Stjepan Špalj

Maximum voluntary molar bite force in subjects with normal occlusion

The aims of this investigation were to determine whether stabilization of maximum voluntary bite force (MVBF) occurs between 15 and 18 years of age in subjects with a normal occlusion, and to assess the influence of gender, body mass index (BMI), morphological occlusion, and jaw function measured by the number of occlusal contacts, overjet, overbite, maximal mouth opening, mandibular deflection during opening, sagittal slide between the retruded contact position and the intercuspal position, and number of dental restorations. The sample comprised 60 Caucasian subjects aged 15 (15 males and 15 females) and 18 (14 males and 16 females) years with a neutral occlusion, balanced facial profile, and absence of a previous orthodontic history. Bite force measurements were undertaken using a portable occlusal force gauge on both the left and the right sides of the jaw in the first molar region during maximal clenching. Two independent samples t-tests and multiple regression were used for statistical analysis. MVBFs were age and gender related (P<0.05). Males showed a significant increase in bite force between 15 and 18 years of age (P=0.002), but gender differences were significant only in the 18-year-olds (P=0.003). In subjects with a neutral occlusion, MVBF could best be predicted using multiple regression from age and gender. The regression model accounted for 31.3 percent of the variance in MVBF (P=0.031), with gender contributing 17.9 percent and age 7.9 percent. Morphological occlusion, jaw function, and BMI explained the remaining 5.5 percent of variance. While controlling for all other parameters, the independent contribution of gender to the prediction of MVBF was 16.2 percent, age 6 percent, number of occlusal contacts 3.2 percent, and BMI 1.3 percent.

Facial profile preferences: Differences in the perception of children with and without orthodontic history

INTRODUCTION Improved facial esthetics can be fully achievable only if facial preferences of the treated group are known. We hypothesized that facial profile perception and preferences could be influenced by orthodontic treatment. METHODS Differences in facial profile preferences between children with and without an orthodontic history were investigated in a sample of 1626 children aged 12 to 19 years (mean age, 14.8 ± 2.2 years) from 24 public schools in Zagreb, Croatia, randomly selected by using a cluster sampling procedure. Eight profile distortions for each sex, morphed by a digital imaging technique, were used for estimation. Analysis of variance (ANOVA), Bonferroni, and 2 independent sample t tests were used to compare the preferences of the groups. RESULTS A straight profile was the most favored in both sexes, regardless of previous orthodontic history. A bimaxillary alveolar protrusive profile with thicker lips was preferred among the female profiles, and a bimaxillary retrusive profile with flat lips and a prominent chin was preferred among the male profiles. Orthodontic history and personal facial profile had little effect, and sex had a slightly greater influence on personal facial profile preferences. CONCLUSIONS It seems that orthodontic therapy has no clinically relevant influence on facial profile preferences. Depending on the patients sex, orthodontists should have different criteria for treating borderline patients with bimaxillary dentoalveolar protrusion and mandibular prognathism.

Influence of surface layer on mechanical and corrosion properties of nickel-titanium orthodontic wires

OBJECTIVE To analyze the effect of various coating formulations on the mechanical and corrosion properties of nickel-titanium (NiTi) orthodontic wires. MATERIALS AND METHODS Uncoated, rhodium-coated, and nitrified NiTi wires were observed with a three-point-bend test, surface roughness (Ra) measurement, scanning electron microscopy, energy dispersive spectroscopy, and electrochemical testing (open circuit potential, electrochemical impedance spectroscopy, and cyclic polarization scan). Differences in the properties of tested wire types were analyzed with analysis of variance and Tukey post hoc test. RESULTS Uncoated and nitrified NiTi wires showed similar mechanical and anticorrosive properties, while rhodium-coated NiTi wires showed the highest Ra and significantly higher modulus of elasticity, yield strength, and delivery of forces during loading but not in unloading. Rhodium-coated NiTi wires also had the highest corrosion current density and corrosion potential, lowest impedance modulus, and two time constants on Bode plot, one related to the Rh/Au coating and the other to underlying NiTi. CONCLUSION Working properties of NiTi wires were unaffected by various coatings in unloading. Nitrification improved corrosion resistance. Rhodium coating reduced corrosion resistance and pronounced susceptibility to pitting corrosion in artificial saliva because of galvanic coupling between the noble coating and the base alloy.

Geometrical design characteristics of orthodontic mini-implants predicting maximum insertion torque

Objective To determine the unique contribution of geometrical design characteristics of orthodontic mini-implants on maximum insertion torque while controlling for the influence of cortical bone thickness. Methods Total number of 100 cylindrical orthodontic mini-implants was used. Geometrical design characteristics of ten specimens of ten types of cylindrical self-drilling orthodontic mini-implants (Ortho Easy®, Aarhus, and Dual Top™) with diameters ranging from 1.4 to 2.0 mm and lengths of 6 and 8 mm were measured. Maximum insertion torque was recorded during manual insertion of mini-implants into bone samples. Cortical bone thickness was measured. Retrieved data were analyzed in a multiple regression model. Results Significant predictors for higher maximum insertion torque included larger outer diameter of implant, higher lead angle of thread, and thicker cortical bone, and their unique contribution to maximum insertion torque was 12.3%, 10.7%, and 24.7%, respectively. Conclusions The maximum insertion torque values are best controlled by choosing an implant diameter and lead angle according to the assessed thickness of cortical bone.

Secular Trend in the Development of Permanent Teeth in a Population of Istria and the Littoral Region of Croatia

The study evaluated secular trends in dental development during a period of 30 years, correlation between dental and chronological age in Istria and the littoral region of Croatia. The sample consisted of 1000 panoramic radiographs of children, aged 6–16 years (mean 10.0 ± 1.8), taken in the period 1977–1979 (N = 500; 243 females) and 2007–2009 (N = 500; 299 females). Dental age was assessed according to Demirjians method. Correlation between chronological and dental age was linear, positive, high, and statistically significant in both periods and genders, ranging from 0.73 to 0.86. Dental age was underestimated when compared to chronological age by 1 year on average, more 30 years ago (−1.35 ± 1.17) than today (−0.63 ± 1.09), less for girls (−0.80 ± 1.22) than boys (−1.21 ± 1.10). A statistically significant positive secular trend in acceleration of dental development was present of 0.72 years during the 30‐year period and was more significant in girls than boys (0.83‐ and 0.51‐year acceleration).

The unique contribution of elements of smile aesthetics to psychosocial well-being.

Pleasant smile aesthetics is an important contributory factor to psychosocial well-being. The aim of this study was to determine the psychosocial influence of smile aesthetics. The study was cross-sectional on a convenient sample that included patients, pupils, students and faculty staff. A total of 155 subjects (36% male) aged 12-39 (mean age 21, interquartile range 19-23) were included. Occlusal characteristics were recorded by the Index of Complexity, Outcome and Need, and smiling frontal view photographs were obtained. Fourteen variables were measured using photogrammetric analysis: smile width, visibility of buccal corridors, maximum teeth exposure, total gingival display, lip thickness, degree of occlusal cant and deviation from golden proportion of the teeth in maxillary intercanine sector. Psychometric instruments included the Psychosocial Impact of Dental Aesthetics Questionnaire and the Rosenberg Self-Esteem Scale. Statistical analysis comprised multiple linear regressions. Malocclusion severity is the most important predictor of psychosocial influence of smile aesthetics and self-esteem, the unique contribution of which accounts for a total of 4-27% of variability. Female gender is associated with higher psychological influence of dental aesthetics while male gender and older age with self-esteem. Malocclusions have higher psychosocial impact than parameters of mini- and micro-aesthetics of smile related to visibility of buccal corridors, amount of teeth exposure, gingival display, lip thickness, presence of occlusal cant and deviation from golden proportion of the teeth. It appears that people are not as focused on details of their smile as they are on distinctive malposition of teeth.

Gender, age, and psychosocial context of the perception of facial esthetics.

OBJECTIVE To explore the effects of gender, age, and psychosocial context on the perception of facial esthetics. METHODS The study included 1,444 Caucasian subjects aged 16 to 85 years. Two sets of color photographs illustrating 13 male and 13 female Caucasian facial type alterations, representing different skeletal and dentoalveolar components of sagittal maxillary-mandibular relationships, were used to estimate the facial profile attractiveness. The examinees graded the profiles based on a 0 to 10 numerical rating scale. The examinees graded the profiles of their own sex only from a social perspective, whereas opposite sex profiles were graded both from the social and emotional perspective separately. RESULTS The perception of facial esthetics was found to be related to the gender, age, and psychosocial context of evaluation (p < 0.05). The most attractive profiles to men are the orthognathic female profile from the social perspective and the moderate bialveolar protrusion from the emotional perspective. The most attractive profile to women is the orthognathic male profile, when graded from the social aspect, and the mild bialveolar retrusion when graded from the emotional aspect. The age increase of the assessor results in a higher attractiveness grade. CONCLUSIONS When planning treatment that modifies the facial profile, the clinician should bear in mind that the perception of facial profile esthetics is a complex phenomenon influenced by biopsychosocial factors. CLINICAL SIGNIFICANCE This study allows a better understanding of the concept of perception of facial esthetics that includes gender, age, and psychosocial context.

Discriminant factor analysis of dental arch dimensions with 3-dimensional virtual models.

INTRODUCTION The form and the size of a dental arch are products of the configuration and the naturally established balance of the jaw, alveolar bone, and muscles. We investigated which arch dimensions mostly discriminate particular dentoalveolar classes and sexes. METHODS Plaster dental casts were collected from 137 white adolescent subjects (71 girls, 66 boys) aged between 15 and 18 years (mean, 16.0 ± 1.2 years) with Class I (43 subjects: 24 girls, 19 boys), Class II (50 subjects: 28 girls, 22 boys), and Class III (44 subjects: 19 girls, 25 boys) malocclusions. Casts were scanned with the ATOS II SO (small objects) scanner (GOM mbH, Braunschweig, Germany) and measured with ATOS Viewer software (version 6.0.2; GOM mbH). RESULTS The major discriminating factors of the particular dentoalveolar classes are the mandibular canine width/depth ratio and the maxillary molar width/depth ratio, which explain 82.8% of the total variability (P <0.001). Class III subjects with the widest and shallowest frontal segment of the mandibular arch and the posterior segment of maxillary arch are clearly distinguished from Class II subjects whose abovementioned segments are the deepest and narrowest. Class I subjects are more similar to Class II than to Class III subjects. The most homogenous are Class III subjects, with 61.1% of them correctly classified, followed by Class II (57.8%) and Class I (52.4%). Sex differences are significant in linear measurements, but not in ratios. CONCLUSIONS Variability of dental arch dimensions and forms is a common characteristic of all dentoalveolar classes. Maxillary arch form is more distinguishing in the posterior segment, and mandibular arch form is more distinguishing in the anterior segment. Class III patients have the most detectable arch form, and Class I the least detectable arch form.

Influence of tobacco smoking on dental periapical condition in a sample of Croatian adults.

SummaryBackgroundSince current evidences support a negative influence of tobacco smoking on the periodontal bone, an increased prevalence or severity of periapical lesions would be expected among smokers. The aim of this study was to investigate the difference in the periapical status of endodontically treated and untreated teeth in current smokers and never-smokers.MethodsThe cross-sectional study included 259 subjects, 108 current smokers and 151 never-smokers, presenting as new patients at the Dental Clinic of the Clinical Hospital Centre Rijeka, Croatia. The periapical index (PAI) was used to assess the periapical status of all teeth, excluding third molars.Results and conclusionsCurrent smokers had higher fraction of teeth with apical periodontitis (AP) than never-smokers (0.13 vs. 0.10; P = 0.025), while fractions of endodontically treated teeth and endodontically treated teeth with AP did not differ significantly. When overall number of teeth was controlled for, smokers were 16.4 times more likely to have AP than a non-smokers (95% CI: 5.7–47.7; P < 0.001) and if a person was male, he was 3.1 times more likely to have AP than if the person was female (95% CI: 1.1–8.9; P = 0.039). The probability of AP increases with increase of age. Smokers will on average have two teeth with AP more than non-smokers, while controlling for gender, age and overall number of teeth.

Translation and validation of the Croatian version of the Oral Impacts on Daily Performances (OIDP) scale

Background/Aim Among numerous sociodental indicators the Oral Impacts on Daily Performance (OIPD) is one of the most broadly applied. The aim of this study was to develop and test psychometric properties of a Croatian version of OIDP scale. Methods The OIDP instrument was translated from English to Croatian in a forward-backward method. The Croatian version was tested for reliability, construct validity and responsiveness on a sample of 702 participants (255 men), aged 18-86 years. Results Internal consistency of Croatian version of the OIDP was acceptable (alpha = 0.80) and 69.4% of the examinees had oral impacts relating to one or several performances. The most frequently affected performance was eating (53.7%). The test-retest reliability was high (r = 0.99; 95% CI: 0.97-0.99), the mean difference between the OIDP summary scores in two-week interval was not statistically significant. In construct validity testing there was statistically significant correlation between OIDP and self-assessed general and oral health, somatisation, depression and Oral Health Impact Profile ranging from 0.157 to 0.516. Responsiveness was confirmed by a significant reduction of oral impacts on daily performances in subjects before and after treatment of acute dental pain (p < 0.001). Conclusion The Croatian OIDP index showed good psychometric properties in terms of construct validity, internal consistency, test-retest reliability and responsiveness confirming its appropriateness for use among Croatian population.