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A Removable Orthodontic Device for the Treatment of Lingually Displaced Mandibular Canine Teeth in Young Dogs Leen Verhaert, DV\{ Sutnwary: Tl4e v,Lnlocclwsion of ti,.ngwntly d.isptaced. rnand,ibwlar cnnine teeth is a. c07,tr.tmon ot'thod.ontic problenoin the d,orwestic dog. Sepernl treattuent wtethod,s haye been tlescribed., and. their nd'ttantages and disnd.vanta.ges ha.ye been extensively reviewed. This nrticle rl'escribes a funct'ional tecbn'ique used.'in 3B d.ogs of d.ffirent breeds for correction of the r'nnlocclusion. The techn,iqwe co,tosists of stiwulat,ing the dog to play with speciflc toys. It is n sitnph, inexpensive, non-invasive techniqwe that has a. saccess rate cuvnpa,rable to conventionnl orthod,ontic techruiqwes for trea.tflxerct of this cononoon rualocclwsion. J Vet Dent 16(2); 69-75, 1999. lntroduction The malocclusion of lingually displaced mandibular canine teeth is a relatively common orthodontic problem in the dog.l-o This malocclusibn may be due to a dental abnormality, a skeletal abnormality, or a combination of both.7'8 The palatal contact of the mandibular canine crown tips frequently causes discomfort and pain, and may lead to mucosal ulceration, infection, and even oronasal fis6lx1ie1.7-10 Several treatment methods have been described to correct the abnormality or to relieve the discomfort of the animal.4,8'I0-13 Movement of the maloccluded teeth may be undertaken using orthodontic appliances: inclined plane (direct or indirect),14-18 talescoping inclined plane,l8 or active force devices (expansion screw, W-wire, modified euad helix).z,a,tl The majority of these are fixed appliances, though removable appliances are also described. Othtr treatment options include surgical repositioning,I3'2o,zru surgical crown reduction anil extracfi91.8,10,r1,r3, All ofthese techniques have advantages and disadvantages) which have been reviewqd extensively.4,6,lz All of them require anesthesia on at least one occasion, with some techniques requiring multiple anes- thetic episodes. This paper describes a very simple, inexpensive, animal- and owner-friendly technique for correction of lingually displaced mandibular canine teeth when no other sbvere malocclirsion is present. Additionally, the technique enhances the animalowner bond. The technique can be described as a behavior modification tecFniqug using a removable orthodontic device. Technique This technique for correcting uncomplicated of lingually cases displaced mandibular canine teeth involves stimulating the dog to play, as often as possible, with specific rubber toys of an appropriate-size and shape. Correct diagnosis is critica-l-for success of treatment. No major jaw length discrepancy should be present. The diastema berween the maxillary third incisor and canine teeth should be wid6 enough to accomodate the mandibular canine tooth in its corre_cted position. Playing with and chewing on a suitable object forces the mandibular canine teeth into a comfortable and more normal occlusal position. The most appropriate objects ro use are toys with a round or oval shape. Toys with ropes or handles should not be used, since dogs tend to take toys in their mouth the easiest way, e.g., by the rope if it is present. The size is important. Too small a toy will not touch both mandibular canines at the same time, and also might be taken too deeply into the mouth. Too large a toy (i.e., one that lies on top of the canine crown tips) might cause intrusive ra[her than lateral tipping pressure and might be uncomfortable, causing the dog to give up playing. The correct size of toy sits in between and just behind the canine teeth, and is larger than the distance between the canine te.eth. and thus applies principally lateral pressure to the reeth while the dog plays. In some dogs very large toys are needed, because the dog holds objects between its carnassial teeth rather than the canine teeth. In that case the toy needs to be so large that it does not fit between the carnassial teeth, as this is likely to result in some Figure l: D9g, with rubber ball (A) and dog with rubber chew toy in its mouth (B). The potential beneficial effect of the toy on lingually displaced mandibular canine teeth can be clearly seen. The toy subjects tl\e teeth to tipping pressure in a labial direction. J. VET DENT. VoL 16 No. 2 June 1999 69 2: Case 17 at initial presentation, left lateral (A) and right lateral (B) views. Although the displacement of the left mandibular canine tooth is only moderate, clinically the situation is severe, with the tip of the crown of the mandibular canine tooth sitting in the periodontal space of the maxillary canine tooth. Figure of rostral, as well as lateral, tippurg of the In selected cases, where rostral as well as lateral tipping is required, carrying the toy between the carnasial teeth can be useful in some degree canine teeth. cases but undesirable in others. The composition and consistency of the object are important. Tl"re toy should be hard rubber, slightly deforming on chewing. Too soft a toy is unlikely to create enough pressure and would be rapidly destroyed b), chewing. Toys that are too hard or abrasive could damage the teeth. The toy should have a smooth surface to avoid excessive tooth wear. Active play for 15 minutes, 3 times per day is the recommended minimum; however, longer and more frequent episodes are prefbrable. The owner is advised to play with the dog as often as possible and to take away all other toys. Assuming a I week learning phase before the treatment becomes effective,2 additibnal rveeks are needed before any benefit from the treatment is likely to be seen. Occlusion is checked 3 weeks following the start of treatment, then again at monthly intervals as necessary. If no movement is seen after 3 weeks, other treatment In 14 dogs with no other malocclusion present, the mandibular canine teeth displacement had been corrected within 2 months, treatment sometimes taking as little as 2 weeks. The time required for correction was recorded for 26 dogs, and ranged from 2-12 weeks. For dogs aged 5 months at the start of treatment, the time required for correction ranged from 2-B weeks (median 3 weeks); for dogs aged SVz months) time required was 2-6 weeks (median 4 weeks); fbr dogs aged 6 months) time required was 3-4 weeks (median 3.5 weeks); for dogs aged 6Vz months, time required was 2-7 weeks (median 4 weeks); for dogs aged7-9 months) time required was 5-12 weeks (median 7 weeks). methods should be considered. Results Thirty-eight dogs, most of them of large and giant breeds, are included in this series of referral cases seen during a2-year period. The results are summarized in Table 1. The extent of displacement of the mandibular canine teeth has been divided into slight, moderate, and severe. Slight displacement indicates that the tips of the mandibular canine teeth contact the buccal half of the diastema between the rnaxillary third incisor and upper canine teeth. Moderate displacement indicates that the canine crown tips press into the palatal half of the diastema, and severe displacement is used for those dogs in which the crown tips of 'the canine teeth impact onto the Table I palate. also includes information on the presence or absence of other malocclusions. Mandibular retrognathia was present in several cases and the severity has been divided into either slight (less than 3mm) or significant (more than 3mm gap between the maxillary and mandibular incisor teeth). Cases were followed for 2 weeks up to 2 years. One case was lost to lbllow-up. Long-term followup in most cases was done by telephone contact with the owner or throllgh the referring veterinarians. No relapses were reported following use of this techruque. 70 Figure 3: Case 17 after 17 days of treatment, left lateral (A) and right lateral (B) views. The mandibular canine crown tips have moved 4mm labially . J. VET. DENT. Vol. 16 No. 2 June 1999 Figure 4: Case 24 at initial presentation, right lateral (A) and left lateral (B) views. Four dogs had retained deciduous canine teeth present in the mandible. The deciduous teeth were extracted. The malocclusion was corrected in these four dogs. One of these dogs also had rostral (incisor) crossbite. Eight dogs had slight to severe narrowing of the mandible (unilateral or bilateral). In a normal occlusion, the mandible needs to be slightly smaller than the maxilla. The buccal face of the mandibular first premolar tooth falls just palatal of the palatal face of the maxillary first premolar tooth. If the mandible is narrow as compared to the maxilla, a gap can be seen between the mandibular and maxillary first pre- ' . molar teeth when looking at the jaws in a ventrodorsal view. The difference between slight and severe was made in an arbitrary way. The lingual displacement of the canine teeth in six of these dogs was corrected in 2 rveeks to 2 months. In one, a Staffordshire terrier, the lingual displacement of the canine teeth Was corrected only on the least affected side, and crorvn reduction was performed on the canine tooth on the severely affected side. In another dog, an Airedale terrier, the tooth moved 3.5mm in 3 weeks, and then continued to move at a rate of 0.5mm per month. Eight dogs had slight or severe mandibular retroganthia, and these had the worst outcome in the series of cases. Three of them, with slight mandibular retrognathism,_were corrected.in 2-3 weeks. One was moving slowly (0.5mm per month), one was unilaterally corrected, and in three dogs the canine teeth did not move. One of these dogs, an Airedale terrier with a severely narrowed and slightly retrognathic mandible, did'not want to play wlth any toys. A combination of acrylic inclined planes attached to the maxillary canine teeth and gingivoplasty of the maxillary third incisor-canine diastema were used to provide relief of the animal's discomfort. One bull terrier with a wry bite and severe narrowing and retrognathism of the right mandible showed no movement of the mandibular canine tooth over a period of 2 months. One Bichon Fris6 had a malpositioned righr mandibular canine.tooth. The root of the mandibular right third incisor tooth blocked any labial movement of the canine tooth, and this incisor tooth was extracted. The malpositioned (ectopic) canine tooth was only half erupted. The root was not exposed after extraction of the incisor, but the remainder of the crown (still in the alveolar bone) was exposed. The canine tooth moved into normal position over a period of 4 months. One mixed breed dog showed a more complex malocclusion. Left mandibular and maxillary deciduous canine teeth were retained. With the J.VET. DENT.Vot.16 No.2 June 1999 Qase 24 four months later, left lateral (C) and right lateral (D) views. mandible being 2mm longer than the maxilla, the permanent mandibular canine teeth were touching the palatal sides of the maxillary third incisor teeth. The left third incisor tooth had already moved buccally, being inclined 45" compared to a normal position. The right third incisor tooth was still in a normal position. To give this dog a more comfortable bite, the left third incisor tooth was extracted. On the right side, only the retained deciduous canine teeth were extracted, and the dog was given a rubber ball to play with. Although the left mandibular canine tooth seemed to be trapped behind the maxillary third incisor tooth) it moved into a normal position over a period of 5 weeks. Discussion Lingually diplaced mandibular canine teeth are a common malocclusion, reported in many breeds.r 6 Several orthodontic treatments have been described. The most widely used are inclined planes, attached to the maxillary teeth) in different forms: direct acrylic inclined plane,l5,rz,ta indirect acrylic or metal inclined plane.ra'r0 In young, growing dogs the use of a telescoping inclined plane is preferable, to overcome the problem of inhibited jaw growth resulting from use of lixed appliances.ro'22 These are all functional devices, which rely on the dog to create orthodontic force when it closes its mouth. Active devices are also used, placed in the mandible. Examples are expansion screws) W-wire, and modi- fied quad-he1ix.2,8,10,13,1e Surgical repositioning is anothtr technique that has been used for movement of maloccluding teet6.ra'zo'zr For these treatments no major jaw discrepancies should be present. When major jaw discrepancies are present) surgical crown reduction (including partial pulpectomy, pulp capping, and surface restoration) of the mandibular ianine teeth is often the best treatment, although extraction is another option.l0,ll {Jse ofan external fixator for forward movement of mandibular canine teeth has been described in a case of mandibular retrognathia.23 Some of these techniques are more appropriate and have fewer adverse effects than otheis. Fbr successful use of any orthodontic appliance, a cooperative dog and owner are necessary.4,S'10,r2 Good oral hygiene is necessary to reduce mucosal inflammation around the appliance, and frequent examination is recommended. All toys should be removed to avoid loss or breakage of the appliance. In the rubber-ball technique, cooperation is also necessary. The owner needs to actively play with the dog and the dog needs to be willing to play. In most cases, when working with young dogs, interest in playing is not a problem. 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L o o o o o o oo Hg 0bI (60 !)- !,E !H d(! ooh (H ox qs I EE € .o o Clinical Features of 38 dogs with Lingually Displaced Mandibular Canine Teeth €oo) oo >\ L a d A o bo 60 c tr bo + 09 6 ! ESE 8EF € E.E c) O c) k o O C) o Fr o c) i.) ! (.) L oo 0 € o o o 6 €oo) (! 0) 3 \o z (.) o) C) F E c.) €t z d € E €i o) z d (! E b{ C) *r q B al J. VET. DENT. Vol. 16 No. 2 June 1999 ,- o o c) o) vt C) o o E o E, o o GI k x o F co F d C) o \o tr B o o d o bo k 4a o6 !'5 €9 gE ** Eo) rt' oo 0.) o o o o o o E rtE sl B L d tr o tr (d 6.) €0) I 9 gE d fiO) 9H lcl EE c)hI co B Gl E6.) o {.) o o €c) o (€ h0 ko c) bo c.r B€ 5q Ftr o! d= (.) E 6 fic) o (D d lr o o o EI o *.* \o *** *{.bl d(D' *bo C) o r-F o dc) k o) o o o rn o C) €' c) E L o o c) c) .A a o € c) 15 o (t o o X ka! 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C) o 1J t IE €o) .A bo L o c) () o L I rn € \o (.) J no) o .Fk & o <g CH o \o c-l rn c.) sf c-) o (! 6 c) ! C) zz c) ot o) s €c)(! (.) n* .o E q) C) c) E E (d bI a (:, o t > -] 6l c.) co ca c.) ra| -o C) 6 in E IL E lr o o. c) o a L ()o) c.) \o t,- \o rn 6) c) L L in irt G' 6 o\ 6l (\| & tr - 0 .A G' l< o n gg E 0)H o B.g lct c! .hE !l I (.) {.) c) o) o) *l p€ 5A od oti c, q o €(l) o o o (€ G) €c) bo Gt a .A 'cl toE ;E H- ai -c =o 3E .E€ Ea Hr C).d oo tr() o 69 Es 90 H€ ,D .= (! o) o o c) () o o dc) (.1 co t o E d 0) o E € d k E J4 (l) c) lri \o o) 6 .6.), k (.) o \o €oc) c) o c) o 6 € c) E o tr o Cd c) li.oo z E 3o o)dL o tr 1.. (\.l \o 6l VET. DENT. Vol. 16 No. 2 June 1999 73 or oval rubber chew toy should be taken away, and several toys,inay induce-more play activity tt .i-""iy one. In m.ukiple dog househojds, many ioy, rn"y bt necessary because tlie older dogs steai toy, fr"i" u younger one. All the commonly used orthodontic techniques require multiple anesthesias with the associated'iisk and expense. The rubber toy technique is inexpen_ sive and avoids the necessiry ilf It wbuld be advisable to obtain full'pre-"n"sth'iria. a"a p*1_lr"atment impres.sions and radiographi, as with'any-orthodon_ bur some owners are not ;lti;t;; l:have!.:hliqye, rheir dogs. ane.sthedsed just to take impressi"ons. As a compromise, hard wax bite wafers can be used to record crown tip positions in most conscious dogs. .Photographs .an be taken to."."ia th. .*t.rri ot malocclusion, taking a rostral, left and right view ofeach case. _The rubber ball technique has several other maior advantages.as compa.red to working *rt,.in. pi.'"i_ ously described appliances, which lan cause several problems.2.4.6.8,t0.t2 In young dogs, jaw growth might be inhibited .by afplian"ces tE"i'iemJrrt th. and'iniiior teeth in fi*.J p"rt_ laxilllJV..canine sep.o.ru.22 When teeth are not fully erupted ai the time a fixed appliance is placed, ;t ii titeli ttrrt .onl trnued eruprion will result in displacement of the applrance.s Pressure from applianies might lead to soft tissue trauma. Good oraihygiene iiri"t -urra"l"ly f"l successfi_rl ourcome whe"n using ihe rubber Datl techntque. (Jral soft tissue traumi from pres_ su.r;, inflammation. and ulceration are very ,nfil;ly wrth this technique . unless rhe dog is allergic to rub_ Der.. law growth is not inhibited as is seen with some ot the fixed applianccs. , People obiiin dogs for their pleasure, but often cto nor spehd enough qualiry time with them. In a world where'ume is money and work is often stress_ $1, r_o time is left for th. .o-p*iorr-that *a, intended to relieve stress in tne nr'.t pta.i. I often Vounq dogs that are bored aid lazy. Th; f-!! moment the owner starts ro actively play with the dog, th9 dog's character changes drimlJlally;;^; strong bond berween owner-and dog is formea. (Jnce owners are used.to playing,_they often will go on doing so because theyied.t#'U."!ni""a .;i"i)^ ment for the dog and themselves. qlay ti.pe required for this technique ffnimum not I<norvn. _ is .Compliance u.i_th specific timing recom_ mendad.ons in this group of dogs.is not knoivn. The rubb.er ball tethnique could be considered to be a modrhcarton of'a technique formerly used in chil_ dren with reverse bite in ihe incisor,;gi;;itp;i;L biting')-z+ Children were taught t3- cGse their f"u+,in a specific yay 9l a *obden rongue sparu_ ta and bite on it lor 5 to I0 minures, 3,timEs p.i dry. This was.attemqted for 2 weeks, u".i f i"rrection was made, another technique was used. "" These time schedules were used as guidelines. In thqte;hnG;; described here, examiniiion is ,..o--.rrd.d aftei 3 weeKs because most owners and animals need I week of learning the technique. age of the animal is an imporranr facror. --Jh. when teeth are only pardy erupted,- the toy needs onty to^gurde the erupting tooth in the correct directron. Once erupted, the tooth needs to be redirect_ r.-?t,., appropriate position. The technique . :_111-, w9lksd m tully erupted teerh as well as in te6th whrch were still e rupting; however, rhe time re.quired for correction was longer in the'fully erupt_ ed teeth. 74 After orthodontic treatment) a retention period is ofthi tooth to its tormer posrtlon. using conventional ortho_ ^V\4ren usually necessary to prevent return oonuc.apptlances fo1 treatment, a retention period is generally considered necessary. In the casb of lin_ cllsplaced mandibular canine teeth, a retention peri.od is usually nor necessary since the natural den_ tat lnterlock retains the canine teeth in t]-re desired position.4,8,r0,r3 With the technique deicribed in this article, additional rerenrion i, p.o"iJ.J-bt;";_ gLta.lty. tinued use of the toy. It appears iirut th.r. ii tittle risk of overcorrection (labioversion) oF-the canine teeth. This did not happen in any bf tfr. ag ;"rii, :,.f:jl.q he.re, even whin very lar[e toys wcre pro_ \.loeo long-term. fu wirh any technique, correcr diagnosis is critical ^ success of treatment. No for major jaw discreoancv should be presenr. the .rr. o'f , ii""i.ly i.'t .ln nathic. mandible, the ourward movemeni of "gl th"e mandlbular canine tooth is inhibired by rhe maxillary '*. canine tooth. In less severe cases, t.inniqu! does seem to work if a very large rubbeiU"tt ls ,rr'eJ .1" tip the canine te6th ,iot only laterally, bui :p ], rosrrally also to a certain exrent. The diaiiema berw.een maxillary third incisor and canine teeth needs to be rvide enough to accomodate the mandibular canine teerh. Lingually displaced mandibular canine teeth have .been described as being primarily caused by reten_ tion of deciduous canind 1s.dr.o,r.i,rs In this ieries of -mandibular 38 cases, only four dogs had retained oectduous canlne teeth. More than 50% of the dogs reported here had a cliniqally clctecrable ;"* t."gif, or width abnormality. Skel'etal malocclirsions ?re considered inherited unless a developmintal cause can reliably identified.8 Owners bf tt es. aogs need,be ro be advised about the heritabiliry of thls condition, and informed that the treated a,ig,houd not be bred. To date.,,there have been no reports of the fre_ quency with which lingually displaced canine teeth as jaw growth contiiues. Early fixed-device :",:,1..1 orthodonuc treatment is not recommended.6,s,r0,22 AJthough treatment as described here -av not h"u. been necessary fbr some of these dogs, tLrere is no reason not to encourage the owner to play with the dog. The success of this very simple and functional that more iesearch is needed technique _suggesrs regarding hedtability and environmental influences on.Jaw development. Some of the minor skeletal niato.cluslons may be produced by lack of function. JtucLes tn dogs have shown an influence of occlusal forces on jaw growth.zs .It has been shown in exper_ rments in rats that food consistency influences'jaw development.26 Feeding commdrcialvlaurit"Ut. dlets may have an influence on jaw develobment and occlusion, because of the lack oifunction.'p;";dil; S. d"g. ym something to- chew ,nlpf"y work wrrh, could be beneficial to"n, "nE jaw gror.r.th and occlusion. . In.properly selected cases (young dogs, no major jaw discrepancies). the .rubbei toyrte.h",riq;e is suc_ wlth correcdon of the maiocclusion within 4 in most caies. This technique eliminates the need for more involved orthod6nti. t..fr"iq".i, which. require multiple anesthetic episodii. The techntque also encourages developme'nt of a strong bond between owner aid animal'du.i"g rh. course cessful weeks of treatment. J. VET. DENT Vot. 16 No. 2 June 1999 The authorlhanks D. A' Crossley for his advice while writing thid article. References l. 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