Patterns of vertical facial growth in Korean adolescents analyzed with mixed-effects regression analysis.

INTRODUCTION: To understand the growth patterns of skeletal open bite and deepbite, we present observations from 9 years of pure longitudinal data based on lateral cephalometric radiographs using mixed-effects regression model analysis. METHODS: In total, 51 children (14 years old) with extreme values for the ratio of lower anterior facial height to total anterior facial height were assigned to 1 of 2 groups: a skeletal open-bite group (11 boys, 14 girls) or a skeletal deepbite group (14 boys, 12 girls). Measurements of total anterior facial height, upper anterior facial height, lower anterior facial height, total posterior facial height, ramus height, and ratio of lower anterior facial height to total anterior facial height were obtained for all subjects. All data were analyzed and interpreted using a mixed-effects regression model analysis with random effects. RESULTS: From these 4 groups at 14 years old, statistically significant differences were observed between the groups when subjects of the same sex were compared; however, statistical significance was not reached between subjects of opposite sexes in each group. Morphologic differences were clearly evident from the start and became more pronounced with age. There were statistical significances in the initial values and increases with age in all 6 variables except for increases with age in the ratio of lower anterior facial height to total anterior facial height. Statistical significance was also reached for morphologic differences between the annual increases in the ratio of lower anterior facial height to total anterior facial height and lower anterior facial height. In general, individual random variability was high in all variables when compared with the annual changes over time. CONCLUSIONS: Divergent patterns were established early and became more pronounced with age, with anterior facial height dimensions primarily contributing to these differences. Individual variations were so pronounced that caution is recommended for all clinical decisions.

Evaluation of early bone response to fluoride-modified and anodically oxidized titanium implants through continuous removal torque analysis.

PURPOSE: To compare between a bioactive and a bioinert implant with different geometries by continuous measurement of the removal torque and calculation of the angular momentum of each surfaced implant. MATERIALS AND METHODS: Six New Zealand white rabbits were used in the study. Each rabbit received 2 implants. A bioactive fluoride-modified implant with a conical connection and microthread design was inserted into one tibia, and a bioinert anodically oxidized implant with an external connection design was inserted into the other. After 2 weeks of implant insertion, the removal torque values were continuously measured according to time. Using the time-torque curve resulting from the measurements, the maximum values were determined, and the angular momenta were calculated. RESULTS: The anodically oxidized implant had significantly higher peak removal torque and angular momentum values than the fluoride-modified implant (P < 0.05). CONCLUSIONS: The impact of the fluoride-modified bioactive implant on early bone response remains unclear. Considering the angular momentum of dental implants may assist in the elucidation of the effect of implant geometry on bone response.

First-Order Mathematical Correlation Between Damping and Resonance Frequency Evaluating the Bone-Implant Interface.

PURPOSE: Various advanced technologies have been designed to estimate dental implant stability, including insertion torque, implant damping using the Periotest, and resonance frequency analysis expressed in implant stability quotient units. This study aimed to establish the relationship between the estimates for these three techniques. MATERIALS AND METHODS: Bovine cortical bone blocks were trimmed to square shapes of precisely controlled thickness and density. Thereafter, 4-mm-diameter × 10-mm-long implants were placed in the bone blocks using 30-, 45-, and 60-Ncm insertion torques. Implant damping and resonance frequency analysis were conducted at four angles for each implant. Spearman correlation coefficients were calculated to examine the relationship between insertion torque, resonance frequency analysis, and implant damping measured values. RESULTS: Resonance frequency analysis and implant damping estimates exhibited a strong inverse correlation (r = -0.98, P < .001). A linear equation was formulated: Periotest value = 15.54 + (-0.26 × implant stability quotient). Implant damping and resonance frequency estimates revealed a weak correlation with insertion torque (P < .05). CONCLUSION: This study mathematically defined a linear correlation between implant damping and resonance frequency estimates, thereby providing a guide for clinicians when deciding the loading time for dental implants using the implant damping or resonance frequency estimates.

Effects of Computer-Aided Manufacturing Technology on Precision of Clinical Metal-Free Restorations.

PURPOSE: The purpose of this study was to investigate the marginal fit of metal-free crowns made by three different computer-aided design/computer-aided manufacturing (CAD/CAM) systems. MATERIALS AND METHODS: The maxillary left first premolar of a dentiform was prepared for all-ceramic crown restoration. Thirty all-ceramic premolar crowns were made, ten each manufactured by the Lava system, Cercon, and Cerec. Ten metal ceramic gold (MCG) crowns served as control. The marginal gap of each sample was measured under a stereoscopic microscope at 75x magnification after cementation. One-way ANOVA and the Duncan's post hoc test were used for data analysis at the significance level of 0.05. RESULTS: The mean (standard deviation) marginal gaps were 70.5 (34.4) µm for the MCG crowns, 87.2 (22.8) µm for Lava, 58.5 (17.6) µm for Cercon, and 72.3 (30.8) µm for Cerec. There were no significant differences in the marginal fit among the groups except that the Cercon crowns had significantly smaller marginal gaps than the Lava crowns (P < 0.001). CONCLUSIONS: Within the limitation of this study, all the metal-free restorations made by the digital CAD/CAM systems had clinically acceptable marginal accuracy.

The reliability of an easy measuring method for abutment convergence angle with a computer-aided design (CAD) system.

PURPOSE: The purpose of this study was to evaluate the intra-rater reliability and inter-rater reliability of three different methods using a drawing protractor, a digital protractor after tracing, and a CAD system. MATERIALS AND METHODS: Twenty-four artificial abutments that had been prepared by dental students were used in this study. Three dental students measured the convergence angles by each method three times. Bland-Altman plots were applied to examine the overall reliability by comparing the traditional tracing method with a new method using the CAD system. Intraclass Correlation Coefficients (ICC) evaluated intra-rater reliability and inter-rater reliability. RESULTS: All three methods exhibited high intra-rater and inter-rater reliability (ICC>0.80, P<.05). Measurements with the CAD system showed the highest intra-rater reliability. In addition, it showed improved inter-rater reliability compared with the traditional tracing methods. CONCLUSION: Based on the results of this study, the CAD system may be an easy and reliable tool for measuring the abutment convergence angle.

Digital veneering system enhances microtensile bond strength at zirconia core-veneer interface.

This study investigated the effect of digital veneering system (DVS) on strengthening the bond between a zirconia core and ceramic veneer. Specimens for Groups 1 (negative control), 2 (positive control), 3, and 4 used conventional porcelain veneering technique on untreated, sandblasted, coloring agent-treated, and modifier-treated zirconia cores respectively. Group 5 used DVS, where glass ceramic veneers­produced by computer-aided milling­were fused to zirconia cores. Microtensile bond strengths (MTBS) at the interface were measured. MTBS results of Groups 1 to 5, expressed in mean (standard deviation), were 28.1 (7.3), 27.8 (6.3), 30.0 (10.2), 32.9 (8.1), and 37.8 (8.1) MPa. The DVS group had significantly higher MTBS than the negative and positive controls (p<0.05). Results showed that DVS enhanced the bond strength between zirconia core and ceramic veneer, indicating that this system could reduce adhesive failure-related complications that frequently occur at the zirconia core-veneer interface.

Comparative fracture strength analysis of Lava and Digident CAD/CAM zirconia ceramic crowns.

PURPOSE: All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident. MATERIALS AND METHODS: Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns. RESULTS: THE MEAN FRACTURE STRENGTHS WERE AS FOLLOWS: 54.9 ± 15.6 N for the Lava CAD/CAM zirconia crowns and 87.0 ± 16.0 N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (P<.001). Lava CAD/CAM zirconia crowns showed a complete fracture of both the veneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain. CONCLUSION: The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain.

Marginal fit of anterior 3-unit fixed partial zirconia restorations using different CAD/CAM systems.

PURPOSE: Few studies have investigated the marginal accuracy of 3-unit zirconia fixed partial dentures (FPDs) fabricated by computer-aided design/computer-aided manufacturing (CAD/CAM) system. The purpose of this study was to compare the marginal fit of zirconia FPDs made using two CAD/CAM systems with that of metal-ceramic FPDs. MATERIALS AND METHODS: Artificial resin maxillary central and lateral incisors were prepared for 3-unit FPDs and fixed in yellow stone. This model was duplicated to epoxy resin die. On the resin die, 15 three-unit FPDs were fabricated per group (45 in total): Group A, zirconia 3-unit FPDs made with the Everest system; Group B, zirconia 3-unit FPDs made with the Lava system; and Group C, metal-ceramic 3-unit FPDs. They were cemented to resin dies with resin cement. After removal of pontic, each retainer was separated and observed under a microscope (Presize 440C). Marginal gaps of experimental groups were analyzed using one-way ANOVA and Duncan test. RESULTS: Mean marginal gaps of 3-unit FPDs were 60.46 µm for the Everest group, 78.71 µm for the Lava group, and 81.32 µm for the metal-ceramic group. The Everest group demonstrated significantly smaller marginal gap than the Lava and the metal-ceramic groups (P<.05). The marginal gap did not significantly differ between the Lava and the metal-ceramic groups (P>.05). CONCLUSION: The marginal gaps of anterior 3-unit zirconia FPD differed according to CAD/CAM systems, but still fell within clinically acceptable ranges compared with conventional metal-ceramic restoration.

The effect of the DLTIDDSYWYRI motif of the human laminin α2 chain on implant osseointegration.

Considerable effort has been directed towards replacing lost teeth using tissue-engineering methods such as titanium implants. A number of studies have tried to modify bioinert titanium surfaces by coating them with functionally bioactive molecules for faster and stronger osseointegration than pure titanium surfaces. Recently, peptides have been recognized as valuable scientific tools in the field of tissue-engineering. The DLTIDDSYWYRI motif of the human laminin-2 α2 chain has been previously reported to promote the attachment of various cell types; however, the in vivo effects of the DLTIDDSYWYRI motif on new bone formation have not yet been studied. To examine whether a laminin-2-derived peptide can promote osseointegration by accelerating new bone formation in vivo, we applied titanium implants coated with the DLTIDDSYWYRI motif in a rabbit tibia model. The application of the DLTIDDSYWYRI motif-treated implant to tibia wounds enhanced collagen deposition and alkaline phosphatase expression. It significantly promoted implant osseointegration compared with treatment with scrambled peptide-treated implants by increasing the bone-to-implant contact ratio and bone area. These findings support the hypothesis that the DLTIDDSYWYRI motif acts as an effective osseointegration accelerator by enhancing new bone formation.