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Frontiers in Bioengineering and... 2023Despite the large demand for dental restoration each year, the design of crown restorations is mainly performed via manual software operation, which is tedious and...
Despite the large demand for dental restoration each year, the design of crown restorations is mainly performed via manual software operation, which is tedious and subjective. Moreover, the current design process lacks biomechanics optimization, leading to localized stress concentration and reduced working life. To tackle these challenges, we develop a fully automated algorithm for crown restoration based on deformable model fitting and biomechanical optimization. From a library of dental oral scans, a conditional shape model (CSM) is constructed to represent the inter-teeth shape correlation. By matching the CSM to the patient's oral scan, the optimal crown shape is estimated to coincide with the surrounding teeth. Next, the crown is seamlessly integrated into the finish line of preparation via a surface warping step. Finally, porous internal supporting structures of the crown are generated to avoid excessive localized stresses. This algorithm is validated on clinical oral scan data and achieved less than 2 mm mean surface distance as compared to the manual designs of experienced human operators. The mechanical simulation was conducted to prove that the internal supporting structures lead to uniform stress distribution all over the model.
PubMed: 38090709
DOI: 10.3389/fbioe.2023.1216651 -
Orthodontics & Craniofacial Research Dec 2023Tooth eruption is a pivotal milestone for children's growth and development. This process involves with the formation of the tooth root, the periodontal ligament (PDL)... (Review)
Review
Tooth eruption is a pivotal milestone for children's growth and development. This process involves with the formation of the tooth root, the periodontal ligament (PDL) and the alveolar bone, as the tooth crown penetrates the bone and gingiva to enter the oral cavity. This review aims to outline current knowledge of the adverse dental effects of antiresorptive medications. Recently, paediatric indications for antiresorptive medications, such as bisphosphonates (BPs), have emerged, and these agents are increasingly used in children and adolescents to cure pathological bone resorption associated with bone diseases and cancers. Since tooth eruption is accompanied by osteoclastic bone resorption, it is expected that the administration of antiresorptive medications during this period affects tooth development. Indeed, several articles studying human patient cohorts and animal models report the dental defects associated with the use of these antiresorptive medications. This review shows the summary of the possible factors related to tooth eruption and introduces the future research direction to understand the mechanisms underlying the dental defects caused by antiresorptive medications.
Topics: Animals; Humans; Child; Adolescent; Tooth Eruption; Tooth Root; Periodontal Ligament; Diphosphonates; Bone Resorption
PubMed: 36714970
DOI: 10.1111/ocr.12637 -
Journal of Indian Society of... 2023To analyze through finite element analysis the stress distribution in peri-implant bone tissues, implants, and prosthetic components induced by the socket shield (SS)...
BACKGROUND
To analyze through finite element analysis the stress distribution in peri-implant bone tissues, implants, and prosthetic components induced by the socket shield (SS) technique in comparison to other techniques used to treat tooth loss.
MATERIALS AND METHODS
A three-dimensional model of a superior central incisor crown supported by implant was modeled and three different placement conditions were simulated: SS - 2.0-mm-thick root dentin fragment positioned between the alveolar buccal wall and implant; heterologous bone graft (HBG) - bovine bone graft positioned the alveolar buccal wall and implant; and control (C) - implant fully placed in bone tissue of a healed alveolus. The model was restricted at the lateral surfaces of the bone tissue and the following loads were simulated: Both oblique (45°) loads of 100 N on the lingual surface of the crown (maximal habitual intercuspation) and 25.5 N on the incisal edge of the crown (tooth contact during mandibular protrusion) were simultaneously applied. Tensile stress, shear stress, compression, and displacement were analyzed in the cortical bone, trabecular bone, dentin root fragment, and bone graft; while equivalent von Mises stresses were quantified in the implant and prosthetic components.
RESULTS
Stress values of SS and HBG in the bone tissues were higher than C, while slight differences within models were observed for dentin root fragment, bone graft, implant, and prosthetic components.
CONCLUSIONS
The SS technique presented the highest stress concentration in the peri-implant tissues.
PubMed: 37593548
DOI: 10.4103/jisp.jisp_356_22 -
Cureus Dec 2023Endodontic treatment is often necessary in the field of dentistry. As the tooth structure is lost during such treatment, the tooth may become weaker and lose some of its... (Review)
Review
Endodontic treatment is often necessary in the field of dentistry. As the tooth structure is lost during such treatment, the tooth may become weaker and lose some of its mechanical qualities. Endodontically treated posterior teeth require cuspal coverage because of their anatomical features. Endocrowns are regarded as a suitable choice for restoring teeth that have undergone endodontic treatment. These restorations are recommended when there is a substantial loss of tooth structure, restricted interocclusal space, or a short clinical crown. They are also contraindicated in case of severe loss of tooth structure where adhesion is not applicable. Endocrowns require a specific preparation design that is distinct from the conventional crown. They can be manufactured by two methods: heat pressing or computer-aided design/computer-aided manufacturing (CAD/CAM). Moreover, several materials have been used in fabricating endocrown restoration. Lithium disilicate glass-ceramic is the most recommended material as it possesses excellent mechanical properties and esthetic results with the ability to bond to tooth structure. In conclusion, several kinds of literature recommend using them for molars. Further research is needed to evaluate this technique for premolar and anterior teeth.
PubMed: 38058523
DOI: 10.7759/cureus.49947 -
Scientific Reports Nov 2023For restoration of extensively damaged teeth preprosthetic treatment measures are necessary. Crown lengthening and extrusion affect the prospective crown-root ratio...
For restoration of extensively damaged teeth preprosthetic treatment measures are necessary. Crown lengthening and extrusion affect the prospective crown-root ratio (CRR). The subject of this in vitro study was to compute CRRs for both treatment approaches. 120 human maxillary central extracted incisors were measured. Measurements were calculated for five treatment groups: C (control), E-2 mm (extrusion of 2 mm), E-4 mm (extrusion of 4 mm), CL-2 mm (crown lengthening of 2 mm), and CL-4 mm (crown lengthening of 4 mm). Tooth (TL), root (RL), and crown lengths (CL) were measured from mesial (m) and facial (f) cemento-enamel junction (CEJ), and respective anatomic (CRR) and effective crown-root ratios (eCRR) were calculated. Following CRR values were computed for C: CRR-m = 0.4 ± 0.1, CRR-f = 0.7 ± 0.1. All crown-root ratios were lower (more favourable) for extrusion compared to crown lengthening (p < 0.001). ECRRs were higher than anatomic CRRs. CRR at mesial CEJ was significantly lower than CRR with facial CEJ as reference (p < 0.001). Mesial measurement-based calculations of CRR typically based on radiographic images should be interpreted with caution as they underestimate the eCRR. CRR can be expected as lower, i.e. more favourable, when teeth are extruded than crown lengthened.
Topics: Humans; Crown Lengthening; Prospective Studies; Crowns; Incisor; Tooth Cervix; Tooth Crown; Tooth Root
PubMed: 37919362
DOI: 10.1038/s41598-023-46354-y