The reliability and reproducibility of cephalometric measurements: a comparison of conventional and digital methods.

OBJECTIVE: The aim of this study was to assess the reliability and reproducibility of angular and linear measurements of conventional and digital cephalometric methods. METHODS: A total of 13 landmarks and 16 skeletal and dental parameters were defined and measured on pre-treatment cephalometric radiographs of 30 patients. The conventional and digital tracings and measurements were performed twice by the same examiner with a 6 week interval between measurements. The reliability within the method was determined using Pearson's correlation coefficient (r²). The reproducibility between methods was calculated by paired t-test. The level of statistical significance was set at p < 0.05. RESULTS: All measurements for each method were above 0.90 r² (strong correlation) except maxillary length, which had a correlation of 0.82 for conventional tracing. Significant differences between the two methods were observed in most angular and linear measurements except for ANB angle (p = 0.5), angle of convexity (p = 0.09), anterior cranial base (p = 0.3) and the lower anterior facial height (p = 0.6). CONCLUSION: In general, both methods of conventional and digital cephalometric analysis are highly reliable. Although the reproducibility of the two methods showed some statistically significant differences, most differences were not clinically significant.

Shear-peel bond strength of orthodontic primers in wet conditions.

OBJECTIVE: The purpose of this in vitro study was to determine whether a hydrophilic primer (Transbond MIP, [MIP]) produces a significant difference in shear/peel bond strength compared with a traditional hydrophobic primer (Transbond XT, [XT]) in wet (W) or dry (D) conditions and if there is a difference in the site of bond failure. DESIGN: A randomized blinded in vitro design. SETTING AND SAMPLE POPULATION: The University of Missouri-Kansas City School of Dentistry. Forty extracted human premolars were divided into four test groups (n = 10 each): MIP-dry conditions (MIPD), MIP-wet conditions (MIPW), XT-dry (XTD) and XT-wet (XTW). EXPERIMENTAL VARIABLE: Orthodontic brackets were bonded to the teeth according to the manufacturer's directions except XTW and MIPW were exposed to moisture. OUTCOME MEASURE: Shear/peel test 24 h after bonding using an Instron at a crosshead speed of 0.5 mm/min and the adhesive remnant index to determine the site of bond failure. RESULTS: The bond strengths (X +/- SD) in MPa were XTD = 8.3 +/- 2.3; XTW = 0.8 +/- 0.7; MIPD = 7.5 +/- 1.8 and MIPW = 7.9 +/- 1.7. The shear/peel bond strengths were significantly different: XTD = MIPD = MIPW > XTW (p < or = 0.01; two-way ANOVA; Tukey HSD). The ARI scores were also significantly different: XTD = MIPD = MIPW > XTW (p < or = 0.01; Chi-square). CONCLUSIONS: Orthodontists who suspect moisture contamination should use a hydrophilic primer during bonding procedures to maintain shear/peel bond strength.

Efficiency of multi-strand steel, superelastic Ni-Ti and ion-implanted Ni-Ti archwires for initial alignment.

In a clinical trial involving 155 dental arches with irregularity > 5 mm, the rate of alignment was used to compare the alignment efficiency of 16 mil superelastic Ni-Ti versus 17.5 mil triple-stranded steel archwires, and to determine whether ion implantation of the Ni-Ti wire improved its performance. Subjects were randomly assigned to archwire types; both 18 and 22 slot edgewise appliances were employed. Pre-treatment equivalence of the experimental groups was verified. Anterior irregularity was determined monthly (using Little's irregularity index) until it decreased below 2 mm, and the elastomeric ligatures were replaced at each appointment. Effective tooth movement occurred with each of the archwire types. There were no significant differences among wires, but the rate of alignment was significantly faster in the lower arch for subjects with the 22 slot appliance.

Microbiological and microhardness evaluation of artificial enamel fissures worn intraorally by humans.

Devices simulating occlusal fissures were constructed from dental enamel and bonded to human maxillary molar teeth for 3 weeks. Facilitation of in vivo caries research in humans is the long-range goal for this model system. In the present investigation, microbial compositions of plaque in the fissural space of the model and natural fissural plaque from teeth bearing the devices were compared. Plaque from models constructed from either bovine or human enamel was also compared. In addition, microhardness of the enamel surfaces was examined before and after oral exposure. Plaque in both bovine and human enamel models differed significantly from natural fissural plaque in several microbial categories. Differences appeared to be related to the increased accessibility of the deep fissural contents of the models. For example, levels of the aciduric Streptococcus mutans and Veillonella species were higher in the models, although levels of a salivary inhabitant, Streptococcus salivarius, were lower. Plaque in bovine and human enamel models was similar, and both models showed significant decreases in enamel microhardness after oral exposure for 3 weeks. The model system should be useful in caries research in that carieslike activity was simulated within a relatively short period of time, and the fissural space became colonized by high levels of cariogenic bacteria.

Microbiological assessment of dental plaque on bovine enamel implants worn intra-orally in children.

Nine caries-active children, each from six to nine years old, wore small removable enamel implants intra-orally for four weeks as part of an effort to develop removable model systems for studying dental plaque in fissures. The implants, consisting of two enamel cubes arranged to simulate a fissural space, were cemented in box preparations in stainless steel crowns on pulpotomized primary molars. Upon removal, the fissural spaces were opened to facilitate plaque harvesting. The plaque samples were cultured, and enamel decalcification of the plaque-exposed surfaces was measured. Quantitative microbial values were compared with those of natural fissure plaque samples from both caries-active (CA) and caries-and restoration-free (CF) children, also from six to nine years old. Streptococcus mutans and S. sanguis levels of fissural insert plaque (FI) and natural fissural plaque from (CA) were similar. Both contained higher S. mutans levels than did plaque from (CF). FI harbored higher concentrations of Lactobacillus and Actinomyces species and lower concentrations of Neisseria species. Otherwise, FI plaque resembled natural fissure plaque. Microhardness of FI plaque-exposed enamel decreased significantly compared with pre-experimental values and showed a significant negative correlation with values for total lactobacilli on selective media, and for S. mutans on non-selective media.