Accuracy and reliability of linear cephalometric measurements from cone-beam computed tomography scans of a dry human skull.

INTRODUCTION: The purpose of this study was to determine the accuracy and reliability of 3-dimensional craniofacial measurements obtained from cone-beam computed tomography (CBCT) scans of a dry human skull. METHODS: Seventeen landmarks were identified on the skull. CBCT scans were then obtained, with 2 skull orientations during scanning. Twenty-nine interlandmark linear measurements were made directly on the skull and compared with the same measurements made on the CBCT scans. All measurements were made by 2 operators on 4 separate occasions. RESULTS: The method errors were 0.19, 0.21, and 0.19 mm in the x-, y- and z-axes, respectively. Repeated measures analysis of variance (ANOVA) showed no significant intraoperator or interoperator differences. The mean measurement error was -0.01 mm (SD, 0.129 mm). Five measurement errors were found to be statistically significantly different; however, all measurement errors were below the known voxel size and clinically insignificant. No differences were found in the measurements from the 2 CBCT scan orientations of the skull. CONCLUSIONS: CBCT allows for clinically accurate and reliable 3-dimensional linear measurements of the craniofacial complex. Moreover, skull orientation during CBCT scanning does not affect the accuracy or the reliability of these measurements.

FGF-23-Klotho signaling stimulates proliferation and prevents vitamin D-induced apoptosis.

Fibroblast growth factor 23 (FGF-23) and Klotho are secretory proteins that regulate mineral-ion metabolism. Fgf-23(-/-) or Klotho(-/-) knockout mice exhibit several pathophysiological processes consistent with premature aging including severe atrophy of tissues. We show that the signal transduction pathways initiated by FGF-23-Klotho prevent tissue atrophy by stimulating proliferation and preventing apoptosis caused by excessive systemic vitamin D. Because serum levels of active vitamin D are greatly increased upon genetic ablation of Fgf-23 or Klotho, we find that these molecules have a dual role in suppression of apoptotic actions of vitamin D through both negative regulation of 1alpha-hydroxylase expression and phosphoinositide-3 kinase-dependent inhibition of caspase activity. These data provide new insights into the physiological roles of FGF-23 and Klotho.

The effect of smoking on osseointegrated dental implants. Part II: Peri-implant bone loss.

PURPOSE: The detrimental effect of cigarette smoking on implant survival has been previously demonstrated. The purpose of this study was to retrospectively investigate the effect of smoking on marginal bone loss around endosseous dental implants. MATERIALS AND METHODS: The sample consisted of 767 Brånemark implants placed in 235 patients between 1979 and 1999. Bone level changes were determined using periapical radiographs taken at annual recall visits for 1 to 20 years following prosthesis insertion. Nonparametric tests and multiple linear regression were used to determine the influence of various factors on peri-implant bone loss during the first year of clinical loading and for all subsequent years. RESULTS: The mean annual bone loss was 0.178 mm +/- 0.401 during the first year of clinical loading and 0.066 mm +/- 0.227 per year thereafter. A positive smoking history was associated with a higher rate of peri-implant bone loss, and the majority of implant failures were observed in this group of patients. Smoking at the time of stage 1 surgery did not appear to predispose implants to more marginal bone loss. CONCLUSION: Cigarette smoking should not be an absolute contraindication for implant therapy; rather, long-term heavy smokers must be informed that they are at a slightly higher risk of late implant failure and are susceptible to more marginal bone loss over the long-term, irrespective of their smoking status at the time of implant placement.

The effect of smoking on osseointegrated dental implants. Part I: implant survival.

PURPOSE: Recent studies implicate smoking as a significant factor in the failure of dental implants. The purpose of this long-term retrospective study was to evaluate the survival of Brånemark endosseous dental implants in relation to cigarette smoking. MATERIALS AND METHODS: The sample consisted of 464 consecutively treated completely and partially edentulous patients who had a total of 1852 implants placed between 1979 and 1999, and who were part of a surgical/prosthodontic prospective treatment outcomes study. The effect of cigarette smoking on implant survival in relation to the time of implant failure, gender, age, surgeon, date and site of implant placement, implant length and diameter, prosthesis design, and occlusal loading considerations was assessed in bivariate and multivariate survival analyses. RESULTS: The overall implant failure rate was 7.72%. Patients who were smokers at the time of implant surgery had a significantly higher implant failure rate (23.08%) than nonsmokers (13.33%). Multivariate survival analysis showed early implant failure to be significantly associated with smoking at the time of stage 1 surgery and late implant failure to be significantly associated with a positive smoking history. Short implants and implant placement in the maxilla were additional independent risk factors for implant failure. CONCLUSION: Cigarette smoking should not be an absolute contraindication for implant therapy; however, patients should be informed that they are at a slightly greater risk of implant failure if they smoke during the initial healing phase following implant insertion or if they have a significant smoking history.