Introduction
It is estimated that oral diseases affect around 3.5 billion people worldwide. Untreated
dental caries in permanent and deciduous teeth affect around 8 and 30% of the worldʼs
population, respectively. Similarly, severe periodontal disease compromises the health
of approximately 10% of the population [1]. The unmet demand for dental services is higher in countries with low and medium
incomes and large populations. Furthermore, oral health problems are more prevalent
in individuals with lower income and educational levels, which also makes them socioeconomic
problems [1], [2]. The costs related to oral health problems are enormous. High-income countries spend
5 – 10% of their total health budget on dental care [3]. This is a challenge for developing countries, which makes the need for prevention
and low-cost treatment alternatives to be implemented [2].
Oral infections can compromise not only the health status of the affected individuals
but also their oral health-related quality of life [4]. Gingivitis and periodontitis are inflammatory diseases associated with several
oral microorganisms, such as Porphyromonas gingivalis and Fusobacterium nucleatum, that damage gingival tissues, periodontal ligaments, and alveolar bones [5], [6]. Dental caries is a multifactorial disease associated with oral microorganisms such
as Streptococcus mutans and Streptococcus oralis, which are involved in dental plaque formation [7], [8]. These microorganisms interact with each other forming more complex structures,
such as biofilms, that colonize inert and biological surfaces [9]. Biofilms make it difficult to control infections since they protect
bacteria against antimicrobial agents [10]. Consequently, the interest in more effective drugs with less adverse effects has
grown, like the ones obtained from natural sources [11].
Natural products for therapeutic applications offer biocompatibility, less adverse
reactions, and low cost [12]. In this context, studies on the efficacy of products containing different medicinal
plant extracts commonly used in many countries have been conducted [4], [13]. Topical gels, dentifrices, oral antiseptics, and intracanal medications, obtained
from active principles of various plants such as cloves, pomegranate, mallow, mastic,
chamomile, and propolis, have shown promising effects in the treatment of oral disorders
[14], [15], [16].
Lippia sidoides is an aromatic bush of the Verbenaceae family, typically found in the Northeast region of Brazil (semiarid climate), where
it is popularly known as “pepper-rosmarin”, and available at a low cost [17], [18]. However, the literature points to its occurrence in many countries in the American
continent, such as Mexico, Guatemala, Cuba, Guyana, Venezuela, and Colombia [19]. Essential oils and other products extracted from this plant (alcoholic, hydroalcoholic,
methanolic extracts, among others), which may come from the leaves (dried or fresh),
stalks or stems, flowers, bark and roots, buds, branches, heartwood, and aerial parts
as well as the whole plant, are rich in monoterpenes like thymol and carvacrol, known
for their antimicrobial effect [20], [21]. Extracts from L. sidoides have been largely
used in traditional Brazilian medicine in the development of antifungal and antibacterial
medications for the treatment of skin and mucosal injuries, as it is considered a
natural topic antiseptic [22], [23]. Several relevant biological activities such as antinociceptive, anti-inflammatory,
antioxidant, antidepressant-like, neuroprotective, and gastroprotective effects have
been reported [24], [25], [26], [27], as well as leishmanicidal, trypanocidal, anthelmintic, antimalarial, insecticidal,
and acaricidal activities [25], [28], [29], [30]. Thus, L. sidoides constitutes a promising natural source of new molecules for the treatment of various
diseases and for the control of several
groups of vectors and pests.
Satisfactory results have been reported regarding the application of this plant in
dentistry, especially in the control of supragingival biofilm, also showing antiplaque
and antigingivitis effects in both human [6], [20], [31], [32], [33], [34] and animal studies [35], [36], [37]. In view of the growing interest of researchers from different fields and the large
number of studies due to the great biological potential of this plant, the aim of
the present study was to systematically review the literature in order to analyze
whether L. sidoides is capable of controlling dental plaque, gingivitis, and periodontitis.
Results and Discussion
This study systematically reviewed clinical and animal studies that tested L. sidoides-based products for controlling dental plaque, gingivitis, and periodontitis. From
the electronic search on 4 databases, 711 citations were identified after deduplication,
and their titles and abstracts were examined. Following the eligibility criteria,
17 articles were considered potentially relevant. After that, the full texts were
read and five randomized controlled clinical trials [6], [20], [32], [33], [34] and three animal studies [35], [36], [37] were included in the review. The flowchart of the study selection and the reasons
for exclusions are presented in [Fig. 1].
Fig. 1 Flow diagram of study selection.
Among the randomized controlled clinical trials, two used crossover designs [33], [34]. The samples in all studies were composed of adults whose ages ranged from 18 to
69 years. The animal studies tested L. sidoides-based products in dogs [36], horses [37], or mice [35]. Botelho et al. [35] was the only study to test the association of L. sidoides essential oil with another plant extract (Myracrodruon urundeuva). L. sidoides composed the formulation of oral products such as toothpaste (20%) [32], mouthrinses (0.6, 1, 10, and 20%) [20], [32], [34], [36], [37], and gels (0.5 and 10%) [6], [33], [35], and they were compared to other products containing antimicrobials commonly used
for the treatment of oral diseases, such as chlorhexidine [6], [20], [34] or cetylpyridinium chloride [32], or to placebo formulations without the active natural compounds [33], [36], [37]. The main methodological characteristics and results of the included studies are
presented in [Tables 1] and [2], according to the study design.
Table 1 Main characteristics of the included human studies regarding the effect of Lippia sidoides on dental plaque and periodontal diseases.
|
Study
|
Country/sample size/age/study design/type of Lippia sidoides extract/part of the plant used
|
Test groups (sample size, mean age, regime)/type of solvent in the formulations
|
Control groups (sample size, mean age, regime)
|
Outcomes/duration of intervention/
follow-up
|
Results
|
|
Nunes et al. [32]
|
|
-
Group 2: 20% L. sidoides dentifrice for toothbrushing (n = 21; mean age not reported; 3×/day)
-
Group 3: 20% L. sidoides mouthrinse (n = 21; mean age not reported; 3×/day, 10 mL)
-
Polisorbate 80, sodium lauryl sulfate
|
-
Group 1 (negative control): commercial dentifrice without L. sidoides for toothbrushing (n = 21; mean age not reported; 3×/day)
-
Group 4 (positive control): cetylpyridinium chloride mouthrinse (n = 21; mean age
not reported; 3×/day, 10 mL)
|
-
Supragingival plaque index (OʼLeary et al. 1972)
-
Duration of intervention: 28 days
-
Follow-up: 0, 7, 15, 21, 28 days
|
Plaque index scores at baseline (T0) and day 28 (T28); Δ = difference between final
and initial scores (percentage of increase/reduction)
-
Commercial dentifrice – T0: 71.4; T28: 67.7; Δ = − 3.7 (− 5.2%)
-
L. sidoides dentifrice: T0: 80.2; T28: 31.3; Δ = − 48.9 (− 61%)
-
L. sidoides mouthrinse: T0: 83.1; T28: 31.1; Δ = − 52.0 (− 63%)
-
Cetylpyridinium chloride mouthrinse: T0: 73.7; T28: 43.7; Δ = − 30.0 (− 41%)
Difference of mean plaque index scores between groups at day 28
-
Group 1 × 2: 36.4 – Superior effect for L. sidoides dentifrice versus commercial dentifrice.
-
Group 1 × 3: 36.6 – Superior effect for L. sidoides mouthrinse versus commercial dentifrice.
-
Group 2 × 3: 0.2 – Similar effect for L. sidoides dentifrice and L. sidoides mouthrinse.
-
Group 2 × 4: − 12.4 – Superior effect for L. sidoides dentifrice versus cetylpyridinium chloride mouthrinse.
-
Group 3 × 4: − 12.6 – Superior effect for L. sidoides mouthrinse versus cetylpyridinium chloride mouthrinse.
The authors did not report results regarding adverse effects.
|
|
Botelho et al. [20]
|
|
|
|
-
Supragingival plaque index (Löe, 1967), gingival index (Löe, 1967), gingival bleeding
index (Ainamo and Bay, 1975)
-
Duration of intervention: 7 days
-
Follow-up: 0, 7, 30 days
|
Mean ± SD scores at baseline (T0) and after 7 (T7) and 30 (T30) days; Δ = difference
between final (30 days) and initial scores (percentage of increase/reduction)
-
Plaque index:
-
1% L. sidoides mouthrinse – T0: 1.72 ± 1.56; T7: 0.75 ± 2.70; T30: 0.59 ± 2.08; Δ = − 1.13 (− 65.7%)
-
0.12% chlorhexidine mouthrinse – T0: 1.75 ± 1.27; T7: 0.64 ± 2.49; T30: 0.53 ± 3.07;
Δ = − 1.22 (− 69.7%)
-
Gingival index
-
1% L. sidoides mouthrinse – T0: 1.54 ± 1.66; T7: 0.58 ± 1.39; T30: 0.47 ± 1.92; Δ = − 1.07 (− 69.5%)
-
0.12% chlorhexidine mouthrinse – T0: 1.61 ± 1.64; T7: 0.58 ± 2.43; T30: 0.46 ± 2.12;
Δ = − 1.15 (− 71.4%)
-
Gingival bleeding index
-
1% L. sidoides mouthrinse – T0: 0.67 ± 0.68; T7: 0.36 ± 1.20; T30: 0.28 ± 0.62; Δ = − 0.39 (− 58.2%)
-
0.12% chlorhexidine mouthrinse – T0: 0.62 ± 1.06; T7: 0.37 ± 0.90; T30: 0.25 ± 1.11;
Δ = − 0.37 (− 59.7%)
Significant decrease in plaque index, gingival index, and gingival bleeding index
occurred for both groups in both follow-up periods (all p < 0.001) compared with baseline
scores. No significant difference between groups for any of the clinical parameters
throughout the study.
Adverse effects were reported by 17 participants (62%) in the test group: mild burning
sensation (44%) and mild and transient altered taste (22%).
Adverse effects were reported by 9 participants (32%) in the control group: mild burning
sensation (14%) and mild and transient altered taste (21%).
|
|
Rodrigues et al. [33]
|
|
|
|
-
Supragingival plaque index (Turesky et al. 1970), gingival index (Löe and Silness,
1963), gingival bleeding index (not reported)
-
Duration of intervention: 21 days (1-month washout)
-
Follow-up: 0, 21 days
|
Mean ± SD scores at baseline (T0) and after 21 days (comparison within groups); Δ
= difference between final and initial score (percentage of increase/reduction)
-
Plaque index
-
Placebo gel – T0: 1.61 ± 0.45; T21: 2.56 ± 0.71 (p = 0.0003); Δ = 0.95 (59%)
-
10% L. sidoides gel – T0: 1.71 ± 0.37; T21: 2.39 ± 0.74 (p = 0.0005); Δ = 0.68 (39.7%)
-
Gingival index
-
Placebo gel – T0: 0.05 ± 0.10; T21: 0.31 ± 0.35 (p = 0.0017); Δ = 0.26 (520%)
-
10% L. sidoides gel – T0: 0.03 ± 0.09; T21: 0.13 ± 0.16 (p = 0.0277); Δ = 0.10 (333%)
-
Gingival bleeding index
-
Placebo gel – T0: 0.02 ± 0.05; T21: 0.13 ± 0.14 (p = 0.0049); Δ = 0.11 (550%)
-
10% L. sidoides gel – T0: 0.01 ± 0.04; T21: 0.06 ± 0.08 (p = 0.0277); Δ = 0.05 (500%)
For the L. sidoides gel group, no relevant antiplaque effect was observed. Also, the mean scores for
both gingival and gingival bleeding indexes in baseline and trial end periods did
not differ significantly (p > 0.01), which shows a positive effect on gingivitis.
At day 21, both plaque index (p = 0.3242) and gingival bleeding (p = 0.0707) were
similar between groups. The gingival index was significantly lower for the L. sidoides group (p = 0.0299).
Participants reported no adverse effects and good acceptance of the test gel.
|
|
Rodrigues et al. [34]
|
|
|
-
Negative control: placebo mouthrinse (n = 10; mean age not reported; 2×/day, 10 mL)
-
Positive control: 0.12% chlorhexidine mouthrinse (n = 10; mean age not reported; 2×/day,
10 mL)
|
|
Mean ± SD scores for plaque index at day 3 (subjects started from a plaque-free dentition)
-
Placebo mouthrinse – T3: 4.33 ± 0.35
-
0.12% chlorhexidine mouthrinse – T3: 3.74 ± 0.70
-
10% L. sidoides mouthrinse – T3: 3.50 ± 0.54
Plaque index at day 3 was statistically superior for the placebo group (p = 0.0324)
and did not differ between groups treated with 0.12% chlorhexidine and 10% L. sidoides mouthrinses (p = 0.0867), thus presenting a similar antiplaque effect.
Participants reported no adverse effects and good acceptance of the test mouthrinse.
|
|
Pereira et al. [6]
|
|
|
|
-
Supragingival plaque index (Turesky et al. 1970), gingival bleeding index (Ainamo
and Bay, 1975).
-
Duration of intervention: 90 days
-
Follow-up: 0, 90 days
|
Mean ± SD scores at baseline (T0) and after 90 days (comparison within groups); Δ
= difference between final and initial scores (percentage of increase/reduction)
-
Plaque index
-
Placebo gel – T0: 2.87 ± 1.00; T90: 2.10 ± 0.56 (p > 0.05); Δ = − 0.77 (− 26.8%)
-
2% chlorhexidine gel – T0: 2.94 ± 0.53; T90: 1.43 ± 0.79 (p < 0.05); Δ = − 1.51 (− 51.4%)
-
10% L. sidoides gel – T0: 3.10 ± 0.68; T90: 1.55 ± 0.79 (p < 0.05); Δ = − 1.55 (− 50.0%)
-
Gingival bleeding index
-
Placebo gel – T0: 0.48 ± 0.08; T90: 0.38 ± 0.12 (p > 0.05); Δ = − 0.10 (− 20.8%)
-
2% chlorhexidine gel – T0: 0.52 ± 0.13; T90: 0.25 ± 0.16 (p < 0.05); Δ = − 0.27 (− 51.9%)
-
10% L. sidoides gel – T0: 0.36 ± 0.10; T90: 0.23 ± 0.09 (p < 0.05); Δ = − 0.13 (− 36.1%)
The L. sidoides group presented a significant reduction for both indexes. The mean values for both
indexes at day 90 were similar to the positive control and significantly lower than
the placebo group. These results show that the 10% L. sidoides gel is an efficient antiplaque and antigingivitis agent.
Good acceptance and no adverse effects for the L. sidoides gel were reported.
|
Table 2 Main characteristics of the included animal studies regarding the effect of L. sidoides on dental plaque and periodontal diseases.
|
Study
|
Country/sample/type of LS extract/part of the plant used
|
Type of LS extract/test groups (sample size, regime)/type of solvent in the formulations
|
Control groups (sample size, regime)
|
Outcomes/duration of intervention/
follow-up
|
Results
|
|
Girão et al. [36]
|
|
|
|
-
Dental plaque, gingivitis, calculus, inflammatory infiltrate.
-
Duration of intervention: 15 days
-
Follow-up: 0, 15 days
|
Median scores at baseline (T0) and after 15 days (T15) (comparison within groups)
Control group
-
Calculus – T0: 3; T15: 3 (p = 0.50)
-
Gingivitis – T0: 3; T15: 3 (p = 0.18)
-
Dental plaque – T0: 2.5; T15: 2 (p = 0.50)
-
Inflammatory infiltrate – T0: 2.5; T15: 2.5 (p = 0.56)
L. sidoides group
-
Calculus – T0: 2.5; T15: 1.5 (p = 0.010)
-
Gingivitis – T0: 2; T15: 1 (p = 0.002)
-
Dental plaque – T0: 4; T15: 2 (p = 0.002)
-
Inflammatory infiltrate – T0: 2.5; T15: 2.0 (p = 0.047)
The scores for all parameters in the L. sidoides group reduced significantly from day 0 to day 15 (p < 0.05), which was not observed
in the control group (p > 0.18). At day 15, the L. sidoides group presented lower scores for calculus (p = 0.005) and gingivitis (p = 0.0005)
compared to the control group. Only the L. sidoides group showed a significant decrease of the inflammatory infiltrate score.
The dogs did not present any side effects to the treatment, such as bad breath or
irritation in the oral cavity.
|
|
Botelho et al. [35]
|
|
-
Experimental periodontitis mice treated with 5% M. urundeuva gel (n = 6; 3×/day) (group MU)
-
Experimental periodontitis mice treated with 0.5% L. sidoides gel (n = 6; 3×/day) (group LS)
-
Experimental periodontitis mice treated with combined 5% M. urundeuva and 0.5% L. sidoides gel (n = 6; 3×/day) (group MU + LS)
-
Polisorbate 80
|
-
Nonexperimental periodontitis mice; no treatment (n = 6) (group NEPD)
-
Experimental periodontitis mice; no treatment (n = 6) (group NT)
-
Experimental periodontitis mice treated with vehicle gel (n = 6; 3×/day) (group VH)
-
Experimental periodontitis mice treated with topical 10% doxycycline gel (n = 6; 3×/day)
(group DOX)
|
-
Horizontal alveolar bone loss, inflammatory cell influx, neutrophil infiltration,
detection of IL-1β and TNF-α
-
Duration of intervention: 11days
-
Follow-up: 0, 11 days
|
Mean ± SD scores after 11 days (*p < 0.05 compared to non-treated group)
Alveolar bone loss
Neutrophil infiltration
Cytokine IL-1β level
Cytokine TNF-α level
Group MU + LS presented a reduction of inflammatory cell influx and a partial preservation
of the cementum and the alveolar process [score: 1 (0 – 1)] when compared to the group
VH, which presented intense inflammatory cell influx, cementum destruction, and complete
alveolar process resorption [score: 3 (2 – 3)].
Among the test groups, the best anti-inflammatory effect was observed for the group
MU + LS, which presented significantly reduced (p < 0.05) alveolar bone loss, inflammatory
cell infiltration, and a partial preservation of the cementum and the alveolar process,
neutrophil infiltration, and cytokine levels in gingival tissue when compared to the
vehicle-treated group. No significant anti-inflammatory effect was observed for the
groups treated with 0.5% L. sidoides gel.
The authors did not report results regarding adverse effects.
|
|
Alencar-Araripe et al. [37]
|
|
|
|
-
Calculus, gingivitis.
-
Duration of intervention: 14 days
-
Follow-up: 0, 3, 7, 14 days
|
Mean ± SD scores at baseline (T0) and after 14 days (T14) (comparison within groups)
Incisors calculus:
Canine calculus:
Gingivitis:
Calculus scores decreased significantly from day 0 to day 14 in the EOLS group, which
was not observed in the control group.
The equines did not present any side effects to the treatment, such as bad breath
or irritation in the oral cavity.
|
Inadequate control of dental biofilm represents a common etiological factor for both
dental caries and periodontal disease, the most prevalent oral pathological condition.
Although mechanical control of biofilm is considered the main method for preventing
and treating such diseases [38], many factors limit the correct execution of the brushing technique by the population,
such as lack of knowledge and motor problems. Therefore, the use of chemical agents
as auxiliary means is recommended [13]. In this context, it is essential that an oral hygiene product modifies the structure
of the biofilm by making microorganisms susceptible to the action of antimicrobial
agents [39]. The flavonoids and terpenes present in L. sidoides extracts are responsible for its antimicrobial effects. Characteristics of lipophilicity
allow these components to interact with the microbial cells, leading to
the microorganism death by increasing the permeability of their membranes [40], [41]. L. sidoides extracts are rich mainly in thymol and carvacrol, known for their antimicrobial properties
[20], [21], whose mechanisms of action are characterized by the dispersion of the polypeptide
chains present in the cell membranes [20], [21], causing cell wall damage and rupture of the membranes, extravasation of cytoplasmic
content, inhibition of efflux pumps, reduction of bacterial motility, prevention in
the formation and rupture of preformed biofilms, and inhibition of membrane ATPases
[42].
The content and proportion of thymol and carvacrol in L. sidoides can vary from 30 – 95%, depending on the region of harvest, season during which the
extracts are obtained, soil and weather conditions, water availability, humidity [43], [44], as well as the part of the plant used. The literature shows that greater amounts
of these components are found especially in the essential oil obtained from the plant
leaves [45]. This may explain the reason why, except for the study of Nunes et al. [32], all studies used the L. sidoides essential oil extracted from leaves in their methodologies. In the included studies,
thymol was the major constituent of the essential oil, presenting different concentrations
of 56.67 [20], 58.7 [6], 66.67 [36], and 70.97% [37]. Carvacrol was the second most concentrated component, presenting concentrations
of 16.73% [20] and 17.1% [6]. Minor constituents included p-cymene (7.13 [20], [36], 7.51 [37], and 8.98% [6]) and caryophyllene (8.30 [37], 10.3 [6], and 11.73% [36]). Other minor components are cited, which vary among reports, and each of them constituted
less than 3% of the extracts used.
All human studies tested the ability of L. sidoides-based products to reduce dental plaque. After a 28-day period of treatment [32], superior reduction in the dental plaque index was observed for both 20% L. sidoides dentifrice (Δ = − 48.9; − 61%) and mouthrinse (Δ = − 52.0; − 63%) when compared to
cetylpyridinium chloride mouthrinse (Δ = − 30.0; − 41%). A significant reduction in
the dental plaque index was observed in subjects after 7 days using a 1% L. sidoides mouthrinse (Δ = − 1.13; − 65.7%) [20], presenting similar results of participants treated with 0.12% chlorhexidine digluconate
mouthrinse (Δ = − 1.22; − 69.7%). In the study of Rodrigues et al. [34], two groups of subjects presenting a plaque-free dentition were included. After
3 days, the mean dental plaque scores of both groups treated either with a 10% L. sidoides (3.50 ± 0.54) or a 0.12%
chlorhexidine digluconate mouthrinse (3.74 ± 0.70) were similar (p = 0.0867) and
significantly lower than the group that used a placebo mouthrinse (4.33 ± 0.35). A
10% L. sidoides gel used for toothbrushing produced a significant reduction in the dental plaque
index after 90 days (Δ = − 1.55; − 50.0%), similar to a 2% chlorhexidine gel (Δ =
− 1.51; − 51.4%) and superior to the reduction observed for the group treated with
a placebo gel (Δ = − 0.77; − 26.8%) [6]. These results suggest a favorable potential for using L. sidoides in the oral cavity to control dental plaque.
Three human studies evaluated gingival outcomes. A significant reduction (p < 0.001)
in both gingival (Δ = − 1.07; − 69.5%) and gingival bleeding indexes (Δ = − 0.39;
− 58.2%) was observed in subjects after a 7-day period using a 1% L. sidoides mouthrinse [20], presenting similar results to participants treated with 0.12% chlorhexidine digluconate
mouthrinse (ΔGI: − 1.15; − 71.4%; ΔGBI: − 0.37; − 59.7%). A 10% L. sidoides gel used for toothbrushing produced a significant reduction in the gingival bleeding
index after 90 days (Δ = − 0.13; − 36.1%), similar to a 2% chlorhexidine gel (Δ =
− 0.27; − 51.9%) and superior to the reduction observed for the group treated with
a placebo gel (Δ = − 0.10; − 20.8%) [6]. In the study of Rodrigues et al. [33], both gingival and gingival bleeding indexes assessed at baseline did not differ
significantly (p > 0.01) after a 21-day period
of treatment with 10% L. sidoides gel [33], which shows a positive effect on gingivitis. These results highlight the performance
of L. sidoides-based products against gingival inflammation.
In two studies [36], [37], animals presenting detectable plaque bacteria, calculus, and signs of gingivitis,
such as redness and gingival edema, were treated with a 0.6% L. sidoides mouthrinse for 2 weeks. A significant reduction in scores of plaque [36], calculus [36], [37], gingivitis [36], [37], and inflammatory infiltrate in marginal gingiva [36] was observed, being superior to the groups treated with placebo products ([Table 3]). In the study of Girão et al. [36], changes in inflammatory infiltration occurred in both intensity and type of cells.
A predominance of polymorphonuclear cells after treatment with the herbal mouthrinse
was observed when compared to the infiltrate rich
in lymphocytes and plasma cells at baseline. These cells are related to the destruction
of bacteria by phagocytosis, as well as to the activation of fibroblastic factors,
allowing collagen formation. Such results corroborate with the human studies and reinforce
the potential that L. sidoides-based products have in maintaining and recovering gingival health by assisting in
plaque control and reducing the formation of dental calculus and signs of gingivitis.
Table 3 Risk of bias assessment for the included animal studies.
|
Selection bias
|
Performance bias
|
Detection bias
|
Attrition bias
|
Reporting bias
|
|
Animal studies
|
Random sequence generation
|
Baseline characteristics
|
Allocation concealment
|
Random housing
|
Blinding
|
Random outcome assessment
|
Blinding
|
Incomplete outcome data
|
Selective reporting
|
|
Girão et al. [36]
|
High
|
Uncertain
|
High
|
High
|
Low
|
High
|
Low
|
Uncertain
|
Low
|
|
Botelho et al. [35]
|
High
|
Uncertain
|
High
|
High
|
High
|
High
|
High
|
Uncertain
|
Low
|
|
Alencar-Araripe et al. [37]
|
Uncertain
|
Uncertain
|
Uncertain
|
High
|
High
|
High
|
Low
|
Uncertain
|
Low
|
Mechanical plaque control by the participants was allowed in three studies [6], [20], [32]. Such a procedure could raise the possibility that the reduction in dental plaque
and gingival inflammation was caused by the mechanical toothbrushing. Although, in
the aforementioned studies, all test and control groups performed similar toothbrushing
either with L. sidoides products or commercial dentifrices given to the participants. Thus, possibly, the
differences observed among groups are due to the active compounds present within each
tested product. In two studies [33], [34], mechanical plaque control was not allowed during the experimental period, which
provides information regarding the efficacy of the tested products in areas of inadequate
plaque control, where dental biofilms are unaffected by the mechanical toothbrushing.
In
the study of Rodrigues et al. [33], the test gels were applied by using a tooth shield, which protected the test area
from the action of saliva and the participants refrained from brushing. Although no
relevant antiplaque effect was observed for the L. sidoides-based product (10%), the herbal gel was effective in the control of gingival inflammation.
The authors mention that toothbrushing and solubilization by saliva may play an important
role in allowing an efficient antiplaque effect of the herbal product.
One study tested L. sidoides-based products by using an experimental periodontitis model in mice [35]. A combined 0.5% L. sidoides essential oil and 5% M. urundeuva gel applied 3 times a day for 11 days significantly reduced (p < 0.05) alveolar bone
loss, neutrophil infiltration, inflammatory cell influx, and cytokine levels (TNF-α and IL-1β) in gingival tissue, as well as promoted a partial preservation of the cementum and
alveolar process, when compared to the group of animals treated with a placebo gel
containing only the vehicle. These results demonstrate the potential protective effect
of the tested gel against periodontal tissue destruction. The protective mechanism
against alveolar bone resorption by the essential oils, especially the thymol fraction,
seems to be related to a significant antimicrobial activity against the periodontal
bacteria, the reduction of the inflammatory reaction, and the action
directly on the osteoclast cells, influencing the balance of calciotropic hormones
[46]. In the mentioned study [35], the group of animals treated with 10% doxycycline gel (positive control) also presented
a significant reduction (p < 0.05) in alveolar bone loss and inflammatory cell influx
and promoted a partial preservation of the cementum and alveolar process. Nevertheless,
no statistical comparison among test and positive control groups was presented. The
synergistic effect of the combined gel allowed better results than the gels containing
the isolated extracts; no significant anti-inflammatory effect was observed for the
groups treated with 0.5% L. sidoides gel or 5% M. urundeuva gel.
The literature presents two other animal studies that tested L. sidoides gels against alveolar bone resorption in mice submitted to a ligature-induced periodontal
disease [47], [48]. The authors observed similarities to the aforementioned study [35], such as control of the inflammatory process in the periodontal region, with a reduction
of proinflammatory cytokines such as TNF-α and IL-1β, and inhibition of neutrophil infiltration on the gingival tissue, shown by the reduction
of myeloperoxidase activity. These studies were not included in the present review
because only separate bioactive constituents of the L. sidoides essential oil were used for the gel formulations, thymol and carvacrol.
Chlorhexidine digluconate is considered the gold standard chemical agent for controlling
bacterial proliferation in the oral cavity [49], [50]. However, undesirable adverse effects such as ageusia, dysgeusia, tooth staining,
supragingival calculus formation, and xerostomia have been reported after prolonged
use [51]. In the study of Botelho et al. [20], burning sensation and altered taste were reported by participants treated with
both 1% L. sidoides (n = 17; 62%) and 0.12% chlorhexidine (n = 9; 32%) mouthrinses. The authors could
not speculate whether the higher occurrence of those effects in the test group was
related to the essential oil components (thymol/carvacrol) or to other substances
within the mouthrinse formulation, such as polysorbate 80 and citric acid. In addition,
the authors point out that studies with different formulations are needed
in order to respond to this question. However, the adverse effects were of transient
nature, not requiring specific interventions. Good acceptance and no adverse effects
for the L. sidoides products were reported in three human studies [6], [33], [34] that tested L. sidoides products at a higher concentration (10%). The herbal products were not able to cause
adverse effects such as abscesses, ulcerations, and allergic reactions, but the authors
did not mention whether the patients complained of burning or change in taste [6], [33], [34]. Also, the animals in two studies [36], [37] did not present any side effects to the treatment, such as bad breath or irritation
in the oral cavity. Although reports of adverse effects in the various
formulations of L. sidoides extracts tested do not contraindicate their use, there is a need to observe these
long-term effects as most studies evaluated only the first hours or days of use. Thus,
such qualitative results would provide valuable information on the safety of those
products.
The antimicrobial products were used in the included studies for periods varying from
3 to 90 days. Satisfactory results were observed even in reduced periods of use. The
treatment with 10% L. sidoides mouthrinse for 3 days [34] significantly reduced dental plaque. After a 7-day treatment with 1% L. sidoides mouthrinse [20], a significant reduction in plaque, gingival, and bleeding indexes was observed,
and the improvement in such parameters remained constant after 30 days. The results
achieved in both studies were statistically similar when compared to the treatment
performed with 0.12% chlorhexidine mouthrinse for the same periods [20], [34]. Only two studies included long-term follow-up evaluations.
Solvents are needed to dissolve essential oils within hygiene products. Among the
included studies, Polysorbate 80 [20], [32], [35] and ethyl alcohol [6], [33], [34] were the most used diluents. In a recent in vitro study, Barreto et al. [52] evaluated an experimental denture cleanser containing L. sidoides essential oil varying its formulation by using different solvents. The authors proposed
the use of sodium lauryl sulfate for being a low-cost surfactant commonly used in
oral hygiene products, which requires a lower L. sidoides essential oil/diluent ratio (1 : 2) for proper essential oil dilution. Although Polysorbate
80 and alcohol were the most common diluents used in previous L. sidoides studies, Barreto et al. [52] mentioned that higher L. sidoides essential oil/diluent ratios are needed for Polysorbate 80 (1 : 10) and ethyl alcohol
(1 : 18) in order to provide a proper encapsulation mechanism of the essential oil.
Also, the authors reported the unpleasant taste of Polysorbate 80 and the dissolutive
and plasticizing effect of ethyl alcohol on dental polymers commonly used for prosthodontic
rehabilitation. Thus, future clinical studies may consider using different diluents
such as sodium lauryl sulfate within the oral hygiene products formulation.
The risk of bias assessment of all included randomized controlled clinical trials
is presented in [Fig. 2]. Three studies specified the method used for random sequence generation [20], [33], [34], and none reported how the concealment of participant allocation in the groups was
performed, which does not make clear whether the randomized inclusion of participants
took place through valid methodologies. Although only one study [20] presented statistical comparison of the groupsʼ sociodemographic characteristics,
which increases the possibility of heterogeneity among experimental groups at the
beginning of treatment, all studies showed that the groups were similar regarding
the outcome variables at baseline and point out that such results indicate effectiveness
of the randomization performed. Thus, uncertain risk bias was conferred
for the criteria randomization process in all studies presented. Most studies
reported the methods used for blinding participants and clinicians involved, except
for the oldest study [32]. Thus, in general, the evaluations and treatments were conducted without prior knowledge
of the nature of the products used. In three studies [20], [32], [33], considerable losses to follow-up occurred. Although the number of lost participants
was balanced among the groups in each study, it is unclear if the reasons for the
losses are associated with the treatment performed, such as dissatisfaction or difficulty
of compliance with the treatments, which represent important results for the evaluation
of the therapy tested. Also, no appropriate analysis was performed to assess the impact
on the final result of the failure to analyze participants in two studies [32], [33]. Due to this, a high risk of bias was detected for the criteria regarding deviations
from the intended interventions. All of them reported the results regarding the outcomes
mentioned in their objectives; the methods used for measuring the outcomes were appropriate
and similar among experimental groups, as well as conducted by assessors unaware of
the intervention received by the participants, thus conferring a low risk for both
criteria missing outcome data and measurement of the reported result. However, no
study mentioned registration of its research protocol in databases for clinical trials,
which conferred an unclear risk of bias for the criteria selection of the reported
results. For the two crossover studies [33], [34], a low risk of bias was conferred for the criteria period and carryover effects,
which means differences between the periods of
evaluation are due to the interventions being compared, as well as it is unlikely
that the effects of the tested interventions given in the first period persisted into
the second period, thus interfering with the effects of the second intervention.
Fig. 2 Risk of bias assessment for the included randomized controlled clinical trials.
The risk of bias assessment of the included animal studies is presented in [Table 3]. Uncertain or high risk of selection bias was found for the animal studies; random
sequence generation and animal concealment were not performed [35], [36], inappropriate methods were used [36], or insufficient information was provided [37]. Therefore, the methodologies may not have ensured equality among groups. Although
researchers were blinded in two studies [36], [37], random methods for animal housing or outcome assessments were not performed in
any study, which implies a high risk of performance and detection bias. It is not
clear if losses occurred in the study samples due to causes related to the treatments.
Nevertheless, there was not a selective report of results in all studies,
implying a low risk of reporting bias.
The present database search identified studies testing L. sidoides extracts that broaden the understanding of the biological activities of this plant,
as well as the possibilities of using it against different oral pathological conditions.
A significant reduction of the salivary level of S. mutans in children with caries [43], [53] has been demonstrated in two clinical studies. The antimicrobial action of L. sidoides was demonstrated against various Candida species [8], [21], [54], [55] and microorganisms isolated from root canals such as Enterococcus faecalis
[56]. The antinociceptive and anti-inflammatory action of L. sidoides, as well as its low toxicity, have been demonstrated [21], [24], [57], [58]. Although in vitro studies were not included in the present review, as well as in vivo studies that did not evaluate dental plaque and periodontal outcomes, their results
may guide clinical trials testing L. sidoides-based products against dental caries and endodontic infections, and in the prevention
and treatment of denture-related infections, as well as in pain control of the stomatognathic
system such as temporomandibular dysfunctions.
Plant-based dental products may lead to the preference of users for the most sustainable
and natural appeal. In general, no controversial results between clinical and animal
studies included in this review were observed, and the findings suggest a favorable
potential for using L. sidoides in oral hygiene products for controlling dental plaque and gingival inflammation.
As most studies tested the essential oil of L. sidoides, future studies could be conducted to evaluate different types of extracts, such
as alcoholic, hydroalcoholic, methanolic, hexanic, aqueous, and dry, as well as tincture
or tea. Clinical studies evaluating different formulations containing L. sidoides extracts against periodontitis are required. Slow-release devices of antimicrobials
for subgingival positioning could be investigated. Also, only two in vivo studies in the literature testing L. sidoides extracts compared oral products containing different natural extracts
[35], [47]. Thus, there is a need for in vivo studies comparing oral products containing L. sidoides crude extracts to other natural products used for oral diseases.
Although most studies have evaluated plaque and periodontal outcomes, a wide variety
of evaluation methods, formulations, concentrations of L. sidoides extracts, and vehicles for the test substances were used in their methodologies.
Differences in the study protocols, control substances, duration of interventions,
and follow-up made comparison between studies difficult; thus, no meta-analysis of
the results was performed. In addition, four studies [32], [33], [34], [35] lack information regarding the chemical composition of the L. sidoides extracts used in the formulations. Quantification and standardization of bioactive
compounds should be sought for future studies.
Due to the quality of the evidence available, these results should be interpreted
carefully, considering the numerous methodological flaws presented by the studies.
Most of the included human studies presented an overall high or unclear risk of bias,
which means that L. sidoides-based oral products may be indicated carefully but not on a regular basis, as the
evidence is not strong enough. More clinical studies, with greater methodological
rigor and control of biases, are necessary in order to enable the reliable use in
humans in clinical practice. As human and animal studies were included, this systematic
review could not have its study protocol registered in a public database. Considering
the importance of such registration for the scientific community, this can be addressed
as a limitation of the present study. Although, for transparency, the review protocol
used is available upon request to the corresponding author.
Materials and Methods
The checklist of PRISMA-P 2015 [59] was used to conduct this systematic review of human and animal studies, which was
based on the question “Are L. sidoides extracts efficient for controlling dental plaque, gingivitis and periodontitis?”.
For the human studies, the aspects of the PICO questions were as follows: patients = subjects
of any age presenting dental plaque, gingivitis, and/or periodontitis; intervention = oral
products containing L. sidoides extracts; comparison = placebo or oral products containing any concentration of cetylpyridinium
chloride, chlorhexidine, or other similar substances used for oral hygiene; outcomes = changes
in dental plaque, gingival, bleeding, and periodontal indexes as well as calculus.
For the animal studies, the aspects of the PICO questions were as follows: problem = animals
presenting dental plaque, calculus, gingivitis, or submitted to a ligature-induced
periodontal disease; intervention = products containing L. sidoides extracts; comparison = placebo or oral products containing any type of antimicrobials
such as doxycycline; outcomes = changes in dental plaque, gingival, bleeding, and
periodontal indexes as well as calculus and inflammatory responses.
This systematic review was not previously registered since it included both human
and animal studies. Articles were selected by searching the databases Medline/PubMed,
SCOPUS, BVS, and Web of Science. The search strategy was librarian assisted and, in
order to make the search more comprehensive, MeSH terms were combined with key words
and synonyms and searched in different systematic reviews. The following search strategy
was constructed for Medline/PubMed (May 6, 2021) and adapted to the different databases:
(Lippia[Mesh] OR Lippia OR Lippias OR “Lippia sidoides”) AND (“Oral Cavity” OR “Cavity,
Oral” OR Tooth[Mesh] OR Tooth OR Teeth OR Saliva[Mesh] OR Saliva OR Salivas OR Mouth[Mesh]
OR Mouth OR “Dental Plaque”[Mesh] OR “Dental Plaque” OR “Plaque, Dental” OR Antiplaque
OR Pathogen OR Pathogens OR Microorganism OR Microorganisms OR Antimicrobial OR Biofilms[Mesh]
OR Biofilms OR Biofilm OR Antibiofilm OR “Bacterial Adhesion” OR “Dental Deposits”[Mesh]
OR “Dental Deposits” OR
“Materia Alba” OR “Deposits, Dental” OR “Dental Deposit” OR “Deposit, Dental”
OR Gingivitis[Mesh] OR Gingivitis OR Gingivitides OR “Gingival Diseases”[Mesh] OR
“Gingival Diseases” OR “Disease, Gingival” OR “Diseases, Gingival” OR “Gingival Disease”
OR Antigingivitis OR Periodontitis[Mesh] OR Periodontitis OR Periodontitides OR Pericementitis
OR Pericementitides OR “Periodontal Diseases”[Mesh] OR “Periodontal Diseases” OR “Disease,
Periodontal” OR “Diseases, Periodontal” OR “Periodontal Disease” OR Parodontosis OR
Parodontoses OR “Pyorrhea Alveolaris” OR “Alveolar Bone Loss”[Mesh] OR “Alveolar Bone
Loss” OR “Alveolar Bone Losses” OR “Alveolar Process Atrophy” OR “Alveolar Process
Atrophies” OR “Alveolar Resorption” OR “Alveolar Resorptions” OR “Resorption, Alveolar”
OR “Resorptions, Alveolar” OR “Bone Loss, Periodontal” OR “Bone Losses, Periodontal”
OR “Periodontal Bone Losses” OR “Periodontal Bone Loss” OR “Periodontal Resorption”
OR “Periodontal Resorptions” OR
“Resorption, Periodontal” OR “Alveolar Bone Atrophy” OR “Alveolar Bone Atrophies”
OR “Bone Atrophies, Alveolar” OR “Bone Atrophy, Alveolar” OR “Bone Loss, Alveolar”
OR Disinfectants[Mesh] OR Disinfectants OR Disinfectant OR Disinfection OR Biocides
OR Biocide OR Cleaner OR Cleaners OR Cleanser OR Cleansers OR Sanitizer OR Sanitizers
OR Sanitization OR Decontamination[Mesh] OR Decontamination OR Dentifrices[Mesh] OR
Dentifrices OR Dentifrice OR “Dental Polishes” OR “Polishes, Dental” OR Toothpastes[Mesh]
OR Toothpastes OR Toothpaste OR Paste OR Toothbrush OR Toothbrushing[Mesh] OR Toothbrushing
OR Toothbrushings OR Mouthwashes[Mesh] OR Mouthwashes OR “Mouth Rinse” OR “Mouth Rinses”
OR “Rinse, Mouth” OR “Rinses, Mouth” OR “Mouth Bath” OR “Bath, Mouth” OR “Baths, Mouth”
OR “Mouth Baths” OR “Mouth Wash” OR “Wash, Mouth”).
The identified articles had their titles and abstracts read by two independent reviewers
(E. L. A., R. R. R.) who used the following aspects for eligibility: type of oral
condition assessed (dental plaque, gingivitis, and/or periodontitis); type of intervention
tested (L. sidoides extracts); type of study (interventional clinical and animal studies). Studies evaluating
natural or synthetic bioactive constituents of L. sidoides, review articles, observational studies, letters to the editor, conference abstracts,
and case reports were excluded. No limit of language, date, intervention, or follow-up
periods was applied. The complete texts of the relevant and potentially relevant reports
were obtained and evaluated by the same reviewers. Only randomized controlled trials
with no restriction for parallel and crossover designs were considered in this review.
Possible disagreements regarding inclusion of an article were discussed and, when
necessary, a third reviewer
was involved for the final decision (F. D. S.). The reference list containing
the identified review articles on related topics and each included article were manually
screened to search for possible studies not found. Kappa scores of 0.93 (titles and
abstracts) and 0.88 (full texts) were reached by the reviewers (E. L. A., R. R. R.).
For the included human studies, data were extracted regarding authors, year of publication,
country and setting where the study took place, sample size, mean age of participants,
study design, type of L. sidoides extract used, part of the plant used to obtain the extracts, type of solvent in the
oral product formulations, interventions (test and control groups), regime of use
and duration for each intervention, follow-up periods, outcomes related to dental
plaque, gingival, and/or periodontal indexes, and main results for each outcome, including
adverse events for both test and control groups, when reported. For the included animal
studies, data were extracted regarding authors, year of publication, country where
the study took place, sample size, type of L. sidoides extract used, part of the plant used to obtain the extracts, type of solvent in the
product formulations, interventions (test and control groups), regime of use and duration
for each intervention,
follow-up periods, outcomes related to dental plaque, gingival, and/or periodontal
indexes, calculus, inflammatory responses, and main results for each outcome, including
adverse events for both test and control groups, when reported. All data were extracted
in an electronic spreadsheet by two independent researchers (R. R. R., E. L. A.).
In case of disagreements, a third researcher was involved for decision making (F. D. S.).
The methodological quality of all included studies was assessed by two independent
reviewers (F. D. S., A. V. P.). For the randomized controlled trials, the risk of
bias was evaluated using the RoB2 tool [60] considering the following domains: randomization process, period and carryover effects,
deviations from the intended interventions, missing outcome data, measurement of the
outcome, and selection of the reported results. For each domain, a positive mark was
used to indicate a low risk of bias, a negative sign for a high risk of bias, and
an exclamation mark when some concerns were identified. For the animal studies, the
SYRCLE tool [61], which is based on the Cochrane Rob tool, was used to evaluate selection bias (random
sequence generation, baseline characteristics, and allocation concealment), performance
bias (random housing and blinding of participants/personnel), detection bias (random
outcome assessment
and blinding of outcome assessment), attrition bias (incomplete outcome data),
and reporting bias (selective reporting). For each parameter, the risk of bias was
considered high, low, or unclear in cases of non-existing information or when no sufficient
details were provided. In cases of disagreement, a decision was made by consensus
between reviewers.
The selected studies presented considerable heterogeneity regarding design, methods,
outcome variables, and data variability making meta-analysis inappropriate. Thus,
the characteristics of the studies were summarized descriptively.
