RELATIONSHIP BETWEEN PROPORTION OF ANTERIOR TEETH AND DENTAL ARCHFORMS IN CLASS I,II AND III MALOCCLUSIONS

Koncept zlatne proporcije je predložen kao općenito estetsko pravilo prilikom procjene dimenzija maksilarnih frontalnih zuba. Cilj istraživanja bio je procijeniti razliku u prevalenciji vrijednosti zlatne proporcije kod ispitanika s malokluzijom klase I, II/1, II/2 i III i utvrditi potencijalne čimbenike koji utječu na prevalenciju zlatne proporcije. Istraživanje je provedeno na 160 sadrenih modela (78 muškog spola i 82 ženskog spola) s podjednakom zastupljenosti malokluzija: Angle klasom I (26,3 %), II/1 (25 %), II/2 (22,5 %) i III (26,3 %). Sadreni modeli su skenirani s ATOS II SO skenerom (GOM GmbH, Braunschweig, Germany) i izmjereni pomoću ATOS Viewer software (version 6.0.2; GOM GmbH). Point-biserijalna korelacijska i logistička regresija korištene su kako bi se utvrdio utjecaj spola, dobi, tipa malokluzije, oblika zubnog luka, dentoalveolarnog nesrazmjera i Littleovog indeksa nepravilnosti na vrijednosti zlatne proporcije. Nije utvrđena značajna razlika u vrijednostima zlatne proporcije između ispitanika s različitim malokluzijama. Najčešća devijacija vrijednosti zlatne proporcije je utvrđena kod ispitanika s klasom II/2 (64 – 69 % na sjekutićima i 67 % na očnjacima) dok je najrjeđa devijacija nađena kod ispitanika klase I (45 – 52 % na sjekutićima i 48 – 55 % na očnjacima). Rezultati ovog istraživanja nisu utvrdili spol, dob, tip malokluzije, oblik zubnog luka, dentoalveolarni nesrazmjer i Littleov indeks nepravilnosti kao značajne prediktore odstupanja od vrijednosti zlatne proporcije kod ispitanika s Angle malokluzijom tipa I, II/1, II/2 i III. Dodatno su provedeni i t-testovi za usporedbu intenziteta Littleovog indeksa nepravilnosti između grupa malog i velikog odstupanja od zlatne proporcije za svaki zub. Koncept zlatne proporcije nije korelirao s Littleovim indeksom nepravilnosti niti za jedan zub niti u jednoj klasi malokluzije. Najveći udio vidljivosti lateralnih sjekutića bio je u klasi II/2, a najmanji u klasi I i III. Odstupanje od vrijednosti zlatne proporcije značajnije je bilo povezano s oblikom luka nego klasom. Što je zubni luk bio četvrtastiji, povećavalo se odstupanje na očnjacima i na središnjem sjekutiću, ali ne i na lateralnim sjekutićima. Klasa II/2 imala je najčešće značajno odstupanje, a klasa I najrjeđe odstupanje od vrijednosti zlatne proporcije.Aim: Golden proportion concept has been proposed as general aesthetic paradigms for evaluation of maxillary anterior teeth. The term golden proportion in smile design theory presumes mathematically constant ratio that defines the dimension between width of maxillary anterior teeth. In this matter the ratio calculated for maxillary lateral incisors and the canines in reference to that of the central incisors are 0.62 and 0.38 respectively. Golden proportion concept presumes that dental aesthetics is optimized if those suggested ratios are repeated when patient smile is viewed from front. Although various authors 3,4 have advocated usage of golden proportion concept as a means for evaluation of symmetry, dominance, and proportion in the smile design there are studies that denote its use as an aesthetic guideline rule or its prevalence in the majority of the population. Studies from the literature mainly reported of golden proportion prevalence in various population or they evaluated the relation of golden percentage with dental attractiveness. According to our knowledge, this is the first study that evaluates the possible relations and significance of various malocclusion features in terms of golden proportion and golden percentage prevalence. The purpose of this study was 1) to evaluate the difference in the prevalence of golden proportion between Angle Class I, Class II/1, Class II/2, and Class III malocclusion groups; and 2) to identify the possible relation between golden proportion and and sex, age, malocclusion type, dental arch form, Little’s index of irregularity, and dentoalveolar discrepancy respectively. Material and methods: Plaster casts from 160 subjects (78 males and 82 females with Class I (26.3%), Class II/1 (25%), Class II/2 (22.5%) and Class III (26.3%) malocclusions were scanned with the ATOS II SO scanner (GOM mbH, Braunschweig, Germany) and measured with ATOS Viewer software (version 6.0.2; GOM GmbH). Inclusion criteria were as follows: permanent dentition; no missing teeth; and absence of: periodontal disease, mesiodistal restoration, partially erupted teeth, tooth anomalies and interproximal tooth wear. Casts were scanned using an ATOS II SO (small objects) scanner (GOM mbH, Braunschweig, Germany). The scanner has point spacing in the range of 0.02 to 0.17mm, a measuring area of 30 x 324 to 250 x 200 mm 2, and measured points of 1,400,000. Fringe patterns were projected into the object’s surface with a white lightand recorded by 2 cameras. The 3D coordinates for each camera pixel were calculated, and a polygonmesh of the object’s surface was generated. Models were measured and analyzed using ATOS Viewer software (version 6.0.2; GOM mbH). ATOS Viewer version 6.0.2.software was used to digitally mark landmark points on each virtual 3D model. Each point was automatically defined by software in a 3D coordinate system with associated values (x, y, z). Point-biserial correlations and logistic regression were performed to identify the association of sex, age, malocclusion type, dental arch form, dentoalveolar discrepancy and Littleʼs index of irregularity with presence of golden proportion. Results: Values of golden proportion did not differ significantly among malocclusion groups. Deviation from golden proportion was most frequently found in Class II/2 (64 - 69% on incisors and 67% on canines) while rarest deviation was determined in Class I (45 - 52% on incisors and 48 - 55% on canines). Absolute deviation from the golden proportion hasnʼt statistically significantly deferred between the jaw sides, however it has differed between the teeth pertaining to the same side. Deviation from the golden proportion on canines depends significantly on the Class as well as on the form of dental arch. The concept of golden proportion did not correlate with Littleʼs index, not for any tooth individually and not in any given Angle Class. Conclusion: Sex, age, malocclusion type, arch form, dentoalveolar discrepancy and Littleʼs index of irregularity were not identified as a significant predictors of deviation from golden proportion. The results of the research indicate that the form of dental arch depends on the Angle Class. It is also indicated that the severity of crowding (dentoalveolar discrepancy) presents significant influence on deviation from the values of golden proportion only with central incisors. The more square dental arch is the bigger is deviation on the canines and on central incisor but not on lateral incisor. As far as Class II/2 is concerned, deviation is significantly reduced on the canine than in Class I and on Class III