Palatal Coverage Research Articles

Influence of Palatal Coverage and Implant Distribution on Implant Strain in Maxillary Implant Overdentures.

Maxillary implant overdentures are often used in clinical practice. However, there is no agreement or established guidelines regarding prosthetic design or optimal implant placement configuration. The purpose of this study was to examine the influence of palatal coverage and implant number and distribution in relation to impact strain under maxillary implant overdentures. A maxillary edentulous model with implants and experimental overdentures with and without palatal coverage was fabricated. Four strain gauges were attached to each implant, and they were positioned in the anterior, premolar, and molar areas. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the implant strains were compared using one-way analysis of variance (P = .05). The palatolabial strain was much higher on anterior implants than on other implants in both denture types. Although there was no significant difference between the strain under dentures with and without palatal coverage, palateless dentures tended to result in higher implant strain than dentures with palatal coverage. Dentures supported by only two implants registered higher strain than those supported by four or six implants. Implants under palateless dentures registered higher strain than those under dentures with palatal coverage. Anterior implants exhibited higher palatolabial strain than other implants regardless of palatal coverage and implant configuration; it is therefore recommended that maxillary implant overdentures should be supported by six implants with support extending to the distal end of the arch.

Influence of Palatal Coverage and Implant Distribution on Denture Strain in Maxillary Implant Overdentures.

As maxillary implant overdentures are being increasingly used in clinical practice, prosthodontic complications related to these dentures are also reported more often. The purpose of this study was to examine the influence of palatal coverage and implant distribution on the shear strain of maxillary implant overdentures. A maxillary edentulous model with implants inserted in the anterior, premolar, and molar areas was fabricated. Two kinds of experimental overdentures, with and without palatal coverage, were also fabricated, and two strain gauges were attached at the midline of the labial and palatal sides. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the shear strain in each denture was compared by analysis of variance (P = .05). In all situations, the shear strain in palateless dentures was significantly higher than in dentures with palate on both sides (P < .05). In dentures with palate, the shear strain was lower when anterior implants were present. Palateless maxillary implant overdentures exhibited much higher strain than overdentures with palate regardless of the implant distribution; this may cause more prosthodontic and implant complications. The most favorable configuration to prevent complications in maxillary implant overdentures was palatal coverage that was supported by more than four widely distributed implants.

The Influence of Palatal Coverage on the Retention Force and Fatigue Resistance of Mini Dental Implant Maxillary Overdenture

Purpose: evaluation and comparison of the influence of palatal coverage on the retention force and fatigue resistance of attachment system of mini dental implant (MDIs) overdenture. Materials and methods: heat-cured polymethylmethacrylate resin maxillary acrylic resin models were used for this study. Five 2.5 × 13 mm dummy mini-dental implants with O-ring attachment were placed parallel to each other. Ten palateless implant retained overdenture, and ten full coverage implant retained overdenture were constructed on the models. Both of them, retention and cyclic fatigue tests of each overdenture were measured using BENDAO tools of the universal testing machine and average reading was calculated. Result: (Group I) mini-dental implant overdenture with palatal coverage recorded higher retention means value (25.55 ± 2.17 N) than (group II) mini-dental implant overdenture without palatal coverage (palate-less overdenture) (24.215 ± 3.64 N). the cyclic fatigue test for the (group I) mini-dental implant overdenture with palatal coverage Showed that the retention decreased significantly with time as indicated by ANOVA test (p < 0.05), While for (group II) mini-dental implant overdenture without palatal coverage (palate-less overdenture) was found that the retention was insignificant decrease in the first month; then it significantly decrease in the remaining periods of the study as indicated by ANOVA test (p < 0.05). Conclusion: Within the limitations of this in vitro study it can be concluded that the mini-dental implant overdenture with palatal coverage showed superior retentive properties when compared with mini-dental implant overdenture without palatal coverage (palate-less overdenture). Both study groups showed a reduction in retention after cyclic fatigue period.

Finite element analysis on stress distribution of maxillary implant-retained overdentures depending on the Bar attachment design and palatal coverage.

PURPOSEThe purpose of this study was to determine the effect of anchorage systems and palatal coverage of denture base on load transfer in maxillary implant-retained overdenture.MATERIALS AND METHODSMaxillary implant-retained overdentures with 4 implants placed in the anterior region of edentulous maxilla were converted into a 3-D numerical model, and stress distribution patterns in implant supporting bone in the case of unilateral vertical loading on maxillary right first molar were compared with each other depending on various types of anchorage system and palatal coverage extent of denture base using three-dimensional finite element analysis.RESULTSIn all experimental models, the highest stress was concentrated on the most distal implant and implant supporting bone on loaded side. The stress at the most distal implant-supporting bone was concentrated on the cortical bone. In all anchorage system without palatal coverage of denture base, higher stresses were concentrated on the most distal implant and implant supporting bone on loaded side.CONCLUSIONIt could be suggested that when making maxillary implant retained overdenture, using Hader bar instead of milled bar and full palatal coverage rather than partial palatal coverage are more beneficial in distributing the stress that is applied on implant supporting bone.

Maxillary 3-implant removable prostheses without palatal coverage on Locator abutments - a case series.

The aim of this study was to present the clinical outcomes of patients with an edentulous maxilla treated with a removable prosthesis without palatal coverage retained by Locator abutments on three titanium implants. All the patients in a private dental clinic consecutively treated up to 6years earlier were invited for a follow-up examination (n=23). Two implants were placed bilaterally and one implant anteriorly in a tripod pattern. All patients underwent a clinical and radiological examination and completed questionnaires related to their experiences and satisfaction with the reconstructions. The prosthesis and implants were examined for adverse biological or technical aspects. Patient satisfaction and quality of life outcomes were collected using a self-reported Denture Satisfaction Scale and OHIP-20. Statistical analyses were limited to descriptive statistics. Twenty-one of 23 invited participants consented to participate. We report in this study the outcomes of the study participants who had received their implants more than 2years ago (n=12). None of their 36 implants gave any indications of mobility or tenderness upon percussion. Suppuration was observed on one implant. Probing around the implants caused no (53%) or minor bleeding (47%). The incidence of adverse biological and technical events was near non-existent. The rates of replacement of male attachments varied, as did any changes of male attachment retention force. All participants described the task of insertion and removal of the prosthesis as unproblematic. The marginal bone loss ranged between 0 and 5.3mm. The OHIP-20 and the Denture Satisfaction Questionnaire scores were high. The results in this clinical study are positive and promising. Admittedly, the study design is purely retrospective and observational with a small participant cohort, so the technical solution of placing three implants in the edentulous maxilla to retain a removable prosthesis should be appraised further in more controlled studies.

Effects of clip materials on stress distribution to maxillary implant overdentures with bar attachments

Statement of problemFracture of maxillary implant overdentures (IODs) is a frequent complication. However, no studies have examined the effects of clip materials on the stress applied to maxillary IODs. PurposeThe purpose of this study was to investigate the effects of clip materials for bar attachments on the stress applied to maxillary IODs without palatal coverage. Material and methodsThis study included finite element analysis and a model study. An edentulous maxillary model with 4 implants and an experimental overdenture with bar attachments was fabricated. Strain gauges were attached on the denture surface adjacent to the end of each clip. Four clip conditions (n=5) were prepared: 3 plastic clips, 1 plastic clip, 3 metal clips, and 1 metal clip. A vertical load of 50 N was applied on the IOD. The maximum principle strain (MPS) was statistically analyzed by 2-way ANOVA and the post hoc Tukey HSD tests with clip materials and clip numbers as factors (α=.05). ResultsThe greatest stress was observed on the resin surface around the end of the clip on the loaded side. The MPSs between both clip materials (P=.048) and numbers (P<.001) differed significantly on the palatal side of the end of the center clip on the loaded side: the MPSs of the metal clips were significantly larger than those of the plastic clips, and the MPS of 1 clip was significantly larger than for 3 clips. ConclusionsThe stress around plastic clips tended to be lower than that around metal clips.

Acrylic orthodontic retainer is not a risk factor for focal Candida colonization in young healthy patients: a pilot study

Denture enhances the risk of Candida colonization because of adherence to acrylic base and interference with salivary rinsing. Acrylic orthodontic appliances may also create retentive areas for food debris and microbial pathogens; moreover, patients are instructed to use the retainers at night, when salivary secretion is reduced. We studied the Candida colonization in orthodontic patients using acrylic retainer. Participants were orthodontic patients with full compliance during the retention phase with no signs or symptoms or being at risk for Candida, divided into users of (a) Hawley retainer (study group) and (b) other retainers (vacuum-formed/fixed bonded retainer; control group). Collected data included demographic characteristics and habits. Samples were collected from palate mucosa, cultured and incubated (28°C) for 3 days. Positive Candida species were recultured to identify the Candida species. Fifty-one patients participated (mean age 20.9 ± 9.6 years); 22 had maxillary Hawley retainer and 29 had maxillary vacuum-formed/fixed bonded retainer. Candida albicans colonization in the hard palate was identified in 2 patients (3.9%)-1 (4.5%) from the Hawley retainer study group and 1 (3.4%) from the control group. The hypothesis that palatal coverage by acrylic orthodontic retainer might enhance Candida colonization on the palatal mucosa is not supported by this pilot study.

Comparison of Retention for Maxillary Overdentures Retained With Mini-Implant With and Without Palatal Coverage (In Vitro Study)

Comparison of Retention for Maxillary Overdentures Retained With Mini-Implant With and Without Palatal Coverage (In Vitro Study)

A Partial Palatal Coverage Overdenture Retained by Zygomatic Implants.

Prosthodontic rehabilitation of an atrophic edentulous maxilla can be challenging and is further complicated when multiple risk factors are present. Fixed prostheses require multiple implants for support/retention organized in biomechanically favorable positions in order to afford a good prognosis. Such suitable implant arrangements in an atrophic edentulous ridge can often be difficult to achieve. Removable prostheses require fewer implants for a favorable prognosis and can furthermore take advantage of the additional anatomical structures for support/retention. This clinical treatment will describe the fabrication of a partial palatal coverage overdenture retained by zygomatic implants.

Contribution of the palate to denture base support: an in vivo study.

The aim of this study was to examine the contribution of the palate to denture base support. Four subjects with tooth- or implant-supported maxillary overdentures were enrolled. Recordings (strain values converted to load values) were performed using miniature strain gauges and force transducers for the following conditions: metal framework only (A), denture base with full palatal coverage (B), and denture base without palatal coverage (C). The palatal-supporting ratio (PSR) was calculated using the equation PSR = (B - C) / A. The PSR values were less than 10% in all subjects, suggesting that the palate plays a minimal role in denture base support.

The 2-implant maxillary overdenture: A clinical report

Maxillary implant overdentures present a number of different challenges in comparison to the established and predictable benefits of mandibular implant overdentures. This report highlights the lack of evidence and conflicting findings in the maxillary implant overdenture literature and presents a clinical treatment of a 2-implant and subsequently 1-implant maxillary overdenture with reduced palatal coverage.

Mechanical Analysis of a Palateless Denture

The purpose of this study was to compare the strain of complete dentures with and without full palatal coverage and to determine the effect of reinforcement. Three types of maxillary complete dentures (with palate, without palate, and without palate but with reinforcement) were fabricated, and reinforcements were made from a cobaltchromium alloy. Strain gauges were attached to the polished surface, and a vertical load was applied in the region of the first premolar and first molar. The strains were statistically compared. The greatest strain occurred on the anterior palatal surface and was tensile in the denture with palatal coverage and compressive in the denture without palatal coverage. Significantly less strain occurred in dentures with reinforcement than without reinforcement.

No differences seen in outcomes between three different methods of orthodontic retention

Three arm, parallel group, patient randomised trial. Seventy-five patients who had just completed a course of treatment with four premolar extractions and fixed straight wire appliances in both jaws (0.022 inch, MBT) having had no previous orthodontics, were randomised by participant ballot sampling. To be eligible they had to be in the permanent dentition, with space deficiencies in both jaws, normal skeletal and dentoalveolar sagittal, vertical and transverse relationships, Class I molars or 3mm anterior or posterior deviation. The three retention methods were: 1) removable vacuum-formed retainer with maxillary canine-to-canine and palatal coverage plus a mandibular canine-to-canine bonded retainer (GroupV-CTC); 2) an identical maxillary vacuum-formed retainer as in Group V-CTC plus stripping of mandibular anterior teeth (Group V-S); and 3) a prefabricated positioner covering all erupted teeth in both jaws (Group P). Patients were given appliances within one hour of debonding, which were worn more for the first than second year then discontinued. Dental casts were taken at four time points; before treatment, on removal of fixed appliances, after 12 months and 24 months of retention. Twenty randomly selected casts were measured by a single blinded assessor on two separate occasions, four weeks apart, using electronic digital callipers for inter-canine width; inter-molar width; arch length; overjet; and overbite. Height and estimated compliance was recorded at every visit. Successful retention using Little's Irregularity Index was considered to be <3.5mm. Seventy-five patients were enrolled, and 69 completed, the trial. The mean active treatment time was 1.7 years and mean age was 14.4 years (SD 1.5) at start of retention. Although there were statistically significant differences for some of the parameters measured, there were no clinically significant differences between the three retention methods. All three were equally effective in retaining orthodontic treatment results and controlling relapse to a clinically significant level even when the results were adjusted for cooperation, initial crowding, growth and gender. The major part of relapse took place during the first year of retention. All three retention methods, V-CTC, V-S and P, retained the orthodontic treatment results and prevented relapse within clinically acceptable levels. Most relapse took place within the first year of retention and changes during the second year were small or negligible.

Impacts of palatal coverage on bolus formation during mastication and swallowing and subsequent adaptive changes

Palatal coverage is often required for elderly edentulous patients with complete dentures. The purpose of this study was to clarify impacts of palatal coverage on bolus formation and subsequent adaptive changes. Subjects were 18 healthy young dentulous adults who wore 1·5-mm-thick palatal plates. Subjects were asked to feed 12 g of bicoloured rice as usual, and the bolus formation by mastication and swallowing in the pharynx was observed using a nasal videoendoscopy. The bolus formation index (BFI), number of mastication strokes until swallowing, visual analogue scale about swallowing easiness and masticatory performance using colour-changeable gum were measured under three conditions: before placement of the palatal plate (day 0), immediately after placement (day 1) and after 7 days of wearing the plate (day 7). BFI and visual analogue scale on day 1 were significantly lower than those on day 0, but those on day 7 significantly recovered to the level of day 0. The number of mastication strokes did not change from day 0 to day 1, however, that on day 7 was significantly higher. Masticatory performance on days 1 and 7 was significantly lower than that on day 0. Although palatal coverage inhibits bolus formation during feeding, subjects increased the number of mastication strokes until swallowing threshold as they adapted to palatal coverage over time. This adaptive change was due to compensate for the lowered masticatory performance to achieve bolus formation for comfortable swallowing.

Within‐Subject Comparison of Maxillary Implant‐Supported Overdentures with and without Palatal Coverage

The purpose of this study was to compare patient-reported outcomes for maxillary implant-supported overdentures with and without palatal coverage. Twenty-one maxillary edentulous patients (six women, 15 men) were included. In total, 42 implants were inserted in the anterior maxilla. All patients received implant-supported overdentures on two retentive anchors with palatal coverage for 2 months. Thereafter, patient satisfaction was assessed by means of questionnaires capturing the oral health impact profile (OHIP) on functional limitation, physical pain, psychological discomfort, physical, psychological and social disability, and handicap. Additionally, cleaning ability, general satisfaction, speech, comfort, esthetics, stability, and chewing ability were rated. Subsequently, palatal coverage was reduced, and the patients wore the overdentures for another 2 months. Patient satisfaction was obtained in the same way as above, and the evaluated parameters were compared for the two overdenture designs. There were no significant differences between implant-supported overdentures with and without palatal coverage for any of the OHIP domains. The evaluation of additional parameters revealed significantly higher patient satisfaction for esthetics (mean difference 8.8 mm ± 24.6) and taste (mean difference 28.4 mm ± 29.9) without palatal coverage, p < .01. Within the limits of this study, maxillary overdentures supported by two implants were equally satisfactory with and without palatal coverage.

A randomized crossover study comparing two mandibular repositioning appliances for treatment of obstructive sleep apnea

The purpose of this study was to determine whether treatment outcomes vary according to the design of the mandibular repositioning appliance (MRA). Two titratable MRA's were compared. The designs differ in advancement hardware and configuration of acrylic both in bulk and interocclusal contact. The primary treatment outcome was the Respiratory Disturbance Index (RDI). Other outcomes that were compared included Sleep Apnea Quality of Life Index (SAQLI), Epworth Sleepiness Scale, oxygen saturation, and subjective feedback regarding experiences with the appliances. Twenty-four subjects were recruited from consecutive referrals for MRA therapy following diagnosis of obstructive sleep apnea (OSA) by polysomnography. Subjects were randomly assigned to a treatment arm of the crossover study. Each subject underwent an initial sleep study with a type III home monitor to establish a baseline RDI. Subjects were then treated with one of the two MRAs determined by random assignment. The MRA self-titration phase was monitored until a treatment position was determined, and the home sleep study was repeated. After a 2-week period without any OSA treatment, subjects received the second MRA and the self-titration treatment protocol was repeated. At completion of treatment with each appliance, subjects answered questionnaires and underwent a sleep study with the type III monitor. The outcome data for each appliance were compared using analysis of variance. Eighteen subjects completed the treatment protocol. There were no significant statistical differences in treatment outcomes between the two appliances. There was a statistically significant (p ≤ 0.05) preference for a MRA design with minimal coverage of teeth and palate. The subjects' appliance selection was consistent with a corresponding reduction in SAQLI score for the selected appliance. Although no statistically significant difference was observed between the two appliances in the outcomes measured, there was a trend toward greater improvement with the appliance with less acrylic resin bulk and less interocclusal contact. MRA selection should favor titratable, unobtrusive designs with appropriate construction to promote acceptance and adherence to MRA therapy.

Marginal bone loss around unsplinted mini-implants supporting maxillary overdentures: a preliminary comparative study between partial and full palatal coverage.

To evaluate and compare marginal bone loss around mini-implants supporting maxillary overdentures with either partial or full palatal coverage. Nineteen edentulous patients complaining of retention problems involving their maxillary dentures were randomly allocated in two groups. Group I (n = 10) received maxillary dentures with full palatal coverage, and group II (n = 9) received maxillary dentures with partial palatal coverage. In total, 114 mini-implants (6 per patient) were inserted using the nonsubmerged flapless surgical approach and loaded immediately with maxillary overdentures. Each implant was evaluated at the time of initial prosthetic loading and at 6, 12, and 24 months thereafter. Radiographic evaluation was performed in terms of vertical and horizontal bone loss. Implant mobility (via Periotest values) was measured using a Periotest device, and patient satisfaction was evaluated with a visual analog scale. The cumulative survival rate was calculated using Kaplan-Meier analysis. After 2 years, the mean vertical bone loss in groups I and II was 5.38 and 6.29 mm, respectively, while the mean horizontal bone loss in groups I and II was 1.52 and 1.93 mm, respectively. Most bone resorption occurred within 6 months after overdenture insertion in both groups. Group II recorded significant higher vertical bone loss and Periotest values than group I at all observation times. The cumulative survival rates of the mini-implants were 78.4% and 53.8% for groups I and II, respectively. All patients were satisfied with their maxillary overdentures in terms of retention and chewing ability. Rehabilitation of edentulous maxillae with unsplinted mini-implants supporting overdentures and in particular with a combination of partial palatal coverage is not recommended because of excessive marginal bone resorption and the higher failure rate of mini-implants than was expected.

Palateless custom bar supported overdenture: A treatment modality to treat patient with severe gag reflex

To suggest a custom bar supported overdenture treatment modality for prosthodontic management of patients with severe gag reflex. Some patients have a severe gag reflex and cannot tolerate conventional maxillary complete dentures with maximum palatal coverage and extensions of all borders. The condition further gets complicated in patients suffering from respiratory problems along with severe gag reflex. Severe gagging acts as a barrier to treat such patients with accepted clinical procedures and prevent patients from wearing the prosthesis. By saving some of the remaining natural teeth and fabricating, a horse shoe shape palateless simple tooth or bar supported overdenture can be successfully used for treating such patients. The remaining maxillary right and left canines were prepared with the tapered round end diamond bur to receive copings of custom bar after intentional root canal treatment of same teeth. Impression was made with light body and putty of the polyvinyl siloxane elastomer with double step putty wash technique. Impression was poured with die stone. Wax pattern of copings with bar was fabricated with inlay wax which was invested and casted. After retrieving the bar, it was finished and its fit was evaluated. The coping-bar assembly was finally cemented with the glass ionomer cement. Palateless overdenture was fabricated by conventional technique used for the fabrication of complete denture. Palateless custom bar supported overdenture procedure can be successfully used for the management of patients with severe gag reflex with improved denture retention, stability, chewing efficiency and comfort of the patient.

Influence of anterior palatal coverage on perception and retention in complete dentures

Oral perception is adversely affected by palatal coverage in complete denture wearers. The purpose of this study was to determine whether an opening in an anterior palatal base enhanced oral perception and the effect of the size of the opening on retention. Ten healthy dentate individuals (5 men, 5 women; age range: 22-29 years) participated in the perception test. The time required to sense a nylon thread embedded in test food was measured. The test was performed with 3 types of experimental palatal form: no-opening; small-opening, where the opening was located in the anterior region of the palatal base; and large-opening, where the opening was located between the incisive papilla and the third palatal rugae. No palatal coverage was used as a control. Retention force was measured by pulling and loading tests. In the pulling test, pulling force was applied to 2 points on the experimental denture base, and in the loading test, loading force was applied to 6 points. Response times (sec) and retention forces (N) were analyzed using a 1-way ANOVA for repeated measurements followed by the Bonferroni test for multiple comparisons (α=.05). A significant difference was observed in response time in fiber perception between bases with or without a small opening (P =.017). In the pulling test, retention force with the small-opening type was 4% lower at the molar region, and 35% lower at the center of gravity than in the no-opening type. Retention force in the large-opening type was lower than in the small-opening type. In the loading test, retention force was 13 N or higher in all 3 types. The small-opening type of palatal coverage improved oral perception and demonstrated sufficient retention force.

Patient Satisfaction with Maxillary 3‐Implant Overdentures Using Different Attachment Systems Opposing Mandibular 2‐Implant Overdentures

Patient-based outcomes with maxillary overdentures on a minimum number of implants, opposing mandibular 2-implant overdentures are not evident in the literature. To evaluate patient's satisfaction with maxillary 3-implant overdentures, opposing mandibular 2-implant overdentures, using two different attachment systems over the first 2 years of service. Forty participants wearing mandibular 2-implant overdentures for 3 years were randomly allocated to one of two similar implant system groups to receive maxillary 3-implant overdentures. Twenty participants were allocated to splinted and unsplinted attachment system treatment groups for each system. Patient satisfaction with pre-treatment complete maxillary dentures, with maxillary 3-implant overdentures at baseline and annually for 2 years, was measured using visual analogue scale questionnaires and the oral health impact profiles. Palatal coverage of the maxillary overdentures was reduced at the first annual recall. Data showed significant improvement in pain reduction, comfort, stability, and function variables of the visual analogue scale after treatment. Analysis by prosthodontic design using visual analogue scale showed no significant difference. The total oral health impact profile-14 scores after treatment for all participants, regardless of prosthodontic design, were significantly lower (more satisfied). The overall oral health impact profile-20E score at baseline was significantly higher (more satisfied) compared with pre-treatment conventional maxillary dentures. No significant changes were observed in the first or second years compared with baseline results. Twenty-two participants (84.6%) preferred reduced palatal coverage, regardless of prosthodontic design, after 1 year. Twenty participants (76.9%) still preferred reduced palatal coverage at the end of the second year. The provision of maxillary 3-implant overdentures to oppose mandibular 2-implant overdentures significantly improve levels of patient satisfaction compared with conventional maxillary dentures.