Anterior occlusion in shortened dental arches

Objectives The aim of this study was to examine the occlusion of anterior teeth in individuals with shortened dental arch (SDA). Material and methods In 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. Results The 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. Conclusions The findings suggest effective compensatory mechanisms relative to the occlusal function in individuals with SDA. Clinical relevance The study delivers further evidence regarding the SDA concept as a viable option in the management of posterior tooth loss.

The Law of Minimum Vertical Dimension: Evidence for Improvement of Dental Occlusion

The law of minimum vertical dimension (MVD) states that “when the mandible moves to reach the maximum intercuspal position, this always involves bringing the mandible and maxilla as close together as possible.” Therefore, after the first occlusal contact is made, the MIP will be reached through reduction of the vertical dimension. Our objective of this study, through an integrative review of the literature review, was to determine whether ignoring this law is a factor that contributes to malocclusion, temporomandibular joint dysfunction, and recurrences of functional orthodontic and orthopedic treatments.We conducted a search of the literature in five of the main electronic scientific databases. The following medical subject heading terms were used in our search: centric relation, dental occlusion, malocclusion, vertical dimension, and mastication. We cross-referenced the descriptors in the following four groups: centric relation and maximum intercuspation; occlusal plane and malocclusion; neuro-occlusal rehabilitation; and vertical dimension and unilateral chewing. From this, we selected 277 potentially eligible articles. Out of these, 209 were excluded in accordance with the exclusion criteria already described. Thus, 65 studies were included in the qualitative synthesis.The articles were also classified according to their impact factor and degree of recommendation, in conformity with the table of the Oxford Centre for Evidence-Based Medicine. The scientific interest in the scope of the articles was also assessed by using three charts developed according to year and country of publication and the percentage of publication. Unilateral chewing creates a vicious cycle of damage that leads to an ever-increasing masticatory deficiency. Most of the articles chosen for this review confirmed that noncompliance with law of MVD was a predisposing factor in cases of relapse, in functional orthodontic and orthopedic treatments, as well as a causal factor in malocclusion and in functional and morphological TMJ dysfunctions.

Comparing occlusal contact quality after aligner and fixed appliance treatment using computerized occlusal analysis during 6 months of retention

Objective Less than ideal contacts have been reported following aligner therapy, which is believed will resolve with settling, despite settling improving occlusal balance has not been scientifically confirmed. The aim of this study was to compare the outcome quality of occlusal contacts in patients treated with fixed appliances or clear aligners. Methods 39 orthodontic patients (14 treated with aligners; 25 with fixed appliances) were evaluated with a digital occlusal analysis system (T-scan10 ™), assessing Maximum Intercuspation contact simultaneity, symmetry, and relative force distribution. The Occlusion Time, the Right/Left force percentage (%R/L), the Anterior/Posterior contact ratio (RAP), and the anteroposterior Center of Force (COF) locations were recorded at treatment completion, and 3 and 6 months after. Results No significant differences in measured occlusal contact quality parameter were found between groups at treatment completion or follow-up (OT, %R, RAP nor COF position). The COF moved posteriorly and remained stable after 3 months, near to the first molar, but was located more anterior in females (p= 0.01). 10 patients finished treatment with marked asymmetry, (%R/L > 50±10%), especially in the fixed appliance group (9/25 =3 6%) versus the aligner group (1/14 = 7%). 1/3 of all patients (both groups combined) after 6 months retention had %R/L imbalances > 50±10%. Conclusions Occlusal contacts were comparable at completion of treatment with aligners or brackets and after 3-6 months of retention. Contacts increased in the posterior region with time, but settling did not improve marked asymmetry in all patients.

Guide Flange Prosthesis with Acrylic Guidance Ramp for Management of Deviation following Segmental Mandibulectomy and Partial Maxillectomy for Gingivobuccal Mucosal Cancer: A Case Report.

Surgical resection of maxilla and /or mandible due to the presence of benign or malignant tumor is most common. Segmental resection frequently causes deviation of mandible towards the defective side and disturbances in maxillomandibular relationship. Variety of materials and techniques have been used for the construction of prosthetic replacement of acquired surgical defects. This case report describes prosthodontic management of a patient who has undergone partial maxillectomy and segmental mandibulectomy using the mandibular guide flange prosthesis with acrylic guidance ramp. This not only helps to correct the deviation but also guides the mandible for achieving occlusal contact with opposing teeth.

Determination of occlusal connections in patients with congenital cleft lip and palate before and after their orthopedic rehabilitation

The aim of this study was to define and analyze the reproducibility of occlusal relationships according to the results of occlusogram in jaw closure using quantitative analysis of occlusion in adult patients with congenital cleft lip and palate before and after their prosthesis with different versions of dentures and types of their constructive features. Materials and methods. The study was conducted on 37 patients with congenital cleft lip and palate, 11 (29.73 %) of whom had right-sided clefts, 11 (29.73 %) – left-sided and 15 (40.54 %) – bilateral. The number of occlusal contact points was measured for all patients before the treatment and after the orthopaedic rehabilitation. Research results. Significant differences were found between the number of occlusal contact points before (unusually small number) and after orthopaedic treatment (significant increase), regardless of the type of cleft (p<0.001). Such conditions in the oral cavity significantly complicate the tactics of orthopaedic rehabilitation, which affects the need to find more complex options for combinations of fixed and removable orthopaedic structures. Conclusion. Based on the conditions and objectives of this study, the application of the basic principles of a multidisciplinary approach determine the possibility of rehabilitation of such patients by orthopedic methods by making different versions of orthopedic structures. Adequate and high-quality prosthesis for defects and deformations of the teeth rows and occlusion in patients with CCLP leads to improved occlusal relationships and increase in the number of occlusal contact points.

Classification and Properties of Dental Zirconia as Implant Fixtures and Superstructures

Various types of zirconia are widely used for the fabrication of dental implant superstructures and fixtures. Zirconia–alumina composites, such as ATZ and NanoZR, are adequate for implant fixtures because they have excellent mechanical strength in spite of insufficient esthetic properties. On the other hand, yttria-stabilized zirconia has been used for implant superstructures because of sufficient esthetic properties. They are classified to 12 types with yttria content, monochromatic/polychromatic, uniform/hybrid composition, and monolayer/multilayer. Zirconia with a higher yttria content has higher translucency and lower mechanical strength. Fracture strength of superstructures strongly depends on the strength on the occlusal contact region. It suggests that adequate zirconia should be selected as the superstructure crown, depending on whether strength or esthetics is prioritized. Low temperature degradation of zirconia decreases with yttria content, but even 3Y zirconia has a sufficient durability in oral condition. Although zirconia is the hardest dental materials, zirconia restorative rarely subjects the antagonist teeth to occlusal wear when it is mirror polished. Furthermore, zirconia has less bacterial adhesion and better soft tissue adhesion when it is mirror polished. This indicates that zirconia has advantageous for implant superstructures. As implant fixtures, zirconia is required for surface modification to obtain osseointegration to bone. Various surface treatments, such as roughening, surface activation, and coating, has been developed and improved. It is concluded that an adequately selected zirconia is a suitable material as implant superstructures and fixtures because of mechanically, esthetically, and biologically excellent properties.

Tooth wear development in the Australian Aboriginal dentition from Yuendumu: A longitudinal study

The analysis of dental wear, at both the microscopic and macroscopic scale, is one of the most widely used tools in archeology and anthropology to reconstruct the diet and lifestyle of past human populations. Biomechanical studies have indicated that tooth wear helps to dissipate the mechanical load over the crown surface, thus reducing the risk of tooth fracture. To date, there are only a few studies that have examined functional tooth wear variation in modern humans. Here we propose to study masticatory efficiency through the use of the Occlusal Fingerprint Analysis method, a well-developed digital approach that allows the reconstruction of the occlusal dynamics occurring during mastication. The aim of this study is to provide the first longitudinal quantitative data of molar and premolar macrowear patterns within a functional context. We examined the mixed and permanent dentition of one Australian Aboriginal child (from ages 8 to 17) from Yuendumu, using high-resolution surface scans of dental casts including both upper and lower arches. Our results suggest that the occlusal macrowear patterns of this individual did not significantly change through time. Occlusal contact parameters such as functional area, inclination and direction remain relatively unaltered throughout childhood and adolescence, indicating little change in the masticatory function of this individual. The functional tooth wear pattern in this individual did not change longitudinally indicating the degree of masticatory efficiency has most probably remained unaltered.