Occlusal stability

Centric relation: A needed reference position

PURPOSE

Centric Relation (CR) is a universally recognized term and an acceptable reference position with a long history of success. The problem is that there is little consensus as to its definition or the method of recording it, and this has created an uprising to abolish it.

METHODS

A review of pertinent literature related to its definition, method of recording, anatomic considerations and long-standing principles was conducted.

RESULTS

CR is an established term but there are valid concerns over its definition and method of recording. There is consensus on using it as a restorative position in a patient in need of full arch reconstruction and there is no substantive clinical research to contradict this. If a clinician decides to use a different position, it should have a different name.

CONCLUSIONS

CR is a reproducible reference position that can be utilized for diagnostic and restorative dental procedures with substantial scientific evidence to support that premise. There are numerous well documented techniques, all of which are intermaxillary, that can replicate the position. There is little scientific evidence to support a premise as to where the exact position of the condyle should be in relation to the fossa. This article is protected by copyright. All rights reserved.

Masticatory performance is influenced by masticatory muscle activity balance and the cumulative occlusal contact area

OBJECTIVE

To investigate the influence of masticatory muscle activity balance, occlusal contact area balance and the area of occlusal contact on masticatory performance in healthy dentate adults.

DESIGN

This cross-sectional study included ninety-three healthy subjects with complete dentition. Surface electromyography (sEMG) was used to record bilateral anterior temporalis activity and masseter muscle activity during maximum voluntary clenching and while chewing a test food. Seven levels of area of occlusal contact and near contact (ACNC) were registered and calculated cumulatively. The percentage overlapping coefficients were calculated for both muscle groups at maximum voluntary clenching and chewing and all levels of ACNC. Masticatory performance was measured by determining the median particle size of frankfurter sausage after 15 chewing cycles. Pearson's correlation and stepwise multiple linear regression analyses were used to assess the correlations between variables and the influence of the variables on masticatory performance, respectively, at the 0.05 level of significance.

RESULTS

Muscle balance during clenching and chewing, all near contact levels of cumulative ACNC and ACNC balance correlated negatively with median particle size (P <  0.05). The model based on stepwise multiple linear regression analysis showed muscle balance during clenching and cumulative ACNC at < 250 μm influenced median particle size.

CONCLUSION

Masticatory muscle activity balance during maximum voluntary clenching and the cumulative amount of near contact area were associated with masticatory performance, suggesting the amount of occlusal contact area-as well the balance of masticatory muscle activity-play a role in masticatory performance.

Managing Excessive Gingival Display Using a Digital Workflow

This technique article describes an approach to managing excessive gingival display by lengthening of the clinical crowns using a digital workflow. An intraoral scanner was used to obtain a template to be used for the crown lengthening surgical procedure considering the patient-desired diagnostic setups while fully seating the template on the patient's teeth during surgery. Using a digital approach for lengthening the clinical crowns decreased the likelihood of the need for postsurgical modifications, thus shortening the treatment duration. After the crown lengthening healed for 12 weeks, full-mouth reconstruction proceeded. Maxillary and mandibular preparation reduction guides were digitally designed and printed to facilitate conservative crown preparations. An intraoral scanner was used to make full-arch scans and interocclusal records for the fabrication of provisional and final crowns. Fully guided implant planning and placement were also executed.

Association of Non-Carious Cervical Lesions with Oral Hygiene Habits and Dynamic Occlusal Parameters

Dentists routinely encounter non-carious cervical lesions (NCCLs) in daily clinical practices. The dental literature is contradictory regarding the occlusal etiology of NCCLs. NCCL is defined as the loss of dental structure at the cemento-enamel junction, with no association of bacteria. The aim of this study was to evaluate the association of dynamic occlusal factors and dental hygiene practices with NCCLs. In total, 100 participants were selected by the random stratified sampling method, 50 each for control and NCCL groups. Information regarding oral hygiene practices, including frequency, duration, force, and technique of brushing, was recorded. Dynamic occlusal parameters like initial contact, occlusion time (OT), disocclusion time (DT), and center of force were recorded with T-scan analysis. The obtained data were analyzed with Pearson's correlation and binary logistic regression. We found that 68% of participants in the NCCL group and 31% in the control group utilized the horizontal brushing technique; 46% of NCCL group participants used hard brush against 7% of participants in the control group. The mean OT was 0.727 and 0.516 s for NCCL and control groups, respectively. The OT and left and right lateral DT were strongly related to NCCL, with r-values of 0.661, 0.642, and 0.534, respectively, with p ≤ 0.001. Using a hard toothbrush was found to be associated with NCCL. The NCCL group had extended mean occlusion time and disocclusion time in all eccentric mandibular movements.

Temporomandibular Disorders: "Occlusion" Matters!

By analogy with the journal's title Pain Research and Management, this review describes TMD Research and Management. More specific are the (1) research aspects of “occlusion,” still one of the most controversial topics in TMD, and (2) as much as possible evidence-based management aspects of “TMD” for the dental practitioner. Research. The disorders temporomandibular dysfunction and the synonymous craniomandibular dysfunction are still being discussed intensely in the literature. Traditionally, attention is mostly devoted to occlusion and its relationship with these disorders. The conclusions reached are often contradictory. Considering the definitions of temporomandibular and craniomandibular dysfunctions/disorders and “occlusion,” a possible explanation for this controversy can be found in the subsequent methodological problems of the studies. Based on a Medline search of these terms over the past 40 years related to contemporary terms such as “Evidence Based Dentistry” and “Pyramid of Evidence,” these methodological aspects are examined, resulting in recommendations for future research and TMD-occlusal therapy. Management. To assist the dental practitioner in his/her daily routine to meet the modern standards of best practice, 7 guidelines are formulated that are explained and accompanied with clinical examples for an evidence-based treatment of patients with this disorder in general dental practices.