A meta-analysis of mandibular intercanine width in treatment and postretention.

The meta-analysis technique of literature review was applied to a total of 26 previous studies to assess the longitudinal stability of postretention mandibular intercanine width. Weighted averages and standard deviations for the means of 1,233 subjects were compared for linear changes in intercanine transverse dimensions during treatment (T1), immediately after treatment (T2), and after removal of all retention (T3). Net change was defined as the difference between means at T3 and T1. Dimensional changes were also evaluated on the basis of patient pretreatment Angle classification, extraction, and nonextraction treatment modalities of each group. Paired two-tail t-tests were performed between T3 and T1 means on all groups at the a priori level of significance set at a < or = 0.05. Statistically significant differences were observed for the following groups: all patients; nonextraction; extraction; Class I; Class I extraction; Class II extraction; and, Class I Division 1 nonextraction. The findings of this study indicate that regardless of patient diagnostic and treatment modalities, mandibular intercanine width tends to expand during treatment on the order of one to two millimeters, and to contract postretention to approximately the original dimension. While statistically significant differences could be demonstrated within various groups, the magnitudes of the differences were not considered clinically important.

Charge-coupled device panoramic radiography: effect of beam energy on radiation exposure.

OBJECTIVE: To determine the consequences for entrance exposure of varying the beam energy and operating current for panoramic radiography using a charge-coupled device receptor. MATERIAL AND METHODS: Images were made of a RANDO average man phantom (Alderson Research Laboratories, Stamford, CT) at kVcp settings of 60, 66, 70 and 80 and an mA of 2.0, 3.2, 6.4 and 10.0. The exposure cycle was set as recommended by the manufacturer at 17.6 s. Diagnostic image quality was rated by a panel of two oral and maxillofacial radiologists and one oral and maxillofacial pathologist. Entrance exposures were assessed using a 3 cc ionization chamber placed at the beam entry points while imaging the molar, premolar, and anterior teeth both using the DigiPan (Trophy Radiologie, Vincennes, France) CCD receptor and conventional T-Mat G film/Lanex Regular screens (Eastman Kodak, Rochester, NY, USA). RESULTS: Acceptable image quality was attained with combinations of 60 kVcp and 3.2, 6.4 or 10 mA, 70 kVcp and 2.0, 3.2 or 6.4 mA; at 80 kVcp irrespective of the mA it was unacceptable. The maximum reduction in entrance dose was 77%, averaged over the three sites, at 70 kVcp and 2 mA. CONCLUSION: The DigiPan receptor produces satisfactory images with saving in entry exposure saving of approximately 70% when compared with a conventional film/rare earth screen combination.

Ten rules for reading clinical research reports.

This was not a scientific assessment of the scientific quality of the papers published by The American Journal of Surgery. It was an informal audit of the adequacy of the data analysis in the clinical research reports appearing in the 1987-1988 issues. As one who has devoted more than three decades to helping a great variety of people make sense of scientific data, I found the overall quality of data analysis in these papers to be above average for the medical literature; and yet, I found many instances of errors so serious as to render invalid the conclusions of the authors. My 10 proposed rules for reading clinical research reports constitute only an interim solution to a very worrisome problem. The real solution must come from the producers of and the gatekeepers for the medical literature.

Submentovertex radiology: cephalometric considerations in temporomandibular dysfunction.

Controversy exists in the literature concerning the association between the radiographic and the clinical features of the temporomandibular dysfunction (TMD). Hence, this study reinvestigated possible correlations between radiographically detected asymmetries and the clinical signs and symptoms of TMD. Complete clinical and radiographic records were gathered from 52 patients sequentially referred for corrected angle tomographs of the temporomandibular joint (TMJ). Measurements from submentovertex (SMV), lateral and posterior-anterior (PA) cephalographs and corrected angle parasagittal tomographs and recorded clinical signs and symptoms of TMD were the data inputs. Significant findings were as follows: a) as the discrepancy in the posterior condyle to pogonion measurement increased, the pogonion and both maxillary and mandibular incisors shifted laterally towards the shorter side; b) as the ANB angle increased, so did the difference in condylar angle measurements between the two condyles; c) the side with the larger condylar angle was positioned forward on the SMV; and d) a perpendicular bisector (Marmary's Centerline) of the line drawn between the right and left foramen spinosum was found to be a reliable baseline reference for SMV analyses. No statistically significant relation was found linking specific signs and symptoms of TMD to maxillofacial asymmetries recorded on SMV, lateral or PA cephalographs. None of the radiographic signs studied were found to be good predictors of specific signs and symptoms in TMD.

The carcinogenic risks of alcoholic beverages: implications for cancer education.

The proper analysis of the data generated by studies of carcinogenic risks of drinking alcoholic beverages would be the application of models from the relatively new approach of meta-analysis. In this study, 441 articles were generated by a 1992 MEDLINE search of the key words "alcohol drinking" and "cancer." Of these, only 29 met the criteria for a formal meta-analysis. For these 29 research reports, the 95% confidence limits for the odds ratio were 1.28 and 1.15, suggesting a weak association between drinking and cancer. This conclusion was rendered even less decisive by the following problems in the studies analyzed: 1) absence of comparable measures of either dosages or drinking patterns; 2) absence of comparable methods of data analysis; 3) absence of comparable measures of other population characteristics; and 4) widely varying results from study to study. For example, the 95% confidence limits for the odds radio of the 16 European studies were 1.14 and 0.98, indicating not even a reliable directional difference between drinking and nondrinking populations. Although the World Health Organization International Agency for Research on Cancer concluded in 1987 that alcoholic beverages are carcinogenic, the scientific literature extant in 1992 provides only very weak support for that finding. There is a need for multiple nonexperimental investigations using methods that will produce results sufficiently comparable to justify the application of the statistical models being generated for the meta-analysis of important questions not subject to direct experimentation.(ABSTRACT TRUNCATED AT 250 WORDS)

Longitudinal predictability of AF-BF value in Angle Class I patients.

AF-BF is a linear cephalometric measure of the anteroposterior jaw relationship in the sagittal plane. A retrospective, longitudinal study was made to determine the mean Caucasian American AF-BF values at ages 8 and 18 years for 30 male and 32 female participants of the Bolton Growth Study. Mean AF-BF values (+/- s.d.) for males were 7.3 +/- 2.7 mm at 8 years and 6.5 +/- 4.2 mm at 18 years. Mean AF-BF values (+/- s.d.) for females were 6.7 +/- 2.1 mm at 8 years and 5.2 +/- 2.9 mm at 18 years. No significant difference was found between the mean AF-BF values for males and females at either age group (P < 0.05). The decrease in AF-BF mean values with increasing age both for males and females was statistically significant. The correlation (r) for the AF-BF values was 0.49 (P < 0.05) for females and 0.86 (P < 0.05) for males. With increasing age, the mean difference between ANB values for females was 1.40 +/- 1.60 and 1.10 +/- 1.40 for males. The correlation of ANB angle and AF-BF provides a clinically useful tool for the cephalometric assessment of anteroposterior sagittal discrepancies of maxillary and mandibular denture bases.

The role of the headgear calendar in headgear compliance.

This study was undertaken to determine the role of the headgear calendar and its relationship to headgear compliance. Headgear timers were used covertly to monitor actual headgear wear of 28 patients for three consecutive orthodontic appointments. Fourteen patients were asked to monitor their daily headgear wear by using a headgear calendar. The other 14 did not use a calendar. The results show that patients who monitor their headgear wear with a headgear calendar are more compliant than those patients who do not (7.9 hours compared with 5.3 hours). All age groups in this study wore their headgear more when a headgear calendar was used with the exception of the > 16-year-old group. There is a high degree of correlation (r2 = 0.60) between the number of hours recorded on the calendar compared with the number of hours actually worn. There was a poor correlation (r2 = 0.02) between the number of hours the patient said he wore his headgear compared with the actual number of hours worn.

Clinical versus quantitative assessment of headgear compliance.

This study was undertaken to determine if clinicians could accurately evaluate headgear compliance. Headgear timers were used covertly to quantitatively assess the headgear compliance of 28 patients over 3 consecutive months. Investigators subjectively evaluated the patients to determine how many hours per day they felt the patient had been wearing the headgear. Investigators were divided into three groups: (1) 5 orthodontists (2 board certified, 3 board eligible--total of 50 years of orthodontic experience); (2) 10 residents; and (3) 11 assistants. At least two investigators from each group evaluated the same person for all three appointments. The average error values were 2.86 hours, 3.27 hours, and 3.61 hours, respectively, for the three groups. The standard deviations were also very large, indicating that no group could accurately or consistently assess headgear wear. In this study no difference was found in compliance between sexes. Patients 10 to 12 years of age were more compliant than those 12 to 14 years of age, which were more compliant than the > 16 age group. The least compliant was the 14 to 16 year age group.

Breast Cancer Detection Demonstration Project data can determine whether the prognosis of breast cancer is affected by the time of surgery during the menstrual cycle.

The purpose of this study was to determine the feasibility of using Breast Cancer Detection Demonstration Project (BCDDP) data to ascertain whether the prognosis of breast cancer in premenopausal women is affected when surgery is performed relative to the different phases of the menstrual cycle. In the Louisville BCDDP only 40 cases were available for study, but even with this small number, the data indicate that survivorship was superior when the surgery was performed between days 7-20 of the menstrual cycle (P < 0.06). One thousand eighty-seven premenopausal women underwent surgery for breast cancer during the first 5 years of the national BCDDP, beginning in 1972. This large number of cases, plus the long period of follow-up should provide sufficient statistical power for us to evaluate if there is any relationship between the day of the menstrual cycle, the day surgery was performed, and prognosis. This feasibility study indicates that these women should be followed up and the appropriate statistical studies should be done.

Ten rules for reading clinical research reports.

This was not a scientific assessment of the scientific quality of the papers published by The American Journal of Surgery. It was an informal audit of the adequacy of the data analysis in the clinical research reports appearing in the 1987-1988 issues. As one who has devoted more than three decades to helping a great variety of people make sense of scientific data, I found the overall quality of data analysis in these papers to be above average for the medical literature; and yet, I found many instances of errors so serious as to render invalid the conclusions of the authors. My 10 proposed rules for reading clinical research reports constitute only an interim solution to a very worrisome problem. The real solution must come from the producers of and the gatekeepers for the medical literature.

Enhancement of wound healing by topical treatment with epidermal growth factor.

Experimental studies in animals have demonstrated that the topical application of epidermal growth factor accelerates the rate of epidermal regeneration of partial-thickness wounds and second-degree burns. We conducted a prospective, randomized, double-blind clinical trial using skin-graft-donor sites to determine whether epidermal growth factor would accelerate the rate of epidermal regeneration in humans. Paired donor sites were created in 12 patients who required skin grafting for either burns or reconstructive surgery. One donor site from each patient was treated topically with silver sulfadiazine cream, and one was treated with silver sulfadiazine cream containing epidermal growth factor (10 micrograms per milliliter). The donor sites were photographed daily, and healing was measured with the use of planimetric analysis. The donor sites treated with silver sulfadiazine containing epidermal growth factor had an accelerated rate of epidermal regeneration in all 12 patients as compared with that in the paired donor sites treated with silver sulfadiazine alone. Treatment with epidermal growth factor significantly decreased the average length of time to 25 percent and 50 percent healing by approximately one day and that to 75 percent and 100 percent healing by approximately 1.5 days (P less than 0.02). Histologic evaluation of punch-biopsy specimens taken from the centers of donor sites three days after the onset of healing supported these results. We conclude that epidermal growth factor accelerates the rate of healing of partial-thickness skin wounds. Further studies are required to determine the clinical importance of this finding.

Diagnosis of perirenal fibrosis by MR imaging.

A case of retroperitoneal perirenal fibrosis resulting in bilateral proximal ureteral obstruction is reported. Magnetic resonance imaging provided tissue specific diagnosis of the disease.

Gadolinium-DTPA enhancement of VX-2 carcinoma of the rabbit kidney on T1 weighted magnetic resonance images.

Experimental renal carcinoma was induced by percutaneous injection of VX-2 carcinoma cells into the left kidney in New Zealand white rabbits. Magnetic resonance imaging (MRI) was performed at 0.15 T before and after intravenous injection of 0.3 mmol gadolinium-DTPA (Gd-DTPA) per kg body weight. Gd-DTPA enhanced the tumors by increasing the signal intensity on T1 weighted images. The enhancement was evident immediately after Gd-DTPA injection, increasing during the observation time of 30 minutes. Histologically the areas of enhancement corresponded well to the viable tumor tissue.

Hydrogen peroxide inhibits glucose metabolism and collagen synthesis in bone.

Effects of H2O2 on bone were evaluated in an organ culture system. Tibiae from chick embryos were incubated for up to 3 days in culture medium containing 0.07 to 20 mM H2O2. Glucose metabolism was monitored by measuring lactate production and oxygen consumption, and collagen synthesis was determined by hydroxylation of proline. In addition to markedly inhibiting these parameters, H2O2 also decreased bone weight and alkaline phosphatase activity. Multiple exposures to H2O2 were somewhat more effective than a single exposure. Since H2O2 inhibits bone at low concentrations in vitro, the results suggest that the potential for harmful effects of H2O2 in the oral cavity should be investigated.

Absence of periodontitis in a population of insulin-dependent diabetes mellitus (IDDM) patients.

The prevalence of periodontitis was studied in a population of insulin-dependent diabetes mellitus (IDDM) patients, aged 10-18, with a variety of disease durations and levels of control. The sample included a number of patients with poorly controlled IDDM of long duration. None of the patients had radiographic signs of periodontitis. When considered in conjunction with previously reported studies, the findings suggest that populations of IDDM patients may differ in susceptibility to the periodontal diseases; thus, generalizations concerning prevalence based on only a few studies may be inappropriate.

Enhancement of Streptococcus mutans colonization by direct bonded orthodontic appliances.

Patients undergoing orthodontic therapy were evaluated for longitudinal changes in relative S. mutans numbers in plaque at discrete sites on the tooth surface associated with direct bond appliances. There was a significant linear increase in the percentage of S. mutans in the total streptococci isolated from the last pre-bracket sample through the last bracket sample.

Mirror-tracing and Embedded Figures tests as predictors of dental students' performance.

Recent studies of the Embedded Figures and Mirror-Tracing Tests as predictors of first-, second-, and third-year dental students' grades were extended to the fourth year, and the comparative utility of the experimental predictors were examined in groups of recent dental graduates categorized by their predental science GPAs and DAT scores. The experimental predictors proved to very strong in graduates whose grades were below average at admission and were the best overall predictors for students who entered dental school with a predental science GPA below 3.0 or a combined DAT score below 4.0. Neither the DATs nor the predental science GPAs contributed consistently as predictors in these below average students. However, the predental science GPA was the best single overall predictor for all graduates (when not categorized as described). the experimental predictors contributed significantly to the predictive utility of the predental science GPA.