Failure load of milled, 3D-printed, and conventional chairside-dispensed interim 3-unit fixed dental prostheses.

Statement Of Problem: New techniques and materials for the laboratory fabrication of interim fixed dental prostheses have gained in popularity, yet how their failure strengths compare with conventional chairside materials is unclear.

Purpose: The purpose of this in vitro study was to compare the strength of computer-aided design and computer-aided manufacturing (CAD-CAM) milled polymethylmethacrylate (PMMA) or 3-dimensionally (3D) printed bis-acryl interim fixed dental prostheses with a traditional chairside-dispensed autopolymerizing bis-acryl prosthesis while taking into account the effect of loading rate and storage time.

Material And Methods: A dentiform mandibular second premolar and second molar with a first molar pontic were prepared and scanned.

Denture Hygiene as It Relates to Denture Stomatitis: A Review.

The wear of dentures carries with it the possibility of an inflammatory response by the denture-bearing tissues. Lack of or improper hygiene has been shown to contribute to denture stomatitis (DS). Although essential, denture hygiene is often overlooked by patients or performed improperly.

Strength and stiffness of interim materials and interim fixed dental prostheses when tested at different loading rates.

Statement Of Problem: How the loading rate might affect the mechanical properties of interim materials and interim fixed dental prostheses is unclear.

Purpose: The purpose of this in vitro study was to compare the material stiffness, material strength, and structural strength of interim 3-unit fixed dental prostheses fabricated from 3 interim materials when stressed at different loading rates.

Material And Methods: Bar-shaped specimens and anatomically correct interim 3-unit fixed dental prostheses with a modified-ridge lap pontic were fabricated from polyethyl methacrylate resin (Trim) and 2 bis-acrylic composite resins (TempSmart; Integrity) (n=10).

Surface Roughness of Milled Lithium Disilicate With and Without Reinforcement After Finishing and Polishing: An In Vitro Study.

Purpose: To determine the efficacy of various finishing and polishing techniques on the surface roughness of two computer-aided design/computer-aided manufacturing (CAD/CAM) materials, lithium disilicate (IPS e.max), lithium disilicate reinforced with lithium aluminosilicate (Straumann n!ce™), and a stackable low-fusing nanofluorapatite glass ceramic (Ceram).

Materials And Methods: Flat specimens (n = 12) per treatment group were fabricated 2 mm thick, 15 mm in length, and 12mm in width.

Comparison of digital surface displacements of maxillary dentures based on noninvasive anatomic landmarks.

Statement Of Problem: Artificial markers called fiducials are commonly used to orient digitized surfaces for analysis. However, when these markers are tangible and placed in the region of interest, they may alter surface topography and influence data analysis.

Purpose: The purpose of this in vitro study was to apply a modified digital surface fitting method based on anatomic landmarks to evaluate denture accuracy and to use 2 different denture processing techniques to evaluate the method.

Does the Sequence of Preclinical Dental Crown Type Preparations Affect Evaluation Scores?

Preclinical dental students must demonstrate aptitude in the preparation of teeth for treatment with several types of fixed dental prostheses. The optimal sequence of instruction and examination of these crown preparations in preclinical fixed prosthodontics is unknown. The aim of this study was to determine if grading scores by faculty and students were affected by changing the sequence of crown type preparations.

Teaching of Fixed Prosthodontics: A Paradigm Shift.

Restorative dentistry is experiencing a significant shift towards a rising usage of tougher all-ceramic materials. This trend must be incorporated into existing fixed prosthodontics academic curricula through the integration of lithium disilicate and zirconium oxide crown preparation guidelines. In addition, crown fabrication techniques have also evolved for these newer materials through digitization of preparations and impressions and their computer-assisted manufacturing.

The anterior cantilever in the implant-supported screw-retained mandibular prosthesis.

Statement Of Problem: When implants are placed interforaminally in mandibular implant-supported screw-retained prostheses, the most anterior implant is usually positioned lingual to the incisors of the prosthesis. This creates an anterior cantilever with the entire prosthesis acting as a class I lever and possibly placing the anterior implant under alternating tension and compression during function.

Purpose: The purpose of this study was to measure the anterior cantilever of randomly chosen patients with restored mandibular implant-supported fixed prostheses, and to establish the proportions of anterior to posterior cantilever lengths relative to the anteroposterior spread.

Operator-induced compressive axial forces during implant gold screw fastening.

Statement Of Problem: The gold screw of an implant is put under tension during fastening. An increase in operator-induced compressive axial force during fastening may diminish screw tension, lower the friction between the screw threads, and allow for increased tightening torque.

Purpose: This study was undertaken to assess and compare the compressive axial forces and torques placed simultaneously on implant gold screws by persons with varying degrees of expertise.

Experimentally induced abutment strains in three types of single-molar implant restorations.

Statement Of Problem: The choice of single-molar implant design is difficult because of a lack of controlled, quantitative biomechanical analyses.

Purpose: This study determined the effect of 3 single-molar implant designs on implant strains under a variety of homologous loading conditions.

Material And Methods: On each implant abutment, 4 strain gauges were placed axially at 90 degrees to each other on the buccal, lingual, mesial, and distal surfaces.

Effect of washers on reverse torque displacement of dental implant gold retaining screws.

Statement Of The Problem: Gold screw loosening is a frequent problem that affects dental implants.

Purpose: This study determined the effect of spring washers on gold screw displacements during applied removal torque in dental implants.

Material And Methods: A 3-unit fixed partial denture was cast in semiprecious alloy and fixed to 2 dental implants with gold-retaining screws.

Influence of mandibular superstructure shape on implant stresses during simulated posterior biting.

Statement Of Problem: Theoretical considerations on the ideal implant-supported prosthetic superstructure shape lack the effect of complex mandibular deformation patterns during function.

Purpose: This study compared implant abutment stresses for idealized superstructures with different cross-sectional shapes and material properties during a simulated, complex biting task.

Material And Methods: A simplified and idealized 3-dimensional finite element computer model was built, which consisted of a sectioned mandible rehabilitated with 5 titanium implants and an attached superstructure beam composed of metal alloy and acrylic resin.

Numerical analysis of a dental implant system preloaded with a washer.

Gold screw loosening is a problem that frequently affects dental implants. The application of a preload has been the main means of preventing loosening. However, this measure has not been able to eliminate its occurrence.

Effect of implant number on transverse bending moments during simulated unilateral loading of mandibular fixed-detachable prostheses.

High bending moments acting on osseointegrated implants due to transverse forces are believed to be potential contributors to mechanical implant failure. Theoretically, the rigidity of a system comprised of five implants would seem to counter these moments more effectively than one with only three implants. To study this, we built an experimental model comprised of five Brånemark implants embedded in an acrylic mandibular edentulous arch and connected by a metal framework.

Digital assessment of occlusal wear patterns on occlusal stabilization splints: a pilot study.

Statement Of Problem: If masticatory load distribution is task-dependent, then the pattern of wear on an acrylic resin occlusal splint over time may affect clinical outcome.

Purpose: This pilot study quantitatively assessed posterior wear after 3 months on the occlusal surfaces of maxillary stabilization splints.

Material And Methods: Subjects with known history of nocturnal bruxism were given heat-cured full-arch acrylic resin occlusal stabilization splints to be worn nocturnally for 3 months.

The association among occlusal contacts, clenching effort, and bite force distribution in man.

The contact area during habitual biting can vary according to the activity of the jaw musculature. Forceful masticatory muscle activity may also induce deformations of the dento-alveolar tissues and the supporting skeleton, yielding various tooth loads despite an apparently even distribution of tooth contacts. To investigate this variability, we measured bite forces simultaneously at multiple dental sites during maximum-effort clenching tasks.

Forces and moments generated at the dental incisors during forceful biting in humans.

A miniature load sensor capable of measuring all forces and all moments simultaneously at a single location in space was used to assess the magnitude and direction of loads that affect the dental incisors during forceful, static biting. While prior approaches have not measured all necessary six degrees of freedom during biting, the complete set of loads is needed to serve as realistic boundary conditions for analytical or computational models of mandibular mechanics. Four subjects were asked to perform controlled and repetitive edge-to-edge incisal biting activities.

Modeling the mechanical behavior of the jaws and their related structures by finite element (FE) analysis.

In this paper, we provide a review of mechanical finite element analyses applied to the maxillary and/or mandibular bone with their associated natural and restored structures. It includes a description of the principles and the relevant variables involved, and their critical application to published finite element models ranging from three-dimensional reconstructions of the jaws to detailed investigations on the behavior of natural and restored teeth, as well as basic materials science. The survey revealed that many outstanding FE approaches related to natural and restored dental structures had already been done 10-20 years ago.

Functional movements of putative jaw muscle insertions.

Background: The craniomandibular muscles control jaw position and forces at the teeth and temporomandibular joints, but little is known regarding their biomechanical behaviour during dynamic function. The objective of this study was to determine how jaw muscle insertions alter position during different jaw movements in living subjects.

Methods: Computer 3D reconstruction of MR images and jaw-tracking were combined to permit the examination of movement with six degrees of freedom.

Deformation of the human mandible during simulated tooth clenching.

Localized corpus and dental arch distortions measured directly on human and animal mandibles suggest complex deformation patterns at other mandibular sites during functional loading. To describe these, we simulated selected static bites on a three-dimensional finite element computer model of the human jaw. Five clenching tasks were modeled: intercuspal position, left group function, left group function plus balancing contact, incisal clenching, and right molar clenching.