FY Zheng | University of Southern California (original) (raw)

Papers by FY Zheng

Research paper thumbnail of Systemic Factors Affecting Prognosis in Restorative and Prosthetic Dentistry

Dental clinics of North America/˜The œDental clinics of North America, Jun 1, 2024

Research paper thumbnail of Rehabilitation of a patient with mandibular flexure using contemporary glass-infiltrated high performance CAD-CAM polymers: A clinical report with 1-year follow-up

The Journal of Prosthetic Dentistry

Research paper thumbnail of The effect of PMMA stimulated Complement-Macrophage cascade on Osteogenesis of Preosteoblast-like MC3T3-E1 cells on PMMA surface

.................................................................................................... more .............................................................................................................................. ii Dedication ........................................................................................................................... v Acknowledgments.............................................................................................................. vi Vita................................................................................................................................... viii List of Tables ................................................................................................................... xiii List of Figures .................................................................................................................. xiv Introduction....................................................................................................................... 17 Chapter 1 Literature Review............................................................................................. 19 1.1 The interaction of complement system and biomaterial surface............................. 19 1.2 Complement system inhibition................................................................................ 22 1.3 Macrophage adhesion and stimulation on biomaterials surface.............................. 23 1.4 Cytokines released by stimulated macrophages and their effects on osteoblast behavior......................................................................................................................... 26 1.5 Biological activity markers for the study of interactions between osteoblasts and biomaterials ................................................................................................................... 28

Research paper thumbnail of The Role of Intraoral Scanners in the Shade Matching Process: A Systematic Review

Journal of Prosthodontics

Research paper thumbnail of Digital Mounting Jigs: A Novel Technique

Digital

The accuracy with which virtual articulators are able to simulate centric and eccentric movements... more The accuracy with which virtual articulators are able to simulate centric and eccentric movements when fabricating definitive restorations has not yet been proven to be on par with mechanical articulators which have been reliably used in restorative dentistry for decades. This may be an issue when working on complex restorative cases utilizing a digital workflow and could result in considerable chairside adjustment time and subsequent loss of occlusal anatomy and morphology. Interchanging between digital and analog workflows is a challenge as accurate cross-mounting is difficult due to the changes that occur as the digital and analog workflows progress. This technique article provides a method for the fabrication of simple digital mounting jigs that enable clinicians and laboratory technicians to mount printed digital wax-ups and working casts back onto a programmed mechanical articulator, opposing diagnostic casts that have originally been mounted by means of a facebow transfer. Th...

Research paper thumbnail of Strength of titanium-zirconium alloy implants with a conical connection after implantoplasty

The Journal of Prosthetic Dentistry

Research paper thumbnail of Aging Alters Cervical Vertebral Bone Density Distribution: A Cross-Sectional Study

Applied Sciences, 2022

Osteoporosis reduces bone mineral density (BMD) with aging. The incidence of cervical vertebral i... more Osteoporosis reduces bone mineral density (BMD) with aging. The incidence of cervical vertebral injuries for the elderly has increased in the last decade. Thus, the objective of the current study was to examine whether dental cone beam computed tomography (CBCT) can identify age and sex effects on volumetric BMD and morphology of human cervical vertebrae. A total of 136 clinical CBCT images were obtained from 63 male and 73 female patients (20 to 69 years of age). Three-dimensional images of cervical vertebral bodies (C2 and C3) were digitally isolated. A gray level, which is proportional to BMD, was obtained and its distribution was analyzed in each image. Morphology, including volume, heights, widths, and concavities, was also measured. Most of the gray level parameters had significantly higher values of C2 and C3 in females than in males for all age groups (p < 0.039). The female 60-age group had significant lower values of Mean and Low5 of C2 and C3 than both female 40- and 5...

Research paper thumbnail of Comparison of Post Space Volume Changes Following Fiber Post Removal Using Er,Cr:YSGG Laser Versus Ultrasonic Instrument

Journal of Prosthodontics, 2021

PURPOSE The purpose of this in vitro study was to compare the post space volume changes following... more PURPOSE The purpose of this in vitro study was to compare the post space volume changes following removal of glass fiber posts in endodontically treated teeth by using erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser to the conventional ultrasonic method. MATERIALS AND METHODS Twelve single-root human extracted teeth were cut into 13mm near cementoenamel junction (CEJ), and then underwent endodontic treatment. The post spaces were prepared to 8mm in length. Glass fiber posts were inserted with self-curing resin cement. Specimens were randomly assigned to laser or ultrasonic methods for their post removal. Post space volumes were measured using micro-computed tomography (micro-CT) before post cementation and after post removal. Dentin thickness was measured after post removal at coronal, middle, and apical third of the root canal space. Paired t-test and t-test were used to compare space volumes between before post cementation and after post removal, and between laser and ultrasonic groups, respectively. RESULTS Six specimens were tested for each group. The average volume change was 6.499 mm3 in laser and 7.418mm3 in ultrasonic method. There was not a significant difference between laser and ultrasonic group in respect of post space volume changes (p = 0.71). Both methods showed significant volume increase following post-removal (p<0.05). Significantly less dentin was lost when laser was used for post removal in the coronal portion of the post space (p = 0.002). CONCLUSIONS Er,Cr:YSGG laser can be used as effective option, comparable to the conventional ultrasonic method when removing posts in endodontically treated teeth. Laser has the potential to provide conservative post removal. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Evaluation of clinical parameters for the stability of 2 types of miniscrews

American Journal of Orthodontics and Dentofacial Orthopedics, 2021

INTRODUCTION The purpose of this research was to compare insertion techniques and effects on mech... more INTRODUCTION The purpose of this research was to compare insertion techniques and effects on mechanical and clinical parameters between 2 types of miniscrews. METHODS Forty-four consecutive patients whose orthodontic treatment involved the use of miniscrews (miniscrew A [MA] and miniscrew B [MB]) for anchorage were included in this study. Miniscrews were placed with predrilling or self-drilling; peak maximum insertion torque (MIT) and Periotest values were measured. Cone-beam computed tomography was performed after the insertion of miniscrews and root proximity determination; cortical bone thickness was also analyzed. Periotest values were measured after the application of orthodontic force. RESULTS Self-drilling produced higher Periotest values (P <0.01) for MA and higher MIT (P <0.01) for MB with closer root proximity (P <0.05). MB had higher MIT and Periotest values with drilling compared with MA (P <0.05); MB also showed closer root proximity (P <0.05). Successful miniscrews had lower MIT (P <0.05) for MB and lower Periotest values (P <0.01) for both MA and MB, with significantly more distant root proximity (P <0.01). Self-drilling produced higher Periotest values at the time of placement (P <0.01) and after 4 weeks (P <0.05) in MA. Drilling produced higher Periotest values for MB at the time of placement (P <0.05). MIT had positive correlations with Periotest values for MB with self-drilling (P <0.01) and with root proximity for MA with drilling (P <0.01). Periotest values had negative correlations with root proximity for MA and the MB group with drilling (P <0.01). CONCLUSIONS For miniscrews with larger diameters, higher MIT may result in more mobility (higher Periotest values). Drilling can avoid root contact and enhance primary stability, thus producing lower Periotest values.

Research paper thumbnail of Multiscale characterization of ovariectomized rat femur

Journal of Biomechanics, 2021

Estrogen deficiency activates bone resorbing cells (osteoclasts) and to a lesser extent bone form... more Estrogen deficiency activates bone resorbing cells (osteoclasts) and to a lesser extent bone forming cells (osteoblasts), resulting in a gap between resorption and formation that leads to a net loss of bone. These cell activities alter bone architecture and tissue composition. Thus, the objective of this study is to examine whether multiscale (10 −2 to 10 −7 m) characterization can provide more integrated information to understand the effects of estrogen deficiency on the fracture risk of bone. This is the first study to examine the effects of estrogen deficiency on multiscale characteristics of the same bone specimen. Sprague-Dawley female rats (6 months old) were obtained for a bilateral ovariectomy (OVX) or a sham operation (sham). Micro-computed tomography of rat femurs provided bone volumetric, mineral density, and morphological parameters. Dynamic mechanical analysis, static elastic and fracture mechanical testing, and nanoindentation were also performed using the same femur. As expected, the current findings indicate that OVX reduces bone quantity (mass and bone mineral density) and quality (morphology, and fracture displacement). Additionally, they demonstrated reductions in amount and heterogeneity of tissue mineral density (TMD) and viscoelastic properties. The current results validate that multiscale characterization for the same bone specimen can provide more comprehensive insights to understand how the bone components contributed to mechanical behavior at different scales.

Research paper thumbnail of The behavior of a zirconia or metal abutment on the implant-abutment interface during cyclic loading

The Journal of Prosthetic Dentistry, 2019

External hexagon implant-abutment connections have been widely used in implant dentistry. 1 A pas... more External hexagon implant-abutment connections have been widely used in implant dentistry. 1 A passive and reliable connection between the implant and restoration is essential for success. 2-6 Passive fit has been defined as, in the absence of external loads, the prosthetic structure not inducing any tension on the implant and its abutment or prosthetic cylinder and thus not on the surrounding bone. 7,8 The absence of a stable connection can

Research paper thumbnail of Stereographic analog application in implant-supported complete rehabilitation: A dental technique

The Journal of Prosthetic Dentistry, 2019

Endosseous implants have been widely adopted for restoring complete and partially edentulous arch... more Endosseous implants have been widely adopted for restoring complete and partially edentulous arches. 1 These prostheses are typically not attached to natural teeth and obtain retention, support, and stability directly from implants integrated into the host bone with no resiliency. 2 The lack of resiliency implies minimal tolerance to occlusal interferences during eccentric jaw movements. 2 The design of prostheses should comply with the patient's dynamic functional movements to minimize unfavorable lateral forces that can be detrimental to prosthetic components and biomechanical implant-bone interfaces, especially on implant-supported fixed prosthesis. 2,3 Hence, a precisely designed and adjusted occlusion is mandatory, but implant-specific occlusion concepts are lacking. 2,3 Recording and replicating functional mandibular movement led to the development of articulators and tracing devices 4,5 that allow the fabrication of prostheses with high precision on definitive casts and minimize chairside adjustments. Prostheses fabricated based on average values may require extensive occlusal adjustment to remove excursive interferences. 6 A straightforward and accurate method has been long used in removable and fixed prosthodontics. 7-10 The engraving method was introduced by Warnekros and Bergstrom 11 and further developed and taught to the profession by Needles 12 and House. 13 Swanson 9 and Wipf 10 have modified and added components to the

Research paper thumbnail of Evaluations of miniscrew type-dependent mechanical stability

Clinical Biomechanics, 2019

Background: Miniscrew has been widely used as an absolute anchorage in orthodontic treatment. Typ... more Background: Miniscrew has been widely used as an absolute anchorage in orthodontic treatment. Types of miniscrew with different diameter, length, shape, and thread dimensions may have a substantial effect on mechanical stability of the miniscrew system. Thus, the objective of this study was to evaluate miniscrew typedependent mechanical stability to assess mechanical properties of miniscrew systems in various thickness of artificial bone block using different measurement tools. Methods: Two types of miniscrews (15 Tomas and 15 AbsoAnchor) were placed in artificial bone block with different thickness of 1.5, 2.0, 3.0 mm. Values of maximum insertion torque, removal torque, Periotest, implant stability quotient, static stiffness, dynamic stiffness, and energy dissipation ability were assessed for each miniscrew system. Findings: The maximum insertion torque, removal torque, implant stability quotient, static and dynamic stiffness values significantly increased when the miniscrews were placed in thicker bone block while Periotest values decreased. The static stiffness, Periotest and implant stability quotient values were significantly correlated each other and also with other mechanical properties (p < 0.001) except tan δ (p > 0.35). However, the slopes of some correlations and absolute values of measurement were significantly different dependent on the miniscrew types (p < 0.025). Interpretation: The current findings suggest that miniscrew type-dependent calibrations are required to estimate mechanical stability of the miniscrew systems despite the utilization of same measurement tool.

Research paper thumbnail of Mechanical and clinical evaluation of the effect of microscrew on root proximity and cortical bone thickness

European Journal of Orthodontics, 2019

Summary Background/Objectives Primary stability is required for successful use of microscrew. Thi... more Summary Background/Objectives Primary stability is required for successful use of microscrew. This study investigated correlations among biomechanical, morphological, and clinical values in relationship to root contact and different placement locations. Materials/Methods Thirty-three microscrews were placed between the molars (n = 18) or in the body of the mandible (n = 15) in three pigs. Insertion torque, Periotest, resonance frequency analysis (RFA), and static and dynamic stiffness were measured. Cone beam computed tomography was performed before and after the insertion of microscrews. Interproximal microscrews were divided into root contacted microscrews (n = 9) and non-root contact microscrews (n = 9). Factorial analysis of variance was conducted, with significance set at P < 0.05. Results A significant difference was observed between bodily and root contacted microscrews in Periotest, RFA, static and dynamic stiffness, Tanδ, and bone density (RFA, P = 0.045; all others, P &...

Research paper thumbnail of Pick-up Impression of Complete Arch Implant-supported Interim Prosthesis

The Journal of oral implantology, Jan 3, 2018

Research paper thumbnail of Characterization of Next-Generation Nickel-Titanium Rotary Endodontic Instruments

Ceramic Transactions, 2013

Research paper thumbnail of DSC Study of Transformations in Clinically Used M-Wire Endodontic Instruments

ABSTRACT Properties of NiTi rotary instruments depend on their microstructural phases, which can ... more ABSTRACT Properties of NiTi rotary instruments depend on their microstructural phases, which can be studied by differential scanning calorimetry. M-Wire instruments (GTX, Dentsply Tulsa Dental Specialties) have superior fatigue resistance compared to conventional rotary instruments manufactured from superelastic NiTi wires in the austenitic condition. Objective: Employ DSC to investigate structural transformations in clinically used (7-8 times) GTX instruments. Methods: Used instruments (N=3 for each size/taper combination) were cut with a diamond saw into 3 segments: tip region, an intermediate segment, and shank region, with each segment 4-5 mm in length. The first group of specimens for DSC analysis consisted of the single segments from each instrument. The second group consisted of all three segments for each instrument. Specimens were cooled from room temperature to -80C, heated to 120C, and cooled back to -80C. The linear heating and cooling rate was 10C per minute (Q1000, TA Instruments), and the DSC cell was purged with nitrogen. Austenite-finish temperatures were compared using ANOVA. Results: Each segment of the used instruments had an Af temperature exceeding 40C. Tip regions of the M-Wire instruments had higher Af temperatures than the middle and shank regions. Minimal differences in Af temperature were found for size/taper combinations and specimens consisting of three segments. Two endothermic peaks were observed in most instruments during the heating cycle, corresponding to transformation from martensite to R-phase, and then to austenite. A single broad exothermic peak for direct transformation from austenite to martensite was generally observed during the cooling cycle. Conclusions: GTX instruments have much higher Af temperatures than conventional superelastic rotary instruments. The DSC peaks indicate that used M-Wire instruments are a mixture of martensite, R-phase and austenite. However, STEM and metallographic examination of M-Wire blanks suggest that substantial stable martensite in these instruments is not detected by DSC.

Research paper thumbnail of Effects of N-vinylcaprolactam containing polyelectrolytes on hardness, fluoride release and water sorption of conventional glass ionomers

The Journal of Prosthetic Dentistry, 2011

Statement of problem. N-vinylcaprolactam (NVC) containing glass ionomers are promising dental res... more Statement of problem. N-vinylcaprolactam (NVC) containing glass ionomers are promising dental restorative materials with improved mechanical properties; however, little information is available on other physical properties of this type of modified glass ionomer, especially their water sorption, fluoride releasing properties and microhardness. Purpose. The purpose of this study was to investigate the effects of NVC-containing polyelectrolytes on microhardness, fluoride release and water sorption of conventional glass ionomer cements (GIC). Material and methods. The terpolymer of acrylic acid (AA), itaconic acid (IA) and N-vinylcaprolactam (NVC) with 8:1:1 and 7:1:2 (AA: IA: NVC) molar ratios was synthesized by free radical polymerization and characterized using 1H-NMR and F TIR. Experimental GIC specimens were made from a 50% solution of the synthesized terpolymer with Fuji IX powder in a 3.6:1 P/L ratio. Specimens were mixed and fabricated at room temperature. Vickers hardness was determined using a microhardness tester. Water sorption and fluoride releasing properties were also investigated. Commercial Fuji IX was used as the control group. All specimens were first conditioned in distilled water at 37°C for 1 day up to 1 month. Results for the experimental GIC were compared with the control group, using 1-way and 2-way ANOVA and the Tukey multiple range test (α=.05). Results. The NVC-modified GIC exhibited higher mean values of Vickers hardness numbers (VHN). However, the data exhibited no statistically significant differences between the experimental and control groups. The experimental cement (TP2) absorbed significantly more water than the control group (P<.034). Additionally, NVC-containing specimens showed comparable fluoride releasing properties with almost the same fluoride burst and continued fluoride release from the bulk of the material. Conclusions. It was concluded that a hydrophilic monomer such as NVC might be able to increase the water sorption and decrease the amount of initial fluoride release of the glass ionomers. Hydrophilic monomer such as NVC might be able to increase the water sorption and decrease the amount of initial fluoride release of the glass ionomers. (J

Research paper thumbnail of Measure of microhardness, fracture toughness and flexural strength of N-vinylcaprolactam (NVC)-containing glass-ionomer dental cements

Dental Materials, 2010

Objectives. To investigate the effects of N-vinylcaprolactam (NVC)-containing terpolymers on the ... more Objectives. To investigate the effects of N-vinylcaprolactam (NVC)-containing terpolymers on the fracture toughness, microhardness, and flexural strength of conventional glass-ionomer cements (GIC). Methods. The terpolymer of acrylic acid (AA)-itaconic acid (IA)-N-vinylcaprolactam (NVC) with 8:1:1 (AA:IA:NVC) molar ratio was synthesized by free radical polymerization and characterized using 1 H NMR and FTIR. Experimental GIC samples were made from a 50% solution of the synthesized terpolymer with Fuji IX powder in a 3.6:1 P/L ratio. Specimens were mixed and fabricated at room temperature. Plane strain fracture toughness (K Ic) was measured in accordance with ASTM Standard 399-05. Vickers hardness was determined using a microhardness tester. Flexural strength was measured using samples with dimensions of 2 mm × 2 mm × 20 mm. For all mechanical property tests, specimens were first conditioned in distilled water at 37 • C for 1 day or 1 week. Fracture toughness and flexural strength tests were conducted on a screw-driven universal testing machine using a crosshead speed of 0.5 mm/min. Values of mechanical properties for the experimental GIC were compared with the control group (Fuji IX GIC), using one-way ANOVA and the Tukey multiple range test at = 0.05. Results. The NVC-modified GIC exhibited significantly higher fracture toughness compared to the commercially available Fuji IX GIC, along with higher mean values of flexural strength and Vickers hardness, which were not significantly different. Significance. It was concluded that NVC-containing polymers are capable of enhancing clinically relevant properties for GICs. This new modified glass-ionomer is a promising restorative dental material.

Research paper thumbnail of Root caries in the geriatric population: epidemiology, etiology, diagnosis, treatment planning and modalities of treatment

dentalforum.ump.edu.pl

Page 1. DENTAL FORUM /2/2008/XXXVI 63 PRACE POGLĄDOWE pracepoglądowe Alireza Moshaverinia1, Fengy... more Page 1. DENTAL FORUM /2/2008/XXXVI 63 PRACE POGLĄDOWE pracepoglądowe Alireza Moshaverinia1, Fengyuan Zheng1, Scott R. Schricker2, Abdel Rahim Mohammad3 Root caries in the geriatric population: epidemiology ...

Research paper thumbnail of Systemic Factors Affecting Prognosis in Restorative and Prosthetic Dentistry

Dental clinics of North America/˜The œDental clinics of North America, Jun 1, 2024

Research paper thumbnail of Rehabilitation of a patient with mandibular flexure using contemporary glass-infiltrated high performance CAD-CAM polymers: A clinical report with 1-year follow-up

The Journal of Prosthetic Dentistry

Research paper thumbnail of The effect of PMMA stimulated Complement-Macrophage cascade on Osteogenesis of Preosteoblast-like MC3T3-E1 cells on PMMA surface

.................................................................................................... more .............................................................................................................................. ii Dedication ........................................................................................................................... v Acknowledgments.............................................................................................................. vi Vita................................................................................................................................... viii List of Tables ................................................................................................................... xiii List of Figures .................................................................................................................. xiv Introduction....................................................................................................................... 17 Chapter 1 Literature Review............................................................................................. 19 1.1 The interaction of complement system and biomaterial surface............................. 19 1.2 Complement system inhibition................................................................................ 22 1.3 Macrophage adhesion and stimulation on biomaterials surface.............................. 23 1.4 Cytokines released by stimulated macrophages and their effects on osteoblast behavior......................................................................................................................... 26 1.5 Biological activity markers for the study of interactions between osteoblasts and biomaterials ................................................................................................................... 28

Research paper thumbnail of The Role of Intraoral Scanners in the Shade Matching Process: A Systematic Review

Journal of Prosthodontics

Research paper thumbnail of Digital Mounting Jigs: A Novel Technique

Digital

The accuracy with which virtual articulators are able to simulate centric and eccentric movements... more The accuracy with which virtual articulators are able to simulate centric and eccentric movements when fabricating definitive restorations has not yet been proven to be on par with mechanical articulators which have been reliably used in restorative dentistry for decades. This may be an issue when working on complex restorative cases utilizing a digital workflow and could result in considerable chairside adjustment time and subsequent loss of occlusal anatomy and morphology. Interchanging between digital and analog workflows is a challenge as accurate cross-mounting is difficult due to the changes that occur as the digital and analog workflows progress. This technique article provides a method for the fabrication of simple digital mounting jigs that enable clinicians and laboratory technicians to mount printed digital wax-ups and working casts back onto a programmed mechanical articulator, opposing diagnostic casts that have originally been mounted by means of a facebow transfer. Th...

Research paper thumbnail of Strength of titanium-zirconium alloy implants with a conical connection after implantoplasty

The Journal of Prosthetic Dentistry

Research paper thumbnail of Aging Alters Cervical Vertebral Bone Density Distribution: A Cross-Sectional Study

Applied Sciences, 2022

Osteoporosis reduces bone mineral density (BMD) with aging. The incidence of cervical vertebral i... more Osteoporosis reduces bone mineral density (BMD) with aging. The incidence of cervical vertebral injuries for the elderly has increased in the last decade. Thus, the objective of the current study was to examine whether dental cone beam computed tomography (CBCT) can identify age and sex effects on volumetric BMD and morphology of human cervical vertebrae. A total of 136 clinical CBCT images were obtained from 63 male and 73 female patients (20 to 69 years of age). Three-dimensional images of cervical vertebral bodies (C2 and C3) were digitally isolated. A gray level, which is proportional to BMD, was obtained and its distribution was analyzed in each image. Morphology, including volume, heights, widths, and concavities, was also measured. Most of the gray level parameters had significantly higher values of C2 and C3 in females than in males for all age groups (p < 0.039). The female 60-age group had significant lower values of Mean and Low5 of C2 and C3 than both female 40- and 5...

Research paper thumbnail of Comparison of Post Space Volume Changes Following Fiber Post Removal Using Er,Cr:YSGG Laser Versus Ultrasonic Instrument

Journal of Prosthodontics, 2021

PURPOSE The purpose of this in vitro study was to compare the post space volume changes following... more PURPOSE The purpose of this in vitro study was to compare the post space volume changes following removal of glass fiber posts in endodontically treated teeth by using erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser to the conventional ultrasonic method. MATERIALS AND METHODS Twelve single-root human extracted teeth were cut into 13mm near cementoenamel junction (CEJ), and then underwent endodontic treatment. The post spaces were prepared to 8mm in length. Glass fiber posts were inserted with self-curing resin cement. Specimens were randomly assigned to laser or ultrasonic methods for their post removal. Post space volumes were measured using micro-computed tomography (micro-CT) before post cementation and after post removal. Dentin thickness was measured after post removal at coronal, middle, and apical third of the root canal space. Paired t-test and t-test were used to compare space volumes between before post cementation and after post removal, and between laser and ultrasonic groups, respectively. RESULTS Six specimens were tested for each group. The average volume change was 6.499 mm3 in laser and 7.418mm3 in ultrasonic method. There was not a significant difference between laser and ultrasonic group in respect of post space volume changes (p = 0.71). Both methods showed significant volume increase following post-removal (p<0.05). Significantly less dentin was lost when laser was used for post removal in the coronal portion of the post space (p = 0.002). CONCLUSIONS Er,Cr:YSGG laser can be used as effective option, comparable to the conventional ultrasonic method when removing posts in endodontically treated teeth. Laser has the potential to provide conservative post removal. This article is protected by copyright. All rights reserved.

Research paper thumbnail of Evaluation of clinical parameters for the stability of 2 types of miniscrews

American Journal of Orthodontics and Dentofacial Orthopedics, 2021

INTRODUCTION The purpose of this research was to compare insertion techniques and effects on mech... more INTRODUCTION The purpose of this research was to compare insertion techniques and effects on mechanical and clinical parameters between 2 types of miniscrews. METHODS Forty-four consecutive patients whose orthodontic treatment involved the use of miniscrews (miniscrew A [MA] and miniscrew B [MB]) for anchorage were included in this study. Miniscrews were placed with predrilling or self-drilling; peak maximum insertion torque (MIT) and Periotest values were measured. Cone-beam computed tomography was performed after the insertion of miniscrews and root proximity determination; cortical bone thickness was also analyzed. Periotest values were measured after the application of orthodontic force. RESULTS Self-drilling produced higher Periotest values (P <0.01) for MA and higher MIT (P <0.01) for MB with closer root proximity (P <0.05). MB had higher MIT and Periotest values with drilling compared with MA (P <0.05); MB also showed closer root proximity (P <0.05). Successful miniscrews had lower MIT (P <0.05) for MB and lower Periotest values (P <0.01) for both MA and MB, with significantly more distant root proximity (P <0.01). Self-drilling produced higher Periotest values at the time of placement (P <0.01) and after 4 weeks (P <0.05) in MA. Drilling produced higher Periotest values for MB at the time of placement (P <0.05). MIT had positive correlations with Periotest values for MB with self-drilling (P <0.01) and with root proximity for MA with drilling (P <0.01). Periotest values had negative correlations with root proximity for MA and the MB group with drilling (P <0.01). CONCLUSIONS For miniscrews with larger diameters, higher MIT may result in more mobility (higher Periotest values). Drilling can avoid root contact and enhance primary stability, thus producing lower Periotest values.

Research paper thumbnail of Multiscale characterization of ovariectomized rat femur

Journal of Biomechanics, 2021

Estrogen deficiency activates bone resorbing cells (osteoclasts) and to a lesser extent bone form... more Estrogen deficiency activates bone resorbing cells (osteoclasts) and to a lesser extent bone forming cells (osteoblasts), resulting in a gap between resorption and formation that leads to a net loss of bone. These cell activities alter bone architecture and tissue composition. Thus, the objective of this study is to examine whether multiscale (10 −2 to 10 −7 m) characterization can provide more integrated information to understand the effects of estrogen deficiency on the fracture risk of bone. This is the first study to examine the effects of estrogen deficiency on multiscale characteristics of the same bone specimen. Sprague-Dawley female rats (6 months old) were obtained for a bilateral ovariectomy (OVX) or a sham operation (sham). Micro-computed tomography of rat femurs provided bone volumetric, mineral density, and morphological parameters. Dynamic mechanical analysis, static elastic and fracture mechanical testing, and nanoindentation were also performed using the same femur. As expected, the current findings indicate that OVX reduces bone quantity (mass and bone mineral density) and quality (morphology, and fracture displacement). Additionally, they demonstrated reductions in amount and heterogeneity of tissue mineral density (TMD) and viscoelastic properties. The current results validate that multiscale characterization for the same bone specimen can provide more comprehensive insights to understand how the bone components contributed to mechanical behavior at different scales.

Research paper thumbnail of The behavior of a zirconia or metal abutment on the implant-abutment interface during cyclic loading

The Journal of Prosthetic Dentistry, 2019

External hexagon implant-abutment connections have been widely used in implant dentistry. 1 A pas... more External hexagon implant-abutment connections have been widely used in implant dentistry. 1 A passive and reliable connection between the implant and restoration is essential for success. 2-6 Passive fit has been defined as, in the absence of external loads, the prosthetic structure not inducing any tension on the implant and its abutment or prosthetic cylinder and thus not on the surrounding bone. 7,8 The absence of a stable connection can

Research paper thumbnail of Stereographic analog application in implant-supported complete rehabilitation: A dental technique

The Journal of Prosthetic Dentistry, 2019

Endosseous implants have been widely adopted for restoring complete and partially edentulous arch... more Endosseous implants have been widely adopted for restoring complete and partially edentulous arches. 1 These prostheses are typically not attached to natural teeth and obtain retention, support, and stability directly from implants integrated into the host bone with no resiliency. 2 The lack of resiliency implies minimal tolerance to occlusal interferences during eccentric jaw movements. 2 The design of prostheses should comply with the patient's dynamic functional movements to minimize unfavorable lateral forces that can be detrimental to prosthetic components and biomechanical implant-bone interfaces, especially on implant-supported fixed prosthesis. 2,3 Hence, a precisely designed and adjusted occlusion is mandatory, but implant-specific occlusion concepts are lacking. 2,3 Recording and replicating functional mandibular movement led to the development of articulators and tracing devices 4,5 that allow the fabrication of prostheses with high precision on definitive casts and minimize chairside adjustments. Prostheses fabricated based on average values may require extensive occlusal adjustment to remove excursive interferences. 6 A straightforward and accurate method has been long used in removable and fixed prosthodontics. 7-10 The engraving method was introduced by Warnekros and Bergstrom 11 and further developed and taught to the profession by Needles 12 and House. 13 Swanson 9 and Wipf 10 have modified and added components to the

Research paper thumbnail of Evaluations of miniscrew type-dependent mechanical stability

Clinical Biomechanics, 2019

Background: Miniscrew has been widely used as an absolute anchorage in orthodontic treatment. Typ... more Background: Miniscrew has been widely used as an absolute anchorage in orthodontic treatment. Types of miniscrew with different diameter, length, shape, and thread dimensions may have a substantial effect on mechanical stability of the miniscrew system. Thus, the objective of this study was to evaluate miniscrew typedependent mechanical stability to assess mechanical properties of miniscrew systems in various thickness of artificial bone block using different measurement tools. Methods: Two types of miniscrews (15 Tomas and 15 AbsoAnchor) were placed in artificial bone block with different thickness of 1.5, 2.0, 3.0 mm. Values of maximum insertion torque, removal torque, Periotest, implant stability quotient, static stiffness, dynamic stiffness, and energy dissipation ability were assessed for each miniscrew system. Findings: The maximum insertion torque, removal torque, implant stability quotient, static and dynamic stiffness values significantly increased when the miniscrews were placed in thicker bone block while Periotest values decreased. The static stiffness, Periotest and implant stability quotient values were significantly correlated each other and also with other mechanical properties (p < 0.001) except tan δ (p > 0.35). However, the slopes of some correlations and absolute values of measurement were significantly different dependent on the miniscrew types (p < 0.025). Interpretation: The current findings suggest that miniscrew type-dependent calibrations are required to estimate mechanical stability of the miniscrew systems despite the utilization of same measurement tool.

Research paper thumbnail of Mechanical and clinical evaluation of the effect of microscrew on root proximity and cortical bone thickness

European Journal of Orthodontics, 2019

Summary Background/Objectives Primary stability is required for successful use of microscrew. Thi... more Summary Background/Objectives Primary stability is required for successful use of microscrew. This study investigated correlations among biomechanical, morphological, and clinical values in relationship to root contact and different placement locations. Materials/Methods Thirty-three microscrews were placed between the molars (n = 18) or in the body of the mandible (n = 15) in three pigs. Insertion torque, Periotest, resonance frequency analysis (RFA), and static and dynamic stiffness were measured. Cone beam computed tomography was performed before and after the insertion of microscrews. Interproximal microscrews were divided into root contacted microscrews (n = 9) and non-root contact microscrews (n = 9). Factorial analysis of variance was conducted, with significance set at P < 0.05. Results A significant difference was observed between bodily and root contacted microscrews in Periotest, RFA, static and dynamic stiffness, Tanδ, and bone density (RFA, P = 0.045; all others, P &...

Research paper thumbnail of Pick-up Impression of Complete Arch Implant-supported Interim Prosthesis

The Journal of oral implantology, Jan 3, 2018

Research paper thumbnail of Characterization of Next-Generation Nickel-Titanium Rotary Endodontic Instruments

Ceramic Transactions, 2013

Research paper thumbnail of DSC Study of Transformations in Clinically Used M-Wire Endodontic Instruments

ABSTRACT Properties of NiTi rotary instruments depend on their microstructural phases, which can ... more ABSTRACT Properties of NiTi rotary instruments depend on their microstructural phases, which can be studied by differential scanning calorimetry. M-Wire instruments (GTX, Dentsply Tulsa Dental Specialties) have superior fatigue resistance compared to conventional rotary instruments manufactured from superelastic NiTi wires in the austenitic condition. Objective: Employ DSC to investigate structural transformations in clinically used (7-8 times) GTX instruments. Methods: Used instruments (N=3 for each size/taper combination) were cut with a diamond saw into 3 segments: tip region, an intermediate segment, and shank region, with each segment 4-5 mm in length. The first group of specimens for DSC analysis consisted of the single segments from each instrument. The second group consisted of all three segments for each instrument. Specimens were cooled from room temperature to -80C, heated to 120C, and cooled back to -80C. The linear heating and cooling rate was 10C per minute (Q1000, TA Instruments), and the DSC cell was purged with nitrogen. Austenite-finish temperatures were compared using ANOVA. Results: Each segment of the used instruments had an Af temperature exceeding 40C. Tip regions of the M-Wire instruments had higher Af temperatures than the middle and shank regions. Minimal differences in Af temperature were found for size/taper combinations and specimens consisting of three segments. Two endothermic peaks were observed in most instruments during the heating cycle, corresponding to transformation from martensite to R-phase, and then to austenite. A single broad exothermic peak for direct transformation from austenite to martensite was generally observed during the cooling cycle. Conclusions: GTX instruments have much higher Af temperatures than conventional superelastic rotary instruments. The DSC peaks indicate that used M-Wire instruments are a mixture of martensite, R-phase and austenite. However, STEM and metallographic examination of M-Wire blanks suggest that substantial stable martensite in these instruments is not detected by DSC.

Research paper thumbnail of Effects of N-vinylcaprolactam containing polyelectrolytes on hardness, fluoride release and water sorption of conventional glass ionomers

The Journal of Prosthetic Dentistry, 2011

Statement of problem. N-vinylcaprolactam (NVC) containing glass ionomers are promising dental res... more Statement of problem. N-vinylcaprolactam (NVC) containing glass ionomers are promising dental restorative materials with improved mechanical properties; however, little information is available on other physical properties of this type of modified glass ionomer, especially their water sorption, fluoride releasing properties and microhardness. Purpose. The purpose of this study was to investigate the effects of NVC-containing polyelectrolytes on microhardness, fluoride release and water sorption of conventional glass ionomer cements (GIC). Material and methods. The terpolymer of acrylic acid (AA), itaconic acid (IA) and N-vinylcaprolactam (NVC) with 8:1:1 and 7:1:2 (AA: IA: NVC) molar ratios was synthesized by free radical polymerization and characterized using 1H-NMR and F TIR. Experimental GIC specimens were made from a 50% solution of the synthesized terpolymer with Fuji IX powder in a 3.6:1 P/L ratio. Specimens were mixed and fabricated at room temperature. Vickers hardness was determined using a microhardness tester. Water sorption and fluoride releasing properties were also investigated. Commercial Fuji IX was used as the control group. All specimens were first conditioned in distilled water at 37°C for 1 day up to 1 month. Results for the experimental GIC were compared with the control group, using 1-way and 2-way ANOVA and the Tukey multiple range test (α=.05). Results. The NVC-modified GIC exhibited higher mean values of Vickers hardness numbers (VHN). However, the data exhibited no statistically significant differences between the experimental and control groups. The experimental cement (TP2) absorbed significantly more water than the control group (P<.034). Additionally, NVC-containing specimens showed comparable fluoride releasing properties with almost the same fluoride burst and continued fluoride release from the bulk of the material. Conclusions. It was concluded that a hydrophilic monomer such as NVC might be able to increase the water sorption and decrease the amount of initial fluoride release of the glass ionomers. Hydrophilic monomer such as NVC might be able to increase the water sorption and decrease the amount of initial fluoride release of the glass ionomers. (J

Research paper thumbnail of Measure of microhardness, fracture toughness and flexural strength of N-vinylcaprolactam (NVC)-containing glass-ionomer dental cements

Dental Materials, 2010

Objectives. To investigate the effects of N-vinylcaprolactam (NVC)-containing terpolymers on the ... more Objectives. To investigate the effects of N-vinylcaprolactam (NVC)-containing terpolymers on the fracture toughness, microhardness, and flexural strength of conventional glass-ionomer cements (GIC). Methods. The terpolymer of acrylic acid (AA)-itaconic acid (IA)-N-vinylcaprolactam (NVC) with 8:1:1 (AA:IA:NVC) molar ratio was synthesized by free radical polymerization and characterized using 1 H NMR and FTIR. Experimental GIC samples were made from a 50% solution of the synthesized terpolymer with Fuji IX powder in a 3.6:1 P/L ratio. Specimens were mixed and fabricated at room temperature. Plane strain fracture toughness (K Ic) was measured in accordance with ASTM Standard 399-05. Vickers hardness was determined using a microhardness tester. Flexural strength was measured using samples with dimensions of 2 mm × 2 mm × 20 mm. For all mechanical property tests, specimens were first conditioned in distilled water at 37 • C for 1 day or 1 week. Fracture toughness and flexural strength tests were conducted on a screw-driven universal testing machine using a crosshead speed of 0.5 mm/min. Values of mechanical properties for the experimental GIC were compared with the control group (Fuji IX GIC), using one-way ANOVA and the Tukey multiple range test at = 0.05. Results. The NVC-modified GIC exhibited significantly higher fracture toughness compared to the commercially available Fuji IX GIC, along with higher mean values of flexural strength and Vickers hardness, which were not significantly different. Significance. It was concluded that NVC-containing polymers are capable of enhancing clinically relevant properties for GICs. This new modified glass-ionomer is a promising restorative dental material.

Research paper thumbnail of Root caries in the geriatric population: epidemiology, etiology, diagnosis, treatment planning and modalities of treatment

dentalforum.ump.edu.pl

Page 1. DENTAL FORUM /2/2008/XXXVI 63 PRACE POGLĄDOWE pracepoglądowe Alireza Moshaverinia1, Fengy... more Page 1. DENTAL FORUM /2/2008/XXXVI 63 PRACE POGLĄDOWE pracepoglądowe Alireza Moshaverinia1, Fengyuan Zheng1, Scott R. Schricker2, Abdel Rahim Mohammad3 Root caries in the geriatric population: epidemiology ...