Normal Bite Research Articles

Cantilever resin-bonded fixed dental prosthesis to substitute a single premolar: Impact of retainer design and ceramic material after dynamic loading.

To evaluate the influence of retainer design and ceramic materials on the durability of minimally invasive cantilever resin-bonded fixed dental prostheses (RBFDPs) after artificial aging. One hundred caries-free human mandibular molars were prepared as abutments for all-ceramic cantilevered fixed dental prostheses using the following retainer designs: One wing (OW), Two wings (TW), Inlay ring (IR), Lingual coverage (LC), and Occlusal coverage (OC). Two ceramic materials were used: monolithic high translucent zirconia(z) and zirconia-reinforced lithium disilicate (ZLS2) (n=10). All restorations were adhesively bonded with resin cement. The thermocycling of the specimens were performed between 5°C and 55°C for 10,000 cycles and then exposed to 240.000 cycles of dynamic loading on a chewing simulator. All surviving specimens were loaded onto the pontic until failure using a universal testing machine. The mean failure load ranged from 124.00 to 627.00 N for the zirconia groups and from 133.30 to 230.00 N for the ZLS2 groups. Regarding the materials, a significantly higher failure load was recorded in the zirconia groups than in the ZLS2 groups (P<0.001), except for OW (P=0.748). Regarding the retainer designs, a significant different failure load was recorded between the different designs except for IR and LC in the zirconia groups, IR and OC, OW and TW, and TW and LC in the ZLS2 groups (P<0.001). Zirconia IR, LC, and OC can be used as cantilever RBFDP in the premolar region. The fracture resistance of the ZLS2 design was below the normal bite force and should not be recommended as the first option.

Three-Dimensional Finite Element Analysis on Mandibular Biomechanics Simulation under Normal and Traumatic Conditions

The main objective was to examine the biomechanical behavior of the mandible under standardized trauma and to develop models of biomechanical responses when the mandible is subjected to various simulated impacts. A homogenous model based on the bone’s average mechanical properties was used. To simulate external loads on the mandible, forces on the chin, forces in an anteroposterior direction, and forces from the basilar edge were applied. To simulate mandibular biomechanics, we employed a model created in the ANSYS v19.0 software. The skull with the temporomandibular joint (TMJ) from the Grabcad website was used as the geometric mandibular model. We attempted to simulate the stresses developed in the mandible by impact forces. The amount of force (F) corresponded to the fall of a five-kilogram body (the head), from a height of two meters (F = 6666.7 N). The impact force was applied perpendicular to an arbitrary surface of an area of 10−3 m2. Impact on the chin region and lateral impact on the mandible, from the basilar edge to the gonion were examined. The investigated clinical situations were mandibular complete dentition; jaw with missing mandibular molars; missing third molar and first and second premolars; missing canine, third molar, first and second premolars, and complete edentation. In a normal bite, the highest stress was on the TMJ area. In case of impact on the chin, in complete edentation, a mandibular fracture occurred; in case of impact on the gonion, all stress values exceed the limit value above which the mandible in the condyle area may fracture.

Tooth size discrepancy in orthodontic patients with skeletal anterior open bite.

To find out if there is any relationship between tooth size discrepancy (TSD) and skeletal anterior open bite (AOB) and to assess the correlation between the amount of AOB and TSD. A total of 100 Class I subjects were included in this study (average age 15.21 ± 2.84 years). Fifty patients had skeletal AOB (>3 mm) and 50 subjects acted as controls and had a normal overbite. Teeth mesio-distal widths were measured using a digital caliper. Anterior, overall, and posterior TSD ratios were calculated. An independent t-test was employed to assess differences between groups and between genders. Pearson correlation coefficient was used to assess the correlation between the amount of AOB and TSD. Significant differences in anterior (p = .038) and posterior (p = .015) TSD ratios were detected. In the skeletal AOB group, no significant gender differences were detected (p > .05), whereas in the normal bite and total sample group, males had smaller posterior teeth compared to females (p < .05). All the differences were smaller than 1 SD of Bolton's ratios. No significant correlation was found between the amount of AOB and TSD ratios (p > .05). Skeletal AOB had larger anterior and smaller posterior mandibular teeth, but the differences were less than 1 SD of Bolton's ratios. Males have smaller mandibular posterior teeth than females. The amount of AOB is not correlated with the TSD ratios.

Comparison of Two Types of Preparation for Laminate Veneer with Three Types of All-Ceramic Materials.

The objective of this study was to compare types of veneer preparations and their combination with three materials. Two finite element models were specially prepared used representing window and wrap around preparation for veneers. The "central incisor" tooth geometry was acquired using a laser scanner, and then its surface was adjusted to form a solid model prior to the removal of each preparation separately. Three materials (Lava Ultimate, IPS e-max, and Celtra) were tested in combination with the preparation type. Bone geometry was simplified as two coaxial cylinders in all models. Each model was subjected to two loading conditions of occlusion (edge-to-edge bite and normal bite). It was observed that cortical, cancellous bone, and periodontal ligament are insensitive to preparation or materials. Their stresses and deformation were within physiological limits. Significant changes appeared on the central incisor tooth structure, cement layer, and veneer layer stresses and deformations under loading cases. Edge-to-edge bite stresses are severe with window-type preparation, and normal bite did not show any critical values on tooth structure, cement layer, or veneer layer. Veneer layer finish line and its contact with the cement layer and tooth structure play a role in the loading transfer mechanism. Preparation type alters the values of stresses on tooth structure, cement, and veneer layers. With window preparation, extreme stresses appear at finish line, while stresses appear under the loading site with wrap around preparation. Veneer and cement layers withstand the load energy with wrap around preparation and reduce tooth structure stresses. Thus, the lifetime of veneer and cement layers might be longer with window preparation.

Acute effects of radiation treatment to submental muscles on burrowing and swallowing behaviors in a rat model.

Swallowing impairments are a major complication of radiation treatment for oropharyngeal cancers, influencing oral intake and quality of life. The timing and functional consequences of radiation treatment on the swallowing process is not clearly understood. A rodent radiation injury model was used to investigate the onset of oral and pharyngeal dysfunctions in deglutition related to radiation treatment. This study tested the hypothesis that (Wall et al., 2013) alterations in normal biting, licking, and swallowing performance would be measurable following 64Gy of fractionated radiation to the submental muscles; and (Kotz et al., 2004) radiation will affect the animal’s general well-being as measured via burrowing activity. Seven rats received radiation using a clinical linear accelerator given in 8 fractions of 8Gy and another seven animals received sham anesthesia only treatment. Swallowing bolus transit/size was assessed via videofluoroscopy, tongue movement during drinking was measured via an electrical lick sensor, and biting was analyzed from acoustic recordings of a vermicelli pasta test. Burrowing activity was measured by the amount of gravel substrate displaced within a container. Measurements were taken at baseline, during treatment (1–4 weeks), and after completion of treatment (weeks 5 & 6). Decreases in licking frequency and increases in inter-lick interval were observed 5- and 6-weeks post-treatment. Significant decreases in burrowing performance, swallowing frequency, and inter-swallow interval were observed starting the last week of treatment and continuing up to 2-weeks after completion. Results suggest that tongue dysfunction is one of the first treatment related feeding problems to present immediately after the completion of radiation to the submental muscles.

Anterior occlusion in shortened dental arches

ObjectivesThe aim of this study was to examine the occlusion of anterior teeth in individuals with shortened dental arch (SDA).Material and methodsIn a case–control clinical study, 41 individuals with SDA and 41 individuals with complete dental arch (CDA) participated. The CDA control group was matched for age and gender. Testing for occlusal contacts of anterior maxillary teeth was conducted by biting on foil strips (8 µm) with subjectively normal bite force (NBF) and maximal bite force (MBF). The data was analyzed on individual and tooth levels.ResultsThe median rates of anterior maxillary teeth with occlusal contacts were 0.67 (NBF) and 0.83 (MBF) in the SDA group and 0.50 (NBF) and 0.83 (MBF) in the CDA group. Within both groups, the contact rates were significantly higher in MBF. The group difference with NBF was significant. A generalized linear model showed that the odds of an anterior maxillary tooth to have an occlusal contact were greater in the SDA both for NBF with an odds ratio (OR) 2.277 and MBF with an OR 1.691.ConclusionsThe findings suggest effective compensatory mechanisms relative to the occlusal function in individuals with SDA.Clinical relevanceThe study delivers further evidence regarding the SDA concept as a viable option in the management of posterior tooth loss.

Prevalence of Malocclusions in Autistic Patients in Isfahan

Introduction: Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders diagnosed by impairments in social interaction and communication with repetitive and restrictive stereotyped behavioral patterns. The Prevalence of autism has been reported to be increased in recent years. This study aimed to assess the prevalence of different types of malocclusion among ASD patients in Isfahan in 2018. Materials &amp; Methods: In a descriptive and cross-sectional trial, 92 ASD patients were studied in the age range of 7-18 years at the center for autism patients in Isfahan. Clinical oral examinations of patients are taken to assess the involved malocclusions (Cl I, Cl II and Cl III malocclusions) and malocclusion traits (deep bite, open bite and cross bite) by an educated dental student under the supervision of an orthodontist under natural light. The data are reported using frequency and percentage indices. Results: Class I malocclusion had the highest prevalence 54.3% (50) among ASD patients and the prevalence of class II and class III were found to be 19.6% (18) and 7.6% (7) respectively. The frequency of malocclusions traits of deep bite, cross bite and the open bite were 27.2% (25), 18.5% (17) and 7.6% (7) respectively. Among of the total patients, 65.2% (60) showed normal bite and 18/5% (17) showed Normal occlusion. Conclusion: ASD patients showed class I, class II and class III malocclusions from the most to least frequency and the most frequent malocclusion traits were also deep bite, cross bite and open bite respectively.

The Prevalence of Temporomandibular Disorders and Dental Attrition Levels in Patients with Posterior Crossbite and/or Deep Bite: A Preliminary Prospective Study.

Background The prevalence of various temporomandibular disorders (TMD) and the severity of attrition in patients with either bilateral or unilateral deep bite and/or posterior crossbite has not been established, nor has the effect of one year of orthodontic treatment on TMD. Methods Of 310 patients presenting with suspected TMD, 160 were diagnosed with various TMD and 150 were TMD-free. Diagnosis was according to the Axis I of the Diagnostic Criteria for TMD. All participants underwent a dental examination, and 100 patients were reevaluated after one year of orthodontic treatment. Fisher's exact test and the proportion test with Bonferroni's correction were used for the categorical univariate analysis. Results There was a significant association (P < 0.001) between deep bite and dental attrition (wear), but not between crossbite and/or deep bite in patients diagnosed with either painful TMD or disc displacement. The risk of sustaining painful TMD when crossbite presented simultaneously on the anterior and the posterior dentition was 2.625-fold greater than when it presented with a normal bite, although this difference was not significant (P=0.286) due to the lack of statistical power. There was no significant sex-related association between the occurrence of either painful TMD or disc displacement. A reduction in TMD findings was demonstrated after one year of treatment, but no statistical power was reached due to the small sample size. Conclusions Deep bite may be related to dental wear but not to pain from TMD and/or disc displacement. Only crossbite that presents simultaneously on the anterior and the posterior dentition (mixed X-bite) may have some effect on the level of pain in TMD, but not on in the prevalence of disc displacement. Confirmation of these conclusions by well-designed studies on larger patient groups is warranted. There was a clinically significant improvement in TMD findings after one year of treatment.

A Study of the Mechanical Characteristics of a Mandibular Parasymphyseal Fracture with Internal Fixation Device Subject to Variable Bite Forces: Finite Element Analysis

In recent times, research into mandibular fracture has gained momentum from advances in scanning techniques, software/algorithm developments and improvements, and numerical structural modeling using the finite-element method (FEM). In this work, the FEM is used to model a mandibular fracture (using an inhomogeneous and orthotropic jaw model) simulating the effect of different bite tasks/forces on the stability of the fixated fracture. Specifically, bilateral and unilateral clenches (using muscle data) were studied using a low-profile 3D 4 × 2 hole mini-plate deployed for fracture fixation. Here, the mandible bone was treated as orthotropic and spatially inhomogeneous. Although the results of stress and displacement analyses, for this fixation hardware, indicate sufficient fixation under normal biting conditions, the results show that the unilateral and ipsilateral bites develop, in general, the highest stresses or displacements. Such results can guide post-surgery recommendation on bite behavior.

Ultrasonographic observation of anterior temporalis and masseter muscle in open bite patients: A comparative study

Aim: The present study was done to compare the muscle thickness of the masseter and anterior temporalis muscle in adults with normal occlusion and anterior open bite using ultrasonography, in rest position and maximum intercuspation. Material and Methods: Ultrasonographic recording of masseter and anterior temporalis thickness of both sides of nine subjects with anterior open bite and normal occlusion was done. Unpaired t test was used for the intergroup comparison of muscle thickness. Results: A significant correlation between the thicknesses of both the muscles in contracted state was found to be more in anterior open bite. There was no statistically significant correlation between thicknesses of both muscles in relaxed state. Conclusion: Since no detailed investigation was done, it will be premature to give a final verdict on the correlation between the masticatory muscle thickness and facial morphology. A long term follow up will provide a new insight for future clinical purpose. Keywords: Ultrasonography, Temporalis muscle, Masseter, Open bite.

Investigation of posterior teeth displacement under normal bite force by an intraoral scanner

Objective: To quantitatively evaluate the change of the long axis angle and the relative displacement of the crown feature points of the posterior teeth under normal bite force utilizing an intraoral scanner, and to provide clinical reference. Methods: From May to December 2019, fifteen graduate volunteers (5 males and 10 females, aged from 22 to 30, with an average age of 25.7 years) from Peking University School and Hospital of Stomatology were recruited to participate in the study. The surface data (U1, L1) of the maxillary and mandibular posterior teeth were scanned by an intraoral scanner i500, and saved as original data. The volunteers were guided to bite in the intercuspal position with normal bite force. The buccal bite data of the posterior teeth were scanned as the basis for registration. The digital casts were imported into Geomagic studio 2013 software and the boundary lines along the gingival margin and mesial and distal contact area of posterior teeth of data (U1, L1) were determined. Long axis of the crown, crown centroid and mesial functional cusp vertex were establishd. The data (U1, L1) were segmented into single tooth. Single tooth was aligned to buccal bite data separately using best-fit alignment command based on the buccal common area of the crown and new casts data (U2, L2) were obtained as the data under bite force. The long axis angle and centroid distance between adjacent teeth (second premolar and first molar, second molar and first molar) were measured and the deviation between data obtained at mouth-open state and that at biting state was calculated. Negative value meant centroid distance became shorter under bite force. The first molar was set as the common area and registrate the U1, L1 to U2, L2. The angle of long axes, and displacement of centroid and of functional cusp vertex between second premolar of two casts were calculated, as well as between second molar of two casts. Wilcoxon signed rank test was used to analyze the differences of teeth displacement between second premolar and second molar, and between maxillary and mandibular jaws with SPSS 26.0 statistical software. Results: The result of second premolar and second molar in the same jaw had no statistical difference (P>0.05). The centroid distance deviation of mandibular second premolar-first molar [-0.022(0.046) mm] was larger than that of maxilla [-0.006 (0.040) mm] (P<0.05). The long axis angle of second premolar itself [0.913°(0.647°)] and centroid distance of second molar itself [0.102 (0.106) mm] on the mandibular jaw were different from that on the maxillary jaw, which were 0.590°(0.550°) and 0.074(0.060) mm respectively (P<0.05). Conclusions: Under bite force, displacement of the second premolar and second molar was present, including the displacement of centroids and deflection of long axes. The mandibular posterior teeth have larger displacement than the maxillary teeth.

CHARACTERISTICS OF THE BIOELECTRIC ACTIVITY OF THE MASTICATORY MUSCLES IN PATIENTS WITH HEARING DEPRIVATION IN PERMANENT OCCLUSION IN THE PHYSIOLOGICAL STATE

The study of the muscles of the maxillofacial area both in normal and pathological occlusions is the area of great interest, since muscle function is an indicator of complex functional relationships of the dento-mandibular system. Hearing impaired patients have many features related to the functional features of the maxillofacial area due to the slight or complete lack of use of facial muscles during speech or through the use of sign language. Hearing impaired children have 100% of bite pathology.&#x0D; The functional state of chewing and temporal muscles in schoolchildren with hearing loss in constant bite at rest was studied. Twenty-five hearing impaired students with permanent dentistry were studied at Poltava Special Boarding School for Deaf Children, who formed the study group. Among them, there were 13 women (62.5%) and 12 men (37.5%). The mean age was 18.7 ± 1.31 years. The control group used the data of the study of patients with constant physiological bite without hearing disorders, determined by M. I. Dmytrenko. The average age was 21.3 ± 1.25 years.&#x0D; The bioelectric activity of the chewing muscles was examined on an electromyographic complex. The average values of oscillation amplitude (μV) of muscle biopotential on both sides were determined. Muscle biopotentials were recorded for five seconds in a state of physiological calm with closed lips.&#x0D; The results show that all indicators of PD of chewing muscles in a state of physiological rest are almost 2 times higher (p˂0,05) in comparison with those of patients with normal hearing and physiological bite. The work of the temporal muscles in schoolchildren with hearing loss is characterized by symmetry. There is also greater electrical activity of the temporal muscle than the masticatory muscles at rest, unlike normal hearing patients.&#x0D; All patients with hearing impairment had 100% prevalence of dental anomalies. Biopotential of chewing muscle of I class. for angle was 2.7 times higher than in patients with the control group. The biopotential of the temporalis muscle in the ICE was 1.8 times higher (p˂0.05), which indicates a constant tension or insufficient muscle relaxation in patients with ICE. In patients with hearing loss of II class. for angle, the average value of the biopotential of the chewing muscle was 2.3 times higher than in patients in 2 group, the temporal muscle was 1.5 times higher.

Pattern of Dental Malocclusion in Orthodontic Patients in Erbil City, Kurdistan Region-Iraq, A Retrospective Study

Aim: Aims of this study were to assess the pattern of malocclusion in Erbil City, Kurdistan region- Iraq.&#x0D; Methods: A retrospective study includes 1212 patients (589 males and 623 females) that attended orthodontic department at the khanzad polyclinic teaching center / Erbil city, Iraq, aged 11-17 years old with a mean age of 13.49 ±1.02 years that randomly selected. The normal occlusion, malocclusion, overjet, overbite, spacing, crowding, cross bite, midline shifting and midline diastema were examined.&#x0D; Results: Study demonstrated that 309 (25.5%) of patients had normal occlusion. Class I malocclusion was found in 655 (72.5%), class II was found in 176 (19.5%), and class III malocclusion 72 (8.0%) patients of all examined. Crowding and midline shifting were observed more frequently in females, however, normal bite and posterior open bite were observed more frequently in males and normal crossbite more frequently in both genders.&#x0D; Conclusion: Results of this study showed class I molar relationship was the most prevalent type of occlusion in Erbil City, Kurdistan Region-Iraq area and the most prevalent malocclusion was crowded.

Square Face Correction by Gonial Angle and Masseter Reduction.

Introduction:The association of mandibular gonial angle, facial height, and jaw relationship in masseteric hypertrophy (MH) has not been adequately described for the typical Indian population. The aim of this study was to report the gonial angle relationship with facial height parameters in cases diagnosed with bilateral MH and its possible influence on the treatment plan.Materials and Methods:This is a retrospective study based on archival records of bilateral MH cases surgically treated over a 10-year period at the author's center. Patients' records fulfilling inclusion and exclusion criteria were considered for the study. Age, gender, upper anterior facial height (UAFH), lower anterior facial height (LAFH), upper posterior facial height (UPFH), ramus height (also a reflection of the lower posterior facial height), and gonial angle were collected along with the type of bite (open/normal/deep), surgical procedure (debulking with/without bone removal), and concomitant jaw bone corrections (yes/no). These were subjected to statistical analysis using SPSS, and P ≤ 0.05 was taken as statistically significant.Results:Overall, 21 patients formed the study group comprising 9 females and 12 males. Gender influenced the UAFH, LAFH, UPFH, ramus height, and gonial angle significantly. Males had higher values than females. Normal bite had an obtuse gonial angle than the deep bite, and the difference was statistically significant (P = 0.036). When the gonial angle was acute or square faced, the need for other surgical procedures was high and the difference was statistically significant (P = 00.048).Discussion and Conclusion:The results are discussed in the light of Indian skeletal anthropometry. The relationship of the gonial angle with facial height parameters in bilateral MH cases in this part of the world is presented.

Mesiodistal angulation of posterior teeth in orthodontic patients with different facial growth patterns.

Background. Mesiodistal and buccolingual angulations of teeth are variable in different malocclusion classes. This study aimed to assess the mesiodistal angulation of posterior teeth in orthodontic patients with vertical, normal, and horizontal facial growth patterns. Methods. This descriptive, cross-sectional study evaluated 150 lateral cephalograms of orthodontic patients. According to cephalometric analysis, facial growth patterns were divided into three groups of normal, horizontal, and vertical (n=50). The angulation of maxillary and mandibular posterior teeth was then measured. Data were analyzed using SPSS 22. Results. The results showed an increase in the mean angle of maxillary and mandibular posterior teeth relative to palatal and mandibular planes in patients with a vertical facial growth pattern. Conversely, their angulation decreased relative to the bisected occlusal plane (BOP). The angulation of posterior teeth decreased relative to palatal and mandibular planes and increased relative to the occlusal plane with an increase in overbite. The mean angle of all maxillary teeth relative to the palatal plane was significantly greater in open bite patients compared to normal and deep bite patients. This value in patients with normal bite was significantly greater than that in deep bite patients (P<0.05). Conclusion. The current results revealed that in patients with a vertical growth pattern, all the posterior teeth had a forward inclination. Conversely, in patients with a horizontal growth pattern, the teeth had a backward inclination.

Quantitative evaluation of palatal bone thickness in patients with normal and open vertical skeletal configurations using cone-beam computed tomography.

PurposeTo perform a comparative analysis of the palatal bone thickness in Thai patients exhibiting class I malocclusion according to whether they exhibited a normal or open vertical skeletal configuration using cone-beam computed tomography (CBCT).Materials and MethodsThirty CBCT images of Thai orthodontic patients (15–30 years of age) exhibiting class I malocclusion with a normal or open vertical skeletal configuration were selected. Palatal bone thickness was measured in a 3.0-mm grid pattern on both the right and left sides. The palatal bone thickness of the normal-bite and open-bite groups was compared using the independent t-test. The level of significance was established at P<.05.ResultsThe palatal bone thickness in the normal-bite group ranged from 2.2±1.0 mm to 12.6±4.1 mm. The palatal bone thickness in the open-bite group ranged from 1.9±1.1 mm to 13.2±2.3 mm. The palatal bone thickness was lower at almost all sites in patients with open bite than in those with normal bite. Significant differences were found at almost all anteroposterior sites along the 3 most medial sections (3.0, 6.0, and 9.0 mm lateral to the midsagittal plane) (P<.05).ConclusionClass I malocclusion with open vertical skeletal configuration may affect palatal bone thickness, so the placement of temporary anchorage devices or miniscrew implants in the palatal area in such patients should be performed with caution.

Effects of the Vertical Malocclusion Types on the Dimension of the Mandibular Condyle.

This study aimed to find the relationship between mandibular condyle morphology and dental malocclusion in patients with anterior open bite, deep bite, and normal overbite. Eighty patients were included in this retrospective study. All patients had skeletal Class II pattern. The initial panoramic radiographs of patients were digitized using a software program, and groups were compared in terms of condylar height, width, area, and perimeter. In addition, changes in the condyle surface shape were detected using the same panoramic radiographs. The mean width was 1.55±0.06 cm in the open bite group, 1.48±0.06 cm in the deep bite group, and 1.38±0.07 cm in the normal bite group. The mean height was 2.17±0.08 cm in the open bite group, 1.95±0.06 cm in the deep bite group, and 1.97±0.08 cm in the normal bite group. The mean area was 2.33±0.13 cm2 in the open bite group, 2.09±0.11 cm2 in the deep bite group, and 2.04±0.14 cm2 in the normal bite group. There was no statistical significant difference between groups in terms of condyle measurements and condyle surface shapes. The results suggest that the vertical malocclusion type does not have a considerable effect on the mandibular condyle measurements and surface shapes.

Relationship between molar occlusion and masticatory movement in lateral deviation of the mandible.

The relationship between molar occlusion and chewing patterns was examined in subjects with laterally deviated mandibles. Twenty-three patients with mandibular deviation from the midline (4mm or more) and skeletal Class I (0°≤ANB≤4°) were divided into 2 groups: normal bite and crossbite. The chewing pattern was classified as normal, reversed, or crossover. The normal bite group had a normal chewing pattern on the affected side 100% of the time and a reversed chewing pattern on the affected and unaffected sides 0% and 7.2% of the time, respectively. Additionally, the normal bite group showed no evidence of a crossover chewing pattern and also had significantly less axial inclination of the mandibular teeth on the affected side compared with the crossbite group; lingual inclination was also evident. The crossbite group had a normal chewing pattern on the affected and unaffected sides 0% and 55.6% of the time, respectively, and reversed and crossover chewing patterns on the affected side 55.6% and 44.4% of the time, respectively. A normal chewing pattern tends to result in lingual axial inclination of the mandibular molars on the affected side, as well as a more consistent chewing pattern.

Root surface areas of maxillary permanent teeth in anterior normal overbite and anterior open bite assessed using cone-beam computed tomography

PurposeThe aim of this study was to compare the root surface areas of the maxillary permanent teeth in Thai patients exhibiting anterior normal overbite and in those exhibiting anterior open bite, using cone-beam computed tomography (CBCT).Materials and MethodsCBCT images of maxillary permanent teeth from 15 patients with anterior normal overbite and 18 patients with anterior open bite were selected. Three-dimensional tooth models were constructed using Mimics Research version 17.0. The cementoenamel junction was marked manually. The root surface area was calculated automatically by 3-Matic Research version 9.0. The root surface areas of each tooth type from both types of bite were compared using the independent t-test (P<.05). The intraclass correlation coefficient was used to assess intraobserver reliability.ResultsThe mean root surface areas of the maxillary central and lateral incisors in individuals with anterior open bite were significantly less than those in those with normal bite. The mean root surface area of the maxillary second premolar in individuals with anterior open bite was significantly greater than in those with normal bite.ConclusionAnterior open-bite malocclusion might affect the root surface area, so orthodontic force magnitudes should be carefully determined.

Distances from the root apices of posterior teeth to the maxillary sinus and mandibular canal in patients with skeletal open bite: A cone-beam computed tomography study.

PurposeThis study determined and compared the distances from the maxillary root apices of posterior teeth to the floor of the maxillary sinus, or maxillary sinus distances (MSDs), and the distances from the mandibular root apices of the posterior teeth to the mandibular canal, or mandibular canal distances (MCDs), in Thai subjects with skeletal open bite and skeletal normal bite.Materials and MethodsPretreatment cone-beam computed tomography (CBCT) images were obtained from 30 Thai orthodontic patients (15 patients with skeletal normal bite and 15 with skeletal open bite) whose ages ranged from 14 to 28 years. The CBCT images of the patients were processed and measured using the Romexis Viewer program. The MSDs and MCDs from the root apices of the maxillary and mandibular second premolar, first molar, and second molar to the maxillary sinus floor or the mandibular canal were measured perpendicularly to the occlusal plane. The Student t test was used for comparisons between the 2 groups.ResultsThe greatest mean MSDs were from the root apex of the second premolars in both groups, whereas the least mean MSDs were from the mesiobuccal root apex of the second molars. The greatest mean MCDs were from the mesial root apex of the first molars, whereas the least mean MCDs were from the distal root apex of the second molars.ConclusionThere were no differences in the mean MSDs or the mean MCDs between the skeletal normal bite group and the skeletal open bite group.