Occlusal equilibration and muscle activity in fixed versus removable mandibular implant supported overdenture.

OBJECTIVES: Single denture rehabilitated patients have negative appraisals regarding oral function, mostly associated by stability and retention issues regarding mandibular prosthetics. Therefore, this study assessed patients' occlusal equilibration, muscle activity, and oral health-related quality of life (OHRQoL) receiving milled removable or fixed mandibular implant retained prostheses. MATERIALS AND METHODS: Twenty-two edentulous mandibular ridges patients were randomly distributed into two groups based on the definitive prosthesis received. Group I: Removable mandibular implant-supported overdenture, Group II: Implant retained fixed prosthesis. Occlusal equilibration was evaluated utilizing Occlusense, muscle activity via Electromyograph (EMG) at delivery, after one, and three months. The OHRQoL was evaluated by Oral Health Impact Profile questionnaire (OHIP-19) before delivery and after follow-ups. Data were collected, tabulated, and analyzed, utilizing independent t-test and One-way ANOVA followed Tukey`s post-hoc test. Significance level set at P ≤ 0.05. RESULTS: Groups I &II showed significant improvement in occlusal equilibration, muscle activity and OHRQoL. Group II demonstrated significantly higher improvement than group I in occlusal equilibration associated with muscle activity after 1 month, and in functional limitations domain in OHRQoL questionnaire after 3 months. CONCLUSION: Implant retained mandibular prosthesis showed improvement in occlusal equilibration, muscle activity, and OHRQoL regardless of prosthesis type employed. Fixed implant-supported prosthesis revealed better outcomes than removable mandibular implant-supported overdenture concerning occlusal equilibration, muscle activity, and OHRQoL regarding functional limitations. CLINICAL RELEVANCE: Implant retained mandibular prosthesis is one of best treatment options for single mandibular completely edentulous patients, as dental implants improved occlusal equilibration, muscle activity, and OHRQoL.

[Rehabilitation of complete edentulism and temporomandibular joint].

Rehabilitation of complete edentulism is naturally related to temporomandibular joint (TMJ) since the proper functioning of complete denture depends on the normal movement of TMJ. This review briefly introduced the design of occlusion in complete denture, characteristic of different occlusal patterns, and key points in registration of maxillomandibular relationship and occlusal adjustment. This review emphasized the significance of complete denture restoration to the health of TMJ.

Finite Element Analysis of Occlusal Interferences in Dental Prosthetics Caused by Occlusal Adjustment.

PURPOSE: To investigate the influence of occlusal interference using finite element analysis (FEA). MATERIALS AND METHODS: The FEA model designed for this study centered on an all-ceramic, bilayered, fixed partial denture (FPD) retained on the maxillary first premolar and first molar, with the second premolar replaced by a pontic. The surrounding structures-such as the neighboring teeth, antagonists, and periodontium-were modeled. Four different loading cases were designed at occlusal interferences of 0, 8, 12, and 24 µm and were loaded by a simulated bite force of 300 N. Principal and von Mises stresses, as well as strain, were evaluated for all included structures. RESULTS: For interferences of 12 and 24 µm, failure-relevant tensile stresses in the veneering layer were observed at the occlusal surfaces. Stress found in the zirconia FPD did not reach fatigue or flexural strength for any test load. CONCLUSION: Peak tensile stress was observed in close proximity to occlusal contact points, increasing with increasing occlusal interference. The FEA results suggest that the majority of occlusal stress is absorbed by the deformation of the periodontal ligament. Framework failure caused by the simulated interferences was not expected. Surface defects may ultimately lead to failure due to fracture or chipping, especially in cases of weaker ceramics or veneering.

CAD-CAM and analog occlusal splints comparison based on the amount of occlusal adjustments. 3D analysis of the volumetric changes: A pilot study.

OBJECTIVE: To evaluate the volumetric changes on occlusal surface of computer-aided design and computer-aided manufacturing (CAD-CAM) occlusal devices fabricated following a fully digital workflow after occlusal adjustment, compared to those fabricated with an analog workflow. MATERIALS AND METHODS: Eight participants were included in this clinical pilot study, receiving two different occlusal devices fabricated with two different workflows, fully analog and fully digital. Every occlusal device was scanned before and after the occlusal adjustments to compare the volumetric changes using a reverse engineering software program. Moreover, three independent evaluators assessed a semi-quantitative and qualitative comparison using visual analog scale and dichotomous evaluation. The Shapiro-Wilk test was performed to validate normal distribution assumption, and a dependent t-Student test for paired variables was used to determine statistically significant differences (p-value < 0.05). RESULTS: The root mean square value was extracted from the 3-Dimensional (3D) analysis of the occlusal devices. The average values of the root mean square were higher for the analogic technique (0.23 ± 0.10 mm) than the digital technique (0.14 ± 0.07 mm) but the differences were not statistically significant (paired t-Student test; p = 0.106) between the two fabrication techniques. The semiquantitative visual analog scale values between the impression for the digital (5.08 ± 2.4 cm) and analog (3.80 ± 3.3 cm) technique were significant (p < 0.001), and statistically significant differences values were assessed for evaluator 3 compared to the other evaluators (p < 0.05). However, the three evaluators agreed on the qualitative dichotomous evaluation in 62% of the cases, and at least two evaluators agreed in 100% of the evaluations. CONCLUSIONS: Occlusal devices fabricated following a fully digital workflow resulted in fewer occlusal adjustments, as they could be a valid alternative to those fabricated following an analog workflow. CLINICAL SIGNIFICANCE: Fabricated occlusal devices following a fully digital workflow could have some advantages over analog workflow such reduce occlusal adjustments at delivery appointment, which can result in reduced chair time and therefore increased comfort for the patient and clinician.

A comparative study based on the mandibular movement track and the movement parameters of the virtual articulator in simulating occlusal adjustment.

OBJECTIVES: This study aimed to compare the effects of virtual adjustment on occlusal interferences in mandibular posterior single crown and three-unit bridge restorations by using the mandibular movement track and the movement parameters of a virtual articulator. METHODS: Twenty-two participants were recruited. Digital casts of the maxillary and mandibular arches were obtained using an intraoral scanner, and the jaw registration system was used to record the data of the mandibular movement track and the movement parameters of the articulator. Four kinds of restorations with 0.3 mm occlusal interferences were designed with dental design software. In particular, single crowns were designed for teeth 44 and 46, whereas three-unit bridges were designed for teeth 44-46 and 45-47, and the corresponding natural teeth were virtually extracted. Virtual adjustment of the restorations was performed using two dynamic occlusal recordings, namely, the mandibular movement track and the movement parameters of the virtual articulator. A reverse-engineering software was used to measure the root-mean-square of the three-dimensional deviation of the occlusal surfaces between natural teeth and the adjusted restorations. The differences between the two methods of virtual-occlusion adjustment were compared and analyzed. RESULTS: For the same group of restorations, the three-dimensional deviation of the mandibular movement track group were lower than those of the virtual articulator group, and the differences were statistically significant (P<0.05). For the four groups of restorations adjusted by the same method, the three-dimensional deviation of the 46-tooth single crown was the largest and the smallest three-dimensional deviation was that of the 44-tooth single crown. Statistical differences existed between the 44-tooth single crown and the other groups (P<0.05). CONCLUSIONS: For the occlusal design of posterior single crown and three-unit bridge, the mandibular movement track could be a more effective approach to virtual occlusal adjustment than the movement parameters of the virtual articulator.

[Effects of three sequential occlusal adjustment methods by articulating papers on the characteristics of implant delayed occlusion for single molar].

PURPOSE: To compare the effects of three occlusal adjustment methods in different sequences by articulating paper on the delayed occlusal characteristics of single molars. METHODS: Thirty-two implants of first molars were divided into group A(n=12), group B (n=12) and group C (n=12) by sequential adjustment according to random number means, and (100+40), (100+50+30) and (100+40+20) µm sequence occlusal papers were used for occlusal adjustment, respectively. TeeTester was used to measure the delay time and force ratio between prosthesis and adjacent teeth at restoration day, 3 and 6 months after restoration, and to record the number of cases readjusting in each group during follow-up. SPSS 25.0 software package was used for data analysis. RESULTS: There were significant differences in delay time between groups at restoration day (P＜0.05), and 3 and 6 months after restoration, delay time of group C was still smaller than that of group A and B (P＜0.05). During follow-up, the time of each group showed a trend of shortening (P＜0.05), but there was still delayed occlusion. Compared with group B and C, the force ratio in group A was lower at each time(P＜0.05). The ratio of each group showed an increasing trend during follow-up (P＜0.05), and group C showed the largest increase (P＜0.001). The number of cases readjusting was relatively small in group A, and the most was in group C(P＜0.05). There was positive correlation between delay time and force difference of prosthesis and adjacent teeth(P＜0.001). CONCLUSIONS: The (100+40) µm sequence group had higher occlusal stability and better clinical applicability. The smaller the occlusal contact space realized by the sequential method, the greater the change might be, which requires close follow-up in clinical practice.

Maxillary occlusal device designed with an anterior platform for guiding the occlusal adjustments during the delivery appointment: A dental protocol.

OBJECTIVE: To describe a technique for fabricating an additively manufactured maxillary occlusal device using a complete digital workflow. CLINICAL CONSIDERATIONS: The maxillary occlusal device design may include an anterior platform to guide the positioning of the mandible in a reproducible position for facilitating the delivery procedure. CONCLUSIONS: The described technique provides a more efficient and less time-consuming method for designing and manufacturing a printed occlusal device, when compared with conventional fabrication techniques. CLINICAL SIGNIFICANCE: The additively manufactured occlusal device designed with an anterior platform guides the positioning of the mandible in a reproducible position, facilitates the delivery procedures, and produces a more efficient and less time-consuming method when compared with conventional methods.

Effect of occlusal equilibration on masticatory muscle activity in females with sleep bruxism: a double-blind randomised controlled trial.

Masticatory muscle activity during sleep has been considered independent of variations in the structural characteristics of the dental occlusion. However, scientific evidence contradicting an occlusal causal role is missing. The purpose of this study was to test the null hypothesis that sleep bruxism (SB) is independent of the presence of occlusal interferences. A total of 17 healthy female subjects (mean [SD] age 24.9 [4.1] years) presenting with SB, and randomly divided into two groups, were evaluated after receiving either elimination of occlusal interferences (Test group) or elimination of sharp margins without change in occlusal contacts (Control group). Audio-video polysomnography (PSG) recordings were undertaken before and after treatment (mean [SD] duration 14.4 [3.8] months). Two subjects in each group (< 2 rhythmic masticatory muscle activity [RMMA]/h) were excluded for statistical analysis. During the total sleep time (TST), the Test group exhibited a higher reduction in frequency of episodes per hour than the Control group (p < 0.05). The reduction in duration of episodes was also higher in the Test group during the TST. The Test group presented an increase in sleep stage N3 (p < 0.05) at the final PSG when compared with the initial PSG, and a higher percentage of N3 (p < 0.05) at the final PSG when compared to the Control group. Elimination of occlusal interferences resulted in a significant reduction of masseter and temporal muscle activity during sleep in females presenting with SB. Based on these results, the null hypothesis is rejected. The hypothesis of occlusal interferences as a risk factor for SB is still patent.

[Study on mandibular movement trajectory and virtual occlusal pre-adjustment under light and heavy bite force].

Objective: To investigate the influence of light and heavy bite force on the mandibular movement trajectories, and the influence of bite force on virtual occlusal pre-adjustment of digital full crown. Methods: From October 2021 to March 2022, 10 postgraduate volunteers (3 males and 7 females, aged 22-26 years) were recruited from Peking University School and Hospital of Stomatology. Maxillary and mandibular digital models of the participants were obtained by intraoral scanning. Jaw relations were digitally transferred under heavy bite force and mandibular movement trajectories under light and heavy bite force were recorded by jaw motion analyser. Three mandibular markers were chosen, namely the mesial proximal contact point of the central incisor (incisal point) and the mesial buccal cusp tips of the bilateral first molars. The three-dimensional displacements of the markers under two kinds of bite force in the intercuspal position (ICP), the sagittal projection of the three-dimensional displacements in the protrusive edge-to-edge position, and the coronal projection of the three-dimensional displacements in the lateral edge-to-edge position of upper and lower posterior teeth were measured. Single-sample t-test was used to compare the three-dimensional displacements and the corresponding sagittal projection and coronal projection with 0, respectively. The left maxillary central incisor and left mandibular first molar were virtually prepared by the reverse engineering software. Then dental design software was used to design digital full crown using the copy method. The mandibular movement trajectories under light and heavy bite force were separately used to guide virtual occlusal pre-adjustment. The three-dimensional deviations (mean deviations and root mean square) between the lingual surface of the left maxillary central incisor or the occlusal surface of the left mandibular first molar and that of the natural tooth before preparation were calculated (light bite force group and heavy bite force group), and the differences between the two groups were compared by the paired t-test. Results: Under the two kinds of bite force, the three-dimensional displacements of the markers in the ICP were (0.217±0.135), (0.210±0.133) and (0.237±0.101) mm, respectively; the sagittal projection of the three-dimensional displacements of the markers in the protrusive edge-to-edge position were (0.204±0.133), (0.288±0.148) and (0.292±0.136) mm, respectively; the coronal projection of the three-dimensional displacements of the mesial buccal cusp tips of the bilateral first molars in the lateral edge-to-edge position were (0.254±0.140) and (0.295±0.190) mm, respectively. The differences between the above displacements and 0 were statistically significant (P<0.05). The results of occlusal pre-adjustment showed that the mean deviations of the lingual surface of the left maxillary central incisor in the light and heavy bite force groups were (0.215±0.036) and (0.195±0.041) mm (t=3.95, P=0.004), respectively. The mean deviations of the occlusal surface of the left mandibular first molar were (0.144±0.084) and (0.100±0.096) mm (t=0.84, P=0.036), respectively. Conclusions: Both the light and heavy bite force have an influence on the mandibular movement trajectories. Virtual occlusal pre-adjustment of prostheses with mandibular movement trajectories under heavy bite force can obtain morphology of lingual or occlusal surfaces closer to the natural teeth before preparation.

Fully digital workflow for replicating treatment dentures: A technique for jaw relation transfer and dynamic occlusal adjustment.

This technique report presents a novel method of digitally replicating a treatment denture and converting it into a definitive denture. The procedure accurately duplicates the appearance of the mucosal surface and border of the treatment dentures, mounts the jaw relation on a virtual articulator to arrange artificial teeth, and optimizes the occlusion based on recorded mandibular motion tracks. This technique uses personalized jaw relation transfer and dynamic occlusal adjustment to establish balanced occlusion, which accomplishes the digital duplication of the treatment denture with high accuracy and minimal effort.

Occlusal adjustment of 3-unit tooth-supported fixed dental prostheses fabricated with complete-digital and -analog workflows: A crossover clinical trial.

AIM: This prospective crossover clinical trial aimed to compare the complete-digital and -analog workflows in terms of occlusal adjustment of 3-unit tooth-supported fixed dental prostheses, operator, and patient preferences. MATERIALS AND METHOD: This study included twelve patients receiving fourteen 3-unit posterior FDPs. 2 FDPs were made for each restoration site: one fabricated in complete-digital workflow comprising intraoral scan with static bite registration (Trios 3) and a monolithic zirconia FDP (test); the other fabricated in complete-analog workflow comprising conventional impression/face-bow transfer and a porcelain-fused-to-metal FDP (control). The FDPs (n=28) were intraorally/provisionally fixed, and quadrant-like intraoral scans were taken for every FDP before & after their occlusal adjustments. Pre- and post-adjustment scans of each FDP were then superimposed using best-fit alignment (GOM Inspect) to measure the volumetric occlusal adjustment amount (mm3) (3Matic) (Mann Whitney U, α=0.05). The patient and operator experience for digital and analog workflows were evaluated using visual analog scales (Wilcoxon test, α=0.05). RESULTS: Mean occlusal adjustments were 7.63 mm3 [±7.02] and 25.95 mm3 [±39.61] for test and control groups, respectively. The volumetric adjustment difference was clinically noticeable but not significant (P=0.12). The impression and digital workflow adjustment were perceived more favorably by both operator (P=0.003, P=0.046, respectively) and the patients (P=0.003, P=0.002, respectively). CONCLUSIONS: Within the limitations of this clinical study, the complete digital workflow with digital static bite-registration provided high occlusal accuracy for short-span tooth-supported FDPs. In addition, the patient and operator preferences significantly favored the digital workflow. CLINICAL SIGNIFICANCE: Complete-digital workflow employing intraoral scanning and model-free fabrication of monolithic-Zr short-span tooth-supported FDPs offers an effective treatment modality with sufficient occlusal accuracy. Therefore complete-digital workflow is a valid alternative for complete-analog workflow comprising conventional impression, face-bow transfer, and use of a semi-adjustable articulator.

Impact of the occlusal contact pattern and occlusal adjustment on the wear and stability of crowns.

OBJECTIVES: To investigate the impact of the occlusal contact situation and occlusal adjustment on wear, roughness, and fracture force of molar crowns. MATERIALS AND METHODS: CAD/CAM crowns (lower right first molar, n = 64; 4 groups à 8, 3Y-TZP zirconia and resin composite) and corresponding antagonists (upper right first molar; 3Y-TZP zirconia) were manufactured. Crowns were constructed according to two principles of occlusion (group "T": Peter K. Thomas' "point-centric" cusp-to-fossa tripodization concept, with 15 contact points; group "RA" Sigurd P. Ramfjord and Major M. Ash, "freedom in centric" concept with four contacts). On one half of the crowns, occlusal adjustment was performed (groups "T adjusted" and "RA adjusted"). All crowns underwent combined thermal cycling (TC) and mechanical loading (ML) (ML: 1.2 × 106 cycles, 50 N, 2 Hz, mouth opening 1 mm; TC: 2 × 3000 cycles, 5/55°C). Wear area and depth of each contact point on the occlusal surfaces of crowns and antagonists were determined using a digital microscope. Surface roughness (Ra, Rz) was measured in and besides (reference) the worn area (3D laser-scanning microscope). Fracture force of the crowns was determined (statistics: Levene-test, one-way-ANOVA; Bonferroni-post-hoc-test; between-subjects effects, Pearson correlation, α=0.05). RESULTS: The resin composite crowns yielded significantly higher mean values for wear area and depth (p < 0.001) and lower fracture forces (p < 0.001). Resin composite surfaces showed increased roughness after TCML while zirconia exhibited smoothened surfaces. The occlusal design significantly impacted wear depth (p = 0.012) and fracture force (p < 0.001). Resin composite crowns with fewer contact points (group RA) showed more wear and lower fracture force. Adjusted resin composite crowns showed increased wear areas and depths (p = 0.009-0.013). For zirconia crowns, the adjustment impacted wear area (p = 0.013), wear depth (p = 0.008), and fracture force (p = 0.006), with adjusted zirconia crowns exhibiting more wear and lower maximum forces until fracture. Zirconia wear depth was also impacted by the occlusal design (p = 0.012). Antagonistic wear was influenced by the restorative material, the occlusal contact pattern, and the adjustment. CONCLUSIONS: The investigated materials show strongly varying performances with zirconia being significantly influenced by the adjustment, while for resin composites, contact design and adjustment had a major impact. CLINICAL RELEVANCE: The results show the necessity of adapting occlusal design and adjustment in order to improve roughness, wear, and stability of zirconia and resin composite crowns.

Comparison of occlusal contact errors of 6 chairside CAD/CAM crowns: a self-controlled clinical study.

OBJECTIVES: The purpose of this self-controlled clinical study was to evaluate the trueness of occlusal contacts of chairside CAD/CAM crowns fabricated using different ceramic materials. MATERIALS AND METHODS: Ten volunteers (8 females, 2 males, average aged 20-30) were recruited in this study registered in the Clinical Trials Registry (#NCT05346744). After tooth preparation on tooth 36 or 46, an optical scan unit (CEREC Omnicam, Sirona Dental Systems, Germany) was utilized to perform the intraoral scanning. For each volunteer, 6 crowns were fabricated via the chairside CAD/CAM process (CEREC, Sirona Dental Systems, Germany) using the following materials: InCoris TZI (ZIR), Celtra Duo (CD), e.max CAD (EMA), UP.CAD (UP), Enamic (ENA) and Hyramic (HY). The microhardness of the milled surfaces was measured through a Vickers hardness Tester (HVS-50Z, Trojan, China). Together with the amount of occlusal adjustment, the occlusal contact trueness at both milling and postprocessing stages were quantitatively analyzed by using a high-precision scanner (ATOS, GOM Technologies, USA) and a reverse engineering software (Geomagic Control, 3D Systems, Rock Hill, SC). The times of chairside occlusal adjustment were also recorded. Data were analyzed by one-way analysis of variance (ANOVA) and ANOVA with randomized block design followed by Bonferroni test (p = 0.05). RESULTS: Significant differences were found in surface microhardness of the materials tested (CD > EMA ~ UP > ENA > HY > ZIR, p < 0.05). Regarding the occlusal contact trueness at milling stage, ZIR showed the lowest (p < 0.05), while no significant difference was found among others (p > 0.05). At postprocessing stage, except for ENA, the occlusal contact trueness of ZIR was significantly lower than that of others (p < 0.05). As for occlusal adjustment amount, ZIR was lower than CD and ENA (p < 0.05). In addition, ENA, HY and ZIR required fewer times of occlusal adjustment than EMA, UP and CD. CONCLUSIONS: The type of chairside CAD/CAM ceramic materials affected the occlusal contact trueness throughout the process of manufacturing and the amount of clinical occlusal adjustment as well. Zirconia exhibited the worst occlusal contact trueness at both milling and postprocessing stages, while the amount of occlusal adjustment was the least, which recommended the least occlusal compensation. CLINICAL RELEVANCE: For better trueness, different negative occlusal offsets are suggested to be applied in the design process, so as to suit the material of the restoration.

A comparative study based on the mandibular movement track and the movement parameters of the virtual articulator in simulating occlusal adjustment / 华西口腔医学杂志

OBJECTIVES@#This study aimed to compare the effects of virtual adjustment on occlusal interferences in mandibular posterior single crown and three-unit bridge restorations by using the mandibular movement track and the movement parameters of a virtual articulator.@*METHODS@#Twenty-two participants were recruited. Digital casts of the maxillary and mandibular arches were obtained using an intraoral scanner, and the jaw registration system was used to record the data of the mandibular movement track and the movement parameters of the articulator. Four kinds of restorations with 0.3 mm occlusal interferences were designed with dental design software. In particular, single crowns were designed for teeth 44 and 46, whereas three-unit bridges were designed for teeth 44-46 and 45-47, and the corresponding natural teeth were virtually extracted. Virtual adjustment of the restorations was performed using two dynamic occlusal recordings, namely, the mandibular movement track and the movement parameters of the virtual articulator. A reverse-engineering software was used to measure the root-mean-square of the three-dimensional deviation of the occlusal surfaces between natural teeth and the adjusted restorations. The differences between the two methods of virtual-occlusion adjustment were compared and analyzed.@*RESULTS@#For the same group of restorations, the three-dimensional deviation of the mandibular movement track group were lower than those of the virtual articulator group, and the differences were statistically significant (P<0.05). For the four groups of restorations adjusted by the same method, the three-dimensional deviation of the 46-tooth single crown was the largest and the smallest three-dimensional deviation was that of the 44-tooth single crown. Statistical differences existed between the 44-tooth single crown and the other groups (P<0.05).@*CONCLUSIONS@#For the occlusal design of posterior single crown and three-unit bridge, the mandibular movement track could be a more effective approach to virtual occlusal adjustment than the movement parameters of the virtual articulator.

Study on mandibular movement trajectory and virtual occlusal pre-adjustment under light and heavy bite force / 中华口腔医学杂志

Objective: To investigate the influence of light and heavy bite force on the mandibular movement trajectories, and the influence of bite force on virtual occlusal pre-adjustment of digital full crown. Methods: From October 2021 to March 2022, 10 postgraduate volunteers (3 males and 7 females, aged 22-26 years) were recruited from Peking University School and Hospital of Stomatology. Maxillary and mandibular digital models of the participants were obtained by intraoral scanning. Jaw relations were digitally transferred under heavy bite force and mandibular movement trajectories under light and heavy bite force were recorded by jaw motion analyser. Three mandibular markers were chosen, namely the mesial proximal contact point of the central incisor (incisal point) and the mesial buccal cusp tips of the bilateral first molars. The three-dimensional displacements of the markers under two kinds of bite force in the intercuspal position (ICP), the sagittal projection of the three-dimensional displacements in the protrusive edge-to-edge position, and the coronal projection of the three-dimensional displacements in the lateral edge-to-edge position of upper and lower posterior teeth were measured. Single-sample t-test was used to compare the three-dimensional displacements and the corresponding sagittal projection and coronal projection with 0, respectively. The left maxillary central incisor and left mandibular first molar were virtually prepared by the reverse engineering software. Then dental design software was used to design digital full crown using the copy method. The mandibular movement trajectories under light and heavy bite force were separately used to guide virtual occlusal pre-adjustment. The three-dimensional deviations (mean deviations and root mean square) between the lingual surface of the left maxillary central incisor or the occlusal surface of the left mandibular first molar and that of the natural tooth before preparation were calculated (light bite force group and heavy bite force group), and the differences between the two groups were compared by the paired t-test. Results: Under the two kinds of bite force, the three-dimensional displacements of the markers in the ICP were (0.217±0.135), (0.210±0.133) and (0.237±0.101) mm, respectively; the sagittal projection of the three-dimensional displacements of the markers in the protrusive edge-to-edge position were (0.204±0.133), (0.288±0.148) and (0.292±0.136) mm, respectively; the coronal projection of the three-dimensional displacements of the mesial buccal cusp tips of the bilateral first molars in the lateral edge-to-edge position were (0.254±0.140) and (0.295±0.190) mm, respectively. The differences between the above displacements and 0 were statistically significant (P<0.05). The results of occlusal pre-adjustment showed that the mean deviations of the lingual surface of the left maxillary central incisor in the light and heavy bite force groups were (0.215±0.036) and (0.195±0.041) mm (t=3.95, P=0.004), respectively. The mean deviations of the occlusal surface of the left mandibular first molar were (0.144±0.084) and (0.100±0.096) mm (t=0.84, P=0.036), respectively. Conclusions: Both the light and heavy bite force have an influence on the mandibular movement trajectories. Virtual occlusal pre-adjustment of prostheses with mandibular movement trajectories under heavy bite force can obtain morphology of lingual or occlusal surfaces closer to the natural teeth before preparation.

[Interpretation of the European Federation of Periodontology S3 level clinical practice guideline for treatment of stage â £ periodontitis].

The S3 level clinical practice guideline for the treatment of stage Ⅳperiodontitis, developed by the European Federation of Periodontology, was published in April 22, 2022 (DOI: 10.1111/jcpe.13639). According to the severity and complexity, stage Ⅳ periodontitis was grouped into four case types, and comprehensive treatment plans were formulated correspondingly in the guideline, including tooth splinting, occlusal adjustment, orthodontic therapy, restorative therapy, and personalized supportive periodontal care as well. The aim of present work is to intensively interpret the key points of the guideline and help the clinicians to understand this guideline better, in order to improve the treatment level of stage Ⅳ periodontitis in China.

Control of occlusal rehabilitation with 3D-printed crowns.

AIM: With the development of new materials, 3D printing has had an immense impact on dentistry. The latest innovations are the direct manufacturing of temporary and permanent crown and bridge restorations, inlays, onlays, and veneers. In the present case report, 3D-printing technology was used to control and adjust the occlusal rehabilitation with 3D-printed crowns. MATERIALS AND METHODS: A 44-year-old male patient with pathologic dental attrition visited the Department of Restorative Dentistry at the University of Würzburg (Würzburg, Germany). The attrition process was far advanced, and no conventional conservative therapy was indicated. For the rehabilitation of the tooth substance loss, dental height, and appearance, a permanent solution with dental crowns was elected. After the preparation, the restorations were constructed digitally. For the control of the occlusal height, appearance, and color, the restorations were fabricated with a 3D printer and temporarily cemented. The crowns showed a high precision, and only minimal occlusal corrections were needed. After a trial period of 2 weeks and another fine occlusal adjustment, the temporary crowns were removed and scanned. The data were matched to the original construction file, which could be used to optimize the final rehabilitation. The final restorations were made of monolithic zirconia, with only minimal occlusal corrections required. CONCLUSION: At the present time, dentistry is experiencing a great shift toward new and interesting production solutions with 3D-printing technologies. Such technologies give dentists the ability to create more predictable and cost-effective treatments. 3D printing is already being used to create temporary and definitive dental crowns as well as complex treatments, as is shown in the present case report. (Int J Comput Dent 2022;25(3):325-332; doi: 10.3290/j.ijcd.b3380909).

Efficacy of tooth splinting and occlusal adjustment in patients with periodontitis exhibiting masticatory dysfunction: A systematic review.

OBJECTIVE: To evaluate the efficacy of tooth splinting (TS) and occlusal adjustment (OA) compared to no TS or OA in patients with periodontitis exhibiting masticatory dysfunction. MATERIAL: The primary outcome criterion was tooth loss (TL), and the secondary outcome parameters were change in probing pocket depth (PPD), change in clinical attachment level (CAL), tooth mobility (TM), and patient-reported outcome measures (PROMs). Literature search was performed on three electronic databases (from 01/1965 to 04/2021) and focused on clinical studies with at least 12 months follow-up. RESULTS: From a total of 1515 publications, 51 articles were identified for full-text reading, of which 2 retrospective case series on TS with low risk of bias and 1 randomized and 2 prospective studies on OA with unclear risk of bias were included. For TS, synthesis of data showed that in 72 patients, 26 out of 311 teeth (weighted mean incidence of TL 8.4%) and 156 out of 1541 teeth with no TS (weighted mean incidence of TL 10.1%) were lost over 2 years following non-surgical periodontal therapy. The randomized controlled clinical trial (RCT) indicated CAL gain for teeth with OA compared to no OA. For the effect of OA on TL, PPD, and TM, heterogeneous data were retrieved from the included studies. CONCLUSIONS: Within the limitations of this review and based on a low level of evidence, it is concluded that TS does not improve survival of mobile teeth in patients with advanced periodontitis. OA on teeth with mobility and/or premature contacts may lead to improved CAL, while the effect of OA on the remaining periodontal parameters remains unclear.

Does the Use of Surface Electromyography Could Improve Quality of Life among Patients Rehabilitated by Mandibular Overdentures on Different Attachments?

Abstract Objective: To analyze and compare changes of quality of life parameter among dental patients rehabilitated by the implant-supported overdentures with different attachment systems. Material and Methods: Forty-eight patients were recruited as a study cohort. The implant placement procedure was based on the results obtained by CBCT scanning and individualized surgical templates manufactured for correct implant placement. Each individual received two k3Pro Implants (Sure Type with 4.0 or 4.5 mm in diameter) at the intraforaminal area due to standard protocol of implantation provided by the manufacturer under local anesthesia. All patients were distributed between two groups based on the fact of using either Locator- or ball-attachments. Rank correlation was measured using Spearman correlation coefficient, while linear correlation was evaluated by Pearson correlation coefficient. Results: No statistically meaningful differences were noted regarding patients' distribution among groups considering age (p>0.05) and gender (p>0.05). Provided patient-level analysis demonstrated that increase of conventional full denture service time was positively correlated with escalation of OHIP-EDENT scores. The most prominent inter-correspondences were noted specifically between longevity of denture service and elevation of scores within "Functional limitation" (r=0.61; p<0.05), "Physical pain" (r=0.51; p<0.05) and "Physical disability" (r=0.57; p<0.05) subdomains. No statistically argumented regressions were noted between increase tendency of OHIP-EDENT scores and gender (p>0.05) or age (p>0.05) parameters. Conclusion: Significant improvements of quality of life measured with OHIP-EDENT were noted for both types of attachments compared to the pre-treatment situation independently of additionally provided surface electromyography-based alignment.

A Multi-Center Disclusion Time Reduction (DTR) Randomized Controlled Occlusal Adjustment Study Using Occlusal Force and Timing Sensors Synchronized with Muscle Physiology Sensors.

Objective-To perform a Randomized Controlled Trial (RCT) Disclusion Time Reduction (DTR) study at five Dental Colleges, using intraoral sensors and muscular electrodes. Methods and Materials-One hundred students were randomly assigned to a treatment group to receive the ICAGD coronoplasty, or a control group that received tooth polishing. All subjects answered symptom questionnaires: Beck Depression Inventory-II, Functional Restrictions, and Chronic Pain Symptom and Frequency. Subjects self-reported after ICAGD or placebo at 1 week, 1 month, 3 months, and 6 months. The Student's t-Test analyzed the measured data. The Mann-Whitney U Test analyzed the subjective data (Alpha = 0.05). Results-The Disclusion Times, BDI-II scores, and Symptom Scales were similar between groups prior to treatment (p > 0.05). At 1 week, all three measures reduced in the treatment group, continuing to decline over 6 months (p < 0.05), but not for the controls (p > 0.05). Symptom Frequency, Functional Restrictions, and Pain Frequencies were higher in the treated group (p < 0.05), but declined after ICAGD compared to the control group (p < 0.05). Conclusions-ICAGD reduced Pain, Functional Restrictions, Symptom Frequency, and Emotional Depression within 1 week, which continued for 6 months. The tooth polishing did not initiate a placebo response.