Excellence In Finishing: Current Concepts, Goals And Mechanics
Excellence In Finishing: Current Concepts, Goals And Mechanics
Dr. Ashok Karad
BDS, MDS, M.OrthRCS [Edin]
Director, Smile Care
Bandra (W), Mumbai, India.
It has been widely recognized for many years that proper finishing is of critical importance inachieving an excellent occlusal result after orthodontic appliance removal. This clinicalpresentation deals with defining finishing goals and achieving them with the appropriatetreatment mechanics for optimal esthetics, function and stability. It highlights certain occlusal- static and dynamic - periodontal as well as esthetic parameters that provide useful guidelinesfor finishing in both the adolescent and adult orthodontic patient.
Keywords Finishing goals, occlusal parameters, periodontal factors.
Stability of the orthodontic treatment result has been atopic of great interest to the profession since theinception of our specialty. The improvements in theposition of teeth achieved after great deal of effort maybe lost to varying degrees, after the removal oforthodontic appliances. Sometimes changes in toothpositions are noticed even during the period when thepatient is using retention appliances. It has beenrecognized for many years that the stability oforthodontic treatment results at least partially dependson the way cases have been finished1. Orthodonticfinishing still remains a continual challenge for theOrthodontist. Preadjusted Edgewise Appliances in theircurrent variations probably represent the biggest stepup the orthodontic evolutionary ladder and providegreat benefits to Orthodontists in all stages of treatment,especially during finishing and detailing. However, insome clinical situations, it requires a great deal of effortand skill to achieve an excellent occlusal result afterappliance removal.
This clinical article deals with defining finishing goalsand achieving them with the appropriate treatmentmechanics for optimal esthetics, function and stability.It highlights certain occlusal - static and dynamic -periodontal as well as esthetic parameters that provideuseful guidelines for finishing in both the adolescentand adult orthodontic patient.
It is author's belief that the orthodontic finishing beginswith diagnosis and treatment planning. With advancesin treatment mechanics, there is hardly an abrupt stageof complicated wire bending to fine tune the toothpositions; rather it is a gradual progression towardfinishing. In the management of a routine orthodonticcase, it is extremely important for a clinician to definefinishing goals at the beginning of treatment andcontinue to focus on them till the finishing stage, inorder to achieve them with appropriate treatmentmechanics. The generally accepted treatmentobjectives are as follows:1,3
- Normal static occlusal relationships - Class Iocclusion with 'Six Keys", 3mm of overjet andoverbite.
- Normal functional movements - a " mutuallyprotected occlusion"
- Condyles in a seated position - in centric relation
- Relaxed healthy musculature
- Normal periodontal health
- Optimal esthetics
- Long-term stability of postreatment tooth positions
The purpose of this presentation is not just to outlinetreatment goals and discuss them in detail. It is theintent of this presentation to inform the orthodonticclinician of the importance of occlusal, periodontaland esthetic parameters, to finish orthodontic cases tothe highest standards.
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Static occlusal parameters
Proper alignment of teeth has been a fundamentalobjective of any orthodontic treatment approach. In Julyof 2000, the American Board of Orthodontics4 furtherclarified and quantified the static occlusal goals byproviding a grading system for study casts andpanoramic radiographs. In the mandibular arch, thelabioincisal edges of the incisors and canines are thedeterminants of anterior alignment. This is becausewhen labioincisal edges are aligned properly, the teethlook the best esthetically and they are the functioningsurfaces of the mandibular anterior teeth. In themaxillary anterior segment, the lingual surfaces of themaxillary incisors and canines are used as a guidelineto establish proper alignment. This is based on the factthat, these surfaces are the functioning surfaces andwhen aligned properly, the anteriors appear to be intheir best esthetic relationship.
In the mandibular posterior segment, the buccal cuspsof mandibular premolars and molars represent thefunctioning surfaces and they are easy to visualizeintraorally. Therefore, these landmarks are used toestablish the proper alignment in the posterior segments,within the patient's acceptable archform. In themaxillary posterior segments, central grooves of themaxillary premolars and molars are used to accessproper alignment. Again, these are used since theyrepresent the functioning surfaces of the maxillaryposterior teeth, and are easy to observe intraorally.
The marginal ridges can be used as a key to achieverelative vertical positioning of the posterior teeth4.During the finishing stage, it is important to make surethat the marginal ridges of adjacent posterior teeth arepositioned at the same level (Fig. 1). This will positionthe cusps and fossae of those teeth at the same level.Once the marginal ridges of the posterior teeth arepositioned at the same relative level, then thecementoenamel junctions are also at the same relativelevel. This will lead to the bone levels between theadjacent teeth being flat, producing a much healthierperiodontal situation for the patient.
The lack of distal root tip in the maxillary secondbicuspids expressed during the finishing stage leads todiscrepancy in the marginal ridge matching between these
teeth and the first molar. This also leads to a lackof occlusal contact in the posteriors4
Transverse relationship of posteriors
During the finishing stage, it is of paramount importanceto evaluate the buccolingual inclination of the posteriorteeth to achieve good intercuspation and preventinterferences during mandibular movements. This shouldbe assessed by evaluating the relationship between thebu ccal and the lingual cusps of the maxillary andmandibular premolars and molars - called the 'Curveof Wilson1. In normal situation, the lingual cusp shouldbe at the same level or within a millimeter of the samelevel as the mandibular buccal CUSpS4. This relationshipmakes the occlusal tables of posterior teeth relativelyflat, therefore, promoting better contact of the maxillarylingual cusps with the fossae of the mandibular posteriorteeth.
The extreme amount of mandibular posterior lingualcrown torque found in many preadjusted applianceprescriptions leads to "rolled-in" mandibular posteriorteeth as a result of expressed torque6,7(Fig. 2).
In the maxillary buccal segment, the palatal cusps ofthe first and second molars are generally slightly longerand extend slightly more occlusal than the buccalCUSpS.4 With the common use of expansion treatmentoften using over-expanded, commercial arch blanks ora limited amount of maxillary posterior expressedbuccal root torque, palatal cusps extend occlusallybeyond their normal limits (Fig. 2). This promotesinappropriate interdigitation between maxillary andmandibular posterior teeth, producing cross archbalancing interferences in the lateral mandibularexcursions8. Therefore, the buccolingual relationship ofposterior teeth should be improved by flattening thecurve of Wilson , minimizing or eliminating thediscrepancies in the posterior overjet, and avoiding theprominence of palatal cusps by reducing the
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Fig. 3: Cephalometric tracingsA - Pre-treatmentB - Post-treatmentC - Pre and Post-treatment superimpositions
lowerposterior torque and increasing the upper7long-term stability. The lower incisor apices should bespread distally to the crowns, and the apices of thelower lateral incisors must be spread more than thoseof the central incisors (Fig. 6). Apex of the lower cuspidshould be positioned distal to the crown. All four lowerincisor apices must be in the same labiolingual plane.The lower cuspid root apex must be positioned slightlybuccal to the crown apex.
The overall inclination of the maxillary and mandibularanterior teeth is best evaluated with a lateralcephalometric radiograph. The interincisal angle playsan important role in esthetics, function and stabilityand should not be based on averages.12 Growthdirection, esthetics and overbite should also beconsidered in determining ideal torque in the maxillaryand mandibular arch. In short, it should beindividualized.
If uncontrolled flaring of the lower incisors is permitted,then increased labial crown torque of the maxillaryincisors would be required to maintain appropriateoverbite/overjet and in the process, more bimaxillaryprotrusive results will be produced, which will bedetrimental to facial esthetics.
Insufficient thickness of maxillary second bicuspidscauses first molar to rotate mesially upon initial wireengagement, causing an increase in
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Class II tendencyand buccal movement of second bicuspid. Also, themarginal ridge discrepancies between the maxillaryand mandibular first and second molars may result fromdifficulties in posterior appliance placement due tolimited visibility, variable clinical crown height,delayed eruption of teeth, and gingival hypertrophy.8
Sondhi13 demonstrated the production of " inappropriateor broken contacts between mandibular first and secondmolars " due to the distal offsets of the first molarattachment found in some popular prescriptions. Thisoffset can displace second molars to the lingual and/or rotate the first and second molars to the mesial,thereby, creating an incorrect match of the adjacentmarginal ridges and contact points.
These discrepancies of treatment must be carefullyevaluated and addressed during the finishing stage inorder to promote proper proximal contacts, marginalridges and alignment in the buccal segments.
Maxillary second bicuspid - a key toocclusion
Ricketts 14 pointed out that the contact position of themax illary second premolar is a key to a properly treatedmalocclusion. The maxillary second premolar shouldhave a normal contact relation with the mesial inclineof the lower first molar which produces an interlockinginto the corresponding interspaces of the lowerpremolars (Fig. 7). This relationship causes the tip ofthe mesiobuccal cusp of the upper first molar to beslightly distal to the mesiobuccal grove of the lowerfirst molar. According to Ricketts this is the mostefficient, most self-cleansing and most self-preservingrelationship in accordance with Nature's plan.
The importance of proper contact points between theteeth in preventing food impaction and stability of thedental arches after orthodontic treatment has been wellunderstood by all specialists. During the finishing stage,three dimensional control of teeth positions and theirrelationship with the adjacent teeth is essential toestablish the location of contact points. Contact pointsor contact surfaces of teeth are generally located inthe occlusal one third of the proximal walls, slightlybuccal to the central fossa in the molar and premolararea with the exception of the maxillary first and secondmolars15,16 (Fig. 8). The contact point between themaxillary central incisors is located at the most incisalone third having a perception of a vertical line. Theposition of contact poi nts in the maxi lIary anteriorsegment, when viewed from front, seems to progressfrom the incisal to cervical , from the central incisorsto the canine (Fig. 8).
Contact points must be observed from two aspects inorder to obtain the proper perspective for their properlocation; the labial or buccal aspect, and the incisalor occlusal aspect.
After the resolution of malocclusion, teeth need to beindividually settled into their final positions beforeappliance removal. In the posterior segment, teeth aregenerally held away from each other in vertical planedue to full size rectangular stainless steel finishingarchwires . The vertical settling of maxillary andmandibular teeth to achieve maximum intercuspationis done by using different configurations of verticalelastics. The more precise the placement of bracketsand tubes, the easier it is to settle the teeth and theless elastics need to be used in this way. The adequacyof posterior teeth interdigitation is evaluated byassessing the contact relationship between the cuspsand fossae of the molars and premolars. Ricketts14pointed out that, without third molars, 16 to 24 occlusalstops or centric stops on each side are adequate for agood balanced occlusion .
The lingual cusps of the maxillary premolars and molarsshould be in contact with the marginal ridges or fossaeof the mandibular premolars and molars4 . In addition,the buccal cusps of the mandibular premolars andmolars should contact the fossae or marginal ridges ofthe maxillary molars and premolars4 Due to lack of anadequate occlusal table, the lingual cusps of themaxillary first premolars may not establish contact withthe mandibular first premolar.
Dynamic occlusal relationships
In addition to achieving the occlusal relationships inClass I as suggested by Angle 17 and the 'six keys toocclusion ' by Andrews 18, other workers I likeWilliamson 19, Aubrey20, Ricketts21, and Roth22 have allexpanded the area of knowledge in occlusion to includethe neuromuscular and bony structures of the TMJ inestablishing orthodontic treatment objectives. Indealing with the various elements of
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functionalocclusion as one of the finishing goals, it is importantto achieve stable centric relation of mandible withmaximum intercuspation of the teeth at this position.In the intercuspal position and retruded contact positionthe mandible should be situated in the same sagittalplane, the distance between the two positions beingless than 1 mm.
There should be harmonious glide path of anterior teeth.These teeth should work against one another to separateor disclude the posterior segments as soon as themandible moves out of centric closure. The properoverbite and overjet established after orthodontictreatment should allow for a gentle glide path.
The canines should provide the main gliding inclinesfor lateral excursions, with no interferences on thebalancing side (Fig. 9). The six mandibular anterior teethand mandibular first bicuspids should articulate withthe maxillary six anteriors during mandibular protrusiveexcursion. In this way, a protrusive load is spread overfourteen anterior teeth with no interferences in theposterior region (Fig. 10). The teeth should not preventthe mandible from entering or leaving any possibleposition that the joints will allow. Therefore, the teethshould direct and maintain the centricity of the condylesin their fossae on closure.
Interincisal relationship - a critical elementof functional occlusion
The optimal position of maxillary and mandibularincisors and their relationship with each other afterorthodontic treatment is one of the key elements offunctional occlusion. According to McHorris,23,24 in theoptimal functional occlusion, the anteriors are in veryclose approximation but do not touch when molars arein occlusion. The lower anteriors engage the lingualincline of the opposing upper anteriors immediately withmandibular movement. The lingual discluding surfaceof the upper anteriors seems to reflect the anatomicalangle or discluding pathway of the mandibular condyles.The ideal anterior disclosure angle is greater than or equalto 5 degrees than the condylar disclosure angle (Fig. 11).
An occlusal interference on the anterior teeth, identifiedduring unforced closure of the mandible, sometimesassociated with a distalizing effect in condylar positionhas been termed as "anterior interference.25 The axialinclinations of maxillary and mandibular anteriors andthe consequent interincisal angle should be proper inorder to avoid anterior interferences after orthodontictreatment.
One of the finishing goals of orthodontic treatment isto position the roots of adjacent teeth parallel to eachother. Other factors being normal, if the roots areparallel to each other, then there will be sufficient bonebetween the roots of teeth. It is considered that moreinterproximal bone will provide greater resistance toperiodontal bone loss if the patient develops periodontaldisease in the future. During the finishing stage, if theteeth are not properly uprighted, especially when thesecond bicuspids or first molars are extracted /missingand the posterior teeth are drifted into that space; thenthe marginal ridges will not be level, proximal contactswill be faulty, with angular bony defects on the mesialaspects of the mesially tipped teeth.
Another clinical situation which demands parallelismof roots of the adjacent teeth is when the maxillarylateral incisor is missing. If the maxillary lateral incisoris missing and the treatment plan involves sufficientopening of lateral incisor space and subsequentrestoration with an osseointegrated implant, then it isimportant to evaluate the position of the roots ofadjacent teeth radiographically. The roots of the centralincisor and canine should be parallel to each other withadequate space between the roots for implantplacement.
Crown Width Discrepancy
Size of the teeth is one of the most important elementsof anterior dental esthetics. Orthodontists are oftenfaced with disproportionate widths
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of anterior teethduring treatment. This tooth size discrepancy iscommonly found in patients with peg-shaped lateralincisors. Even after getting the teeth perfectly alignedand the arch forms properly establ ished withorthodontic treatment, the abnormal shape and smallersize of lateral incisor pose esthetic problems.
The Golden proportion can be called the building blocksof nature itself. This ratio is an ideal ratio that can bemathematically defined as 1 :1.618 (Fig. 12). It has beenobserved that when this rule of good proportion isfollowed, the result is something that is naturallyattractive and pleasing to the eye. Smiles can be madeattractive by following these mathematical rules ofnature to create harmony, symmetry, and proportion. 16,27
We can use the proportion to define the length: widthfor each tooth, Also the width of central incisor is ingolden proportion to the lateral incisor width which inturn is in proportion with the mesial width of theCanine26.
It is therefore imperative to restore the size of themalformed lateral incisors after the completion oforthodontic treatment for good overall treatment result(Fig. 13 & 15). Duringthe finishing stage of orthodontictreatment, if excessive space exists in the anteriorsegment, it should be redistributed to restore the propercrown width (Fig. 14). If insufficient space exists torestore these teeth, an adequate space should be gainedwhich will permit the restoration of proper crown width.To determine the space required to restore the crownwidth, during the treatment planning stage, constructionof a diagnostic wax-up is an important step to visualizethe final result. After removal of the fixed orthodonticappliances, provisional restorations should be givenbefore final restorations to avoid relapse.
Replacement of missing laterals with implants
Dental agenesis occurs quite frequently, especially ofthe maxillary lateral incisors, and it presents a truechallenge to an esthetic solution. For a long time, manyclinicians had suggested an alternative treatmentapproach by moving the entire lateral segment mesiallyto place the cuspid in the lateral incisor position,However, this approach ends up with compromisedresults that do not fulfill the esthetic requirements ofgood orthodontic treatment, since the cuspid has a verydifferent crown and root shape to that of the lateralincisor, as well as a darker shade. When missing lateralincisor space is closed by moving the entire lateralsegment mesially, lateral excursions are made usingbicuspids, which have shorter, thinner roots; thus,functional requirements are also not fulfilled either.
If fixed restoration is the treatment of choice, it requiresreshaping neighboring teeth, with consequent removalof varying amounts of enamel, and eventual risk ofgingival recession , caries etc. The osseo-integratedimplant is the most conservative and biologicalmethod , since the missing tooth can be replacedwithout damaging the neighboring teeth.
If the use of implants is the part of treatment plan forthe missing lateral incisors, it is necessary to decidethe exact placement of implants, evaluate the smileline and gingival contour. When the lateral incisorsare missing, there is usually no adequate space torestore them due to drifting of the adjacent teeth (Fig.16). In such cases, it is essential to gain adequate spacewith orthodontics for the placement of implant andcrown restoration for good esthetic result (Fig, 17). Theexact amount of space created should be according tothe proposed size of lateral incisors, which should beproportionate to the width of the central incisors, Afteropening up of sufficient space, acrylic teeth may beselected closer to the shade of the patient's teeth,bracketed and attached to the arch wire for estheticpurposes. Before the orthodontic appliances areremoved it is important to evaluate radiographicallythe position of the roots of adjacent teeth.
The roots of the central incisors and canines on eitherside in case of bilaterally missing laterals should beparallel to each other with adequate space betweenthe roots for implant placement (Fig. 18 & 19). Beforeremoval of orthodontic appliances, it is common tosee adequate space for the prosthesis and inadequatespace between the roots of the adjacent teeth for animplant. This usually occurs due to
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tipping movementof adjacent teeth, which requires proper uprighting ofthe roots during the finishing stage of orthodontictreatment. The minimum space of 6.5mm betweenadjacent roots is required to place a standard implantof 3mm width.
Color, contour and the health of the gingival tissuesprovide the framework and backdrop for the estheticsmile. Even if the case is well finished with orthodontictreatment, abnormal ity of the gi ngiva either in the formof loss of papilla, asymmetrical pattern and excessivedisplay. leads to a poor result. It is therefore essentialto have proper gingival architecture and display toachieve a maximum esthetic result. As a general rule,a line drawn at the level of the free gingival margin ofthe anterior segment will show the free gingival marginof the centra l incisors and the cuspids to be at the sameheight and that of the lateral incisors to be slightlycoronal 28 (Fig. 20).
Furthermore, the most apical point of the gingiva orthe gingival zenith is located just distal of the longax is of the central incisors and cuspids, whereas thegi ngival zenith for the lateral incisors coincides withtheir long axis l6,29 (Fig. 20). In other words, the heightof the gum line across the face of the tooth should becentered on the lateral incisors, and positioned in thedistal 1/3rd of the face of the tooth for the centrals andcanines. This gives the gingiva a semi-circularappearance for lateral incisors and an ellipticalappearance for central incisors and canines.
During the process of eruption the whole periodontalaparatus is carried with the erupting tooth. When thereis asymmetric eruption of the teeth it will also result indiscrepancies in heights of the underlying crestal bone.This, in turn, results into asymmetries in gingivalheights (gingival zenith) from one side of the arch tothe other. This type of a clinical situation can bemanaged orthodontically by intrusion or extrusion ofteeth (Fig. 21, 22 & 23).
Modern orthodontic treatment is aimed at creating thebest possible occlusal relationships within thework of acceptable facial esthetics and stabilityocclusal result. It is extremely important for aclinical to define finishing goals at the begining oftreatment and continue to focus on them till thefinishing stage, in order to achieve them withappropriate treatment mechanics. This article hasprovided certain occlusal - static and dynamic -periodontal as well as esthetic parameters that outlineuseful guidelines for finishing in both the adolescentand adult orthodontic patient. Also, choosing the bestpossible treatment options from other specialties andcombining them as a part of the optimal treatment planbased on scientificrationale should be the aim for thebenefit of the patient.
I thank Dr. Ratnadeep Patil for his clinical assistancein rendering Perio-restorative treatment when indicated.Sincere thanks to Ms. Arlene Fernandes, Dr.Kavita Ramanathan and Dr. Ken DCunha for their professionalassistance in preparing this manuscript, andMr. Nikhil Patel for his assistance in imaging.
Dr. Ashok Karad, BDS, MDS, M.OrthRCS [Edin]
Diplomate, Indian Board of Orthodontics
Director, Smile Care, IndiaSmile Care, 13, Geetanjali, 234, S.v. Road,
Bandra (west), Mumbai 400050. India
Tel: 022-26431670/71 Fax: 022-6416342 e-mail:email@example.com
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