Axial and tilted implant surgical technique assisted by an autonomous dental implant robot: A clinical report.

Optimal implant placement is essential for long-term implant survival and satisfactory prosthodontic outcomes. Autonomous dental implant robots have been reported to achieve accurate implant placement with satisfactory outcomes. This clinical report describes the use of an autonomous dental implant robot for axial and tilted implant placement in an edentulous mandible.

Primary maxillary sinus carcinosarcoma with multidisciplinary management: a case report with 4 years follow-up and literature review.

BACKGROUND: Primary maxillary sinus carcinosarcoma (CS) is an extremely rare malignant tumor characterized by biphasic histologic components, lack of standardized treatment, high recurrence rate, and poor prognosis. This paper presents a case of primary maxillary sinus CS and its treatment. CASE PRESENTATION: A 39-year-old female patient complained of right facial pain and maxillary teeth numbness on March 21, 2018. Computed tomography examination revealed a malignant mass with osteolytic destruction. Preoperative biopsy suggested sarcomatoid carcinoma or CS. A total right maxillectomy under general anesthesia was performed on April 12, 2018. The final staging was T3N0M0 (ACJJ 2019). Postoperative radiotherapy and chemotherapy were performed. On May 26, 2018, the patient received the first cycle of doxorubicin plus ifosfamide. Two days before radiotherapy, the patient received an intra-oral prosthesis. From June 20, 2018, to August 22, 2018, the patient received concurrent chemoradiotherapy: radiotherapy (60 Gy in 30 fractions) and the second cycle of doxorubicin. Then, the patient received four cycles of doxorubicin plus ifosfamide. The patient was followed for 39 months with no evidence of disease. CONCLUSION: Using multidisciplinary therapy, clinical-stage T3N0M0 (ACJJ 2019) maxillary sinus CS may achieve a good prognosis.

Finite element analysis of maxillary first molar with a 4-wall defect and 1.5-mm-high ferrule restored with fiber-reinforced composite resin posts and resin core: The number and placement of the posts.

STATEMENT OF PROBLEM: Whether fiber-reinforced composite (FRC) posts should be inserted in root canals to restore teeth with multiple roots remains unclear. PURPOSE: The purpose of this finite element analysis (FEA) study was to determine the optimal use of FRC posts in an endodontically treated maxillary first molar with a 4-wall defect and 1.5-mm-high ferrule. MATERIAL AND METHODS: Eight different models of a maxillary first molar were established: no post (NP), post in palatal root (P), post in distobuccal root (DB), post in mesiobuccal root (MB), posts in palatal root and distobuccal root (P+DB), posts in palatal root and mesiobuccal root (P+MB), posts in 2 buccal roots (DB+MB), and posts in all roots (P+DB+MB). Two types of loading were applied: a force of 800 N parallel to the long axis of the tooth to simulate the vertical masticatory force and another force of 225 N at 45 degrees to the long axis of the tooth to simulate the lateral masticatory force. The equivalent stresses on the external surfaces of the tooth tissue, the internal surfaces of the root canals and in the posts, as well as the maximal shear stresses on the post-core interface and the core-dentin interface, were calculated with FEA. RESULTS: All the models showed similar maximal equivalent stress values on the external surfaces of the tooth tissue, and stress concentrations were found at the cervical and furcation area. On the internal surfaces of root canals, an increase of equivalent stress at the middle third of the canals with posts and a decrease at the cervical third were observed. Under vertical loading, the P+DB+MB group showed the largest equivalent stress in the post (76.45 MPa in the palatal post), the DB+MB group showed the largest shear stress on the post-core interface (19.02 MPa), and the MB group showed the largest shear stress on the core-dentin interface (12.07 MPa). Under lateral loading, the P+DB+MB group showed the largest equivalent stress in the post (60.11 MPa in the mesiobuccal post) and the largest shear stress on the post-core interface (13.48 MPa) and the DB group showed the largest shear stress on the core-dentin interface (21.03 MPa). CONCLUSIONS: One post in the palatal canal was found to be appropriate for the FRC post and resin core restoration of a maxillary first molar with a 4-wall defect and 1.5-mm-high ferrule. An additional post in the mesiobuccal canal could help disperse lateral occlusal force and improve retention of the restoration.

Need for dental care among medical staff working in the China Antarctic stations.

Even though China Antarctic medical care has made huge progress, dental care has always been a neglected area. Dental health is well-known to be closely related with life quality and work efficiency. Hence, knowing the dental care situation there and providing ways to improve are urgently needed. We choose doctors who worked in China Antarctic station as a window to see the whole picture by sending questionnaire. The results showed dental visits ranked second high, the ratio of doctors who got pre-departure dental knowledge education and screen is low. What is worse, none of them got any after-departure dental check. Their dental knowledge is not as good as we expect, and they were troubled by dental problems in Antarctic. Interestingly, most dental problems were treated by non-dentist with no essential equipment, but 2/3 of them were satisfied with the outcome. As for the dental-related diet and behaviour, snacks eating and alcohol drinking are the strongest predictors of dental pain and gum problem. Those findings are crucial to Antarctic dental care and research.

Finite element analysis of maxillary first molar with mesial-occlusal-distal-palatal defect restored with different post-and-core strategies.

Purpose: To explore which restoration strategy generates the most favorable stress distribution in an endodontically-treated maxillary first molar with mesial-occlusal-distal-palatal defect. Methods: Models with one post in palatal canal (PP), each post in palatal and distobuccal canals (PDP), each post in palatal and mesiobuccal canals (PMP), and each post in all canals (PDMP) were established for an endodontically-treated maxillary first molar with mesial-occlusal-distal-palatal defect either with fiber-reinforced composite (FRC) post or gold alloy cast (GAC) post. A 400-N vertical force and a 225-N lateral force were respectively applied. The Mohr-Coulomb stress ratio (σMC ratio) in the residual tooth structure (RTS), the resin cement, and the crowns, the tensile stress (σt) and compressive stress (σc) in the FRC posts, the von-Mises stress ratio (σvM ratio) in the GAC post-and-cores, and the σt and shear stress (σs) at the adhesive interfaces were calculated using finite element analysis. Results: FRC posts generated lower σMC ratio than GAC posts in the RTS (0.3274-0.3643 vs. 0.3399-0.4118). Among the FRC post groups, the PDMP group got the lowest σs at the dentin-post interface (14.92 MPa) and the abutment-crown interface (8.242 MPa) under vertical loading, as well as the lowest σMC ratio in the RTS (0.3381) and the lowest σs at the dentin-post interface (38.00 MPa) under lateral loading. Conclusions: From the point of stress distribution, placing FRC posts in the palatal, distobuccal, and mesiobuccal canals is the optimal strategy in restoring a severely damaged maxillary first molar, provided that lateral occlusal force is reduced.

Initial Development of an Immediate Implantation Model in Rats and Assessing the Prognostic Impact of Periodontitis on Immediate Implantation.

BACKGROUND: To establish an immediate implantation rat model and to evaluate the effects of pre-existing periodontitis and two different socket rinse solutions on immediate implantation prognosis. METHODS: Sprague-Dawley (SD) rats were randomly divided into three groups before immediate implantation, including the control group, the group with experimentally induced periodontitis (EP), in which rats have been experimentally induced periodontitis before implantation, and the group with induced periodontitis and with extraction sockets rinsed with three percent H2O2 (EP-H2O2), in which rats have been induced periodontitis before implantation, and extraction sockets were rinsed with three percent H2O2. Periodontitis was induced by ligating the thread around the molars for four weeks. Six weeks after titanium alloy implants were self-tapped and left to heal transmucosally, maxillae were dissected after the clinical examination to perform micro-CT and histological analysis. RESULTS: An immediate implantation model was successfully built in rats. There was no significant difference in implant survival rates between the EP and control groups. However, the clinical examination results, micro-CT analysis, and histological analysis in EP and EP-H2O2 groups showed a significantly worse prognosis than in the control group. Three percent H2O2 showed a similar effect with saline. CONCLUSION: This study presented a protocol for establishing a rat immediate implantation model and showed that periodontitis history might negatively affect the prognosis of immediate implantation. These findings urge caution and alternative strategies for patients with periodontal disease history, enhancing the long-term success of immediate implantation in dental practice. Additionally, the comparable outcomes between 3% H2O2 and saline suggest the use of saline as a cost-effective and safer alternative for implant site preparation in dental practice.

Possible variation of the human oral bacterial community after wearing removable partial dentures by DGGE.

Although it is well-known that variations of the microbial community in a specific location of human body may be associated with some diseases, the developing change of the oral microbiota related to oral diseases before and after wearing the removable partial dentures (RPD) is not completely understood. In this study, three kinds of samples (saliva, supra- and subgingival plaque, and oral mucosal surfaces) were collected from the 10-patients group at three different times: before, 1-month and 6-months after the treatment. Ten healthy adults were also selected as the control group. Denaturing gradient gel electrophoresis was applied to identify the bacterial profiles and to analyze the dynamics of the oral microbial population in the pre- and post-therapy. The ANOVA of Repeated Measurement Data indicated that, in the saliva and mucosal surfaces, wearing RPDs caused significant change of numbers of amplicons. As many as 607 amplicons were chosen to cut out and re-amplify by PCR. After cloning and sequencing, a total of 16 bacterial genera were identified. The health-associated genera such as Streptococcus, Neisseria, Rothia, Corynebacterium, Leptotrichia, Gemella, Veillonella, Selenomona and Actinomyces tended to decrease, whereas the disease-associated species including Streptococcus mutans tended to increase. In general, wearing RPDs influenced the diversity of the bacterial species in the oral microbial ecosystem. It is noteworthy that the oral environment will be changed from the healthy status towards the disease status after the treatment.

Preparation and characterization of two novel osteoinductive fishbone-derived biphasic calcium phosphate bone graft substitutes.

Many studies have reported on the conversion of natural resources into xenografts with hydroxyapatite (HA) as major component, but the extraction of biphasic calcium phosphate (HA/ß-TCP) from animal bones and transformation into bone graft substitutes are rarely reported. In this research, two kinds of fish bones were made into granular porous biphasic calcium phosphate bone graft substitutes with particle sizes between 500 to 1000 µm through a series of preparation procedures (Salmo salar calcined at 900°C named Sa900 and Anoplopoma fimbria calcined at 800°C named An800). The chemical composition was characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The morphology and porous structure of the scaffolds were comparatively analyzed by scanning electron microscopy (SEM) and mercury porosimeter. The specific surface area of materials was measured by the nitrogen adsorption technique based on BET theory. Cytotoxicity and ectopic osteogenesis were also carried out to investigate the biocompatibility and osteoinductive potential of these materials. The results showed that both fishbone-derived scaffolds were composed of HA and ß-TCP with different proportions, and numerous interconnected pores with different sizes were observed at the surface of materials. An800 had higher total porosity reaching 74.8% with higher interconnectivity and micropores mostly distributed at 0.27 µm and 0.12 µm, while Sa900 had a higher specific surface area and higher intraparticle porosity with nanopores mostly distributed at 0.07 µm. CCK-8 assays and Live/dead staining demonstrated excellent biocompatibility. Material-induced osteoid formation were observed on the interface of both internal pores and periphery of materials after implantation in muscle pouch of Wistar rats for 8 weeks which indicated some extent of osteoinductive potential of materials. The possible mechanism of material-induced osteogenesis and the effects of chemical composition, surface topography, and spatial structure on osteogenesis were also discussed in this paper.

[Reliability of an improved measurement system used in three-dimensional reconstruction of stomatognathic system by cutting and scanning layer-by-layer].

OBJECTIVE: To reconstruct 3D shape of edentulous jaw by using improved measurement system and to analyze the precision of this method. METHODS: Standard edentulous jaw models were measured with a improved measurement system by cutting and scanning layer-by-layer, and the 3D shape of the models was reconstructed by image processing with specialty software. Ten cubic plaster modes were reconstructed by the same way, data of every border before and after reconstruction were measured and analyzed. RESULTS: Data of edentulous jaw models were obtained. The errors in ten cubic before and after reconstruction were not significantly different (P > 0.05), data measured in horizontal plane were not significantly different (P > 0.05), and data measured in altitude direction were significantly different (P < 0.01), data measured after reconstruction were less than before, the error was (0.09 +/- 0.08) mm. CONCLUSION: The improved cutting and scanning measurement system can be fit for the 3D reconstruction of stomatognathic system with high precision.

[The bond properties of Vitadur alpha on dental zirconia framework material].

PURPOSE: To evaluate the bond properties of Vitadur alpha on dental zirconia framework material. METHODS: Vitadur alpha was sintered on the surface of four groups' presintered zirconia ceramic plates which were dealt with respective procedures. SEM, energy distribution spectrum and thermal shock test were applied to evaluate the sintering properties of such interfaces. Shear bond strength of Vitadur alpha-zirconia interfaces were measured, and the results were analysed by ANOVA method. RESULTS: Satisfying result was obtained in Vitadur alpha sintered on the zirconia framework material, furthermore, chemical combination between the two laminates were confirmed by means of energy distribution spectrum. The shear bond strength of 3Y-TZP-Vitadur alpha dentin differed under different surface conditionings: highest shear bond strength appeared in the group conditioned with water sand paper (35.1662MPa), shear bond strength of the group conditioned with sandblast (27.8283MPa) was better than that of non-conditioning group (20.9677MPa), diamond condition group had the lowest shear bond strength (15.3025MPa), significant difference existed between each group (P<0.01). CONCLUSION: Further clinical research could be carried out on Vitadur alpha and zirconia ceramic framework under conditioning with sandblast.