Denture Base Specimens Research Articles

In vitro evaluation of the influence of repairing condition of denture base resin on the bonding of autopolymerizing resins

Statement of problem Bonding failures of repair resin to denture base resin occurs when denture base resin is wet, however, little is known of how water relates to failures. Purpose This study evaluated the influence of water absorbed in denture base resin on the bond strength and resistance to cyclic thermal stresses of autopolymerizing resins bonded to denture base resin. Material and methods Denture base resin disks (n = 180; 12 mm diameter and 3 mm thick) were fabricated from heat-polymerized acrylic resin (Lucitone 199). The disks were divided into groups (n=60) with 3 conditions of water content: (1) complete water saturation (control), (2) superficial desiccation by blowing air on the specimen, or (3) complete desiccation. Each denture base specimen received 1 of 3 surface treatments (n=20) including: (1) no treatment, (2) airborne-particle abrasion, or (3) methylene chloride application. An autopolymerizing repair resin (Repair Material, n=10) or reline resin (Tokuso Rebase Normal set, n=10) was applied to the bonding area (5 mm diameter) and polymerized at 37°C for 10 minutes. The resistance to cyclic thermal stress was determined after subjecting the specimens to 50,000 thermal cycles between 4°C and 60°C water baths with a 1-minute dwell time (n=5 per group). Bond strength (MPa) was measured by shear bond testing at a 1.0 mm/min crosshead speed until the applied resin debonded from denture base resin. Data were statistically analyzed by 3-way analysis of variance and multiple comparisons among the groups were performed with Bonferroni test (α =.05). Results The mean bond strengths of repair resin to airborne-particle–abraded denture base specimens were not significantly influenced by either thermal cycling or water content. The mean bond strengths of reline resin significantly decreased after thermal cycling ( P<.0001) regardless of the conditions of surface treatment and water content. For methylene chloride treated specimens, bond strengths of both repair and reline resins to completely water saturated specimens were significantly higher than those of completely desiccated specimens ( P=.0048 for repair resin, P<.0001 for reline resin) after thermal cycling. Conclusions Bond strengths of autopolymerizing resin to denture base resin were not significantly influenced by water content of denture base resin but were significantly influenced by resin type, thermal cycling, and surface treatment.

Repair of denture base resin using woven metal and glass fiber: Effect of methylene chloride pretreatment

Statement of problem. A durable repairing system for denture base fracture is desired to avoid recurrent fracture. Purpose. This study evaluated the strength and modulus of elasticity of repaired acrylic specimens reinforced with various processes. Material and methods. Transverse strength and modulus of elasticity of repaired acrylic denture base specimens were evaluated with a 3-point bending test and compared with a heat-polymerized control. Autopolymerizing acrylic resin was used with woven metal fiber and glass fiber with and without methylene chloride surface treatment (n = 6 per group). The specimens were cut in half and fixed in a metal mold to obtain a space for placing the repairing resin. A cavity was prepared when metal or glass fiber was used. All specimens were stored in 37°C distilled water for 48 hours before the test. All data were statistically analyzed with 1-way ANOVA, and differences among groups were analyzed with Fisher test (P≤.05). Results. The mean value of the transverse strength for the control was 87.2 MPa. The specimens repaired by glass fiber with methylene chloride surface treatment exhibited the highest transverse strength (96.8 MPa), which was significantly higher than that of the control (P≤.05). The elastic modulus of the specimens repaired by glass fiber with methylene chloride surface treatment (4189.3 MPa) was significantly greater than that of the control (2683.7 MPa) at a 95% level of confidence. The values of transverse strength and elastic modulus were highest when the surface treatment was combined with a reinforcing glass fiber. Conclusion. Reinforcement with glass fiber and methylene chloride pretreatment produced transverse strength and a modulus of elasticity higher than the control. (J Prosthet Dent 2001;85:496-500.)

Denture reliners—direct, hard, self-curing resin

A survey of the properties of six brands of direct, hard, self-curing denture re-liners revealed that most such reliners harden with considerable rise in temperature. When cured under clinical conditions, porous resins result. Knoop number, water solubility, recovery values and transverse strength of relined denture base specimens are poorer than those for self-curing denture base resins. Color stability of most brands is unsatisfactory. Detail reproduction of the surface of the tissue appears adequate. No significant war page or dimensional change of relined dentures was noted. The direct reliners are not adequate for long-term serviceability and should be considered as temporary expedients.