Hiroshi Maruo

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.

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.

Effect of etching and light-curing time on the shear bond strength of a resin-modified glass ionomer cement

The aim of this study was to assess the influence of etching and light-curing time on the shear bond strength (SBS) and adhesive remnant index (ARI) of a resin-modified glass ionomer cement (RMGIC) upon debonding of orthodontic brackets. Sixty-eight bovine permanent incisors were obtained and embedded in acrylic resin. Edgewise metallic brackets were bonded to the teeth with Fuji Ortho LC RMGIC. The specimens were randomly assigned to 4 groups, using the following etching and light-curing times: G1: 10% polyacrylic acid and 40 s (control); G2: 37% phosphoric acid and 40 s; G3: 10% polyacrylic acid and 50 s; and G4: 37% phosphoric acid and 50 s. Shear test was performed at 0.5 mm/min and the ARI was assessed. G2 (3.6 ± 0.98 MPa) presented significantly higher (p<0.05) SBS than G1 (2.76 ± 0.86 MPa) and G4 (2.86 ± 0.68 MPa), and there was no statistically significant difference (p>0.05) between G2 and G3 (2.94 ± 0.67 MPa). ARI presented prevalence of scores 2 and 3 in all groups. RMGIC SBS enhanced with 37% phosphoric acid etching and 40 s light-curing time, but this did not occur when the light-curing time was increased, regardless of the acid used. RMGIC presented prevalence of failures at the adhesive/bracket interface.

Influence of Natural Bovine Enamel Roughness on Bond Strength after Etching

OBJECTIVE To determine and compare the longitudinal and transverse roughness parameters of the enamel surface of bovine teeth and evaluate the influence of these parameters on bond strength. MATERIALS AND METHODS Ninety bovine incisors were used. The surface roughness of enamel was measured with a profilometer. For each tooth, five readings were taken in the longitudinal plane and five were taken in the transverse plane of the long axis of the tooth in an area equal to the size of the bracket base. The metal brackets were bonded with Transbond XT, and bond strength was evaluated in a universal test machine. RESULTS There was a statistical correlation (P < .01) between the longitudinal and transverse roughness measurements. There was no correlation between roughness measurements (longitudinal and transverse) and bond strength (P > .05), nor was there a correlation between total roughness (longitudinal Ra and transverse Ra) and bond strength. The Students t-test showed that there was a statistically significant difference (P < .05) between longitudinal and transverse roughness. CONCLUSION The transverse roughness is greater than the longitudinal roughness, there is a strong correlation between longitudinal and transverse roughness, and there is no correlation between enamel roughness and bond strength.

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.

Nicotine effect on bone remodeling during orthodontic tooth movement: Histological study in rats

Introduction Nicotine is harmful to angiogenesis, osteogenesis and synthesis of collagen. Objective The aim of this study was to investigate the effect of nicotine on bone remodeling during orthodontic movement in rats. Methods Eighty male Wistar rats were randomly divided into three groups: Group C (control), group CM (with orthodontic movement) and group NM (nicotine with orthodontic movement) groups. The animals comprising groups C and CM received 0.9% saline solution while group NM received nicotine solution (2 mg/kg). A nickel-titanium closed-coil spring was used to induce tooth movement. The animals were euthanized and tissue specimens were processed histologically. We quantified blood vessels, Howships lacunae and osteoclast-like cells present in the tension and compression areas of periodontal ligaments. The extent of bone formation was evaluated under polarized light to determine the percentage of immature/mature collagen. Results We observed lower blood vessel densities in the NM group in comparison to the CM group, three (p < 0.001) and seven (p < 0.05) days after force application. Osteoclast-like cells and Howships lacunae in the NM group presented lower levels of expression in comparison to the CM group, with significant differences on day 7 (p < 0.05 for both variables) and day 14 (p < 0.05 for osteoclast-like cells and p < 0.01 for Howships lacunae). The percentage of immature collagen increased in the NM group in comparison to the CM group with a statistically significant difference on day 3 (p < 0.05), day 7 (p < 0.001), day 14 (p < 0.001) and day 21 (p < 0.001). Conclusions Nicotine affects bone remodeling during orthodontic movement, reducing angiogenesis, osteoclast-like cells and Howships lacunae, thereby delaying the collagen maturation process in developed bone matrix.

Treatment of an adult with several missing teeth and atrophic old mandibular first molar extraction sites

This report describes the orthodontic treatment of a woman, aged 34 years 2 months, with several missing teeth and atrophic mandibular first molar extraction sites. We had planned to close the spaces from the missing maxillary canines with mesial movement of the premolars and molars. In the mandibular arch, protraction of the second molars into first molar extraction sites and reduction of the mandibular incisor protrusion were performed. No miniscrews or bone plates were used. A modified helical loop was used, and it can be considered a simple and an efficient orthodontic method of closing the spaces without mesial or lingual tipping and rotation. Pleasing esthetic and functional results were achieved.

Orthodontic-prosthetic treatment of an adult with a severe Class III malocclusion.

This case report describes the treatment of a 37-year-old woman with multiple restored and missing teeth, a Class III subdivision malocclusion, and complete dental crossbite. Treatment options included orthognathic surgery and an orthodontic-prosthetic approach. The patient opted for nonsurgical treatment with space opening for prosthetic replacement of the first maxillary molars.

Orthodontic intrusion of maxillary incisors: a 3D finite element method study

Objective: In orthodontic treatment, intrusion movement of maxillary incisors is often necessary. Therefore, the objective of this investigation is to evaluate the initial distribution patterns and magnitude of compressive stress in the periodontal ligament (PDL) in a simulation of orthodontic intrusion of maxillary incisors, considering the points of force application. Methods: Anatomic 3D models reconstructed from cone-beam computed tomography scans were used to simulate maxillary incisors intrusion loading. The points of force application selected were: centered between central incisors brackets (LOAD 1); bilaterally between the brackets of central and lateral incisors (LOAD 2); bilaterally distal to the brackets of lateral incisors (LOAD 3); bilaterally 7 mm distal to the center of brackets of lateral incisors (LOAD 4). Results and Conclusions: Stress concentrated at the PDL apex region, irrespective of the point of orthodontic force application. The four load models showed distinct contour plots and compressive stress values over the midsagittal reference line. The contour plots of central and lateral incisors were not similar in the same load model. LOAD 3 resulted in more balanced compressive stress distribution.