Odilon Guariza-Filho

Insertional torque and axial pull-out strength of mini-implants in mandibles of dogs.

INTRODUCTION The objectives of this study were to evaluate insertional torque of mini-implants (MI) for orthodontic anchorage, to compare their axial pull-out strength at 0 (T0), 15 (T15), and 60 (T60) days after placement, to determine initial and peri-implant cortical bone thickness, and to analyze the correlations among these variables. METHODS Sixty MI were placed in the mandibles of 10 dogs. Peak insertional torque values were recorded, and, after the animals were killed, specimens were prepared. The MI were aligned with a testing machine to register axial pull-out strength. Cortical bone thickness was measured after removal of the MI. Statistical analyses were conducted with ANOVA and Tukey HSD tests. RESULTS Pull-out strength and peri-implant cortical bone thickness had differences (P <0.01) at the various times. The T0 value showed the highest pull-out strength, and the smallest peri-implant cortical bone thickness was at T60. There was a regular correlation between pull-out strength and peri-implant cortical bone thickness at T0 (r = 0.44, P = 0.05). There was no correlation between insertional torque and pull-out strength, and insertional torque and initial cortical bone thickness. CONCLUSIONS Pull-out strength is greater immediately after placement of MI, cortical bone thickness decreases because of bone resorption, and insertional torque is not an efficient method for predicting the retention of MI.

Sliding resistance with esthetic ligatures: an in-vitro study.

INTRODUCTION This study was developed to evaluate in vitro the properties related to sliding resistance of esthetic ligatures. METHODS Frictional force of 6 ligatures--2 conventional, 2 specially coated elastomeric, Teflon-coated (Dupont, Wilmington, Del) stainless steel, and stainless steel (control) ligatures--were studied by sliding 0.019 x 0.025-in stainless steel wire through the 0.22-in slot of stainless steel bracket. Elastomeric ligatures were tested for frictional and tensile forces under 3 experimental conditions: recent stretching, after 21 days of simulated stretching in artificial saliva, and a demineralizing/remineralizing regimen. Statistical analysis was conducted with ANOVA and Games-Howell tests. RESULTS There was high correlation between frictional and tensile forces of elastomeric ligatures, with reduction of both after 21 days. The demineralizing/remineralizing regimen reduced the frictional forces of ligatures to the same level as the ligatures in artificial saliva. Teflon-coated and stainless steel ligatures showed the lowest initial frictional forces, but there was no difference in friction of stainless steel and post-stretched elastomeric ligatures. CONCLUSIONS Frictional forces generated by esthetic elastomeric ligatures under simulated oral environments are not stable and are more related to tensile force than to surface characteristics of the ligatures.

Multiloop edgewise archwire in the treatment of a patient with an anterior open bite and a long face.

An adolescent girl with an Angle Class III malocclusion, excessive lower facial height, and anterior open bite sought nonsurgical treatment. She was treated with a multiloop edgewise archwire (MEAW). In association with a chincup, MEAW mechanics allowed the successful correction of the anterior open bite and the molar relationship, without major alterations of the patients profile. Combined orthodontic and surgical treatment should be considered for patients with skeletal anterior open-bite malocclusion. For patients who do not want surgery, however, MEAW treatment is an alternative that can have excellent results.

Metal and ceramic bracket effects on human buccal mucosa epithelial cells.

OBJECTIVE To test the null hypothesis that metal and ceramic brackets have no effect on the epithelial cells of the buccal mucosa. MATERIALS AND METHODS Two metal and two ceramic brackets were bonded in 21 individuals of both sexes. With the use of liquid-based exfoliative cytology, morphometric and morphologic changes in buccal mucosa cells adjacent to these brackets were determined and were compared at three time points: baseline (T0), 60 days after placement (T1), and 30 days after removal of the brackets (T2). RESULTS A decrease in nuclear area and an increase in cytoplasmic area occurred in the buccal mucosa cells adjacent to the brackets at T1 (P < .01). At T2, this altered morphometry persisted only in cells adjacent to the metal brackets, although to a lesser degree than at T1 (P < .01). A greater decrease in nuclear area was noted in cells adjacent to the metal brackets than in those next to the ceramic brackets (P < .01). At T0, the proportions of surface and subsurface cells were similar, but at T1, a predominance of surface cells was observed (P < .05). At all time points, smears of cells appeared normal or normal with some inflammatory changes. CONCLUSION The hypothesis is rejected. Placement of metal and ceramic brackets in the buccal cavity induces cellular alterations. These alterations do not suggest malignancy.

Dental enamel roughness with different acid etching times: Atomic force microscopy study

Objective: An important characteristic of human dental enamel not yet studied in detail is its surface roughness in mesoscopic scale. This study evaluated quantitatively and qualitatively the surface topography of acid etched enamel with different etching times. Materials and Methods: Ninety-six human maxillary bicuspids were randomly distributed into three groups ( n =32): T0 (control), pumiced; T15, 35% phosphoric acid etched enamel for 15 s; T30, 35% phosphoric acid etched enamel for 30 s. Roughness measurements Ra, Rz and root mean square (RMS) and 3D images of enamels topography were obtained with atomic force microscopy (AFM), which is a powerful technique to obtain direct measurements on microscale features. Results and Conclusions: Roughness variables Ra, Rz and RMS presented statistically significant differences to all groups ( P <0.000), with values increasing with etching time. This increase was greater from T0 to T15 than from T15 to T30. Enamel surface alterations T15 to T30 occur mainly due to increase in height and deepening of prisms central region.

Insertion torque, pull-out strength and cortical bone thickness in contact with orthodontic mini-implants at different insertion angles.

This study aimed to evaluate biomechanical behaviour of inclined orthodontic mini-implants by analyzing its insertion torque (IT), axial pull-out strength (APS), and cortical bone thickness in contact with mini-implant (CBTC). A total of 102 mini-implants were inserted at 90 degree, 60 degree, and 45 degree to the surface of synthetic bone. Peak IT was measured, and the mini-implants were aligned with the mechanical testing machine to record the APS. The cortical bone thickness in contact with each mini-implant was measured after the pull-out test and the data were subjected to statistical analyses. The 45 degree group had a significantly higher IT compared with the 90 degree group (P < 0.05). There was a statistically significant increase in the average of cortical bone thickness in CBTC across the three groups (P < 0.05). A negative correlation between the angulation and the CBTC (r = -0.95, P < 0.05) and a positive correlation between the APS and the CBTC were observed (r = 0.34, P < 0.05). Mini-implants that are inserted more inclined to the surface of the bone provide greater IT and an increased contact with the cortical bone. The greater the CBTC, the greater is the APS.

Root formation of an autotransplanted tooth

Traumatic injuries with loss of anterior teeth occur more frequently in children. Treatment of the dental trauma is complex and requires a comprehensive and accurate diagnostic and treatment plan. It is also important to consider the biological, functional, esthetic, and economic aspects. The purpose of this article is to show a case report with a successful root formation and periodontal healing after autotransplantation of maxillary second right premolar in place of maxillary right central incisor site. Tooth autotransplantation may be considered as a viable treatment option instead of a conventional prosthetic and implant rehabilitation.

Bone stress and strain after use of a miniplate for molar protraction and uprighting: a 3-dimensional finite element analysis.

INTRODUCTION The aim of this study was to use the finite element method to evaluate the distribution of stresses and strains on the local bone tissue adjacent to the miniplate used for anchorage of orthodontic forces. METHODS A 3-dimensional model composed of a hemimandible and teeth was constructed using dental computed tomographic images, in which we assembled a miniplate with fixation screws. The uprighting and mesial movements of the mandibular second molar that was anchored with the miniplate were simulated. The miniplate was loaded with horizontal forces of 2, 5, and 15 N. A moment of 11.77 N·mm was also applied. The stress and strain distributions were analyzed, and their correlations with the bone remodeling criteria and miniplate stability were assessed. RESULTS When orthodontic loads were applied, peak bone strain remained within the range of bone homeostasis (100-1500 μ strain) with a balance between bone formation and resorption. The maximum deformation was found to be 1035 μ strain with a force of 5 N. At a force of 15 N, bone resorption was observed in the region of the screws. CONCLUSIONS We observed more stress concentration around the screws than in the cancellous bone. The levels of stress and strain increased when the force was increased but remained within physiologic levels. The anchorage system of miniplate and screws could withstand the orthodontic forces, which did not affect the stability of the miniplate.

Tissue responses resulting from tooth movement surgically assisted by corticotomy and corticision in rats

OBJECTIVE To compare the histological responses in corticotomy- and corticision-assisted tooth movement. MATERIALS AND METHODS Ninety Wistar rats were divided into three groups: C (control-tooth movement only), CT (tooth movement + corticotomy), and CI (tooth movement + corticision). Surgeries were performed on the vestibular and lingual cortical bone of the maxillary first molar. Tooth movement was carried out with nickel-titanium closed coil springs having a force of 30 g. The rats were sacrificed at 3, 14, and 28 days. To evaluate the number of osteoclasts and amount of root resorption, a tartrate-resistant acid phosphatase stain was used. Hematoxylin and eosin staining was performed for areas of hyalinization, and the organic bone matrix was stained with picrosirius. RESULTS The CT group showed a greater number of osteoclasts than did the C group on day 3 (P < .05). At the same time point, the CT and CI groups showed a delayed onset of organic bone matrix remodeling and a lower incidence of root resorption than did the C group (P < .05). There were also fewer hyalinization areas in the CI group than in the C group on day 3 (P < .05). CONCLUSIONS Corticotomy effectively increased bone resorption during the early stages of tooth movement, but this increase was not observed for corticision. The surgical procedures did not accelerate organic bone matrix remodeling. Corticotomies and corticisions decreased the risk of root resorption only during the early stages of movement. Corticision reduced the level of hyalinization, while corticotomy did not.

Influence of different beverages on the force degradation of intermaxillary elastics: an in vitro study

Objective: The aim of this study was to evaluate in vitro the effects of frequently ingested beverages on force degradation of intermaxillary elastics. Material and Methods: One hundred and eighty 1/4-inch intermaxillary elastics (TP Orthodontics) were immersed into six different beverages: (1) Coca-Cola®; (2) Beer; (3) Orange juice; (4) Red wine; (5) Coffee and (6) artificial saliva (control). The period of immersion was 15 min for the first and second cycles and 30 min for the third to fifth cycles. Tensile forces were read in a tensile testing machine before and after the five immersion cycles. One-way repeated measures ANOVA was used to identify significant differences. Results: Force degradation was seen in all evaluated groups and at all observation periods (p<0.05). A greater degree of degradation was present at the initial periods, decreasing gradually over time. However, no statistically significant differences were seen among groups at the same periods, showing that different groups behaved similarly. Conclusion: The chemical nature of the evaluated beverages was not able to influence the degree of force degradation at all observation periods.