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Introduction The purpose of this study was to examine changes in registration accuracy after including occlusal surface and incisal edge areas in addition to the buccal surface when integrating laser-scanned and maxillofacial cone-beam computed tomography (CBCT) dental images. Methods CBCT scans and maxillary dental casts were obtained from 30 patients. Three methods were used to integrate the images: R1, only the buccal and labial surfaces were used; R2, the incisal edges of the anterior teeth and the buccal and distal marginal ridges of the second molars were used; and R3, labial surfaces, including incisal edges of anterior teeth, and buccal surfaces, including buccal and distal marginal ridges of the second molars, were used. Differences between the 2 images were evaluated by color-mapping methods and average surface distances by measuring the 3-dimensional Euclidean distances between the surface points on the 2 images. Results The R1 method showed more discrepancies between the laser-scanned and CBCT images than did the other methods. The R2 method did not show a significant difference in registration accuracy compared with the R3 method. Conclusions The results of this study indicate that accuracy when integrating laser-scanned dental images into maxillofacial CBCT images can be increased by including occlusal surface and incisal edge areas as registration areas.

The purpose of this study was to determine the effects of cola and other acidic drinks on etched tooth enamel in a simulated oral environment. The test beverages were cola, orange soda, lemon soda, and sparkling mineral water. Sixty extracted premolars were divided into an experimental group (n = 40) and a control group (n = 20). Half of the buccal surface of each tooth in the experimental group was coated with wax. The teeth were etched for 60 seconds with 37% phosphoric acid, and half of the teeth were also bonded. The experimental group was further divided into 4 subgroups of 5 teeth each, and each subgroup was exposed to 1 of the test beverages in a thermocycling apparatus. The apparatus was designed to keep the teeth in artificial saliva for 2 hours and in the soft drink at room temperature for 15 minutes. This procedure was performed 3 times a day for 5 days. The control group was also divided into 4 subgroups of 5 teeth each. Half of the buccal surface of each tooth in 2 subgroups was coated with wax, and the teeth in the other 2 were left uncoated. One waxed and 1 unwaxed subgroup were then etched, and the other waxed and unwaxed subgroups were etched and bonded. The waxed subgroups were stored in artificial saliva for 5 days, and the unwaxed subgroups were examined without further exposure to liquids. Surfaces exposed to acidic soft drinks were compared with control surfaces under a scanning electron microscope. Defect zone borders were observed between the exposed areas and the wax-coated areas of teeth in the experimental groups, especially the subgroups exposed to cola, orange soda, and lime soda. Fewer defect zones were observed on teeth exposed to sparkling mineral water. The results indicate that acidic soft drinks cause enamel demineralization on etched tooth surfaces.

The objective of this study was to compare 3 orthodontic adhesives in the areas of shear-peel bond strength, location of adhesive failure, and extent of enamel cracking before bonding and after debonding of orthodontic brackets. The adhesives included a composite resin control (Transbond XT; 3M/Unitek, St Paul, Minn), a resin-modified glass ionomer cement (Fuji Ortho LC; GC America Corp, Alsip, Ill), and a polyacid-modified composite resin under dry and saliva-contaminated conditions (Assure; Reliance Orthodontic Products Inc, Itasca, Ill). Metal brackets were bonded to the buccal surfaces of 160 (4 groups of 40) human premolars. The bonded teeth were stored in deionized water at 37 degrees C for 30 days and thermocycled for 24 hours before debonding with a Universal Instron (Instron Corp, Canton, Mass) testing machine. The extent of cracking in the buccal surfaces was evaluated under 16x magnification before bonding and after debonding. Although the bond strength of the composite resin control (20.19 MPa) was significantly greater (P

The purpose of this study was to compare the conventional acid-etch technique with an air abrasion surface preparation technique. Eighty freshly extracted noncarious human premolar teeth were randomly divided into the following 4 groups: (1) acid etched with 37% phosphoric acid for 15 seconds (Express Dental Products, Toronto, Canada), (2) sandblasted with 50 mu aluminum oxide by a microetcher (Danville Engineering Inc, Danville, Calif), (3) polished with pumice followed by acid etched with 37% phosphoric acid for 15 seconds, (4) sandblasted with 50 mu aluminum oxide by a microetcher followed by acid etched with 37% phosphoric acid for 15 seconds. All the groups had stainless steel brackets (Dentaurum, Standard Edgewise) bonded to the buccal surface of each tooth with no-mix adhesive (Express Dental Products, Toronto, Canada). A Lloyd testing machine (Lloyd Instrument LR 30K; Segensworth West, Foreham, UK) was used to determine tensile bond strengths at a crosshead speed of 0.5 mm/sec. The mean bond strength values of these are as follows: the only sandblasted group was 38.05 +/- 9.93 N; the only acid-etched group was 62.72 +/- 11.44 N; the group that was polished with pumice followed by acid etched was 69.78 +/- 14.87 N; and the group that was sandblasted followed by acid etched was 89.31 +/- 13. 34 N. The statistical analysis was done by an analysis of variance and Scheff¿e test. The sandblasting followed by acid etching group had significantly higher bond strength values when compared to the other 3 groups. This study showed that sandblasting should be followed by acid etching to produce enamel surfaces with comparable bond strength. The current findings indicate that enamel surface preparation using sandblasting with a microetcher alone results in a significantly lower bond strength and should not be advocated for clinical use as an enamel conditioner.

The clinical importance of the three-dimensional effects of the force systems supplied by appliance designs used for retraction has long been appreciated. However, quantification of these force systems is not as well known. In this work, a numerical method is used to provide quantitative insight into three-dimensional effects for typical appliance designs. One problem that occurs clinically is the axial rotation of a single rooted tooth as a result of the forces being applied by the retraction device on the tooth's buccal surface. An out-of-plane preactivated bend can be used to counteract this rotation. The proposed numerical method can accurately determine the force systems resulting from this out-of-plane preactivation as well as the in-plane force systems. It is shown that the out-of-plane effects are independent of the in-plane behaviour so that the usual forces and moment to force ratios are maintained. (Am J Orthod Dentofac Orthop 1997;112:378-92.)

This article describes a new nondestructive optical method for evaluation of lesion regression in vivo. White spot caries lesions were induced with orthodontic bands in two vital premolars of seven patients. The teeth were banded for 4 weeks with special orthodontic bands that allowed plaque accumulation on the buccal surface. The teeth were left in the dentition for 2 or 4 weeks after debanding. Regular oral hygiene with a nonfluoridated toothpaste was applied during the entire experimental period. The optical scattering coefficient of the banded area was measured before banding and in 1-week intervals thereafter. The scattering coefficient returned to the sound value in an exponential manner, the half-value-time for left teeth being 1.1 week, for right teeth 1.8 weeks, these values being significantly inequal (p = 0.035). At the start of the regression period, the scattering coefficient of left teeth lesions was 2.5 as high as of right teeth lesions, values being inequal with p = 0.09. It is concluded that regression of initial lesions in the presence of saliva is a relatively rapid process. The new optical method may be of clinical importance for quantitative evaluation of enamel lesion regression developed during fixed appliance therapy.

The purpose of this study was to investigate the cariostatic effect of two glass ionomer cements on in vivo demineralization of partly uncovered enamel beneath orthodontic bands. A 4-week clinical trial was conducted on a group of five patients with nine pairs of premolars to be extracted for orthodontic purposes. Specially designed orthodontic bands were cemented with either Ketac-Cem (K-C) or Aqua-Cem (A-C). A local cariogenic milieu was created between the buccal surface of the premolars and the inner surface of the bands to secure plaque accumulation. The mineral content of the teeth was quantified by microradiography. The data were compared with data from a previous study of patients in the same age group with bands that had been cemented with a non-F cement. After comparison with the non-F group, the lesion depth (ld) was reduced by 63% for K-C and by 55% for A-C. This reduction was statistically significant at the 2.5% level (t test). The total mineral loss in teeth cemented with glass ionomer cements (delta Z) was reduced, in comparison with the loss in teeth cemented with non-F cement, by 49% with K-C and by 27% with A-C. The differences were statistically significant only for the K-C group (t test, p less than 0.025). There were no significant differences between the two glass ionomer cements with respect to either lesion depth or total mineral loss values (paired t test; p greater than 0.05). This investigation shows that fluoride released from glass ionomer cements contributes substantially to demineralization "reduction." However, these cements do not provide complete caries protection in sites where access is difficult.

Introduction The aim of this clinical trial was to compare the effects of 2 protocols for single-phase comprehensive treatment of Class II Division 1 malocclusion (bonded Herbst followed by fixed appliances [BH + FA] vs headgear followed by fixed appliances and Class II elastics [HG + FA]) at the pubertal growth spurt. Methods Fifty-six Class II patients were enrolled in the trial and allocated by personal choice to 2 practices, where they underwent 1 of 2 treatment protocols (28 patients were treated consecutively with BH + FA, and 28 patients were treated consecutively with HG + FA). All patients started treatment at puberty (cervical stage [CS] 3 or CS 4) and completed treatment after puberty (CS 5 or CS 6). Lateral cephalograms were taken before therapy and 6 months after the end of comprehensive therapy, with an average interval of 28 months. Longitudinal observations of a matched group of 28 subjects with untreated Class II malocclusions were compared with the 2 treated groups. Analysis of variance (ANOVA) with post-hoc tests was used for statistical comparisons. Discriminant analysis was applied to identify preferential candidates for the BH + FA protocol on the basis of profile changes (advancement of soft tissues of the chin). Results The success rate (full occlusal correction of the malocclusion after treatment) was 92.8% in both treatment groups. The BH + FA group showed a significant increase in mandibular protrusion. The increase in effective mandibular length (Co-Gn) was significantly greater in both treatment groups when compared with natural growth changes in the Class II controls. Significantly greater improvement in sagittal maxillomandibular relationships was found in the BH + FA group. Retrusion of maxillary incisors and mesial movement of mandibular molars were significant in the HG + FA group. The BH + FA group showed significantly greater forward movement of soft-tissue B-point and pogonion compared with both the HG + FA and the control groups. Two pretreatment variables were significant (F = 4.48; P Conclusions Class II treatment with either protocol during the pubertal growth spurt induces significant favorable dentoskeletal and occlusal changes. Functional jaw orthopedics had a greater favorable impact on the advancement of the chin. The clinical indications for the preferential use of the Herbst appliance at puberty are a small mandibular angle and mandibular retrusion before treatment. When treated with the BH + FA protocol, these Class II patients have the greatest probability of achieving significant improvement in the profile by advancement of the soft tissues of the chin.

D e n t a l implants are increasingly used as a source of orthodontic anchorage. They may be placed solely for that purpose or used first for anchorage and then as prosthetic abutments. Several methods have been described for attaching orthodontic brackets to dental implants. Roberts 1 suggests forming a loop in the orthodontic wire and securing it to the implant with the cover screw of a transcutaneous post, and Higuchi and Slack 2 reported attaching the bracket to a composite crown. Shapiro and Kokich 3 embedded an orthodontic bracket in the buccal surface of a cast semiprecious crown, as did Stean. 4 We have found that soldering the orthodontic bracket directly to the second stage nonrotating gold