Crown-root Ratio Research Articles

PERTUMBUHAN STEK BATANG BUAH NAGA MERAH (Hylocereus costaricensis L.) BERBAGAI UKURAN AKIBAT PEMBERIAN AIR KELAPA DENGAN CARA YANG BERBEDA

Dragon fruit is one type of plant that is quite popular in Indonesia because of its sweet taste and high selling price. Dragon fruit has various types, including dragon fruit with red flesh, white flesh with yellow skin color and red skin with white flesh. Dragon fruit contains high betacharotene and antioxidants to prevent cancer and ward off free radicals. The fiber content in it can facilitate digestion, prevent colon cancer, and cope with diabetes. The objectives of this study were to determine effect of length stem cuttings on the growth of red dragon fruit cuttings, effect of different methods of giving between immersion and watering coconut water on the growth of dragon fruit cuttings, and interaction lengths cuttings and how to give coconut water to the growth of dragon fruit cuttings. The results showed that red dragon fruit stem lengths of 25 cm and 30 cm give better results than 15 cm and 20 cm. Dragon fruit stem lengths of 25 cm and 30 cm had a significant effect on bud emergence variables, number of shoots, average shoot length per cuttings and number of roots, but the root length variables, root wet weight and root shoot ratio were not significantly different. The method of giving coconut water shows that watering is better than soaking. but on the variable number of shoots per cuttings, the average length of shoots per cuttings, root wet weight and root crown ratio had no significant effect. There is no interaction between rod length and means giving coconut water to the growth of red dragon fruit cuttings on all observed variables.

PENGARUH PEMBENAH TANAH TERHADAP PERTUMBUHAN DAN PRODUKSI TIGA VARIETAS PADI PADA TANAH ASAL KARANGANYAR BERBASIS PUPUK ORGANIK BIO-SLURRY

The study aimed to compare the growth and production of rice between three varieties, namely Ciherang, IR 64 (Membrano), and Inpari 23 (Aromatic) without or with soil amendment application (dolomite) on andosol soil from Karanganyar. The research design used was a split-plot with a Completely Randomized Design. The main plot is treatment without soil amendment (R1) and with soil amendment (dolomite) (R2). Subplots were Ciherang (V1), IR 64 (V2), and Inpari 23 (V3) varieties. Parameters observed were plant height, number of panicles, panicle emergence age, crown weight, root weight, root crown ratio, strawweight, grain weight, 1000 grain weight, and harvest index. The results showed that the variety factor had a significant effect (P<0,05) on the age of panicle emergence and the number of panicles. The age of panicle emergence and the best number of panicles was found in the IR 64 variety. Variety factors had no significant effect on plant height, crown weight, root portion weight, root canopy ratio, strawweight, grain weight, 1000 grain weight, and harvest index. Soil amendment factors have no significant effect on growth, biomass production, and rice production. It can be concluded that the most superior rice growth and production is IR 64 variety followed by Ciherang and Inpari 23 varieties.

Application of High-Frequency Conduction for Persistent Apical Periodontitis: A Case Report

We report the case of a 39-year-old male with Persistent Apical Periodontitis (PAP) caused by infection in an uninstrumented area, wherein conventional chemical root canal treatment is not possible, which was sterilized via highfrequency conduction. He underwent root canal filling after multiple endodontic treatments for tooth #4. As symptoms recurred, he was referred to our department with the chief complaint of dull pain during mastication. Present symptoms were percussion pain of the tooth, buccal mucosa swelling at the apical portion, and grade 1 mobility. Radiography revealed inadequate root canal filling. A radiolucent image 5×6 mm in diameter and with an unclear boundary was observed around the apex. External root resorption was mainly observed in the apical foramen, with a crown root ratio of approximately 1:1. Using 6% sodium hypochlorite under dental microscopy, chemomechanical root canal preparation was performed. Passive ultrasonic irrigation and calcium hydroxide application were conducted three times; however, periapical tissue inflammation did not subside. Therefore, the patient was diagnosed with PAP, and the uninstrumented area was sterilized via high-frequency conduction. High-frequency currents were applied to the apex, root surface, and periapical lesion at 500 kHz and 90 V; periapical tissue inflammation resolved after 2 weeks. Subsequently, the root canal was filled. Follow-up radiography revealed a bone regeneration-like image at 2 months. Bone defects healed at 11 months. Although surgical endodontic therapy is conventionally performed in PAP patients, high-frequency conduction could be a minimally invasive nonsurgical endodontic treatment option for uninstrumented areas in PAP patients.

SHORT IMPLANTS- AN EVOLVING TREND- A REVIEW

Short implants have been proposed as one of the positive treatment options for compromised edentulous regions. Decreased bone height, poor bone quality often limit the use of conventional implants and usually necessitate complex surgical procedures like sinus lift or bone augmentations which are associated with increased morbidity, treatment time and cost. Though the crown root ratio of short implants is controversial, they have demonstrated a high success rate with innovations that have bolstered its effectiveness through the modifications in micro and macro surface topography, surgical bone drilling protocols and implant diameter. Photo functionalization of implants and customized implants using 3D printing are some of the promising developments in short implants. KEYWORDS: Short Implants, Implant surface topography, Bone grafting, Photo functionalization, Customized Implants

Outcomes and prognostic factors of apical periodontitis by root canal treatment and endodontic microsurgery-a retrospective cohort study.

The aim of this study was to analyze the outcome and prognostic factors of root canal treatment (RCT) and endodontic microsurgery (EMS) in the treatment of apical periodontitis (AP), respectively, and to compare the outcome and prognostic factors between initial RCT and nonsurgical retreatment (re-RCT) for AP. Patients with AP were recruited from the Stomatology Department of Peking University Third Hospital from January 2016 to December 2019. Data were collected by medical records review. Univariate analysis of treatment outcome was performed for the total RCT group, initial RCT group, re-RCT group and EMS group, respectively. Multivariate logistic regression was performed for the three RCT groups, respectively, but not for the EMS group. The overall success of treatment for AP was 73.8%. The success rate of RCT in 229 cases was 70.7%, while that of EMS in 34 cases was 94.1%. The failure of RCT was significantly higher for elderly patients [odds ratio (OR) =1.025, P=0.013], teeth with incomplete fracture (OR =7.082, P=0.013), teeth with a greater crown root ratio (OR =1.198, P=0.029), teeth treated by a general dentist (OR =2.16, P=0.042) and teeth with unqualified treatment (OR =2.841, P=0.002). Of the 166 teeth treated by initial RCT, the success was 68.1%. A greater crown root ratio (OR =1.333, P=0.004) was identified as a risk factor for treatment. Of the 63 teeth treated by re-RCT, the success was 77.8%. A lower success was observed in teeth with unqualified treatment (OR =5.291, P=0.018). With regard to EMS, the univariate analysis showed that none of the variables were significantly related to the outcome. For AP treated by RCT, age, incomplete tooth fracture, crown root ratio, doctor classification and unqualified treatment had a strong impact on determining outcome. For initial RCT, crown root ratio was a significant outcome predictor, while for re-RCT, unqualified treatment was a strong statistically significant factor. No significant difference was found between the success of initial RCT and re-RCT for AP.

Conservative management of discolored maxillary central incisor with open apex using Mineral Trioxide Aggregate (MTA) apical plug and walking bleach Method: A case report.

Esthetics enhancement is a better treatment option for a non-fracture discolored traumatic maxillary central incisor (Max CI). The traumatic injury occurred in Max CI teeth because it was present in the most anterior region of the jaw. Necrosis (pulpal) in Max CI is the second commonest complication after fracture due to trauma. Open apex, incomplete root development, root shortening, roots with a poor remaining dentinal thickness (RDT), and a compromised crown root ratio all these factors affect the survival prognosis of traumatized teeth. Nowadays MTA based bio regenerative material helps in treatment strategies like apexification that was a popular treatment of open apex cases. Necrosis associated discoloration is managed with a conservative approach non-vital bleaching, less time consuming, and satisfy the economical and esthetic aspect for the patient.

Effect of vertical malocclusions on root crown ratio of maxillary teeth-A cross-sectional radiographic study

Root resorption is the loss of apical root tissue which is implicated by decrease in root-crown ratio. It usually effects from external surface to pulp chamber if not identified in the early stage. Several natural conditions place roots at risk of resorption without any pathology. Knowing the pressure or etiology of the resorption will help the orthodontist in the treatment aspect. To date literature regarding root resorption due to various malocclusions is deplete in Indian population. To measure and assess the root crown ratios of maxillary incisors with vertical malocclusions, deleterious habits, and validate by two different radiographic techniques.90 Patients enrolled for the orthodontic treatment were allocated to three groups - open bite, deep bite &amp; control groups and were subdivided based on nail biting habit. Panoramic radiographs, Periapical radiographs (by paralleling technique) for maxillary incisors (360 teeth) were taken and traced. Length of the root &amp; crown were assessed and root crown ratios were calculated and the results substituted to statistics using SPSS. Comparison of Root-crown ratios in vertical malocclusions, revealed statistically significant (P &amp;#60; 0.001) differences in Open bite group for all maxillary incisors in both panoramic and periapical radiographs. No statistical significant differences were found in the deep bite group. Significant association was found between nail biting habit and Root-crown ratio. Gender predilection was found to be absent.Decreased Root- crown ratios were observed in open bite patients. Nail biting patients show significant root resorption. Both panoramic radiographs and periapical radiographs with paralleling technique can be used for assessing root resorption.

Evaluation of the relationship between non-caries cervical lesions and the tooth and periodontal tissue: An ex-vivo study using micro-computed tomography

The purpose of this study was to analyze the relationship between the height and depth of buccal non-carious cervical lesions (NCCLs) and the relationship between the size of buccal NCCLs and clinical crown-root ratio of both buccal and lingual (palatal) sides using micro-computed tomography (micro-CT) images of the teeth and periodontal tissues from the cadavers. The micro-CT images of 56 teeth and their supporting tissues were obtained from 17 cadavers. From these images, the height and depth of NCCLs and the length of the buccal and lingual (palatal) clinical crowns were measured, and the conventional/modified clinical crown-root ratios were calculated. The height and depth ratio of NCCLs were analyzed statistically with the conventional/modified crown-root ratios by Pearson’s correlation and multiple regression. According to the Pearson’s correlation, the height and depth of buccal NCCLs were positively correlated with the modified buccal clinical crown-root ratio (p < 0.001 and p = 0.013, respectively). The regression model composed of variables of crown-root ratios explained the height of buccal NCCLs, and the prominent factor of the model was the modified buccal clinical crown-root ratio (p < 0.001). Moreover, the depth of buccal NCCLs was also explained by the regression model, and its prominent factor was the proportion of modified buccal and lingual (palatal) clinical crowns (p = 0.004). The buccal NCCLs were related to the crown-root ratios; particularly, the level of buccal gingival margin could be associated with the formation of buccal NCCLs.

Stainless steel and NiTi torque archwires and apical root resorption.

ObjectiveThe amount of apical root resorption when using the torque-segmented archwire (TSA) was investigated as well as the extent and direction of the therapeutically indicated apical movement and the treatment duration.Materials and methodsThe degree of apical root resorption in 18 randomly chosen Class II and Class I patients treated with the TSA, as well as in 18 conventionally treated patients were evaluated using pre- and posttreatment panoramic radiographs. The sagittal and vertical apical movements and inclination changes were determined based on pre- and posttreatment lateral cephalograms. Nonparametric tests were applied to test between treatment groups and steps. The Mann–Whitney U test, Kruskal–Wallis, Pearson correlation and Wilcoxon signed-rank test were applied for statistical analysis (p < 0.05).ResultsThe incidence of root resorptions was 89–94.4% in low or moderate level. The relative root–crown ratio (rRCR) was not statistically different between the TSA and control groups except tooth 12. The axis of the incisors in the TSA group was significantly improved. The main direction of movement of the apices of the central incisors was retrusion and extrusion. No interdependence between the amount of resorption and the parameters of treatment duration, extent and direction of apical movement were found.ConclusionThe results of the study showed that the amount of apical root resorption with the TSA is slight to moderate and can be compared to conventional orthodontic treatment. The TSA is hence a suitable method for applying targeted torques to the incisors.

Relationship Between Crown to Root Ratio and Alveolar Bone Support in Patients With Unilateral Cleft Lip and Alveolus.

To evaluate the tooth lengths, crown to root ratios (CRRs), and alveolar bone support (ABS) around cleft-adjacent maxillary central incisors (U1s) in patients with unilateral cleft lip and alveolus (UCLA) and to investigate the relationships between CRR and ABS. This is a retrospective study. Cleft Lip and Palate Care Center of Shanghai Ninth People's Hospital, Shanghai, China. Fifty-eight Chinese patients with UCLA. Cone beam computed tomography data from 58 nonsyndromic patients with UCLA (36 males, 22 females; mean age = 12.65 ± 3.64 years) were evaluated. Crown length and root length, alveolar bone thickness (ABT), and the distances between the cementoenamel junction and alveolar bone crest on 4 surfaces of cleft-adjacent U1 were measured and compared with those of noncleft side in the same patients. Crown to root ratio and frequency of dehiscence were calculated and comparisons were also made between cleft and noncleft sides. Regression analysis was performed to explore the association between CRR and ABS. The CRR of cleft-adjacent U1 and alveolar bone crest heights (ACHs) on the 4 surfaces were significantly greater than those of noncleft side (P < .01). A 3 mm labial, all lingual, and apico-distal ABTs decreased on the cleft side (P < .01). A positive correlation was found between lingual ACH and CRR (R = 0.316, P < .05), between the 3 mm (R = 0.417, P < .05) and 6 mm labial (R = 0.448, P < .05) ABT and CRR. A negative correlation was found between the 3 mm and 6 mm labial ABTs and the root length. It can be suggested that the CRR is related to ACH and ABT. The lingual ACH, the 3 mm, and 6 mm labial ABTs tend to increase with the increasing CRR.

Apexification of blunder buss apex using novel internal matrix technique: A case report

Permanent teeth with incomplete root development results in teeth with short root, roots with very thin walls, and an inadequate crown-root ratio, which overshadows their survival prognosis. Further due to internal bleeding from the pulp the teeth may become gray or black-brown, posses a great esthetic challenge. This case presents both endodontic and aesthetic management of incompletely developed root at Cvek stage 1 with perio glass as apical matrix restored with MTA and aesthetic rehabilitation with zirconia premium crown. Key words : Blunderbuss apex, Bio-active glass, MTA

Effects of 3 different residual root treatments after post-and-core restoration: An in vitro fracture resistance experiment and finite element analysis

Statement of problemCrown-lengthening procedures (CLPs) and orthodontic eruption procedures (OEPs) improve the biomechanical properties of residual root restoration. However, their use is limited by clinic time, cost, and crown-root ratio. An inner shoulder retention form (ISRF) overcomes these limits; however, whether ISRF meets the biomechanical requirements is unclear. PurposeThe purpose of this in vitro and finite element analysis (FEA) study was to evaluate the effects of 3 residual root treatments (ISRF, CLP, and OEP) on premolar fracture resistance and stress distribution after post-and-core restoration. Material and methodsThirty-two extracted mandibular second premolars were screened and randomly divided into 4 groups (n=8): a 2-mm ferrule restoration group (NPR2; control group) and 3 experimental groups (0.5×0.5-mm ISRF [ISRF0.5], 2-mm CLP [CLP2], and 2-mm OEP [OEP2]). After removal of the crown, endodontic treatment, and embedding and restoration, the specimens were loaded on a universal tester (crosshead speed of 0.1 mm per minute) at 30 degrees to the long axis of the tooth until fracture. Fracture resistance and pattern were analyzed. Four groups were added in FEA: 1-mm ferrule restoration group (NPR1), 1.0×1.0-mm ISRF (ISRF1), 1-mm CLP (CLP1), and 1-mm OEP (OEP1). The maximum principal stress peak (σmax), maximum displacement, and stress distribution were evaluated. ResultsMean fracture load ±standard deviation was 796.23 ±155.61 N (NPR2), 650.32 ±150.43 N (ISRF0.5), 385.38 ±149.92 N (CLP2), and 542.93 ±79.34 N (OEP2); these differences were statistically significant (F=12.724; P<.001). The main fracture patterns were decementation from the lingual crown margin and oblique root fracture in ferrule restoration groups and post-and-core decementation and oblique fracture starting from the middle proximal surface in the ISRF groups without ferrules. In FEA, the results of NPR2, ISRF0.5, CLP2, and OEP2 were consistent with the in vitro experiments and provided stress distribution and displacement information. ConclusionsTeeth with crown dentin ferrules showed higher fracture resistance and lower stress concentration. For residual roots, ISRF and OEP showed no differences, but CLP had lower fracture resistance and higher stress concentration.

Immediate anterior tooth replacement by using an esthetic fixed bridge: A case report

IntroductionLoss of teeth due to extraction is often found in some cases. Preserving interproximal soft tissue and preventing alveolar bone from collapse due to tooth extraction is the most challenging issue. Ovate pontic design can give a natural look like the teeth out of a healthy gingiva. It can be achieve if temporary bridge with ovate pontic was made immediately after extraction expecting the pontic design becomes a guideline on gingival healing process. ObjectiveTo rehabilitate maxillary anterior tooth loss after extraction with bridge prostheses using ovate pontic design to restore the esthetic. CaseA male aged 26 years came to a Specialist Clinic of Prosthodontics Faculty of Dentistry, University of Indonesia with complaints of the discolored and loosened maxillarry anterior teeth. Intraoral and radiographic examination showed non vital maxillary right central incisor with periapical radiolucency, mobility grade 3, discolored, and cervical caries with crown–root ratio is 2:1. While maxillary right lateral incisor is vital with periapical radiolucency, mobility grade 3, crown–root ratio is 2:1. The treatment performed were extraction of maxillary right central and lateral incisor, and temporary bridge with abutment maxillary right canine, maxillary left central and lateral incisor. ConclusionBridge prostheses with ovate pontic is an alternative treatment in cases of anterior tooth loss post-extraction requiring esthetic restorations.

The correspondence of 3D supporting bone loss and crown-to-root ratio to periodontitis classification.

Assessing the application of three-dimensional clinical attachment loss (3D-CAL), 3D supporting bone loss (3D-SBL), supracrestal tissue attachment (STA), and crown-to-root ratio (CRR) in evaluating the 2017 periodontitis classification. We analysed ninety single-rooted human premolars with micro-computed tomography. The amount of 3D-SBL, linear radiographic bone loss (RBL), and CRR corresponding to various periodontitis stages as well as the statistical significance was investigated. From a 3D perspective, the premolars with a 21% of 3D-SBL at 2.0mm coronal root length (RL) and 15% RBL corresponded to the periodontitis stage I. Premolars with a 44% of 3D-SBL at coronal 4.2-4.4mm RL and 33% RBL accorded with the periodontitis stage II. Excluding the consideration of STA, CRR=5:6 and 4:3 were associated with the levels at 15% and 33% RBL, respectively. A greater percentage of 3D-CAL than that of 2D-CAL is significant at evaluated levels. It is feasible to correlate the 3D-SBL, 3D-CAL, and STA parameters to evaluate the stages of periodontitis severity. However, the current use of RBL and CAL as applied for staging in the 2017 classification might be inconsistent with the evaluated premolar roots length, when STA dimensions are considered.

Root-crown ratio: a new method for measurement of orthodontic external apical root resorption

ABSTRACT Purpose: External Apical Root Resorption (EARR) is an undesirable but unavoidable side effect of orthodontic treatment. The various methods proposed for its evaluation, e.g. Intraoral Periapical (IOPA) X-ray and Orthopantomogram (OPG) x-rays use linear measurements which have errors due to magnification and angulations of x-rays. Root-crown ratio as measured on digital OPGs, which are essential diagnostic records for all orthodontic patients were used for the first time to assess root resorption. Methods: A two-step method was used, first to check the v alidation of OPG measurement with IOPA x rays. The first step involved the measurement of Root-crown ratio on digital OPG and IOPA by 5 independent examiners on IC measure software. The second step involved the measurement of root resorption as Root-crown ratio on pretreatment and post-treatment OPG X rays of 32 treated orthodontic patients all of which were treated by a single orthodontist. Digital OPG images of all patients were traced in Picassa software. In both steps, root-crown ratio was assessed by modified Lind method. Results: The results of first step did not show any significant differences in examiners to read the IOPA and OPG x rays. The results of the second step showed 11.8% root resorption in maxillary central incisors and 4% root resorption in lateral incisors. Similarly, maxillary and mandibular molars showed 1.6% and 5.1% resorption, respectively. The resorption in mandibular molars was significantly more compared to pretreatment value. There was apparently no effect of extraction treatment or treatment time on the amount of resorption. Conclusion: The study concluded that root-crown ratio can be used as an effective and efficient alternative method to quantify root resorption on OPG X rays and possibly alleviate the need for taking IOPA x rays in orthodontic patients thereby reducing the radiation exposure.

Prognostic Factors of Grade 2-3 Endo-Periodontal Lesions Treated Nonsurgically in Patients with Periodontitis: A Retrospective Case-Control Study

Background Endo-periodontal lesions are bacterial infectious diseases involving both the periodontal and pulp tissues with poor outcomes. It is hard for clinicians to predict their prognosis. The aim of this study is to investigate the factors affecting the prognosis of endo-periodontal lesions. Methods A total of 140 teeth diagnosed with grade 2-3 endo-periodontal lesions in patients with periodontitis were recruited in this study. They were divided into high and low responder groups, according to the clinical symptoms and parameters of the teeth involved after nonsurgical treatment of both the endodontic and periodontal components. Clinical parameters and symptoms were compared before and after treatment, and gender, age, smoking, and all clinical parameters were compared between high and low responder groups using univariate analyses. Logistic regression was applied to evaluate the independent effects on endo-periodontal lesion prognosis. Results Compared with the clinical parameters at baseline, the values of tooth mobility (TM), periapical index (PAI), and discomfort when chewing were decreased after endodontic therapy, and the values of periodontal probing depth (PD), clinical attachment level (CAL), sulcus bleeding index (SBI), TM, simplified oral hygiene index (OHI-S), full-mouth periodontitis severity, PAI, and discomfort when chewing were decreased after periodontal therapy. Univariate analysis revealed that smoking, PD, CAL, TM, PAI, clinical crown-root ratio (CR), full-mouth periodontitis severities, and the number of root canals were significantly different between the high and low responder groups (P < 0.05). The logistic regression analysis showed that smoking, PD, CAL, full-mouth periodontitis severities, and the number of root canals remained significantly associated with grade 2-3 endo-periodontal lesions in patients with periodontitis (P < 0.05). The logistic regression analysis showed that smoking, PD, CAL, full-mouth periodontitis severities, and the number of root canals remained significantly associated with grade 2-3 endo-periodontal lesions in patients with periodontitis (Conclusions and Practical Implications. High PD and CAL, multirooted teeth, smoking, and serious full-mouth periodontitis indicated a poor prognosis for teeth with grade 2-3 endo-periodontal lesions.

Association Between Gender and Open Apex Among Patients Visiting A Private Dental College

Traumatic injuries in childhood may disrupt root development leading to a tooth with open apex. When permanent teeth with incomplete roots undergo pulpal necrosis they develop roots which are very short, these roots contain very thin walls. They also have a tendency to show inadequate crown-root ratio, which leads to poor prognosis of the tooth. The current study aims to evaluate the association between gender and open apex. The study participants included the patients visiting the out patient department of a private dental college from June 2019 to March 2020. A total of 86,000 case sheets and radiographs associated with the case sheets were reviewed and the data of the 47 patients diagnosed with open apex were further analysed. The data was formulated by reviewing the case sheets of the patients and the data was statistically analysed using Statistical Product and Service Solution software. Within the limits of the study, open apex is more predominant among the male population(83.0%) when compared to the female population (17.0%) and it can be seen that the incidence of open apex is higher for all the teeth in males (11-75.0%, 12-60.0%. 21-89.5%, 22,31,36,41-100%). Chi-square analysis was done and there was no statistically significant association between gender and incidence of open apex. (Pearson chi-square value-4.594; df- 6 ; p-value =0.597>0.05).

Increased nitrogen deposition increased the competitive effects of the invasive plant Aegilops tauschii on wheat

Based on an external nitrogen source NH4NO3, the impacts of different nitrogen deposition treatments (i.e., CK, N5, N10, and N15) on the growth of the A. tauschii and its competition with wheat were investigated. This experiment was conducted in pots using simulated N deposition tests. The results showed that: (1) the plant height, leaf area, and tiller number of both monocultured and mixed planted A. tauschii and wheat increased gradually with increasing nitrogen deposition. In the same nitrogen deposition treatment, the tiller number of A. tauschii was significantly higher than that of wheat. (2) In both monoculture and mixed planting pots, the root biomass and root–crown ratios of A. tauschii to wheat decreased with increasing nitrogen deposition. However, the leaf–biomass ratio of the former showed a gradual increasing trend with increasing nitrogen deposition. (3) Under monoculture and mixed planting modes, the chlorophyll content of A. tauschii increased consistently with increasing nitrogen deposition, but the chlorophyll content of wheat first increased and then decreased. Moreover, the SOD activity, relative conductivity, and MDA content of A. tauschii and wheat constantly increased with increasing nitrogen deposition. (4) In the mixed planting pots, the relative yield of A. tauschii was > 1. The competition balance index of this plant was > 0 and increased with increasing nitrogen deposition. In a nutshell, the ability of A. tauschii to compete with wheat is gradually enhanced with increasing nitrogen deposition; and its adaptability to high nitrogen stress surpasses that of the latter.

The Effect of Crown Lengthening on the Outcome of Endodontically Treated Posterior Teeth: 10-year Survival Analysis

IntroductionThe purpose of this study was to investigate the effect of a crown lengthening (CL) procedure and the crown-root ratio after CL on the long-term survival of endodontically treated teeth (ETT). MethodsPermanent posterior teeth with opposing dentition that had received adequate nonsurgical root canal treatment (NSRCT) and a full-coverage crown between January 1, 2006, and January 1, 2016 were included in this retrospective study. The data collected included dates of the NSRCT, time of extraction if extracted, age, sex, location, the crown-root ratio after CL, and the presence of a lesion. All included ETT were divided into 2 groups:1.the CL group, CL was indicated and performed after NSRCT before crown placement and2.the control group: ETT with adequate ferrule after NSRCT. Data were analyzed using the Kaplan-Cox regression model (α = 0.05). Results5-year survival rates of ETT in the control and CL groups were 88.6% and 82.2%, respectively (P > .05). The 10-year survival rates of ETT in the control and CL groups were 74.5% and 51%, respectively (P < .05). ETT that received the CL procedure after NSRCT were almost 2.3 times more likely to get extracted compared with ETT that did not need the CL procedure at the 10-year follow-up (hazard ratio = 2.29, P < .05). Also, ETT with an inadequate crown-root ratio (1:1) after CL showed the lowest survival rate (40%) compared with ETT with an adequate crown-root ratio (<1:1). ConclusionsA crown-root ratio of 1:1 after osseous CL may affect the long-term survival of ETT. Despite the promising survival rate of ETT with an adequate crown-root ratio after CL, the long-term survival of NSRCT with an inadequate crown-root ratio (1:1) should be considered in the treatment planning phase. Also, it is worth mentioning that the results of the present study should be evaluated in future prospective studies.

Ethnic differences in the root to crown ratios of the permanent dentition.

Root resorption due to orthodontic tooth movement may adversely affect the root-crown (R/C) ratios of permanent teeth, especially in patients with Short Root Anomaly (SRA), a poorly understood disorder affecting root development. Evaluation of SRA R/C ratios to normal dentition would facilitate diagnosis and orthodontic treatment planning. However, reference values are not available for all ethnicities. Our goal was to determine R/C ratios of permanent teeth and their relationship to gender and ethnicity. A retrospective study of 333 patients (109 Caucasians, 112 African Americans and 112 Hispanics) from the University of Alabama at Birmingham School of Dentistry. Root lengths and crown heights were measured from panoramic radiographs of 6241 teeth using modified Lind's method. A linear mixed model was used to compare the R/C ratios of teeth among subgroups (gender, ethnicity). The mean R/C ratios varied from 1.80 to 2.21 for the maxillary teeth and 1.83-2.49 for the mandibular teeth. Gender differences in R/C ratios were found to be significant only for the lower central incisors (P<0.05). Hispanics showed significantly lower ratios for most teeth compared to the other two groups (P<0.05). There were significant differences in R/C ratios between African Americans and Caucasians in the upper lateral incisors, lower central incisors and lower first premolars (P<0.05). Our results suggest that ethnicity is an important factor in determining the R/C ratios of permanent teeth. Therefore, when diagnosing developmental conditions such as SRA, ethnic group-specific reference values should be considered.