Table 1 Summarizes the characteristics of included studies

Serel Arslan et al. [26]

II (RCT)

80 CP: 50 in treatment group, 30 in control group (mean age 3.5 ± 1.9 years)

Children received Functional Chewing Training. It was conducted five times a day and five times a week over a period of 12 weeks

Traditional oral motor exercises were given to the control group. Over a period of 12 weeks, it was conducted five times a day, 5 days a week

- Chewing function by (KCPS)

- Feeding behaviors by (BPFAS)

- The FUCT group showed a significant improvement (p < .001); however, the control group showed no change (p = 0.07).

- All 8BPFAS parameters improved significantly in the FUCT group (p < 001), while four BPFAS parameters improved significantly in the control group (p = 0.02, p = .03, p = .02, p = .01).

Inal et al. [27]

II (RCT)

32 CP:16 in the study group, 16 in the control group (4 to 6 years)

The intervention group received the FUCT. It was performed 5 sets (1 set = 20 min) each day over a period of 12 weeks

Children received classical oral motor exercise program.

It was performed 5 sets (1 set = 20 min) each day over a period of 12 weeks

- Tongue thrust severity by (TTRS)

- Drooling severity and frequency by (DSFS)

- Chewing performance by (KCPS)

Chewing performance (p = 0.001), tongue thrust severity (p = 0.046) and drooling severity (p = 0.002) all improved in the FUCT group, while drooling frequency (p = 0.082) remained unchanged. The control group showed no improvement in chewing performance, tongue thrust, drooling severity, and frequency.

Harris and Dignam [28]

IV (Non-randomized quasi-experimental design)

20 CP ages: group 1 from 8 to 15 years, group 2 from 11 to 18 years, group 3 from 6 to 8 years, and group 4 from 6 to 9 years

The program was followed by group 1 for 14 months. They wore chin cups for the first six months, then continued in the droolers’ classes. Group 2 followed the program for 11 months. They wore chin cups for the first three months, then continued in droolers’ classes.

Group 3 was a 9-month participant in the program. They did not wear chin cups, but attended droolers’ classes. A fourth group served as controls, i.e. They did not wear chin cups or go to droolers’ classes.

Drooling by Scales which weigh to the nearest 0.1 g

Improvement in group 1 was88 percent, improvement in group 2 was 75 percent, improvement in group 3 was 28 percent and group 4 had no improvement nor worsening.

Fatima et al. [29]

IV (Withdrawal design)

15 CP (4 to 15 years)

Oral motor exercises, with a 24-h gap between two sessions and each session conducted for 30 min over a period of 6 months.

Drooling by (DSFS)

Drooling was reduced significantly (p < .05).

Russo et al. [16]

IV (Withdrawal design)

22 CP (5 to 15 years)

(Muscle vibration) The training was 3 days long and was repeated three times each day. Each application took ten minutes to complete, with a 60-s gap between each of the three applications/10 days.

Drooling by DIS, DFSS, VAS, and DQ

Statistically significant differences between base line and (10 days, 1month and 3 months) p < 0.001 in all scales. No statistically significant differences between 10 days to 1 month, 10 days to 3 months, and 1 month to 3months in all scales.

Iammatteo et al. [30]

IV (Withdrawal design)

2 CP (first subject 2 years and 7 months and the other subject 2 years and 11 months)

Oral facilitation techniques: Treatment took place over 12 days of intervention.

Drooling by an OHAUS 700 series triple balance

Speech by tape recorder

Decreasing drooling for both participants: participant 1 nonsignificant, participant 2 statistically significant.

Not increasing bilabial vocalization

Domaracki and Sisson [31]

IV (withdrawal experimental design)

2 subjects, both 10 years

Hourly treatment of oral motor stimulation, then vibration for 10s

Drooling by momentary time sampling procedure

Decreasing drooling by oral motor stimulation but vibration did not have additional therapeutic effects when applied.