Conical Crown Research Articles

Measurement and analysis of the crown conical degree of maxillary incisors in patients with congenital tooth agenesis caused by different gene mutations

Objective: To measure the crown conical degree of the remaining maxillary incisors in patients with congenital tooth agenesis, and to analyze the influence of different gene mutations on the crown conical degree of patients. Methods: Whole exome sequencing was performed on 85 patients with congenital tooth agenesis (50 males, 35 females, median age 19 years old) who visited the Department of Prosthodontics, Peking University School and Hospital of Stomatology from January 2019 to January 2023. The pathogenic gene was identified. The width of the crowns of the maxillary central and lateral incisors at the incisal 1/3 and gingival 1/3 were measured on the panoramic radiograph, and the ratio was defined as the crown conical degree. The smaller the ratio is, the more likely is the crown to be peg shaped teeth. The control group was matched by age and gender with 85 other patients with intact maxillary permanent incisors who were treated in the Department of Prosthodontics, Peking University School and Hospital of Stomatology from January 2019 to January 2023. The conical degree of the tooth agenesis group was compared with the control group by t-test, and the differences in the crown conical degree in different gene mutation groups were compared using one-way analysis of variance, and the multiple comparisons among gene groups were carried out using the LSD method. Results: Among the 85 tooth agenesis patients, the numbers of patients in each gene mutation group were 20 in ectodysplasin A (EDA) group, 8 in ectodysplasin A receptor (EDAR) group, 15 in wingless-type MMTV integration site family, member 10A (WNT10A) group, 16 in paired box 9 (PAX9) group, 10 in Msh homeobox 1 (MSX1) group, 10 in low-density Lipoprotein receptor related protein 6 (LRP6) group, and 6 in bone morphogenetic protein4 (BMP4) group. The number of missing teeth were 1-27, median number 15 among the tooth agenesis patients. There was no significant difference in the conical degree between the left and right homonymous teeth in the congenital tooth agenesis group and the control group (P>0.05). The crown conical degree of maxillary central incisor and lateral incisor in the congenital missing teeth group (0.95±0.24, 0.90±0.22) was significantly smaller than that in the control group (1.12±0.09, 1.13±0.09) (t=-8.50, P<0.001; t=-11.47, P<0.001). In WNT10A mutants, the conical degree of lateral incisors (0.89±0.18) was less than that of central incisors (1.07±0.15)(t=3.68, P<0.001). The conical degree of central incisors and lateral incisors (0.70±0.23, 0.57±0.15) of EDA mutants was significantly lower than that in patients with other gene mutations (P>0.05). Conclusions: Compared with the normal control group, the remaining maxillary central and lateral incisors of the seven gene mutation groups of patients with congenital tooth agenesis all had different degrees of conical crown. Among them, the crown conical degree of maxillary central and lateral incisors of the EDA mutation was the most severe, and the WNT10A mutation affected the maxillary lateral incisors more specifically.

Retentive force of a conical crown with CAD/CAM-fabricated PEEK and zirconia secondary crowns on titanium implant abutments.

This study aimed to evaluate the retentive force of polyetheretherketone (PEEK) and zirconia secondary crowns on ready-made titanium implant abutments (with height, diameter, and taper as 5.5 mm, 4.5 mm, and 6°, respectively) as the primary crown. PEEK, zirconia, and titanium secondary crowns were fabricated using a CAD/CAM system. Insertion and removal tests of secondary crowns on the primary crown were conducted for 2,000 cycles. The initial retentive forces recorded at the 100th cycle for PEEK, zirconia, and titanium were 13.0±7.9, 2.9±2.6, and 27.6±1.7 N, respectively. The retentive forces of PEEK and zirconia showed no significant difference among all cycles. However, the retentive force of the titanium used as a control decreased (20.3±2.8 N) significantly at the 2,000th cycle. Although the retentive force of PEEK was lower than that of titanium, it was within the range that can provide a suitable retentive force of 5 N for removable dental prostheses.

New evidence of the architecture and affinity of fossil trees from the Jurassic Purbeck Forest of southern England

ABSTRACT We document the habit and affinity of the most complete Mesozoic Era tree to be excavated in the UK. The fossil was found in situ in a palaeosol of the Upper Jurassic Purbeck Group of southern England (Tithonian: ca. 150–145 million years). It comprises over 100 permineralized (silicified) pieces that represent a rooted stump and fallen trunk, together weighing more than two tonnes. This exceptional specimen was excavated in a manner that retained the original associations among its parts, providing a unique insight into the overall habit and mode of growth. A laser scanning approach was used to facilitate the investigation, producing the largest 3D reconstruction of a plant fossil. Anatomical details reveal that the wood belongs to the fossil-genus Agathoxylon. Despite an estimated growth age of more than 200 years, the tree was of modest size, not greatly exceeding 12 m in height. The main trunk bifurcated, developing into a decurrent, spreading crown. Its habit differed significantly from most modern arborescent conifers, which have pole-like central trunks and narrow, conical crowns, and from known growth forms in the Cheirolepidiaceae, an important extinct group of Mesozoic conifers. These findings extend our knowledge of the growth architecture of Jurassic conifers, which were prominent and diverse elements of seasonally arid, low to mid-latitude coastal communities during the Late Mesozoic.

Treatment of reduced interocclusal space with a cone crown telescopic denture after increasing the vertical dimension of occlusion: A case report

Treatment of reduced interocclusal space with a cone crown telescopic denture after increasing the vertical dimension of occlusion: A case report

First Record of Alternaria alternata causing necrosis of Thuja (Thuja occidentalis) in Kazakhstan.

Thuja is one of the ornamental plants used for landscaping parks and health resorts. The plant is distinguished by a pyramidal and conical crown shape and the presence of many thin branches with scale-shaped needles, green all year round. In addition, this plant has a number of antimicrobial properties, which affects the popularity of the plant in landscaping the health resort territory (Bakht et al. 2020, Chindyaeva et al. 2020). In January 2020, symptomatic Thuja plants were observed in Southern Kazakhstan. Symptoms included distortion of the crown. External examination of the trees revelaed the presence of white fluffy mycelium on Thuja branches. The branches acquired a yellow color with a necrotic lesion developing below the affected area. Samples of infected branches from different Thuja trees (n = 13) were collected. The infected branches were cut into small pieces (5 × 5 mm), washed in 70% ethanol for 30 min, and then rinsed three times with sterile distilled water. Later, these pieces were placed on Sabouraud's medium (Laboratorios Conda S.A., Spain) and incubated at 28°C for 7 days. Yellow-green colonies grew from the pieces of wood. The colonies had a light gray-whitish aerial mycelium. Conidia (n = 35) were pale to dark brown in color, irregular and ellipsoid to ovoid conical in shape. The size of the conidia varied from 5 to 25 µm × 6 to 12 µm (n = 40) with longitudinal and transverse septations. These morphological characters were previously described and corresponded to the Alternaria alternata (Simmons et al. 2007). Genomic DNA was extracted from mycelium using the liquid nitrogen and phenol-chloroform extraction method (Butler 2012). A 568 bp product of the Alt a1 gene and 472 bp product of the calmodulin protein-coding gene was amplified using following primer pairs Alt-for/Alt-rev (Hong et al. 2005) and CALDF1/CALDR1, respectively (Lawrence et al. 2013) (Integrated DNA Technologies, Inc., Coralville, IA, USA). The PCR reaction was done in a SimpliAmp thermal cycler (Applied biosystems, Waltham, MA, USA) under the following conditions: initial denaturation at 94 °C for 1 min, 35 cycles at 94°C for 30 s to denature, 57°C for 1 min for annealing, and 72°C for 1 min for extension. A final extension step at 72°C for 10 min was also included. The sequencing was done using BigDye® Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems) and the sequence was deposited in GenBank with accession no. OL542696 calmodulin). These sequences were compared with other sequences in the GenBank by using the BLAST analysis (MZ222274.1 and MN473132.1). The phylogenetic analysis was carried out with MEGA 6 software (The Pennsylvania State University, University Park, PA, USA). To confirm the pathogenicity, 10 thuja branches from healthy trees from another area without visible pathologies were inoculated with a suspension of conidia (100 conidia/ml; obtained from 2-week-old cultures). Control samples were inoculated with sterile distilled water. The inoculated branches were placed in sterile plastic containers to maintain high humidity and incubated for 10 days at 28°C. After 7 days, irregular shaped lesions and fungal growth was observed at the site of inoculation. The affected area gradually increased in size with simioar symptomatology to that described above. Re-isolation of the pathogen and identification based on morphological features and sequencing confirmed the presence of the A. alternata pathogen. To our knowledge, this is the first report of A. alternata causing branches of thuja in Kazakhstan. Thuja is a rare plant species for this region; the cost and care are expensive. This case will allow timely diagnosis of the disease caused by Alternaria spp. in the future. It is necessary to develop preventive measures and a protocol for the treatment of thuja from a fungal infection. Bakht, J., 2020. Antibacterial activity of the crude extracts from medicinally important Thuja occidentalis. Pak J Pharm Sci. 33(2): 627-630. PMID: 32276908. Butler, J.M., 2012. Chapter 2 - DNA extraction methods. pp. 29-47 in Butler JM (Ed) Advanced topics in forensic DNA typing: Methodology. San Diego, Academic Press. doi: 10.1016/C2011-0-04189-3. Chindyaeva., L.N., et al. 2020. Comparative assessment of the phytoncidity of woody plants in the selection of species for landscaping: the possibility of use in sanatorium-and-spa practice. Vopr Kurortol Fizioter Lech Fiz Kult. 97(4): 44-51. Russian. doi: 10.17116/kurort20209704144. Hong, S.G. et al. 2005. Alt a1 allergen homologs from Alternaria and related taxa: analysis of phylogenetic content and secondary structure. Fungal Genet Biol 42:119-129. doi:10.1016/j.fgb.2004.10.009 Lawrence, D.P. et al. 2013. The sections of Alternaria: formalizing species-group concepts. Mycologia 105: 530-546. DOI: 10.3852/12-249. Simmons, E. G., 2007. Alternaria: An Identification Manual. CBS, Fungal Biodiversity Center, Utrecht, Netherlands.

Experimental investigation on the erosion-deposition characteristics around isolated plants of different shapes in a wind tunnel

• Plant shape has an important effect on the patterns of erosion and deposition. • The erosion and deposition areas around plant usually increase with blowing time. • Tree model has a larger erosion area than slender plant under similar frontal area. • Tree with short trunk and dense crown is better for sparse plant erosion control. Accurate description of the characteristics of erosion and deposition around single model plants of different shapes is important to evaluate the protective role of plants in wind erosion control. The variation of bed topography with time was measured in a wind tunnel for two flexible models and two rigid tree-like models. The bed surface height close to the plant decreases forming a deep well, while in the lee, a deposition area generally appears whose shape is affected by plant type. The local wind erosion rate on both sides usually decreases with time, and the deposition area in the lee with the local erosion rate less than zero gradually moves downwind with time while disappears for the tree-like plant model with a long trunk and a large crown. Under similar frontal areas of plants, both the erosion and deposition areas around the tree-like plant with a short trunk and conical crown, and the flexible plant with a large upper part and a small lower part are generally larger than that around the slender flexible plant. The rigid tree-like plant with a short trunk and a dense conical crown is better for erosion control due to the smallest net erosion rate and the erosion area similar to the deposition area, while the other plant models have larger net erosion rate and much larger erosion area.

Upgrading removable denture design by using strategic implants: A case report

Inserting a dental implant in a strategic position under a removable partial denture (RPD) can upgrade the RPD design by changing a mainly tissue-supported RPD to an implant-tissue-supported RPD or an implant-tooth-tissue-supported RPD with better retention, support, and stability. Case presentationThe patient (female, 77-year-old) was unsatisfied with her maxillary and mandibular clasp-retained removable dentures (RDs). Medical, social, and systemic health evaluations revealed that the patient was healthy. Dental history, intraoral and extraoral examinations, functional screening, and esthetic analyses revealed that the patient had a reduced vertical dimension, resulting in pseudo-class III malocclusion and angular cheilitis. Strategic implants were used to improve the retention, support, and stability of the new RDs. The maxillary canine 23 (World Dental Federation notation) and maxillary premolar 24 were used to retain the maxillary conical crown attachments. Three strategic mini-implants were inserted in the positions of teeth 12, 13, and 14 to support and retain the maxillary RPD. Two locators above the standard implants (33 and 43) were used to support and retain the mandibular overdenture. An improvement in the oral health-related quality of life and patient satisfaction with respect to the maxillary and mandibular RDs was observed immediately after using the new RDs. This improvement did not diminish after a year. ConclusionHerein, using strategic implants to support the maxillary RPD and two standard implants under the mandibular overdenture improved the oral health-related quality of life and patient satisfaction with respect to the maxillary and mandibular prostheses in terms of the retention, stability, support, eating ability, speaking ability, appearance, and cleanability.

Assessment of Permeability Windbreak Forests with Different Porosities Based on Laser Scanning and Computational Fluid Dynamics

Accurate modeling of windbreaks is essential for the precise assessment of wind protection performance. However, in most windbreak studies, the models used the approximate shape of the simulated trees, resulting in significant differences between the simulated results and the actual situation. In this study, terrestrial laser scanning (TLS) was used to extract tree parameters, which were used in a quantitative structural model (AdQSM) to recreate the tree structure and restore the wind field environment using the computational fluid dynamics software PHOENICS. In addition, we compared the bias, precision, and accuracy of porosity of Ginkgo biloba (with elliptical crown) and Populus alba (with conical crown), which have been commonly used in previous windbreak studies. The results showed that AdQSM has a high reduction rate and ability to reproduce the field conditions of the study area. After wind field simulation, the wind speed root mean square errors of the point cloud model at three heights (3, 6, and 9 m) were 0.272, 0.377, and 0.437 m/s, respectively, and the wind speed correlation coefficients r were 0.967, 0.965, and 0.937, respectively, which were significantly more accurate than those of the remaining two structures. Finally, the porosity of the windbreak forest obtained using the modeled sample plot showed a higher correlation with the wind permeability coefficient than that obtained using the existing approach. Windbreak models with three different porosities under the same conditions had different effects on the wind environment, particularly the location of the maximum wind speed reduction, variation of wind speed with porosity, and recovery rate of leeward wind speed. TLS can accurately extract windbreak factors and calculate the porosity, thus greatly improving the reliability of windbreak effect research in windbreak forests. This study provides a promising direction for future research related to the simulation of windbreak effects in windbreak forests.

Retentive force of conical crowns combining zirconia and fiber-reinforced composite

PurposeThis study investigated the retentive force of conical crowns combining zirconia primary and fiber-reinforced composite (FRC) secondary crowns and their changes due to aging. MethodsZirconia primary crowns were produced with a convergence angle of 3°. Thirty-two secondary crowns were milled from FRC and divided into two groups (n = 16/group) based on the polishing method of the secondary crown inner surfaces: diamond paste (Group 1) and silicone points (Group 2). After fitting the secondary crowns with different fitting forces (F), loosening forces (L) were determined. Tests were repeated after an occlusal stop (OS) was added to the secondary crown and artificial aging (10,000 insertion/removal cycles). Data were compared using the Wilcoxon and Mann–Whitney U tests. ResultsCrowns without an OS showed L/F ratios of 0.4586 (Group 1) and 0.4104 (Group 2). With an OS, maximum retention was not significantly affected by the polishing method and could be limited to Lmax = 19.31±7.77 N (Group 1) and Lmax = 16.12±5.92 N (Group 2). ConclusionsThese findings suggest that the combination of conical zirconia primary and FRC secondary crowns can obtain acceptable retentive forces that are not affected by aging if the inner surfaces are polished with diamond paste. OS generation could limit maximum retention, but should be adjusted if the target value of 10 N is not to be exceeded. With a change of the convergence angle to 4°, L/F values for crowns without an OS would be close to 1/3, which is considered ideal for conical crowns. Clinical significanceThe combination of zirconia primary crowns and FRC secondary crowns was found feasible to ensure the required retention for clinical use over a long time span. Furthermore, it offers an alternative to metal-based restorations while ensuring high levels of biocompatibility and esthetics.

TREE CANOPY HEIGHT ESTIMATION AND ACCURACY ANALYSIS BASED ON UAV REMOTE SENSING IMAGES

Abstract. The development of unmanned aerial vehicle (UAV) technology makes the traditional method of danger tree monitoring more digital and convenient. In order to explore the accuracy of tree height measurement by general consumer UAV, this paper takes a campus of University as the research area. The high-resolution images acquired by UAV were processed and compared the accuracy of extracting tree height based on the digital canopy height model (CHM) and point cloud information, respectively. The experimental results show that the mean absolute error of tree height based on point cloud extraction is 10.28cm, which is better than that based on CHM. The tree height extracted from CHM will be less than the measured height. In addition, the accuracy of extracting the height of round crown is better than that of cone crown. The correlation between the measured and true values of the two methods was 0.987 and 0.994, respectively, which indicates that the method of danger tree monitoring by UAV is feasible.

Thuja ×soeegaardii (Cupressaceae) – a new name for an old hybrid

Thuja ×soeegaardii, a hybrid of Th. plicata Donn ex D.Don and Th. standishii (Gordon) Carrière, is described as a new nothospecies from the Kórnik Arboretum, Poland, based on plants obtained in 1988 from the Botanical Garden in Gothenburg, Sweden. The hybrid was found for the first time at the Hørsholm Arboretum, Denmark, in 1938, among seedlings grown from seeds collected from Thuja standishii. Plants grown from rooted scions of this hybrid were planted in several places within the Hørsholm Arboretum. Soon, the hybrid plants were gifted to the Botanical Gardens in Copenhagen and Gothenburg as well to the Poulsen’s Plant Nursery in Kvistgård. In 1967 seedlings were sent from Kvistgård to the National Ar­boretum in Washington, where one of them developed into a particularly showy, lush and vigorous plant characterized by a dense, narrow, conical crown. The offspring obtained from rooted scions turned out to be very drought and wind-resistant, especially suitable for the formation of tall hedges and windbreak screens. This plant, now very widespread in cultivation, especially in the United States, goes by the name of Thuja ‘Green Giant’. In terms of morphology, many features of Th. ×soeegaardii are intermediate as compared to the parent species. From the Th. plicata, it differs by the following characteristics: leaves not or only weakly shining above, lateral leaves with inwardly curved (not straight) apices, the apical part of lower central leaves thickened and slightly bent from the stem (not appressed), glands on central leaves only weakly vis­ible, central leaves of primary shoots acuminate (not long acuminate) and seed wings sparsely papillose in the upper part (only rarely smooth). From Th. standishii, it can be distinguished by the less glaucous upper leaf surface, the less protruding apical part of lower central leaves, at least faintly visible glands on central leaves, acuminate (not acute) central leaves of primary shoots and less distinctly papillose upper part of seed wings.

A Case Report on Implant-Supported Telescopic Prosthesis—A Gerodontic Enhancement

One of the most challenging and demanding endeavors in the field of prosthodontics is the rehabilitation of an edentulous mandible. Implants have been used to support mandibular or maxillary prosthetic rehabilitation. Advantages of using implants are increased retention, increased chewing ability, and also easy access to oral hygiene procedures. For decades, the use of telescopic and conical crowns are in practice to connect natural teeth and not many cases have been reported in the literature of telescopic crowns placed on implants to support the prosthesis. Telescopic crowns provide the best possible distribution of force to the abutment teeth and can improve the patient’s oral health-related quality of life. The use of telescopic crowns as attachments for implant-supported overlying prostheses may be a viable treatment option for edentulous mandible. The functional and the aesthetic enhancement by telescopic retainers are favorable features for many challenging situations.This case report discusses a 60-year-old male, who reported to the department of prosthodontics with three implants and two bi-cortical screws that were placed in a completely edentulous mandibular arch by a private practitioner one year back and this situation was prosthodontically managed by us with an implant-supported telescopic removable prosthesis.

Ellis-Van Creveld Syndrome, neonatal teeth and breastfeeding impairment: a case report

ABSTRACT Because of multisystemic impairment in patients with Ellis-van Creveld syndrome, multidisciplinary care may be demanded since birth to assure breastfeeding. This report presents a case of an Ellis-van Creveld infant that was facing breastfeeding difficulties because of maxillary neonatal teeth. A 3 months old male infant with Ellis-van Creveld syndrome was referred to Pediatric Dentistry Department because of two upper neonatal teeth causing breastfeeding difficulties. Clinical examination revealed that teeth position was compatible to 51 and 61, and both presented uncommon ectopic soft tissue placement, conical crown and hypoplastic enamel covered by a large amount of dental biofilm. Radiography indicated they were of normal series and had 2/3 of crown completion. Due to teeth mobility that impaired breastfeeding, treatment option was exodontia. Early tooth eruption, such as in natal and neonatal teeth, by itself can’t be considered a reason for exodontia. But exodontia must be considered when an early erupted tooth(s) impairs breastfeeding, especially in systemically compromised infants. In this present case report, after teeth extraction, the infant was able to breastfeed and gain weight properly.

An elderly patient treated with a cone crown telescopic denture: A case report

An elderly patient treated with a cone crown telescopic denture: A case report

Influence of rigidity of retainers on dynamic behavior of implant-supported removable partial dentures

BackgroundImplant-supported removable partial dentures (ISRPDs) are an effective treatment for partially edentulous patients. ISRPDs improve patients’ satisfaction and oral function to a greater extent than RPDs by improving denture stability and enhancing support. However, the effect of a type of direct retainer on displacement of the abutment teeth and dentures in ISRPDs remains unclear. Therefore, we made a resin mandibular model of unilateral mandibular distal-extension partial edentulism for mechanical simulation and compared the dynamic behavior of the abutment teeth and the denture base among different tooth-borne retainers with various rigidities for RPDs and ISRPDs.MethodsA resin mandibular model for mechanical simulation that had unilateral mandibular distal-extension edentulism and was missing the first molar, second molar, first premolar, and second premolar, and a denture fabricated from the patient’s computed tomography images were used. Three types of direct retainers with different connecting rigidities were evaluated. The vertical displacement of the denture base and buccal and lingual sides and the mesial displacement of the abutment teeth were measured.ResultsRegardless of the rigidity of the direct retainers and loading positions, the displacement of the denture bases in the ISRPDs was significantly smaller than that in the RPDs (P < 0.001). There was no significant difference in vertical displacement of the denture bases among direct retainers with various connecting rigidities in the ISRPDs. Conversely, horizontal displacement of the abutment teeth in both the RPDs and ISRPDs tended to be larger with the cone crown telescope, which has high rigidity, than with the cast cingulum rest and wire clasp, which have much lower rigidities.ConclusionOur results suggested that cast cingulum rest and wire clasps as direct retainers are appropriate ISRPDs to minimize denture movement and suppress displacement of the remaining teeth in patients with unilateral mandibular distal-extension partial edentulism.

Core discing characteristics and mitigation approach by a novel developed drill bit in deep rocks

Core discing often occurs in deep rocks under high-stress conditions and has been identified as an important characteristic for deep rock engineering. This paper presents the formation mechanism of core discing firstly. Then, the interaction between diamond drill bits and rock was analyzed based on numerical modeling. A novel drill bit with an inner conical crown for the mitigation of core discing was designed and verified by simulation experiments. The mitigation method was applied in the cavern B1 of CJPL-II and satisfactory results had been achieved. The percentage of core discing had been obviously decreased from 67.8% when drilling with a rectangular crown drill bit, to 26.5% when an inner conical crown drill bit had been adopted. This paper gives full insight into core discing characteristics and provides a new method for core discing mitigation; it will potentially contribute to stress measurement in deep rock engineering.

Особенности роста разных форм сосны обыкновенной в кустарничково-сфагновом типе леса устья реки Онега

Pinus sylvestris L. is the main tree species of forest ecosystems in the European North of Russia, therefore, in-depth studies of the diversity of forms and growth processes of this plant are important. Forms in pine stand out according to morphological and other characteristics. In conditions of prolonged excessive soil moisture, the joint growth of various forms of pine is observed. The aim of the work is to study the growth of various forms of pine according to morphostructural characteristics in the shrub-sphagnum forest type estuary of the Onega River. Investigations of tree growth (according to the form of seed cone scales apophysis and crown habit) were carried out in shrub-sphagnum pine forests of different ages in the north-west of the European part of Russia (northern taiga subzone). Morphometric measurements of the vegetative and generative spheres in the forms of scots pine were made. It is established that the advantage in morphometric characteristics, average values ​​of radial growth, late and early wood has a pine tree with a «convex» apophysis form. The advantage with respect to the morphometric characteristics of the trunk and crown is form with «ordinary» crown habit. The «ordinary» form has larger cones, a larger value of radial growth and macrostructural parameters of wood compared to the «swamp».

A case report of a partially edentulous patient with severe dry mouth treated by a cone crown telescope denture

A case report of a partially edentulous patient with severe dry mouth treated by a cone crown telescope denture

A case report of prosthetic treatment using a magnetic attachment and cone crown telescope for a patient with high aesthetic demands

A case report of prosthetic treatment using a magnetic attachment and cone crown telescope for a patient with high aesthetic demands

Assessing the Impacts of Various Factors on Treetop Detection Using LiDAR-Derived Canopy Height Models

Canopy height models (CHMs) were utilized to detect treetops and estimate individual-tree parameters. The treetop detection based on CHMs was affected by surface topography and crown characteristics. However, their effects have not been well studied. Therefore, this paper aimed at assessing the impacts of aforementioned factors to facilitate treetop identification from LiDAR-derived CHMs. To fulfill this objective, we first extended and improved the previous models for cases with various terrains. Then, a new theoretical model was developed to quantify treetop displacements for ellipsoidal tree crowns. Finally, we further analyzed the treetop displacements due to terrain slope, crown radius, crown shape, and offset distance to the slope surface. Our analysis indicates that the vertical displacement increases exponentially with terrain slope; thus, the effect of terrain slope must be considered over extremely steep areas; larger errors are observed for trees with a large crown radius; the treetop displacements are highly correlated with crown shape, the effect of topographic normalization can be neglected for conical crowns with a large crown angle, and the elliptical crown shape can reduce the treetop detection errors; and treetop displacements increases with offset distance to the slope surface in Case 2 , while opposite results are observed in Case 5 . In addition, the results also demonstrate that the effect of slope-distorted CHMs may be quite different for different types of tree crowns and terrains. Overall, this paper makes a significant contribution to the development of theoretical models for quantifying treetop displacements. Furthermore, our findings provide a theoretical basis and guidance for better identifying treetops from LiDAR-derived CHMs.