TY - JOUR
T1 - Rapid palatal expansion. Part 3
T2 - Strains developed during active and retention phases
AU - Brosh, Tamar
AU - Vardimon, Alexander Dan
AU - Ergatudes, Costas
AU - Spiegler, Adir
AU - Lieberman, Myron
N1 - Funding Information:
This study was supported in part by the Preminger Foundation grant 960070 and the Lefco Foundation grant 960680.
PY - 1998
Y1 - 1998
N2 - Patterns of strain accumulation/dissipation during the active and retention phases of rapid palatal expansion treatment were studied in a preliminary animal model (5 cats) followed by clinical study (14 patients). Two uni-axial strain gauges were bonded to the arms of a hyrax screw. The strain gauges were wired intraorally to a common male connector and protected against salivary assault. For strain registration, the connector was hooked to a switch and balance instrument and a digital strain indicator. The screw was activated (4 × 1/4 turn) every 3 to 4 days and strain and interarch distances were measured during rapid palatal expansion active and retention phases. Interarch distances were also measured during the relapse phase. Both studies share the same results. Strains and expansion increased progressively during active and retention phases of rapid palatal expansion. No difference between anterior and posterior strain was found. An immediate dental strain response that occurred during screw activations (intrasession strain) was related to tooth compression in the PDL. During the 3 to 4 day pause, a delayed skeletal strain response (intersession strain) developed that was inverted or continuous to the preceding intrasession strain. Complete dissipation of residual strains was limited to the first 1 to 3 active phase sessions. Strain accretion resulted essentially from intersession strain build-up. Strain level was preserved during the retention phase, apparently due to relapse strains. Relapse strains could not be measured but are inferred from the predominant interarch rebound measured during the relapse phase. Clinically, an extension of the intersession intervals and the retention phase are recommended.
AB - Patterns of strain accumulation/dissipation during the active and retention phases of rapid palatal expansion treatment were studied in a preliminary animal model (5 cats) followed by clinical study (14 patients). Two uni-axial strain gauges were bonded to the arms of a hyrax screw. The strain gauges were wired intraorally to a common male connector and protected against salivary assault. For strain registration, the connector was hooked to a switch and balance instrument and a digital strain indicator. The screw was activated (4 × 1/4 turn) every 3 to 4 days and strain and interarch distances were measured during rapid palatal expansion active and retention phases. Interarch distances were also measured during the relapse phase. Both studies share the same results. Strains and expansion increased progressively during active and retention phases of rapid palatal expansion. No difference between anterior and posterior strain was found. An immediate dental strain response that occurred during screw activations (intrasession strain) was related to tooth compression in the PDL. During the 3 to 4 day pause, a delayed skeletal strain response (intersession strain) developed that was inverted or continuous to the preceding intrasession strain. Complete dissipation of residual strains was limited to the first 1 to 3 active phase sessions. Strain accretion resulted essentially from intersession strain build-up. Strain level was preserved during the retention phase, apparently due to relapse strains. Relapse strains could not be measured but are inferred from the predominant interarch rebound measured during the relapse phase. Clinically, an extension of the intersession intervals and the retention phase are recommended.
UR - http://www.scopus.com/inward/record.url?scp=0032134946&partnerID=8YFLogxK
U2 - 10.1053/od.1998.v114.a85568
DO - 10.1053/od.1998.v114.a85568
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AN - SCOPUS:0032134946
SN - 0889-5406
VL - 114
SP - 123
EP - 133
JO - American Journal of Orthodontics and Dentofacial Orthopedics
JF - American Journal of Orthodontics and Dentofacial Orthopedics
IS - 2
ER -