Citation ABSTRACTFixed prosthodontic failures are varied and complex. Complications associated with conventional fixed prostheses are dental caries, need for endodontic treatment, periodontal disease. Poor esthetic is one of the most frequent reasons for replacing failed restorations. Knowledge regarding the clinical complications enhances clinicians to complete a thorough clinical examination and diagnosis, and to develop an esthetic-driven treatment plan including the selection of bleaching agent, the reconstruction type, and the ceramic material. This article illustrates several clinical complications of full coverage restorations, and discusses different therapeutic modalities which have to be combined and synchronized to enhance the esthetic outcome of the final fixed prostheses.

The successful use of zirconia ceramics for the fabrication of tooth-supported restorations has encouraged clinicians to extend its application for implant-supported restorations. CAD/CAM technology in combination with zirconia ceramic has increasingly gained popularity in implant dentistry [1]. Zirconia implants were introduced into dental implantology as an alternative to titanium implants. Zirconia seems to be a suitable implant material because of its opacity, mechanical properties, biocompatibility, and low plaque affinity.Apical bone loss and gingival recession associated with implants often uncover portions of the metal implant, revealing a bluish discoloration of the overlying gingiva. The use of zirconia implants avoids this complication and accedes to the request of many patients for metal-free implants. The inflammatory response and bone resorption induced by ceramic particles are less than those induced by titanium particles, suggesting the biocompatibility of ceramics [2].Today, the majority of implant manufacturers offer zirconia abutments for aesthetic implant-supported restorations. Abutments are available in prefabricated or customized forms and can be prepared in the dental laboratory either by the technician or by utilizing CAD/ CAM techniques. The biocompatibility of zirconia toward soft connective and epithelial tissue is essential [1]. Moreover, Y-TZP abutments may promote soft tissue integration, while favorable peri-implant soft tissues may be clinically achieved adjacent to zirconia abutments and zirconia healing caps. Besides strength considerations, Y-TZP implant abutments offer metal-like radiopacity for better radiographic evaluation, and, ultimately, reduced bacterial adhesion, plaque accumulation and inflammation risk. A systematic review revealed that zirconia abutments could maintain an equivalent bone level in comparison to titanium, gold and aluminum oxide ones [3]. In a randomized controlled trial, 20 customized non HIPed-based zirconia single-tooth implant abutments and 20 customized titanium singletooth implant abutments were followed for 3 years, with no fractures or loosening of abutments in both group and a 100% survival rate reported [4].

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Weakened teeth are varied in terms of causes and effects. The most common etiology of dental tissue loss is dental caries leading to endodontic treatment. This can cause an enormous esthetic problem because of the subsequent discoloration of the weakened tooth. Knowledge regarding the clinical complications enhances clinicians to complete a thorough clinical examination and diagnosis, and thus to develop the appropriate treatment satisfying the esthetic expectations of the patient. In this short communication, we discuss different therapeutic modalities (endodontic treatment, internal bleaching, fiber reinforced reconstruction, and fixed restorations) which have to be associated to enhance biological, functional and mainly esthetic outcome of final fixed restorations. Keywords: Dental caries; Endodontic treatment; Bleaching; Fiber reinforced post and core reconstruction; Prosthesis Short communicationThe primary factors for loss of tooth structure include dental caries, endodontic access preparation, and root canal preparation. In fact, after preparation of mesial occlusal distal (MOD) cavities, the fracture strengths of teeth were reduced to approximately 54% of their original strength. Although, the reduction of fracture resistance and hardness of teeth are generally the main consequences of endodontic treatment. This latter cannot cause deshydratation and brittleness after root canal treatment [1]. On the other hand, intracoronal whitening is highly recommended for discolored teeth treated endodontically [2]. While studies on the effects of bleaching on morphological changes to dental tissue are contradictory, some of them have confirmed the responsibility of bleaching agents for reducing the reducing the fracture resistance of tooth and inducing its fracture [2,3]. Researches showed ion release from both enamel and dentin after bleaching with different concentration of hydrogen peroxide, others demonstrated lowered phosphorus and calcium levels with a decrease of the mean Ca/P value after bleaching with 10% of carbamide peroxide [3]. However, Rotstein et al. [4] studied the effects of sodium perborate mixed with water on the modifications of chemical elements of tooth, and showed that the sulfur level included on the cementum was reduced. This proved that the organic composition was damaged. In opposite to many studies, the concentrations of phosphorus and calcium were maintained, indicating that the inorganic component was not affected. To conclude, Maleknejed, et al. [3] proved that the diameter of dentinal tubule were increased by all bleaching agents which foster alterations of the mineral composition of dentin, with the exception of sodium perborate mixed with water.With the presence of weakened and endodontically restored tooth, posts are needed to allow the clinician to rebuild enough tooth structure to retain restoration [5]. Therefore, Salameh, et al. [1] suggested the necessity of fiber posts placement in the root canal and thus to enhance mechanical behavior of the tooth even under full...