LITHUANIAN UNIVERSITY OF HEALTH SCIENCES VETERINARY ACADEMY
Faculty of veterinary medicine
Pauline Hausmann
A comparison of equine dental abnormalities in two different feeding types
Dviejų skirtingų šėrimo tipų arklių dantų anomalijų palyginimas
MASTER THESIS
of integrated studies of veterinary medicine
Supervisor : Lekt. Kestutis Maslauskas
THE WORK WAS DONE IN THE DEPARTMENT OF LARGE ANIMAL SURGERY CONFIRMATION OF THE INDEPENDENCE OF DONE WORK
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TABLE OF CONTENTS
SUMMARY………...………....………...……….. 3
INTRODUCTION………... 5
1. REVIEW OF LITERATURE……....……….. 6
1.1. Equine Teeth structural elements ..……….…………..………. 6
1.1.1. Enamel………...………. 6
1.1.2. Dentin ………....………. 7
1.1.3. Cement ………... 7
1.1.4. Dental pulp ………. 7
1.2. Equine teeth anatomy ....……….... 8
1.2.1. Teeth formula ………. 8
1.2.2. Incisors ………... 9
1.2.3. Canines ………..………. 9
1.2.4. Cheek teeth ………... 9
1.3. Mastication movement ...……….. 10
1.4. Dental examination technique ………....……….… 11
1.5. Common dental abnormalities ………..… 12
2. RESEARCH METHODS AND MATERIAL ………. 17
2.1. Research material ………. 17
2.2. Equine dental examination record ………... 18
2.3. Statistical Analysis methods ……….... 20
3. RESEARCH RESULTS……….... 22
3.1. Research group ………. 22
3.2. Common observation on dental examination ………...… 24
3.3. Common abnormalities ………....… 26
3.4. Uncommon abnormalities ……….... 27
3.5. Treatment ……….……….… 28
4. DISCUSSION OF RESEARCH RESULTS………. 29
CONCLUSION ……… 30
RECOMMENDATIONS ………...………..… 31
SUMMARY
A comparison of equine dental abnormalities in two different feeding types Pauline Hausmann
A cohort study was performed to analyse different equine dental abnormalities and to identify possible connections to their nutritious behaviour. Dental records were obtained of 52 sedated horses from october 2019 - november 2020 in two different large animal clinics in Germany by full mouth examination. The horses were grouped according to their feeding type : First group being held outdoors or having access to hay for at least 18 hours / day ( 40,4 % ) and the second one being mainly fed with concentrates and additionally around 3 kilogram of hay / silage ( 59,6 % ). A total amount of 21,2 % of horses showed no dental abnormalities of which 81,8 % belong to group one. Several abnormalities were found within the first group (total 33,3 %); all being distributed on a low count (sharp enamel points, hooks, missing teeth etc). The most common abnormalities (p < 0,05) within the second group were hooks, sharp enamel points and oral lacerations (total 93,5 %). The cases showed a correlation between the enhanced development of certain abnormalities and horses being fed mainly fed by concentrates and limited access to high-fiber feed.
SANTRAUKA
Dviejų skirtingų šėrimo tipų arklių dantų anomalijų palyginimas Pauline Hausmann
Buvo atliktas kohortinis tyrimas, siekiant išanalizuoti ir įvertinti įvairius žirgų dantų sutrikimus nustatyti galimas sąsajas su jų šėrimo tipu. Nuo 2019 m. Spalio iki 2020 m. Lapkričio mėn. Dviejose skirtingose stambių gyvūnų klinikose Vokietijoje, atlikus išsamius klinikinius tyrimus, buvo gauti dantų įrašai iš 53 seduotų arklių. Žirgai buvo sugrupuoti pagal jų šėrimo tipą: pirmoji grupė buvo laikoma lauke arba turėjo galimybę gauti šieno mažiausiai 18 valandų per dieną (40,4 %), o antroji grupė buvo šeriama koncentratais ir papildomai 3 kg šieno / siloso (59,6 %). Iš viso 21,2 % arklių nebuvo dantų anomalijų, 81,8 % jų priklauso 1 grupei. Pirmoje grupėje buvo nustatyta keletas anomalijų (iš viso 33,3 %); visi yra suskirstyti į nedidelį skaičių (aštrios lydymosi taškai, kabliukai, trūkstami dantys ir kt.). Dažniausios antrosios grupės anomalijos (p<0,05) buvo kabliukai, aštrūs lydymosi taškai ir burnos įtrūkimai (apskritai 93,5 %). Šie atvejai parodė
koreliaciją tarp padidėjusio tam tikrų anomalijų vystymosi ir žirgų, šeriančių daugiausia koncentratais, ir ribotos galimybės gauti daug skaidulų turinčio pašaro.
INTRODUCTION
During evolution the modern horse (Equus caballus) developed from Hyracotherium, meaning “rabbit-like animal” that lived circa 55 million years ago. (1, 2)
This precursor possessed brachydont (short-crowned) teeth that suited a diet based on lush, soft leaf vegetation high in simple carbohydrates and proteins.
To cope with vegetation getting more fibrous, more abrasive and less nutritious and the fact of a higher energy demand due to increased body size of the developing horse, it required a lot of changes in tooth structure.
These changes included a great increase in teeth length (hypsodonty) and an almost lifelong dental eruption. (2, 3, 4)
Nowadays a lot of horses are fed on concentrates being high in energy without the possibility to display their natural chewing behaviour on low energy, high fibrous feedstuff for several hours per day. (3, 5)
An increased demand on dental corrections and corrections of stereotypic behaviour, such as constant chewing of wood or crib biting, has been demonstrated in the last decades and raises the question of possible correlation. (5, 6)
Objective of research :
To draw a possible correlation between different feeding types and development of dental abnormalities
Research task :
1. to be able to perform complete dental examination using full mouth speculum 2. to identify the most common dental abnormalities
3. to identify possible causes of certain dental abnormalities associated with different feeding types
1.
REVIEW OF LITERATURE
1.1.
EQUINE TEETH STRUCTURAL ELEMENTS
The dentition of modern horses (Equus caballus) is highly specialized to the ingestion of high fibrous, abrasive and low energy plants and therefore differs from other mammals.
Every tooth is composed of the crown (Corona dentis), tooth neck (collum dentis) and the tooth root (radix dentis). The crown is divided in two parts, the one being visible ( Corona clinica) and the one being embedded within the gingiva termed as reserve crown. (7, 8)
Its structural elements are enamel, dentine, cement and dental pulp forming long crowned teeth (hypsodont) with the exception of the canine and first premolar teeth. (7 - 9)
1.1.1.
Enamel (enamelum)Enamel in general represents the hardest component of all body tissues consisting of 96% hydroxyapatite crystals and 4% organic material produced by ameloblasts.
At the time of eruption the complete amount of enamel is produced and can not be replaced resulting in a progressive decrease during lifetime. (8, 9)
Kilic et al have been describing the equine enamel structure by two different types.
Equine enamel type 1 is extremely hard and therefore favouring a prolonged chewing process (up to 18h/ day), which explains being the main component of cheek teeth.
Equine enamel type 2 is softer in comparison as it lacks the parallel orientation and therefore has a “spaghetti-like” presentation, making it more resistant to bursting. It is mainly found in the incisors of horses to enable the forceful fibrous food uptake without the appearance of idiopathic fractures (in contrast to cheek teeth). (8 - 11)
To deal with the immense force that is needed for grinding the high fiber nutrition, the cheek teeth not only have one layer of enamel around the periphery of the teeth as the incisors. They possess extensive infolding of enamel to prevent the wear out of the smoother cementum and dentine. (8)
1.1.2.
Dentine (dentinum)Dentine, being the main teeth component, is produced by odontoblasts and is composed of approximately 70% mineralized tissue with 30% organic content being capable of repairing itself. (9, 10 ) Several types of dentine are present :
Primary dentine is deposited prior to dental eruption and soon gets worn away by natural mastication. Secondary dentine is similar to primary dentine but has a slight difference in composition being more susceptible to become coloured by food pigments and therefore can be used for age determination.
Tertiary dentine is formed if the pulp is exposed to noxious stimuli to prevent further pulpar damage. (10 - 13)
Fig. 1. longitudinal and transverse section of a maxillary cheek tooth (14)
1.1.3. Cement (cementum)
Cement represents the softest of three calcified dental tissues containing approximately 50% organic components and similar to bone. It is divided into peripheral and infundibular cement. Especially in the cheek teeth the amount of peripheral cementum is greatest, surrounding the deep enamel infoldings and attributing to “ mechanical strength and wear resistance”. (8, 9, 12)
1.1.4. Dental pulp
located within the dental pulp cavity. Due to the continuous eruption of hypsodont teeth and the constant occlusal wear down, secondary dentin has to be formed to prevent pulpar exposure. In case of a pulpar exposure tertiary dentine might be able to seal off the pulpar chamber to prevent any further damage. (9, 10)
Dacre described the presence of one pulp horn present in incisors, canines and first premolar in contrast to the presence of five horns in the cheek teeth with exception of the first and last, which have one to two additional horns. (15)
1.2.
EQUINE TEETH ANATOMY
1.2.1.
Horse teeth formula
Deciduous dentition formula :Permanent dentition formula :
Each quadrant consists of three Incisors ( I 1- I 3 ), one canine tooth ( C ), four premolar teeth ( P 1 - P 4 ) and three molar teeth ( M 1- M 3 ). (8, 10)
Functional relevance is attributed to the incisors ( I 1 - I 3 ) , three of premolars ( P 2-4) and the molars ( M1 - M3) . (16)
The canine tooth as well as the first premolar, also termed as wolf teeth, lost their function during evolution, so that they are not developed in every horse nowadays. Especially the canine teeth are usually only developed for male horses. (16, 17)
Premolar and molar teeth are together termed as cheek teeth ( CT ). (18)
3 I 1 C 3 M
3 I 1 C 3 M
3 I (1 C) 3 P (4 P) 3 M
1.2.2.
Incisors ( I 1 - I 3 )
An arcade is formed by the lower and respectively from the upper jaw incisors, which is curved in younger age and becoming shallower with age due to progressive wear. This is also demonstrated by the occlusal angle, which changes with age from almost 180° after eruption, to about 90° at 15 years of age. (18, 19)
After the wear off of the infundibular cup a small ring of infundibular enamel located on the lingual aspect of the occlusal surface is visible , which is called the “enamel spot” . (7, 9, 19)
The exposure of secondary dentine that has been deposited within a former pulp cavity is referred to as the dental star, which aids age determination. (9, 13, 19, 20)
A high possibility of the development of a hook on the caudal aspect of the occlusal surface of I 3 is caused by incomplete occlusal contact between the upper and lower I 3. (18)
1.2.3.
Canine teeth ( C 1 )
The canine teeth are usually only developed in male horses erupting at an age of 4 - 6 years and are non-functional.
In contrast to other equine teeth they are not in direct contact with each other, as the maxillary one is more caudal positioned than the mandibular canine.
Still it is not fully clear if the canine teeth are brachydont ( shortcrowned) or hypsodont. They possess a small vertical orientated clinical crown ( 1 - 2 cm high) and may have reserve crowns up to 7 cm in length. (12) The dental pulp cavity is approximately located 1 cm away from the occlusal surface. (12, 21)
1.2.4.
Cheek teeth : Premolars ( P 1 -P 4 ) + Molars ( M 1 - M 3 )
The first premolar teeth, which also termed wolf tooth, is only developed in about 24 % of mares and 15 % of male horses. Like with the canine teeth it is not fully clear if the wolf teeth are of hypsodont or brachydont nature. They erupt at an age of approximately 1 year and often are lost by the changing of the second premolar at an age of 2,5 years. (12)The second, third and fourth premolar teeth are termed as the frontal cheek teeth, which in contrast to the caudal cheek teeth have deciduous precursors.
angulated towards each other. All cheek teeth have lophodont appearance referring to the intensive enamel infolding at the occlusal surface serving the permanent grinding motion of fibrous, abrasive food stuff. (9, 13)
1.3.
Mastication movement
In central occlusion only the lingual third of the occlusal surface of maxillary cheek teeth is in contact with the buccal half of the occlusal surface of mandibular cheek teeth.
This condition is termed ansiognathie as it is formed by a narrower and straighter lower archarde in comparison to the upper one. (8, 16)
The mastication movement can be divided within three phases : opening, closing and power stroke. During power stroke the lower archarde is being compressed along the upper archarde to crash and shred food particles. The length of this sweeping highly depends on the ingested nutrition. (22)
1.4.
DENTAL EXAMINATION TECHNIQUE
Generally a dental examination consists of observation as well as the palpation of teeth and bone structures ( referred as the hard tissue) and the soft tissues (oral mucosa, tongue, palate, lymph nodes, lips and salivary glands).
The intensity of carried out procedures greatly depend upon history, regularity of dental treatment and abnormal finding during general dental examination. (24)
The observation of mastication movement aids towards the detection of a restricted
mandibular movement. Sometimes it might be possible to identify if it is only unilateral or bilateral by this. By the fixation of the head by one hand and the lateral manipulation of the mandibula with the other hand the animal's response to this is evaluated visually, acoustically as well as manually. At a dislocation of 0,5 - 2,5 cm the occlusal surfaces of the maxillar and mandibular cheek teeth come into contact. A dislocation for several millimeters more should demonstrate the separation of the incisors by 2 - 6 mm referring to a normal angulation of the occlusal surfaces of the cheek teeth (18, 25).
Deep palpation of the cheeks may not be tolerated by the horse, raising a possible correlation to the presence of sharp enamel overgrowths on the buccal aspect of the cheek teeths. Also major dental irregularities (e.g. tooth absence) and the formation of food pockets might be detected by this method. (18)
Further examinations of the teeth are carried out on the sedated horse using a full mouth speculum and bright illumination after a thorough rinsing of the oral cavity with water to remove any kind of retained food particles. (18, 25)
Hard and soft tissues are being carefully palpated and visually assessed for abnormalities.
A dental mirror as well as an endoscope aids the detection of any kind of abnormalities within the caudal oral cavity that are otherwise easily missed due to the great length of it and the limited degree of jaw opening.
Olfactory assessment is performed to detect any kind of malodor, which indicates possible anaerobic infections (e.g. food pocket formation with resulting periodontal disease). (18)
Radiography and scintigraphy might be used in severe cases to determine the degree of certain dental diseases. (26)
Fig. 3. Full Mouth speculum with attached illumination lamp (27)
1.5.
COMMON DENTAL ABNORMALITIES
Cheek teeth overgrows
A difference in the strength of the harder enamel and the softer cement and dentine leads to protruding enamel folds on the occlusal surface. In case of suboptimal mastication movements enamel protrudes at the lingual or buccal site of the cheek teeth might develop. (18)
Leue described a more vertical than lateral mastication movement associated with the chewing of concentrates and a higher incidence of the development of sharp enamel points. (28)
Fig. 4. Sharp Enamel Points with resulting oral laceration (29)
Diastema
The occlusal surfaces of the equine cheek teeth are usually pressed together by the angulated second premolar and third molar, so that they act as a single grinding unit.
In any case of widening between those teeth, food becomes impacted during chewing movement, which with time will process downwards causing pain and secondary periodontal disease.
In presence of transverse overgrowths these interdental spaces will eventually become wider. (9, 18, 32)
Hooks
As the occlusal surfaces of the maxillary and mandibular premolar and molar teeth are not at full occlusion, centralized overgrowths termed as hooks might develop. The most common side for the development of hooks is the cranial part of the maxillar second premolar and the caudal aspect of the last mandibular cheek tooth. (31)
Fig. 6. Hook formation on second Premolar (29)
Disorders of Incisors
A variety of disorders of incisors are described in literature , ranging from Overbite (maxillary incisors protruding the mandibular incisors rostrally), Sow mouth (representing the contrary to the overbite), retained deciduous caps to displaced or supernumerary incisors. In relation to the topic of this research especially abnormalities of incisor wear are of interest. A normal jaw movement is marked by a separation of the incisors while being in closed, lateral sweeping position. In case of overgrowth of one incisor this movement is restricted, refusing the normal grinding motion. (3, 15, 22 - 24)
Fig. 7. Incisor misalignment (32)
Periodontal disease
Periodontal disease refers to an inflammation of all supporting tooth structures ( gingiva, periodontal ligaments, cementum, and alveolar bone ). (16, 19)
A division is made to the inflammation only referring to the gingiva ( Gingivitis).
Liyou pointed out that once sharp enamel points are present, gingivitis and in the course periodontal disease will develop resulting in a restricted lateral movement due to pain. Also pocket formation with intrapped food particles might result. (25)
Soft tissue injuries
Soft tissue ulceration may develop due to sharp enamel points, hook formation, fractured teeth or displaced teeth resulting in biting problems and quidding. (8)
EOTRH (Equine odontoclastic tooth resorption and hypercementosis)
EOTRH refers equally to tooth resorption as well as hypercementosis of the incisors and canine teeth, especially in mature horses. The etiology causing alveolar bone lysis and prominent hypercementosis of the incisor teeth roots is still unclear. (34)
Fig. 9. EOTRH (35)
Shear mouth
In case of not reduced cheek teeth overgrowths, the occlusal surface that is usually
angulated by 10 - 15 ° will develop a greater degree termed as shear mouth. It will develop when the horse is chewing on one side more than on the other resulting in a one sided faster wear down. (9, 16)
Wave mouth
Wave mouth refers to an uneven surface of occlusal surfaces of the cheek teeth. It might develop due to different rates of cheek teeth eruptions or due to single overgrown teeth that constantly grind down the opposing teeth. (31)
2.
RESEARCH METHODS AND MATERIALS
2.1.
Research material
The research was carried out from october 2019 until november 2020 in two different Large animal clinics in western part of Germany.
Dental examinations were performed on 52 horses ( 30 geldings and 22 mares) using standing sedation and full mouth speculum.
Equine dental examination / treatment records were filled for every horse. Special attention in regard to this research was paid to the nutrition plan of each horse in regard to form two groups. One being held free range with 18 or more hours per day on pasture or hay / straw ad libitum and the second being fed on concentrates and an approximate amount of 3 kilogram of hay or silage per day.
For sedation and analgesia a combination of detomidine chloride (Domosedan) 0,01-0,015 mg/kg bodyweight and butorphanol- tartrate (Butomidor) 0,02 - 0,03 mg / kg body weight was injected intravenously. Examination of the oral cavity was performed, after rinsing thoroughly with warm water, using a Haussmann full-mouth speculum with bright illumination.
2.3.
Equine dental examination / treatment record
Date :
Complaint : ⃝⃝⃝⃝⃝routine dental care / recheck
Last dental examination / treatment (date) : __________________________________________ Feeding Type / amount : pasture (18h +) concentrates + pasture (3h) / hay (< 3kg)
Recent Observations : weight loss / feed dropping / quidding / abnormal chewing / ….. Performance Problems : heat tilt / tossing / resistance/ ….
PHYSICAL EXAMINATION :
BCS : __ / 5
Temperature : ___°C Respiratory rate : ___/min Heart rate : ___/min CRT : ____
current medications :
________________________________
Odor : normal / oral / nasal
TMJ : sensitive / not sensitive Dissymmetry : L / R enlarged Cheeks : normal / lacerations Tongue : normal / lacerations Palate : normal / abnormal
Gums : normal / periodontal pockets / diastema Lips : normal / abnormal
Other findings :
_____________________________ Horse name
Breed
Age / Date of birth Sex Color Usage of horse Owner Address Phone number
Administered medications
time of administration administration route chosen medication (amount) 1. _________________________________________________________________________________________ 2. _________________________________________________________________________________________ 3. _________________________________________________________________________________________ 4. _________________________________________________________________________________________ 5. _________________________________________________________________________________________ (*M3 / M2 /… →Gingiva)
Exam findings Treatment
Incisors Canines Wolf teeth 100 CT 200 CT 300 CT 400 CT M3 M2 M1 P4 P3 P2 WT C I3 I2 I1 I1 I2 I3 C WT P2 P3 P4 M1 M2 M3 111 110 109 108 107 106 105 104 103 102 101 201 202 203 204 205 206 207 208 209 210 211 411 410 409 408 407 406 405 404 403 402 401 301 302 303 304 305 306 307 308 309 310 311 M3 M2 M1 P4 P3 P2 WT C I3 I2 I1 I1 I2 I3 C WT P2 P3 P4 M1 M2 M3
Rostrocaudal motion : restored / could not be restored / was not impacted before treatment Recommended procedures : X ray / Extraction / CT
Handed out medications : ____________________________________________________ Special instructions : ________________________________________________________ Recheck / next dental appointment : 1 week / 1 month / 3 months / 6 months / 1 year
‘
2.4.
Statistical analysis methods
The data of each parameter assessed by the dental examination record from every horse were transferred to Microsoft Excel chart. Subsequent calculations were performed using IBM SPSS® software version 26 and Python 3.6.
The proportion for each evaluated characteristics was calculated in percentage within the two groups and the count of horses demonstrated using bar charts.
P values smaller than 0,05 were defined as statistically significant in regard to a correlation between the feeding type and the development of equine dental diseases.
3.
Research results
3.1.
Research group
Fifty Two horses were grouped according to their feeding type. One group had free pasture access for approximately 18 hours / day or equally hay fed ad libitum (40,4 % ) . The other group is fed mainly on concentrates and additionally a portion of hay or silage of approximately 3 kilograms (59,6 % ).
Fig. 10. Age distribution within research group
Within each group the age distribution was noted.
In the age group of 2 - 5 years 6,5 % were fed on concentrates in contrast to more than the double amount having free access to pasture (14,3 %).
6 - 15 year old horses were mostly fed on concentrates (45,1 %) while 33,3 % were held free range. 48,4 % of horses aged older than 15 years were fed on concentrates and 52,4 % had unlimited pasture access.
Fig. 11. Regular dental treatment prior to dental examination
Regular dental treatment (at least once per year) was performed on 59,6 % of all examined horses ( on 33,3 % of all pasture held horses; on 77,4 % of concentrate fed horses).
40,4 % were not examined regularly (22,6 % concentrate fed and triple the amount (66,7 % ) of horses having free pasture access).
3.2.
Common observations in research group
Fig. 12. Common observations at dental examination
42,3 % of all examined horses (p>0,05) showed no signs of discomfort while riding or chewing as well as no response to the deep palpation by harshly compressing the cheek against the buccal rim of occlusal surface of maxillary cheek teeth (52,4 % free range ; 35,5 % fed on concentrate).
Pain during the deep palpation of maxillary cheek teeth was demonstrated by 34,6 % of all horses ( 42,9 % pasture held ; 29,0 % concentrate fed).
48,4 % of concentrated feed horses displayed difficulties eating in contrast to 38,1 % of horses having unlimited access to fibrous food.
Fig. 13. Horses being affected with one or more dental abnormalities
Horses showing no dental abnormalities attributed to a total of 21,2 % (p<0,01).
Showing a 6,6 times higher count in horses with permanent access to fibrous food (42,9 %), whereas only 6,5 % of concentrated fed horses were diagnosed without any abnormalities.
78,8 % of horses were diagnosed with any or multiple kinds of dental abnormalities.
57,1 % of them were held free range and almost one and a half the amount of them were fed with concentrates ( 93,5 %).
3.3.
Common abnormalities
Fig. 14. Common abnormalities
The most common abnormal findings were demonstrated in this chart (p<0,01). In horses fed with concentrate the most common were sharp enamel points (80,6 %), hooks (48,4 % ) and therefore misalignment of incisors (32,4 %). Only 6,5 % having no abnormalities. In free range horses a total of 42,9 % demonstrated no abnormalities. Sharp enamel points (28,6 %), hooks (19 % ) and incisor misalignment (14,3 % ) were represented at half or even a third of the count of concentrate fed horses.
3.4.
Uncommon abnormalities
Fig. 15. Uncommon abnormalities
Several uncommon abnormalities (p> 0,05) were found during dental examination.
More common was the presence of oral lacerations (14,3 % free range; 16,1 % concentrate fed), overgrown tooth (19,0 % free range; 16,1 % contrate fed) and periodontal disease ( 14,3 % free range ; 12,9 % concentrate fed).
Horses being held outdoors had a three times higher count missing a tooth (19,0 % ); a 4.5 times higher count on displaced teeth (14,3 %); and a 7 times higher count in the presence of diastema (23,8 %).
Worn wear was only demonstrated in 9,5 % of free range living horses.
3.5.
Treatment
Fig. 16. Treatment
Only a total amount of 21,2 % of all horses (p<0,01) were not recommended to perform any kind of treatment (42,9 % having constant access to pasture / hay; 6,4 % of concentrate fed horses). The most common procedure that needed to be performed was floatation ( 38,1 % of free range horses in comparison two and a half times more on concentrated fed horses).
Extraction of one or more teeth was performed on 9,7 % of all concentrate fed horses ( almost double the amount in pasture held horses).
4.
DISCUSSION OF RESULTS
Bonin, Clayton, Lanovaz and Johnston described a limited lateral movement while chewing pellets or concentrates and the possible arising of dental abnormalities. This was clearly demonstrated in the number of horses affected with any kind of abnormalities (81,8 % of them had free pasture access). They also stated that the position of maxilla to mandibula at different heights changes, which in turn gives a more regular teeth abrasion at the mastication of grass with different heights. By the ingestion of concentrates the horse head is mostly at a height of 1,10 - 1,20 m favouring a protrusion of the mandibula. This constant head position whilst mastication was also demonstrated by the abnormalities found in this study (e.g. the prevalence of hook formation at the cranial aspect of the second premolar of the maxilla of concentrated fed horses ). (22)
Ralston, Foster, Divers, Hintz stated the effect on food digestibility and better mastication due to regular dental treatment, which was demonstrated in the severity of dental abnormalities found in horses being examined regularly. (36)
Taylor Et al. studied 228 dental casts from horses living free range and being held captive. It showed that captive held horses or horses with limited access to abrasive foodstuff had a higher incidence of dental abnormalities. (37) This finding correlates with the research results that showed a higher incidence of the formation of sharp enamel points and hooks of horses not having
unlimited access to an abrasive diet.
Of course a more reliable result would have been demonstrated if a dental treatment was performed approximately one year in advance for each horse to the recording of dental abnormalities, so that the noted dental abnormalities were more reliable. Still most of the horses were examined at least annually or even every 6 months (concentrate fed horses - 77,4 %).
CONCLUSIONS
1. Complete dental examinations using full mouth speculum were performed to identify the most common abnormalities.
2. Most common dental abnormalities were sharp enamel points, hooks and incisor misalignment within both feeding groups.
3. The different forms of feeding behaviour demonstrated different numbers of dental
abnormalities in the affected horses showing that the limited lateral mastication movement while chewing concentrates and a limited amount of hay is the main cause of sharp enamel points, hooks and thereof resulting oral lacerations.
RECOMMENDATIONS
The dental examinations of those two different fed horse groups showed an enhanced development of certain dental abnormalities such as sharp enamel points, hooks, incisor misalignment and oral lacerations.
The assurance of an unlimited access to feed being high in fiber demonstrated itself as an useful technique to slow down these processes. As well as it satisfies the natural behaviour of horses that are evolutionarily determined on a slow food uptake up to 18 hours / day and prevents the development of stereotypic behaviour that some horse owners are faced with nowadays.
Regular dental examinations should be performed to correct small abnormalities as soon as possible regardless of age, gender, feeding type and appearance of the horse.
LIST OF LITERATURE
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4. Gorrell C. Equine dentistry : Evolution and structure. Equine veterinary journal. 29 (3). 1997. p. 169-70
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