A survey of the pre-bonding preparation of denture teeth and the efficiency of dewaxing methods

Bonding Behavior of Conventional PMMA towards Industrial CAD/CAM PMMA and Artificial Resin Teeth for Complete Denture Manufacturing in a Digital Workflow

When applying a digital workflow, custom artificial resin teeth have to be integrated into a milled complete denture base, using polymethylmethacrylate (PMMA) applied with a powder–liquid technique. Debonding of denture teeth from dentures is reported to be a frequent complication. No evidence is provided as to which method of surface treatment may enhance the bonding strength. The bonding strength between artificial teeth and PMMA (Group A, n = 60), as well as between the PMMA and industrial PMMA (Group B, n = 60), was investigated following no treatment, monomer application, sandblasting, oxygen plasma, and nitrogen plasma treatment. Surface-roughness values and SEM images were obtained for each group. Shear bond strength (SBS) and fracture mode were analyzed after thermocycling. Within Group A, statistically significant higher SBS was found for all surface treatments, except for nitrogen plasma. In Group B, only nitrogen plasma showed a statistically lower SBS compared to the reference group which was equivalent to all surface treatments. Conclusions: Within the limitations of the present study, the monomer application can be proposed as the most effective surface-treatment method to bond custom artificial teeth into a milled PMMA denture base, whereas nitrogen plasma impairs the bonding strength.

The bond between acrylic resin denture teeth and the denture base: recommendations for best practice

Failure of the bond between denture teeth and base acrylic resin has been shown to be a cause of denture failure leading to inconvenience and costly repair. The optimal combination of acrylic resin denture tooth, denture base material, laboratory protocol and processing method has not yet been established. Extensive research enables the following recommendations for best practice to be made. Adopt practices that maximise the strength of the bond: select appropriate denture teeth; select base acrylic resin from the same manufacturer as the denture teeth; remove the glaze from ridgelaps of the denture teeth; apply monomer to the ridgelaps of the denture teeth before packing the base acrylic resin dough; use the manufacturers' recommended liquid/powder ratio; follow the manufacturers' recommended curing cycle; allow the flask to cool slowly and rest before deflasking. Adopt practices that avoid factors detrimental to bond strength: remove all traces of wax from the ridge laps of the denture teeth; remove all traces of mould seal from the ridgelaps of the denture teeth. It is evident that a number of factors are involved which may assist or prevent formation of an adequate bond, suggesting that attention to detail by the dental technician may be the most critical factor.

A comparison of shear bond strength of ceramic and resin denture teeth on different acrylic resin bases

The purpose of this study is to compare the shear bond strength of different resin bases and artificial teeth made of ceramic or acrylic resin materials and whether tooth-base interface may be treated with aluminium oxide sandblasting. Experimental measurements were carried on 80 specimens consisting of a cylinder of acrylic resin into which a single tooth is inserted. An ad hoc metallic frame was realized to measure the shear bond strength at the tooth-base interface. A complete factorial plan was designed and a three-way ANalysis Of VAriance (ANOVA) was carried out to investigate if shear bond strength is affected by the following factors: (i) tooth material (ceramic or resin); (ii) base material (self-curing or thermal-curing resin); (iii) presence or absence of aluminium oxide sandblasting treatment at the tooth-base interface. Tukey post hoc test was also conducted to evaluate any statistically significant difference between shear strength values measured for the dif-ferently prepared samples. It was found from ANOVA that the above mentioned factors all affect shear strength. Furthermore, post hoc analysis indi-cated that there are statistically significant differences (p-value=0.000) between measured shear strength values for: (i) teeth made of ceramic material vs. teeth made of acrylic resin material; (ii) bases made of self-curing resin vs. thermal-curing resin; (iii) specimens treated with aluminium oxide sandblasting vs. untreated specimens. Shear strength values measured for acryl-ic resin teeth were on average 70% higher than those measured for ceramic teeth. The shear bond strength was maximized by preparing samples with thermal-curing resin bases and resin teeth submitted to aluminium oxide sandblasting.

Bonding of acrylic denture teeth to MMA/PMMA and light-curing denture base materials: the role of conditioning liquids

OBJECTIVES

The connection between resin denture teeth and the denture base is essential for the integrity of partial and full dentures. The aim of the present study was to analyse the bond strength of acrylic denture teeth to two light curing denture base materials compared to the gold-standard (MMA/PMMA) using different conditioning liquids.

METHODS

The ridge laps of 220 identical denture teeth were ground and pre-treated using different conditioning liquids (MMA, an experimental conditioning liquid as well as the two commercially available liquids Palabond and Versyo.bond). The denture base materials (PalaXpress, Versyo.com, Eclipse) were applied using a split mould to obtain tensile bond strength specimens of identical shape. Ten specimens per test group were either stored in water for 24h or thermocycled (5000×, 5-55°C) prior to tensile bond strength testing (cross-head speed 10mm/min). Data was subjected to parametric statistics (α=0.05).

RESULTS

The three-way ANOVA revealed a significant influence of the material, pre-treatment as well as the storage. PalaXpress showed the highest bond strength (24.3MPa) of all materials tested after TC, whereas the use of MMA led to the most constant results. Lower values were recorded for Versyo.com (17.5MPa) and Eclipse (10.4MPa) bonded with Versyo.bond.

CONCLUSIONS

The results indicate that MMA/PMMA based denture base resins provide reliable and durable bond strength to acrylic denture teeth. Using light-curing denture base materials requires the application of appropriate conditioning liquids to obtain acceptable bond strength. The use of MMA affects bond strength to light-curing denture base materials.

CLINICAL SIGNIFICANCE

The pre-treatment of denture teeth is critical regarding their bond-strength to denture base materials and in turn for the integrity of removable full and partial dentures. Light-curing denture base resins are more sensitive to the correct tooth pre-treatment compared to conventional MMA/PMMA materials, requiring specific conditioning liquids.

Effect of pre-processing methods on bond strength between acrylic resin teeth and acrylic denture base resin

OBJECTIVES

This study evaluated the effects of various pre-processing methods on the bond strength between resin and denture teeth.

BACKGROUNDS

Debonding of acrylic resin teeth from denture base material is a problem for patients wearing complete dentures.

MATERIALS AND METHODS

Four experimental groups (n = 30) were investigated by subjecting tooth-resin bonding to tensile loading. Specimens were prepared and tested according to the methods of the International Standards Organization (ISO 22112:2005) using a special assembly. Four pre-processing surface treatments of teeth were applied: (i) ST(1), no treatment applied (control); (ii) ST(2) , wax solvent (Dewaks, Faber Kimya & Ilaç, Turkey); (iii) ST(3), boiling water followed by conditioning with methyl methacrylate (MMA) monomer (Meliodent, Bayer Dental, Germany); (iv) ST(4), boiling water followed by wax solvent agent and finally MMA monomer application. Bond strength test was performed using a universal testing machine.

RESULTS

All the strength values of the test groups were within clinically acceptable limits. The lowest values were from the ST(1) group and the highest values were in the ST(4) group.

CONCLUSIONS

Wax elimination methods affected bonding strength. Application of wax solvent and MMA monomer to the ridge lap surfaces of the teeth gave the best results. In clinical practice, this application procedure may decrease the bonding failure of denture teeth.

Effect of aluminium oxide particle sandblasting on the artificial tooth-resin bond

AIM

The influence of tooth ridge-lap surface sandblasting with aluminium oxide particles was evaluated on the adhesion of artificial teeth to acrylic resins.

METHODS

Specimens were made with the acrylic resin adhered to teeth (BioCler GII), according to an unmodified surface, glossy surface sandblasted with 50-μm particles and conventional (Classico) or microwaved (Onda Cryl) resin, and a glossy surface sandblasted with 100-μm particles and Classico or Onda Cryl resin. The shear bond test was performed in an Instron machine using a 500-N load cell and cross-speed of 1 mm/min.

RESULTS

The analysis of variance revealed significant difference in the tooth-resin shear bond strength for resin, surface treatment, and interaction. For conventional resin, control, 50-, and 100-μm particles showed statistically-different values; for microwaved resin, the control showed less statistical difference when compared to 50- and 100-μm particle treatments; for between resins, only the 100-μm particle treatment showed statistically-different values, with lower values for the microwaved resin. Mixed failures (cohesive in the resin and adhesive) were predominantly observed in all groups. Mixed (cohesive in the tooth and adhesive) or adhesive failures were not observed.

CONCLUSIONS

Sandblasting with different aluminium oxide particle sizes produced different effects on the shear strength values of the tooth-resin bond.

Bonding acrylic teeth to acrylic resin denture bases: a review

Partial or complete dentures are more commonly constructed for the elderly group of the population. Teeth debonding from the dentures can be frustrating to the patients as well as the dentist. Research has been carried out and is continuing to study the issue of bonding acrylic teeth to the denture base resin. The present review takes into account the majority of research papers published in the last five decades for determining the bond strength. Selection of more compatible combinations of denture base resins and acrylic teeth may reduce the number of prosthesis fractures and the resultant repairs.

An investigation of the variables which may affect the bond between plastic teeth and denture base resin

OBJECTIVES

The failure of the bond between acrylic resin denture base material and resin teeth remains a significant problem. This study evaluated the tensile bond strength of specimens produced by commonly employed tooth preparation and processing methods as used in dental laboratories.

METHODS

Twenty-two experimental groups, each consisting of 36 specimens, were investigated by subjecting the tooth-resin bond to tensile loading. The groups were allocated to one of five experimental sets to investigate: (a) effect of resin dough time, (b) effect of tooth surface condition, (c) effect of processing variables, (d) effect of monomer cementing, and (e) effect of acrylic resin cement. The results were analysed statistically using a one factor ANOVA and a Student t test.

RESULTS

A significantly stronger bond was obtained when the resin was packed late in the dough stage, and a superior bond, in all cases, when high-impact resin was used. Tooth surface modification by grinding or grooving made no significant difference when compared with unmodified surfaces. Wax-contaminated surfaces produced highly significant weaker bonds. Time of introduction and duration of water-bath processing had no significant effect on bond strength. Monomer cementing of the tooth surface, especially with high-impact monomer. significantly improved the bond strength. The application of resin cements was found to produce the most significant increase in denture tooth bond strength.

CONCLUSIONS

The important steps in obtaining a consistently high value denture tooth bond are thorough dewaxing of the tooth surface followed by the application of a suitable resin cement.