ORIGINAL Sepet ARTICLE et al
Relationship Between Mandibular Incisor Irregularity and Type of Occlusion in Ankyloglossia Elif Sepeta/Cagla Yildizb/Arzu Pinar Erdemc/Goksen Ikikarakayalib/ Feyza Nur Gorkenb/Sinem Kurub Purpose: To investigate the relationship between the lingual frenulum length with mandibular incisor irregularity and type of occlusion in children with ankyloglossia. Materials and Methods: Eighty children aged between 7 and 12 years with ankyloglossia enrolled in the study. The patients were classified according to Kotlow’s classification. Mandibular incisor crowding was measured and the molar relationship was determined. The data were analysed statistically using Fisher’s exact test, X 2 and Pearson’s correlation. Results: Of the 80 patients, 45 (56.3%) had mild, 23 (28.8%) had moderate and 12 (15%) had severe ankyloglossia. Fifty-nine (73.8%) of the patients had mild irregularity, 18 (22.5%) had moderate and 3 (3.8%) had severe irregularity. In 56 (70%) of the patients, Class I occlusion was observed, 17 (21.3%) had Class II and 7 (8.8%) had Class III occlusion. No significant differences were found between types of ankyloglossia with mandibular incisor irregularity and occlusion types. A significant positive correlation was determined between the length of the lingual frenulum length and mandibular incisor irregularity. There were significant positive correlations between the lingual frenulum length, incisor irregularity and age. Conclusion: Mild and moderate types of ankyloglossia are unrelated to mandibular incisor crowding and occlusion type. Key words: ankyloglossia, crowding, occlusion type Oral Health Prev Dent 2015;13:59-63 doi: 10.3290/j.ohpd.a32135
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nkyloglossia, commonly called ‘tongue-tie’, is a congenital anomaly characterised by an abnormally short lingual frenum, which may restrict tongue tip mobility (Lalakea and Messner, 2003). There is much controversy regarding this condition. Differences of opinion regarding its definition, clinical significance, need for surgical intervention and timing of treatment can all be found in the scientific literature. Otolaryngologists, oral surgeons, paediatricians, speech therapists and lactation consult-
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Professor, Department of Paediatric Dentistry, Faculty of Dentistry, Istanbul University, Capa, Istanbul, Turkey.
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Research Assistant, Department of Periodontology, Faculty of Dentistry, Istanbul University, Capa, Istanbul, Turkey.
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Dentist, Department of Paediatric Dentistry, Faculty of Dentistry, Istanbul University, Capa, Istanbul, Turkey.
Correspondence: Prof. Dr. Elif Sepet, Istanbul University, Faculty of Dentistry, Department of Paediatric Dentistry, 34093, Capa, Istanbul, Turkey. Tel: +90-212-414-2020-30309, Fax: +90-212-5310515. Email:
[email protected]
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Submitted for publication: 28.01.13; accepted for publication: 09.05.13
ants may all voice different opinions regarding the various aspects of ankyloglossia (Messner and Lalakea, 2000; Lalakea and Messner, 2003). The condition varies in the degree of its severity from mild mucous membrane bands to complete tethering of the tongue to the floor of the mouth (Jang et al, 2011). The clinical consequences of ankyloglossia include infant breastfeeding difficulties, speech disorders, various mechanical and social issues related to restricted tongue movement as well as orthodontic anomalies (Fletcher and Meldrum, 1968; Horton et al, 1969; Messner and Lalakea, 2000). Sometimes low tongue posture may exert a forward and downward pressure on the mandible with different consequences for facial development (Fletcher and Meldrum, 2000). Several clinical reports suggested that ankyloglossia may produce anterior open bite and mandibular protrusion malocclusions because of tongue posture (Tuerk and Lubit, 1959; Whitman and Rankow, 1961; Horton et al, 1969).
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Fig 1 Abnormally short, thick frenulum which caused the tongue to become heart-shaped upon protrusion.
Fig 2 Caliper measurement of the length of tongue from the base to the tip.
The relationship between the length of the lingual frenulum and crowding of mandibular incisors has not yet been investigated. Due to different complications of tongue-tie, this study aimed to investigate the relationship between the lingual frenulum length and mandibular incisor irregularity and type of occlusion. The test hypothesis was that crowding of mandibular incisors and occlusion type may be related to the median lingual frenulum length.
‘free tongue’ is defined as the length of tongue from the insertion of the lingual frenum into the base of the tongue to the tip of the tongue. A caliper was used to measure this distance. The patient was instructed to put the tip of his or her tongue on the incisal papilla, and open the mouth to the maximum extent. This measurement represented the maximum lingual frenulum length in the middle of the tongue-tie (Fig 2). To reduce the measurement error by hand pressure to the lingual frenulum, the length was recorded as the caliper touched the soft tissue as lightly as possible; the average value of triplicate measurements was also recorded. The patients were classified according to Kotlow’s classification (Kotlow, 1999): 1. Clinically acceptable, normal range of free tongue greater than 16 mm 2. Class I: mild ankyloglossia, 12 to 16 mm 3. Class II: moderate ankyloglossia, 8 to 11 mm 4. Class III: severe ankyloglossia, 3 to 7 mm 5. Class IV: complete ankyloglossia, less than 3 mm
MATERIALS AND METHODS The sample was collected from patients who were scheduled for dental treatment at Istanbul University, Department of Paediatric Dentistry, Istanbul, Turkey. The Ethics Committee of Istanbul University, Faculty of Medicine approved this study (2012/1624-1256) and parents supplied written, informed consent to participate in the study. The selection criteria were as follows: no history of (1) previous lingual frenectomy, (2) previous orthodontic treatment, (3) previous orthognathic surgery or (4) disorders of the temporomandibular joint and jaw muscles. Eighty children with ankyloglossia (38 girls and 42 boys) aged between 7 and 12 years enrolled in the study. Clinically, ankyloglossia was diagnosed based on the physical characteristics of the patients’ oral anatomy. The main criterion was the frenulum being abnormally short and thick, which caused the tongue to become heart-shaped upon protrusion (Fig 1). Additional criteria included signs of functional impairment, such as an inability to protrude the tongue past the gum line and other indications of decreased tongue mobility. The term
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Mandibular incisor crowding was measured with Little’s irregularity index and divided into three groups: mild, moderate, and severe (Little, 1975): • Mild: 1 to 3.9 mm • Moderate: 4 to 6.9 mm • Severe: 7 to 9.9 mm Impressions for dental casts were obtained from the children. The measurements were performed directly from the mandibular cast with a caliper (calibrated to at least tenths of a millimetre) held parallel to the occlusal plane. The linear displacement of the adjacent anatomic contact points of the mandibular incisors was determined, with the
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A
B
C
D
A+B+C+D+E=irregularity index
Fig 3 Measurement of mandibular incisor crowding according to Little’s irregularity index.
Table 1 Patient baseline characteristics, types of ankyloglossia, occlusion and levels of mandibular incisor irregularity.
Fig 4 The molar relationship according to Angle’s classification. A: Class I; B: Class I with other dental problems; C: Class II; D: Class III.
N (%) Gender Age (mean±SD) Type of ankyloglossia
Type of occlusion
Lower incisor irregularity
Male Female
42 (52.5) 38 (47.5)
9.36 ± 1.71 Class I Class II Class III
45 (56.3) 23 (28.8) 12 (15)
Class I Class II Class III
56 (70) 17 (21.3) 7 (8.8)
Mild Moderate Severe
59 (73.8) 18 (22.5) 3 (3.8)
sum of the five measurements representing the patient’s irregularity index value (Fig 3). The molar relationship was determined according to Angle’s classification (Tang and Wei, 1993). The classification is based on where the buccal groove of the mandibular first molar contacts the mesiobuccal cusp of the maxillary first molar: on the cusp (Class I, neutrocclusion or normal occlusion); distal to the cusp by at least the width of a premolar (Class II, distocclusion); mesial to the cusp (Class III, mesiocclusion) (Fig 4). All measurements were performed by the same investigator to eliminate inter-examiner variability. The data were analysed using the statistical package NCSS 2001 (Number Cruncher Statistical System; Kaysville, UT, USA). Fisher’s Exact and the chi-square test were used to evaluate the statistical differences and Pearson’s correlation was used to determine the strength of the relationships between parameters.
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Table 2 Relationship between ankyloglossia class, irregularity index and occlusion class
Ankyloglossia
Class I (N=45) n (%)
Class II Class III (N=23) (N=12) n (%) n (%)
Significance
Type of irregularity Mild 29 (64.4) 20 (87) 10 (83.3) X2: 7.56 Moderate 15 (33.3) 2 (8.7) 1 (8.3) P = 0.109 Severe 1 (2.2) 1 (4.3) 1 (8.3) Type of occlusion Class I Class II Class III
34 (60.7) 14 (25) 8 (14.3) X 2: 1.79 8 (47.4) 6 (35.3) 3 (17.6) P = 0.774 3 (42.9) 3 (42.9) 1 (14.3)
RESULTS A total of 80 patients were identified as having the diagnosis of ankyloglossia. Forty-two subjects were males and 38 were females. The median age was 9.36 ± 1.71 years. Of the 80 patients, 45 (56.3%) had mild ankyloglossia, 23 (28.8%) had moderate and 12 (15%) were classified as having severe ankyloglossia. Patient baseline characteristics, types of ankyloglossia, occlusion and levels of mandibular incisor irregularity are presented in Table 1. The most frequent ankyloglossia type was mild. Of the 80 patients, 59 (73.8%) had mild mandubular incisor irregularity, 18 (22.5%) had moderate and 3 (3.8%) were classified as having severe irregularity. Fifty-six (70%) of the patients had Class I, 17 (21.3%) had Class II and 7 (8.8%) had Class III occlusion. The relationship between types of ankyloglossia, irregularity index and occlusion type is presented in Table 2.
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No significant differences were found between types of ankyloglossia and mandibular incisor irregularity. The relationship between ankyloglossia and occlusion types was also not significant. A significant positive correlation (r = 0.247; P = 0.027) was determined between the lingual frenulum length and mandibular incisor irregularity. There were significant positive correlations (r = 0.383; P = 0.0001) between the lingual frenulum length and age as well as between incisor irregularity and age (r = 0.284; P = 0.011).
DISCUSSION For more than a century, many theories have attempted to explain the aetiology of malocclusion. Most have stated that it is congenital (Horowitz et al, 1960; Markovic, 1992), but more recently, greater emphasis has been placed on the influence of the environment, especially the activity and the posture of the oral soft tissues (Mew, 1986; Fletcher and Meldrum, 2000; Ruffoli et al, 2005). Ankyloglossia or tongue-tie is manifest as an abnormal attachment of the lingual frenulum connecting the mobile tongue and the floor of the mouth. The pharyngeal musculature can enhance some aetiological trends toward the forward push of the tongue in this low posture of ankylosed tongue, thus leading to growth of the mandible in a more prognathic manner (Petit and Davis, 1986). Jang et al, (2011) stated that the skeletal Class III malocclusion is related to the median lingual frenulum length and restricted mouth opening. Ankyloglossia is a congenital oral anomaly which may occur alone or be found as a part of certain malformation syndromes (Mintz et al, 2005). Different studies indicate that 2 genes are associated with the condition. The first encodes the transcription factor TBX22, which when mutated results in X-linked cleft palate with ankyloglossia (Braybrook et al, 2001; Braybrook et al, 2002; Marçano et al, 2004). More recently, LGR5 gene mutations were reported in a Brazilian family who exhibited ankyloglossia associated with tooth number anomalies (Acevedo et al, 2010). The results of the present study did not confirm the test hypothesis that crowding of mandibular incisors and occlusion type are related to the median lingual frenulum length. Similarly, there are only a few clinical reports that suggested a relationship between ankyloglossia and craniofacial morphology (Tuerk and Lubit, 1959; Hopkin, 1967; Jang et al, 2011).
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The vertical lingual frenulum length is frequently short in the newborn, and as the infant grows, the tongue becomes longer and thinner at the tip, often decreasing the severity of tongue-tie (Neville et al, 1995; Kotlow, 1999). The tongue, following the neural growth curve, reaches its full size at approximately 8 years (Proffit and Mason, 1975). Ankyloglossia is asymptomatic; the condition may resolve spontaneously or affected children may learn to compensate adequately for their decreased lingual mobility (Lalakea and Messner, 2003). Children aged between 7 and 12 years were enrolled in this study. The positive correlations between the tongue length and age can be explained by the contiuning development of craniofacial structures. The mandibular incisor irregularity increased with age; similarly, our results also suggest the tendency toward malocclusion increases with age. The relative influence of genetic and environmental factors in the aetiology of malocclusion has been a matter of debate. Jaw size and tooth size could be inherited independently and as genetically dominant traits. Oral habits, aberrations in eruption, premature loss of primary teeth and the caries process are environmental/behavioural factors. Genetic and environmental factors may work together in the aetiology of malocclusion. In a longitudinal study, it was reported that more than 58% of dental crowding was observed in the anterior region during the period of eruption (Mochizuki and Machida, 1998). According to the study by Little et al (1981), dental crowding appeared and increased in the anterior region with age. The factors that influence dental crowding at the stage of eruption of the permanent dentition include the position of the permanent tooth germs, the timing of the loss of deciduous teeth and permanent tooth eruption, the order of replacement of the dentition from deciduous to permanent, the soft tissue pressure and the position of the opposing teeth (Shigenobu et al, 2007). In particular, crowding in the anterior region is reported to be influenced by the linguoversion of the lateral incisor germ, lack of space for eruption of the lateral incisor, lip pressure and tongue pressure (Proffit, 2000; Shigenobu et al, 2007).
CONCLUSION The subjects enrolled in this study had mostly mild and moderate ankyloglossia. It can be concluded that mild and moderate types of ankyloglossia may
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have no or only slight effects on mandibular incisor crowding and occlusion type. To clarify the role of the lingual frenulum, especially its relationship with crowding of mandibular incisors, future research is recommended to focus on subjects with severe ankyloglossia. Besides length of the lingual frenulum, the mobility and volume of the tongue must be examined. Clarification of the relationship between the ankyloglossia types and malocclusions could provide early and better treatment.
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