A. Silvest rini Biavat i* , A. Signori* * , A. Cast aldo* * * , G. M at arese* * * * , M . M igliorat i* * Department of Orthodontics, University of Genoa, Italy * * Department of Health Sciences, Section of Biostatistics, University of Genoa, Italy * * * Department of Orthodontics, University of Trieste, Italy * * * * Department of Orthodontics, University of M essina, Italy e-mail: armando.silvestrini@tin.it Incidence and distribution of deciduous molar ankylosis, a longitudinal study A BSTRACT Aim To study incidence and distribution of deciduous molar ankylosis. M a t e r i a l s a n d m e t h o d s Study design: longitudinal retrospective study. A total of 512 consecutive subjects (aged 5 to 15 years) w ere examined at the Orthodontics and Paediatric Dentistry Department of the Genoa University School of Dentistry; for each subject an ortopantomography x-ray w as taken. Result s Thirty-four children w ere affected by deciduous molars ankylosis (6.6% ). A statistically significant difference was revealed between the distributions: the lower deciduous molars were ankylosed more frequently than the upper ones (P<0.001); the second deciduous molars were ankylosed more frequently than the first molars (P<0.001). No statistical significance w as found betw een sex and number of infraoccluded teeth (P=0.74). Conclusion This study found an incidence of deciduous molar ankylosis of about 6.6% ; the lower deciduous molars and second deciduous molars were ankylosed more frequently (P<0.001). alveolar bone supporting it. Ankylosis seldomly affects the permanent dentition, w hile it has a frequency of 6-8% in deciduous molars, causing, in the most severe cases, local malocclusions, delayed and hook-shaped morphology of bicuspid roots, and a tendency to impaction of the tooth underneath the ankylosed molar (Fig. 1). Diagnosis must necessarily be based on clinical and x-ray findings, because the histological examination, w hich is the proper diagnostic criterion, is not practicable in a longitudinal research. Steigman [1973] had in view to check the earliest age at w hich ankylosis becomes clinically det ect able, t o determine the distribution frequency, and to investigate the most frequently affected arch. For this reason 1042 children aged 3 to 6 years w ere examined. Among the deciduous molars examined, 9.2% had ankylosis. At three years of age, it w as found an incidence of about 8.4% . The incidence of ankylosis w as greater in the low er dental arch (P<0.001). The first deciduous molars w ere affected more often than the second molars (P<0.001) both in the maxilla and in the mandible. In females the mandibular deciduous first molars and the maxillary deciduous second molars w ere affected more frequently (P<0,001); in males the maxillary deciduous first molars and the mandibular deciduous second molars w ere affected more frequently (P<0.5 and P<0.01 respectively). The reason for the disparity in frequency betw een first and second deciduous molars and betw een upper and low er dental arches is unknow n. Other authors report a great variation in ankylosis frequency in deciduous dentition; unfortunately in many researches the age of children examined is not mentioned. Among these, w e mention [all reported in M ueller et al., 1983] an European research [Dechaume and Cauhepe, 1948], in w hich 40 cases of ankylosis w ere found among 60.000 children (0.07% ); an english study [Andlaw, 1974] on 1.539 children (5 to 11 years) w hich found a 3.2% incidence of ankylosis; in other studies, done in the U.S.A., ankylosis w as found to have a 3.2% incidence in 2.105 children (8-12 years) [Brearley and M cKibben, 1973]; 6.9% in 1.641 patients (2,5- 14,5 years) [Lamb and Reed, 1968]; 3.7% in 2,234 children from 6 to 12 years [Krakow iak, 1978]. M ueller [M ueller et al., 1983] planned a research in order to investigate the incidence of ankylosis by means of bite-w ing x-rays in 1,895 United States patients (aged from 7 to 12 years), of a very heterogeneous ethnic Keyw ords: Tooth ankylosis; Deciduous molars. Int roduct ion Ankylosis has been described by M c Call e Wald [Falconi et al.,1987] and is a dental anomaly of unknow n aetiology that causes bone bridges betw een root cementum and alveolar bone; for this reason, ankylosis hampers the normal development of t he t oot h involved and, consequently, prevents tooth eruption and grow th of the EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY • VOL. 12/3-2011 FIG. 1 - Hooked bicuspid roots under ankylosed primary molars. 175 SILVESTRINI BIAVATI A. ET AL. population (78.3% Caucasian, 9.3% African Americans, 8.9% Hispanic, and 3.5% of mainly Asian American). This study examined the incidence of ankylosis related to sex, ethnic background and exposure to communal w ater fluoridation. Chi square analyses w ere used to determine t he relat ionships bet w een ankylosis and ot her characteristics of the patients. The incidence of ankylosis w as 9.9% , w ith no significant differences betw een the different geographic areas; no significant differences w ere found betw een the fluoridated and non fluoridated areas in the incidence of ankylosis (P>0.05); the difference in the incidence of ankylosis betw een males and females w as not significant (P>0.05); the highest incidence w as found among Hispanic (11.5% ) and Caucasian subjects (10.6% ). African Americans and other ethnic groups w ere w ell below the overall average (5.5% and 3.2% respectively). There w as a statistically significant relationship betw een the race of the child and the prevalence of ankylosis (P<0.05). The mandibular first molar show ed the highest frequency of ankylosis (P<0.001), in a tw ice ratio versus second deciduous molar. Sixty-four children had at least one ankylosed tooth on each side. Of them, 87% w ere Caucasian and w ithin this subgroup, 71.4% w ere females. In other ethnic groups the observations w ere so few to make it impossible a statistical comparison. These results revealed a higher incidence of ankylosis (9.9% ) than that reported in previous studies, probably due to the higher age of the children examined or to the diagnostic method used, w hich w as based on radiographic criteria. In this paper w e study the incidence and distribution of deciduous molar ankylosis. M at erials and met hods using SPSS Advanced M odels 17.0 statistical analysis softw are for W indow s and M acintosh, provided by the Department of Health Sciences, Section of Biostatistics, Genoa University, Italy. The error of the method for the linear measurements w as evaluated by repeating the measurements of 30 randomised teeth. The ICC w as 0.71. Result s Thirty-four patients had ankylosis of one or more deciduous teeth (6.6% among the examined group); the total ankylosed deciduous teeth found w ere 88. In Table 1, for each patient examined age, sex, number, type and position of ankylosed teeth are reported; distribution in dental arches are reported in Figures 2, 3 and 4. As for sex, 17 males and 17 females had deciduous molar ankylosis, in a 1:1 rat io. The amount of infraocclusion w as distributed as follow s: • from 1 to 2 mm: 53 molars; • from 2.5 to 4 mm: 25 molars; • from 4.5 to 9 mm: 6 molars. Low er molars w ere more inf raoccluded t han t he corresponding upper ones (15 subjects had at least one infraoccluded upper molar w hile 32 subjects had at least one infraoccluded low er molar) (Table 1). A statistically significant difference w as found betw een the distributions of upper and low er molars (P<0.001) (Table 2), also confirmed considering males and females separately (P=0.006 for males and P=0.002 for females). A statistically significant difference w as found betw een the distributions of first and second deciduous molar (P<0.001). In males and females respectively a total of 15 At the Orthodontic and Paediatric Dentistry Department in Genoa University School of Dentistry (Italy) w ere visited 512 consecutive Caucasians patients, aged 5 to 15 years. Diagnosis of ankylosis w as made clinically, f rom radiographs and from study models. The amount of infraocclusion w as measured in millimeters, to determine the difference in height betw een the affected tooth and the occlusal plane [Darling and Levers, 1973], using a gauge on cast models; minimum amount w as considered 1 mm infraocclusion. St at ist ical analysis The Chi-square test w as used to evaluate differences betw een sex and number of infraoccluded teeth, and the W ilcoxon signed-rank t est w as used t o evaluat e differences betw een the distributions of first and second deciduous molars and betw een the distributions of upper and low er molars. An independent samples t-test w as used to compare the means of infraocclusion amounts in all first molars and in all second molars, w hile the paired samples t-test w as used to compare the means of infraocclusion amount of first and second molars for patients w ho had both teeth involved. Lastly, the M annWhitney U-test w as performed to assess differences in f irst , second, upper and low er molars and t heir distributions w ith respect to sex. The statistical difference w as tested at P < 0.05. These analyses w ere carried out 176 FIG. 2 - Distribution of ankylosed teeth for sex and age. FIG. 3 - Distribution of ankylosed first primary molars. EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY • VOL. 12/3-2011 LONGITUDINAL STUDY OF DECIDUOUS M OLAR ANKYLOSIS Sex Ankylosed teeth in each patient 1 2 3 4 5 F 4 4 5 3 1 M 3 7 3 2 2 Total 7 11 8 5 3 P 0,74 TABLE 1 - Distribution of number of ankylosed teeth in each patient for sex. Discussion FIG. 4 - Distribution of ankylosed second primary molars. and 7 first molars and a total of 29 and 37 second molars w ere recorded, but no statistical significance w as found betw een sex and number of infraoccluded teeth (P=0.74). Regarding maxillary and mandibular first and second molar, no statistical significant difference w as found betw een male and female subjects: males and females show ed respectively 3 and 2 infraoccluded maxillary first molars (P=0.95), 6 and 9 maxillary second molars (P=0.45), 12 and 5 mandibular first molars (P=0.12), 23 and 28 mandibular second molars (P=0.34). Regarding the amount of infraocclusion (Table 3) a statistically significant difference w as found betw een first and second molars, considering all infraoccluded first molars versus all infraoccluded second molars (P=0.001), w hile w hen considering only the paired samples analysis for patients w ho presented both infraoccluded first and second deciduous molars the mean difference w as not statistically significant (P=0.11). The mean amount of infraocclusion w as about -1.91 ± 0.45 mm for the first deciduous molars and -2.59 ± 1.45 mm for the second deciduous molars. Concerning the age of patients and incidence of ankylosis, a greater number of ankylosed teeth w as detected betw een 8 and 10 years w ith a peak at 9 years old in males and at 9 and 10 years old in females. N patient > Maxilla * > Mandible * * Same number Total 2 P Ankylosed molar < 0.001 > First decidous* * * 27 > Second decidous* * * * 5 Same number 34 The incidence of ankylosis found in this study (6.6% ) stands halfw ay betw een the results found by the abovementioned authors. This research is based on x-rays examinations: this permitted to put in evidence even not severe ankylosis, measured on orthopantomograms in mm. About the greater incidence in the mandible, w e found these data in agreement w ith those of Steigman et al. [1973] and M ueller et al. [1983]; on the contrary, w e found a greater incidence of second deciduous molar ankylosis (73% betw een ankylosed molars resulting in this investigation), w hile several authors (but not all) found a greater incidence of first molar ankylosis. The low er deciduous molars w ere ankylosed more frequently than the upper ones (P<0.001), in agreement w ith Biederman [1962]; the second deciduous molars w ere ankylosed more frequently than the first molars (P<0.001). No statistical significance w as found betw een sex and number of infraoccluded teeth (P=0.74) as reported by M ueller. W it h respect t o ot her aut hors f or maxillary and mandibular first and second molar no statistical significant difference w as found betw een males and females; though betw een males mandibular first molars and mandibular second molars resulted more affected w hile betw een females mandibular second molars resulted much more involved. Steigman confirmed a higher incidence of ankylosed mandibular second molars in males. M esser and N of patient P 5 < 0.001 26 3 Total 34 TABLE 2 - Upper/Lower * : patients with more upper ankylosed teeth than lower; * * : patients with more lower ankylosed teeth than upper; * * * : patients with more first decidous ankylosed molars than first;* * * * : patients with more second decidous ankylosed molars than first Teeth involved N First decidous ankylosed molar Second decidous molar 22 66 M ean infraoccl. -1,91 -2,59 SD t-test Value P 0,45 1,45 3,351 0,001 1,802 0,11 Patients w ith both first and second decidous molars involved First decidous molar 9* -1,91 0,47 Second decidous molar -2,72 1,09 * : number of patients EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY • VOL. 12/3-2011 ankylosed teeth and first/second ankylosed molars. TABLE 3 - T-test to compare means of infraocclusion in first and second ankylosed deciduous molars. 177 SILVESTRINI BIAVATI A. ET AL. Cline [1980] described the possibility of infrabony dental rotation, leading to a lack of space. Kurol and Koch [1985], in a longitudinal study about the effects of ankylosed molars extraction, in w hich they follow ed 15 children affected by not severe deciduous mandibular molar infraocclusion (2 to 4.5 mm), making extractions only in one side, pointed out that in the nonextraction side the degree of infraocclusion w orsened, but all deciduous molars exfoliated normally and all successors erupted spontaneously. Starnes [1998] indicated in 6 to 8 years the age of interception of any condition that can influence the grow th pattern, tooth development, and eruption. Kurol [2002] underlined that progressive infraocclusion cause tipping of adjacent teeth, bone defects, and hindered or delayed eruption of permanent successors. Early removal w as therefore recommended, especially w hen the permanent successor is in an incorrect position. Reopening or maintaining space must be considered before extractions are performed. Because of tipping of neighbouring teeth and roots thinness, surgical removal may present difficulties. Kurol [2006] also stated that, if permanent successor is in a normal position, early extraction of the ankylosed deciduous molar is unnecessary. We agree, underlying that w e alw ays paid a special at t ent ion t o t he normal development of premolar roots: altered morphologies, such as root enlargements or apical hooks, have been noticed in our clinical experience (Fig. 1), that may definitively hinder the eruption of the tooth. Loriat o et al. [2009] point ed out t hat , since dentoalveolar ankylosis can cause negative effects on occlusal development, early diagnosis and an effective treatment plan are essential to prevent further eruption deviations and more severe malocclusion. Conclusion This longit udinal ret rospect ive st udy show ed an incidence of deciduous molar ankylosis of about 6.6% ; the low er deciduous molars (mainly second deciduous molars) w ere those ankylosed more frequently (P<0.001). The amount of infraocclusion w as distributed as follow s: • from 1 to 2 mm: 53 molars; • from 2,5 to 4 mm: 25 molars; 178 • from 4,5 to 9 mm: 6 molars. No statistical significant difference w as found betw een sex and number of infraoccluded teeth (P=0.74). Ref erences Andlaw RJ. Submerged deciduous molars. A review, with special reference to the rationale of treatment. J Int Assoc Dent Child. 1974 Dec;5:59-66. Biederman W. Etiology and treatment of tooth ankylosis. Am. J. Orthod.1962 Sep; 48: 670-683. Brearley LJ, McKibben DH Jr. Ankylosis of deciduous molar teeth. I. Prevalence and characteristics. ASDC J Dent Child. 1973 Jan-Feb;40:5463. Darling AI, Levers BG. Submerged human decidous molars and ankylosis. Arch Oral Biol 1973 Aug 18:1021-1040. Dechaume M, Cauhepe J. Retention of deciduous molars. Dent Rec (London). 1948 Jul;68:173-175. Falconi P, Caprioglio D, Genone B, Magni F, Tenti FV. Ortognatodonzia. Firenze: USES;1987. Krakowiak FJ. Ankylosed deciduous molars. ASDC J Dent Child 1978 JulAug;45:288-292. Kurol J, Koch G. The effect of extraction of infraoccluded decidous molars: a longitudinal study. Am J Orthod1985;1:46-55. Kurol J. Early treatment of tooth-eruption disturbances. Am J Orthod Dentofacial Orthop 2002 Jun;121:588-591. Kurol J. Impacted and ankylosed teeth: why, when, and how to intervene. Am J Orthod Dentofacial Orthop 2006 Apr;129(4 Suppl):S86-90. Lamb KA, Reed MW. Measurement of space loss resulting from tooth ankylosis. ASDC J Dent Child 1968 Nov;35:483-486. Loriato LB, M achado AW, Souki BQ, Pereira TJ. Late diagnosis of dentoalveolar ankylosis: impact on effectiveness and efficiency of orthodontic treatment. Am J Orthod Dentofacial Orthop 2009 Jun;135:799-808. Messer LB, Cline JT. Ankylosed deciduous molars: results and treatment recommendations from an eight-year longitudinal study. Pediatr Dent 1980;2:37-47. Mueller CT, Gellin ME, Kaplan AL, Bohannan HM. Prevalence of ankylosis of deciduous molars in different region of the USA. J Dent Child 1983: 213218. Starnes LO. Comprehensive phase I treatment in the middle mixed dentition. J Clin Orthod 1998;32:98-110. Steigman S, Koyoimdjisky-Kaye E, Matrai Y. Submerged deciduous molars in preschool children: an epidemiologic survey. J Dent Res 1973;52:322-326. Yilmaz RS, Darling AI, Levers BGH. Mesial drift of human teeth assessed from ankylosed deciduous molars. Archs oral Biol 1980;25:127-131. EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY • VOL. 12/3-2011