Effect of implant angulation and patrice on the retention of overdenture attachment systems: An in vitro study.

Purpose: To test the retention of two different overdenture attachment matrices and straight abutments when implants are placed at 0-, 15-, and 30-degree diverging angulations as well as the retention of 15-degree-angled abutments to correct the overall angulation to 0-degrees.

Materials And Methods: Matching aluminum blocks were machined to incorporate two dental implants at 0-degree, 15-degree, and 30-degree relative angulations and overdenture attachments to simulate a two-implant overdenture. At 0-degree, 15-degree, and 30-degree implant angulation, straight abutments were studied.

Biomechanical analysis of the osseointegration of porous tantalum implants.

Statement Of Problem: Although implants containing porous tantalum undergo osseointegration, whether this material significantly alters new bone formation and improves implant stability during healing in comparison to titanium is unclear.

Purpose: The purpose of this in vivo study was to determine the influence of the inclusion of porous tantalum into a dental implant on the biomechanical properties of the bone-implant interface and peri-implant bone which may contribute to secondary implant stability.

Material And Methods: Threaded titanium implants with a porous tantalum midsection (Trabecular Metal Dental Implant; Zimmer Biomet) or without (Tapered Screw-Vent; Zimmer Biomet) were placed in rabbit tibiae and allowed to heal for 4, 8, or 12 weeks.

Nanoscale properties and deformation of human enamel and dentin.

This research uses quasi-static nanoindentation and nanoscratching to quantify human tooth deformation as a function of enamel rod and dentin tubule orientations at the nanoscale. Nanoindentation tests were performed on enamel and dentin to determine elastic modulus, hardness, and observe fracture. Additionally, nanoscratch tests were performed to determine pileup geometry and parameters such as recovery, scratch hardness, and scratch roughness.

Bone response to porous tantalum implants in a gap-healing model.

Objectives: The objective of this study was to determine the relative osteogenic behavior of titanium implants with or without a porous tantalum modification when placed with a gap between the implant and existing bone.

Materials And Methods: A gap-healing model in the rabbit tibia was used for placement of titanium implants. Forty-eight rabbits received 96 implants, with 48 of the implants containing a porous tantalum middle section and the remaining 48 implants were composed of solid titanium.

Sensitivity of corneal biomechanical and optical behavior to material parameters using design of experiments method.

The optical performance of the human cornea under intraocular pressure (IOP) is the result of complex material properties and their interactions. The measurement of the numerous material parameters that define this material behavior may be key in the refinement of patient-specific models. The goal of this study was to investigate the relative contribution of these parameters to the biomechanical and optical responses of human cornea predicted by a widely accepted anisotropic hyperelastic finite element model, with regional variations in the alignment of fibers.

Multivariate evaluation of the cutting performance of rotary instruments with electric and air-turbine handpieces.

Statement Of Problem: Laboratory studies of tooth preparation often involve single values for all variables other than the one being tested. In contrast, in clinical settings, not all variables can be adequately controlled. For example, a new dental rotary cutting instrument may be tested in the laboratory by making a specific cut with a fixed force, but, in clinical practice, the instrument must make different cuts with individual dentists applying different forces.

Designed experiment evaluation of key variables affecting the cutting performance of rotary instruments.

Statement Of Problem: Laboratory studies of tooth preparation are often performed under a limited range of conditions involving single values for all variables other than the 1 being tested. In contrast, in clinical settings not all variables can be tightly controlled. For example, a new dental rotary cutting instrument may be tested in the laboratory by making a specific cut with a fixed force, but in clinical practice, the instrument must make different cuts with individual dentists applying a range of different forces.

Integrity of implant surface modifications after insertion.

Purpose: The surface integrity associated with implant placement was examined to determine whether the topography of common implant surface modifications is retained after implant insertion.

Materials And Methods: Turned (TU), acid-etched (AE), and anodized (AN) experimental implants prepared in-house were inserted into polyurethane foam blocks using a standard drilling protocol at maximum torque of 37 Ncm. Qualitative analysis of the surfaces of preinserted and postinserted implants was done by scanning electron microscopy (SEM), and quantitative analysis of the implant threads was performed by interferometry.

Performance of single-use and multiuse diamond rotary cutting instruments with turbine and electric handpieces.

Statement Of Problem: As single-use rotary cutting instruments and electric handpieces become more available, the performance of these instruments with electric as compared to turbine handpieces requires evaluation. In addition, if rotary cutting instruments marketed as single-use instruments are used for multiple patients, the effects on their performance of cleaning, sterilization, and repeated use are of interest to the clinician.

Purpose: The purpose of the study was to evaluate how the cleaning, autoclaving, and repeated use of single-use and multiuse rotary cutting instruments, with either a turbine or electric handpiece, affected their performance.

In vitro comparison of the cutting efficiency and temperature production of ten different rotary cutting instruments. Part II: electric handpiece and comparison with turbine.

Statement Of Problem: The cutting behavior of dental rotary cutting instruments is influenced by the handpiece used. While the turbine handpiece has been extensively tested in previous studies, limited published information exists on the use of rotary cutting instruments with the electric handpiece system and on possible interactions between rotary cutting instruments and handpiece type.

Purpose: The purpose of this study was to examine the cutting performance of a wide selection of rotary cutting instruments tested with the electric handpiece and compare the results with those of the air-turbine handpiece (Part I), identifying possible interactions between handpiece type and rotary cutting instruments.

In vitro comparison of the cutting efficiency and temperature production of 10 different rotary cutting instruments. Part I: Turbine.

Statement Of Problem: Standards to test the cutting efficiency of dental rotary cutting instruments are either nonexistent or inappropriate, and knowledge of the factors that affect their cutting performance is limited. Therefore, rotary cutting instruments for crown preparation are generally marketed with weak or unsupported claims of superior performance.

Purpose: The purpose of this study was to examine the cutting behavior of a wide selection of rotary cutting instruments under carefully controlled and reproducible conditions with an air-turbine handpiece.

Measurement of the rotational misfit and implant-abutment gap of all-ceramic abutments.

Purpose: The specific aims of this study were to measure the implant and abutment hexagonal dimensions, to measure the rotational misfit between implant and abutments, and to correlate the dimension of the gap present between the abutment and implant hexagons with the rotational misfit of 5 abutment-implant combinations from 2 manufacturers.

Materials And Methods: Twenty new externally hexed implants (n = 10 for Nobel Biocare; n = 10 for Biomet/3i) and 50 new abutments were used (n = 10; Procera Zirconia; Procera Alumina; Esthetic Ceramic Abutment; ZiReal; and GingiHue post ZR Zero Rotation abutments). The mating surfaces of all implants and abutments were imaged with a scanning electron microscope before and after rotational misfit measurements.

Effect of subgingival depth of implant placement on the dimensional accuracy of the implant impression: an in vitro study.

Statement Of Problem: In some instances, an implant needs to be placed deep subgingivally, which may result in a less accurate impression of the implant. PURPOSE.: The purpose of this study was to evaluate the effect of subgingival depth of implant placement on the accuracy of implant impressions.

Sensitivities of medial meniscal motion and deformation to material properties of articular cartilage, meniscus and meniscal attachments using design of experiments methods.

This study investigated the role of the material properties assumed for articular cartilage, meniscus and meniscal attachments on the fit of a finite element model (FEM) to experimental data for meniscal motion and deformation due to an anterior tibial loading of 45 N in the anterior cruciate ligament-deficient knee. Taguchi style L18 orthogonal arrays were used to identify the most significant factors for further examination. A central composite design was then employed to develop a mathematical model for predicting the fit of the FEM to the experimental data as a function of the material properties and to identify the material property selections that optimize the fit.

The influence of drill wear on cutting efficiency and heat production during osteotomy preparation for dental implants: a study of drill durability.

Purpose: The authors evaluated, under conditions simulating implant placement, the cutting efficiency, durability, heat production, and wear of implant drills.

Materials And Methods: Osteotomies were performed on bovine ribs using a surgical unit mounted in a testing apparatus. A software program controlled the apparatus and recorded temperatures, depths, and drilling times.

Tooth preparation: a study on the effect of different variables and a comparison between conventional and channeled diamond burs.

Purpose: The purpose of this study was to evaluate the different variables involved in tooth cutting to characterize intrapulpal temperature generation, cutting efficiency, and bur durability when using conventional and channeled diamond burs.

Materials And Methods: Forty premolars and 60 molars were selected for the study. Four diamond burs were paired according to grit size: 125-microm grit: Brasseler Coarse (Control 1) and TDA System (Test 1) burs; and 180-microm grit: Brasseler CRF (Control 2) and NTI Turbo Diamond (Test 2) burs.

Verification jig for implant-supported prostheses: A comparison of standard impressions with verification jigs made of different materials.

Statement Of Problem: Implant verification jigs are routinely used during the fabrication of implant-supported prostheses. The dimensional accuracy of these jigs is unknown.

Purpose: The purposes of this study were to (1) compare the dimensional accuracy of verification jigs with that of conventional impression procedures and (2) measure the dimensional accuracy of 3 resin materials used to fabricate verification jigs.