Research Spotlight

Swidi, A. J., A. E. Griffin and P. H. Buschang (2019). “Mandibular alignment changes after full-fixed orthodontic treatment: a systematic review and meta-analysis.” Eur J Orthod 41(6): 609-621.

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BACKGROUND: Although post-treatment mandibular alignment has been extensively investigated, the findings remain controversial. OBJECTIVES: The objective was to assess mandibular alignment changes, as measured by the irregularity index, of patients who underwent full-fixed orthodontic treatment and were followed up at least 1 year after retention. SEARCH METHODS: MEDLINE, EMBASE, and Cochrane library, in addition, the reference lists of included studies, were screened. The search was conducted up to April 2018. SELECTION CRITERIA: The study designs included both interventional and observational studies of orthodontic patients who received either extraction or non-extraction treatment. DATA COLLECTION AND ANALYSIS: The interventional studies were assessed using the Cochrane Collaboration’s risk of bias assessment tool. The quality of the observational studies was evaluated using National Institution of Health quality assessment tools. The first two authors independently applied the eligibility criteria, extracted the data, and assessed the risk of bias. Any conflicts were resolved with consensus discussion with the third author. RESULTS: The search retrieved 11 326 articles, 170 of which were assessed for eligibility. There were 44 studies included in the qualitative assessments and 30 in the meta-analyses. The studies included 1 randomized control trial (RCT) and 43 observational studies. The RCT was judged to have a high risk of bias and all of the observational studies had either fair or poor quality. The meta-analysis was based on studies judged to be of fair quality, including a total of 1859 patients. All meta-analyses were performed using random-effect models. The standardized mean difference between post-treatment and post-retention irregularity was 1.22 (95% CI, 1.04-1.40) and 0.85 (95% CI, 0.63-1.07) after extraction and non-extraction treatments, respectively. There was a substantial heterogeneity for the extraction (I2 = 75.2%) and non-extraction (I2 = 70.1%) studies. The follow-up duration (1-10 versus 10-20 years) explained 33% of the heterogeneity, with longer follow-up studies showing more irregularity. LIMITATIONS: The quality of evidence provided by the studies was low. There was a risk of publication bias, and the search was limited to English language. CONCLUSIONS AND IMPLICATIONS: Post-treatment mandibular irregularity increases are limited. Irregularity increases are slightly greater in patients treated with mandibular premolars extractions, and in patients followed up over longer periods of time. REGISTRATION: The study protocol was not registered.

Song, A., W. Dai, M. J. Jang, L. Medrano, Z. Li, H. Zhao, M. Shao, J. Tan, A. Li, T. Ning, M. M. Miller, B. Armstrong, J. M. Huss, Y. Zhu, Y. Liu, V. Gradinaru, X. Wu, L. Jiang, P. E. Scherer and Q. A. Wang (2019). “Low- and high-thermogenic brown adipocyte subpopulations coexist in murine adipose tissue.” J Clin Invest Nov 25. pii: 129167. [Epub ahead of print].

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Brown adipose tissue (BAT), as the main site of adaptive thermogenesis, exerts beneficial metabolic effects on obesity and insulin resistance. BAT has been previously assumed to contain a homogeneous population of brown adipocytes. Utilizing multiple mouse models capable of genetically labeling different cellular populations, as well as single-cell RNA sequencing and 3D tissue profiling, we discovered a new brown adipocyte subpopulation with low thermogenic activity coexisting with the classical high-thermogenic brown adipocytes within the BAT. Compared with the high-thermogenic brown adipocytes, these low-thermogenic brown adipocytes had substantially lower Ucp1 and Adipoq expression, larger lipid droplets, and lower mitochondrial content. Functional analyses showed that, unlike the high-thermogenic brown adipocytes, the low-thermogenic brown adipocytes have markedly lower basal mitochondrial respiration, and they are specialized in fatty acid uptake. Upon changes in environmental temperature, the 2 brown adipocyte subpopulations underwent dynamic interconversions. Cold exposure converted low-thermogenic brown adipocytes into high-thermogenic cells. A thermoneutral environment had the opposite effect. The recruitment of high-thermogenic brown adipocytes by cold stimulation is not affected by high fat diet feeding, but it does substantially decline with age. Our results revealed a high degree of functional heterogeneity of brown adipocytes.

Ribeiro, G. L. U., H. B. Jacob, M. Brunetto, J. da Silva Pereira, O. Motohiro Tanaka and P. H. Buschang (2019). “A preliminary 3-D comparison of rapid and slow maxillary expansion in children: A randomized clinical trial.” Int J Paediatr Dent Nov 22. [Epub ahead of print].

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BACKGROUND: This study compared the effects of rapid maxillary expansion (RME) and slow maxillary expansion (SME) using cone-beam computed tomography (CBCT). AIM: To evaluate the skeletal and dentoalveolar effects differences produced by two different maxillary expansion protocols. DESIGN: Eligibility criteria included maxillary transverse deficiencies in children (mean age, 8.18 years old), randomly assigned to either: RME and SME. At the outcome analysis phase a sample of 29 subjects has been analyzed (RME group, N=16 and SME group, N=13). CBCT scans taken before expansion and six months later were evaluated. Five posterior and 6 anterior transverse measurements were made at different vertical levels. Treatment changes were analyzed using paired t-tests; independent t-tests were used to compare the two groups. RESULTS: There were statistically significant (p<.05) increases in maxillary width at the skeletal, alveolar and dental levels for both groups, with significantly smaller increases at the more superior than inferior levels. The RME group exhibited statistically larger width increases than the SME group for all measures except interorbital width, anterior alveolar process width, and intercanine width. The group differences were greater for anterior than posterior apical base widths. CONCLUSIONS: Rapid maxillary expansion produced greater orthopedic effects than slow maxillary expansion, with the greatest effects occurring in the anterior apical base.

Revilla-Leon, M., R. Fogarty, J. J. Barrington, A. Zandinejad and M. Ozcan (2019). “Influence of scan body design and digital implant analogs on implant replica position in additively manufactured casts.” J Prosthet Dent Nov 28. pii: S0022-3913(19)30487-1. [Epub ahead of print].

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STATEMENT OF PROBLEM: Additive manufacturing (AM) technologies can be used to fabricate definitive casts for implant-supported restorations. However, information regarding the accuracy of the implant replica position on the polymeric AM cast generated with different scan bodies and digital implant replica systems is lacking. PURPOSE: The purpose of this in vitro study was to compare with a conventional stone cast the linear and angular discrepancies of the implant analog positions in a polymeric AM cast obtained from 3 different scan body and digital implant replica systems. MATERIAL AND METHODS: A partially edentulous maxillary typodont with 3 implant replicas (Implant replica RP Branemark system; Nobel Biocare) was prepared. Two duplicating methods were evaluated: conventional (CNV group) and AM (AM group) procedures. For the CNV group, polyvinyl siloxane open-tray implant impressions (CNV) were made at room temperature (23 degrees C). The AM group was further divided into the subgroups Elos Medtech, Nt-Trading, and Dynamic Abutment. For the Elos Medtech subgroup, the corresponding scan bodies were placed on each implant, and the typodont was digitized by using a laboratory scanner (E3 scanner; 3Shape). The same procedure was repeated with the remaining subgroups. All the AM polymer casts were fabricated at once by using the same 3D printer (Eden 500V; Stratasys). Ten specimens of each group were obtained (n=10). A coordinate-measuring machine (CMM) was used to measure the position of each implant replica, and distortion was calculated for each system at the x-, y-, and z-axes and 3D distortion measurement (3D=x(2)+y(2)+z(2)). The Shapiro-Wilk test revealed that the data were not normally distributed. The Kruskal-Wallis and pairwise Mann-Whitney U tests (alpha=.05) were used for the analysis. RESULTS: The CNV group presented significantly higher linear discrepancy than the Dynamic Abutment group on the x- and y-axes. On the z-axis, however, the CNV group showed significantly lower linear discrepancy than the Nt-Trading and Dynamic Abutment groups. The 3D linear discrepancy was 12 +/-12 mum for the CNV group, 4 +/-100 mum for the Elos Medtech group, 8 +/-52 mum for the Nt-Trading group, and 5 +/-19 mum for the Dynamic Abutment. The CNV group demonstrated a significantly higher angle than the Nt-Trading group but a significantly smaller angle than the Elos Medtech and Dynamic Abutment groups. CONCLUSIONS: The AM groups had lower 3D discrepancies than the CNV group. The Dynamic Abutment group had significantly better accuracy for the mesiodistal and buccolingual implant replica positions than the CNV group, but the conventional procedures had significantly better results for the apicocoronal implant replica position. Scan body and digital implant replica design systems only influenced the accuracy of the angular implant replica position on the AM casts.

Reddy, L. V., R. Bhattacharjee, E. Misch, M. Sokoya and Y. Ducic (2019). “Dental Injuries and Management.” Facial Plast Surg 35(6): 607-613.

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Traumatic dental injuries affect 1 to 3% of the population, and disproportionately affect children and adolescents. The management of these injuries incorporates the age of patients, as children between 6 and 13 years of age have a mixed dentition. This helps to preserve the vitality of teeth that may be salvaged after a traumatic event. The clinical examination of these cases involves a thorough examination of the maxilla and mandible for associated fractures and any lodged debris and dislodged teeth or tooth fragments. The objective is to rule out any accidental aspiration or displacement into the nose, sinuses, or soft tissue. After ruling out any complications, the focus is on determining the type of injury to the tooth or teeth involved. These include clinical examination for any color change in the teeth, mobility testing, and testing for pulp vitality. Radiographic evaluation using periapical, occlusal, panoramic radiographs, and cone beam computed tomography is performed to view the effect of trauma on the tooth, root, periodontal ligament, and adjoining bone. The most commonly used classification system for dental trauma is Andreasen’s classification and is applied to both deciduous and permanent teeth. Managing dental trauma is based on the type of injury, such as hard tissue and pulp injuries, injuries to periodontal tissue, injuries of the supporting bone, and injuries of the gingiva and oral mucosa. Hard-tissue injuries without the involvement of the pulp typically require restoration only. Any pulp involvement may require endodontic treatment. Fractures involving the alveolar bone or luxation of the tooth require stabilization which is typically achieved with flexible splints. The most common procedures employed in managing dental injuries include root canal/endodontics, surgical tooth repositioning, and flexible splinting. Recognition and treatment of these injuries are necessary to facilitate proper healing and salvage of a patient’s natural dentition, reducing future complications to patients.