Vertical Root Research Articles

Vertical Root Distribution of Different Cover Crops Determined with the Profile Wall Method

Many benefits of cover crops such as prevention of nitrate leaching, erosion reduction, soil organic carbon enhancement and improvement of soil structure are associated with roots. However, including root characteristics as a criterion for cover crop selection requires more knowledge on their root growth dynamics. Seven cover crop species (crimson clover, winter rye, bristle oats, blue lupin, oil radish, winter turnip rape and phacelia) were grown in a two-year organically managed field experiment in Germany to screen them for root intensity and vertical root distribution. Root length density (RLD) and proportion of root length in large-sized biopores were determined before and after winter with the profile wall method. RLD and cumulative root length were analysed using a three-parameter logistic function, and a logistic dose-response function, respectively. Fibrous rooted winter rye and crimson clover showed high RLD in topsoil and had a shallow cumulative root distribution. Their RLD increased further during winter in topsoil and subsoil. The crops with the highest RLD in the subsoil were taprooted oil radish, winter turnip rape and phacelia. Bristle oat had intermediate features. Blue lupin had low RLD in topsoil and subsoil. Phacelia, oil radish, winter turnip rape and bristle oat showed the highest share of root length in biopores. These complementary root characteristics suggest that combining cover crops of different root types in intercropping may be used to enhance overall RLD for maximizing cover crop benefits.

Impacts of Underground Coal Mining on the Roots of Xeromorphic Plant: A Case Study

The ground movement induced by underground mining operation affects or even damages the roots of land plants with resultant vegetation deterioration. The adaptability of land plant to mining disturbance is species dependent. In this study, several typical xeromorphic plants growing in Shendong Coalfield, an arid and semiarid area of northwestern China, were compared in terms of root distribution and lengths. Distinct element method-based models were established to investigate the evolution of stress and deformation of topsoil during underground coal excavation, indicating that incongruous dislocations associated with tensile or shear deformation of soil blocks contribute to the negative effects on the roots of land plant. Furthermore, in the same scenario of deep-seated coal seam extraction, numerical modeling with more sophisticated topsoil blocks and plant roots visually indicated that most parts of the vertical root cracked, while pivotal parts of horizontal roots remained almost intact. Field data of vegetation communities in unexploited and exploited areas at two coal mines of Shendong Coalfield in terms of the coverage, density, and frequency, which showed a good agreement with modeling results, reveal that plants with more developed horizontal roots have stronger adaptability to mining disturbance, and should be cultivated more to become the dominant species in coal mining areas.

Occurrence of Vertical Root Fractures after Apical Surgery: A Retrospective Analysis

IntroductionVertical root fractures (VRFs) are among the most frequent causes of tooth loss, mainly of endodontically treated teeth. However, very few data is available about the occurrence of VRFs following apical surgery. MethodsPatient charts from 864 patients with 1058 teeth treated with apical surgery (September 1999 to December 2018) were retrospectively evaluated, if a VRF had occurred after surgery. The following, possibly influencing factors were analyzed: sex and age, type of treated tooth, primary versus resurgery, technique of root-end preparation, and timepoint of VRF diagnosis. Endpoints were either tooth extraction or the last follow-up. ResultsThe study cohort (55% women, 45% men) had a mean age of 52.00 ± 13.97 years (range 9–93 years). The overall rate of VRFs after apical surgery was 4% (42 of 1058 teeth). Among these 42 teeth, 33.3% were mandibular first molars and 26.2% were maxillary second premolars. The most frequently affected root was the mesial root of mandibular first molars (28.6%). With regard to the study parameters, significant differences of VRF rates were observed only for the type of tooth treated. ConclusionsA low VRF rate of 4% was observed in this study. VRFs commonly occurred in maxillary premolars and mandibular molars, with the mesial root of mandibular first molars affected most frequently. This is in line with previous reports about VRFs in endodontically treated teeth without additional apical surgery.

The Buffalo study: Outcome and associated predictors in endodontic microsurgery- a cohort study.

To (i) evaluate and compare the outcome of endodontic microsurgery (EMS) using periapical radiographs (PAs) and cone-beam computed tomography (CBCT) scans; (ii) identify prognostic factors affecting the outcome; and (iii) correlate the effect of guided tissue regeneration (GTR) on the pattern of apical bone remodelling. Eighty-two patients (101 teeth) who received EMS were included and followed-up using clinical and radiographic examinations (PAs and CBCT scans). Two calibrated endodontists evaluated the radiographic healing (favourable or unfavourable) by assessing PAs and CBCT. The success (favourable radiographic outcome with no clinical symptoms) and survival rates (tooth retention without clinical symptoms) were calculated, and the cause of failure (diseased or fractured) was identified. Pre-treatment (age, sex, tooth type, position, sequence of treatment, quality of root canal before surgery, presence/absence of through-and-through lesion, presence/absence apico-marginal defect) and treatment (presence/absence of errors during surgery, type of error (major or minor), retro-preparation depth, presence/absence of an isthmus, retro-filling material used, presence/absence bone graft material and/or resorbable membrane) factors were recorded. Data were analysed statistically to determine the inter-observer, intra-observer and inter-radiographic agreements. Univariate, bivariate and logistic regression analysis were used to determine prognostic factors affecting the outcome and the effect of GTR on the pattern of apical bone remodelling. The significance level was set at 5%. Sixty-eight patients (83 teeth) presented for outcome evaluation (recall rate: 84%). The survival rate was 93%. The success rate was 88% using PA and 86% using CBCT when vertical root fracture (VRF) cases were included and 94% using PAs, and 91% using CBCT when VRF cases were excluded. The intra- and inter-observer agreements were substantial using CBCT, slight to a fair agreement using PA (P<0.001), and slight to moderate for inter-radiographic agreement. The occurence of a major procedural error during surgery was the only negative predictor for the outcome of EMS (P=0.013). GTR did not affect the success rate or the type of healing when assessed using PA but it affected the type of healing on CBCT scans (complete vs incomplete healing) and the pattern of cortical plate remodelling (P<0.001). The success and survival rate of endodontic microsurgery was very high, and the occurrence of a major procedural error during surgery was the only factor affecting the outcome. GTR did not improve the outcome, but did affect the quality of apical bone remodelling following EMS.

Assessment of outcome of root canal treatment performed on an incomplete fracture non vital permanent first molar

Tooth infraction is usually of three types 1) confined to enamel (craze lines) and usually do not require treatment 2) related to cuspal fracture that typically do not involve pulp 3) more centrally located that do involve the pulp. Vertical root fracture (VRF) are longitudinal fracture that originate in root of teeth in contrast to tooth infraction that originate in the crown. VRF occurs usually in endodontically treated teeth. This case report represent tooth infraction originating in the tooth crown on the distal marginal ridge and propagating into the pulp chamber and DEJ(dentino enamel junction). Root canal treatment was performed and in a 7 month follow up period, there was a remarkable improvement in the supporting periodontal structures with bone deposition/remodelling in the crestal and furcation area/region and patient was quite satisfied with the treatment outcome.

Clinical decision‐making and importance of the AAE/AAOMR position statement for CBCT examination in endodontic cases

To compare conventional radiographic and cone beam computed tomography (CBCT) findings with reference to the American Association of Endodontics and American Academy of Oral and Maxillofacial Radiology (AAE/AAOMR) joint position statement and to determine the effect of the CBCT on the initial diagnoses and treatment plans in a single-centre Postgraduate Endodontic Programme. The clinical CBCT scans of patients, treated at the Endodontic Department of the University of British Columbia, were reviewed for CBCT referrals by comparing them with corresponding radiographs. The features considered were periapical lesions, missed/extra canals, root fractures, complex anatomy, calcified canals and root resorption of tooth/teeth in question. Reasons for the CBCT prescriptions were assigned to 3 groups: to formulate the primary diagnosis, to confirm the diagnosis achieved by clinical examination and conventional radiographs, and to assist in treatment planning. Variables were compared statistically using chi-square and McNemar tests. A total of 128 CBCT examinations were performed on 110 patients. No CBCT examination was performed more than once on the same tooth. Overall, 76% of CBCT examinations were performed on previously root filled teeth. CBCT images revealed a significantly higher incidence of periapical lesions (P=0.002), missed canals (P<0.001), vertical root fractures (P=0.004) and complex anatomy (P=0.008) than periapical radiographs. CBCT was prescribed most frequently to assist surgical treatment planning (62%) rather than for generating a diagnosis (9%) or confirming diagnoses (29%). Both the diagnosis (P=0.001) and the treatment plan (P=0.005) initially made by examining periapical radiographs were altered significantly by the subsequent CBCT examination by revealing information such as new periapical lesions, missed canals or involvement of buccal or lingual cortical bone. CBCT examinations were prescribed mainly to assist treatment planning rather than for diagnosis. The majority of CBCT examinations were performed on previously root filled teeth. The additional information obtained from CBCT scans resulted in the alteration of the initial diagnoses as well as subsequent treatment plans in 59 out of 128 cases.

SPLITTING FOR SURVIVAL – A CASE REPORT

Vertical root fractures of endodontically treated teeth are an exasperating complication that often leads to extraction of the tooth. Early detection and management of vertical root fractures, remain a vexing issue that has caused endless anguish for both the patient as well as the dental practitioner. Bicuspidization is a surgical procedure wherein the mesial and distal roots of primarily the mandibular molars are separated with their respective crown segments. This in turn helps the patient maintain effective oral hygiene by using an interdental brush, as it eliminates the presence of a furcation. This article elucidates the treatment procedure of a mandibular molar by biscuspidization.

The mechanism of the plant roots' soil-reinforcement based on generalized equivalent confining pressure.

BackgroundTo quantitatively evaluate the contribution of plant roots to soil shear strength, the generalized equivalent confining pressure (GECP), which is the difference in confining pressure between the reinforced and un-reinforced soil specimens at the same shear strength, was proposed and considered in terms of the function of plant roots in soil reinforcement.MethodsIn this paper, silt loam soil was selected as the test soil, and the roots of Indigofera amblyantha were chosen as the reinforcing material. Different drainage conditions (consolidation drained (CD), consolidation undrained (CU), and unconsolidated undrained (UU)) were used to analyse the influences of different root distribution patterns (horizontal root (HR), vertical root (VR), and complex root (CR)) and root contents (0.25%, 0.50%, and 0.75%) on the shear strength of soil-root composites.ResultsThe cohesion (c) values of the soil-root composites varied under different drainage conditions and root contents, while the internal friction angle (φ ) values remain basically stable under different drainage conditions. Under the same root content and drainage conditions, the shear strength indexes ranked in order of lower to higher were HR, VR and CR. The GECP of the soil-root composites with a 0.75% root content was 1.5–2.0 times that with a 0.50% root content and more than 5 times that with a 0.25% root content under the CD and CU conditions. The GECP in reinforced soil followed the sequence of CD > CU > UU. The GECP of the plant roots increased as confining pressure increased under CD and CU conditions while showed a complex change to the confining pressure under the UU condition.ConclusionIt was concluded that the evaluation of plant root reinforcing soil based on GECP can be used to measure effectively the influences of roots on soil under different drainage conditions and root distribution patterns.

Positive tree diversity effect on fine root biomass: via density dependence rather than spatial root partitioning

The importance of species richness to ecosystem functioning and services is a central tenet of biological conservation. However, most of our theory and mechanistic understanding is based on diversity found aboveground. Our study sought to better understand the relationship between diversity and belowground function by studying root biomass across a plant diversity gradient. We collected soil cores from 91 plots with between 1 and 12 aboveground tree species in three natural secondary forests to measure fine root (≤ 2 mm in diameter) biomass. Molecular methods were used to identify the tree species of fine roots and to estimate fine root biomass for each species. This study tested whether the spatial root partitioning (species differ by belowground territory) and symmetric growth (the capacity to colonize nutrient‐rich hotspots) underpin the relationship between aboveground species richness and fine root biomass. All species preferred to grow in nutrient‐rich areas and symmetric growth could explain the positive relationship between aboveground species richness and fine root biomass. However, symmetric growth only appeared in the nutrient‐rich upper soil layer (0–10 cm). Structural equation modelling indicated that aboveground species richness and stand density significantly affected fine root biomass. Specifically, fine root biomass depended on the interaction between aboveground species richness and stand density, with fine root biomass increasing with species richness at lower stand density, but not at higher stand density. Overall, evidence for spatial (i.e. vertical) root partitioning was inconsistent; assumingly any roots growing into deeper unexplored soil layers were not sufficient contributors to the positive diversity–function relationship. Alternatively, density‐dependent biotic interactions affecting tree recruitment are an important driver affecting productivity in diverse subtropical forests but the usual root distribution patterns in line with the spatial root partitioning hypothesis are unrealistic in contexts where soil nutrients are heterogeneously distributed.

Root depth development in tropical perennial forage grasses is related to root angle, root diameter and leaf area

Tropical perennial grasses that can rapidly establish deep roots have a greater potential to survive soil surface drying sooner after establishment. This research aimed to identify species that establish deep roots quickly and to investigate the mechanisms that drove rapid vertical root development. Perennial grass species Brachiaria brizantha, Brachiaria decumbens, Brachiaria humidicola, Brachiaria hybrid Mulato II, Brachiaria mosambicensis, Panicum maximum, Setaria sphacelata and Cynodon dactylon were grown in rhizotrons that facilitated measurement of the rate of root depth development, the rate of root length development, photosynthesis and morphological traits. Principal component analysis was employed to separate grass species according to functional traits of vertical root development and their growth strategies. P. maximum established roots more rapidly to 50 cm depth than the other species examined and accumulated biomass and leaf area faster. It was differentiated from other species by a greater percentage of fine root length (< 0.2 mm diameter), a higher photosynthetic rate and ratio of root length to leaf area according to the principal component analysis. The growing degree days required for root establishment to 50 cm depth was negatively correlated with the percentage of fine root length, and positively correlated with root angle. The exponential rate of root depth development per growing degree day increased with average root diameter in B. humidicola and B. hybrid Mulato II, indicating a conservative growth strategy. Rapid vertical root development with a narrow root angle, higher photosynthetic rate, higher ratio of root length to leaf area and higher percentage of fine roots were apparent mechanisms that enabled P. maximum to establish deep roots faster than other species. P. maximum appears to be better able to avoid water stress during surface drying by accessing profile moisture. Greater average root diameter and percentage of root length with higher diameters was related to increased exponential rate of root depth development and wide root angle.

Vertical fine-root distributions in five subalpine forest types shifts with soil properties across environmental gradients

Vertical fine-root distribution determines the potential for acquisition of resources throughout soil profiles; yet, variation among forest types and changes in vertical distribution with environments are poorly understood. We examined vertical root distributions of different forest communities to determine how belowground strategies shift across different forest types and along edaphic gradients. Specific root length and diameter of fine roots as well as fine-root biomass, length and area densities were measured in sequential soil layers at 10 cm depth increments across 118 forest plots representing five subalpine forest types. Evergreen forest types, including evergreen oaks, were more deeply rooted than birch forests. Differences in rooting depth were due to the dominant tree species identity, not to variations in shrub or herbaceous components. Within forest types, soil nutrients and physical properties contributed to shifts rooting depth but not root morphology. Vertical distributions of fine roots represent critical inputs of plant carbon into soils as well as different capacities for the acquisition of soil resources. Our findings identify consistent patterns of rooting distributions among forest types that may be predictable based on more easily measured root and soil properties and can improve efforts to model rooting depth profiles in forest communities.

Association between longitudinal tooth fractures and visual detection methods in diagnosis

ObjectivesThis study investigated the distribution of longitudinal tooth fractures (LTFs) according to the patient’s age and analyzed the association between visual detection methods and the types of LTFs. MethodsPatients with symptomatic teeth with LTFs were examined at the department of conservative dentistry in a dental hospital from September 1, 2009 to March 31, 2014. Naked eye examination, staining with a dye, operating microscopy, transillunimation, and periapical radiography were used to identify the fracture lines. Diagnostic surgery was performed to visualize the fracture line in some cases with vertical root fractures. The final diagnosis was based on the American Association of Endodontists (AAE) classification: cracked tooth, fractured cusp, split tooth, and vertical root facture. The probability density function for each type of LTF was calculated to assess the risks of LTF development according to age. The association between the detection methods and types of LTFs was identified using the association plot. ResultsA total of 245 teeth with LTFs were enrolled. Overall, 71.8% of LTFs was observed in patients aged 40–69 years, and 65.7% of LTFs were diagnosed as cracked teeth. The mean age in patients with cracked teeth was 49.3 years, while the mean age in patients with fractured cusps was 59.1 years. A significant association was observed between the detection method and type of LTF (p < 0.001). ConclusionsCracked tooth was the most common type of LTF. The probability of occurrence of cracked teeth peaked in patients aged approximately 50 years, while the probability of occurrence of fractured cusps peaked in patients aged approximately 60 years. Cracked teeth were detected most often using transillumination. Clinical significanceLTFs occurred mostly in patients aged 40 years and older. Transillumination is useful for the diagnosis of cracked teeth.

Do the tube current and metal artifact reduction influence the diagnosis of vertical root fracture in a tooth positioned in the vicinity of a zirconium implant? A CBCT study.

To evaluate the influence of the tube current and metal artifact reduction (MAR) tool on the diagnosis of vertical root fractures (VRF) in a tooth adjacent to a zirconium implant, in cone-beam computed tomography (CBCT) images. Thirty single-rooted teeth (15 with VRF and 15 control group) were individually positioned in a mandible, and scanned with the OP300 CBCT unit. Images were acquired using a standardized protocol: 5 × 5 cm field of view, 0.08-mm voxel size, and 90 kVp. Each tooth was scanned with and without a zirconium implant in its vicinity, using different tube currents (4 mA, 8 mA, and 10 mA) and conditions of MAR (enabled × disabled). Diagnostic values were calculated for each protocol, and compared by multi-way analysis of variance. The ROC curve and sensitivity values did not differ significantly among the tube currents, regardless of the presence of the implant and MAR condition (p > 0.05). There were also no significant differences among the tube currents for the specificity values (p > 0.05); however, the specificity differed significantly between the "with implant" and "without implant" conditions, within the same MAR condition and tube current (p < 0.05). Specificity was significantly lower when the implant was present (p < 0.05). The presence of a zirconium implant impairs the diagnosis of VRF in teeth adjacent to the artifact-generator material. Neither the tube current nor the MAR tool is effective in improving this diagnostic task. Therefore, in this clinical scenario, the use of the lowest tube current (4 mA), without MAR activation, is recommended. Considering that the tube current is one of the main factors that influence the radiation dose and image quality in CBCT, and that metal artifacts negatively influence the diagnosis of VRF in areas adjacent to the artifact-generator material, it is important to evaluate the effect of this energetic parameter in the diagnosis of VRF in teeth adjacent to zirconium implants.

Influence of Metal Post in Adjacent Teeth in the Detection of Vertical Root Fracture Using Cone-beam Computed Tomography with Different Acquisition Parameters

IntroductionThe aim of the present study was to evaluate the detection of vertical root fracture (VRF) in the presence of adjacent teeth restored with a metal post and the influence of acquisition parameters (tube current and metal artifact reduction [MAR] algorithm) on this diagnostic task. MethodsCone-beam computed tomographic images of 10 single-rooted teeth were acquired before and after the simulation of VRF. The acquisitions were set up to simulate different conditions regarding the presence of adjacent teeth restored with a metal post (control, 1 adjacent tooth, and both adjacent teeth), different tube currents (4, 8, and 10 mA), and the use of MAR (without MAR and with MAR). Images were assessed by 5 oral and maxillofacial radiologists using a 5-point scale for the presence of VRF. Diagnostic values were calculated and compared by 2-way analysis of variance (significance level of 5%). ResultsThe area under the receiver operating characteristic curve (Az) values for VRF detection were affected by the presence of adjacent teeth and the variation of milliamperes. For 4 mA, when both restored teeth were present, Az values were significantly lower than the control group (P ≤ .05). In the presence of both restored teeth, 8 mA presented significantly higher Az values compared with 4 mA (P ≤ .05). ConclusionsThe presence of both adjacent teeth restored with a metal post impairs VRF detection; however, an increase in tube current up to 8 mA may aid in this diagnostic task. Moreover, the MAR tool does not seem to be efficient in those cases.

Variability of water supply affected shoot biomass and root depth distribution of four temperate grassland species in monocultures and mixtures

AbstractAimsResearch on the effects of extreme rainfall events on ecosystem function has primarily focussed on drought or flooding events, which usually include changes to mean or total rainfall, annually or over a season. However, less is known about the effects of increased rainfall variability without change to mean or total amounts. We investigated the effects of increased variation of water supply on shoot and root biomass as well as the distribution of root biomass of four grassland plant species, grown in monoculture and mixture communities.MethodsPerennial ryegrass (Lolium perenne L., shallow-rooting grass), chicory (Cichorium intybus L., deep-rooting forb), white clover (Trifolium repens L., shallow-rooting legume) and red clover (Trifolium pratense L., deep-rooting legume) were established in mesocosms. Four plants of the same species were grown in monoculture communities and one of each species grown in four-species communities. Water supply was manipulated such that; compared with a baseline level with low variation in water supply, there was a treatment with medium variation (±40%) and another with high variation (±80%). Shoot and root biomass were measured, and vertical root distribution models fitted.Important FindingsCompared with the low variation treatment, shoot biomass was significantly reduced under high variation for white clover, red clover and four-species communities. Under all conditions, four-species communities produced more shoot and root biomass than predicted by species performance in monoculture (overyielding). Under increased water variation, chicory monocultures allocated a higher proportion of root biomass to deeper soil layers while the total root biomass of white clover monocultures was significantly reduced. These results indicate that increased variability of water supply can negatively affect the shoot and root biomass production of single and multi-species grasslands. There is a need for further investigation of water variation effects on the functioning of multi-species grassland systems at field scale.

Affordable and robust phenotyping framework to analyse root system architecture of soil-grown plants.

The phenotypic analysis of root system growth is important to inform efforts to enhance plant resource acquisition from soils; however, root phenotyping remains challenging because of the opacity of soil, requiring systems that facilitate root system visibility and image acquisition. Previously reported systems require costly or bespoke materials not available in most countries, where breeders need tools to select varieties best adapted to local soils and field conditions. Here, we report an affordable soil-based growth (rhizobox) and imaging system to phenotype root development in glasshouses or shelters. All components of the system are made from locally available commodity components, facilitating the adoption of this affordable technology in low-income countries. The rhizobox is large enough (approximately 6000cm2 of visible soil) to avoid restricting vertical root system growth for most if not all of the life cycle, yet light enough (approximately 21kg when filled with soil) for routine handling. Support structures and an imaging station, with five cameras covering the whole soil surface, complement the rhizoboxes. Images are acquired via the Phenotiki sensor interface, collected, stitched and analysed. Root system architecture (RSA) parameters are quantified without intervention. The RSAs of a dicot species (Cicer arietinum, chickpea) and a monocot species (Hordeum vulgare, barley), exhibiting contrasting root systems, were analysed. Insights into root system dynamics during vegetative and reproductive stages of the chickpea life cycle were obtained. This affordable system is relevant for efforts in Ethiopia and other low- and middle-income countries to enhance crop yields and climate resilience sustainably.

Applying synthetic radiography to intraoral tomosynthesis: a step towards achieving 3D imaging in the dental clinic.

A practical approach to three-dimensional (3D) intraoral imaging would have many potential applications in clinical dentistry. Stationary intraoral tomosynthesis (sIOT) is an experimental 3D imaging technology that holds promise. The purpose of this study was to explore synthetic radiography as a tool to improve the clinical utility of the images generated by an sIOT scan. Extracted tooth specimens containing either caries adjacent to restorations (CAR) or vertical root fractures (VRF) were imaged by sIOT and standard dental radiography devices. Qualitative assessments were used to compare the conspicuity of these pathologies in the standard radiographs and in a set of multi-view synthetic radiographs generated from the information collected by sIOT. The sIOT-based synthetic 2D radiographs contained less artefact than the image slices in the reconstructed 3D stack, which is the conventional approach to displaying information from a tomosynthesis scan. As a single sIOT scan can be used to generate synthetic radiographs from multiple viewing angles, the interproximal space was less likely to be obscured in the synthetic images compared to the standard radiograph. Additionally, the multi-view synthetic radiographs can potentially improve the display of CAR and VRFs as compared to a single standard radiograph. This preliminary experience combining synthetic radiography and sIOT in extracted tooth models is encouraging and supports the ongoing study of this promising approach to 3D intraoral imaging with many potential applications.

Quantitative effects of solar radiation on maize lodging resistance mechanical properties

Abstract Lodging adversely affects maize (Zea mays L.) yields and quality, especially under low sunlight conditions. Here, we investigated the effects of different levels of solar radiation on maize lodging. To study the quantitative effects of different solar radiation on the lodging resistant mechanism of maize stalks, we chose two maize cultivars, Xianyu 335 (XY335) and Zhengdan 958 (ZD958), and grew them in two regions that receive the most abundant solar radiation in Xinjiang and Ningxia China in 2018 and 2019. Maize plants were exposed to different shade levels (15 % (S1), 30 % (S2), 50 % (S3), and natural light as the control (CK)) and different planting densities (4.5 × 104 (D1), 7.5 × 104 (D2), 9 × 104 (D3), 10.5 × 104 (D4), and 12 × 104 (D5) plants ha− 1) to create different solar radiation conditions. The results showed that lodging percentage was significantly negatively correlated with the stalk bending strength (SBS), rind penetration strength (RPS), vertical root pulling resistance (VRPR), dry weight per unit length (DWUL), the cellulose and lignin content and grain yield which significantly decreased with decreasing total intercepted photosynthetically active radiation (TIPAR). Quantitative analysis showed that for every 1 MJ m- 2 reduction in TIPAR, the SBS and RPS decreased by 0.0667 N and 0.075 N, DWUL and the content of cellulose and lignin of maize stalk significantly decreased with decreasing TIPAR, by 0.88 mg cm− 1, 0.3 mg g- 1 and 0.06 mg g− 1, respectively. Lodging percentage was significantly negatively correlated with TIPAR, the lodging percentage increased by 0.17 % with a decrease in TIPAR of 1 MJ m- 2. Comparison of cultivars revealed that the rate of decrease in SBS, RPS, VRPR, DWUL and the cellulose and lignin content were greater for XY335 than for ZD958, indicating that the stalk strength of XY335 was more sensitive than ZD958 to decreasing levels of TIPAR. However, SBS, RPS, DWUL and the cellulose and lignin content of XY335 were higher than ZD938 and the lodging percentage of XY335 was lower than ZD958 which meant that XY335 had a stronger stalk strength to resistance to lodging. This is important for understanding lodging resistance and developing cultivars suited to different solar radiation conditions in different regions, as well as to changing solar radiation conditions induced by global climate change.

Dentin thickness as a risk factor for vertical root fracture in endodontically treated teeth: a case-control study.

This study evaluated factors associated with vertical root fracture in endodontically treated teeth, using a cone-beam computed tomography (CBCT) image database. The sample for this case-control study consisted of 81 CBCT scans of teeth with vertical root fracture (VRF) and 81 CBCT scans of non-fractured teeth, matched by age, sex, and tooth position. The analyzed variables included dentin thickness, an intraradicular post, an adjacent implant, and a missing adjacent tooth. Student's t test test was used to compare the quantitative variables. The chi-square test was used to compare the categorical variables. Logistic regression was performed to evaluate the association between the presence of VRF and the independent factors assessed. The mean dentin thickness of fractured teeth was 1.3mm, whereas that of non-fractured ones was 1.5mm (p < 0.001). There was no difference between the fractured and non-fractured groups, regarding implant frequency or missing adjacent tooth (p > 0.05). There were a significantly larger number of teeth with posts in the fractured versus non-fractured group (p = 0.007). However, dentin thickness ≤ 1.3mm was the only factor associated with VRF in the multiple regression model (OR = 3.60, 95%CI = 1.76-7.37). Dentin thickness may influence the development of VRF. Dentin thickness ≤ 1.3mm is associated with a greater likelihood of fracture than ≥ 1.4mm. This study suggests there may be a minimum amount of safe dentin thickness that should be preserved after endodontic instrumentation.

Analysis of Factors Causing Extraction of Endodontically Treated Teeth-A Retroprospective Study

Aim: To study and analyze the various reasons for extraction of endodontically treated teeth. Material and Method: 150 Endodontically treated teeth were reviewed, and the following reasons were recorded: patient’s age, gender, type of tooth; presence and type of coronal restoration; motive of consultation; reasons for extraction. Results: Pain was the primary reason for consultation .Mandibular first molar was the most common tooth involved followed by maxillary first molars. coronal failure where the main reason for extraction of endodontically treated teeth, this was due to neglegance in replacing permanent restoration where only 16% of the cases had either full veneer crown or post and core, followed by periodontal disease, vertical root fracture and non restorable caries. Conclusion: A good coronal restoration is required for a successful long term outcomes.