ABSTRACT
In some clinical conditions minimally invasive complete crown tooth preparations are indicated. This is especially true when gross removal of tooth structure would weaken the remaining tooth or violate the vitality of the dental pulp. The purpose of this study was to investigate the influence of [1] exposed lingual zirconia with veneered zirconia crowns, and [2] reduced lingual thickness of monolithic lithium disilicate crowns on the fracture resistance of the crowns after cyclic loading. Metal-ceramic crowns with exposed lingual metal served as controls. Twenty-four maxillary central incisor crowns were fabricated in identical shape on metal testing dies in 3 groups: metal-ceramic crowns [MC, n = 8], veneered zirconia crowns [VZ, n = 8], and monolithic lithium disilicate crowns [MO, n = 8]. A conservative preparation design with 0.75 mm lingual clearance was used for each crown system. All crowns were cemented to their corresponding crown preparations with self-adhesive resin cement [Multilink Automix]. The crowns were subjected to 1000 cycles of thermal cycling, then cyclic loading of 111 N by means of a stainless steel ball, and 50,000 cycles of loading were applied for the fatigue test. Fatigue loading was followed by a continuously increasing compressive load, at a crosshead speed of 1 mm/min until failure. The compressive load [N] required to cause failure was recorded. Means were calculated and analyzed with one-way ANOVA and the Tukey HSD test [alpha = .05]. There was a significant difference between MO vs. MC [P = 0.0001], MO vs. VZ [P = .0001], and VZ vs. MC [P = .012]. There was a significant difference in the mean fracture resistance of MC, VZ, and MO crowns in this in vitro study. The MC group recorded the highest mean fracture strength
Subject(s)
Dental Porcelain , Dental Veneers , Zirconium , Incisor , Maxilla , ToothABSTRACT
Numerous methods of restoring endodontically treated teeth have been advocated, and the prognosis of the treatment varies depending on the materials and techniques used. The objective of this study was to improve the understanding of contemporary philosophies and techniques of restoring endodontically treated teeth in Kuwait to serve as a baseline for continuous quality improvement of dental care in Kuwait. A questionnaire [English and Arabic versions] that comprehensively reviewed philosophies and techniques of restoring endodontically treated teeth was prepared. A research assistant identified prosthodontists, endodontists and general dentists practicing in government clinics in Kuwait. The sample represented 63% of the prosthodontists employed by the Ministry of Health, 91% of the endodontists and 7% of the general practitioners. Surveys were hand-carried by the research assistant and distributed to all dentists in the study group. Although all responses were anonymous, all surveys were numbered for tracking, and the research assistant returned to the government clinics repeatedly until all questionnaires [100%] were recovered. Data from the returned questionnaires were tabulated and statistical analysis for associations was conducted by using chi2 tests. Almost 60% of dentists in the survey involved in the treatment of endodontically treated teeth believed a post would reinforce the tooth. One third of the respondents used or recommended the use of one-piece dowel crowns [Richmond crowns]. One third lacked familiarity with the ferrule effect, and several misconceptions relative to the optimal length of a post were also recorded. The vast majority of general dentists in the survey did not report involvement in the treatment of 30 or more endodontically treated teeth per year. Conclusions: The majority of the respondents misunderstood the purpose of a post, and there were misconceptions regarding the optimal length of a post. One third did not report familiarity with the ferrule effect, which is an important restorative component. One third used or recommended an obsolete method of restoration with a one-piece dowel crown