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1.
J Contemp Dent Pract ; 22(3): 219-223, 2021 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-34210918

RESUMEN

AIM AND OBJECTIVE: This study aims to evaluate the effect of different resin cements on the bond strength (BS) of custom-made glass fiber posts (GFPs) using the push-out test. MATERIALS AND METHODS: Twenty-four uniradicular bovine teeth were selected. The crowns were sectioned at the cementoenamel junction, and the root canals were treated. The post spaces of the teeth were prepared to a length of 12 mm to receive a GFP. The specimens were randomly assigned to three experimental groups (n = 8), according to the resin cement used to fix the GFPs: RelyX U200 (U200), Allcem Core (ACC), and Allcem Dual (ACD). Each specimen was sectioned into six slices per root third (cervical, middle, and apical), which were subjected to the push-out test. BS values were calculated and compared using the Kruskal-Wallis and Friedman tests. RESULTS: There were significant differences in the middle third, according to the resin cement type used (p < 0.05). ACD showed lower BS values (p < 0.05). Significant differences were observed for ACD among the thirds of the slices, with the lowest values also observed for the middle third (p < 0.05). CONCLUSION: The present study shows that ACC and U200 showed higher BS values compared with ACD, and were also less influenced by the depth of the root dentin. CLINICAL SIGNIFICANCE: The restoration of endodontically treated teeth is a challenge in dentistry, and, in most cases, will require installation of fiberglass pins. In this respect, several types of resin cements are indicated for cementation of these pins; for this reason, their adhesiveness must be adequately investigated. Conventional cements and self-adhesive cements have shown satisfactory performance in cementing the custom-made GFPs, thereby making these cements satisfactory clinical choices. The present study suggests that ACD had lower performance than the other two cements evaluated.


Asunto(s)
Recubrimiento Dental Adhesivo , Técnica de Perno Muñón , Animales , Bovinos , Cavidad Pulpar , Análisis del Estrés Dental , Dentina , Vidrio , Ensayo de Materiales , Cementos de Resina
2.
J Adhes Dent ; 23(4): 309-318, 2021 Jul 23.
Artículo en Inglés | MEDLINE | ID: mdl-34269541

RESUMEN

PURPOSE: Thanks to adhesive techniques and strengthened glass ceramics, ultrathin bonded occlusal veneers have been recently introduced. However, since a universally accepted thickness limit for ultrathin ceramics has yet to be established, their resistance to fracture needs to be better investigated. The purpose of this in vitro study was to evaluate the effect of dentin bonding on the flexural properties (ie, fracture load and flexural strength) of a lithium-disilicate (LD) glass ceramic when used in thicknesses equal to or less than the manufacturer's recommendations for occlusal restorations. MATERIALS AND METHODS: A total of 96 dentin slices (2.0 mm thick and 15 mm long) were obtained by sectioning bovine teeth along their long axes. LD slices of different thicknesses (1.5 mm/1.3 mm/1.0 mm/0.8 mm/0.6 mm) and 15 mm in length were cut from CAD/CAM LD blocks (IPS e.max CAD-C16). In each of 5 experimental groups, 16 dentin slices were adhesively luted to 16 LD slices (n = 16) of the same thickness, in order to create 16 bi-layered dentin-LD bonded assemblies. In the control group, the 16 remaining dentin slices were conventionally cemented to 1.5-mm-thick LD slices (n = 16) using a resin-modified glass-ionomer cement (FujiCEM 2). All dentin-LD assemblies were cut perpendicularly to their joint interface, in order to obtain 1-mm-wide, 15-mm-long bi-layered prismatic beams, having the following final thicknesses: for the 5 experimental groups, 2 mm (dentin layer) + 1.5 mm/ 1.3 mm/1.0 mm/0.8 mm/0.6 mm (LD layer); for the control group, 2 mm (dentin layer) + 1.5 mm (LD layer). All prismatic beams were subjected to a three-point bending test (14-mm span, load applied on the LD side). Fracture loads (N) and flexural strengths (MPa) were recorded. Data were analyzed using one-way ANOVA on ranks tests (α = 0.05). The correlations between the recorded flexural strengths and the dentin:LD thickness ratio and between the flexural strength and the luting strategy were also investigated. The failure modes were observed and classified. RESULTS: No statistically significant differences were recorded between the conventionally luted control group (LD thickness 1.5 mm; fracture load 35.26 N; flexural strength 60.44 MPa) and the thinnest adhesively luted experimental group (LD thickness 0.6 mm; fracture load 28.97 N; flexural strength 90.01 MPa) in terms of fracture load and flexural strength. A fracture involving both the dentin and the LD of the bi-layered prismatic beam, but without any debonding between the LD and the dentin substrates of the broken specimen, was the most common failure mode observed on the adhesively luted samples. CONCLUSION: Compared to conventional cementation, when LD is bonded to dentin, the flexural properties of the whole system are improved, and the two different substrates seem to behave like a single unit. Once adhesively luted, 0.6-mm-thick LD has the same fracture load and flexural strength as that of the conventionally luted 1.5-mm-thick LD.


Asunto(s)
Resistencia Flexional , Litio , Animales , Bovinos , Cerámica , Diseño Asistido por Computadora , Porcelana Dental , Análisis del Estrés Dental , Dentina , Ensayo de Materiales , Propiedades de Superficie
3.
Head Face Med ; 17(1): 24, 2021 Jul 07.
Artículo en Inglés | MEDLINE | ID: mdl-34233698

RESUMEN

BACKGROUND: Determine the exact slot dimension of a sample of a MBT prescription stainless steel conventional brackets from different manufacturers to compare the actual values with the nominal ones declared by the manufacturers and to verify the compliance with tolerance limits given by the ISO 27020:2019. Different batches from each manufacturer were evaluated to determine whether or not they are different in size. In addition, the geometry of the slot walls was assessed. METHODS: 360 stainless steel preadjusted orthodontic brackets of 12 different manufacturers were assessed. All brackets had a nominal slot size of 0.022 by 0.028 inches, belonged to the right upper central incisor, and were fabricated with the metal injection molding technique (MIM). For each manufacturer, three different manufacturing batches were evaluated. Brackets were coded using a single-blind design. RESULTS: All bracket systems in the study group except one displayed a statistically significant difference with the nominal declared value, although only four of the systems did not comply with the tolerance limits established by the ISO 27020:2019. In most of the systems, the slot height was oversized when compared to the nominal one. A significant interbatch variability was found in most of the evaluated systems. Most of the brackets walls were divergent. CONCLUSIONS: The dimensional accuracy of commercially available metal brackets is not guaranteed. The respect for the norm should be enforced as well as the quality controls along the manufacturing process since orthodontic brackets are a precision medical device.


Asunto(s)
Soportes Ortodóncicos , Análisis del Estrés Dental , Humanos , Ensayo de Materiales , Diseño de Aparato Ortodóncico , Alambres para Ortodoncia , Método Simple Ciego , Acero Inoxidable
4.
J Contemp Dent Pract ; 22(4): 422-426, 2021 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-34267013

RESUMEN

AIM: The aim of this literature review is to determine whether endocrowns are a reliable alternative for endodontically treated teeth with extensive loss of tooth structure, the indications and contraindications of this restorative choice, the principles that should be followed for tooth preparation and which material is most appropriate for endocrown fabrication. BACKGROUND: Rehabilitation of endodontically treated teeth with severe coronal destruction has always been a challenge for the dental clinician. Until recently, the fabrication of a metal-ceramic or all-ceramic full-coverage crown along with a metal or glass fiber post has been the "gold standard" proving its efficacy via numerous clinical studies. With the development of CAD/CAM technology and the evolution of dental materials, new minimally invasive techniques have been introduced with less need for adjustments and less incorporation of structural defects. One of them, the "monoblock technique," proposed by Pissis in 1995, was the forerunner of endocrown restoration, a term used by Bindl and Mörmann to describe an all-ceramic crown anchored to the internal portion of the pulp chamber and on the cavity margins, thus obtaining macromechanical retention provided by the axial opposing pulpal walls and microretention attained with the use of adhesive cementation. REVIEW RESULTS: Endocrowns require a decay-oriented preparation taking advantage of both the adhesion and the retention from the pulp-chamber walls, they are strongly indicated in endodontically treated molars in cases where minimal interocclusal space and curved or narrow root canals are present and they should be manufactured from materials that can be bonded to the tooth structure. CONCLUSION: Endocrowns are a reliable alternative to traditional restorative choices, given that the clinicians respect the requirements and indications describing this technique. CLINICAL SIGNIFICANCE: Traditional restorative techniques demanding tooth substance removal and minimizing the opportunity for reinterventions should be reconsidered.


Asunto(s)
Coronas , Diente no Vital , Porcelana Dental , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Humanos , Ensayo de Materiales
5.
Indian J Dent Res ; 32(1): 98-103, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34269245

RESUMEN

Objective: This study aimed to evaluate the effects of Coca-Cola®, Sprite®, and Maaza® on Microleakage, shear bond strength (SBS) and adhesive remnants underneath orthodontic brackets. Materials and Methods: A total of 192 human premolar teeth were used in this study. The sample was divided into four groups: Artificial saliva (control) [Group 1], Coca-Cola [Group 2], Sprite [Group 3] and Maaza [Group 4]. All the samples were stored in artificial saliva and immersed in their respective testing media (except the control group) for 15 minutes 3 times a day, separated by intervals of 8 hours. The immersion cycle was repeated for 15 days. After the immersion cycle, 24 teeth from each group were tested for SBS and adhesive remnant index subsequently. The remaining 24 teeth from each group underwent dyeing with methylene blue and were analyzed stereomicroscopically to evaluate microleakage underneath the brackets. Kolmogorov-Smirnov and Shapiro normality tests were performed and homogeneity of variance was tested with the Levene test. One-way ANOVA and Kruskal-Wallis tests were carried out separately for SBS, ARI and microleakage. Statistical analyses were performed using SPSS 20 for Windows (SPSS Inc., Chicago) software. Results: Coca-Cola showed a significant reduction in SBS and microleakage (p < 0.05) compared to the other groups. ARI did not show any significant differences between any groups (p > 0.05). The mean microleakage scores were higher for the gingival side of the brackets compared to the incisal side. Both Sprite and Maaza showed significant differences compared to artificial saliva, despite the SBS not being statistically significant (p > 0.05). Conclusions: A significant reduction of SBS was observed in Coca-Cola while increased microleakage was seen in all three drinks compared to artificial saliva.


Asunto(s)
Recubrimiento Dental Adhesivo , Soportes Ortodóncicos , Bebidas Gaseosas , Cementos Dentales , Análisis del Estrés Dental , Humanos , Ensayo de Materiales , Soportes Ortodóncicos/efectos adversos , Resistencia al Corte , Propiedades de Superficie
6.
Int J Esthet Dent ; 16(3): 262-279, 2021 Aug 17.
Artículo en Inglés | MEDLINE | ID: mdl-34319663

RESUMEN

AIM: To investigate whether different restoration designs, overlay types, and full crowns in posterior teeth have similarly acceptable marginal sealing and quality. MATERIALS AND METHODS: For Part 1 of the present study (investigation of fracture resistance), 70 extracted molars were divided into five groups (N = 14), prepared with four different posterior indirect adhesive restoration (PIAR) overlay design types, according to the adhesthetics classification. The groups were: 1. Butt Joint; 2. Full Bevel; 3. Shoulder; 4. Full Crown; 5. Sound Tooth. For Part 2 of the study (present article; marginal quality), there was no group 5, and only 56 of the 70 extracted molars were used. Seven expert dentists performed all the preparation and cementation phases with codified protocols. A CAD/CAM workflow was used to realize the 56 monolithic lithium disilicate restorations. The samples were tested with thermomechanical loading (TML) and the marginal quality evaluated. The data relating to fracture resistance are presented in Part 1 of this study (Int J Esthet Dent 2021;16:2-17). RESULTS AND CONCLUSIONS: In terms of marginal quality after TML, within the limitations of the present study, in molar teeth (without endodontic treatments) restored with different monolithic ceramic lithium disilicate PIAR designs, it is possible to present the following conclusions.


Asunto(s)
Coronas , Diseño de Prótesis Dental , Cementación , Cerámica , Diseño Asistido por Computadora , Cementos Dentales , Porcelana Dental , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Humanos , Ensayo de Materiales
7.
J Clin Pediatr Dent ; 45(3): 171-176, 2021 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-34192760

RESUMEN

The purpose of this study was to determine and compare the shear force (N) required to fracture or dislodge an all-ceramic zirconia-based crown using different luting cement with those of polycarbonate crown and strip crown for the primary anterior teeth in vitro. STUDY DESIGN: Four groups of esthetic restoration for primary anterior teeth were tested for fracture strength: 1) Fifteen all-ceramic zirconia-based crowns cemented with glass ionomer cement, 2) Fifteen all-ceramic zirconia-based crowns bonded with a self-adhesive resin cement, 3) Fifteen polycarbonate crowns cemented with a polymer reinforced zinc-oxide eugenol and 4) Fifteen resin strip crowns. All restorations were placed and cemented on reproductions of dies in an independent laboratory at Delhi, India. All samples underwent loading until fracture or dislodgement with the Universal Testing Machine. The force in Newton (N) required to produce failure was recorded for each sample and the type of failures was also noted and characterized. One-way analysis of variance (ANOVA) test and the Tukey and Scheffe's post hoc comparisons were used for statistical analyses. RESULTS: In this invitro study, results were measured in Newtons (N). Group 1 (410.9±79.5 N) and Group 2 (420.5±57.8 N) had higher fracture strength than Group 3 (330.3±85.6 N) and Group 4 (268.4±28.2 N). These differences were statistically significant at P≤.05 among the sample groups. No significant difference was found between groups 1 and 2 (P = 0.984) nor between groups 3 and 4 (P =0.104). Among type of failures, majority of restoration fractures for zirconia-based crowns and resin strip crowns were due to cohesive failures and polycarbonate crowns had predominantly mixed failures. CONCLUSIONS: Under the limitations of this in vitro study, it could be concluded that all-ceramic zirconia-based crowns attained the highest fracture strength among all restorative samples tested regardless of the type of luting agent employed (P<.01). Cohesive failures were commonly observed in the zirconia crowns and resin strip crowns, whereas polycarbonate crowns revealed predominately mixed failures.


Asunto(s)
Estética Dental , Resistencia Flexional , Coronas , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Humanos , India , Ensayo de Materiales , Cementos de Resina , Diente Primario , Circonio
8.
J Mech Behav Biomed Mater ; 120: 104565, 2021 08.
Artículo en Inglés | MEDLINE | ID: mdl-34087536

RESUMEN

OBJECTIVES: The aim of this work was to evaluate the biomechanical behavior of one-piece zirconia implants with a functionally graded bioglass (BG) layer as compared to monolithic zirconia and BG-coated implants, using the finite element method (FEM). METHODS: Zirconia disks were infiltrated with bioglass S53P4 and then morphologically inspected by scanning electron microscopy (SEM) followed by mechanical analyses on micro-indentation tests for further biomechanical validation using the finite element method (FEM). On modeling, zirconia dental implants anchored into mandibular bone were simulated on occlusal loading as recorded under mastication. Three types of implants were simulated: i) free of BG coating, ii) with 100 µm or 150 µm thick conventional BG coatings; and iii) with graded BG coatings involving 3 different chemical composition distributions. The stress state at both implant and bone were evaluated using the FEM. The mechanically-induced bone remodelling was analyzed through the bone strain results. RESULTS: Infiltration of BG into a zirconia structure resulted in a ∼100 µm thick layer with an exponential-like gradation of chemical composition and properties. Regarding the FEM calculations, the BG coating induced up to 30% decrease on stress in the implant body when compared to the monolithic zirconia implant. The gradient of chemical composition also improved the stresses' distribution. The stresses distribution towards the BG-coatings were significantly high and could lead to failure. Stresses on the bone were recorded down to its strength threshold, with insignificant influence of the coating layer. The bone strain values on all models indicates further bone remodelling although BG-coated and BG-graded zirconia implants showed the highest strain magnitude that may enhance the mechanical stimulation for bone maintenance. SIGNIFICANCE: Graded BG-zirconia dental implants showed enhanced overall biomechanical behaviour as compared to the BG-coated or monolithic zirconia dental implants. Also, such biomechanical improvements noticed for the BG-graded system should be considered in combination with the well-known osseointegration benefits of bioactive glasses.


Asunto(s)
Implantes Dentales , Fenómenos Biomecánicos , Cerámica , Análisis del Estrés Dental , Análisis de Elementos Finitos , Estrés Mecánico , Circonio
9.
Comput Methods Biomech Biomed Engin ; 24(4): 358-374, 2021 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-34121526

RESUMEN

Finite element analysis was used to compare the effect of different implant lengths on atrophic mandible with full-arch fixed prostheses. Four models were constructed with different implant lengths: 4, 6, 8 and 10 mm. A 100-N occlusal load was applied. The stress at the bone level, implant, and prosthetic components were obtained. Similar behavior was observed for all groups, except for 4 mm, which showed more discrepant values ​​for all prosthetic components. Although longer implants presented better biomechanical behavior, the 4 mm implant seems to be a viable alternative for severely atrophic mandibles, however, further studies need to be carried out.


Asunto(s)
Implantes Dentales , Diseño de Prótesis Dental , Prótesis Dental de Soporte Implantado , Análisis del Estrés Dental , Mandíbula/cirugía , Boca Edéntula/cirugía , Atrofia , Fenómenos Biomecánicos , Tornillos Óseos , Pilares Dentales , Análisis de Elementos Finitos , Humanos , Soporte de Peso
10.
Am J Dent ; 34(3): 157-162, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-34143586

RESUMEN

PURPOSE: To evaluate the effect of different substrate stiffness [sound dentin (SD), resin composite core (RC) or metal core (MC)] on the stress distribution of a zirconia posterior three-unit fixed partial denture (FPD). METHODS: The abutment teeth (first molar and first premolar) were modeled, containing 1.5 mm of axial reduction, and converging axial walls. A static structural analysis was performed using a finite element method and the maximum principal stress criterion to analyze the fixed partial denture (FPD) and the cement layers of both abutment teeth. The materials were considered isotropic, linear, elastic, homogeneous and with bonded contacts. An axial load (300 N) was applied to the occlusal surface of the second premolar. RESULTS: The region of the prosthetic connectors showed the highest tensile stress magnitude in the FPD structure depending on the substrate stiffness with different core materials. The highest stress peak was observed with the use of MC (116.4 MPa) compared to RC and SD. For the cement layer, RC showed the highest values in the molar abutment (14.7 MPa) and the highest values for the premolar abutment (14.4 MPa) compared to SD (14.1 and 13.4 MPa) and MC (13.8 and 13.3 MPa). Both metal core and resin composite core produced adequate stress concentration in the zirconia fixed partial denture during the load incidence. However, more flexible substrates, such as composite cores, can increase the tensile stress magnitude on the cement. CLINICAL SIGNIFICANCE: The present study shows that the choice of the cast core and metallic post by the resin composite core and fiberglass post did not improve the biomechanical behavior of the FPD. This choice must be performed based on clinical criteria (other) than mechanical.


Asunto(s)
Dentadura Parcial Fija , Circonio , Análisis del Estrés Dental , Análisis de Elementos Finitos , Estrés Mecánico
11.
Am J Dent ; 34(3): 171-176, 2021 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-34143589

RESUMEN

PURPOSE: To evaluate the stress distribution of inlays fabricated with restorative materials of different elastic moduli under two functional loading conditions by using three-dimensional (3D) finite element analysis (FEA) models of a second maxillary premolar. METHODS: A 3D model of a sound maxillary left second premolar and its supporting bone was generated in a previous study and reutilized under permission of the authors for the present study. Inlay models obtained from the sound tooth were then assigned according to the type and inherent elastic modulus of the restorative material used, as follows: microhybrid composite (Filtek Z250); indirect resin composite (Paradigm); lithium disilicate reinforced glass ceramic (IPS e.max Press); and type III gold alloy. The geometric models were then exported for 3D FEA. All materials were considered isotropic, homogeneous, and linear-elastic. A static load of 100 N was applied in two conditions: axially at both cusps (axial loading) and at the mesial marginal ridge (proximal loading). Maximum principal and von Mises stresses were used to analyze the stress distribution pattern in inlays and sound premolar models. RESULTS: Under axial loading condition, either resin composite, ceramic or type III gold alloy inlays generated a similar biomechanical behavior, especially in terms of stress distribution in the remaining tooth structure and cusp deflection. However, higher tensile stresses were observed along the proximal gingival margin of the preparation under proximal loading in the Z250 and Paradigm models, as well as a greater cusp deflection. In contrast, a deflection like the sound model was observed in the ceramic and gold inlay models. CLINICAL SIGNIFICANCE: Restorative materials with higher elastic modulus, such as dental ceramics and type III gold alloys, seem to be the best choice for maxillary premolars restored with inlays in the presence of occlusal contact on the marginal ridge.


Asunto(s)
Porcelana Dental , Incrustaciones , Diente Premolar , Resinas Compuestas , Materiales Dentales , Análisis del Estrés Dental , Análisis de Elementos Finitos , Ensayo de Materiales , Estrés Mecánico
12.
Int J Oral Maxillofac Implants ; 36(3): 423-431, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34115054

RESUMEN

PURPOSE: Bone density and implant primary stability parameters have been introduced that are based on calculating (1) the average of the instantaneous torque needed to keep the rotation speed of a bone density probe constant while it descends into bone or (2) the integral of the instantaneous torque-depth curve at implant insertion (I), a quantity that is equal to the insertion energy multiplied by a constant. This study aimed to determine how these two quantities are affected by the presence and thickness of a cortical bone layer. MATERIALS AND METHODS: An instantaneous torque-measuring micromotor was used to measure the density of six double-layer polyurethane foam blocks mimicking different cortical/cancellous bone combinations. Twenty measurements per block were collected, averaged, and compared. The insertion torque and the integral (I) of the instantaneous torque-depth curve at implant insertion were recorded when 20 3.75 × 12-mm cylindrical implants were inserted in each of nine blocks, including three single-layer blocks simulating the absence of a cortical layer, under three final cortical (countersink) preparations: 4.0, 3.7, and 3.5 mm. The relationship between the insertion torque, the integral of the instantaneous torque-depth curve at implant insertion (I), cortical thickness, and the final diameter preparation were investigated with regression and best-fit slope analyses. RESULTS: Bone density measurements showed that the average of the instantaneous torque at probing allowed differentiation of five of six different bone classes (hard-hard, hard-normal, hard-soft, normal-normal, normal-soft, soft-soft); the post hoc analysis of variance (ANOVA) comparisons were all statistically significant except for the hard-soft-normal-soft pair. The insertion torque and the integral (I) of the instantaneous torque-depth curve at implant insertion increased proportionally with cortical bone thickness (Pearson's r > 0.96 in all cases). CONCLUSION: When the final preparation varied from 3.7 mm to 3.5 mm, the insertion torque-thickness plot slope did not change significantly, while that of the instantaneous torquedepth curve integral (I)-thickness plot did change, suggesting that the torque-depth curve at implant insertion integral (I) may detect the increase in implant stability consequent to slight anatomical changes or changes in the site preparation protocol better than the insertion torque when measuring the cortical bone layer stress while undergoing insertion. These findings concerning bone density and primary stability should be investigated further using different experimental settings. If confirmed, they might generate improvements in the predictability of implant and prosthetic rehabilitation outcomes.


Asunto(s)
Implantación Dental Endoósea , Implantes Dentales , Densidad Ósea , Análisis del Estrés Dental , Poliuretanos , Torque
13.
Int J Oral Maxillofac Implants ; 36(3): 451-459, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34115058

RESUMEN

PURPOSE: Microcomputed tomography (micro-CT) is a relatively new modality to investigate mechanical deformations. The purpose of this study was to assess the microgap at the implant-sleeve connection of a new two-piece dental implant with a replaceable sleeve. MATERIALS AND METHODS: Implants were assembled with 25-degree angulated abutments. Micro-CT was used to assess implant-sleeve connection gaps under the following mechanical conditions: (1) unloading; (2) compressive 10,000 cyclic loading with 400 N; (3) static compressive load of 200 N or 400 N for 24 hours. RESULTS: The mean gap in the unloaded sample was 2.9 ± 0.9 µm. The mean gap difference after cyclic compressive load was 0.3 ± 0.15 µm, demonstrating a negligible effect for the cyclic loading. Under static compressive load, there was no increase in microgap size at 200 N. At 400 N, a significant (P < .05) increase was noted. While the mean values increased by 1.9 µm, the most pronounced significant increase in mean microgap was noted in the direction of force application (5.1 ± 2.14 µm), while a significant decrease in mean microgap (1.2 ± 1.47 µm) was noted on the opposite side. CONCLUSION: The mechanical behavior of the implant-sleeve connection under static and dynamic loads was found to be within the previously reported range of implant dentistry.


Asunto(s)
Implantes Dentales , Pilares Dentales , Diseño de Implante Dental-Pilar , Análisis del Estrés Dental , Ensayo de Materiales , Microtomografía por Rayos X
14.
Int J Oral Maxillofac Implants ; 36(3): 485-491, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34115062

RESUMEN

PURPOSE: To evaluate the factors that could influence the fracture resistance of implant-supported posterior monolithic zirconia crowns. MATERIALS AND METHODS: Sixty zirconia molar crowns with three different occlusal thicknesses of 0.5, 1.0, and 1.5 mm (20 samples per group) were prepared for implant abutments using a CAD/CAM system. In each group, 10 crowns were luted on the abutment with resin cement (Panavia F), and the other 10 crowns were luted with resin-modified glass-ionomer cement (Ketac Cem Plus). Dynamic loading (1.2 × 106 cycles; 70 N) and thermal cycling were applied to the samples using a chewing simulator before evaluating their fracture resistance with a universal testing machine and examining their fracture type using a stereomicroscope. One-way analysis of variance (ANOVA), the Duncan test, and two-way ANOVA were used for data evaluation (α = .05). RESULTS: The occlusal thickness (P < .001) and cement type (P < .01) affected the fracture load of the monolithic zirconia crowns. The highest fracture resistance was found in 1.5-mm-thick crowns luted with resin cement (4,212 ± 501 N), and the lowest fracture resistance was found in 0.5-mm and 1-mmthick crowns luted with resin-modified glass-ionomer cement (1,198 ± 116 N and 1,197 ± 66 N). A significant difference was not found in the mean maximum fracture load between the 1.5-mm-thick crowns cemented with resin cement and glass-ionomer resin cement. CONCLUSION: Both the occlusal thickness and cement type remarkably affected the fracture resistance of the crowns, but occlusal thickness was more significant. Implant-supported posterior zirconia crowns can withstand physiologic occlusal forces even with a thickness as low as 0.5 mm. Resin luting cement is recommended for implant-supported posterior zirconia crowns with reduced occlusal thickness.


Asunto(s)
Implantes Dentales , Porcelana Dental , Diseño Asistido por Computadora , Coronas , Diseño de Prótesis Dental , Análisis del Estrés Dental , Cementos de Ionómero Vitreo , Ensayo de Materiales , Cementos de Resina , Circonio
15.
Int J Oral Maxillofac Implants ; 36(3): 492-501, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34115063

RESUMEN

PURPOSE: To evaluate the abutment removal torque and the morphologic aspects of wear in frictional Morse taper connections after axial loading with or without biofilm immersion. MATERIALS AND METHODS: Thirty sets of Morse taper implants and prosthetic abutments were divided into six groups based on the number of mechanical loading cycles and immersion in biofilm derived from human saliva: without load, without biofilm; without load, with biofilm; 100,000 cycles of load, without biofilm; 100,000 cycles of load, with biofilm; 500,000 cycles of load, without biofilm; and 500,000 cycles of load, with biofilm. Mechanical loading was applied at a force of 80 ± 15 N with a frequency of 2 Hz for 100,000 or 500,000 cycles. After removal torque evaluation, the internal surface of the implants was evaluated by scanning electron microscopy and optical profilometer. The results were statistically analyzed at a significance level of P = .05. RESULTS: Overall, the removal torque increased for samples submitted to loading (100,000 cycles of load, without biofilm = 83.8 ± 15.8 Ncm; 100,000 cycles of load, with biofilm = 160.6 ± 16.2 Ncm; 500,000 cycles of load, without biofilm = 147.0 ± 29.3 Ncm; 500,000 cycles of load, with biofilm = 154.5 ± 14.0 Ncm) compared to samples without loading (without load, without biofilm = 23.0 ± 9.4 Ncm; without load, with biofilm = 27.2 ± 7.5 Ncm). The removal torque was not different between groups that received the same number of loading cycles and varied on biofilm exposure (P > .05). However, samples immersed in biofilm showed higher values of removal torque. Surface analysis revealed that the damage on the internal surface of implants was lower in samples not submitted to cyclic mechanical loading (P < .05) independently of immersion in biofilm medium. CONCLUSION: Cyclic mechanical load on the frictional implant-abutment connection of Morse taper implants increased the removal torque of abutments. The findings of this research suggest that the presence of biofilm can potentially increase the removal torque in frictional Morse taper connections, although more studies are recommended to support this affirmation. Oral biofilm did not interfere with the presence of wear areas along the internal surface of Morse taper implants but increased the roughness values.


Asunto(s)
Diseño de Implante Dental-Pilar , Implantes Dentales , Biopelículas , Pilares Dentales , Análisis del Estrés Dental , Humanos , Ensayo de Materiales , Torque
16.
Int J Oral Maxillofac Implants ; 36(3): e51-e62, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34115067

RESUMEN

PURPOSE: Clinical cases have shown that pterygoid implants are a successful alternative solution for the rehabilitation of atrophic posterior maxillae; however, little research on the biomechanical behavior has been produced. This study created 3D models of pterygoid implant-supported prostheses and compared the stress and strain distributions in the pterygoid implants and surrounding bone using finite element analysis. MATERIALS AND METHODS: Three-dimensional models of a standardized human skull, pterygoid implants, and conventional dental implants were created using Simpleware, based on microcomputed tomography (micro-CT) and CBCT images. Six constructs with varying implant positions and numbers were designed to simulate various clinical scenarios for patients with complete maxillary edentulism. Finite element volume meshes were created and exported to ABAQUS, where the modulus of elasticity and Poisson ratio were assigned for each respective structure. Two load scenarios were simulated with conditions as follows: (1) 150-N axial loading; and (2) 150-N axial loading with simultaneous 50-N lateral loading. Then, the Von Mises stress and maximum principle strain distributions for all models were collected, analyzed, and compared. RESULTS: The maximum stress and strain in the pterygoid implants and surrounding bone under both loading scenarios were found in model 4, which had two pterygoid implants and two anterior implants, at the implant-abutment connection and crestal bone of the premolar region, respectively. The stress and strain in the pterygoid implants for all constructs analyzed were at values within the limit of material strength. Additionally, the stress and strain in the surrounding bone for all constructs analyzed were at values within the bone resorption threshold. The maximum stress in the surrounding bone for all models with pterygoid implants was lower than the stress in the control model, which contained no pterygoid implants. CONCLUSION: Pterygoid implants decreased the stress and strain level in the surrounding bone for all cases studied. Additional concern should be placed on the crestal bone of the premolar region and the implant-abutment connections of the pterygoid implants, since these locations had the highest recorded values.


Asunto(s)
Implantes Dentales , Maxilar , Fenómenos Biomecánicos , Prótesis Dental de Soporte Implantado , Análisis del Estrés Dental , Análisis de Elementos Finitos , Humanos , Maxilar/diagnóstico por imagen , Maxilar/cirugía , Estrés Mecánico , Microtomografía por Rayos X
17.
Int J Oral Maxillofac Implants ; 36(3): 538-545, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34115069

RESUMEN

PURPOSE: The purpose of this study was to survey practicing clinicians and determine if differences existed concerning their use of torque-limiting devices (TLDs) and screw-tightening protocols, comparing this with existing universal industry standards. MATERIALS AND METHODS: A nine-question survey was administered with 428 dentists providing data for three specific areas: (1) demographic information-TLD ownership, device age, frequency of use, and observations of screw loosening; (2) recognition information-calibration, reading measurements of the TLD, and the meaning of preload; (3) usage information-screw-tightening protocols and effect of speed during actioning of the TLD. Data collection was compared with industry standards for use of hand torque tools including ISO-6789 1,2:2017 and related texts pertaining to screw fastener protocols. RESULTS: The beam-type TLD was the most popular; however, 33% surveyed used it incorrectly. Most TLDs being used were older than 1 year, with only 6% calibrated. Forty-eight percent observed screw loosening less than once per year, while 44% reported three or more occurrences per year. A similar number used the TLD for implant placement and abutment screw tightening. Screw-tightening protocols varied. Preload was not understood by the majority of those surveyed. CONCLUSION: Dentistry does not appear to adhere to the protocols and standards recommended by other industries that also rely on screw-fastening mechanisms and TLDs. Further education and training appears to be warranted in this area of implant dentistry to reduce the risks of screw-associated complications.


Asunto(s)
Pilares Dentales , Implantes Dentales , Tornillos Óseos , Análisis del Estrés Dental , Torque
18.
Int J Oral Maxillofac Implants ; 36(3): 569-573, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34115073

RESUMEN

PURPOSE: The aim of this preclinical study was to evaluate whether implant flossing could leave floss residues in three different implant-prosthetic conditions. MATERIALS AND METHODS: Using an anatomical model, three different conditions were studied: correct connection between the implant and abutment and complete insertion of the implant threads into the plaster (control group); misfit of approximately 220 to 230 µm between the implant platform and abutment in the absence of any thread exposure (misfit group); partial exposure of implant threads but absence of misfit (thread group). Twenty-one microstructured tapered threaded implants were divided among the three groups. Each sample was subjected to a flossing procedure using spongy floss, standardized in terms of movement, frequency, time, and pressure. Subsequently, a stereomicroscope examination with a standardized magnification of 10× was performed in order to highlight the possible presence of floss residues on the implant surface. RESULTS: No floss residue was ever detected for the control group. Both misfit and thread groups showed floss residues that were discernible in two different types: microfilaments and amorphous particles. Statistical analysis showed a significant difference for the presence of floss remnants between the control group and the other two experimental groups (P = .005). No difference was observed between the misfit and thread groups. CONCLUSION: This study shows that exposed threads and misfit can induce the release of floss residues during maintenance procedures.


Asunto(s)
Pilares Dentales , Implantes Dentales , Implantes Dentales/efectos adversos , Análisis del Estrés Dental
19.
Stomatologiia (Mosk) ; 100(3): 13-18, 2021.
Artículo en Ruso | MEDLINE | ID: mdl-34180619

RESUMEN

OBJECTIVE: To study the effect of the occlusal surface of a natural tooth, cement-retained and screw-retained fixed partial dentures supported by dental implants and the coefficient of friction on the stress distribution in the peri-implant bone at maximum and minimum principal stresses. MATERIAL AND METHODS: Study of maximum and minimum principal stresses in models with natural teeth and artificial crowns supported by dental implants, taking into account the coefficient of friction using the finite element analysis. RESULTS: In models represented by fixed partial dentures supported by dental implants and a natural tooth, the maximum tensile stresses arise in the cortical bone in the cervical region of the artificial crown, and the maximum compressive stresses occur both in the cortical layer in the cervical region of the artificial crown and in the cervical region of the tooth. In models with two fixed partial dentures supported by dental implants or two natural teeth, the stress distributions in the cortical layers in the upper and lower jaw are almost identical. CONCLUSION: Modeling the antagonist and adding to the FEA model is important in order to determine the precise and realistic direction of the resulting force vector. Amplification of the number of contact areas should be considered when modeling the occlusal surface of artificial crowns supported by dental implants.


Asunto(s)
Implantes Dentales , Boca Edéntula , Coronas , Prótesis Dental de Soporte Implantado , Análisis del Estrés Dental , Dentadura Parcial Fija , Análisis de Elementos Finitos , Humanos , Estrés Mecánico
20.
J Mech Behav Biomed Mater ; 121: 104604, 2021 09.
Artículo en Inglés | MEDLINE | ID: mdl-34087550

RESUMEN

The aim of this study was to evaluate the effect of in-lab simulation procedures performed on a lithium disilicate ceramic luted to a dentin-analogue material regarding the fatigue performance and topographic changes. Lithium disilicate ceramic (IPS e.max CAD) discs (Ø = 13.5 mm and 1.5 mm of thickness) were produced in different ways: milled in a CAD/CAM system (CAD/CAM - control group); mirror-polished (POL group); produced in-lab and ground with #60 silicon carbide paper (SiC group); with #60 wood sandpaper (WS group); with a fine diamond bur (DB group); or with a CAD/CAM bur adapted in a handpiece with a custom mandrel (MANDREL group). The ceramic discs were adhesively luted (Multilink N) onto dentin analogue discs (Ø = 12 mm and 2 mm of thickness) and fatigue testing (n = 19 discs) was performed by step-stress methodology (initial load of 200 N; step-size of 50 N; 10,000 cycles per step; 20 Hz). Surface roughness and contact angle analysis were also performed. According to Kaplan-Meier and post-hoc Mantel-Cox (log-rank), distinct fabrication methods affected the fatigue performance of bonded glass-ceramic discs (p< 0.001). The CAD/CAM group presented the lowest fatigue failure loads (1250 N) and number of cycles for failure (185,000), while the POL groups obtained the highest results (1752 N; 284,444 cycles). The in-lab groups had intermediate values (1355 - 1526 N; 206,052 - 238,684 cycles). Polished specimens presented the lowest roughness values (Ra = 0.041 µm), while the SiC (1.604 µm), WS (1.701 µm), and MANDREL (1.867 µm) groups showed statistically similar roughness values to the CAD/CAM group (1.738 µm). Despite differences before etching, the contact angle was similar among the milled and simulated groups after etching, except for the polished group. Even with some topographic similarities, the tested in-lab simulation methods were not able to mimic the milled specimens in terms of fatigue findings, leading to distinct magnitude of overestimations of the results.


Asunto(s)
Cerámica , Diseño Asistido por Computadora , Porcelana Dental , Análisis del Estrés Dental , Ensayo de Materiales , Propiedades de Superficie
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