IU Indianapolis ScholarWorks :: Browsing by Author "Garetto, Lawrence P."

Browsing by Author "Garetto, Lawrence P."

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A Manpower Study of Orthodontic Specialists for the State of Indiana
(1992) Clark, David B.; Roberts, W. Eugene; Arbuckle, Gordon R.; Garner, LaForrest D.; Garetto, Lawrence P.; Shanks, James C.
Dental manpower has been studied at national, state and local levels.2, 4, 6, 11, 14, 15, 17-19 Manpower studies of orthodontic specialists also have been conducted,1, 5, 13, 16 but there has been no recent manpower study relative to orthodontic specialists in Indiana. The purpose of this study was to evaluate the busyness and distribution of orthodontic specialists in Indiana and project the need for orthodontists. In early 1990 a survey questionnaire was mailed to Indiana orthodontists. A telephone survey of orthodontic receptionists/appointment clerks was conducted during the same time period to obtain a separate source of data relative to practice busyness and to help evaluate the reliability of the mailed survey questionnaire. The distribution of orthodontists was evaluated by comparing the state population-to-orthodontist ratio to county and regional ratios. The response rate of the mailed survey questionnaire was 91 percent. The ages of orthodontists were evenly distributed with the exceptions of the 46-50 year age group and groups approaching retirement ages. The perceived level of busyness was low with a busyness index of 1.32. A relatively short wait was necessary to examine and start new patients, and few reported a waiting list. There was a high response emphasizing no need for additional orthodontists. Seventy percent felt that they were not busy enough; 99 percent reported that they would like more patients; and many desired large numbers of additional patients (41 or more). A large number of orthodontists had satellite offices or were considering establishing satellite offices with an insufficient patient base listed as the primary reason. There was a significant difference between the number of additional patients desired based on the age of the orthodontist. More orthodontists reported that patient loads were remaining the same or declining rather than increasing. The present data did not support the premise that the number of patients started was less than that seen in previous studies, suggesting that the low perception of busyness may be related to other factors such as a more recent decline in patient load, improved efficiency, decreased profitability or a combination of these or other factors. The telephone survey differed significantly from the mailed survey questionnaire indicating a possible bias in the survey questionnaire. A geographic maldistribution of orthodontists in Indiana was found. A slight increase in the number of orthodontists over the next decade would be necessary to maintain the present population-to-orthodontist ratio. However, the declining child population, representing the majority of orthodontic patients, will require a reduction in the number of orthodontists to maintain the present adjusted population-to-orthodontist ratio or patient-to orthodontist ratio over the next two decades.
Analysis of Bone Remodeling in the Mandibular Condyle of Female Retired-Breeder Rabbits Following Altered Loading
(1992) Hunt, J. Todd; Garetto, Lawrence P.; Roberts, W. Eugene; Arbuckle, Gordon R.; Brown, David T.; Shanks, James C.
Previous studies have associated increased occlusal loads with degenerative changes of the temporomandibular joint (TMJ). The purpose of this study was to analyze effects of increased occlusal loads in adult animals. It was hypothesized that increased functional loading would cause degeneration of the mandibular condyle. Twelve female retired-breeder rabbits (mean age = three years, one month) were divided equally into three experimental groups and one control group. Each of the experimental rabbits received maxillary and mandibular light-cured anterior splints at the beginning of the study to create a bilateral posterior openbite (~2 mm). Theoretically, this should have resulted in increased loads to the TMJ. The first two groups wore the appliances for six and 12 weeks, respectively, prior to euthanasia. The third group wore the appliances for 12 weeks and then had them removed for 12 weeks prior to being euthanized. Fluorescent bone labels were utilized, and the specimens were analyzed histomorphometrically. The cartilage thickness was not statistically different between groups, nor were there any signs of cartilage degeneration. There was a trend, however, toward thinner condylar cartilage in the 12-week group. The six-week group showed significantly less labeled subchondral bone than the control group (0.5 ± 0.1 % versus 2.6 ± 0.3%, respectively; p<.05). The six- and 12-week groups both revealed significantly less periosteal surface label of the condylar neck than the control group (1.5 ± 0.8% and 5.3 ± 1. 7% versus 22.0 ± 3.5%, respectively; p<.05). Likewise, they both showed significantly more label at the cartilage-bone interface (1.0 ± 0.2% and 1.4 ± 0.2% versus 0.4 ± 0.2%, respectively; p<.05) and moderately more label along the trabecular surfaces than the control group. These results indicated that the increased loading of the mandibular condyle initially (at six weeks) depressed remodeling of the subchondral bone and decreased periosteal bone formation. Modeling increased at the cartilage-bone interface and potentially along the trabecular bone surfaces. With continued elevated occlusal loads (at 12 weeks), modeling still was quite active at the cartilage-bone interface and on the trabecular surfaces. Periosteal surface modeling remained depressed compared to the control group, but remodeling in the subchondral bone region increased to that of the control group. The 12/12-week group tended to show findings similar to the control group. This suggests that once loading was returned to normal, the condyle also returned toward preexperimental physiologic conditions. Although this study did not show the obvious degenerative changes one typically equates with osteoarthrosis, the elevated modeling at the cartilage-bone interface following increased joint loads was consistent with the early degenerative changes observed by Radin et al. in their joint-loading model. However, the rapid osseous changes seen in this study refute the theory that the adult TMJ is unable to adapt to altered functional loading.
Assessment of Osteoporosis Risk Factors in the Female Dental Patient: A Demographic Study
(1996) Becker, Angela R.; Garetto, Lawrence P.; Arbuckle, Gordon R.; Clark, David B.; Roberts, W. Eugene; Shanks, James C.
Osteoporosis has become a major public health problem as the size of the elderly population has continued to increase. While it is unclear as to the exact relationship between systemic bone disease and the craniofacial skeleton, the dental implications of osteoporosis could include dental implant failure, decreased residual ridge height, and unsuccessful orthodontics or oral surgery procedures. While these concerns remain speculative, it is important for dentists to recognize patients who exhibit high risk for osteoporosis. The purpose of this study was to evaluate risk factors for osteoporosis exhibited by female dental patients at Indiana University School of Dentistry and to assess this risk among the various dental specialty subpopulations. Based on general population averages, we hypothesized that approximately 20 percent of the female patients were at high risk for osteoporosis and that differences would be found among the various dental subpopulations. We also hypothesized that the number of teeth present would decrease as the risk for osteoporosis increased. A 12 question survey assessment tool was devised and administered to 220 female dental patients 18 years and older. This survey asked the patient to report selected vital statistics, menstrual status, and other aspects of lifestyle. The average overall age of the patients was 48.2±1.1 years. Of the 220 subjects, 34 percent exhibited serious risk factors for osteoporosis. The orthodontic subpopulation contained the fewest number of patients at high risk for osteoporosis (6 percent). However, they were also the youngest group (33.9±2.0). The complete denture subpopulation had the highest number of patients at high risk for osteoporosis (53 percent) and was the oldest (60.0±2.3). There was a trend for number of teeth to decrease as the risk for osteoporosis and age increased. We also found that in women who had taken hormone replacement therapy for at least five years, there was no association between number of teeth and years postmenopause. However, women who had very little or no hormone replacement therapy, there was a strong correlation for number of teeth retained to decrease as the number of years postmenopause increased (r=0.6). We concluded that there is a difference in dental subpopulations for osteoporosis risk. The clinical implications are that osteoporosis risk is much higher in specific classes of dental patients. Clinicians treating these patients must recognize the need to refer high risk patients for appropriate medical assessment.
Bone Remodeling and Strain Variation Following Altered Mandibular Condyle Loading in Retired Breeder Rabbits
(1993) Puntillo, Anthony M.; Garetto, Lawrence P.; Roberts, W. Eugene; Arbuckle, Gordon R.; Chen, Jie; Burr, David B.
Several investigators have demonstrated modeling of the mandibular condyle foil following a change in load. A recent study evaluated the effect of age on the ability of the condyle to adapt to such a change. The present study explored the early changes in the mandibular condyles of retired breeder rabbits following an alteration in load, and attempted to quantify this load. Twelve female retired breeder New Zealand white rabbits were divided into four equal groups. Under general anesthesia strain gauges were placed on the lateral inferior body of the mandible bilaterally in two of the groups. Two days post-surgery acrylic splints were placed on the anterior teeth (resulting in a posterior open bite) of one the strain gauge groups and one group that did not receive strain gauges. The splints were maintained for 26 days. A control group received neither strain gauges nor splints. Intravital bone labels were administered to all groups to allow for histomorphometric analysis of condylar modeling and remodeling. In addition, principal strain measurements were recorded pre- and post-splint placement. The histomorphometric findings revealed a significant (p<.03) decrease in the subcondylar space of animals that received splints. Splinted animals also showed a significant increase in labeled surface area (p<.02) and in volume percent label (p<.05) of the trabeculae in the condylar neck region. In addition, surgical placement of the strain gauges significantly (p<.05) decreased the labeling of the periosteal surface in the neck region. The strain gauges proved functional in most rabbits for only a few days and registered large variations and no discernible differences in average maximum microstrain, and average change in microstrain. It was concluded from these results that an incisal prematurity (causing a posterior openbite), 26 days in duration, caused an increase functional load on the condyle. This load resulted in an increase in trabecular label and decrease in porosity of the subchondral plate. The decreased subcondylar space is possibly an indication of stiffening in this region. A stiffening of this nature has been suggested in previous studies to be a precursor to osteoarthritic degeneration.
Cell Kinetic Analysis of Osteoblast Histogenesis in the Rat Mandibular Condyle Following Exposure to Hard and Soft Diets
(1991) Stenftenagel, Brenda Kay; Roberts, W. Eugene; Shanks, James C.; Garetto, Lawrence P.; Hohlt, William H.; Schaaf, Jack E.
Microgravity of spaceflight has been associated with inhibition of bone formation, decreased number of osteoblasts (Ob), and suppression of Ob histogenesis. This study was designed to study Ob histogenesis, i.e., the proliferation and differentiation of cells producing Ob. Inhibition of Ob formation seems to be a principal factor in osteopenia induced by spaceflight. Osteoblast histogenesis is a stress/strain mediated mechanism and appears to be gravity dependent under certain conditions. On Spacelab-3 (SL-3), the rat mandibular condyle was evaluated as a model for space study. Data indicated an increase in A+ A' cells (noncommitted and committed self-perpetuating precursor cells), and a decrease in C + D type cells (preosteoblasts that are in the G1 or G2 stage of the cell cycle), accompanied by a decrease in Obs. A stress/strain mediated increase in nuclear volume (A'=> C) is an important rate-limiting step in Ob differentiation. It is hypothesized that this step is inhibited in microgravity. Additional ground studies are needed to confirm these data and define the mechanism of action. Studies have shown that a soft diet decreases overall mechanical loading of the masticatory apparatus. A soft diet was used in this study to simulate the potential microgravity-like effects of decreased mechanical loading on the mandibular condyle, i.e., a decreased masticatory force was used as a model for microgravity. Eighteen male, Sprague-Dawley rats (six to eight weeks of age) were divided into three groups: 1) the experimental group maintained on a soft paste diet; 2) a control group, pair fed equal amounts of food as the experimental group; and 3) a control group fed ad libitum. Both control groups were fed standard Purina TM Rat Chow (sPRC) pellets. The experimental diet consisted of sPRC, crushed and mixed with sufficient water to form a paste. After two weeks on their respective diets, each animal was injected i.p. with xylenol orange, a bone label. One week later calcein green was administered similarly. Two days after the last label, animals were injected i.p. with 3H-thymidine at 8 a.m. One hour later each animal was anesthesized with ketamine and decapitated. Mandibles were fixed for 72 hours. Nuclear morphometry and labeling index data were collected from autoradiographs prepared from demineralized sections. Due to technique problems, only three paste group condyles and five condyles from each of the control groups could be examined. Results showed no significant differences at p < 0.05 in labeling index. Nuclear morphometry data indicated a significant difference in L, A+ A', C, and C + D cells. Rats fed a paste diet had on the average 12 percent more type A+ A' cells, and 17-25 percent less C + D combined cells than the two control groups. These data indicate a similar shift in Ob histogenesis to the left (more A + A' cells) as that found in the POL and the condyle of rats flown in space. These findings support the hypothesis that osteopenia induced in spaceflight may be the result of a reduction in a local mechanical component, or a lack of anti-gravity posturing. Therefore, it may be concluded that a soft paste diet mimics microgravity by decreasing mechanical loading and inhibiting the stress/strain mediated increase in nuclear volume (A'=> C). The condyle from rats fed a soft diet may be a valuable model for studying osteopenia.
Cell Kinetic Analysis of Osteoblast Histogenesis in the Rat Periodontal Ligament Following Exposure to Hard and Soft Diet
(1991) Colter, Robert D.; Roberts, W. Eugene; Garetto, Lawrence P.; Hohlt, William F.; Newell, Donald; Shanks, James C.
This is the first in a series of experiments designed to investigate the effect of local and systemic factors on osteoblast histogenesis in rats. A soft diet is an experimental means thought to decrease the overall mechanical loading (a local factor) on the masticatory apparatus. Eighteen Sprague-Dawley rats were divided into three equally sized groups: 1) an experimental group, which was maintained on a soft paste diet; 2) a control group, pair fed with the experimental group; and 3) a control group fed ad libitum. Both control groups continued to eat standard Purina rat chow pellets. Twenty-three days later all animals were injected subcutaneously with 1.0 μCi/ g tritiated thymidine and sacrificed one hour later. The maxillae of the animals were dissected and sectioned. The periodontal ligament (PDL) of the mesial surface of the mesial root of the first molar was analyzed microscopically 110 μm above and below the mid root area. Nuclear size was used to determine the stage of osteoblast differentiation. The labeling index was used to determine the proliferative activity of the cells. The distance of cells from the nearest major blood vessel (NMBV) was measured and the cells were grouped into one to four extravascular zones. For each zone, cell density was determined. PDL widths were measured to evaluate tooth function. If osteogenesis is due primarily to stress and strain on bones, then rats maintained on the soft diet should show a decreased labeling index, increased number of A and A' cells, decreased number of C and D cells, and an unaltered vascularly-oriented cell density gradient. The number of osteoblastic precursor cells (A and A' cells) close to blood vessels should increase relative to the number of preosteoblastic cells (C and D) further from the vessels. Also, the width of the PDL space in the soft diet rats should be narrower since their function was decreased. The results of this study did not support the hypothesis that a decrease in masticatory stress and strain within the rat periodontal ligament due to softened dietary consistency reduces osteoblast histogenesis. No differences were seen in the PDL widths or the vascularly-oriented cell density gradient between groups. High levels of A+A' cells were seen paravascularly for all groups, and their relative numbers decreased as one moved away from the blood vessel into a lower cell density area, supporting previous studies. No differences were seen in the fractional distribution of A+A' cells or C+D cells between groups, as was hypothesized, except for a higher level of A+A' cells in the pair fed group across all zones. This latter finding was probably due to physiologic variation and the small sample sizes used in this study. Decreased masticatory stress and strain due to a softened diet did not reduce osteoblast histogenesis. Further research needs to investigate systemic factors which may influence bone formation.
Cell Kinetics of Osteoblast Histogenesis in Evolving Rabbit Secondary Haversian Systems Using a Double Labeling Technique with [³H]-Thymidine and Bromodeoxyuridine
(1995) Sim, Yeongsuk; Roberts, Eugene; Garetto, Lawrence P.; Katona, Thomas R.; McDonald, James L.; Seifert, Mark F.
The mechanism for internal cortical bone remodeling is orchestrated by the evolving secondary Haversian systems (SHSs), which originate on the surfaces of Volkmann's canals. During this coupled process, a cortical tunnel advances by the cutting cone of osteoclasts and closes by the bone-forming trail of osteoblasts. This study investigated the hypothesis that osteoblast histogenesis, within evolving SHSs of larger animals, is a vascular-related process, i.e., less differentiated osteogenic cells reside in close proximity to the advancing central blood vessel (CBV) while differentiating osteoblast precursors migrate toward the bone surface and become osteoblasts. Using a double-labeling method with [3 H]-thymidine and bromodeoxyuridine (BrdU), this study examined cell kinetics in 120 SHSs per rabbit at 12 hour intervals up to 72 hours after labeling. A total of 7 rabbits were injected with alizarin complexone (-1 O days: 20 mg/kg/day), tetracycline (-3 days: 10 mg/kg/day), [3H]-thymidine (time zero: 0.25 μCi/gm), and BrdU (1 hour before sacrifice: 25 mg/kg). The femoral midshaft was used for undecalcified fluorescent microscopic analysis of new bone vs. old bone and two adjacent diaphyseal tissues were demineralized for nuclear volume morphometric analysis of cells via light microscopy. Evolving SHSs demonstrating intense remodeling activity were selected for detailed cell kinetic analysis. The results showed that BrdU labeled cells were consistently located at the leading edge of the CBV (within 160 μm of its tip) and that the [3H]thymidine labeled cells were progressively left behind the advancing CBV (160 μm from the tip of CBV by 72 hours). The labeling indices (sampled 1 hour after labeling) between BrdU (10.6 ± 0.3 %) and [3H]-thymidine (14.4 ± 1.3 %) were comparable. Lightly labeled A+A' cells (identified as osteoprogenitor cells) remained in close approximation to the surface of the CBV (within 25 μm) and C+D cells (preosteoblasts) were located closer to bone-forming surfaces (~50 μm away from the CBV). The number of osteoblasts were increased up to 60 hours and about 22.5 ± 6.6 % of them survived to become osteocytes. The B cell compartment, characteristic of osteogenic tissues with a dense connective tissue component such as the periodontal ligament (POL), was essentially absent in the SHSs in this study. Although the direction of evolving SHSs was highly variable (caudally directed: 53.4 ± 11.2 % and rostrally directed: 41.6 ± 8.1 %), the osteogenic process along the advancing CBV was remarkably consistent. These results support the hypothesis that osteoblast histogenesis, associated with cortical bone remodeling, is a vascular-oriented differentiation process closely related to the internal angiogenesis within the evolving SHS. The primary proliferating region supporting osteogenesis was consistently located at the advancing tip of the CBV, suggesting the presence of a self-renewing, perivascular proliferative pool of cells accompanying the advancing vessel. In addition, a secondary proliferating region of cells trails the advancing CBV, providing for lateral migration of preosteoblasts to bone surfaces where they complete their development into functional osteoblasts. This study provides further insight into the similarities and differences in osteoblast histogenesis within evolving SHSs from adult rabbits and the more extensively studied rat POL model.
Cephalometric Similarity Among Parents of Individuals with Sporadic Isolated Cleft Palate : Is There Evidence for an Inherited Predisposition?
(1999) Sammons, Edward M.; Ward, Richard E.; Hartsfield, James K., Jr.; Avery, David R.; Hathaway, Ronald R.; Garetto, Lawrence P.
Isolated cleft palate is one of the most frequent congenital conditions that affect the oral and facial structures, yet its etiology remains obscure. Previous studies of both cleft palate (CP) and cleft lip and/ or palate [CL(P)] have shown that there may be unusual facial characteristics among the parents of such sporadic cases. Such findings have been used to support the possibility that there are predisposing familial (genetic) factors for both conditions. However, previous studies have generally not controlled for the possibility of genetic heterogeneity or for different contributions from each of the parents. The objective of this study is to examine parents of individuals with CP in order to test the hypothesis that these "non cleft" individuals have abnormal facial structures. Lateral (LA) and Posterior-Anterior (PA) cephalograms were examined from thirty parents of fifteen individuals with sporadic CP. Seventeen LA and twenty-five PA variables were obtained on each subject and converted to standardized "z-scores" through comparison to published age and sex matched reference data. Multivariate cluster analysis was used to define groupings of individuals who shared similar patterns of facial features. Results demonstrate that as a group, relatives of CP individuals show significantly different patterns of facial measurements compared to reference norms. Values significantly larger (p < 0.05) from parental data included: ANS-Me, PNS-ANS, S-N-Pg, Ar-Go-Me, MoL-MoR, NSR-NCR. Values significantly smaller (p < 0.05) from parents included: N-ANS, S-Ba, PNS-ANS / N-ANS, PNS-ANS/ N-Pg, N-S-Ba, ZyLZyR, GoL-GoR, GoNL-GoNR, CRO-CNS, CNS-SD, CNS-Me, ID-Me, MxR-ZyR, MeGoR. These findings were not entirely consistent with those few previously reported findings. Additional analysis of the present data demonstrated that such inconsistencies may be due in part to the presence of distinct phenotypic subgroupings within the parental sample. Cluster analysis identified two such subgroups. Significant findings (p < 0.05) that were smaller for Cluster 1 relative to Cluster 2 included: N-Me, ANS-Me, S-Go, PNS-ANS, Ar-Go, CNS-SD, MxR-ZyR. Significant variables that were larger for Cluster 1 included: S-N-Pg. In addition, gender was significantly different across clusters with Cluster 1 containing 75 percent female individuals and Cluster 2 containing 67 percent male individuals. These results extend those reported in other studies by demonstrating that unusual facial patterns, when present are not uniformly distributed in parents of sporadic cases of CP. Phenotypic assessment in conjunction with multivariate analysis may help to identify families in which there is a significant heritable component for CP.
Cephalometric similarity among parents of individuals with sporadic isolated cleft palate: is there evidence for an inherited predisposition?
(1999) Sammons, Edward M.; Ward, Richard E.; Avery, David R.; Hathaway, Ronald R.; Garetto, Lawrence P.; Hartsfield, James K., Jr.
Isolated cleft palate is one of the most frequent congenital conditions that affect the oral and facial structures, yet its etiology remains obscure. Previous studies of both cleft palate (CP) and cleft lip and/ or palate [CL(P)] have shown that there may be unusual facial characteristics among the parents of such sporadic cases. Such findings have been used to support the possibility that there are predisposing familial (genetic) factors for both conditions. However, previous studies have generally not controlled for the possibility of genetic heterogeneity or for different contributions from each of the parents. The objective of this study is to examine parents of individuals with CP in order to test the hypothesis that these "non cleft" individuals have abnormal facial structures. Lateral (LA) and Posterior-Anterior (PA) cephalograms were examined from thirty parents of fifteen individuals with sporadic CP. Seventeen LA and twenty-five PA variables were obtained on each subject and converted to standardized "z-scores" through comparison to published age and sex matched reference data. Multivariate cluster analysis was used to define groupings of individuals who shared similar patterns of facial features. Results demonstrate that as a group, relatives of CP individuals show significantly different patterns of facial measurements compared to reference norms. Values significantly larger (p < 0.05) fro1n parental data included: ANS-Me, PNS-ANS, S-N-Pg, Ar-Go-Me, MoL-MoR, NSR-NCR. Values significantly smaller (p < 0.05) from parents included: N-ANS, S-Ba, PNS-ANS/ N-ANS, PNS-ANS/ N-Pg, N-S-Ba, ZyL-ZyR, GoL-GoR, GoNL-GoNR, CRO-CNS, CNS-SD, CNS-Me, ID-Me, MxR-ZyR, Me-GoR. These findings were not entirely consistent with those few previously reported findings. Additional analysis of the present data demonstrated that such inconsistencies may be due in part to the presence of distinct phenotypic sub groupings within the parental sample. Cluster analysis identified two such subgroups. Significant findings (p < 0.05) that were smaller for Cluster 1 relative to Cluster 2 included: N-Me, ANS-Me, S-Go, PNS-ANS, Ar-Go, CNS-SD, MxR-ZyR. Significant variables that were larger for Cluster 1 included: S-N-Pg. In addition, gender was significantly different across clusters with Cluster 1 containing 75 percent female individuals and Cluster 2 containing 67 percent male individuals. These results extend those reported in other studies by demonstrating that unusual facial patterns, when present are not uniformly distributed in parents of sporadic cases of CP. Phenotypic assessment in conjunction with multivariate analysis may help to identify families in which there is a significant heritable component for CP.
Comparison of Tensile Bond Strengths of Glass Ionomer Cements Using Hydroxyapatite Coated and Uncoated Orthodontic Brackets
(1993) Ng, Richard I. Cheng Hin; Hohlt, William F.; Moore, B. Keith; Oshida, Yoshiki; Garetto, Lawrence P.; Roberts, W. Eugene; Shanks, James C.
The use of glass ionomer cements (GIC) in orthodontics as a bonding agent has been receiving considerable attention due to its favorable properties, ie., physico-chemical adhesion to enamel, fluoride leaching capabilities and less traumatic bonding procedure to tooth structure. GIC ability to bond to the hydroxyapatite (HA) in the tooth enamel was tested utilizing an HA coated bracket developed by American Orthodontics. This study compared in vitro tensile bond strengths of four dental adhesives: Ketac-cem™ (KC), Vitrebond™ (VB), Transbond™ (TB) or Unite™ (UN), when used to bond to HA coated brackets and non-HA coated brackets. Bovine incisors were divided into eight groups of 20 specimens each. Each group included either an HA coated or non-HA coated bracket and one of the four adhesives. The brackets are manufactured with a Tricalcium Phosphate (TPC) coating, which is converted to an HA coating by the addition of -OH during autoclaving. The coated and non-coated brackets were bonded to the bovine teeth, which were embedded in epoxy resin blocks to fabricate the testing specimen. All of the specimens were stored in distilled water at room temperature for two weeks. This was followed by thermocycling after which the specimens were returned to water storage for an additional two weeks. The specimens were tested in tension on an lnstron Testing Machine until bond failure occurred. Mode of bond failure was determined visually by light microscope. The mean tensile bond strengths for KC and VB were each significantly less (p< 0.05) than the other three materials, while UN and TB were not significantly different. KC was the weakest at 0.68± 0.31 MPa, while UN was the strongest, 4.38±0.84 MPa. When comparing the GIG alone, there was a significant difference (p<0.0001) between the VB and the KC. The resins were not significantly different from each other. Differences between coated and non-coated were significant at p<0.05 with the noncoated brackets having the higher strength. Adhesive failure at the bracket interface for the two bracket types showed no difference for KC. TB and UN showed this type of failure significantly more with the coated brackets (p<0.05), and VB showed the opposite and more failure with non-coated brackets (p<0.01). The tensile bond strength of GIG continues to be significantly less than those of existing resins. The bond failure also revealed a high degree of within group variability. Trends relating failure mode to tensile bond strength could not be established. Greater bond strengths with the coated brackets and the GIG were not shown; however in the case of VB, the tendency for the coated brackets to fail less frequently at the bracket adhesive interface shows some promise. Further studies of these coated brackets are still warranted.

Browsing by Author "Garetto, Lawrence P."

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