12.4(1.7), and 11.5(1.4). Overall porosity ranged from 2.4(0.9)% for Kerr Tytin, 2.7(0.7)% for Filtek Z250, 8.0(1.1)% for GC Fuji IX, and 12.3(1.1)% for Doxadent. There was no difference between Z250 composite and Tytin amalgam, but differences existed between them with Fuji IX and Doxadent. No statistically significant difference (p>0.05) in porosity occurred among different restoration regions (mesial, distal and occlusal box) for any material. Total porosity levels for different measurement methods (point counting versus direct counting) were remarkable consistent (p>0.05).

Based on results of this limited study, the new directly placed ceramic restorative material (Doxadent) contains significantly (p<0.05) higher bulk porosity levels than both amalgam and composite. This may explain the lower than expected mechanical property values reported in other studies.