Labial inverse dilaceration of bilateral maxillary central incisors: A case report

BACKGROUND Dilaceration is a rare dental developmental anomaly characterized by an abrupt deviation along the longitudinal axis of the root in which an angulation forms between the root and the crown.Here,we report on dilacerated bilateral maxi-llary central incisors in mixed dentition.CASE SUMMARY A 10-year-old girl presented with a chief complaint of unerupted central incisors.An oral examination and radiography provided the basis for a diagnosis of dilaceration of the maxillary central incisors.After surgical exposure of the impacted teeth,a button with an attached chain was applied to the palatal surface of teeth 11 and 21.After 8 mo,a button was bonded to the labial surface of the crown to fix an elastic chain and move the teeth toward the maxillary arch.Finally,a fixed appliance was applied to tooth alignment to Class 1 malocclusion using a 0.019×0.025-inch nickel-titanium wire.After 3 years of follow-up,the clinical findings and radiographic assessment showed that the roots had developed with vital dental pulp and healthy periodontium,were acceptable aesthetically,and showed no resorption.CONCLUSION The rare occurrences of dilacerated bilateral maxillary central incisors can be successfully treated through surgical exposure and orthodontics.

Apical Root Resorption in Maxillary Incisors When Employing Micro-implant and J-hook Headgear Anchorage: A 4-month Radiographic Study

This study evaluated,over a 4-month study period,the amount of apical root resorption occurring in maxillary central incisors following their retraction when employing either micro-implant or J-hook headgear anchorage.The prospective randomised clinical trial was conducted in Orthodontic Clinic,College of Stomatology,China from 2008-2009.Subjects are patients requiring fixed appliances on waiting list (n=20).In female Han Chinese patients aged from 16-26 years,standardized periapical radiographs from 10 randomly assigned patients with maxillary protrusions comprising the micro-implant group,and from 10 similar patients comprising the J-hook headgear group,were assessed for maxillary central incisor apical root resorption.Measurements before and after orthodontic therapy were also obtained from lateral cephalometric radiographs to calculate incisor horizontal retraction and vertical intrusion distances.Estimated retraction force vectors were calculated in horizontal and vertical directions for both treatment groups.Data analysis employed t-tests and the Pearson correlation test,with α=0.05 for statistical significance.The results showed that when compared with the J-hook group,significantly more apical root resorption shortening of the maxillary central incisors was observed in the micro-implant group (1.27 mm difference,95% CI=0.70-1.84,P<0.001),which was associated with a significantly larger retraction distance (P=0.004) and a smaller vertical force component (P<0.0001).We are led to conclude that continuous activation of the nickel-titanium coil springs used in the micro-implant group resulted in significantly more apical root resorption shortening and maxillary central incisor retraction than when intermittent J-hook retraction was employed.The employment of continuous duration orthodontic forces presents a risk for increased apical root resorption that requires careful radiographic monitoring.

Non-surgical management of dens invaginatus type IIIB in maxillary lateral incisor with three root canals and 6-year follow-up:A case report and review of literature

BACKGROUND The presence of dens invaginatus(DI)complicates treatment of any tooth,from diagnosis to access cavity and biomechanical preparation and obturation.Reports of successful non-surgical management of DI type IIIB in maxillary lateral incisor are rare.Here,we report such a case,with three root canals and a long follow-up.CASE SUMMARY A 13-year-old female patient presented with mild pain in the maxillary right lateral incisor(#7)for 10-15 d.On examination,the tooth was slightly rotated,with slight tenderness on percussion and grade I mobility but with no caries,pockets or restorations and non-vital pulp(via vitality tests).Radiographic examination revealed unusual configuration of the tooth’s root canals,with an enamel-lined invagination extending to the apex,suggesting the possibility of DI Oehler’s type IIIB and a periapical radiolucency.Widening the access cavity lingually revealed one distinct buccal orifice and two distinct palatal orifices;under higher magnification of a dental operating microscope(DOM),the mesio palatal and disto-palatal orifices were observed as connected by a C-shaped groove.The root canals were prepared with hand K-files following a step-back technique,and obturated using a combination technique of lateral condensation and vertical compaction.At the 6-year follow-up,the patient was asymptomatic,and the periapical radiography displayed significant healing around the apical end of the root.CONCLUSION Proper knowledge of unusual root canal anatomy is required in treating DI.Conventional methods of root canal treatment can successfully resolve such complex cases,facilitated by DOM and cone-beam computed tomography.

Implant site development using titanium plate and platelet-rich fibrin for congenitally missed maxillary lateral incisors:A case report

BACKGROUND Bone deficiency and soft tissue atrophy in the absence of maxillary lateral incisors are among the most challenging problems for implant clinicians.Autologous bone grafting is the gold standard for bone augmentation,but not without limitations.Platelet-rich fibrin(PRF),a biodegradable autologous biomaterial,has been widely used for bone and soft tissue management.Moreover,titanium plate is an advantageous barrier due to its good space-maintaining ability.However,there is a lack of literature on implant site development using titanium plate and PRF for congenitally missing maxillary lateral incisors.CASE SUMMARY The patient was a 19-year-old girl with a congenitally missing tooth(#12).She underwent implant placement and simultaneous autologous bone grafting with titanium plate and PRF.At the follow-up visit 15 d post-procedure,the vascularization of soft tissue was visible.There was no swelling or pain after the surgery.Six months postoperatively,bone regeneration was evident.Subsequently,the definitive restoration was placed,and the patient was satisfied with the esthetic outcomes.CONCLUSION Implant site development using titanium plate and PRF for congenitally missing maxillary lateral incisors is a feasible procedure.In this case,the labial bone plate was displaced but remained connected to the base bone,ensuring blood supply.The titanium plate fixed the labial bone plate and maintained the osteogenic space,while the PRF provided growth factors and leukocytes for bone and soft tissue regeneration.Furthermore,the procedure reduced the surgical complexity and adverse reactions,displaying outstanding esthetic outcomes.

Clinical Management of Mid-Root Fracture in Maxillary Central Incisors:Case Reports

Management of mid-root fractures presents a formidable challenge for clinicians because of the difficulty of achieving a stable reunion of fracture fragments. This article presents two varied treatment options for mid-root fractures. A 15-year-old female reported an impact injury to the maxillary anterior teeth 2 days after its occurrence. Clinically,the maxillary left central incisor was palatally-extruded with a negative vitality response and radiographic evidence of an oblique fracture at the middle third of the root. An endodontic implant was employed which utilized an open technique and has been on follow-up for ten months. A 32-year-old male reported an injury,which resulted in a mobile maxillary right central incisor,three months after its occurrence. Through clinical and radiographic means,a discolored,extruded,and non-vital maxillary right central incisor with an oblique root fracture at the alveolar-crest level was observed. Exploratory surgery was performed; an apical barrier was created with a mineral trioxide aggregate and obturated with gutta percha. The fragments were stabilized with a fiber post and patient has been on follow-up for five months. Short-term follow-up for both of the cases showed promising results both clinically and radiographically.

Cone-Beam Computed Tomography Evaluation of the Positions of Unerupted Maxillary Canines with Incisor Root Resorption

Purpose: To establish a new coordinate system using the incisive canal and incisive foramen in cases confirmed to have root resorption in the maxillary incisor region by cone beam computed tomography (CBCT) to investigate the positions of the central and lateral incisor roots and erupting maxillary canine tooth crowns in the horizontal plane. Methods: Nine patients (two males;mean age: 10.5 years old) with suspected incisor root resorption due to erupting maxillary canines on panoramic X-ray images and in whom incisor root resorption was confirmed on CBCT images were evaluated. A control group of 12 patients with a supernumerary tooth on one side (three males;mean age: 8.6 years old) was also examined. X, Y, and Z-axes were defined, and the positions of the centers of the central incisor root (U1) and lateral incisor root (U2) and the canine cusp (U3) were examined, along with alveolar process width and length. Results: In the control group, U1, U2, and U3 were located within a certain range without overlap, while, in the incisor root resorption group, U3 overlapped with U1 and U2 and tended to deviate centrally. U2 tended to be located further posteriorly than U3. The anteroposterior diameter of the alveolar process was 1.2 mm shorter in the incisor root resorption group (p < 0.05). Conclusions: The risk of incisor root resorption accompanying canine eruption can be evaluated early by investigating the canine position on a horizontal plane established on the upper anterior tooth dentition CT images with a coordinate system using the incisive canal and incisive foramen.

Opinions of traditional birth attendants in Ibadan, Nigeria, towards reversal of eruption sequence of primary central incisors in infants

Introduction: Traditional birth attendants (TBA’s) have been a good medium for transferring health education messages in culturally acceptable ways. It is believed that they will be a good asset to demystify the misconceptions associated with reversal of eruption sequence in the community. Aim: To assess the opinions of TBA’s towards reversal of eruption sequence of primary central incisors in infants. Methods: A cross sectional study was conducted among all consenting TBA’s in the five urban local government areas in Ibadan, using a pretested 17-item semi structured interviewer administered questionnaire. Results: Forty eight (29.4%) respondents will be astonished at seeing children erupting upper primary central incisors before the lowers, while 25 (15.3%) will regard them as strange. Thirty five (21.1%) respondents felt this condition was due to evil spirits while 13 (8.0%) believed that child’s parents had breached traditional taboos. There was a correlation between negative beliefs about this variation and age (p = 0.038) and education (p = 0.020). Their opinion on the families of the affected children was hideous as (13.5%), (23.3%) and (27.6%) regarded it as a curse, embarrassment and abomination respectively and this was associated with their educational status (p = 0.014). Many (61.3%) of the respondents would advise the parents to hide or get rid of such children whilst (33.7%) advocated for extraction and only 8 (4.9%) felt child and the tooth should be left alone. Conclusion: Many of the TBA’s have dissenting mind-sets towards such children and their families. The practices of many of the TBA’s towards such teeth are disturbing and necessitate urgent intervention. The risks are that wrong advice may be given to such parents by the TBA’s and affected children may be deserted, abandoned, stigmatized and exposed to hazards. Older and less educated TBA’s have a greater tendency to believe these misconceptions.

Radiographic study of the root canal system of mandibular incisors in Palestinian population

Aim: The aim of this study was to survey the root canal morphology of mandibular incisor teeth in a Palestinian population using radiographic approach. Materials and Methods: Five hundred and twenty two extracted mandibular incisor teeth were randomly collected from Palestinian population. The teeth were radiographed from a mesiodistal direction and examined for the presence of a second canal and for the type of canal configuration. Results: All teeth had single root. Three hundred and sixty nine teeth (70.7%) had one canal (type I Vertucci classification). The rest (29.3%) had a second canal (type II and III). Conclusion: Mandibular central and lateral teeth were mostly found to have one root and Type I canal system.

Treatment of Skeletal CL II Patient with Maximum Lower Incisor Protrusion and Minimum Overjet with Rahhal Functional Appliance

Treatment of skeletal Cl II includes functional orthopedic treatment, head-gears, extraction of the upper premolars and orthognathic surgery. To treat any patient with functional appliances (bite jumping) an adequate overjet is necessary. In this case an 11 years old female patient has skeletal CLII due to mandibular deficiency with ANB angle 8 degrees, overbite: 3 mm, overjet: 1 mm, extremely convex profile and underdeveloped chin due to the hyper muscle contraction of the lower lip to obtain oral seal. To obtain an adequate overjet lower first premolars were extracted and maximum retraction using mini screws (for maximum anchorage) was applied. Afterwards Rahhal functional appliance was used by the patient 16 hours a day for 6 months and 10 hours a day for another 6 months for retention. After that fixed orthodontic treatment was completed. Lateral cephalometrics were taken, traced and analyzed. In the result Skeletal CLI was obtained (ANB 4 degree), straight facial profile, normal over bite overjet and particular chin development were noticed. As a conclusion, in skeletal CLII malocclusions, lower incisor protrusion will cause a contraindication for functional treatment. Extraction of the lower premolars and retraction of the lower incisors followed by functional orthopedic treatment is an efficient method to treat these cases instead of waiting for orthognathic surgery, also reducing the muscle pressure on the chin will change the development characteristics of it.

Average Odontometric Value of the Width of the Upper Central Incisor in the Congolese Bantu of Kinshasa, Democratic Republic of Congo

Objective: The aim of this study was to determine the average values of width of the upper central incisor (WUCI) in Congolese Bantu and compare them to those of Caucasians and Asiatic. Material and Methods: It was a prospective cross-sectional study carried out at the Université de Kinshasa on the Congolese Bantu, Department of Dental Medicine, from March 2020 to March 2021. A maxillary imprint was taken by Jeltrate-type alginate. The measurement of two healthy upper central incisors (UCI) was carried out by the hard plaster casting type 4, with a brand caliper, carbon fiver composite mark. The study was approved by the Ethics Committee of the School of Public Health in the Université de Kinshasa and verbal consent was obtained from each participant. Results: The Average Width of the UCI was 8.74 mm ± 0.56. The average width of the right Upper Central incisor (RUCI) and the left UCI (LUCI) was 8.71 mm ± 0.57 and 8.77 mm ± 0.56, respectively. The average width of the RUCI and LUCI was not the same for men and women (p 0.001). A significant difference was observed between the average of the RUCI and the 18 - 28 and 40 - 50 age group (p = 0.056) as well as for the average LUCI (p = 0.085). The width average of UCI between the Congolese Bantu with those of Caucasians and Asians was significantly different (p = 0.000 and p = 0.009). Conclusion: The average width of the RUCI and LUCI was different among sex and age group. The average width of UCI of the Congolese Bantu is different from that of Caucasians and Asians.

Determinants Factors for the Choice of the Width Prosthetic Upper Central Incisor: Review of the Literature

Materials and Methods: The authors conducted a review of the literature around the theme, determinants of the choice of the width of the upper central incisor (WUCI), through search web including Pub Med, Inari and Google. Fifteen of the most recent publications since 2005 have been selected from twenty publications. Sample size (n), age range (AR), average bi zygomatic distance (BZD), choice determinants, type of study, and mathematical formula between WUCI and BZD were the study’s interest variables. Sociodemographic characteristics, facial anatomical marks and the size of the patient’s teeth for anterosuperior were the main factors to be assessed. Results: Out of 22 included articles, the Asian continent represents 59% in which India is the leading country with 27.3% followed by American 22.8%. The most Determinants choice for the width upper central incisor in craniofacial and anterior teeth method from the published papers were BZD (100%;n = 22) and WUCI (81.8%;n = 18). Conclusion: Application of mathematical formulation maybe help to predict the exact width of the upper central incisor.

Molar incisor hypomineralization and pre-eruptive intracoronal lesions in dentistry-diagnosis and treatment planning

The aim of this study is to report the diagnostic features, prevalence, mineral content, clinical significance and treatment options of molar incisor hypomineralization(MIH) and pre-eruptive intracoronal lesions(PEIR), in order to minimize miss-treatment of primary and permanent teeth in young children.MIH was defined as the occurrence of hypomineralization of one up to four permanent first molars from a systemic origin and frequently associated with affected incisors. PEIR are lesions that are located in the occlusal portion of the crown of unerupted permanent or primary teeth. The prevalence of MIH was reported between 2.5%-40% in the permanent first molars and 0%-21.8% in primary second molars. PEIR was observed in 2%-8% of children, mainly in mandibular second premolars and second and third permanent molars. A number of possible causes for MIH were mentioned, including environmental changes, diet and genetics in prenatal and postnatal periods, but all are questionable. In PEIR, the resorption of the intracoronal dentine begins only after crown development is complete and is caused by giant cells resembling osteoclast observed histologically on the dentine surface close to the pulp. The mineral content in MIH is reduced in comparison to normal enamel and dependent on the severity of the lesion. In PEIR the resorbed surface of enamel showed less mineral content. The hypomineralized enamel in MIH is not suitable for restorations with amalgam or composite materials, and the best material should be based on remineralization material like glass-ionomers. Similar, the resorbed dentin surface in PEIR should be covered by the biocompatible and remineralizing glass-ionomer cement.

Alveolar Ridge Preservation of an Extraction Socket of Fractured Maxillary Lateral Incisor

Background: Alveolar ridge resorption still continues to be a problem in oral surgery. Cause of bone resorption is including tooth extraction, periodontal disease and inflammatory periapical pathologies. Various methods and materials have been suggested to minimize this resorption. Aim: Goal of this case report is to present alveolar ridge preservation (ARP) following horizontally fractured maxillary lateral incisor with allograft in the aesthetic zone. Case presentation: 30-year-old female patient with fractured tooth was treated by grafting and insertion dental implant. Fractured tooth extraction was performed and extraction socket augmentation was performed by allograft and covered with collagen membrane. Augmented area was treated with bone-level implant. Definitive prosthesis single-tooth porcelain-fused-to-zirconia restorations were fabricated. Conclusions: Before implant insertion, extraction and grafting socket procedure is appropriate treatment for of fractured teeth with granulation tissue.

柔化辊和光滑压辊对单板质量及旋切参数的影响(英文)

为了比较柔化辊和光滑辊对旋切单板质量的影响,对加拿大Forintek研究所的一台小型旋切机进行了改造,安装了数字控制装置并配置了两种压辊。按照L9(34)正交试验组织试验,每组变量设定值重复实验2次,共旋切了45段云杉木段。在其他参数设置相同的情况下,考查了旋刀倾角(PA)、垂直间隙(VG)和水平间隙(HG)3个变量对单板旋切质量的影响,并比较了压辊形式对单板质量的影响。结果表明:采用柔化辊旋切的单板的湿单板卷曲率比光滑压辊下降了60%,单板厚度较均匀,厚度偏差较小;柔化辊与光滑压辊的最佳旋切设置完全不同。柔化辊的最佳旋切设置为:旋刀倾角90.5°,垂直间隙9.84mm,水平间隙2.79mm;光滑压辊的最佳旋切设置为:旋切倾角88.5°,垂直间隙11.75mm,水平间隙2.54mm。

柔化辊旋切参数对旋切单板质量的影响(英文)

在胶合板生产中,用柔化辊取代固定压尺可释放单板内应力、降低单板厚度偏差和卷曲变形。为了考察柔化辊对单板柔化、单板质量改善的效果,在一部小型旋切机上安装齿形柔化辊和控制系统。设定3个变量为旋刀倾角(PA)、垂直间隙(VG)和水平间隙(HG),按照L9(34)正交试验组织试验,每组变量设定值2次重复,并用相应的旋切软件研究木段旋切时的压缩率,以及压缩率为零时木芯的直径,以确认每组可控变量设定都能进行旋切。单板质量的主要评价指标为湿单板厚度、干单板厚度及其偏差以及单板卷曲变形。试验结果表明,当旋刀倾角增加时,单板厚度偏差和卷曲变形值减少,但单板粗糙度加大;垂直间隙减小时,单板卷曲值减小,湿单板厚度偏差增大,但干单板厚度偏差变化很小;水平间隙增加时,单板厚度随之增大,而单板厚度偏差降低。最好的旋切变量设定值为:旋刀倾角90.5°,垂直间隙9.84mm,水平间隙2.79mm。

Management of the palato-radicular groove with a periodontal regenerative procedure and prosthodontic treatment:A case report

BACKGROUND Palato-radicular groove(PRG)is defined as an anomalous formation of teeth.The etiology of PRG remains unclear.The prognosis of a tooth with a PRG is unfavorable.The treatment of combined periodontal-endodontic lesions requires multidisciplinary management to control the progression of bone defects.Some researchers reported cases that had short-term observations.The management of teeth with PRGs is of great clinical significance.However,to date,no case reports have been documented on the use of bone regeneration and prosthodontic treatment for PRGs.CASE SUMMARY This case reported the management of a 40-year-old male patient with the chief complaint of slight mobility and abscess in the upper right anterior tooth for 15 d and was diagnosed with type II PRG of tooth 12 with combined endodonticperiodontal lesions.The accumulation of plaque and calculus caused primary periodontitis and a secondary endodontic infection.A multidisciplinary management approach was designed that included root canal therapy,groove sealing,a periodontal regenerative procedure,and prosthodontic treatment.During a 2-year follow-up period,a good prognosis was observed.CONCLUSION This report indicates that bone regeneration and prosthodontic treatment may contribute to the long-term favorable prognosis of teeth with PRGs.

A study of the rotation rate of single-rooted teeth in dogs

Sixteen one-year-old dogs were used in our experiment.We rotated the maxillary secondincisors of the dogs,applying a force of 100g and a moment of 550g·mm.The duration of theexperiment varied from 72h to 8 weeks.Activation was performed once every 2 weeks and the impressions were taken in order to measure the angles of rotation.The results of our experiment showthat the rotation rate of single-rooted tooth in dogs is 3.04/week.The graph shows the form ofgradual stairs.This paper introduces a new specialized experimental apparatus for tooth rotation.The angles of rotation are measured geometrically.

Improved super-elastic Ti-Ni alloy wire for treating adult skeletal class III with facial asymmetry:A case report

BACKGROUND Correcting severe skeletal class III malocclusion with facial asymmetry in adults through orthodontic treatment alone is difficult.CASE SUMMARY In this case report,we describe orthodontic treatment and lower incisor extraction without orthognathic surgery for a 27-year-old man with a transverse discrepancy.The extraction sites were closed using an elastic chain.The use of intermaxillary elastics,improved super-elastic Ti-Ni alloy wire,and unilateral multibend edgewise arch wire was crucial for correcting facial asymmetry and the midline deviation.CONCLUSION After treatment,the patient had a more symmetrical facial appearance,acceptable overjet and overbite,and midline coincidence.The treatment results remained stable 3 years after treatment.This case report demonstrates that a minimally invasive treatment can successfully correct severe skeletal class III malocclusion with facial asymmetry.

Contour changes in human alveolar bone following tooth extraction of the maxillary central incisor

The purpose of this study was to apply cone-beam computed tomography （CBCT） to observe contour changes in human alveolar bone after tooth extraction of the maxillary central incisor and to provide original mor- phological evidence for aesthetic implant treatment in the maxillary anterior area. Forty patients were recruited into the study. Each patient had two CBCT scans （CBCT I and CBCT II）, one taken before and one taken three months after tooth extraction of maxillary central incisor （test tooth T）. A fixed anatomic reference point was used to orient the starting axial slice of the two scans. On three CBCT I axial slices, which represented the deep, middle, and shallow layers of the socket, labial and palatal alveolar bone widths of T were measured. The number of sagittal slices from the start point to the pulp centre of T was recorded. On three CBCT II axial slices, the pulp centres of extracted T were oriented according to the number of moved sagittal slices recorded in CBCT I. Labial and palatal alveolar bone widths at the oriented sites were measured. On the CBCT I axial slice which represented the middle layer of the socket, sagittal slices were reconstructed. Relevant distances of T on the sagittal slice were measured, as were the alveolar bone width and tooth length of the opposite central incisor. On the CBCT II axial slice, which represented the middle layer of the socket, relevant distances recorded in CBCT I were transferred on the sagittal slice. The height reduction of alveolar bone on labial and palatal sides was measured, as were the alveolar bone width and tooth length of the opposite central incisor at the oriented site. Intraobserver reliability assessed by intraclass correlation coefficients （ICCs） was high. Paired sample t-tests were performed. The alveolar bone width and tooth length of the opposite central incisor showed no statistical differences （P〈0.05）. The labial alveolar bone widths of T at the deep, middle, and shallow layers all showed statistical differences. However, no palatal alveolar bone widths showed any statistical differences. The width reduction of alveolar bone was 1.2, 1.6, and 2.7 mm at the deep, middle, and shallow layers, respectively. The height reduction of alveolar bone on labial and palatal sides of T both showed statistical differences, which was 1.9 and 1.1 mm, respectively.

Morphometric Analysis of Maxillary Central Incisor to Determine its Crown Form: A Model‑based Cross‑sectional Study

The size and shape of tooth crowns are morphogenetically predetermined during embryogenesis.The maxillary central incisors have contributed to sexual dimorphism,and several classifications of the form of maxillary central incisors are available in the literature.We,in the present study,aimed to analyze the mesiodistal(MD)measurements at two levels of maxillary central incisor,to determine its crown form.The study was conducted on 100 dental plaster models(50 males and 50 females).The MD dimensions at the contact area level MD_incisal(MD_I)and at the gingival papilla level(MD_G)and the gingivo‑incisal height of the crown were measured in the dental models using digital Vernier caliper.The data were analyzed using SPSS version 16 statistical software.The mean values of all the three parameters measured were slightly greater for males and also for the left central incisors.There were no significant differences in all the three variables when the right and left incisors were compared.Significant differences were noted when the parameters are compared between genders.The height/width ratio of crown showed a significant difference between male and female.The value of the ratio between the two MD dimensions(MD_I and MD_G)was used to determine the crown form.The ratio between the MD dimensions at incisal and gingival area showed a significant difference between genders and no such significance was found between right and left central incisors.There is a significant difference in the form of maxillary central incisors between male and female samples and not between right and left.The MD dimensions at incisal and gingival thirds decide the form of crown.