Assessment of physical/mechanical properties and cytotoxicity of dual-cured resin cements containing Sr-bioactive glass nanoparticles and calcium phosphate.

The aim was to develop dual-cured resin cements containing Sr-bioactive glass nanoparticles (Sr-BGNPs; 5 or 10 wt%) and monocalcium phosphate monohydrate (MCPM; 3 or 6 wt%). Effects of additives on degree of monomer conversion (DC), biaxial flexural strength/modulus, shear bond strength (SBS), mass/volume change, color stability, ion release, and cytotoxicity were examined. Controls included material without reactive fillers and Panavia SA Plus (PV). Experimental cements showed higher DC than PV regardless of light activation (p<0.05). Mean SBS and color stability were comparable between experimental cements and PV. Cell viability upon the exposure to sample extracts of experimental cements was 80%-92%. High additive concentrations led to lower strength and modulus than PV (p<0.05). The additives increased mass change, reduced color stability, and promoted ion release. The experimental resin cements demonstrated acceptable mechanical/chemical properties and cytotoxicity. The additives reduced the strength but provided ion release, a desirable action to prevent recurrent caries.

Quantitative parameters of digital occlusal analysis in dental implant supported restorative reconstruction recent 5 years: a systematic review.

OBJECTIVE: The aims of this systematic review were to evaluate the clinical masticatory performance of implant-supported restorations, observe the occlusal force changes in the distribution of the implant restoration and reveal the positive and negative contributing factors of implant design and components based on the outcomes of digital occlusal measurement. MATERIAL AND METHODS: An extensive search was conducted through PubMed and CENTRAL to identify clinical trials on implant-retained restorations using digital occlusal analysis methods. Two researchers assessed the identified studies and data extraction independently, and the data synthesis strategies without meta-analysis that summarizes the effect estimates were adopted. RESULTS: The search screened 3821 titles and abstracts, then full-text analysis for 26 articles was performed, and 14 studies were included in the quantitative synthesis. Four of six studies for implant-retained overdenture showed statistically significant improved bite force when immediate loading (p = .00045, .00005, .00055, and .00005, respectively), and no statistically significant results in the other two studies (p = .225, .371, respectively.) However, the results of the favoured intervention were not statistically significant (p = .104, .166, respectively) in two studies of single posterior implant restorations. In all three studies, the bite force distributed on the implant prostheses of partially fixed implant-retained restoration increased statistically significantly (p = .013, .001, .05, respectively). CONCLUSIONS: The edentulous restoration supported by implants seems to significantly improves bite force and chewing efficiency compared with conventional dentures. Regular quantitative occlusal measurement is recommended to avoid the possible risk of overload. Smaller implants size and relatively small and flexible attachment designs may be more conducive to the stability and retention of the restoration of atrophy of alveolar bone.

Effects of Sr/F-Bioactive Glass Nanoparticles and Calcium Phosphate on Monomer Conversion, Biaxial Flexural Strength, Surface Microhardness, Mass/Volume Changes, and Color Stability of Dual-Cured Dental Composites for Core Build-Up Materials.

This study prepared composites for core build-up containing Sr/F bioactive glass nanoparticles (Sr/F-BGNPs) and monocalcium phosphate monohydrate (MCPM) to prevent dental caries. The effect of the additives on the physical/mechanical properties of the materials was examined. Dual-cured resin composites were prepared using dimethacrylate monomers with added Sr/F-BGNPs (5 or 10 wt%) and MCPM (3 or 6 wt%). The additives reduced the light-activated monomer conversion by ~10%, but their effect on the conversion upon self-curing was negligible. The conversions of light-curing or self-curing polymerization of the experimental materials were greater than that of the commercial material. The additives reduced biaxial flexural strength (191 to 155 MPa), modulus (4.4 to 3.3), and surface microhardness (53 to 45 VHN). These values were comparable to that of the commercial material or within the acceptable range of the standard. The changes in the experimental composites' mass and volume (~1%) were similar to that of the commercial comparison. The color change of the commercial material (1.0) was lower than that of the experimental composites (1.5-5.8). The addition of Sr/F-BGNPs and MCPM negatively affected the physical/mechanical properties of the composites, but the results were satisfactory except for color stability.

Biomechanical Aspects of Various Attachments for Implant Overdentures: A Review.

There have been considerable recent technological developments for implant overdenture attachments. This study presents an overview of the biomechanical and biomolecular aspects of various attachments for implant overdenture. Available articles on attachments for implant overdenture were reviewed from January 1980 to August 2021 in the ScienceDirect, MEDLINE/PubMed, and Web of Science resources, and relevant studies were included in this study. We focused on the following topics: attachment systems, retention of various attachments, stress distribution with different attachments, the design and fabrication of attachments, digital techniques in overdenture attachments, and the effects of attachments in peri-implant health. We found that plastic resin is commonly used for ball and bar attachments, whereas nylon resin is commonly used in locator attachments. The locator system offers a valuable attachment option for implant-retained overdenture. Attachment retention reduces while lateral force increases with implant inclination in overdenture. The higher the retention of an overdenture attachment, the higher the transferred stresses. Additionally, clip loading produces more stress in implants and precision elements than bar-retained dentures. As such, we conclude that the ball and locator systems the best overdenture systems due to their superior tissue response, survival rate, and patient satisfaction.

Accurate Tongue-Palate Pressure Sensing Device to Study Speech Production and Swallowing in Patients with Complete Denture.

OBJECTIVES: The mechanical interactions between tongue and palate are crucial for speech production and swallowing. In this study, we presented examples of pressure signals that can be recorded with our PRESLA system (PRESLA holds for the French expression "PRESsion de la LAngue" [Pressure from the tongue]) to assess these motor functions, and we illustrate which issues can be tackled with such a system. MATERIALS AND METHODS: A single French-speaking edentulous subject, old wearer of a complete denture, with no speech production and swallowing disorders, was recorded during the production of nonsense words including French alveolar fricatives, and during dry and water swallowing. The PRESLA system used strain-gauge transducers that were inserted into holes drilled in the palatal surface of a duplicate of the prosthesis at six locations that were relevant for speech production and swallowing. Pressure signals were postsynchronized with the motor tasks based on audio signals. RESULTS: Patterns of temporal variations of the pressure exerted by the tongue on the palate are shown for the two studied motor tasks. It is shown for our single subject that patterns for fricative /s/ are essentially bell shaped, whereas pressure signals observed for water swallow begin with a maximum followed by a slow decrease during the rest of the positive pressure phase. Pressure magnitude is almost 20 times larger for water swallow than for /s/ production. CONCLUSIONS: This study illustrates the usefulness of our PRESLA system for studying speech production and swallowing motor control under normal and pathological conditions.

Study of tongue-palate pressure patterns during the hold phase in the production of French denti-alveolar and velar stops.

The hold phase of the stop consonants is crucial for a successful production of the release and the acoustic burst. Concurrently, it is also associated with weak acoustic energy and minimal movement, so that conventional acoustic and kinematic approaches are not relevant to investigate motor control. This paper presents an innovative experimental method to study speech motor control during this phase, based on meticulous measurement of the time variation of the mechanical pressure exerted by the tongue against the palate and also characterizing tongue-palate interaction. The concept is based on using miniature transducers with enhanced response characteristics inserted in different locations of the complete denture of edentulous subjects without perturbing the articulation. The study was done with a French-speaking adult whose maxillary denture was duplicated and mounted with six strain gauge transducers. The experiment was done with denti-alveolar and velar stop consonants with two vowel contexts. The results illustrate the potential of such device to analyse speech motor control when contact constrains tongue movements.