Senka Meštrović

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.

Salivary microbial and nonmicrobial parameters in children with fixed orthodontic appliances

OBJECTIVE To determine the physiologic changes of salivary flow rate, pH, and buffer capacity and the levels of Streptococcus mutans and Lactobacillus spp in patients undergoing fixed orthodontic treatment. MATERIALS AND METHODS The study included 23 patients scheduled for fixed orthodontic therapy. All subjects received equal braces, bands, and brackets, bonded with the same material. Stimulated saliva samples were taken before placement of the appliance, and at weeks 6, 12, and 18 during the therapy. Salivary flow rate and salivary pH were measured, and the salivary buffer capacity was determined. Saliva samples were cultivated on selective microbial agar for microorganism detection. RESULTS A significant (P < .05) increase in stimulated salivary flow rate and salivary pH was found. The salivary levels of S mutans and Lactobacillus spp also inscreased significantly (P < .05), and the major peak was at week 12 of fixed orthodontic therapy. CONCLUSION The 6th to 12th week of orthodontic therapy is the period of the most intensive intraoral growth of S mutans and Lactobacillus spp and a time of very intensive salivary functions and physiologic response.

Proportions in the upper lip-lower lip-chin area of the lower face as determined by photogrammetric method.

This study is concentrated on the lower face profile, the emphasis being given to the lips and chin area which have been analysed by various proportions. A sample consisted of 110 subjects (52 males and 58 females) with good soft tissue profile, dental class I and Caucasian type. All the records were taken in the natural head position (NHP) and all measurements were performed using the computer and by the same operator. Using the photographs of the facial profile, seven vertical measurements were taken and seven indices used to determine the relationships between measurements of the lower third of the face, lower lip, chin and upper lip. Almost all the vertical profile measurements were greater in males than in females. The only variables with no gender differences were lower (Li-Sto) and upper vermilion heights (Ls-Sto). The largest portion of the lower face was occupied by the chin and the smallest by the lower lip height in both genders. All indices were greater in females except (IND7) representing chin/lower third of the face proportion, which was greater in males. Some acknowledged aesthetic guidelines must be followed when determining orthodontic plan for optimal aesthetics. The proportional relationships found in our sample are a valuable contribution and might serve as a template for vertical facial analysis of the lower face in this patient population.

Dental and occlusal features in patients with palatally displaced maxillary canines

The aim of the present study was to determine the dental and occlusal features that could contribute to the aetiology of palatally displaced canines (PDCs). The material consisted of pre-treatment dental casts of 50 patients (36 females and 14 males) with unilateral and bilateral PDCs aged 14-16 years (mean 15.6 +/- 1.6 years). These were compared with a control group of 50 treated subjects (25 males and 25 females) of the same age with normally erupted maxillary canines. The following parameters were measured on the dental casts: the mesiodistal (MD) and buccolingual (BL) width of each maxillary tooth, the maxillary interpremolar and intermolar widths, overjet and overbite, dentoalveolar arch relationship (based on incisor classification), and missing or anomalous teeth. The differences between the PDC group and controls were determined using a Students t-test. P values less than 0.05 were considered significant. PDCs occurred most frequently in subjects with a Class I occlusion. Sixteen per cent of the PDC subjects had congenital absence or peg-shaped lateral incisors or congenital absence of the second premolar, demonstrating a clear association between palatal impaction of the maxillary canine and anomalous or congenital tooth absence. The overjet was significantly smaller in the PDC female subjects, especially in those with unilateral impaction (P < 0.05). Overbite was significantly greater in PDC male subjects compared with the controls, especially in bilateral impaction cases. There was no statistically significant difference between the groups with regard to the maxillary transverse dimensions, maxillary MD widths, or palatal height for either gender.

Tooth size discrepancy in orthodontic patients among different malocclusion groups

An appropriate relationship of the mesiodistal (MD) widths of the maxillary and mandibular teeth favours optimal post-treatment results. The aims of this study were to determine whether there is a difference in the incidence of tooth size discrepancies among different skeletal malocclusion groups and if gender dimorphism exists. The dental casts and lateral cephalometric radiographs of 301 Croatian subjects (127 males and 174 females, mean age 16.86 +/- 2.93 years) were selected from a larger sample of records of the archives of the Orthodontic Department, School of Dental Medicine, University of Zagreb, Croatia. The subjects were from malocclusion groups according to Angle classification, with the corresponding skeletal characteristics. The MD dimensions of all teeth from first molar to first molar were measured on the dental casts using digital callipers. Statistical analysis was undertaken using Kolmogorov-Smirnov, t, and Scheffés tests and one-way analysis of variance. A statistically significant gender difference was found in anterior ratio (P = 0.017). A significant difference in the overall and posterior ratio was observed between Class II and Class III subjects. There was a tendency for mandibular tooth size excess in subjects with an Angle Class III malocclusion and for maxillary tooth size excess in those with an Angle Class II malocclusion. The percentage of subjects more than 2 standard deviations from Boltons means for anterior and overall ratios was 16.28 and 4.32, respectively.

Antimicrobial effect of different brushing frequencies with fluoride toothpaste on Streptococcus mutans and Lactobacillus species in children with fixed orthodontic appliances

Objective To evaluate the antimicrobial effect of different frequencies of brushing with fluoride toothpaste on the levels of salivary mutans streptococci and lactobacilli in children undergoing fixed orthodontic treatment. Methods The study included 22 patients scheduled for fixed orthodontic therapy distributed between 2 groups with different hygiene regimes. All the subjects received identical braces, bands, and brackets bonded with the same material. Stimulated saliva samples were obtained before placement of the appliance and at 6, 12, and 18 weeks during the therapy. Saliva samples were cultured on selective microbial agar for the detection of microorganisms. Results Salivary mutans streptococci were significantly suppressed throughout the experimental period in the group that brushed 4 times a day as compared to the group that brushed twice a day. Salivary lactobacilli were not significantly affected by the frequency of brushing with 0.32% sodium fluoride (NaF) toothpaste. Conclusions The use of 0.32% NaF-containing toothpaste more than 3 times a day has effective antimicrobial activity on mutans streptococci but not lactobacilli in the saliva of children with fixed orthodontic appliances.

Clinical and microbiological parameters in patients with self-ligating and conventional brackets during early phase of orthodontic treatment.

OBJECTIVE To determine the effect of different bracket designs (conventional brackets and self-ligating brackets) on periodontal clinical parameters and periodontal pathogens in subgingival plaque. MATERIAL AND METHODS The following inclusion criteria were used: requirement of orthodontic treatment plan starting with alignment and leveling, good general health, healthy periodontium, no antibiotic therapy in the previous 6 months before the beginning of the study, and no smoking. The study sample totaled 38 patients (13 male, 25 female; mean age, 14.6 ± 2.0 years). Patients were divided into two groups with random distribution of brackets. Recording of clinical parameters was done before the placement of the orthodontic appliance (T0) and at 6 weeks (T1), 12 weeks (T2), and 18 weeks (T3) after full bonding of orthodontic appliances. Periodontal pathogens of subgingival microflora were detected at T3 using a commercially available polymerase chain reaction test (micro-Dent test) that contains probes for Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, and Treponema denticola. RESULTS There was a statistically significant higher prevalence of A actinomycetemcomitans in patients with conventional brackets than in patients with self-ligating brackets, but there was no statistically significant difference for other putative periodontal pathogens. The two different types of brackets did not show statistically significant differences in periodontal clinical parameters. CONCLUSION Bracket design does not seem to have a strong influence on periodontal clinical parameters and periodontal pathogens in subgingival plaque. The correlation between some periodontal pathogens and clinical periodontal parameters was weak.

Analysis of the soft tissue profile in Croatians with normal occlusions and well-balanced faces

The aim of the study was to test the hypothesis that there is no difference between the soft tissue profile of Croatian and white North American adults. Facial profile photographs were taken of 110 Croatians (52 males and 58 females) with normal occlusions and well-balanced faces (age 22-29 years). The findings were also compared with a white Brazilian group. An independent Students t-test (P < 0.05) was used to compare the soft tissue parameters of Croatians with those of North Americans and to assess gender differences. The soft tissue profile measurements that showed significant gender dimorphism (P < 0.001) were the true vertical line [(TVL)-nasal tip (NT)] and TVL-point B, indicating that the males had slightly greater nasal prominence (mean difference: 1.32 mm) and deeper labial sulci (mean difference: 2.04 mm) compared with the females. The upper lip was the same for both genders (1.25 mm), while the lower lip was 0.97 mm more prominent in females than in males. All soft tissue variables, except TVL-NT showed significant differences between Croatian and white American female subjects (P = 0.096). For male subjects, nasolabial angle was the only variable that showed no statistically significant difference between the two populations. A universal standard of facial aesthetic is not applicable to diverse white populations. These differences should be considered in diagnosis and treatment planning for Croatians, together with their individual characteristics.

Soft tissue profile typology: results of the cluster analysis.

The aim of the study was to establish a mathematical classification of normal soft tissue profile by cluster analysis based on linear and angular photogrammetric measurements.The sample consisted of 110 subjects, 52 males (mean age, 28.7 y) and 58 females (mean age, 25.7 y), with good and balanced soft tissue profile and dental class 1 occlusal relationship and were white. The measurements were made with standardized photographic records taken in natural head position.The 39 soft tissue variables (27 linear and 12 angular) were classified according to similarity by cluster analysis. Males and females were separated in an effort to identify representative values for each group. The squared Euclidean distance was used for distance measurement, and the Ward method was used for cluster analysis. Measurement variables for cluster analysis were standardized using z score. Four recognizable types of soft tissue profiles were obtained in both sexes, which differ mostly with regard to the position of the lips and prominence of the chin. This study found a highly significant sex dimorphism in the soft tissue profile, presenting that the form difference is both a size and a shape difference between male and female soft tissue profiles. The lower third of the face expressed most of the sex differences.

Scanning electron microscope comparative surface evaluation of glazed-lithium disilicate ceramics under different irradiation settings of Nd:YAG and Er:YAG lasers

OBJECTIVE To evaluate the surface of glazed lithium disilicate dental ceramics after irradiation under different irradiation settings of Nd:YAG and Er:YAG lasers using a scanning electron microscope (SEM). MATERIALS AND METHODS Three glazed-press lithium disilicate ceramic discs were treated with HF, Er:YAG, and Nd:YAG, respectively. The laser-setting variables tested were laser mode, repetition rate (Hz), power (W), time of exposure (seconds), and laser energy (mJ). Sixteen different variable settings were tested for each laser type, and all the samples were analyzed by SEM at 500× and 1000× magnification. RESULTS Surface analysis of the HF-treated sample showed a typical surface texture with a homogenously rough pattern and exposed ceramic crystals. Er:YAG showed no effect on the surface under any irradiation setting. The surface of Nd:YAG-irradiated samples showed cracking, melting, and resolidifying of the ceramic glaze. These changes became more pronounced as the power increased. At the highest power setting (2.25 W), craters on the surface with large areas of melted or resolidified glaze surrounded by globules were visible. However, there was little to no exposure of ceramic crystals or visible regular surface roughening. CONCLUSIONS Neither Er:YAG nor Nd:YAG dental lasers exhibited adequate surface modification for bonding of orthodontic brackets on glazed lithium disilicate ceramics compared with the control treated with 9.5% HF.