Purpose: This study evaluated biomechanical behavior of endocrown and post-core restorations produced from computer aided design/computer aided manufacturing (CAD/CAM) and traditional materials in severely damaged teeth that lack a ferrule and assessed the associated failure risk of resin cement.
Methods: A phantom maxillary central incisor and mandibular second premolar were trimmed 1 mm coronally to the cemento-enamel junction, the root canals were enlarged, and the teeth were scanned. Data were transferred to a solid modeling software. Twenty-two models were constructed, including endocrowns (hybrid ceramic, lithium disilicate, and polyetheretherketone [PEEK]) and post-cores (glass-fiber post/composite core; glass-fiber single-piece post-core; PEEK single-piece post-core; gold single-piece post-core). Hybrid ceramic and lithium disilicate crowns were modeled on the post-cores. Loads of 100 N for the central incisor and 300 N for the premolar were applied in a 45° oblique direction. von Mises stresses were analyzed on both root dentin and restorations, and the failure risks for the resin cement were calculated.
Results: The highest stresses were found at the roots of the PEEK endocrown (37.6 MPa) for the central incisor and of the lithium disilicate endocrown for the premolar (40.0 MPa) among endocrown groups. PEEK endocrowns had the lowest stress within the restoration and presented a higher risk of cement failure. The glass-fiber post/composite core groups demonstrated the highest adhesive and cohesive failure risks for post cement.
Conclusions: For the central incisor and mandibular premolar, lithium disilicate and PEEK endocrowns, respectively, generated less stress at the root. However, PEEK endocrowns had a higher risk of cement failure.
This study presented a novel three-dimensional finite element analysis of the biomechanical behavior of various CAD/CAM and conventional materials in the endocrown and post-core restorations of structurally compromised teeth lacking a ferrule. The results demonstrated that lithium disilicate and PEEK optimized stress distribution depending on the tooth’s location (anterior or posterior), whereas gold post-core systems provide superior root stress mitigation. Notably, PEEK exhibited a higher risk of cement failure despite the lower internal stress levels. These findings offer evidence-based insights to guide clinicians in material selection, highlighting the importance of aligning mechanical performance with clinical demands for long-term restorative success.
Purpose: Psoriasis is a complex, chronic inflammatory keratosis of unclear origin that is challenging to treat. In patients with psoriasis suspected of having metal allergies, the removal of oral metallic prostheses contributes to the alleviation of psoriasis symptoms. However, the relationship and mechanism of the metal removal effect and improvement in psoriasis symptoms in patients with metal allergies are unknown. This study aimed to investigate the relationship between metal allergies and psoriasis using an animal model.
Methods: In the metal allergy model, 4-week-old rats were sensitized and treated with nickel (II) chloride (NiCl2) solution (provocation model). In the psoriasis model, imiquimod (IMQ) cream was applied to the shaved dorsal skin of rats (IMQ model). To create a psoriasis/metal-allergy composite rat model, we combined the provocation and IMQ models (provocation + IMQ model). Macroscopic observation, histological analysis, and quantitative gene expression analyses were performed to evaluate outcomes.
Results: In the IMQ model, psoriasis-like symptoms were visually observed from day 2 to day 9. In the provocation + IMQ model, psoriasis-like symptoms persisted for at least 11 days. Histological analysis revealed epidermal thickening and an increase in the number of interleukin (IL)-17-positive cells in the provocation + IMQ model on days 7 and 9. The gene expression of IL-17 in the submandibular lymph nodes and spleen increased in the provocation + IMQ model.
Conclusions: The induced state of Ni allergy may contribute to the maintenance of psoriasis pathology through IL-17 activity.
In patients with suspected dental metal allergies, psoriasis symptoms improved after removal of the metal from the oral prosthesis. However, the relationship and mechanism of the metal removal effect and improvement of psoriasis symptoms in patients with metal allergies remain unknown. This study investigated the relationship between metal allergies and psoriasis using an animal model. The results suggested that nickel allergy may prolong psoriasis via IL-17 production in the submandibular lymph nodes and spleen.
Purpose: This study aimed to investigate the association between denture restoration and cognitive impairment through a meta-analysis and to assess the correlation between different degrees of tooth loss.
Study selection: Observational studies exploring the association between denture restoration and cognitive function were systematically searched across six databases from January 2000 to January 2024. Two researchers independently searched electronic databases and extracted relevant studies from all articles.
Results: This study included 24,252 participants from six observational studies. The risk ratio and 95% confidence interval (CI) were used to compare the risk of cognitive impairment. Participants who experienced tooth loss without dentures had a 1.27-fold (95% CI: 1.20–1.38) higher risk of cognitive impairment, whereas those with dentures had only a 1.01-fold (95% CI: 0.92–1.12) higher risk. In the dose-response analysis, the risk of cognitive impairment in the non-denture group increased by 1.009 times (95% CI: 1.006–1.012) for each tooth lost, whereas the denture restoration group showed a 1.003 times (95% CI: 1.000–1.006) increased risk. The years of follow-up and clinical measurement tools simultaneously explained this heterogeneity.
Conclusions: This study provides detailed evidence of a potential association between denture restoration and a reduced risk of cognitive impairment. Furthermore, there was a correlation between denture restoration and a reduced impact of the number of teeth lost on the risk of cognitive impairment. Therefore, timely and reasonable denture restoration may contribute to prevent cognitive impairment.
The association between oral health and cognitive function has been attracting attention in geriatric research. This review synthesized evidence from observational studies and offered valuable insights into the potential preventive role of denture restoration in cognitive impairment. Although causality cannot be established, timely denture rehabilitation may help attenuate the adverse cognitive impact of tooth loss. These results underscore the broader relevance of prosthodontic care for restoring oral function and supporting cognitive health, particularly in aging populations.
Purpose: Fixed restorations and dental enamel have different structures that produce different wear on opposing teeth, resulting in clinical problems. Therefore, it is necessary to determine the type of restoration that causes less wear on naturally opposing teeth to make recommendations. The objective of this study was to systematically analyze the evidence from observational studies and clinical trials on enamel wear in different ceramic restorations.
Study selection: The designs of the included studies were randomized clinical trials (RTCs), non-randomized clinical trials (non-RTCs), and observational studies (OS). The studies must answer the research question, be available in full text, be written in English or Spanish, and have had at least six months of follow-up. Protocol number: CRD42023397759.
Results: After screening 499 records, 20 RTCs were subjected to data extraction, 10 were excluded, 10 were included in the systematic review, and only 5 were included in the network meta-analysis. The risk of bias assessment reported moderate to high risk of bias, quality, and certainty of evidence was evaluated and rated as moderate. Network meta-analysis showed higher enamel wear was observed in natural dental enamel against metal-ceramic antagonists.
Conclusions: Enamel wear occurs in all teeth, even when the antagonist is a natural tooth. The wear is larger on surfaces with the ceramic crown antagonists studied (metal-ceramic, glazed zirconia, and polished zirconia). It is necessary to conduct additional clinical trials with larger follow-up periods and sample sizes.
Enamel wear is a critical concern in prosthetic dentistry and affects occlusal stability, aesthetics, and long-term function. This systematic review compared metal-ceramic, glazed zirconia, and polished zirconia crowns to determine their effects against enamel surfaces. The findings demonstrated that polished zirconia crowns produced the least enamel wear among the tested materials, underscoring their clinical advantage over metal-ceramic and glazed zirconia. This study provides valuable evidence to guide clinicians in material selection, particularly for patients at high risk of enamel wear.
Purpose: This network meta-analysis (NMA) of randomized controlled trials (RCTs) aimed to identify effective initial conservative treatment strategies for patients with temporomandibular joint disorders (TMD).
Study selection: RCTs comparing treatment options for TMD published between January 2000 and July 2021 were retrieved from the databases of PubMed and Embase via a comprehensive electronic search. Patients diagnosed with myalgia (muscle pain) or arthralgia (joint pain) according to pain-related Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) were eligible for inclusion. Twelve treatment options and a placebo were included in the mutual comparisons. The risk of bias was assessed using Risk of Bias 2.0. Forest plots of direct comparisons between individual studies were created using MetaInsight. NMA was performed using R statistical software (netmeta).
Results: Twenty-four RCTs involving 1336 patients assessing pain and 12 RCTs involving 614 patients assessing maximal mouth opening were identified. Low-level laser therapy (standard mean difference [SMD]: -2.12, 95% confidence interval [CI]: -3.18, -1.06), self-exercise (SMD: -1.51, 95% CI: -2.82, -0.2), and stabilization splints (SMD: -1.16, 95% CI: -2.02, -0.29) were effective in improving pain; however, the certainty of evidence was very low. Self-exercise (SMD: 0.71, 95% CI: -0.58, 2.01), stabilization splints (SMD: 0.65, 95% CI: -0.09, 1.39), and low-level laser therapy (SMD: 0.63, 95% CI: -0.34, 1.6) were effective in improving maximal mouth opening; however, the certainty of evidence was very low.
Conclusions: Stabilization splints, self-exercise, and low-level laser therapy may be effective in the initial treatment of TMD.
The efficacy of conservative treatment in the early stages of temporomandibular disorders (TMD) remains unclear. Among the treatment options implemented within three months, stabilization splinting, self-exercise, and low-level laser therapy improved pain and maximal mouth opening during the early stages of pain-related TMD.
A systematic review of digital removable partial dentures. Part II: CAD/CAM framework, artificial teeth, and denture base
Released on J-STAGE: January 11, 2022 | Volume 66 Issue 1 Pages 53-67
Atsushi Takaichi, Kenji Fueki, Natsuko Murakami, Takeshi Ueno, Yuka Inamochi, Junichiro Wada, Yuki Arai, Noriyuki Wakabayashi
Views: 277
Marginal adaptation and fracture resistance of milled and 3D-printed CAD/CAM hybrid dental crown materials with various occlusal thicknesses
Released on J-STAGE: April 08, 2024 | Volume 68 Issue 2 Pages 326-335
Pisit Suksuphan, Nantawan Krajangta, Pavinee Padipatvuthikul Didron, Thanakorn Wasanapiarnpong, Thanasak Rakmanee
Views: 269
The biological width around implant
Released on J-STAGE: February 24, 2021 | Volume 65 Issue 1 Pages 11-18
Zheng Zheng, Xiaogang Ao, Peng Xie, Fan Jiang, Wenchuan Chen
Views: 264
A systematic review of digital removable partial dentures. Part I: Clinical evidence, digital impression, and maxillomandibular relationship record
Released on J-STAGE: January 11, 2022 | Volume 66 Issue 1 Pages 40-52
Kenji Fueki, Yuka Inamochi, Junichiro Wada, Yuki Arai, Atsushi Takaichi, Natsuko Murakami, Takeshi Ueno, Noriyuki Wakabayashi
Views: 254