Changes of bite force and occlusal contacts in the retention phase of orthodontic treatment: A controlled clinical trial

Is the quality of occlusal contacts comparable after aligner and fixed orthodontic therapy? A non-randomized cohort comparison using computerized occlusal analysis during 6 months of retention

OBJECTIVE

Less than ideal contacts have been reported following aligner therapy, but it is considered a transitory problem, spontaneously resolving with the phenomenon of settling. Methods: Thirty-nine orthodontic patients (14 treated with aligners; 25 with fixed appliances) were evaluated with a digital occlusal analysis system (T-scan™10), assessing Maximum Intercuspation contact simultaneity, symmetry, and relative force distribution at treatment completion and after 3 and 6 months.

RESULTS

No significant differences in occlusal contact quality were found between groups at treatment completion or follow-up. The center of force moved posteriorly and remained stable after 3 months but was located more anteriorly in females (p = 0.01). One-third of patients (both groups combined) had marked contact force asymmetry even after 6 months' retention. Conclusion: Occlusal contacts were comparable at completion of treatment with aligners or brackets and after 3-6 months of retention. Settling did not improve marked asymmetry in all patients.

Occlusal contact changes in patients treated with clear aligners: A retrospective evaluation using digital dental models

INTRODUCTION

This study used digital intraoral scans to evaluate how clear aligner treatment affects occlusal contacts and to determine the influence of sex and age on contact changes. Results were compared with contact changes that occur during fixed appliance therapy.

METHODS

Patients included in this study were treated in a University setting and private practice. Inclusion criteria were a Class I malocclusion treated nonextraction with clear aligners and the presence of pretreatment and posttreatment digital intraoral scans. Scans were imported into specialized software, and occlusal contacts were analyzed. The effects of age and sex on contact changes during clear aligner treatment were determined. Changes in occlusal contacts were compared with changes that occur during nonextraction treatment of patients with a Class I relationship using fixed edgewise appliances.

RESULTS

A total of 45 clear aligner patients fit the eligibility criteria. Clear aligner treatment reduced the percentage of tight, near, and approximating contacts, whereas the percentage of open and no contacts increased. These changes in occlusal contacts were greater for the older age group studied. Genderinfluenced occlusal contact changes in the anterior dentition only where the decrease in near contacts and increase in open contacts were greater for males. These results for patients treated with clear aligners were similar to those for patients treated with fixed appliances; both treatment modalities reduced close occlusal contacts at the time active treatment was completed.

CONCLUSIONS

These results indicated that when clear aligners or fixed appliances are used to treat a Class I malocclusion, the resulting occlusion immediately after debonding is not as "tight" as it was at pretreatment.

The association between orthodontic treatment and temporomandibular disorders diagnosis and disease characteristics

BACKGROUND

The association between orthodontic treatment and temporomandibular disorders (TMD) has been contentious in the literature.

OBJECTIVES

To analyse the associations between orthodontic treatment and TMD diagnosis and diseases characteristics.

METHODS

This case-control study included 291 individuals, 192 TMDs and 99 controls. All patients underwent assessment based on a questionnaire and a clinical examination according to Axis I of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Differences in orthodontic treatment between TMDs and controls, as well as across different TMD diagnoses within the TMD group were analysed. Patients who underwent orthodontic treatment were compared to those who did not, regarding their trauma history, bruxism, aggressive teeth brushing, level of oral hygiene, pain scores, muscle tenderness scores and subjective sleep quality.

RESULTS

Of the 291 participants, 119 (40.9%) underwent orthodontic treatment and 172 (59.1%) had no orthodontics experience. Orthodontic treatment included: mandibular orthodontic treatment (102 subjects) and maxillary orthodontic treatment (113 subjects) of those 47 used a headgear. Following multivariate analysis among TMDs, orthodontic treatment was associated with a good level of oral hygiene versus poor (Odds ratio [OR]: 5.17 [1.04-25.59]), lower number of tender muscles [OR = 0.84 (0.74-0.96)] and lower (better) Pittsburgh Sleep Quality Index (PSQI) scores (OR = 0.86 [0.76-0.97]). None of the studied parameters maintained a statistically significant association with orthodontic treatment in the multivariate analysis among the entire study population.

CONCLUSIONS

Utilising a holistic approach, this study supports the main hypothesis that orthodontic treatment is not associated with TMD diagnosis and disease characteristics.

Comparison of efficacy of thermoplastic retainer with round and rectangular bonded lingual wire retainer in the mandible two years after orthodontic treatment: a randomised controlled trial

OBJECTIVE

To analyse three protocols in maintaining the stability of orthodontic therapy results and their effect on gingival health.

MATERIALS AND METHODS

Sixty-six subjects (pre-therapeutic age 11-18 years; 68% female) randomly allocated into three retention groups of equal size were analysed. The first group had a 0.673 × 0.268 mm (0.027 × 0.011 inches) rectangular braided steel retention wire bonded to the lingual surfaces of all mandibular teeth from canine to canine, and the second group had a 0.406 mm (0.016 inches) round twisted steel wire. The third group was the control, without wires, and only with vacuum-formed retainers. All three groups had vacuum-formed removable retainers in the maxilla. The frequency of wire detachment/breakage/loss of retainer, the occurrence of crowding of mandibular incisors, and changes in intercanine width and gingival health were monitored.

RESULTS

Incidence and severity of relapse differed between groups (p = 0.001 and 0.049) being most common in the removable retainer group (incidence 68.2%; severity 0.7 ± 1.0 mm), followed by the round wire group (36.4%; 0.5 ± 1.2 mm) and rectangular wire group (13.6%; 0.1 ± 0.1 mm). The intercanine width decreased more without a bonded retainer (incidence 68.2%; severity 0.5 ± 0.7 mm) and with the round wire more (45.5%; 0.5 ± 0.7 mm) than with the rectangular (27.3%; 0.1 ± 0.3 mm). The difference was significant for incidence (p = 0.025), but not severity. Detaching of the wires/breakage/loss of retainer was similar. There were no significant differences in the accumulation of biofilm, calculus and gingivitis between appliances.

CONCLUSION

A rectangular wire is the most effective in retention, and the impact of retention appliances on gingival health is similar.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT05121220. Registered 02 October 2021 - Retrospectively registered.

CLINICAL RELEVANCE

Studying guidelines for reducing relapse, proper use of materials and appliances, the behavior of retention wires according to their profile in the retention phase, and possibilities of maintaining oral health will contribute to improving the stability of orthodontic therapy results.

Surgical vs nonsurgical treatments in patients with anterior open-bite have similar effects in occlusal function: A 2-year follow-up study

INTRODUCTION

This study aimed to investigate changes in bite force (BF) and occlusal contact area after anterior open-bite (AOB) treatment and compare the changes in surgical vs nonsurgical treatment.

METHODS

This retrospective study included patients with AOB compared with normal occlusion. AOB was corrected by either intrusion of the maxillary molars (intrusion group, n = 19) or orthognathic surgery (surgery group, n = 37). The control group (n = 35) had a normal overbite relationship. Records of lateral cephalograms, BF, and occlusal contact area taken before (T0), immediately after (T1), and 2 years after (T2) orthodontic treatment were compared within and among the 3 groups.

RESULTS

The open-bite group, including intrusion and surgery groups, had a lower BF and less occlusal contact area than the control group at T0 and T1 (P <0.001). However, there were no significant differences among the 3 groups at T2 (P >0.05). The intrusion and surgery groups showed no significant differences throughout the observation period extending from T0 to T2 (P >0.05). Although BF and occlusal contact area decreased at T1 compared with T0, they increased during retention and showed higher values at T2 than at T0.

CONCLUSIONS

Treatment of AOB improved BF and occlusal contact area 2 years posttreatment. Orthognathic surgery and molar intrusion using orthodontic miniscrews can improve occlusal function similarly. Orthodontists can select either method depending on malocclusion severity and patient demand.

Masticatory muscle activity and oral health-related quality of life in patients wearing clear thermoplastic versus wrap-around retainers : A randomized controlled trial

AIM

To evaluate the surface electromyography (sEMG) activity of the superficial masseter and anterior temporalis muscles at rest, during maximum voluntary clenching (MVC), and mastication, over 6 months of wearing clear thermoplastic or wrap-around retainers. Furthermore, the patients' oral health-related quality of life was assessed using the Oral Impacts on Daily Performance (OIDP) index at 6 months.

MATERIALS AND METHODS

Sixty patients aged 14-39 years (19 males/41 females) who received upper and lower retainers after finishing orthodontic treatment were recruited. The patients were randomly divided into a clear thermoplastic retainer group (n = 30) or a wrap-around retainer group (n = 30). The sEMG activity was recorded at retainer delivery (T0), after 3 months (T1), and after 6 months of wearing (T2). The OIDP index was evaluated at T2.

RESULTS

None of the sEMG parameters for the masseter and temporalis muscles were different between the two groups at T0, T1, or T2. Over the period of 6 months, both masticatory muscles in both groups demonstrated increased sEMG activity during MVC and mastication; however, only the temporalis muscle demonstrated decreased normalized sEMG activity at rest (P < 0.05). The frequency and severity of the OIDP in the eating aspect at T2 was low and similar in both groups.

CONCLUSIONS

sEMG activity of the two masticatory muscles tended to increase during MVC and mastication, while temporalis muscle activity tended to decrease at rest during the observation period, regardless of retainer type. Notably, these sEMG changes did not affect the patients' subjective masticatory function.

Occlusal Contact Surface Changes and Occlusal Force Distribution Between Vacuum-Formed Retainers and Other Retainers: A Systematic Review

The present systematic review was done to assess the available literatures on changes in the number of occlusal contacts (NOC), occlusal contact surface areas, and occlusal force distribution (OFD) with vacuum-formed retainers (VFRs) or clear overlay retainers during retention and to compare them with other retainers. Six electronic databases (Web of Science, Scopus, PubMed, Cochrane Library, Lilacs, and Google Scholar) were searched. Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) reporting on occlusal contact changes with VFRs were included. A total of nine articles were included in this review: three RCTs, five prospective controlled trials (PCTs), and one CCT. The Cochrane risk of bias tool and ROBINS-I tool were used for risk of bias assessment. The three RCTs showed moderate risk of bias, and out of five CCTs, four showed low risk of bias, and one showed moderate risk of bias. One CCT showed a low risk of bias in the ROBINS-I tool. Two out of four studies reported improved occlusal surface area (OSA) with VFRs when assessed at the end of six months and 12 months; one out of four studies reported improved NOC; and one study reported a decrease in OFD anteriorly and an increase in OFD posteriorly after two months of retention. On comparison between the groups, the other retainer groups showed more NOCs compared to VFRs. The limited available evidence suggests an increase in OSA and no change in NOCs and OFD with VFRs during retention. No significant differences between VFRs and other retainers for OSA and OFD were noted, and more NOCs were noted for other retainer groups.

Changes in the distribution of occlusal forces in the course of the orthodontic retention phase : A prospective cohort study

PURPOSE

Aim of the present study was to assess the relative distribution of occlusal forces after orthodontic treatment and during the first 3 months of the retention phase using a computerized occlusal analysis system (T-Scan, Tekscan Inc., Norwood, MA, USA).

MATERIALS AND METHODS

A total of 52 patients were included in this prospective cohort study and underwent analysis of occlusal forces on the level of tooth, jaw-half, and -quadrant during a 3-month period. Furthermore, differences between three retention protocols (group I: removable appliances in both jaws; group II: fixed 3-3 lingual retainers in both jaws; group III: removable appliance in the maxilla and fixed 3-3 lingual retainer in mandible) were assessed with Wilcoxon signed-rank tests at 5%.

RESULTS

Directly after debonding, measured forces distribution were similar to published references for untreated samples. In the following, no significant difference was found between retention protocols II and III with regard to the asymmetry of the anterior occlusal forces. Both groups maintained an asymmetric force distribution in the anterior segment during the study period. There was also no difference between groups II and III in the distribution of occlusal forces for the posterior segments. Both retention concepts kept the symmetrical distribution of occlusal forces stable over the observation period. The retention concept of group I demonstrated a symmetrical distribution of occlusal forces in the anterior segment after debonding and this remained stable during the 3‑month period. In the posterior segment, no improvement of the initially asymmetric masticatory force distribution could be observed.

CONCLUSIONS

All three studied retention protocols showed stability in retaining their original symmetrical or asymmetrical occlusal force distribution posteriorly/anteriorly during the 3‑month observation period. Therefore, an even distribution of occlusal forces should be the aim of the finishing phase, as no relative benefit of any single retention scheme in terms of post-debond improvement during the retention phase was seen.

Computerized dynamic occlusal analysis and its correlation with static characters in post-orthodontic patients using the T-Scan system and the ABO objective grading system

OBJECTIVES

This study was conducted to detect the overall performance of both static and dynamic occlusion in post-orthodontic patients using quantified methods, and to ascertain the correlation between the two states of occlusion.

MATERIALS AND METHODS

A total of 112 consecutive patients evaluated by ABO-OGS were included in this study. Based on the pre-treatment Angle's classification of the malocclusion, samples were divided into four groups. After removing orthodontic appliances, each patients underwent the American Board of Orthodontic objective grading system (ABO-OGS) and T-Scan evaluations. All the scores were compared within these groups. Statistical evaluation included reliability tests, multivariate ANOVA, and correlation analyses (p < 0.05 was considered significant).

RESULTS

The mean ABO-OGS score was satisfactory and did not differ by Angle classifications. The indices making substantial contributions to ABO-OGS were occlusal contacts, occlusal relationships, overjet, and alignment. Disocclusion time in post-orthodontic patients was longer than normal. Occlusion time, disocclusion time, and force distribution during dynamic motions were considerably influenced by static ABO-OGS measurements, especially occlusal contacts, buccolingual inclination, and alignment.

CONCLUSION

Post-orthodontic cases that passed the static evaluation of clinicians and ABO-OGS may nevertheless be left with dental casts interference in dynamic motions. Both static and dynamic occlusion should be extensively evaluated before ending orthodontic treatment. Further research is needed on dynamic occlusal guidelines and standards.

Debonding of orthodontic appliance changes salivary physicochemical properties and favors regression of active caries lesions: A 13-week follow-up study

AIM

This prospective cohort study aimed to investigate whether orthodontic appliance removal (OAR) combined with caries-preventive strategies and fluoride varnish treatments alters salivary physicochemical properties, changes the activity of carbonic anhydrase VI (CA VI_ACT ) and α-amylase (α-AML_ACT ), and favors the regression of active caries lesions (ACL).

DESIGN

Twenty-two individuals aged between 13 and 24 years were assessed for the presence of visible biofilm, daily sugar exposure, caries activity, salivary flow rate (SFR), pH, buffering capacity (BC), and CA VI_ACT and α-AML_ACT activity at baseline, and 1, 5, and 13 weeks after OAR. Variables were assessed using repeated-measures analysis of variance, Cochran's Q and McNemar's test, and Pearson's correlation.

RESULTS

We observed a significant decrease in the number of ACL at the 5-week (29% reduction) and 13-week follow-ups (58% reduction). At the 5- and 13-week follow-ups, the percentage of visible biofilm and sugar exposure decreased, whereas the salivary pH and α-AML_ACT activity significantly increased. BC and CA VI_ACT remained unchanged throughout the follow-up.

CONCLUSION

OAR combined with caries-preventive strategies and fluoride varnish treatments favored the regression of ACL and increased salivary pH and α-AML_ACT activity, whereas BC and CA VI_ACT remained stable.

Comparison of settling of occlusion in modified and full coverage thermoplastic retainers using T-scan

Objectives:

The main intent of the study was to evaluate and compare the occlusal bite forces after settling between conventional and modified thermoplastic retainer groups using T-Scan.

Material and Methods:

This study comprised a total of 20 patients, who approached the retention phase after completion of fixed orthodontic therapy. After debonding (T0), occlusal analysis using the T-Scan system was done at centric occlusion. Group I (control) – 10 patients received the conventional thermoplastic retainer and Group II (experimental) – 10 patients received the modified thermoplastic retainer. Patients were instructed to wear the retainer continuously for 6 months except while eating and brushing. T-scan analysis after 6 months (T6) was done to evaluate the changes in occlusal bite forces. The obtained data were evaluated using STATA/IC software version 16.1 at a predetermined probability value of 0.05 which was considered significant.

Results:

The result obtained from this study was suggestive of significant improvement in bite force levels at centric occlusion in the modified thermoplastic group compared with the conventional group. Comparing the right (P < 0.17) and left (P < 0.01) posterior region, there was significant increase on the left side. A significant increase at maximum centric occlusion (P < 0.01) was seen in the region of the first molars. The anterior region did not show any improvement (P < 0.62) after 6 months of retention.

Conclusion:

Partial coverage of thermoplastic retainer significantly improves the occlusal contacts and force levels. The maximum change was seen in the posterior region and the minimum change in the anterior region at centric occlusion.

In vitro performance and fracture resistance of interim conventional or CAD-CAM implant-supported screw- or cement-retained anterior fixed partial dentures

STATEMENT OF PROBLEM

Interim restorations represent an essential clinical treatment step; however, limited information is available concerning the performance of computer-aided design and computer-aided manufacturing (CAD-CAM) interim materials.

PURPOSE

The purpose of this in vitro study was to evaluate the performance and fracture load of resin anterior implant-supported interim fixed partial dentures (IFPDs).

MATERIAL AND METHODS

Identical anterior resin IFPDs (maxillary central incisor to canine; n=16 per material) were milled from polymethylmethacrylate (PMMA) or di-methacrylate (DMA) systems with different filler content. The IFPD groups were split to simulate a chairside (cemented implant-supported prosthesis) or laboratory procedure (screw-retained implant-supported prosthesis). A cartridge DMA material served as a control. After interim cementation, combined thermocycling and mechanical loading (TCML) was performed on all restorations to approximate a maximum of 2.5 years of clinical function. Behavior during TCML and fracture force was determined, and failures were analyzed. The data were statistically investigated (Kolmogorov-Smirnov test, 1-way-ANOVA; post hoc Bonferroni, Kaplan-Meier survival, α=.05).

RESULTS

Drop out during TCML varied between no failures and complete failure during loading. For most systems, failure occurred between 120 000 and 600 000 mechanical loading cycles. For IFPDs without a screw channel fracture, values varied between 644 ±263 N and 987 ±101 N. Those with a screw channel fracture failed between 493 ±89 N and 951 ±248 N. Individual IFPDs had significantly higher mean fracture loads (P<.002), but the mean fracture values between IFPDs with and without a screw channel were not significantly different (P>.137). Failures were characterized by fracture of the connector (n=53) followed by mixed failures (n=22) or fractures at the abutment (n=21).

CONCLUSIONS

These interim materials are sufficiently fracture resistant for the fabrication of implant-supported anterior IFPDs and are expected to survive between 6 months and 2 years before failure. The stability of IFPDs depended on the type of material but not on the restoration design (with or without a screw channel).

Comparison of Occlusal Contact Changes During Retention Between Hawley-Type Retainers and Other Retention Appliances: A Systematic Review

Background: Achieving adequate and broad occlusal contacts following orthodontic treatment usually is performed during retention phase, and it ensures good intercuspation of posterior teeth and post-treatment stability.

Objective: To investigate the changes in occlusal contacts with the use of Hawley-type retainers (Hawley’s and wrap around retainers) and compare them with other retention appliances.

Methods: The search included articles that were published until December 2018 in three popular databases. Selection criteria comprised studies evaluating number and area of occlusal contact changes during or at the end of retention phase, following orthodontic treatment. After study retrieval and selection, data extraction and individual study risk of bias assessment was performed using the Cochrane Risk of Bias tool.

Results: A total sum of eight studies reporting on outcome comparison between Hawley-type retainers with other retention appliances and untreated controls were selected. In all the eight studies, the risk of bias was unclear since blinding and random sequence generation was not reported. In all the eight reported studies, it was concluded that the number of occlusal contacts improved during retention period with Hawley type retainers, but when comparisons were done in between retainers, only two studies reported that Hawley-type retainers were better.

Conclusion: This systematic review concludes that the number and area of occlusal contacts improved during retention with Hawley-type retainers. The overall quality of available literature is poor and unclear to support the conclusion that Hawley-type retainers are better than other existing retainers in improving occlusal contacts.

Classification of the journal category "oral surgery" in the Scopus and the Science Citation Index Expanded: flaws and suggestions

Objectives

The aim of this study was to evaluate the journal category “oral surgery” in Scopus and in the Science Citation Index Expanded (SCIE).

Materials and Methods

The Journal of Oral and Maxillofacial Surgery (JOMS), The Journal of the Korean Association of Oral and Maxillofacial Surgeons (JKAOMS), and The Journal of Prosthodontic Research (JPR) were selected from the Scopus list of journals as oral surgery journals. Maxillofacial Plastic and Reconstructive Surgery (MPRS) was selected from PubMed as a Scopus oral surgery title. From these titles, 10 recently published articles were collected and used for reference analysis.

Results

The percentage of citations from oral surgery journals was 26.7%, 24.5%, and 40.1% for JKAOMS, MPRS, and JOMS, respectively. In total, 1.1% of JPR's citations were from oral surgery journals and significantly fewer from other journals (P<0.001). The percentage of citations from dentistry journals excluding oral surgery journals was 11.9%, 34.4%, and 15.8% for JKAOMS, MPRS, and JOMS, respectively. For JPR, 80.6% of citations were from dentistry journals and significantly more were from other journals (P<0.001).

Conclusion

Selected samples revealed that JPR is incorrectly classified as an oral surgery journal in Scopus. In addition, the scientific interaction among JKAOMS, MPRS, and JOMS was different to JPR in the reference analysis.

Efficacy of the mini tooth positioner in improving orthodontic finishes

INTRODUCTION

The primary objective of this study was to assess the effectiveness of the mini tooth positioner in improving the quality of orthodontic treatment outcomes, as measured by the American Board of Orthodontics (ABO) cast-radiograph evaluation (CRE).

METHODS

Thirty patients were treated prospectively with a minipositioner for 4-6 weeks immediately after debond. Sixteen patients who had received a maxillary vacuum-formed retainer (VFR) and fixed mandibular canine-to-canine retainer at time of debond were enrolled retrospectively as control subjects. Models from time of debond (T1) were graded with the use of the ABO CRE and compared with models obtained 4-6 weeks after debond (T2) for each group.

RESULTS

For the minipositioner group, the overall CRE score improved significantly by an average of 6.77 points. Significant improvements were noted in the categories of alignment and rotations (-0.68), marginal ridges (-1.40), buccolingual inclination (-0.45), overjet (-0.97), and occlusal contacts (-3.00). For the control group, overall CRE score improved significantly by an average of 1.16 points. Only the categories of overjet (-0.38) and occlusal contacts (-1.22) showed significant improvements.

CONCLUSIONS

The minipositioner is an effective tool in improving the overall finish of orthodontic treatment. In the 4-6 weeks after debond evaluated in this study, the minipositioner significantly outperformed the maxillary VFR/mandibular fixed canine-to-canine retainer in improving final treatment outcomes.