Résumé
Statement of the Problem: Considering the limitations of conventional sintering of zirconium oxide [ZrO[2]] copings, shortening the sintering time can be proposed as an alternative method for making the copings
Purpose: This study aimed to assess the effects of sintering time on compressive strength of Yttria Tetragonal Zirconia Polycrystal [Y-TZP] copings
Materials and Method: Thirty copings of pre-sintered 3Y-TZP blanks were milled and sintered in a special furnace for three different durations [n=10 per group]. The sintering time was 1 h 15 min for IPS e.max ZirCAD, 4 h 20 min for Speed ZrO[2], and 7 h 20 min for the conventional ZrO2 group. The specimens were cemented on the brass dies by using conventional glass ionomer cement. The copings were verti-cally loaded until fracture by using a universal testing machine. The data were ana-lyzed through one-way analysis of variance [ANOVA] and post hoc test to compare the mean differences of compressive strength yielded in three study groups [Alpha=0.05]
Results: The mean +/- SD of compressive strength value was [3617 +/- 543.54] N for IPS-e.maxZirCAD group, [2663 +/- 508.11] N for Speed ZrO2 group, and [1662 +/- 466.71 N] for conventional ZrO2 group. There were statistically significant differ-ences among compressive strength values of the tested groups [p< 0.05]. The highest compressive strength values were obtained from the IPS e.max ZirCAD group
Conclusion: Within the limitations of this in vitro study, it can be concluded that compressive strength of the zirconia copings is affected by the sintering time. High compressive strength of zirconia copings can be obtained by shortening the sintering time
Résumé
OBJECTIVES: Hormonal changes during menopause alter a woman's susceptibility to some disorders. Information regarding the prevalence of temporomandibular disorder (TMD) in menopausal women is limited in the literature. In this study, the prevalence and severity of TMDs were compared between menopausal and non-menopausal women. MATERIALS AND METHODS: The study included 140 women (69 premenopausal and 71 postmenopausal) 45 to 55 years of age that were examined in Shiraz Dental School, Shiraz in Iran. The Helkimo clinical dysfunction index (Di) was used to evaluate temporomandibular joint (TMJ) dysfunction. The data were analyzed using chi-square and Fisher's exact tests. RESULTS: Occurrence of TMD was significantly higher in menopausal than non-menopausal women (P < 0.001). All the TMD criteria based on Helkimo Di except range of mandibular movement were significantly more common in menopausal women. The range of mandibular movement was not significantly different between menopausal and non-menopausal women (P=0.178). CONCLUSION: The results from this study show that TMD can be considered more common and severe in menopausal than non-menopausal women. This finding indicates that, similar to other conditions in menopausal women such as arthritis and osteoporosis, TMD should be taken into consideration by dental and medical professionals.
Sujets)
Femelle , Humains , Arthrite , Iran , Ménopause , Ostéoporose , Prévalence , École dentaire , Articulation temporomandibulaire , Troubles de l'articulation temporomandibulaireRésumé
Statement of the Problem: The success of metal- ceramic- restorations [MCR] depends on the presence of strong bond between porcelain and metal substructure
Purpose: The purpose of this study was to evaluate the effect of hot pressing technique on the bond strength of a metal-porcelain composite in comparison to layering technique
Materials and Method: Thirty Nickel-Chromium specimens were produced by two methods; conventional porcelain layering on metal and hot pressing [n=15]. Bond strengths of all specimens were assessed by the means of three-point bending test according to ISO 9693: 1999 [E] instructions. The data were analyzed using Students t-test [p< 0.001]
Results: The mean +/- SD bond strength of conventional and hot pressing technique was 48.29 +/- 6.02 and 56.52 +/- 4.97, respectively. Therefore, the conventional layering technique yielded significantly lower mean bond strength values than hot pressing technique [p< 0.001]
Conclusion: This study showed that it is possible to improve metal-porcelain bond strength significantly by applying an overpressure during porcelain firing
Résumé
Statement of the Problem: One disadvantage of cement-retained crowns is the lack of predictable irretrievability. This problem can be overcome through designing a screw access hole in the metal substructure of cement-retained restoration and using porcelain stain to define this area
Purpose: This study aimed to evaluate the influence of existence of screw access hole on porcelain fracture resistance of metal-ceramic implant-supported crowns
Materials and Method: Thirty six standardized metal-ceramic crowns were fabricated and divided into 3 groups [n=12]; group 1 conventional cement-retained metalceramic crowns as control group, group 2 cement-retained MC crowns in which porcelain stain was used to define the location of screw access channel, and group 3 cement-retained metal-ceramic crowns in the metal substructure of which a hole and ledge was designed in the location of screw access channel. The specimens were cemented [TempBond, Kerr] to their dedicated abutments. A hole was made in the location of screw access channel in group 2 and 3 and filled with photo-polymerized composite resin [3M; ESPE]. All specimens were thermocycled and loaded in universal testing machine at crosshead speed of 2mm/min until fracture. Mean values of load at fracture were calculated in each group and compared with One-way ANOVA [alpha=0.05]
Results: Mean value of the load required to fracture the restorations was 1947 +/- 487 N in group 1, 1927 +/- 539 N in group 2, and 2170 +/- 738 N in group 3. No statistically significant difference was found between the fracture resistance values of the three groups [p> 0.05]
Conclusion: Presence of screw access channel in cement-retained implant restorations does not compromise fracture resistance