The effects of a periodontal ligament analogue on occlusal contact forces.

Background: Previous bench-top studies examined the details of the mechanical environment of rigidly fixed occluding teeth. It was demonstrated that during each chomp, contacting molar teeth experience in-occlusal-plane forces (F ) that are highly transient in magnitude and direction.

Objectives: The objectives of this study are to identify F behaviours that are attributable to the presence of a visco-elastic periodontal ligament (PDL) analogue, and to assess the necessity of incorporating it into future studies.

The combined effects of salivas and occlusal indicators on occlusal contact forces.

Background: Some occlusal detection products are designed for use on dry teeth, but this is not always achieved. Others are suited for dry and wet applications.

Objective: The objective of this study is to assess the combined effects, on occlusal contact forces, of two previously studied affecting variables-occlusal detection products and saliva.

The mechanics of dental occlusion and disclusion.

Background: The mechanical environment associated with occluding teeth is the foundation for a wide range of research topics, clinical practice and dogma, product development and marketing, and medico-legal issues. The purpose of this study was to experimentally examine the relationships between occlusal factors and their impact on the associated contact forces.

Methods: Matching pairs of 0°, 20°, 33° and 40° cusp first molar denture teeth were placed into Class I, II and III molar relationships.

Biology of biomechanics: Finite element analysis of a statically determinate system to rotate the occlusal plane for correction of a skeletal Class III open-bite malocclusion.

Introduction: In the absence of adequate animal or in-vitro models, the biomechanics of human malocclusion must be studied indirectly. Finite element analysis (FEA) is emerging as a clinical technology to assist in diagnosis, treatment planning, and retrospective analysis. The hypothesis tested is that instantaneous FEA can retrospectively simulate long-term mandibular arch retraction and occlusal plane rotation for the correction of a skeletal Class III malocclusion.

Microdamage generation by tapered and cylindrical mini-screw implants after pilot drilling.

Objective: To investigate the relationship between mini-screw implant (MSI) diameter (1.6 vs 2.0 mm) and shape (tapered vs cylindrical) and the amount of microdamage generated during insertion.

Comparison of stainless steel and titanium alloy orthodontic miniscrew implants: a mechanical and histologic analysis.

Introduction: The detailed mechanical and histologic properties of stainless steel miniscrew implants used for temporary orthodontic anchorage have not been assessed. Thus, the purpose of this study was to compare them with identically sized titanium alloy miniscrew implants.

Methods: Forty-eight stainless steel and 48 titanium alloy miniscrew implants were inserted into the tibias of 12 rabbits.

An analytical approach to 3D orthodontic load systems.

Objective: To present and demonstrate a pseudo three-dimensional (3D) analytical approach for the characterization of orthodontic load (force and moment) systems.

Materials And Methods: Previously measured 3D load systems were evaluated and compared using the traditional two-dimensional (2D) plane approach and the newly proposed vector method.

Results: Although both methods demonstrated that the loop designs were not ideal for translatory space closure, they did so for entirely different and conflicting reasons.

Effects of first- and second-order gable bends on the orthodontic load systems produced by T-loop archwires.

Objective: To measure the effects of first- and second-order gable bends on the forces and moments produced by a commercially available closing T-loop archwire.

Materials And Methods: A dentoform-simulated space closure case was mounted on an orthodontic force tester. Sixteen gable bend combinations were placed in the archwires, which were then activated using standard clinical procedures.

A qualitative engineering analysis of occlusion effects on mandibular fracture repair mechanics.

Objectives. The purpose of this analytical study was to examine and critique the engineering foundations of commonly accepted biomechanical principles of mandible fracture repair. Materials and Methods.

The effects of application time of a self-etching primer and debonding methods on bracket bond strength.

Objective: To test the manufacturer's recommendation for the application rubbing time of a self-etching primer (Transbond Plus, 3M Unitek) and to compare the resulting bond strength of a resin composite (Transbond XT, 3M Unitek) in the traditional laboratory tension on all four wings with a simulation of the clinical single-wing lift-off debonding instrument (LODI; 3M Unitek).

Materials And Methods: Flattened stainless-steel maxillary incisor orthodontic brackets (Victory Series, 3M Unitek) were bonded to 108 flattened bovine incisors. The enamel was rubbed with the self-etching primer for 0, 5 (the manufacturer's recommendation), and 10 seconds during a 10-second application.

The effect of pH levels on nonlatex vs latex interarch elastics.

Objective: To evaluate the force decay characteristics of nonlatex vs latex interarch elastics within the normal range of salivary pH levels.

Materials And Methods: Two nonlatex groups and one latex quasi-control group were tested. Elastics were stretched to 15 mm and were held for 10 seconds (baseline), 4 hours, 8 hours, and 12 hours in artificial saliva solutions with pH levels of 5.

Does the center of resistance depend on the direction of tooth movement?

Introduction: The objective of this study was to compare the locations of the centers of resistance (CRes) in the buccolingual (BL) and mesiodistal (MD) directions of the mandibular central incisors of 6 dogs.

Methods: Based on microcomputed tomography images of the teeth and their supporting tissues, solid models were used to build finite element models.

Results: The CRes locations for the 6 specimens were determined for displacements in the BL and MD directions with finite element calculations.

An engineering analysis of dental occlusion principles.

Introduction: The purpose of this study was to develop an analytical model of contacting teeth, based on principles of basic engineering statics. The model would be used to demonstrate the interactions between occlusal contacts and tooth loading (forces and moments) and to critique occlusion-related dogma.

Methods: Free-body diagrams were drawn to depict 2 teeth in occlusal contact.

Orthodontic mechanotransduction and the role of the P2X7 receptor.

Introduction: The P2X7 receptor plays a crucial role in bone biology and inflammation. Its main function is to promote necrotic tissue metabolism by ensuring a normal acute-phase inflammatory response. We used a mouse model to describe and compare orthodontic mechanotransduction in wild-type and P2X7 knock-out mice.

Comparison of the Bolton Standards to longitudinal cephalograms superimposed on the occipital condyle (I-point).

Objective: To compare traditional superimposition on sella turcica and the anterior cranial base (SACB) to superimposition referenced at the occipital condyle (I-point) for demonstrating craniofacial growth and development.

Materials And Methods: Tracings for ages 8, 10, 12, 15 and 18 were chosen from the Bolton Standards of Dentofacial Developmental Growth to compare superimposition with the traditional longitudinal reference at SACB (anterior curvature of sella turcica and anterior cranial base) to reference at I-point on the antero-inferior contour of the occipital condyles in norma lateralis. The serial tracings were superimposed using both the sagittal and postero-anterior (PA) tracings.

Force system generated by an adjustable molar root movement mechanism.

Introduction: Tooth movement simulation is important for planning the optimal force system and appliance design to correct a specific malocclusion. Experimental verification of a 3-dimensional force system is described for a unique molar root movement strategy that can be adapted to many clinical scenarios.

Methods: The force system was measured for molar root movement springs that had adjustable alpha (anterior) and beta (posterior) moments.

Tooth positioner effects on occlusal contacts and treatment outcomes.

Objective: To determine if an increase in tooth contacts is the principal effect of tooth positioner wear.

Materials And Methods: Patient charts from a consecutive series were reviewed until a sample of 100 cases that used a tooth positioner was obtained. One hundred control cases were randomly selected from patients treated at the same period.

Three-dimensional mechanical environment of orthodontic tooth movement and root resorption.

Introduction: The tension-compression theory of bone mechanotransduction is ubiquitous in orthodontics. However, partly due to deficiencies in the characterization of the mechanical environment, there is no consensus on the mechanisms that link stimuli to root resorption and bone response. In this study, we analyzed the predominant directions of tension and compression in the alveolar structures.

Complete orthodontic load systems on teeth in a continuous full archwire: the role of triangular loop position.

Introduction: A novel approach to characterizing orthodontic spring-generated force and moment systems has been developed. This method allows simultaneous measurement of all 6 force and moment components acting on a tooth.

Methods: A continuous full archwire space-closure technique was simulated, and the complete force and moment systems acting on the teeth adjacent to the extraction space were measured.

A comparison of the shear-peel and third-order bond strengths of orthodontic brackets with 2 etch techniques and the role of bracket asymmetry.

Introduction: Innovations in orthodontic bonding are inevitably followed by a flurry of studies to ascertain efficacy. Unfortunately, the published reports are often contradictory or highly variable. The primary purpose of this study was to analyze protocols that measure orthodontic bracket bond strength.

Flaws in root resorption assessment algorithms: role of tooth shape.

Introduction: The purposes of this study were to analyze and critique the mathematical algorithms used in the clinical assessment of root resorption.

Methods: Geometric constructions and derived mathematical expressions were used to investigate the influence of tooth shape on the relationships between tooth, root, and crown lengths and their respective sizes as measured on before and after radiographs. results: The ambiguities of root-loss assessment protocols are demonstrated.

Fracture resistance and fracture resistance after fatigue loading of 4 different post and cores in endodontically treated teeth.

This article discusses the fracture resistance of 4 post and core systems including a combined obturator/post system before and after fatigue loading. The obturator/post demonstrated the highest fracture resistance values. The use of a combined obturator/post with a single resin endodontic sealer/luting cement seems promising.

Effect of loading mode on bond strength of orthodontic brackets bonded with 2 systems.

Introduction: A new orthodontic bracket bonding method or material invariably spawns bond strength studies examining the efficacy of the innovation. The primary purpose of this project was to ascertain whether the mode of in-vitro bracket debonding used in a study affects the measured bond strength. The secondary aim was to compare the bond strengths of 2 different bonding systems.

The effects of first- and second-order gable bends on forces and moments generated by triangular loops.

Introduction: Triangular loops are frequently used for space closure. Studies of this loop have focused on dimensional and in-plane (second-order) gable-bend influences on the generated forces and moments, but there have been no investigations into the effects of out-of-plane (first-order) gable bends. Both bends are generally needed to accomplish tooth translation.