Horizontal Thickness Research Articles

Assessment of dehydrothermally cross-linked collagen membrane for guided bone regeneration around peri-implant dehiscence defects: a randomized single-blinded clinical trial.

PurposeThe aim of this study was to determine the clinical feasibility of using dehydrothermally cross‐linked collagen membrane (DCM) for bone regeneration around peri-implant dehiscence defects, and compare it with non-cross-linked native collagen membrane (NCM).MethodsDehiscence defects were investigated in twenty-eight patients. Defect width and height were measured by periodontal probe immediately following implant placement (baseline) and 16 weeks afterward. Membrane manipulation and maintenance were clinically assessed by means of the visual analogue scale score at baseline. Changes in horizontal thickness at 1 mm, 2 mm, and 3 mm below the top of the implant platform and the average bone density were assessed by cone-beam computed tomography at 16 weeks. Degradation of membrane was histologically observed in the soft tissue around the implant prior to re-entry surgery.ResultsFive defect sites (two sites in the NCM group and three sites in the DCM group) showed soft-tissue dehiscence defects and membrane exposure during the early healing period, but there were no symptoms or signs of severe complications during the experimental postoperative period. Significant clinical and radiological improvements were found in all parameters with both types of collagen membrane. Partially resorbed membrane leaflets were only observed histologically in the DCM group.ConclusionsThese findings suggest that, compared with NCM, DCM has a similar clinical expediency and possesses more stable maintenance properties. Therefore, it could be used effectively in guided bone regeneration around dehiscence-type defects.

Horizontal pachymetric profile for the detection of keratoconus

Purpose: To evaluate the ability of horizontal thickness profile to distinguish keratoconus from normal corneas, and compare the accuracy of these indices with more complex tomographic indices. Methods: In a retrospective study, one eye randomly selected from 225 patients with bilateral keratoconus and 335 patients with normal corneas were included. All patients were examined by a corneal specialist and underwent the examination of corneal tomography, Pentacam HR (Oculus, Wetzlar, Germany). Data of horizontal pachymetric profile passing through the apex of 6 mm was evaluated. With these data, the thickness at the corneal apex (P.apice), the thickness of the thinnest point of the horizontal profile (P.min.H), the pachymetric progression from the thinnest point to the thickest (PPmin-max), the average pachymetric progression in the meridian as reference the average from the normal population (PPmed) and the fitness with a second degree polynomial trendline (R2). An artificial intelligence model was built to combine this data. The performance for distinguishing normal keratoconus was evaluated by ROC curves. Results: All of these indices were statistically different between the two groups (p <0.001). The area under the ROC curve (AUC) thickness at the apex and TP were 0.904 and 0.938, respectively. The tomographic index with higher AUC was BAD-D (0.997). Regarding the horizontal profile, the AUC of PP.min.H and PPmin-max were 0.915 and 0.927, respectively. The fitness to the trendline to the horizontal thickness graph AUC was 0.896. The best performance was obtained with the PPmed (AUC 0.932 sensitivity = 84.4% and specificity of 92.5%). The artificial intelligence model combining all items derived from horizontal profile improved performance (AUC 0.991 Sensitivity = 96% and specificity of 98%). Conclusion: The horizontal thickness profile can detect keratoconus, with a capacity comparable to more complex indices. This type of analysis can provide the basics for new approaches, using data present in simpler devices than the tomographer reducing the cost for the patients.

Vertical and horizontal corneal epithelial thickness profile using ultra-high resolution and long scan depth optical coherence tomography.

PurposeTo determine the vertical and horizontal thickness profiles of the corneal epithelium in vivo using ultra-long scan depth and ultra-high resolution spectral domain optical coherence tomography (SD-OCT).MethodsA SD-OCT was developed with an axial resolution of ∼3.3 µm in tissue and an extended scan depth. Forty-two eyes of 21 subjects were imaged twice. The entire horizontal and vertical corneal epithelial thickness profiles were evaluated. The coefficient of repeatability (CoR) and intraclass correlation (ICC) of the tests and interobserver variability were analyzed.ResultsThe full width of the horizontal epithelium was detected, whereas part of the superior epithelium was not shown for the covered super eyelid. The mean central epithelial corneal thickness was 52.0±3.2 µm for the first measurement and 52.3±3.4 µm for the second measurement (P>.05). In the central zone (0–3.0 mm), the paracentral zones (3.0–6.0 mm) and the peripheral zones (6.0–10.0 mm), the mean epithelial thickness ranged from 51 to 53 µm, 52 to 57 µm, and 58 to 72 µm, respectively. There was no difference between the two tests at both meridians and in the right and left eyes (P>.05). The ICCs of the two tests ranged from 0.70 to 0.97 and the CoRs ranged from 2.5 µm to 7.8 µm from the center to the periphery, corresponding to 5.6% to 10.6% (CoR%). The ICCs of the two observers ranged from 0.72 to 0.93 and the CoRs ranged from 4.5 µm to 10.4 µm from the center to the periphery, corresponding to 8.7% to 15.2% (CoR%).ConclusionsThis study demonstrated good repeatability of ultra-high resolution and long scan depth SD-OCT to evaluate the entire thickness profiles of the corneal epithelium. The epithelial thickness increases from the center toward the limbus.

Less Invasive Surgical Procedures Using Narrow-Diameter Implants: A Prospective Study in 20 Consecutive Patients

Narrow-diameter implants (NDIs) are increasingly produced and used in implant dentistry, especially since the introduction of new, more resistant materials. The objective of the present study was to evaluate the clinical performance of NDIs (3.3 mm) placed in thin alveolar crests. Twenty consecutive patients needing implant-supported fixed partial dentures and presenting an alveolar thickness ≤6 mm were treated with 1 or several NDIs. The surgical protocol was chosen according to the clinical situation: (1) flapless, (2) mini-cervical flap, (3) wide flap, (4) wide flap + guided bone regeneration (GBR). Implants were immediately loaded if the primary stability was higher than 20 Ncm. Implant survival and success, prosthodontic success rates, and patient-centered outcomes were evaluated after a follow-up period of 1 year. A total of 39 implants were placed in 20 patients, 12 and 27 implants in the anterior regions and in the posterior mandible, respectively. All but 1 implant reached an insertion torque higher than 20 Ncm and were loaded within 48 hours. The implant survival and success rates both reached 94.7%. The need for GBR was avoided in 60% of the implant sites. The mean peri-implant bone remodeling after a follow-up period of 1 year was -0.35 mm at the implant level. Peri-implant bone remodeling was higher in the posterior region, when the alveolar crest was thinner than 4 mm and GBR was required in addition. In conclusion, use of NDIs to restore partial edentation in sites with limited horizontal thickness seems to be an effective treatment option that prevented GBR in the majority of the present cases. Immediate provisionalization of NDIs does not seem to impair the results.

Research on Continuous Injection Direct Rolling Process for PMMA Optical Plate

Continuous injection direct rolling (CIDR) combined intermittent injection and rolling process is a new technology for molding optical polymer plates with microstructured patterns; research on forming PMMA optical plates is an aspect of it in this paper. The equipment of CIDR process consists of plastic injection module, precision rolling module, and automatic coiling module. Based on the establishing mathematical CIDR models, numerical analysis was used to explode the distribution of velocity, temperature, and pressure in injection-rolling zone. The simulation results show that it is feasible to control the temperature, velocity, and injection-rolling force, so it can form polymer plate under certain process condition. CIDR experiment equipment has been designed and produced. PMMA optical plate was obtained by CIDR experiments, longitudinal thickness difference is 0.005 mm/200 mm, horizontal thickness difference is 0.02/200 mm, transmittance is 86.3%, Haze is 0.61%, and the difference is little compared with optical glasses. So it can be confirmed that CIDR process is practical to produce PMMA optical plates.

A randomized controlled clinical multicenter trial comparing the clinical and histological performance of a new, modified polylactide‐co‐glycolide acid membrane to an expanded polytetrafluorethylene membrane in guided bone regeneration procedures

To compare the clinical and histological outcomes of a resorbable modified polylactide/polyglycolide acid (PLGA) test membrane and a titanium-reinforced expanded polytetrafluorethylene (ePTFE) control membrane used for guided bone regeneration (GBR) around dental implants. A total of 40 patients with peri-implant dehiscence-type defects were randomly allocated to a GBR procedure using either a modified PLGA test or an ePTFE control membrane. Soft tissue condition, implant integration, adverse events and quality of life were recorded during the 6-month healing period. At re-entry peri-implant bone defect dimensions were measured and compared with values recorded at implant/GBR surgery. A biopsy was retrieved for qualitative and quantitative histological analyses. A comparison between the groups was conducted using non-parametric statistical tests. Soft tissue complications were observed in five test patients and two control patients. Except for soft tissue complications and incomplete regeneration, no procedure- or device-related adverse events were observed. The vertical bone defect component was, in mean, reduced by-5.1 mm (95% CI -6.8, -3.3) in the test group and -6.9 mm (95% CI -8.2, -5.5 mm) in the control group. The mean residual vertical defect height measured 1.2 ± 2.4 mm in the test group and 0.3 ± 1.1 mm in the control group meaning a mean defect resolution of 81% in the test group and 96% in the control group (P = 0.161). The horizontal bone thickness at implant shoulder level decreased from a mean of 3.2 mm to 1.4 mm (-56%, mean -1.7 mm, 95% CI -2.3, -1.1) in the test group and from 3.3 mm to 2.5 mm (-24%, mean -0.8 mm, 95% CI -1.3, -0.3) in the control group (P = 0.022). Qualitative and quantitative histological analyses did not show significant differences in the tissue composition between groups. Peri-implant GBR was successfully performed using either of the membranes. The control membrane was able to better maintain the horizontal thickness of regenerated bone and revealed less soft tissue complications. No statistically valid evidence about the superiority of one membrane was found in any other parameters. Soft tissue dehiscences occur with both types of membranes and can impair the amount of regenerated bone.

Vertical and Horizontal Thickness Profiles of the Corneal Epithelium and Bowman's Layer after Orthokeratology

To investigate thickness profile changes of the corneal epithelium and Bowman's layer at the vertical and horizontal meridians with overnight myopia orthokeratology (OK) lenses. Twenty subjects (age range: 19-33 years) wore reverse-geometry rigid gas-permeable OK lenses in both eyes for 30 days. Before lens wear and after 1, 7, and 30 days of overnight lens wear, evaluation of lens fitting, visual acuity examination, corneal topography, and ultra-high resolution optical coherence tomography (UHR-OCT) were performed. The central, midperipheral, and peripheral cornea were imaged in both the horizontal and vertical meridians. Custom software was produced to acquire the thickness profiles of the epithelium and Bowman's layer. Unaided visual acuity and refraction were improved significantly after OK lens wear. The central corneal epithelium thinned in the horizontal and vertical meridians after one night of lens wear (P < 0.05). In the horizontal meridian, the epithelium thickened at the temporal and nasal midperipheries (P < 0.05), while the superior midperipheral epithelium thinned in the vertical meridian. There were no changes in the thickness profile of Bowman's layer during the study period. Overnight wear of OK lenses caused the central corneal epithelium to thin in both the vertical and horizontal meridians, while the midperipheral nasal and temporal epithelium became thicker and the superior midperipheral epithelium became thinner. The thickness of the central or midperipheral Bowman's layer in either meridian did not change. Improved vision acuity after overnight OK lens wear can be attributed to changes in the corneal epithelium and not Bowman's layer.

Topographic Analysis of Maxillary Premolars and Molars and Maxillary Sinus Using Cone Beam Computed Tomography

This study evaluated the anatomical characteristics of the maxillary premolars and molars and the maxillary sinus using cone beam computed tomography (CBCT) for dental implant treatment. Ten linear items and 1 angular item on 30 sites in 30 patients were measured on 3-dimensional computed tomography images using CBCT. The vertical relationship between the maxillary sinus and the maxillary molars was classified into 5 categories. The horizontal thickness of the buccal alveolar bone was thinnest on the maxillary first premolars, and the horizontal thickness of the palatal alveolar bone was thickest on the maxillary second molars. Type II was most common on the maxillary first molars. The internal angle at the maxillary premolars was significantly greater than that at the maxillary molars. The internal angle and vertical distance between the apex of the roots and the maxillary sinus floor showed a positive correlation on the maxillary first premolars (P = 0.003). For the selection of an appropriate approach on dental implant treatment, the evaluation of maxillary premolars and molars using of CBCT can be recommended.

Age-related differences in microstructure, density and biomechanics of vertebral cancellous bone of Chinese males

The conventional lumbar separation was performed by removing soft tissue, subsidiary structures and leaving only the vertebral body. The vertebral body was cut into two halves along the median sagittal plane, keeping the upper and lower end plates of each half, which were subsequently used for biomechanical, morphological and density experiments. From the age of 20–29 to 30–39 years, both the horizontal trabecular thickness (Tb.Th) and vertical Tb.Th decreased; the horizontal and vertical Tb.Sp increased; the plate-like trabecular Tb.Th decreased; the apparent density and volume ratio decreased; and the elastic modulus and the ultimate stress decreased; with all changes being statistically significant (p < 0.01). Similar trends were obtained from ages 40–49 to 50–59, although the changes were not significant (p > 0.05), except for the reduction in ultimate stress (p < 0.05). With aging, the collagen cross-linking capacity declined; the thicknesses of the collagen fibrils were variable, ranging from almost the same to loose, sparse or disordered thickness; and the finer collagen fibrils between the thick filaments were disorganized. In males aged from 20 to 59 years old, the horizontal and vertical Tb.Th and the plate-like Tb.Th of the vertebral body decreased, while the horizontal and vertical Tb.Sp increased. Additionally, the density, elastic modulus and the ultimate stress of the cancellous bone decreased with age. Thus, the associated changes of bone microstructure, density and biomechanics with age may lead to an increased risk of osteoporosis and fracture.

Vertical and Horizontal Corneal Epithelial Thickness Profiles Determined by Ultrahigh Resolution Optical Coherence Tomography

To measure vertical and horizontal thickness profiles of the central and peripheral corneal epithelium and determine if daytime changes occur. Forty eyes of 20 normal subjects were imaged by ultrahigh resolution spectral domain optical coherence tomography to profile the corneal epithelial thickness from the edge of Bowman layer to the central cornea across the vertical and horizontal meridians. Measurements were made at 10:00 AM and again at 6 and 8 hours later. The baseline vertical meridional epithelial thickness was thinnest, 42.9 ± 4.1 μm, at the edge of Bowman layer in the superior region. It increased in thickness (P < 0.01), toward the central cornea. The central epithelium averaged 52.5 ± 2.4 μm, becoming thickest, 55.2 ± 2.5 μm, in the inferior pericentral region. It thinned toward the inferior periphery, reaching 51.3 ± 5.1 μm at the edge of Bowman layer (P < 0.01). Along the horizontal meridian, the epithelium was thickest at the nasal side, 58.6 ± 5.1 μm, and temporal side, 59.3 ± 6.6 μm, near the edges of Bowman layer. It thinned toward the central cornea. There were no significant changes in the epithelial thickness at any location over 8 hours. Epithelial thickness varied over the horizontal and vertical meridians and appeared stable during the daytime.

Synchronization Control Strategy Applied in Two Cylinders System of Rolling Mill

The inner parameters and outside load of operating-side and driving-side subsystems of rolling mill are different. This difference can lead to an unequal horizontal thickness difference distribution of strip. Synchronous system is being widely applied in industrial field, in order to solve the problem of synchronization control based on two cylinders system of rolling mill, a mathematical model of hydiaulic system is presented, then, a kind of dynamic synchronous control strategy is applied. In the part of controller, the parameters of PID controller are adjusted by self-study. So the PID controller has the capability of self-adaptation. Experimental results show that the method can reduce synchronization error from to and improve the quality of the plate and strip.

Poster 76: Radiological Study of the Dimensions of the Zygomatic Arch for Rigid Fixation Tangentially

In comminuted unstable zygomatic arch fractures or old arch fractures, closed reduction may be very difficult to achieve via Gillie's approach, and osteosynthesis may be required because of instability. This study was carried out to verify whether the dimensions of the zygomatic arch are consistently large enough for rigid fixation tangentially by applying microplates and screws on the upper border using temporal hairline approach. The 3D facial bone CTs of 60 adults with intact zygomatic arches were reviewed. Three points were designated on each arch: point A, the middle of the articular tubercle; point B, where the vertical height of the arch is minimal; and point C, the center point between point B and the G-line. The vertical thickness of the arch was measured at these points as a guide for screw length; the horizontal thickness was measured at these points as a guide for screw and plate size. These values were analyzed statistically with paired samples T-test using SPSS 15.0 for Windows. The mean minimum vertical thickness values were 6.89 mm on the right and 6.75 mm on the left. The mean minimum horizontal upper-margin thickness values were 3.09 mm on the right and 2.98 mm on the left. The mean minimum horizontal lower-margin thickness values were 3.98 mm on the right and 3.86 mm on the left. The dimensions of adult zygomatic arches were sufficiently large enough to permit rigid fixation with the use of 1 mm titanium microplates and 6 mm screws. This method for open reduction and rigid fixation can be safely applied to instable comminuted or old zygomatic arch fractures, and may also be expanded into malar reduction procedures.

Split crest con strumenti vibranti a bassa frequenza: un caso clinico

Objectives Split-crest osteotomies are used to increase the thickness of edentulous ridges during implant insertion. The purpose of this case report is to illustrate the advantages of performing these procedures with low-frequency vibration, air-driven, non-piezoelectric handpieces, which are the most suitable instruments for carrying out thin osteotomies. Materials and methods We report the case of a 68-year-old patient with edentulous ridge at sites 4.5, 4.6, and 4.7. The crest was thin and the masticatory mucosa reduced. First, the ridge was osteotomized with vibrating tools on a sonic, air-driven handpiece (Sonosurgery ®, Komet/Brasseler, Lemgo, Deutschland), and the vestibular cortical plate was distracted. Tapered implants were inserted during the same session, and the spaces between the implants were filled with equine collagen sponge. Results and conclusions The procedure resulted in substantial augmentation of the horizontal thickness of the edentulous ridge and masticatory mucosa, which allowed satisfactory implant prosthetic rehabilitation of the posterior lower right sector. Thanks to the angles and reduced thickness (0.25 mm) of their cutting surfaces, the sonic air-driven tools allowed us to make thin, highly precise osteotomies.

Viscous lock-exchange in rectangular channels

In a viscous lock-exchange gravity current, which describes the reciprocal exchange of two fluids of different densities in a horizontal channel, the front between two Newtonian fluids spreads as the square root of time. The resulting diffusion coefficient reflects the competition between the buoyancy-driving effect and the viscous damping, and depends on the geometry of the channel. This lock-exchange diffusion coefficient has already been computed for a porous medium, a two-dimensional (2D) Stokes flow between two parallel horizontal boundaries separated by a vertical height H and, recently, for a cylindrical tube. In the present paper, we calculate it, analytically, for a rectangular channel (horizontal thickness b and vertical height H) of any aspect ratio (H/b) and compare our results with experiments in horizontal rectangular channels for a wide range of aspect ratios (1/10 to 10). We also discuss the 2D Stokes–Darcy model for flows in Hele-Shaw cells and show that it leads to a rather good approximation, when an appropriate Brinkman correction is used.

The effect of non-resorbable membrane on buccal bone healing at an immediate implant site: an experimental study in dogs

For successful implant treatment in the esthetic area, stable hard tissue and soft tissue are very important. At the buccal side without buccal bone defects, prophylactic guided bone regeneration (GBR) with bone substitute was frequently used for achieving thick buccal bone. The aim of this study was to evaluate the effect of GBR using a non-resorbable membrane in an immediate implant site without bone defects. Immediate implants were placed into the mandibles of four mongrel dogs. In the experimental group (TM group), a non-resorbable membrane was placed and fixed onto the buccal bone plate around the implant. In the control group, the implants were placed without membrane coverage. After 12 weeks, the dogs were sacrificed and histological specimens were prepared. The vertical distances from the smooth-rough surface interface (SRI) to the gingiva, the first-bone contact, and the bone crest were measured on the buccal and lingual sides. The horizontal thicknesses of the gingiva and bone at 0, 1, 2, and 3 mm below the SRI were measured. In the TM group, first-bone contact on the buccal side was more coronally positioned approximately 0.8 mm than the control group (P=0.041). The buccal bone thickness of the TM group was well preserved and there was no difference between the buccal and lingual sides. Comparing the control group, implants of the TM group had 1 mm thicker buccal bone (P=0.0051 at bone 1 mm level, P=0.002 at bone 2 mm level). In the control group, buccal bone loss was observed and buccal bone was about 1 mm thinner than the lingual bone (P<0.05). GBR with a non-resorbable membrane and no bone graft substitute could help to preserve buccal bone thickness on the immediate implant site without defects.

Reply to comments by Robert P. Comer

In his letter, Comer (1986) addresses three different points whch bear on three related publications on load-induced flexure of elastic plates (Comer 1983; Ward 1984; Wolf 1985a). As his first point is primarily an annotation to his own publication on the subject (Comer 1983), I will restrict my reply to the remaining two points. Comer’s (1986) second criticism refers to my statement on similarity (Wolf 1985a, p. 27 1). If the sentence under discussion has been construed to state that geometrical similarity between two otherwise identical plate models implies their physicaZ similarity, this represents a misinterpretation. Clearly, non-dimensional analysis of elastic-plate flexure cannot be formulated in terms of a geometrical scale-length (see, e.g. Wolf 1984). My statement therefore purports to draw attention to something different: I expect the accuracy of thin-plate theory to be comparable for two models provided that the ratios between horizontal load dimension and plate thickness are comparable. This is obviously not completely supported by Comer’s (1983) results (see his fig. 3). Inspection of fig. 2 in Wolf (1 985a), however, illustrates that neglecting pre-stress in thick-plate theory overestimates the response. More specifically, the figure shows that the differences increase with horizontal load dimension and with plate thickness. As the linear scale of the model in Comer’s (1983) fig. 3(c) is larger than the scale of the model in fig. 3(a), I therefore conclude that including pre-stress in his thick-plate theory would reduce the relative discrepancies in fig. 3(c) by more than in fig. 3(a) so that they would become comparable. For further clarification, I calculate peak deflections for two geometrically similar models. In the first model, disc-load radius and elastic-plate thickness are 200 km; the second model is scaled down by a factor of four (the other parameters are as in Wolf 1985a). Compared with the response according to my thick-plate theory, the thin-plate deflection is reduced by 15 and 10 per cent, respectively. I am therefore entitled to denote the relative discrepancies as ‘similar’. Whereas this is a minor subtlety, Comer’s (1986) final comment on the relation between special and general solutions is of greater import. It is certainly legitimate to point out that

Double Flap Incision Design for Guided Bone Regeneration: A Novel Technique and Clinical Considerations

Premature membrane exposure for guided bone regeneration may result in complications, such as inadequate bone regeneration, inflammatory reactions, and wound infection. This paper presents a clinical case of a novel incision-flap design used to advance the flap to enhance tension-free primary closure for the vertical ridge augmentation. A 61-year-old white man presented with the chief complaint of wanting to replace his posterior mandibular teeth. A severe alveolar bone deformity vertically and horizontally (Seibert Class III) was noticed, especially over the mental foramen area. A staged guided bone regeneration procedure prior to the implant installation was chosen as the most optimal treatment. A partial-thickness flap, separating the mucosal flap from the periosteum overlying the alveolar bone, was used to advance the flap. During the healing period, neither soft tissue dehiscence nor membrane exposure were noted. Clinical and radiographic evaluation revealed a 4- to 5-mm gain in vertical height and a noticeable increase in horizontal thickness. After the 6 to 8 months of healing for both sites, two implants were placed on each side with good primary stability and without complications. This technique facilitates flap advancement by the tension-free nature of the design and enhances soft tissue maintenance during the course of regeneration. This approach, the separation of the periosteal layer and the mucosal layer, can be used as an alternative to overcome some of the limitations with conventional technique.

The effect of non-resorbable barrier membrane on the change of buccal and lingual alveolar bone in immediate implant placement into periapically infected extraction sockets

Purpose: Many researches showed loss of alveolar bone in fresh extraction socket and even in case of immediate implant placement. The aim of this study was to evaluate the effect of non-resorbable barrier membrane on the change of buccal and lingual alveolar bone in immediate implant placement into periapically infected extraction sockets. Materials and methods: Immediate implants were placed into artificially induced periapical lesion of mandibular premolars after complete debridement using buccal bone defect made by a 6mm trephine bur in 4 mongrel dogs. Before flap repositioning, a non-resorbable barrier membrane was placed on the buccal defect in the experimental group. No membrane was placed in the control group. In 12 weeks after placement, the dogs were sacrificed and undecalcified histologic specimens were prepared. The vertical distance from the smooth-rough surface interface(SRI) to gingiva, 1st bone contact and bone crest were measured in buccal and lingual side. The horizontal thicknesses of gingiva and bone at 0, 1, 2 and 3 mm below SRI were measured. Results: The buccal bone was resorbed more than lingual bone in both groups and there was statistical significance(p<0.05). The distances from SRI to 1st bone contact were 2.45±2.35 mm in experimental group and 4.49±3.10 mm in control group. In all vertical level, lingual bone was thicker than buccal bone(p<0.05). Conclusion: Buccal bone was reduced more than lingual bone in immediate implant placement into periapically infected extraction sockets. Placement of non-resorbable barrier membrane reduced the buccal bone resorption. However there was no statistical significance. (J Korean Acad Periodontol 2009;39:71-76)

Chest Wall Thickness in Military Personnel: Implications for Needle Thoracentesis in Tension Pneumothorax

Needle thoracentesis is an emergency procedure to relieve tension pneumothorax. Published recommendations suggest use of angiocatheters or needles in the 5-cm range for emergency treatment. Multidetector computed tomography scans from 100 virtual autopsy cases were used to determine chest wall thickness in deployed male military personnel. Measurement was made in the second right intercostal space at the midclavicular line. The mean horizontal thickness was 5.36 cm (SD = 1.19 cm) with angled (perpendicular) thickness slightly less with a mean of 4.86 cm (SD 1.10 cm). Thickness was generally greater than previously reported. An 8-cm angiocatheter would have reached the pleural space in 99% of subjects in this series. Recommended procedures for needle thoracentesis to relieve tension pneumothorax should be adapted to reflect use of an angiocatheter or needle of sufficient length.

Effects of the Local Soil Nonuniformity Upon Performances of Ground Grids

The effects are studied of the material for leveling spread over and of installation channels led through substation site upon the safety risk associated with grounding. The main ground grid performances in case of ground faults are analyzed for various ratios of overlaid material and surrounding soil resistivities and horizontal dimensions and thickness of the overlaid material. Also, the effects of the installation channels dug along various routes upon the potential distribution on the ground surface and step voltages are considered. It was shown that the mentioned local nonuniformities can substantially affect the safety performances of the ground grid and that they should be carefully taken into consideration. The local soil irregularities considered have been modeled by applying the method of finite elements.