Occlusal interference during mastication can cause pathological tooth mobility

Trueness of Maxillomandibular Relationship in 3D-printed and Conventional Casts

OBJECTIVES

To compare the trueness of maxillomandibular relationship between articulated 3D-printed and conventional diagnostic casts in maximum intercuspation (MIP).

METHODS

Reference casts were articulated in MIP, and scanned using a Coordinate Measurement Machine (CMM, n=1). Digital scans were made from the reference casts by using an intraoral scanner (IOS, n=10) (Trios 4; 3Shape A/S). IOS scans were processed to create 3D-printed casts by using MAX UV385 (Asiga) and NextDent 5100 (3DSystems) 3D-printers. The conventional workflow implemented vinylpolysiloxane (VPS) impressions and Type IV stone. Stone and 3D-printed casts were articulated and digitized with a laboratory scanner (E4; 3Shape A/S). The 3D-printed casts were scanned on two occasions: with and without positioning pins. Inter-arch distances and 3D-contact area were measured and compared. Statistical tests used were Shapiro-Wilk, Levene's, Welch's t-test, and 2-way ANOVA (α=.05).

RESULTS

IOS group showed similar or better maxillomandibular relationship trueness than stone casts and 3D-printed casts (p<0.05). 3D-contact area analysis showed similar deviations between 3D-printed and stone casts (p>0.05). The choice of 3D-printer and presence of positioning pins on the casts significantly influenced maxillomandibular relationship trueness (p<0.05).

CONCLUSIONS

Articulated 3D-printed and stone casts exhibited similar maxillomandibular relationship trueness.

CLINICAL SIGNIFICANCE

Although 3D-printing methods can introduce a considerable amount of deviations, the maxillomandibular relationship trueness of articulated 3D-printed and stone casts in MIP can be considered similar.

Quantitative evaluation of the proximal contact area gap change characterization under intercuspal occlusion by intraoral 3D scanning: Food impaction with tight proximal contact

OBJECTIVE

This study aimed to present three indicators that represent the proximal contact area gap change under intercuspal occlusion and to see if and how these indicators influence food impaction with tight proximal contact.

MATERIALS AND METHODS

Ninety volunteers were recruited for bite force measurement and intraoral scanning. Three-dimensional surface data and buccal bite data were obtained for 60 impacted and 60 non-impacted teeth. The scanning data were imported into the Geomagic Studio 2013 to measure three indicators, which included the gap change maximum (Δdm, μm), the buccolingual position of Δdm (P), and the gap expanded buccolingual range (S, mm). The difference between two groups of three indicators and their relationship with food impaction with tight proximal contact were analyzed by the t test, the Pearson chi-squared test, the nonparametric Mann-Whitney U test, and the binary logistic regression analysis (a = 0.05).

RESULTS

All indicators (Δdm, P, and S) were statistically different (p < 0.001, p = 0.002, and p < 0.001) in the impacted and non-impacted groups. Food impaction with tight proximal contact was affected by Δdm and S (p < 0.001, p = 0.039), but not by P (p = 0.409).

CONCLUSION

The excessive increase of the gap change maximum and the gap expanded buccolingual range under bite force promoted the occurrence of food impaction with tight proximal contact.

CLINICAL SIGNIFICANCE

The use of intraoral scanning to measure the characteristics of the proximal contact area gap change under bite force may help to deepen our understanding of the pathogenesis of food impaction with tight proximal contact. Importantly it can provide a reference basis for individualizing and quantifying occlusal adjustment treatment.

Effect of artificial eccentric occlusal interferences on masticatory performance: A randomised double-blind clinical trial

BACKGROUND

Occlusal interferences lead to changes in mandibular kinematics to compensate and improve function. However, the effects of different types of eccentric disturbance on the comminution capacity are not known.

OBJECTIVE

To determine the immediate effect of eccentric occlusal interferences on masticatory performance.

METHODS

This crossover clinical trial included 12 healthy dentate subjects aged 25.2 ± 3.3 years who were randomly submitted to seven types of occlusal interference: unilateral and bilateral laterotrusive and mediotrusive, protrusive, dummy and control (no interference). The interference forms were planned in a semi-adjustable articulator, fabricated with composite resin and adhered to the mandibular first molars such that subjects' maximum intercuspation was maintained. Masticatory performance and the chewing rate during 20 cycles were evaluated during subjects' comminution of silicone test food under one interference condition per test day; the multiple sieve method was applied to the comminuted particles. The interference was removed upon test completion, and a 1-week washout period was applied between tests.

RESULTS

Comminuted median particle sizes were larger under unilateral (4.94 ± 0.41 mm) and bilateral (4.81 ± 0.49 mm) laterotrusive, bilateral mediotrusive (4.65 ± 0.50 mm) and protrusive (4.83 ± 0.54 mm) interferences (p < .05) than under the control (4.01 ± 0.52 mm) and dummy (4.18 ± 0.58 mm) conditions (p < .05). Only unilateral and bilateral laterotrusive interferences narrowed the comminuted particle size dispersion (p < .05). The chewing rate did not differ among conditions (p = .1944).

CONCLUSION

Artificial eccentric interferences had an immediate adverse effect on masticatory performance by resulting in larger comminuted particles.

CLINICAL TRIAL REGISTRATION

Brazilian Registry of Clinical Trials (RBR-8g5zfg8).

Revised FDI criteria for evaluating direct and indirect dental restorations-recommendations for its clinical use, interpretation, and reporting

OBJECTIVES

The FDI criteria for the evaluation of direct and indirect dental restorations were first published in 2007 and updated in 2010. Meanwhile, their scientific use increased steadily, but several questions from users justified some clarification and improvement of the living document.

MATERIALS AND METHODS

An expert panel (N = 10) initiated the revision and consensus process that included a kick-off workshop and multiple online meetings by using the Delphi method. During and after each round of discussion, all opinions were collected, and the aggregated summary was presented to the experts aiming to adjust the wording of the criteria as precisely as possible. Finally, the expert panel agreed on the revision.

RESULTS

Some categories were redefined, ambiguities were cleared, and the descriptions of all scores were harmonized to cross-link different clinical situations with possible management strategies: reviewing/monitoring (score 1-4), refurbishment/reseal (score 3), repair (score 4), and replacement (score 5). Functional properties (domain F: fracture of material and retention, marginal adaptation, proximal contact, form and contour, occlusion and wear) were now placed at the beginning followed by biological (domain B: caries at restoration margin, hard tissue defects, postoperative hypersensitivity) and aesthetic characteristics (domain A: surface luster and texture, marginal staining, color match).

CONCLUSION

The most frequently used eleven categories of the FDI criteria set were revised for better understanding and handling.

CLINICAL RELEVANCE

The improved description and structuring of the criteria may help to standardize the evaluation of direct and indirect restorations and may enhance their acceptance by researchers, teachers, and dental practitioners.

Occlusal Indicators Used in Dental Practice: A Survey Study

Introduction

The function of the masticatory apparatus is complete when the dentition is intact with contact between the individual teeth and proper occlusion with the antagonists. For years, occlusal contacts have been studied to determine their exact location and describing various materials and methods for their registration such as paper foil, silk, and Shimstock foil. For years, occlusal contacts have been studied to determine their exact location and describe various materials and methods for their registration such as paper foil, silk, shim stock foil, the T-Scan system, and more recently the OccluSense system. The primary aim of the study was at evaluating which of the occlusal indicators is the most commonly used in practice, and the secondary aim was whether dentists are willing to use digital methods to examine occlusion.

Materials and Methods

The main primary information of the survey was collected by sending electronically anonymous questionnaires to 2014 dentists, randomly selected from all regions of the country. 228 questionnaires were filled in and returned. To achieve the goal of the study, the self-developed questionnaire was created and tested to survey the opinion about the use of occlusal indicators in dental practice. Each questionnaire contains questions about the sociodemographic and professional status of the people in the group and their opinion about the positives and negatives and the effectiveness of occlusal indicators.

Results

The obtained results confirm the statement that the most frequently used occlusal indicator in dental practice is the articulation paper. Articulation foil and silk are used less frequently than articulation paper. Of the listed quality indicators, Shimstock foil is rarely used in practice. Of the indicated quantitative indicators, the T-Scan system is more used than the OccluSense system. In the era of rapid technology development, the opinion and desire of dentists to increasingly want to introduce in their clinical practice quantitative methods are the digital diagnosis of occlusion.

Conclusion

In any dental practice, if technically possible, digital methods would be used, giving more accurate and reliable data on the registered occlusal contacts.

Comparison of Two Generations of Systems for Digital Occlusion Examination

BACKGROUND: The modern concept of occlusion includes the relationship between teeth, masticatory muscles, and temporomandibular joints in function and dysfunction. Occlusion can be defined very simply: it means the contacts between teeth. Qualitative and quantitative methods are used to register and evaluate occlusal contacts. The T-Scan handpiece model was updated in 2015 as T-Scan Novus (software version 9.1) and the latest updated one being the T-Scan version 10 software introduced in 2018. AIM: The purpose of this study is to demonstrate the capabilities and results of two generations of systems - T-Scan III and T-Scan Novus. MATERIALS AND METHODS: For the realization of the set goal, the occlusion of a patient with the initials S.K. is examined with two systems. The patient is 43 years old with intact teeth, Angle’s class I jaw relation. The study with T-Scan III was conducted in 2015 and with T-Scan Novus in 2019. RESULTS: The software of both systems uses a graphical interface, which transforms the data obtained during the recording of the occlusion as the model of the upper dentition of the patient in T-Scan III and the upper and lower dentition in T-Scan Novus. Registered occlusal contacts are illustrated as 2D and 3D images of different colors. The graph force/time shows the power versus time from the first contact to the end of the movie. The timing table displays the patient’s total occlusal bite timing, and the force applied. T-Scan Novus software allows you to import digital fingerprint files of the upper and lower dentition in.stl format. CONCLUSION: The software program of the system version 9.1 provides better visualization of dental arches making it much more informative than other versions. The T-Scan system allows fast and accurate registration and analysis of occlusion.

Comparison of two computerized occlusal analysis systems for indicating occlusal contacts

PURPOSE

The purpose of this study was to compare the performance of Accura to that of the T-scan for indicating occlusal contacts.

MATERIALS AND METHODS

Twenty-four subjects were selected. Their maxillary dental casts were scanned with a model scanner. The Stereolithography files of the casts were positioned to align with the occlusal plane. Occlusal surfaces of every tooth were divided into three to six anatomic regions. T-scan and Accura recordings were made during two masticatory cycles. The T-scan and Accura images were captured at the maximum bite force and overlapped to the cast. Photographs of interocclusal records were used as the reference during overlap. The occlusal contacts were counted to compare the T-scan and Accura. McNemar's test was used for statistical significance and the corresponding P-values were calculated from a chi-square distribution with one degree of freedom. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Accura were calculated relative to the T-scan values as a control.

RESULTS

No statistical differences (P>.05) were found between the T-scan and Accura methods. The accuracy of Accura was 75.8%, sensitivity was 82.1%, specificity was 60.1%, PPV was 82.9%, and NPV was 60.1%.

CONCLUSION

Accura could be another possible option as a computerized occlusal analysis system for indicating occlusal contacts at maximum intercuspation.

Wear and damage at the bonded interface between tooth enamel and resin composite

OBJECTIVE

To investigate the wear mechanisms and evolution of damage in tooth enamel-resin composite bonded interfaces caused by sliding contact, and to develop an understanding of interface degradation from a tribological viewpoint that supports clinical recommendations for improving interface integrity.

METHODS

Reciprocating wear tests were performed on bonded interface samples involving commercial resin composite (Tetric N Ceram Bulk Fill), resin cement (Rely X U200) and tooth enamel using the ball-on-flat configuration. The bonded samples were subjected up to 5 × 10⁴ cycles of sliding contact, and the wear depth and wear track morphology were characterized after increments using white light interferometry and scanning electron microscopy, respectively. Optical microscopy was also used to evaluate cracks and their propagation in the samples.

RESULTS

In the early stages of sliding contact, wear evolved most rapidly at the interface, followed by the enamel and the resin composite. Gradually, the difference between the wear depth at the interface and other areas decreased. Furthermore, cracks and brittle fracture appeared in the enamel during the early stages of wear, adjacent to the interface. With continuing cyclic loading, enamel wear manifested primarily as ploughs, with discontinuous pits and peeled material. Cracking decreased to only a few cracks extending to the inner enamel and parallel to the interface.

CONCLUSIONS

Cracking and damage occurred in the enamel during the early stages of sliding contact and accelerated by poor margin finishing. Cracks caused by wear under sliding contact could be one of the reasons for secondary caries and tooth discoloration.

Association between dental implants in the posterior region and traumatic occlusion in the adjacent premolars: a long-term follow-up clinical and radiographic analysis

Purpose

The aim of this retrospective study was to determine the association between dental implants in the posterior region and traumatic occlusion in the adjacent premolars, using data collected during from 2002 to 2015.

Methods

Traumatic occlusion in the adjacent premolars was assessed by examining clinical parameters (bleeding on probing, probing pocket depth, fremitus, and tooth mobility) and radiographic parameters (loss of supporting bone and widening of the periodontal ligament space) over a mean follow-up of 5 years. Clinical factors (gender, age, implant type, maxillary or mandibular position, opposing teeth, and duration of functional loading) were evaluated statistically in order to characterize the relationship between implants in the posterior region and traumatic occlusion in the adjacent premolars.

Results

The study inclusion criteria were met by 283 patients, who had received 347 implants in the posterior region. The incidence of traumatic occlusion in the adjacent premolars was significantly higher for splinted implants (P=0.004), implants in the maxillary region (P<0.001), and when implants were present in the opposing teeth (P<0.001). The other clinical factors of gender, age, and duration of functional loading were not significantly associated with traumatic occlusion.

Conclusions

This study found that the risk of traumatic occlusion in the adjacent premolars increased when splinted implants were placed in the maxillary molar region and when the teeth opposing an implant also contained implants.

Occlusal adjustment associated with periodontal therapy--a systematic review

OBJECTIVES

Occlusal adjustment as part of periodontal therapy has been controversial for years, mostly because the literature does not provide enough evidence regarding the influence of trauma from occlusion (TfO) on periodontitis. The need for occlusal adjustment in periodontal therapy is considered uncertain and requires investigation. The aim of this systematic review was to identify and analyse those studies that investigated the effects of occlusal adjustment, associated with periodontal therapy, on periodontal parameters.

DATA

A protocol was developed that included all aspects of a systematic review: search strategy, selection criteria, selection methods, data collection and data extraction.

SOURCES

A literature search was conducted using MEDLINE via PubMed, the Cochrane Central Register of Controlled Trials, and EMBASE.

STUDY SELECTION

Three reviewers screened the titles and abstracts of articles according to the established criteria. Every article that indicated a possible match, or could not be excluded based on the information given in the title or abstract, was considered and evaluated. On final selection, four articles were included.

CONCLUSIONS

Although the selected studies suggest an association between occlusal adjustment and an improvement in periodontal parameters, their methodological issues (explored in this review) suggest the need for new trials of a higher quality. There is insufficient evidence at present to presume that occlusal adjustment is necessary to reduce the progression of periodontal disease.

CLINICAL SIGNIFICANCE

Although it is still not possible to determine the role of occlusal adjustment in periodontal treatment, adverse effects have not been related to occlusal adjustment. This means that the decision made by clinicians whether or not to use occlusal adjustment in conjunction with periodontal therapy hinges upon clinical evaluation, patient comfort, and tooth function.

Morphofunctional aspects of dental implants

Although oral implantology is among the most beneficial developments of modern dentistry, the widely spread opinion that the long-term outcome of implants is superior to that of natural teeth has been refuted. To evade uncritical extractions, the morphofunctional properties of natural teeth and implant-supported restorations are compared from a proprioceptive and occlusal trauma perspective. The periodontal ligament of natural teeth provides the central nerve system with feedback for sensory perception and motor control. Conversely, the lack of such proprioception causes lower tactile sensitivity and less coordinated masticatory muscle activity in implant-borne restorations and makes them more prone to occlusal overload and possible subsequent failure. Moreover, occlusal anomalies may be conducive to parafunctional activity, craniomandibular disorder, tinnitus, and headache. Oral implantology, therefore, has to take appropriate account of occlusal conditions and the biomechanical and neuromuscular aspects of masticatory function.

The effect of experimental occlusal interferences on nerve growth factor levels in periodontal tissues

OBJECTIVE

To test the hypothesis that experimental occlusal interferences increase the nerve growth factor (NGF) levels in periodontal tissues and cause an up-regulation of preprotachykinin-A (PPTA) mRNA.

BACKGROUND

NGF is related to hyperalgesia and inflammation. PPTA mRNA, a primer of substance P, is a possible factor in the aetiology of pain.

METHODS

Experimental interferences were created by placing inlays in the right maxillary molars of 15 dogs. The right side molars formed the experimental group. The left side molars served as controls. Three dogs with cavities prepared without changing the occlusion formed a sham group. The dogs in the first group were sacrificed, 3 at each time, after 3, 7, 14, 30, and 60 days. The sham group was sacrificed after 14 days. The levels of NGF in periodontal tissues and PPTA mRNA in the trigeminal ganglions were detected by ELISA and TR-PCR. Comparisons were made with paired t-tests and a multivariate MANOVA test.

RESULTS

On all measurement days, there were higher levels of NGF mRNA, PPTA mRNA, and NGF on the experimental than on the control side in 14 of 15 comparisons and in the sham group. NGF production in periodontium was time-dependent. No differences in NGF protein levels were observed between the control and the sham groups.

CONCLUSION

The results which need confirmation in further tests are of clinical interest. They indicate that occlusal experimental interferences may be an etiologic factor in oral facial pain by increasing mRNA and NGF protein levels in the periodontal tissues.

Stomatognathic adaptive motor syndrome is the correct diagnosis for temporomandibular disorders

Temporomandibular disorder is a generic and inadequate conception to be used as a diagnosis. It fails to express the etiology or the pathophysiology and it is mainly associated with the anatomical site. Moreover, the clinical condition presents a mandibular motor problem and not a joint problem. The hypothesis presents the new diagnosis stomatognathic motor adaptive syndrome, which comprehend a motor response and the adaptive processes it induces. Inadequate occlusal contacts cause the mandible to shift in order to reach an ideal intercuspal position. The condylar displacements are proportional to such movements. Temporomandibular joint (TMJ) receptors respond to the capsular mechanical stress and the information reaches the trigeminal sensory nuclei. The mandibular modified position seems to be relevant information and may interfere with catecholaminergic neurotransmission in basal ganglia. The main motor responses comprise increased jaw muscle tone, decreased velocity of movements and incoordination. The overload of muscle function will produce adaptive responses on many stomatognathic structures. The muscle adaptive responses are hypertonia, pain, fatigue and weakness. Temporomandibular joint presents tissue modification, disc alteration and cracking noise. Periodontium show increased periodontal membrane, bone height loss and gingival recession. Teeth manifest increased wear facets, abfraction and non-accidental fractures. The periodontal and teeth adaptive processes are usually identified as occlusal trauma. The altered stomatognathic functions will show loss of velocity during mastication and speech. Fatigue, weakness in jaw muscle and difficulties to chew hard food are related to hypertonia. Incoordination between stomatognathic muscles groups is found, causing involuntary tongue/cheek biting and lateral jaw movements on speech. Otologic complaints, as aural fullness and tinnitus, are related to the tensor tympani muscle, innervated by the trigeminal nerve.