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Objectives Although the shortened dental arch (SDA) concept is a widely accepted strategy to avoid overtreatment, little is known on its impact on oral health-related quality of life (OHRQoL). This multicenter randomized controlled trial aimed to investigate the OHRQoL for removable partial dental prostheses (RPDP) with molar replacement versus the SDA concept. Material and methods In both groups, missing anterior teeth were replaced with fixed dental prosthesis. Two hundred fifteen patients with bilateral molar loss in at least one jaw were included. The Oral Health Impact Profile (OHIP-49) was completed before; 6 weeks (baseline), 6 months, and 12 months after treatment; and thereafter annually until 5 years. Results Of the initial cohort, 81 patients were assigned to the RPDP group and 71 to the SDA group (age, 34 to 86 years). Before treatment, the median OHIP score was similar in both groups (RPDP, 38.0; SDA, 40.0; n.s.). Results indicate marked improvements in OHRQoL in both groups between pretreatment and baseline (RPDP, 27.0; SDA, 19.0; p  ≤ 0.0001) which continued in the RPDP group until the 1-year follow-up ( p  = 0.0002). These significant reductions in OHIP scores are reflected in its subscales. No further differences were seen within and between groups during the remainder observation period. Conclusion Both treatments show a significant improvement in OHRQoL which continued in the RPDP group until the 1-year follow-up. No significant differences were seen between groups. Clinical relevance For improving OHRQoL, it is not necessary to replace missing molars with a RPDP.

Background The aim of this prospective clinical study was to compare the mean durability and the failure rates of two types of orthodontic retainers. Methods Orthodontic patients (142) aged between 14 and 28 years were recruited in this study. The polyethylene woven ribbon (Ribbond, Seattle, WA, USA) retainer was compared with a 0.0175-in flexible spiral wire (Respond, Ormco, Glendora, CA, USA) retainer. When treatment was completed, the retainers were bonded from canine to canine in the maxillary and the mandibular arches of the participants. In the follow-up visits, the patients were re-evaluated every 3 months over a period of 18 months. The time taken for the retainers to remain without any fracture was appraised. Kaplan-Meier analysis and the logrank test were employed to identify significant differences in the survival functions between the groups. The rates of the retainers' failure between the groups were analyzed using Chi-square test. Results It was revealed that the mean survival of the flexible spiral wire retainer was 15.34 ± 0.47 and 15.60 ± 0.42 months in the maxillary and mandibular arches, respectively. The mean survival of the ribbon retainer was 13.95 ± 0.55 and 14.26 ± 0.57 months in the maxillary and mandibular arches, respectively. Ribbon retainers showed a failure rate of 50% in the maxillary and 42.6% in the mandibular arches. Flexible spiral retainers showed a failure rate of 36.5% in the maxillary and 37.8% in the mandibular arches. The differences were not statistically significant. Regarding the evaluation period, the differences had limited clinical significance. Conclusion The mean survival time and the failure rates of the polyethylene woven ribbon retainer were comparable to the flexible spiral wire retainer during the 18 months after orthodontic treatment.

Background Most orthodontists believe that fixed retainers are necessary to maintain ideal dental relationships. However, untoward side effects might result from their long-term placement. The aim of this study was to evaluate the clinical and radiographic effect of two commonly used fixed retainers on the health of the periodontium. Methods Thirty patients were randomly divided into two groups to receive either a fiber-reinforced composite retainer or a spiral wire retainer extended on the lingual surfaces of both maxillary and mandibular arches from canine to canine. Periapical radiographs were obtained from the patients at the time of placement of the retainers and after the 6-month period to assess the radiographic conditions of the periodontium. Clinical examination was carried out at the same two time intervals. Results Even though there were no significant differences between the two groups of study at the beginning of the trial, there were statistically significant differences after the 6-month follow-up regarding the main outcomes of the study. Nearly all indices showed to deteriorate after 6 months in the fiber-reinforced group, while in the spiral wire group, this was not the case. As for the secondary outcomes, radiographic examination did not reveal any statistically significant differences after 6 months or between the two groups. Conclusions It can be concluded that spiral wire retainers elicit less detrimental periodontal response in the short-term follow-up compared to fiber-reinforced composite retainers as revealed by the primary outcomes of the study. Trial registration ClinicalTrials.gov: NCT01314729

Intraoral digital impressions have been stated to meet the clinical requirements for some teeth-supported restorations, though fewer evidences were proposed for larger scanning range. The aim of this study was to compare the accuracy (trueness and precision) of intraoral digital impressions for whole upper jaws, including the full dentitions and palatal soft tissues, as well as to determine the effect of different palatal vault height or arch width on accuracy of intraoral digital impressions. Thirty-two volunteers were divided into three groups according to the palatal vault height or arch width. Each volunteer received three scans with TRIOS intraoral scanner and one conventional impression of whole upper jaw. Three-dimensional (3D) images digitized from conventional gypsum casts by a laboratory scanner were chose as the reference models. All datasets were imported to a specific software program for 3D analysis by \"best fit alignment\" and \"3D compare\" process. Color-coded deviation maps showed qualitative visualization of the deviations. For the digital impressions for palatal soft tissues, trueness was (130.54±33.95)μm and precision was (55.26±11.21)μm. For the digital impressions for upper full dentitions, trueness was (80.01±17.78)μm and precision was (59.52±11.29)μm. Larger deviations were found between intraoral digital impressions and conventional impressions in the areas of palatal soft tissues than that in the areas of full dentitions (p<0.001). Precision of digital impressions for palatal soft tissues was slightly better than that for full dentitions (p = 0.049). There was no significant effect of palatal vault height on accuracy of digital impressions for palatal soft tissues (p>0.05), but arch width was found to have a significant effect on precision of intraoral digital impressions for full dentitions (p = 0.016). A linear correlation was found between arch width and precision of digital impressions for whole upper jaws (r = 0.326, p = 0.034 for palatal soft tissues and r = 0.485, p = 0.002 for full dentitions). It was feasible to use the intraoral scanner to obtain digital impressions for whole upper jaws. Wider dental arch contributed to lower precision of an intraoral digital impression. It should be confirmed in further studies that whether accuracy of digital impressions for whole upper jaws is clinically acceptable.

The discovery of Entelognathus revealed the presence of maxilla, premaxilla, and dentary, supposedly diagnostic osteichthyan bones, in a Silurian placoderm. However, the relationship between these marginal jaw bones and the gnathal plates of conventional placoderms, thought to represent the inner dental arcade, remains uncertain. Here we report a second Silurian maxillate placoderm, which bridges the gnathal and maxillate conditions. We propose that the maxilla, premaxilla, and dentary are homologous to the gnathal plates of placoderms and that all belong to the same dental arcade. The gnathal-maxillate transformation occurred concurrently in upper and lower jaws, predating the addition of infradentary bones to the lower jaw.

We describe two new cynodonts from the early Late Triassic of southern Brazil. One taxon, Bonacynodon schultzi gen. et sp. nov., comes from the lower Carnian Dinodontosaurus AZ, being correlated with the faunal association at the upper half of the lower member of the Chañares Formation (Ischigualasto-Villa Unión Basin, Argentina). Phylogenetically, Bonacynodon is a closer relative to Probainognathus jenseni than to any other probainognathian, bearing conspicuous canines with a denticulate distal margin. The other new taxon is Santacruzgnathus abdalai gen. et sp. nov. from the Carnian Santacruzodon AZ. Although based exclusively on a partial lower jaw, it represents a probainognathian close to Prozostrodon from the Hyperodapedon AZ and to Brasilodon, Brasilitherium and Botucaraitherium from the Riograndia AZ. The two new cynodonts and the phylogenetic hypothesis presented herein indicate the degree to which our knowledge on probainognathian cynodonts is incomplete and also the relevance of the South American fossil record for understanding their evolutionary significance. The taxonomic diversity and abundance of probainognathians from Brazil and Argentina will form the basis of deep and complex studies to address the evolutionary transformations of cynodonts leading to mammals.

Objectives To develop and validate a new method to acquire reference distances. Materials and methods A method to accurately register the intraoral position of precision balls was developed to generate reference values for the in-vivo assessment of impression accuracy and tested in vitro. Therefore, metal occlusal veneers with a special abutment carrying precision balls were provisionally attached to specific positions on the patient’s dental arch (anatomical model with PMMA covered metal teeth). To register the precision ball positions, form-congruent counterparts were jointed to the abutments, adhesively fixed to a transfer aid, removed and digitized with a laboratory scanner. First, the distance determination using a transfer aid and a laboratory scanner was validated. Second, the process was tested for an anatomic situation. Results When measuring distances using a transfer aid and a laboratory scanner, distances could be detected with an accuracy of less than 5 μm. Using the new test setup on the anatomical model, the intraoral scanners more accurately reproduced scan volumes up to one quadrant, with deviations between the actual scan data sets/plaster models and the reference data set of < 52 μm for Primescan, < 82 μm for Omnicam, and < 125 μm for conventional impression. Longer distances tended to be more accurately represented by the conventional impression (Primescan < 304 μm; Omnicam < 328 μm; conventional impression < 164 μm). Conclusions The developed method seems suitable for determining the clinical accuracy of conventional and digital complete arch impressions. Clinical relevance For determining the clinical accuracy of conventional or digital impressions, reference values are crucial.

A 3D tooth model segmented with the use of deep learning (DL) method program (CephX) as well as MIMICS software (manual segmentation) will be evaluated for reliability in the presented work. In addition, the segmented model was compared with the intraoral scan (IOS)-generated 3D tooth model in terms of the Bolton ratio and arch dimensions. A total of 30 patients attending the College of Dentistry/University of Baghdad with records of IOSs and CBCT scans were included. CBCT has been transformed into a 3D digital tooth model segmented with the use of MIMICS software and an AI-based program (CephX), and the Bolton ratio and arch dimensions (length and width) were measured utilizing Geomagic Control X software. Statistical analyses, including the mean and standard deviation, were performed, and a paired t-test was used to assess the systematic bias between the three methods. Bland-Altman plots and intraclass correlation (ICC) analysis were used to assess the agreement between the three methods. The means of CephX, MIMICS, and IOS of all analyses were mostly similar, and the difference between them was greatest in the anterior Bolton ratio of IOS and CephX images. The systematic bias demonstrated no significant difference (p value > 0.05) between CephX and MIMICS, but CephX versus IOS and MIMICS versus IOS demonstrated significant differences (p value < 0.05) in several measurements, such as Bolton ratios and arch length. Agreement using ICC revealed good to excellent reliability overall, but moderate agreement in overall Bolton between MIMICS-IOS and between CephX-IOS, anterior Bolton and interpremolar distance between CephX-MIMICS, and poor agreement in anterior Bolton between MIMICS-IOS and between CephX-IOS was found. Bland-Altman plots showed that CephX and MIMICS were consistent, implying minimal systematic bias. Digital and AI-driven tooth segmentation (MIMICS and CephX), and IOS methods generally provide consistent and reliable measurements in terms of the Bolton ratio and arch dimensions. However, caution is advised when interpreting certain Bolton ratio values because discrepancies and lower agreement may occur.

Aim Traditionally, the widest mesio-distal tooth dimensions are used to analyze space requirements in treatment planning. However, in reality, it is the arch form dependent interproximal contact locations that determine the space required for tooth alignment. The aim of this study was to evaluate the influence of expansion and constriction of dental arch width on the space required for alignment of upper and lower incisors. Materials and methods Fifty digital dental arch model pairs were segmented and aligned using OnyxCeph 3D™ software (Image Instruments, Germany). 3D coordinates of actual interproximal contact points were extracted from the digital setups. The mesio-distal space requirement for each tooth was determined by measuring the linear distance between its interproximal contact points projected on the occlusal plane. The dental arch was then expanded and narrowed in 2-mm increments at its distal ends, and the space requirement for each incisor was determined again after each increment. Results Statistical analysis using linear models revealed a small increase in space required for incisor alignment with increasing arch width (p < 0.05). An average increase in space requirement of 0.03 mm and 0.04 mm was observed per 1-mm expansion of the maxillary and mandibular arches, respectively. The corresponding values ​​for constriction were 0.05 mm per 1-mm arch width change for both jaws. Conclusion The influence of dental arch form on the mesio-distal space required for incisor alignment is negligible. Hence, this factor may be ignored in the decision to apply dental arch expansion or premolar extraction in patients with anterior crowding.

Objectives This study aimed to investigate the dynamic changes in dental arch size and shape in children with normal occlusion and to evaluate and visualize the effects of early orthodontic treatment. Methods A total of 274 normal occlusion subjects (4 to 12 years, mean age 7.38 years) were selected from a pool of 2,695 school-age children in Chengdu. These subjects were divided into 5 age groups according to Hellman’s dental ages. The complete dental arch forms were described using polynomial fitting curves. To observe changes in arch size, the average arch width, depth, and perimeter were measured for each group. To analyze changes in arch shape, the arch forms were normalized using the max-min normalization and then divided into 6 clusters (grouping of shapes) using the k-means algorithm. The proportions of these clusters across different age groups were then determined. Results The periods of rapid occlusal development occur between the ages of 4 to 8 years and 11 to 12 years, during which the arch width, depth, and perimeter increase rapidly. As children grow, the complete dental arch shape becomes more elongate. To assess and visualize early orthodontic treatment effects, typical normal arch shapes can be scaled to fit the size of individual cases. Conclusion The size and shape of arch form change dynamically from late primary dentition to early permanent dentition. Notably, the arch depth tends to increase more than the arch width. Clinical relevance A well-conducted early orthodontic treatment may bring the arch form closer to the typical normal one.