Edmond H.N. Pow

Intensity-modulated radiotherapy for early-stage nasopharyngeal carcinoma: A prospective study on disease control and preservation of salivary function

Xerostomia is a uniform complication after radiotherapy (RT) for nasopharyngeal carcinoma (NPC). Dosimetric studies suggested that intensity‐modulated RT (IMRT) can spare part of the parotid glands from high‐dose radiation. Disease control and salivary function after IMRT for early‐stage NPC was studied prospectively.

Preservation of quality of life after intensity‐modulated radiotherapy for early‐stage nasopharyngeal carcinoma: Results of a prospective longitudinal study

Xerostomia is a ubiquitous complication after conventional radiotherapy for nasopharyngeal carcinoma (NPC) that seriously impairs patient quality of life (QOL). The effect on QOL of parotid‐sparing intensity‐modulated radiotherapy (IMRT) for early‐stage NPC was assessed prospectively.

A new modified laser pretreatment for porcelain zirconia bonding

OBJECTIVES The aim of this study was to compare the effects of three different surface treatments in enhancing porcelain zirconia bonding. METHODS Totally, 160 densely sintered zirconia specimens were prepared and randomly divided into four study groups: control (no treatment, Group C), sandblasting (Group S), sandblasting followed by regeneration firing (Group SH), and laser irradiation (pulse mode) on a CO₂ laser system (Group L). After surface treatment, porcelain powders were veneered on zirconia surface. Half of the specimens in each group were evaluated without aging (initial shear bond strength - initial SBS), and the other half was tested after being stored in water for one month (aging SBS). X-ray diffractometry (XRD) was used to observe any crystallographic transformation at zirconia surface. Results were statistically analyzed using analysis of variance (ANOVA) and Turkey test (=0.05). RESULTS The initial average SBS values of Group S, Group SH, and Group L were 31.3 ± 5.7 MPa, 29.2 ± 7.0 MPa and 32.1 ± 7.5 MPa, respectively. The differences among these three groups were not significant. The control group had significantly lower value, 24.8 ± 6.7 MPa, than those of Group S and Group L. Furthermore, there was no significant difference between initial and aging values in each group. XRD analysis showed that sandblasting caused tetragonal to monoclinic phase transformation. Regeneration firing reversed such a transformation. However, crystallographic transformation could not be detected in laser treated specimens. SIGNIFICANCE Both sandblasting and laser irradiation increased porcelain zirconia bond strength. The presented new modified laser pre-treatment might be an alternative way to sandblasting for improving zirconia/porcelain integration.

Salivary gland function and xerostomia in southern Chinese following radiotherapy for nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is rare among Caucasians but very common among southern Chinese. No information is presently available on the relationship between salivary gland function and xerostomia in irradiated southern Chinese. Salivary gland function and xerostomia were measured in irradiated NPC patients, recently diagnosed NPC patients, and a matched control group. Stimulated whole saliva was collected from each participant and flow rate, pH and buffer capacity measured. All participants completed a multi-item dry mouth questionnaire. Comparisons were made using Chi-square and Mann-Whitney tests and correlations assessed using Spearmans rank correlation coefficients. The mean saliva flow rate and pH were significantly lower and the buffer capacity impaired in irradiated NPC patients compared with the other groups (P<0.01). Significantly more irradiated NPC patients had negative impacts associated with dry mouth generally, sticky saliva, and hoarse voice (P<0.01). Subjective dry mouth symptoms and associated reduced saliva flow were also relatively common in non-irradiated participants. Salivary gland hypofunction and xerostomia were major complications in irradiated NPC patients. In irradiated and non-irradiated southern Chinese, subjective dry mouth symptoms appeared to be correlated with actual salivary gland function.

Comparison of mechanical properties of three machinable ceramics with an experimental fluorophlogopite glass ceramic

STATEMENT OF PROBLEM Fluorophlogopite glass ceramic (FGC) is a biocompatible, etchable, and millable ceramic with fluoride releasing property. However, its mechanical properties and reliability compared with other machinable ceramics remain undetermined. PURPOSE The purpose of this in vitro study was to compare the mechanical properties of 3 commercially available millable ceramic materials, IPS e.max CAD, Vitablocs Mark II, and Vita Enamic, with an experimental FGC. MATERIAL AND METHODS Each type of ceramic block was sectioned into beams (n=15) of standard dimensions of 2×2×15 mm. Before mechanical testing, specimens of the IPS e.max CAD group were further fired for final crystallization. Flexural strength was determined by the 3-point bend test with a universal loading machine at a cross head speed of 1 mm/min. Hardness was determined with a hardness tester with 5 Vickers hardness indentations (n=5) using a 1.96 N load and a dwell time of 15 seconds. Selected surfaces were examined by scanning electron microscopy and energy-dispersive x-ray spectroscopy. Data were analyzed by the 1-way ANOVA test and Weibull analysis (α=.05). Weibull parameters, including the Weibull modulus (m) as well as the characteristic strength at 63.2% (η) and 10.0% (B10), were obtained. RESULTS A significant difference in flexural strength (P<.001) was found among groups, with IPS e.max CAD (341.88 ±40.25 MPa)>Vita Enamic (145.95 ±12.65 MPa)>Vitablocs Mark II (106.67 ±18.50 MPa), and FGC (117.61 ±7.62 MPa). The Weibull modulus ranged from 6.93 to 18.34, with FGC showing the highest Weibull modulus among the 4 materials. The Weibull plot revealed that IPS e.max CAD>Vita Enamic>FGC>Vitablocs Mark II for the characteristic strength at both 63.2% (η) and 10.0% (B10). Significant difference in Vickers hardness among groups (P<.001) was found with IPS e.max CAD (731.63 ±30.64 H(V))>Vitablocs Mark II (594.74 ±25.22 H(V))>Vita Enamic (372.29 ±51.23 H(V))>FGC (153.74 ±23.62 H(V)). CONCLUSIONS The flexural strength and Vickers hardness of IPS e.max CAD were significantly higher than those of the 3 materials tested. The FGCs flexural strength was comparable with Vitablocs Mark II. The FGCs Weibull modulus was the highest, while its Vickers hardness was the lowest among the materials tested.

Evaluation of four surface coating treatments for resin to zirconia bonding.

OBJECTIVES To compare the effects of four surface coating methods on resin to zirconia shear bond strength. MATERIAL AND METHODS Eighty pre-sintered zirconia discs were prepared and randomly divided into five study groups according to the corresponding methods of surface treatments as follows: group C (control group, fully sintered without any surface treatment), group S (fully sintered and then sandblasted with silica coated alumina powder), group G (fully sintered and then coated with glazing porcelain followed by acid etching), group Si (pre-coated with silica slurry then fully sintered), and group Z (coated with zirconia particles and then fully sintered). The observation of surface morphology and elemental composition analysis were conducted by SEM and EDX. Self-adhesive resin cement stubs (diameter 3.6mm and height 3mm) were then bonded on the zirconia discs with a cylindrical shape. Both initial and artificial aged (including 30-day water storage, thermal cycling for 3000 and 6000 cycles) shear bond strengths were then evaluated. RESULTS All the tested coating methods showed significantly higher shear bond strengths than the control group, in both dry and aged conditions. Group S produced the strongest initial zirconia/resin bonding (19.7MPa) and the control group had the lowest value (8.8MPa). However, after thermal cycling, group Z exhibited the highest mean value. All the samples in the control group failed in the thermal cycling. Both different coating methods (p<0.001) and various aging treatments (p<0.001) produced significant influence on resin-zirconia shear bond strength. CONCLUSIONS A reliable and durable resin zirconia bonding is vital for the longevity of dental restorations. Silica coating might be a reliable way in enhancing adhesion between resin and zirconia.

Oral stereognosis in stroke and Parkinson's disease: a comparison of partially dentate and edentulous individuals

Abstract. Oral stereognosis was measured in partially dentate and edentulous patients with stroke, Parkinsons disease, and an age and gender-matched control group. Stereognostic tests involving conventional free intra-oral manipulation of test objects were undertaken in the partially dentate and edentulous with and without complete dentures. Comparisons were made using the unpaired t-test and ANOVA. Edentulous stroke patients without dentures had significantly greater error scores and fewer correct identifications compared with partially dentate stroke patients. Stereognostic measures were similar in the partially dentate and edentulous with dentures, within experimental groups. In the partially dentate, there were no differences in stereognostic measures between the three groups. Stereognostic measures were poorer in edentulous stroke patients with and without dentures compared with the edentulous control group. Partially dentate stroke patients are less likely to have impaired oral stereognosis than edentulous stroke patients.

Static and fatigue mechanical behavior of three dental CAD/CAM ceramics

PURPOSE The aim of this study was to measure the mechanical properties and fatigue behavior of three contemporary used dental ceramics, zirconia Cercon(®) (ZC), lithium disilicate e.max(®) CAD (LD), and polymer-infiltrated ceramic Enamic(®) (PIC). METHODS Flexural strength of each CAD/CAM ceramic was measured by three point bending (n=15) followed by Weibull analysis. Elastic modulus was calculated from the load-displacement curve. For cyclic fatigue loading, sinusoidal loading with a frequency of 8Hz with minimum load 3N were applied to these ceramics (n=24) using three point bending from 10(3) to 10(6) cycles. Fatigue limits of these ceramics were predicted with S-N fatigue diagram. Fracture toughness and Vickers hardness of the ceramics were measured respectively by single edge V-notch beam (SEVNB) and microindentation (Hv 0.2) methods. Chemical compositions of the materials׳ surfaces were analyzed by EDS, and microstructural analysis was conducted on the fracture surfaces by SEM. One-way ANOVA was performed and the level of significance was set at 0.05 to analyze the numerical results. RESULTS The mean flexural strength of ZC, LD, and PIC was respectively 886.9, 356.7, and 135.8MPa. However, the highest Weibull modulus belonged to PIC with 19.7 and the lowest was found in LD with 7.0. The fatigue limit of maximum load for one million cycles of ZC, LD, and PIC was estimated to be 500.1, 168.4, and 73.8GPa. The mean fracture toughness of ZC, LD, and PIC was found to be respectively 6.6, 2.8, and 1.4MPam(1/2), while the mean Vickers hardness was 1641.7, 676.7, and 261.7Hv. Fracture surfaces followed fatigue loading appeared to be smoother than that after monotonic loading. CONCLUSIONS Mechanical properties of ZC were substantially superior to the two other tested ceramics, but the scattering of data was the least in PIC. The fatigue limit was found to be approximately half of the mean flexural strength for all tested ceramics.

A prospective study of the impact of nasopharyngeal cancer and radiotherapy on the psychosocial condition of Chinese patients

Radiotherapy (RT) promises optimistic results in the treatment of nasopharyngeal cancer (NPC). The objective of the current study was to map out prospectively the impact of NPC and RT on patients from diagnosis to 1 year posttreatment.

Insights into Porcelain to Zirconia Bonding

Abstract The application of zirconia, ZrO2, as a biomaterial in medicine started in the early 1980s. Since then, numerous studies have been conducted on this special ceramic material to assess and discover its unique characteristics in practical biomedical applications. Also, zirconia has manifested its extraordinary advantages for use in dental clinical practice since the late 1990s, such as its excellent biocompatibility, good aesthetical appeal and outstanding biomechanical properties. With the development of fabrication methods and more extensive comprehension of this material, zirconia has been employed in more and more dental restorations from single crowns and root canal posts to long-span fixed dentures and, very recently, even as dental implants. However, there are still some drawbacks in its dental applications. Such drawbacks are its relatively weak bonding with porcelain when compared with metal-ceramic system, less reliable bonding with resin-based adhesives, and possible failures caused, e.g., by the effects of low temperature degradation. Although many studies have been carried out on porcelain to zirconia bonding, a thorough understanding of its real mechanism is still far from being achieved. The effects of different treatments before or during the veneering procedure are not clearly elucidated, thus they need further investigations. The aim of this article is to outline the characteristics of zirconia and descriptions of porcelain to zirconia interfacial bonding based on the research conducted in the past few years.