Accuracy of augmented reality-assisted vs template-guided apicoectomy - an ex vivo comparative study.

AIM: The aim of the present ex vivo study was to examine the accuracy of augmented reality-assisted apicoectomies (AR-A) versus template-guided apicoectomies (TG-A). MATERIALS AND METHODS: In total, 40 apicoectomies were performed in 10 cadaver pig mandibles. Every pig mandible underwent two AR-A and two TG-A in molar and premolar teeth. A crossed experimental design was applied. AR-A was performed using Microsoft HoloLens 2, and TG-A using SMOP software. Postoperative CBCT scans were superimposed with the presurgical planning data. The deviation between the virtually planned apicoectomy and the surgically performed apicoectomy was measured. The primary (angular deviation [degrees]) and secondary (depth deviation [mm]) outcome parameters were measured. RESULTS: Overall, 36 out of 40 apicoectomies could be included in the study. Regarding the primary outcome parameter (angular deviation), there was no significant difference between AR-A and TG-A. The mean values were 5.33 degrees (± 2.96 degrees) in the AR-A group, and 5.23 degrees (± 2.48 degrees) in the TG-A group. The secondary outcome parameter (depth deviation) showed no significant difference between the AR-A group of 0.27 mm (± 2.32 mm) and the TG-A group of 0.90 mm (± 1.84 mm). In this crossed experimental design, both techniques overshot the target depth in posterior sites, as opposed to not reaching the target depth in anterior sites (P < 0.001). CONCLUSION: Augmented reality (AR) technology has the potential to be introduced into apicoectomy surgery in case further development is implemented.

A Computational Perspective of the Role of the Thalamus in Cognition.

The thalamus has traditionally been considered as only a relay source of cortical inputs, with hierarchically organized cortical circuits serially transforming thalamic signals to cognitively relevant representations. Given the absence of local excitatory connections within the thalamus, the notion of thalamic relay seemed like a reasonable description over the past several decades. Recent advances in experimental approaches and theory provide a broader perspective on the role of the thalamus in cognitively relevant cortical computations and suggest that only a subset of thalamic circuit motifs fits the relay description. Here, we discuss this perspective and highlight the potential role for the thalamus, and specifically the mediodorsal (MD) nucleus, in the dynamic selection of cortical representations through a combination of intrinsic thalamic computations and output signals that change cortical network functional parameters. We suggest that through the contextual modulation of cortical computation, the thalamus and cortex jointly optimize the information and cost trade-off in an emergent fashion. We emphasize that coordinated experimental and theoretical efforts will provide a path to understanding the role of the thalamus in cognition, along with an understanding to augment cognitive capacity in health and disease.

Ensemble inhibition and excitation in the human cortex: An Ising-model analysis with uncertainties.

The pairwise maximum entropy model, also known as the Ising model, has been widely used to analyze the collective activity of neurons. However, controversy persists in the literature about seemingly inconsistent findings, whose significance is unclear due to lack of reliable error estimates. We therefore develop a method for accurately estimating parameter uncertainty based on random walks in parameter space using adaptive Markov-chain Monte Carlo after the convergence of the main optimization algorithm. We apply our method to the activity patterns of excitatory and inhibitory neurons recorded with multielectrode arrays in the human temporal cortex during the wake-sleep cycle. Our analysis shows that the Ising model captures neuronal collective behavior much better than the independent model during wakefulness, light sleep, and deep sleep when both excitatory (E) and inhibitory (I) neurons are modeled; ignoring the inhibitory effects of I neurons dramatically overestimates synchrony among E neurons. Furthermore, information-theoretic measures reveal that the Ising model explains about 80-95% of the correlations, depending on sleep state and neuron type. Thermodynamic measures show signatures of criticality, although we take this with a grain of salt as it may be merely a reflection of long-range neural correlations.

Oral lipoma: Case report and review of literature.

Lipoma is a benign neoplasm that primarily affects the middle-aged individuals and has a rare oral cavity occurrence. Given its noninvasive behavior and low recurrence rate, surgical conservative management should be regarded as the best therapeutic option. This paper highlights two patients along with their improved conditions following the treatment.

Theoretical Principles of Multiscale Spatiotemporal Control of Neuronal Networks: A Complex Systems Perspective.

Success in the fine control of the nervous system depends on a deeper understanding of how neural circuits control behavior. There is, however, a wide gap between the components of neural circuits and behavior. We advance the idea that a suitable approach for narrowing this gap has to be based on a multiscale information-theoretic description of the system. We evaluate the possibility that brain-wide complex neural computations can be dissected into a hierarchy of computational motifs that rely on smaller circuit modules interacting at multiple scales. In doing so, we draw attention to the importance of formalizing the goals of stimulation in terms of neural computations so that the possible implementations are matched in scale to the underlying circuit modules.

Local field potentials primarily reflect inhibitory neuron activity in human and monkey cortex.

The local field potential (LFP) is generated by large populations of neurons, but unitary contribution of spiking neurons to LFP is not well characterised. We investigated this contribution in multi-electrode array recordings from human and monkey neocortex by examining the spike-triggered LFP average (st-LFP). The resulting st-LFPs were dominated by broad spatio-temporal components due to ongoing activity, synaptic inputs and recurrent connectivity. To reduce the spatial reach of the st-LFP and observe the local field related to a single spike we applied a spatial filter, whose weights were adapted to the covariance of ongoing LFP. The filtered st-LFPs were limited to the perimeter of 800 µm around the neuron, and propagated at axonal speed, which is consistent with their unitary nature. In addition, we discriminated between putative inhibitory and excitatory neurons and found that the inhibitory st-LFP peaked at shorter latencies, consistently with previous findings in hippocampal slices. Thus, in human and monkey neocortex, the LFP reflects primarily inhibitory neuron activity.

Comprehensive Treatment of Upper Lip Arteriovenous Malformation.

Arteriovenous malformations are uncommon congenital disorders in vascular development. They frequently involve craniofacial structures and result in a morphogenic abnormality with ominous arteriovenous shunting. We present a huge AVM of the upper lip in an 18-year-old patient who was successfully treated by the combination method of presurgical endovascular embolization and complete resection of the lesion. Subsequent surgical defect in upper lip, which involved more than two-third of the lip length, was reconstructed via Webster's modification of cheek advancement flap.

High-frequency oscillations in human and monkey neocortex during the wake-sleep cycle.

Beta (ß)- and gamma (γ)-oscillations are present in different cortical areas and are thought to be inhibition-driven, but it is not known if these properties also apply to γ-oscillations in humans. Here, we analyze such oscillations in high-density microelectrode array recordings in human and monkey during the wake-sleep cycle. In these recordings, units were classified as excitatory and inhibitory cells. We find that γ-oscillations in human and ß-oscillations in monkey are characterized by a strong implication of inhibitory neurons, both in terms of their firing rate and their phasic firing with the oscillation cycle. The ß- and γ-waves systematically propagate across the array, with similar velocities, during both wake and sleep. However, only in slow-wave sleep (SWS) ß- and γ-oscillations are associated with highly coherent and functional interactions across several millimeters of the neocortex. This interaction is specifically pronounced between inhibitory cells. These results suggest that inhibitory cells are dominantly involved in the genesis of ß- and γ-oscillations, as well as in the organization of their large-scale coherence in the awake and sleeping brain. The highest oscillation coherence found during SWS suggests that fast oscillations implement a highly coherent reactivation of wake patterns that may support memory consolidation during SWS.

Nonsyndromic Isolated Temporal Bone Styloid Process Fracture.

INTRODUCTION: Fracture of the styloid process (SP) of the temporal bone is a rare traumatic injury in normal individuals who are not suffering from Eagle's syndrome. Diagnosis and management of this problem requires comprehensive knowledge about its signs and symptoms. This study aimed to present an isolated styloid process fracture in a nonsyndromic patient. CASE PRESENTATION: A 50-year-old male patient was referred to our department with a complaint of sore throat. However, presentation of the problem resembled the symptoms of temporomandibular joint disorder (TMD). Fracture of the SP of the temporal bone was detected on the radiographs. Conservative treatment was undertaken for the patient. The symptoms diminished after about four months. CONCLUSIONS: Physicians should be aware of the signs and symptoms of different pain sources to prevent misdiagnosis and maltreatment.

Dynamic Balance of Excitation and Inhibition in Human and Monkey Neocortex.

Balance of excitation and inhibition is a fundamental feature of in vivo network activity and is important for its computations. However, its presence in the neocortex of higher mammals is not well established. We investigated the dynamics of excitation and inhibition using dense multielectrode recordings in humans and monkeys. We found that in all states of the wake-sleep cycle, excitatory and inhibitory ensembles are well balanced, and co-fluctuate with slight instantaneous deviations from perfect balance, mostly in slow-wave sleep. Remarkably, these correlated fluctuations are seen for many different temporal scales. The similarity of these computational features with a network model of self-generated balanced states suggests that such balanced activity is essentially generated by recurrent activity in the local network and is not due to external inputs. Finally, we find that this balance breaks down during seizures, where the temporal correlation of excitatory and inhibitory populations is disrupted. These results show that balanced activity is a feature of normal brain activity, and break down of the balance could be an important factor to define pathological states.

Diagnostic Factors of Odontogenic Cysts in Iranian Population: A Retrospective Study Over the Past Two Decades.

BACKGROUND: Early diagnosis of odontogenic cysts due to their silent progression is always a challenging problem for clinicians. OBJECTIVES: The current study aimed to evaluate the frequency of odontogenic cysts and related factors in a selected Iranian population. PATIENTS AND METHODS: The current cross-sectional study was conducted on 312 patients' recorded data in Taleghani Hospital, Tehran, Iran, from April 1993 to December 2013. All related data were extracted from the records and categorized in tables. The correlation between the variables was analyzed by either chi-square or multinominal logistic regression tests. The P values < 0.05 were considered significant. RESULTS: Evaluation of 312 patients' records (185 males and 127 females) with the mean age of 27.6 showed that Odontogenic Keratocyst (OKC) was the most common odontogenic cyst of all followed by the dentigerous cyst as the second most common lesion. Most of the patients were in the second or third decades of their lives, although there was no statistically significant age distribution. The finding of the current study showed that calcifying odontogenic cyst (COC) occurrence was significantly related to the history of trauma. Enucleation and curettage of the odontogenic cysts were the most common treatment plans of all. CONCLUSIONS: The current study showed that clinicians should consider the many factors associated with the occurrence of odontogenic cysts.

Microleakage of Four Dental Cements in Metal Ceramic Restorations With Open Margins.

BACKGROUND: Fixed prosthodontics is a routine dental treatment and microleakage is a major cause of its failure. OBJECTIVES: The aim of this study was to assess the marginal microleakage of four cements in metal ceramic restorations with adapted and open margins. MATERIALS AND METHODS: Sixty sound human premolars were selected for this experimental study performed in Tehran, Iran and prepared for full-crown restorations. Wax patterns were formed leaving a 300 µm gap on one of the proximal margins. The crowns were cast and the samples were randomly divided into four groups based on the cement used. Copings were cemented using zinc phosphate cement (Fleck), Fuji Plus resin-modified glass ionomer, Panavia F2.0 resin cement, or G-Cem resin cement, according to the manufacturers' instructions. Samples were immersed in 2% methylene blue solution. After 24 hours, dye penetration was assessed under a stereomicroscope and analyzed using the respective software. Data were analyzed using ANOVA, paired t-tests, and Kruskal-Wallis, Wilcoxon, and Mann-Whitney tests. RESULTS: The least microleakage occurred in the Panavia F2.0 group (closed margin, 0.18 mm; open margin, 0.64 mm) and the maximum was observed in the Fleck group (closed margin, 1.92 mm; open margin, 3.32 mm). The Fleck group displayed significantly more microleakage compared to the Fuji Plus and Panavia F2.0 groups (P < 0.001) in both closed and open margins. In open margins, differences in microleakage between the Fuji Plus and G-Cem as well as between the G-Cem and Panavia F2.0 groups were significant (P < 0.001). In closed margins, only the G-Cem group displayed significantly more microleakage as compared to the Panavia F2.0 group (P < 0.05). Paired t-test results showed significantly more microleakage in open margins compared to closed margins, except in the Fuji Plus group (P = 0.539). CONCLUSIONS: Fuji Plus cement exhibited better sealing ability in closed and open margins compared to G-Cem and Fleck cements. When using G-Cem and Fleck cements for full metal ceramic restorations, clinicians should try to minimize marginal gaps in order to reduce restoration failure. In situations where there are doubts about perfect marginal adaptation, the use of Fuji Plus cement may be helpful.

Cutaneous Metaplastic Synovial Cyst: A Case Report and Literature Review.

INTRODUCTION: Cutaneous metaplastic synovial cyst (CMSC) is a rare cutaneous lesion characterized by a tender subcutaneous nodule, which usually occurs at the site of previous surgical or local trauma. Histologically, the lesion includes a cystic structure with villous-like projections and a lining mimicking hyperplastic synovium. CASE PRESENTATION: We reported the first case of CMSC which developed at the surgical incision site of treatment of a maxillofacial fracture. In addition, we reviewed English literature to evaluate all previously reported CMSC cases and discussed its clinical and histopathological features and etiology. From 1987 to now, reviewing the English literature about CMSC includes 17 studies that described 28 cases, and our presented case was the 29th. There was no sex predilection and age of patients ranged from 7 to 82 years, but most of them were over 40 years. We can see this lesion in any site of the body and hand/arm is the most prevalent involved region (28% cases). Most of the patients had a history of previous local trauma or operation in the involved area. CONCLUSIONS: Although the actual etiology of CMSC remains unclear, trauma, as the most probable etiologic factor, plays a role in development of CMSC. Surgical excision of the lesion is the preferable treatment choice and rate of recurrence is low.

Comprehensive treatment and rehabilitation of a patient with maxillary arteriovenous malformation.

Arteriovenous malformations (AVMs) of the maxilla are rare and potentially life-threatening conditions that can pose a therapeutic dilemma. We reported the first case of maxillary AVM in a 15-year-old girl who was treated by marginal hemimaxillectomy including overlying palatal mucosa and immediate replantation of the segment after removing the AVM tissues and teeth and covering by a full-thickness pedicled temporal muscle flap rotated into the mouth. Then, this preserved bone underwent distraction osteogenesis and dental implant rehabilitation successfully. This method was previously used for the definitive treatment of mandibular AVMs, and in this case, we applied this method for the first time in maxillary AVMs. In conclusion, this surgical method may be considered as a safe, convenient, and effective treatment and reconstructive modality for such vascular malformations in the maxilla and restores function and symmetry of the jaws while obviating the need for bone harvesting and future major reconstructive operations.

Intracranial meningioma at the site of a previous cranial penetrating trauma due to shrapnel.

Meningiomas are common and mostly benign intracranial tumors, which originate from arachnoid cells of the meninges, and account for approximately 25% of all primary intracranial tumors. Many external etiological factors have been described as etiology of meningioma in the literature, one of which is head trauma. However, trauma as a cause of meningioma remains a controversial subject. Here, a case of a patient with posttraumatic meningioma, who was wounded 25 years before, is presented. The assessment of the clinical characteristics of the patient and those reported in the literature seem to confirm that, in some cases, head trauma may be a factor contributing to the development of meningioma.

Simultaneous chin onlay bone graft using elongated coronoid in the treatment of temporomandibular joint ankylosis.

Temporomandibular joint (TMJ) ankylosis is a disabling condition that causes problems in mastication, digestion, speech, appearance, and hygiene. Treatment goals are to restore the joint function, to improve facial appearance, and to reestablish harmony among them. To achieve these goals, various strategies have been reported as 1-stage or multistage protocols. We describe a novel method to augment the chin structure with elongated coronoid process of the mandible, which is a sequence of TMJ ankylosis. By this 1-stage treatment that includes gap arthroplasty with interpositional temporalis fascia graft and chin augmentation with autogenous bone graft (elongated coronoid), functional disability and facial deformity of the patient with TMJ ankylosis were improved simultaneously.

Keratoameloblastoma, a very rare variant of ameloblastoma.

The keratoameloblastoma is a rare histologic variant of ameloblastoma. Fewer than 15 cases of keratoameloblastoma have been documented in the literature. We report a new case of keratoameloblastoma in a 21-year-old female patient with a unilocular radiolucent lesion between the roots of the right mandibular incisors. We describe the clinical, radiographic, and histopathologic features of this lesion along with a review on the characteristics of previous cases. We also discuss about classification and management of this lesion.

Pseudoaneurysm of the superficial temporal artery following penetrating trauma.

Pseudoaneurysm of superficial temporal artery (STA) is an uncommon complication of blunt and penetrating trauma. It accounts for only 1% of all traumatic aneurysms. Most pseudoaneurysms of STA present as a painless pulsating mass, and its diagnosis can be made with physical examination and ultrasound or computed tomography angiogram. The treatment of choice is ligation and resection. This report includes a review of the anatomy, histopathology, etiology, diagnosis, and treatment options for STA pseudoaneurysm and presents a very rare documented case of STA pseudoaneurysm following penetrating trauma that was presented to the hospital with severe hemorrhage, and surgical resection of the lesion mandated the external carotid artery to be exposed for proximal control.

Pattern of odontogenic infections at a tertiary hospital in tehran, iran: a 10-year retrospective study of 310 patients.

OBJECTIVE: To retrospectively evaluate the treated cases with odontogenic abscess and identify the outcome of odontogenic infections, their characteristics and treatment modalities. MATERIALS AND METHODS: This retrospective study was performed by collecting data from 310 patient records at the oral and maxillofacial surgery department of Taleghani hospital, Tehran, Iran from January 2001 to January 2011. The variables were age, gender, affected teeth, affected facial spaces, type of bacterial source, type of antibiotic therapy, previous medication, hospital stay, body temperature on admission and past medical history. RESULTS: The patients' ages were between 2 and 84 years and 62.6% of the patients with odontogenic infection were younger than 35 years old. Most of the patients had a body temperature of 37-37.5°C. The most involved teeth were mandibular third molar. Deciduous teeth contained 6.4% of the involved teeth, among which mandibular molars were the most involved. 24.3% of the patients were hospitalized for 4 days. Streptococci were the most detected bacterial strain. The most involved anatomic space was the buccal space and 22.5% of the cases had multi space involvement and 17 cases had Ludwig's angina. The most common used antibiotic regimens were penicillin G and metronidazole or cefazolin and metronidazole. The mortality rate was 1%, all of whom had Ludwig's angina. CONCLUSION: The main affected facial spaces were buccal and submandibular spaces. The most common used antibiotic was penicillin, proving its effectiveness in the treatment of jaw infections. Odontogenic abscesses are mostly related to the eruption of mandibular molars.

The antibacterial properties of composite resin containing nanosilver against Streptococcus mutans and Lactobacillus.

AIM: The aim was to evaluate the antibacterial properties of composite resin containing nanosilver against Streptococcus mutans (SM) and Lactobacillus (L). MATERIALS AND METHODS: Nanosilver was added to Z250 composite at 0.5 and 1% by weight. In order to confirm the homogenous distribution of the nanoparticles in the composite resin, SEM-EDX analysis was performed on one sample in each group. Z250 composite without nanosilver was used as control. Direct contact test was used to test the antibacterial properties of nanoparticle-loaded composites: 0.001 ml of 0.5 Mc Farland suspension of MS and L was placed on composite disks, and incubated for 1 hour in 5 to 10% CO2 incubator at 37°C. Samples were placed in 0.5 ml of sterile BHI broth and incubated for 2 hours in CO2 incubator. Afterwards, 0.001 ml liquid from each medium was distributed on blood agar plates and incubated for 48 hours in CO2 incubator. The numbers of bacterial colonies were counted visually. Data were analyzed using Two-way ANOVA and Tukey HSD test. Significance level was set at 0.05. RESULTS: Addition of nanosilver to composite resin had a significant effect on reduction of the number of SM and L colonies (p = 0.000). The antibacterial properties of composite resins are different depending on the concentration of nanosilver (p = 0.014). Tukey test indicated that increase in the concentration of nanosilver caused the increase in antibacterial properties of composite resin. CONCLUSION: Addition of silver nanoparticles to Z250 composite could significantly inhibit the growth of Streptococcus mutans and Lactobacillus on the surface of this composite. CLINICAL SIGNIFICANCE: The addition of nanosilver to Z250 composite could inhibit the growth of SM and L on the surface of the restoration and therefore prevent the occurrence of secondary caries.