Load distribution in fixed space maintainers: a strain-gauge analysis.

PURPOSE: The purpose of this study was to compare the biomechanics of space maintainers supported by primary and permanent teeth. METHODS: Photoelastic models of permanent and primary teeth with a single missing tooth space were cast, and band-and-loop, direct-bonded, and fiber-reinforced space maintainers were fabricated. Linear strain-gauges were bonded next to the teeth and in the middle of the missing tooth space. Strain gauge signals were quantified during 50 N and 100 N static axial load applications on the molar, maintainer, and anterior support at 10 KHz using a data acquisition device and associated computer software. RESULTS: Regardless of the tooth being restored, strains around the molar teeth and the maintainer region were comparable between the groups under molar and maintainer loading (P>.05). Under 100 N loading on the anterior support, the highest strains were observed in the direct-bonded group (P<.01). Direct-bonded design led to higher strains than the band-and-loop design under 100 N maintainer loading, whereas the strain output of other designs were comparable. CONCLUSION: Load distribution of band-and-loop, direct-bonded, and fiber-reinforced space maintainers seem comparable, although direct-bonded maintainers could lead to higher strain concentrations in the buccal side due to bending moments.

Cortical bone strains around straight and angulated immediate orthodontic microimplants: a pilot study.

PURPOSE: To measure strains around orthodontic implants upon torque tightening and loading and to assess correlations between factors influencing primary stability. MATERIALS AND METHODS: Self-drilling implants were placed into bovine iliac crest blocks after CT assessments. Upon bonding of strain gauges on bone adjacent to the implants, strain measurements were performed using a data acquisition system during torque tightening and 250 g orthodontic force application by elastic chains. RESULTS: The torque required to place straight implants (12.16 N.cm) was higher than 30- to 40-degree angulated implants (9.31 N.cm) (P < 0.05). Cortical bone strain amplitudes of both implant placements were comparable (P > 0.05). Strains during torque tightening of straight (196 µÎµ) and tilted (114 µÎµ) implants were higher than those obtained during orthodontic loading (20-30 µÎµ). Despite the positive and direct relationship found between torque and torque strain output, strong correlations between other parameters could not be detected. CONCLUSION: Vertically aligned and 30- to 40-degree angulated immediate orthodontic microimplants are associated with low amplitude strains upon torque tightening and orthodontic loading.

Tilted orthodontic micro implants: a photoelastic stress analysis.

The aim of this study was to examine peri-implant stresses around orthodontic micro implants upon torque-tightening and static load application by quasi-three-dimensional photoelastic stress analysis. Self-tapping orthodontic micro implants were progressively inserted into photoelastic models at 30, 45, 70, and 90 degrees and insertion torques were measured. Stress patterns (isochromatic fringe orders) were recorded by the quasi-three-dimensional photoelastic method using a circular polariscope after insertion and 250 g static force application. Torque-tightening of implants generated peri-implant stresses. Upon insertion, 90 degree placed implants displayed the lowest and homogeneous stress distribution followed by 30, 70, and 45 degree tilted implants. Static loading did not dramatically alter stress fields around the implants tested. The highest alteration in stress distribution was observed for the 90 degree placed implant, while 70 degree tilted implant had the lowest stresses among tilted implants. Torque-tightening of orthodontic micro implants creates a stress field that is not dramatically altered after application of static lateral moderate orthodontic loads, particularly at the cervical region of tilted implants.

Primary stability and histomorphometric bone-implant contact of self-drilling and self-tapping orthodontic microimplants.

INTRODUCTION: The aim of this study was to evaluate the primary stability and the histomorphometric measurements of self-drilling and self-tapping orthodontic microimplants and the correlations between factors related to host, implant, and measuring technique. METHODS: Seventy-two self-drilling and self-tapping implants were placed into bovine iliac crest blocks after computed tomography assessments. Insertion torque values, subjective assessments of stability, and Periotest (Medizintecknik Gulden, Modautal, Germany) measurements were performed for each implant. Twelve specimens of each group were assigned to histologic and histomorphometric assessments. RESULTS: The differences between insertion torque values, most Periotest values, and subjective assessments of stability scores were insignificant (P >0.05). The bone-implant contact percentage of the self-drilling group (87.60%) was higher than that of the self-tapping group (80.73%) (P <0.05). Positive correlations were found between insertion torque value, cortical bone thickness, and density in both groups (P <0.05). Negative correlations between insertion torque values and Periotest values were mostly observed in the self-drilling group (P <0.05). Positive correlations were found between bone-implant contact percentages, cortical bone densities, and insertion torque values in both groups (P <0.05). The differences between insertion torque values and corresponding subjective assessments of stability scores were different in both groups (P <0.05). CONCLUSIONS: The differences in insertion torque values, Periotest values, and subjective assessments of stability scores of self-drilling and self-tapping implants were insignificant. Self-drilling implants had higher bone-implant contact percentages than did self-tapping implants. Significant correlations were found between parameters influencing the primary stability of the implants.