[Method and accuracy of determining the jaw position of repositioning splint with the aid of digital technique].

OBJECTIVE: To establish the workflow of determining the jaw position of repositioning splint with the aid of digital technique, and to evaluate the accuracy of this workflow and compare the accuracy of raising different vertical dimensions in vitro. METHODS: A volunteer was recruited. The data of full-arch scans, cone beam computed tomography (CBCT) image and ultrasonic jaw motion tracking of the volunteer were acquired. The full-arch scans were merged with the CBCT image, which were then matched to the jaw motion tracking reference system. The jaw position of repositioning splint was determined when the anterior teeth opening was 3 mm and the condyle was in centric relation of the fossa in the sagittal plane. A digital repositioning splint was designed in the software based on virtual articulator and fabricated with additive manufacturing technique. After the splint was tried in, another CBCT image was taken and a qualitative analysis was conducted to compare the position of condyle between these two CBCT images. In the in vitro study, standard dental plaster casts with resin ball markers attached to the base were mounted onto a fully adjustable articulator in the intercuspal position. The dental casts were scanned by an extraoral scanner to establish digital models. The ultrasonic jaw motion tracking device was used to obtain simulated jaw movements on the articulator, which was repeated for three times. The digital models and data of jaw movements were merged in one coordination with the aid of bite forks. The jaw position of repositioning splint was determined by adjusting data of jaw movements, each of which was used to determine three vertical jaw positions 4 mm, 5 mm, and 6 mm with the horizontal jaw position of protrusion 2 mm. The virtual articulators with differently adjusted jaw movements were applied in designing repositioning splints, and the final repositioning splints and virtual jaw relationships were exported in STL format. Then the repositioning splints were fabricated with additive manufacturing technique and tried in plaster casts on the mechanical articulator, which were scanned and the jaw relationships on the mechanical articulator were exported later. The virtual jaw relationships and scanned jaw relationships were registered according to lower models and displacement of upper models was calculated. Ball markers were fit to acquire the coordinates of centers and absolute difference values of centers along three coordinating axes X, Y, and Z were calculated. One-way analysis of variance was conducted using SPSS 18.0 software to compare deviations of the three different vertical jaw relationships in two-side test and the significance level was 0.05. RESULTS: With the aid of multi-source data fusion and individualized jaw motion, the clinical workflow of determining jaw position of repositioning splint was preliminarily established. The designed jaw position was realized on the right and the condyle was more inferior than the designed position on the left. Both displacement of the upper models and absolute difference values of centers showed no significant differences (P>0.05) in different vertical jaw dimensions. The displacement of the upper models was (0.25±0.04) mm. The absolute difference values of centers along the three coordinating axes X, Y, and Z were respectively (0.08±0.01) mm, (0.30±0.02) mm, and (0.21±0.04) mm. CONCLUSION: A novel method of determining the jaw position of repositioning splint with the aid of digital technique is established. It is proved to be feasible by try-in after multi-data fusion, computer-aided design and computer-aided manufacturing. As is shown in vitro, it is accurate to apply this method in adjusting jaw position. Further clinical trial will be designed to evaluate its clinical effect.

The potential role of phagocytic capacity in the osteolytic process induced by polyethylene wear particles.

Osteolysis induced by ultra-high molecular weight polyethylene wear particles is the major cause of long-term failure of artificial joints. We examined the effects of wear particles on bioactivity by analysing the biophysical aspects of particle phagocytosis. We estimated the maximum number of internalized particles (the phagocytic capacity) for particles of various sizes and shapes. We demonstrated that elongated particles had a smaller phagocytic capacity than spherical particles of the same volume. A review of the literature showed that the ratio of particle concentration (number of particles/number of cells) to phagocytic capacity is critical for particle-induced biological responses. When this ratio was < 1, the biological response was approximately proportional to the ratio itself. When this ratio was > 1, limited changes in the biological response were observed. The saturation level of the phagocytic capacity for a particle population appears to reflect the degree of polyethylene particle-induced biological response.

Segmental dilatation of the ileum as an unusual cause of gastrointestinal bleeding: report of one case.

We report a case of segmental dilatation of the ileum in a 10-month-old male infant. Intermittent loose black-colored stool passage and normocytic anemia were noted at the initial visits to our hospital. There was no symptom or sign of intestinal obstruction such as abdominal distention or vomiting. On physical examination, he was found to be pale but his abdomen was soft and flat. Digital examination revealed brownish stool tinged with black-colored oil-like stool but no polyp. Laboratory studies excluded coagulopathy, hemolytic anemia and lead poisoning. During hospitalization, he was treated with nothing per mouth, intravascular fluids, ranitidine, and transfusion of packed red blood cells. All examinations including panendoscopy, Technetium-99m (99mTc)-pertechnetate Meckel's diverticulum scan, and double contrast colon series revealed no organic lesion except that 99mTc-red blood cell bleeding scans showed abnormal bleeding in the small intestine. Because of his persistent gastrointestinal bleeding with unknown cause, we did an exploratory laparotomy when the patient was 13 months old and idiopathic segmental dilatation of the ileum was confirmed. The dilated segment is supposed to be idiopathic because of histologically proven normal muscle layers without ectopic tissue. This case suggests that segmental dilatation of the ileum can only present as gastrointestinal bleeding without intestinal obstruction.