The effect of clear aligner treatment on masticatory muscles (masseter, temporalis) activity in adults: a systematic review and meta-analysis.

BACKGROUND: The use of clear aligners is becoming more common for aesthetic orthodontic treatment, but there are still concerns about how they affect mastication biomechanics in the short and long term. The clear aligners treatment (CAT) mechanism changes the position of the mandible and maxilla, especially impacting the masseter muscle. Surface electromyography (sEMG) proves to be a useful method to evaluate masticatory muscle activity (MMA). OBJECTIVES: To analyze the effect of clear aligners treatment on alterations in masticatory muscles (masseter, temporalis) using surface electromyography. SEARCH METHODS: Five databases (PubMed, Web of Science, SCOPUS, Cochrane Library, and Google Scholar) were searched up to March 2024. SELECTION CRITERIA: Studies in which MMA was evaluated after the installation of orthodontic clear aligners. DATA COLLECTION AND ANALYSIS: Screening, data extraction, and quality assessments were performed by four investigators independently. The data, which evaluated temporalis and masseter muscle characteristics during CAT using surface electromyography, was extracted, and the quality of the studies was evaluated. The risk of bias was assessed using the Newcastle-Ottawa Scale (NOS). RESULTS: Six studies (two prospective cohort studies, three observational longitudinal studies, and one observational longitudinal case-control study) with low and moderate risk of bias were included in the qualitative synthesis. Six of these were also included in the meta-analysis. Our study investigated the dynamics of masseter and temporalis muscle activity during CAT. The results show that during maximal voluntary clenching, the masseter muscle demonstrated a significant initial increase (P < .05) followed by a subsequent non-significant decrease. It also showed that submaximal voluntary clenching consistently exhibited a significant reduction in muscle activity throughout the study period (P < .01). Assessment of muscle activity at the mandibular resting position revealed a variety of responses, with some participants showing a significant increase while others exhibited non-significant changes (P < .05, P > .05, respectively). However, the meta-analysis showed a non-significant difference in measuring masseter and temporalis muscles activity during CAT. CONCLUSIONS: Based on existing evidence, it is reasonable to conclude that CAT affected MMA. During maximal voluntary clenching, masseter muscle activity initially increased but later decreased, while temporalis muscle activity showed mixed results. Submaximal voluntary clenching revealed a consistent decrease in muscle activity over time. Mandibular resting position assessments showed both increases and no significant changes in muscle activity. However, the existing literature is insufficient to draw concrete conclusions; therefore, well-conducted further research is needed to confirm this statement. REGISTRATION: This systematic review and meta-analysis were registered in the International Prospective Register of Systematic Reviews (PROSPERO CRD42024522231).

Correlation Between Third Molar Mineralization and Midpalatal Suture Maturity: A Cone Beam Computed Tomography Study.

BACKGROUND Midpalatal suture ossification varies in patients of different ages, which can lead to making inaccurate presumptions when considering effective treatment timing based on chronological age. Chronological age provides only general information, whereas dental development correlates with skeletal growth, which suggests that tooth mineralization could be considered to be a precise criterion for determining the midpalatal suture's maturity. The present study was conducted to investigate the association between third-molar mineralization and midpalatal suture's maturation stages using cone-beam computed tomography (CBCT) images. MATERIAL AND METHODS The study involved 97 CBCT images of patients aged 8-37 years with normal growth and development. Subjects with cleft lip and palate, caries treatment, or present cavities in the third molars were not included in the study. The stages of midpalatal suture ossification were evaluated according to the protocol suggested by Angelieri et al, and the third-molar mineralization degree was measured by the Demirjian index. Statistical analysis was performed to evaluate correlations between the variables. RESULTS Patients with advanced third-molar mineralization stages were found to have greater midpalatal suture maturity. A statistically significant positive correlation was found between the stages of third-molar mineralization and midpalatal suture maturation (R=0.814, P<0.01). Third-molar development was also found to be associated with chronological age (R=0.883, P<0.01). CONCLUSIONS A measure of third-molar mineralization does not allow for accurate determination of the midpalatal suture maturation stage.

Influence of the use of remineralizing agents on the tensile bond strength of orthodontic brackets.

This study aimed to evaluate the influence of the use of remineralizing agents on the tensile bond strength. The study sample consisted of 80 recently extracted molars, which were randomly divided into four experimental groups (n = 20): groups FG1 and FG30, in which fluoride varnish was used, and groups RG1 and RG30, in which Recaldent tooth mousse was used. The mesiobuccal surfaces served as experimental, and distobuccal as control (n = 80). Brackets were bonded to both surfaces and were submitted to a tension test at different time intervals (T1 and T30). Tensile bond strength (TBS) and the amount of adhesive remnant (ARI) were assessed. A statistically significantly lower mean of TBS compared to the control group was found only in the FG1 group (p < 0.001), and no significant difference was found between the other groups. The FG1 group showed significantly higher ARI scores (p < 0.001) compared to the control group. No significant difference was found between the other groups. In conclusion, bonding brackets one day after applying fluoride varnish significantly reduced the TBS, but after 30 days it was set back to an optimal value. The use of Recaldent before orthodontic treatment had no adverse effect.

Post-Treatment Status of Impacted Maxillary Central Incisors following Surgical-Orthodontic Treatment: A Systematic Review.

Background and Objectives: The aim of this systematic review was to summarize currently available data of published articles that have investigated the post-treatment status of impacted maxillary central incisors (ICI) treated by the surgical-orthodontic approach. Materials and Methods: MEDLINE, Scopus, Cochrane Oral Health Group's Trials Register, and ScienceDirect electronic databases were systematically searched with no publication date restrictions up to January 2021. Data assessing the status of ICI after combined surgical-orthodontic treatment and forced eruption duration were extracted, and the quality of the studies was evaluated. Results: In total, 7074 studies were identified, of which 42 articles were assessed for eligibility through full-text evaluation. Seven included studies (five retrospective studies, one randomized clinical trial, and one prospective clinical trial) met the inclusion criteria, representing 211 patients with unilaterally impacted maxillary incisors. The risk of bias ranged from moderate to high. The results show that the root length of immature ICIs increased significantly but remained shorter than that of homonym teeth at post-treatment. Periodontal parameters of treated ICIs were in a clinically acceptable range. Measurements of the alveolar bone showed a reduction of bone thickness and support. The average forced eruption duration ranged from 8.0 ± 4.5 to 14.41 ± 4.03 months. Conclusions: Based on existing evidence, it is reasonable to conclude that the surgical-orthodontic treatment affected the post-treatment status of ICI; however, the current literature is insufficient to draw concrete conclusions. Further well-conducted multi-center randomized studies with a large sample are needed to confirm this statement.

The effect of botox for the correction of the gummy smile: A systematic review.

PURPOSE: The aim of the systematic review was to analyze the effectiveness of Botox injections for the treatment of the gummy smile. MATERIALS AND METHODS: The systematic literature search was done in the databases: PubMed, Embase and Cochrane Library. The articles published from 2013 to 2020 were searched. Only studies on humans were included in this systematic literature review. RESULTS: During the initial search a total number of 139 articles were detected. However, after the removal of duplications 105 articles were left. Regarding the application of inclusion and exclusion criteria, 6 articles were selected for this systematic literature review. CONCLUSIONS: The results of this study suggested that botulinum toxin was an efficient method to treat the gummy smile.

Heritability of mandibular asymmetries in sagittal direction: A cephalometric study.

AIM OF THE WORK: If we figure out mandible asymmetry etiology, we can inspire further scientific research, create more effective treatment schemas and recommend means of prophylaxis that could stop mandible asymmetry development. The aim of this work was to analyze monozygotic and dizygotic twins' mandibular asymmetry in sagittal direction using cephalometric data and to analyze its dependence of genetic and environmental factors. MATERIAL AND METHODS: Study sample consisted of 80 dizygotic (DZ) and 80 monozygotic (MZ) twins of same sex. 3 cephalometric measurements were made to determine mandible asymmetry in sagittal direction. Indexes of mandibular asymmetry (IMA1, IMA2) were calculated. Data analysis was done using Microsoft Excel (2013). Genetic and environmental factors influencing mandible asymmetry was determined. RESULTS: Mandibular dental asymmetry was bigger in monozygotic twins' group but the results were not statistically significant. Mandibular skeletal asymmetry was significantly bigger in dizygotic twins' group: IMA1(DZ)=3.05±1.94, IMA1(MZ)=1.92±1.05, p=0.005. IMA2(DZ)=3.12±2.04, IMA2(MZ)=1.88±1.04, p=0.004. Distance between distal borders of the ramus is mostly determined by genetic factors. CONCLUSIONS: 1. Mandibular skeletal asymmetry was significantly bigger in dizygotic twins' group. Mandibular dental asymmetry and symmetry did not differ in groups significantly. 2. Skeletal mandible's asymmetry is more determined by genetics than environmental factors, but lower molars' sagittal position is determined more by environment.

Relationship between the Position of Impacted Third Molars and External Root Resorption of Adjacent Second Molars: A Retrospective CBCT Study.

BACKGROUND AND OBJECTIVES: Impacted third molars (ITM) are the most commonly-impacted teeth. There is a risk for ITM to cause a number of pathological conditions, and external root resorption (ERR) of adjacent teeth is one of the most prevalent. Retaining or prophylactic extraction of ITM is a polemic topic. External root resorption of adjacent teeth is one of possible indications for prophylactic removal of ITM. The aim of this study was to assess the relationship between external root resorption (ERR) on the distal aspect of second molars' roots and positional parameters of ITM. Methods: Cone beam computed tomography scans of 109 patients (41 males, 68 females; mean age 26.4 ± 7.9 years) with 254 ITM (131 in the maxilla and 123 in the mandible) were retrospectively analyzed. Positional parameters of ITM (mesio-distal position, angulation, impaction depth, and available eruption space) were evaluated. The presence, location, and depth of ERR of adjacent second molars were assessed. Results: Analysis showed a relationship between ITM impaction depth, mesial inclination angle, and the presence of ERR. Mesial inclination angle of more than 13.6° increased the odds of ERR occurrence by 5.439 (95% CI, 2.97-9.98). ITM presence at the level of ½ of roots of the adjacent second molar or more apically increased the odds of ERR occurrence by 2.218 (95% CI, 1.215-4.048). No significant correlation was detected between the occurrence of ERR and patient age, gender, or the available eruption space in the mandible. Depth of ERR did not depend on its location. Conclusions: Incidence of ERR in second molars is significantly associated with mesial inclination and a deep position of ITM.

Impact of Fluorosis on the Tensile Bond Strength of Metal Brackets and the Prevalence of Enamel Microcracks.

The objective of this in vitro study was to determine the effects of dental fluorosis on the tensile bond strength of metal brackets bonded to human teeth and to evaluate the changes in the tooth enamel surface after debonding. The study sample consisted of 68 recently extracted human upper premolars, which were divided into 2 groups: the fluorosis group (34 fluorosed teeth) and the control group (34 healthy teeth). Identical premolar metal brackets were bonded on the buccal surfaces of the teeth. Both groups were submitted to a tension test using a universal testing machine. The number and length of the enamel microcracks in the buccal surface of each tooth were determined before bracket bonding and after debonding using a stereomicroscope. The percentage adhesive remnant index (PARI) was calculated after debonding. The results showed that the tensile bond strength (TBS) of brackets bonded to fluorosed teeth was 21.08% lower than that of brackets bonded to healthy teeth (p < 0.0001). The length of the enamel microcracks on fluorosed teeth increased by 47.4% after debonding, whereas the control group showed an increase of only 12.6%. The PARI showed lower values for fluorosed teeth in comparison to the control group (p = 0.047). In conclusion, dental fluorosis has a negative impact on tensile bond strength and the length of microcracks formed after bracket debonding.

The impact of the hyoid bone position on the pharyngeal airway characteristics among different facial skeletal patterns.

OBJECTIVE: To identify the impact of the hyoid bone position on the pharyngeal airway characteristics among different facial skeletal patterns. MATERIALS AND METHODS: The orthodontic patients from the patients' data base of the Lithuanian University of Health Sciences base were examined. On each cephalogram 5 linear, 3 angular skeletal and 6 linear soft tissue landmarks were traced and measured using AudaxCeph program. The radiographs were divided into the three groups according to the ANB angle: control group, with skeletal class I (ANB angle 1-5°), study group 1 with skeletal Class II (ANB angle >5°), study group 2 with skeletal Class III (ANB angle <1°). All measurements and relations between dento-facial complex anatomical structures were statistically evaluated using IBM SPSS Statistics software. RESULTS: 261 patients (156 females, 105 males, aged between 7 and 35 years) were selected. The skeletal class II group consisted of 114, class III group - 59 and class I - 88 patients' cephalograms. Hyoid bone distance both to cervical third vertebrae and mandibular symphysis, maxilla and mandibular length, inferior airways space significantly differed between the Angle classes. Inferior airway space had a significantly positive correlation with all measurements, associated with hyoid bone. CONCLUSION: Inferior airway space was significantly narrower and the hyoid bone localization was in more posterior superior position in the skeletal class II in comparison with other both groups. Decrease of the hyoid bone distance to the third cervical vertebrae, mandibular symphysis and mandibular plane led to the narrower inferior airways space.

Genetic and environmental influences on third molar root mineralization.

OBJECTIVE: To assess the genetic and environmental influences on the variability of human third molar (M3) root mineralization stages via a twin study. DESIGN: The study sample consisted of 162 same-sex twins (66 dizygotic and 96 monozygotic, mean age: 17.9 years) with normal growth and development. Panoramic radiographs were evaluated to assess root mineralization stages of the upper and lower third molars, using the method of Demirijian et al. (1973). Zygosity was established using 15 specific DNA markers. RESULTS: Females developed their third molar roots earlier in life than males. Monozygotic twins (MZ) demonstrated higher intra-pair correlations for M3 root development stages than did DZ twins. An ACE model with additive genes, as well as common and specific environmental factors, provided the best explanation of variation in M3 root development. The mineralization of M3 roots showed highly additive genetic determination, varying from 60 to 63%, whereas a common environment contributed from 25 to 27%, and a specific environment only accounted 14% of the total variation, at most. CONCLUSIONS: A considerable proportion of the total variability of the third molar root mineralization rate can be attributed to additive genetic effects, while common and specific environmental effects have a smaller, yet significant, impact.

The Impact of Genetics and Environmental Factors on the Position of the Upper Third Molars.

PURPOSE: The purpose of this study was to estimate the importance of heredity in the position of the upper third molars. MATERIALS AND METHODS: Panoramic radiographs and lateral cephalograms of same-gender twins were analyzed. The determination of zygosity was performed by means of DNA tests with polymerase chain reaction for the amplification of short tandem repeats and 15 specific DNA markers. Data were estimated by the relative influence of additive genetic factors (A), nonadditive genetic factors (D), the common or shared environment (C), and unique environmental factors (E). RESULTS: The study sample consisted of 212 twins: 80 dizygotic and 132 monozygotic twins. The genetic analysis showed that the best-fitting model for the size of the molars and their angulations was AE (additive genetic factors and unique environmental factors), in which the additive genetic factors had up to 84% influence and specific environment had up to 40%. Therefore, the ACE (additive genetic factors, common or shared environment, and unique environmental factors) model showed higher significance for the tooth eruption level. The heritability estimates were up to 59%, specific environment contributed up to 16%, and common environment reached 30%. CONCLUSIONS: Genetic factors play a key role in the position of the upper third molars.

Impact of genetics on third molar agenesis.

The purpose of this investigation was to determine the impact of heritability on third molar agenesis in twins. The study sample consisted of 284 same sex twins (172 monozygotic and 112 dizygotic), whose mean ages were 19.7 ± 4.3 and 18.9 ± 4.8 years, respectively. The monozygotic group consisted of 36.3% males and 63.7% females, while the dizygotic group consisted of 50.1% males and 49.9% females. The zygosity of the twins was established using 15 specific DNA markers. The prevalence of third molar agenesis in monozygotic twins was 19.6%, which was higher than in the dizygotic twins group (15.50%) (p = 0.004). In both groups, third molar agenesis was more frequent in the maxilla than in the mandible (p = 0.000). Agenesis of the maxillary third molars was mostly affected by additive genetic factors (62-63%), with the common environment and the specific environment accounting for up to 25% and 13%, respectively. In contrast, agenesis of the lower third molars was associated with a higher additive genetic determination (81-83%), with the specific environment accounting for 17% to 19%. The study's conclusion is that the formation of the third molars follicle is strongly controlled by additive genetic factors.

The magnification in the lower third and second molar region in the digital panoramic radiographs.

BACKGROUND: The aim of this study was to determine the accuracy of linear measurements of the lower third and second molar crowns in the digital panoramic radiographs and to compare them with plaster models as the calibration standard. MATERIALS AND METHODS: The digital panoramic radiographs and plaster models of the orthodontic patients were used in the study. Standardized metal calibration gauges (MCGs) were bonded to the buccal surface of the lower molars bilaterally. Measurements in the panoramic radiographs were done using Dolphin Imaging 11.8 Premium program. RESULTS: Forty-one panoramic radiographs and diagnostic plaster models of the orthodontic patients (mean age 18.45 ± 2.35) were analyzed. Eighty-two lower third molars, 82 second molars, and 82 first molars were evaluated. The magnification coefficients (MCC) calculated according to the plaster models ranged from 1.07 to 1.08. The magnification coefficients calculated according to the bonded MCG were about 1.04. The differences between the teeth groups and right-left sides were not statistically significant (P > 0.05). Spearman correlation showed a positive medium correlation between the magnification using the calibration with plaster models and metal gauges (P < 0.05). CONCLUSIONS: The magnification in the lower first, second, and third molars regions showed almost the same values. The calculation of magnification coefficient using bonded metal calipers was more accurate than calculation according to the plaster models, but the differences were not statistically significant. The use of the plaster models for calibration of the magnification coefficient in the good-positioned lower molars' region might be used as an alternative to the bonded MCGs.

The effect of the teeth bleaching with 35% hydrogen peroxide on the tensile bond strength of metal brackets.

The objective of this study was to determine the effects of teeth bleaching on the tensile bond strength of metal brackets bonded with light-curing adhesive system to the human enamel. 40 recently extracted human permanent molars were used for the study. The mesial buccal surface of each tooth was used as a control group and the distal buccal surface was used as an experimental group. Control group surfaces were not submitted to bleaching, while experimental group surfaces were bleached with in-office bleaching material containing 35% hydrogen peroxide. 30 days after the bleaching, identical premolar metal brackets were bonded to each surface using light-curing adhesive. Both groups were submitted to a tension test, using a universal machine. The tensile bond strength of brackets bonded to the bleached enamel was 15% lower than that of brackets bonded to the unbleached enamel. After debonding, more adhesive was left on the bracket base in experimental group than in the control group. The conclusion of this study was that bleaching with an in-office bleaching material containing 35% hydrogen peroxide reduced the tensile bond strength of orthodontic bracket adhesive to the enamel surface.

Evaluation of skeletal maturity using maxillary canine, mandibular second and third molar calcification stages.

OBJECTIVE: The objective of this study was to evaluate whether the calcification stages of maxillary canine, mandibular second molar, and mandibular third molar can be used for assessment of growth phase. MATERIALS AND METHODS: The study group consisted of 274 subjects. Pre-treatment digital panoramic and lateral cephalometric radiographs of the patients were analysed. The patients' age was ranging from 7 to 19 years. Right maxillary canine, mandibular second molar and third molar were used as a sample. The teeth mineralization was assessed using modification of Gleiser and Hunt method. The skeletal maturation was assessed by the cervical vertebrae maturation (CVM) method. RESULTS: A significant association was found between CVM stage 2 and maxillary canine (UC) stage 4, mandibular second molar (LM2) stage 4, and mandibular third molar (LM3) stage 1. CVM stage 3 corresponded with UC stage 5, LM2 stage 5, LM3 stage 2. CVM stage 4 matched with UC stage 5, LM2 stage 6 and LM3 stage 3. The highest correlations between CVM and calcification stages were in the group of the maxillary canine (r = 0.812, P < 0.01) and mandibular second molar (r = 0.824, P < 0.01). LIMITATIONS: Limitation of our study was that the study sample was not very big and the distribution value in the groups was very high, so it was impossible to check more statistical parameters. CONCLUSIONS: The calcification stages of UC, LM2, and LM3 as indicators of skeletal maturity could be clinically used with caution, until this method is verified with a larger sample group.

Do wisdom teeth induce lower anterior teeth crowding? A systematic literature review.

OBJECTIVE: Individuals with dental crowding are the most frequent patients in the orthodontic practice.The purpose of this article is to find out if the lower third molars are the main reason of crowding in the lower dental arch. As well to find out other factors which can influence the lower incisors crowding. METHODS: The aim was to identify studies and reviews related to the effect of the lower third molars on the lower dental arch crowding. A literature survey was performed using Medline database. Used key words were lower third molar, influence of wisdom teeth, wisdom teeth and anterior crowding, lower dental arch changes. The articles from 1971 to 2011 related to topic were identified. Selected articles were published in dental journals in English. Full texts of the selected articles were analyzed. Articles about the dental crowding after orthodontic treatment were not included. All studies accomplished with human participants. RESULTS: It was found 223 articles but only 21 articles corresponded to selected criteria and were analyzed. This review is based on the investigations of 12 laboratory researchers, 4 clinical researches, 2 questionnaires and 3 literature reviews. CONCLUSION: The results are quite contradictory: some authors support the opinion that lower third molars cause teeth crowding, the others confirm conversy. Exist other factors affecting the mandibular incisors crowding: dental (teeth crown size, dental arch length loss, poor periodontal status and primary teeth loss), skeletal (growth of the jaws and malocclusion) and general (age and gender).

Lower dental arch changes after bilateral third molar removal.

OBJECTIVE: To evaluate the changes in lower dental arch after bilateral lower third molars removal. MATERIAL AND METHODS: The study group consisted of 30 non-orthodontic patients (mean age 25,5 years, refered for bilateral lower third molars removal. Orthopantomograms and dental casts were made before and 6-8 months after surgical removal of lower third molars. Transversal lower arch widths between lower canines and second premolars and lower arch total tooth size-arch lenght discrepancy were evaluated on dental casts. The angulation of lower second premolars, first and second molars was measured in horizontal and mandibular planes on orthopantomograms. RESULTS: No significant difference of inter-canine and inter-premolar transversal width was noticed. No significant changes were observed in total tooth-size lenght discrepancy, except in S1 segment consisted of first and second premolar and the canine on the right quadrant of the lower dental arch. The angulation of second premolars and first molars did not show any significant changes, however there were statistically significant changes between angulation of lower second molars on both sides. CONCLUSIONS: After bilateral removal of lower third molars, lower second molars awhile showed a tendency to move backwards, but no obvious relationship between the third molar and anterior crowding was observed. Whereas the observation time is short and the patient's age is young and it can not be concluded that lower third molars cause the changes in the dental arch.

Prevalence of teeth number anomalies in orthodontic patients.

OBJECTIVES: The purpose of this study was to determine if the prevalence of teeth number anomalies (TNA) is more frequent in orthodontic patients than in common population and what is TNA clinical manifestation. MATERIAL AND METHODS: The records of 824 orthodontic patients (average age 15.22 years) from Orthodontic Clinic of Lithuanian University of Health Sciences were analyzed. The radiographs were analyzed by trained observer who followed a pre-established protocol: general observation of the teeth including third molar, followed by a systematic analysis of the erupted and unerupted teeth number in each quadrant. Descriptive statistics were performed for the study variables. A chi-square test was used to determine the difference in the prevalence of hypodontia between the genders. A value of P<0.05 was considered significant. RESULTS: The prevalence of hypodontia was 17.11 percent with no statistically significant difference between the genders (P>0.05). More frequently teeth were missing in the lower jaw: in the upper jaw - 10.3%, in the lower - 12.5% without statisticaly significant diference. Unilateral occurrence of dental agenesis was 1.5 times more common than bilateral occurrence. If more than one tooth was missing, usually other missing tooth was in the same group and in the same jaw. The upper and lower third molars were the most frequently missing teeth, followed by the mandibular second premolar. The prevalence of hyperdontia was 0.85 percent. Mesiodens was the most frequently found supernumerary tooth. CONCLUSIONS: It was found, that 17.96% of orthodontic patients had teeth number anomalies. The upper and lower third molars were the most frequently missing teeth, followed by the mandibular second premolar. Hypodontia occurred more frequently than hyperdontia. Mesiodens was the most frequently found supernumerary tooth. The results confirm that TNA are more often found in orthodontic patients and these patients should be treated with multidisciplinary approach.

Effect of the lower third molars on the lower dental arch crowding.

Increasing lower dental arch crowding with the age is a recognized clinical problem, and one that has become more apparent in recent years as more adults retain their teeth longer. One of the theories is that the erupting third molars push anterior teeth forward and cause their crowding. On the other hand, a number of studies found no correlation between lower third molars and lower incisor crowding. Because of all these contrasting findings this study was started to re-evaluate correlation between third molars presence and lower dental arch crowding. The study group consisted of 91 subjects with an average age 21.01+/-4.13 years. The individual, quantitative and cast-based analytical registration of crowding was based on the measurements of mesiodistal width of teeth and related to the length of the appropriate segment of the lower dental arch. No statistically significant third molar presence-specific differences were recorded in the lower dental arch crowding between the groups with erupted, unerupted and agenesis of third molars. Although differences between the groups were not statistically significant, some tendency for crowding in the anterior part of lower dental arch was more expressed in the groups with the presence (erupted 0.57 mm and unerupted 0.74 mm) of third molars, than with agenesis (surplus space 0.03 mm). Nevertheless, the present study do not provide enough evidence to incriminate third molars as being the only or even major etiologic factor in the late lower dental arch crowding.