Evaluation of pulpal response at varying remaining dentin thickness in teeth restored with resin bulk fill composite, conventional glass ionomer cement and silver amalgam: Histomorphometric analysis

Abstract

Objective: To compare and evaluate the pulp response to GC glass ionomer cement, SDR plus bulk fill composite and amalgam against gold standard calcium hydroxide cement at varying remaining dentin thickness, in teeth planned for orthodontic extraction.

Method: Thirty-eight human premolars were prepared with 2 mm or 2.5 mm depth cavities. They were restored with GC conventional glass ionomer cement, SDR plus bulk fill composite, amalgam, or lined with Dycal and restored with GIC. Two teeth were used as intact controls. After a 7-day interval, the teeth were extracted and processed for histological examination of the pulp and the thickness of the remaining dentin between the cavity floor and pulp tissue.

Results: All experimental groups showed some degree of inflammatory response. A significantly higher inflammatory response and more tissue disorganization were observed with SDR bulk fill composite (p < 0.05) compared to Glass ionomer cement, amalgam and Dycal at both cavity depths of 2 mm or 2.5 mm. The mean RDTs ranged from 346 μm to 1025 μm.

Conclusions: The study concluded that critical RDT varies for different restorative materials. It was observed that both glass ionomer cement and amalgam demonstrated acceptable biocompatibility when used in deep cavities. At the same time, SDR plus bulk fill composite proved to be the least biocompatible.

Keywords: AMALGAM; GIC; HISTOMORPHOMETRIC ANALYSIS; INFLAMMATORY RESPONSE; RDT; SDR BULK-FILL FLOWABLE COMPOSITE.

Graphical abstract

Fig. 1

Illustration of study design.

Fig. 2

Clinical procedure of cavity preparation and restoration, A) Burs with resin stop, cavity template, B) Prepared cavity, C) and F) cavity restored with amalgam, D) and G) cavity restored with SDR plus bulk fill composite, E) Pre operative photograph of patient.

Fig. 3

Histopathological examination. A) Restored tooth embedded in resin block, B) H/E stained slide of tooth section, C) Radiograph of restored extracted tooth displaying RDT, D) Histomorphometric analysis of histological tooth section where cavity floor (CF), remaining dentine thickness (RDT) and pulp (P) are marked.

Fig. 4

Histopathological examination of tooth sections. Group A GIC restorationsThe odontoblast layer related to the cavity floor was preserved (white oblique arrows). Note the normal cell-free (black vertical arrow) and cell-rich (black horizontal arrow) zones with no inflammatory pulp reaction (RDT = 1200 μm), b) Disruption of the odontoblast layer as well as slight pulp inflammation associated with discrete tissue disorganization was observed. Grade 1 inflammatory reaction (RDT = 801 μm), c) the odontoblast layer related to the cavity floor was slightly disrupted. GRADE 2 inflammatory reaction (RDT = 266 μm). Group B SDR plus bulk fill restorations d) The pulp layers were disorganized, and the subjacent pulp exhibits dilated and congested blood vessels (white arrow) among inflammatory mononuclear cells. (RDT = 895 μm), e) The pulp layers were completely disorganized, and the subjacent pulp exhibits a large number of inflammatory mononuclear cells (score 3 inflammatory response) (RDT = 301 μm). Group C Amalgam restorations f) The odontoblast layer related to the cavity floor was preserved (black oblique arrows). Note the normal cell-free (black vertical arrow) and cell-rich (white horizontal arrow) zones with no inflammatory pulp reaction (RDT = 1023 μm), g) Disruption of the odontoblast layer as well as slight pulp inflammation associated with mild tissue disorganization was observed. Score 1 inflammatory reaction (RDT = 564 μm). Group D Control, h) in Dycal lined tooth the pulp tissue subjacent to the cavity floor exhibited partial disruption of the odontoblast layer (arrows). Note the discrete disorganization of the adjacent pulp tissue in which mononuclear inflammatory cells (RDT = 289 μm), i) Intact sound premolar exhibited normal histological characteristics. Note the continuous and homogeneous odontoblast layer as well as the defined cell-free and cell-rich zones. H/E, × 400.