Finite element analysis of stress distribution on residual root structure in socket shield procedure following immediate dental implant placement: an in vitro study.

BACKGROUND: The success of implants in the socket shield technique relies on stress experienced by root fragments within the socket. Although there is no consensus on optimal root fragment thickness, varying thicknesses and dynamic implant placement induce stress in various directions and degrees. This study aimed to assess biomechanical response and stress distribution across different root fragment thicknesses in the socket shield procedure. METHODS: This in vitro study was conducted to assess and compare the stress distribution on residual root structures of varying thicknesses positioned within the labial aspect of the maxillary incisor socket during immediate implant placement of standard dimensions. The procedure involved applying an insertional torque of 40 Ncm, and the analysis was conducted using finite element analysis software. RESULTS: Utilizing the Numerical Technique with Abaqus software for explicit dynamics, von Mises stress and principal strain were analyzed on the root structure and bone under nonlinear contact conditions during implant torque application. For Model A, a loading torque of 40 Ncm was applied vertically on the implant, along with a horizontal force of 20 N on the root structure and bone. Results indicated maximum stress of 12.68 MPa on the root structure with a thickness of 0.5 mm and 5.61 MPa on the bone, with principal strains of 6.82E-03 and 4.10E-03, respectively. In Model B, with a root structure thickness of 1.0 mm, the maximum stress increased to 19.70 MPa, while the bone stress rose to 9.51 MPa, with principal strains of 1.03E-02 and 6.09E-03. Model C, with a root structure thickness of 1.5 mm, exhibited a maximum stress of 21.58 MPa on the root and 10.12 MPa on the bone, with principal strains of 1.16E-02 and 6.10E-03. Lastly, in Model D, with a root structure thickness of 2.0 mm, the maximum stress on the root structure and bone escalated to 28.74 MPa and 11.38 MPa, respectively, with principal strains of 1.55E-02 and 8.31E-03. CONCLUSIONS: As the thickness of the shield increases (ranging from 0.5 to 2 mm) in socket shield procedures with immediate implant placement, both stress on the root fragment and bone and principal micro-strain escalate. However, employing a shield thickness within the range of 0.5 to 2 mm does not lead to any adverse stress generation on the residual root fragment. However, for enhanced safety, it is recommended to restrict the maximum diameter and extension of the root fragment to 1.5 mm when considering implant sizes and socket diameter for the socket shield technique.

Long-Term Benefits of Cenchrus fungigraminus Residual Roots Improved the Quality and Microbial Diversity of Rhizosphere Sandy Soil through Cellulose Degradation in the Ulan Buh Desert, Northwest China.

Long-term plant residue retention can effectively replenish soil quality and fertility. In this study, we collected rhizosphere soil from the residual roots of annual Cenchrus fungigraminus in the Ulan Buh Desert over the past 10 years. The area, depth, and length of these roots decreased over time. The cellulose content of the residual roots was significantly higher in the later 5 years (2018-2022) than the former 5 years (2013-2017), reaching its highest value in 2021. The lignin content of the residual roots did not differ across samples except in 2015 and reached its highest level in 2021. The total sugar of the residual roots in 2022 was 227.88 ± 30.69 mg·g-1, which was significantly higher than that in other years. Compared to the original sandy soil, the soil organic matter and soil microbial biomass carbon (SMBC) contents were 2.17-2.41 times and 31.52-35.58% higher in the later 3 years (2020-2022) and reached the highest values in 2020. The residual roots also significantly enhanced the soil carbon stocks from 2018-2022. Soil dehydrogenase, nitrogenase, and N-acetyl-ß-D-glucosidase (S-NAG) were significantly affected from 2019-2022. The rhizosphere soil community richness and diversity of the bacterial and fungal communities significantly decreased with the duration of the residual roots in the sandy soil, and there was a significant difference for 10 years. Streptomyces, Bacillus, and Sphigomonas were the representative bacteria in the residual root rhizosphere soil, while Agaricales and Panaeolus were the enriched fungal genera. The distance-based redundancy analysis and partial least square path model results showed that the duration of residual roots in the sandy soil, S-NAG, and SMBC were the primary environmental characteristics that shaped the microbial community. These insights provide new ideas on how to foster the exploration of the use of annual herbaceous plants for sandy soil improvement in the future.

The effect of different ferrule heights and crown-to-root ratios on fracture resistance of endodontically-treated mandibular premolars restored with fiber post or cast metal post system: an in vitro study.

BACKGROUND: This study aimed to investigate the effects of different ferrule heights and crown-to-root ratios on the fracture resistance of endodontically-treated premolars restored with fiber post or cast metal post system. METHODS: Eighty extracted human mandibular first premolars with single root canal were treated endodontically and cut from 2.0 mm above the buccal cemento-enamel junction, to create horizontal residual roots. The roots were randomly divided into two groups. The roots in group FP were restored with a fiber post-and-core system, while the roots in group MP were restored with a cast metal post-and-core system. Each group was divided into five subgroups with different ferrule heights (0: no ferrule; 1: 1.0 mm ferrule; 2: 2.0 mm ferrule; 3: 3.0 mm ferrule; 4: 4.0 mm ferrule). All specimens were subsequently restored with metal crowns and embedded in acrylic resin blocks. The crown-to-root ratios of the specimens were controlled at approximately 0.6, 0.8, 0.9, 1.1, and 1.3 of the five subgroups, respectively. Fracture strengths and fracture patterns of the specimens were tested and recorded by a universal mechanical machine. RESULTS: Mean fracture strengths (mean ± standard deviation (kN)) of FP/0 to FP/4 and MP/0 to MP/4 were: 0.54 ± 0.09, 1.03 ± 0.11, 1.06 ± 0.17, 0.85 ± 0.11; 0.57 ± 0.10, 0.55 ± 0.09, 0.88 ± 0.13, 1.08 ± 0.17, 1.05 ± 0.18 and 0.49 ± 0.09, respectively. Two-way ANOVA revealed significant effects of different ferrule heights and crown-to-root ratios on the fracture resistance (P < 0.001), but no difference in fracture resistance between two post-and-core systems (P = 0.973). The highest fracture strengths of the specimen were found with the ferrule length of 1.92 mm in group FP and 2.07 mm in group MP, the crown-to-root ratio of which in 0.90 and 0.92 respectively., there is a significant difference in fracture patterns among the groups(P < 0.05). CONCLUSIONS: When a certain height of ferrule is prepared and a cast metal or fiber post-and-core system is restored for the residual root, the clinical crown-to-root ratio of the tooth after restoration should be kept within 0.90 to 0.92, so as to improve the fracture resistance of endodontically-treated mandibular first premolars.

A rare case of residual root myiasis caused by Clogmia albipunctata larvae (Diptera: Psychodidae).

BACKGROUND: Dental injury caused by caries and trauma is the main cause of residual roots. Food trapped in the residual roots is difficult to clean. If the residual roots are not treated and cared for in time, flies can take advantage as soon as hygiene slips. Here, we present a rare case of human residual root myiasis caused by Clogmia albipunctata larvae, never previously reported. CASE PRESENTATION: A 26-year-old lady found two active, living larvae in her mouth while brushing her teeth. She did not present with fever, pain and any uncomfortable oral feeling. The intraoral examination revealed the right second mandibular molar was severely damaged as a result of caries, leaving a residual tooth root. The mucosa above it was mildly erythematous and edematous. No larvae and no inflamed gums were observed in her mouth. When normal saline was used to flush the area of the residual root with a syringe, four larvae appeared from the residual root. The larvae were observed by naked eye and under a light microscope. They were identified as the mature stage larvae of Clogmia albipunctata. Because the patient was in lactation, medication was not recommended. Treatment included the removal of all visible larvae followed by flushing the residual root with normal saline three times a day. The patient was followed-up weekly for one month. No more larvae were found and the erythematous and edematous mucosa healed completely. CONCLUSIONS: The existence of a residual root can result in residual root myiasis. Myiasis caused by Clogmia albipunctata larvae or other fly larvae should be considered in cases of residual root infection.

Do submerged roots hinder orthodontic treatment or the use of implants?

ABSTRACT Introduction: In clinical practice, submerged roots are found with high frequency, and their presence can change the planning of dental movements and implant placement. Objectives: To provide explanations of possible developments in the area involved, according to the evolutionary stage of the process, at the time of diagnosis. Discussion: After atrophy of the periodontal ligament and epithelial remnants of Malassez, ankylosis of the bone with the submerged root occurs, and initiates a process of replacement resorption. Until this process reaches the most advanced stage, this area represents an increased "bone" density, and if some care is not taken, this can generate resorption problems in the tooth to be moved. Whereas implants can be placed, despite the presence of the submerged root, irrespective of the stage of evolution. Conclusion: It is natural for the onset of alveolodental ankylosis and tooth replacement resorption to occur in submerged roots, and its stage of evolution will be decisive in the approach to be adopted in clinical planning.

RESUMO Introdução: A frequência, na prática clínica, das raízes submersas é elevada, e sua presença pode modificar o planejamento de movimentações osteodentárias e da instalação de implantes. Objetivo: Apresentar as explicações das possíveis evoluções na área envolvida, de acordo com o estágio evolutivo do processo, no momento do diagnóstico. Discussão: Depois da atrofia do ligamento periodontal e dos restos epiteliais de Malassez, o osso anquilosa-se com a raiz submersa, e se inicia a reabsorção por substituição. Até se chegar ao estágio mais avançado, essa área representa uma densidade "óssea" aumentada, o que pode gerar problemas reabsortivos no dente a ser movimentado, caso alguns cuidados não sejam tomados. Por outro lado, os implantes podem ser aplicados, apesar da presença da raiz submersa, independentemente da fase evolutiva. Conclusão: É natural que, em raízes submersas, se instale a anquilose alveolodentária e a reabsorção dentária por substituição, e o seu estágio evolutivo será determinante na conduta a ser adotada no planejamento clínico.

[Digital workflow of orthodontic and prosthetic treatment for subgingival residual root preservation guided by target restoration space].

The use of orthodontic traction to preserve healthy subgingival residual root is a classical method combining the treatment of restoration and orthodontics. Based on the target restoration space (TRS), by establishing a TRS digital model, the final traction position of the subgingival residual root can be preset. After evaluating the key parameters such as crown-to-root ratio and minimum crown height, clinicians can estimate the treatment time and exclude cases with bad preset position. The time of traction treatment can be effectively reduced, and the efficiency and efficacy of the entire treatment can also be improved.

An in vitro study evaluating the effect of ferrule design on the fracture resistance of endodontically treated mandibular premolars after simulated crown lengthening or forced eruption methods.

BACKGROUND: The purpose of this study was to evaluate the effect of ferrule design on the fracture resistance of endodontically treated mandibular first premolars after simulated crown lengthening and orthodontic forced eruption methods restored with a fiber post-and-core system. METHODS: Forty extracted and endodontically treated mandibular first premolars were decoronated to create lingual-to-buccal oblique residual root models, with a 2.0 mm height of the lingual dentine wall coronal to the cemento-enamel junction, and the height of buccal surface at the cemento-enamel junction. The roots were divided randomly into five equal groups. The control group had undergone incomplete ferrule preparation in the cervical root, with 0.0 mm buccal and 2.0 mm lingual ferrule lengths (Group F0). Simulated surgical crown lengthening method provided ferrule preparation of 1.0 mm (Group CL/F1) and 2.0 mm (Group CL/F2) on the buccal surface, with ferrule lengths of 3.0 mm and 4.0 mm on the lingual surface, respectively. Simulated orthodontic forced eruption method provided ferrule preparation of 1.0 mm (Group OE/F1) and 2.0 mm (Group OE/F2) on the buccal surface and ferrule lengths of 3.0 mm and 4.0 mm on the lingual surface, respectively. After restoration with a glass fiber post-and-core system and a cast Co-Cr alloy crown, each specimen was embedded in an acrylic resin block to a height on the root 2.0 mm from the apical surface of the crown margin and loaded to fracture at a 135° angle to its long axis in a universal testing machine. Data were analyzed statistically using two-way ANOVA with Tukey HSD tests and Fisher's test, with α = 0.05. RESULTS: Mean fracture loads (kN) for groups F0, CL/F1, CL/F2, OE/F1 and OE/F2 were as follows: 1.01 (S.D. = 0.26), 0.91 (0.29), 0.73 (0.19), 0.96 (0.25) and 0.76 (0.20), respectively. Two-way ANOVA revealed significant differences for the effect of ferrule lengths (P = 0.012) but no differences for the effect of cervical treatment methods (P = 0.699). The teeth with no buccal ferrule preparation in control group F0 had the highest fracture resistance. In contrast, the mean fracture loads for group CL/F2 with a 2.0-mm buccal and 4.0-mm lingual ferrule created by simulated crown lengthening method were lowest (P = 0.036). CONCLUSIONS: Increased apically complete ferrule preparation resulted in decreased fracture resistance of endodontically treated mandibular first premolars, regardless of whether surgical crown lengthening or orthodontic forced eruption methods been used.

Clinical effect of minimally invasive extraction of anterior tooth residual root by root separation / 实用医学杂志

Objective To investigate the clinical effect of minimally invasive extraction of anterior tooth residual root after root separation.Methods A total of 400 patients receivinganterior tooth residual root extraction were collected in the clinic of oral and maxillofacial surgery department between January 2015 and December 2016.The patients were divided into a control group and a study group according to their sequence to see the doctor,with an odd for the study group and an even for the control group.In the study group,residual roots were separated mesiodistally by high speed turbine before using minimally invasive extraction tool;while in the control group residual roots were extracted only using minimally invasive extraction tool.The surgical duration,postoperative damage rate of the lip side plate,degree of pain and patient satisfaction in the two groups were analyzed.Results The surgical duration was shorter in the study group compared with the control group (P ＜ 0.05).The postoperative damage rate of the lip side plate and the degree of pain were lower,while patient satisfaction was higher in the study group than in the control group (P ＜ 0.05).Conclusions The postoperative damage rate of the lip side plate is significantly lower in minimally invasive extraction of anterior tooth residual root after root separation.Smaller trauma is conducive to the implant afterwards.Root separation in minimally invasive extraction of anterior tooth residual root is valuable for clinical application.

Effects of main post combined with auxiliary pile on the fracture resistance of the flat-shaped residual roots / 实用口腔医学杂志

20 first mandibular premolars were randomly divided into 2 groups(n =10).The teeth in experimental group were treated by fi-ber main post in combination with auxiliary pile,in control group by single fiber main post,and then were restored by metal crown.They were fixed in universal testing machine.The fracture load(N)of experimental and control group was (846.50 ±40.33)and (437.90 ±41.15) respectively(P <0.01).

Computed tomography evaluation of residual root thickness after pre-flaring using gates Glidden drills: The sequence effect.

AIM: The aim of the present study is to evaluate the residual root thickness in mesiolingual (ML) canals of mandibular molars after pre-flaring using different sequences of Gates-Glidden (GG) drills. MATERIALS AND METHODS: Computed tomography (CT) scans of the ML canals of 60 mandibular first molars were provided from areas within 1, 2, 3 and 4 mm of the furcation area and minimum initial root thickness (MIRT) of concave areas was measured at each level. The samples were divided into two groups (G1 and G2) which were prepared by the step-back and crown-down techniques, respectively. In both groups, anti-curvature filing was used. On secondary CT images of the samples in the same position, the minimum residual root thickness (MRRT) and the amount of removed dentin were analyzed by t-test and ANOVA. RESULTS: There was no significant difference for MIRT between the two groups. The MRRT was greater in the G2 group in all the sections, with no significant difference between them. The average of MRRT was not <0.5 mm in any of the groups or sections. CONCLUSION: Based on the results of this study when the appropriate root thickness is present initially, GG drills used in any sequence may be suitable, safe and cost effective for pre-flaring of mesial canals of mandibular first molars with preserving the root thickness of furcation areas.

In vitro fracture resistance of endodontically treated anterior teeth with varying ferrule heights and configurations with glass-fiber post / 实用口腔医学杂志

The extracted human maxillary central incisors were endodontically treated and restored with glass-fiber post. Then they were randomly divided into four groups and tested. Results showed that groups with ferrule more than 2 mm had higher fracture resistence than others.

The application of the post crowns with wings to the restoration of the subgingival residual roots and residual crowns of anterior maxillary teeth / 医学研究生学报

Objective:To presents a new way of constructing post crowns for the anterior maxillary teeth which had the subginginval crown fracture more than 3 mm.To discusse the difficulties in the restoration of the subgingival residual roots and residual crowns of anterior maxillary teeth,and to explore the principles of the new restoration by the casting post-core and the porcelain fused mental crowns with wings. Methods: 23 patients(26 teeth) which had crown fracture more than 3 mm under the gingival were enrolled in this study.After those residual roots and crowns were endodontically treated following the conventional root canal therapy,the casting post-core and the porcelain fused mental crowns with wings were applied to reconstructing those missing crowns. Results: After 3 months to 5 years clinic observation,restored crowns were still stable with good retention and fracture resistance. Conclusion: Those residual roots and crowns can be preserved by this innovative way and can also acquire satisfactory effects in esthetics and functions.

Clinical analysis of seventeen patients after using column split-core crown to repair residual crown and root of mandibular second molar / 实用口腔医学杂志

Discussed how to use column split-core crown to repair the indications of the residual crown and root of posterior teeth,as well as its clinical results.Root canal treatment of the residual root,repaired the residual crown and root of posterior teeth with column split-core crown,and then used it as a fixed bridge abutment.No loose,no pain,no loss and jaw bite was in a good recovery compare to the standard after 1-2 years follow-up.It is a good method to use column split-core crown to repair the residual crown and root of posterior teeth under certain conditions.

Medical Ethics Analysis on Different Treatment Plans of Residual Crown And Root / 中国医学伦理学

The residual crown and root has very important physiological significances,but there are many problems in the clinical treatment,such as overtreatment and defensive treatment,etc.This article analyze the background and causes of these problems,and provids some corresponding ways to solve them.

Restoration of multiple residual roots and crowns with the zirconia all-ceramic crown/bridge:A clinical report / 实用口腔医学杂志

Based on the properties of the zirconia all-ceramic material,this report presented a clinical application with the zirconia all-ceramic crown/bridge for restoration of multiple residual roots and crowns.

An evaluation of glass fiber-reinforced composite resin post core for severe defect restoration of front teeth / 实用口腔医学杂志

In order to explore the clinical effect of the glass fiber-reinforced composite resin post core for severe defect restoration of front teeth,sixty-two teeth were restored for forty-one patients with severe defect restoration of front teeth by glass fiber-reinforced composite resin post core plus alumina all-ceramic crown.Through 0.6-2.0 years follow up,all the prosthesis worked very well without breaking or falling off,no gum coloring except two posts fell off after the restoration at sixth month.The patients satisfied with the restoration.

Establishment of three-dimension finite element mode of residual root restored with post-core crown / 重庆医科大学学报

Objiect:To generate three-dimension finite element mode of the first maxillary molar residual root restored with post-core crown,to analyse the stress of post-core crown of posterion tooth.Methods:Models were generate by CT scan,Mimics software and Abaqus software. Result:The three-dimensional models of the first maxillary molar residual root restored with post-core crown were generated. Conclusion:The generated three-dimensional models of the first maxillary molar residual root restored with post-core crown.were highly similar in geometry and mechanics to the real instance,which could be used to study stress of posterion tooth residual root restored with post-core crown

Three-dimensional finite element analysis of various tooth heights of ferrule effect in post crown / 西安交通大学学报(医学版)

Objective To investigate the stress distribution in various tooth heights of ferrule effect in post crown,and to evaluate the biomechanical mechanism in post crown.Methods The three-dimensional finite element entity grid model was constructed,which was a maxillary central incisor restored with post and porcelain fused to metal crown (PFM crown).By imitating the various tooth heights under static loading,the dentin stress was analyzed.Results The stress distribution had an increasing tendency from tooth cervix to root,but it could be decreased by ferrule structures and the decrease degree accorded with the region and height of ferrule.The ferrule effect of the wrapping 1 cm coronal tooth could decrease the stress of the tooth cervix obviously but 2 cm decreased a little.Conclusion The crown wrapping 1 cm coronal can produce ferrule effect obviously and protect the tooth.We can choose to use crown wrapping 2 cm coronal to care the tooth condition.