Effect of different surface treatments and ceramic primers on shear bond strength of self-adhesive resin cement to zirconia ceramic

Aims

To evaluate the effect of different surface treatments and ceramic primers on the shear bond strength (SBS) of self-adhesive resin cement to zirconia ceramic.

Materials and Methods

A total of 40 zirconia discs (10 mm in diameter and 3 mm in height; StarCeram Z-Med, H.C. Starck, Selb, Germany) were prepared from pre-sintered zirconia blocks. Discs were divided into two groups according to surface treatment: (a) airborne particle abrasion (sandblasting) with 50-μm Al₂O₃ particles and (b) 9.5% hydrofluoric acid etching. Each of these groups was subdivided into two groups according to the type of primer applied: (a) Z-Prime Plus primer and (b) Clearfil Ceramic Primer. A self-adhesive resin cement (Multilink Speed, Ivoclar Vivadent, Schaan, Liechtenstein) was used to bond with polyethylene molds. All specimens were tested at thermocycled (5000 cycles at 5-55°C for 30 s) conditions. The SBS of the luting cement to the ceramic was measured in a universal testing machine (1 mm/min).

Results

The sandblasted groups showed significantly higher SBS values than the acid-etched groups for both primers (P = 0.0001). Independent of the surface treatment, the Z-Prime Plus primer groups showed higher SBS values than the Clearfil Ceramic Primer groups (P = 0.0001).

Conclusions

Sandblasting is a more effective method to increase bond strength on zirconia ceramics than hydrofluoric acid etching, and the application of Z-Prime Plus primer increases SBS better than Clearfil Ceramic Primer.

Orofacial operant behaviors and electrophysiological properties of trigeminal ganglion neurons following masseter muscle inflammation in rats

Orofacial muscle pain is a significant clinical problem because it affects eating, speaking, and other orofacial functions in patients. However, mechanisms underlying orofacial muscle pain are not fully understood. In the present study we induced orofacial muscle pain by injecting Complete Freund's Adjuvant (CFA) into masseter muscle of rats and assessed pain by the orofacial operant test. In comparison with the control group, CFA-injected animals (CFA group) showed decreases in operant behaviors, suggesting the presence of orofacial pain. Trigeminal ganglion (TG) neurons innervating masseter muscles were retrograde-labeled with DiI and their electrophysiological properties studied using patch-clamp recordings. About 20% of DiI-labeled TG neurons showed spontaneous action potentials (APs) in the CFA group but none in the control group. AP rheobase levels were significantly lower in DiI-labeled TG neurons of the CFA group than in the control group. Membrane input resistance of DiI-labeled TG neurons was significantly higher in the CFA group than in the control group. Several other membrane parameters were also different between DiI-labeled TG neurons of the CFA and control groups. Voltage-dependent currents were examined and the most significant changes following CFA were background K⁺ currents, which showed significantly smaller in DiI-labeled TG neurons of CFA group compared to the control group. Collectively, orofacial muscle pain in CFA model is accompanied with changes of electrophysiological properties and background K⁺ currents in TG neurons that innervate masseter muscles.

Orofacial neuropathic pain induced by oxaliplatin: downregulation of KCNQ2 channels in V2 trigeminal ganglion neurons and treatment by the KCNQ2 channel potentiator retigabine

Neuropathic pain induced by chemotherapy drugs such as oxaliplatin is a dose-limiting side effect in cancer treatment. The mechanisms underlying chemotherapy-induced neuropathic pain are not fully understood. KCNQ2 channels are low-threshold voltage-gated K⁺ channels that play a role in controlling neuronal excitability. Downregulation of KCNQ2 channels has been proposed to be an underlying mechanism of sensory hypersensitivity that leads to neuropathic pain. However, it is currently unknown whether KCNQ channels may be downregulated by chemotherapy drugs in trigeminal ganglion neurons to contribute to the pathogenesis of chemotherapy-induced orofacial neuropathic pain. In the present study, mechanical sensitivity in orofacial regions is measured using the operant behavioral test in rats treated with oxaliplatin. Operant behaviors in these animals show the gradual development of orofacial neuropathic pain that manifests with orofacial mechanical allodynia. Immunostaining shows strong KCNQ2 immunoreactivity in small-sized V2 trigeminal ganglion neurons in controls, and the numbers of KCNQ2 immunoreactivity positive V2 trigeminal ganglion neurons are significantly reduced in oxaliplatin-treated animals. Immunostaining is also performed in brainstem and shows strong KCNQ2 immunoreactivity at the trigeminal afferent central terminals innervating the caudal spinal trigeminal nucleus (Vc) in controls, but the KCNQ2 immunoreactivity intensity is significantly reduced in oxaliplatin-treated animals. We further show with the operant behavioral test that oxaliplatin-induced orofacial mechanical allodynia can be alleviated by the KCNQ2 potentiator retigabine. Taken together, these findings suggest that KCNQ2 downregulation may be a cause of oxaliplatin-induced orofacial neuropathic pain and KCNQ2 potentiators may be useful for alleviating the neuropathic pain.

Fracture resistance and failure modes of lithium disilicate or composite endocrowns

Purpose

The aim of this study was to determine the fracture strength of endocrowns made of lithium disilicate ceramic and two different indirect resin composites.

Materials and Methods

Forty human mandibular molars were randomly separated into four groups (n = 10 in each group) - Group IN: control group, Group IPS: endocrowns made of lithium disilicate ceramic (IPS e.max CAD, IvoclarVivadent, Schaan, Liechtenstein); Group SL: Endocrowns made of Solidex microhybrid composite (Shofu, Ratingen, Germany); and Group GR: Endocrowns made of Grandia microhybrid composite (GC Europa, Leuven, Belgium). In all of the groups, dual-cure resin cement (Relyx Ultimate Clicker, 3M ESPE, St. Paul, MN, USA) was used to cement the endocrowns. All of the teeth were subjected to fracture by means of a universal testing machine (Instron), and compressive force was applied. The failure type and location after fracture were classified. The data were analyzed using one-way ANOVA, Tukey's post hoc test, and Chi-square test (P < 0.05).

Results

Group IPS showed significantly higher fracture strength than Groups SL and GR (P < 0.05). There was no significant difference between the SL and GR groups (P > 0.05). In Group SL, 80% of the specimens exhibited favorable fractures; also, 60% of the specimens exhibited favorable fracture in group GR, and only 10% of the specimens exhibited favorable fracture in group IPS.

Conclusions

The lithium disilicate ceramic endocrowns exhibited higher fracture resistance than indirect composite groups. Both of the composite endocrowns showed more favorable failure than the lithium disilicate ceramic endocrowns.

Role of KCNQ2 channels in orofacial cold sensitivity: KCNQ2 upregulation in trigeminal ganglion neurons after infraorbital nerve chronic constrictive injury

Sensitivity to cooling temperatures often becomes heightened in orofacial regions leading to orofacial cold allodynia/hyperalgesia after chronic trigeminal nerve injury. KCNQ2 channels are involved in controlling excitability of primary afferent neurons and thereby regulate sensory functions under both physiological and pathological conditions. In the present study, we sought to determine whether KCNQ2 channels in trigeminal nerves are involved in regulating orofacial operant behavioral responses to cooling stimulation. We also sought to examine whether chronic trigeminal nerve injury may alter KCNQ2 channel expression in trigeminal ganglions. Using the orofacial operant tests, animals show cold allodynia/hyperalgesia in orofacial regions following infraorbital nerve chronic constrictive injury (ION-CCI), which could be alleviated by subcutaneous administration of retigabine, a KCNQ2 activator. In contrast, subcutaneous administration of the KCNQ2 inhibitor XE991 directly elicits cold allodynia/hyperalgesia in sham animals. Using immunostaining, we show that KCNQ2 channels are primarily expressed in small-sized TG neurons. Interestingly, KCNQ2 channel expression becomes significantly upregulated in TG neurons following the ION-CCI. Our results suggest that KCNQ2 channels are involved in regulating orofacial cold sensitivity. Upregulation of KCNQ2 channels may be a compensatory change in attempting to limit injury-induced trigeminal hyperexcitability.

The effect of morphometric and anatomic relationship of gallbladder to the liver on standard laparoscopic cholecystectomies and proposal of a new anatomical classification

OBJECTIVE

Anatomical variations of the extrahepatic biliary tree are frequently seen and may cause challenging conditions for surgeons. We aimed to investigate the morphological variations of the gallbladder in patients who underwent cholecystectomy and their effects during and after the surgery, by using a new anatomical classification.

PATIENTS AND METHODS

Dissection time, perioperative bleeding, perioperative/postoperative complication rates, the difference between preoperative/postoperative hematocrit and leukocyte levels of 164 symptomatic cholelithiasis patients who underwent laparoscopic cholecystectomy were evaluated. The patients' gallbladders were categorized in "seven" different types regarding their anatomical positions and morphometric relations with the liver's acute margin and fossa of the gallbladder. Relations between these gallbladders types and perioperative/postoperative parameters were also examined.

RESULTS

The median time to complete the dissection of the gallbladder from the fossa was 375.5 seconds. The mean length of the fossa was 68.06 ± 15.08 mm, the average size of the gallbladder was 92.10 ± 18.79 mm. A positive correlation was found between dissection time and length of fossa vesica and also in the size of the gallbladder (p = 0.003, p = 0.034). Moreover, a positive correlation was found between the dissection time and the perioperative perforation risk of the gallbladder (p = 0.005). The most common type of gallbladder was type I and III (23.2%). The least common gallbladder type among the patients assessed as part of the study was type VI (6.7%). When the gallbladder types were compared, the perioperative perforation rate of the gallbladder wall was found to be significantly higher in morphological type V (p = 0.014).

CONCLUSIONS

The perioperative perforation rate of the gallbladder wall was found significantly higher in morphological type V. To perform a safe cholecystectomy, surgeons should be aware of anatomical variations of the gallbladder and its relations with the liver parenchyma, which are important for surgical strategies.

New Technologies and Concepts for Rehabilitation in the Acute Phase of Stroke: A Collaborative Matrix

The process of developing a successful stroke rehabilitation methodology requires four key components: a good understanding of the pathophysiological mechanisms underlying this brain disease, clear neuroscientific hypotheses to guide therapy, adequate clinical assessments of its efficacy on multiple timescales, and a systematic approach to the application of modern technologies to assist in the everyday work of therapists. Achieving this goal requires collaboration between neuroscientists, technologists and clinicians to develop well-founded systems and clinical protocols that are able to provide quantitatively validated improvements in patient rehabilitation outcomes. In this article we present three new applications of complementary technologies developed in an interdisciplinary matrix for acute-phase upper limb stroke rehabilitation - functional electrical stimulation, arm robot-assisted therapy and virtual reality-based cognitive therapy. We also outline the neuroscientific basis of our approach, present our detailed clinical assessment protocol and provide preliminary results from patient testing of each of the three systems showing their viability for patient use.