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PubMed1994

The effects of nerve injury on ligament healing in a rat model.

The presence of an intact nerve supply is important in the regeneration of injured tissue in some animals. It has not been determined whether an intact nerve supply is important in ligamentous healing. The authors hypothesize that the nerve supply of a ligament might have a significant effect on its healing. The purpose of this paper was to determine whether injury to the nerve supply of the medial collateral ligament in a rat model results in poor ligament healing (which would suggest that intact nerve supply enhances ligament repair). Clinically, such a finding would demonstrate the importance of avoiding injury to nerve-ligament systems in reparative ligament surgery. Twenty three rats underwent complete bilateral dissection of the major nerves supplying the medial collateral ligament, and each ligament was transected at the level of the tibial tuberosity. The major nerve supplies of the experimental ligaments were destroyed by segmental excision, either distally at the medial articular nerves or proximally at the saphenous nerve, while the control ligament's nerve supplies were left intact. The rats were euthanized at 12 days, and each medial collateral ligament was tested biomechanically using a hydraulic materials testing machine. This time point was chosen because the rat ligament transection site heals rapidly, causing the ligament to avulse from its tibial insertion instead of rupturing at the transection site at later time points. This rat medial collateral ligament injury model has shown statistically significant differences in healing at this time point in numerous experiments evaluating the effects of other variables on ligament healing.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1997

Evolution of repellent tolerances in representative arthropods.

Eight commercial insect repellents were tested against Ornithodoros parkeri (Acari: Argasidae), Dermacentor variabilis (Acari: Ixodidae), Aedes aegypti (Diptera: Culicidae), and Xenopsylla cheopis (Siphonaptera: Pulicidae). Patterns of tolerance to the test materials were distinctive for each test species. Levels of tolerance were coded as character state 0 (sensitive), 1 (intermediate), or 2 (tolerant) and mapped on a cladogram reflecting the accepted classification of the test species. Character state 0 was regarded as primitive, as indicated by the ontology of repellent tolerances in ticks. Aedes aegypti was least evolved and X. cheopis was most evolved in tolerance to repellents. Multiple parallelism of the arachnid and X. cheopis lines occurred in the evolution of the observed tolerances.

Aedes↗

PubMed1977

Enamel bonding plastic materials in modifying the form of abutment teeth for the better functioning of partial prostheses.

The potential uses of enamel bonding sealants and composite filling materials in increasing the retentive form of abutment teeth and covering the preparations for the occlusal supports of partial prostheses were studied in laboratory conditions. The materials tested were Nuva and Concise sealants and composite resins. Extracted permanent human molars, premolars and canines were inserted into acrylic blocks, two teeth in each block. An unretentive clasp framework was made on every test block. A retention prominence was built up separately of sealants and of composite materials occlusally to the tip of each clasp arm. The bond strength and wear resistance of the materials was tested in a device designed for this study. The bond of the prominences was very good, only two out of 114 prominences loosened. The retention gained with prominences was, on average, 18 N measured by the force needed for removal. The decrease in the total retention of the four clasp arms was measured by the force needed to remove the clasp framework. The total retention of the prominences made of Nuva and Concise sealants after 5000 removals was 53 and 50% of the original, when long, flexible clasp arms were used. The corresponding figures for composite resins were 56 and 59%. Short rigid clasp arms caused a distinctly faster abrasion. The prominences made of sealants, in particular, were abraded rapidly, one-fifth of retention being left after 3000 removals.

Composite Resins↗

PubMed2004

Celluloid strip-finished versus polished composite surface: difference in surface discoloration in microhybrid composites.

The aim of this study was to compare the surface discoloration of polished and celluloid strip-finished composite surfaces in microhybrid type composites and to determine whether or not the discoloration of a celluloid strip-finished composite surface is reduced if oxygen inhibition on the surface can be prevented. The composite surfaces were celluloid-strip finished (group 1), polished (group 2), or celluloid-strip finished under nitrogen gas purging (group 3). Z100, Spectrum, and Aelitefil were used as the test materials. After each surface treatment, the samples were stored in 37 degrees C distilled water for 24 h and placed in a disclosing solution (0.2% Erythrosin, pH 7.0) for 7 days in the dark. A computer controlled spectrophotometer was used to determine the CIELAB co-ordinates (L*, a*, b*). For each composite, the degree of discoloration among the groups was compared with a one-way ANOVA test. A Dunnett's t-test was then performed to compare the colour change in group 1 with that of group 2 or group 3. In all materials, there were no statistical differences in the surface discoloration between group 1 and group 2. In the Aelitefil and Spectrum test materials, the samples in group 3 showed a lower level of discoloration than the those in group 1. In Z100, there was no statistical difference. In microhybrid composites, there was no difference in surface discoloration between celluloid strip-finished and the polished surface. Nitrogen gas purging during the polymerization process on the celluloid strip-finished composite surface might be useful for reducing the discoloration celluloid strip-finished surface in microhybrid composites.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1990

The use of visible light-curing composites in bonding ceramic brackets.

Three hundred and fifty bovine teeth were bonded with a ceramic bracket using nine different materials. Five of the materials were composites used in conservative dentistry, two were light-curing orthodontic adhesive test materials, and two were chemically curing adhesives. Four of the materials were modified by dilution with resin. With the proper consistency, it was found that the use of primer was not necessary. Adequate strength was observed within a 20-second curing time. No statistical difference in bond strength was observed among the materials. It is concluded that light-curing adhesives can offer several advantages in the bonding of ceramic brackets.

Aluminum Oxide↗

PubMed2002

Effect of argon-beam coagulation on the integrity of suture material.

PURPOSE: To evaluate the effect of argon-beam coagulator (ABC) energy on suture materials. MATERIALS AND METHODS: Six absorbable and nonabsorbable suture materials (polyglactin, chromic catgut, polydioxanone, silk, poliglecaprone, and Gore-Tex) were placed under tension and exposed to ABC energy to determine breaking times. Subsequently, all suture materials were exposed to limited ABC energy, and tensiometry was used to determine decreases in breaking strengths. RESULTS: Among the suture materials tested, Gore-Tex was the most resistant to ABC energy. Although absorbable suture materials were less resistant than nonabsorbable suture materials, 2-0 polyglactin manifested the greatest resiliance to deterioration with ABC energy exposure. CONCLUSIONS: The ABC has differential effects on suture materials. Larger-gauge suture materials are more resistant to ABC than smaller materials. Similarly, nonabsorbable sutures are generally more resilient to ABC energy than absorbable materials. Among the suture materials evaluated in our in vitro model, 2-0 Gore-Tex was best suited for vascular ligation, and 2-0 polyglactin is optimal for renal collecting system closure if ABC is anticipated as an adjunct for hemostasis.

Absorbable Implants↗

PubMed2004

In vitro antibacterial activities of root-canal sealers by using two different methods.

The purpose of this in vitro study was to evaluate the antibacterial activity of five different root-canal sealers (RoekoSeal, Ketac-Endo, AH Plus, Sealapex, Sultan). With the use of Enterococcus faecalis as a test organism, both the agar-diffusion test (ADT) and direct-contact test (DCT) were performed. For DCT, sealers were mixed and placed on the sidewall of microtiter plate wells. A 10-microl bacterial suspension was placed on the tested material samples. Bacteria were allowed to directly contact to the sealers for 1 h at 37 degrees C. Bacterial growth was then spectrophotometrically measured through every 30 min for 19 h by using an Anthos Labtec HT 2. For ADT, a 200-microl bacterial suspension was spread on brain-heart infusion agar plates. Freshly mixed sealers were poured into uniform wells punched in the agar. After periods of incubation at 37 degrees C for 24 h and 7 days in humid atmosphere, the zones of inhibition of bacterial growth on agar plates were observed and measured. Ketac-Endo, Sultan, and AH Plus had similar results for DCT. These sealers were more potent bacterial-growth inhibitors than Sealapex and RoekoSeal. According to ADT, RoekoSeal showed no antibacterial activity. There was no significant difference among AH Plus, Sealapex, and Sultan (p > 0.05). Ketac-Endo demonstrated lower antimicrobial activity than these sealers (p < 0.05). Time had no effect on the antibacterial activity of the tested sealers (p > 0.05). The antibacterial efficiency of the materials varied according to the tests used. It was concluded that the technique, time, and ingredients of the tested material can affect the results of the microbiological studies.

Anti-Bacterial Agents↗

PubMed1999

In vitro release of hydroxyl ions from calcium hydroxide gutta-percha points.

In endodontic practice, calcium hydroxide is widely used for a number of reasons associated with its high pH. The purpose of the present study was to determine in vitro the alkalizing potential of newly introduced calcium hydroxide gutta-percha points that are proposed for temporary filling of root canals. The materials tested were: calcium hydroxide gutta-percha points; chemical pure calcium hydroxide powder mixed with distilled water; and Reogan rapid, a nonsetting calcium hydroxide preparation. The materials were placed into dialysis tubing and transferred into plastic vials containing bidistilled water. Measurements were taken by a digital pH meter after 10, 20, and 30 s; 1, 15, and 30 min; and 1, 2, 3, 24, 48, 72, 96, and 120 h. The calcium hydroxide containing gutta-percha points showed a significantly lower alkalizing potential than Reogan rapid and calcium hydroxide mixed with distilled water (p < 0.05).

Analysis of Variance↗

PubMed2007

Comparative study of the wear behavior of composites for posterior restorations.

This investigation sought to compare the abrasive wear rates of resin composites designed for posterior applications. Seventy-five specimens were fabricated with conventional hybrid (Charisma and Filtek Z250) or packable composites (Filtek P60, Solitaire II and Tetric Ceram HB), according to a randomized complete block design (n = 15). Specimens were finished and polished metallographically and subjected to abrasive wear which was performed under a normal load of 13N at a frequency of 2 Hz using a pneumatic device (MSM/Elquip) in the presence of a mucin-containing artificial saliva. Wear was quantified profilometrically in five different locations of each specimen after 1,000, 5,000, 10,000, 50,000 and after every each 50,000 through 250,000 cycles. A split-plot ANOVA showed a significant difference between the wear resistance of composites (alpha = 0.05). Tukey's test ascertained that while the composites Filtek Z250 and Charisma wore significantly less than any other of the materials tested, Tetric Ceram HB experienced the greatest wear rates. Filtek P60 and Solitaire II showed intermediate rates of material removal. The wear pattern of composites proved to be biphasic with the primary phase having the faster wear rate. In conclusion, packable resin composites may not have superior wear compared to conventional hybrid composites.

Analysis of Variance↗

PubMed1991

Evaluation of seven in vitro alternatives for ocular safety testing.

Seven in vitro assays were evaluated to determine if any were useful as screening procedures in ocular safety assessment. Seventeen test materials (chemicals, household cleaners, hand soaps, dishwashing liquids, shampoos, and liquid laundry detergents) were tested in each assay. In vivo ocular irritation scores for the materials were obtained from existing rabbit low volume eye test (LVET) data. The seven assays evaluated included the silicon microphysiometer (SM), luminescent bacteria toxicity test (LBT), neutral red assay (NR), total protein assay (TP), Tetrahymena thermophila motility assay (TTMA), bovine eye/chorioallantoic membrane assay (BE/CAM), and the EYTEX system (ETS). For the seventeen materials used in this study there was a significant correlation between the in vivo irritant potential and in vitro data for all the tests except the EYTEX System (SM, r = -0.87; LBT, r = -0.91; NR, r = -0.85; TTMA, r = 0.78; TP, r = -0.86; ETS, r = 0.29). The irritation classifications provided by the BE/CAM also did not correspond with the actual in vivo irritancy potential of the test materials. The result of this study suggested it may be possible to classify materials into broad irritancy categories with some of the assays. This would allow their use as screens prior to limited in vivo confirmation in the ocular safety assessment process.

Allantoin↗

PubMed2001

Evaluating acrylic and glass-ionomer cement strength using the biaxial flexure test.

Frequently, bone cement strengths are evaluated from uniaxial tests, such as three- or four-point flexure. Measurement of material strength in this manner may not provide an accurate characterisation of a bone cements true load-bearing capacity. In most orthopaedic applications, there exists a state of biaxial stress and so biaxial strength information is most useful. To address this issue, the biaxial flexure strength of two polymethylmethacrylate orthopaedic (PMMA) bone cements and two glass-ionomer dental cements have been determined. The biaxial strength of orthopaedic bone cements have been compared to the three-point bending strength. Furthermore, the calculated theoretical biaxial strength was compared with a value of biaxial strength utilising the finite element method. For all materials tested the calculated biaxial strength is significantly greater than the three-point bending strength. The biaxial test offers several advantages over three-point bending because it critically explores surface flaws--as it does not matter in which orientation the crack lies. However, it does minimise the volume or surface area investigated and also the edge effect. The difference in strength calculated for the two testing methods can be explained quantitatively in terms of the volume of material under stress. This work has demonstrated that the biaxial flexure test can be used for the testing of orthopaedic bone cements.

Acrylic Resins↗

PubMedDate not supplied

Arthrodesis of the equine proximal interphalangeal joint: a mechanical comparison of 2 parallel 5.5 mm cortical screws and 3 parallel 5.5 mm cortical screws.

OBJECTIVE: To compare the biomechanical characteristics and mode of failure of 2 techniques using parallel 5.5 mm screws for pastern joint arthrodesis in horses. STUDY DESIGN: Randomized block design, for horse (1-5), method of fixation (two 5.5 mm screws versus three 5.5 mm screws), side (right, left), and end (front, hind). Constructs were tested to failure in 3-point bending. SAMPLE POPULATION: Twenty limbs (5 cadavers). METHODS: A combined aiming device was used to facilitate screw placement. Two parallel 5.5 mm screws were inserted in lag fashion in 1 limb of a pair, and three 5.5 mm screws were inserted in the contralateral limb. Constructs were then tested in 3-point bending in a dorsal-to-palmar (plantar) direction using a materials testing machine at a loading rate of 19 mm/s. Maximal bending moment at failure and stiffness were obtained from bending moment-angular deformation curves. RESULTS: There was no significant difference between two and three 5.5 mm screw constructs for bending moment and stiffness (P<.05). All constructs ultimately failed by bone fracture or screw bending. For proximal interphalangeal (PIP) joint arthrodesis constructs loaded in 3-point bending, no significant effect of treatment, side, or end on maximal bending moment or stiffness was detected. CONCLUSIONS: Two 5.5 mm cortical screws inserted in parallel should provide a surgically simpler and equally strong PIP joint arthrodesis compared with three 5.5 mm cortical screws. CLINICAL RELEVANCE: Two 5.5 mm cortical screws inserted in parallel for PIP joint arthrodesis should perform similarly under conditions used in this study, as three 5.5 mm screws inserted in a similar manner, when loaded under bending.

Animals↗

PubMed2005

The biomechanical analysis of a tendon fixation device for flexor tendon repair.

PURPOSE: Stainless steel suture is high in tensile strength but is not widely used in flexor tendon repair because of difficulty with handling and knot tying. The purpose of this study was to examine the biomechanical characteristics of the single-strand multifilament stainless steel Teno Fix device (Ortheon Medical, Winter Park, FL) designed for zone II flexor digitorum profundus (FDP) tendon repair. METHODS: Sixty cadaveric flexor tendons were transected and randomized to receive a Teno Fix or 4-stranded (3-0 or 4-0 braided polyester) suture repair; all repairs were tested with and without a 5-0 monofilament polypropylene circumferential epitendinous suture. By using a material testing system all tendons were tested to failure in tension using a linear model with a loading rate of 1 mm/s. Stiffness, force, and energy at both 2-mm gap and peak force were calculated from the resulting force-displacement curves. RESULTS: The 2-mm gapping force was significantly greater for the Teno Fix and the 3-0 repairs than for the 4-0 repairs. The energy absorbed up to 2-mm gap was significantly greater for the Teno Fix, however, than for all suture repairs both with and without a circumferential suture. There was no statistically significant difference in peak force or energy absorbed at peak force between the Teno Fix and suture repairs; the average gap at peak force for all repairs was 5.2 mm. The addition of a circumferential suture increased the 2-mm gapping and peak forces of the Teno Fix repair to 54.5 N and 66.7 N, respectively. CONCLUSIONS: Increased strength and energy absorbed at 2-mm gap and ease of installation makes the Teno Fix a promising repair method.

Biomechanical Phenomena↗

PubMed2004

Comparison of predicted and derived measures of volatile organic compounds inside four new relocatable classrooms.

UNLABELLED: Our objective was to develop a process for selecting interior finish materials having low impacts with respect to emissions of toxic and odorous volatile organic compounds (VOCs) for school relocatable classrooms (RCs). A laboratory study identified alternate materials with low VOC emissions. Two pairs of RCs then were constructed. One RC per pair contained standard interior materials; the other incorporated alternate materials. The pairs were sited side-by-side at two California elementary schools in fall 2001. Fifteen target VOCs, including the toxicants formaldehyde, acetaldehyde, vinyl acetate, phenol, toluene, and naphthalene, were measured during school hours over 8 weeks in the succeeding fall cooling season. Indoor minus outdoor VOC concentrations with an advanced HVAC operated were low; only formaldehyde concentrations exceeded 5 p.p.b. Classroom VOC concentrations were predicted based on emission factors (microg/m(2)/h), material quantities and design ventilation rates. These were compared to average adjusted concentrations measured when the occupied classrooms were operating at near the code-minimum ventilation rate. For 16 of the possible 42 comparisons, measured concentrations agreed within a factor of two of predicted the predicted values. Concentrations of six of 10 VOCs were significantly lower in modified RCs though average differences were mostly less than 1 p.p.b. PRACTICAL IMPLICATIONS: Laboratory-based material testing combined with modeling and field validation to select low VOC-impact interior finish materials helped achieve the aim of providing generally acceptable air quality in new school relocatable classrooms (RCs). The accuracy of the combined process was evidenced by the correct prediction of air quality impacts, though small, due to material VOC emissions when the study RCs were ventilated at code-minimum requirements. The process could be generalized to other manufacturers and classroom types. Material selection also is important to accommodate reduced ventilation rate conditions, which likely occur in many classrooms.

Air Pollution, Indoor↗

PubMed1996

Determination of the total attenuation coefficient for six contact lens materials using the Beer-Lambert law.

The Beer-Lambert law has been used to determine the total attenuation coefficient, mu t, of three hard and three soft contact lens materials. The three hard contact lens materials were PMMA, Polycon II and Boston IV whereas the 3 soft materials were chosen with differing water contents of 38, 55 and 70%, respectively. The total attenuation coefficients of all six materials were obtained from measurements of the axial transmission at 632.8 nm of a series of plano powered lenses varying in axial thickness from 0.5 to 3.5 mm. The value of the total attenuation coefficient depends on both scattering and absorption and hence PMMA and Boston IV, which both incorporated a handling tint, showed significantly higher values (P < 0.0001) of mu t (0.562 +/- 0.010 mm-1 and 0.820 +/- 0.008 mm-1, respectively) than Polycon II (mu t = 0.025 +/- 0.005 mm-1). A comparison between Polycon II and the three hydrated soft contact lens materials showed a significant increase (P < 0.02) in the total attenuation coefficients for the 38% and 55% water content materials, and a weakly significant increase for the 70% water content soft lens material (P < 0.1). On the assumption that the absorption coefficients of these four materials are approximately constant, then this change would be due to an increase in the scattering coefficient of the material and could contribute to an increase in intraocular scatter. No significant difference (P > 0.5) was found between any of the hydrated soft contact lens materials tested.

Contact Lenses↗

PubMed2000

Antimicrobial activity and flow rate of newer and established root canal sealers.

Endodontic sealers that possess both optimum flow ability and antimicrobial properties may theoretically assist in the elimination of microorganisms located in confined areas of the root canal system. The antimicrobial effects and the flow rate of the following sealers were investigated and compared: Kerr Pulp Canal Sealer EWT, Grossman's Sealer, ThermaSeal, Sealer 26, AH Plus, and Sealer Plus. The agar diffusion test was used to assess the antimicrobial activity of the sealers. In the flow assay, the sealers were placed between two glass slabs and a weight of 500 g was placed on the top of the glass. The diameters of the formed discs were recorded. All root canal sealers tested showed some antimicrobial activity against most of the microorganisms. There were no significant differences between the materials tested (p > 0.05). All root canal sealers also flowed under the conditions of this study. Statistical analysis of the results revealed that AH Plus and Kerr Pulp Canal Sealer EWT had flow values significantly superior to the other sealers tested (p > 0.05). Taken together, these findings suggest that these sealers have the potential to help in the microbial control in the root canal system.

Agar↗

PubMed2005

Antibacterial activity of two adhesive systems using various microbiological methods.

PURPOSE: To compare the antibacterial activities of two dentin bonding systems (DBS), Clearfil Protect Bond and Xeno III, by agar well, paper and dentin disks, and a cavity tooth model. MATERIALS AND METHODS: For the well technique, the test materials were filled in the agar wells inoculated with Streptococcus mutans (ATCC 25175). The paper disks were embedded in adhesives and placed on the seeded agar plates for the second technique. The adhesives were applied on the dentin disks and placed in holes in the plates for the third technique. After 48 h, the zones of inhibition were measured. In the cavity tooth model test, 3 cavities were prepared in the flat occlusal dentin of extracted human molars. The teeth were left in S. mutans for 72 h to allow bacterial invasion. The DBS were applied in the same manner as in clinical application on each of the two infected cavities and the third was left unapplied for control. The teeth were kept in saline for 72 h. Standard amounts of dentin chips were obtained from the cavity walls and the number of bacteria recovered was counted. RESULTS: The results were analyzed by factorial ANOVA and Dunnett C test. Clearfil Protect Bond primer exhibited the greatest inhibition zones followed by Consepsis and unpolymerized Xeno III in all the techniques tested (p < or = 0.05). Clearfil Protect Bond resulted in significantly less bacterial recovery than Xeno III by the tooth cavity method (p < or = 0.05). CONCLUSION: Clearfil Protect Bond was found to be the most antibacterial material with all the techniques used. Furthermore, Clearfil Protect Bond was able to inactivate the bacteria in the cavity more effectively than Xeno III.

Anti-Bacterial Agents↗

PubMed2006

Assessment of the sealing ability of a new root canal obturation material.

This study was designed to compare the leakage allowed by different obturation materials, using a fluid-transport method. Sixty-six single-rooted human anterior teeth were fully instrumented by using the "step-back" technique and irrigated with 5.25% sodium hypochlorite. The smear layer was removed by washing in 10 ml of 17% EDTA. The specimens were randomly divided into three experimental groups of 18 teeth each, plus two groups of 6 teeth each for positive and negative controls. The specimens were obturated by the lateral condensation technique, with gutta-percha and AH 26 or AH plus sealers, or Epiphany sealer and Resilon core material. The fluid transport method used in this study gave quantitative results and allowed nondestructive evaluation of the specimens. The teeth filled with gutta-percha and AH 26 exhibited the most leakage. The least leakage was seen with Epiphany sealer and Resilon core material. The differences in leakage among the groups were statistically significant (p < 0.05). It was concluded that of the materials tested under the conditions of this study, Epiphany allowed the least leakage.

Dental Leakage↗