In vivo vs. in vitro color stability of hybrid ceramic and resin nanoceramic blocks used for endocrowns: A new method.

PURPOSE: To evaluate and compare in vitro and in vivo color parameters of hybrid ceramic, resin nanoceramic, and artificial acrylic resin teeth. METHODS: For the in vitro stages, 120 specimens (2 mm) were prepared from Vita Enamic (VE), Lava Ultimate (LU), CeraSmart (CS), and acrylic teeth (IV), and immersed in coffee, red wine, and distilled water for 24, 72, and 144 hours. For the in vivo stage, 16 individuals received a complete denture that had upper premolars made of VE, LU, CS blocks, and IV. The color was measured at 1, 3, and 6 months. Color difference (ΔE00), translucency (TP), and contrast ratio (CR) were obtained using a spectrophotometer. Shapiro Wilk, one-way ANOVA, and repeated measures ANOVA were used for statistical analysis. RESULTS: ΔE00 of VE and LU were higher than CS and IV (P< 0.05). ΔTP of VE and LU were lower than CS and IV (P< 0.05). ΔTP of CS was higher in red wine compared to coffee. ΔCR of CS and IV were increased with prolonged immersion (P< 0.001). ΔE00 and ΔCR were similarly affected in coffee and red wine. All discolorations were higher than clinical acceptability (ΔE00> 1.77). For in vivo stages, ΔE00 of VE and LU increased over time (P< 0.01). No difference was detected between in vivo and in vitro ΔE00 of CS (P> 0.05). ΔE00 of VE, LU, and IV was higher in in vitro stages. LU and VE showed lower color stability; their use in esthetic regions is questionable. The prolonged immersion increased discoloration. Coffee and red wine had a similar effect on discoloration and opalescence. Discoloration in laboratory conditions did not correspond to the clinical discoloration according to the new method presented in this study. CLINICAL SIGNIFICANCE: The use of CAD-CAM blocks for endocrowns is rising; however, Lava Ultimate and Vita Enamic showed lower color stability, thus, their use in esthetic regions is questionable. This is the first study that investigates the discoloration of CAD-CAM blocks in clinical use. Discoloration in laboratory conditions did not correspond to the clinical discoloration.

Biomechanical properties of a 3D printing polymer for provisional restorations and artificial teeth.

OBJECTIVES: To characterize a resin-based polymer used for 3D printing (3D) provisional restorations and artificial teeth by evaluating relevant material's properties (flexural strength (σf), elastic modulus (E), water sorption (Wsp) and solubility (Wsl)) and biocompatibility, and comparing to a bis-acryl composite resin (BA) and a heat-cured acrylic resin (AR). METHODS: Structures were fabricated from 3D, BA and AR. Bar-shaped specimens (n = 30) were submitted to three-point flexure (in 37ºC water and constant displacement rate: 1 ± 0.3 mm/min) until fracture to calculate σf and E. Additional specimens (n = 30) were aged in 37ºC distilled water for six months before testing for σf. Disc-shaped specimens (n = 5) were dried in desiccators and oven until weight stability was reached, then they were immersed in distilled water for seven days, weighed and submitted to the drying process to obtain Wsp and Wsl. SRB and MTT assays were used to evaluate biocompatibility. Data were statistically analyzed using Kruskal Wallis, Student-Newman-Keuls (α = .05), and Weibull distribution. ANOVA and Tukey (α = .05) were used to evaluate the biocompatibility data. RESULTS: 3D structures showed higher σf than AR after aging. The BA showed the lowest values for σf and E, at baseline and after aging. All materials showed Wsp and Wsl values within the recommended standard values. AR structures showed lower cell viability (71.9%) than 3D (92.9%) and BA (90.8%) when using the SRB test. No difference was found when using MTT (p > .05). SIGNIFICANCE: The evaluated polymer-based 3D printing material showed adequate biomechanical behavior for using as a provisional restoration and artificial teeth.

Orthodontic shear bond strength and ultimate load tests of CAD/CAM produced artificial teeth.

OBJECTIVES: To investigate whether artificial CAD/CAM processed (computer-aided design/manufacturing) teeth could be a feasible option for the production of dental in vitro models for biomechanical testing. MATERIAL AND METHODS: Disks (n = 10 per group) made from two different CAD/CAM-materials, one fiber-reinforced composite (FRC; Trinia, Bicon) and one polymethylmethacrylate-based resin (PMMA; Telio CAD, Ivoclar Vivadent), as well as bovine teeth (n = 10), were tested for their shear bond strength (SBS) and scored according to the adhesive remnant index (ARI). In addition, CAD/CAM-manufactured lower incisor teeth were tested for their ultimate load (Fu). RESULTS: With regard to SBS, both PMMA (17.4 ± 2.2 MPa) and FRC (18.0 ± 2.4 MPa) disks showed no significant difference (p = 0.968) compared to bovine disks (18.0 ± 5.4 MPa). However, the samples differed with regard to their failure mode (PMMA: ARI 4, delamination failure; FRC: ARI 0 and bovine: ARI 1.6, both adhesive failure). With regard to Fu, FRC-based teeth could withstand significantly higher loads (708 ± 126 N) than PMMA-based teeth (345 ± 109 N) (p < 0.01). CONCLUSION: Unlike PMMA-based teeth, teeth made from FRC showed sufficiently high fracture resistance and comparable SBS. Thus, FRC teeth could be a promising alternative for the production of dental in vitro models for orthodontic testing. CLINICAL RELEVANCE: CAD/CAM-processed teeth made from FRC enable the use of standardized geometry and constant material properties. Using FRC teeth in dental in vitro studies has therefore the potential to identify differences between various treatment options with rather small sample sizes, while remaining close to the clinical situation.

[Automated digital superimposition of the 3D model and archival photographs of full removable dentures in forensic dentistry]. / Avtomatizirovannoe tsifrovoe issledovanie v sudebno-stomatologicheskoi ekspertize dlya sopostavleniya ob"emnoi modeli i arkhivnykh fotografii polnykh s"emnykh protezov.

THE AIM THE STUDY: The purpose of the work is to perform automated alignment of two-dimensional archival photographs of the first prosthesis and a digital model of the complete removable prosthesis by superposition in order to determine or deny their possible belonging to one user. MATERIALS END METHODS: The superposition was carried out in the Exocad program (DentalCAD 3.0 Galway) using the standard 2D-3D alignment algorithm of the «SmileDesign¼ module; in the same program. In addition, Keynote and Fusion 360, and Autodesk programs were used. Statistical measurements were carried out at the statistically significant level of p<0.05. RESULTS: A comparison of four different-angle and different-scale photographic images of a removable denture of the upper jaw teeth with a three-dimensional copy of the same version of the prosthesis of the life physician of the royal family E.S. Botkin was made. When superimposing a digital three-dimensional model and a two-dimensional photograph of the original prosthesis with marked anthropometric points (n=51), 21 of them coincided or touched each other (41.2%). Another 26 points were located side by side (distance up to 1.5 mm) (50.9%) and 4 did not coincide (distance >1.5 mm, but no more than 3.5-4 mm) (7.8%). When the reference points were combined, the contours, the configuration of the relief and the peripheral boundaries of all three objects mostly coincided. The linear longitudinal and transverse dimensions of the bases of the prostheses also mostly coincided. The exception was the distal border of the bases, and the level of the cutting edges of the anterior artificial teeth, where complete coincidence was not observed, due to differences in the degree of erasability. CONCLUSION: Comparison of the original prosthesis from Ipatiev's house and its stereolithographic model was a test for the accuracy of the matching method used. The stereotype of the compared images is proved and the consistency of the possibility of computer combination of three-dimensional and two-dimensional objects is confirmed. The use of traditional methods of forensic identification and evaluation of the results by methods of mathematical statistics allowed us to conclude that the two different complete removable dentures of the upper jaw depicted in the photographs belong to one user.

Comparison of two optical devices used for artificial tooth color selection.

BACKGROUND: Correct color assessment and the selection of the color of the prosthetic restoration are important aspects of prosthetic treatment, which significantly affect the success of the treatment. OBJECTIVES: The aim of this study was to compare 2 commercial devices used for tooth color selection. MATERIAL AND METHODS: The color of maxillary right central incisors and right canines was assessed in a group 100 patients aged 22-40 years (25.11 ±3.24 years), using the Easyshade® spectrophotometer and the ShadeStar® colorimeter. Two visual shade guides were used as references for the tests - VITA VITAPAN® Classical and VITA 3D­Master. The 2 instruments and the 2 visual shade guides were assessed in terms of agreement in tooth color selection. RESULTS: There were statistically significant differences between the 2 instruments in terms of agreement in tooth color selection as well as between the 2 shade guides. The VITA VITAPAN Classical shade guide was shown to be more accurate in tooth color selection than VITA 3D­Master. There was agreement between the Easyshade spectrophotometer and ShadeStar colorimeter measurements for incisors in 49% of cases with the VITA VITAPAN Classical shade guide and in 22% of cases with VITA 3D­Master. In the comparative analysis of the Easyshade and ShadeStar devices with regard to the measurements performed on canines there was 52% agreement for the VITA VITAPAN Classical shade guide and 32% agreement for VITA 3D­Master. CONCLUSIONS: The VITA VITAPAN Classical system demonstrated superior agreement in shade selection as compared to the VITA 3D­Master system. A low degree of agreement between the optical devices used in the selection of the color of artificial teeth may indicate optical differences between devices from different manufacturers.

Effect of retention hole designs in artificial teeth on failure resistance of the connection with thermoplastic resin.

This study aimed to evaluate the effect of retention hole designs in artificial teeth on failure resistance of the connection with a thermoplastic denture base resin. Artificial teeth with the following retention hole designs were attached to polyester and polyamide resins: no hole, vertical hole, horizontal hole, and vertical and horizontal holes. An artificial tooth with no hole attached to polymethyl methacrylate was prepared as the control. The load was applied until connection failure occurred between the artificial tooth and resin, and failure resistance was detected. Although the control showed the highest resistance, the artificial tooth with vertical and horizontal holes showed higher resistance than those with other retention hole designs in both thermoplastic resins. Providing vertical and horizontal retention holes in artificial teeth may be effective in improving failure resistance of the connection with thermoplastic resins.

Characterization of various acrylate based artificial teeth for denture fabrication.

Acrylic resins-based artificial teeth are frequently used for the fabrication of dentures has and contribute a very strong share in the global market. However, the scientific literature reporting the comparative analysis data of various artificial teeth is scarce. Focusing on that, the present study investigated various types of commercially available artificial teeth, composed of polymethyl methacrylate (PMMA). Artificial teeth are characterized for chemical analysis, morphological features, thermal analysis, and mechanical properties (surface hardness, compressive strength). Different types of artificial teeth showed distinct mechanical (compression strength, Vickers hardness) and thermal properties (thermal gravimetric analysis) which may be attributed to the difference in the content of PMMA and type and quantity of different fillers in their composition. Thermogravimetric analysis (TGA) results exhibited that vinyl end groups of PMMA degraded above 200 °C, whereas 340-400 °C maximum degradation temperature was measured by differential thermal analysis (DTA) for all samples. Crisma brand showed the highest compressive strength and young modulus (88.6 MPa and 1654 MPa) while the lowest value of Vickers hardness was demonstrated by Pigeon and Vital brands. Scanning electron microscope (SEM) photographs showed that Crisma, Pigeon, and Vital exhibited characteristics of a brittle fracture; however, Artis and Well bite brands contained elongated voids on their surfaces. According to the mechanical analysis and SEM data, Well bite teeth showed a significantly higher mechanical strength compared to other groups. However, no considerable difference was observed in Vickers hardness of all groups. Graphical abstract.

Effects of conventional and heated tobacco product smoking on discoloration of artificial denture teeth.

STATEMENT OF PROBLEM: Cigarette smoke can cause discoloration of artificial denture teeth. However, studies on the effects of heated tobacco product smoke on artificial denture teeth are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effects of conventional cigarette and heated tobacco product smoke on the color stability of artificial denture teeth. MATERIAL AND METHODS: Ninety maxillary central incisor denture teeth (Endura Anterior HC5 A3; Shofu) were randomly divided into 3 groups (n=30). Teeth in the control group were exposed to air; those in group CC were exposed to conventional cigarette (Marlboro Medium; Philip Morris) smoke, and those in group HT were exposed to heated tobacco product (IQOS 2.4 plus holder, Marlboro Heets Silver; Philip Morris) smoke. Before the experiment, the shade of the artificial denture teeth was evaluated in accordance with the Commission International de I'Eclairage (CIELab) color system by using a spectrophotometer (Shadepilot; DeguDent GmbH). The average CIELab value was estimated by scanning the entire labial surface of each specimen. To simulate smoking, standard conditions described by the Coresta Recommended Method N°22 were used-the puff duration was 2 seconds, with a 60-second interval between puffs. For each cigarette, 6 puffs and 6 intervals were simulated across 372 seconds. A total of 105 cigarettes were used based on a smoking simulation of 15 cigarettes each day for 7 days. The teeth in the control group were stored in fresh air in the smoke chamber for the same period as those in the experimental groups. After the experiment, L∗, a∗, and b∗ values were measured, and ΔE was calculated to evaluate the color change. All statistical analyses were performed with a statistical software program using a paired t test to determine discoloration after exposure to cigarette smoke. One-way ANOVA and the Tukey test were used to evaluate the significant differences between groups (α=.05). RESULTS: Lightness was significantly lower in the CC and HT groups (P<.001). All CIELab values showed statistically significant differences in the CC group. The greatest color change was observed in the CC group (ΔE=6.93 ±0.59), whereas the HT group showed a clinically imperceptible color change (ΔE=0.79 ±0.21). Discoloration was minimal in the CC group (ΔE=0.34 ±0.13). CONCLUSIONS: Conventional cigarette and heated tobacco product smoke can change the color of denture teeth. Heated tobacco product smoke causes less discoloration of denture teeth.

CAD-CAM milled complete dentures with custom disks and prefabricated artificial teeth: A dental technique.

A digital complete denture was manufactured from a disk customized for each patient. The custom disk was made of resin and contained prefabricated artificial teeth. Both the denture base and the artificial teeth in the custom disk were milled in this technique, resulting in dentures with a high bond strength between the artificial teeth and denture base, excellent esthetics because of the prefabricated artificial teeth, and accurate occlusion because of the custom occlusal surface.

A systematic review of digital removable partial dentures. Part II: CAD/CAM framework, artificial teeth, and denture base.

PURPOSE: This study comprehensively reviewed the current status of the digital workflow of removable partial dentures (RPDs) and summarized information about the fabrication methods and material properties of the dental framework, artificial teeth, and denture base. STUDY SELECTION: We performed a systematic review of the literature published in online databases from January 1980 to April 2020 regarding RPD fabrication and materials used in the related digital technology. We selected eligible articles, retrieved information regarding digital RPDs, and conducted qualitative/quantitative analyses. In this paper, the computer-aided design/computer-aided manufacturing (CAD/CAM) framework, artificial teeth, and denture base materials are reported. RESULTS: A variety of materials, such as cobalt-chromium alloy, titanium, zirconia, and polyether ether ketone, are used for dental CAD/CAM frameworks. The mechanical strength of the metal materials used for the CAD/CAM framework was superior to that of the cast framework. However, the fitness and surface roughness of the framework and clasp fabricated using a selective laser melting (SLM) method were not superior to those obtained via cast fabrication. Most material properties and the surface roughness of poly methyl methacrylate (PMMA) discs used for digital RPDs were superior to those of heat-cured PMMA. CONCLUSION: The use of a CAD/CAM framework and PMMA disc for digital RPDs offers numerous advantages over conventional RPDs. However, technical challenges regarding the accuracy and durability of adhesion between the framework and denture base remain to be solved. In digital fabrication, human technical factors influence the quality of the framework.

Comparative Effect of Different Surface Treatments on the Shear Bond Strength of Two Types of Artificial Teeth Bonded To Two Types of Denture Base Resins.

PURPOSE: This in vitro study aims to assess the impact of various surface treatments on the shear bond strength (SBS) of two types of artificial teeth and denture base resins (DBRs). MATERIALS AND METHODS: Two types of DBRs (CAD/CAM-milled and heat-polymerized) and two types of denture teeth (acrylic and composite) were investigated. Teeth were cut into slices (5 × 5 × 2 mm) and divided according to surface treatment into four subgroups (n = 10): no treatment (control), air abrasion (Alumina-blasting; AB), bur roughening, and dichloromethane (DCM) subgroups. According to manufacturer recommendations, the treated tooth slices were bonded to the acrylic disk of DBRs. The SBS test was performed using a universal testing machine. ANOVA was used for results analysis followed by Tukey's post hoc tests (α = 0.05). RESULTS: DCM and AB increased the SBS of acrylic teeth to heat-polymerized DBR compared with other groups (p < 0.001). All surface treatments showed no significant difference in CAD/CAM DBR with acrylic teeth (p = 0.059; AB, p = 0.319; bur roughening, p = 0.895; DCM), while there was a significant decrease in SBS with composite teeth (p ˂ 0.001). Between teeth, acrylic teeth showed a statistically significant increase in SBS compared to composite teeth (p < 0.001). CONCLUSION: AB and DCM application improved the SBS for acrylic teeth with the heat-polymerized DBR when compared with the untreated group, but none of the surface treatment agents showed significant improvement with CAD/CAM DBR. All surface treatment agents reduced the SBS for composite teeth with CAD/CAM DBR while AB only increased the SBS with heat-polymerized DBR.

Trueness and precision of artificial teeth in CAD-CAM milled complete dentures with custom disks.

STATEMENT OF PROBLEM: Insufficient information is available regarding the trueness and precision of artificial teeth in computer-aided design and computer-aided manufacturing (CAD-CAM) milled complete dentures fabricated from custom disks, including prefabricated teeth. PURPOSE: The purpose of this in vitro study was to determine the trueness and precision of the position of the artificial teeth arranged in CAD-CAM milled complete dentures manufactured by using a custom disk method and to compare the trueness and precision of different tooth types and the occlusal surface and entire surface of the teeth. MATERIAL AND METHODS: The milling data were designed by using a CAD software program. Four types of artificial teeth (maxillary-left central incisor, mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar) were arranged concentrically in the disk with 3 corresponding teeth per disk. Five custom disks were milled based on the milling data. The sample size for maxillary-left central incisor, mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar was 15. The standard tessellation language data were obtained by scanning the milled disks with cone beam computed tomography. The obtained data were superimposed by using a CAD software program to assess the trueness and precision of the tooth positions. For the occlusal surface, the data were superimposed after trimming to assess the trueness and precision of the tooth position with respect to the entire tooth surface. After data superimposition, the deviation was analyzed by using a 3-dimensional analysis software program to obtain the mean absolute error values and color maps. The data were analyzed by using 2-way ANOVA and the Games-Howell post hoc test (α=.05). RESULTS: Significant differences were found in the mean absolute error values of the position trueness of the entire surface between the different teeth, except for maxillary-left first premolar and maxillary-left first molar (P<.05). Moreover, significant differences in the mean absolute error values of the precision for the entire surface were observed between mandibular-left central incisor and maxillary-left first premolar, as well as between mandibular-left central incisor and maxillary-left first molar (P<.05). The mean absolute error values of the position trueness of the occlusal surface were significantly smaller than those for the entire tooth surface for mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar (P<.05). Finally, the mean absolute error values of the position precision of the occlusal surface were significantly smaller than those for the entire tooth surface for mandibular-left central incisor and maxillary-left first premolar (P<.05). CONCLUSIONS: The trueness and precision of the posterior teeth were higher than that of anterior teeth. The trueness of the movement of the artificial teeth during the manufacturing of dentures by using the custom disk method was found to be within a clinically acceptable range.

Avaliação qualitativa de dentes artificiais de resina acrílica após escovação simulada / Qualitative evaluation of artificial acrylic resin teeth after simulated brushing

Introdução: os dentes artificiais de resina acrílica são amplamente utilizados na confecção de próteses, por apresentarem propriedades físicas, mecânicas e biológicas, além de características de fácil manuseio. No entanto, devido sua característica de baixa resistência à abrasão, a escovação pode levar à perda de massa dos dentes artificiais e aumento da rugosidade. Objetivo: avaliar de forma qualitativa a rugosidade superficial e polimento de dentes artificiais das marcas Hereaus Premium; Trilux e Vita, após período de 1 ano de escovação, com fotografias em Lupa Estereoscópica. Metodologia: para a realização deste estudo, serão utilizados 10 dentes artificiais de cada marca comercial (Trilux, Vita e Hereaus Premium). Os dentes serão fixados com resina ortoftálica em tubo de PVC de 15 mm de espessura. Para o teste de abrasão, será usada uma máquina de escovação simulada com escovas de dentes de cerdas macias e solução de pasta de dente. As imagens serão obtidas com câmera digital acoplada a lupa estereoscópica. A rugosidade superficial e o polimento serão analisados antes da escovação simulada e após 12 meses de escovação através das imagens. Resultados: após o teste de abrasão foi observado a presença de um desgaste superficial e/ou ranhuras na superfície dos dentes artificiais em todos os grupos. Porém não houve um padrão similar entre os corpos de prova de um mesmo grupo. Conclusão: Pode-se concluir que a escovação provocou o aumento da rugosidade superficial e alteração no polimento em todos os dentes artificiais utilizados.

Introduction: acrylic resin artificial teeth are widely used in the manufacture of dentures, as they have physical, mechanical and biological properties, in addition to easy handling characteristics. However, due to its characteristic of low abrasion resistance, brushing can lead to loss of mass of artificial teeth and increase in roughness. Objective: qualitatively evaluate the surface roughness and polishing of artificial teeth of Hereaus Premium brands; Trilux and Vita, after a 1-year brushing period, with photographs using a Stereoscopic Magnifying Glass. Methodology: for this study, 10 artificial teeth of each commercial brand will be used (Trilux, Vita and Hereaus Premium). Teeth will be fixed with orthophthalic resin in a 15 mm thick PVC tube. For the abrasion test, a simulated brushing machine with soft bristle toothbrushes and toothpaste solution will be used. Images will be obtained with a digital camera coupled to a stereoscopic magnifying glass. Surface roughness and polishing will be analyzed before simulated brushing and after 12 months of brushing through the images. Results: after the abrasion test, the presence of surface wear and/ or grooves on the surface of the artificial teeth was observed in all groups. However, there was no similar pattern between the specimens of the same group. Conclusion: it can be concluded that brushing caused an increase in surface roughness and change in polishing in all artificial teeth used.

[Advances in computer aided design and computer aided manufacturing of removable partial denture].

Computer aided design, numerically controlled milling, additive manufacturing and other digital technologies have been widely used in clinical practice of prosthodontics. The application of these technologies not only changed the design and manufacturing workflow of removable partial denture (RPD), but also improved the production efficiency of dentures, and changed the design and manufacturing concept of dentures. A large number of researches on computer aided design and computer aided manufacturing (CAD/CAM) of RPD have emerged in recent years, including researches on the properties of selective laser melting metal powder and other new dental materials, the innovative design of retainers, connectors, artificial teeth and other denture components, high precision manufacturing of the RPD framework, denture base and artificial teeth, quantitative laboratory evaluations of the accuracy, adaption and mechanical properties of RPD with new structures and made of new materials, clinical evaluations of RPD and others. This paper introduces these recent developments in CAD/CAM of RPD.

Impact of artificial teeth occlusal morphology on bimaxillary denture treatment in elderly: a clinical trial.

PURPOSE: To evaluate the performance of complete dentures (CD) with anatomical and nonanatomical teeth in completely edentulous elderly individuals regarding oral health-related quality of life (OHRQoL), satisfaction, masticatory performance (MP), need for adjustment after CD placement, and patient preference for occlusal type. MATERIALS AND METHODS: A randomized crossover clinical trial comprising 50 edentulous elderly individuals was conducted. The participants were divided into two groups: AT-NT (rehabilitated initially with anatomical teeth and 3 months later with nonanatomical teeth) and NT-AT (rehabilitated initially with nonanatomical teeth and 3 months later with anatomical teeth). OHRQoL was analyzed using the OHIP-EDENT; a satisfaction questionnaire was applied; MP was evaluated by the median particle size (×50) after chewing an artificial test food; and the number of adjustments of the prosthesis base was assessed quantitatively. RESULTS: Overall, 34 elderly individuals (mean age: 69 years) were analyzed. No significant difference was observed between CD users with anatomical and nonanatomical teeth for OHRQoL (P = .674), satisfaction (P = .725), MP (P = .849), or number of adjustments (P = .135). Most subjects (52.9%) did not express a preference for any occlusal surface type. However, among those with a preference, the majority (32.4%) opted for nonanatomical teeth. CONCLUSION: Both posterior tooth types are eligible for oral rehabilitation in elderly users of conventional CDs, as the variables were not influenced by occlusal morphology. However, further studies are warranted in highly resorbed mandibular edges or in cases of adaptation difficulties, as the results may differ.

Titanium Wear of Dental Implants from Placement, under Loading and Maintenance Protocols.

The objective of this review was to analyze the process of wear of implants leading to the shedding of titanium particles into the peri-implant hard and soft tissues. Titanium is considered highly biocompatible with low corrosion and toxicity, but recent studies indicate that this understanding may be misleading as the properties of the material change drastically when titanium nanoparticles (NPs) are shed from implant surfaces. These NPs are immunogenic and are associated with a macrophage-mediated inflammatory response by the host. The literature discussed in this review indicates that titanium NPs may be shed from implant surfaces at the time of implant placement, under loading conditions, and during implant maintenance procedures. We also discuss the significance of the micro-gap at the implant-abutment interface and the effect of size of the titanium particles on their toxicology. These findings are significant as the titanium particles can have adverse effects on local soft and hard tissues surrounding implants, implant health and prognosis, and even the health of systemic tissues and organs.

Bond strength of artificial teeth to thermoplastic denture base resin for injection molding.

This research was conducted to investigate the bond strength between artificial teeth and a thermoplastic denture base resin for injection molding with different surface preparations for use in flexible resin removable partial dentures. Composite resin denture teeth and acrylic denture resin teeth were bonded to three types of thermoplastic denture base resins for injection molding (polyamide, polyester, and polycarbonate) and a conventional heat-polymerized polymethyl methacrylate (PMMA) resin (control). The ridge lap surfaces of the artificial teeth were classified into four groups based on the type of ridge lap surface treatment applied (n=10): no treatment, ethyl acetate, small T-shaped tunnel, and large T-shaped tunnel. The specimens were tested for bond strength. The results showed that the ethyl acetate treatment was ineffective for enhancing the bond strength (p>0.05) between the artificial teeth and thermoplastic denture base resin for injection molding, whereas the T-shaped tunnel was quite effective in this regard (p<0.05).

Comparison of artificial tooth position in dentures fabricated by heat curing and additive manufacturing.

BACKGROUND: The purpose of this study was to compare the displacement of tooth arrangement in dentures fabricated by additive manufacturing (AM) and heat curing. METHODS: Three-dimensional (3D) scanning was performed for edentulous jaw models. After the teeth were arranged, 3D scanning for the wax denture was performed. Heat-cured dentures were fabricated with heat-cure polymer resin. Based on data obtained by subtracting the model data from wax denture data, AM dentures were fabricated from ultraviolet-cured acrylic resin. Accuracy was verified by superimposing heat-cured and AM dentures on the tooth region data from the wax dentures and measuring displacement of the tooth arrangement. RESULTS: In the maxillary dentures, the amount of tooth displacement for the heat-cured dentures and for the AM dentures ranged from -0.08 to +0.06 mm and from -0.25 to +0.06 mm respectively. A significant difference was observed between two dentures. In the mandibular dentures, the amount of tooth displacement for the heat-cured dentures and for the AM dentures ranged from -0.09 to +0.07 mm and from -0.03 to +0.07 mm respectively. No significant difference was observed between two dentures. CONCLUSIONS: The artificial teeth of the maxillary dentures fabricated by AM showed a greater displacement compared to those by heat curing.