Effect of Different Surface Treatments on Biaxial Flexural Strength of Yttria-stabilized Tetragonal Zirconia Polycrystal.

INTRODUCTION: Ceramics are widely applied in dentistry owing to their excellent mechanical and physical attributes. The most popular ceramics are Lava™, KaVo Everest, and Cercon. However, it is unclear whether or not a different surface treatment along with low-temperature aging and mechanical loading (ML) affects the physical properties of computer-aided design (CAD)/computer-aided manufacturing (CAM)-machined yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic. AIM: The objective of this research was to assess the impact of various surface treatments as air-particle abrasion, ML, low-temperature degradation (LTD), and their cumulative effects on biaxial flexural properties of Y-TZP. MATERIALS AND METHODS: Totally, 50 specimens were fabricated by CAD-CAM machining from Cercon® and divided into five groups following different surface treatments as control (C), air-particle abrasion (Si), ML, LTD, and cumulative treatment (CT) group. Results were investigated by two-way analysis of variance (ANOVA) and Tukey honest significant difference (HSD) test. RESULTS: The highest biaxial flexural strength was observed in the Si group (950.2 ± 126.7 MPa), followed by the LTD group (861.3 ± 166.8 MPa), CT group (851.2 ± 126.5 MPa), and the least with ML (820 ± 110 MPa). A significant difference was observed in the two-way ANOVA test. X-ray diffraction (XRD) analysis showed that the control group consists of 100% tetragonal zirconia and the maximum amount of monoclinic phase was obtained after LTD. CONCLUSION: No negative effect on biaxial flexural strength was observed; indeed, it increases the biaxial strength. Hence, these surface treatments can be done in routine clinical practice to improve the performance of ceramic restoration.

Definitive guiding flange prosthesis: A definitive approach in segmental mandibulectomy defect.

Mandibular discontinuity defects following a segmental mandibulectomy defects present a major challenge to the rehabilitation team. With no immediate intervention to rehabilitate the patient, definitive mandibular guidance prostheses with a metal guiding flange and acrylic teeth on the resected side can be used successfully to stabilize the occlusion and correct the deviation. The present case report describes the prosthodontic rehabilitation of a patient with a segmental mandibulectomy using a mandibular prosthesis with a metal guide flange and a maxillary stabilizing metal framework.

Effect of palatal form on movement of teeth during processing of complete denture prosthesis: An in-vitro study.

AIM: The aim of this in-vitro study was to assess the influence of shallow and deep palatal forms on the movement of teeth during the processing of complete denture prosthesis. MATERIALS AND METHODS: Maxillary casts with shallow and deep palatal forms were selected and duplicated to make 10 casts of each palatal form. Base plates were constructed and teeth were arranged in their anatomic positions. Metal pins with true apex were placed on the central groove of the right and left first molars and one on the incisive papilla area as a reference point. Casts were scanned using i-CAT Vision Q 1.9 (i-CAT cone beam 3D dental imaging system by Imaging Sciences International, PA, USA), which has 360° rotational tomography. The distances between the apices of metallic pin inserts on the teeth and fitted point of reference were recorded in buccopalatal axes at waxed up stage, after deflasking, and after finishing and polishing. RESULTS: Results showed a statistically significant movement of teeth in shallow and deep palatal forms during all stages of complete denture processing. In shallow palatal form dentures, there was a significant tooth movement in palatal direction between Stages 1 and 2 (P ≤ 0.05) and buccal movement between Stages 2 and 3. In deep palatal form dentures, teeth showed a statistically significant (P ≤ 0.05) movement in buccal direction during all stages of denture processing. CONCLUSION: Teeth showed significant movement during processing of acrylic resin dentures. Overall, the movement of teeth in shallow palatal form dentures was in palatal direction, whereas in deep palatal form dentures, the movement of teeth was in buccal direction.