## 5 Discussion  
Most papers agree that a deep bite is difficult to treat with aligners, and anterior intrusion and posterior extrusion are difficult to achieve, but not all papers share the same opinion. Although the patients had different malocclusions (the patient in case number 1 had undergone an extractive treatment in the past and had a relapse, while the patient in case number 2 had a class II malocclusion with complete dentition), the same protocol to treat their deep bite malocclusion was effective. It is also important to report that both cases had dental arch contraction and crowding. The resolution of these two features of malocclusion helped with the correction of the deep bite because it was in part corrected with the relative intrusion of the anterior lower teeth. Relative intrusion is a combination of intrusion and labial tipping. [PERSON] et al., stated that the vertical movements of intrusion and extrusion are more difficult with the aligners [30]. From the systematic review by [PERSON] et al., knowledge emerged that the least predictable movements with Invisalign are rotations and vertical movements [32]. According to a recent review of the literature conducted by [PERSON] on the efficacy of Invisalign therapy on different types of malocclusions, Invisalign was found to be effective for tipping and rotation movements. Moreover, the results of Invisalign therapies may be comparable with those of fixed multibracket therapies in the case of little or medium crowdings in adult patients who do not require extractions [33; 34]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Measurements** & **Result** & **Mean** & **S.D.** & **Severity** \\ \hline SNA & 82.68 & 81.77 & 6.0 & \\ SNB & 79.04 & 80.42 & 5.3 & \\ ANB & 3.64 & 2.05 & 1.8 & \\ Bjork sum & 393.11 & 393.97 & 3.7 & \\ FMA & 22.58 & 25 & 4.0 & \\ Gonial angle & 129.98 & 122.38 & 4.9 & * \\ APDI & 81.92 & 85.98 & 4.0 & * \\ ODI & 71.74 & 73.35 & 5.9 & \\ Combination factor & 153.66 & 159.3 & 7.1 & \\ A to N-Perp (FH) & 3.26 & 1.1 & 2.7 & \\ B to N-Perp (FH) & \(-0.71\) & \(-3.5\) & 2.0 & * \\ Pog to N-Perp (FH) & 2.95 & \(-0.3\) & 2.5 & * \\ FH to AB & 83.80 & 81 & 3.0 & \\ A-B to mandibular plane & 73.62 & 69.3 & 2.5 & * \\ Wits appraisal & 1.39 & \(-2.24\) & 0.3 & *** \\ Overlet & 3.11 & 2 & 2.0 & \\ Overbite & 1.81 & 2 & 2.0 & \\ U1 to FH & 110.99 & 116.52 & 6.0 & \\ U1 to SN & 100.46 & 109.31 & 6.0 & * \\ U1 to UOP & 62.99 & 55 & 4.0 & * \\ IMPA & 94.70 & 95 & 5.5 & \\ L1 to LOP & 64.50 & 66 & 5.0 & \\ Interincisal angle & 131.73 & 128 & 5.3 & \\ Cant of occlusal plane & 4.04 & 9.3 & 3.8 & * \\ U1 to NA (mm) & 2.32 & 4 & 3.0 & \\ U1 to NA (deg) & 17.78 & 22 & 5.0 & \\ L1 to NB (mm) & 4.32 & 4 & 2.0 & \\ L1 to NB (deg) & 26.85 & 25 & 5.0 & \\ Upper incisal display & 2.77 & 3 & 1.5 & \\ Upper lip to E-plane & \(-8.01\) & 0 & 2.0 & *** \\ Lower lip to E-plane & \(-5.83\) & 0 & 2.0 & ** \\ Nasolabial angle & 109.41 & 95 & 5.0 & ** \\ \hline \hline \end{tabular} \({}^{*}\) Low; ** Medium; *** High.  
\end{table} 
Table 4: Post-treatment cephalometric values of case number 2. Invisalign was found not to be very effective in arch expansions through a bodily movement of the teeth, in the closure of the extraction spaces, in the correction of vertical occlusal contacts and in the resolution of major malocclusions. It has been found that some malocclusions, such as minor dental misalignments or anterior dental open bites, can be treated with more prediction using aligners [29; 35]. On the contrary, malocclusions characterized by a deep bite are more complex to treat [36]. A study by [PERSON] et al. analyzed patients with skeletal deep bites treated with Invisalign G5 and virtual bite ramps versus patients treated with fixed orthodontic devices. This study showed that there is no difference in the effectiveness of treatment between fixed and Invisalign equipment [31]. Additionally, according to [PERSON] and [PERSON], the correction of a deep bite was difficult with the transparent aligners.