3D Digital Image Correlation Analysis of the Shrinkage Strain in Four Dual Cure Composite Cements.

The introduction of resin-based cements and an adhesive-bonding system in daily dental practice has given the opportunity to increase the retention of previously conventional cemented restorations and the optimal results in esthetic. This experimental study employed the 3D Digital Image Correlation Method (3D-DIC) for detecting shrinkage strain in four dual cured composite cements. The aim was to visualize measure, analyze, and compare strain fields in four resin-based cements using the 3D-DIC method. A total of 72 samples were divided into 4 groups considering variations in sample types, diameter, and thickness. Four types of composite cements: RelyX U200 (3 M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Multilink Automix (Ivoclar Vivadent, Schaan, Liechtenstein), and SeT PP (SDI, Australia) were used. Each type had diameters of 3 mm, 4 mm, and 5 mm, respectively, combined with two different values of thickness: 1 mm and 2 mm. Thickness had an important role on strain detected in all tested materials showing higher strain in samples with 2 mm thickness compared to 1 mm samples. Shrinkage strain values were the highest in Set PP samples indicated the possibility of undesirable de-bonding.

Association Between Dentition Status and Malnutrition Risk in Serbian Elders.

PURPOSE: The aim of this study was to find the correlation between the number, type, and placement of symmetric functional tooth units and the nutritional status using body mass index (BMI) and Mini Nutritional Assessment (MNA) in patients with both maxillary and mandibular removable partial dentures. MATERIALS AND METHODS: A randomized study was conducted at the Clinic for Prosthodontics, School of Dentistry, University of Belgrade, Serbia, followed by determination of number of functional tooth units. After insertion of the prostheses, the nutritional status was assessed, using BMI and MNA form. Nutritional status was reviewed 12 months after prosthetic treatment. Number of teeth and age were analyzed using analysis of variance and t test. For other variables such as BMI baseline, BMI follow-up, MNA baseline, MNA follow-up, change in BMI, and change in MNA, Kruskal-Wallis Test or Mann-Whitney Test were used. RESULTS: The results on the MNA changes showed that patients with symmetric natural functional tooth units had significantly higher values (2.9 ± 0.8) compared with patients without natural functional tooth units (1.9 ± 0.6) or with asymmetric natural functional tooth units (1.6 ± 0.4). Patients with asymmetric artificial functional tooth units had significantly lower change in MNA (1.9 ± 0.4) than those with symmetric artificial functional tooth units (2.6 ± 0.9). CONCLUSION: The findings of this study suggest that adequate rehabilitation with symmetric positioning of the functional tooth units can improve the nutritional status of partially edentulous patients.

Prevalence and Clinical Effects of Certain Therapy Concepts among Partially Edentulous Serbian Elderly.

PURPOSE: This study was conducted to identify the prevalence of partially edentulous individuals in Serbia and to identify prosthodontic treatment used for their rehabilitation as well as to compare prosthodontic treatment concepts among Serbian elderly participants who answered closed-format questionnaires. MATERIALS AND METHODS: The study was conducted at the Clinic for Dental Prosthetics, University of Belgrade, Military Medical Academy and the Department of Prosthodontics of Home Centre Belgrade; the study consisted of 120 participants. A questionnaire with closed-format questions regarding the influence of applied therapy concepts for participants with Kennedy Class I partial edentulism was created. Statistical software SPSS 11.5 was used for data analysis. Chi-square tests were performed, and p-values were calculated for each parameter. RESULTS: A total of 1081 people were examined; 730 participants were partially edentulous in at least one jaw. Five hundred forty-one participants wore Kennedy Class I maxillary or mandibular removable partial dentures (RPDs). Ninety percent of the patients were restored with RPDs; 60% of participants were unrestored, had shortened dental arches, and requested alternative therapeutic solutions. Significantly lower needs for new treatments were identified in participants with fixed dental prostheses (7.5%). CONCLUSIONS: Kennedy Class I was the most common type of partial edentulism among Serbian elderly, usually treated with RPDs. Elderly participants with the applied shortened dental arch and RPD therapy concepts requested alternative therapeutic solutions more often than those rehabilitated with fixed partial dentures.

Finite element analysis of compressive stress and strain of different implant forms during vertical loading.

This study analyzed the influence of platform switching on the stress/strain distribution of vertically loaded implants. Employing finite element analysis, the aim of this study was to determine the distribution of stresses and strains generated by a simulated vertical load on different implant models positioned in the molar region with respect to changes of implant design and biomechanics. Two different implant designs, one with and one without platform switching, with the same length (11.5 mm) and diameter of (3.80 mm) were analyzed. Both virtual implant-bone models were subjected to a load of 500 N. The results showed that the maximum stress/strain in implant-bone samples was located in the area of the implant neck, with stress/strain values decreasing in the apical direction. It was found that the implant design with platform switching developed lower stresses and strains than the implant design without platform switching.

Optical aspect of deformation analysis in the bone-denture complex.

The aim of this study was to register and measure any deformation of mandible models under load. The method for full field measurement of strain is done by using the ARAMIS three-dimensional image correlation system. The system uses two digital cameras that provide a synchronized stereo view of the specimen and the results show the complete strain field during the tests. The biggest deformation values were just under the working force of the biggest intensity 500 N, and for the region of the lower second premolar the deformation is 625 microm. The following study is presented that highlight the use of stereometric measuring system for modern research. It is shown that this measuring methodology can capture the trends of the experiments.

Analysis of the compressive strain below the removable and fixed prosthesis in the posterior mandible using a digital image correlation method.

It was the purpose of this study to determine and analyse strains in the bone of posterior mandible below the removable and fixed partial dentures using Digital Image Correlation Method. Dried mandible with shortened dental arch (Kennedy Class 1) was used in the experiment. The mandible model was prepared for accepting two types of restorations for bilaterally missing molars conventional therapy, and removable and fixed partial dentures were manufactured following standard prosthetic protocol. The models with prosthetic restorations placed in situ were subjected to loading of 50-300 N, and photographed using two digital cameras as part of the digital image correlation method equipment. Afterwards, the obtained data for strains within restored mandible during loading ciclus were analysed in the software Aramis and graphically presented. Percentage size of the mandible strains within the line section are from 0.14 to 0.19% for the removable partial denture experimental model and 0-0.14% for the fixed partial denture experimental model. The study has demonstrated that Digital Image Correlation method can be used to measure strain on the mandible surface and replacements during loading and that from biomechanical perspective both therapeutic modalities can be equally useful for the restoration of the mandible with bilaterally distal edentulous spaces.

Biomechanical behavior of restored and unrestored mandible with shortened dental arch under vertical loading condition.

The aim of this in vitro study was to investigate the strain distribution of the compressed mandible bone under the applied restoration- removable partial denture and to compare with the same but unrestored mandible under vertical (occlusal) load and to find out whether removable partial denture-restored or unrestored mandible causes greater strain effect on supporting tissue. Four mandible models were tested during loading for the purpose of strain measuring. Digital image correlation system (GOM - German Optical Measuring, Braunschweig, Germany), used for measuring strain consists of two digital cameras and software ARAMIS (6.2.0, Braunschweig, Germany). Remaining teeth suffer from greater strain in the mandible model without removable partial denture (7.5-10%). On the contrary, mandible with removable partial denture shows the maximum strain below the denture saddle (3.5%). However, it can be noticed that the marginal bone of the second lower praemolar in both experimental models is deformed whether the mandible model has (2.8%) or has not (10%) replacement. Within the limitations of this study the higher strain is observed in mandible model without replacement and the strain is limited locally, in the bone region that surrounds remaining teeth and mental foramen.

Compressive strains and displacement in a partially dentate lower jaw rehabilitated with two different treatment modalities.

BACKGROUND: Understanding of the biomechanical consequences of the stresses generated to the supporting bone during occlusal loading is significant for improving the design and clinical planning process in partial edentulism therapy. OBJECTIVE: The aim of this study was to analyse the distribution of strain and displacement on the partially dentate lower jaw rehabilitated with an partial denture (RPD) and to compare it to the strain and displacement distribution on a partially dentate lower jaw rehabilitated with a cantilever fixed partial denture (FPD). MATERIAL AND METHODS: The experimental models were a partially dentate mandible with full-arch PFM crowns and RPD and a partially dentate mandible rehabilitated with a full-arch cantilever FPD. Strains and displacement were measured using the Digital Image Correlation Method. RESULTS: Displacement values of the first experimental model ranged from 0.31 to 0.54 mm with strains from 1.35 to 2.34%. Analysis of the second experimental model results showed displacement values from 0 to 0.34 mm, while strains were in the range of 0-1.40%. CONCLUSION: Higher displacements and strains of bone tissue were observed below the RPD, especially in the region of the distal abutment and distal portion of the free-end saddle. Strains within bone and the bone-denture contact area were mostly influenced by the teeth and denture vertical displacement.

Optical metrology analysis of the lower jaw deformations.

BACKGROUND/AIM: New optical stereometric methods based on both contact and noncontact mechanisms for displacement measurement have become common methods in biomechanical behavior research of biomaterials, bone and soft tissue. The aim of this study was to register and measure possible deformations of the lower jaw (mandible) with the intact dental arch using optical metrology method. METHODS: The system for full field measurement of deformations (strains) comprised of two digital cameras for a synchronized stereoview of the specimen, and the Aramis software. RESULTS: The maximum mandibular bone strains were measured in the regions of the lower first premolar and the lower second molar. In the action force of 500 N simulated in the region of the first lower premolar the intensity of deformation was 86 microm. The value of maximum strain in the bone around the molars was 24 microm for the force of 500 N acting on the second lower molar. When it comes to premolars, 3-5 times stronger deformation was observed in the region of the first lower premolar, compared to the deformation values of the second lower premolar area. CONCLUSION: Under loading of the applied forces the measured strains were in the elastic deformation area, meanning that the dependence of force and deformity is linear. The highest values of strain measurements obtained by the optical method were found in the jaw bone tissue around the loading teeth, and the bony regions of the triangle and mental region. According to the obtained results from the Aramis processing software it can be concluded that this method is applicable in a variety of biomedical research.