Equine Dental Disorders

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1 Equine Dental Disorders BEVA Continuing Professional Development and Client Education Prof P M Dixon The University of Edinburgh Copyright The University of Edinburgh and The British Equine Veterinary Association

2 The horse evolved in the Americas circa 55 million years ago. Dawn horse (hyracotherium) was a rabbit sized animal that browsed on soft leaves had short teeth (brachydont) similar to human or canine teeth

3 Large intestine of equidae Climatic Changes 55 million years ago Change of vegetation Development of caecal & colon microbial digestion of cellulose Enlargement of caecum and colon

4 Brachydont teeth of Dawn horse changed to Hypsodont (long crowned) teeth to cope with eating an abrasive grass diet (contains high levels of silica) for up 18 hours/day

5 Evolution and migrations of horses

6 Drawings of wild horses: Lascaux Caves in France -15,000 years BC Horses were only a food source then

7 First evidence of equine domestication Bit-induced cheek teeth damage in a fossil equine skull dated circa 4000 BC found near the Black Sea

8 Signs of Dental Disease in Horses Many horses will suffer dental disease without showing any obvious signs of disease Affected Horses may: Drop partially chewed food (quid) Pack food into cheeks Have poorly digested food present in faeces Have bitting or head carriage problems Suffer weight Loss only in extreme cases

9 Quidding food is sign of painful dental disease

10 Feeding forage to assess mastication Assess if normal loud crunching sounds are made during chewing Assess if horse chews with both sides of mouth Assess if quidding or food packing in cheeks occur

11 Hamster Like Food packing in cheeks with painful dental disease

12 Painful dental disease Large quantities of undigested grain in faeces Long and large fibrous particles in faeces Much nourishment not obtained from food

13 Weight Loss only Occurs with Longstanding & Severe Dental Disease

14 itting and Head Carriage Disorders Disorders around contact areas of Bit, Bridle and Noseband Large Cheek Teeth Overgrowths that Restrict Jaw Movement Other sharp overgrowths that contact the Cheeks and Tongue

15 Dental Examination Equine dental examination and treatment cannot be performed without use of a full mouth speculum (gag) Some horses will need to be sedated for dental examination

16 Deciduous Incisors (milk teeth) Erupt at circa 01s (Central) 1 week of age 02s (Middle) 6 weeks 03s (Corner) 6-9 months (Rule of thumb - 6 days, 6 weeks & 6 months)

17 Permanent Incisors Erupt at circa: Central (01s) 2½Years Middle (02s) 3½ Years Corner (03s) 4½ Years

18 Age-related changes in 301 or 401 incisor appearance 18 years 24 years 12 years 4 years 6-7 years Labial Aspect Infundibulum Secondary dentine ( star )

19 Why ageing cannot be accurate Pulp directly beneath occlusal surface Pulp deep beneath occlusal surface Deep infundibulum Shallow infundibulum

20 Aged horse -very worn incisors

21 Anisognathia Maxillary CT Rows are 20-25% (median 23%) further apart than Mandibular CT Rows Note also the angulated surface of the CT

22 Lateral excursion test Close the jaws and force the lower jaw sideway After 1 cm or so the jaws will be forced apart This is caused by the angulated surface of the upper and lower cheek teeth coming into contact

23 OVERJET (upper incisors rostral) Parrot mouth Overshot jaw Overbite Rarely causes a problem grazing Inherited defect?

24 Severe Overbite (upper incisors rostral to and overlying lower incisors)

25 Severe 06 and 11 overgrowths along with parrot mouth

26 Orthodontic Treatment of Foal with Overjet Drilling between cheek teeth to fit steel wires for orthodontic brace

27 Brace fitted between cheek teeth and incisors to slow down growth of upper jaw

28 Orthodontic treatment of marked overbite using a wire brace and acrylic biteplate

29 Before and after 3 months bracing overjet almost fully corrected

30 Successful Bracing of Overbite in Foal

31 Underjet ( Sow Mouth, Monkey Mouth ) Sow mouth Undershot jaw Underbite Uncommon Incisors clinically insignificant CT overgrowths occur Surgical correction is difficult

32 Retained Deciduous Incisors Usually lie in front of permanent tooth (arrow) Cause displacement (caudal) of permanent tooth If loose, remove with forceps If firmly attached, remove with dental elevators

33 Full length retained incisor Local anaesthesia of mental nerve Alveolar wall being removed for extraction

34 Alveolar Wall Removed on Labial Aspect of a 5 cm Long, Retained 702

35 Supernumerary Incisors Develop in addition to the 6 normal permanent adult incisors Have long ( up to 7cm) reserve crowns Lie close to reserve crowns & roots of normal permanent incisor Usually cause little problem Often best not to remove

36 Supernumerary Incisor (SI) causing palatal displacement of 101 and 201 and diastemata SI

$fractures of$

37 Traumatic complicated (pulp exposed) fractures of permanent incisors

38 Fractured 103 (corner incisor) with exposure of pulp in a young horse Good candidate for endodontic treatment a) Remove dead pulp (arrow) b) Seal off healthy underlying pulp c) Tooth will continue to erupt and should come into wear eventually

39 Fractured Incisors Receiving Endodontic (root canal) Treatment

40 Different stages of Endodontic Treatment of a Fractured Incisor

41 Traumatic Damage to Upper Incisors with Overgrowths on Opposing Incisors

$Old lower incisor fractures with secondary overgrowths in$

42 Old lower incisor fractures with secondary overgrowths in opposing incisors This horse can only chew in one direction

43 Incisor fractures in a Crib Biter

44 Abnormal Incisor Wear in a Young Crib Biter

45 Young horse with caries of incisor (210) Must not mistake the normal brown chalky covering (cement) of many equine teeth as caries Dental Caries is uncommon in Horses May be associated with high molasses levels in diets Caries is most common in infundibula of upper cheek teeth

46 Treatment of incisor caries Clockwise: Removal of caries, apply acid etching soln, apply bonding agent & defect filled with a modern composite filling

47 Slope or Slant Mouth Indicates the horse has been chewing in just one direction Often is sign of a severe problem with cheek teeth Diagnose and treat the cheek teeth problems first

48 Reducing sloping incisor overgrowths after correcting the underlying CT problems

49 Reducing incisor overgrowths with power and manual instruments

50 Slight Wry Nose can cause abnormal incisor misalignment & wear

51 Severe Wry Nose in Foal Wry nose can be corrected in some foals May need extensive nasal surgery also Ethical considerations if foal severely deformed

52 Incisor Diastema in an Aged Horse Causing Food Impaction and Gingivitis There should be no spaces between the occlusal surface of adjacent teeth Narrow spaces can be most problematic as they can act like valves i.e. diastema(ta) trapping food

53 Incisor diastemata can be treated by widening space with diamond coated disc or a saw blade

54 Canine Teeth ( Tushes ) Present in male horses Erupt at circa 5 years of age

55 Calculus accumulation on canine (and adjacent incisor) The lower canines are predisposed to accumulating calculus Calculus can cause severe gingivitis of adjacent gums Remove calculus and brush canines weekly to prevent recurrence

56 Extraction of an infected canine tooth long reserve crown and roots (<7.5cm)

57 Wolf Teeth (05s ; 1 st Premolar) No deciduous precursors Erupt at circa 1 year of age Many lost when 1st upper deciduous cheek tooth ( cap ) is shed If of normal small size and in normal position can they cause bitting problems?

58 Lower Wolf Tooth Lower wolf teeth are uncommon (arrows) They often interfere with bit and are best extracted

59 Displaced (rostro-laterally) Wolf tooth Protruding Towards the Cheeks and Causing Bitting Problems

60 Palpating a rostrally displaced wolf tooth

61 ocal anaesthesia and/or Infraorbital nerve block for wolf tooth extraction in sedated horses

62 Wolf tooth extraction Can involve extensive elevation of the tooth Considerable injury can be caused by unqualified personnel Horses should be vaccinated against Tetanus

63 Complete Extraction of Wolf Teeth with Musgrave-type Elevator

$lead to fracture of wolf tooth Development of$ $and post extraction images of a fractured wolf$

64 Fractured Wolf tooth Attempted extraction can lead to fracture of wolf tooth Development of bitting problems not present previously Pre and post extraction images of a fractured wolf tooth

65 Developmental cheek teeth disorders Retention of deciduous cheek teeth ( caps ) Diastema(ta) Displacement of cheek teeth rows Supernumerary cheek teeth

66 Retained Caps Caps - the remnants of deciduous (milk) teeth Normally shed during eruption of the underlying permanent tooth Loose, retained caps can cause oral pain

67 Use of Cap extractors to remove loose retained cap There is much variation between horses in the age at which caps are shed Premature cap removal can damage the underlying tooth

68 Elephants don t get diastema ne large tooth in wear - lasts 10 years (x 7 teeth)

69 Diastema Occlusal surfaces of Cheek Teeth (CT) should be tightly compressed together Act as one functional grinding surface Angulation of 1st, against 5th & 6th CT compresses CT row

70 Cheek Teeth Diastema(ta) Food trapped between CT Will eventually get packed into periodontal spaces Is the most painful equine dental disease Difficult to diagnose usually caudal, lower CT affected A small diastema can be more problematic than a large diastema

71 Open-Mouth radiography X-Ray showing 2 diastemata between Upper cheek teeth

72 Diastema between 106 and 107

are angulated reasonably Dental buds developed too

73 Cheek Teeth Diastemata Diastemata present between all of lower CT Severe periodontal disease Teeth are angulated reasonably Dental buds developed too far apart This horse was euthanased on humane grounds

74 Standing sinus surgery to treat diastema that is allowing food into sinus

75 Treatment of Diastema Replace long fibre food e.g. hay with grass, or short chopped foods e.g. grass or alfalfa cubes can be successful also need 2-3 times annual rasping Removal of overgrowths that develop opposite diastemata is essential

76 Removal of impacted food Long handled dental pick High pressure water or air picks Transient improvement only

77 Widening a Diastema to prevent food pocketing A specialised veterinary procedure

78 Widening Diastemata Danger of opening into pulp of tooth Danger of overheating adjacent pulp Careful evaluation of cases and training of personnel required

79 Severe 06 and 11 overgrowths along with parrot mouth

81 Reducing tall overgrowths of (206) 1 st cheek tooth with power instrument

82 Sharp Overgrowths ( Beaks ) of upper 06s causing bitting problems 206 overgrowth has been removed

83 Caudal lower cheek teeth overgrowths (11s) (arrows) are also common in parrot mouthed horses and are often missed

84 Cheek Teeth Displacements Developmental Overcrowding of arcades during eruption often bilateral - Usually 4th and 5th cheek teeth (09s & 10s) - Medial or lateral displacement -Rotation of tooth may also be present Acquired More common Usually lower 10s and 11s in older horses

85 Developmental cheek teeth displacements of 409 and 310

86 Horse with displaced cheek tooth growing into its cheeks This horse had a history of being difficult on bit and had routine treatment by an unqualified EDT for many years without detection of this very painful problem

87 Slight Medial displacement of 310 & 311 with high occlusal angulation Diastema (D) between D 309

88 Widespread dental displacement in a geriatric horse with secondary diastemata and overgrowths Neglected mouth

89 Cheek Teeth Displacements Will result in malocclusion and thus overgrowths and also diastemata and periodontal disease TREATMENT Removal of overgrowths every 6 months with mild displacements and widening of diastemata Extraction of tooth if severe displacement and periodontal disease present

90 Supernumerary CT (Polyodontia) Means more than 6 permanent cheek teeth in a row A caudal (7th) upper CT is most common Supernumerary tooth may be connated (i.e. a double tooth)

91 7th 6th 5 th 8 th

92 Supernumerary CT Malocclusion, overgrowths and periodontal disease can occur TREATMENT Remove overgrowths If severe periodontal disease present - extract tooth

93 Oligodontia Means absence of normal tooth / teeth True equine oligodontia is rare Absence of teeth in older horses (see figure) is common Results in overgrowths on opposing CT and drifting of adjacent CT into vacant space

94 Oligiodontia absence of permanent lower 09s and 11s

95 Dental overgrowths (Stepmouth) due to loss of opposite teeth

96 Anisognathia Maxillary Arcades are spaced 20-25% (median 23%) wider apart than Mandibular Arcades

97 Transverse section of young equine skull Young Teeth have: - large pulp cavities Are: - primarily composed of enamel Have: - minimal dentine

98 Normal Angulation of CT CT occlusal angles are usually degrees but can be up to 35 degrees in normal horses (Brown 2005) 10 o 35 o

99 Initial crushing stroke during mastication Resting Crushing stroke

100 Power stroke of mastication

101 Hay or Grass Hard Food Lateral Jaw Movements are Reduced when Eating Hard Feed

102 Sites of enamel overgrowths and subsequent trauma from enamel overgrowths

103 Enamel overgrowths on mandibular cheek teeth can cause ulceration of the tongue and bitting problems

104 Large vertical ridges on lateral edges of upper cheek teeth are a common site of enamel overgrowths

105 Ulcerated cheeks caused by maxillary CT overgrowths

106 Sharp enamel ridges causing cheek ulceration at areas of bridle and noseband contact - subsequent bitting problems

107 Shearmouth If dental overgrowths are not treated they will eventually involve all of the occlusal surfacecausing abnormal angulation of over 45 degrees

108 Wavemouth and Shearmouth Multiple overgrowth disorders are common This horse mainly chews with its normal left side

109 Smooth Mouth Old Horse Cheek teeth enamel largely worn away Some teeth worn down to individual roots Softer dentine & cementum become smooth -no good for grinding These horses will need young grass or chopped forage to maintain weight

110 Frequency of routine dental examination and floating (if necessary) can vary Age Young horse shedding caps & older horse with some missing teeth need frequent care Work - e.g. dressage horse check 6 monthly vs. retired horse, brood mare examine >12 monthly

Frequency of routine dental examination and floating (if necessary) Predisposing abnormalities? e.g. slight parrot mouth, neglected overgrowths or a displaced tooth?

111 Frequency of routine dental examination and floating (if necessary) Predisposing abnormalities? e.g. slight parrot mouth, neglected overgrowths or a displaced tooth? Will need more frequent rasping Level of concentrates feeding e.g. fully outdoors permanently may have little enamel overgrowths vs. horse fed 5kg of hard food per day

112 A variety of shapes and sizes of rasps are required to float teeth properly

113 Different rasps different sites

114 Motorised dental instruments Speeds up work especially in removing large overgrowths

115 Dental floating should remove enamel overgrowths but leave an effective ( i.e. irregular) occlusal surface

116 Inappropriate power instrument floating Soft tissue damage and haemorrhage Excessive removal of occlusal surface including dentine Deep exposure of odontoblast processes painful chewing for weeks May expose pulp apical infection

117 Normal Transverse Ridges

118 Tall ( exaggerated ; accentuated ) Transverse Ridges Will cause abnormal wear of opposite tooth May restrict rostro-caudal mandibular movement Should be reduced to level of other transverse ridges

119 Fractures of Cheek Teeth and Supporting Bones Trauma e.g. kicks from other horses Unskilled operators using dental shears Bit damage Spontaneous Fractures - upper cheek teeth a) Lateral Slab Fractures b) Midline infundibular fractures

120 Trauma Fracture of Mandible and Invariably of Cheek Teeth

121 Severe oro-facial infection following iatrogenic damage to 6 th mandibular C.T. (311) from dental shears by untrained operator

122 Bitting injuries Severe damage can be caused to gingiva, cheeks, bones and teeth by rough use of bits The bit is made of steel - the mouth of sensitive tissues!

123 Bit injury can lead to severe damage (sequestration) of mandible Repeated Bit damage can eventually cause severe bony damage to bars of mouth ( polo pony mouth ) and even to 1 st cheek teeth

124 Displaced Fracture of Rostral Mandible Horses play with drop-down handles in boxes and then trap their lower jaw Repaired by wiring the incisors to canine or cheek teeth

$Cheek Teeth These fractures$ develop spontaneously Common

125 Lateral Slab Fractures of Cheek Teeth These fractures develop spontaneously Common in the upper cheek teeth especially 4 th (09) Fracture tends to displace into the cheeks - painful

$fractures of these teeth Right - food impacted into$

126 Advanced caries of infundibula of upper cheek teeth Coalescence of caries (Left) can lead to midline fractures of these teeth Right - food impacted into fracture will spread out the fractured tooth into cheeks and hard palate

$sagittal fracture caused by advanced$

127 Cheek Tooth extracted because of midline sagittal fracture caused by advanced infundibular caries

$system ) and filled to help prevent fracture and apical infection of$

128 Severe caries of upper cheek teeth can be cleaned out ( sandblaster system ) and filled to help prevent fracture and apical infection of tooth

129 Apical (tooth root) infections in cheek teeth Because of long reserve crowns of equine cheek teeth these infections will usually cause deep infections of the supporting bones The signs will depend on which tooth and so which supporting bones are infected

130 Exposure of the pulp causes some apical infections

131 Ventral swelling and excoriation of the mandible due to apical infection of a mandibular cheek tooth usually develop soon after eruption of tooth

132 Sinus tract and swelling of ventral mandible due to cheek teeth apical infections in young horses

133 Diagnosis of apical infections requires radiography of suspect teeth Some dental radiographs can be difficult to interpret - even by experts

134 Transverse section through rostral skull of young horse Infection of 1 st and 2 nd maxillary cheek teeth (arrow) cause facial swelling and possibly tracts externally or into nasal cavity

135 Transverse Section through Caudal Aspect of Young Equine Skull The last 4 Cheek Teeth lie in the sinuses and infection of these teeth will cause sinusitis difficult and expensive to treat

136 Dental examination in a horse with sinusitis -to assess caudal maxillary CT

137 Diagnosis of sinusitis may require endoscopy, radiography, sinoscopy and scintigraphy

138 Treatment of Apical Infection Very early cases may respond to prolonged antibiotic courses Dental Extraction usually required by: - Oral Extraction - Repulsion - Buccotomy Endodontic (Root canal treatment) poor success to date

139 Repulsion of infected cheek tooth under general anaesthesia Intra-operative X-rays being taken to ensure the right tooth is repulsed

140 Left - infected tooth being punched into oral cavity Right - mandibular wound being partly sutured after tooth repulsed

141 Repulsion of cheek Teeth Teeth are often fragmented during repulsion Many cases will need further treatment

142 Dental wax or bone cement plugs are placed into empty alveolus following dental repulsion

143 Oro-mandibular fistula following dental repulsion

144 Buccotomy dental extraction An incision is made through the cheeks to gain access to the teeth risk of nerve and parotid duct damage

145 Oral extraction of cheek teeth An old-fashioned method recently re-introduced general anaesthesia not required reduced level of post-operative problems wide range of instruments and good technique required

146 Use of molar Separators During Oral Extraction of 107

147 Oral Extraction of 107 in 6 yo horse Fulcrum being used on a well loosened tooth

148 Successful Oral Extraction in Young Horses Left: Mandibular CT partly elevated prior to extraction Right: 10cm long upper cheek tooth orally extracted in a 5yo

149 Endodontic Treatment of Apical Infection Limited Success to Date

150 Over 500 BEVA Members have attended postgraduate courses on equine dentistry in the last 8 years

Index. Note: Page numbers of article titles are in boldface type.

Index. Note: Page numbers of article titles are in boldface type. Index Note: Page numbers of article titles are in boldface type. A Adult performance horse dental care in, 505 519 bit seat reduction in, 514 515 canine teeth disorders, 515 diagnostic nerve blocks in,