Effect of banding on cuspal flexure.
Cuspal flexure (in ïŽm) resulting from 100 N occlusal load, with and without a stainless steel band cemented, is shown in Table 1. Despite a wide range in cuspal flexure amongst teeth (5.8â33.4 ïŽm, Table 1), banding reduced cuspal flexure in all teeth. The pattern of flexure change in each tooth can be seen in Figure 1. The greatest reduction in flexure occurred in those teeth with the highest initial cusp deflection. Overall, the mean flexure of teeth with a band was less than one-half that of the same teeth without a band (P < 0.001, paired t-test based on logtransformation) (Table 2). Despite this reduction in flexure, the strongest teeth without a band showed lower cuspal deflection than the weakest teeth with a band in place.
Table 1. Cuspal flexure ( m) of maxillary premolars with MOD cavities and endodontic access, with and without band present.
Figure 1. Effect of stainless steel bands on cuspal flexure of maxillary premolars. Each line shows the pattern of change for each tooth separately.
Table 2. Paired differences between cuspal flexure of maxillary premolars, with and without a band present.
Table 3. Load required (N) to fracture maxillary premolars with MOD cavities and endodontic access, with and without a band.
a. Two teeth did not fracture at the maximum load of 2000 N.
Effect of banding on fracture resistance.
From 10 pairs of maxillary premolars, only six pairs could be used for statistical analysis. Two teeth without a band were fractured during the initial positioning of the teeth before the results were being recorded, and two teeth with a band (from different pairs) did not fracture at maximum loading (2000 N). The results of the fracture test with and without stainless steel bands using contralateral teeth from the same subject are seen in Tables 3 and 4. The range of loads was also wide in the fracture tests, as in the cuspal deflection results, with considerable overlap in fracture loads between banded and unbanded teeth. Based on comparisons of teeth from the same subject (paired t-test), teeth with a band had higher fracture resistance, with a difference of 366â742 N (95% confidence interval, P < 0.001). The differences between matched pairs are shown in Figure 2.
Most teeth with the band present fractured initially by enamel chipping off the cusp tips, followed by separation of the cusps through the proximal surface at higher load. Two teeth remained intact until the maximum loading, other than both cusp tips chipping. The patterns of fracture of teeth without the bands were similar to those in teeth with the band.
Table 4. Paired differences between load required to fracture maxillary premolars, with and without a band.
n = 6 pairs.
Figure 2. Effect of stainless steel bands on fracture resistance of maxillary premolars. Each line shows the pattern of change for each pair.