Richard R. Bevis

Bond strength of ceramic brackets under shear stress: an in vitro report.

The shear bond strength and the potential enamel damage on debonding of various currently available ceramic and stainless steel brackets were examined in vitro using extracted premolar teeth. The brackets were divided into two groups, one bonded with a new light-cured orthodontic adhesive and the other with a conventional chemically cured system. An Instron Universal testing machine was used to apply the shear stress. Mean, standard deviation, and extreme values were calculated for each group. Statistical analysis showed that the mean shear bond strength of the silane chemical bond provided by some ceramic brackets is significantly higher (p less than 0.05) than the mean of the mechanical bond of other ceramic and stainless steel brackets. There was no statistically significant difference between the mean shear bond strength of the two adhesives used. Mechanical bonds failed primarily within the adhesive itself, whereas chemical bonds failed predominantly at the adhesive-bracket interface. Single-crystal ceramic brackets tend to be more brittle than the polycrystalline ones. Strong chemical bonds can potentially lead to enamel failure on debonding.

The Presurgical Status of the Alveolar Cleft and Success of Secondary Bone Grafting

OBJECTIVE The primary purpose of this study was to evaluate presurgical status of the alveolar cleft site and success of secondary alveolar bone grafting. DESIGN Thirty patient records were retrospectively reviewed. Patients selected for inclusion had isolated cleft of at least the primary palate. Patients with additional anomalies were not selected. The study population consisted of 15 female sites and 16 male cleft sites. There were two bilateral cleft lip and palate (CLP) patients and 28 unilateral CLP patients. The age at the time of the secondary alveolar bone grafting ranged from 7 years to 14 years, 4 months. SETTING The study was conducted at the Cleft Palate Clinic at the University of Minnesota, School of Dentistry. METHOD Presurgical radiographs taken at least 1 month prior to the secondary bone grafting and postsurgical radiographs taken at least 6 months after bone surgery were measured. Measurements included size of the cleft defect and bone support for distal and mesial teeth adjacent to the cleft. Evaluation of success was determined on the basis of postsurgical measurements of satisfactory, intermediate, and unsatisfactory outcomes. RESULTS AND CONCLUSION The size of the cleft defect was not correlated with the success rate of the secondary alveolar bone grafting. If the amount of distal bone support for the mesial tooth was the same as those in a periodontally healthy individual, a satisfactory outcome was 5.8 times more likely. If the amount of mesial bone support for the distal tooth was the same as those in a periodontally healthy individual, the satisfactory outcome was 3.8 times more likely. Although not a primary purpose of the study, it was found that in this study population, if the patient was female, a satisfactory outcome was 3.8 times more likely.

Enamel abrasion from ceramic orthodontic brackets under an artificial oral environment

The purpose of this investigation was to examine the potential enamel abrasion on contact with stainless steel and various ceramic orthodontic brackets under a simulated oral environment. Three groups of eight lower premolar ceramic brackets and one group of eight stainless steel brackets were used from four different manufacturers. An upper premolar was brought in contact with the bracket bonded to a lower premolar tooth and subjected to a lateral excursion type of movement by the artificial oral environment. A constant load of approximately 2 lb was used for the masticatory force. The rate of chewing was 1 cycle/sec. The teeth were subjected to 15, 60, and 100 masticatory cycles. The before-and-after occlusal surfaces of the upper premolars were compared by means of a computerized profiling system and the enamel volume loss was calculated. Qualitative changes, such as rate of enamel wear, were examined visually by means of computer graphics and the scanning electron microscope. Abrasion scores (mean +/- SD) in mm3 were 0.015 +/- 0.01 from the metal brackets and 0.135 +/- 0.103, 0.255 +/- 0.242, and 0.581 +/- 0.524 from the three ceramic bracket groups. The abrasion scores were significantly different at p less than 0.05. Ceramic brackets caused significantly greater enamel abrasion than stainless steel brackets. Artificial mouth in vitro testing gave a good indication of clinical performance of orthodontic brackets.

Periodontal evaluation of canines erupted through grafted alveolar cleft defects.

Two to eight years after receiving autogenous iliac crest grafts for treatment of alveolar cleft defects, eighteen patients who had unilateral cleft palate were evaluated for their periodontal status. When cleft-associated canines were compared with contralateral control canines, no statistically significant differences were found between specific surface values for plaque index, gingival index, or probing depths. Attachment loss was found to be greater (less than 0.72 mm) on the mesio-facial, facial, and mesio-palatal surfaces of the cleft-associated canines than on the control canines. Fifty-six per cent of the cleft-associated canines required surgical exposure and 44% also required orthodontic assistance to erupt to a functional occlusion. Osseous grafting of alveolar cleft defects resulted in satisfactory clinical periodontal support for cleft-associated canines.

Evaluation of the ceramic/ceramic interface

The purpose of this study was to investigate bond strength for ceramic orthodontic brackets bonded to dental porcelain. The following factors were tested. Two types of ceramic brackets were placed on two different types of porcelain surfaces with two different bonding systems. Three different debonding techniques, and various composite removal techniques and surface restoration techniques were used. Two hundred porcelain samples were used that duplicated the labial surface of a maxillary right central incisor. Bond strengths were measured with an Instron Universal testing machine (Instron Corp., Canton, Mass.). Mean bond strength and standard deviations were calculated and significance was determined with analyses of variance (ANOVA) and a chi-square test. Composite removal and polishing methods were investigated by scanning electron microscopy. The results showed that tensile type debonding methods are the least likely to damage the porcelain surface. Some brackets (Unitek Corp., Minn.) having a higher bond strength (p < or = 0.01) fractured the porcelain surface when tested in the shear debonding mode. The bonding materials tested were comparable to adhesion studies of similar brackets to enamel. The Ormco primer-Concise porcelain bonding system was significantly stronger (p < or = 0.01) than the Scotchprime-Transbond. Composite removal by careful use of a carbide bur, followed by the use of the Shofu porcelain adjustment kit and porcelain glaze polish, restored the finish to a normal porcelain surface after debonding. The study showed that shear and tensile debonding forces for glazed porcelain with the use of silane primer, were comparable with those reported in the literature for enamel, thus clinically sufficient. At the same time, preservation of the glaze allowed an almost ideal polishing of the porcelain surface after debonding.

Enamel surface abrasion from ceramic orthodontic brackets: A special case report

The purpose of this report is to present a dramatic case of enamel abrasion from ceramic orthodontic appliances that was discovered only after appreciation of the initial findings of a study underway at the Department of Orthodontics, University of Minnesota. An artificial oral environment used in this study to simulate mastication also is described. The potential detrimental effects of ceramic appliances on tooth contact are discussed. All aspects of any new material should be investigated before its clinical application to prevent undesired side effects.

The sagittal split osteotomy of the mandible

Modifications of the sagittal split osteotomy of the mandible have essentially reduced the major drawbacks of the procedure, such as condyle displacement, short-term skeletal relapse, and protracted maxillomandibular fixation and mental nerve dysesthesia. These techniques have proved effective over a period of 4 years in fifty-seven patients treated.

Apertognathia (open bite) and its surgical management

The etiology, diagnosis, and management of apertognathia are reviewed. 2 apertognathia cases treated with LeFort I osteotomy and adjunctive procedures are presented.

Anterior maxillary osteotomy in a patient with congenital port-wine stain

Abstract A case of anterior maxillary osteotomy in a patient with facial asymmetry associated with a facial and oral port-wine stain is reported. Consideration of the vascular syndromes associated with port-wine stain, and thorough clinical, conventional radiographic, and arteriographic examinations are essential prior to any major orthognathic surgery.