Post-insertion sensitivity with a bonded etched cast metal prosthesis. Case report

The effect of dentine surface treatment on pulpward pressure transmission during crown cementation: a laboratory study

Thirty extracted human premolars received standardised full crown preparations. The teeth were randomly assigned into three groups: smeared (control), etched (phosphoric acid gel), and bonded (Scotchbond MP). Each tooth was perfused with saline to establish perfusion rates at baseline for all groups, and the post-etching stage for etched and bonded groups, post-bonding stage for bonded group, and post-cementation stage for all groups. Crowns made with four layers of die-spacing were cemented with zinc phosphate cement at 100N. Pulpal pressures were measured with a pressure transducer. It was concluded that dentine bonding agents may have the potential to reduce pulpal damage caused by pressure transmission from cementation.

The effect of seating force and die spacing on pulpward cementation pressure transmission: a laboratory study

Pulpward pressure transmission during crown cementation occurs via the dentinal tubules. The present study investigated the effect of crown seating forces and the effect of increasing the die spacing on pulpward pressure transmission. Twenty upper premolars were prepared with 1 mm shoulder margins for non-precious metal full crowns. A 0-104 kPa pressure transducer (Mediamate EA, Data Instruments, Baltimore, MD, USA) was connected, via the sectioned root of the premolar, to the pulp chamber which was perfused with saline at 83 kPa driven by nitrogen gas, for two hours prior to cementation. Crowns with 2 or 6 layers of die-spacing were seated with 25 N or 100 N force using zinc-phosphate cement. The pressure transducer was connected to a Wheatstone bridge (Measurements Group, Instruments Division) and the extent of crown seating and output from the pressure transducer was recorded. Results indicate that 25 N seating force produced a lower mean pulpward pressure (41 +/- 54 Pa) compared to the 100 N seating force (251 +/- 276 Pa). Seating was significantly improved with 6 layers of die-spacing (seating discrepancy 18 +/- 12 mm) compared with 2 layers (139 +/- 111 mm). It is concluded that a higher seating force increases pulpward pressure transmission. Increasing die spacing improved crown seating but did not affect the amount of pressure transmitted.

Antibacterial properties of eight dental cements

The antibacterial action of a light-cured glass polyalkenoate Vitrebond and an adhesive resin luting agent Panavia Ex was investigated and compared with six previously tested dental cements. The bacterial cultures used were six strains of Streptococcus mutans, six of Streptococcus sanguis and six cultures of carious debris from carious lesions. A modification of the agar diffusion method was used to test the antibacterial action of freshly mixed cements. In addition the cements were allowed to set and their antimicrobial action was tested by incubation for 5 days in sucrose broth inoculated with the test cultures. All the freshly mixed materials had an antibacterial action. A two-way analysis of variance and Tukey-Student range analysis showed that Vitrebond had a significantly greater zone of inhibition than Aquacem, IRM, Dycal, Dycal VLC, Ceramco and GC Elite (P = 0.001). Freshly mixed Panavia Ex exhibited minimal antibacterial action. After 5 days the antibacterial properties of all the cements were reduced.

Movement of resin cement components through acid-treated dentin during crown cementation in vitro

This study examined the hypothesis that components of crown cements may be forced through acid-treated dentin during cementation. Freshly extracted, human third molar teeth were prepared to accept full crowns. Roots were removed to allow irrigation of the pulp chamber with saline before, during, and after crown placement with resin dentin bond and resin composite cement. Saline samples were collected and analyzed by high performance liquid chromatography to identify and quantify resin components arriving in the pulp space. Two components of the bond-cement system used were identified in the pulp space samples immediately after crown cementation. These were 2-hydroxyethylmethacrylate and 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane. The amounts of these components in the pulp space decreased when the bonding agent was cured prior to crown placement. The results of this study supported the hypothesis that crown cementing components may flow through acid-treated dentin during crown cementation.

A retrospective clinical evaluation of resin-bonded bridges inserted at the Adelaide Dental Hospital

The clinical performance of resin-bonded Rochette and Maryland bridges inserted by various operators at the Adelaide Dental Hospital is reported. Thirty-four Rochette bridges (30 anterior, 4 posterior) and 228 Maryland bridges (150 anterior, 78 posterior) were assessed. Clinical data were compiled on types of bridge failure, factors influencing bridge retention, and the effects of the prostheses on abutment teeth and supporting tissues. The failure rate for Rochette bridges over 6 years was 75 per cent with a median survival of 2.14 years. Debonding occurred in 70 per cent of bridge failures. The failure rate for Maryland bridges over 5 years was 42 per cent with a median survival of 2.60 years. Pontic fracture (29 per cent) and debonding (20 per cent) were the main failures observed. Porcelain pontics performed significantly better than the processed hybrid resin pontics (P < 0.01). The main reasons for debonding included occlusal stresses, non-retentive bridge designs and resin cement failure. A life-table analysis showed no significant difference in the overall cumulative survival rates between Rochette and Maryland bridges. Bridge design and the choice of pontic material and resin cement emerged as significant factors influencing the success rate of the bridges examined.