ABSTRACT
Objectives: metal-ceramic restorations are the standard by which all esthetic restorations are measured. Fracture of dental restorations is a multifactorial problem, which is serious and costly. Debonding of porcelain from the metal substructure and the bond strength depend on many factors. The purpose of this study was to determine whether the opaque porcelain thickness has a significant effect on metal ceramic bond strength utilizing the ISO 9663 standard crack initiation test
Methods: thirty rectangular Ni-Cr metal bars [25×5×0.3mm] were fabricated according to ISO9663 standards. The metal bars were divided into three groups of 10. Opaque, body and enamel Noritake porcelain were applied on the middle of the bar according to ISO9663 standards up to 1mm porcelain thickness. The opaque porcelain thicknesses were 0.1, 0.2, and 0.3 mm, respectively in the three groups. The 3-point bending test was applied according to the ISO9663 standards and fracture strength [F[fail]] was measured using a universal testing machine with a crosshead speed of 1.5mm/minute
Results: analyses of the data by one-way ANOVA demonstrated no significant differences in bond strength among the three experimental groups [P=0.26]
Conclusion: within the limitations of this study, it is concluded that 0.1mm opaque porcelain provides sufficient bond strength between metal and ceramic in metal-ceramic restorations
ABSTRACT
The attrition of anterior teeth leads to the loss of efficient anterior guidance, which protects posterior teeth from wear during lateral excursions. This clinical report describes a 48-year-old man with diagonal tooth wear and posterior mandibular tooth loss. The clinical diagnosis was based on a complete oral examination, photos, functional analysis of lateral excursion movements, general health condition and behavioral aspects such as diet and bruxism. A mandibular partial overlay denture was used to reestablish the occlusal plane after the decision of restoring the vertical dimension of occlusion [OVD] by anatomical landmarks and physiological measurements. Once the compatibility of new OVD was approved and accepted, and followed for six months, fixed implant and tooth supported restorations were fabricated
A satisfactory clinical result was achieved by restoring OVD by 7 mm and avoiding advanced periodontal crown lengthening. Successful full mouth rehabilitation for a severely worn dentition can be achieved through good clinical management with long-term success to improve the quality of life
ABSTRACT
The standard of treatment of edentulous people is implant retained overdenture. The aim of this study was to compare the effect of different implant location [ABDE, 6AE6, 6BD6] on the retention and stability of mandibular implant overdenture with ball attachment. An experimental study was designed. An acrylic resin model of edentulous mandible with six implant in the location of first molars, first premolar and between lateral incisor and canine on the left and right side was fabricated. A metallic overdenture was fabricated precisely adapted to the model and attached to a Zwick testing machine [crosshead speed of 51 mm/min]. The ball attachments were screw in three ways. First the balls in ABDE, then ball in 6AE6 and then balls in 6BD6 position were screwed. Dislodging tensile forces were applied in three vertical, oblique, anterior-posterior directions for each sample. For each of these three situations, five tests were done. The maximum dislodging force was measured. Normal distributions of data were analyzed with Shapiro-Wilk test. Levene test analazed the variances. A Three-way ANOVA test was employed followed by Tukey's test. The amount of vertical load is significantly higher than the oblique and Ant-post load [P<0.001]. The amount of ant-post load is signifivantly higher than the oblique load [P<0.001]. The average of MDF is significantly higher in 6BD6 position [P<0.001]. This average is also signifivatnly lower in ABDE position [P<0.001]. The amount of measured force in ABDE and 6BD6 position was the least and the most respectively [ABDE=64.51 N and 6AE6=66.06 N]. Vertical and oblique dislodging force are the minimum and maximum measured forces respectively [mean vertical= 87.95 N, mean Lateral= 48.1 N and mean Ant.Post= 63.5 N] Lateral and Ant.Post dislodgment values are higher in 6BD6 and 6AE6 respectively. In vertical dislodgment the retention values in the most in 6BD6 position. Vertical retention in higher than lateral and Ant.Post retentions. The more posterior position the distal implant the more the retention and stability