P. Malara

Selected toxic and essential heavy metals in impacted teeth and the surrounding mandibular bones of people exposed to heavy metals in the environment

BackgroundThe elemental composition of bones and teeth can allow exposure to heavy metals in the environment to be estimated. The aim of this study was to determine whether impacted mandibular teeth and the surrounding bones can be used as biomonitoring media to assess exposure to heavy metals.MethodsThe research materials were 67 impacted lower third molars and samples of the cortical bone removed when the wisdom teeth were surgically extracted. The samples were from people living in two areas with different environmental concentrations of heavy metals. The cadmium, chromium, copper, iron, lead, manganese, and zinc concentrations in the samples were determined by atomic absorption spectrometry with flame atomization.ResultsThe cadmium and lead concentrations in the impacted third molars and the bones surrounding the teeth were significantly higher for people living in the relatively polluted Ruda Slaska region than for people living in Bielsko-Biala region. Significantly higher chromium, copper, manganese, and zinc concentrations were found in the bones surrounding the impacted teeth from people living in Ruda Slaska than in the bones surrounding the impacted teeth from people living in Bielsko-Biala. The cadmium concentrations in impacted teeth and the surrounding bones were significantly positively correlated.ConclusionThe results indicated that impacted mandibular teeth and the surrounding mandibular bones may reflect the exposure of people to cadmium and lead in the environment. This conclusion, however, must be verified in future research projects designed to exclude the possibility of additional dietary, occupational, and other types of exposure to heavy metals.

Use of finite element analysis for the assessment of biomechanical factors related to pain sensation beneath complete dentures during mastication

Statement of problem. The pain commonly suffered by denture wearers during mastication is not documented in the objective biomechanical criteria for the pressure pain threshold. Purpose. The purpose of this finite element analysis study was to determine whether the pressures developed beneath a removable mandibular complete denture during mastication would exceed the average pressure pain threshold in patients for whom the denture foundation had an acceptable load‐bearing capacity. Material and methods. A patient with an acceptable load‐bearing denture foundation was modeled with finite element analysis. The denture/mucosa interface was modeled as a sliding or detaching interface. A convex mandibular residual ridge, resilient mucosa, and denture were modeled in computer‐aided design (CAD) software using curves and cross sections. A unilateral vertical occlusal load of 100 N was assumed only for model verification, and an oblique mastication load of 141 N was assumed for simulated mastication with balanced articulation. The nonworking‐side occlusal contact was simulated in 2 situations: prompt nonworking‐side occlusal contact and delayed nonworking‐side occlusal contact by setting an initial distance of 0.1 mm or 1 mm between the denture and a flat solid above the nonworking side. Results. The denture was held to the mucosa under vertical force and a maximum pressure of 203 kPa. The denture was tilted under an oblique mastication load and achieved stability through nonworking‐side occlusal contact. This means that the denture was supported not only by the denture foundation but also by the nonworking‐side occlusal contact and had a downwardly directed stabilizing reaction force. The denture was weakly supported on the delayed nonworking‐side occlusal contact compared with the prompt nonworking‐side occlusal contact and weakly supported on the denture foundation. In delayed nonworking‐side occlusal contact, the pressure beneath the denture was 783 kPa (>pressure pain threshold) compared with 484 kPa (<pressure pain threshold) in prompt nonworking‐side occlusal contact. Despite the lower reaction force of the foundation in delayed nonworking‐side occlusal contact, the pressure beneath the denture increased, indicating a reduction in the load transfer area due to the inclined position of the denture. Friction on the mucosal surface was over 14‐fold higher for the delayed nonworking‐side occlusal contact. Conclusions. The pressure beneath a removable mandibular complete denture exceeded the average pressure pain threshold and was supported with a large slide, which produced friction. Although the value of the load on the occlusal side did not change, the pressure under the denture increased and the force of nonworking‐side occlusal contact decreased because of increasing distance to nonworking‐side occlusal contact.

Screw-retained full arch restorations –methodology of computer aided designand manufacturing

Purpose: The aim of the paper is to present the designing and manufacturing process of the screw-retained superstructure of the dental arch in the maxilla based on six implants using CAD/CAM technology. Design/methodology/approach: The methodology is presented on the example of the implantoprosthetic treatment in a 55-year-old female patient with a significant deficit of the alveolar bone. 6 implants were placed to achieve a good anchorage for the ceramic suprastructure. The prosthetic reconstruction was milled out of a zirconium dioxide block and covered with veneering ceramics to obtain good aesthetics of the restoration. Special copings were designed and manufactured to achieve stabile connection between the implants and the suprastructure. Findings: To properly plan the prosthetic work rebuilding the alveolar ridge on dental implants it is necessary to plan the final prosthetic work before implant placement planning the number of implants and their location in the bones and the possibility of using a fixed or a mobile suprastructure. Practical implications: Design of the suprastructure has to take into account the following factors: 1. The number of implants, copings and openings for the abutment screws, 2. Arrangement of teeth in the prosthesis, 3. The shape of the alveolar ridge, 4. The shape of the space for the porcelain and for the individual crowns, which will be pasted on the suprastructure. Originality/value: For technological reasons it is not possible to make an extensive suprastructure in a single piece. It is necessary to execute the foundation of the reconstruction of the alveolar ridge and the teeth in one piece and separately the individual crowns. It is possible, however, to design and manufacture the complex screw-retained prosthetic suprastructures by means of CAD/CAM technology.