Group-Based Key Management Protocol for Energy Efficiency in Long-Lived and Large-Scale Distributed Sensor Networks

As wireless sensor networks grow, so does the need for effective security mechanisms. We propose a cryptographic key-management protocol, called energy-efficient key-management (EEKM) protocol. Using a location-based group key scheme, the protocol supports the revocation of compromised nodes and energy-efficient rekeying. The design is motivated by the observation that unicast-based rekeying does not meet the security requirements of periodic rekeying in long-lived wireless sensor networks. EEKM supports broadcast-based rekeying for low-energy key management and high resilience. In addition, to match the increasing complexity of encryption keys, the protocol uses a dynamic composition key scheme. EEKM also provides group-management protocols for secure group communication. We analyzed the energy efficiency and security of EEKM and compared it to other key-management protocols using a network simulator

Soft Tissue Dimensions Following Tooth Extraction in the Posterior Maxilla: A Randomized Clinical Trial Comparing Alveolar Ridge Preservation to Spontaneous Healing

Background: To assess the soft tissue dimension following tooth extraction and alveolar ridge preservation in the posterior maxilla compared to spontaneous healing. Methods: Thirty-five patients randomly assigned to alveolar ridge preservation (ARP) and spontaneous healing (SH) after maxillary molar extraction. The crestal, buccal, and palatal gingival thickness at 6 months was measured around virtually placed implant fixtures using superimposed cone-beam computed tomography and intraoral scan taken at 6 months. Buccal mucogingival junction (MGJ) level change over 6 months was estimated using intraoral scans obtained at suture-removal and 6 months. Results: The crestal gingiva was significantly thinner in group ARP (−1.16 mm) compared to group SH (p < 0.05). The buccal and palatal gingiva was significantly thinner at the implant shoulder (IS) level in group ARP (buccal: −0.75 mm; palatal: −0.85 mm) compared to group SH (p < 0.05). The thickness at 2 mm below the IS of both sides and the buccal MGJ level change were similar in both groups (p > 0.05). Conclusions: ARP in the posterior maxilla resulted in a thinner soft tissue on top of and at the prospective level of the implant shoulder at 6 months. The buccal MGJ level changed minimal for 6 months in both groups

Radiographic and Histologic Analysis 1–2 Years after Alveolar Ridge Preservation in Maxillary Premolar and Molar: A Case Report

After tooth extraction, notable ridge alterations occur due to resorption of bundle bones during the healing process. In areas with thin or damaged socket walls and multiple adjacent tooth extraction, dimensional changes are more prominent in the marginal proportion. In addition to the marginal changes, upper molar teeth are also vulnerable to pneumatization of the maxillary sinus. To reduce dimensional changes in extraction sockets, alveolar ridge preservation (ARP) is favored by many clinicians in areas where a large amount of dimensional change is expected. This case report presents two cases of ARP using collagenated demineralized bovine bone mineral and demineralized porcine bone mineral in the apically involved upper premolar and molar, respectively. Implants were placed one and two years, respectively, after the ARP. Radiographic analyses of residual bone height and volume were measured using cone-beam-computed tomography (CBCT) and histologic analysis of newly formed mineralized bone and residual graft material percentages were measured from the collected tissue samples using a trephine bur. Implants were placed using a simple technique, without any additional bone grafts at the marginal proportion. The ARP technique could maintain the alveolar bone height and volume, as well as minimize the invasiveness of surgical procedures during implant surgery

A Forwarding Pointer-Based Cache Scheme for Reducing Location Management Cost in PCS Networks

This paper proposes a forwarding pointer-based cache scheme (PB-Cache scheme) that can reduce the signaling cost for location management in PCS networks. In the existing cache scheme, the use of cache information can effectively reduce the signaling traffic for locating frequently called mobile users. However, when the cache information is obsolete, it results in much more signaling traffic than that of the IS-41. In order to solve this problem, we propose a new location cache scheme called the PB-Cache scheme, which exploits a user’s movement locality as well as call locality. Even if the cached information is not up-to-date, the called user can be found by tracing forwarding pointers starting from that VLR pointed in the cache instead of querying the HLR. Thus, the PB-Cache scheme can effectively reduce the frequent access to the HLR and the signaling traffic for location management. Moreover, it distributes the signaling and database access load on the HLR to the VLR’s. Analytical results indicate that the PB-Cache scheme significantly outperforms the other schemes when a user’s call-to-mobility ratio is high or the signaling traffic to the HLR is heavy

Soft tissue substitutes to increase gingival thickness: Histologic and volumetric analyses in dogs

OBJECTIVES To evaluate the histologic and volumetric changes of gingival tissues following grafting with collagen-based matrices at labial aspect of teeth in canines. MATERIALS AND METHODS Gingival augmentation was performed in the mandibular incisor area using two types of xenogeneic cross-linked collagen matrices (CCMs), bovine CCM for BCCM group and porcine CCM for PCCM group, whereas the contralateral sides remained untreated (B-control group and P-control group). Descriptive histology, histometric and volumetric analyses were performed after 12 weeks. For statistical comparison between each test group and respective control group, paired t test was used for histometric analysis, and repeated-measured analysis of variance was used for volumetric analysis (p < 0.05). RESULTS An increased number of rete pegs and an enhanced formation of new blood vessels were observed at both grafted sites compared to the corresponding control sites. There was statistically significant gain of horizontal thickness only in BCCM group (1.36 ± 0.27 mm vs. 1.26 ± 0.34 mm; p < 0.05) compared to the B-control groups. CONCLUSION BCCM was effective for gingival augmentation in terms of horizontal thickness at the labial aspect of teeth at 12 weeks post-surgery