Ridge Crest Research Articles

Preclinical Investigation on the Effect of Collagen Matrix With Polydeoxyribonucleotide at Buccally Positioned Implants.

The objective of this study is to investigate the effect of collagen matrix with polydeoxyribonucleotide (PDRN) at two concentrations on keratinized tissue (KT) regeneration for buccally positioned implants in canines. Four implants were placed in the edentulous mandible of five dogs simultaneously with KT removal. The implants were positioned buccally with respect to the ridge crest. After 2 months, KT augmentation was performed applying the following treatment modalities:(1) free gingival graft (FGG), (2) xenogeneic collagen matrix (XCM), (3) XCM loaded with 2 mg/mL PDRN (PDRN2), and (4) XCM loaded with 4 mg/mL PDRN (PDRN4). All animals were sacrificed 3 months later. Outcomes included clinical (KT height) and histomorphometric measurements (KT height/length, level of the mucosa, mucosal thickness, supracrestal soft tissue height). Clinical and histomorphometric KT formation at 3 months was greatest in groups with FGG (4.70 ± 1.00/3.94 ± 0.93 mm) and PDRN2 (4.85 ± 1.43/3.95 ± 0.87 mm). Group PDRN2 (1.87 ± 1.50 mm) showed a higher marginal mucosal level with respect to the implant platform compared to other groups (range: 0.57 ± 0.97-0.69 ± 1.14 mm). All groups presented a soft tissue thickness of < 2 mm on the buccal aspect of the implants. Based on the limitations of this pilot preclinical study, XCM with 2 mg/mL of PDRN demonstrated a potential for KT augmentation.

The Plot against Mt Hurun: How Cold War Targeting of Nuclear Missiles Sparked the Peli Movement, East Sepik Province, Papua New Guinea

ABSTRACT Considerable academic research has focused on the Peli Movement of the East Sepik Province of Papua New Guinea, one of the largest and most prominent of so-called millenarian movements in New Guinea’s history. In 1971, Peli attracted thousands of people to witness the removal of cement markers that an American geodetic team, as part of a Cold War project to improve nuclear missile targeting, had sunk into the summit of Mt Hurun (Turu), the highest peak in the coastal Prince Alexander Range. Removing the markers, people believed, would trigger political equality with, and access to, the European estate. It has yet to be explained, however, why Peli’s followers felt this particular action would produce such a dramatic result. Drawing on just over 24 months’ field research in 1979–81, 1987, 1991, and 1997 in Sima village in Mt Hurun’s high foothills, close to the Peli Movement’s centre, this paper contends that local views of what the mountain incarnates and the implications of burying stones in hilltops or ridge crests all but dictated the form of people’s actions and the millennial-like results they expected.

Geomorphic History Determined by a New Glacial History Paradigm and Topographic Map Interpretation, Towanda Creek Drainage Basin, PA (USA)

Pennsylvania&amp;rsquo;s Towanda Creek drainage basin geomorphic history is determined by using a recently proposed geology and glacial history paradigm (which predicts massive and prolonged southwest oriented continental ice sheet meltwater floods flowed across Pennsylvania) when interpreting previously unexplained topographic map drainage system and erosional landform evidence. The new paradigm explains most of the region&amp;rsquo;s erosional landforms including barbed tributaries, drainage divides, through valleys (valleys crossing drainage divides), water and wind gaps, valley orientations, entrenched meanders, through valley and gap floor elevations, regional ridge crest elevations, upland area elevations, and intervening lowland elevations. The new paradigm suggests the present-day northeast-oriented Towanda Creek drainage basin formed as immense and prolonged southwest-oriented floods first lowered a low relief surface (now preserved if preserved at all by the region&amp;rsquo;s highest elevations) in the area between the present-day northeast-trending Blossburg and Barclay synclinal uplands and also to the south of the Barclay synclinal upland. Those floodwaters after flowing across the present-day northeast-oriented Towanda Creek drainage basin flowed in a southwest direction through the now southwest-oriented Lycoming and Loyalsock Creek drainage basins and then to and along a now northeast oriented West Branch Susquehanna River valley segment before continuing in a southwest direction along what is now the Allegheny Front. Headward erosion of today&amp;rsquo;s southeast-oriented North Branch Susquehanna River valley segment between Pittston and Athens, Pennsylvania captured and reversed the beheaded southwest-oriented floodwaters to create the northeast-oriented Towanda Creek drainage system seen today.

Evaluation of canalis sinuosus and accessory canal morphology by cone-beam computed tomography.

To evaluate canalis sinuosus (CS) and accessory canalis sinuosus (AC) morphology and their relationship with the impacted canine on cone-beam computed tomography (CBCT) images. The diameter and location of the CS, its distance from the nasal cavity (NC-CS), its distance from the buccal cortical plate (BC-CS), and its distance from the alveolar ridge crest (AR-CS) were evaluated on 1000 CBCT scans. The prevalence and termination of AC and the presence of impacted canines were also evaluated. CS was detected in 89 (8.9%) of 1000 CBCTs. The mean CS diameter was found as 1.34 ± 0.53mm. No statistically significant difference was found between gender, age, direction, and CS presence and diameter. CS was most frequently seen in regions 11 (23.6%) and 13 (23.6%). The average NC-CS, BC-CS, and AR-CS length was 6.14, 6.06 and 4.35mm, respectively. AC was detected in 22 patients (24.71%). There was no statistically significant difference between the presence of AC and gender, age, CS diameter, NC-CS, BC-CS, and AR-CS distance. BC-CS length and AR-CS length were statistically significantly higher in patients with impacted canines. It should be kept in mind that the CS diameter, NC-CS, BC-CS, and AR-CS distance may increase in the presence of an impacted canine and the integrity of the neurovascular structure should be preserved. The fact that the CS is often localized in the palatial region requires a detailed evaluation of the anterior maxillary region with three-dimensional imaging methods.

POLYAMIDE FLEXIBLE DENTURES – A BETTER OR WORSE STRATEGY

Background: Polyamide dentures have added advantages over the acrylic dentures in terms of esthetics, comfort and versatility to adapt to the undercut areas. However, the effect of flexibility of these dentures from the view of residual ridge resorption has always been obscure. The aim of this study is to compare the type of denture base with the distribution of masticatory forces by examining the changes on the alveolar mucosa in the histological picture before and after insertion of two widely used dentures. Materials and methods: A total of 20 participants were included in the study, among which 10 patients were allocated for acrylic removable partial dentures and 10 patients were allocated for polyamide flexible removable partial dentures. The patients were asked to rinse their mouth and cement spatula was used to collect the epithelial mucous cells noninvasively by scraping the crest of the residual alveolar ridge with light pressure in premolar-molar area both before insertion and 2 weeks after insertion of the removable partial dentures. The said swab was then smeared on a clean glass slide and fixed in 95% ethyl alcohol and was stained by Papanicolaou (PAP) stain. The PAP-stained smear was analyzed for the presence of keratinized cells and the number of keratinocytes was counted for both acrylic and polyamide denture groups. Results: The results show that both types of denture bases altered the alveolar mucosal keratinization but there was a significant difference in number of keratinized cells between all the three groups. Polyamide flexible partial dentures showed more ortho-keratinized epithelium, which favours better occlusal load distribution. Conclusion: The results concluded that there was decreased masticatory load on the residual alveolar ridge under polyamide denture group due to the flexibility of the denture base material compared to that of the acrylic denture group.

Clinical and radiographic changes following transcrestal sinus augmentation: A scoping review of the last 25 years.

Maxillary sinus floor elevation is a surgical procedure intended to increase the volume of the bone vertically to accommodate dental implant placement. This intervention is frequently required for implant installation in the posterior maxilla, where the bone may be insufficient for securing implants of necessary length and stability. Sinus floor elevation can be completed either through a direct approach with a "window" through the lateral wall of the alveolar ridge or an indirect "transcrestal/transalveolar" sinus floor elevation (TSFE), which accesses the sinus floor through the crest of the edentulous ridge. Our study aims to provide a comprehensive scoping review of research conducted over the past 25 years on TSFE, specifically. A literature search aimed at identifying pertinent literature for the purpose of this PRISMA-ScR-compliant scoping review was conducted. Only randomized controlled trials, non-randomized controlled trials, prospective cohort studies, and case series that met the eligibility criteria were selected. Relevant data from these studies were extracted. Primary outcome measures included radiographic bone levels and implant failure >5 years. Secondary outcome measures included implant stability at time of placement and complications. Interventions reported in the selected studies were grouped based on treatment modality, which were then compared with the control therapy (traditional osteotome technique) after a minimum of 12 months healing period. Our search yielded 633 records, and after deduplication, 574 of these were screened. Application of the eligibility criteria led to the inclusion of 37 articles in the final selection. Case selection for included studies enrolling subjects: Four different transcrestal sinus elevation treatment modalities were identified: (a) osteotome, (b) piezoelectric surgery, (c) osseodensification, and (d) hydraulic techniques. Due to the heterogeneity of the studies, no superior approach for TSFE could be identified. Overall, all techniques demonstrated high implant survival rates. Comprehensive understanding of the patient's medical history, available armamentarium, and post-operative complications/management strategies are all essential to the completion of a successful TSFE approach for implant placement in the posterior maxilla, regardless of the treatment modality used.

ASSESSMENT OF THE ANATOMICAL STRUCTURE OF CANALIS SINUOSUS IN THE ANTERIOR MAXILLA TO AVOID SURGICAL COMPLICATIONS

Aims: The study's objective was to evaluate the canalis sinuosus (CS) anatomical structure in the front maxilla in order to prevent surgical problems in an adult Yemeni population sample acquired using cone-beam computed tomography (CBCT). Materials and Methods: A retrospective descriptive cross-sectional study was carried out to assess 226 participants' CBCT pictures. 452 sides in total were assessed. There were 140 females (61.9%) and 86 males (38.1%) among the samples. The age distribution was 18–34 years (65%) and over 35 years (35%), with a mean age of 32.13. Version 25 of the Statistical Package of the Social Sciences (SPSS) was used for all statistical analyses. Result: It was discovered that 160 right (35.4%) and 175 left (38.7%) of the 226 patients and 452 sides had CS. Among these individuals, 117 (51.8%) had unilateral CS and 109 (48.2%) had bilateral CS. The CS was 8.12 mm from the nasal cavity floor (D1), 6.99 mm from the buccal cortical bone ridge (D2), and 13.47 mm from the crest of the alveolar ridge (D3), as the mean distances were measured. Males and females had somewhat higher mean values for the linear measurements D1 and D3, but females had slightly higher mean values for the linear measurement D2. The CS had a mean diameter of 1.11 mm. Left central incisor area was the most commonly observed location of CS, and palataly was the most frequently recorded location of CS. Conclusion: Since the CS is present in 100% of adult Yemenis, it is imperative that general practitioners and maxillofacial surgeons become more knowledgeable about the position and structure of the CS. Peer Review History: Received 19 May 2024; Reviewed 12 July 2024; Accepted 23 August; Available online 15 September 2024 Academic Editor: Dr. Iman Muhammad Higazy, National Research Center, Egypt, imane.higazy@hotmail.com Average Peer review marks at initial stage: 5.5/10 Average Peer review marks at publication stage: 7.0/10 Reviewers: Prof. Gorkem Dulger, Duzce University, Turkey, gorkemdulger@yandex.com Dr. George Zhu, Tehran University of Medical Sciences, Tehran, Iran, sansan4240732@163.com

Underestimates of Orographic Precipitation in Idealized Simulations. Part II: Underlying Causes

Abstract Warm-sector orographic precipitation in a midlatitude cyclone encountering a ridge is simulated in a “Cyc+Mtn” experiment. A second “Shear” simulation is conducted with horizontally uniform unidirectional flow over the same mountain having thermodynamic and cross-mountain wind profiles identical to those on the centerline in the “Cyc+Mtn” simulation. The relationship between integrated vapor transport (IVT) and orographic precipitation in the Mtn+Cyc case is consistent with observations, yet the same IVT in the Shear simulation produces far less precipitation. The difference between the precipitation rates in the Cyc+Mtn and Shear cases is traced to differences in the cross-mountain moisture-flux convergence and is further isolated to differences in the cross-mountain-velocity convergence over the windward slope. The winds at the ridge crest are stronger in the Shear case, leading to more velocity divergence and decreased moisture-flux convergence. The stronger ridge-crest winds in the Shear case are produced by a stronger mountain wave, which persists after being generated during the artificial startup of the Shear simulation. Initializing with a gradually ramped-up unidirectional flow and integrating to a quasi-steady state fails to adequately capture the processes regulating the leeside circulations. Even worse results are obtained if the shear flow is instantaneously accelerated from rest. An alternative microphysical explanation for the precipitation difference between the Cyc+Mtn and Shear simulations is examined using additional numerical experiments that enhance the seeder–feeder process. Although such enhancements increase precipitation, the increase is too small to account for the differences between the Cyc+Mtn and Shear simulations. Significance Statement Our results highlight the difficulty in conducting studies of mesoscale atmospheric circulations in isolation from their surrounding environment. This approach often allows for more computationally efficient and detailed analysis of the target phenomena by reducing the size of the computational domain. But, at least in the case of orographic precipitation, such isolation can significantly limit the realism of the simulated process.

A method of impressing flabby ridge

Flabby ridge remained a challenge in dental clinical practice to obtain an accurate impression for edentulous patients. During the traditional impression making process, the excessive and displaceable soft tissue are usually compressed. In this article, we presented an impression method by using a modified special stock tray, impression compound and polyvinyl siloxane impression materials.•the suitable stock tray was modified with holes about 5 mm diameter in the corresponding area to the crest of the flabby ridge.•the primary impression was made by position the modified tray with the softened compound impression on the edentulous ridge, avoiding the area of the flabby ridge.•the final accurate impression was obtained by using the light body polyvinyl siloxane impression material.

Mechanical and Thermal Forcing for Upslope Flows and Cumulus Convection over the Sierras de Córdoba

Abstract The upslope flow processes affecting the vertical extent of orographic cumulus convection are examined using observations from the Cloud, Aerosol, and Complex Terrain Interactions (CACTI) Field Campaign. Specifically, clear-air returns from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) C-band radar (CSAPR2) are used to characterize the structure and variability of the ridge-normal (i.e., up/downslope) flow components, which transport mass to the crest of Argentina’s Sierras de Córdoba and contribute to convective initiation. Data are compiled for the entire CACTI period (Oct-Apr), including days with clear skies, shallow cumuli, cumulus congestus, and deep convection. To examine shared variability amongst &gt;70,000 radar scans we use (a) a principal component analysis (PCA) to isolate modes of variability in the upslope flow, and (b) composite analysis based on convective outcomes, determined from GOES16 satellite observations. These data are contextualized with observed surface sensible heat fluxes, thermodynamic profiles, and synoptic-scale analysis. Results indicate distinct thermally and mechanically forced upslope flow modes, modulated by diurnal heating and synoptic-scale variations, respectively. In some instances, there is a superposition of thermal and mechanical forcing, yielding either deeper or shallower upslope flow. The composite analyses based on satellite data show that successively deeper convective outcomes are associated with successively deeper upslope flow layers that more readily transport mass to the ridge crest in conjunction with lower lifting condensation levels, facilitating convective initiation. These results help to isolate the forcing mechanisms for orographic convection, and thus provide a foundation for parameterizing orographic convective processes in coarse resolution models.

Onshore sediment transport enhancement and evolution of bedforms: Laboratory experiments of beach ploughing

Progressive coastal retreat has been an issue exacerbated in recent years due to climate change. Sand is eroded from beaches during the winter and partially recovered during summer by slow accretion processes. The development of new working with nature techniques that produce enhanced beach accretion could help recover most of the sand lost during winter and thus reduce the impact of climate change on beaches. The presence of bedforms contribute to increasing onshore sediment transport, but few studies have been performed to quantify their effect. In this study, the evolution and effect of artificially created bedforms on onshore sediment transport were analysed in prototype-scale laboratory experiments. The tested bedforms mimicked a beach ploughing of the intertidal area, with a wavelength of 1.6 m and height of 0.25 m, corresponding to the ploughing dimensions that a tractor can perform. Two tests were performed with the same initial morphology, medium sand (D50 = 0.318 mm), sea state conditions (Hs = 0.3 m, Tp = 7 s) that produced accretion, and different water levels that represent two tidal states. The experimental flume was longitudinally split into two equal channels of 1 m wide, allowing the simultaneous simulation of a natural control geometry and a ploughed geometry, facilitating the comparison and assuring the very same sea conditions. The presence of ploughed bedforms produced two effects: (1) an acceleration of natural accretion rates reaching 40%, and (2) onshore sediment transport due to the migration of the bedforms. The acceleration of natural accretion was explained by the extra bottom roughness induced by the bedforms, which produced more wave dissipation through bottom friction and thus more accretive conditions. The ploughed height decreased exponentially as waves broke over the crest of the ridges, which almost disappeared after 2–3 h of wave action. As a result, the extra bottom roughness also decreased as time passed. Consequently, the nature-assisted beach enhancement technique of ploughing should be applied at each low tide to produce a cumulative effect. Plough bedforms migrated onshore at a rate of approximately 0.2 m/h during the first hour, mobilizing onshore up to 61 kg m−1 h−1 of sediment. Ripples appeared on the tops of the ridge crests and migrated faster onshore, contributing to the migration of the ploughed bedforms. These results demonstrated the importance of considering bedforms while studying accretion processes and the potential of ploughing as an innovative strategy of working with nature to enhance beach recovery.

Cone-beam CT evaluation of post-extraction alveolar bone changes at the maxillary incisor sites in an East Asian population: A cross-sectional study

ObjectiveUnderstanding the characteristics of alveolar bone resorption in an East Asian population after maxillary incisor extraction and providing a reference for implant treatment plans. Study designCone-beam computerized tomography (CBCT) data of 125 East Asian patients with unilateral extraction of maxillary incisors for 3 months were collected. The alveolar bone width and height in the extraction sites were measured and compared with the corresponding contralateral sites. ResultsThe differences in alveolar bone width between the extraction site and contralateral site were as follows: 4.11 mm, 2.68 mm, and 2.09 mm (3 mm, 5 mm, 7 mm apical from CEJ of the contralateral tooth). Data are expressed as the median. The horizontal resorption ratio of alveolar bone was 49.94 %, 31.5 %, and 24.46 %. The difference in alveolar bone height was 0.78 mm. The vertical resorption ratio was 7.78 %. The resorption did not differ significantly between sexes and was not significantly affected by tooth positions. ConclusionsIn the studied East Asian population, significant horizontal and vertical alveolar bone resorption occurs after natural healing of maxillary incisor extraction for 3 months. The closer to the alveolar ridge crest, the more significant the horizontal resorption, resulting in an “inverted triangle” shape residual alveolar bone.

Does Implant Placement Below the Ridge Reduce Crestal Bone Loss? A Split-Mouth Randomized Controlled Clinical Trial.

Reducing crestal bone loss (CBL) around implants allows for soft tissue stability and long-term success. The aim of the present study was to evaluate the extent of CBL in implants placed with the implant shoulder at the equi-crestal level and 2 mm below the alveolar ridge at 2, 12, 36, and 60 months. A split-mouth randomized controlled clinical trial was conducted by selecting subjects with Kennedy Class IV partial edentulism of the lower jaw. Two implants were inserted, of equal length and diameter, one equi-crestal and the other sub-crestal, in the site corresponding to the lateral incisor. Intraoral periapical radiographs with Rinn centering devices were performed at the time of implant insertion (T0), at 2 (T1), 12 (T2), 36 (T3), and 60 months (T4). Descriptive statistics and the T-test were used, setting the significance to P⩽ 0.05. Twenty-five subjects were recruited, with a mean age of 65 years (SD 9.88, range 42-82). No subject dropped out. A total of 50 implants were inserted, 25 at crestal and 25 sub-crest level. At the 60-month follow-up, no implant or prosthetic failure was recorded. An average loss of -0.81 mm was recorded in the crestal implant group (n.25; SD: 0.40; max-min: -1.6 - -0.1) while in the implants positioned below the crest the average CBL was -0.87mm (n.25; SD: 0.41; max-min: -2 - -0.2); however, the higher CBL in the sub-crestal implant group was not statistically significant (P&#61;0.65). Comparing the mean CBL values of the two groups at the various follow-ups, a greater crestal bone resorption was recorded in sub-crest implants between T0 and T1 (-0.25 vs -0.1) and between T1 and T2 (-0.39 vs -0.23), while in subsequent follow-ups a greater, statistically significant (P&#61;0.01), crestal bone loss was recorded in ridge implants between T3 and T4 (-0.05 vs -0.18). Over time, therefore, the extent of CBL seems to be reduced in implants placed below the crest, with bone retention above the implant shoulder. Ultimately, although the position of the implant shoulder relative to the crestal ridge doesn't affect the CBL, sub-crestal placement is recommended in order to reduce the risk of exposure of the rough surface of the implant.

Suspended particulate matter influence on dissolved Nd concentration and isotopic composition along GEOTRACES section GP16

The role of suspended particulate matter in the biogeochemical cycling of neodymium (Nd) in the ocean is not well understood. This study reports the measurement of dissolved Nd concentrations and isotopes (<0.2 um), and particulate Nd concentrations along the Eastern Pacific Zonal Transect (EPZT, GP16) as part of the GEOTRACES program. The western part of the EPZT cruise track is influenced by a hydrothermal plume, observed between 2200 and 2800 m, originating at the southern East Pacific Rise. This setting allows for the investigation of the role of particulate matter in Nd biogeochemical cycling and its contribution in modifying the distribution of dissolved Nd. Results show that the highest removal of dissolved Nd (∼ 21 %) was observed near the hydrothermal ridge crest, decreasing to ∼ 8 % at the westernmost station. Here, we report the partition coefficient (Kd) of each particle constituent (e.g., lithics, CaCO3, POM, Opal, Fe-phase, Mn-phase) to show that particle composition plays an important role in Nd removal alongside particle mass. Along the plume, both particulate Mn and Fe contributed to the removal of Nd, with Mn playing the dominant role in sites closest to the vent. At the western stations, below the plume, the concentration of both dissolved and particulate Nd increased with depth, with particulate Nd one to two orders of magnitude lower than measured in the dissolved phase. The increase in dissolved Nd with depth in the interval below the plume could result either from the continuing remineralization of raining particles or the influx of dissolved Nd from bottom sediments. Close to the ridge crest, where the hydrothermal Nd input is at its highest, there is a hint of local modification of dissolved εNd signature, however not large enough to affect the use of εNd as a water mass tracer.

Assessment of the correlation between supracrestal gingival tissue dimensions and other periodontal phenotypes components via the digital registration method: a cross‑sectional study in a Chinese population

BackgroundSupracrestal gingival tissue dimensions (SGTDs) has been considered to be an essential element of periodontal phenotype (PP) components. This study aimed to explore the relationship between SGTDs and other PP components by digital superposition method that integrated cone beam computed tomography (CBCT) with intraoral scanning.MethodsThis cross-sectional study was conducted at the Stomatology Hospital of Fujian Medical University. Participants were recruited based on the inclusion and exclusion criteria. The data obtained from the digital scanner (TRIOS 3, 3Shape, Denmark) and CBCT images were imported into the TRIOS software (Implant Studio, 3Shape, Denmark) for computing relevant parameters. The significant level was set at 0.05.ResultsA total of 83 participants with 498 maxillary anterior teeth were finally included. The mean values of supracrestal gingival height (SGH) and the distance from the cementoenamel junction (CEJ) to the crest of the alveolar ridge (CEJ-ABC) on the buccal site were significantly higher than palatal SGH (SGH-p) and palatal CEJ-ABC (CEJ-ABC-p). Men exhibited taller CEJ-ABC and SGH-p than women. Additionally, tooth type was significantly associated with the SGH, SGH-p and CEJ-ABC-p. Taller SGH was associated with wider crown, smaller papilla height (PH), flatter gingival margin, thicker bone thickness (BT) and gingival thickness (GT) at CEJ, the alveolar bone crest (ABC), and 2 mm apical to the ABC. Smaller SGH-p displayed thicker BT and GT at CEJ, the ABC, and 2 and 4 mm apical to the ABC. Higher CEJ-ABC showed lower interproximal bone height, smaller PH, flatter gingival margin, thinner GT and BT at CEJ, and 2 mm apical to the ABC. Smaller CEJ-ABC-p displayed thicker BT at CEJ and 2 and 4 mm apical to the ABC. On the buccal, thicker GT was correlated with thicker BT at 2 and 4 mm below the ABC.ConclusionSGTDs exhibited a correlation with other PP components, especially crown shape, gingival margin and interdental PH. The relationship between SGTDs and gingival and bone phenotypes depended on the apico-coronal level evaluated.Trial registrationThis study was approved by the Biomedical Research Ethics Committee of Stomatology Hospital of Fujian Medical University (approval no. 2023-24).

Featured Cover

The cover image is based on the Original Article The facial–coronal ridge crest alterations after single immediate implant placement and provisionalization with thin buccal plate phenotype in anterior maxilla: A radiographic case‐series study by Chun Yi DMD et al., https://doi.org/10.1111/cid.13280. image

Efficacy of Alveolar Ridge Preservation in Periodontally Compromised Molar Extraction Sites: A Systematic Review and Meta-Analysis.

To investigate the efficacy of alveolar ridge preservation (ARP) in periodontally compromised molar extraction sites. An electronic search was performed on 10th November 2023 across five databases, seeking randomised/non-randomised controlled trials (RCTs/NCTs) that included a minimum follow-up duration of four months. The RoB2 and Robins-I tools assessed the risk of bias for the included studies. Data on alveolar ridge dimensional and volumetric changes, keratinized mucosal width, and need for additional bone augmentation for implant placement were collected. Subsequently, a meta-analysis was carried out to derive the pooled estimates. Six studies were incorporated in the present review, and a total of 135 molar extraction sockets in 130 subjects were included in the meta-analysis. ARP was undertaken in 68 sites, and 67 sites healed spontaneously. The follow-up time ranged from 4 to 6 months. The meta-analysis of both RCTs and NCTs showed significant differences in mid-buccal ridge width changes at 1 mm level below ridge crest with a mean difference (MD) of 3.80 (95% CI: 1.67-5.94), mid-buccal ridge height changes (MD: 2.18; 95% CI: 1.25-3.12) and volumetric changes (MD: 263.59; 95% CI: 138.44-388.74) in favour of ARP, while the certainty of evidence is graded low to very low. Moreover, ARP appeared to reduce the need for additional sinus and bone augmentation procedures at implant placement with low certainty of evidence. Within the limitations of this study, alveolar ridge preservation in periodontally compromised extraction sites may, to some extent, preserve the ridge vertically and horizontally with reference to spontaneous healing. However, it could not eliminate the need for additional augmentation for implant placement. Further, longitudinal studies with large sample sizes and refined protocols are needed.

Numerical investigation of seismic amplification characteristics in loess ridge region of Xiji, northwest China.

The seismic effects on sloped terrain, which are of paramount importance for engineering design and earthquake risk mitigation, have always been a central focus of earthquake engineering research. In this study, generalized geometric models of loess ridges at varying heights were created, and a three-dimensional nonlinear numerical model was established using FLAC3D. Seismic ground motion time histories at different frequencies and actual earthquake ground motion records were input into the model to analyze the peak acceleration amplification effects experienced by the surface of loess ridges when subjected to SV waves. The study's outcomes reveal that seismic amplification on the slopes of loess ridges is characterized by non-linearity with respect to slope height. Instead, it exhibits rhythmic variations, with the rate of change in these rhythms increasing in correspondence with the frequency of seismic motion and the height of the slope. Under low-intensity seismic motion, a linear increase in acceleration amplification is observed at the ridge's crest concerning the height of the loess ridge. However, under high-intensity seismic motion, the relationship between amplification and slope height becomes less significant. Typically, the peak acceleration at the ridge's crest is reported to be 1.5 to 2.5 times that observed at the slope's base. The amplification effect at the ridge's crest is more pronounced in the low-frequency and high-frequency segments when compared to the mid-frequency range. Conversely, significant amplification is observed in the high-frequency range in the lower sections of the slope near the base. It is further noted that the amplification effect at the ridge's crest displays distinct behavior at different frequencies, characterized by narrow frequency bands of maximum amplification, with peak amplification factors exceeding 10 in some cases. These research findings have practical significance and provide valuable references for engineering construction and seismic risk mitigation planning in loess regions.

New perspectives in the treatment of the severe atrophic posterior maxilla: interpositional sandwich osteotomy combined with sinus floor grafting - a novel technique

Purpose: Dental implant installation in the posterior maxilla depends fundamentally on the presence of an adequate bone quantity. Tooth loss in the posterior maxilla is followed by extensive loss of the alveolar ridge and increased maxillary sinus pneumatization that often makes implant installation difficult to achieve. Maxillary sinus floor augmentation is traditionally the common surgical technique to overcome this situation. When the deficiency in the vertical dimension relates more to severe ridge resorption, crestal ridge augmentation should also be considered. Posterior maxillary sandwich osteotomy combined with sinus augmentation, using inter–positional bone graft might be a viable option to address this problem. This study describes a successful implementation of this technique to solve a severe vertical osseous ridge defect under the sinus floor. Material and Methods: A two–stage lateral wall sinus floor augmentation combined with inter–positional sandwich osteotomy followed by the insertion of dental implants with adequate length and diameter was performed. Deproteinized natural bovine bone mineral (DBBM) covered by a resorbable collagen membrane were used. Rehabilitation of this area was completed by a standard prosthetic protocol. Results: As a result of completing the above procedure favourable bone mass and form was created to enable implant placement in positions that are optimal from a prosthetic and esthetic point of view in terms of reshaping the alveolar crest and normali- zing the interocclusal distance improving the crown–implant ratio. Conclusion: This case demonstrates a step–by–step illustration of an innovative technique for overcoming a vertical ridge defect combined with increased maxillary sinus pneumatization. It can be concluded that this novel technique is recommended to meet the dimensional requirements of bone augmentation both crestal and intrasinusal in severe atrophic posterior maxilla to achieve an improved alveolar plane, equalized crown–to–implant ratios, and a more favourable gingival shape.

Astronomical Alignments from Structures Surrounding Giant Animal Effigy Mounds at El Paraiso, Peru

Abstract We previously reported astronomical alignments with the principal temple of the archaeological site of El Paraiso in coastal Peru. Here we describe a new investigation of nine small platform mounds associated with the two giant animal effigy mounds at the site. A total station map of the site permits possible astronomical alignments to be measured directly from the AutoCAD map by Pixelstick or AutoCAD. We corrected alignments for obliquity and for the apparent curvature of the sun and moon over the crest of nearby ridges. Azimuths for astronomical events were obtained from Starry Night Pro Plus 6.4.3. We found that 13 of 14 alignments were within 1° of the predicted astronomical values (and all 14 were within 1.5°). To account for these findings and those of the giant animal platform effigy mounds at the site, we propose a cosmology in the Late Preceramic period of solar and lunar alignments and the linkage of supernatural animals to dark cloud constellations. The building of these mounds was directed by astronomer priests. A shared belief in a cosmology that included a punishing force may have eased transactions by engendering trust among individuals living across river valleys and at different altitudes.