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ORIGINAL ARTICLEPOJ 2012:4(2) 48-55Comparison of tooth and arch dimensions in dentalcrowding and spacingSaman Faruquia, Mubassar Fidab, Attiya ShaikhcAbstractIntroduction: Any disproportion between tooth and arch dimensions predisposes to dental crowdingand spacing, which are the most common forms of malocclusion. Hence, the objective of this study is tocompare these elements between normal, crowded and spaced dental arches.Material and Methods: A sample of 90 dental casts was collected and space analysis was performed bysubtracting the sum of mesio-distal (MD) dimensions of all teeth (except the permanent molars) from thearch length. On the basis of this space analysis, the sample was divided into three groups, namelynormal, crowded and spaced arches. ANOVA and Bonferroni post-hoc were performed for thecomparison between the groups. A level of significance (p 0.05) was used for the statistical tests.Results: There was a statistically significant difference in the MD dimensions of upper canines, upperfirst molars and lower incisors between crowded and normal arches (p 0.05), and upper incisors, lowercanines and lower premolars between spaced and normal arches (p 0.05). A statistically significantdifference was also found in the bucco-lingual (BL) dimensions of upper lateral incisors, upper rightpremolars, lower premolars and lower first molars between spaced and normal arches (p 0.05); in thearch perimeters between crowded and normal arches, as well as in the upper arch perimeters, lowerinter-canine (IC) widths and lower inter-premolar (IP) widths between spaced and normal arches(p 0.05).Conclusions: The normal dental arches differ from crowded and spaced dental arches in tooth and archdimensions.Keywords: Crowding; spacing; tooth dimension; arch dimensionIntroductionDental crowding and spacing are the mostcommon forms of malocclusion.3 Crowdeddentition means that there is insufficientroom for the teeth to erupt in an idealposition. As a result, the teeth may beimpacted, rotated or displaced. On the otherhand, dental spacing means that there isexcessive space between the teeth or theproximal contact between the teeth is absent.A combination of etiological factors has beenrecognized in an attempt to better understandthese dental problems. Although heredity,4environment,4 ethnicity,5 and secular trends6are possible etiologies of crowding andspacing reported in the literature, a relevantconcern in this context is the causative role ofvarious clinical characteristics. A range ofstudies3-5,7 has been conducted to show theassociation of size of the teeth and arches butthe results are contradictory.The tooth-size arch-length discrepancy(TSALD) has been an area of interest of manyAwell-aligned set of teeth ascertainesthetics and stability. Furthermore, aperfect tooth position provides idealconditions for good health and optimal careof teeth. However, the dental arch continuityand integrity is a result of harmony betweentoothandarchdimensions.Anydisproportion between these elementspredisposes to dental crowding and spacing,1which are considered detrimental to dentalhealth and function. Apart from variousfunctional incapacities, these malocclusionsmay be a source of compromised smileesthetics and low self-esteem.2aBDS,Resident, Department of Orthodontics, The Aga KhanUniversity Hospital, Karachi, PakistanbCorresponding Author; BDS, MCPS, FCPS, PGD HIMS,Associate Professor and Program Director, Department ofOrthodontics, The Aga Khan University Hospital, Karachi,Pakistan. Email: mubassar.fida@aku.educBDS, M.Orth, FCPS, Assistant Professor and ProgramCoordinator, Department of Orthodontics, The Aga KhanUniversity Hospital, Karachi, Pakistan48

POJ 2012:4(2) 48-55Material and Methodsresearchers and several factors such as toothdimensions, arch widths and lengths havebeen found to be related to this discrepancy.Initially, Siepel8 showed that the positions ofteeth in the dental arch can be determined byconsidering the size of the teeth and theamount of space available for them in thedental arch. This was followed by a study byLundström9 reporting two factors accountablefor dental crowding i.e. the increase in mesiodistal (MD) dimensions of teeth and thedecrease in dental arch dimensions.The biometric study by Puri et al3 confirmedthat crowded arches consistently had largerteeth than the normal arches. They alsoshowed that smaller teeth, particularly thesmall mandibular incisors are responsible fordental spacing. In addition to the MDdimensions of teeth, the bucco-lingual (BL)dimensions have also been found to affect thedental alignment. In a recent study, thepermanent crown dimensions in young menwith naturally good occlusions werecompared with those who requiredorthodontic treatment.10 The results showedthat tooth crown dimensions (MD as well asBL) were significantly larger in subjects withmalocclusions than in those with goodocclusions. In contrast, Bernabe and FloresMir11 showed that crowded and normalarches differ significantly in their MD toothsizes and arch length but not in their BL toothsizes. Loren12 found a significant associationbetween malalignment of teeth and archwidth, however he concluded that arch lengthand incisor crown diameter do not vary inindividuals with and without malalignment.Dental crowding and spacing are theconsequences of TSALD which is a significantarea to investigate because it has an influenceon treatment methods and retention. Hence,the present study was planned with theobjective of comparing the tooth and archsizes between normal, crowded and spaceddental arches.This cross-sectional study was conducted attheorthodonticclinic.Priortocommencement of treatment, informedconsent was obtained from patients and/orparents that their records might be used forresearch purpose. A sample of 90 dental castsof Pakistani subjects aged above 11 years wascollected. The dental casts were selected fromthe records of the patients seekingorthodontic treatment which met theinclusion criteria: (1) pretreatment casts ofsubjects with no prior history of orthodontictreatment, (2) well erupted permanentdentition permitting proper measurements ofcrown dimensions, and (3) good qualityorthodontic casts. Casts with any toothdevelopmentaldisorder,missing,supernumerary or carious teeth, worn outdentition, or large coronal restorations werenot included in this study.The TSALD was calculated in each arch as thenumerical difference between the sum of MDtooth dimensions and the arch perimetermesial to the first permanent molars. Thegrouping of sample was done on the basisthis space discrepancy. In this study, archeswith a space discrepancy of 0 3 mm weredefined as normal, arches with a spacediscrepancy of more than - 4 mm weredefined as crowded and arches with a spacediscrepancy of more than 4 mm werelabeled as spaced arches.A total of 90 casts met the criteria of groupingand they were divided into normal, crowded,and spaced dental arches groups with 30 castsin each group. Each group was furtherdivided into 15 maxillary and 15 mandibularcasts.For each cast, the following parameters wererecorded: the MD and BL crown diameters ofall teeth except the second and thirdpermanent molars; the inter-canine (IC), interpremolar (IP) and inter-molar (IM) widths;the arch perimeter; and the arch depth. TheMD crown width was measured as thegreatest distance between the contact points49

POJ 2012:4(2) 48-55of the approximal surfaces of the dentalcrown, with the calipers parallel to theocclusal and buccal surfaces (Fig 1).1 The BLcrown diameter was measured as the greatestdistance between the facial and lingualsurfaces of the crown, taken at right angles tothe plane in which the mesiodistal diameter istaken (Fig 2).13 IC width was measured as thehorizontal distance between the cusp tips ofthe canines (Fig 3),14 IP width as thehorizontal distance between the distal pit ofthe maxillary first premolar (Fig 3) or thedistal fossae of the mandibular firstpremolar,14 and IM width as the horizontaldistance between the central fossae of themaxillary first molars (Fig 3) or the distobuccal cusp tips of the mandibular firstmolars.14Arch depth was taken as theperpendicular distance between the incisoredges of central incisors and a line connectingthe mesial surfaces of the first molars on bothsides (Fig 3).15Figure 2: Measurement of bucco-lingual (BL)dimension of teethFigure 3: Measurement of arch dimensions:a, inter-canine (IC) width; b, maxillary interpremolar (IP) width; c, maxillary inter-molar(IM) width; d, arch depthUp to 5 pairs of dental casts were examinedeach day to evade eye exhaustion. One weekafter the data collection, 10 dental casts wererandomlyselectedandreplicatedmeasurements were made by the sameinvestigator to detect any measurement error,however, Pearson correlation did not showany statistically significant difference for theintra-examiner reliability (r 0.93, p 0.01).All data were analyzed with SPSS software(version 19.0, SPSS Inc., Chicago). Descriptivemeasures such as means, standard deviations,and standard errors of the mean werecalculated for each variable. Oneway analysisFigure 1: Measurement of mesio-distal (MD)dimension of teethAll the measurements were made by oneexaminer using a digital vernier caliper (0-150mmME00183,Dentaurm,Pforzheim,Germany) with accuracy of 0.02 mm andreliability of 0.01 mm manufacturer’sspecification.50

POJ 2012:4(2) 48-55of variance (ANOVA) was used to comparethe three groups and Post Hoc Bonferroni testwas applied to assess group differences in thecrown and arch dimensions. A level ofsignificance (p 0.05) was used for thestatistical tests.except first permanent molars betweencrowded and spaced arches.The comparison of BL dimensions of teethbetween normal, crowded, and spaced dentalarches showed that maxillary lateral incisorsand all premolars and first molars weresignificantly different in the three groups(Table III). When Post Hoc Bonferroni testwas applied to further assess the inter-groupvariations (Table IV), no significant differencewas noticed in the BL dimensions of teethbetween normal and crowded arches.Whereas, a statistically significant differencewas found in the BL dimensions of maxillarylateral incisors and right premolars, andmandibular premolars and first molarsbetween normal and spaced dental arches.A statistically significant difference wasdetermined in all the arch dimensionsbetween normal, crowded, and spaced dentalarches with the exception of mandibular archdepth (Table V). Table VI shows theintergroupcomparisonconfirmingastatistically significant difference in the archperimeter of maxillary and mandibular archesbetween normal and crowded arches. Whennormal and spaced arches were compared, asignificant difference was observed in thearch perimeter of maxillary arches, and ICand IP widths of mandibular arches.ResultsThe comparison of MD dimensions of teethbetween normal, crowded, and spaced dentalarches by ANOVA showed that all teethexcept mandibular first permanent molarswere significantly different in the threegroups (Table I). Table II illustrates the groupdifferences in the MD tooth dimension usingPost Hoc Bonferroni test. When the maxillarycasts were compared, a statistically significantdifference was found in the MD dimensionsof canines and first permanent molarsbetween normal and crowded arches, in theMD dimensions of all incisors betweennormal and spaced arches, and in the MDdimensions of all teeth between crowded andspaced arches. When mandibular casts werecompared, there was a statistically significantdifference in the MD dimensions of allincisors between normal and crowded arches,in the MD dimensions of canines andpremolars between normal and spacedarches, and in MD dimensions of all teethTable I: Comparison of MD dimensions of teeth in three groupsToothDental Arch(N 90)Maxilla(n 45)Mandible(n 010.0010.0020.0010.0010.069N 90One-way ANOVAp-value 0.0551