CATEGORY 60 AUSTRALASIAN DENTIST CLINICAL Use of high-strength zirconia materials for long-span bridges By Prof. Dr Danimir Jevremovic Today, the use of metal-free ceramics is a milestone in aesthetic dentistry. The lack of grayish appearance of metal frameworks provides exceptional aesthetic properties of all-ceramics. High biocompatibility allows a very good gingival response. In addition, the machinability of ceramic blocks and discs permits the fabrication of precise restorations, that are produced in a minimum of time. Zirconia is a high-strength oxide ceramic, that enables the fabrication of multi-unit metal-free restorations. Initially, zirconia cores were layered with ceramics to achieve good aesthetic results. Despite generally acceptable results, chipping was one of the major issues that could occur with this type of restorations. In recent years, great efforts have been made towards the introduction of monolithic metal-free crowns and bridges as those restorations have great mechanical properties. In addition, the elimination of layering also eliminates the susceptibility to chipping and delamination. Long-span bridges represent a specific challenge for metal-free materials. Achieving mechanical and translucency requirements requires the combination of different zirconia powders. To meet this challenge, 3Y-TZP and 5Y-TZP zirconia are combined in a single disc. Powders with 3Y-TZP content provide high strength, while 5Y-TZP particles enable very good light transmission and close-to-enamel aesthetic properties. There are some 3Y/5Y material combinations, that can be found in the market today. However, the only one disc that provides an internal seamless progression of strength, shade and translucency is IPS e.max ZirCAD Prime (Ivoclar Vivadent, Liechtenstein). These discs are made using GTtechnology. The gradual change in translucency provides high aesthetic results without visible layers. Case report The Patient, a 42-year-old male, came into the practice for his smile enhancement. Besides aesthetics, he was also dissatisfied with this function of his existing restoration. During the anamnesis, the patient provided information about his impacted upper left canine. He had also undergone ortho treatment several years ago. The inspection reveals a shift in the upper jaw midline of the maxilla, compared to the facial midline (Fig. 1). Prof. Dr Danimir Jevremovic The occlusal plane is irregular (Fig. 2). In addition, there is a Maryland bridge in the region 22-23. The lateral incisors have a significantly different shape, especially the tooth width is noticeably different (Fig. 3). In the molar area, there is a tooth-totooth contact, while from the premolars an open byte can be detected (Figs 4, 5.). Tooth 15 has a big, old composite MOD filling (Figs 6, 7). Detailed occlusal examination reveals a missing canine guidance. On the right side, the lower canine 43 occludes with teeth 12 and 11, promoting their abrasion. Such a contact is a consequence of inadequate lateral incisor width. On the left side, the lack of guidance is a repercussion of the impacted upper canine. The treatment plan firstly deploys pre-prosthodontics ortho therapy (Fig. 8). A change of tooth position is necessary because a sufficient occlusal pattern cannot be achieved. The goals of orthodontic Fig. 1: Patient profile picture. Note the misalignment of the jaw and facial midlines. Fig. 4: Intraoral left lateral view (mirror). Occlusal irregularities in the molar region. Fig. 6: Intraoral picture upper jaw occlusal view. Fig. 5: Intraoral right lateral view (mirror). Class II occlusal contracts in the lateral segment. Fig. 7: Intraoral picture lower jaw occlusal view. Fig. 3: Intraoral picture of the upper jaw. There is a big difference in the width of lateral incisors. Fig. 2: Intraoral picture of the occlusion using OptraGate for lip and cheek retraction. The irregularity of the occlusal plane is visible.
RkJQdWJsaXNoZXIy MTc3NDk3Mw==