Skeletal pattern in subjects with hypodontia - a cephalometric study

Cilj je ovoga istraživanja bio odrediti profil mekih tkiva, skeletne i dentalne odnose kod ispitanika s hipodoncijom, utvrditi utjecaj opsežnosti i lokalizacije hipodoncije, kao i procijeniti jesu li opsežnost i lokalizacija hipodoncije značajni prediktori skeletnih karakteristika. Uzorak od 194 ispitanika (75 muškoga i 119 ženskoga spola; dobi 10-18 godina, medijan 14) izdvojen je iz baze podataka pacijenata Zavoda za ortodonciju Stomatološke klinike Kliničkoga bolničkog centra Zagreb. Prema opsežnosti hipodoncije ispitanici su podijeljeni u tri skupine: blaga (nedostatak 1–2 zuba), umjerena (nedostatak 3–5 zuba) te ozbiljna hipodoncija (nedostatak 6 ili više zuba). Prema lokalizaciji hipodoncije u zubnom luku ispitanici su također podijeljeni u tri skupine: anteriorna (interkanina regija), posteriorna (regija premolara i molara) te antero-posteriorna hipodoncija (kombinacija prethodnih dviju skupina). U istraživanju je napravljena rentgenkefalometrijska analiza laterolateralnih kraniograma snimljenih kao dio standardnoga postupka prije početka ortodontske terapije. Razmatrana su trideset i tri angularna i linearna parametra, podijeljena u tri kategorije: skeletni odnosi, dentalni odnosi i profil mekih tkiva. Prilikom analize u obzir se uzela i lokalizacija hipodoncije po čeljustima. U obradi podataka primijenjene su diskriminacijska analiza i multipla linearna regresija. Povećanjem broja zuba koji nedostaju povećavala se sklonost prema maksilarnom retrognatizmu (smanjenjem vrijednosti kuta SNA), smanjivala prednja donja visina lica, povećavala retruzija gornjih i donjih inciziva te povećavala udaljenost usnica od E linije. Ozbiljna antero-posteriorna hipodoncija pokazala je najveća odstupanja kefalometrijskih parametara u odnosu na blagu i umjerenu anteriornu i posteriornu hipodonciju. Bila je povezana s tendencijom prema razvoju malokluzija Kl III, smanjenom donjom prednjom visinom lica, konkavnijim profilom, retruzijom gornjih i donjih inciziva, povećanim interincizalnim kutom te povećanom udaljenošću usnica od E linije. Neprisutnost hipodoncije u objema čeljustima pokazala se kao značajan prediktor povećanoga nagiba gornjih inciziva. Rezultati ovoga istraživanja ortodontima bi u budućnosti mogli biti vrlo korisni tijekom kliničkoga rada, s obzirom na to da bilo koji od dijagnostičkih parametara profila te skeletnoga i dentalnoga razvoja može biti ključan u planiranju terapije.Introduction: Hypodontia is the congenital absence of one or more teeth and is the most common developmental anomaly of human dentition. Treating hypodontia is in general considered to be the most difficult among orthodontists and multidisciplinary approach is often required. Identification of potential common craniofacial characteristics of subjects with hypodontia would greatly facilitate complicated treatment plan. Objective: The objective of this study was to determine the soft tissue profile, skeletal and dental relationships in subjects with hypodontia by using cephalometric radiographic methods. Furthermore, the objective was to analyze the effects of severity and pattern as well to evaluate whether severity and pattern of hypodontia are significant predictors of cephalometric parameters. Materials and methods: The sample was gained from the patients' database of the Department of Orthodontics, Dental Clinic, Clinical Hospital Center Zagreb. It consisted of 194 subjects (75 males and 119 females) aged 10-18, with a mean age of 14 years, diagnosed with permanent dentition hypodontia. Based on the severity of hypodontia sample was divided into mild (1-2 missing teeth), moderate (3-5 missing teeth) and severe groups (6 or more missing teeth). The location of missing teeth was used to further divide the sample into anterior (intercanine region), posterior (premolars and molars) and anteroposterior groups. In addition, jaw localization of hypodontia was also considered. Customized cephalometric analysis was performed by DOLPHIN IMAGE software (v.11.5) on lateral cephalograms that were taken as a part of a standard procedure prior to treatment. On each cephalogram, twenty two hard and soft tissue landmarks were identified, from which thirty three angular and linear parameters were recorded and analysed. Parameters were classified into three categories: skeletal, dental and soft tissue profile relationships. Discriminant analysis and multiple linear regression were used in order to process the data. The results were compared to Croatian cephalometric standards according to Zagreb 82 MOD2 analysis. Results: Decrease of SNA angle values (tendency towards maxillary retrognathism), decrease of anterior lower facial height, retrusion of the incisors, and retrusion of the lips were observed to be proportional to the increase of number and location of tooth agenesis. Aneroposterior and severe hypodontia groups showed the largest cephalometric differences, compared to other subgroups: smaller ANB angle values (tendency towards Class III malocclusion), smaller anterior lower facial height (ANS-Me), retrusion of both upper and lower incisors, greater interincisal angle (U1:L1), and a greater Li-E distance. The absence of hypodontia in both jaws was shown to be a significant predictor of increased inclination of upper incisors. Conclusion: Hypodontia has a significant effect on craniofacial morphology. Due to increase in number and location of missing teeth it could be expected that alveolar bone development would be more and more insufficient. As a result, maxillary retrognathism and shortening of anterior face height occur. When many teeth are missing, others tend to fulfill the gaps by inclinating, which was demonstrated by a larger retrusion of the incisors, especially the lower ones. Consequently, the lower lip is retruded, which, in combination with a tendency towards Class III, leads to a more concave profile