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Biomedical subjects

B R Lang

Publications and source records attributed to B R Lang.

At least 37 records · Page 2Linked to original sources
PubMed1996

Complete denture occlusion.

Available research has not identified a superior tooth form or arrangement to fulfill the requirements of complete denture patients in the areas of comfort, function, and esthetics. Therefore, it appears logical to use the least complicated approach to fulfill these requirements. This approach begins with the development of a philosophy of occlusion and selection of a concept to satisfy the philosophy. A balanced articulation appears to be most appropriate because of tooth contacts observed during nonfunctional activities of patients. Occlusal schemes to fulfill these occlusal concepts are many and varied. In the opinion of the author, the lingualized articulation concept using tooth molds specifically designed for this concept seems to be the most logical and least complicated approach in occlusal rehabilitation of edentulous patients.

Bite Force↗
PubMed1995

Silane to enhance the bond between polymethyl methacrylate and titanium.

The machined surface of wrought titanium frameworks used in implant-supported, fixed prostheses does not bond well with acrylic resin. Surface pretreatment has been suggested to enhance the retention of polymethyl methacrylate to machined titanium surfaces. This study evaluated a new bonding material (Rocatec) to determine its effect on the bond strength between titanium and polymethyl methacrylate. Twenty rod-shaped specimens of grade 2 titanium (7.6 x 0.3 cm in diameter) were divided into two groups of 10 samples. Group A received no pretreatment and group B was pretreated with 110 microns alumina air abrasive and the Rocatec material. Heat-cured denture base resin was processed around each titanium sample in a cylindrical shape approximately 0.9 x 1.5 cm. A Shell-Nielsen shear test was performed with a universal testing machine at a crosshead speed of 0.5 mm/minute to determine the bond strength in megapascals (MPa). Group B specimens (23.8 +/- 1.78 MPa) had a shear strength 68% greater than group A (16.1 +/- 1.61 MPa) (p 0.0001). The results of this study indicated that surface pretreatment of grade 2 titanium with 110 microns alumina air abrasive plus Rocatec bonding material significantly enhances the shear bond strength to PMMA.

Air Pressure↗
PubMed1995

A new computer-assisted method for fabrication of crowns and fixed partial dentures.

The availability of high-technology systems that use computer-aided design and computer-aided machining is on the increase. One such system is the Procera system, which is currently providing cost-effective, high-quality dental restorative services to dental laboratories and to dentists. A reduction in cost to the dentist, and ultimately to the patient, is a major advantage of the Procera system. Cost benefits combined with its continued success in producing crowns and fixed partial dentures that meet professional standards of care should enhance the acceptance of this new technology.

Computer-Aided Design↗
PubMed1994

A comparison of the color stability of conventional and titanium dental porcelain.

Simulation of naturally appearing enamel in fixed prosthodontics is best achieved with porcelain. This study investigated the color stability of two different dental porcelains, Ceramco and Procera, after they were exposed to 900 hours of accelerated aging. Twenty titanium plates provided the substrate to which the Procera porcelain samples in shades A3, A3.5, C3, and D3 were fired, five in each shade. An equal number of metal-ceramic alloy (Olympia) plates were cast to the same dimensions to form the 20 substrates to which Ceramco porcelain was fired. The four shades of porcelain were again added to each of the samples. Commission International de l'Eclairage L a b readings were recorded with a Minolta Chroma Meter II before and after exposure to 900 hours of accelerated aging simulation. After the aging process the color differences between the pretest and posttest condition were calculated. Although statistical comparisons demonstrated a difference in color change (p < or = 0.05) between Ceramco and Procera porcelain in three of the shades tested, critical remarks of color refer to both types having "slight" color change. In terms of color stability, neither porcelain had "noticeable" changes after 900 hours of accelerated aging.

Color↗
PubMed1994

A review of traditional therapies in complete dentures.

The number of persons in the United States and Canada over 65 years of age who are edentulous and in need of complete dentures appears to be decreasing as a percent of the total population (by the year 2030), but the total number of patients needing these services will be almost the same as it is today. Administering complete denture prosthodontics to geriatric patients will continue to be a formidable part of the general dentistry practice well into the next century despite changing demographics. Careful dental evaluation of the patient through a well-structured examination and care based on sound principles and concepts continues to be the standard that must be provided. A lifetime commitment by the patient to a program of recall and maintenance for continuous monitoring of the dentures and the oral tissues is essential for older adult edentulous patients. We should periodically review these traditional therapies to improve our knowledge.

Aged↗
PubMed1993

The shear strength of polymethyl methacrylate bonded to titanium partial denture framework material.

Premachined titanium frameworks are used in implant-supported fixed complete-arch prostheses. Traditionally, retentive mechanisms are incorporated in the wax patterns to provide retention between polymethyl methacrylate and the cast framework. Nontraditional forms of retention are needed with machined frameworks. This study determined whether three different surface characteristics of titanium improve the bond shear strength of polymethyl methacrylate. Thirty rod shaped specimens of titanium were divided into three equal groups: group 1 received no pretreatment; group 2 was pretreated with 110 microns alumina air abrasive; and group 3 was pretreated with 110 microns alumina air abrasive plus silane (clear). Denture resin was processed around each specimen. A Shell-Nielsen shear test was then performed at a crosshead speed of 0.5 mm/minute to determine the bond shear strength in kilograms per square centimeter. The bond shear strength of group 3 was 63% greater than group 1 (significant, p < 0.01; ANOVA-Scheffé interval 63 kg/cm2). The results of this study indicated that surface pretreatment of titanium with 110 microns alumina air abrasive plus silane coating significantly enhances the bond shear strength of polymethyl methacrylate.

Aluminum Oxide↗
PubMed1993

Measurement of composite resin filler particles by using scanning electron microscopy and digital imaging.

Composite resins are routinely classified on the basis of filler particle size for purposes of research, clinical applications, and communications. The size and characterizations of filler particles have also been considered a significant factor in the rate of wear of composites. Making valid correlations between the filler particles within a composite and wear requires accuracy of filler particle size and characterization. This study was initiated to examine two methods that would (1) qualify the filler particle content of a composite resin and (2) quantify the number, size, and the area occupied by the filler particles in composite resins. Three composite resins, BIS-FIL I, Visio-Fil, and Ful-Fil, were selected as the materials to be examined, on the basis of their published composite classification type as fine particle. The findings demonstrated that scientific methods are available to examine qualitatively and measure quantitatively the composite resin filler particles in terms of their numbers, sizes, and area occupied by use of a scanning electron microscope and digital imaging. Significant differences in the filler particle numbers, sizes, and the area occupied were found for the three composite resins in this study that were classified as fine particle.

Acetone↗
PubMed1993

The potential for bonding titanium restorations.

PURPOSE: The use of titanium for implants has shown the biological acceptance of the metal. Recently, methods of using titanium for restorations, crowns, and bridges have been introduced using both cast and spark erosion systems for fabrication. A potential also exists for using titanium for bonded (Maryland) bridges. MATERIALS AND METHODS: In this study, the potential for bonding titanium was investigated by cementing with various adhesives: (A) metal to metal, (B) metal to enamel, and (C) comparing with a known procedure of bonding nickel-chromium. Truncated cones of pure titanium were fabricated with a 5-mm circular face for bonding to a larger titanium disc embedded in a plastic ring. A special jig was used to pull the bonded cone from the disc on an Instron tensile testing machine (Instron Corporation, Canton, MA). The resin-metal adhesives used were: (1) Infinity, (2) Metabond, (3) All-Bond 2, and (4) Panavia. These were compared with (5) nickel-chromium cones sandblasted and bonded to nickel-chromium with Panavia. Titanium cones were also bonded to human enamel with (6) Panavia and (7) Metabond. The 10 samples in each group were subjected to tensile force, and point of fracture was recorded. The data were subjected to an analysis of variance with a Scheffe F test at the 95% level of significance. RESULTS: The results of tensile forces in MPa were (1) Infinity, 28.1 +/- 3.6; (2) Metabond, 28.1 +/- 1; (3) All-Bond 2, 49.5 +/- 4.3; (4) Panavia, 57.9 +/- 3.1; (5) Panavia to nickel-chromium, 42.9 +/- 6.6; (6) Panavia to enamel, 18.5 +/- 4.7; and (7) Metabond to enamel, 19.3 +/- 3.5. Titanium was most effectively bonded with All-Bond 2 and Panavia, with Panavia samples significantly better than Panavia to nickel-chromium samples. CONCLUSIONS: It was concluded that titanium bonded restorations with certain adhesive cements were a definite possibility.

Analysis of Variance↗
PubMed1993

Identification of oxide layers of commercially pure titanium in response to cleaning procedures.

The composition and thickness of the oxide formed on commercially pure titanium disks were analyzed after the disks were subjected to one of four surface treatments: (1) cleaning with the initial Brånemark regimen, (2) Brånemark regimen and autoclaving, (3) Brånemark regimen and radiofrequency glow discharge (RFGD) treatment for 5 minutes, and (4) Brånemark regimen and RFGD treatment followed by storage for 30 days. Electron spectroscopy for chemical analysis showed titanium dioxide to be the prominent oxide; no significant differences in the thickness of the oxide layers were found.

Analysis of Variance↗
PubMed1992

Determining the force absorption quotient for restorative materials used in implant occlusal surfaces.

It has been hypothesized that the type of material used to form the occlusal surface of restorations retained by dental implants may impart a "dampening effect" to the bone-implant interface. This study compared the force transmitted to human bone by gold, porcelain, and resin occlusal surfaces in a simulated implant occlusal rehabilitation. A Branemark self-tapping implant was placed in a human cadaver mandible with a stacked three element strain gauge cemented to the lingual cortical plate. An Instron testing machine was used to apply an axial force, through a peanut sample, to a restoration that contained interchangeable occlusal surfaces. Applied force was divided by recorded microstrain at the bone-strain gauge junction to derive a calculated ratio, or force absorption quotient. No statistically significant difference of the force absorption quotient between the occlusal surfaces of gold, porcelain, and resin was observed.

Absorption↗
PubMed1992

Early detection of osseointegration using scanning electron microscopy and the interfacial biopsy chamber: a pilot study.

This pilot project attempted to demonstrate microscopic evidence of osseointegration in a controlled environment as originally presented by Brånemark. The Interfacial Biopsy Chamber was developed to collect titanium/tissue serial biopsies of the implant-tissue interface at various stages of wound healing. It was surgically placed in two Flemish giant rabbits and titanium/tissue biopsies were collected at 35 and 70 days. The biopsies were examined using scanning electron microscopy (x2000, x3200, and x7500) and light microscopy (x230). Osseous tissue was found in intimate contact with the titanium implant surface with no evidence of an intervening fibrous layer. Cells with the morphological characteristics of osteoblasts were observed covering the titanium surface. Processes extending from the main body of these cells were in intimate contact with the titanium surface, following the machining striations. The photomicrographs were similar to those presented earlier by Brånemark. The project also suggested the use of the Interfacial Biopsy Chamber as a research instrument for the collection of implant/tissue interface serial biopsy samples.

Animals↗
PubMed1992

Lingualized integration: tooth molds and an occlusal scheme for edentulous implant patients.

The interface of bone and soft tissue to dental implants has been extensively documented, while the influence of biomechanics and the occlusal interface continues to be overlooked. Yet that same occlusal interface may ultimately be the prime factor in the lifetime survival rate of dental implants. What is lacking, for the practitioner, is a clear concept of the occlusal rehabilitation which is required and appropriate for the totally edentulous implant patient. Lingualized integration represents an occlusal scheme using specific tooth molds designed to improve the likelihood of maximum intercuspation and an absence of deflective occlusal contacts, provide cusp height for selective occlusal reshaping, and achieve a natural and pleasing appearance. Factors in the articulation and arrangement of the posterior teeth to assure the attainment of the fundamental goals of comfort, function, and appearance in occlusal rehabilitation for edentulous implant patients are included.

Dental Implants↗
PubMed1992

Filler particle size and composite resin classification systems.

The currently used composite resin classification systems need review if they are to continue to serve as descriptives and quantitative parameters denoting the filler particle content of these materials. Examination of the particles in 12 composite resins using a technique of washing the filler particles from the matrix of the composite resin was presented as yet another method of grouping composites according to filler particle content. Light microscopic examination of the filler particles that remained provided a separation of the 12 materials into four easily distinguished groups based on filler particle sizes. The wear of the 12 composite resins determined in a previous study was examined in relation to the classification of the materials by the currently available systems. The wear values were also examined using the groupings of the materials according to their filler particle sizes as determined by separating the particles from the matrix by the washing technique. Grouping composites on the basis of the filler particle sizes found after washing was easily correlated with wear and supported the suggestion that composites with smaller filler particles wear less.

Acrylic Resins↗
PubMed1992

The in vivo wear resistance of 12 composite resins.

PURPOSE: The in vivo wear resistance of 12 composite resins were compared with an amalgam control using the Latin Square experimental design. Sixteen edentulous patients wearing specially designed complete dentures formed the experimental population. MATERIALS AND METHODS: The Michigan Computer Graphics Measurement System was used to digitize the surface of the control and composite resin samples before and after 3-month test periods to obtain wear data. The 12 composite resins selected for this investigation based on their published composite classification types were seven fine particle composites, three blends, and two microfilled composite resins. The Latin Square experimental design was found to be valid with the factor of material being statistically different at the 5% level of significance. Wear was computed as volume loss (mm3/mm2), and all of the composites studied had more wear than the amalgam control (P = .001). RESULTS: After 3 months, the mean (error) of wear of the amalgam was 0.028 (0.006). Means (error) of wear for the 12 composites were ranked from most to least wear by mean wear volume loss. CONCLUSION: The absence of any relationship between mean wear volume loss and the volume percentage filler was confirmed by the correlation coefficient r = -0.158.

Analysis of Variance↗
PubMed1991

Determination of the accuracy of three die systems.

This article reports the findings of two interrelated projects that measured the accuracy of electroplated, epoxy resin, and polyurethane die materials against a master tooth, using the Michigan Computer Graphics Coordinate Measuring System (MCGCMS). In the first phase, on occlusal die morphology, replications of a master tooth were used to validate the MCGCMS reliability. Eighteen total data sets derived from three silver-plated dies and three epoxy resin dies were then compared with a representative data set of the master tooth. The mean differences for all silver-plated die and epoxy die measurements against the master ranged from -42 to -49 and -46 to -230 microns/mm2, respectively. In the second phase, two epoxy die materials and a polyurethane system were compared with a master tooth in an identical manner. In paired comparisons to the master tooth, mean differences for Epoxydent material, epoxy resin, and polyurethane dies ranged from -147 to -153, -149 to -230, and -56 to -168 microns/mm2, respectively. A Student t test using a CLR ANOVA was performed between the master tooth and the five die systems. A significant difference was revealed between the enamel-silver difference and the enamel-Epoxydent difference data at the 95% confidence level. A significant difference also occurred between enamel-silver and enamel-epoxy resin. It was concluded that silver-plated dies are acceptable replicas of a master tooth. Epoxydent and epoxy resin dies did not provide reliable replications when compared with the silver-plated dies. Epoxy and polyurethane replications, although reported as accurate, were inconclusive.

Analysis of Variance↗
PubMed1989

The bone biopsy chamber: an improved method of collecting osseous tissue.

The bone biopsy chamber (BBC) has been developed for implantation in bone to permit the serial biopsy of osseous tissues to study osseointegration. This device improves the currently available methodology for studying the implant/osseous interfacial zone by providing a means of collecting osseous samples for microscopic evaluation in the least invasive manner, and without euthanization or en bloc resection. The advantages of the BBC were verified through its implantation in the tibia of five young adult Flemish Giant rabbits and the serial collection of osseous samples. Following the recommended surgical procedures to implant the BBC and obtain osseointegration, osseous samples were collected from the five rabbits at 30-, 60-, and 90-day test periods for histologic evaluations. Bone specimens were embedded in preparation for staining using modified goldner trichrome, toluidine blue, and gallocyanin. Each of the sections demonstrated clear evidence of biocompatibility, the different cellular components and stages of osteogenesis, and that osseous tissue biopsies were possible using this device.

Animals↗
PubMed1988

The effect of recasting on the oxidation layer of a palladium-silver porcelain alloy.

The oxidation zone of a commercial palladium-silver porcelain alloy was compared after repeated casting with and without the addition of new alloy. The intensity of palladium, silver, tin, indium, and O K-alpha near the oxidation zone was analyzed with XMA. The intensity curves of tin, silver, and oxygen increased progressively through each generation despite the addition of new alloy. The thickness of the oxidation zone and the microporosities at the internal oxidation zone increased through each generation without the addition of new alloy. Although the findings indicated that the oxidation zone was favorably formed by adding new alloy, 50% by weight, for four generations, the silver and metallic oxides of the oxidation zone increased through each generation. The reuse of the palladium-silver porcelain alloy remains questionable.

Dental Alloys↗