A composite DNA element that functions as a maintainer required for epigenetic inheritance of heterochromatin.

Epigenetic inheritance of heterochromatin requires DNA-sequence-independent propagation mechanisms, coupling to RNAi, or input from DNA sequence, but how DNA contributes to inheritance is not understood. Here, we identify a DNA element (termed "maintainer") that is sufficient for epigenetic inheritance of pre-existing histone H3 lysine 9 methylation (H3K9me) and heterochromatin in Schizosaccharomyces pombe but cannot establish de novo gene silencing in wild-type cells. This maintainer is a composite DNA element with binding sites for the Atf1/Pcr1 and Deb1 transcription factors and the origin recognition complex (ORC), located within a 130-bp region, and can be converted to a silencer in cells with lower rates of H3K9me turnover, suggesting that it participates in recruiting the H3K9 methyltransferase Clr4/Suv39h. These results suggest that, in the absence of RNAi, histone H3K9me is only heritable when it can collaborate with maintainer-associated DNA-binding proteins that help recruit the enzyme responsible for its epigenetic deposition.

Understanding the role of P-type ATPases in regulating pollen fertility and development in pigeonpea.

The P-type ATPase superfamily genes are the cation and phospholipid pumps that transport ions across the membranes by hydrolyzing ATP. They are involved in a diverse range of functions, including fundamental cellular events that occur during the growth of plants, especially in the reproductive organs. The present work has been undertaken to understand and characterize the P-type ATPases in the pigeonpea genome and their potential role in anther development and pollen fertility. A total of 59 P-type ATPases were predicted in the pigeonpea genome. The phylogenetic analysis classified the ATPases into five subfamilies: eleven P1B, eighteen P2A/B, fourteen P3A, fifteen P4, and one P5. Twenty-three pairs of P-type ATPases were tandemly duplicated, resulting in their expansion in the pigeonpea genome during evolution. The orthologs of the reported anther development-related genes were searched in the pigeonpea genome, and the expression profiling studies of specific genes via qRT-PCR in the pre- and post-meiotic anther stages of AKCMS11A (male sterile), AKCMS11B (maintainer) and AKPR303 (fertility restorer) lines of pigeonpea was done. Compared to the restorer and maintainer lines, the down-regulation of CcP-typeATPase22 in the post-meiotic anthers of the male sterile line might have played a role in pollen sterility. Furthermore, the strong expression of CcP-typeATPase2 in the post-meiotic anthers of restorer line and CcP-typeATPase46, CcP-typeATPase51, and CcP-typeATPase52 in the maintainer lines, respectively, compared to the male sterile line, clearly indicates their potential role in developing male reproductive organs in pigeonpea.

Assessment of space changes in the lower dental arch after the premature unit loss of a primary molar: A randomized clinical trial.

BACKGROUND: Premature loss of primary teeth presents a significant challenge in oral health, with conflicting views on using space maintainers. AIM: To assess mandibular arch space changes associated with premature lower primary molar (PM) loss with or without a space maintainer. DESIGN: A randomized clinical trial with children (6-9 years old) with premature loss of a lower PM divided into two groups: control group (CG), without a space maintainer, and intervention group (IG), with a space maintainer. Dental casts were measured at baseline, 3 months, and 6 months. Linear distance; intercanine width and length; and arch width, length, and perimeter were measured. ANOVA and t-test were applied (p = .05). RESULTS: Twenty-six patients (mean: 7.3 years; standard deviation [SD]: 0.92) were included: 14 in CG and 12 in IG. CG had a greater space loss (-0.9 mm; SD: 0.45) than IG (-0.4 mm; SD: 0.61) at 3 months (p < .05). No difference between the groups was observed after 6 months (p = .610). CG decreases space at 6 months, especially with the first permanent molars without intercuspation (-2 mm; SD: 0.71; p = .007). CONCLUSION: Premature lower PM loss resulted in reduced arch space loss after 6 months, regardless of a space maintainer use. CG showed more loss of space when the first permanent molars lacked intercuspal relationship.

Arm design of band and loop space maintainer affects its longevity: a patient-specific finite element study.

Fixed space maintainers (FSMs) are commonly utilized in pediatric dentistry to prevent space loss following premature tooth extraction. Although previous studies have examined the survival rates and causes of FSM failure, the impact of arm design on failure has not been investigated. This study aimed to investigate the tensile and compressive stresses related to FSMs with different arm designs and evaluate the effect of arm designs on FSM failure. Cone beam computed tomography images of a child who experienced premature loss of a primary mandibular left second molar tooth were retrieved from our database, then processed and simulated using the Rhinoceros software. Finite element analysis was performed to evaluate the stresses on four distinct FSM arm designs under simulated chewing forces. The results showed that the straight-arm FSM design exhibited the highest von Mises principal stress, while FSMs with curved arms and surrounding primary mandibular left first molar in the mesial area demonstrated the lowest von Mises stress accumulation. Intense stress accumulation on the distal surface of tooth 74 was observed in the test models due to the transmitted forces by the FSM. The maximum principal stresses accumulated at the base of the alveolar socket of the mesial root of tooth 36, while the minimum principal stresses were identified at the mesio-marginal area of the alveolar crest. The arm design played a crucial role in enabling the appliance to effectively withstand the stresses accumulating on the Space maintainer (SM) and orthodontic band. Bending the SM arms to match the surrounding profile with curvature increased the stress absorption capacity by increasing the arm length.

Development of male sterile lines of CMS chilies (Capsicum annuum L.) from F1 hybrids.

Selfing and crossing methods were used to develop the cytoplasmic male sterility (CMS) lines from 2 elite F1 hybrids of CMS hot chilies. The pungency of the CMS lines was improved by backcrossing with the B cultivar. The first and second backcrossed progenies of the CMS lines showed significantly higher capsaicin contents than the F1 hybrids. One good female line K16 × BBC2 (K16), was selected and backcrossed with 3 good maintainer cultivars, C5, C9 and C0. Some incomplete male sterility of pollens was demonstrated in the F1 hybrids and the 1st backcrossed progenies while the partial sterility disappeared by the stage of the second and third generations of backcrossing. When K16 and P32 were crossed with restorers, fruit yields and yield components of certain F1 hybrids, parental lines and commercial varieties were significantly different. Heterosis of yield and yield components of the F1 hybrid chilies was significant. When K16 was used as a female parent, positive and significant heterosis of the F1 hybrids was the same as P32. Moreover, significant GCA of the restorer lines, C7, C8 and C9, was observed in some horticultural characteristics. Furthermore, significant differences of the specific combining ability of some characteristics were observed in a few F1 hybrids.

Fully digital workflow for the fabrication of a tooth-colored space maintainer for a young patient.

OBJECTIVES: Preventive orthodontic therapy with a band and loop is recommended to reduce the prevalence and severity of malocclusion on premature loss of a primary molar. However, when young patients are less cooperative and have a severe gag reflex, using traditional impression methods may be challenging. The use of a conventional metal space maintainer (SM) requires manual laboratory procedures and does not provide optimal esthetics. Moreover, gingival submergence of the wire and gingivitis caused by metal structures may occur. This clinical report describes a complete digital workflow for the fabrication of a zirconia SM to overcome these limitations. CLINICAL CONSIDERATIONS: An 8-year-old boy with a band and loop SM for a missing primary mandibular right second molar presented with plaque accumulation around the band, soft tissue impingement by the loop, and loss of cement. A reverse band and loop SM had been proposed for the restoration of the primary mandibular right first molar. After conservative tooth preparation, a digital impression procedure was performed. A customized band and loop SM was designed using a computer-aided design software and milled out of the zirconia block. After sintering, the SM was luted with adhesive resin cement. CONCLUSIONS: Using an intraoral scanner, computer-aided design, and computer-aided manufacturing technology, the limitations of traditional impression procedures were overcome, and a zirconia SM with mechanical, biological, and esthetic advantages was fabricated. CLINICAL SIGNIFICANCE: Advancements in dental materials and digital technologies allow for the efficient fabrication of a tooth-colored SM with an improved patient satisfaction and reduced human error.

Dental arch spatial changes after premature loss of first primary molars: a systematic review and meta-analysis of split-mouth studies.

BACKGROUND: This study aimed to evaluate spatial changes in dental arches resulting from premature loss of first primary molars and assess the necessity of a space maintainer. METHODS: We searched the electronic databases PubMed, Cochrane Library, ClinicalTrials, and EMBASE. Split-mouth studies involving unilateral premature loss of a primary first molar were included. Quality assessment of selected studies made use of the ROBINS-I tool. Mean space differences were calculated for the D + E and D spaces, arch width, arch length, arch perimeter. RESULTS: Of the 329 studies considered, 11 split-mouth studies were selected, including 246 cases in the maxilla and 217 in the mandible from 477 individuals aged 5-10 years. Over the medium-term follow-up period (6-24 months), space loss was 0.65 mm in the maxillary D + E (MD 0.65, 95% CI 0.15-1.16, P = 0.01), 1.24 mm in the mandibular D + E (MD 1.24, 95% CI 0.60-1.89, P < 0.01), and 1.47 mm in the mandibular D (MD 1.47, 95% CI 0.66-2.28, P < 0.01). There was no significant change in arch width, length, or arch perimeter between the initial and follow-up examinations (P > 0.05). CONCLUSIONS: After premature loss of first primary molars, space can be lost, but the amount of loss would not affect arch width, length, or arch perimeter over the 6-24 months follow-up period.

Improving blast resistance of maintainer line DRR 9B by transferring broad spectrum resistance gene Pi2 by marker assisted selection in rice.

Hybrid rice technology offers great promise to further enhance rice production and productivity for global food security. Improving hybrid rice parental lines is the first step in developing heterotic rice hybrids. To improve resistance against blast disease, a maintainer line DRR 9B was fortified with a major broad-spectrum blast resistance gene Pi2 through marker-assisted selection. The rice blast caused by Magnaporthe oryzae is a major disease and can cause severe yield losses upto 100%. The NILs of Samba Mahsuri namely BA-23-11-89-12-168 possessing Pi2 was utilized as a donor parent. The PCR-based molecular marker tightly linked to Pi2 gene was used for the foreground selection at BC1F1 generation. The molecular marker tightly linked to the major fertility restorer gene Rf4 was used for negative selection (i.e., selection of plants possessing non fertility restoring alleles) at BC1F1 generation to identify maintainer lines. The positive plants with Rf4 gene were added to the restorer pool for restorer line development. At each stage, MAS for Pi2 coupled with stringent phenotypic selection for agro-morphological and grain quality traits were exercised. At BC1F3 generation, one hundred families were screened against blast disease at uniform blast nursery (UBN) and selected resistant lines were advanced to next generations. In the BC1F5 generation plants were subjected to agro-morphological evaluation for yield and yield-contributing traits. The selected plants at BC1F5 generation were crossed with DRR 9A to assess the maintainer ability of blast resistance lines and for further CMS line conversion for hybrid rice breeding for developing blast resistance rice hybrids.

A biotechnology-based male-sterility system for hybrid seed production in tomato.

Incorporating male sterility into hybrid seed production reduces its cost and ensures high varietal purity. Despite these advantages, male-sterile lines have not been widely used to produce tomato (Solanum lycopersicum) hybrid seeds. We describe the development of a biotechnology-based breeding platform that utilized genic male sterility to produce hybrid seeds. In this platform, we generated a novel male-sterile tomato line by clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated mutagenesis of a stamen-specific gene SlSTR1 and devised a transgenic maintainer by transforming male-sterile plants with a fertility-restoration gene linked to a seedling-colour gene. Offspring of crosses between a hemizygous maintainer and the homozygous male-sterile plant segregated into 50% non-transgenic male-sterile plants and 50% male-fertile maintainer plants, which could be easily distinguished by seedling colour. This system has great practical potential for hybrid seed breeding and production as it overcomes the problems intrinsic to other male-sterility systems and can be easily adapted for a range of tomato cultivars and diverse vegetable crops.

Computer-aided design of polyetheretherketone for application to removable pediatric space maintainers.

BACKGROUND: The premature loss of primary teeth is a common problem in pediatric dentistry, resulting in disruption of the arch integrity. Hence, space maintainers (SM) used for maintaining spaces are necessary. However, current methods of making removable space maintainers (RSM) have some limitations. METHODS: Digital models of dentition defects were obtained by using a scanning technique coupled with laser medical image reconstruction. The digital RSMs were designed using the 3Shape software. They were manufactured using two methods: polyetheretherketone (PEEK), and conventional methods (20 RSMs per group). For qualitative evaluation, the Likert five-point scale was used by 10 experts to obtain a score for 40 RSMs. The spaces between the tissue surfaces of the RSMs and the models were replaced using silicone, and the maximum and mean distances, as well as the standard deviation, were measured. A three-dimensional variation analysis was used to measure these spaces. The student's t-test and Satterthwaite t-test were used to compare the differences in the spaces for the various materials. RESULTS: The PEEK RSMs were found to fit the models well. In the qualitative assessment, the mean experts' scores for the PEEK and conventional groups were 1.80 ± 0.40 and 1.82 ± 0.40, and there was no significant difference between the two groups (p = 0.875). In the quantitative assessment, the mean spaces for the PEEK digital RSMs and the conventional RSMs were 44.32 ± 1.75 µm, and 137.36 ± 18.63 µm, respectively, and the differences were statistically significant (p < 0.001). In addition, there were significant differences in the maximum space and the standard deviation between the two groups. CONCLUSION: Digitally designed and integrated RSMs were found to be superior to those produced using the conventional method. 3D variation analysis results showed that the mean distances and standard deviations of the PEEK groups were significantly smaller than those of conventional group (p < 0.01). A PEEK-manufactured RSM produced using CAD/CAM would be extremely suitable for clinical applications.

Comparative transcriptome analysis in Chinese cabbage (Brassica rapa ssp. pekinesis) for DEGs of Ogura-, Polima-CMS and their shared maintainer.

Cytoplasmic male sterility (CMS) is maternally inherited trait, which hinders the ability to produce viable pollen in plants. It serves as a useful tool for hybrid seed production via exploiting heterosis in crops. The molecular mechanism of CMS and fertility restoration has been investigated in different crops. However, limited number of reports is available on comparison of Ogura- and Polima-CMS with their shared maintainer in Chinese cabbage. We performed transcript profiling of sterile Ogura CMS (Tyms), Polima CMS (22m2) and their shared maintainer line (231-330) with an aim to identify genes associated with male sterility. In this work, we identified 912, 7199 and 6381 DEGs (Differentially Expressed Genes) in 22m2 Vs Tyms, 231-330 VS 22m2 and 231-330 Vs Tyms, respectively. The GO (Gene Ontology) annotation and KEGG pathway analysis suggested that most of the DEGs were involved in pollen development, carbon metabolism, lipase activity, lipid binding, penta-tricopeptide repeat (PPR), citrate cycle and oxidative phosphorylation, which were down-regulated in both CMS lines. This result will provide an important resource for further understanding of functional pollen development, the CMS mechanism and to improve molecular breeding in Chinese cabbage.

Metabolomic characterization of sunflower leaf allows discriminating genotype groups or stress levels with a minimal set of metabolic markers.

INTRODUCTION: Plant and crop metabolomic analyses may be used to study metabolism across genetic and environmental diversity. Complementary analytical strategies are useful for investigating metabolic changes and searching for biomarkers of response or performance. METHODS AND OBJECTIVES: The experimental material consisted in eight sunflower lines with two line status, four restorers (R, used as males) and four maintainers (B, corresponding to females) routinely used for sunflower hybrid varietal production, respectively to complement or maintain the cytoplasmic male sterility PET1. These lines were either irrigated at full soil capacity (WW) or submitted to drought stress (DS). Our aim was to combine targeted and non-targeted metabolomics to characterize sunflower leaf composition in order to investigate the effect of line status genotypes and environmental conditions and to find the best and smallest set of biomarkers for line status and stress response using a custom-made process of variables selection. RESULTS: Five hundred and eighty-eight metabolic variables were measured by using complementary analytical methods such as 1H-NMR, MS-based profiles and targeted analyses of major metabolites. Based on statistical analyses, a limited number of markers were able to separate WW and DS samples in a more discriminant manner than previously published physiological data. Another metabolic marker set was able to discriminate line status. CONCLUSION: This study underlines the potential of metabolic markers for discriminating genotype groups and environmental conditions. Their potential use for prediction is discussed.

Construction of a multicontrol sterility system for a maize male-sterile line and hybrid seed production based on the ZmMs7 gene encoding a PHD-finger transcription factor.

Although hundreds of genetic male sterility (GMS) mutants have been identified in maize, few are commercially used due to a lack of effective methods to produce large quantities of pure male-sterile seeds. Here, we develop a multicontrol sterility (MCS) system based on the maize male sterility 7 (ms7) mutant and its wild-type Zea mays Male sterility 7 (ZmMs7) gene via a transgenic strategy, leading to the utilization of GMS in hybrid seed production. ZmMs7 is isolated by a map-based cloning approach and encodes a PHD-finger transcription factor orthologous to rice PTC1 and Arabidopsis MS1. The MCS transgenic maintainer lines are developed based on the ms7-6007 mutant transformed with MCS constructs containing the (i) ZmMs7 gene to restore fertility, (ii) α-amylase gene ZmAA and/or (iii) DNA adenine methylase gene Dam to devitalize transgenic pollen, (iv) red fluorescence protein gene DsRed2 or mCherry to mark transgenic seeds and (v) herbicide-resistant gene Bar for transgenic seed selection. Self-pollination of the MCS transgenic maintainer line produces transgenic red fluorescent seeds and nontransgenic normal colour seeds at a 1:1 ratio. Among them, all the fluorescent seeds are male fertile, but the seeds with a normal colour are male sterile. Cross-pollination of the transgenic plants to male-sterile plants propagates male-sterile seeds with high purity. Moreover, the transgene transmission rate through pollen of transgenic plants harbouring two pollen-disrupted genes is lower than that containing one pollen-disrupted gene. The MCS system has great potential to enhance the efficiency of maize male-sterile line propagation and commercial hybrid seed production.

Evaluation of Skeletal and Dental Effects of Lower Lingual Arches.

OBJECTIVE: A lower lingual arch is usually recommended as a holding device to maintain arch length and to prevent mesial migration of the mandibular first molars. Despite its widespread use, comparatively little is known about the effects of a lower lingual holding arch on preservation of lower arch dimensions and tooth position and the impact of the device on mandibular growth. The aim of this study is to evaluate the skeletal and dental effects of the lower lingual holding arch with regard to arch dimension, positions of mandibular molars and incisors, and usual mandibular growth. STUDY DESIGN: Thirty-four children (18 males and 16 females) who needed space maintainers were included in the present study. The patients were divided into two groups according to whether they were missing second primary molars on one or both sides. Group I comprised 16 children (8 males and 8 females, average age 8.8 ± 0.9 years) with a missing second primary molar on one side; Group II comprised 18 children (10 males and 8 females, average age 8 ± 0.7 years) with extractions on both sides. Lateral cephalograms, dental pantomograms, and study casts of the patients were taken at the beginning and the end of the study period. Average treatment time was 20.4 ± 4 months. RESULTS: Lower incisors moved forward and Incisor Mandibular Plane Angle (IMPA°) increased in both treatment groups. Statistically significant differences between the groups were found when comparing pre-treatment and post-treatment arch dimension and position of mandibular molars. Results were better for lingual arches with extraction on one side than with extraction on both sides Conclusions: A lingual arch seems to be an effective tool for maintaining arch length, and was not found to impair mandibular growth.

Clinical Success of Fiber-reinforced Composite Resin as a Space Maintainer.

INTRODUCTION: The early loss of deciduous molars is a frequently encountered problem in dentistry. Various space maintainer designs were developed to prevent the loss of the space. The aim of this study was to evaluate long-term clinical performance and survival rates of fiber-reinforced composite resin (FRCR) as a space maintainer clinically. MATERIALS AND METHODS: This study was designed on 44 children who had early missed deciduous molars. Space maintainers were prepared on plaster models of patients and fixed directly to the adjacent teeth. Survival rate and whether it causes any damage to adjacent teeth were examined clinically and radio-graphically for 24 months or until failure. Kaplan-Meier survival analysis was used for the statistical analyses. RESULTS: Overall, 16.2% of space maintainers were dislodged and accepted to be failed at the end of 12 months. At the 24-month control, 52.2% success was stated with the FRCR space maintainer and because of permanent tooth eruption, 31.8% of space maintainer were taken out. The mean duration of space maintainers was measured to be 14.8 ± 3.48 months. There was no statistical significance between survival time and gender, tooth number, localization, and measured space (p > 0.05). CONCLUSION: After all 24 months follow-up, as well as esthetic properties of FRCR space maintainer, their applicability in a single seance and strength against the forces are determined as the advantages of the technique. CLINICAL SIGNIFICANCE: The FRCR space maintainers can be thought of as alternatives to metal space maintainers.

Initial Stresses induced in Permanent Maxillary First Molar in Mixed Dentition under Normal Masticatory Forces: A Finite Element Study.

OBJECTIVE: The cross-arch space maintainers are used to prevent mesio-distal movement of teeth under physiologic forces, contrary to adult orthodontics where these are used as anchorage against orthodontic forces. Stresses in periodontal ligaments (PDL) are supposed to be different in pediatric dentistry and need to be studied. This study aimed to create mathematical model and calculated the initial stresses generated in the PDL and the behavior of movement in developing permanent maxillary first molar under masticatory forces using 3D finite element analyses (FEA). STUDY DESIGN: Data acquisition, image processing, geometric modeling followed by FE analyses was done under vertical load of 70N. The generated stress and tooth displacement were observed with or without primary second molar, mesial to permanent maxillary first molar. RESULTS: Masticatory forces resulted in insignificant initial PDL stresses and mesial displacement of permanent maxillary first molar in the intact arch. In the case of missing primary second molar, maximum stresses were on the palatal root and the tooth showed greater mesial displacement with mesio-palatal rotation. CONCLUSIONS: Any space maintainer preventing mesio-palatal rotation of permanent maxillary first molar, under physiologic masticatory loadings, may be inserted in case of multiple tooth loss.

An empirical study of software ecosystem related tweets by npm maintainers.

The npm ecosystem is crucial for the JavaScript community and its development is significantly influenced by the opinions and feedback of npm maintainers. Many software ecosystem maintainers have utilized social media, such as Twitter, to share community-related information and their views. However, the communication between npm maintainers via Twitter in terms of topics, nature, and sentiment have not been analyzed. This study conducts an empirical analysis of tweets by npm maintainers related to the software ecosystem to understand their perceptions and opinions better. A dataset of tweets was collected and analyzed using qualitative analysis techniques to identify the topic of tweets, nature, and their sentiments. Our study demonstrates that most tweets belong to the package management category, followed by notifications and community-related information. The most frequently discussed topics among npm maintainers in the package management category are usage scenarios. It appears that the nature of tweets mostly shared by npm maintainers is information, followed by question and answer, respectively. Additionally, the sentiment analysis reveals that npm maintainers express more positive sentiments towards notification and community-related discussion while expressing more neutral opinions towards the package management related discussion. This case study provides valuable insights into the perceptions and opinions of the npm maintainers regarding the software ecosystem and can inform future development and decision making.

Assessment of Knowledge and Utilization of Prefabricated Band and Loop Space Maintainers in Primary Dentition Among Dentists: A Cross-Sectional Questionnaire Study.

INTRODUCTION: Preserving primary dentition is essential for maintaining optimal oral health and development in children. Premature loss of primary teeth due to caries, infection, crowding, or trauma can necessitate orthodontic intervention and lead to various complications. Space maintainers are critical for preserving arch space until the eruption of permanent teeth, thereby preventing issues such as ectopic eruption, crowding, and malocclusion. Despite their advantages, prefabricated space maintainers (PSMs) are underutilized. This study aims to evaluate the knowledge, attitudes, and practices of Indian dentists regarding PSMs in primary teeth. METHODOLOGY: A cross-sectional questionnaire survey was conducted among 100 dental practitioners in Chennai. A 10-item self-administered questionnaire, developed based on a comprehensive literature review and expert consultations, assessed demographics, knowledge of PSM indications and techniques, current practices, perceived barriers, and preferences for continuing education. The questionnaire's reliability was confirmed with a Cronbach's alpha value of 0.85. Descriptive statistics, including frequencies and percentages, were used to summarize the participants' demographic characteristics, knowledge levels, and current practices related to PSMs. RESULTS: Of the 100 respondents, 86 (86%) were males and 14 (14%) were females. Only 19 (19%) reported using PSMs, while 36 (36%) used conventional space maintainers. A significant proportion (42 (42%)) of the respondents held a master's degree in dental surgery, yet only 11 (11%) had participated in Continuing Dental Education (CDE) programs on space maintainers. The perceived benefit of PSMs being a single appointment procedure was acknowledged by 82 (82%) of the respondents, whereas 76 (76%) participants identified cost as a major drawback. Notably, 45 (45%) practitioners did not consider PSMs necessary. CONCLUSION: This survey highlights notable obstacles in the adoption of PSMs among Indian dentists, emphasizing the need for focused educational initiatives. Improving knowledge and practices related to PSMs can enhance pediatric dental care and oral health outcomes in India.

Clinical Evaluation of Different Designs of Fixed Space Maintainer: A Randomized Clinical Trial.

Purpose: Evaluation of survival rates for three space maintainers (SMs) of different designs compared to the standard one. Materials and methods: A total of 52 extraction sites in children aged 4-7 years with prematurely lost primary molars were selected for this study. The whole sample was divided into four groups of 13 each. In group I, Band and Loop (B&L); group II, single-sided Band and Loop (Ss B&L); group III, Direct Bonded Wire (DBW); and group IV, Tube and Loop (T&L). Children were recalled at 3, 6, 9, 12, and 15 months. Cumulative survival rates of SMs were estimated using the Kaplan-Meier method with a logrank test. Results: Although there was a nonsignificant difference in the number of failed cases among all groups, the overall survival rate for group I was 69.2%, group II was 53.8%, group III was 38.5%, and group IV was 30.8% at the end of the study. The failure types for B&L were solder breakage (75% of the total failure rate) and cement dissolution (25%); for Ss B&L, they were solder breakage with lost loop (50%), soft tissue impingement (33%), and dislodgment (17%); for DBW, they were composite-wire interface debonding (75%) and enamel-composite interface debonding (25%); and finally, for T&L, they were lost T&L (56%), soft tissue impingement (22%), and total loss (22%). Conclusion: Banded SMs survived for a longer time than bonded ones, with superior performance for B&L compared to Ss B&L. In addition, bonded SMs required strict isolation conditions. DBW could be used in the maxilla rather than the mandible and was preferable for older children. How to cite this article: Hemdan ME, H El Kalla IHH, El Agamy RA. Clinical Evaluation of Different Designs of Fixed Space Maintainer: A Randomized Clinical Trial. Int J Clin Pediatr Dent 2024;17(4):442-450.

Stress induced on permanent mandible first molar and space maintainer under normal masticatory forces: a finite element study.

Background: The band and loop space maintainer is used to maintain the missing space of deciduous molars which are lost early. When the second deciduous molar is lost prematurely, the stress on the first permanent molar during different degrees of development may vary when it is the abutment. The design and use of the space maintainer may also lead to damage of the loop. The purpose of this article is to use the finite element method to study the stress on the first permanent molar and the loop with or without occlusal contact, with the first permanent molar of four different degrees of development serving as the abutment. We aimed to guide the clinical design and use of the space maintainer. Methods: We developed finite element models of the mandibular first permanent molar and the band and loop space maintainer, and simulated alveolar bone, periodontal ligament (PDL), enamel and dentin. The four developmental stages were 1/2 (I), 2/3 (II), 3/4 (III) and full development (IV). Ansys Workbench was used to analyze the effects of root development and occlusal contact between the loop and the opposite jaw on abutment teeth and the loop. Abutment teeth were statically loaded vertically and obliquely with a force of 70 N. The loop was statically loaded vertically with a force of 14 N. The stress on all structures and the displacement trends of the loop were calculated. Results: The stress on enamel, dentin, PDL and alveolar bone were similar, and the concentration was consistent. But if there was occlusal contact, the loop produced maximum displacement at the near middle edge of contact with the anterior teeth. When the loop was in occlusal contact with the opposing occlusal tooth, the peak value of the equivalent stress on the space maintainer under vertical load was: group I > group IV > group III > group II, and the maximum principal stress peak change was: group I > group III > group II > group IV. The change of the equivalent stress peak value of the loop under oblique load was: group I > group III > group IV > group II, and the maximum principal stress peak change was: group III > group I > group II > group IV. When the loop was not in occlusal contact with the opposing occlusal tooth, the peak value of the equivalent stress on the space maintainer under vertical load was: group IV > group I > group II > group III, and the maximum principal stress peak change was: group IV > group I > group II > group III. The change of the equivalent stress peak value of the space maintainer under oblique load was: group I > group IV > group II > group III, and the maximum principal stress peak change was: group I > group IV > group II > group III. Conclusions: Our results suggested that whenever possible, choosing the teeth with nearly complete root development as the abutment of the space maintainer is advisable. The design and use of the band and loop space maintainer should avoid occlusal contact with the occlusal teeth to prevent deformation of the loop.