ABSTRACT
Methyl methacrylate-based (MMA-based) bonding resins have been used in orthodontics because they offer easy removal of both the bonded bracket and the residual adhesive at case completion. However, these materials are not cross-linked, and the brackets bonded with this type of product may undergo drifting when subjected to temperatures slightly higher than those in the mouth. This research investigated the influence of heat on the debonding characteristics of a MMA-based bonding resin compared with those of a BIS-GMA-based system. The temperature of initial bracket movement, as well as of final bracket displacement, was noted for a variety of applied loads (141, 226, 425, 934, and 1727 gm) with stainless steel brackets bonded to etched bovine enamel. The results showed that the MMA-based material underwent a glass transition near 47 degrees C in which the initiation of bracket drift resulted on the tooth surface. This temperature proved independent of the applied load. Further heating resulted in the release of heat from the resin as a result of further curing. The extent of bracket drift associated with this secondary heat release was dependent on the applied load. The debonding temperature of the BIS-GMA-based system was three to six times greater than that of the MMA-based product. Practitioners should be aware that brackets bonded with MMA-based resins have the potential for drifting when subjected to temperatures within the normal range of hot fluids consumed by their patients. Bracket drift could result in deactivation of orthodontic force and could prolong the treatment time.
Subject(s)
Dental Cements/chemistry , Dental Debonding , Methylmethacrylates/chemistry , Orthodontic Brackets , Polymethacrylic Acids/chemistry , Adhesives/chemistry , Analysis of Variance , Animals , Bisphenol A-Glycidyl Methacrylate , Cattle , Dental Stress Analysis , Hot Temperature , Orthodontic Brackets/adverse effects , Regression AnalysisSubject(s)
Dental Care/psychology , Pain/psychology , Toothache/psychology , Anxiety/therapy , HumansABSTRACT
In 149 cases, blood pressure response to glucagon test did not exceed 20/10 mm Hg more than the response in the cold pressor test control and was considered negative. Plasma catecholamine level increases may be seen in 95% of patients without pheochromocytomas. Among six patients with pheochromocytomas, urinary metanephrine levels were of diagnostic importance in two with isolated pheochromocytoma and in one with the multiple endocrine neoplasia of type 2 (MEN-type 2). Urinary metanephrine determinations yielded false-negative results in three patients with MEN-type 2, while vanilmandelic acid level was normal in one and nephrotomograms were positive in two of these three. These results suggest that the early diagnosis of pheochromocytoma in patients with MEN-type 2 may be difficult and may require multiple biochemical and roentgenographic investigations.
Subject(s)
Blood Pressure/drug effects , Catecholamines/blood , Glucagon , Pheochromocytoma/diagnosis , Adolescent , Adult , Aged , Child , Female , Humans , Kidney/diagnostic imaging , Male , Metanephrine/urine , Middle Aged , Parathyroid Diseases/genetics , Pheochromocytoma/genetics , Thyroid Neoplasms/genetics , Tomography, X-Ray , Vanilmandelic Acid/urineABSTRACT
On 247 of the 1,711 scintiscans (15%), the appearance of renal or urinary tract areas differed sufficiently from normal to merit mention in interpretation. For 162 patients (195 surveys), the abnormalities noted were classified as "minor." For 39 patients (52 surveys), the abnormalities noted were classified as "major"--that is, confirmed by other means or considered of major importance to diagnosis and management. Of these, 9 were filling defects (2 each were renal cell carcinoma, simple cyst, and polycystic disease; 3 were a mass of undetermined nature) and 30 were unilateral or bilateral urinary tract obstruction indicated by hydroureter and massive retention in renal area(s). These obstructive manifestations were associated with primary pelvic or prostatic malignancy or extension of malignant disease; in nine patients, progression or remission of obstruction was noted on sequential imaging. These changes were compatible with changes in clinical status and may afford an added means of following response to therapy in appropriate patients.
