Mandibular Incisors Research Articles

Options for Access Cavity Designs of Mandibular Incisors: Mechanical Aspects from Finite Element Study

IntroductionThis study investigated different access cavity designs of mandibular anteriors in terms of their effect on the biomechanical behavior and longevity using finite element analysis (FEA). MethodsA 3-dimensional model of a mandibular incisor was created for FEA. After validating the intact tooth (IT) model, 4 experimental models were developed (traditional lingual access cavity [TLA], facial access cavity [FAC], incisal access cavity [ICA], and cervical access cavity [CVA]). Cyclic loading was simulated, and the number of cycles until failure (NCF) was compared to the IT model. Stress distribution patterns, maximum von Mises stresses (vMSs), and maximum principal stresses (MPSs) were analyzed mathematically. The safety factor was also calculated and demonstrated. ResultsThe maximum vMS registered on the IT model was 134.16 MPa. The FCA and the CVA provided the highest NCF (193.7% compared with the IT model) followed by ICA (58.2%) and TLA (21.4%). The vM and MPS analysis revealed that the lingual surface is a primary stress channel, and the presence of an access cavity significantly weakens the tooth structure. Although the maximum vMS registered for the IT model was 134.16 MPa, the maximum vMS was 73.97 MPa for both the FCA and the CVA, 152.27 MPa for the ICA, and 173.63 MPa for the TLA. ConclusionsThe facial and cervical access cavity designs provided considerable reinforcement to the endodontically treated mandibular incisors. With advancements in esthetic restorative materials and endodontic instruments, facial access design could emerge as the new standard for access cavity preparation in mandibular incisors.

Use of chin sling for conservative treatment of mandibular fracture in a guinea pig (Cavia porcellus).

To describe a treatment for a mandibular fracture in a guinea pig (Cavia porcellus). A 6-month-old sexually intact male guinea pig referred for a 24-hour history of hyporexia. Physical examination showed lateral displacement of the incisors and inflammation and crepitation during mandible lateralization. Imaging tests revealed a minimally displaced complete oblique fracture of the left mandible with fracture of the left mandibular first premolar tooth and incisor tooth. Conservative treatment was established by placing a chin sling (CS) to immobilize the jaw and a nasogastric tube for nutritional support. Imaging tests repeated 3 weeks later showed initial callus formation, and the conservative treatment was discontinued. Follow-up examinations showed appetite and progressive weight gain. Five months later, the clinical crown of the left mandibular incisor was absent and a resorptive lesion on the left mandibular first premolar tooth was detected. Complete ossification of the fracture without premolar and moler teeth elongation was observed on control imaging tests. Ten months after initial examination, the patient was reportedly healthy with no signs of pain or dental disease. Jaw fracture treatments in guinea pigs are poorly described in the literature. Surgical treatment can be challenging in this species due to its skull and dental anatomy. Although CS was originally employed to increase the congruency of premolar and molar teeth after coronal reduction, this device yielded satisfactory results as a noninvasive, inexpensive treatment of a mandibular fracture in this guinea pig. Alopecia on the back of the head was the only undesired adverse effect associated with the CS.

Effect of Endo-Z bur or Bladesonic ultrasonic tip on the adaptation of filling material. A micro-CT study.

This study aimed to evaluate the effect of apicoectomy performed with a bur or an ultrasonic tip on the adaptation of the filling material to root canal dentin. Twenty human mandibular incisors were selected and prepared with a ProDesign Logic system up to diameter 40/.05. The root canals were filled with Bio-C Sealer (Angelus, PR, Brazil) using the single cone technique and were stored at 37ºC and 95% relative humidity for 7 days. After this period, the apicoectomy of the 3 millimeters of the root apex was performed using Endo-Z bur (Dentsply Sirona) or Bladesonic ultrasonic tip (Helse Ultrasonic, Santa Rosa de Viterbo, Brazil) (n=10). The specimens were scanned by micro-computed tomography (micro-CT; SkyScan 1176) with a voxel size of 8.74 µm after obturation and after apicoectomy. The percentage of voids at the interface between the filling material and the root canal wall was evaluated in the apical 4 mm of the root after apicoectomy, besides the time cutting to both devices. The data obtained were submitted to paired and unpaired t-tests (α = 0.05). Endo-Z and Bladesonic increased the percentage of voids between the filling material and the dentin after apicectomy (p<0.05), and they were similar (p>0.05). Endo-Z has a shorter time to perform apicoectomy compared to Bladesonic (p<0.05). Apicectomies with Endo-Z or Bladesonic could harm the material/dentin interface, while the Endo-Z bur was faster than the Bladesonic ultrasonic tip.

Pseudo transposition of the mandibular lateral incisor to the first premolar space: A literature review and case series.

Tooth transposition is the positional interchange of two adjacent teeth, which may be incomplete or complete. The root apex may remain in a normal position despite a severely displaced crown. The aim of this paper is to provide a literature review on the incidence, aetiology and treatment options for pseudo-transposed mandibular incisors. A case series is also presented highlighting the various management techniques that have been utilised in treating five cases of pseudo-transposed mandibular lateral incisors.

Effectiveness of tubular coaxial nickel-titanium and copper nickel-titanium orthodontic aligning archwires: A randomized clinical trial

This study aimed to compare tubular coaxial-NiTi and copper-NiTi orthodontic aligning archwires in terms of teeth alignment, patients' pain perception, and root resorption. Orthodontic patients aged 12 years or older, having Little's irregularity index (LII) of 5-9mm were randomly allocated to either the copper-NiTi group or tubular coaxial-NiTi group with a 1:1 allocation ratio. The archwire sequence was 0.014-inch followed by 0.018-inch for the copper-NiTi group and 0.016-inch followed by 0.018-inch for the tubular coaxial-NiTi group. Each archwire was left in place for eight weeks before progressing to the next size. Good quality impression for the lower arch before treatment (T0) and thereafter every 4 weeks up to 16 weeks was taken to measure LII. Evaluation of pain perception was performed using a visual analog scale (VAS) during the first week following each archwire insertion. Assessment of root resorption was undertaken at T0 and after 16 weeks by taking periapical radiographs for mandibular central incisors using the long cone paralleling technique. A total of 33 patients were randomized and selected for participation. Of those, 31 patients with a mean age of 15.45±2.22 who completed the trial were included in the analyses (15 patients in the copper-NiTi group and 16 patients in the tubular coaxial-NiTi group). In both groups, the irregularity index significantly decreased after 16 weeks of treatment with an overall reduction of 5.22mm for the copper-NiTi group and 6.03mm for the tubular coaxial-NiTi group. However, the difference between the two groups was not statistically significant. Likewise, pain perception and root resorption were not significantly different between the two study groups. Both copper-NiTi and tubular coaxial-NiTi archwires were equally effective in terms of teeth alignment, patients' pain perception, and root resorption. Consideration could be given to the cost and clinician preference when selecting an initial archwire. the trial was registered in ClinicalTrials.gov on 26/05/2022 with a registration ID: NCT05391542, https://clinicaltrials.gov/ct2/show/NCT05391542.

Evaluation of Second Canals in Mandibular Incisors using Magnification: A Cross-Sectional Study

Background: It is essential to have a thorough understanding of the typical anatomy of the root canal system, as well as the various common and uncommon anatomical variations, in order to achieve successful treatment outcomes.Objective: To determine the frequency and pattern of two canals in mandibular incisors using magnifying loupe Material and Methods: This study at Saidu College of Dentistry in Swat included 385 participants selected consecutively. Inclusion criteria were males and females aged 20-60 years with mandibular incisor-related dental conditions. Exclusion criteria were local anesthesia allergies, internal root resorption, calcified canals, and pregnancy. The number of canals was recorded radiographically using the SLOBE technique. Canals were classified using Vertucci's system. Canal frequencies were analyzed by gender and tooth types using chi-square tests (p&lt;0.05).Results: The mean age was 33.97±11.10 years. Of the participants, 215 (55.84%) were males. The highest numbers of tooth types were found among the left lateral incisors (n=148, 38.44%) and left central incisors (n=122, 31.69%). Second canal was found 139 participants (36.10%). Among these, Type I (n=84, 21.82%) was the most common two-canal pattern, followed by Type III (n=36, 9.35%). When analyzing the canal types within the single canal group, Type I was the most prevalent in both males (23.26%) and females (20.00%). The frequencies of Types II, III, and IV were similar between genders and did not exhibit significant differences (p=0.865). The distribution of canal types varied across tooth types, with Type I being the most common, but not statistically significant (p=0.652).Conclusion: The presence of a second canal in the mandibular incisors is quite common. The most common pattern of two canals, according to the Vertucci classification, was Type I, followed by Type III.Keywords: Magnification, Mandibular incisors, Second canals, Vertucci classification

Comparative evaluation of three materials used for fragment reattachment in uncomplicated crown fracture-An in vitro study using bovine teeth.

The recommended treatment for uncomplicated crown fractures is bonding the fractured fragment or the fragment reattachment. A paucity was identified regarding the studies comparing the efficacy of micro-hybrid and nanohybrid composites in fragment reattachment. Hence, the present study aimed to evaluate and compare three materials for bonding of fragments rehydrated by humidification in teeth with uncomplicated crown fractures. Eighty mandibular bovine incisors with similar dimensions and free of any structural deformities were fractured similar to the technique followed in previous studies. Fracture was simulated, fragments, and stumps were coded, stumps were stored in artificial saliva and the fragments were dehydrated at room temperature and pressure. They were randomly assigned to Group-1 (no rehydration), Group-2 (rehydrated and bonded by flowable nanohybrid composite-3M Filtek Supreme Syringe Flowable Composite Resin-A2, Sao Paulo, Brazil), Group-3 (rehydrated and bonded by flowable micro-hybrid composite- Ruby Flow, InciDental, England, United Kingdom), and Group-4 (rehydrated and bonded by light-cured Glass-Ionomer-Cement-Voco Ionoseal, Cuxhaven, Germany). The samples were subjected to a universal testing machine to evaluate the force required to fracture the bonded fragments. The highest median value of the force required to fracture was recorded for Group 2 (208.4 N) followed by Group 3 (195.2). The force required to fracture the bonded fragments was lowest in Group 4 (67.2 N) which was lower than the negative control (131.4 N). The differences between the observations in Groups 2 and 3 were not found to be statistically significant. The nano and micro-hybrid composites showed greater force required to fracture than fragments bonded by LC-GIC. Dehydrated fragments bonded using nanocomposites performed better than rehydrated fragments bonded by using LC-GIC.

Efficacy of Different Irrigant Activation Systems on Debris and Smear Layer Removal: A Scanning Electron Microscopy Evaluation.

Irrigation is an essential component of root canal treatment to enable cleaning beyond the reach of mechanical instruments. The study aimed to assess and compare the efficacy of different final irrigation protocols, including sonic- and ultrasonic-powered irrigant-activation systems, on debris and smear layer removal in the coronal, middle, and apical thirds of straight oval root canals. Straight oval root canals of 60 human mandibular incisors were prepared to size 40.04 and divided into four groups (n = 15) according to the final irrigation protocols: (a) Eddy sonic activation (b) endosonic passive ultrasonic irrigation (PUI), (c) irrisafe PUI, and (d) manual syringe and needle irrigation with no additional activation, which served as control. After the treatment procedures, the roots were split and observed using scanning electron microscopy. The presence of remaining debris and smear layer at the coronal, mid-root, and apical thirds of the canals were evaluated using a score system and statistically analyzed using multinominal models with significance level set at p < 0.05. None of the final irrigation protocols completely removed all debris and smear layer from all root canals. When the syringe and needle were used without activation, more debris and smear layer were found in the apical third of the canals. Activation of the final irrigant with each of the three devices significantly reduced the presence of debris in the apical third, compared to the syringe and needle final irrigation, with no difference among the three activation devices. Eddy and irrisafe activation also significantly reduced the residual smear layer in the apical third, compared to syringe and needle alone, while the reduction in the remaining smear layer by endosonic activation did not reach the significance level. Removal of debris and smear layer from the apical part of the root canal by syringe and needle irrigation alone may be significantly improved by using sonic or ultrasonic activation of the final irrigant. Endosonic activation was less effective in removal of smear layer from the apical part of the canals compared to the other two activation systems.

Real-World Evidence on the Prevalence of Molar Incisor Hypomineralization in School Children from Bucharest, Romania.

Molar incisor hypomineralization (MIH) is an understudied and underrecognized clinical entity occurring in children. We performed a cross-sectional study to determine the real-world prevalence of MIH among school children undergoing routine dental checkups at one primary and middle school in Bucharest, Romania. Our study cohort consisted of 266 children with evaluable data, of which 143 (53.8%) were males, with a median age of 10 years old (interquartile range: 8-11 years). In this study cohort, we have identified a prevalence of 14.3% (n = 38 cases) of MIH. Among patients diagnosed with MIH, hypomineralizations were present in 47.4% of children on the maxillary first molar, 92.1% on the mandibular first molar, 94.7% on the maxillary incisor, 36.8% on the mandibular incisor, and 5.3% on the deciduous second molar. We identified the maxillary incisor and the mandibular first molar as the most important examined sites significantly associated with the presence of MIH (p < 0.0001 each), highlighting the importance of paying focused attention to these sites during routine dental care in children. In order to establish the diagnosis of MIH, findings of hypomineralization should be present on at least one permanent first molar, according to the case definition currently in use; this definition does not include findings on the incisors. Thus, our finding that hypomineralization of the maxillary incisors is significantly associated with MIH is particularly important. While incisor hypomineralization is not diagnostic of MIH, based on our results, we conclude that it should raise the suspicion of MIH and lead to an attentive examination of the permanent molars in order to establish timely diagnosis.

Deep bite -An insight

Deep bite is one of the most common malocclusion which affects children and even adults leading to a number of oral health problems. Patients with deep bite encounter periodontal and temporomandibular problems. Deep overbite refers to the increase of overlap of maxillary incisors over mandibular incisors beyond normal coverage of 30-40%. There are many factors which lead to the development of deep bite like inherent and acquired factors. Inherent factors like tooth morphology, skeletal patterns, rotation of condyle affects the bite. Acquired factors like muscle habits, loss of posterior tooth support or lateral tongue thrust may affect the bite. Deep bite can be corrected by number of different methods which include intrusion of anterior teeth, extrusion of posterior teeth or a combination of both. In non-growing patients surgical treatment is a suitable option to achieve stable results.This article describes various appliances and their biomechanics involved for correcting deepbite malocclusion

Anchorage Augmentation Technique in Cases of Procumbent Mandibular Incisors Employing Temporary Anchorage Devices with Class II Correctors

Anchorage Augmentation Technique in Cases of Procumbent Mandibular Incisors Employing Temporary Anchorage Devices with Class II Correctors

Micro-osteoperforations facilitated alignment of mandibular incisors: A case series

Micro-osteoperforations facilitated alignment of mandibular incisors: A case series

Comparison of the dentin tubule penetration of AH Plus, WellRoot ST, and MTA BioSeal after obturation, retreatment, and re-shaping of the root canals.

It was aimed to compare the dentine tubule penetration of AH Plus, MTA Bioseal, and WellRoot ST after filling, retreating, and reshaping the root canals by using a novel microscopic method. Seventy-five mandibular incisors with single root canals were shaped with Protaper Next system (PTN; X2-25/0.06) The teeth were obturated with AH Plus labeled with Rhodamin B and MTA Bioseal or WellRoot ST sealer which were labeled with Fluo-3. Then the root canal fillings were removed with Protaper Universal Retreatment files. At the last stage, the teeth were reshaped with PTN (X3-30/0.07). The samples were transversally sectioned and examined using a Cytation 5 reader and Gen5 software regarding the mean and the maximum depth of sealer penetration. No significant difference was observed between the groups, except for the 6 mm level after reshaping the root canals (p < .05). It is not possible to completely remove the sealer remnants from the dentin walls even after reshaping the root canals. RESEARCH HIGHLIGHTS: Even after reshaping the root canals in the retreatment procedure, it is not possible to completely remove the filling residues of the epoxy-resin-based, calcium-silicate-based and MTA-based endodontic pastes from the dentin walls.

Temperature changes in the pulp chamber and bleaching gel during tooth bleaching assisted by diode laser (445 nm) using different power settings

The aim of this in vitro study was to investigate the safety of using blue diode laser (445 nm) for tooth bleaching with regard to intrapulpal temperature increase operating at different average power and time settings. Fifty human mandibular incisors (n = 10) were used for evaluating temperature rise inside the pulp chamber and in the bleaching gel during laser-assisted tooth bleaching. The change in temperature was recorded using K thermocouples for the five experimental groups (without laser, 0.5, 1, 1.5 and 2 W) at each point of time (0, 10, 20, 30, 40, 50 and 60 s). As the average power of the diode laser increases, the temperature inside the pulp chamber also increases and that of the bleaching gel was significantly higher in all the experimental groups (p < 0.05). However, the intrapulpal temperature rise was below the threshold for irreversible thermal damage of the pulp (5.6 °C). Average power of a diode laser (445 nm) ranging between 0.5–2 W and irradiation time between 10–60 s should be considered safe regarding the pulp health when a red-colored bleaching gel is used. Clinical studies should confirm the safety and effectiveness of such tooth bleaching treatments. The outcomes of the present study could be a useful guide for dental clinicians, who utilize diode lasers (445 nm) for in-office tooth bleaching treatments in order to select appropriate power parameters and duration of laser irradiation without jeopardizing the safety of the pulp.

Ex vivo detection of mandibular incisors’ root canal morphology using cone-beam computed tomography with 4 different voxel sizes and micro-computed tomography

BackgroundIn recent years, cone-beam computed tomography (CBCT) has been widely used to evaluate patients’ root canal anatomy due to its high resolution and noninvasive nature. As voxel size is one of the most important parameters affecting CBCT image quality, the current study evaluated the diagnostic potential of CBCT with 4 different voxel sizes in the detection of double root canal systems and accessory canals (ACs) in permanent mandibular incisors.MethodsA total of 106 extracted mandibular permanent incisors were collected from the dental clinics, and then were scanned by using micro-CT with a voxel size of 9 μm. The teeth were then fixed in the tooth sockets of human dry mandibles and scanned by using a CBCT device with 4 different voxel sizes (300, 200, 250, and 125 μm). Four observers detected in blind the root canal morphology of the teeth according to the CBCT images, and the presence or absence of a double root canal system, and the presence or absence of ACs, were scored according to a 5-point scale, respectively. Receiver operating characteristic (ROC) analysis was performed, and DeLong test was used to compare the area under the curve (AUC) values and the micro-CT data was taken as a gold standard.ResultsAmong 106 sample teeth, 25 specimens with a double root canal system were identified by the micro-CT. ROC curve analysis of the data obtained by the four observers showed that in the detection of double root canal systems, the AUC values ranged from 0.765 to 0.889 for 300 μm voxel size, from 0.877 to 0.926 for 250 μm voxel size, from 0.893 to 0.967 for 200 μm voxel size, and from 0.914 to 0.967 for 125 μm voxel size (all p < 0.01). In general, we observed a trend that the AUC values, sensitivity, and specialty increased with the decrease in the voxel size, and significantly higher AUC values were detected in 125 μm voxel size images. In the detection of ACs, ROC curve analysis showed that among the four observers, the AUC values ranged from 0.554 to 0.639 for 300 μm voxel size, from 0.532 to 0.654 for 250 μm voxel size, from 0.567 to 0.626 for 200 μm voxel size, and from 0.638 to 0.678 for 125 μm voxel size. CBCT images at a voxel size of 125 μm had a weak diagnostic potential (AUC: 0.5–0.7, all p < 0.05) in the detection of AC, with a lower sensitivity ranging from 36.8 to 57.9% and a higher specialty ranging from 73.6 to 98.8%.ConclusionsCBCT with 300 μm voxel size could only provide moderate diagnostic accuracy in the detection of a double canal system in mandibular incisors. CBCT with a voxel size of 125 μm exhibited high diagnostic value in the detection of double canal systems, while showing low but statistically significant value in the detection of ACs.

Does the traditional or digital dental model measurement method affect the results?: A validation study

Objective: The aim of this study is to evaluate the accuracy, reliability and reproducibility of measurements made on digital models obtained using OrthoAnalyzer (3Shape, Copenhagen, Denmark) and Materialize 3 matic (MIMICS , Leuven, Belgium) software by comparing them with measurements made on dental plaster models.&#x0D; Methods: The teeth of 50 individuals were measured and plaster models were obtained. In addition, digital images were obtained from the patients with Trios intraoral scanner. A total of 30 linear measurements were made using OrthoAnalyzer and Materialize 3 matic software, including the mesiodistal width of the teeth, arch perimeter, intercanine and intermolar distances. All measurements were made by two different examiners. For the first and second measurements of the first examiner, intraexaminer reliability was calculated using intraclass correlation coefficients (ICCs), two way mixed model, consistency type. &#x0D; Results: The largest mean difference between Materialize 3 matic and caliper measurements was -0.136 mm in maxillary right first premolar and maxillary left lateral incisor. The smallest mean difference was 0.0029 mm in the mandibular left lateral incisor. In transverse measurements, the largest mean difference was found in the upper intercanine distance of 0.117 mm, and the smallest mean difference was 0.0086 mm in the upper intermolar distance. The largest mean difference between OrthoAnalyzer and caliper measurements was 0.107 mm in the maxillary right lateral incisor, and the smallest mean difference was 0.0049 mm in the maxillary left lateral incisor. &#x0D; Conclusions: Linear distance measurements with three-dimensional digital models are a valid, reliable and reproducible method compared to plaster models.

Three-dimensional evaluation of alveolar bone and pharyngeal airway dimensions after mandibular dentition distalization in patients with Class III malocclusion: a retrospective study

BackgroundTo three-dimensionally evaluate changes of the alveolar bone around the mandibular anterior teeth and pharyngeal airway dimensions in adults with Class III malocclusion before and after orthodontic treatment of mandibular dentition distalization.MethodsIn this retrospective study, cone-beam computed tomography (CBCT) scans of 20 patients with Class III malocclusion who underwent mandibular dentition distalization were obtained both before and after treatment. Three-dimensional changes of the thickness and vertical marginal bone levels around mandibular incisors and canines were assessed and compared. And airway volumes of the palato-, glosso-, laryngopharynx and the minimum axial area were measured and compared before and after treatment.ResultsA significant decrease of lingual bone thickness of mandibular incisors, partial labial and lingual bone thickness of canines were observed (P < 0.05). The reduction in root length of incisors and canines, labial and lingual vertical marginal bone levels were significant after orthodontic treatment. No significant correlations between mandibular dentition distalization and pharyngeal airway dimensions were observed.ConclusionsMandibular dentition distalization could result in the loss of alveolar bone around anterior teeth in Class III malocclusion, especially for the cervical marginal bone. Pharyngeal airway dimensions were not affected to a high extent after distalization.Trial registrationRetrospctively registered.

Dental tissue changes in juvenile and adult mice with osteogenesis imperfecta.

Osteogenesis imperfecta (OI), a disorder of type I collagen, causes skeletal deformities as well as defects in dental tissues, which lead to increased enamel wear and smaller teeth with shorter roots. Mice with OI exhibit similar microstructural dentin changes, including reduced dentin tubule density and dentin cross-sectional area. However, the effects of these mutations on gross dental morphology and dental tissue volumes have never been characterized in the osteogenesis imperfecta murine (OIM) mouse model. Here we compare mineralized dental tissue measurements of OIM mice and unaffected wild type (WT) littermates at the juvenile and adult stages. The maxillary and mandibular incisors and first molars were isolated from microCT scans, and tissue volumes and root length were measured. OIM mice have smaller teeth with shorter roots relative to WT controls. Maxillary incisor volumes differed significantly between OIM and WT mice at both the juvenile and young adult stage, perhaps due to shortening of the maxilla itself in OIM mice. Additionally, adult OIM mice have significantly less crown enamel volume than do juveniles, potentially due to loss through wear. Thus, OIM mice demonstrate a dental phenotype similar to humans with OI, with decreased tooth size, decreased root length, and accelerated enamel wear. Further investigation of dental development in the OIM mouse may have important implications for the development and treatment of dental issues in OI patients.

Comparisons of Dental Anomalies in Orthodontic Patients with Impacted Maxillary and Mandibular Canines.

To assess the presence and possible associations between the type of dental anomalies and maxillary and mandibular canine impactions in orthodontic patients treated for canine impaction, panoramic radiographs of orthodontic patients treated for canine impaction were assessed for the presence of associated dental anomalies. A random sample of orthodontic patients without canine impaction matched for age and gender served as controls. Descriptive and exact inferential statistics were implemented in order to assess potential associations between canine impaction and dental anomalies. A total of 102 orthodontic patients with 70 maxillary (MaxCI) and 32 mandibular (ManCI) canine impactions were assessed. The control group included 117 orthodontic patients. Dental anomalies were present in more than 50% of patients with impacted canines and in 20% of the controls. Tooth agenesis was significantly more common in the MaxCI group when compared to the ManCI group, while supernumerary teeth and canine transmigration were registered more often in the ManCI group. When compared to the control group, peg-shaped maxillary lateral incisors and tooth agenesis were significantly more prevalent in the MaxCI group, while canine transmigration, supernumerary teeth, the agenesis of mandibular incisors and tooth transpositions were significantly more prevalent in the ManCI group. The impaction of other teeth was significantly more common in both canine impaction groups when compared to the controls. The prevalence of dental anomalies in orthodontic patients with impacted canines was higher than in orthodontic patients without canine impaction. Different types of tooth anomalies were found in the MaxCI and ManCI groups.

Comparison of masticatory myofunctional rehabilitation combined with conventional functional appliances for the treatment of class Ⅱ, division 1 malocclusion. A retrospective cohort study

ObjectiveTo estimate the clinical efficacy of early masticatory myofunction rehabilitation combined with conventional functional appliances for the treatment of class Ⅱ, division 1 malocclusion in orthodontic children during the growing phase. Materials and methodA comparative retrospective cohort study, enrolled patients diagnosed with class Ⅱ/1 in the stage of late mixed or early permanent dentition. Patients were divided into a TBA group (Cohort 1): receiving Twin-block appliance treatment; and a MMR group (Cohort 2): receiving either early masticatory myofunction rehabilitation as adjunctive therapy combined with the same conventional functional appliances. The study variables were active (Phase 1) treatment duration, oral esthetic subjective impact score (OASIS), several cephalometric indices calculated from X-ray photographs, the maximum voltage (mV) and asymmetry index (AsI) of anterior temporalis (TA) and masseter muscles (MM) before and after treatment. Complications were also recorded. ResultsA total of 424 cases were enrolled. The mean treatment duration in the MMR group was 168.33 days (SD: 25.43) and 215.00 days (SD: 28.81) in the TBA group; mean difference: -46.67 days (95% CI: [-81.62, -11.71]), P<0.001. For the OASIS outcome measure, there was no statistically significant difference between the mean total scores for the MMR group (18.83±7.73) or TBA group (17.67±6.47) groups adjusted to include pre-treatment OASIS scores (P = 0.783). After treatment, sella-nasion-B point (SNB), mandibular incisor angle, maxillary base and mandibular base in both two groups were significantly increased, while AB plane angle (ANB), maxillary incisor angle, overjet and overbite were significantly decreased. The mV and AsI of TA and MM were also improved following treatment. However, no significant differences were observed between two groups. ConclusionOur results confirmed that early masticatory myofunction rehabilitation in combination with conventional TBA for patients in the growing phase was significantly effective in the management of class Ⅱ/1 in orthodontic treatment, which could significantly shorten the treatment duration and had the similar improvement in the cephalometry data, OASIS scores and masticatory muscles function when comparing to conventional TBA alone.