Jurassic shuotheriids show earliest dental diversification of mammaliaforms.

Shuotheriids are Jurassic mammaliaforms that possess pseudotribosphenic teeth in which a pseudotalonid is anterior to the trigonid in the lower molar, contrasting with the tribosphenic pattern of therian mammals (placentals, marsupials and kin) in which the talonid is posterior to the trigonid1-4. The origin of the pseudotribosphenic teeth remains unclear, obscuring our perception of shuotheriid affinities and the early evolution of mammaliaforms1,5-9. Here we report a new Jurassic shuotheriid represented by two skeletal specimens. Their complete pseudotribosphenic dentitions allow reidentification of dental structures using serial homology and the tooth occlusal relationship. Contrary to the conventional view1,2,6,10,11, our findings show that dental structures of shuotheriids can be homologized to those of docodontans and partly support homologous statements for some dental structures between docodontans and other mammaliaforms6,12. The phylogenetic analysis based on new evidence removes shuotheriids from the tribosphenic ausktribosphenids (including monotremes) and clusters them with docodontans to form a new clade, Docodontiformes, that is characterized by pseudotribosphenic features. In the phylogeny, docodontiforms and 'holotherians' (Kuehneotherium, monotremes and therians)13 evolve independently from a Morganucodon-like ancestor with triconodont molars by labio-lingual widening their posterior teeth for more efficient food processing. The pseudotribosphenic pattern passed a cusp semitriangulation stage9, whereas the tribosphenic pattern and its precursor went through a stage of cusp triangulation. The two different processes resulted in complex tooth structures and occlusal patterns that elucidate the earliest diversification of mammaliaforms.

Sensory nerve regulates progenitor cells via FGF-SHH axis in tooth root morphogenesis.

Nerves play important roles in organ development and tissue homeostasis. Stem/progenitor cells differentiate into different cell lineages responsible for building the craniofacial organs. The mechanism by which nerves regulate stem/progenitor cell behavior in organ morphogenesis has not yet been comprehensively explored. Here, we use tooth root development in mouse as a model to investigate how sensory nerves regulate organogenesis. We show that sensory nerve fibers are enriched in the dental papilla at the initiation of tooth root development. Through single cell RNA-sequencing analysis of the trigeminal ganglion and developing molar, we reveal several signaling pathways that connect the sensory nerve with the developing molar, of which FGF signaling appears to be one of the important regulators. Fgfr2 is expressed in the progenitor cells during tooth root development. Loss of FGF signaling leads to shortened roots with compromised proliferation and differentiation of progenitor cells. Furthermore, Hh signaling is impaired in Gli1-CreER;Fgfr2fl/fl mice. Modulation of Hh signaling rescues the tooth root defects in these mice. Collectively, our findings elucidate the nerve-progenitor crosstalk and reveal the molecular mechanism of the FGF-SHH signaling cascade during tooth root morphogenesis.

Premature gray hair development in the interbrow region owing to the loss of maxillary first molars in young mice.

The exact sites of premature hair graying and whether tooth loss causes this condition remain unknown. In this study, we aimed to explore the effect of reduced mastication on premature hair graying. Maxillary first molars were extracted from young mice, and the mice were observed for 3 months, along with non-extraction control group mice. After 3 months, gray hair emerged in the interbrow region of mice in the tooth extraction group but not in the control group. The expression of tyrosinase-related protein-2 (TRP-2) mRNA was lower in the interbrow tissues of young mice without maxillary molars than in those with maxillary molars. Tooth loss leads to interbrow gray hair growth, possibly because of weakened trigeminal nerve input, suggesting that reduced mastication causes premature graying. Thus, prompt prosthetic treatment after molar loss is highly recommended.

Hypoxia-inducible factors in postnatal mouse molar dental pulp development: insights into expression patterns, localisation and metabolic pathways.

Hypoxia is relevant to several physiological and pathological processes and this also applies for the tooth. The adaptive response to lowering oxygen concentration is mediated by hypoxia-inducible factors (HIFs). Since HIFs were shown to participate in the promotion of angiogenesis, stem cell survival, odontoblast differentiation and dentin formation, they may play a beneficial role in the tooth reparative processes. Although some data were generated in vitro, little is known about the in vivo context of HIFs in tooth development. In order to contribute to this field, the mouse mandibular first molar was used as a model.The expression and in situ localisation of HIFs were examined at postnatal (P) days P0, P7, P14, using RT-PCR and immunostaining. The expression pattern of a broad spectrum of hypoxia-related genes was monitored by customised PCR Arrays. Metabolic aspects were evaluated by determination of the lactate level and mRNA expression of the mitochondrial marker Nd1.The results show constant high mRNA expression of Hif1a, increasing expression of Hif2a, and very low expression of Hif3a during early postnatal molar development. In the examined period the localisation of HIFs in the nuclei of odontoblasts and the subodontoblastic layer identified their presence during odontoblastic differentiation. Additionally, the lower lactate level and higher expression of mitochondrial Nd1 in advanced development points to decreasing glycolysis during differentiation. Postnatal nuclear localisation of HIFs indicates a hypoxic state in specific areas of dental pulp as oxygen demands depend on physiological events such as crown and root dentin mineralization.

Fibroblast growth factor signalling regulates the development of tooth root.

Fibroblast growth factor (FGF) signalling plays a crucial role in the morphogenesis of multiple tissues including teeth. While the role of the signal has been studied in tooth crown development, little is known about root development. Of several FGF ligands involved in hard tissue formation, we suggest that FGF18 regulates the development of murine tooth roots. We implanted FGF18-soaked heparin beads into the lower first molar tooth buds at postnatal day 6 (P6), followed by transplantation under the kidney capsule. After 3 weeks, FGF18 significantly facilitated root elongation and periodontal tissue formation compared to the control. In situ hybridisation showed that Fgf18 transcripts were initially localised in the dental pulp along Hertwig's epithelial root sheath at P6 and P10 and subsequently in the dental follicle cells at P14. Fgf receptors were expressed in various dental tissues during these stages. In vitro analysis using the dental pulp stem cells revealed that FGF18 inhibited cell proliferation and decreased expression levels of osteogenic markers, Runx2, Alpl and Sp7. Consistently, after 1 week of kidney capsule transplantation, FGF18 application did not induce the expression of Sp7 and Bsp, but upregulated Periostin in the apical region of dental mesenchyme in the grafted molar. These findings suggest that FGF18 facilitates molar root development by regulating the calcification of periodontal tissues.

Hypoconulid loss in cercopithecins: Functional and developmental considerations.

Cercopithecins differ from papionins in lacking a M3 hypoconulid. Although this loss may be related to dietary differences, the functional and developmental ramifications of hypoconulid loss are currently unclear. The following makes use of dental topographic analysis to quantify shape variation in a sample of cercopithecin M3s, as well as in a sample of Macaca, which has a hypoconulid. To help understand the consequences of hypoconulid loss, Macaca M3s were virtually cropped to remove the hypoconulid and were also subjected to dental topographic analysis. The patterning cascade model and the inhibitory cascade model attempt to explain variation in cusp pattern and molar proportions, respectively. These models have both previously been used to explain patterns of variation in cercopithecines, but have not been examined in the context of hypoconulid loss. For example, previous work suggests that earlier developing cusps impact the development of later developing cusps (i.e., the hypoconulid) and that cercopithecines do not conform to the predictions of the inhibitory cascade model in that the size of the molars is not linear moving distally. Results of the current study suggest that the loss of the hypoconulid is associated with a reduction in dental topography among cercopithecins, which is potentially related to diet, although the connection to diet is not necessarily clear. Results also suggest that the loss of the hypoconulid can be explained by the patterning cascade model, and that hypoconulid loss explains the apparent lack of support for the inhibitory cascade model among cercopithecines. These findings highlight the importance of a holistic approach to studying variation in molar proportions and developmental models.

Sex-biased sampling may influence Homo naledi tooth size variation.

A frequent source of debate in paleoanthropology concerns the taxonomic unity of fossil assemblages, with many hominin samples exhibiting elevated levels of variation that can be interpreted as indicating the presence of multiple species. By contrast, the large assemblage of hominin fossils from the Rising Star cave system, assigned to Homo naledi, exhibits a remarkably low degree of variation for most skeletal elements. Many factors can contribute to low sample variation, including genetic drift, strong natural selection, biased sex ratios, and sampling of closely related individuals. In this study, we tested for potential sex-biased sampling in the Rising Star dental sample. We compared coefficients of variation for the H. naledi teeth to those for eight extant hominoid samples. We used a resampling procedure that generated samples from the extant taxa that matched the sample size of the fossil sample for each possible Rising Star dental sex ratio. We found that variation at four H. naledi tooth positions-I2, M1, P4, M1-is so low that the possibility that one sex is represented by few or no individuals in the sample cannot be excluded. Additional evidence is needed to corroborate this inference, such as ancient DNA or enamel proteome data, and our study design does not address other potential factors that would account for low sample variation. Nevertheless, our results highlight the importance of considering the taphonomic history of a hominin assemblage and suggest that sex-biased sampling is a plausible explanation for the low level of phenotypic variation found in some aspects of the current H. naledi assemblage.

New craniodental fossils of Paranthropus robustus from Kromdraai, South Africa (2014-2017 excavations).

Since the initial discovery of Paranthropus robustus at the site of Kromdraai in 1938, the hypodigm of this species has been expanded by subsequent work at the localities of Swartkrans and Drimolen, with a few fossils also known from Cooper's D, Gondolin and Sterkfontein Member 5. Beginning in 2014, systematic excavations at Kromdraai uncovered a large and previously unknown fossiliferous area, shedding light on Units O and P in the earliest part of the site's stratigraphic sequence. The aim of this paper is to provide detailed descriptions and illustrations of 30 P. robustus craniodental specimens recovered between 2014 and 2017 within the Unit P deposits at Kromdraai. This new sample predates all prior conspecific specimens found at this site (including the holotype of P. robustus from Kromdraai, TM 1517). Its basic dental morphology dimensions and cranial features are compared in a preliminary analysis with other P. robustus samples. The P. robustus sample from Kromdraai Unit P documents previously unknown portions of the P. robustus juvenile cranium. The new dental and cranial remains aid in the exploration of potential morphological distinctions between site-specific P. robustus samples and are compared favorably in size and morphology with the small P. robustus specimens from Drimolen (e.g., DNH 7). These findings do not support the hypothesis that the specimens from Drimolen belong to a different taxonomic group. Instead, they reinforce the presence of a significant degree of sexual dimorphism within P. robustus. The Kromdraai Unit P specimens also contribute to the biodemographic profile of P. robustus. The notable prevalence of infants (i.e., juvenile individuals before the emergence of their first permanent molars) mirrors the natural mortality profiles observed in wild chimpanzees. This suggests a closer resemblance in the processes of accumulation in Kromdraai Unit P and Drimolen than at Swartkrans.

MRI segmentation of tooth tissue in age prediction of sub-adults - a new method for combining data from the 1st, 2nd, and 3rd molars.

PURPOSE: We aimed to establish a model combining MRI volume measurements from the 1st, 2nd and 3rd molars for age prediction in sub-adults and compare the age prediction performance of different combinations of all three molars, internally in the study cohort. MATERIAL AND METHOD: We examined 99 volunteers using a 1.5 T MR scanner with a customized high-resolution single T2 sequence. Segmentation was performed using SliceOmatic (Tomovision©). Age prediction was based on the tooth tissue ratio (high signal soft tissue + low signal soft tissue)/total. The model included three correlation parameters to account for statistical dependence between the molars. Age prediction performance of different combinations of teeth for the three molars was assessed using interquartile range (IQR). RESULTS: We included data from the 1st molars from 87 participants (F/M 59/28), 2nd molars from 93 (F/M 60/33) and 3rd molars from 67 (F/M 45/22). The age range was 14-24 years with a median age of 18 years. The model with the best age prediction performance (smallest IQR) was 46-47-18 (lower right 1st and 2nd and upper right 3rd molar) in males. The estimated correlation between the different molars was 0.620 (46 vs. 47), 0.430 (46 vs. 18), and 0.598 (47 vs. 18). IQR was the smallest in tooth combinations including a 3rd molar. CONCLUSION: We have established a model for combining tissue volume measurements from the 1st, 2nd and 3rd molars for age prediction in sub-adults. The prediction performance was mostly driven by the 3rd molars. All combinations involving the 3rd molar performed well.

The survival of periodontally treated molars in long-term maintenance: A systematic review and meta-analysis.

AIM: This systematic review and meta-analysis aimed to determine the survival of periodontally treated molars during maintenance care and identify the risk factors associated with molar loss among patients with periodontitis who received professional periodontal therapy and maintenance. MATERIALS AND METHODS: Longitudinal studies with a minimum follow-up duration of 5 years published until 28 August 2023 were retrieved from the following databases: the Cochrane Library, Embase, MEDLINE and Web of Science. All included studies reported data on molar retention. Meta-analysis was performed using Review Manager 5.4. A modified version of the Newcastle-Ottawa Scale was used to evaluate the study quality. Statistical results of analyses of the overall survival rate and molar loss are presented as estimated standardized mean differences, whereas the results of the analyses of risk factors are presented as risk ratios with 95% confidence intervals (95% CIs). RESULTS: From among the 1323 potentially eligible reports, 41 studies (5584 patients, 29,908 molars retained at the beginning of maintenance therapy, mean follow-up duration of 14.7 years) were included. The pooled survival rate of the molars during maintenance therapy was 82% (95% CI: 80%-84%). The average loss of molars was 0.05 per patient per year (95% CI: 0.04-0.06) among the patients receiving long-term periodontal maintenance (PM) therapy. Fifteen factors were examined in this meta-analysis. Six patient-related factors (older age, lack of compliance, smoking, bruxism, diabetes and lack of private insurance) and five tooth-related factors (maxillary location, high probing pocket depth, furcation involvement, higher mobility and lack of pulpal vitality) were identified as risk factors for molar loss during maintenance therapy. CONCLUSIONS: The findings of the present study suggest that the long-term retention of periodontally compromised molars can be achieved. The average number of molars lost per decade was <1 among the patients receiving long-term PM therapy. Older age, noncompliance, smoking, bruxism, diabetes, lack of private insurance coverage, maxillary location, furcation involvement, higher mobility, increase in the probing pocket depth and loss of pulpal vitality are strong risk factors for the long-term prognosis of molars.

Flapless early implant placement into the uncalcified provisional matrix-Does it lead to osseointegration of the implant? A preclinical study.

AIM: To test whether early implant placement into the extraction socket containing an uncalcified provisional matrix leads to successful osseointegration and stable marginal bone levels. MATERIALS AND METHODS: In six mongrel dogs, the mandibular molars were extracted. Three weeks later, early implant placement was performed according to three experimental protocols: (i) flapless implant placement with preservation of the provisional matrix; (ii) flap elevation, socket debridement and implant placement; and (iii) flap elevation, socket debridement, implant placement and guided bone regeneration (GBR). One untreated extraction socket served as a control group. Data analyses were based on histologic slides 3 months after implant placement. RESULTS: There were no differences in bone-to-implant contact between the three experimental groups (66.97%, 58.89% and 60.89%, respectively) (inter-group comparison p = .42). Marginal bone levels, first bone-to-implant contact as well as the thickness of the connective tissue did not reveal any significant differences between the groups (p = .85, .60 and .65, respectively). CONCLUSIONS: Flapless early implant placement into posterior extraction sockets was as effective as an open flap approach in conjunction with GBR. Mineralization of the socket seems to occur irrespective of the presence of dental implants or biomaterials.

Comparative Gene Signature of Nociceptors Innervating Mouse Molar Teeth, Cranial Meninges, and Cornea.

BACKGROUND: The trigeminal ganglion (TG) collects afferent sensory information from various tissues. Recent large-scale RNA sequencing of neurons of the TG and dorsal root ganglion has revealed a variety of functionally distinct neuronal subpopulations, but organ-specific information is lacking. METHODS: To link transcriptomic and tissue-specific information, we labeled small-diameter neurons of 3 specific subpopulations of the TG by local application of lipophilic carbocyanine dyes to their innervation site in the dental pulp, cornea, and meninges (dura mater). We then collected mRNA-sequencing data from fluorescent neurons. Differentially expressed genes (DEGs) were analyzed and subjected to downstream gene set enrichment analysis (GSEA), and ion channel profiling was performed. RESULTS: A total of 10,903 genes were mapped to the mouse genome (>500 reads). DEG analysis revealed 18 and 81 genes with differential expression (log 2 fold change > 2, Padj < .05) in primary afferent neurons innervating the dental pulp (dental primary afferent neurons [DPAN]) compared to those innervating the meninges (meningeal primary afferent neurons [MPAN]) and the cornea (corneal primary afferent neurons [CPAN]). We found 250 and 292 genes differentially expressed in MPAN as compared to DPAN and to CPAN, and 21 and 12 in CPAN as compared to DPAN and MPAN. Scn2b had the highest log 2 fold change when comparing DPAN versus MPAN and Mmp12 was the most prominent DEG when comparing DPAN versus CPAN and, CPAN versus MPAN. GSEA revealed genes of the immune and mitochondrial oxidative phosphorylation system for the DPAN versus MPAN comparison, cilium- and ribosome-related genes for the CPAN versus DPAN comparison, and respirasome, immune cell- and ribosome-related gene sets for the CPAN versus MPAN comparison. DEG analysis for ion channels revealed no significant differences between the neurons set except for the sodium voltage-gated channel beta subunit 2, Scn2b . However, in each tissue a few ion channels turned up with robust number of reads. In DPAN, these were Cacna1b , Trpv2 , Cnga4 , Hcn1 , and Hcn3 , in CPAN Trpa1 , Trpv1 , Cacna1a , and Kcnk13 and in MPAN Trpv2 and Scn11a . CONCLUSIONS: Our study uncovers previously unknown differences in gene expression between sensory neuron subpopulations from the dental pulp, cornea, and dura mater and provides the basis for functional studies, including the investigation of ion channel function and their suitability as targets for tissue-specific analgesia.

Accuracy of open-sleeved vs. closed-sleeved static computer-assisted implant systems in immediate maxillary molar implant placement: An in vitro study.

OBJECTIVES: The objective of this study is (1) to compare the accuracy of an open-sleeved static computer-assisted implant system (sCAIS) with a closed-sleeve sCAIS and free-hand approach in immediate implant placement (IIP) of maxillary molar sites and (2) to investigate the influence of socket morphology on these approaches. MATERIALS AND METHODS: Ninety partially edentulous duplicated maxillary models simulating three different molar sockets (type A, B, and C based on Smith and Tarnow's classification) were investigated. Three modalities, including sCAIS with open-sleeves, sCAIS with closed-sleeves, and free-hand approach, were applied separately to 30 models with 120 sockets. A customized Python script automatically measured the deviations between the virtual and actual implant positions for all 360 implants. RESULTS: The 3D deviations of sCAIS were significantly influenced by the socket and sleeve types. Both guided groups exhibited significantly less deviation than the free-hand approach. Type A and C sockets resulted in better implant positions than type B socket sites. In type B sockets, the open-sleeve group achieved significantly less deviation compared to the closed-sleeve group, with respect to apical global (1.34 ± 0.53 vs. 1.84 ± 0.59 mm), coronal horizontal (0.68 ± 0.36 vs. 0.93 ± 0.34 mm), apical horizontal (1.21 ± 0.59 vs. 1.74 ± 0.63 mm), and angular (3.30 ± 1.41 vs. 4.41 ± 1.96°) deviations. CONCLUSIONS: Guided implant surgery significantly reduces deviations during molar IIP compared to free-hand procedures. Furthermore, the use of open-sleeve sCAIS appears to be more effective in minimizing deviations in type B sockets when compared with the closed-sleeve guided system.

Contribution of initial lymphatics to oral wound healing after tooth extraction.

Lymphatics are involved in the resolution of inflammation and wound healing, but their role in the oral wound healing process after tooth extraction has never been investigated. We therefore sought to evaluate the healing process following the extraction of maxillary molars in two transgenic mouse models: K14-VEGFR3-Ig mice, which lack initial mucosal lymphatic vessels, and K14-VEGFC mice, which have hyperplastic mucosal lymphatics. Maxillary molars were extracted from both transgenic mouse types and their corresponding wild-type (WT) controls. Mucosal and alveolar bone healing were evaluated. A delayed epithelialization and bone regeneration were observed in K14-VEGFR3-Ig mice compared with their WT littermates. The hampered wound closure was accompanied by decreased levels of epidermal growth factor (EGF) and persistent inflammation, characterized by infiltrates of immune cells and elevated levels of pro-inflammatory markers in the wounds. Hyperplastic mucosal lymphatics did not enhance the healing process after tooth extraction in K14-VEGFC mice. The findings indicate that initial mucosal lymphatics play a major role in the initial phase of the oral wound healing process.

Comprehensive Analysis of Mandibular First Molar Root and Canal Morphology in Saudi Patients Using Cone Beam Computed Tomography (CBCT).

BACKGROUND The goal of conventional endodontic therapy is to clean the root canal system thoroughly, restore tooth function, and prevent re-infection. Success depends on understanding root canal morphology, resolving apical periodontitis, and using proper techniques. Studies highlight variations in root canal anatomy, with cone-beam computed tomography (CBCT) being crucial for accurate diagnosis despite its high cost and limited availability. MATERIAL AND METHODS This retrospective study reviewed CBCT images of 1820 (907 male, 913 female) patients aged 18 to 78 years. Analysis included 2081 mandibular first molars for variations in root and canal morphology and right- and left-side symmetry. Inter-orifice distance was measured, along with distance from the cementoenamel junction (CEJ) to the level of canal bifurcation. RESULTS In this study, 96.01% of teeth had 2 roots and 3.89% had 3 roots. The percentages of canal configuration were 77.70% for 3 canals, 21.58% for 4 canals, 0.67% for 2 canals, and 0.05% for 1 canal. The inter-orifice distance was 2.07 mm for 2 canals in 1 root and 2.86 mm for 2 canals in separate distal roots. Distance from the CEJ to canal bifurcation varied significantly between 2 canals within 1 distal root (3.35 mm), 2 canals in separate distal roots (1.60 mm), as well as between distal (3.35 mm) and mesial roots (1.10 mm). CONCLUSIONS In mandibular first molars, only 3.89% have additional distolingual roots. Sex and ethnicity showed no influence on number of roots and canals. Distal canals showed a deeper bifurcation and greater inter-orifice distance than did mesial canals.

Edible Bite Force Sensor: A Novel Approach to Measuring Bite Force in Biomedical and Dental Applications.

BACKGROUND Measurement of bite force plays a crucial role in assessment of the masticatory system. With a growing interest in detecting occlusal irregularities, bite force sensors have garnered attention in the biomedical field. This study aimed to introduce a hydrogel bite force sensor, based on hydroxyethyl-cellulose-fructose-water (HEC-F-water), for premolar and molar teeth, and to evaluate it using optical profilometry, infrared spectroscopy (FTIR), and Instron Tension testing system, with 2.5 cm (1 inch) margins at top, bottom, right, and left. MATERIAL AND METHODS We fabricated 20 HEC-F-water hydrogel samples sized with surface of 1×1 cm, with 2 different widths - 1 mm and 5 mm. The samples were characterized using optical profilometry and FTIR and their electrical characteristics were determined using an impedance analyzer. Aluminum (Al) electrodes, fabricated using Cutting Plotter, were used to form a HEC-F-water-based transducer, which was used for bite force sensing. The Instron tensile testing system was employed, utilizing 3D printed models of the upper and lower jaw, to simulate biting. Forces in the range between 40 N and 540 N were exerted upon the transducer, and the output change in the electrical signal was measured. RESULTS The study determined the transfer function between bite force and capacitance. The fabricated sensor exhibited a sensitivity of 3.98 pF/N, an input range of 500 N, output range of 2 nF, and accuracy of 95.9%. CONCLUSIONS This study introduces an edible bite force sensor employing an edible hydrogel as a dielectric, presenting a novel avenue in the development of edible sensorics in dentistry.

Boundary of mandibular molar distalization in orthodontic treatment: A systematic review and meta-analysis.

To explore the mandibular retromolar space length (MRSL), initial root-inner cortex contact percentage (IRCCP), and the various factors that influence mandibular molar distalization. Searches were undertaken in PubMed, EMBASE, Web of Science, Cochrane Library, Scopus, and grey literature (Google Scholar and OpenGrey) for eligible cross-sectional observational studies measuring the MRSL and IRCCP in healthy adult patients. The risk of bias and evidence quality were evaluated using the Joanna Briggs Institute's checklist and GRADE framework. Thirteen studies involving 1169 patients were included for qualitative synthesis. Seven of these studies were eligible for quantitative analysis. Meta-analysis showed that the mean MRSL at the subfurcation-6 mm plane in Asian normodivergent cases was 3.78 mm (95% confidence interval [CI]: 2.81-4.35; I2 = 79.7%) for skeletal Class-I malocclusions, 3.02 mm (95% CI: 2.10-3.94; I2 = 62.5%) for Class-II, and 4.43 mm (95% CI: 3.14-5.73; I2 = 75.1%) for Class-III. The mean MRSL at the sub-cementoenamel junction (CEJ)-10 mm plane for Asian, Class-I, normodivergent cases was 3.28 mm (95% CI: 2.44-4.12; I2 = 68.9%). The mean IRCCP for Asian, Class-I, normodivergent cases was 27.2% (95% CI: 0.22-0.32; I2 = 0%). In Asian normodivergent cases, MRSL ranges from 3.28 to 4.43 mm with a 27.2% IRCCP for Class-I. Cone-beam computed tomography imaging is recommended for measuring the MRSL in the apex region particularly before molar distalization. Factors influencing MRSL and IRCCP include different races, skeletal patterns, facial types, and third-molar status.

Mandibular second molar extraction: A retrospective cohort study of spontaneous occlusal changes in adolescent patients.

OBJECTIVES: Evaluate long-term spontaneous occlusal changes following L7 extraction in adolescent patients. MATERIALS AND METHODS: Study models of 144 participants (63 males, 81 females) retrospectively assessed prior to L7 extraction (9-16 years old; T1) and following L8 eruption (14-25 years old; T2). All received upper fixed appliances. A sub-group (n = 86) received no lower fixed appliances and acted as controls. Occlusal changes were compared between treatment (lower fixed appliance) and control (no lower fixed appliance) groups using PAR index. At T2, L8 occlusal outcome was assessed using ABO grading system. RESULTS: Mean follow-up period 6 (SD 2) years. At T1, lower scores observed in control group for Lower Anterior (P < .001), Midline (P = .033) and Lateral Segments (P = .040) components. At T2, lower scores continued being observed in control group for Midline (P < .001) and Lateral segment (P = .019) components. Higher decrease in Lower Anterior PAR scores observed in treatment group (<.001) with comparable scores between groups at T2 (P = .057). Similar PAR score changes between groups for Lateral Segments, Overjet and Overbite components. At T2, no significant difference observed in Total PAR score reduction between control (83%) and treatment (82%) groups. Good-to-acceptable occlusal outcome of the L8 observed in 81.55% of cases at T2 with no difference between groups. CONCLUSION: In growing patients with mild mandibular crowding, extraction of L7 followed by upper fixed appliance therapy, leads to favourable occlusal changes over a 6-year follow-up period, with or without lower fixed appliance therapy, being an alternative extraction protocol where lower fixed appliance therapy is not recommended.

The short- and long-term effects of congenital occlusion loss of the unilateral first permanent molar on the temporomandibular joint morphology and position: A retrospective study based on cone-beam computed tomography.

OBJECTIVE: To investigate the effects of congenital unilateral first permanent molar occlusal loss (CUMOL) on the morphology and position of temporomandibular joint (TMJ). MATERIALS AND METHODS: Cone-beam computed tomography (CBCT) images of 37 patients with CUMOL (18 males and 19 females, mean age: 13.60 ± 4.38 years) were divided into two subgroups according to the status of second molar (G1: the second molar not erupted, n = 18, G2: second molar erupted, n = 19). The control group consisted of 33 normal occlusion patients (9 males and 24 females, mean age: 16.15 ± 5.44 years) and was divided into 2 subgroups accordingly (G3: the second molar had not erupted, n = 18, G4: the second molar had erupted and made contact with the opposing tooth, n = 15). Linear and angular measurements were used to determine the characteristics of TMJ. RESULTS: In G1, the condyle on the side of the CUMOL shifts posteriorly, with significant side differences observed in Anterior space (AS, P < .05) and Posterior space (PS, P < .05). However, with the eruption of the second permanent molars, in G2, the condyle on the CUMOL side moves posteriorly and inferiorly. This results in significant lateral differences in the AS (P < .05), PS (P < .05), and Superior space (SS, P < .05). Additionally, there is an increase in the thickness of the roof of the glenoid fossa (TRF) on the CUMOL side (P < .05), and a decrease in the inclination of the bilateral articular eminences (P < .05). CONCLUSIONS: CUMOL can affect the position and the morphology of the condyle and was associated with the eruption of the second permanent molars. Before the eruption of the second permanent molars, CUMOL primarily affects the position of the condyle. After the emergence of the second permanent molars, CUMOL leads to changes in both the condyle's position and the morphology of the glenoid fossa.

Comparison of maxillary transversal changes between auxiliary beta-titanium expansion arch and miniscrew-assisted rapid palatal expansion.

OBJECTIVE(S): This study compared buccal bone thickness, dental inclinations and maxillary transverse width dimensions changes between auxiliary beta-titanium expansion arch (AEA) and miniscrew-assisted rapid palatal expansion (MARPE). MATERIALS AND METHODS: The sample consisted of 29 patients, aged between 18 and 40 years, with transverse maxillary deficiency and treated without extractions, divided into two groups: group AEA: comprised 13 individuals (initial mean age: 29.23 ± 9.13 years) treated using auxiliary beta-titanium expansion arch; group MARPE: comprised 16 patients (initial mean age: 24.92 ± 7.60 years) treated with miniscrew-assisted rapid palatal expansion. Buccal bone thickness, dental inclinations and transverse width dimensions (dental, nasal base and jugular) were measured in cone-bean computed tomographies at pre- and post-treatment stages. The variables were compared using the independent t-test. RESULTS: The buccal bone thickness was similar for both groups at the post-treatment stage. The second premolars were significantly more buccal inclined in the AEA group and the right maxillary first molars in the MARPE group. The intercanine and intermolar distances were statistically significantly greater in the MARPE group. Changes in dental arch transverse dimensions were significantly greater for the MARPE group. CONCLUSION: Both treatment protocols corrected the maxillary transverse discrepancy; however, MARPE provided greater correction.