Effects of novel dental chews on oral health outcomes and halitosis in adult dogs

Abstract

Periodontal disease (PD) is the most common clinical condition occurring in adult dogs. The objective of this study was to evaluate the benefits of daily dental chew administration on oral health outcomes in adult dogs. Twelve adult (mean age = 5.31 ± 1.08 yr; mean BW = 13.12 ± 1.39 kg) female beagle dogs were used in a replicated 4 × 4 Latin square design consisting of 28-d periods. On day 0 of each period, teeth were cleaned by a veterinary dentist blinded to treatments. Teeth then were scored for plaque, calculus, and gingivitis by the same veterinary dentist on day 28 of each period. Breath samples were measured for malodor (volatile sulfur compounds) on days 1, 7, 14, 21, and 27 of each period. All dogs consumed the same commercial dry diet throughout the study. Control dogs were offered the diet only (CT), while treatment groups received the diet plus one of three dental chews. Two novel chews (Bones & Chews Dental Treats [BC]; Chewy, Inc., Dania Beach, FL and Dr. Lyon’s Grain-Free Dental Treats [DL]; Dr. Lyon’s, LLC, Dania Beach, FL) and a leading brand chew (Greenies Dental Treats [GR]; Mars Petcare US, Franklin, TN) were tested. Each day, one chew was provided 4 h after mealtime. All tooth scoring data were analyzed using the Mixed Models procedure of SAS (version 9.4; SAS Institute, Cary, NC). Halimeter data were analyzed using repeated measures using the Mixed Models procedure of SAS and testing for differences due to treatment, time, and treatment * time interaction. Data are reported as LS means ± SEM with statistical significance set at P < 0.05. DL performed at the same level as the leading brand, GR, as both resulted in lower (P < 0.05) plaque coverage and thickness scores, calculus coverage scores, and day 27 volatile sulfur concentrations compared with CT. Additionally, DL reduced (P < 0.05) volatile sulfur compounds on day 14 when compared with CT. BC reduced (P < 0.05) calculus coverage and day 27 volatile sulfur concentrations compared with CT. Our results suggest that the dental chews tested in this study may help slow the development and/or progression of PD in dogs.

Introduction

Periodontal disease (PD) is the most common clinical condition in adult dogs, affecting 75% to 85% of dogs over the age of 3 yr (Stella et al., 2018; Summers et al., 2019) and is suggested to be the most undertreated animal health condition (Niemiec, 2008). PD is characterized by both gingivitis and periodontitis, the former condition is inflammation of the gingiva (gums) and the latter is inflammation of the nongingival periodontal tissues (the periodontal ligament and the alveolar bone) (Harvey, 2005). These conditions can develop as a result of plaque buildup on the teeth, which harbor bacteria that can cause an immune response and inflict damage to oral tissues (Stepaniuk, 2019). When allowed to progress, PD can result in tooth loss, bone loss, halitosis (oral malodor), and chronic pain, which can lead to reduced food intake (Harvey, 2005). Canine PD incidence increases with age and as the average life expectancy of dogs continues to rise, it is increasingly important to maintain the oral health of dogs to prevent discomfort and ensure a good quality of life throughout their entire lifetime (Harvey et al., 1994).

Microbiota that inhabit the mouth are known to cause immune and inflammatory responses, inflicting damage to oral tissues (Stepaniuk, 2019). Moreover, halitosis (oral malodor or bad breath) is often associated with PD and is caused by the microbial metabolism of proteinaceous substrates in the mouth. Volatile sulfur compounds generated by these bacteria cause malodor and are indicative of PD pathogenesis (Culham and Rawlings, 1998). By reducing the buildup of microbiota and food particles remaining in the mouth, halitosis may be reduced, reflecting a decreased risk of PD progression. The reduction of volatile sulfur compounds may not only reflect a reduction in PD but also in the disruption of human–animal relationships due to oral malodor.

Several methods for oral care are available to aid in the prevention of PD. First, the American Veterinary Medicine Association recommends that all dogs visit a veterinarian at least once a year so that their teeth and gums can be examined. For many pets, those that do not have adequate home care, have signs of PD, and can handle anesthesia safely, it is recommended that dogs have professional teeth cleaning and polishing. This is done under anesthesia using ultrasonic instruments, which remove plaque and calculus from tooth surfaces. In addition to this periodic cleaning, it is helpful to use at-home techniques to remove the plaque biofilm, to slow the accumulation of calculus, and to maintain good oral health. Daily tooth brushing is the gold standard of at-home canine oral care (Gorrel and Rawlings, 1996; Gorrel and Bierer, 1999; Stepaniuk, 2019). However, this method is not always feasible due to the lack of dog cooperation and/or owner compliance. While not as effective as tooth brushing, daily dental chew consumption may provide a convenient adjunctive means to slow the progression of plaque and calculus buildup, which ultimately may lead to PD (Allan et al., 2019). As novel dental chews enter the market, there is growing interest in evaluating their efficacy in preventing plaque and calculus buildup through mechanical action. If successful, dental chews may be a convenient tool for the prevention of PD while providing dogs an enjoyable treat (Gorrel and Rawlings, 1996; Brown and McGenity, 2005; Quest, 2013).

Dental chews may differ in their nutrient and ingredient composition, the inclusion of functional ingredients or additives (e.g., polyphosphates and binding agents), processing methods (e.g., injection molding and extrusion), size, shape, and physicochemical properties (e.g., density, abrasiveness, and hardness). Other factors such as dog size, the dental surface used when chewing, individual animal predisposition and behavior, and time spent chewing will also impact chew effectiveness. Given all of the factors involved, science-based treat formulations and product testing should be completed before a dental chew is commercially available to pet owners. Therefore, the objective of this study was to determine the differences in gingivitis, plaque, and calculus scores and halitosis of adult dogs consuming novel dental chews compared with control dogs consuming only a dry, extruded diet. We hypothesized that gingivitis, plaque, and calculus scores and halitosis would be lower in adult dogs consuming novel dental chews compared with controls eating a kibble diet only and as low as dogs consuming a leading brand chew.

Materials and Methods

All procedures were approved by the University of Illinois Institutional Animal Care and Use Committee prior to experimentation (IACUC #18067).

Animals, treatments, and experimental design

Twelve adult female beagle dogs (mean age = 5.31 ± 1.08 yr; mean BW = 13.12 ± 1.39 kg) were used in a replicated 4 × 4 Latin square design. Dogs were housed individually in pens (1.0 m wide by 1.8 m long) in a humidity- and temperature-controlled animal facility. Dogs had access to fresh water at all times and were fed once daily to maintain BW. When allotted to dental chew treatments, food intake was adjusted to compensate for the energy provided by the chews. Dogs were weighed once weekly prior to feeding, with BW of all dogs remaining constant throughout the study. Dogs were fed at 8:00 a.m. each morning and were given 1 h to consume their food. Leftover food was weighed each day to calculate intake. Four hours after eating their diet, dogs received their dental chews.

Prior to the start of the study, all dogs underwent a physical examination, and serum chemistry values were evaluated. A dental evaluation was performed by a veterinary dentist to confirm the presence and integrity of all teeth to be scored in order to confirm trial eligibility. The experiment consisted of four 28-d periods. On day 0 of each period, dogs had teeth cleaned and polished by a veterinary dentist. The same blinded veterinary dentist scored teeth on day 28 of each period, then ultrasonically cleaned and polished the teeth so that day 28 of each period served as day 0 for the subsequent period. Breath samples were measured for malodor on days 1, 7, 14, 21, and 27 of each period.

All dogs were fed a commercial diet (American Journey Salmon & Sweet Potato Recipe, American Journey, LLC, Dania Beach, FL) throughout the study. No additional treats, chew toys, or other dental interventions were permitted for the duration of the study. No active anti-plaque or anti-calculus substances were included in chew formulations. Dogs were allotted to one of four treatments in each experimental period:

• Diet only (control, CT);

• Diet + Bones & Chews Dental Treats, Chewy, Inc., Dania Beach, FL (BC);

• Diet + Dr. Lyon’s Grain-Free Dental Treats, Dr. Lyon’s, LLC, Dania Beach, FL (DL);

• Diet + Greenies Dental Treats, Mars Petcare US, Franklin, TN (GR).

The GR chew tested was produced by injection molding into a knucklebone shape in one end and the shape of a toothbrush in the other end, with ridges at the end shaped like a brush. The regular-sized chew, which is recommended for dogs weighing 25 to 50 lb (11 to 22 kg), was approximately 10 cm long × 2.5 cm wide, weighed about 28 g, and was estimated to contain 91 kcal. The DL chew tested was produced by injection molding into the shape of a knucklebone in each end, with ridges also being present on one end. The medium-sized chew, which is recommended for dogs weighing 25 to 50 lb (11 to 22 kg), was approximately 8.5 cm long × 3.5 cm wide at the widest point, weighed about 32 g, and was estimated to contain 98 kcal. The BC chew tested, which is recommended for all dog sizes, was a long, slender chew with a six-point-shaped cross-section. It was produced by extrusion, approximately 12.5 cm long × 1.5 cm wide, weighed about 24 g, and estimated to contain 70 kcal.

When given chews, all dogs were monitored to ensure consumption and to prevent swallowing of large pieces and/or choking. They were given 1 h to consume their dental chew. Any remaining treats and treat pieces were collected and weighed.

Gingivitis, plaque, and calculus scoring

On day 28 of each period, gingivitis, plaque, and calculus scoring were conducted according to Gorrel et al. (1999) modified to omit measurements on the maxillary and mandibular premolar 2 (Harvey et al., 2012; Supplementary Table S1). The same veterinary dentist conducted all gingivitis, plaque, and calculus scoring and was blinded to all treatment regimens. For each measurement, the maxillary incisor 3, canine, premolar 3, premolar 4, and molar 1 and the mandibular canine, premolar 3, premolar 4, and molar 1 were scored. This selection allowed for the scoring of various types of teeth, including those used to nip and tear food (incisors and canines) as well as teeth used to shear and crush food (premolars and molars).

To assess gingivitis, after an initial visual evaluation of the gingiva, a periodontal probe (Williams model, Cislak Manufacturing, Inc., Niles, IL) was placed subgingivally on the buccal side of each tooth, and values were assigned via visual assessment of inflammation and bleeding, if present, upon probing. The scores for each measure within the dog were combined to obtain a mean score. Plaque levels were evaluated by using Trace Disclosing Solution (Young Dental, Earth City, MO) to cover the teeth, followed by a gentle rinse of water to remove the excess. Plaque was hence revealed and subsequently scored for coverage and thickness according to Gorrel et al. (1999) using the anatomical landmarks described in Hennet et al. (2006) to divide the teeth into gingival and occlusal portions (Supplementary Table S1). Calculus scores were based on the visual assessment of coverage and thickness on the mesial, buccal, and distal portions of the tooth. When all scorings were complete, supra- and sub-gingival scaling and supra-gingival polishing were done on all teeth with a fine-grade prophy paste (Uni-Pro Medium Grit Prophy Paste, Henry Schein, Melville, NY) to reestablish a clean mouth model for the next study period. Although quantitative light-induced fluorescence has recently been validated to quantify canine plaque (Wallis et al., 2016) and calculus (Wallis et al., 2018), the use of trained, blinded scorers is recommended by the Veterinary Oral Health Council.

Halitosis measurement

On days 1, 7, 14, 21, and 27, breath samples were analyzed for total volatile sulfur compound concentrations using a Halimeter (Interscan Corp, Simi Valley, CA). Halimeter measurements were conducted 3 h after dental chew administration. Halitosis measurements were obtained for each dog using a clean plastic straw as an extension of the Halimeter air drawing hose. A clean straw was used for each measurement. The tube was placed over the dog’s tongue and approximately even with the maxillary fourth premolar. The mouth was held gently shut while ensuring that the straw was not bent by the teeth or blocked by the tongue of the dog. The highest reading of volatile sulfur compounds over a period of approximately 30 s was displayed by the Halimeter and recorded. The machine was allowed to return to 0 (about 60 to 120 s) before the next measurement was taken. Each dog was measured three times and a mean score was calculated.

Anesthesia for dental scoring

The hair over the left or right cephalic vein was clipped, the site was aseptically prepared, and a 20-gauge intravenous catheter was placed in the cephalic vein for the administration of sedative and anesthetic agents, and intravenous fluids. Following catheterization, butorphanol (0.3 mg/kg) was administered intravenously and dogs were pre-oxygenated. Anesthesia was then induced with etomidate with or without a co-induction of midazolam (0.3 mg kg⁻¹) or lidocaine (2 mg kg⁻¹). Dogs were orotracheally intubated and transferred to isoflurane delivered in oxygen to maintain anesthesia. Intravenous fluids (Lactated ringer’s solution) were run at 5 mL/kg/h throughout anesthesia and active heating with a forced-air warmer was provided to maintain normothermia. Cardiovascular and respiratory function was monitored continuously using an anesthetic multiparameter monitor. Supplementary anesthetic agents and cardiovascular support were administered as needed based on the decision of the attending veterinary anesthesiologist.

Proximate and texture analysis

Diet and treat samples were dried at 55 °C in a forced-air oven and then were ground in a Wiley mill (model 4, Thomas Scientific, Swedesboro, NJ) through a 2-mm screen and then analyzed for dry matter (DM), organic matter, and ash according to AOAC (2006; methods 934.01 and 942.05). Crude protein content of diets and treats was calculated from Leco (TruMac N, Leco Corporation, St. Joseph, MI) total nitrogen values according to AOAC (2006; method 992.15). Total lipid content as acid-hydrolyzed fat was determined according to the methods of the American Association of Cereal Chemists (1983) and Budde (1952). Diet and treats were analyzed for gross energy as measured by bomb calorimetry (Model 6200, Parr Instruments Co., Moline, IL). Texture analysis was done in triplicate using a texture analyzer (TA.HD Plus; Texture Technologies Corp., Scarsdale, NY; Stable Microsystems, Godalming, UK). The equipment settings included 2.0 mm/s pretest speed, 1.0 mm/s test speed, and 10 mm/s post-test speed, and load cell capacity of 30 kg. Breaking strength was measured using a 3-point bend ring (A/3PB) accessory attached to the texture analyzer.

Statistical analysis

All tooth scoring data were analyzed using the Mixed Models procedure of SAS (version 9.4; SAS Institute, Cary, NC). Halimeter data were analyzed using repeated measures using the Mixed Models procedure of SAS, testing for differences due to treatment, time, and treatment * time interaction. Data are reported as LS means ± SEM with statistical significance set at P < 0.05.

Results

Diet and dental treat ingredients and analyzed chemical composition information are provided in Table 1, with images of all treats provided in Supplementary Figure S1. The diet contained approximately 6.5% moisture and 36% crude protein (DM basis), 17% acid-hydrolyzed fat (DM basis), and 10% ash (DM basis). In general, treats were palatable and well consumed by dogs. Dogs consuming less than 85% of their assigned chews (by weight) over the course of each experimental period were excluded due to lack of compliance. As a result, data from two DL, one BC, and one GR treatment were excluded (n = 10, 11, and 11, respectively). Dogs were closely monitored throughout the study. No injuries were caused by the treats.

Table 1.

Ingredient and chemical composition of the diet and dental chews fed to adult dogs

Item	Diet1	BC2	DL3	GR4
DM, %	93.7	85.2	80.8	85.5
Organic matter, % DM	90.6	96.6	96.8	94.3
Crude protein, % DM	36.3	16.7	25.7	33.2
Acid-hydrolyzed fat, % DM	17.1	1.6	3.9	6.7
Gross energy, kcal/g DM	5.1	4.4	4.7	4.9
Hardness, Newtons	------	140.5	61.21	58.45

¹Diet, American Journey Salmon & Sweet Potato Recipe (American Journey, LLC, Dania Beach, FL). Ingredients: deboned salmon, chicken meal, turkey meal, peas, sweet potatoes, chickpeas, pea protein, chicken fat (preserved with mixed tocopherols), dried plain beet pulp, natural flavor, flaxseed, menhaden fish meal, blueberries, carrots, salt, salmon oil, dried kelp, fructooligosaccharides, choline chloride, vitamin E supplement, mixed tocopherols (preservative), ferrous sulfate, zinc proteinate, zinc sulfate, iron proteinate, Yucca schidigera extract, niacin supplement, copper sulfate, potassium chloride, sodium selenite, d-calcium pantothenate, copper proteinate, riboflavin supplement, vitamin a supplement, manganese sulfate, thiamine mononitrate, manganese proteinate, pyridoxine hydrochloride, vitamin B12 supplement, calcium iodate, vitamin D3 supplement, folic acid, dried Bacillus coagulans fermentation product, and rosemary extract.

²BC, Bones & Chews Dental Treats (Chewy, Inc., Dania Beach, FL). Ingredients: rice flour, wheat flour, vegetable glycerin, pork gelatin, natural chicken flavor, calcium sulfate, dried cultured skim milk, powdered cellulose, and salt.

³DL, Dr. Lyon’s Grain-Free Dental Treats (Dr. Lyon’s, LLC, Dania Beach, FL). Ingredients: potato flour, pea protein, vegetable glycerin, pea starch, gelatin, water, natural flavor, sunflower lecithin, ground flaxseed, sunflower seed oil, citric acid, zinc propionate, peppermint oil, and mixed tocopherols.

⁴GR, Greenies Dental Treats (Mars Petcare US, Franklin, TN). Ingredients: wheat flour, wheat gluten, glycerin, gelatin, oat fiber, water, lecithin, natural poultry flavor, minerals (dicalcium phosphate, potassium chloride, calcium carbonate, magnesium amino acid chelate, zinc amino acid chelate, iron amino acid chelate, copper amino acid chelate, manganese amino acid chelate, selenium, and potassium iodide), dried apple pomace, choline chloride, fruit juice color, vitamins (dl-alpha tocopherol acetate [source of vitamin E], vitamin B12 supplement, d-calcium pantothenate [vitamin B5], niacin supplement, vitamin A supplement, riboflavin supplement [vitamin B2], vitamin D3 supplement, biotin, pyridoxine hydrochloride [vitamin B6], thiamine mononitrate [vitamin B1], and folic acid), and turmeric color.

Plaque

Plaque coverage was 12.3% lower for dogs consuming DL and 13.3% lower for dogs consuming GR compared with control dogs (P = 0.003; P = 0.0002, respectively). Plaque thickness also was 17.4% lower for dogs consuming DL and 15.5% for dogs consuming GR compared with control dogs (P = 0.0001; P = 0.0002), and 11.6% lower (P = 0.0471) for dogs consuming DL compared with dogs consuming BC (Figure 1).

Figure 1.

Plaque coverage and thickness for dogs consuming dental chews or diet alone. Values represent LS means ± SEM. ^a–cMean values with unlike letters were different (P < 0.05).

Calculus and gingivitis

Calculus coverage was 36.9% lower for dogs consuming DL, 31.6% lower for dogs consuming GR, and 20.4% lower (P ≤ 0.0001) for dogs consuming BC compared with control dogs. Calculus coverage was 20.7% lower for dogs consuming DL and 14.1% lower for dogs consuming GR compared with dogs consuming BC (P = 0.0009; P = 0.02; Figure 2). Calculus thickness was not affected by treatment. Gingivitis scores were very low for all dogs (mean scores = approximately 1.1) and were not different among treatment groups (data not shown).

Figure 2.

Calculus coverage and thickness for dogs consuming dental chews or diet alone. Values represent LS means ± SEM. ^a–cMean values with unlike letters were different (P < 0.05).

Halitosis

A significant (P < 0.0001) treatment * time interaction was observed for breath malodor in the form of volatile sulfur compounds as measured in ppb by a Halimeter (Figure 3). On day 14, breath volatile sulfur compounds were lower (P = 0.02) for dogs consuming DL compared with control dogs. On day 27, breath volatile sulfur compounds were lower (P < 0.0001) for dogs consuming BC, DL, or GR compared with control dogs.

Figure 3.

Oral malodor for dogs consuming dental chews or diet alone. Values represent LS means ± SEM changes from baseline. *At day 14, DL was lower (P < 0.05) than CT; at day 27, BC, DL, and GR were lower (P < 0.05) than CT.

Discussion

PD is a common disease, but some preventable measures are available. The onset of PD may lead not only to animal discomfort but also to a disturbance in owner–pet relationships via oral malodor, poor appearance of teeth, changes in dog behavior, and veterinary costs (Harvey, 2005). Tooth brushing is considered to be the gold standard of oral care for dogs. However, this often is not a feasible option due to lack of dog cooperation and/or owner compliance. In a recent survey of over 200,000 Swedish dog owners, only 29% said that regular tooth brushing was very important, 32.2% said it was fairly important, and nearly 40% thought it was of minor importance or not important at all (Enlund et al., 2020). When asked how often in the last month they had brushed their dog’s teeth with a toothbrush, approximately 20% said they had brushed them at least once weekly, with over 29% saying a single time that month, and over 45% saying they had never brushed their teeth. Dental chews are a promising method to prevent or slow the progression of PD in dogs due to their convenience for the owner and acceptance by dogs. In a recent survey, over half of the dog owners think that dental chews are very important or fairly important for good dental health, and nearly 60% stated that they had purchased dog treats for dental care purposes in the past month (Enlund et al., 2020). These data are in line with that of Morelli et al. (2020), who reported that 55% of treats purchased by dog owners are for dental care.

Several studies conducted over the past 25 yr have used similar assessments to determine the effects of dental chews akin to those investigated in the current study (Gorrel and Bierer, 1999; Gorrel et al., 1999; Brown and McGenity, 2005; Clarke et al., 2011; Quest, 2013; Allan et al., 2019). Similar to what was done in the current study, the majority of these studies used a “clean mouth” test model to assess the efficacy of a novel dental chew (chew + diet) against a diet alone. Various experimental designs (e.g., completely randomized design, crossover design, and Latin square), dog breeds (e.g., toy breeds, beagles, and mixed breed), and lengths of intervention (e.g., 28 d; 42 d; 56 d) have been used. However, most studies have trained, blinded personnel assess the plaque, calculus, and gingivitis scores according to the methods recommended by the Veterinary Oral Health Council and those used in the current study (Hale, 2011; http://www.vohc.org). Given the subjective nature of dental scoring and varying treat types, results of dental chew administration have varied. However, numerous studies have shown improvements in multiple PD measures (Gorrel and Rawlings, 1996; Brown and McGenity, 2005). A few studies also have measured and shown benefits on halitosis (Gorrel and Bierer, 1999; Gorrel et al., 1999; Clarke et al., 2011; Quest, 2013).

In the current study, three commercially available dental chews were compared. Similar to previous studies, measures often associated with PD were evaluated to assess the efficacy of the dental chews. The scoring system used was adapted from Gorrel et al. (1999), which has been commonly implemented to assess the development of PD in dogs. Plaque coverage, plaque thickness, and calculus coverage were improved by the chews tested in the current study. The 12% to 17% reduction in plaque coverage and thickness and the 20% to 35% reduction in calculus coverage in the current study were significant but lower than those reported by previous studies (Gorrel et al., 1999; Brown and McGenity, 2005; Quest, 2013; Marx et al., 2016). In those studies, calculus coverage was reduced by 35% to 70%, while plaque coverage was reduced by 30% to 40%.

Halitosis was also improved over time. All dogs eating chews maintained relatively low volatile sulfur compound concentrations (<25 ppb increase from baseline) throughout the study, but they increased steadily over time in the control group. The ~75% lower concentration in volatile sulfur compounds observed at day 28 in dogs fed chews vs. controls of the current study was much greater than those of other studies, where only ~7% (Clarke et al., 2011), ~20% (Gorrel et al., 1999), and 45% (Quest, 2013) lower values were reported. Calculus thickness was not affected by treatment; this may be due to treatment period length not being long enough to allow for significant buildup. Given that plaque scores varied among treatments, a longer treatment period may result in quantifiable differences in calculus thickness as accumulating plaque mineralizes. A similar conclusion can be drawn in regard to gingivitis results in this study. Gingivitis scores were not different among treatment groups, which may be due to insufficient time to impact inflammatory processes surrounding gum tissue.

It has been established that daily consumption of dental chews by dogs can help inhibit plaque and calculus accumulation as well as retard the development of gingivitis and halitosis (Gorrel and Bierer, 1999; Gorrel et al., 1999; Clarke et al., 2011; Quest, 2013). It should be stated that treats of an appropriate size should be fed to dogs. An appropriately sized chew should match the tooth and mouth size and strength, providing sufficient abrasion on the dental surface and chew time. Treats of appropriate size will also limit caloric intake. To avoid nutrient imbalances and risk of obesity, treats and chews should be limited to a maximum of 10% of total caloric intake (Baldwin et al., 2010; Brooks et al., 2014).

Novel chews differ in key features such as formulation, shape, and hardness; however, they should be tested to verify effectiveness. The formulation of dental chews affects their hardness and abrasiveness. The dental chews evaluated in this study varied widely in ingredients, nutrient composition, and hardness. GR contains wheat gluten, which lends to the semi-moist consistency that provides chewing resistance and, therefore, increased contact with the teeth. In DL, this function is likely provided by pea protein and gelatin, while BC contains pork gelatin. Fiber sources such as oat fiber in GR and powdered cellulose in BC may also support a scrubbing effect during mastication of the treat. The amount of fiber may also affect the level of abrasion, but the guaranteed crude fiber maximum concentrations of the chews tested were not greatly different (DL: 3.5%; BC: 4.5%; GR: 6.0%).

This study had a few limitations. First, the length of the experimental periods was only 28 d. While this length of time is typical of oral health tests, longer intervention periods may have demonstrated more impressive changes. Second, the length of time that it took for dogs to consume chews was not recorded. Third, the side of the mouth and main teeth used to chew the treats were not recorded. Knowing the chewing time, the side of mouth used, and method of chewing, may have provided useful information. Lastly, we did not measure the fecal scores of dogs consuming chews or the nutrient digestibility of treats tested. The breakdown of treats was measured in vitro previously and shown to be high, but it would have been useful to include these data in vivo too.

In conclusion, the dental treats evaluated in the current study exhibited the ability to reduce several measures implicated in PD onset and progression. Briefly, plaque scores, calculus scores, and halitosis measurements were reduced but varied among treat types. DL performed similarly to GR, as both treats resulted in a reduction in plaque coverage and thickness scores, calculus coverage scores, and breath volatile sulfur concentrations compared with controls. BC dental treats reduced calculus coverage scores when compared with control as well as breath volatile sulfur concentrations at day 27. Longer treatment periods would likely have allowed more insight into long-term differences in calculus thickness and gingivitis development among treatments. Overall, daily administration of DL, GR, and BC dental treats may be helpful to prevent or slow the progression of PD in dogs.

Supplementary Data

Supplementary data are available at Journal of Animal Science online.

Glossary

Abbreviations

DM

dry matter

PD

periodontal disease

Conflicts of interest statement

L.L. is an employee of Chewy, Inc. All other authors have no conflict of interest.