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1.
Angle Orthod ; 88(2): 227-232, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29337632

RESUMO

OBJECTIVES: To test a proof-of-concept that the accuracy and reliability of alveolar bone height measurements from orthodontic grade (large field-of-view [FOV], large voxel-size) cone-beam computed tomography (CBCT) images may be improved by using pixel gray values. MATERIALS AND METHODS: Twenty fresh cadaver pig heads underwent CBCT scans (17 × 23 cm FOV, 0.4-mm voxel size). Buccal alveolar bone heights of maxillary first molars were measured using the conventional vision-based (VB) and the proposed gray value-assisted (GVA) methods. The GVA methods entailed localization of landmarks through observation of gray value pattern changes across tissue boundaries followed by mathematical calculation of distances between landmark pixels. Interrater reliability and accuracy of CBCT measurements made by all methods were statistically analyzed by comparing with physical measurements (gold standards). RESULTS: The interrater reliability of CBCT measurements made by GVA methods was comparable to physical measurements but higher than those made by the VB method. The GVA (bend-down pattern) method yielded average measurements similar to physical measurements, while those obtained by the VB and the GVA (straight pattern) methods were significantly larger (repeated measures analysis of variance, P < .001). The GVA (bend-down pattern) method also produced significantly more measurements within one voxel size of physical measurements than did the VB and GVA (straight pattern) methods (Chi-square tests, P < .017). CONCLUSIONS: These data confirm a concept that local gray value change patterns may be used to improve the accuracy and reliability of alveolar bone height measurement from large FOV and large voxel-size CBCT images.


Assuntos
Processo Alveolar/diagnóstico por imagem , Tomografia Computadorizada de Feixe Cônico , Processo Alveolar/anatomia & histologia , Pontos de Referência Anatômicos , Animais , Tomografia Computadorizada de Feixe Cônico/métodos , Dente Molar/anatomia & histologia , Dente Molar/diagnóstico por imagem , Radiografia Dentária/métodos , Reprodutibilidade dos Testes , Suínos
2.
J Mech Behav Biomed Mater ; 60: 48-55, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26773652

RESUMO

The objective of the current study was to examine whether peri-implant bone tissue properties are different between the buccal and lingual regions treated by growth factors. Four dental implant groups were used: titanium (Ti) implants, alumina-blasted zirconia implants (ATZ-N), alumina-blasted zirconia implants with demineralized bone matrix (DBM) (ATZ-D), and alumina-blasted zirconia implants with rhBMP-2 (ATZ-B). These implants were placed in mandibles of six male dogs. Nanoindentation elastic modulus (E) and plastic hardness (H) were measured for the buccal and lingual bone tissues adjacent and away from the implants at 3 and 6 weeks post-implantation. A total of 2281 indentations were conducted for 48 placed implants. The peri-implant buccal region had less bone quantity resulting from lower height and narrower width of bone tissue than the lingual region. Buccal bone tissues had significant greater mean values of E and H than lingual bone tissues at each distance and healing period (p<0.007). Nearly all implant treatment groups displayed lower mean values of the E at the lingual bone tissues than at the buccal bone tissues (p<0.046) although the difference was not significant for the Ti implant group (p=0.758). The DBM and rhBMP-2 treatments stimulated more peri-implant bone remodeling at the lingual region, producing more immature new bone tissues with lower E than at the buccal region. This finding suggests that the growth factor treatments to the zirconia implant system may help balance the quantity and quality differences between the peri-implant bone tissues.


Assuntos
Remodelação Óssea , Implantação Dentária Endóssea , Implantes Dentários , Osso Hioide/fisiologia , Mandíbula/fisiologia , Animais , Cães , Masculino
3.
J Prosthet Dent ; 97(6): 357-65, 2007 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-17618918

RESUMO

STATEMENT OF PROBLEM: Production of precisely fitting fixed partial denture implant superstructures with titanium alloys is limited by casting techniques that introduce distortion. After alignment of the framework with existing implants, the remaining misfit may generate stresses that cause screw loosening and adversely affect the implant/bone interface. PURPOSE: The purpose of this study was to prepare diffusion-bonded joints between superplastic (SP) Ti-6Al-4V plates and indenters (representing analogs to implant-supported fixed frameworks and abutments) and determine if this process has potential for producing strong, dimensionally precise prostheses. MATERIAL AND METHODS: Seven sets of trial indenter and plate specimens with dimensions of 6.4 mm x 6.4 mm x 5 cm and 8.5 mm x 1.5 cm, respectively, were prepared. Several indenter designs were used (35- or 45-degree half-angle, presence or absence of a notch, and SP versus no SP condition for Ti-6Al-4V); all plates were prepared from SP Ti-6Al-4V. For the results-guided experimental design, there was 1 trial indenter/plate combination for each design/processing condition. Diffusion bonding was performed at 10(-6) Torr, while the temperature was increased 10 degrees C/min to 900 degrees or 920 degrees C. Following 10 minutes of equilibration, the indenter was pressed 2.5 mm into the plate at 0.13 mm/min. Joint strength was evaluated in tension, and the ductile or brittle character of fracture surfaces was assessed by the presence or absence of a dimpled rupture surface from secondary electron SEM observations. Fractured specimens were cross-sectioned and examined with an optical microscope to evaluate overall joint integrity and quality, and used for Vickers hardness measurements to gain insight into the variation in mechanical properties of the indenter and plate with distance from the joint. One-way ANOVA (alpha=.05) was used to compare hardness at the joint for the trial specimen with highest joint strength with hardness values for adjacent regions at 125-mum intervals in the indenter and plate. The Ryan-Einot-Gabriel-Welsch (REGW) multiple range test was used to identify any specific location having significantly (alpha=.05) different hardness. Backscattered electron SEM observations were also performed on the cross-sectioned specimens to investigate whether a layer of alpha-stabilized titanium, which would decrease joint strength, was present. Fits of Ti-6Al-4V implant analogs prepared by this diffusion-bonding process were assessed qualitatively from visual observation. RESULTS: The maximum joint strength of 820 MPa was achieved for a diffusion bonding temperature of 900 degrees C for an SP Ti-6Al-4V indenter with a 35-degree half-angle and no notch. This joint strength is nearly 90% of the maximum tensile strength of the parent Ti-6Al-4V, which can range from approximately 930 to 1015 MPa. The hardness at the joint was significantly higher (P<.05) than the hardness of the indenter and plate at 125-mum distances from the joint. The mean hardness of the indenter at 125 mum from the joint was significantly greater (P<.05) than the mean hardness of the plate at a distance of 500 mum from the joint. All other mean hardness values at the different measurement distances from the joint were not significantly different. Ductile fracture occurred for all superplastic processing conditions, and no alpha-titanium layer was present. Minimal asperities were observed with the optical microscope, and fits of implant prosthesis analogs were considered acceptable. CONCLUSIONS: A 900 degrees C processing condition for diffusion-bonding an SP Ti-6Al-4V indenter with a 35-degree half-angle and no notch to a Ti-6Al-4V SP plate yielded a joint with nearly the same strength as the parent alloy. Use of this processing temperature with a 0.13 mm/min rate of pressing the indenter into the plate yielded minimal distortions for implant prosthesis analogs when observed visually.


Assuntos
Materiais Dentários/química , Prótese Dentária Fixada por Implante/métodos , Planejamento de Dentadura/métodos , Prótese Parcial Fixa , Titânio/química , Ligas , Dureza , Testes de Dureza/métodos , Resistência à Tração
4.
Biomaterials ; 23(15): 3279-87, 2002 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12102199

RESUMO

The present in vitro study investigated select functions (specifically, proliferation, synthesis of intracellular proteins, alkaline phosphatase activity, and deposition of calcium-containing mineral) of osteoblasts (the bone-forming cells) cultured on carbon fibers with nanometer dimensions. Carbon fiber compacts were synthesized to possess either nanophase (i.e., dimensions 100 nm or less) or conventional (i.e., dimensions larger than 100 nm) fiber diameters. Osteoblast proliferation increased with decreasing carbon fiber diameters after 3 and 7 days of culture. Moreover, compared to larger-diameter carbon fibers, osteoblasts synthesized more alkaline phosphatase and deposited more extracellular calcium on nanometer-diameter carbon fibers after 7, 14, and 21 days of culture. The results of the present study provided the first evidence of enhanced long-term (in the order of days to weeks) functions of osteoblasts cultured on nanometer-diameter carbon fibers; in this manner, carbon nanofibers clearly represent a unique and promising class of orthopedic/dental implant formulations with improved osseointegrative properties.


Assuntos
Materiais Biocompatíveis , Carbono , Osteoblastos/fisiologia , Fosfatase Alcalina/metabolismo , Osso e Ossos , Cálcio/metabolismo , Divisão Celular , Células Cultivadas , Implantes Dentários , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Osseointegração , Osteoblastos/citologia , Tamanho da Partícula , Próteses e Implantes , Biossíntese de Proteínas
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