Luis Alberto Bravo

RAPID MAXILLARY EXPANSION. A STUDY OF THE LONG-TERM EFFECTS

A study was made to determine whether skeletal alterations usually produced by rapid maxillary expansion may be compensated for in time by growth and/or comprehensive orthodontic treatment. In 30 patients, orthodontic treatment was started with rapid maxillary expansion, followed by fixed appliances, not combined with any other form of orthopedic device. Mean treatment time was 3.1 years. Nine measurements from the Ricketts analysis were studied, based on lateral cephalometric radiographs. Records were taken before orthodontic treatment and after completion of active therapy. A statistical analysis was made of the nine variables used, reflecting the vertical and anteroposterior skeletal proportions of the face, contrasting the changes before and after treatment. Of all the variables studied, the four that change with age according to the Ricketts analysis (mandibular plane angle, maxillary height, facial depth and facial convexity), yielded statistically significant differences after treatment, indicative of normal growth. The five remaining variables that remain constant with age according to the Ricketts analysis (facial axis, lower facial height, total facial height, palatal plane inclination and maxillary depth) showed no significant changes after treatment, also indicative of normal growth.

A Comparison of the Shear Bond Strength of a Resin Cement and Two Orthodontic Resin Adhesive Systems

The object of this study was to compare the shear bond strength and the quantity of adhesive remaining on the tooth after the debonding of brackets bonded with two light-cured orthodontic resin adhesive systems (Transbond XT and Light-Bond) and a dual-cured resin cement (RelyX Unicem). Seventy-five premolars were divided into three groups. In each group, brackets were bonded with one of the adhesives according to the manufacturers instructions. Shear bond strength was measured using a universal test machine at a crosshead speed of one mm/min, and adhesive remnant was quantified using image analysis equipment. Our results showed that the resin cement produced significantly lower bond strength than the two orthodontic resin adhesive systems. It was also observed that the bond strength produced by Light-Bond was significantly greater than that of Transbond XT. RelyX left significantly less remnant adhesive than Transbond XT and Light-Bond. Between the two orthodontic systems, Light-Bond left significantly less adhesive on the tooth than Transbond XT.

Influence of a Nonrinse Conditioner on the Bond Strength of Brackets Bonded with a Resin Adhesive System

The objective of this study was to compare the effect of a nonrinse conditioner (NRC) and the conventional acid-etch technique on the shear bond strength and the adhesive remnant on the tooth after debonding brackets bonded with the resin orthodontic adhesive system Transbond XT. A total of 40 human premolars were divided into group I, phosphoric Acid/Transbond XT (n = 25) and group II, NRC/ Transbond XT (n = 15). Shear bond strength was measured with a universal test machine with a crosshead speed of 1 mm/min. The adhesive remnant was quantified using image analysis equipment. Scanning electron microscope (SEM) observations were also carried out to observe enamel surfaces treated with each product. No significant differences were observed in the bond strengths of the two groups evaluated. The amount of adhesive remnant on the tooth after debonding was significantly less when conditioning the enamel with NRC compared with phosphoric acid. SEM observations showed that the NRC produced a more conservative etch pattern than phosphoric acid.

Mandibular remodeling measured on cephalograms: 2.*

This study quantifies the differences in the perceived pattern of mandibular remodeling when two different methods are used to superimpose roentgenographic images of the mandible. Lateral cephalograms for a group of subjects with metallic implants of the Bjork type were superimposed twice; first on the metallic implants and then independently on mandibular anatomic structures according to a common “best fit” rule. In this article, we compare the between-superimposition differences in the perceived displacements of condyle, gonion, menton, pogonion, and Point B. Mean differences between the two superimpositional techniques were smaller than had been anticipated. For the 7-year time interval between 8.5 and 15.5 years, the largest mean differences between methods were 2.70 mm in the horizontal direction at condyle, 1.90 mm in the vertical direction at condyle, and 1.52 mm in the vertical direction at gonion. None of the other between-superimposition differences had a mean value in excess of 1 mm. The individual case variability between the two methods was, however, quite considerable, a finding that we believe has bearing on the confidence that can be placed in individual case analyses in clinical orthodontics. A preliminary attempt has been made to represent and discuss the magnitude of this problem.

The effects of two soft drinks on bond strength, bracket microleakage, and adhesive remnant on intact and sealed enamel

The purpose of this study was to evaluate the effects of Coca-Cola and Schweppes Limón on bond strength, adhesive remnant, and microleakage beneath brackets. One hundred and twenty upper central incisor brackets were bonded to bovine incisors and divided into three groups: (1) Control, (2) Coca-Cola, and (3) Schweppes Limón. The teeth were submerged in the drinks three times a day for 15 minutes over a 15 day period. Shear bond strength (SBS) was measured with a universal testing machine, and adhesive remnant evaluated using image analysis equipment. Microleakage at the enamel-adhesive and adhesive-bracket interfaces was determined using methylene blue. One hundred and eight teeth were used for scanning electron microscopy to determine the effect of the drinks on intact and sealed enamel. SBS and adhesive remnant data were analysed using the Kruskal-Wallis test (P < 0.05) and microleakage using the Kruskal-Wallis and Mann-Whitney tests applying Bonferroni correction (P < 0.017). No significant differences were found in SBS and adhesive remnant between the groups (P > 0.05). Microleakage at the enamel-adhesive interface for groups 2 and 3 was significantly greater than for group 1 (P < 0.017). At the adhesive-bracket interface, microleakage was significantly greater in group 2 than in group 1 (P < 0.017) while microleakage in group 3 did not differ significantly from either group 1 or 2 (P < 0.017). The drinks produced enamel erosion, loss of adhesive and microleakage. Coca-Cola and Schweppes Limón did not affect the SBS of brackets or the adhesive remnant.

Third Molar Agenesis and Craniofacial Morphology

OBJECTIVE To test the null hypothesis that agenesis of wisdom teeth is not related with any particular craniofacial morphology. MATERIALS AND METHODS Ninety-seven patients (aged 13-19 years) were selected and divided into three groups: (1) bilateral agenesis of maxillary third molars, (2) bilateral agenesis of mandibular third molars, and (3) control group without agenesis. Presence or absence of third molars was determined using ortopantomographs. Cephalometric analysis was carried out from lateral teleradiographs, which included linear, angular, and proportional measurements. When data obtained were distributed normally it was analyzed by means of single-factor variance analysis and the Scheffé test (P < .05). When data did not show normality, the Kruskal-Wallis test (P < .05) and the Mann-Whitney test were applied using Bonferroni correction (P < .017). Multivariance discrimination analysis was also carried out. RESULTS Values obtained for the mandibular plain of Groups 1 and 2 were significantly lower than those of the Control Group (P =.00 and P =.00, respectively). For Group 2 lower face height was significantly less than for the control group (P =.01), whilst the mandibular arch and the articular angle were significantly greater than in the Control Group (P =.000 and P = .02, respectively). Multivariance discrimination analysis obtained a correct classification in 58.8% of cases. CONCLUSION The hypothesis is rejected. Agenesis of the maxillary third molars was related to a reduced mandibular plane angle. Patients with agenesis of the mandibular third molars showed a diminished lower third and a mandibular morphology characteristic of the brachyfacial pattern.

Water and saliva contamination effect on shear bond strength of brackets bonded with a moisture-tolerant light cure system.

OBJECTIVE To evaluate the effects of water and saliva contamination on shear bond strength of brackets bonded with a moisture-tolerant light cure system. MATERIALS AND METHODS Brackets were bonded to 240 bovine lower incisors divided into 12 groups. Four bonding procedures were evaluated, including (1) TSEP/Transbond XT, (2) TMIP/ Transbond XT, (3) TSEP/Transbond PLUS, and (4) TMIP/Transbond PLUS, each under three different bonding conditions: without contamination, with water contamination, and with saliva contamination. Shear bond strength was measured with a universal testing machine. The adhesive remnant on the teeth was quantified with the use of image analyzing equipment. RESULTS Without contamination, bond strengths for the four procedures were similar (P > .05). TSEP/Tranbond PLUS and TMIP/Transbond PLUS left significantly less adhesive on the teeth after debonding than TSEP/Transbond XT and TMIP/Transbond XT (P < .008). Bond strength and adhesive remaining for TMIP/Transbond XT contaminated with water or saliva showed significantly worse performance than the other procedures evaluated (P < .008). Contamination (with water or saliva) did not affect either bond strength or adhesive remaining on the teeth for TSEP/ Transbond XT, TSEP/Transbond PLUS, or TMIP/Transbond PLUS (P > .017), although for TMIP/ Transbond XT, both variables showed significant reductions after contamination (P < .017). CONCLUSION TSEP/Transbond PLUS, TMIP/Transbond PLUS, and TSEP/Transbond XT showed greater tolerance to wet conditions than was shown by TMIP/Transbond XT.

Effect of Saliva Contamination on the Shear Bond Strength of Orthodontic Brackets Bonded with a Self- Etching Primer

This study evaluates the effect of saliva contamination at different stages of the bonding brackets procedure using the self-etching primer Adper Prompt L-Pop (3M ESPE, Minneapolis, Minn) and the resin orthodontic adhesive system Transbond XT (3M). A total of 70 brackets were bonded to human extracted premolars, which were divided into four groups: group 1, uncontaminated (control); group 2, saliva application before priming; group 3, saliva application after priming; and group 4, saliva application before and after priming. Shear bond strength was measured with a universal test machine. The adhesive remnant on the tooth after debonding was determined using image analysis equipment. Significant differences were only observed between group 1 (12.42 +/- 3.27) and groups 2 (9.93 +/- 4.50) and 4 (9.59 +/- 2.92) (P < .05). Concerning the adhesive remnant, no significant differences were found between the groups evaluated (P > .05).

Normal maxillary and mandibular growth and dentoalveolar development in Macaca mulatta A longitudinal cephalometric study from 2 to 5 years of age

Normal maxillary and mandibular growth and dentoalveolar development were examined in a longitudinal study of 10 male Macaca mulatta monkeys. Metallic implants were placed in the jaws of the monkeys as markers, and head films were taken semiannually from 2 to 5 years of age. The results showed that maxillary and mandibular growth is associated with rotational changes that are mostly in an anterior direction and are about twice as great in the mandible (9.4 degrees) as in the maxilla (4.2 degrees). These rotations are largely masked--about 75% in the maxilla and 90% in the mandible--by modeling within the jaws. Similarly, differential vertical dentoalveolar development almost completely masked the rotation of the occlusal plane that results from the rotation of the jaws, which created the impression that the occlusal plane is stable during growth. Peak growth velocity was reached on average at 3 years of age in the maxilla and mandible, with some individual variation. No major growth changes occurred after 3.5 to 4 years of age.

In vitro study of force decay of latex and non-latex orthodontic elastics.

The aim of this study was to evaluate the force decay of two brands of orthodontic elastics, both offering latex and non-latex products. Samples were subjected to continuous stretching, measuring force at 5 seconds, 8 hours, and 24 hours in both dry and wet conditions. Five hundred samples were used, GAC® and Lancer® 0.25 inch and 4 oz, divided into testing sample sizes of n = 25 per group. For the dry test, elastics were kept stretched to three times their internal diameter for 5 seconds (initial force), 8 hours, and 24 hours; for the wet test, they were stretched for 8 and 24 hours. Both brands showed initial forces significantly greater than those specified by the manufacturers (P < 0.05). Comparing wet/dry conditions, there was a greater force loss in the wet medium than the dry. As for elastic composition (latex or non-latex), the only significant difference found was between Lancer elastics with and without latex in dry conditions, force loss being greater for latex-free elastics. Comparing brands, there was greater force loss with GAC than with Lancer. Comparing elastic force at the eight-hour mark and the twenty-four hour mark to the initial force (only in wet conditions), GAC latex and non-latex and Lancer latex elastics showed significantly less force at eight and twenty four hours than initially. On the other hand, Lancer non-latex was the only type of elastics that did not show a significant decrease in its initial elastic characteristics at eight hours in wet conditions. Nevertheless, Lancer non-latex did show significantly less force in wet conditions at twenty four-hours than the forces observed initially and at eight-hours.