Removable partial prosthesis combined with swallowing training is an efficient clinical solution for oral cancer post-operation patients with palatal defect and dysphagia: a prospective study.

OBJECTIVE: Dysphagia is one of the major complications of oral cancer patients, and is disturbing thousands of patients worldwide. Our study aim to evaluate the clinical efficacy of prosthesis combined with swallowing training on palatal defect and dysphagia in post-operative oral cancer patients. MATERIALS AND METHODS: Sixteen oral cancer patients with palatal defect and dysphagia post-operation were treated with removable prosthesis and individualized swallowing function training. Swallowing function of patients before and after treatment was analyzed and compared by videofluoroscopic swallowing examination. The severity of depression and life quality were evaluated by Depression Scale (SDS) and Functional Assessment of Cancer Therapy-Head and Neck (FACT-H&N) scores, respectively. RESULTS: Oral transit time (OTT) significantly shortened after treatment (P < 0.01), and Penetration-Aspiration Scale (PAS) scores was significantly higher after treatment (P < 0.001). Different consistency bolus showed different risk of aspiration. Thickened liquids were related to lower PAS scores (P < 0.001). SDS standard score was significantly lower after treatment (P < 0.05). The total score of FACT-H&N after treatment was significantly higher (P < 0.05). No patients came back for regressed swallowing function during the follow-up period (17.06 ± 2.376 months). CONCLUSION: Removable prosthesis and swallowing training can significantly improve swallowing function, reduce depression degree, and improve quality of life (QOL). CLINICAL RELEVANCE: Removable prosthesis combined with swallowing training is a cheap and effective method to improve QOL in patients with palate defect and dysphagia after oral cancer.

Thread shape affects the stress distribution of torque force on miniscrews: a finite element analysis.

This study aimed to investigate the effect of miniscrews thread shape on the stress distribution receiving a torque load. Seven thread shapes (S,V1,V2,B1,B2,R1,R2) models were constructed and a 6 Nmm-torque load was applied. The order of maximum equivalent stress (EQV) value was V1 > V2 > B1 > R1 > R2 > B2 > S. The order of maximum displacement of miniscrew (Max DM) value was S > B2 > R1 = V1 > B1 > V2 > R2. Model R2 may be the most appropriate thread shape affording a torque force.

Finite Element Analysis of Bone Stress around Micro-Implants of Different Diameters and Lengths with Application of a Single or Composite Torque Force.

BACKGROUND: Stress on the bone surrounding dental micro-implants affects implant success. PURPOSE: To compare the stress on the bone surrounding a micro-implant after application of a single force (SF) of 200 g or a composite force (CF) of 200 g and 6 N.mm torque. MATERIALS AND METHODS: Finite element models were developed for micro-implant diameters of 1.2, 1.6, and 2.0 mm, and lengths of 6, 8, 10, and 12 mm and either a SF or CF was applied. The maximum equivalent stress (Max EQS) of the bone surrounding the micro-implant was determined, and the relationships among type of force, diameter, and length were evaluated. RESULTS: The Max EQS of the CF exceeded that of the SF (P< 0.05). The effect of force on stress was related to implant diameter, but not to implant length. The larger CF led to greater instability of the micro-implant and the effect was most pronounced at an implant diameter of 1.2 mm. The use of implant diameters of 1.6 mm and 2.0 mm produced no significant difference in implant stability when either a CF or SF was applied. CONCLUSION: When considering the use of an implant to perform three-dimensional control on the teeth, the implant diameter chosen should be > 1.2 mm.

[Influence of the diameter and length of the mini-implant on the primary stability after loading with composite forces].

OBJECTIVE: To investigate the influence of the diameter and length of the mini-implant on the primary stability after loading with composite forces (CF) which contained torque and horizontal forces (HF). METHODS: Ninety-six finite element models were established by the combination of mini-implant and bone, diameters (1.2 mm, 1.6 mm, 2.0 mm) and length (6 mm, 8 mm, 10 mm, 12 mm). There were 12 sizes, each size corresponded with 8 models. Group HF (each size n = 4) was loaded with 1.96 N horizontal force and Group CF (each size n = 4) was loaded with composite force which contained 6 N·mm torque and 1.96 N horizontal force. The maximum displacement of mini-implant with different force directions, implant diameters and lengths were evaluated. RESULTS: The effect of force direction on the displacement related to diameter of mini-implant. The maximum displacement under load with HF respectively was changed with the changing of diameter[1.2 mm: (7.71 ± 0.49) µm; 1.6 mm: (3.94 ± 0.31) µm; 2.0 mm: (2.32 ± 0.43) µm], which were smaller than the maximum displacement of Group CF [1.2 mm: (9.22 ± 0.63) µm; 1.6 mm: (4.62 ± 0.52) µm; 2.0 mm: (2.69 ± 0.49) µm] (P < 0.05). When diameter was 1.2 mm, the difference of the maximum displacement [(1.61 ± 0.22) µm] between Group HF and CF was more obvious than that when the diameter was 1.6 mm or 2.0 mm [(0.64 ± 0.12), (0.49 ± 0.06) µm] (P < 0.05). CONCLUSIONS: The composite force had unfavorable effect on the primary stability of the mini-implant. The diameter of the mini-implant had better be larger than 1.2 mm when the composite forces were applied.