Bactericidal Efficacy of Photodynamic Therapy Against Periodontal Pathogens in Periodontal Disease: A Systematic Review

Abstract

Objective: The aim of this study was to assess the bactericidal efficacy of antimicrobial photodynamic dynamic therapy (aPDT) as an adjunct to scaling and root planing (SRP) against periodontal pathogens. Background data: SRP followed by laser therapy has better clinical outcomes than conventional SRP alone. Materials and methods: The question addressed was “Does aPDT as an adjunct to SRP exhibit better bactericidal effect against periodontal pathogens than the use of SRP alone in periodontal disease?” MEDLINE^®/PubMed, Embase, Scopus, Web of Science, and Google Scholar databases were searched from 1977 to December 2015, using different combinations of key words. Review articles, in vitro and experimental studies, and articles in languages other than English were excluded. Results: Seventeen clinical studies were included. Laser wavelengths and duration of irradiation ranged between 470 and 810 nm and 60 and 300 sec, respectively. All studies showed that aPDT application was effective in reducing the counts of periodontal microbes at follow-up. Four studies showed significantly reduced bacterial counts for aPDT as an adjunct to SRP compared with SRP alone. Thirteen studies showed comparable reduction in the counts of periodontal bacteria when aPDT alone or as an adjunct to SRP was compared with SRP alone. Conclusions: The bactericidal efficacy of aPDT as an adjunct to SRP against periodontal pathogens in periodontal disease remains debatable.

Introduction

Periodontal disease is highly prevalent among adults, which affects 90% of the population worldwide.¹ Periopathogenic bacteria such as Porphyromonas gingivalis (Pg), Tannerella forsythia (Tf), Treponema denticola (Td) and Aggregatibacter actinomycetemcomitans (Aa) show particularly strong associations with periodontal disease.² The pioneer colonizers in chronic periodontal disease are the gram-negative strict anaerobes Pg, Tf, and Td, which are collectively described as the major “red complex.”’^3
–5 These key virulent bacteria cause tissue damage by increasing the expression of proinflammatory cytokines.^2,6 Aa is a nonmotile, gram-negative coccobacillus that favorably grows in a facultative anaerobic, microaerophilic, and capnophilic environment, and belongs to the family of Pasteurellaceae.^7,8 Aa and Pg are major pathogens frequently associated with aggressive periodontitis, although they are also found in chronic periodontitis.^2,9 It is suggested that these periodontal pathogens produce several potentially pathogenic substances including chemotaxis-inhibiting factor, outer-sheath-associated peptidases, leukotoxin, collagenases, chemotrypsin-like proteinases, and endotoxin, which allow bacteria to colonize the periodontal pocket and initiate the destruction of tissues.^10

–13

Eradication of microbes is the mainstay in the management of periodontal disease, and the conventional treatment for such infections can be achieved by standard mechanical debridement such as scaling and root planing (SRP) with the adjunctive use of systemic antibiotics.^14,15 Despite microbiological improvements, antibiotics have several untoward effects in which bacterial resistance cannot be overruled.¹⁶ SRP has some physical limitations as well, which attenuates complete elimination of calculus and bacterial deposits from deep periodontal pockets.^17,18 To overcome the limitations of scaling and root planing and to reduce the bacterial load, antimicrobial photodynamic therapy (aPDT) has been proposed as a treatment strategy for elimination of bacteria in periodontal disease.^19,20 The mechanism of action of aPDT involves three main components including light, a photosensitizer (PS), and oxygen. Upon administration of PS dye in the periodontal pocket, excitation with light of a specific wavelength leads the PS to undergo a transition from ground singlet state to a higher-energy triplet state that reacts with endogenous oxygen to produce singlet oxygen and other radical species, causing a rapid and selective destruction of the target bacterial species.^21,22

The benefits of aPDT includes further suppression of periopathogenic bacteria and risk of bacteraemia.^23,24 In a clinical trial by Moreira et al.,¹⁹ periodontitis patients treated with aPDT as an adjunct to SRP showed significant reduction in the counts of all four major periodontal pathogens (Pg, Tf, Td, and Aa) compared with those treated with SRP alone at 3-month follow-up. However, Rühling et al.,²⁵ in a similar trial, showed comparable outcomes in the counts of periodontal pathogens treated with aPDT as an adjunct to SRP and SRP alone at 3-month follow-up. Therefore, there appears to be a controversy with regard to the bactericidal efficacy of aPDT as an adjunct to SRP in reducing the counts of periodontal pathogens in periodontal disease.

The aim of the present study was to systematically review the bactericidal efficacy of aPDT as an adjunct to SRP against four major periodontal pathogens – Aa, Pg, Tf, and Td – in periodontal disease.

Materials and Methods

Focused question

Based on the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines,²⁶ a specific question was constructed. The addressed focused question was “Does aPDT as an adjunct to SRP exhibit better bactericidal effect against Aa, Pg, Tf, and Td than the use of SRP alone in periodontal disease?”

Selection criteria

Eligibility criteria were as follows: (1) original articles; (2) prospective clinical trials; (3) intervention, involving application of aPDT as an adjunct to SRP in treating periodontal disease; (4) controls, involving application of SRP in treating periodontal disease; (5) studies reporting any four major periodontal pathogens Aa, Pg, Tf, and Td in vivo after aPDT application in periodontal disease; and (6) studies published in English only.

The exclusion criteria included; review articles, in vitro and experimental studies, ex vivo studies, case reports, commentaries, interviews, and updates.

Search strategy

The authors (Z.A., U.D., A.H.S., and M.A.A.) searched the MEDLINE^®/PubMed, Embase, Scopus, Web of Science, and Google Scholar databases from 1977 up to and including December 2015 for appropriate articles addressing the focused question. A structured and logical approach to literature searching was used to identify the relevant articles that reported the bactericidal efficacy of PDT against any one or all four periodontopathogens Aa, Pg, Tf, and Td in periodontal disease. Reference lists of original studies were hand searched to identify any articles that could have been missed during the initial search. Hand searching of the following journals was performed: J Clin Periodontol, J Periodontol, J Lasers Med Sci, Lasers Surg Med, Photodiagnosis Photodyn Ther, Photochem Photobiol Sci, J Periodontal Implant Sci, J Nat Sci Biol Med, Clin Oral Investig, and J Periodontol Implant Dent. Any disagreements regarding study selection were resolved via discussion. Electronic database searches were performed using different combinations of Medical Subject Headings (MeSH) terms and free text words: photochemotherapy, photodynamic therapy, microbiology, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia , Treponema denticola , periodontal disease, periodontitis, chronic periodontitis, aggressive periodontitis.

Screening methods

Titles and abstracts of articles that satisfied the selection protocol were screened by the authors and checked for agreement. Full texts of studies judged by title and abstract to be relevant were read and independently assessed against the eligibility criteria. Following this, reference lists of original and review articles that were found to be pertinent in the previous step were hand searched and checked for agreement via discussion among the authors.

Study selection

The search protocol is presented in Fig. 1. A total of 59 studies were initially identified. Forty-two studies that did not fulfil the eligibility criteria were excluded (Appendix A). In total, 17 studies^{19,20,25,27

–40} were included and processed for data extraction. All studies were performed at either universities or healthcare centers. Figure 1 shows the study identification flow chart with the reasons for exclusion of articles.

FIG. 1.

Study identification flow chart.

Methodological study quality assessment

Two authors (Z.A. and S.A.A.S.) independently assessed the methodological quality of the included studies according to a scoring system developed by the Jadad quality scale⁴¹ for reporting randomized controlled trials. This scale is used to score randomized controlled trials on the basis of three items, which are randomization, blinding of examiner or patients, and an account of all the patients; for example, loss to follow-up. The scores range from 0 to 5 points, with a higher score indicating higher study quality.

Results

General characteristics of included studies

Nine studies^{19,20,28,29,33

–36,40} included in the present review had split-mouth design. In all included studies,^{19,20,25,27

–40} number of individuals ranged between 10³⁵ and 58,³⁸ with mean age ranging between 29.0²⁹ and 52.0³⁶ years. All included studies reported the number of female participants, which ranged between 3³³ and 39²⁵ individuals. All the included studies^{19,20,25,27

–40} used aPDT with SRP in the test group. Two studies^20,34 used additional group of PS in their test group, whereas Birang et al.,²⁸ and Cappuyns et al.,³⁶ used laser therapy (LT) in their test group. One study⁴⁰ used curcumin gel combined with LT and PDT in their test group. Fifteen studies^{19,20,25,28

–31,33

–40} used SRP alone, whereas two studies^27,32 used PS with SRP in the control group. Fourteen studies^{20,25,27,28,30

–34,36

–40} included chronic periodontitis subjects whereas three studies^19,29,35 included patients with aggressive periodontitis. In all included studies, the follow-up period ranged from 4³¹ to 48²⁷ weeks (Table 1). All the enrolled participants had a complication-free healing period with no side effects related to aPDT, except for one participant who developed abscess during the follow-up period.²⁵

Table 1.

General Characteristics of the Included Studies

					Study groups
Author et al. (year)	Study design	Sample size; M/F ratio	Mean age in years (range)	Periodontal disease	(n) Test	(n) Control	Follow-up (weeks)	Main outcome
Carvalho et al.²⁷ (2015)	RCT	34; 18/16	aPDT: 48.2 PS: 51.9 (35–75)	CP	18 aPDT + SRP	16 PS + SRP	Up to 48	Aa, Pg, Tf, and Td counts were comparable among both groups at follow-up
Sreedhar et al.⁴⁰ (2015)	RCT (split mouth design)	15; 7/8	NR (35–55)	CP	15 curcumin gel + SRP 15 curcumin LT + SRP 15 curcumin aPDT + SRP	15 SRP	Up to 12	Aa and Pg counts were comparable among all groups at follow-up
Birang et al.²⁸ (2015)	RCT (split mouth design)	20; 7/13	37.2 (18–72)	CP	20 LT + SRP 20 aPDT + SRP	20 SRP	Up to 12	Aa, Pg, and Td counts were comparable among all groups at follow-up
Moreira et al.¹⁹ (2015)	RCT (split mouth design)	20; 2/18	30.6 (NR)	AP	20 aPDT + SRP	20 SRP	Up to 12	Aa, Pg, Tf, and Td counts significantly reduced in test group at follow-up
Kolbe et al.²⁰ (2014)	RCT (split mouth design)	22; 10/12	48.52 (32–75)	CP	22 aPDT + SRP 22 PS + SRP	22 SRP	Up to 24	Aa, Pg, and Tf counts were comparable among all groups at follow-up
Chitsazi et al.²⁹ (2014)	RCT (split mouth design)	24; 9/15	29.0 (NR)	AP	24 aPDT + SRP	24 SRP	Up to 12	Aa counts were comparable among both groups at follow-up
Petelin et al.³⁰ (2014)	RCT	27; 15/12	US: 51.0 aPDT: 47 SRP: 43 (36–64)	CP	9 US 9 aPDT	9 SRP	Up to 24	Aa, Pg, Tf, and Td counts significantly reduced in aPDT compared with US and SRP
Jung et al.³¹ (2014)	RCT	38; 24/14	36.28 (23–58)	CP	21 aPDT + SRP	17 SRP	Up to 4	Aa, Pg, Tf, and Td counts were comparable among both groups at follow-up
Luchesi et al.³² (2013)	RCT	37; 11/26	aPDT: 50.75 PS: 50.24 (NR)	CP	37 aPDT + SRP	37 PS + SRP	Up to 24	Aa, Pg, and Tf counts were comparable among both groups at follow up
Noro Filho et al.³³ (2012)	RCT (split mouth design)	12; 9/3	44.8 (NR)	CP	12 aPDT + SRP	12 SRP	Up to 24	Aa, Pg, and Tf counts were comparable among both groups at follow-up
Theodoro et al.³⁴ (2012)	RCT (split mouth design)	33; 12/21	43.12 (35–55)	CP	33 aPDT + SRP 33 PS + SRP	33 SRP	Up to 24	Aa, Pg, and Tf counts significantly reduced in aPDT compared with PS and control group at follow-up
Novaes Jr. et al.³⁵ (2012)	RCT (split mouth design)	10; 2/8	31 (18–35)	AP	10 aPDT + SRP	10 SRP	Up to 12	Aa counts significantly reduced in test group whereas Pg, Tf, and Td counts significantly reduced in the control group at follow-up
Cappuyns et al.³⁶ (2012)	RCT (split mouth design)	32; 23/9	52.0 (36–74)	CP	32 LT + SRP 32 aPDT + SRP	32 SRP	Up to 24	Aa, Pg, Tf, and Td counts were comparable among all the groups at follow-up
Rühling et al.²⁵ (2010)	RCT	54; 15/39	48.0 (NR)	CP	25 aPDT + SRP	29 SRP	Up to 12	Aa, Pg, Tf, and Td counts were comparable among both groups at follow-up
Chondros et al.³⁷ (2009)	RCT	24; 10/14	aPDT: 48.3 SRP: 50.6 (NR)	CP	12 aPDT + SRP	12 SRP	Up to 24	Td counts significantly increased in test group, whereas Aa, Pg, and Tf counts were comparable among both groups at follow-up
Polansky et al.³⁸ (2009)	RCT	58; 22/36	aPDT: 48.9 SRP: 48.5 (25–67)	CP	30 aPDT + SRP	28 SRP	Up to 12	Pg, Tf, and Td counts were comparable among both groups at follow-up
Christodoulides et al.³⁹ (2008)	RCT	24; 11/13	45 (36–56)	CP	12 aPDT + SRP	12 SRP	Up to 24	Aa, Pg, Tf, and Td counts were comparable among both groups at follow-up

RCT, randomized clinical trial; aPDT, antimicrobial photodynamic therapy; CP, chronic periodontitis; AP, aggressive periodontitis; SRP, scaling and root planning; LT, laser therapy; PS, photosensitizer; NR, not reported; US, ultrasonic scaling; Aa, Aggregatibacter actinomycetemcomitans; Pg, Porphyromonas gingivalis; Tf, Tannerella forsythia; Td, Treponema denticola.

Laser and photosensitizer related parameters

Diode lasers with wavelengths ranging between 470 and 810 nm were used. Power output, energy fluence, and duration of irradiation were 75 mW, 212.23 J/cm², and 60–180 sec, respectively (Table 2). Power density ranging between 13 and 500 mW/cm² were used. Fifteen studies^{19,20,25,27,29,30,32

–40} included in the systematic review used either methylene blue (MB),^20,27,32,33 toluidine blue (TBO),^29,34,39 phenothiazine chloride (PTC),^{19,30,35

–38} tolonium chloride,²⁵ or curcumin⁴⁰ as PS. In all included studies,^{19,20,25,27

–40} PS was placed in the periodontal pockets for 1–5 min. Studies^{19,25,27,29,30,32

–35,37

–40} reporting the frequency of aPDT application ranged from one to four times throughout the study period. Five studies^{19,20,32,33,37} reported the concentration of PS, which was 10 mg/mL, whereas one study³⁶ reported 0.1 mg/mL, and one study⁴⁰ reported the concentration as 10 mg/g.

Table 2.

Laser and Photosensitizer Parameters of Included Studies

Author et al. (year)	Wavelength (nm)	Energy fluence (J cm ^–2 )	Power output (mW)	Power density (mW cm ^–2 )	Duration of irradiation (sec)	Types of PS	Pre-irradiation time (min)	Concentration of PS (mg/mL)	Frequency of aPDT application
Carvalho et al.²⁷ (2015)	660	90	40	NR	90	MB	5	NR	4
Sreedhar et al.⁴⁰ (2015)	470	NR	NR	620	300	Curcumin gel	5	10^a	3
Birang et al.²⁸ (2015)	810	NR	NR	500	NR	NR	NR	NR	NR
Moreira et al.¹⁹ (2014)	670	2.49 per site 14.94 per tooth	75	250	60	PTC	1	10	4
Kolbe et al.²⁰ (2014)	660	129	60	NR	60	MB	1	10	NR
Chitsazi et al.²⁹ (2014)	670–690	NR	75	NR	120	TBO	2	NR	1
Petelin et al.³⁰ (2014)	660	NR	NR	60	60	PTC	3	NR	3
Jung et al.³¹ (2014)	635	NR	NR	13	180	NR	NR	NR	NR
Luchesi et al.³² (2013)	660	129	60	NR	NR	MB	1	10	1
Noro Filho et al.³³ (2012)	660	57.14	30	428	133	MB	5	10	1
Theodoro et al.³⁴ (2012)	660	64.28	30	400	150	TBO	1	NR	1
Novaes Jr. et al.³⁵ (2012)	660	212.23	NA	60	60	PTC	1	NR	1
Cappuyns et al.³⁶ (2012)	660	NR	40	NR	60	PTC	1	0.1	NR
Rühling et al.²⁵ (2010)	635	NR	100	NR	60	TC	1/2	NR	1
Chondros et al.³⁷ (2009)	670	NR	NR	75	NR	PTC	1	10	1
Polansky et al.³⁸ (2009)	680	NR	75	NR	60	PTC	3	NR	1
Christodoulides et al.³⁹ (2008)	670	NR	75	NR	60	TBO	3	NR	1

PS, photosensitizer; PTC, phenothiazine chloride; TBO, toluidine blue; MB, methylene blue; TC, tolonium chloride; NR, not reported; aPDT, antimicrobial photodynamic therapy. ^aExpressed in mg/g.

Microbiologic-related parameters of the included studies

Sixteen studies reported the counts of Aa^{19,20,25,27

–37,39,40} and Pg^{19,20,25,27,28,30

–40}, whereas 14 studies^{19,20,25,27,30

–39} and 11 studies^{19,25,27,28,30,31,35

–39} reported Tf and Td counts respectively at follow-up. The bacterial counts were expressed in mean ± SD, mean total counts and proportions (Table 3).

Table 3.

Microbiological Parameters of Included Studies

Author et al. (year)	Microbiological analysis	Aggregatibacter actinomycetemcomitans	Porphyromonas gingivalis	Tannerella forsythia	Treponema denticola
Carvalho et al.²⁷ (2015)	PCR	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:
		Baseline: 4.09 ± 0.83	Baseline: 2.32 ± 2.10	Baseline: 2.80 ± 1.63	Baseline: 3.45 ± 2.32
		Follow-up: 4.71 ± 1.04	Follow-up: 3.59^a ± 1.92	Follow-up: 1.99 ± 1.43	Follow-up: 4.38 ± 2.58
		PS + SRP:	PS + SRP:	PS + SRP:	PS + SRP:
		Baseline: 4.74 ± 1.34	Baseline: 1.30 ± 1.63	Baseline: 2.22 ± 1.76	Baseline: 2.96 ± 2.33
		Follow-up: 4.42 ± 1.43	Follow-up: 1.93 ± 2.16	Follow-up: 1.83 ± 1.50	Follow-up: 4.20 ± 2.75
Sreedhar et al.⁴⁰ (2015)	Culture method	Curcumin gel + SRP:	Curcumin gel + SRP:	NR	NR
		Baseline: 136.86 ± 8.66	Baseline: 132.80 ± 10.19
		Follow-up: 105.66^a ± 9.7	Follow-up: 98.66^a ± 13.51
		Curcumin LT + SRP:	Curcumin LT + SRP:
		Baseline: 144.33 ± 9.04	Baseline: 133.60 ± 11.24
		Follow-up: 93.13^a ± 9.39	Follow-up: 89.33^a ± 8.01
		Curcumin PDT + SRP:	Curcumin PDT + SRP:
		Baseline: 140.53 ± 6.70	Baseline: 134.20 ± 12.30
		Follow-up: 81.66^a ± 8.72	Follow-up: 81.20^a ± 6.85
		SRP:	SRP:
		Baseline: 137.00 ± 12.24	Baseline: 133.0 ± 15.88
		Follow-up: 108.13^a ± 7.72	Follow-up: 101.53^a ± 13.85
Birang et al.²⁸ (2015)	PCR	aPDT + SRP:	aPDT + SRP:	NR	aPDT + SRP:
		Baseline: 2912 ± 2103	Baseline: 1487 ± 701		Baseline: 1725 ± 777
		Follow-up: 622^a ± 358	Follow-up: 500^a ± 239		Follow-up: 650^a ± 396
		LT + SRP:	LT + SRP:		LT + SRP:
		Baseline: 2520 ± 671	Baseline: 17.6 ± 689		Baseline: 1720 ± 841
		Follow-up: 8200^a ± 573	Follow-up: 4.9^a ± 280		Follow-up: 690^a ± 615
		SRP:	SRP:		SRP:
		Baseline: 2233 ± 1090	Baseline: 15.11 ± 826		Baseline: 1722 ± 591
		Follow-up: 555^a ± 245	Follow-up: 4.55^a ± 343		Follow-up: 355^a ± 287
Moreira et al.¹⁹ (2015)	Checkerboard DNA-DNA hybridization technique	aPDT + SRP^b	aPDT + SRP^b	aPDT + SRP^b	aPDT + SRP^b
		Baseline: 10 × 10⁵	Baseline: 30 × 10⁵	Baseline: 32 × 10⁵	Baseline: 9 × 10⁵
		Follow-up: 1^a × 10⁵	Follow-up: 12^a × 10⁵	Follow-up: 7^a × 10⁵	Follow-up: 5 × 10⁵
		PS + SRP	PS + SRP	PS + SRP	PS + SRP
		Baseline: 12 × 10⁵	Baseline: 35 × 10⁵	Baseline: 28 × 10⁵	Baseline: 7 × 10⁵
		Follow-up: 1^a × 10⁵	Follow-up: 16^a × 10⁵	Follow-up: 6^a × 10⁵	Follow-up: 5 × 10⁵
Kolbe et al.²⁰ (2014)	PCR	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	NR
		Baseline: 2.5 ± 2.4	Baseline: 2.3 ± 1.9	Baseline: 4.4 ± 2.8
		Follow-up: 2.2 ± 1.8	Follow-up: 1.6^a,b ± 1.9	Follow-up: 3.7 ± 2.6
		PS + SRP:	PS + SRP:	PS + SRP:
		Baseline: 1.9 ± 1.9	Baseline: 1.6 ± 2.1	Baseline: 3.4 ± 2.1
		Follow-up: 2.4 ± 2.1	Follow-up: 1.4 ± 1.8	Follow-up: 3.7 ± 1.8
		SRP:	SRP:	SRP:
		Baseline: 2.7 ± 3.1	Baseline: 1.6 ± 1.4	Baseline: 4.9 ± 3.6
		Follow-up: 2.7 ± 2.5	Follow-up: 1.0^a ± 1.4	Follow-up: 4.7 ± 3.8
Chitsazi et al.²⁹ (2014)	PCR	aPDT + SRP:	NR	NR	NR
		Baseline: 161610
		Follow-up: 1707^a
		SRP:
		Baseline: 129880
		Follow-up: 2703^a
Petelin et al.³⁰ (2014)	PCR + Checkerboard DNA-DNA hybridization technique	aPDT:	aPDT:	aPDT:	aPDT:
		Baseline: 23%	Baseline: 43%	Baseline: 79%	Baseline: 66%
		Follow-up: 13%^a	Follow-up: 28%^a	Follow-up: 55%^a	Follow-up: 37%^a,b
		US:	US:	US:	US:
		Baseline: 18%	Baseline: 60%	Baseline: 80%	Baseline: 69%
		Follow-up: 5%^a	Follow-up: 53%^a	Follow-up: 85%	Follow-up: 73%
		SRP:	SRP:	SRP:	SRP:
		Baseline: 20%	Baseline: 50%	Baseline: 55%	Baseline: 42%
		Follow-up: 23%	Follow-up: 28%^a	Follow-up: 28%^a	Follow-up: 35%^a
Jung et al.³¹ (2014)	PCR	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:
		Baseline: 0.21 ± 0.95	Baseline: 1.50 ± 1.88	Baseline: 3.16 ± 2.06	Baseline: 2.29 ± 2.61
		Follow-up: 0.20 ± 0.93	Follow-up: 0.57^a ± 1.45	Follow-up: 1.53 ± 2.07	Follow-up: 2.21 ± 2.69
		SRP:	SRP:	SRP:	SRP:
		Baseline: 0.51 ± 1.45	Baseline: 1.60 ± 2.28	Baseline: 2.13 ± 2.39	Baseline: 2.78 ± 2.79
		Follow-up: 0.71 ± 2.00	Follow-up: 1.10^a ± 2.09	Follow-up: 1.43 ± 2.30	Follow-up: 1.70 ± 2.76
Luchesi et al.³² (2013)	PCR	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	NR
		Baseline: 2.96 ± 3.25	Baseline: 2.38 ± 3.00	Baseline: 6.46 ± 1.86
		Follow-up: 1.61 ± 2.55	Follow-up: 1.56^a ± 2.69	Follow-up: 4.86^a ± 2.94
		PS + SRP:	PS + SRP:	PS + SRP:
		Baseline: 2.51 ± 3.76	Baseline: 2.59 ± 3.11	Baseline: 6.39 ± 1.70
		Follow-up: 1.91 ± 2.89	Follow-up: 2.38 ± 2.88	Follow-up: 6.17 ± 1.70
Noro Filho et al.³³ (2012)	PCR	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	NR
		Baseline: 33%	Baseline: 50%	Baseline: 50%
		Follow-up: 0%^a	Follow-up: 18%^a	Follow-up: 18%^a
		SRP:	SRP:	SRP:
		Baseline: 33%	Baseline: 50%	Baseline: 68%
		Follow-up: 0%^a	Follow-up: 8%^a	Follow-up: 25%^a
Theodoro et al.³⁴ (2012)	PCR	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	NR
		Baseline: NR	Baseline: NR	Baseline: NR
		Follow-up: 26.1%	Follow-up: 57%	Follow-up: 57%
		PS + SRP:	PS + SRP:	PS + SRP:
		Baseline: NR	Baseline: NR	Baseline: NR
		Follow-up: 13.6%	Follow-up: 36.4%	Follow-up: 45%
		SRP:	SRP:	SRP:
		Baseline: NR	Baseline: NR	Baseline: NR
		Follow-up: 16%	Follow-up: 36%	Follow-up: 28%
Novaes Jr. et al.³⁵ (2012)	Checkerboard DNA-DNA hybridization technique	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:
		Baseline: 0.27 ± 0.25	Baseline: 18 × 10⁵	Baseline: 10 × 10⁵	Baseline: 2.0 × 10⁵
		Follow-up: 0.02^a,b ± 0.01	Follow-up: 28^a × 10⁵	Follow-up: 30^a × 10⁵	Follow-up: 3.0 × 10⁵
		SRP:	SRP:	SRP:	SRP:
		Baseline: 0.33 ± 0.30	Baseline: 28 × 10⁵	Baseline: 32 × 10⁵	Baseline: 7.0 × 10⁵
		Follow-up: 0.26 ± 0.25	Follow-up: 4.0^a × 10⁵	Follow-up: 5.0^a × 10⁵	Follow-up: 3.0^a × 10⁵
Cappuyns et al.³⁶ (2012)	Checkerboard DNA-DNA hybridization technique	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:
		Baseline: 7 × 10⁶	Baseline: 16 × 10⁶	Baseline: 22 × 10⁶	Baseline: 18 × 10⁶
		Follow-up: 4 × 10⁶	Follow-up: 11 × 10⁶	Follow-up: 19 × 10⁶	Follow-up: 16 × 10⁶
		LT + SRP:	LT + SRP:	LT + SRP:	LT + SRP:
		Baseline: 4 × 10⁶	Baseline: 19 × 10⁶	Baseline: 23 × 10⁶	Baseline: 21 × 10⁶
		Follow-up: 6 × 10⁶	Follow-up: 13 × 10⁶	Follow-up: 16 × 10⁶	Follow-up: 16 × 10⁶
		SRP:	SRP:	SRP:	SRP:
		Baseline: 5 × 10⁶	Baseline: 19 × 10⁶	Baseline: 22 × 10⁶	Baseline: 19 × 10⁶
		Follow-up: 2 × 10⁶	Follow-up: 12 × 10⁶	Follow-up: 18 × 10⁶	Follow-up: 14 × 10⁶
Rühling et al.²⁵ (2010)	PCR	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:
		Baseline: 1.8 × 10⁷	Baseline: 6.3 × 10⁷	Baseline: 5.9 × 10⁷	Baseline: 6.2 × 10⁷
		Follow-up: 1.8 × 10⁷	Follow-up: 6.0 × 10⁷	Follow-up: 6.0 × 10⁷	Follow-up: 5.6 × 10⁷
		SRP:	SRP:	SRP:	SRP:
		Baseline: 1.8 × 10⁷	Baseline: 5.9 × 10⁷	Baseline: 5.9 × 10⁷	Baseline: 6.0 × 10⁷
		Follow-up: 1.8 × 10⁷	Follow-up: 5.9 × 10⁷	Follow-up: 5.9 × 10⁷	Follow-up: 6.1 × 10⁷
Chondros et al.³⁷ (2009)	PCR	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:
		Baseline: 0.5	Baseline: 1.0	Baseline: 1.5	Baseline: 0.7
		Follow-up: 0.4	Follow-up: 1.0	Follow-up: 1.5	Follow-up: 1.25
		SRP:	SRP:	SRP:	SRP:
		Baseline: 0.1	Baseline: 1.2	Baseline: 1.8	Baseline: 1.0
		Follow-up: 0	Follow-up: 0.75	Follow-up: 1.65	Follow-up: 0.4
Polansky et al.³⁸ (2009)	Checkerboard DNA-DNA hybridization technique	NR	NR	NR	NR
Christodoulides et al.³⁹ (2008)	Checkerboard DNA-DNA hybridization technique	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:	aPDT + SRP:
		Baseline: 0.9 ± 2.3	Baseline: 0.3 ± 1.0	Baseline: 1.3 ± 2.3	Baseline: 1.1 ± 1.70
		Follow-up: 0.7 ± 1.9	Follow-up: 0.2 ± 0.6	Follow-up: 1.2 ± 2.2	Follow-up: 1.0 ± 1.7
		SRP:	SRP:	SRP:	SRP:
		Baseline: 0.3 ± 0.8	Baseline: 0.4 ± 1.1	Baseline: 1.70 ± 2.4	Baseline: 1.3 ± 2.1
		Follow-up: 0.3 ± 1.20	Follow-up: 0.3 ± 0.9	Follow-up: 0.5 ± 1.20	Follow-up: 0.5 ± 1.0

PCR, polymerase chain reaction; aPDT, antimicrobial photodynamic therapy; SRP, scaling and root planning; PS, photosensitizer; LT, laser therapy; NR, not reported; US, ultrasonic scaling.

Significant intragroup difference related to baseline.

Significant difference between the groups.

Main outcomes of the study

All studies^{19,20,25,27

–40} reporting periodontal pathogen profile, showed that aPDT application was effective in reducing the counts of all the four major pathogens, except one study,³⁷ in which the counts of Td were significantly increased at follow-up. Four clinical studies^19,30,34,35 showed significant reduction in the counts of Aa, Pg, Tf, and Td for aPDT as an adjunct to SRP as compared with SRP alone at follow-up. Novaes et al.³⁵ showed significant reduction only in Aa counts for aPDT as an adjunct to SRP, whereby counts of Pg, Tf, and Td were only significantly reduced in the SRP group at follow-up. Thirteen studies^{20,25,27
–29,31
–33,36

–40} showed comparable reduction in the counts of bacteria when aPDT as an adjunct to SRP was compared with SRP alone.

In studies^20,34 utilizing PS in their test groups, Theodoro et al.³⁴ showed significant reduction in the Aa, Pg, and Tf counts in the aPDT group as compared with the groups treated with PS and SRP alone. Kolbe et al.²⁰ showed comparable outcome among all the groups for reduction in the Aa, Pg, and Tf counts at follow-up.

In studies^28,36 utilizing LT without PS in their test groups, comparable bacterial counts among aPDT, LT, and SRP groups were shown at follow-up.

One study⁴⁰ utilized curcumin combined with SRP, LT, and aPDT in their test groups. Comparable bacterial counts among all the three groups were reported at follow-up.

Quality of the clinical studies

All the studies^{19,20,25,27

–40} included in this systematic review were randomized controlled trials. In the studies included, randomization was performed by the use of coin toss,^31,35,37,39 computer- generated sequence,^{25,27,32
–34,36} opaque sealed envelopes,¹⁹ and randomized charts.²⁸ Thirteen studies^{19,20,25,27,29,31

–34,36

–39} reported the power and sample size calculation. The quality of six studies^{19,25,28,31
–33} was regarded as high, because these studies received a score of 4 and 5. Eight studies^{20,27,29,34

–37,39} were graded as moderate, receiving a score of 3, whereas three studies^30,38,40 were graded as poor, receiving a score of 2 or 1 (Table 4).

Table 4.

Assessing the Quality of Included Randomized Controlled Trials Using the Jadad Scale

Author et al. (year)	Randomization		Blinding		An account of all patients	Total score
Carvalho et al.²⁷ (2015)	+1	+1	+1	-	-	3
Sreedhar et al.⁴⁰ (2015)	0	0	0	0	+1	1
Birang et al.²⁸ (2015)	+1	+1	+1	-	+1	4
Moreira et al.¹⁹ (2014)	+1	+1	+1	+1	+1	5
Kolbe et al.²⁰ (2014)	+1	+1	+1	-	-	3
Chitsazi et al.²⁹ (2014)	+1	-	+1	-	+1	3
Petelin et al.³⁰ (2014)	+1	-	-	-	+1	2
Jung et al.³¹ (2014)	+1	+1	+1	-	+1	4
Luchesi et al.³² (2013)	+1	+1	+1	-	+1	4
Noro Filho et al.³³ (2012)	+1	+1	+1	-	+1	4
Theodoro et al.³⁴ (2012)	+1	+1	+1	-	-	3
Novaes Jr. et al.³⁵ (2012)	+1	+1	-	-	+1	3
Cappuyns et al.³⁶ (2012)	+1	+1	-	-	+1	3
Rühling et al.²⁵ (2010)	+1	+1	+1	+1	+1	5
Chondros et al.³⁷ (2009)	+1	+1	-	-	+1	3
Polansky et al.³⁸ (2009)	0	0	-	-	+1	1
Christodoulides et al.³⁹ (2008)	+1	+1	-	-	+1	3

Discussion

The present study reviewed the in vivo bactericidal efficacy of aPDT as an adjunct to SRP against four major periodontal pathogens in periodontal disease. All included studies^{19,20,25,27

–40} showed that adjunctive treatment with aPDT reduced periopathogenic microorganism counts in periodontal disease, except that by Chondros et al.³⁷ in which Td counts were significantly raised, and that by Novaes et al.,³⁵ in which the counts of Pg, Tf, and Td were significantly increased in the aPDT group as compared with the SRP group at follow-up. Multiple explanations for the bactericidal effect of aPDT are proposed. These include DNA structural breakdown, efflux of potassium ions, modification of cell membrane proteins, and disruptions in the cell-wall synthesis.^22,42 It is also postulated that PS penetrates the outer membrane of the bacterium by the mechanism of the transfer of hydrogen ions. PS rapidly reacts with oxygen to form reactive oxygen species,^22,43 resulting in bacterial cell destruction.

Results from nearly 24% of the studies^19,30,34,35 that fulfilled our eligibility criteria showed significantly better bactericidal effect for aPDT as an adjunct to SRP than for SRP alone against periodontal pathogens. However, 76% of the studies^{20,25,27
–29,31
–33,36

–40} showed comparable reduction in the counts of Aa, Pg, Tf, and Td when adjunctive use of aPDT was compared with use of SRP alone. It is noteworthy that the included studies had significant heterogeneity in the parameters related to aPDT. For example, the laser wavelengths in the studies,^30,34,35 showing significant reduction in the counts of periodontal pathogens in the aPDT group as compared with the SRP group was 660 nm, in contrast to the studies^{28,29,37
–39} that showed comparable results between aPDT and SRP groups, whose laser wavelength ranged from 670 to 810 nm. Laser wavelength has an overall effect on the bactericidal efficacy of aPDT.⁴⁴ It is possible that increasing the wavelength of lasers in the studies^19,30,34,35 showing significant bactericidal effect of aPDT as compared with SRP could have modified the study outcomes.

Analysis of the studies reviewed also reveals a possible correlation between laser power density and the reduction of periodontal pathogen counts. Clinical studies^19,30,34,35 that showed significant reduction of Aa, Pg, Tf, and Td with the adjunctive use of aPDT as compared with SRP had a higher range of laser power densities (60–400 mW/cm²) than the studies^31,37 showing comparable periodontal bacteria reduction for aPDT and SRP application (13–75 mW/cm²). However, a relationship between laser power density and the bactericidal efficacy of aPDT remains to be established. Further, the type of PS used varied among the included studies and only 5^{19,20,32,33,37} out of 16 studies^{19,20,25,27

–39} reported the concentration of PS, which was 10 mg/mL. The dose of photosensitization in aPDT is a combination of different parameters of PS, light, and its acting time in the tissues and oxygen.^45,46 It is evident from the previous discussion that the variations in light wavelengths, laser power densities, types of PS, and their concentration would have resulted in a nonstandardized overall dose of aPDT in the included studies. Therefore, to assess the efficacy aPDT as an adjunct to SRP in eradicating major periodontal pathogens in periodontal disease, further randomized clinical trials with standardized laser and PS parameters are warranted.

The initiating step for the photosensitizing mechanism is light absorption by the PS resulting in excited singlet state and triplet excited state.⁴⁵ The interaction of a triplet excited state with surrounding molecules causes type I and type II photo-oxidative reactions causing bacterial cell death.⁴⁵ Interestingly, from all the included studies systematically reviewed, two studies^20,34 used only PS in their test group without application of light for eradication of Aa, Pg, and Tf. In these studies,^20,34 all three bacterial counts were comparable in PS application between baseline and follow-up; however, significant reduction in the counts of Aa, Pg, and Tf resulted from aPDT application at follow-up. These outcomes highlight the significance of the combined use of PS and light activation for the bactericidal efficacy of aPDT against Aa, Pg, and Tf.

A higher prevalence of Aa has been reported in tissue samples from aggressive periodontitis patients in comparison with those with chronic periodontitis.⁴⁷ As SRP is the mainstay in the management of chronic periodontitis, it is well recognized that antibiotic treatment as an adjunct to SRP is employed in the management of aggressive periodontitis.^15,48 Interestingly, the type of periodontal disease included in the clinical studies reviewed varied. In 3^19,29,35 out of 16 included studies,^{19,20,25,27

–39} only aggressive periodontitis patients were included, and antibiotic therapy as an adjunct to SRP was not employed. In the presence of the varying prevalence of Aa and different disease conditions (some more favorable than other for the growth of Aa) as reported in the studies included^{19,20,25,27

–40} in the present review, it is impossible to ascertain the bactericidal efficacy of aPDT as an adjunct to SRP against Aa, Pg, Tf, and Td in periodontal disease. Therefore, studies with standardized inclusion criteria and treatment regimens are recommended in this regard.

Conclusions

The bactericidal efficacy of aPDT as an adjunct to SRP against periodontal pathogens in periodontal disease remains unclear, given that the reported findings were inconsistent.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

Appendix A: List of Excluded Studies. Reason for Exclusion is Shown in Parenthesis.

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