Jeff Nickel

• University of Missouri–Kansas City

Objective To review the ecological validity of outcomes from current research involving temporomandibular disorders (TMDs), with an emphasis on chronic myofascial pain and the precocious development of degenerative disease of the temporomandibular joint (TMJ). Materials and Methods Current approaches used to study TMDs in terms of neuromechanics,...

Objective To compare the efficacy and efficiency of treatment with clear aligners (CAT) vs fixed appliances (FAT) in adolescents with Class I and II moderate to severe malocclusions. Materials and Methods One operator’s (Garfinkle) cases from 2014 to 2019, started at age 12–18 years, with pre- and posttreatment records were identified and used acc...

Introduction: This study tested orthognathic surgery effects on temporomandibular joint (TMJ) compressive stresses. Methods: Pre- (T1) and post-surgery (T2) cone-beam computed tomography images were collected from consenting subjects aged ≥15 years. Anatomical data were used to measure surgical changes in anteroposterior mandibular position and...

Objectives To determine if temporomandibular joint (TMJ) compressive stresses during incisor biting (1) differed between growing children over time, and (2) were correlated with Frankfort Horizontal-mandibular plane angle (FHMPA, °) and ramus length (Condylion-Gonion (Co-Go), mm). Materials and Methods Three-dimensional anatomical geometries, FHMP...

Purpose/objective Competence is expected of each beginning dentist and orthodontist. However, the broad definition of competence presents a challenge to academic programs in identifying the level of cognition for students to achieve competence. This study aimed to determine the Didactic Clinical Skills Development curriculum content and competency...

The biggest challenge to improve the diagnosis and therapies of Craniomaxillofacial conditions is to translate algorithms and software developments towards the creation of holistic patient models. A complete picture of the individual patient for treatment planning and personalized healthcare requires a compilation of clinician-friendly algorithms t...

Objectives To test the hypotheses that mechanobehavior scores (MBS) were correlated with mandibular ramus lengths (Co-Go) and differed between facial phenotypes. Materials and Methods Subjects gave informed consent to participate. Co-Go (mm), mandibular plane angles (SN-GoGn, °), and three-dimensional anatomy were derived from cephalometric radiog...

The temporomandibular joint (TMJ) disc nutrient environment profoundly affects cell energy metabolism, proliferation, and biosynthesis. Due to technical challenges of in vivo measurements, the human TMJ disc extracellular nutrient environment under load, which depends on metabolic rates, solute diffusion, and disc morphometry, remains unknown. Ther...

Objective: A third focused workshop explored how to transfer novel findings into clinical orthodontic practice. Setting and sample population: Participants met at the Scottsdale Plaza Resort, 12-16 September 2018 for the Consortium for Orthodontic Advances in Science and Technology 2018 Innovators' Workshop. Thirty speakers and four lunch-hour f...

Aims: To test whether women with temporomandibular disorder (TMD)-related pain showed higher psychosocial scores and higher awake- and sleep-time jaw muscle activities (characterized by duty factors) compared to pain-free controls and whether psychosocial scores and the jaw muscle duty factors were associated. Methods: Subjects gave informed con...

Craniofacial secondary cartilages of the mandibular condyle and temporomandibular joint (TMJ) eminence grow in response to the local mechanical environment. The intervening TMJ disc distributes normal loads over the cartilage surfaces and provides lubrication. A better understanding of the mechanical environment and its effects on growth, developme...

Aims: THE OBJECTIVE WAS TO INVESTIGATE IF GENDER DIFFERENCES EXIST IN THE ASSOCIATIONS BETWEEN PERIODONTITIS AND TYPE 2 DIABETES. DISPROPORTIONATE DISPARITIES BY GENDER WERE FOUND TO EXIST IN RATES OF BOTH PERIODONTITIS AND DIABETES WITH RESPECT TO DEMOGRAPHICS AND BEHAVIOURAL PREDICTORS THAT CANNOT BE EXPLAINED SOLELY BY THE WELL-ESTABLISHED ASSO...

Periodontal disease, a complication of diabetes mellitus (DM), may cause teeth loss and bone loss which is a major health‐related threat for a large number of Americans. Lowering the prevalence of moderate and severe periodontitis is an objective of Healthy People 2020 in the US and a strategic plan of the U.S. Center for Disease Control and Preven...

We report a disposable point-of-care sensing platform specific to salivary cortisol detection. The sensor is inkjet printed on a paper substrate with a metalloporphyrin based macrocyclic catalyst ink that can electrochemically reduce cortisol, captured by aptamer functionalized magnetic nanoparticles. The sensor consists of a thin magnet disc, alig...

Energy densities (ED, mJ/mm3) quantify mechanical work imposed on articular cartilages during function. This cross-sectional study examined differences in temporomandibular joint (TMJ) ED during asymmetric versus symmetric jaw closing in healthy females versus males. ED component variables were tested for differences between and within sexes for tw...

To determine whether behavioral factors differ among metabolic conditions and self-reported health, and to determine whether self-reported health is a valid predictor of metabolic syndrome (MetS). A total of 2997 individuals (≥ 40 years old) were selected from four biennial U.S. National Health and Nutrition Examination Surveys (2007–2014). A set o...

Objectives: To determine whether dolichofacial (Frankfort horizontal mandibular plane angle (FHMPA) ≥30°) vs brachyfacial (FHMPA ≤22°) phenotypes differ in temporomandibular joint (TMJ) loads and whether these differences correlate longitudinally with mandibular ramus height (Condylion-Gonion, Co-Go). Setting and sample population: Lateral and p...

Objectives: To test whether mechanobehaviour (temporomandibular joint (TMJ) loads, jaw muscle use) was different between facial types and correlated with ramus height (Condylion-Gonion, mm). Setting and sample population: University of Missouri-Kansas City (UMKC) Orthodontic Clinic. Ten dolichofacial and ten brachyfacial adolescents (Sella-Nasio...

Objective: A second focused workshop explored how to transfer novel findings into clinical orthodontic practice. Setting and sample population: Participants met in West Palm Beach (Florida, USA), on 9-11 September 2016 for the Consortium for Orthodontic Advances in Science and Technology 2016 Innovators' Workshop (COAST). Approximately 65 regist...

Objectives: To test that the speed of tooth translation is not affected by stress magnitude and growth status. Setting and sample population: Advanced Education Orthodontic clinics at the Universities of Nebraska Medical Center and Missouri-Kansas City. Forty-six consenting subjects with orthodontic treatment plans involving maxillary first prem...

Background: Temporomandibular disorder (TMD) incidences are believed to be related to parafunctional behaviors like teeth clenching. Objectives: This pilot study aimed to (i) develop an automated clench-detection algorithm, and (ii) apply the algorithm to test for differences in nocturnal clenching in women with and without TMD. Methods: Subje...

Cartilage fatigue may be a factor in the precocious development of degenerative changes in the temporomandibular joint (TMJ). This cross-sectional study estimated potential for cartilage fatigue via TMJ energy densities (ED) and jaw muscle duty factors (DF), which were combined to calculate mechanobehavioral scores (MBS) in women with (+) and witho...

Objectives: To investigate the ploughing mechanism associated with tractional force formation on the temporomandibular joint (TMJ) disc surface. Setting and sample population: Ten left TMJ discs were harvested from 6- to 8-month-old male Yorkshire pigs. Materials and methods: Confined compression tests characterized mechanical TMJ disc propert...

Objective: Cartilage fatigue, due to mechanical work, may account for the early development of degenerative joint disease in the temporomandibular joint (TMJ), and why women are 3-times more likely to be afflicted. This study tested for gender differences in mechanical energy densities in women and men with healthy TMJs. Design: Eighteen women a...

It is unknown if females and males use jaw muscles similarly during exercise. This pilot study assessed jaw elevator muscle duty factors (DFs=time of muscle activity/total recording time) at repeated sessions to test if DFs are reliable and different between sexes during exercises in two environments. Ten female and seven male subjects recruited fr...

The role of mechanics in degenerative joint disease of the temporomandibular joint (TMJ) is largely unknown. Objectives were to: 1) develop an empirical model to relate variables of cartilage mechanics and tractional forces; and 2) use the empirical model to estimate tractional forces for calculations of work done (mJ) and energy densities (mJ/mm(3...

Cartilage fatigue, due to mechanical work, may account for precocious development of degenerative joint disease in the temporomandibular joint (TMJ). This study compared energy densities (mJ/mm³) in TMJs of three diagnostic groups. Sixty-eight subjects (44 women, 24 men) gave informed consent. Diagnostic criteria for temporomandibular disorders (DC...

To bring together orthodontic stakeholders from academics, industry, and private practice for a series of thematically focused workshops to explore and develop the transfer of novel approaches into clinical orthodontic practice. Twenty-seven invited speakers, eight poster presenters, and participants of the Consortium for Orthodontic Advances in Sc...

Pain-related temporomandibular disorders (TMDs) are the most prevalent conditions among TMDs. There is contrasting evidence available for association of pain-related TMD and masticatory muscle activity (MMA). The present investigation assesses the associations between MMA levels of masseter and temporalis muscles during awake and sleep among pain-r...

To determine differences in masticatory muscle usage between temporomandibular joint disorders diagnostic groups. Seventy-one informed and consented subjects (27 men; 44 women) participated at the University at Buffalo. Research diagnostic criteria and imaging data were used to categorize subjects according to the presence/absence (+/-) of TMJ disc...

Subjects with/without temporomandibular joint disorders (TMJD) were tested for differences in muscle forces. School of Dental Medicine, University at Buffalo. Ninety-one subjects were classified in four groups based on the presence/absence (±) of chronic myofascial and/or TMJ pain (P) and bilateral disc displacement (DD). Validated numerical models...

The term 'oral parafunctional behaviours' encompasses behaviours that are different from those required for, or associated with, physiological functional needs such as mastication, communication, swallowing or breathing. Previous reports have associated waking-state oral parafunctional behaviours with biopsychosocial characteristics such as female...

Aim and background: The objective of this study was to determine if duty factors (DF) of low-magnitude MMA during awake and sleep periods were associated with self-reports of anxiety, depression, and somatic symptoms, and if so, whether or not any associations were modified by gender or the presence of pain. Limited information is currently availa...

The temporomandibular joint (TMJ) is a structure of substantial importance in clinical orthodontics. This chapter provides an in-depth background on the applications of three-dimensional (3D) imaging to temporomandibular joint disorder (TMJD) diagnostics and therapeutics, and highlights clinical and biological data that are essential to attain comp...

Objective: Numerical modeling predicts higher TMJ forces for those with disc displacement (DD) compared to healthy subjects (Iwasaki et al. 2009) and for increased muscle forces during jaw loading. Thus, this pilot study tested if individuals with/without temporomandibular disorders (TMDs) use their masticatory muscles similarly during molar biting...

Objectives: It is unknown if women and men use jaw muscles during exercise consistently and similarly. This pilot study assessed jaw muscle duty factors (DF%=time of muscle activity/total recording timex100) at repeated sessions to test if: DFs are (1) measurable, (2) reliable, and (3) different between genders during leg-extension exercises. Met...

Objective: To test the hypothesis that during the day and night, masticatory muscle activities is greater in individuals with temporomandibular disorders. Method: MRI and Research Diagnostic Criteria were used to categorize 71 informed and consenting subjects according to TMJ disc position (+DD = disc displacement) and pain status (+P = presence...

In this study, we investigated the effects of the magnitudes of applied stress and growth status on the speed of tooth movement. Eighty-two maxillary canines in 41 subjects were retracted for 84 days by estimated stresses of 4, 13, 26, 52, or 78 kPa applied continuously via segmental mechanics. Dental impressions made at intervals of 1 to 14 days r...

Objective: To evaluate the effect of type of light curing unit and associated total energy output on the degree of conversion (DC) of orthodontic bracket adhesive and bracket shear bond strength (SBS). Methods: Orthodontic brackets (Victory Series/MBT, 3M-Unitek) were bonded to extracted third molars using a light-cured bracket adhesive (Transbon...

Objective: It is unknown if variations in masticatory muscle orientation explain predicted TMD diagnostic group differences in lateral pterygoid muscle forces during static biting (Kohlmeier et al., 2012, J Dent Res, 91(SI A):578). Method: Research Diagnostic Criteria and magnetic resonance TMJ images were used by calibrated examiners to classify...

Differences in facial form are expected to be linked to function; however, evidence for these relations is equivocal. Objectives: This study determined if young adults (T3) with dolichofacial (Frankfort-Horizontal Mandibular Plane Angle (FHMPA)≥30°) versus brachyfacial (FHMPA≤22°) features showed differences in FHMPA and temporomandibular joint (TM...

Objective: To compare three-dimensional tooth movements resulting from relatively higher and lower stresses in a split-mouth design. Materials and methods: Eight volunteers whose maxillary first premolars were removed for orthodontic treatment participated. Each subject's maxillary canines were retracted by randomly assigned constant stresses of...

Objective: To test the hypothesis that during awake- and sleep-states, masticatory muscle activities are greater in subjects with TMJ disc displacement and pain (+DD/+Pain) compared to subjects with/without disc displacement and without pain (+DD/-Pain and –DD/-Pain). Method: MRI and Research Diagnostic Criteria and were used to categorize 40 inf...

Objectives: To evaluate the effect of fluoride prophylactic agents and static load on the unloading mechanical properties and surface quality of nickel-titanium (NiTi) orthodontic closed coil springs. Methods: Medium force springs (G&H Wire Orthoforce, 1.2 mmx12 mm) were immersed in phosphate buffered saline (PBS) or PBS combined with daily 2-min...

Craniofacial morphology is commonly assumed to influence orofacial functions and vice versa. Objectives: This pilot study aimed to evaluate jaw mechanics and muscle behavior in adolescents with two different craniofacial morphologies. Methods: Ten dolichofacial and ten brachyfacial (SN-GoGn angles ≥37° and ≤27°, respectively) subjects consented to...

The objective of this chapter is to review the literature which describes the evolving roles of cone-beam computed tomography (CBCT) in cephalometric analysis for evaluation of dental and craniofacial structures and orthodontic treatment outcomes. Despite inherent limitations associated with conventional two-dimensional (2D) cephalograms, these con...

It is unknown whether or not intraoral vibrations affect stick-slip behavior at orthodontic bracket-archwire interfaces. In this study, we evaluated bracket-archwire stick-slip behavior as a function of ligation method and archwire vibration. In-vivo archwire vibrations were measured to obtain frequencies and amplitudes for ex-vivo testing. A piezo...

Despite the importance of sliding contact in diarthrodial joints, only a limited number of studies have addressed this type of problem, with the result that the mechanical behavior of articular cartilage in daily life remains poorly understood. In this paper, a finite element formulation is developed for the sliding contact of biphasic soft tissues...

Objective: To determine TMD diagnostic group differences in TMJ disc mechanics due to the effects of normal (perpendicular) load. Method: In accordance with IRB oversight, fifty-two subjects (30 female; 22 male) participated. Research Diagnostic Criteria-calibrated investigators classified subjects based on signs of disc displacement (DD) and pai...

Central nervous system organization of masticatory muscles determines the magnitude of joint and muscle forces. Validated computer-assisted models of neuromuscular organization during biting were used to determine organization in individuals with and without temporomandibular disorders (TMD). Ninety-one individuals (47 women, 44 men) were assigned...

Objectives: Friction associated with stick-slip behavior at the bracket-wire interface is likely to affect rates of orthodontic tooth movement. To date, no reported data describe characteristics of intraoral archwire vibration and whether or not vibration differentially affects stick-slip behavior at the bracket-wire interface of self-ligating comp...

Pain is common during orthodontic treatment yet little is known about pain experiences with respect to magnitude of tooth loads. Objectives: The purpose of this pilot study was to assess longitudinally pain intensity and quality using a validated self-report. Methods: Eight subjects (five males, 3 females) who required maxillary first premolar ex...

Objectives: It is unknown whether differences in mechanics may explain inter-individual variability in muscle forces during biting. To test this hypothesis, we used numerical modeling to test for differences in muscle forces amongst subjects with and without temporomandibular disorders. Methods: IRB approved Research Diagnostic Criteria and MRI i...

Gonzalez Y, Iwasaki LR, McCall Jr WD, Ohrbach R, Lozier E, Nickel JC. Reliability of electromyographic activity vs. bite-force from human masticatory muscles. Eur J Oral Sci 2011; 119: 219–224. © 2011 Eur J Oral Sci The reproducibility of electromyographic (EMG) activity in relation to static bite-force from masticatory muscles for a given biting s...

Cone-beam computed tomography (CBCT) might be more accurate in identifying radicular surface lesions compared with digital periapical radiography. In this study, we compared these techniques in detecting simulated root resorption lesions. A porcine mandible was used to support 10 human maxillary central incisors. CBCT and digital periapical radiogr...

Extended-storage alginates with purported dimensional stability for up to 100 hrs are often used for impressions shipped to orthodontic digital model companies. During the winter months, some model companies recommend storing the impressions with isopropyl alcohol to counteract the potential effects of freezing during shipment. However, the efficac...

Individuals with and without TMJ disc displacement (DD) and pain (Pain) may behave differently in terms of masticatory muscle use. Objective: To test whether or not duty factors of masticatory muscle activities can be measured in DD and Pain subjects . Methods: Institutional regulations were applied and Research Diagnostic Criteria and MRI were use...

Mechanical fatigue failure may account, in part, for clinical differences in human temporomandibular joints (TMJs). Therefore, energy input to tissues should be considered. Objectives: This pilot study measured and compared energy densities (ED) in TMJs of 18 subjects (ten females, eight males) with TMJ disc displacement (+DD) and 14 subjects (seve...

Objective: To test the accuracy of neuromuscular objectives of minimization of joint loads (MJL) or muscle effort (MME) to predict masseter and temporalis muscle activities during static biting on incisors and molars. Methods: According to institutional guidelines, Research Diagnostic Criteria, and MR imaging, 93 subjects (49 women, 44 men) were as...

Analysis of previous data suggested the hypothesis that temporomandibular joint (TMJ) eminence shapes develop ideally to minimize joint loads. Hence, we tested this hypothesis in nine females and eight males in each of two groups, with and without TMJ disc displacement. Participants provided anatomical data used in a joint load minimization numeric...

The likelihood of development of degenerative joint disease (DJD) of the temporomandibular joint (TMJ) is related to the integrity of the TMJ disc. Predilection for mechanical failure of the TMJ disc may reflect inter-individual differences in TMJ loads. Nine females and eight males in each of normal TMJ disc position and bilateral disc displacemen...

Authors – Nickel J, Spilker R, Iwasaki L, Gonzalez Y, McCall WD, Ohrbach R, Beatty MW, Marx D Objectives – To determine the combined effects 1) of stress‐field aspect ratio and velocity and compressive strain and 2) joint load, on temporomandibular joint (TMJ) disc mechanics. Setting and Sample Population – Fifty‐two subjects (30 ♀; 22 ♂) participa...

Tractional forces on the temporomandibular joint (TMJ) disc predispose tissue fatigue. This study tested the hypotheses that tractional forces: (1) increased with stress-field velocity (V) and aspect ratio (AR, contact area diameter/cartilage thickness), and compressive strain (epsilon); and (2) varied depending on cartilage thickness. Porcine TMJ...

Disorders of the temporomandibular joint (TMJ) afflict 3-29% of people aged 19-40 years. Degenerative joint disease (DJD) of the TMJ generally occurs 15 years earlier than in other human joints and 1.5-2 times more often in women than men. The TMJ disc is the primary stress distribution mechanism within the joint. Mechanical failure of the TMJ disc...

To investigate genetic, biologic, and mechanical factors that affect speed of human tooth movement. Setting and Sample Population - Sixty-six maxillary canines in 33 subjects were translated distally for 84 days. Distal compressive stresses of 4, 13, 26, 52, or 78 kPa were applied to maxillary canines via segmental mechanics. Dental casts and gingi...

Predetermined masticatory muscle forces have been used to simplify calculations for computer modeling of human jaw mechanics. Force magnitudes have been based on an assumed relationship between EMG and bite force. Recent work suggests that EMG-bite force relationships vary depending on tooth tipping moments produced by different bite force directio...

TMJ eminence morphology provides important constraint forces in static mandibular mechanics, and thus, affects activities of muscles and subsequent joint loads during biting. In healthy subjects, eminence morphologies were reported to be consistent with a neuromuscular objective of minimization of joint load (MJL). Objective: To test for significan...

Currently the mechanics of the orthodontic appliance is the primary tool for the clinician to conduct and control tooth movement. In the future, increased knowledge of the genetic and environmental factors affecting the biology of the patient may allow improved predictability and control of the direction, nature, and speed of orthodontic tooth move...

The aim of this study was to assess the critical energy required to induce flaw propagation in the temporomandibular joint (TMJ) disc when tensile and shear stresses were applied. J-integrals were measured for Mode I and III fractures because excessive tensile and shear stresses promote disc failure. Single edge notch (Mode I) and trouser tear (Mod...

Static mechanical analyses of the masticatory apparatus often assume that jaw muscle activity, as measured using electromyography (EMG), is linearly and constantly related to magnitude of bite force during biting, regardless of bite force-induced tooth-tipping moments. The objective of this study was to test the hypothesis that the relationship bet...

The variables affecting speed of tooth movement are unquantified. In particular, the effects of stress and human biological variations are unknown. Therefore, our objectives in this study were to determine relationships between (1) stress and velocity of tooth translation (v(t)), and (2) interleukin-1 (IL-1) gene cluster polymorphisms, IL-1beta and...

The pathomechanics of degenerative joint disease of the temporomandibular joint (TMJ) may involve fatigue produced by mechanical work on the articulating tissues. This study tested the hypotheses that mechanical work in the TMJ (i) varies with the type of mandibular activity, and (ii) is evenly distributed over TMJ surfaces. Ten healthy human parti...

Unlabelled: Mechanical fatigue-related degeneration of the temporomandibular joint (TMJ) disc may be promoted by tractional forces. This study tested the hypotheses that tractional forces following static loading of the TMJ disc: (1) increase with compressive strain at the start of movement, and (2) are velocity-dependent during movement. Sixty-fo...

Tooth movement has been studied largely with respect to the force required for tipping when pressure distribution varies along the length of the periodontal ligament. But important factors for effective canine translation include the nature and magnitude of applied stress and the patient's cell biology. The purpose of this research was to test 3 hy...

The etiology of degenerative disease of the TMJ may involve fatigue produced by surface tractional forces and compressive stresses. This study tested the time-dependent effects of compressive loading and stress-field translation on TMJ disc-surface tractional forces and stresses. In laboratory experiments with 50 porcine discs, an acrylic indenter...

Aims: To test the effects of occlusal force (OF) angle on the variations in predicted muscle and temporomandibular joint (TMJ) forces during unilateral molar bites. Methods: The craniomandibular (CM) geometries of 21 individuals were determined from lateral and posteroanterior cephalometric radiographs. These geometries were used in a numerical mod...

To test the effects of occlusal force (OF) angle on the variations in predicted muscle and temporomandibular joint (TMJ) forces during unilateral molar bites. The craniomandibular (CM) geometries of 21 individuals were determined from lateral and posteroanterior cephalometric radiographs. These geometries were used in a numerical model based on min...

The efficiency of tooth movement associated with orthodontic sliding mechanics can be compromised by friction between arch wire and tube or bracket slot. The described studies measured the apparent coefficient of static friction (μa) during sliding along an arch wire. Known moments were applied to simulate tooth tipping. Measurements tested whether...

Development of the components of the temporomandibular joint (TMJ) is thought to reflect joint loading. The aims of this project were to test 3 hypotheses: whether effective eminence morphology, masticatory muscle forces, and predicted TMJ forces during chincup loading of the mandible were consistent with the objectives of minimization of joint loa...

The central nervous system controls the muscles of mastication and may dictate muscle outputs according to a biologically important objective. This study tested the hypotheses that (a) the effective sagittal TMJ eminence morphology, and (b) the outputs of the masticatory muscles during static biting, are consistent with minimisation of joint loads...

The efficiency of tooth movement associated with some orthodontic mechanics can be compromised by friction between archwire and bracket. This study examined the effects of bracket ligation forces (F(N Ligation)) and mastication on friction when sliding a bracket along an archwire. Preliminary data from 5 orthodontists and 5 orthodontic residents ch...

Muscle forces determine joint loads, but the objectives governing the mix of muscle forces involved are unknown. This study tested the hypothesis that masticatory muscle forces exerted during static biting are consistent with objectives of minimization of joint loads (MJL) or muscle effort (MME). To do this, we compared numerical model predictions...

To test for orthotropy in the stress-strain behavior of the temporomandibular joint (TMJ) disc under repeated physiologic loading before and after an impact event. Two groups, each consisting of 10 discs, were subjected to repeated tensile cycling in the dorsoventral (group 1) and mediolateral (group 3) direction. Two additional groups, each consis...

This study sought to compare differences in neocartilage produced over time from two types of resorbable scaffold materials. One material was entirely synthetic and contained a polyglycolic acid-poly-L-lactic acid matrix (PGA-PLLA). The second scaffold material was bioactive and consisted of a four-layered construct of porcine small intestinal subm...

Investigations of the changes in the mechanics of the craniomandibular system as a result of treatment have been limited by the lack of validated models of this system. The aims of this project were to (1) validate numerical model predictions of temporomandibular joint (TMJ) eminence morphology and muscle forces produced during molar biting and (2)...

The purpose of this study was to characterize the tensile stress-strain behavior of the porcine temporomandibular joint (TMJ) disk with respect to collagen orientation and strain rate dependency. The apparent elastic modulus, ultimate tensile strength, and strain at maximum stress were measured at three elongation rates (0.5, 50, and 500 mm/min) fo...

The pathomechanics of osteoarthritis in the human temporomandibular joint (TMJ) are unknown. Compromised lubrication is a potential factor, but, lubrication within even the normal TMJ is not understood completely. Weeping lubrication is a concept that may be applicable to the TMJ. A characteristic of weeping lubrication is a slow increase in fricti...

The cytokines interleukin-1 beta (IL-1 beta) and IL-1 receptor antagonist (IL-1RA) probably play a part in orthodontic tooth movement. Here, the force magnitudes and the area of force application in the compressed periodontal ligament (PDL) were controlled and the velocity of tooth movement correlated with concentrations of IL-1 beta and IL-1RA in...

Movement over the surface of the temporomandibular joint (TMJ) disc produces tractional forces. These forces potentially increase the magnitude of shear stresses and contribute to wear and fatigue of the disc. Theoretically, tractional forces in all synovial joints are the result of frictional forces, due to rubbing of the cartilage surfaces, and p...

Conventional orthodontic therapy often uses force magnitudes in excess of 100 g to retract canine teeth. Typically, this results in a lag phase of approximately 21 days before tooth movement occurs. The current project was undertaken to demonstrate that by using lower force magnitudes, tooth translation can start without a lag phase and can occur a...

Movement over the surface of the temporomandibular joint (TMJ) disc produces tractional forces. These forces potentially increase the magnitude of shear stresses and contribute to wear and fatigue of the disc. Theoretically, tractional forces in all synovial joints are the result of frictional forces, due to rubbing of the cartilage surfaces, and p...

An in vitro experimental technique was developed to measure the stress-distribution properties of this disc. Discs were tested for conditions of increasing load and decreasing congruity between loading surfaces. Peak stresses and pressure gradients increased linearly as load on the disc increased. For a given load, as congruity of the surfaces decr...

The influence of condylar position on congruity of the surfaces of the temporomandibular joint (TMJ) was determined. The degree of congruity between the loading surfaces of the condyle and the eminence varied depending on condylar position. Better congruity of surfaces was found in condylar positions consistent with molar biting. Incongruity betwee...