Evaluation of stress patterns produced by implant-retained overdentures and implant-retained fixed partial denture

The purposes of this study were to photoelastically measure the biomechanical behavior of 4 implants retaining different cantilevered bar mandibular overdenture designs and to compare a fixed partial denture (FPD). A photoelastic model of a human edentulous mandible was fabricated, which contained 4 screw-type implants (3.75 × 10 mm) embedded in the parasymphyseal area. An FPD and 3 overdenture designs with the following attachments were evaluated: 3 plastic Hader clips, 1 Hader clip with 2 posterior resilient cap attachments, and 3 ball/O-ring attachments. Vertical occlusal forces of 100 N were applied between the central incisor and unilaterally to the right and left second premolars and second molars. Stresses that developed in the supporting structure were monitored photoelastically and recorded photographically. The results showed that the anterior loading, the overdenture with 3 plastic Hader clips, displayed the largest stress concentration at the medium implant. With premolar loading, the FPD and overdenture with 3 plastic Hader clips displayed the highest stresses to the ipsilateral terminal implant. With molar loading, the overdenture with 3 ball/O-ring attachments displayed the most uniform stress distribution in the posterior edentulous ridge, with less overloading in the terminal implant. It was concluded that vertical forces applied to the bar-clip overdenture and FPD created immediate stress patterns of greater magnitude and concentration on the ipsilateral implants, whereas the ball/O-ring attachments transferred minimal stress to the implants. The increased cantilever in the FPD caused the highest stresses to the terminal implant.     

Focal dermal hypoplasia: a case report and literature review

Focal dermal hypoplasia (FDH), also known as Goltz-Gorlin syndrome, is an autosomal dominant disease affecting tissues derived from the ectoderm and mesoderm. Knowledge and early diagnosis of the craniofacial alterations commonly found in patients with FDH provide oral health care professionals with effective preventive and therapeutic tools. This article aims to review the craniofacial characteristics present in FDH and the main systemic manifestations that have implications for dental management, while presenting a new case of the syndrome with novel oral findings.     

Surface roughness of orthodontic band cements with different compositions

Objectives

The present study evaluated comparatively the surface roughness of four orthodontic band cements after storage in various solutions.

Material and Methods

eight standardized cylinders were made from 4 materials: zinc phosphate cement (ZP), compomer (C), resin-modified glass ionomer cement (RMGIC) and resin cement (RC). Specimens were stored for 24 h in deionized water and immersed in saline (pH 7.0) or 0.1 M lactic acid solution (pH 4.0) for 15 days. Surface roughness readings were taken with a profilometer (Surfcorder SE1200) before and after the storage period. Data were analyzed by two-way ANOVA and Tukey''s test (comparison among cements and storage solutions) or paired t-test (comparison before and after the storage period) at 5% significance level.

Results

The values for average surface roughness were statistically different (p<0.001) among cements at both baseline and after storage. The roughness values of cements in a decreasing order were ZP>RMGIC>C>R (p<0.001). After 15 days, immersion in lactic acid solution resulted in the highest surface roughness for all cements (p<0.05), except for the RC group (p>0.05). Compared to the current threshold (0.2 µm) related to biofilm accumulation, both RC and C remained below the threshold, even after acidic challenge by immersion in lactic acid solution.

Conclusions

Storage time and immersion in lactic acid solution increased the surface roughness of the majority of the tested cements. RC presented the smoothest surface and it was not influenced by storage conditions.     

Histomorphometric analysis of the bone-implant contact obtained with 4 different implant surface treatments placed side by side in the dog mandible

PURPOSE: The different implant systems available today present several types of surface treatment, with the aim of optimization of bone-implant contact. This study compared 4 different types of implant surfaces. MATERIALS AND METHODS: The first, second, third, and fourth mandibular premolars were extracted from 5 young adult mongrel male dogs. Ninety days after removal, four 3.75-mm-diameter, 10-mm-long screw-type implants (Paragon) were placed with different surface treatments in mandibular hemiarches. The dogs received 2 implants of each of the following surface treatments: smooth (machined), titanium plasma spray (TPS), hydroxyapatite coating (HA), and sandblasting with soluble particles (SBM). The implants were maintained unloaded for 90 days. After this period, the animals were sacrificed, and the hemimandibles were extracted and histologically processed to obtain non-decalcified sections. Two longitudinal ground sections were made for each implant and analyzed under light microscopy coupled to a computerized system for histomorphometry. RESULTS: The following means were obtained for bone-implant contact percentage: machined = 41.7%, TPS = 48.9%, HA = 57.9%, and SBM = 68.5%. DISCUSSION: The means for all treatments that added roughness to the implant surface were numerically superior to the mean found for the machined surface. However, this difference was statistically significant only between groups SBM and machined (Tukey test, P < .05). CONCLUSIONS: The SBM-treated surface provided a greater bone-implant contact than a machined surface after 90 days without loading in this model.     

Founder effect and ancestral origin of the spinocerebellar ataxia type 7 (SCA7) mutation in Mexican families

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant disease characterized by progressive cerebellar ataxia and macular degeneration causing progressive blindness. It accounts for 1 to 11.6 % of spinocerebellar ataxias (SCAs) cases worldwide and for 7.4 % of SCA7 cases in Mexico. We identified a cluster of SCA7 families who resided in a circumscribed area of Veracruz and investigated whether the high incidence of the disease in this region was due to a founder effect. A total of 181 individuals from 20 families were studied. Four microsatellite markers and one SNP flanking the ATNX7 gene were genotyped and the ancestral origin and local ancestry analysis of the SCA7 mutation were evaluated. Ninety individuals from 19 families had the SCA7 mutation; all were found to share a common haplotype, suggesting that the mutation in these families originated from a common ancestor. Ancestral origin and local ancestry analysis of SCA7 showed that the chromosomal segment containing the mutation was of European origin. We here present evidence strongly suggesting that the high frequency of SCA7 in Veracruz is due to a founder effect and that the mutation is most likely of European origin with greatest resemblance to the Finnish population.     

Effect that an educational program for cystic fibrosis patients and caregivers has on the contamination of home nebulizers

OBJECTIVE:

To describe the pathogens found in home nebulizers and in respiratory samples of cystic fibrosis (CF) patients, and to evaluate the effect that a standardized instruction regarding cleaning and disinfection of nebulizers has on the frequency of nebulizer contamination.

METHODS:

We included 40 CF patients (22 males), all of whom used the same model of nebulizer. The median patient age was 11.2 ± 3.74 years. We collected samples from the nebulizer mouthpiece and cup, using a sterile swab moistened with sterile saline. Respiratory samples were collected by asking patients to expectorate into a sterile container or with oropharyngeal swabs after cough stimulation. Cultures were performed on selective media, and bacteria were identified by classical biochemical tests. Patients received oral and written instructions regarding the cleaning and disinfection of nebulizers. All determinations were repeated an average of two months later.

RESULTS:

Contamination of the nebulizer (any part) was detected in 23 cases (57.5%). The nebulizer mouthpiece and cup were found to be contaminated in 16 (40.0%) and 19 (47.5%), respectively. After the standardized instruction had been given, there was a significant decrease in the proportion of contaminated nebulizers (43.5%).

CONCLUSIONS:

In our sample of CF patients, nebulizer contamination was common, indicating the need for improvement in patient practices regarding the cleaning and disinfection of their nebulizers. A one-time educational intervention could have a significant positive impact.     

Pain Hypervigilance is Associated with Greater Clinical Pain Severity and Enhanced Experimental Pain Sensitivity Among Adults with Symptomatic Knee Osteoarthritis

Background

Pain hypervigilance is an important aspect of the fear-avoidance model of pain that may help explain individual differences in pain sensitivity among persons with knee osteoarthritis (OA).

Purpose

The purpose of this study was to examine the contribution of pain hypervigilance to clinical pain severity and experimental pain sensitivity in persons with symptomatic knee OA.

Methods

We analyzed cross-sectional data from 168 adults with symptomatic knee OA. Quantitative sensory testing was used to measure sensitivity to heat pain, pressure pain, and cold pain, as well as temporal summation of heat pain, a marker of central sensitization.

Results

Pain hypervigilance was associated with greater clinical pain severity, as well as greater pressure pain. Pain hypervigilance was also a significant predictor of temporal summation of heat pain.

Conclusions

Pain hypervigilance may be an important contributor to pain reports and experimental pain sensitivity among persons with knee OA.     

A 2-year observational study of patients with relapsing-remitting multiple sclerosis converting to glatiramer acetate from other disease-modifying therapies: the COPTIMIZE trial

Studies suggest that patients with relapsing-remitting multiple sclerosis (RRMS) who do not benefit from other disease-modifying treatments (DMTs) may benefit from converting to glatiramer acetate (GA). COPTIMIZE was a 24-month observational study designed to assess the disease course of patients converting to GA 20 mg daily from another DMT. Eligible patients had converted to GA and had received prior DMT for 3–6 months, depending on the reasons for conversion. Patients were assessed at baseline and at 6, 12, 18, and 24 months. In total, 672 patients from 148 centers worldwide were included in the analysis. Change of therapy to GA was prompted primarily by lack of efficacy (53.6 %) or intolerable adverse events (AEs; 44.8 %). Over a 24-month period, 72.7 % of patients were relapse free. Mean annual relapse rate decreased from 0.86 [95 % confidence interval (CI) 0.81–0.91] before the change to 0.32 (95 % CI 0.26–0.40; p < 0.0001) at last observation, while the progression of disability was halted, as the Kurtzke Expanded Disability Status Scale (EDSS) scores remained stable. Patients improved significantly (p < 0.05) on measures of fatigue, quality of life, depression, and cognition; mobility scores remained stable. The results indicate that changing RRMS patients to GA is associated with positive treatment outcomes.     

Functional Role of Glucose Metabolism,Osmotic Stress,and Sodium-Glucose Cotransporter Isoform-Mediated Transport on Na+/H+ Exchanger Isoform 3 Activity in the Renal Proximal Tubule

Na⁺-glucose cotransporter 1 (SGLT1)-mediated glucose uptake leads to activation of Na⁺-H⁺ exchanger 3 (NHE3) in the intestine by a process that is not dependent on glucose metabolism. This coactivation may be important for postprandial nutrient uptake. However, it remains to be determined whether SGLT-mediated glucose uptake regulates NHE3-mediated NaHCO₃ reabsorption in the renal proximal tubule. Considering that this nephron segment also expresses SGLT2 and that the kidneys and intestine show significant variations in daily glucose availability, the goal of this study was to determine the effect of SGLT-mediated glucose uptake on NHE3 activity in the renal proximal tubule. Stationary in vivo microperfusion experiments showed that luminal perfusion with 5 mM glucose stimulates NHE3-mediated bicarbonate reabsorption. This stimulatory effect was mediated by glycolytic metabolism but not through ATP production. Conversely, luminal perfusion with 40 mM glucose inhibited NHE3 because of cell swelling. Notably, pharmacologic inhibition of SGLT activity by Phlorizin produced a marked inhibition of NHE3, even in the absence of glucose. Furthermore, immunofluorescence experiments showed that NHE3 colocalizes with SGLT2 but not SGLT1 in the rat renal proximal tubule. Collectively, these findings show that glucose exerts a bimodal effect on NHE3. The physiologic metabolism of glucose stimulates NHE3 transport activity, whereas, supraphysiologic glucose concentrations inhibit this exchanger. Additionally, Phlorizin-sensitive SGLT transporters and NHE3 interact functionally in the proximal tubule.The kidney proximal tubule (PT) is the site where the reabsorption of approximately 70% of filtered sodium bicarbonate occurs. It is mainly performed by the Na⁺/H⁺ exchanger isoform 3 (NHE3).¹ The physiologic importance of NHE3 became evident after the development of NHE3 knockout mice, which presented mild metabolic acidosis and volume depletion with reduced BP, underscoring the role of NHE3 in volume homeostasis.²It has been shown that NHE3 physically and functionally interacts with dipeptidyl-peptidase IV, an enzyme that degrades and inactivates the incretin hormone glucagon like peptide-1.³ The inhibition of dipeptidyl-peptidase IV and the action of glucagon like peptide-1 were shown to inhibit NHE3 and promote natriuresis.^3–8 Additionally, various conditions and substances related to glucose metabolism, including diabetes, insulin, ATP, and glucose, modulate NHE3 in different tissues, showing a close relationship between carbohydrate homeostasis and NHE3 activity.^9–12Plasma glucose concentration is maintained at a constant level by a complex system, in which the kidneys perform a pivotal role by reabsorbing all the filtered glucose in the PT.¹³ In addition, the kidneys and liver are the only organs that express the glucose-6-phosphatase enzyme, thus enabling them to perform gluconeogenesis.^14,15 This enzyme is only expressed in the PT,¹⁶ highlighting the importance of this kidney segment in carbohydrate metabolism.It has been shown that the kidneys metabolize 20% of the glucose consumed in a meal.¹⁴ The PT has a low expression of hexokinase but the highest concentration and activity of glucose-6-phosphate dehydrogenase, indicating that this segment is able to metabolize glucose.^16,17 However, it is currently believed that the PT uses noncarbohydrate compounds as energy sources.¹⁷With relation to glucose uptake, the majority of filtered glucose is reabsorbed by the low-affinity, high-capacity sodium-glucose cotransporter isoform 2 (SGLT2). Some glucose is also reabsorbed by the high-affinity, low-capacity sodium-glucose cotransporter isoform 1 (SGLT1).¹³ Recently, SGLT2 inhibitors have been approved for the treatment of hyperglycemia in diabetic patients. The use of these inhibitors has been shown to decrease blood glucose, glycated hemoglobin, postprandial glucose, insulinemia, and body weight.^18–20The role of glucose uptake in the modulation of NHE3 activity in the small intestine has been extensively studied. Experiments have shown that glucose uptake through SGLT1 promotes intracellular NHE3-dependent alkalinization.^21–26 However, functional differences between intestinal and renal NaHCO₃ NHE3-mediated reabsorption have not been established. These two systems differ physiologically, because the gastrointestinal system is exposed to fluctuations in glucose concentration between the periods of fasting and after meals.¹³ The presence of large amounts of solutes within the intestinal cells after meals modulates membrane transporters, such as glucose transporter 2 (GLUT2) and NHE3,^21,27 an important process for nutrient absorption.Although the synergistic activation between SGLT1 and NHE3 has been observed in the intestine,²¹ it is not known if this process also occurs in the kidneys. Considering that the kidneys also express SGLT2 and the particularities of glucose availability in this organ, the goal of the present work was to determine the effect of glucose and SGLT activity on NHE3 in the renal PT.