A modification to the incisor classification of malocclusion

Evaluation of the bioelectrical activity of the masticatory muscles in patients with narrowed maxillary transverse dimension compared to the occlusal norm

OBJECTIVE

The aim of the study was to determine how the electrical activity of the temporalis, masseter and sternocleidomastoid muscles differs in children with reduced transverse jaw dimension compared to children with normal occlusion.

DESIGN

It was a experimental study. Thirty-seven patients were included in the study. 18 in the study group received orthodontic treatment with removable appliances and 19 subjects were classified as normal occlusion subjects in the control group. A panoramic X-ray and digital intraoral scan were taken, followed by an surface electromyography of three muscle pairs (temporalis muscles, masseter muscles, sternocleidomastoid muscles) in resting position, while clenching and clenching on cotton rollers.

RESULTS

There was significantly greater activity in the experimental group than in the control group comparing muscles: temporalis muscles and masseter muscles in the resting position. Additionally, significantly greater activity of muscles in the control group was found during clenching. However, the asymmetry index of muscles indicates that there is significantly greater asymmetry of muscles activity in the experimental group. Compared to children with normal occlusion, children with a narrowed transverse dimension of the jaw have statistically significant differences in the bioelectrical activity of the temporalis, masseter and sternocleidomastoid muscles, as well as greater asymmetry in the bioelectrical voltage of the masseter muscles.

CONCLUSIONS

Patients with reduced transverse dimension of the jaw are characterized by increased resting activity of the masticatory muscles and reduced functional activity of the masticatory muscles. These patients have increased asymmetry in the bioelectrical tension of the masticatory muscles.

Mini-implant assisted orthodontic correction of lip and occlusal cant of a young adult: A case report

Patients seek orthodontic treatment to correct unesthetic and asymmetric smiles because even a minimal cant of 4 is well perceived by a layperson. This case report describes a nonsurgical orthodontic management of iatrogenic occlusal canting in a 22-year-old female, who developed it during a previous orthodontic treatment for an impacted canine. The iatrogenic cant was corrected by the intrusion of the left mandibular segment followed by extrusion of left maxillary segment using mini-implants. Mini-implants were inserted in the mandibular left buccal segment (the first between canine and premolar, the second between the second premolar and first permanent molar), and the intruded mandibular posteriors were stabilized with the help of stainless-steel ligature (0.012″ SS) tied to the mini-implant. The expected correction of the occlusal cant, asymmetric gingival and tooth exposure, and soft tissue lip cant were corrected resulting in a significant improvement in smile aesthetics at the end of orthodontic treatment. After a follow-up period of 24months, the results were stable.

Myopia & painful muscle form of temporomandibular disorders: connections between vision, masticatory and cervical muscles activity and sensitivity and sleep quality

The main aim of this study is to evaluate the effects of painful muscle form of temporomandibular disorders and myopia on the connections between the visual organ, the bioelectrical activity and sensitivity of the masticatory and cervical muscles, and sleep quality. Subjects were divided into 4 groups (Myopia & TMDs, Myopia (Without TMDs), Emmetropic & TMDs and Emmetropic (Without TMDs)). The study was conducted in the following order of assessment: examination for temporomandibular disorders, assessment of the muscle activity by electromyograph, pressure pain thresholds examination, ophthalmic examination and completion of the Pittsburgh Sleep Quality Index. It was observed that the Myopia & TMDs group had higher muscle tenderness, higher resting and lower functional muscle bioelectrical activity. The visual organ is clinical related to the masticatory and cervical muscles. TMDs and myopia alter masticatory and cervical muscle activity. The thickness of the choroid in people with myopia is related to muscle tenderness. TMDs and myopia impair sleep quality. It is recommended to determine the number of people with refractive error and its magnitude in the sEMG study in order to be able to replicate the research methodology.

Evaluation of Change in the Facial Profile and Aesthetics in Relation to Incisor Position in Both Maxillary and Mandibular Arches

Background The orthodontist is often confronted with the need to predict soft tissue profile changes that may result from the orthodontic treatment. The problem arises because the contribution of many of the factors influencing the soft tissue profile still needs to be fully understood. The complexity of the problem is increased in growing patients in whom the post-treatment soft tissue profile is the result of both growth and orthodontic treatment. A primary motivation for seeking orthodontic treatment is a desire to improve dental and facial aesthetics. To achieve balance in the facial profile treated orthodontically, it is essential to identify the underlying skeletal hard tissue and soft tissue parameters. The present study evaluated the changes in facial profile and aesthetics in relation to incisor position. Materials and methods Samples for this study consisted of pre-treatment lateral cephalograms of the Indian population (n = 450) having different incisor relationships. Subjects aged between 18 and 30 years were included. Angular and linear measurements were taken to analyse the incisor relationship with soft tissue parameters. Results The majority (61.2%) of subjects belonged to the age group of 18-30 years. The overall female-to-male ratio in the study was 7:3. The parameter U1 to L1 was abnormal in 86.8% of subjects. Similarly, the parameters S-line upper lip (UL), S-line lower lip (LL), E-line UL, and E-line LL were found abnormal in 93.9%, 86.8%, 82.6%, and 70.1% of subjects, respectively. A significant agreement was found between U1 to L1 and E-line UL and U1 to L1 and E-line LL. Conclusions The present study concludes that facial aesthetics combines soft and hard tissue corrections, not just based on occlusal relationships but also considering facial harmony. Thus, the incisor relationship is an important asset and strongly correlates with other soft tissue and hard tissue parameters that improve facial aesthetics for the individual undergoing orthodontic treatment.

Dental and skeletal changes associated with long-term oral appliance use for obstructive sleep apnea: A systematic review and meta-analysis

An oral appliance (OA) is an effective treatment option for patients with obstructive sleep apnea (OSA), but dental and skeletal changes have been detected by many studies after long-term OA use. Better understanding of the long-term side effects may decrease discontinuation of OA use and assist clinicians to make informed decisions. Accordingly, a systematic review and meta-analysis were performed to evaluate the dental and skeletal changes associated with OAs designed to advance the mandible. The quality of the studies was determined by using the risk of bias assessment tool for non-randomized studies (RoBANS), and 12 studies were included in the meta-analysis. OA use was associated with a significant decrease of overjet (OJ) and overbite (OB), and it was suggested that both parameters decreased along with the duration of treatment. Meta-analysis also demonstrated a significant increase of L1-MP. However, there were no significant changes of skeletal modifications or mandibular rotation. Changes of incisor inclination were suggested to make a contribution to reduction of OJ and OB. In conclusion, long-term OA use was associated with dental changes. The results of this study provide information for clinicians about the long-term effects of OAs.

New prediction equations for the estimation of maxillary mandibular canine and premolar widths from mandibular incisors and mandibular first permanent molar widths: A digital model study

OBJECTIVE

The primary aim of the study was to generate new prediction equations for the estimation of maxillary and mandibular canine and premolar widths based on mandibular incisors and first permanent molar widths.

METHODS

A total of 2,340 calculations (768 based on the sum of mandibular incisor and first permanent molar widths, and 1,572 based on the maxillary and mandibular canine and premolar widths) were performed, and a digital stereomicroscope was used to derive the the digital models and measurements. Mesiodistal widths of maxillary and mandibular teeth were measured via scanned digital models.

RESULTS

There was a strong positive correlation between the estimation of maxillary (r = 0.85994, r(2) = 0.7395) and mandibular (r = 0.8708, r(2) = 0.7582) canine and premolar widths. The intraclass correlation coefficients were statistically significant, and the coefficients were in the strong correlation range, with an average of 0.9. Linear regression analysis was used to establish prediction equations. Prediction equations were developed to estimate maxillary arches based on Y = 15.746 + 0.602 × sum of mandibular incisors and mandibular first permanent molar widths (sum of mandibular incisors [SMI] + molars), Y = 18.224 + 0.540 × (SMI + molars), and Y = 16.186 + 0.586 × (SMI + molars) for both genders, and to estimate mandibular arches the parameters used were Y = 16.391 + 0.564 × (SMI + molars), Y = 14.444 + 0.609 × (SMI + molars), and Y = 19.915 + 0.481 × (SMI + molars).

CONCLUSIONS

These formulas will be helpful for orthodontic diagnosis and clinical treatment planning during the mixed dentition stage.

Maxillary and mandibular anterior crown width/height ratio and its relation to various arch perimeters, arch length, and arch width groups

OBJECTIVE

To investigate the maxillary and mandibular anterior crown width/height ratio and its relation to various arch perimeters, arch length, and arch width (intercanine, interpremolar, and intermolar) groups.

MATERIALS AND METHODS

The calculated sample size was 128 subjects. The crown width/height, arch length, arch perimeter, and arch width of the maxilla and mandible were obtained via digital calliper (Mitutoyo, Japan). A total of 4325 variables were measured. The sex differences in the crown width and height were evaluated. Analysis of variance was applied to evaluate the differences between arch length, arch perimeter, and arch width groups.

RESULTS

Males had significantly larger mean values for crown width and height than females (P ≤ 0.05) for maxillary and mandibular arches, both. There were no significant differences observed for the crown width/height ratio in various arch length, arch perimeter, and arch width (intercanine, interpremolar, and intermolar) groups (P ≤ 0.05) in maxilla and mandible, both.

CONCLUSIONS

Our results indicate sexual disparities in the crown width and height. Crown width and height has no significant relation to various arch length, arch perimeter, and arch width groups of maxilla and mandible. Thus, it may be helpful for orthodontic and prosthodontic case investigations and comprehensive management.

Reliability of three methods of occlusion classification

Four orthodontic faculty at one dental school classified 25 dental casts according to the classification systems of Angle, Katz, and the British Incisor Classification. The dental casts were selected from a pool of 350 pretreatment graduate orthodontic cases and were those deemed the most atypical. The results demonstrated that Katz's classification was more reliable than both Angle and the British. Angle's classification was the least reliable of the three methods.

Consultant opinion on orthodontic treatment plans used by dental practitioners: a pilot study

Prior to 1987, dental practitioners in England and Wales intending to carry out all but the simplest orthodontic treatment within the National Health Service, were required to submit pretreatment study models, details of the orthodontic assessment and the proposed treatment plan to the Dental Estimates Board prior to starting treatment. Models taken at the end of treatment were required by the Board to enable payment to be made. In this pilot study, the acceptability of orthodontic treatment plans used by practitioners working in the General Dental Services was assessed by eight hospital consultants, using information about 40 cases submitted to the Dental Estimates Board in 1987/88. All consultants considered a high proportion of plans to be unacceptable, but agreement between the consultants was variable and some agreed with one another on very few plans. A single scorer used the weighted PAR (Peer Assessment Rating) index to assess the degree of departure from normal occlusion of both pre- and post-treatment models. Using accepted standards, only nine cases were greatly improved (PAR reduction > 70%) and the mean percentage reduction in PAR score was low. Consultant opinion on the appropriateness of treatment planning was not related to the outcome of orthodontic treatment.