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Introduction
Skills and Expertise
Publications
Publications (129)
Aim
To qualitatively and quantitatively evaluate the formation and maturation of peri‐implant soft tissues around ‘immediate’ and ‘delayed’ implants.
Materials and Methods
Miniaturized titanium implants were placed in either maxillary first molar (mxM1) fresh extraction sockets or healed mxM1 sites in mice. Peri‐implant soft tissues were evaluated...
An implant-supported prosthesis may have as few as three supporting implants, and the loss of one of them may lead to the loss of the entire structure. The framework of the Trefoil design is a standard bar made of high-strength titanium. Cyclic loading of metals and metal structures brings about the effect reducing the strength characteristics and...
Xue Yuan B Liu P Cuevas- [...]
Jill Helms
The capacity of a tissue to continuously alter its phenotype lies at the heart of how an animal is able to quickly adapt to changes in environmental stimuli. Within tissues, differentiated cells are rigid and play a limited role in adapting to new environments; however, differentiated cells are replenished by stem cells that are defined by their ph...
In the late 1990s, we learned from the pioneers the use of zygomatic implants to anchor dental restorations. Due to the youth of the technique at that time, the knowledge transmitted was rather intuitive. The surgical prescription was applicable to all patients, and no criteria or protocols had been developed to adapt the intervention to the differ...
Purpose:
The purpose of this document is to clarify the biomechanical principles involved when zygoma implants are placed under functional loads.
Methods:
Two independent reviewers conducted electronic search of the literature from January 2000 to February 2023 describing the biomechanical principles involved using the zygoma implant for maxilla...
Aim:
Autologous bone grafts consolidate faster than bone graft substitutes (BGSs) but resorb over time, which compromises implant support. We hypothesized that differences in consolidation rates affected the mechanical properties of grafts and implant stability, and tested whether a pro-osteogenic protein, liposomal WNT3A (L-WNT3A), could accelera...
The main objectives of this work were to assess the efficiency, ease-of-use, and general performance of a novel osseoshaping tool based on first-user clinical experiences and to compare these observations with preclinical data generated in rodents using a miniaturized version of the instrument. All patients selected for the surgery presented challe...
The roles of Wnt/β-catenin signaling in regulating the morphology and microstructure of craniomaxillofacial (CMF) bones was explored using mice carrying a constitutively active form of β-catenin in activating Dmp1-expressing cells (e.g., daβcatOt mice). By postnatal day 24, daβcatOt mice exhibited midfacial truncations coupled with maxillary and ma...
Objectives:
Teeth connect to bone via a periodontal ligament whereas implants connect to bone directly. Consequently, masticatory loads are distributed differently to periodontal versus peri-implant bone. Our objective was to determine how masticatory loading of an implant versus a tooth affected peri-implant versus periodontal bone remodeling. Ou...
Aim
To evaluate the similarities and differences in barrier function of a peri‐implant epithelium (PIE) versus a native junctional epithelium (JE).
Materials and methods
A mouse model was used wherein titanium implants were placed sub‐occlusally in healed extraction sites. The PIE was examined at multiple timepoints after implant placement, to cap...
Nanoscale surface modifications influence peri-implant cell fate decisions and implant loading generates local tissue deformation, both of which will invariably impact bone healing. The objective of this study is to determine how loading affects healing around implants with nanotopography. Implants with a nanoporous surface were placed in over-size...
Objectives
Our objective was to test the hypothesis that local delivery of a WNT protein therapeutic would support osseointegration of an unstable implant placed into an oversized osteotomy and subjected to functional loading.
Materials and Methods
Using a split‐mouth design in an ovariectomized (OVX) rat model, 50 titanium implants were placed in...
Objectives:
Oral implants transmit biting forces to peri-implant bone. In turn, those forces subject peri-implant bone to mechanical stresses and strains. Here, our objective was to understand how peri-implant bone responded to conditions of normal versus hyper-loading in a mouse model.
Material and methods:
Sixty-six mice were randomly assigned...
Statement of problem
There is a long-held assumption that teeth are superior to implants because the periodontal ligament (PDL) confers a preeminent defense against biologic and mechanical challenges. However, adequate analysis of the literature is lacking. As a result, differential treatment planning of tooth- and implant-supported restorations ha...
Introduction
Few interspecies comparisons of alveolar bone have been documented, and this knowledge gap raises questions about which animal models most accurately represent human dental conditions or responses to surgical interventions.
Objectives
The objective of this study was to employ state-of-the-art quantitative metrics to directly assess an...
Introduction
Physiological root resorption is a common occurrence in mammalian teeth, which suggests that there must be a corollary consisting of physiological cementum repair. The mechanism(s) responsible for this physiological repair process is unknown and was the focus of this study.
Methods
Using a rat model, we explored first the prevalence o...
Background:
Autologous bone can be harvested from the flutes of a conventional drill or from a bone scraper; here we compared whether autologous bone chips generated by a new slow-speed instrument were more osteogenic than the bone chips generated by conventional drills or bone scrapers. Additionally, we tested whether the osteogenic potential of...
Aims
Surgeons and most engineers believe that bone compaction improves implant primary stability without causing undue damage to the bone itself. In this study, we developed a murine distal femoral implant model and tested this dogma.
Methods
Each mouse received two femoral implants, one placed into a site prepared by drilling and the other into t...
Objective:
Primary stability is a prerequisite for implant osseointegration. Some degree of misfit between an implant and its osteotomy is required to ensure primary stability, and this is typically achieved by undersizing an implant osteotomy. In this preclinical study, we aimed at understanding the relationship between misfit, insertion torque,...
Experimental studies on the effect of micromotion on bone healing around implants are frequently conducted in long bones. In order to more closely reflect the anatomical and clinical environments around dental implants, and eventually be able to experimentally address load‐management issues, we have developed a system that allows initial stabilizat...
Purpose:
This systematic review was prepared as part of the Academy of Osseointegration (AO) 2018 Summit, held August 8-10 in Oak Brook Hills, Illinois, to assess the relationship between the primary (mechanical) and secondary (biological) implant stability.
Materials and methods:
Electronic and manual searches were conducted by two independent...
Q. Xu Xue Yuan X. Zhang- [...]
Jill Helms
Despite an extensive literature documenting the adaptive changes of bones and ligaments to mechanical forces, our understanding of how tissues actually mount a coordinated response to physical loading is astonishingly inadequate. Here, using finite element (FE) modeling and an in vivo murine model, we demonstrate the stress distributions within the...
Of all geometric shapes, a tri-oval one may be the strongest because of its capacity to bear large loads with neither rotation nor deformation. Here, we modified the external shape of a dental implant from circular to tri-oval, aiming to create a combination of high strain and low strain peri-implant environment that would ensure both primary impla...
The preservation of bone viability at an osteotomy site is a critical variable for subsequent implant osseointegration. Recent biomechanical studies evaluating the consequences of site preparation led us to rethink the design of bone-cutting drills, especially those intended for implant site preparation. We present here a novel drill design that is...
X. Zhang Xue Yuan Q. Xu- [...]
Jill Helms
A soft food diet leads to changes in the periodontal ligament (PDL). These changes, which have been recognized for more than a century, are ascribed to alterations in mechanical loading. While these adaptive responses have been well characterized, the molecular, cellular, and mechanical mechanisms underlying the changes have not. Here, we implicate...
With the introduction of high-speed cutting tools, clinicians have recognized the potential for thermal damage to the material being cut. Here, we developed a mathematical model of heat transfer caused by drilling bones of different densities and validated it with respect to experimentally measured temperatures in bone. We then coupled these comput...
When bone implants are loaded, they are inevitably subjected to displacement relative to bone. Such micromotion generates stress/strain states at the interface that can cause beneficial or detrimental sequels. The objective of this study is to better understand the mechanobiology of bone healing at the tissue-implant interface during repeated loadi...
Aging is associated with a function decline in tissue homeostasis and tissue repair. Aging is also associated with an increased incidence in osteopenia and osteoporosis, but whether these low bone mass diseases are a risk factor for delayed bone healing still remains controversial. Addressing this question is of direct clinical relevance for dental...
Xue Yuan Xibo Pei Y Zhao- [...]
Jill Helms
The aim of this study was to gain insights into the biology and mechanics of immediate postextraction implant osseointegration. To mimic clinical practice, murine first molar extraction was followed by osteotomy site preparation, specifically in the palatal root socket. The osteotomy was positioned such that it removed periodontal ligament (PDL) on...
Our long-term objective is to devise methods to improve osteotomy site preparation and, in doing so, facilitate implant osseointegration. As a first step in this process, we developed a standardized oral osteotomy model in ovariectomized rats. There were 2 unique features to this model: first, the rats exhibited an osteopenic phenotype, reminiscent...
Background:
Osteotomies have been performed for centuries yet there remains a remarkable lack of consensus on optimal methods for cutting bone. There is universal agreement, however, that preserving cell viability is critical.
Purpose:
To identify mechanobiological parameters influencing bone formation after osteotomy site preparation.
Material...
A variety of clinical classification schemes have been proposed as a means to identify sites in the oral cavity where implant osseointegration is likely to be successful. Most schemes are based on structural characteristics of the bone, for example, the relative proportion of densely compact, homogenous (type I) bone versus more trabeculated, cance...
L Wang Y Wu K C Perez- [...]
Jill Helms
Bone condensation is thought to densify interfacial bone and thus improve implant primary stability, but scant data substantiate either claim. We developed a murine oral implant model to test these hypotheses. Osteotomies were created in healed maxillary extraction sites 1) by drilling or 2) by drilling followed by stepwise condensation with tapere...
The mammalian skeleton performs a diverse range of vital functions, requiring mechanisms of regeneration that restore functional skeletal cell populations after injury. We hypothesized that the Wnt pathway specifies distinct functional subsets of skeletal cell types, and that lineage tracing of Wnt-responding cells (WRCs) using the Axin2 gene in mi...
Skulls are amongst the most informative documents of evolutionary history but a complex geometry, coupled with composite material properties and complicated biomechanics, have made it particularly challenging to identify mechanical principles guiding the skull’s morphogenesis. Despite this challenge, multiple lines of evidence, for example the rela...
The periodontal ligament (PDL) functions as an enthesis, a connective tissue attachment that dissipates strains created by mechanical loading. Entheses are mechanoresponsive structures that rapidly adapt to changes in their mechanical loading; here we asked which features of the PDL are sensitive to such in vivo loading. We evaluated the PDL in 4 p...
Aim:
Implant osseointegration is not always guaranteed and once fibrous encapsulation occurs clinicians have few options other than implant removal. Our goal was to test whether a WNT protein therapeutic could rescue such failed implants.
Materials and methods:
Titanium implants were placed in over-sized murine oral osteotomies. A lack of primar...
Implants placed with high insertion torque (IT) typically exhibit primary stability, which enables early loading. Whether high IT has a negative impact on peri-implant bone health, however, remains to be determined. The purpose of this study was to ascertain how peri-implant bone responds to strains and stresses created when implants are placed wit...
Background: Patients with isolated cleft palates exhibit normal growth potential but surgical intervention often results in midfacial hypoplasia. Why surgical repair causes this is not well understood. We identified a region that appeared to function as a growth center and tested whether surgical disruption of this site had an effect on midfacial g...
A proper definition of the 'optimal' number of implants to support a full arch prosthesis should go beyond solely a listing of the number of implants used in a treatment plan; it should be based upon a biomechanical analysis that takes into account several factors: the locations of the implants in the jaw; the quality and quantity of bone into whic...
In pediatric surgeries, cutaneous scarring is frequently accompanied by an arrest in skeletal growth. The molecular mechanisms responsible for this effect are not understood. Here, we investigated the relationship between scar contracture and osteogenesis. An excisional cutaneous wound was made on the tail of neonatal mice. Finite element (FE) mode...
Complete edentulism is a common problem in many countries and can be a serious disability. It concerns about one-fifth of the adult world population, in some countries reaching 50% at the age of 50. The decline in the prevalence of edentulism is offset by the increase of the elderly population. This leads to an increasing demand for implant-based t...
Children with unoperated cleft palates have nearly normal growth of their faces whereas patients who have had early surgical repair often exhibit midfacial hypoplasia.Surgical repair is responsible for the underlying bone growth arrest but the mechanisms responsible for this surgical sequelae are poorly understood. We simulated the effect of cleft...
To determine the key biological events occurring during implant failure then use this knowledge to develop new biology-based strategies that improve osseointegration.
Wild-type and Axin2(LacZ/LacZ) adult male mice underwent oral implant placement, with and without primary stability. Peri-implant tissues were evaluated using histology, alkaline phos...
Dental implants have become a routinely used technique in dentistry for replacing teeth. However, risks of failure are still experienced and remain difficult to anticipate. Multiscale phenomena occurring around the implant interface determine the implant outcome. The aim of this review is to provide an understanding of the biomechanical behavior of...
Many of our assumptions concerning oral implant osseointegration are extrapolated from experimental models studying skeletal tissue repair in long bones. This disconnect between clinical practice and experimental research hampers our understanding of bone formation around oral implants and how this process can be improved. We postulated that oral i...
Edited by: R. Baron Keywords: Dental Histology Maxilla Oral cavity Mice Model Many of our assumptions concerning oral implant osseointegration are extrapolated from experimental models studying skeletal tissue repair in long bones. This disconnect between clinical practice and experimental research hampers our understanding of bone formation around...
Implant loading can create micromotion at the bone-implant interface. The interfacial strain associated with implant micromotion could contribute to regulating the tissue healing response. Excessive micromotion can lead to fibrous encapsulation and implant loosening. Our objective was to characterize the influence of interfacial strain on bone rege...
Unlabelled:
While in vitro studies have shown that nanoscale surface modifications influence cell fate and activity, there is little information on how they modulate healing at the bone-implant interface.
Aim:
This study aims to investigate the effect of nanotopography at early time intervals when critical events for implant integration occur....
The primary cilium is an organelle that senses cues in a cell's local environment. Some of these cues constitute molecular signals; here, we investigate the extent to which primary cilia can also sense mechanical stimuli. We used a conditional approach to delete Kif3a in pre-osteoblasts and then employed a motion device that generated a spatial dis...
When an implant is placed into bone, an interface is created. This interface has a critical biomechanical function: it must support the implant in bone. However, failure of implant fixation (i.e., implant “loosening”), continues to be a leading cause of implant failure [1,2]. While there are a number of factors involved in this problem, it is recog...
Cell-biomaterial interactions for different material compositions were evaluated through quantitative examination of in vitro cell spreading behavior and shear-induced cell detachment. Biomaterial substrates consisted of identically prepared, well characterized bulk samples of implant grade cp Ti, Ti-6AI-4V, and Synamel. 3T3 fibroblasts were seeded...
The strength of a Wnt-based strategy for tissue regeneration lies in the central role that Wnts play in healing. Tissue injury triggers local Wnt activation at the site of damage, and this Wnt signal is required for the repair and/or regeneration of almost all tissues including bone, neural tissues, myocardium, and epidermis. We developed a biologi...
Evidence that nanoscale surface properties stimulate and guide various molecular and biological processes at the implant/tissue interface is fostering a new trend in designing implantable metals. Cutting-edge expertise and techniques drawn from widely separated fields, such as nanotechnology, materials engineering and biology, have been advantageou...
Osseointegration is critical for implant fixation, and mechanical stimuli play a role in this process. Our long term goal is to investigate the relationship between local mechanical environment and osseointegration. In this paper, as a first step in the study, we constructed an approximate D model of the in-vivo test and focused on calculating the...
Osseointegration and Dental Implants offers a comprehensive guide to the state of the art of implant dentistry. Based around the proceedings of the Toronto Osseointegration Conference Revisited, it gathers together information on all aspects of implant dentistry and osseointegration, from basic scientific background, such as the biology of osseoint...
The Healing Bone-Implant Interface: Role of Micromotion and Related Strain Levels in TissueReferences
While bone healing occurs around implants, the extent to which this differs from healing at sites without implants remains unknown. We tested the hypothesis that an implant surface may affect the early stages of healing. In a new mouse model, we made cellular and molecular evaluations of healing at bone-implant interfaces vs. empty cortical defects...
Due to the aging population and the increasing need for total joint replacements, osseointegration is of a great interest for various clinical disciplines. Our objective was to investigate the molecular and cellular foundation that underlies this process. Here, we used an in vivo mouse model to study the cellular and molecular response in three dis...
The majority of cells are equipped to detect and decipher physical stimuli, and then react to these stimuli in a cell type-specific manner. Ultimately, these cellular behaviors are synchronized to produce a tissue response, but how this is achieved remains enigmatic. Here, we investigated the genetic basis for mechanotransduction using the bone mar...
Originally published in Int Dent J 2003; 53 supplement 2: 409-433
BACKGROUND:
Clinicians need quality research data to decide which dental implant should be selected for patient treatment. AIM(S)/OBJECTIVE(S): To present the scientific evidence for claims of relationship between characteristics of dental implants and clinical performance.
STUDY D...
Clinicians need quality research data to decide which dental implant should be selected for patient treatment. AIM(S)/OBJECTIVE(S): To present the scientific evidence for claims of relationship between characteristics of dental implants and clinical performance.
Systematic search of promotional material and Internet sites to find claims of implant...
The aim of this study was to compare the force and moment distributions that develop on different implant overdenture attachments when vertical compressive forces are applied to an implant-retained overdenture.
The following attachments were examined: Nobel Biocare bar and clip (NBC), Nobel Biocare standard ball (NSB), Nobel Biocare 2.25-mm-diamete...
Export Date: 19 October 2012, Source: Scopus
Instrumented interbody implants were placed into the disc space of a motion segment in two baboons. During the animal's activities, implants directly measured in vivo loads in the lumbar spine by telemetry transmitter.
Develop and test an interbody implant-load cell and use the implant to measure directly loads imposed on the lumbar spine of the ba...
Research in biomaterials and biomechanics has fueled a large part of the significant revolution associated with osseointegrated implants. Additional key areas that may become even more important--such as guided tissue regeneration, growth factors, and tissue engineering--could not be included in this review because of space limitations. All of this...