In vivo dentin microhardness beneath a calcium-phosphate cement

Abstract

A minimally invasive caries-removal technique preserves potentially repairable, caries-affected dentin. Mineral-releasing cements may promote remineralization of soft residual dentin. This study evaluated the in vivo remineralization capacity of resin-based calcium-phosphate cement (Ca-PO(4)) used for indirect pulp-capping. Permanent carious and sound teeth indicated for extraction were excavated and restored either with or without the Ca-PO(4) base (control), followed by adhesive restoration. Study teeth were extracted after 3 months, followed by sectioning and in vitro microhardness analysis of the cavity floor to 115-microm depth. Caries-affected dentin that received acid conditioning prior to Ca-PO(4) basing showed significantly increased Knoop hardness near the cavity floor. The non-etched group presented results similar to those of the non-treated group. Acid etching prior to cement application increased microhardness of residual dentin near the interface after 3 months in situ.

Figure 1.

Allocation of teeth (status/group) and location of hardness indentation in each tooth section. (A) Sample distribution. (B) Diagram of Knoop indentations at cavity floor.

Figure 2.

Microhardness of the cavity floor (p-values in the Table). KHN in caries-affected or sound dentin measured at 25, 55, 85, and 115 µm from the interface into dentin. Connection of datapoints per group by a line provides the regression lines for each group from 25 µm up to 115 µm into dentin toward the pulp. CN (N = 12 sections, with N = 36 datapoints at each depth): Values ranged from 45.6 KHN (close to the interface) up to 53.9 and 53.6 KHN (at 85 µm and 115 µm, respectively). CE (N = 15 sections, with N = 45 datapoints at each depth): started at 60.4 KHN (close to the interface) and increased up to the deepest point (66.3 KHN at 115 µm). CU (N = 12 sections, with N = 36 datapoints at each depth): Values ranged from 49.4 KHN (close to the interface), increasing to 53.4 KHN (at 85 µm) and slightly decreasing to 52.3 KHN (at 115 µm). SE_SU_SN (pooled; N = 34 sections, with N = 102 datapoints at each depth): Sound specimens, whether treated or not, showed similar KHN levels of approximately 82 KHN at each depth (range, 81.1 to 83.0 KHN from depths of 25 to 115 µm). Close to the interface, KHN levels of CE were 32% higher than those of CN, but still 26% lower than those of the pooled sound group.

Figure 3.

Representative SEM of the dentin/RCPC interface after 3 mos in vivo. RCPC: Resin Calcium-Phosphate Cement: m = matrix, i = inorganic phase. A, artifact due to specimen fixation; D, dentin; arrow, crystals obliterating tubules.