Translucency and Strength of Lithium Disilicate for Computer-Aided Design and Manufacturing at Different Thermal Temperatures and Thicknesses: An In Vitro Study

To manufacture dental restorations composed of lithium disilicate (LD) through the computer-aided design and manufacturing (CAD/CAM) process, thermal refinement is an essential process that can affect the optical and mechanical properties of ceramics. In this study, we aimed to evaluate the translucency and flexural strength of lithium disilicate glass-ceramic for CAD/CAM using different thermal refinement schedules and thicknesses by measuring the total transmission of light through the specimen and calculating the peak load of the specimen until fracture in a piston-on-three-ball test, respectively. The results showed that a lower translucency was exhibited in thicker specimens, and the flexural strength decreased in the order of 1.0, 0.5, and 2.0 mm (p < 0.05). The lithium disilicates thermally refined at a heat of 820 degrees were shown to have the highest biaxial flexural strength (p < 0.05). These findings suggest that it is possible to adjust transparency and strength according to the clinical situation by choosing an appropriate thickness and thermal refinement process.

Evaluation of Implant Stability According to Implant Placement Site and Duration in Elderly Patients: A Prospective Multi-Center Cohort Study

The aim of this prospective study is to investigate implant stability and the reliability of different measuring devices according to implant placement site and duration in patients aged over 65 years. The study evaluated 60 implants (diameter: 3.5/4.0/4.5/5.0 mm and length: 8.5/10.0/11.5 mm) in 60 patients aged ≥ 65 years. The implant placement sites were divided into six evenly distributed sections (n = 10), i.e., maxillary right-posterior, A; maxillary anterior, B; maxillary left-posterior, C; mandibular right-posterior, D; mandibular anterior, E; mandibular left-posterior, F. Participants visited the hospital six times: implant surgery, 1V; stitch removal, 2V; 1-month follow-up, 3V; 2-month follow-up, 4V; before final restoration delivery, 5V; and after final restoration delivery, 6V. The implant stability was evaluated with the Osstell Mentor (ISQ), Periotest M (PTV), and Anycheck (IST). The mean values of ISQ, PTV, and IST were analyzed (α = 0.05). ISQ, PTV, and IST results of 4V and 5V were significantly higher than those of 1V (p < 0.05). The lowest ISQ results occurred in the E location at 4V and 5V (p < 0.05). In all mandibular locations, IST results of 6V were significantly higher than those of 1V, 2V, 3V, and 4V (p < 0.05). ISQ results were negatively correlated with PTV and positively correlated with IST, and PTV was negatively correlated with IST. By considering various factors affecting the stability of the implant, it is necessary to determine the appropriate implant load application time. This could help increase the implant success rate in elderly patients. And as a diagnostic device for implant stability and the evaluation of osseointegration in elderly patients, Anycheck was also able to prove its relative reliability compared to Osstell ISQ Mentor and Periotest M.

Reliability of implant stability measuring devices depending on various clinical conditions: an in vitro study

PURPOSE

The aim of this study was to evaluate the reliability of implant stability measuring devices depending on the location of the implant and the position of the patient.

MATERIALS AND METHODS

Six implants were installed in different dentate sextants of six artificial bone models. Implant stability was measured in three conditions of the bone model (without mounting on a phantom head, mounted on a phantom head in supine position, and mounted on a phantom head in upright position). A resonance frequency analysis device (Osstell) and two damping capacity analysis devices (Periotest and Anycheck) were used to measure implant stability. The values measured outside the phantom head were treated as controls, and the values inside the phantom head were compared using an independent t-test.

RESULTS

Osstell showed different results in two of the six divisions in both the supine and upright positions compared to outside of the mouth (P < .05). Periotest showed different results in all six parts in the supine position and in five parts in the upright position compared to outside of the mouth (P < .05). While Anycheck showed different results in five areas in the supine position compared to outside of the mouth, it showed different results in only one area in the upright position (P < .05).

CONCLUSION

In the difficult implant position for the operator to access, the implant stability measuring devices show less reliability. The accessibility of implant is greatly affected in the order of Osstell, Anycheck, and Periotest.

Clinical Validation of Dental Implant Stability by Newly Designed Damping Capacity Assessment Device during the Healing Period

Background and Objectives: To evaluate the stability of a dental implant and the effectiveness of a newly designed damping capacity assessment device by improving the number of blows and strength evaluated by a prospective clinical study. Materials and Method: The stability of dental implants was measured in 50 implants in a total of 38 patients. Measurements were performed using Anycheck and Periotest M devices, twice in total, divided into buccal and lingual directions. In addition, measurements were performed on the day of surgery, two weeks, one month, two months, and three months after surgery for a total of five times. After the standardization of the measured values, the differences and changes over time for each device were observed. Result: No difference in standardized values between the two devices was observed at any time point. In both devices, stability decreased at two weeks postoperatively but gradually increased thereafter. No differences were observed in the values according to the measurement direction. Conclusions: The damping capacity of Anycheck was similar to that of Periotest M. After a slight decrease in stability two weeks after implant placement, implant stability increased over time.

Effects of Post-Curing Time on the Mechanical and Color Properties of Three-Dimensional Printed Crown and Bridge Materials

Three-dimensional (3D) printing is increasingly being utilized in the dental field. After fabricating a prosthesis using a 3D printed resin, a post-curing process is required to improve its mechanical properties, but there has been insufficient research on the optimal post-curing conditions. We used various 3D printed crown and bridge materials in this study, and evaluated the changes in their properties according to post-curing time by evaluating the flexural strength, Weibull modulus, Vickers hardness, color change, degree of conversion, and biocompatibility. The obtained results confirmed that the strength of the 3D printed resin increased when it was post-cured for 60–90 min. The Vickers hardness, the degree of conversion, and biocompatibility of the 3D printed resins increased significantly around the beginning of the post-curing time, and then increased more gradually as the post-curing time increased further. It was observed that the color tone also changed as the post-curing time increased, with some groups showing a ΔE₀₀ value of ≥ 2.25, which can be recognized clinically. This study has confirmed that, after the printing process of a 3D printed resin was completed, a sufficient post-curing time of at least 60 min is required to improve the overall clinical performance of the produced material.

The reliability of Anycheck device related to healing abutment diameter

PURPOSE

The purpose of this in vitro study was to examine the reliability of the Anycheck device and the effect of the healing abutment diameter on the Anycheck values (implant stability test, IST).

MATERIALS AND METHODS

Thirty implants were placed into three artificial bone blocks with 10 Ncm, 15 Ncm, and 35 Ncm insertion torque value (ITV), respectively (n = 10). (1) The implant stability was measured with three different kinds of devices (Periotest M, Osstell ISQ Mentor, and Anycheck). (2) Five different diameters (4.0, 4.5, 4.8, 5.5, and 6.0 mm) of healing abutments of the same height were connected to the implants and the implant stability was measured four times in different directions with Anycheck. The measured mean values were statistically analyzed.

RESULTS

The correlation coefficient between the mean implant stability quotient (ISQ) and IST value was 0.981 (P<.01) and the correlation coefficient between the meant periotest value (PTV) and IST value was −0.931 (P<.01). There were no statistically significant differences among the IST values with different healing abutment diameters.

CONCLUSION

There was a strong correlation between the Periotest M and Anycheck values and between the ISQ and IST. The diameter of the healing abutment had no effect on the Anycheck values.

Temporal Control of WNT Activity Regulates Tooth Number in Fish

Wnts determine cell polarity, cell proliferation, and cell differentiation during embryogenesis and play an essential role during tooth development initiation and morphogenesis. Wnt/β-catenin signaling has a time-dependent role in development because various signaling molecules that mutually interact are involved in the pathway, and tight regulation of the pathway is essential for normal development. Studies investigating how the Wnt/β-catenin signaling pathway controls the different stages of tooth development are rare. Specifically, the effects of Wnt/β-catenin signaling loss of function on different stages of tooth development are currently unknown. Here, we report the stage-dependent role of Wnt/β-catenin signaling in tooth development. In vivo loss and gain of function of Wnt/β-catenin signaling were implemented through the genetic overexpression of DKK1 with heat shock-inducible transgenic models and the pharmacologic inhibition of β-catenin destruction complex formation in zebrafish, respectively. We demonstrated that transient inhibition of Wnt/β-catenin signaling interrupted tooth development in a stage-dependent manner and conditional activation of Wnt/β-catenin signaling during 4V morphogenesis inhibited the development of 3V. These findings suggest that Wnt/β-catenin signaling plays an important role in the morphogenesis of teeth and the initiation of sequential tooth development in a stage-dependent manner.

Effect of Irradiance and Exposure Duration on Temperature and Degree of Conversion of Dual-Cure Resin Cement for Ceramic Restorations

This study investigated the effects of irradiance and exposure duration on dual-cured resin cements irradiated through ceramic restorative materials. A single light-curing unit was calibrated to three different irradiances (500, 1000, and 1500 mW/cm²) and irradiated to three different attenuating materials (transparent acryl, lithium disilicate, zirconia) with 1-mm thicknesses for 20 or 60 seconds. The changes in irradiance and temperature were measured with a radiometer (or digital thermometer) under the attenuating materials. The degree of conversion (DC) of dual-cure resin cement after irradiation at different irradiances and exposure durations was measured with Fourier transform near infrared spectroscopy. Two-way analysis of variance revealed that irradiance ( p<0.001) and exposure duration ( p<0.001) significantly affected temperature and DC. All groups showed higher DCs with increased exposure times ( p<0.05), but there were no statistically significant differences between the groups irradiated with 1000 mW/cm² and 1500 mW/cm² ( p>0.05). Higher-intensity irradiances yielded higher temperatures ( p<0.05), but exposure time did not affect temperature when materials were irradiated at 500 mW/cm² ( p>0.05).

A DN-mda5 transgenic zebrafish model demonstrates that Mda5 plays an important role in snakehead rhabdovirus resistance

Melanoma Differentiation-Associated protein 5 (MDA5) is a member of the retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) family, which is a cytosolic pattern recognition receptor that detects viral nucleic acids. Here we show an Mda5-dependent response to rhabdovirus infection in vivo using a dominant-negative mda5 transgenic zebrafish. Dominant-negative mda5 zebrafish embryos displayed an impaired antiviral immune response compared to wild-type counterparts that can be rescued by recombinant full-length Mda5. To our knowledge, we have generated the first dominant-negative mda5 transgenic zebrafish and demonstrated a critical role for Mda5 in the antiviral response to rhabdovirus.

Effect of light-curing, pressure, oxygen inhibition, and heat on shear bond strength between bis-acryl provisional restoration and bis-acryl repair materials

PURPOSE

This study aimed to discover a way to increase the bond strength between bis-acryl resins, using a comparison of the shear bond strengths attained from bis-acryl resins treated with light curing, pressure, oxygen inhibition, and heat.

MATERIALS AND METHODS

Self-cured bis-acryl resin was used as both a base material and as a repair material. Seventy specimens were distributed into seven groups according to treatment methods: pressure - stored in a pressure cooker at 0.2 Mpa; oxygen inhibition- applied an oxygen inhibitor around the repaired material,; heat treatment - performed heat treatment in a dry oven at 60℃, 100℃, or 140℃. The shear bond strength was measured with a universal testing machine, and the shear bond strength (MPa) was calculated from the peak load of failure. A comparison of the bond strength between the repaired specimens was conducted using one-way ANOVA and Tukey multiple comparison tests (α=.05).

RESULTS

There were no statistically significant differences in the shear bond strength between the control group and the light curing, pressure, and oxygen inhibition groups. However, the heat treatment groups showed statistically higher bond strengths than the groups treated without heat, and the groups treated at a higher temperature resulted in higher bond strengths. Statistically significant differences were seen between groups after different degrees of heat treatment, except in groups heated at 100℃ and 140℃.

CONCLUSION

Strong bonding can be achieved between a bis-acryl base and bis-acryl repair material after heat treatment.

A modified laparoscopic ureterolithotomy by pulling ureter with Carter-Thomason fascial closure and ureter incision by broken 15th blade

BACKGROUND AND AIMS

To evaluate the efficacy and safety of a modified laparoscopic ureterolithotomy for the treatment of upper ureteral stones; this method involved the use of a Carter-Thomason fascial closure device, a broken 15th blade.

MATERIAL AND METHODS

From February 2009 to December 2012, 38 patients with unilateral upper ureteral stones were examined and classified into 2 groups: one group underwent conventional laparoscopic ureterolithotomy (n = 21) and the other group underwent modified laparoscopic ureterolithotomy (n = 17). The modified laparoscopic ureterolithotomy consisted of the use of a Carter-Thomason fascial closure to extract the black silk along with the nylon tape. The ureter incision was made with a modified instrument consisting of a needle holder with a broken 15th blade tip.

RESULTS AND CONCLUSIONS

Patient demographics were similar in both groups. No significant differences were detected between the conventional laparoscopic ureterolithotomy and modified laparoscopic ureterolithotomy groups with respect to operating time, estimated blood loss, and stone clearance rates. Drain-indwelling times were significantly shorter in modified laparoscopic ureterolithotomy patients than in conventional laparoscopic ureterolithotomy patients (3.2 ± 1.3 vs 4.7 ± 1.5 days). Hospital stay was significantly lesser in modified laparoscopic ureterolithotomy patients than in conventional laparoscopic ureterolithotomy patients (4.3 ± 1.2 vs 5.2 ± 1.2 days). No differences were detected in the ureteral stent indwelling time for the two groups. The use of the Carter-Thomason fascial closure facilitated ureter handling, and the use of a needle holder with a broken 15th blade tip enabled a sharp and precise ureteral incision. Our method allows early removal of the drain and thus earlier patient discharge.

Abstract P2-09-18: Identification of synergistic drug combination for HER2 positive breast cancer

Breast cancer is one of the leading causes of death worldwide. 25-30% of breast cancer has HER2 gene amplification, which tend to give rise to poorly-differentiated and high grade tumor with a higher likelihood of spreading. Currently, trastuzumab and lapatinib are the only two FDA-approved treatments that target HER2 positive breast cancer. However, resistance to both drugs is already reported. Since breast cancer is considered to be one of genetic diseases caused by multiple gene aberrations, we used synergistic drug combination as a strategy to overcome these growth signaling pathway abnormalities. To identify new drug combination with lapatinib, we performed a cell-based screen against a library of clinical drugs of 3,200 compounds. Triptolide, a traditional Chinese medicine emerged from the screen with strong synergistic effect with lapatinib in HER2 positive breast cancer cells. This effect was specific to HER2 positive breast cancer. The whole HER2 signaling pathway was inhibited and more cells underwent apoptosis. Besides, both HER2 protein and mRNA levels were decreased in cells treated with the combination. This drug combination was also effective in breast cancer xenograft models of mice. Together, these findings suggest that both triptolide and lapatinib can be used as a promising drug combination for HER2 positive breast cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-09-18.

Altered sensation caused by peri-implantitis: a case report

Frequently reported is a case wherein a lesion caused by periodontitis or periapical lesion in a natural tooth enlarged, invaded the inferior alveolar nerve canal, and induced paresthesia. Cases wherein paresthesia occurred because of peri-implantitis have been rarely reported. The patient in this case report had experienced transient paresthesia after implant placement and recovered normal sensation 3 months later. Thirteen years later, this patient visited the authors' hospital with paresthesia in the same region because the peri-implantitis progressed to the apex of the implant. One week after removal of the implant, sense recovery and pain relief started, and 15 days after removal, the paresthesia and pain completely disappeared. For patients who experience transient paresthesia and recovery owing to nerve damage caused by the placement of an implant in the mandibular molar or premolar area, or in patients in whom the implant is close to the inferior alveolar nerve canal or the mental nerve, the spread of inflammation caused by peri-implantitis can induce paresthesia.

Effects of the immobilization of heparin and rhPDGF-BB to titanium surfaces for the enhancement of osteoblastic functions and anti-inflammation

PURPOSE

This study was to investigate the effects of recombinant human platelet-derived growth factor (rhPDGF-BB) and heparin to titanium surfaces for enhancement of osteoblastic functions and inhibition of inflammation activity.

MATERIALS AND METHODS

The anodized titanium discs, not coated with any material, were used as a control group. In heparinized- Ti group, dopamine was anchored to the surface of Ti substrates, and coated with heparin. In PDGF-Ti group, rhPDGF-BB was immobilized onto heparinized Ti surface. The surface morphologies were investigated by the scanning electron microscope in each group. The release kinetics of rhPDGF-BB were analyzed, and cytotoxicity tests for each group were conducted. The biocompatibilities were characterized by measuring cell proliferation, alkaline phosphatase activity, and calcium deposition using MG-63 cells. Statistical comparisons were carried out by one-way ANOVA tests. Differences were considered statistically significant at ^*P<.05 and ^**P<.001.

RESULTS

The combination of rhPDGF-BB and heparin stimulated alkaline phosphatase activity and OCN mRNA expression in osteoblastic cells (^*P<.05 and ^**P<.001). MG-63 cells grown on PDGF-Ti had significantly higher amounts of calcium deposition than those grown on anodized Ti (^**P<.001). Heparinized Ti was more anti-inflammatory compared to anodized Ti, when exposed to lipopolysaccharide using the transcript levels of TNF-α and IL-6 of proinflammatory cytokine (^*P<.05 and ^**P<.001).

CONCLUSION

The result of this study demonstrated that the incorporation of rhPDGF-BB and heparin onto Ti surface enhanced osteoblastic functions and inhibited inflammation.

The effect of immobilization of heparin and bone morphogenic protein-2 to bovine bone substitute on osteoblast-like cell's function

PURPOSE

This study was performed to investigate the ability of recombinant human-bone morphogenic protein-2 immobilized on a heparin-grafted bone substrate to enhance the osteoblastic functions.

MATERIALS AND METHODS

The Bio-Oss®, not coated with any material, was used as a control group. In rhBMP-2-Bio-Oss® group, rhBMP-2 was coated with Bio-Oss® using only deep and dry methods (50 ng/mL, 24 h). In heparinized rhBMP-2-Bio-Oss® group, dopamine was anchored to the surface of Bio-Oss®, and coated with heparin. rhBMP-2 was immobilized onto the heparinized- Bio-Oss® surface. The release kinetics of the rhBMP-2-Bio-Oss® and heparinized rhBMP-2-Bio-Oss® were analyzed using an enzyme-linked immunosorbent assay. The biological activities of the MG63 cells on the three groups were investigated via cytotoxicity assay, cell proliferation assay, alkaline phosphatase (ALP) measurement, and calcium deposition determination. Statistical comparisons were carried out by one-way ANOVA test. Differences were considered statistically significant at ^*P<.05 and ^**P<.001.

RESULTS

The heparinized rhBMP-2-Bio-Oss® showed more sustained release compared to the rhBMP-2-Bio-Oss® over an extended time. In the measurement of the ALP activity, the heparinized group showed a significantly higher ALP activity when compared with the non-heparinized groups (P<.05). The MG63 cells cultivated in the group with rhBMP-2 showed increased calcium deposition, and the MG63 cells from the heparinized group increased more than those that were cultivated in the non-heparinized groups.

CONCLUSION

Heparin increased the rhBMP-2 release amount and made sustained release possible, and heparinized Bio-Oss® with rhBMP-2 successfully improved the osteoblastic functions.

Factors associated with participation in providing buccal cell DNA for a genetic epidemiologic study

AIMS

Our aim was to investigate factors associated with participation in buccal cell DNA collection using a large-scale prospective cohort study.

METHODS

Of the 183,634 Korea Medical Insurance Corporation (KMIC) prospective cohort study enrollees, 44,773 (36,794 men) were randomly selected. Buccal cell collection kits were mailed and collected from March to September 2004. Epidemiologic characteristics measured at baseline (1990 or 1992) and during follow-up (1998) were compared between respondents and nonrespondents.

RESULTS

Among the 13,084 (29.2%) respondents, 78.7% submitted usable samples (DNA concentration ≥3 μg). After adjustments for either or both age and family history of chronic disease, participation in men was positively associated with old age, a family history of chronic disease, low subjective health status, and regular exercise, and negatively associated with current smoking status. In women, only old age was associated with participation. Low body mass index (BMI) (<18.5 kg/m(2)), blood pressure, total cholesterol, and fasting blood glucose level were negatively associated with participation in men after adjustments for age and family history of chronic disease, but not in women, except for low BMI.

CONCLUSIONS

In this study, collecting buccal cell DNA by mailed survey has a low success rate (29%), and there appear to be a nonresponse bias and gender differences in the collection process.

Operative treatment of congenital torticollis

There were 47 patients with congenital muscular torticollis who underwent operative release. After a mean follow-up of 74 months (60 to 90), they were divided into two groups, one aged one to four years (group 1) and the other aged five to 16 years (group 2). The outcomes were assessed by evaluating the following parameters: deficits of lateral flexion and rotation, craniofacial asymmetry, surgical scarring, residual contracture, subjective evaluation and degree of head tilt. The craniofacial asymmetry, residual contracture, subjective evaluation and overall scores were similar in both groups. However, group 2 showed superior results to group 1 in terms of the deficits of movement, surgical scarring and degree of head tilt. It is recommended that operative treatment for congenital muscular torticollis is postponed until the patient can comply successfully with post-operative bracing and an exercise programme.

Surgical treatment for congenital arteriovenous malformation: 10 years' experience

OBJECTIVES

We report our 10 years experience of the surgical treatment of congenital arteriovenous malformation (AVM).

METHODS

We retrospectively reviewed the medical records of 145 patients with AVM who visited Samsung Medical Center in Korea from 1994 to 2003. Among the 145 patients, 21 patients were operated on. Preoperative embolo/sclerotherapy was done in 20 out of the 21 patients.

RESULTS

The surgically treated AVMs were 13 cases of head and neck lesions, four cases of upper extremity lesions, one case each of back lesion, uterus lesion, lower extremity lesion and multiple site lesions. There were 10 patients with the extratruncular infiltrating type, nine patients with the extratruncular limited type, one patient with a truncular superficial AV fistula and one patient with a mixed type. Fourteen cases were operated on for cosmetic reasons and since they had localized lesions, and five cases were operated on for tissue necrosis. Fourteen cases were cured by a single operation, yet seven cases needed several sessions of operation to cure the AVM or to promote wound healing after surgery.

CONCLUSION

The surgical treatment of AVM is a challenging issue for vascular surgeons. To minimise the complications related to surgery, a multidisciplinary team approach should be considered.

Diagnosing and optimizing water treatment processes by using particle counter: a case study in Korea

The goal of the flocculation process is to change the particle size distribution to best suit the subsequent processes. Although several methods exist to evaluate the flocculation process, no single universally accepted method has yet to be developed. The purpose of this paper is to present experiences whereby particle counting was used in the diagnosis and optimization of the flocculation process. A commercially available on-line continuous particle counter has been used in evaluating the design and the operation of this process at two conventional Water Treatment Plants. The evaluation is based on particle dynamics, i.e., the change of the number of small and large particles. Some design deficiencies in the distribution channel and flocculation process have been identified from this method, and thus some operational parameters are suggested for optimum performance. Because the optimum condition may be site-specific, the method presented in this paper will be beneficial in the evaluation of the flocculation process at other water treatment plants.

Discoid lateral meniscus in children: clinical manifestations and morphology

The authors investigated the correlation between the clinical manifestations and the morphology of discoid lateral meniscus. Thirty-eight children, age 5 to 17 years, with 39 cases of discoid lateral meniscus underwent an arthroscopic procedure and magnetic resonance imaging. The two most frequent preoperative clinical manifestations were pain and extension block. In 19 cases without surface tear, the most frequent clinical manifestation was extension block. In the sagittal magnetic resonance images, the mean thickness of the anterior portion of the discoid lateral meniscus (7.77 mm) in the group with extension block exceeded that (4.02 mm) in the group without extension block. Extension block was significantly more common in patients with the anterior hypertrophy type and the slab (anterior-posterior diffusely hypertrophic) type than in the posterior hypertrophy type by the modified Hall classification. As a result, extension block was significantly correlated with the morphology of the menisci. Also, the thickened anterior portion of the discoid lateral meniscus may be considered one of the mechanical factors that limit knee extension.

Antibacterial activity of xanthorrhizol from Curcuma xanthorrhiza against oral pathogens

The antibacterial activity of xanthorrhizol, isolated from the methanol extract of Curcuma xanthorrhiza roots, was evaluated against oral microorganisms in comparison with chlorhexidine.

An examination of the stress distribution in a soft-lined acrylic resin mandibular complete denture by finite element analysis

PURPOSE

The aim of this study was to calculate the effect of a soft liner on stress distribution within a mandibular complete denture. Although patients have welcomed soft-lined complete dentures, early fracture is one of the main reasons for failure. To minimize and prevent prosthesis fracture, the understanding of the stress distribution within a prosthesis is important.

MATERIALS AND METHODS

A 3-dimensional finite element model of a mandibular complete denture for a severely reduced residual alveolar ridge was constructed. The stress was calculated with linear static finite element analysis. The stress distribution in the soft-lined acrylic resin mandibular complete denture was compared with that of a conventional acrylic resin denture. The resulting stresses were displayed in terms of von Mises equivalent stress and the major principal stresses according to 5 different loading conditions: vertical loads in premolar, molar, and incisor regions; and oblique loads in premolar and molar regions.

RESULTS

Oblique loads produced higher levels of stress in the labial notch regions than vertical loads, where tension was the primary mode of stress. Significantly reduced levels of von Mises stress were calculated in soft-liner layers under all loading conditions. Acrylic resin denture base portions, however, exhibited higher levels of von Mises stress in soft-lined complete dentures.

CONCLUSION

Three-dimensional finite element analysis gave a realistic explanation of denture fractures and patient response to mandibular complete dentures with and without soft linings. Control of excess lateral occlusal contact might be helpful to reduce the probability of a fracture in soft-lined mandibular complete dentures.

Residual monomer concentrations in denture-base acrylic resin after an additional, soft-liner, heat-cure cycle

OBJECTIVES

To determine the effects on methylmethacrylate (MMA) monomer concentration of a second heat-cure cycle introduced for the purpose of processing a denture soft-liner.

METHODS

Two denture-base resins (Lucitone199 and Trevalon; Dentsply International, York, PA, USA) were selected. Heat-cure cycles were S (73 degrees C/90 min + 100 degrees C/30 min); L (73 degrees C/9 h); SM (S + 100 degrees C/2 h); LM (L + 100 degrees C/2 h). Cycles SM and LM thus simulated the effect of a further, soft-liner, heat-cure cycle. Groups (n = 6) of the specimens of the denture-base were prepared in the form of thin polymer disks. Monomer was then obtained from the broken fragments of disks by acetone extraction. Concentrations of MMA monomer were determined by reversed-phase high performance liquid chromatography (HPLC). Two-way ANOVA and independent sample t-tests were used to compare the results.

RESULTS

The cycle S, applied to Lucitone199, gave a mean concentration of 1.95 wt% MMA (SD 0.24). The cycle L gave the highest level of residual concentration of MMA monomer in both materials. Cycles SM and LM, applied to Trevalon and Lucitone199, gave significant reductions of residual concentration of MMA monomer (p < 0.05).

SIGNIFICANCE

The HPLC method was suitable for determining the amount of residual monomer in the denture-base acrylic resin. A further (soft-liner) heat-cure cycle had a statistically significant effect on reducing residual monomer concentrations, and this may have an effect upon mechanical properties.

Genu valgum in children with coxa vara resulting from hip disease

Three patients with chronic hip disease and progressive coxa vera deformity also had an unrecognized compensatory ipsilateral genu valgum until the primary hip deformity had been corrected operatively. This unrecognized genu valgum may become subtly worse in a growing child because of lateralization of the mechanical axis of the lower extremity with respect to the knee joint. Operative correction of coxa vara acutely moves the mechanical axis farther laterally, causing the occult genu valgum to become clinically apparent. The genu valgum may subtly worsen over time in a growing child because of lateralization of the lower extremity mechanical axis with respect to the knee joint, with the resulting abnormal Hueter-Volkmann forces across the physis causing progressive genu valgum. Recognition of occult genu valgum before correcting coxa vara in children allows the surgeon the better to advise the family about the need for possible subsequent operations on the knee.

Effect of the distraction rate on the activity of the osteoblast lineage in distraction osteogenesis of rat's tibia. Immunostaining study of the proliferating cell nuclear antigen, osteocalcin, and transglutaminase C

The purpose of this study was to investigate kinetics of the osteoblast lineage in the periosteum and endosteum according to different distraction rates in distraction osteogenesis of rat's tibia. An osteotomy was performed on 144 rats at the proximal diaphysis of the left tibia. The lengthening process was started after a latency period of 3 days, with varying distraction rates of 0.25 mm (group I), 0.5 mm (group II), 0.75 mm (group III), 1.0 mm (group IV) and proceeded until a 3.5 mm length gain was achieved. The animals that had an osteotomy alone, without lengthening, served as a control (group V). Immunohistochemical staining of proliferating cell nuclear antigen (PCNA), osteocalcin, and transglutaminase C (TGase C) were done on the four animals in each group sacrificed at post-distraction days 1, 3, 5, 7, 14, and 28 in order to observe the temporal changes among the experimental and control groups. Also, in order to compare the staining rates at a given length gain among the groups, animals in each group were additionally sacrificed 2 days post-distraction in group II; 2 and 4 days in group III; and 1.5, 2 and 2.5 days in group IV. The results of the expression rates of PCNA, osteocalcin, and TGase C in each group were analyzed quantitatively. The immunohistochemical study on callotasis of rat's tibia revealed that the osteoblast lineage in the periosteum is more activated than that in the endosteum for proliferation and differentiation by distraction, suggesting that the periosteum plays a more important role in neoosteogenesis in the distraction gap. Daily distraction rates ranging from 0.25 mm to 0.75 mm in two increments is appropriate for successful distraction osteogenesis of rat's tibia, but the rate of 0.25 mm a day is significantly better than that of 0.75 mm as was made evident in the immunohistochemical observations.

Chemopreventive effect of green tea (Camellia sinensis) against cigarette smoke-induced mutations (SCE) in humans

Green tea (Camellia sinensis) is consumed daily between the meals or after meals in Japan and other Asian countries. In recent years, green tea and its major polyphenolics have been demonstrated to prevent chemically induced tumors in a variety of experimental animal models system. The exact mechanism(s) of its anticarcinogenic activity remains to be elucidated, but green tea polyphenolics have demonstrated antimutagenic, anticarcinogenic, antioxidant, and antipromotional effects, including inhibition of Phase I and inducing Phase II enzymes. Enzyme activities of glutathione peroxidase, catalase, and quinone reductase, and glutathione S-transferase are also induced. However, a paucity of green tea effects in humans prompted us to investigate antimutagenic effects of green tea against smoke-induced mutation in humans. Chemopreventive effects of green tea and coffee among cigarette smokers were examined in 52 clinically healthy male subjects between 20-51 years of age. Blood specimens were obtained from non-smokers (Group I), smokers (II), smokers consuming green tea (III), and smoker/coffee drinkers (IV). The mean years of cigarette smoking (> 10 cigarettes/day) of Groups II, III, and IV ranged from 13.4-14.7 years. Daily intake of green tea and coffee was 3 cups/day/6 months (III and IV). The frequencies of sister-chromatid exchange (SCE) in mitogen-stimulated peripheral lymphocytes from each experimental group were determined and statistically analyzed. SCE rates were significantly elevated in smokers (9.46 +/- 0.46) vs. non-smokers (7.03 +/- 0.33); however, the frequency of SCE in smokers who consumed green tea (7.94 +/- 0.31) was comparable to that of non-smokers, implying that green tea can block the cigarette-induced increase in SCE frequency. Coffee, by contrast, did not exhibit a significant inhibitory effect on smoking-induced SCE.

Evolution of a specific fluorogenic derivatization of ivermectin for bioanalytical applications. A review

The evolution of the fluorogenic derivatization of ivermectin is traced through a series of continual modifications that have resulted in improvements in speed and sensitivity. Since the original development of this selective analytical technique, the reaction time has been shortened from 24 h at 100 degrees C to < 30 s at room temperature and, through modifications of the derivatization reagent and catalyst, the sensitivity has also been increased 50-fold to 20 pg of analyte with no significant decrease in precision. A procedure is reported, based on the use of fluorescence derivatization, which eliminates the use of solid-phase columns for sample preparation and fluorophore isolation, and is faster and less cumbersome than previous methods. The method was evaluated with cattle and canine plasma samples over the concentration range 1.0-40 ng ml-1 of ivermectin. It has an accuracy of 1.9% (mean relative error) over this concentration range and a precision of 5.6% (RSD) at the 1 ng ml-1 ivermectin concentration level in a 1 ml plasma sample.

Identification of the secondary degradates of L-648,548 in an animal health formulation

L-648,548 is a semisynthetic analog of avermectin. During stability investigations of this compound in an animal health formulation, two new degradates were discovered. These degradates (L-648,548 phenol and its 8,9-Z isomer) were identified as the reaction products of 5-oxo-L-648,548 formed by oxidation of L-648,548. Addition of base to the reaction medium containing 5-oxo-L-648,548 was found to catalyze the formation of L-648,548 phenol via a postulated dehydration by an E1cb elimination followed by the rapid tautomerization of the C5 carbonyl. Photolysis of L-648,548 phenol with visible light (including ambient laboratory lighting) was found to readily produce 8,9-Z-L-648,548 phenol. This transformation was confirmed to be exclusively a photoinduced process.

Surgical correction of idiopathic medical femoral torsion

We reviewed 28 hips in 14 patients with severe bilateral idiopathic medial femoral torsion which had been corrected by intertrochanteric rotation osteotomy using crossed pins for fixation and a hip spica. There were 10 girls and 4 boys with a mean age of 7 years and 9 months. All had functional and cosmetic disability before operation. The average follow up was for 3 years and 9 months. Full correction was achieved in 27 hips. In one partial avascular necrosis of the femoral head occurred one year after operation and was treated by an acetabular augmentation procedure with a satisfactory outcome.

Chemopreventive effect of green tea (Camellia sinensis) among cigarette smokers

Chemopreventive effects of green tea and coffee among cigarette smokers were examined in 52 clinically healthy male subjects between 20 and 52 years of age. Blood specimens were obtained from nonsmokers (group I), smokers (group II), smokers consuming green tea (group III), and smokers drinking coffee (group IV). The mean number of cigarette smoking years (> 10 cigarettes/day) in groups II-IV ranged from 13.4 to 14.7 years. Daily intake of green tea and coffee was 2-3 cups/day for 6 months (groups III and IV). The frequencies of sisterchromatid exchange (SCE) in mitogen-stimulated peripheral lymphocytes from each experimental group were determined and analyzed statistically. SCE rates were elevated significantly in smokers (9.46 +/- 0.46) versus nonsmokers (7.03 +/- 0.33); however, the frequency of SCE in smokers who consumed green tea (7.94 +/- 0.31) was comparable to that of nonsmokers, implying that green tea can block the cigarette-induced increase in SCE frequency. Coffee, in contrast, did not exhibit a significant inhibitory effect on smoking-induced SCE.

A modified Wagner technique for femoral lengthening in skeletally mature patients with poliomyelitis

A modified Wagner technique using an Orthofix was employed for femoral lengthening in 62 skeletally mature patients with residual poliomyelitis. The first stage was similar to that of the original Wagner technique. However, distraction was started after 5 to 7 days at a rate of 1.5 mm per day. At the second stage, a neutralization plate was applied and a corticocancellous iliac strut graft inserted in the distracted site, preferably under compression. Cast immobilisation was not used and a long leg brace with a thigh corset allowed early knee movement and weightbearing. The average age at operation was 26 years and 6 months. The period of follow-up averaged 3 years and 2 months, and the average amount of lengthening was 4.2 cm. The overall rate of complication was 34%.

Liquid chromatographic determination of ivermectin in animal plasma with trifluoroacetic anhydride and N-methylimidazole as the derivatization reagent

Ivermectin is a potent anthelmintic agent which was detected at low concentrations in cattle plasma by LC after conversion to a fluorescent derivative. This was accomplished by reaction with acetic anhydride (AA) and pyridine for 24 h at 100 degrees C or with AA and N-methylimidazole (NMIM) for 1 h at 95 degrees C. Substituting trifluoroacetic anhydride (TFAA) for AA reduced the reaction time to less than 30 s at 25 degrees C, yielding an intensely fluorescent derivative with substantially fewer reagent by-products. The need for further sample preparation after derivatization with TFAA-NMIM was thereby eliminated, and detection limits of less than 20 pg ml-1 ivermectin could be achieved with 1 ml of plasma by a considerably simpler analytical procedure.

Sister-chromatid exchanges in 52 Korean women living in the vicinity of an industrial complex

Sister-chromatid exchanges (SCE) were examined in the peripheral lymphocytes of 52 Korean women living in the vicinity of an industrial complex. They were generally non-smokers ranging from 22 to 56 years of age. The mean SCE score of the volunteers was 6.01 +/- 0.15 (SE). Only coffee intake produced a significant increase of SCE by comparison with the mean SCE for those that did not take coffee. Other parameters, including alcohol intake, working in industry and the presence of hepatitis B surface antigen (HBsAg), did not produce an increase in SCE. There was no effect on SCE due to age.

Tn5 insertions in the agrocin 84 plasmid: the conjugal nature of pAgK84 and the locations of determinants for transfer and agrocin 84 production

The kanamycin-resistance transposon Tn5 was randomly introduced into pAgK84, a 47.7-kb plasmid coding for agrocin 84 production in Agrobacterium. Using such marked plasmids, pAgK84 was found to be conjugal. It could be transferred to several Agrobacterium strains including those harboring octopine- or nopaline-type Ti plasmids. Its presence has no effect on Ti plasmid functions such as opine utilization and tumorigenicity, but it does confer agrocin 84 immunity upon previously sensitive strains. The plasmid could also be conjugally transferred to a Nod+ Fix+ strain of Rhizobium meliloti. The production of agrocin 84 is expressed in all Agrobacterium and Rhizobium transconjugants tested. The agrocin plasmid could not be introduced into restrictionless Escherichia coli or Pseudomonas aeruginosa recipients by conjugation or transformation. The sites of 92 independent Tn5 insertions were mapped on pAgK84. These insertions are dispersed over the entire length of the plasmid. Analysis of the sites and effects of the Tn5 insertions has allowed us to construct a functional map of pAgK84. Forty-three of these insertions, spanning a 20-kb segment of the plasmid, abolished or greatly reduced the production of agrocin 84. The presence of two insertions within this segment having an effect on agrocin production suggests that at least three regions of the plasmid are involved in agrocin 84 biosynthesis. Fourteen of the Tn5 insertion derivatives are no longer conjugally transferable. These insertions all map to a single region of the plasmid and define about 3.5-kb as being associated with transfer functions.

Direct determination of avermectins in plasma at nanogram levels by high-performance liquid chromatography

22,23-Dihydroavermectin B1a (I) is determined in animal plasma over the concentration range 5-60 ng/ml by reverse-phase high-performance liquid chromatography (HPLC) with UV photometric detection. Prior to HPLC the sample is isolated by gravity-fed adsorption column chromatography on Florisil. The delta 2 isomer of I (designated as compound III) is used as an internal standard, and the conversion of I to this isomer by base hydrolysis is described. An accuracy of 2 ng/ml (mean deviation) and a precision in the range of 1-3 ng/ml (standard deviation) were observed for the method. The limit of detection is 2 ng/ml based on the background observed for normal cattle plasma. The method is applicable to bioavailability studies of I at usual therapeutic concentrations.

Fluorometric determination of thiazole-containing compounds

Fluorescence spectroscopy was applied to the development of sensitive analytical methods for the determination of thiazole and several congeners that contain substituted thiazole rings. Treatment to yield thionine, previously used spectrophotometrically to measure thiazole and fluorometrically only for sulfur determinations in inorganic systems, is further characterized and illustrated with the determination of the antibiotic thiopeptin. This method is selective for submicrogram quantities of thiazole rings in the presence of fused-ring derivatives and reduced analogs. It has a precision of +/- 2% RSD (n = 11) at the 15-ng/ml thiazole concentration level with a signal-to-noise ratio of 3:1. For thiopeptin, this method has an accuracy of 5% mean relative error (n = 8) over the 5--20-ppm range in medicated feed.

Further studies on the colorimetric determination of ronidazole in feeds

A previously published colorimetric method for determining ronidazole, (1-methyl-5-nitro-imidazol-2-yl)methyl carbamate, can be used as an analytical technique for measuring the stability of this drug in medicated feeds. Although the color reaction per se is not selective, elution profiles of ronidazole and its demonstrated hydrolytic degradation product, 1-methyl-2-hydroxymethyl-5-nitroimidazole, show that the chromatographic separation used in the sample preparation efficiently isolates the drug from the degradation product. No interference was found in feeds containing 0.010% ronidazole and up to 0.010% degradation product.

Colorimetric determination of arprinocid in feed

An analytical method has been developed for the determination of arprinocid (9-(2-chloro-6-fluorophenylmethyl)-9H-purin-6-amine) in feed, based upon measurement of the absorbance of the diazo chromophore formed from a product of zinc reduction of the drug in acidic solution. The analyte is extracted from the feed into chloroform in the presence of a pH 7 phosphate buffer and isolated by adsorption chromatography on alumina, followed by partitioning between hexane and 0.15M HCl. The reduction product in the aqueous phase is then treated for colorimetric measurement. This procedure has been applied to determining 0.0010--0.0080% arprinocid in feed with a precision of less than 5% relative standard deviation near the middle of this concentration range. Of 32 feed additives examined, only zoalene and sulfamethazine were serious interferences. A study and discussion of several factors, e.g., reaction time, pH, and amount of zinc metal, that affect the analytical reactions are also included.