Recent Advances in 3D Printing of Polymers for Application in Prosthodontics.

Contemporary mass media frequently depict 3D printing as a technology with widespread utilization in the creation of dental prosthetics. This paper endeavors to provide an evidence-based assessment of the current scope of 3D printing's integration within dental laboratories and practices. Its primary objective is to offer a systematic evaluation of the existing applications of 3D-printing technology within the realm of dental prosthetic restorations. Furthermore, this article delves into potential prospects, while also critically examining the sustained relevance of conventional dental laboratory services and manufacturing procedures. The central focus of this article is to expound upon the extent to which 3D printing is presently harnessed for crafting dental prosthetic appliances. By presenting verifiable data and factual insights, this article aspires to elucidate the actual implementation of 3D printing in prosthetic dentistry and its seamless integration into dental practices. The aim of this narrative review is twofold: firstly, to provide an informed and unbiased evaluation of the role that 3D printing currently plays within dental laboratories and practices; and secondly, to instigate contemplation on the transformative potential of this technology, both in terms of its contemporary impact and its future implications, while maintaining a balanced consideration of traditional dental approaches.

Application of Soft Relining Materials in Dental Medicine - Clinical Results.

AIM: The objective of this study was to carry out an in vivo investigation of patients wearing dentures relined with soft materials, assuming their positive and negative alterations in time. MATERIALS AND METHODS: A direct survey method was used to gather data from 23 patients included in this study (11 male and 12 female patients). Twenty-seven dentures were made (12 partial and 15 total dentures) 9 of which in chairside procedures, 11 - in a laboratory, and 7 were made using the direct-indirect method. Patients were included in regular follow-ups at one month and six months, and at one, two, and three years after dentures delivery. The study started in 2014 and continued till 2017. RESULTS AND DISCUSSION: All participants completed questionnaires which included questions related to changes in retention and stability of the relined dentures, changes in color and softness, in bond strength, and inflammation. CONCLUSION: There were no significant differences in the behavior of the different groups of materials at six months. After six months we observed decline in the bond strength of the vinyl-polysiloxane (VPS) materials, as well as increased staining and hardness in the poly-methyl-methacrylate (PMMA).

Analysis of stresses in hard dental tissues generated by clinical application of retentive root canal posts.

INTRODUCTION: Exact adjustment of retentive posts to the length of root canals is an important prerequisite for the effectiveness of post systems. AIM: To determine stresses generated in hard dental tissues of upper and lower canines by the application of root canal posts. MATERIAL AND METHODS: The finite element method was used to create models of upper and lower canines. Loading by a vertical force of Pw = 24 N and a horizontal force of Pv = 15 N was investigated. Twenty two partial dentures and total overdentures in 17 patients were constructed and retained by devices for intraroot retention, placed in canine roots. 16 upper and lower canines were restored by steel posts and composite resin cores. RESULTS AND DISCUSSION: Equivalent stresses were the greatest at the opening of the root canal. Their maximal values during horizontal loading (6.2 - 6.8 MPa) were several times as high as the values during vertical loading (1.0 - 1.1 MPa). The maximal equivalent stresses were in the range of 20 - 25 MPa, when the diameter of the root canal was 1.5 x 10(-3) mm smaller than the diameter of the post. CONCLUSIONS: Stresses generated in canine roots with retentive posts during horizontal loading are greater than the stresses induced by vertical loading. Attempts for forceful placement of posts in insufficiently enlarged root canals produce stresses of considerable magnitude which could result in cracks and fractures of hard dental tissues.

Injection Shrinkage аnd Water Sorption of Some Thermoplastic Dental Materials

Objective: To evaluate the change of diameter of different injection-molded thermoplastic materials. Material and Methods: Four thermoplastic injection-molded materials were analyzed (Bre.flex 2nd edition, Vertex ThermoSens, Perflex Biosens and Polyan IC). A total of 432 test samples were made in the form of an "hourglass". All samples were divided into three groups: Group I (Control) - consisting of 36 test samples for each type of material, that was not exposed to artificial aging or a wet environment; Group II - consisting of 36 test samples for each type of material, that were artificially aged through dehydration; Group III - specimen were subjected to artificial aging without dehydration. The diameter of each specimen was measured with a digital caliper. Data were analysed using the Student's t-test. Results: Regarding to shrinkage, the samples from the Bf Control group have a mean value of 1.56 mm and was observed a shrinkage of the injection-molded polyamide material within 0.25%. The comparison between the samples from Group II and Group III showed statistically significant differences (p<0.001). There were no significant differences between groups for Thermosens and Biosens (p>0.05). The comparison between Group II and Group III for Polyan IC samples shows that Group III has a higher arithmetic mean value (p<0.01). Conclusion: Shrinkage of the polymers during the injection process is present in all materials. The thermocycling and the storage in a dry or in a wet environment of the samples results in a change of the diameter in almost every single type of material.

Phenomenon of domination of the strongest contacts in centric occlusion.

OBJECTIVE: The number and distribution of occlusal contacts in centric occlusion (CO) and centric relation have been studied by a number of authors. All these studies have one thing in common--they define the greatest number of occlusal contacts between the molars. The purpose of the present study was to register the maximum clenching forces in CO, as well as to analyze the anatomic and functional factors that determine their localization on teeth. METHOD AND MATERIALS: The study included 42 subjects, aged 19 to 26 years, with intact dentition and Class I Angle occlusion; 38 persons had 1 to 4 restorations on the premolars and molars. The occlusal contacts were investigated in CO by the T-Scan system (Sentek) on wax and silicone impressions. The force loads in different sections of the dentition were differentiated by an additionally developed computer program. RESULTS: The T-Scan analysis and the developed computer program revealed that the maximum values of the clenching forces were recorded on the third molars. The strongest contacts found by the T-Scan system were successfully visualized in wax and silicone impressions. CONCLUSION: The maximum clenching forces of the masticatory muscles recorded by the T-Scan system were located in CO at the third molars in a dentition of 32 teeth and at the second molars in a dentition of 28 teeth. If the above-mentioned phenomenon is not taken into consideration in clinical practice, occlusal contacts may be created that will unfavorably transfer the specific clenching forces to a more medially located molar in cases of occlusal restoration of the same molar by a restoration or a single crown.