Roughness of pontic materials and dental plaque

Analyse the effect of different investment techniques and pattern materials on surface roughness of raw Ni-Cr castings - An In Vitro study

Aims:

This study aimed to analyze the effect of different investment techniques and pattern materials on the surface roughness of raw castings from nickel-chromium alloy.

Settings and Design:

This is an experimental in vitro study carried out in Bharati Vidyapeeth Dental College and Hospital, Sangli, Maharastra.

Materials and Methods:

Sixty square-shaped wax patterns, measuring 10 mm × 10 mm × 2 mm, were divided into four groups. A phosphate-bonded investment material (Bellasun, Bego, Germany) was used to invest 15 samples of inlay wax and kept under normal atmospheric pressure and the remaining 15 wax patterns were invested under a pressure of 3 bars for 30 min, and then allowed to bench set for another 30 min. The same investing techniques were carried out for the remaining thirty samples made from pattern resin.

Statistical Analysis Used:

The surface roughness (μm) of the castings was measured by a profilometer. Student's “unpaired t-test” was used for the statistical analysis.

Results:

Specimens that were invested at atmospheric pressure had significantly more surface roughness (μm) values than those invested under increased pressure (P < 0.01).

Conclusions:

Wax patterns exhibited the least surface roughness when invested under pressure and can be recommended as the material and technique of choice. In addition, resin patterns invested under increased pressure produced smoother casting surface than those invested at atmospheric pressure, and the difference is highly significant.

Assessing the Accuracy of Casting and Additive Manufacturing Techniques for Fabrication of a Complete Palatal Coverage Metal Framework

PURPOSE

To provide information regarding the accuracy of additive manufacturing in comparison to conventional casting, specifically for fabrication of complete palatal coverage metal frameworks.

MATERIALS AND METHODS

Three additive manufacturing techniques were tested: selective laser melting (SLM), electron beam melting (EBM), and computer-aided design/cast (CADcast), with conventional casting as the control. Both the SLM and EBM groups were tested pre- and post-finishing, for a total of six test groups (n = 10/group). A digital master design was used as the standard to which all frameworks were digitally compared by best-fit analysis, which generated root mean square values using proprietary software. A one-way ANOVA was conducted to test for statistical differences among materials, followed by a post-hoc multiple comparison test (Tukey's test HSD). Surface roughness for one framework arbitrarily selected from each group was analyzed using a profilometer.

RESULTS

There was a significant difference in accuracy among the materials (F = 99.79, p < 0.0001). A post-hoc Tukey test indicated that CADcast differed significantly from the other five materials (i.e., most accurate, p < 0.01). EBM prefinished and EBM finished were both significantly different from the other materials (i.e., least accurate). Color mapping images help visualize the differences between each framework compared to the master design. The surface roughness values ranged from 22 to 63.5 µm, with CADcast being the smoothest, and EBM prefinished the roughest.

CONCLUSIONS

CADcast and SLM techniques were as or more accurate than the conventional technique for producing an uncomplicated framework design. Further investigation is recommended regarding the surface roughness of additive manufacturing products and potential biological complications.

Surface Roughness of Monolithic and Layered Zirconia Restorations at Different Stages of Finishing and Polishing: An In Vitro Study

PURPOSE

To evaluate surface roughness and topography of different zirconia-based restorations at various steps of finishing and polishing.

MATERIALS AND METHODS

Seventy-five zirconia discs were fabricated and divided into 3 layered and 2 monolithic groups: layered conventional (VM9; Vita), layered pressed (PM9; Vita), layered digital (TriLuxe Forte; Vita), opaque monolithic (Ceramill Zi; Amann Girrbach), and translucent monolithic (Zolid FX; Amann Girrbach). Surface roughness testing (Ra, Rz) and scanning electron microscopy were performed at the glazed, unglazed, finished, polished, super-polished, and super-polished with diamond paste steps. One-way ANOVA and Tukey tests were used for statistical analysis.

RESULTS

There were significant differences in all groups among the different steps (p < 0.001, F = 77.67 for layered conventional; p < 0.001, F = 133.90 for layered pressed; p < 0.001, F = 47.94 for layered digital; p < 0.001, F = 48.05 for zirconia opaque; p < 0.001, F = 43.91 for zirconia translucent). For the layered groups, glazed stage was significantly different from all other steps (p < 0.001). For the layered conventional and digital groups, polishing using diamond paste was not significantly different from the polished and super-polished steps (p = 0.448, p = 0.153), while for the layered pressed group, polishing using diamond paste was not significantly different from the super polished step (p = 0.815). For monolithic groups, there were no significant differences between the polished and super-polished steps (p = 0.957 for zirconia opaque, p = 1.00 for zirconia translucent). Both the diamond paste and super-polished steps showed no significant differences (p = 0.620, p = 0.550) from the glazed surface in the opaque zirconia group.

CONCLUSIONS

Surface roughness of monolithic and layered zirconia was improved by polishing; however, only opaque zirconia reached the level of surface roughness of the glazed stage. Type of buildup affected the surface roughness of adjusted ceramics, with monolithic zirconia showing lower surface roughness than layered zirconia. Polishing with diamond paste provided no significant improvement in the surface roughness of monolithic or layered zirconia.

CO2 Laser Glazing Treatment of a Veneering Porcelain: Effects on Porosity, Translucency, and Mechanical Properties

This work tested CO2 laser as a glazing agent and investigated the effects of irradiation on the porosity, translucency, and mechanical properties of veneering porcelain. Sixty discs (diameter 3.5 × 2.0 mm) of veneering porcelain for Y-TZP frameworks (VM9, VITA Zahnfabrik) were sintered and had one of their faces mirror polished. The specimens were divided into six groups (n=10/group) according to surface treatment, as follows: no treatment-control; auto-glaze in furnace following manufacturer's instructions (G); and CO2 laser (45 or 50 W/cm(2)) applied for four or five minutes (L45/4, L45/5, L50/4, L50/5). Optical microscopy (Shimadzu, 100×) was conducted and the images were analyzed with Image J software for the determination of the following porosity parameters: area fraction, average size, and Feret diameter. The translucency parameter studied was masking ability, determined by color difference (ΔE) over black and white backgrounds (CM3370d, Konica Minolta). Microhardness and fracture toughness (indentation fracture) were measured with a Vickers indenter (HMV, Shimadzu). Contact atomic force microscopy (AFM) (50 × 50 μm(2), Nanoscope IIIA, Veeco) was performed at the center of one sample from each group, except in the case of L45/5. With regard to porosity and translucency parameters, auto-glazed and laser-irradiated specimens presented statistical similarity. The area fraction of the surface pores ranged between 2.4% and 5.4% for irradiated specimens. Group L50/5 presented higher microhardness when compared to the G group. The higher (1.1) and lower (0.8) values for fracture toughness (MPa.m(1/2)) were found in laser-irradiated groups (L50/4 and L45/4, respectively). AFM performed after laser treatment revealed changes in porcelain surface profile at a submicrometric scale, with the presence of elongated peaks and deep valleys.

The effect of repeated firings on the color change and surface roughness of dental ceramics

PURPOSE

The color of the ceramic restorations is affected by various factors such as brand, thickness of the layered the ceramic, condensation techniques, smoothness of surface, number of firings, firing temperature and thickness of dentin. The aim of this study was to evaluate the color change and surface roughness in dental porcelain with different thicknesses during repeated firings.

MATERIALS AND METHODS

Disc-shaped (N=21) metal-ceramic samples (IPS Classic; Ivoclar Vivadent; Shaar, Liechtenstein) with different thickness were exposed to repeated firings. Color measurement of the samples was made using a colorimeter and profilometer was used to determine surface roughness. ANOVA and Tukey tests with repeated measurements were used for statistical analysis.

RESULTS

The total thickness of the ceramics which is less than 2 mm significantly have detrimental effect on the surface properties and color of porcelains during firings (P<.05).

CONCLUSION

Repeated firings have effects on the color change and surface roughness of the dental ceramics and should be avoided.

Effect of two different finishing systems on surface roughness of feldspathic and fluorapatite porcelains in ceramo-metal restorations: Comparative in vitro study

Objective:

The objective of present study was to qualitatively and quantitatively evaluate and compare the effect of two ceramic finishing systems and diamond polishing paste on surface texture of two ceramic materials.

Methodology:

The 40 test specimens were randomly divided into two main groups (Group I and Group II). Which were subsequently veneered with feldspathic porcelain and fluorapatite leucite porcelain systems respectively. The samples in Test group I and Test group II were subjected to different abrasion and finishing systems (Soft Lex and White silicon and grey rubber respectively). The surface roughness of all the four groups was assessed qualitatively using the scanning Electron Microscope and profilometer.

Results:

The surface roughness of Feldspathic and fluorapetite porcelain increased after abrasion and finishing as compared to auto-glazed porcelin. The surface roughness was more in grey rubber disc group (Gp Ib) as compared to the soft lex disc groups. After polishing with the diamond paste, there was reduction in the surface roughness of both the disc groups. The Mean Ra values of the Feldspathic porcelain at three intervals were 0.52 ± 0.06, 0.54 ± 0.06, 0.32 ± 0.06 and 0.50 ± 0.04, 1.25 ± 0.10, 0.45 ± 0.6 respectively for grey rubber disc and soft lex groups. The Mean Ra values of Fluorapetite porcelain at three intervals were 0.40 ± 0.06, 0.52 ± 0.06, 0.30 ± 0.03 and 0.41 ± 0.04, 1.17 ± 0.09, 0.39 ± 0.07 respectively for grey rubber disc and soft lex groups.

Discussion and Conclusion:

The surface roughness was less in the polished samples as compared to the auto-glazed porcelain. The findings were more reinforcing in the soft lex group as compared to the white/grey rubber disc group. Between the two porcelain systems, the Fluorapatite leucite porcelain specimens exhibited better surface smoothness than feldspathic porcelain.

Effects of Surface Abrasion on the Flexural Strength of Glazed and Re-glazed Metal Ceramics: An In Vitro Study

The functional surfaces of the porcelain fused to metal fixed partial dentures are often abraded to adjust occlusion, such restorations are often found to fail in service. This study was therefore conducted to study the effect of surface abrasion on flexural strength of glazed porcelain fused to metal samples. It was also the aim of this study to find the effect of re-glazing on flexural strength of abraded samples. A total of ninety glazed porcelain fused to metal bar samples of the dimension 15 mm × 2 mm × 1.5 mm were fabricated. These samples were then divided into three groups (30 samples each) according to the surface treatments: group A-glazed (control); group B-abraded and group C-abraded and then re-glazed (self-glazed). Flexural strength was measured by using three point bend test on universal testing machine (texture analyser) with a cross-head speed of 0.6 mm/min. Peak force at the time of failure for all the samples was recorded. Statistical analysis found that mean flexural strength was highest for group A-80.65 ± 12.81 MPa; as compared to group B-74.18 ± 10.74 MPa and group C-77.85 ± 9.39 MPa. Student's t test indicated that the difference in the flexural strength between groups A and B was significant while it was non-significant between groups B and C and also between groups A and C. The 'f' test indicated that the difference between the groups was non-significant. This study therefore showed that there is a marked decrease in the flexural strength of the porcelain fused to metal restorations after occlusal abrasion. The study also found that reglazing of these restorations may not restore their flexural strength significantly.

An in vitro study to identify a ceramic polishing protocol effecting smoothness superior to glazed surface

Polishing is taken up as an alternative to reglazing after adjustments of glazed ceramic prosthesis. An in vitro study was carried out to evaluate three different ceramic polishing systems and their combinations to identify a method that would achieve surface smoothness superior to the glazed surface. 77 glazed feldspathic porcelain disc surfaces, of diameter 12.5 mm and thickness 2 mm were constituted into seven groups of 11 specimen surfaces each. The glazed surfaces in the first group served as control (C). They were not subjected to deglazing or polishing. The remaining 66 surfaces underwent deglazing. The deglazed surfaces in the second group (D) were retained as such and did not undergo polishing. The deglazed surfaces in the third group (Wh), were polished using a polishing wheel (CeraMaster). In the fourth group (K), an adjustment kit (Porcelain Adjustment kit) was used for polishing the deglazed surfaces. The fifth group (Wx) was polished with diamond particle-impregnated wax (Dura-Polish Dia). In all these three groups, polishing was done for 40 s. The deglazed surfaces of the sixth group (WhWx) were polished initially with polishing wheel for 40 s and then with diamond particle-impregnated wax for 40 s. In the seventh group (KWx), the deglazed surfaces were polished with an adjustment kit (Porcelain Adjustment kit) for 40 s followed by diamond particle-impregnated wax (Dura-Polish Dia) for 40 s. In the sixth and seventh groups, the total polishing time was 80 s each. From each group, one specimen was set aside for scanning electron microscopy (SEM). The remaining ten specimens in each group underwent colorimetry and profilometry. Colorimeter (Minolta CR-200b ChromaMeter; Minolta, Osaka, Japan) was used to measure parameters according to CIE L*a*b* colour system and colour difference (ΔE) between control and other groups were calculated. Profilometer (Talysurf CLI 2000) was used to measure the surface roughness (Ra). The data were statistically analysed by one way ANOVA and Tukey HSD tests. The colour differences were well within the acceptable range of 3.3 units in groups subjected to polishing. Polishing with porcelain adjustment kit alone, diamond particle-impregnated wax alone or polishing wheel followed by diamond wax created surfaces with smoothness comparable to the glazed surfaces. The group polished by adjustment kit followed by diamond particle-impregnated wax showed surface roughness significantly less than the glazed surfaces. The SEM observations were corroboratory. It can be concluded that polishing with porcelain adjustment kit followed by diamond particle-impregnated wax, created surfaces significantly smoother than the glazed specimens with no significant negative effect on colour and thus can be a technique superior to glazing.

An in vitro investigation to compare the surface roughness of auto glazed, reglazed and chair side polished surfaces of Ivoclar and Vita feldspathic porcelain

The change in surface roughness after different surface finishing techniques has attracted the attention of several prosthodontists regarding wear of opposing teeth or restorative material and the strength; plaque retention and appearance of the restoration. However, there is considerable controversy concerning the best methods to achieve the smoothest and strongest porcelain restorations after chair side clinical adjustments. The purpose of this in vitro study was to compare the average surface roughness of a self-glazed surface, a chair side polished surface and a reglazed surface of ceramic. Two feldspathic porcelain, namely VITA VMK94 (Vita Zahnfabrik, Bad Sachingen, Germany) and IVOCLAR CLASSIC (Vivadent AG, FL-9494 Schaan, Liechtenstein) were selected to fabricate 20 specimens of each in the shape of shade guide tabs. A medium-grit diamond rotary cutting instrument was used to remove the glaze layer, and then the surface of half the specimens were re-glazed and the other half were polished using a well-defined sequence of polishing comprising of: Shofu porcelain polishing system, White gloss disc/polishing wheel, Silicone cone with diamond polishing paste and finally with small buff wheel with pumice slurry. The surface roughness (Ra) (μm) of the specimens was evaluated using a profilometer and scanning electron microscope. The data were statistically analyzed by using Student's t test. The results had shown that there is no statistically significant difference both quantitatively and qualitatively, between the surface roughness of reglazed and chair-side polished surface. In addition, both reglazed and chair-side polished surfaces are better than the autoglazed surface. Within all the groups, there is no significant difference between companies. Polishing an adjusted porcelain surface with the suggested sequence of polishing will lead to a finish similar to a re-glazed surface. Therefore chair-side polishing can be a good alternative to reglazing for finishing adjusted porcelain surface.

Evaluation of efficiency of manual polishing over autoglazed and overglazed porcelain and its effect on plaque accumulation

PURPOSE

The aim of this study was to evaluate the efficiency of manual polishing over autoglazed and overglazed porcelain and their effect on plaque accumulation.

MATERIALS AND METHODS

Thirty-six porcelain discs were fabricated out of which 18 each was subjected for autoglazing and overglazing. Half surface of the discs was left intact; the remaining half was roughened with medium grit diamond bur. Roughened surfaces were repolished by porcelain polishing kits (Shofu, DFS, Eve). All the surfaces were evaluated by the perthometer and SEM. Six discs from each sample were placed in human volunteer's mouth for 72 hours to evaluate the plaque accumulation. Acquired data was subjected to ANOVA comparative evaluation.

RESULTS

Roughened surfaces had average roughness value of 2.88±0.1935 µm. The repolished surfaces by porcelain correction kits Shofu, DFS and Eve, average roughness value reduced to 0.6250±0.1036, 0.9192±0.0953, 0.9017±0.1305 respectively. Autoglazed and overglazed surfaces showed the mean roughness value (Ra) of 0.4217±0.0685, 0.3450±0.0729. SEM study showed the improved surfaces when subjected for polishing. Plaque accumulation percentage was the highest on roughened surface (93.83±6.2552%), followed by porcelain discs polished by commercial kits. Autoglazed surfaces found to be the best surfaces with the least plaque accumulation (0.5237±0.4209%).

CONCLUSION

All the polishing kits used in the study reduced the average roughness by approximately 77%. Corrected porcelain surfaces should ideally be reglazed, alternatively, polish the surfaces before final cementation.

Saliva and tongue coating pH before and after use of mouthwashes and relationship with parameters of halitosis

OBJECTIVES

The aim of this work was to evaluate saliva and tongue coating pH in oral healthy patients with morning bad breath before and after use of different oral mouthrinses.

MATERIAL AND METHODS

Saliva and tongue coating pH of 50 patients allocated in 5 groups were measured respectively by a digital pHmeter and color pH indicators, before, immediately after and 30 min after rinsing 5 different mouthrinses: cetilpiridine chloride associated with sodium chloride, triclosan, enzymatic solution, essential oil and distilled water.

RESULTS

Only triclosan and essential oil increased salivary pH immediately after rising. The enzymatic solution decreased salivary and tongue coating pH immediately after rinsing.

CONCLUSIONS

Salivary pH tended to be acidic while tongue coating pH tended to be alkaline, even after rising. Triclosan and essential oil mouthrinses increased salivary pH immediately after rinsing. Enzymatic solution decreased saliva and tongue coating pH immediately after rising.

Flexural strength of fluorapatite-leucite and fluorapatite porcelains exposed to erosive agents in cyclic immersion

Objective

The aim of this study was to evaluate the flexural strength of two porcelain materials (IPS d.SIGN and IPS e.max Ceram) exposed to erosive agents

Material and Methods

One hundred and twenty bar-shaped specimens were made from each of fluorapatite-leucite porcelain (IPS d.SIGN) and fluorapatite porcelain (IPS e.max Ceram) and divided into 8 groups of 15 specimens each. Six groups were alternately immersed in the following storage agents for 30 min: deionized water (control), citrate buffer solution, pineapple juice, green mango juice, cola soft drink and 4% acetic acid. Then, they were immersed for 5 min in deionized water at 37°C. Seven cycles were completed, totalizing 245 min. A 7^th group was continuously immersed in 4% acetic acid at 80°C for 16 h. The final, 8^th, group was stored dry at 37°C for 245 min. Three-point bending tests were performed in a universal testing machine. The data were analyzed statistically by 2-way ANOVA, Tukey’s HSD test and t-test at significance level of 0.05.

Results

The flexural strengths of all groups of each porcelain after exposure to erosive agents in cyclic immersion did not differ significantly (p>0.05). For both types of porcelain, dry storage at 37°C yielded the highest flexural strength, though without significant difference from the other groups (p>0.05). The flexural strengths of all groups of fluorapatite porcelains were significantly higher (p<0.05) than those of the fluorapatite-leucite porcelains.

Conclusions

This study demonstrated that the erosive agents evaluated did not affect the flexural strength of the tested dental porcelains.

The effect of acidic agents on surface ion leaching and surface characteristics of dental porcelains

STATEMENT OF PROBLEM

Acidic food and sour fruits and drinks have been investigated for their destructive effects on enamel. However, their effect on porcelain restorations has not been widely examined.

PURPOSE

The purpose of this study was to evaluate the ion leaching of porcelains immersed in acidic agents.

MATERIAL AND METHODS

Fifty-five discs (12.0 mm in diameter and 2.0 mm in thickness) were made from each of 4 types of porcelain (VITA VMK 95, Vitadur Alpha, IPS Empress Esthetic, and IPS e.max Ceram). Baseline data of elemental compositions of all storage agents were recorded. Four groups of discs (n=10) were then immersed in acidic agents (citrate buffer solution, pineapple juice, and green mango juice) and deionized water (control) at 37 degrees C for 168 hours. One group was immersed in 4% acetic acid at 80 degrees C for 168 hours. After immersion, fluids from all specimens for each acidic agent were measured for ion leaching with an inductively coupled plasma optical emission spectroscopy. Surface characteristics of specimens were examined using scanning electron microscopy (SEM). Data were analyzed using 3-way repeated ANOVA and Tukey HSD multiple comparisons (alpha=.05).

RESULTS

This study revealed that each type of porcelain had significantly leached the various ions to varying degrees after being immersed in acidic agents (P<.001 for all comparisons). SEM photomicrographs showed surface destruction of all porcelains.

CONCLUSIONS

Acidic agents used in this study affected elemental dissolution of the 4 types of porcelains evaluated.

Chemical durability and microhardness of dental ceramics immersed in acidic agents

OBJECTIVE

To evaluate the microhardness and surface elemental compositions of ceramics immersed in acidic agents.

MATERIAL AND METHODS

Thirty-five ceramic disc specimens were made from each of four types of ceramic (VMK 95, Vitadur Alpha, Empress Esthetic and IPS e.max Ceram). Before immersion, baseline data of Vicker's microhardness and elemental composition were recorded. Four groups of discs (seven per group) were then immersed in acidic agents (citrate buffer solution, pineapple juice and green mango juice) and deionized water (as a control) for 168 h at 37 degrees C. One group was immersed in 4% acetic acid at 80 degrees C for 168 h. After immersion, specimens were evaluated and data were analyzed using two-way ANOVA with repeated measurements and a paired t-test at a significance level of 0.05.

RESULTS

The microhardness values of four types of ceramic significantly decreased after being immersed in acidic agents (p < 0.05). The elemental compositions of ceramics mainly comprise silicon, aluminium and potassium. These compositions also decreased after immersion (p < 0.05).

CONCLUSIONS

The acidic agents used in this study affected the microhardness and elemental dissolution of ceramics. The main elemental compositions of ceramics (silicon, aluminium and potassium) decreased after being immersed in acidic agents.

Comparison of porcelain surface and flexural strength obtained by microwave and conventional oven glazing

STATEMENT OF PROBLEM

Although the superior qualities of microwave technology are common knowledge in the industry, effects of microwave glazing of dental ceramics have not been investigated.

PURPOSE

The purpose of this study was to investigate the surface roughness and flexural strength achieved by glazing porcelain specimens in a conventional and microwave oven.

MATERIAL AND METHODS

Thirty specimens of each type of porcelain (Omega 900 and IPS d.Sign) were fabricated and sintered in a conventional oven. The specimens were further divided into 3 groups (n=10): hand polished (using diamond rotary ceramic polishers), microwave glazed, and conventional oven glazed. Each specimen was evaluated for surface roughness using a profilometer. The flexural strength of each specimen was measured using a universal testing machine. A 2-way ANOVA and Tukey HSD post hoc analysis were used to determine significant intergroup differences in surface roughness (alpha=.05). Flexural strength results were also analyzed using 2-way ANOVA, and the Weibull modulus was determined for each of the 6 groups. The surfaces of the specimens were subjectively evaluated for cracks and porosities using a scanning electron microscope (SEM).

RESULTS

A significant difference in surface roughness was found among the surface treatments (P=.02). Follow-up tests showed a significant difference in surface roughness between oven-glazed and microwave-glazed treatments (P=.02). There was a significant difference in flexural strength between the 2 porcelains (P<.005), but no significant difference in flexural strength by surface treatment (P=.48). The Weibull modulus value for the Omega 900 microwave-glazed group was the highest (1.9) as compared to the other groups.

CONCLUSIONS

The surface character of microwave-glazed porcelain was superior to oven-glazed porcelain. Omega 900 had an overall higher flexural strength than IPS d.Sign. Weibull distributions of flexural strengths for Omega 900 oven-glazed and microwave-glazed specimens were similar. SEM analysis demonstrated a greater number of surface voids and imperfections in IPS d. Sign as compared to Omega 900.

The effects of porcelain polishing systems on the color and surface texture of feldspathic porcelain

STATEMENT OF PROBLEM

After the adjustment of glazed porcelain surfaces, the surfaces are roughened and must be reglazed or polished with different porcelain polishing systems to improve the esthetic appearance and strength of the porcelain restorations.

PURPOSE

The purpose of this in vitro study was to compare the effect of different porcelain polishing methods on the color and surface texture of a feldspathic ceramic.

MATERIAL AND METHODS

Ninety porcelain (Vitadur Alpha) discs (10 x 2 mm) were fabricated in a silicone mold and divided into 9 groups (n=10). A medium-grit diamond rotary cutting instrument was used to remove the glaze layer, and then the surface was polished using 1 of the 4 following polishing systems or a combination thereof: polishing paste (Ultra II), polishing stick (Diamond Stick), polishing wheel (CeraMaster), or an adjustment kit (Porcelain Adjustment Kit). No surface treatments were applied to the control group. Color measurements were made using a colorimeter (Minolta CR-321 ChromaMeter) according to the CIE L( *)a( *)b( *) color system. Color differences (DeltaE) between the control group and experimental groups were calculated. The acceptable level was chosen as 3.3 DeltaE units. Then the surface roughness (Ra) (microm) of the same specimens was evaluated using a profilometer. The data were statistically analyzed by 1-way analysis of variance and Tukey HSD tests (alpha=.05). To evaluate the effects of the polishing systems on the ceramic surfaces at a microscopic level, an additional 9 feldspathic ceramic specimens were prepared and polished to represent each of the 9 groups. These specimens were examined under a scanning electron microscope (SEM).

RESULTS

Polishing techniques significantly affected the color of the feldspathic ceramic (P<.001). The DeltaE values ranged from 1.03 to 3.36. No significant differences were found within the adjustment kit groups or within the polishing wheel groups. All specimens polished with the various techniques showed significantly different Ra values than the control specimens (P<.001), except for the groups polished using the adjustment kit. The highest Ra and DeltaE values were obtained with the use of polishing paste and polishing stick alone (P<.001). The SEM observations demonstrated that the polishing techniques affected the smoothness of the porcelain surface.

CONCLUSIONS

The evaluation of the polishing techniques showed that the use of an adjustment kit alone or preceding polishing paste or polishing stick application created surfaces as smooth as glazed specimens. The use of polishing paste alone did not improve the smoothness of the porcelain surface. The color differences of all groups were found to be at the acceptable level.

Comparison of three systems for the polishing of an ultra-low fusing dental porcelain

STATEMENT OF THE PROBLEM

With the introduction of newer dental porcelains, there exists the need to evaluate different porcelain polishing systems available on the market.

PURPOSE

The purpose of this study was to compare the surface roughness produced by 3 different porcelain polishing systems on an ultra-low fusing porcelain.

MATERIAL AND METHODS

Sixty-three ultra-low fusing porcelain (Finesse) discs (10 x 2 mm) were fabricated and randomly divided into 3 groups (n=21). Both sides of each disc were abraded with a medium-grit diamond bur. One side was autoglazed and was considered a control. The other side was polished until the surface appeared shiny to the naked eye using 1 of 3 porcelain polishing kits (Axis Dental, Jelenko, and Brasseler systems). The surface of each disc was evaluated quantitatively with surface profilometry and qualitatively using scanning electron microscopy (SEM). A mean roughness profile (Ra) value was determined for each side of each specimen to describe the overall roughness of the surface. The Ra mean difference for each specimen was determined by subtracting the mean experimental readings (polished surface) from the mean control readings (glazed surface) and was used for the statistical analysis. The data were analyzed using analysis of variance followed by a Tukey multiple comparison test (alpha=.05). Representative specimens from each group were evaluated by scanning electron microscopy.

RESULTS

The Axis porcelain polishing system produced a smoother surface than the Brasseler or Jelenko systems (0.586 +/- 0.256, 0.306 +/- 0.238, and 0.277 +/- 0.230, respectively). No significant difference was found between the Jelenko and Brasseler porcelain polishing kits (F=10.6, P <.001). The images obtained through SEM were evaluated and found to be consistent with the profilometer readings.

CONCLUSION

Within the limitations of this study, all 3 porcelain polishing systems produced a surface smoother than the autoglazed surface of Finesse. The Axis system provided a significantly smoother surface compared to the Brasseler and Jelenko polishing systems.

Cervical margin design with contemporary esthetic restorations

The contemporary dentist has a wide variety of options to use in the restoration of extensively damaged or previously restored teeth. Metal-ceramic and all-ceramic crowns are frequently used to restore esthetics and function. One of the essentials for success with either option is proper tooth preparation, which includes proper selection and preparation of the cervical margin of the preparation.

Periodontal tissue responses after insertion of artificial crowns and fixed partial dentures

PURPOSE

The purpose of this review was, first, to critically evaluate published evidence on the effects of artificial crowns and fixed partial dentures (FPDs) on adjacent periodontal tissue health, and second to synthesize this evidence into meaningful summaries. Restoration qualities that contribute to inflammatory responses were identified based on strength of evidence, and variables that should be controlled in future investigations were outlined. Such information is necessary to accurately predict the prognosis of periodontal tissues adjacent to crowns or FPDs.

METHODS

Clinical trial and epidemiologic evidence published in English was collected. The effects of crowns or FPDs on gingival inflammation, probing depths, and bone loss were evaluated based on accuracy of measurement, reliability of measurement, and/or appropriateness of data analysis.

RESULTS

Crowns and FPDs increased the incidence of advanced gingival inflammation adjacent to restorations, particularly if restorations had intracrevicular finish line placement, poor marginal adaptation, or rough surfaces. However, because of the limitation in the accuracy and reliability of probing depth measurements, reports of greater mean probing depths of crowned teeth, which tended to be less than 1 mm greater than control teeth, should be questioned. Finally, crowns and FPDs in general did not accelerate the rate of adjacent bone loss.

CONCLUSION

Clinically deficient restorations, as well as clinically acceptable restorations, can contribute to gingival inflammation. However, with the limitations of the applied methods of measurement, current evidence has not shown an increased attachment loss adjacent to crowns or FPDs. Future trials should document periodontal health before therapy and periodically after restoration insertion so that each tooth serves as its own control. In future studies, the periodontal disease history of the patient, the influence of the restoration on plaque formation, and the composition of the crevicular microflora must be recorded.

Effects of resin composite components on glucosyltransferase of cariogenic bacterium

The aim of our study was to investigate the effect of resin composite components on glucan synthesis by glucosyltransferase (GTase) derived from a cariogenic bacterium, Streptococcus sobrinus B13. The eluates from cured composites stored in 0.05 mol/L potassium phosphate buffer (KPB) (pH 6.8) for 2 weeks at 37 degrees C stimulated the formation of water-insoluble glucan, whereas those from amalgam inhibited it. This finding suggests that the eluates from the resin composites enhance GTase activity and contribute to plaque formation. In the individual resin components, a diglycidyl methacrylate and triethylene glycol dimethacrylate significantly enhanced GTase activity. However, most polymerization inhibitors and accelerators were potent inhibitors of enzyme activity. Thus, GTase stimulation by eluates from resin composites is hypothesized to be heavily dependent on the effect of the eluated resin monomers, even though the other eluting components had inhibitory effects on GTase.

Porphyromonas gingivalis, Prevotella intermedia and Bacteroides forsythus in plaque subjacent to bridge pontics

This study examined the distribution of P. gingivalis, P. intermedia and B. forsythus in plaque on metallic and porcelain pontics adjacent to healthy and inflamed mucosa. Subpontic plaque was collected from 33 inflamed and 31 healthy sites. Plaque suspension was incubated with specific rabbit antisera to P. gingivalis (FDC 381), P. intermedia (ATCC 25261) and B. forsythus (FDC 335), and the labelled cells disclosed with fluorescein-labelled goat-anti-rabbit IgG by indirect immunofluorescence microscopy. Mean proportions of P. gingivalis, P. intermedia, and B. forsythus at inflamed sites were 0.60+/-0.75, 2.48+/-2.28, and 0.44+/-0.64% respectively, and at healthy sites 0.21+/-0.43, 1.27+/-1.05, and 0.15+/-0.18% respectively. These differences were statistically significant. Almost all sites were positive for P. intermedia, whereas only 12/31 healthy and 21/33 inflamed sites were positive for P. gingivalis. 18/31 healthy and 28/33 inflamed sites were positive for B. forsythus. P. intermedia was recovered in higher proportions from metallic pontics adjacent to inflamed sites (MI) than healthy sites (MH) or porcelain pontics next to inflamed (PI) or healthy sites (PH). P. gingivalis is was recovered in higher proportions from MI than PH. We conclude that both the nature of the pontic material and the health status of the mucosa affect the composition of the associated microbiota.

Polishing systems for dental ceramics

The increasing use of ceramic crowns and inlays in posterior teeth has highlighted the clinical difficulties involved in achieving a good surface finish after corrective grinding. In the present work several polishing systems and techniques were compared, initially using only one dental ceramic, Vita Mark I. The two systems that produced the best results were then further used for the polishing of several different dental ceramics, mainly newer types. The initial surface roughness and the surface condition attained after various polishing stages were evaluated by using a surface roughness analyzer. In the initial test series the SofLex system and the Shofu Porcelain Laminate Polishing Kit produced the best results; they were therefore chosen for the second part of the investigation. In this the two polishing systems concerned produced a satisfactory surface finish in a clinically acceptable time for all the ceramics tested. The use of a diamond-containing polishing past did not improve the surface smoothness obtained with the SofLex system but gave a more varied result for the Shofu system.

Efficacy of a porcelain refinishing system in restoring surface finish after grinding with fine and extra-fine diamond burs

Commercial porcelain refinishing kits are claimed to restore the surface finish on porcelain after adjustments in circumstances that preclude reglazing. This study investigates the efficacy of one such kit in restoring a Vitadur N porcelain surface finish after grinding with fine (30 microns grit-red band) and extra-fine (15 microns grit-yellow band) high-speed diamond burs. The production of the porcelain test samples, the refinishing procedures, and the refinishing times were standardized throughout. Techniques were selected to simulate clinical practice. Randomly selected examples of surfaces created during refinishing were subjected to scanning electron microscopy, using standard kV and tilt angle settings, and to surface profilometry tracings. Roughness average (Ra) readings were recorded for each test specimen for every surface finish. Ra readings were analyzed statistically using a two-way unbalanced model for analysis of variance. Although refinishing after grinding with a 15 microns grit bur produced surfaces significantly smoother than on specimens previously ground with the 30 microns grit burs, the surfaces remained significantly rougher than when originally glazed. It is concluded that, using the type of kit tested, burs of a grade finer than the existing 15 microns grit yellow band types would be appropriate for porcelain adjustments to permit subsequent refinishing to a surface smoothness comparable to the original glaze.

The influence of surface finish and in-vitro pellicle on contact-angle measurement and surface morphology of three commercially available composite restoratives

Three commercially available composites (Concise, Occlusin and Heliomolar) had surface finishes of varying roughness. Concise and Occlusin were cured against glass and Mylar, or were polished with a white stone or Soflex discs, producing four different surface finishes. Heliomolar was cured against glass or finished with a Vivadent polisher. Each specimen was immersed in water (without pellicle) or artificial saliva (with pellicle) and photographed with a captive air bubble. The influence of pellicle on contact-angle measurements and hence adhesiveness was determined. Scanning electron microscopy of pellicle-free and pellicle-conditioned surfaces was also performed. The effect of the pellicle on all Concise specimens was profound, tending to increase adhesiveness of the smooth (glass and Mylar) surfaces and decrease adhesiveness of the roughened (white stone and Soflex disc) polished surfaces. The pellicle-conditioned smooth Occlusin surfaces behaved similarly, but not the polished specimens, having similar contact-angle measurements after pellicle deposition. Heliomolar had significantly reduced contact-angle measurements after pellicle formation, and thus increased adhesiveness. The influence of the pellicle on surface finish characteristics may be significant, and may vary according to the composite used.

Color consistency, plaque accumulation, and external marginal surface characteristics of the collarless metal-ceramic restoration

Four techniques for making collarless metal-ceramic restorations were investigated in this study to examine the final color consistency, the bacterial plaque accumulation, and the surface characteristics of the porcelain margin. Twenty crowns were constructed and data revealed the superiority of the platinum foil technique in producing consistent color, whereas the shoulder porcelain technique resulted in the most significant color deviation. Metal surfaces exhibited the greatest in vitro bacterial plaque accumulation (42.43%), and the margins of the platinum foil technique accumulated the least plaque (7.23%). In addition, the wax binder and the platinum foil techniques produced the smoothest surfaces, whereas again the shoulder porcelain technique exhibited pronounced surface roughness. From the obtained results, and with the limitations of this in vitro study, one can speculate that surface roughness is not a predominant factor in the initial process of bacterial plaque accumulation.

Refinishing of porcelain by using a refinishing kit

Dental porcelain occasionally requires adjustment in circumstances that preclude reglazing. Porcelain refinishing kits are now available commercially. The effects of using one such kit on Vita VMK bonded porcelain was investigated qualitatively and quantitatively using scanning electron microscopic and surface profilometric techniques, respectively. The kit proved incapable of restoring a surface glaze to porcelain adjusted using a fine (red band) diamond bur, but was capable of reducing significantly the surface roughness (Ra) of adjusted porcelain. The importance of distinguishing between the integrity of the surface glaze and measurements of surface roughness is discussed. Confining the application of refinishing procedures to the surface adjusted is important to avoid unnecessary removal of the original surface glaze.

Polished versus autoglazed dental porcelain

This study compared the finishes on dental porcelain polished with four different polishing paste systems with oven reglazing and with a porcelain adjustment kit without a polishing paste. The polished/reglazed samples were rated according to quality of finish by independent observers and by scanning electron microscopy. On the basis of visual examination, two of the polishing paste systems tested were found to produce a surface equal to or better than oven glazing. On the basis of SEM examination, oven glazing was found to produce a better surface than the other polishing methods. Not all porcelain polishing systems produce a surface comparable to oven-glazed porcelain, and porcelain polishing systems should be chosen carefully.

99mTc-MDP adsorption of some dental alloys with varying surface roughness: effect of oral environment

The purpose of this study was to measure the surface characteristics of some dental alloys by 99mTc-MDP adsorption and to investigate the effect of oral environment on 99mTc-MDP adsorption. Sample discs of five different dental alloys were prepared. The surfaces were sandblasted, ground with sandpaper, polished and electrolysed in succession. The surface roughness of each disc was measured by the use of a profilometre. Contact angles (theta) of the surfaces were also measured. 99mTc-MDP adsorption of the discs was determined both prior to and after 2 h of exposure to the oral environment. Our results indicated that the discs sandblasted and electrolysed had the maximum surface roughness and those polished the minimum surface roughness. The 99mTc-MDP adsorption showed variation according to the type of alloy used and its surface roughness prior to exposure to the oral environment. After exposure 99mTc-MDP adsorption was essentially the same for all the alloys.

Influence of pontic material on alveolar mucosal conditions

The purpose of the present study was to investigate plaque accumulation and inflammatory changes in the mucosa beneath fixed bridge pontics of various materials, in patients cleaning the infrapontic space daily. Fixed bridges with a tight but non-compressive contact to the mucosa in the pontic area and with interchangeable test specimens placed in the pontic base were constructed for five patients. During 4-wk periods the following materials were tested: alloys with a high or a low gold content, silver-palladium, cobalt-chromium, nickel-chromium and also a dental porcelain or a composite restorative resin. Between the test periods a "sanitary pontic" was used to enable recovery of the alveolar mucosa. Clinical examinations including exudate measurements demonstrated that the alveolar mucosa remained healthy irrespective of the material used when the dental floss was used regularly. The amount of plaque on the test specimens of the seven dental materials showed no consistent differences. The composition of the bacterial deposits showed no regular pattern. This investigation has demonstrated that patients maintaining a high standard of oral hygiene are able to prevent the development of inflammatory changes in the alveolar mucosa in contact with fixed bridge pontics irrespective of the pontic material used.

An analysis of margin configurations for metal-ceramic crowns

Major types of margin configurations for ceramometal crowns are reviewed. This is one of the most commonly misunderstood and poorly practiced aspects of fixed prosthodontics. The resultant underprepared teeth produce discolored gingiva and chalky crowns.

Plaque accumulation on Teflon-coated metal

This study demonstrated that plaque accumulation was reduced and plaque removal facilitated by the TFE coating. These findings suggest that the TFE coating has a practical application for pontics and the proximal and cervical surfaces of crowns. These inaccessible surfaces are not easily cleaned by brushing.

A sanitary "arc-fixed partial denture": concept and technique of pontic design

The design of and rationale for a sanitary arc-fixed partial denture have been described. Reproduction of the anatomic contours of a certain portion of the buccal and lingual surfaces is believed to be responsible for the significant increase in patients' acceptance of this type of pontic design.

Current theories of crown contour, margin placement, and pontic design

Crown contours which promote favorable tissue response follow these guidelines: (1) buccal and lingual contours are flat; (2) embrasure spaces should be open; (3) contacts should be high (incisal one third) and buccal to the central fossa (except between first and second molars); and (4) furcations should be "fluted" or barreled out." Margins should be supragingival where possible. The pontic design of choice is the modified ridge lap for posterior spaces and the ridge-lap facing for anterior spaces.

Tissue response to posterior denture base-type pontics

Several factors have been presented that must be evaluated when selecting an appropriate posterior pontic design. Because of the controversy that exists with regard to using posterior denture base pontics, a long-span fixed partial denture was followed for 14 months. Results indicate that tissue health can be maintained, while tissue proliferation is inevitable. There is no one posterior pontic design that can be used to satisfy all requirements. Optimal pontic design can be accomplished only if each situation is evaluated on an individual basis and an appropriate design selected. Further controlled longitudinal clinical research of pontic design is mandatory for expansion of the ability to predict optimal prognosis.