After the enamel was removed, the scalloped structure of the DEJ was exposed (). In most specimens scallop boundaries were clearly defined. Towards the cervical area, scalloped structure became weaker with the boundaries being poorly defined. Scallop sizes of posterior teeth appear larger than those of anterior teeth.
SEM image of specimen M.1 (left mandibular third molar): scallops and microscallops, original magnification: 1500 ×.
Results of statistical analysis including standard deviation and confidence intervals are summarised in . A 4 × 3 repeated measures two-way analysis of variance was conducted to determine whether scallop area varied with tooth type (molars, premolars, canines and incisors) and between different specimens of the same tooth type. Results of the analysis indicated a main effect for tooth type, F(3,177) = 67.102, p < 0.05, with the scallops of molars having the largest area (M = 1311 μm2), followed by premolars (M = 1130 μm2), incisors (M = 788 μm2) and canines (M = 616 μm2). There was also a main effect for specimen, F(2,118) = 26.898, p < 0.05, and there were differences between patterns of area for tooth types across specimens (i.e. type*specimen interaction) F(6,354) = 19.042, p < 0.05. This means that we need to reject our null hypothesis. Bonferroni pairwise comparison shows that despite the small number of tooth samples, differences between tooth types were within the level of significance (p < 0.05). Results of statistical analysis of scallop area with tooth type for all specimens are shown in .
Scallop area ± 95% confidence interval for tooth types and specimens. Differences between tooth types and specimens are statistically significant (p < 0.05).
As third molars, which were used in this study, are known to show variation in their morphology and structure compared to other teeth, a 3 × 3 repeated measures two-way ANOVA was conducted for premolars, canines and incisors only. Results showed a main effect for tooth type, F(2,118) = 63.715, p < 0.05, and a main effect for tooth specimen, F(2,118) = 8.052, p < 0.05. There was no significant interaction effect.
In an additional 4 × 3 repeated measures two-way ANOVA it was studied whether scallop circularity varied with tooth type and between different specimens of the same tooth type. For circularity, results of the analysis indicated no main effect for type F(3,177) = 1.275, p > 0.05. There was, however, a main effect for specimen, F(2,118) = 12.225, p < 0.05. No interaction effects (type*specimen) were found, F(6,354) = 0.977, p > 0.05. Results for scallop shape (circularity) are shown in Table 2. As the main effect for specimen is significant for both scallop area and circularity, results are presented for each specimen rather than pooled together for tooth types ().
Within scallops smaller structures, known as microscallops,3
are found (). Appearance of these microscallops varies greatly and in several specimens they were hardly visible. Due to this variation in visibility and appearance, size of microscallops was not evaluated statistically.
For each specimen, scallop area was determined at three locations, as Whittaker had reported differences in scallop size with intratooth location.7
In our study, one specimen (a right mandibular canine) showed differences in scallop size with intratooth location during preliminary qualitative inspection. This might be caused by the fact that in the cervical area the clear distinction between “scallop boundaries” and “inner septae” (i.e.
structures within a scallop) was not possible, resulting in a much smaller apparent scallop area. Due to this uncertainty, this specimen was not included in the evaluation and was replaced by another canine. Of those samples included in statistical evaluation (3 teeth for each type: molars, premolars, canines and incisors), one specimen showed significant differences in scallop area with intratooth location (P.2, repeated measures one-way ANOVA, p