Digital imaging analysis with mathematical morphology and fractal dimension for evaluation of periapical lesions following endodontic treatment

OBJECTIVE

To see if a method for digitizing trabecular pattern of bone could be used to quantitatively evaluate changes in bone pattern following endodontic treatment of teeth with periapical osteolytic lesions.

STUDY DESIGN

Periapical radiographs were digitized and further processed with mathematical morphology operations known as skeletonization. The trabecular patterns resulting from this skeletonization process were further analyzed with fractal dimension analysis using box-counting.

RESULTS

The periapical area in digitized radiographic images showed fractal behavior. Twenty-five of 27 patients showed increase of the fractal dimension after root canal treatment. Significant changes of the box-counting could be noted 3 months after root canal treatment (P < .05).

CONCLUSIONS

Mathematical morphology operation and box-counting might be helpful in early detection of changes of periapical trabecular pattern after root canal treatment.

A pilot study applying digital radiography for estimating ratio of supported single-root surface area

BACKGROUND

The prognosis of a tooth with periodontitis is affected by the amount of supporting bone. A key factor in retaining a tooth is the ratio of supported root surface. Currently, root surfaces cannot be accurately measured using conventional dental radiographs, which only measure the length of bone support on proximal surfaces.

METHODS

Eight extracted, single-rooted teeth were 3-dimensionally digitized using a contact technique for true surface area measurements. Root length, projection area, and pixel values were then measured on digital radiographs. The accuracy of the ratio estimation of supported surface area from linear, area, and pixel values was calculated and compared.

RESULTS

The mean error from linear estimation was 7.9%; the mean error from area estimation was 1.0%; and the mean error from pixel value estimation was 1.3%. One-way analysis of variance (ANOVA) showed significant differences in all estimations while Scheffé's analysis further revealed significant differences only in the linear estimation.

CONCLUSIONS

A three-dimensional digitizing device could be used as a non-destructive method of measuring root surface area. The ratio of supported single-root surface area could be estimated with high accuracy from the projected area data acquired on the digital dental radiographs. The thickness data as reflected from the pixel values in the digital images did not improve the estimation accuracy. Estimations using only length data yielded significantly less accuracy. Digital dental x-ray images provide the potential for estimating the ratio of supported root surface efficiently.

Effects of prosthesis materials and prosthesis splinting on peri-implant bone stress around implants in poor-quality bone: a numeric analysis

PURPOSE

A 3-dimensional finite element model consisting of a bone block and 2 simulated premolar crowns supported by 2 adjacent cylindric implants without immediately surrounding cortical bone was generated and used to investigate the effects of prosthesis materials and prosthesis splinting on the peri-implant bone stress under static loads.

MATERIALS AND METHODS

The peri-implant maximum equivalent bone stress (von Mises [VM] stress) was evaluated when a vertical or a horizontal load of 1 N was applied to the center of a single resin, gold alloy, or porcelain crown, nonsplinted or splinted to the adjacent crown.

RESULTS

The numeric results indicated that: (1) in a single crown, no significant difference could be found in the maximum VM stress between different materials for both vertical and horizontal loading; (2) splinting the crowns reduced the maximum VM stress induced by the horizontal load, and the maximum VM stress increased about 14% for the horizontal loading when the restorative material was changed from gold alloy or porcelain to resin.

DISCUSSION

Under the condition of this study's analysis, prosthesis materials of a single crown have insignificant effects on the peri-implant bone stress. Splinting the crowns reduced the peri-implant bone stress under horizontal load, and gold alloy and porcelain each demonstrated less peri-implant bone stress than resin in the splinted crown situation under static horizontal load.

CONCLUSION

Splinting the crowns of adjacent implants with relatively stiff restorative materials is recommended for implants surrounded by poor-quality bone.

Trace Metals' abnormalities in hemodialysis patients: relationship with medications

A multicenter collaborative study was performed to investigate the prevalence of abnormal blood contents of 6 trace metals, copper (Cu), zinc (Zn), aluminum (Al), lead (Pb), cadmium (Cd), and mercury (Hg), in hemodialysis (HD) patients and to analyze their relationship with the medications, such as CaCO3, Ca acetate, Al containing phosphate-binding agents, 1,25-dihydroxy vitD3, 1-hydroxy vitD3, and erythropoietin (EPO), as well as hematocrit level, by chi-square statistics. From 6 medical centers in Taiwan, we included 456 patients in maintenance HD for more than 4 months for this study, and they had continued the previously mentioned medications for at least 3 months. Blood samples were collected before initiating HD, and atomic absorption spectrophotometry was used to measure plasma levels of Cu, Zn, and Al as well as whole blood levels of Pb, Cd, and Hg. Three hundred seventy-five (78%) of the HD patients had low plasma Zn levels, that is, <800 microg/L, and the mean (+/-SD) concentration was 705.8 (+/-128.23) microg/L in all subjects. One hundred forty-one (31%) of the HD patients had high plasma Al, that is, >50 microg/L, and the mean (+/-SD) was 44.30 (+/-28.28) microg/L in all subjects. Three hundred thirty-three (73%) of the dialysis patients had high Cd levels, that is, >2.5 microg/L, and the mean (+/-SD) was 3.32 (+/-1.49) microg/L in all subjects. The majority of HD patients had normal blood levels of Cu, PB, and Hg. Only 21 (4. 6%), 5 (1.1%), and 3 (0.06%) patients had elevated blood levels of Cu, Pb, and Hg, respectively. Their mean (+/-SD) blood concentration of Cu, Pb, and Hg were 1,049.78 (+/-233.25) microg/L, 7.45 (+/-3.95) microg/dL, and 3.17 (+/-25.56) microg/L, respectively. Three patients had elevated plasma Hg concentrations, that is, 546, 12.6, and 24.0 microg/L, respectively. In the 152 normal healthy age and sex matched control group, the blood levels of Al, Cd, and Pb were all significantly lower than the HD patients. However, the levels of Cu and Zn were higher in the control group. The Hg level was not significantly different in both groups. There was no statistical difference between patients with normal and abnormal blood levels of trace metals in various medications except Al containing phosphate binder. The Al containing phosphate binder users had significantly higher plasma Al levels (54.71 +/- 26.70 versus 41.15 +/- 28.03 microg/L, p < 0.001) and hematocrit levels (29.61 +/- 4.61 versus 27. 81 +/- 3.91, p < 0.0005). There was no statistical correlation between erythropoietin (EPO) dose and hematocrit level in these patients. In conclusion, the blood level of trace metals of these HD patients except Al was not related to their medications. However, caution must be exercised in interpreting this result as dose and duration of medication; efficiency of HD and water treatment may play an important role. Otherwise, environmental factors, diet, and the aging process may contribute to the trace metal burden in uremia. Thus, Zn and Cu are abundant in seafood, and Cd is abundant in contaminated plants such as rice.

Cholesterol crystal embolization causing acute renal failure

Acute renal failure due to cholesterol embolization is a complication of severe generalized arteriosclerotic disease. It occurs spontaneously, or more often, as a complication of major medical or surgical procedures such as angiography and vascular surgery. The demonstration of characteristic cholesterol crystals in tissue biopsy specimens is a pathognomonic finding. However, renal cholesterol embolism may be clinically diagnosed when renal failure develops after known inciting factors or together with systemic manifestations of atheromatous embolization such as lower extremity livedo reticularis and focal digital ischemia. We report two cases of acute renal failure in which cholesterol embolization was found in skin and renal biopsies. One patient's renal function stabilized, but not to the basal level and the other patient developed end-stage renal disease.

Dead on arrival study in Kaohsiung area

Dead on arrival (DOA) is a distressful situation for most medical personnel and families. There are few papers about this topic in Taiwan though most DOAs are unexpected and sudden with or without underlying disease as predisposing factors. From January 1, 1993 to December 31, 1993, 487 DOA patients were sent to 4 large hospitals in the Kaohsiung area (including Kaohsiung City and Kaohsiung County). A retrospective study was carried out through questionnaires. The incidence was 0.22%, the male to female ratio was 2.25, and the largest age group was 61 to 75 years old. Most patients were sent to nearby hospitals and sent by non-medical personnel with non-ambulance motor vehicles. It is hard to define the exact time from arrest to arrival at the hospital, but the initial cardiac rhythm was mostly asystole. Only 1.44% of DOA patients survived and only 9.24% responded to resuscitation. About 31.42% of patients had no evident cause of death, 40.04% non-trauma deaths, and 28.54% trauma deaths. Most of the underlying diseases were treated regularly by medical specialists if past history could be traced. Though our emergency medical service system (EMSS) has been active since 1990, there are still several drawbacks. Public education of cardiopulmonary resuscitation, easy access to EMSS, and appropriate management in hospitals must be stressed. With the improvement of prehospital care, EMSS, and in-hospital care, there will be a decrease in DOA patients.