Effects of cyanoacrylates on die stone

Surface Coating of Gypsum-Based Molds for Maxillofacial Prosthetic Silicone Elastomeric Material: Evaluating Different Microbial Adhesion

PURPOSE

To compare the adhesion of three microorganisms on modified and unmodified silicone elastomer surfaces with different surface roughnesses and porosities.

MATERIALS AND METHODS

Candida albicans, Streptococcus mutans, and Staphylococcus aureus were incubated with modified and unmodified silicone groups (N = 35) for 30 days at 37°C. The counts of viable microorganisms in the accumulating biofilm layer were determined and converted to cfu/cm² unit surface area. A scanning electron microscope (SEM) was used to evaluate the microbial adhesion. Statistical analysis was performed using t-test, one-way ANOVA, and post hoc tests as indicated.

RESULTS

Significant differences in microbial adhesion were observed between modified and unmodified silicone elastomers after the cells were incubated for 30 days (p < 0.001). SEM showed evident differences in microbial adhesion on modified silicone elastomer compared with unmodified silicone elastomer.

CONCLUSIONS

Surface modification of silicone elastomer yielding a smoother and less porous surface showed lower adhesion of different microorganisms than observed on unmodified surfaces.

Surface Coating of Gypsum-Based Molds for Maxillofacial Prosthetic Silicone Elastomeric Material: The Surface Topography

PURPOSE

This study aimed to compare the surface roughness of maxillofacial silicone elastomers fabricated in noncoated and coated gypsum materials. This study was also conducted to characterize the silicone elastomer specimens after surfaces were modified.

MATERIALS AND METHODS

A gypsum mold was coated with clear acrylic spray. The coated mold was then used to produce modified silicone experimental specimens (n = 35). The surface roughness of the modified silicone elastomers was compared with that of the control specimens, which were prepared by conventional flasking methods (n = 35). An atomic force microscope (AFM) was used for surface roughness measurement of silicone elastomer (unmodified and modified), and a scanning electron microscope (SEM) was used to evaluate the topographic conditions of coated and noncoated gypsum and silicone elastomer specimens (unmodified and modified) groups. After the gypsum molds were characterized, the fabricated silicone elastomers molded on noncoated and coated gypsum materials were evaluated further. Energy-dispersive X-ray spectroscopy (EDX) analysis of gypsum materials (noncoated and coated) and silicone elastomer specimens (unmodified and modified) was performed to evaluate the elemental changes after coating was conducted. Independent t test was used to analyze the differences in the surface roughness of unmodified and modified silicone at a significance level of p < 0.05.

RESULTS

Roughness was significantly reduced in the silicone elastomers processed against coated gypsum materials (p < 0.001). The AFM and SEM analysis results showed evident differences in surface smoothness. EDX data further revealed the presence of the desired chemical components on the surface layer of unmodified and modified silicone elastomers.

CONCLUSIONS

Silicone elastomers with lower surface roughness of maxillofacial prostheses can be obtained simply by coating a gypsum mold.

Dimensional changes in gypsum fragments bonded with cyanoacrylate

PURPOSE

Accidental fractures may occur during manipulation and transportation of plaster casts. In clinical practice, plaster fragments may be bonded without harming the accuracy of the final denture, provided that the bonding agent does not cause dimensional alterations. Cyanoacrylate could be a good material because of its ease of use, quick set, wide availability, and low cost. The aim of this study was to assess the dimensional alteration of Type IV plaster fragments bonded with a cyanoacrylate-based adhesive.

MATERIALS AND METHODS

Ten hexagonal regular prisms were made of Type IV plaster, with two reference marks on one of the faces. The distance between the marks was measured under a comparison microscope. After this, the prisms were fractured so that the fracture line would be between the two reference marks, bonded with a cyanoacrylate-based universal adhesive and measured again.

RESULTS

The mean difference between the measurements performed before and after fracture and bonding of the fragments was 0.0194 mm. At a level of significance of 0.05, there was no statistically significant difference between the measurements before and after fracture and bonding of the dies (p = 0.1582).

CONCLUSION

It may be concluded that bonding of Type IV plaster fragments with a cyanoacrylate-based adhesive did not cause significant dimensional alterations.

Fixed Rehabilitation of an ACP PDI Class III Patient

This clinical report documents the treatment of a 63-year-old Caucasian female Prosthodontic Diagnostic Index Class III patient using dental implants and a fixed prosthetic reconstruction. The treatment involved the fabrication of single crowns and fixed partial dentures retained by natural teeth in the maxillary arch. The posterior segments of the mandibular arch were rehabilitated with fixed partial dentures retained by endosseous implants.

Study of the physical properties of type IV gypsum, resin-containing, and epoxy die materials

STATEMENT OF PROBLEM

Little published information is available comparing the properties of recently developed resin-modified gypsum and epoxy resin die materials, which are claimed to be superior to conventional type IV gypsum die materials.

PURPOSE

This study compared the properties of 3 new die materials and 2 conventional type IV gypsum products.

METHODS AND MATERIAL

The linear dimensional change, detail reproduction, surface hardness, abrasion resistance, and transverse strength of 2 recently introduced, resin-modified gypsum die materials (Resinrock and Milestone), a new epoxy resin die material (Epoxy-Die), and 2 conventional type IV gypsum die materials (Silky-Rock and Die-Stone) were studied.

RESULTS

All gypsum products expanded, whereas the epoxy resin material contracted during setting. The epoxy resin exhibited much better detail reproduction, abrasion resistance, and transverse strength than the gypsum materials, which were similar in these properties. A conventional type IV gypsum exhibited the highest surface hardness, whereas the epoxy resin had the lowest value.

CONCLUSION

The resin-modified gypsum products were not significantly superior to the conventional type IV gypsum die materials. In general, the epoxy resin exhibited the best properties of the materials studied; however, its setting shrinkage may necessitate alterations in technique to achieve well-adapted castings.

Double-casting method for fixed prosthodontics with functionally generated path

STATEMENT OF PROBLEM

The construction of precise fixed prostheses that are harmonious within the stomatognathic function has been regarded as a critical requirement for successful oral rehabilitation. However, techniques for construction have been unsuccessful in producing a prosthesis that can be inserted without intraoral occlusal adjustment.

PURPOSE

In this study, a new method of constructing a precise prosthesis that requires limited occlusal adjustment at the final seating is described.

MATERIAL AND METHODS

The precision of this method was compared with a conventional method. Fourteen artificial crowns were fabricated on an experimental abutment by using both double-casting and conventional methods. The distances between the cusp tips and occlusal surfaces of the abutments, which were measured on wax/resin patterns and resultant crowns, were recorded to estimate clinical error for each method.

RESULTS

Error for the double-casting method was markedly less than the conventional method. This study demonstrated that a new double-casting method was precise and sufficiently reliable for clinical application.

Effect on the fit of removable partial denture frameworks when master casts are treated with cyanoacrylate resin

Master casts of improved dental stone were made from irreversible hydrocolloid impressions of a metal model. Half of the master casts were treated with cyanoacrylate resin and half were untreated controls. They were sent to a dental laboratory for framework fabrication. The returned frameworks were examined for acceptability and their completeness of seating was determined. The frameworks fabricated on the treated master casts fit significantly better than the controls. The improved seating may be attributed to an increased surface hardness, increased abrasion resistance, and improved surface morphology, but further study is necessary.