## 4 Discussion  
We have presented here results on the use of bone-borne distractors for maxillary expansion in two groups of patients. Among the adolescent patients, we obtained a success rate of 100% in the girls and of 89% in the boys (corresponding to 8 out of 9 boys) after one week of treatment, this did not change in the second week of observation. The results in the younger group of patients were similar to those obtained by [PERSON] et al. (2018), even though the procedure they employed was different: they performed one turn of the screw per day (0.2 mm per turn), whereas our procedure used 0.5 mm expansion a day. The success rate reported in [PERSON] et al. (2018) was 100% in both sexes in their two younger age groups (from 11 to 19 years). They used an expansion procedure similar to ours, but with Hyrax-type expanders. This may suggest that the speed of expansion does not play a significant role in the process of maxillary suture opening in younger patients. In our adult patients, expansion for one week produced a diastema in 54% of the women and in none of the men; this was a significant difference. At the next appointment one week later, diastema had occurred in 92% of women and in 33% of men; this result was also statistically significantly different. The overall success rate in the adult group of thirteen females and nine males was 68%. This differs from the results of [PERSON] et al. (2018), who had a success rate of 84% in a group of nineteen female adults and eight male adults, and where the difference between the sexes was not statistically significant. On the other hand, they had an 86% success rate among their female adults, whereas we saw a 92% success rate among female adults. Our research and theirs followed different protocols: they waited twelve weeks after the implants were installed; a distraction of 0.34 mm per day was then recommended for the first week (0.5 mm in our protocol). They also measured the forces with a spring scale, ensuring they did not exceed 500 cN. This was not measured in our protocol. However, our patients were verbally instructed not to activate the distractor with too much force. If a patient had difficulty activating it, then he or she was to abandon it or carry it out at intervals. So, if patients attempt to activate the device in the evening but feel either too much resistance from the screw or too much tension in the facial area, then they are to abandon activation. They might take a one-hour break before attempting activation again. Patient medical history data show that this type of activation in stages yields positive results. Similar results on distraction in patients fifteen years and older were obtained by [PERSON] et al. (2018), despite their different expansion protocol. This group saw success in 93% of females and in 54% of males, which is similar to our results for females. They also pointed out that there were no successful male cases older than thirty. Our oldest male patient was 26 years old, while our oldest female was 39. This might suggest that interdigitation is not the only factor that can make the palatal suture inseparable: the success of palatal distraction may also be associated with age and sex. A prospective study by [PERSON] et al. (2018) found a success rate of 94% in a group of 34 patients who ranged in age from 16 to 34 and, 26 of whom were women and 8 of whom were men. However, they did employ a longer observation time of 23 to 39 days. Our present research agrees with the positive results obtained for distraction periods longer than two weeks. The research of [PERSON] et al. (2018) on palatal distraction in rats explained the histological process as