Educational interventions in health services and oral health: systematic review

Menegaz, Aryane Marques; Silva, Alexandre Emídio Ribeiro; Cascaes, Andreia Morales

doi:10.11606/S1518-8787.2018052000109

Aryane Marques Menegaz

Universidade Federal de Pelotas. Faculdade de Odontologia. Programa de Pós-Graduação em Odontologia. Pelotas, RS, Brasil

Alexandre Emídio Ribeiro Silva

Universidade Federal de Pelotas. Faculdade de Odontologia. Programa de Pós-Graduação em Odontologia. Pelotas, RS, Brasil

Universidade Federal de Pelotas. Faculdade de Odontologia. Departamento de Odontologia Social e Preventiva. Pelotas, RS, Brasil

Andreia Morales Cascaes Correspondence: Andreia Morales Cascaes, Departamento de Odontologia Social e Preventiva, Faculdade de Odontologia – UFPel, R. Gonçalves Chaves, 457 96015-560 Pelotas, RS, Brasil E-mail: andreia.cascaes@ufpel.edu.br

Universidade Federal de Pelotas. Faculdade de Odontologia. Programa de Pós-Graduação em Odontologia. Pelotas, RS, Brasil

Universidade Federal de Pelotas. Faculdade de Odontologia. Departamento de Odontologia Social e Preventiva. Pelotas, RS, Brasil

Correspondence: Andreia Morales Cascaes, Departamento de Odontologia Social e Preventiva, Faculdade de Odontologia – UFPel, R. Gonçalves Chaves, 457 96015-560 Pelotas, RS, Brasil E-mail: andreia.cascaes@ufpel.edu.br

Authors’ Contribution: Design and planning of the study: AMM, AMC. Collection, analysis, and interpretation of the data: AMM, AMC, AERS. Preparation or review of the study: AMM, AMC. All authors have approved the final version of the study and assume public responsibility for its content.

Conflict of Interest: The authors declare no conflict of interest.

Characteristics of the studies		n	%
Place of the study
	Developed countries	7	50.0
	Developing countries	7	50.0
Type of study
	Randomized and controlled test	9	64.2
	Before and after	5	35.8
Type of health service
	Primary health care center	7	50.0
	Ontological clinic	3	21.4
	Hospital	3	21.4
	Medical clinic	1	7.2
Target audience
	Parents and their children	9	64.2
	Pregnant women	3	21.4
	Children	1	7.2
	Women who use public services	1	7.2
Type of educational resource or strategy used^* * Some studies have used more than one type of resource; the percentage values shown are individual for each type of resource.
	Oral advice/Guidance	13	92.9
	Giving out handouts/Pamphlets	7	50.0
	Giving out toothbrushes and toothpastes	6	42.8
	Posters in health services	2	14.3
	Demonstration of brushing in macromodels	2	14.3
	Sending of postcards by mail	1	7.2
	Video demonstration	1	7.2
	Photo album demonstration	1	7.2
	Giving out sippy cups	1	7.2
	Phone calls	1	7.2
Professional who implemented the intervention
	More than on professional	6	42.8
	Dentist	3	21.4
	Community health agent	3	21.4
	Physician	1	7.2
	Nurse	1	7.2
Dosage of the intervention (number of contacts)
	1 to 3	7	50.0
	4 to 12	5	35.8
	Not informed	2	14.2
Maximum time for evaluation (months)
	2 to 6	3	21.4
	7 to 12	5	35.8
	13 to 24	1	7.2
	36 to 60	3	21.4
	Not informed	2	14.2
Follow-up rate above 80%
	No	7	50.0
	Yes	5	35.8
	Not informed	2	14.2
Outcomes
	Clinical	6	42.8
	Behavioral	3	21.4
	Clinical and behavioral	5	35.8

Authors, year	Report	External validity	Bias^* * Question 14 of the Downs and Black instrument was excluded.	Confounding	Power	Sum
Authors, year	(0 to 10)	(0 to 3)	(0 to 6)	(0 to 6)	(0 to 1)	(0 to 26)
Chaffee et al.⁸8. Chaffee BW, Feldens CA, Vitolo MR. Cluster-randomized trial of infant nutrition training for caries prevention. J Dent Res. 2013;92(7):29-36. https://doi.org/10.1177/0022034513484331 https://doi.org/10.1177/0022034513484331... (2013)	10	3	5	6	1	25
Mohebbi et al.³⁹39. Mohebbi SZ, Virtanen JI, Vahid-Golpayegani M, Vehkalahti MM. A cluster randomised trial of effectiveness of educational intervention in primary health care on early childhood caries. Caries Res. 2009;43(2):110-8. https://doi.org/10.1159/000209343 https://doi.org/10.1159/000209343... (2007)	9	3	6	6	1	25
Vachirarojpsian et al.⁵⁷57. Vachirarojpisan T, Shinada K, Kawaguchi Y. The process and outcome of a programme for preventing early childhood caries in Thailand. Community Dent Health. 2005;22(4):253-9. (2005)	8	3	6	5	0	22
Davies et al.¹⁰10. Davies GM, Duxbury JT, Boothman NJ, Davies RM, Blinkhorn AS. A staged intervention dental health promotion programme to reduce early childhood caries. Community Dent Health. 2005;22(2):118-22. (2005)	8	3	5	3	1	20
Raj et al.⁴⁶46. Raj S, Goel S, Sharma VL, Goel NK. Short-term impact of oral hygiene training package to Anganwadi workers on improving oral hygiene of preschool children in North Indian City. BMC Oral Health. 2013;13(67):1472-6831. https://doi.org/10.1186/1472-6831-13-67 https://doi.org/10.1186/1472-6831-13-67... (2003)	8	3	5	2	1	19
Blinkhorn et al.²2. Blinkhorn AS, Gratrix D, Holloway PJ, Wainwright-Stringer YM, Ward SJ, Worthington HV. A cluster randomised, controlled trial of the value of dental health educators in general dental practice. Br Dent J. 2003;195(7):395-400. https://doi.org/10.1038/sj.bdj.4810566 https://doi.org/10.1038/sj.bdj.4810566... (2003)	6	1	6	3	1	17
Cibuka et al.⁹9. Cibulka NJ, Forney S, Goodwin K, Lazaroff P, Sarabia R. Improving oral health in low-income pregnant women with a nurse practitioner-directed oral care program. J Am Acad Nurse Pract. 2011;23(5):249-57. https://doi.org/10.1111/j.1745-7599.2011.00606.x https://doi.org/10.1111/j.1745-7599.2011... (2011)	9	0	5	2	1	17
Frazão et al.¹⁹19. Frazao P, Marques D. Effectiveness of a community health worker program on oral health promotion. Rev Saude Publica. 2009;43(3):463-71. https://doi.org/10.1590/S0034-89102009005000016 https://doi.org/10.1590/S0034-8910200900... (2009)	7	3	4	2	1	17
Wagner et al.⁵⁸58. Wagner Y, Greiner S, Heinrich-Weltzien R. Evaluation of an oral health promotion program at the time of birth on dental caries in 5-year-old children in Vorarlberg, Austria. Community Dent Oral Epidemiol. 2014;42(2):160-9. https://doi.org/10.1111/cdoe.12072 https://doi.org/10.1111/cdoe.12072... (2013)	7	3	3	3	1	17
Strippel et al.⁵⁴54. Strippel H. Effectiveness of structured comprehensive paediatric oral health education for parents of children less than two years of age in Germany. Community Dent Health. 2010;27(2):74-80. https://doi.org/10.1922/CDH_2223Srtippel07 https://doi.org/10.1922/CDH_2223Srtippel... (2010)	8	0	4	3	1	16
Larsen et al.²⁹29. Larsen CD, Larsen MD, Ambrose T, Degano R, Gallo L, Cardo VA, Jr. Efficacy of a Prenatal Oral Health Program Follow-up with Mothers and their Children. N Y State Dent J. 2016;82(3):15-20. (2016)	8	1	4	1	1	15
Gauba et al.²²22. Gauba K, Goyal A, Mittal N. A CAMBRA Model For High Caries Risk Indian Children: A Pragmatic Comprehensive Tailored Intervention. J Clin Pediatr Dent. 2016;40(1):36-43. https://doi.org/10.17796/1053-4628-40.1.36 https://doi.org/10.17796/1053-4628-40.1.... (2016)	8	0	4	1	1	13
Whittle et al.⁶¹61. Whittle JG, Whitehead HF, Bishop CM. A randomised control trial of oral health education provided by a health visitor to parents of pre-school children. Community Dent Health. 2008;25(1):28-32. https://doi.org/10.1922/CDH_2143Whittle05 https://doi.org/10.1922/CDH_2143Whittle0... (2008)	5	0	5	2	1	13
Moskovitz et al.⁴²42. Moskovitz M, Abud W, Ram D. The influence of an oral health education program provided in a community dental clinic on the prevalence of caries among 12-14 year-old children. J Clin Pediatr Dent. 2009;33(3):259-64. https://doi.org/10.17796/jcpd.33.3.r3p7351l5x52737u https://doi.org/10.17796/jcpd.33.3.r3p73... (2009)	7	0	2	2	0	11
Average (SD)	7.7 (1.3)	1.6 (1.4)	4.6 (1.2)	2.9 (1.6)	0.9 (0.4)	17.6 (4.2)

Authors, year	Control group	Intervention group	p	Relative impact of intervention (%)
Daily brushing at least twice a day
Cibulka et al.⁹9. Cibulka NJ, Forney S, Goodwin K, Lazaroff P, Sarabia R. Improving oral health in low-income pregnant women with a nurse practitioner-directed oral care program. J Am Acad Nurse Pract. 2011;23(5):249-57. https://doi.org/10.1111/j.1745-7599.2011.00606.x https://doi.org/10.1111/j.1745-7599.2011... (2011)	I: NI F:NI	I: average score 1.8 (SD = 0.62) F: average score 2.0 (SD = 0.69)	0.013	11.0
Davies et al.¹⁰10. Davies GM, Duxbury JT, Boothman NJ, Davies RM, Blinkhorn AS. A staged intervention dental health promotion programme to reduce early childhood caries. Community Dent Health. 2005;22(2):118-22. (2005)	I: NI F: 34%	I: NI F: 52%	< 0.001	52.9
Frazão et al.¹⁹19. Frazao P, Marques D. Effectiveness of a community health worker program on oral health promotion. Rev Saude Publica. 2009;43(3):463-71. https://doi.org/10.1590/S0034-89102009005000016 https://doi.org/10.1590/S0034-8910200900... (2009)	-	I: 73% F: 88%	> 0.05	20.6
Raj et al.⁴⁶46. Raj S, Goel S, Sharma VL, Goel NK. Short-term impact of oral hygiene training package to Anganwadi workers on improving oral hygiene of preschool children in North Indian City. BMC Oral Health. 2013;13(67):1472-6831. https://doi.org/10.1186/1472-6831-13-67 https://doi.org/10.1186/1472-6831-13-67... (2013)	-	I: 4.1% F: 9.9%	< 0.001	141.5
Vachirarojpisan et al.⁵⁷57. Vachirarojpisan T, Shinada K, Kawaguchi Y. The process and outcome of a programme for preventing early childhood caries in Thailand. Community Dent Health. 2005;22(4):253-9. (2005)	I: NI F: 26.7%	I: NI F: 41.8%	< 0.001	56.6
Wagner et al.⁵⁸58. Wagner Y, Greiner S, Heinrich-Weltzien R. Evaluation of an oral health promotion program at the time of birth on dental caries in 5-year-old children in Vorarlberg, Austria. Community Dent Oral Epidemiol. 2014;42(2):160-9. https://doi.org/10.1111/cdoe.12072 https://doi.org/10.1111/cdoe.12072... (2013)	They conclude that mothers who participated in the intervention started brushing the teeth of their children earlier and more frequently using fluoride toothpaste. Results in numbers are not shown.
Use of baby bottle
Davies et al.¹⁰10. Davies GM, Duxbury JT, Boothman NJ, Davies RM, Blinkhorn AS. A staged intervention dental health promotion programme to reduce early childhood caries. Community Dent Health. 2005;22(2):118-22. (2005)	Stopped using baby bottle
	I: NI F: 18%	I: NI F: 33%	0.04	83.3
Strippel et al.⁵⁴54. Strippel H. Effectiveness of structured comprehensive paediatric oral health education for parents of children less than two years of age in Germany. Community Dent Health. 2010;27(2):74-80. https://doi.org/10.1922/CDH_2223Srtippel07 https://doi.org/10.1922/CDH_2223Srtippel... (2010)	Frequency of bottle feeding with cariogenic content during the day
	I: NI F:41%	I: NI F: 32%	< 0.001	-21.9
Vachirarojpisan et al.⁵⁷57. Vachirarojpisan T, Shinada K, Kawaguchi Y. The process and outcome of a programme for preventing early childhood caries in Thailand. Community Dent Health. 2005;22(4):253-9. (2005)	Sleep using a bottle
	I: 44% F: 35.1%	I: 43.7% F: 40.4%	> 0.05	^* * The change was greater in the control group than in the intervention group.
Consumption of sweets
Cibulka et al.⁹9. Cibulka NJ, Forney S, Goodwin K, Lazaroff P, Sarabia R. Improving oral health in low-income pregnant women with a nurse practitioner-directed oral care program. J Am Acad Nurse Pract. 2011;23(5):249-57. https://doi.org/10.1111/j.1745-7599.2011.00606.x https://doi.org/10.1111/j.1745-7599.2011... (2011)	Intake of soft drinks more than twice a day
	I: 21% F: 23%	I: 18% F: 11%	< 0.05	-48.7
Gauba et al.²²22. Gauba K, Goyal A, Mittal N. A CAMBRA Model For High Caries Risk Indian Children: A Pragmatic Comprehensive Tailored Intervention. J Clin Pediatr Dent. 2016;40(1):36-43. https://doi.org/10.17796/1053-4628-40.1.36 https://doi.org/10.17796/1053-4628-40.1.... (2016)	Consumption of a cariogenic diet
	-	I: Average 8.47 (SD = 5.18) F: Average 2.37 (SD = 2.23)	< 0.001	-72.1
Strippel et al.⁵⁴54. Strippel H. Effectiveness of structured comprehensive paediatric oral health education for parents of children less than two years of age in Germany. Community Dent Health. 2010;27(2):74-80. https://doi.org/10.1922/CDH_2223Srtippel07 https://doi.org/10.1922/CDH_2223Srtippel... (2010)	Introduction of sugars in food at 7 months
	I: NI 32%	I: NI F: 24%	< 0.001	-25.0
Vachirarojpisan et al.⁵⁷57. Vachirarojpisan T, Shinada K, Kawaguchi Y. The process and outcome of a programme for preventing early childhood caries in Thailand. Community Dent Health. 2005;22(4):253-9. (2005)	Frequent consumption of sugary drinks during the day at 24 months of age
	I: NI F: 66%	I: NI F: 61%	0.013	-7.6
	Consumption of sweets between meals
	I: 92.1% F: 90.6%	I: 88.3% F: 91.5%	> 0.05	^* * The change was greater in the control group than in the intervention group.
Use of dental services
Cibulka et al.⁹9. Cibulka NJ, Forney S, Goodwin K, Lazaroff P, Sarabia R. Improving oral health in low-income pregnant women with a nurse practitioner-directed oral care program. J Am Acad Nurse Pract. 2011;23(5):249-57. https://doi.org/10.1111/j.1745-7599.2011.00606.x https://doi.org/10.1111/j.1745-7599.2011... (2011)	Went to the dentist last year
	I: 30.1% F: 32.9%	I: 27.4% F: 56.9%	0.006	1.061.0
Frazão et al.¹⁹19. Frazao P, Marques D. Effectiveness of a community health worker program on oral health promotion. Rev Saude Publica. 2009;43(3):463-71. https://doi.org/10.1590/S0034-89102009005000016 https://doi.org/10.1590/S0034-8910200900... (2009)	Frequent or very frequent use of dental services
	-	I: 25.3% F: 57.1%	< 0.001	125.7
Wagner et al.⁵⁸58. Wagner Y, Greiner S, Heinrich-Weltzien R. Evaluation of an oral health promotion program at the time of birth on dental caries in 5-year-old children in Vorarlberg, Austria. Community Dent Oral Epidemiol. 2014;42(2):160-9. https://doi.org/10.1111/cdoe.12072 https://doi.org/10.1111/cdoe.12072... (2013)	They conclude that mothers who participated in the intervention reported more use of dental services in those who received the intervention. Results in numbers are not shown.

Authors, year	Index	Control group	Intervention group	p	Relative impact of intervention (%)
Dental caries
Blinkhorn et al.²2. Blinkhorn AS, Gratrix D, Holloway PJ, Wainwright-Stringer YM, Ward SJ, Worthington HV. A cluster randomised, controlled trial of the value of dental health educators in general dental practice. Br Dent J. 2003;195(7):395-400. https://doi.org/10.1038/sj.bdj.4810566 https://doi.org/10.1038/sj.bdj.4810566... (2003)	dmft	I: 2.2 (SD 2.3) F: 3.2 (SD 2.8)	I: 2.0 (SD 2.2) F: 2.6 (SD 2.6)	0.21	-33.3
Chaffee et al.⁸8. Chaffee BW, Feldens CA, Vitolo MR. Cluster-randomized trial of infant nutrition training for caries prevention. J Dent Res. 2013;92(7):29-36. https://doi.org/10.1177/0022034513484331 https://doi.org/10.1177/0022034513484331... (2013)	Average dmfs (with white spots)	I: zero F: 3.6 (SD 6.9)	I: zero F: 2.8 (SD 5.4)	0.25	-22.2
	Average of the decayed component of the dmfs	I: zero F: 3.0 (SD 6.8)	I: zero F: 2.1 (SD 5.0)	0.18	-30.0
Davies et al.¹⁰10. Davies GM, Duxbury JT, Boothman NJ, Davies RM, Blinkhorn AS. A staged intervention dental health promotion programme to reduce early childhood caries. Community Dent Health. 2005;22(2):118-22. (2005)	Average dmft	I: NI F: 1.7	I: NI F: 1.1	< 0.001	-35.3
	Average dmfs	I: NI F: 3.8	I: NI F: 2.6	0.008	-31.6
Gauba et al.²²22. Gauba K, Goyal A, Mittal N. A CAMBRA Model For High Caries Risk Indian Children: A Pragmatic Comprehensive Tailored Intervention. J Clin Pediatr Dent. 2016;40(1):36-43. https://doi.org/10.17796/1053-4628-40.1.36 https://doi.org/10.17796/1053-4628-40.1.... (2016)	They have not used the index. They were based on their own criteria and characterized it as “chance to avoid new cavities”	-	I: Average 12.5 (SD 13.5) F: Average 72.7 (SD 14.4)	< 0.001	481.6
Larsen et al.²⁹29. Larsen CD, Larsen MD, Ambrose T, Degano R, Gallo L, Cardo VA, Jr. Efficacy of a Prenatal Oral Health Program Follow-up with Mothers and their Children. N Y State Dent J. 2016;82(3):15-20. (2016)	They have not used the index. Presence or absence of dental caries	I: zero F: 29 children without dental caries (69%)	I: zero F: 19 children without dental caries (39%)	0.015	-43.5
Mohebbi et al.³⁹39. Mohebbi SZ, Virtanen JI, Vahid-Golpayegani M, Vehkalahti MM. A cluster randomised trial of effectiveness of educational intervention in primary health care on early childhood caries. Caries Res. 2009;43(2):110-8. https://doi.org/10.1159/000209343 https://doi.org/10.1159/000209343... (2007)	Average of enamel caries WHO criteria (1997)	I: 0.08 (SD 0.4) F: 0.48 (SD 1.0)	Group A I: 0.25 (SD 0.7) F: 0.15 (SD 0.5)	0.283	Group A -108.0
	Average of enamel caries WHO criteria (1997)	I: 0.08 (SD 0.4) F: 0.48 (SD 1.0)	Group B I: 0.25 (SD 0.7) F: 0.35 (SD 1.0)	0.283	Group B -92.0
	Average of dentin caries WHO criteria (1997)	I: 0.03 (SD 0.25) F: 0.23 (SD 0.95)	Group A I: 0.04 (SD 0.2) F: 0.02 (SD 0.2)	0.719	Group A -107.6
	Average of dentin caries WHO criteria (1997)	I: 0.03 (SD 0.25) F: 0.23 (SD 0.95)	Group B I: 0.14 (SD 0.8) F: 0.12 (SD 0.3)	0.719	Group B -102.1
Moskovitz, et al.⁴²42. Moskovitz M, Abud W, Ram D. The influence of an oral health education program provided in a community dental clinic on the prevalence of caries among 12-14 year-old children. J Clin Pediatr Dent. 2009;33(3):259-64. https://doi.org/10.17796/jcpd.33.3.r3p7351l5x52737u https://doi.org/10.17796/jcpd.33.3.r3p73... (2009)	Average of the decayed component of the DMFT	I: NI F: 5.9	I: NI F: 3.2	< 0.001	-45.8
	Average DMFT	I: NI F: 7.5	I: NI F: 6.8	> 0.05	-9.3
Raj et al.⁴⁶46. Raj S, Goel S, Sharma VL, Goel NK. Short-term impact of oral hygiene training package to Anganwadi workers on improving oral hygiene of preschool children in North Indian City. BMC Oral Health. 2013;13(67):1472-6831. https://doi.org/10.1186/1472-6831-13-67 https://doi.org/10.1186/1472-6831-13-67... (2013)	Average dmft	-	I: 2.1 (SD 3.2) F: 1.9 (SD 1.4)	0.060	-9.5
Vachirarojpisan et al.⁵⁷57. Vachirarojpisan T, Shinada K, Kawaguchi Y. The process and outcome of a programme for preventing early childhood caries in Thailand. Community Dent Health. 2005;22(4):253-9. (2005)	Cavitated and non-cavitated caries lesions^* * Criteria of Drury et al. (1999).	I: 1.7 (SD 2.6) F: 7.7 (SD 5.2)	I: 1.9 (SD 2.7) F: 7.8 (SD 5.0)	> 0.05	-11.4
Wagner et al.⁵⁸58. Wagner Y, Greiner S, Heinrich-Weltzien R. Evaluation of an oral health promotion program at the time of birth on dental caries in 5-year-old children in Vorarlberg, Austria. Community Dent Oral Epidemiol. 2014;42(2):160-9. https://doi.org/10.1111/cdoe.12072 https://doi.org/10.1111/cdoe.12072... (2013)	Average dmfs	I: zero F: 5.2 (SD 6.4)	I: zero F: 3.2 (SD 7.4)	< 0.05	-38.5
	Average dmft	I: zero F: 2.4 (SD 4.1)	I: zero F: 1.5 (SD 2.5)	< 0.05	-37.5
Whittle et al.⁶¹61. Whittle JG, Whitehead HF, Bishop CM. A randomised control trial of oral health education provided by a health visitor to parents of pre-school children. Community Dent Health. 2008;25(1):28-32. https://doi.org/10.1922/CDH_2143Whittle05 https://doi.org/10.1922/CDH_2143Whittle0... (2008)	Average dmfs	I: zero F: 2.2 (36 months)	I: zero F: 2.0 (36 months)	> 0.05	-15.2
	Average dmfs	I: zero F: 4.8 (60 months)	I: zero F: 4.0 (60 months)	> 0.05	-15.2
Periodontal conditions
Blinkhorn et al.²2. Blinkhorn AS, Gratrix D, Holloway PJ, Wainwright-Stringer YM, Ward SJ, Worthington HV. A cluster randomised, controlled trial of the value of dental health educators in general dental practice. Br Dent J. 2003;195(7):395-400. https://doi.org/10.1038/sj.bdj.4810566 https://doi.org/10.1038/sj.bdj.4810566... (2003)	Dental plaque - NI Index	I: NI F: 61%	I: NI F: 53%	0.16	-13.1
Raj et al.⁴⁶46. Raj S, Goel S, Sharma VL, Goel NK. Short-term impact of oral hygiene training package to Anganwadi workers on improving oral hygiene of preschool children in North Indian City. BMC Oral Health. 2013;13(67):1472-6831. https://doi.org/10.1186/1472-6831-13-67 https://doi.org/10.1186/1472-6831-13-67... (2013)	Dental plaque - NI Index	-	I: 75.5% F: 66.5%	< 0.001	-11.9
	Gingival bleeding	-	I: 1.7% F: 2.2%	0.671	29.4
	Calculus	-	I: 78.3% F: 54.1%	< 0.001	-30.9

[1] Correspondence: Andreia Morales Cascaes, Departamento de Odontologia Social e Preventiva, Faculdade de Odontologia – UFPel, R. Gonçalves Chaves, 457 96015-560 Pelotas, RS, Brasil E-mail: andreia.cascaes@ufpel.edu.br

Brasil

Brasil

Educational interventions in health services and oral health: systematic review

ABSTRACT

OBJECTIVE

METHODS

RESULTS

CONCLUSIONS