A 6-year follow-up study of oral function in shortened dental arches. Part I: Occlusal stability

Effect of rehabilitation by using the shortened dental arch concept on the thickness of the masseter muscle and occlusal force: A pilot study

STATEMENT OF PROBLEM

Knowledge of the effect of a shortened dental arch on masseter muscle thickness and occlusal force is sparse but could help clinicians understand how a shortened dental arch might affect the stomatognathic system.

PURPOSE

The purpose of this pilot clinical study was to evaluate and compare the masseter muscle thickness and occlusal force of participants rehabilitated by using a shortened dental arch with matched completely dentate individuals.

MATERIAL AND METHODS

Twelve partially edentulous participants with a minimum of 1 posterior occluding pair on each side of the arch were enrolled in the study. The mandibular arch of these participants was rehabilitated by using a single posterior mandibular implant crown (group S). The maxillary arch of all participants in group S was intact. Masseter muscle thickness (cm) and occlusal force (N) were recorded before (T1) and 6 months after implant rehabilitation (T2) for each participant. Twelve participants were selected as controls (group C). They were matched for age, sex, height, and weight with group S and evaluated for masseter muscle thickness and occlusal force. Masseter muscle thickness was evaluated by using ultrasonography during the rest position and maximum volumetric clenching. Occlusal force was measured with an occlusal force measuring appliance. All recordings were done for the left and right sides of the arch. Descriptive analysis was followed by comparison between groups and within group S by using the paired t test (α=.05).

RESULTS

Higher masseter muscle thickness and higher occlusal force were observed in group C than in group S before and after rehabilitation. An increase in masseter muscle thickness in the rest position and in maximum volumetric clenching was observed within group S after rehabilitation. Before rehabilitation, a difference in the masseter muscle thickness between group S and group C was statistically significant for the left side at the rest position (P=.017) and during maximum volumetric clenching (P=.016). After rehabilitation, the difference between group S and group C was not statistically significant for masseter muscle thickness at the rest position (P=.890 for right side and P=.555 for left side) and during maximum volumetric clenching (P=.109 for right side and P=.755 for left side). The difference in occlusal force between group S and group C was statistically significant for the right side and left side (P<.001) before rehabilitation and statistically not significant after rehabilitation (P=.161 for the right side and P=.134 for the left side).

CONCLUSIONS

Rehabilitation following the concept of a shortened dental arch increased masseter muscle thickness and occlusal force in partially edentulous individuals, making the masseter muscle thickness and occlusal force comparable with those of a completely dentate arch.

Treatment alternatives for the rehabilitation of the posterior edentulous maxilla

Rehabilitation of the edentulous maxilla with implant-supported fixed dental prostheses can represent a significant clinical challenge due to limited bone availability and surgical access, among other factors. This review addresses several treatment options to replace missing teeth in posterior maxillary segments, namely the placement of standard implants in conjunction with maxillary sinus floor augmentation, short implants, tilted implants, and distal cantilever extensions. Pertinent technical information and a concise summary of relevant evidence on the reported outcomes of these different therapeutic approaches are presented, along with a set of clinical guidelines to facilitate decision-making processes and optimize the outcomes of therapy.

Effect of the posterior stop on temporomandibular disorders: A systematic review

Background. Temporomandibular disorders have common signs and symptoms, including pain in the masticatory muscles, limitation or deviation in a mandibular range of motion, and other common patient complaints, such as headache and earache. The main focus of this study was to collect comprehensive and integrated data on the effect of the posterior stop on temporomandibular joint disorders, as well as prevention, treatment, and follow-up care for the patients. Methods. The authors conducted the search in PubMed, SCOPUS, Web of Science, Cochrane Library, CINHAL, Medline, ProQuest, Google Scholar, Magiran, IranDoc, SID, and Iranmedex databases for relevant articles. A list of selected study sources, related conferences, and grey literature were manually searched in addition to the databases mentioned above. A 21-year time limit was imposed (2000-2021). Results. Finally, 16 articles were selected to be reviewed in this systematic review. The designs of the included studies were heterogeneous, and due to the low number of studies covered, the authors could not carry out a meta-analysis. Conclusion. The causes of temporomandibular disorders are multifactorial and complex. Therefore, it is difficult to investigate the relationship between this disorder and predictors. The results of the present study indicate that to determine the effect of the posterior stop on temporomandibular joint disorders, more clinical trials and case-control studies should be conducted.

Anterior occlusion in shortened dental arches

Objectives

The aim of this study was to examine the occlusion of anterior teeth in individuals with shortened dental arch (SDA).

Material and methods

In a case–control clinical study, 41 individuals with SDA and 41 individuals with complete dental arch (CDA) participated. The CDA control group was matched for age and gender. Testing for occlusal contacts of anterior maxillary teeth was conducted by biting on foil strips (8 µm) with subjectively normal bite force (NBF) and maximal bite force (MBF). The data was analyzed on individual and tooth levels.

Results

The median rates of anterior maxillary teeth with occlusal contacts were 0.67 (NBF) and 0.83 (MBF) in the SDA group and 0.50 (NBF) and 0.83 (MBF) in the CDA group. Within both groups, the contact rates were significantly higher in MBF. The group difference with NBF was significant. A generalized linear model showed that the odds of an anterior maxillary tooth to have an occlusal contact were greater in the SDA both for NBF with an odds ratio (OR) 2.277 and MBF with an OR 1.691.

Conclusions

The findings suggest effective compensatory mechanisms relative to the occlusal function in individuals with SDA.

Clinical relevance

The study delivers further evidence regarding the SDA concept as a viable option in the management of posterior tooth loss.

Normative and subjective need for dental prosthesis: accuracy and agreement in a population based-study

The aim of our study was to compare normative need for dental prosthesis (estimated by dentists) with subjective need (self-reported) by testing the accuracy and agreement and comparing direction and magnitude of associations with independent variables using both as outcomes. A representative sample of a birth cohort study (n = 900) was assessed at 31 years of age. Subjective need was obtained from questionnaire. Both normative and subjective need variables were dichotomized in (a) individuals with need for dental prosthesis and (b) without need for dental prosthesis. Accuracy was assessed by sensitivity (SE), specificity (SP), positive (PPV) and negative (NPV) predictive values. Agreement of normative and subjective need was assessed estimating kappa index. Sex, income, educational level, use of dental services and self-reported oral health were used to compare the associations with normative and subjective need. Prevalence of normative need was 48.9% and subjective need was 34.9%. Agreement (kappa: 0.43) and accuracy between normative and subjective need for dental prosthesis was low (SE: 56.5, 95%CI: 50.3-62.6; SP: 85.8, 95%CI: 81.1-89.7; PPV: 79.1, 95%CI: 72.6-84.7; NPV: 67.3, 95%CI: 62.1-72.2). When considering individuals with loss in anterior teeth, results showed a good agreement (kappa: 0.82) and accuracy between normative and subjective need (SE: 93.3, 95%CI: 68.1-99.8; SP: 88.9, 95%CI: 51.8-99.7; PPV: 93.3, 95%CI: 68.1-99.8; NPV: 88.9, 95%CI: 51.8-99.7). Direction and magnitude of associations with normative and subjective need were similar. Thus, normative need for dental prosthesis differs from subjective need in adults, except when anterior losses are present.

Dentists' Attitudes in Jordan towards the Shortened Dental Arch Concept: A Cross-Sectional Study

Aims

To assess the awareness, knowledge, attitudes, and application of the shortened dental arch (SDA) concept by dentists in Jordan.

Materials and Methods

In this cross-sectional survey, a questionnaire was disseminated to a random sample of 150 dentists working in private practices, university hospitals, or governmental institutes. The chi-square (X ² ) test was used to examine associations.

Results

One hundred and six dentists responded (70.7% response rate). Fifty-five were females. 82.1% were aware of the SDA concept. The fewer the years of experience, the more likely the dentists were aware of the SDA concept (X ² , P=0.024) and the more likely they learned about it through undergraduate education (X ² , P < 0.001). In a hypothetical clinical situation of a patient >50 years of age with missing molar teeth, 45.3% agreed that the molars should be replaced, while 54.7% did not agree. Improving mastication was the main reason for agreeing (81.6%), while having reduced functional benefit was the main reason for disagreeing (64.9%). The treatment modality most commonly recommended was implants fixed partial dentures (84.9%). Of those aware of SDA, 67.8% agreed it could have a useful place in treatment planning within Jordan. Cost reduction for patients was the main reason for this answer, as reported by 51% of those who agreed. 26.4% did not apply SDA for any of their patients, while 50.6% applied it for <10% of their patients.

Conclusion

The majority of the dentists was aware of the SDA concept and had a positive attitude towards it; however, few of them applied it in their practice.

Biological complications of removable dental prostheses in the moderately reduced dentition: a systematic literature review

OBJECTIVES

The aim of the present study was a systematic review and subsequent meta-analysis on biological complications of removable prostheses in the moderately reduced dentition.

MATERIALS AND METHODS

A systematic literature search in established medical databases (MEDLINE, EMBASE, BIOSIS, SciSearch, Cochrane, FIZ Technik Web) and a hand search of relevant dental journals was conducted. The search terms were relevant MeSH terms, free search terms, and combinations of the two. The search included randomized controlled trials, prospective and retrospective studies with data on biological complications of removable dental prostheses in the moderately reduced dentition with at least 15 participants, an observation period of at least 2 years, and a drop-out rate of less than 25%. The selection of relevant publications was carried out at the title, abstract, and full-text level by at least two of the authors involved. The publications included were tabulated and analyzed.

RESULTS

Of the original 12,994 matches, 1923 were analyzed by title, 650 by abstract, and 111 according to the full text. A total of 42 publications were ultimately included. The following parameters were evaluated.

TOOTH LOSS

Results varied, depending on the observation period, between 0 and 18.1% for clasp-retained removable dental prostheses (RDPs), between 5.5 and 29% for attachment-retained RDPs, and between 5.5 and 51.7% for double crown-retained RDPs.

CARIES

Results varied, depending on the observation period, between 0 and 32.7% for clasp-retained RDPs, between 1.8 and 29% for attachment-retained RDPs, and between 1.8 and 16.4% for double crown-retained RDPs.

ENDODONTIC TREATMENT

Results varied, depending on the observation period, between 3.5 and 19.2% for clasp-retained RDPs, between 6.9 and 16.4% for attachment-retained RDPs, and between 0.6 and 13.9% for double crown-retained RDPs.

TOOTH FRACTURE

Results varied, depending on the observation period, between 1.7 and 5.3% for clasp-retained RDPs, between 12.7 and 40% for attachment-retained RDPs, and between 0.4 and 4.4% for double crown-retained RDPs.

TOOTH MOBILITY

There were no changes or improvements for clasp-retained RDPs. The better the pre-treatment and supportive care is, the smaller the differences are. For double crown-retained RDPs, a slight increase was found in one study. The results for the parameters probing depth and radiological bone loss were inconclusive.

GINGIVAL RECESSION

Gingival recession seemed to be favored by a mandibular sublingual bar. Compared to fixed restorations, removable restorations seemed to be associated with a more pronounced need for dental treatment. Stringent pre-treatment and supportive care reduced the complication rates.

CONCLUSIONS

Heterogeneous study designs and data analyses rendered a meta-analysis impossible, so that an evaluation at the highest level of evidence could not be performed.

CLINICAL RELEVANCE

Within the limitations of this study, it would be correct to state that removable dental prostheses require intensive maintenance. Suitable pre-treatment and supportive care can lower the complication rates, in the absence of which they constitute trigger factors for (additional) biological complications.

The importance of communication in the construction of partial dentures

Removable partial dentures (RPDs) are still a very important treatment modality in general dentistry to replace missing teeth. With the increase in popularity of implants, RPDs are sometimes seen as an 'old-fashioned' treatment option and if not carefully designed can be damaging to oral tissue and aesthetically less favourable. However, there is still a significantly large cohort of patients for whom RPDs are the best option for replacement of teeth either due to a failing dentition, inappropriate anatomy or financial considerations. This article explores the importance of effective three way communication with the patient, the laboratory and the dental nurse to support the provision of reliable and predictable prosthodontic outcomes.

INTRODUCTION

Significance of mandibular molar replacement with a dental implant: a theoretical study with nonlinear finite element analysis

Background

Dental implants are frequently applied to unilateral defects in the mandible. However, implant placement in the molar region of the mandible can be difficult due to anatomical structure. The aim of this study was to evaluate the distribution of occlusal force in a mandibular shortened dental arch (SDA) with implants.

Methods

Three-dimensional finite element (FE) models of the mandible with varying numbers of teeth and implants were constructed. Models Im6 and Im67 contained one and two implants in the defect of the left molar region, respectively. Models Im456 and Im4567 contained three and four implants in the defect of the left premolar and molar regions, respectively. Model MT67 contained a defect in the molar region with no implant placed. Model MT7 represented natural dentition without a left second molar, as a control. Modification of the condition of occlusal contacts assuming the intercuspal position was performed before analysis under load 400 N; therefore, the load condition as total force on the occlusal surface was 400 N. FE analyses were subsequently performed under load conditions of loads 100, 200, and 800 N. The distribution of reaction forces on the occlusal surface and the mandibular condyle was investigated.

Results

Force distribution in models Im67 and Im4567 appeared to be symmetrical under all load conditions. Occlusal force distribution in models Im6 and Im456 was similar to that in model MT7. However, the occlusal force at the second premolars on the defect side in those models was larger under loads 100 and 200 N. Conversely, the occlusal force on the first molars was much larger than that in model MT7 under load 800 N.

Conclusions

Within the limitations of this theoretical study, we demonstrated that restoration with the same number of implants as missing teeth will show almost symmetric occlusal force distribution, and it will produce less biomechanically stress for a unilateral defect of the mandible. However, if restoration of a missing second molar with an implant is impossible or difficult, then an SDA with implants may also be acceptable except for individuals with severe bruxism.

Impact of Removable Partial Dental Prostheses on the Oral Health-Related Quality of Life of a South African Cohort with Varied Distributions of Missing Posterior Teeth

PURPOSE

To determine the impact of removable partial dental prostheses on satisfying the daily functioning and quality of life (QoL) of adult patients with different distributions of missing posterior teeth.

MATERIALS AND METHODS

A cross-sectional interventional study was carried out on 80 patients having variously distributed posteriorly shortened and interrupted arches. Treatment comprised provision of partial dentures by senior dental students, supervised by senior clinical teachers who had knowledge of the potential benefits of the shortened dental arch (SDA) concept. The Oral Impacts on Daily Performance Index was completed before and 6 months after prosthetic treatment across groups comprising Kennedy Classes I, II, and III arches. Analysis included descriptive statistics and associations and comparisons between variables.

RESULTS

Mean age of patients was 57.4 years (SD = 13.1), many were retired (72.2%), and a majority were females (60%). Most patients lived in urban areas (95%), and were largely unemployed (63.3%). At pretreatment, only 31.3% of patients reported having good dental health and satisfaction with their current oral state, while 82.5% said they had a great need for treatment. The negative oral impacts that were most frequently experienced were those of eating (67.5%), smiling (50%), and being emotionally disturbed (63.8%). Post-treatment, 76.3% indicated good oral health and satisfaction with no significant differences between the 3 Kennedy groups. Any further negative impacts were reported mostly for Kennedy Classes I and II.

CONCLUSIONS

Overall, significant reductions of negative impacts were observed following treatment with dentures, across the 3 Kennedy groups, with respect to improved function, satisfaction, and oral health-related QoL. The findings confirm the reliance by partially dentate patients in all 3 Kennedy groups on dentures for improved oral health, although the possible benefits of the SDA concept as an alternative treatment option was not specifically explored.

Is the shortened dental arch still a satisfactory option?

Aims Dental practitioners may hold the view that missing posterior teeth should be replaced to ensure a healthy masticatory system and satisfactory oral function. However, the shortened dental arch (SDA) concept is still in use, but after 35 years is it acceptable? This review searches the literature for the evidence and opinions regarding the suitability of the SDA as a current treatment modality.Methods Medline and PubMed databases were searched for relevant terms, all the abstracts were assessed and articles selected according to the pre-set exclusion and inclusion criteria.Results The search yielded 1,895 articles and after the assessment of the abstracts and application of the exclusion and inclusion criteria, 44 articles were selected for this review. These included 11 cohort studies, two longitudinal studies, two animal studies, three cross sectional studies, eight clinical studies and 18 case control studies. There appears to be a trend over the past three decades for more papers to be opposed to the SDA concept.Conclusion Evidence that the SDA causes pathology is lacking. Clinicians, healthcare authorities and patients have shown favourable attitudes towards the SDA and this continues, although there is an increase in studies opposing the concept and some are dissatisfied with this option. The concept remains viable particularly for the medically compromised patient or where restorations are considered unsuitable but further more specific studies are warranted.

The randomized shortened dental arch study: influence of two different treatments on interdental spacing over 5 years

OBJECTIVES

Being a secondary outcome in a multicenter randomized controlled trial, the present analysis focused on interdental spacing in the shortened dental arch (SDA). The aim was to evaluate changes in interdental spacing in dependence of two different treatments after an observation period of up to 5 years.

MATERIAL AND METHODS

Patients were either treated with a partial removable dental prosthesis (PRDP) for molar replacement (PRDP group) or according to the SDA concept aiming at a premolar occlusion (SDA group) in a randomized manner. Interdental spacing in the anterior region was measured with gauges and categorized as "0" (<0.1 mm), "1" (<0.5 mm), "2" (0.5-1 mm), and "3" (>1 mm). The statistical analysis was performed with analysis of variance models followed by linear contrast.

RESULTS

Ninety-one patients (SDA n = 41, PRDP n = 50) were included. Changes of interdental spacing were detected in 70.7 % of all cases. A significant difference between the mean score changes was found in the mandible comparing the PRDP group and the SDA group. The respective mean score changes from baseline to 5 years were 0.23 (SD 0.49) for the PRDP group and 0.02 (SD 0.30) for the SDA group (p = 0.023).

CONCLUSIONS

Major interdental spacing could be observed in neither of the groups. The SDA concept resulted in a slightly better outcome.

CLINICAL RELEVANCE

When deciding whether to replace missing molars, the present results give further support to the SDA concept.

A field survey of the partially edentate elderly: Investigation of factors related to the usage rate of removable partial dentures

Although the shortened dental arch (SDA) concept has been known to all over the world, acceptance of the SDA concept as an oral health standard can be questionable from the patients' point of view, even if it is biologically reasonable. Furthermore, because the health insurance system covers removable partial dentures (RPDs) for all citizens in Japan, SDA patients seem to prefer to receive prosthetic treatment to replace the missing teeth. However, there were few field surveys to investigate the usage rate of RPDs in Japan. The purpose of this study was to determine the usage rate of RPDs in older Japanese subjects and to investigate the factors related to the usage of RPDs. Partially edentate participants (n = 390) were included in this study. Oral examinations were conducted to record several indices. The Cochran-Armitage trend test was used to evaluate the relationship between the number of missing teeth and the usage rate of RPDs. Chi-squared tests and logistic regression analysis were conducted to evaluate the factors related to the usage rate of RPDs. Usage of RPDs had a significantly positive association with the number of missing distal extension teeth and bilaterally missing teeth. The usage rate of RPDs increased as the number of missing distal extension teeth increased (P for trend < 0·001). The conclusion of this study was that participants with missing distal extension teeth had higher usage rates of RPDs than other participants, and the usage rate increased as the number of missing distal extension teeth increased.

A study of dentists' preferences for the restoration of shortened dental arches with partial dentures

OBJECTIVE

This study aimed to use a utility method in order to assess dentists' preferences for the restoration of shortened dental arches (SDAs) with partial dentures. Also, the impact of patient age and length of the SDA on dentists' preferences for the partial dentures was investigated.

MATERIALS AND METHODS

Totally, 104 subjects holding a basic degree in dentistry and working as staff members in a private dental college in Saudi Arabia were interviewed and presented with 12 scenarios for patients of different ages and mandibular SDAs of varying length. Participants were asked to indicate on a standardized visual analog scale how they would value the health of the patient's mouth if the mandibular SDAs were restored with cobalt-chromium removable partial dentures (RPDs).

RESULTS

With a utility value of 0.0 representing the worst possible health state for a mouth and 1.0 representing the best, dentists' average utility value of the RPD for the SDAs was 0.49 (sd= 0.15). Mean utility scores of the RPDs across the 12 SDA scenarios ranged between 0.35 and 0.61. RPDs that restored the extremely SDAs attracted the highest utility values and dentists' utility of the RPD significantly increased with the increase in the number of missing posterior teeth. No significant differences in dentists' mean utility values for the RPD were identified among SDA scenarios for patients of different ages.

CONCLUSION

Restoration of the mandibular SDAs by RPDs is not a highly preferred treatment option among the surveyed group of dentists. Length of the SDA affects dentists' preferences for the RPD, but patient age does not.

Differences in functional outcomes for adult patients with prosthodontically-treated and -untreated shortened dental arches: a systematic review

This review examined differences in functional outcomes and patient satisfaction when shortened dental arches are left untreated compared to their restoration to complete arch lengths with different prosthodontic interventions.

METHODS

A protocol was developed according to the criteria for a systematic review. All relevant databases were searched to identify appropriate clinical trials regardless of language or publication status. Predetermined eligibility criteria were applied, trial quality assessed and data extracted for each study. Relevant outcomes assessed were: functioning ability, patient satisfaction and harmful effects on oral structures.

RESULTS

Searches yielded 101 articles: 81 from electronic databases and 20 from reference lists of retrieved articles (PEARLing searches). Sixty-nine citations were assessed for eligibility after removing 32 duplicate records. After reading titles and abstracts, a total of 41 records were excluded and the full-texts of the remaining 28 records were read. Only 21 records were included for the SR because 7 records were excluded after reading the full-text reports. These 21 records report the outcomes of four randomized controlled trials (RCTs) and one non-randomized clinical trial (CT) which were pre-specified and used for this review. No on-going studies were found and no eligible studies were excluded for failure to report the reviewer's pre-specified outcomes. Outcomes were reported in the retrieved 21 articles. A narrative explanation of the pre-specified outcomes is reported for the 3 comparison groups (which were based on the different interventions used for the individual clinical trials). The shortened dental arch as a treatment option is encouraging in terms of functioning, patient satisfaction and cost-effectiveness. By using only high quality studies it was expected that the results would be more reliable when making conclusions and recommendations, but some of the included studies had to be downgraded due to methodological errors.

Pressure distribution of implant-supported removable partial dentures with stress-breaking attachments

PURPOSE

This in vitro study investigated the pressure distribution of the implant-supported removable partial dentures (RPDs) with the stress-breaking attachments under the occlusal force.

METHODS

The experimental model of bilateral missing premolars and molars was modified from a commercial simulation model. Five pressure sensors were embedded near the bilateral first molars, first premolars, and medio-lingual alveolar crest. Two implants were placed near the second molars, and they were connected to the denture base using the following conditions: complete separation between the denture base and implant with cover screws (CRPD), flexible connection with a stress-breaking ball (SBB) attachment, and rigid connection without stress breaking with healing caps (HC). The pressure at five different areas of the soft tissue and the displacement of the RPDs were simultaneously measured, loading up to 50 N. The coefficient of variation (CV) for each connection was calculated from all data of the pressure at five areas to evaluate the pressure distribution.

RESULTS

The pressure on medio-lingual alveolar crest and molars of the HC was less than SBB and CRPD. In contrast, the pressure on premolars of SBB was greater than for the HC and CRPD. The CV of SBB was less than that of HC and CRPD. Denture displacement of HC and SBB was less than for CRPD.

CONCLUSIONS

Within the in vitro limitations, precise denture settlements and pressure distribution under the denture base could be controlled using an SBB attachment. An SBB attachment might be able to protect the implant from harmful force.

Effect of implant-supported prosthesis on the bite force and masticatory efficiency in subjects with shortened dental arches

The aim of the study was to assess changes in bite force and masticatory efficiency in shortened dental arch (SDA) subjects rehabilitated with implant-supported restoration for 1st molar. Ten SDA subjects with bilaterally missing mandibular molars (experimental group) were recruited. In each subject, one tapered threaded implant was placed bilaterally in 1st mandibular molar region and restored. Masticatory efficiency was evaluated objectively by measuring the released dye from chewed raw carrots, with a 'spectrophotometer' at 530 nm preoperatively and at 3 months after restoration. Bite force was evaluated using 'bite force measuring appliance' preoperatively, at 6 weeks and at 3 months after restoration. Ten completely dentate-matched subjects (in terms of age, sex, height and weight) acted as control. The results revealed that as compared with the control group, the experimental group showed significantly less (P < 0.05) mean maximum bite force at pre-restoration and at 6 weeks after restoration. Although at 3 months the mean maximum bite force value was less than the control group but the mean difference was statistically insignificant. The mean difference of masticatory efficiency between control and experimental group was statistically significant (P < 0.05) before restoration, but was statistically insignificant at 3 months after restoration. Thus it was concluded that after the restoration of mandibular arch with implant-supported prosthesis, both bite force and masticatory efficiency of all SDA subjects increased and were comparable to that of matched completely dentate subjects after 3 months.

Cost-effectiveness of tooth replacement strategies for partially dentate elderly: a randomized controlled clinical trial

OBJECTIVE

To conduct a cost-effectiveness analysis comparing two different tooth replacement strategies for partially dentate older patients, namely partial removable dental prostheses (RDP) and functionally orientated treatment based on the shortened dental arch concept (SDA).

METHODS

Ninety-two partially dentate older patients completed a randomized controlled clinical trial. Patients were randomly allocated to two treatment groups: the RDP group and the SDA group. Treatment effect was measured using impact on oral health-related quality of life (OHrQOL), and the costs involved in providing and maintaining care were recorded for all patients. Patients were followed for 12 months after treatment intervention. All treatment was provided by a single operator.

RESULTS

The total cost of achieving the minimally important clinical difference (MID) in OHrQOL for an average patient in the RDP group was €464.64. For the SDA group, the cost of achieving the MID for an average patient was €252.00. The cost-effectiveness ratio was therefore 1:1.84 in favour of SDA treatment.

CONCLUSION

With an increasingly ageing population, many patients will continue to benefit from removable prostheses to replace their missing natural teeth. From a purely economic standpoint, the results from this analysis suggest that the treatment of partially dentate older adults should be focused on functionally orientated treatment because it is simply more cost-effective.

Reappraisal of the removable partial denture as a treatment option for the shortened dental arch

For patients with shortened dental arches, many treatment options are available. The existing situation can be maintained by stabilizing the present dentition and improving the occlusion without extending the arch. Alternatively, the shortened dental arch can be extended by either a free-end saddle removable partial denture, cantilevered fixed bridge, or by an implant-supported prosthesis. The free-end saddle removable partial denture can be considered a simple, non-invasive, and relatively cheap treatment option for the shortened dental arch. It was believed that such prosthodontic rehabilitation would be beneficial for the patients in terms of improving oral functions. However, the existing literature indicates that the prognosis of free-end saddle removable partial denture is not predictable, it is problematic, and its contribution to oral functions in patients with shortened dental arches is considered to be dubious. This paper reviews and summarizes the current literature about the outcome of extending the shortened dental arch by a free-end saddle removable partial denture. It also outlines factors that may affect the prognosis of this prosthetic treatment.

[Preventive strategies in prosthetic dentistry]

Despite the success in preventing oral diseases, the prevalence of tooth loss in the German population remains high and increases with age. Today, the advances in prosthetic dentistry allow necessary tooth replacement following preventive strategies-after considering benefits and risks. Modern treatment options improve the overall prognosis of the stomatognathic system and the quality of life of the affected patients significantly. Hereby, adverse iatrogenic effects can be minimized or even completely avoided by extending the traditional treatment spectrum, e.g., using adhesively fixed restorations and implant-supported restorations, and refraining from placing restorations that are unnecessary from the medical point of view. Generally, patients benefit greatly from prosthetic treatment and the achieved health gain is remarkably high. It encompasses not only the recovery of the impaired oral functions but also extends to the whole human organism, including nutrition, digestion, musculoskeletal system, as well as mental and social well-being.

The association between individual and contextual factors and functional dentition status among adults in Rio Grande do Sul State, Brazil: a multilevel study

Functional dentition plays an important role in maintaining masticatory function, which is closely related to the number of teeth present in the mouth. The objective of this study was to investigate the association between individual and contextual factors and functional dentition (defined as the presence of at least 20 teeth) in Brazilian adults. This was a multilevel cross-sectional population-based study with a two-level structure and a total sample of 10,407 adults from 84 municipalities (counties). The exposures at both levels were demographic, socioeconomic, and oral health treatment-related. Multivariate analyses showed that higher prevalence rates of functional dentition were associated (p < 0.01) with municipalities having higher mean income and fluoridated water supply and with individuals living in urban areas, younger adults, males, those with more schooling and higher income, those that reported having visited the dentist in the previous 12 months, and those with access to information on prevention. The findings suggest that research on tooth loss and functional dentition should take different socioeconomic factors into account.

Tooth-related risk factors for tooth loss in community-dwelling elderly people

OBJECTIVE

To appropriately explore risk factors for tooth loss operating at the tooth-level, subject-related factors and a hierarchical data structure have to be considered. The purpose of this study was to evaluate tooth-related and subject-related risk factors affecting tooth loss.

METHODS

A 10-year longitudinal survey was carried out on 286 elderly subjects. At baseline, the prosthodontic status and abutment function of the 5574 teeth were recorded. Tooth loss was defined as the main outcome variable, and a multilevel logistic regression model considering subject and tooth levels was applied.

RESULTS

Tooth loss was found in 75% of subjects and most frequently in molars. A multivariable, multilevel logistic regression revealed that the following tooth-related variables were significantly related to tooth loss over 10 years: maxillary teeth, multirooted teeth, single crowns, abutment teeth for a fixed/removable partial denture (FPD/RPD), and periodontally involved teeth. Among them, single crowns, abutment teeth for an FPD, and teeth with severe periodontal disease at baseline had the highest odds of 5.1, 6.0, and 7.1, respectively.

CONCLUSIONS

The findings of this study suggest that tooth loss is the result of complex interactions of tooth-related factors. Several tooth-related variables including multirooted teeth, abutments, and single crowns were found to be possible risk factors for tooth loss. Thus, these findings confirm and underline the potential benefit of minimizing prosthetic treatment of molars.

Edentulism and shortened dental arch in Brazilian elderly from the National Survey of Oral Health 2003

OBJECTIVE

To describe the distribution of edentulism and estimate the prevalence of functional dentition and shortened dental arch among elderly population.

METHODS

A population-based epidemiological study was carried out with a sample of 5,349 respondents aged 65 to 74 years obtained from the 2002 and 2003 Brazilian Ministry of Health/Division of Oral Health survey database. The following variables were studied: gender; macroregion of residence; missing teeth; percentage that met the World Health Organization goal for oral health in the age group 65 to 74 years (50% having at least 20 natural teeth); presence of shortened dental arch; number of posterior occluding pairs of teeth. The Chi-square test assessed the association between categorical variables. The Kruskal-Wallis and Mann-Whitney tests were used to assess differences of mean between number of posterior occluding pairs teeth, macro-region and gender.

RESULTS

The elderly population had an average of 5.49 teeth (SD: 7.93) with a median of 0. The proportion of completely edentulous respondents was 54.7%. Complete edentulism was 18.2% in the upper arch and 1.9% in the lower arch. The World Health Organization goal was achieved in 10% of all respondents studied. However, only 2.7% had acceptable masticatory function and aesthetics (having at least shortened dental arch) and a mean number of posterior occluding pairs of 6.94 (SD=2.97). There were significant differences of the percentage of respondents that met the World Health Organization goal and presence of shortened dental arch between men and women. There were differences in shortened dental arch between macroregions.

CONCLUSIONS

The Brazilian epidemiological oral health survey showed high rate of edentulism and low rate of shortened dental arch in the elderly population studied, thus suggesting significant functional and aesthetic impairment in all Brazilian macroregions especially among women.

Effect of implant support on distal extension removable partial dentures: in vitro assessment

The implants in implant-supported removable partial dentures (RPDs) are placed in the edentulous ridge to stabilize the RPD and minimize the resultant rotational movement. This study investigated the effect of implant placement on RPD stability. A model simulating a mandibular bilateral distal extension missing was fabricated using epoxy resin and silicone impression material as thin (1 mm) and thick (2 mm) soft tissues. Five pressure sensors (PS-10K, Kyowa, Tokyo, Japan) were attached near the left and right first molars (#36 and #46), first premolars (#34 and #44) and medio-lingual alveolar crest. Five bilateral distal extension RPDs with Co-Cr frameworks were conventionally fabricated. After the implants were placed at the bilateral second molar areas, healing caps (4.5 mm high) were connected to the denture base with autopolymerized resin to support the RPD. As in a conventional RPD, sealing screws were placed without connecting them. Loads up to 5 kg were applied, and the pressure and displacement of the RPDs (n = 5) were simultaneously measured and analysed using the Wilcoxen test (alpha = 0.05). There was less pressure on both thin and thick soft tissues, the #36, #46 and the medio-lingual alveolar crest from the implant-supported RPD than from the conventional RPD (P < 0.05). There were no significant differences in pressure on #34 and #44 between the two RPDs (P > 0.05). There was significantly less denture displacement of the implant-supported RPD than of the conventional denture (P < 0.05). Implant support helped prevent the displacement of distal extension RPDs and decreased the pressure on soft tissues.

What dentition assures oral function?

OBJECTIVE

To evaluate the relationship between dentition and oral function.

MATERIAL AND METHODS

A search of the English literature was undertaken using PubMed and appropriate keywords. Citations were identified and hand sorted to confirm their validity against our inclusion criteria. Four specific areas of oral function were addressed; (I) masticatory function, (II) aesthetics, satisfaction and psychosocial ability, (III) occlusal support and stability and (IV) other functionality including tactile perception, phonetics and taste.

RESULTS

From an initial pool of 1460 citations, 83 articles met the inclusion criteria. These were summarized and relevant data extracted for incorporation into the review. Masticatory efficiency (assessed as comminution efficiency) and masticatory ability (self-reported) are both linked to the number of teeth. A minimum of 20 teeth with nine to 10 pairs of contacting units (including anterior teeth) is associated with adequate efficiency and ability. Tooth numbers below that level yield impaired masticatory efficiency and are likely to result in reduction in reported masticatory ability. Aesthetics and satisfaction are markedly impaired with loss of anterior teeth. Satisfaction is most likely to be achieved in people who also retain a premolar dentition. Further, there is little increase in satisfaction seen in subjects who retained molar teeth. However, there are marked variations in subjective measures of aesthetics and psychosocial comfort between age groups, social classes, cultures, regions and countries. For most people, occlusal support and stability are obtained with three to four functional posterior units with a symmetrical pattern of tooth loss or five to six units with an asymmetrical pattern. There was no relationship between occlusal factors and symptoms of temporomandibular dysfunction. Phonetics may be maintained even with large anterior restorations. Patients generally attribute a low significance to phonetics, tactile perception and taste compared with mastication and appearance.

CONCLUSIONS

The World Health Organization goal for the year 2000, namely to maintain a natural dentition of not less than 20 teeth throughout life, is substantiated by the current literature review as this proposed dentition will assure an acceptable level of oral function.

Orthodontic and prosthetic rehabilitation of unilateral free-end edentulous space

Most patients prefer fixed dentures, even in the presence of uni and bilateral free-end saddle. The most suitable treatment for this is an implant or implant-supported prosthetic restoration. A combined prosthetic and orthodontic treatment with distalization of a posterior tooth towards the edentulous region is an alternative approach. This study involved a 34.3 year old female patient who had a free-end edentulous space on the left mandibula and missing 1st and 3rd molars on the right mandibula. The patient was offered both a removable partial denture and implant treatment options. A detailed explanation of her situation and suitable treatments were given but she refused both options. Therefore, an alternative combined treatment involving prosthodontic and orthodontic disciplines was performed. The second premolar tooth was distalized orthodontically and used as a distal bridge abutment. After 65 months, prosthetic restoration was functional and abutment teeth and periodontium were pathology free, and the patient was satisfied with the results.

A review of the shortened dental arch concept focusing on the work by the Käyser/Nijmegen group

The aims of this paper were to review the literature on shortened dental arches with special focus on publications of the Käyser/Nijmegen group, and to evaluate the discussions on the shortened dental arch concept found in the literature. A MEDLINE (PubMed) search was conducted for articles in English published in the dental literature from 1966 to November 2005. The search revealed epidemiological, cross-sectional and longitudinal clinical studies as well as opinion papers, the majority of which were published by the Dutch group. The studies found in general no clinically significant differences between subjects with shortened dental arches of three to five occlusal units and complete dental arches regarding variables such as masticatory ability, signs and symptoms of temporomandibular disorders, migration of remaining teeth, periodontal support, and oral comfort. The findings from cross-sectional studies were corroborated longitudinally. No systematic clinical study with conflicting results was found. The shortened dental arch concept was accepted by a great majority of dentists but not widely practised. The studies reviewed showed that shortened dental arches comprising anterior and premolar teeth in general fulfil the requirements of a functional dentition. It may therefore be concluded that the concept deserves serious consideration in treatment planning for partially edentulous patients. However, with ongoing changes, e.g. in dental health and economy, the concept requires continuing research, evaluation and discussion. Patients' needs and demands vary much and should be individually assessed but the shortened dental arch concept deserves to be included in all treatment planning for partially edentulous patients.

Efficacy of a posterior implant support for extra shortened dental arches: a biomechanical model analysis

The purpose of this study was to test the efficacy of utilizing implants underneath distal free-end denture bases to establish a stable occlusal support for extreme shortened dental arches (ESDA). The authors constructed a two-dimensional finite element model of the ESDA where only lower anterior teeth remain. Posterior occlusal support was provided by a fixed partial denture with an osseointegrated implant (IFPD), fixed cantilever partial denture (CFPD), or a removable partial denture with or without an implant underneath (IRPD and RPD). A dentate mandible model was the control. When muscle vectors simulating clenching force were applied, stress levels on the temporal bone surface area under each configuration were compared, to evaluate the efficacy in establishing the occlusal support. The largest stress increase in temporal bone was found in the ESDA situation followed by the RPD. The least amount of stress increase was found with the IFPD followed by IRPD when the implant was placed in the molar region. The stress increase with IRPD was about 20-45% of the amount with RPD. Our results suggest that IFPD provides most favourable and stable occlusal support, however, IRPD with a single posterior implant also provide stable occlusal support with reducing the stress levels in the temporomandibular joint.

The shortened dental arch: A review of the literature

The functional demands of patients are highly variable and individual, requiring dental treatment to be tailored to the individual's needs and adaptive capability. The World Health Organization indicates that a functional, esthetic, natural dentition has at least 20 teeth, while the literature indicates that dental arches comprising the anterior and premolar regions meet the requirements of a functional dentition. The English-language peer-reviewed literature pertaining to the short dental arch (SDA) was identified through the Medline search engine covering the period between 1966 and the present and critically reviewed. This treatment option for the partially dentate patient may provide oral functionality, improved oral hygiene, comfort, and, possibly, reduced costs.

Biomechanics of cantilever fixed partial dentures in shortened dental arch therapy

PURPOSE

The purpose of the present study was to investigate, by means of 3-dimensional finite element analysis, aspects of the biomechanics of cantilever fixed partial dentures replacing the maxillary canine in shortened dental arch therapy. The null hypothesis was that no differences would be identified by finite element analysis in the mechanical behavior of the 2 designs of cantilever fixed partial denture under different scenarios of occlusal loading.

MATERIALS AND METHODS

Single- and double-abutted cantilever fixed partial dentures were modeled and analyzed using the finite element packages PATRAN and ABAQUS. Displacement and maximum principal stresses (magnitude and location) within the fixed partial dentures, supporting structures, and the periodontal ligament/bone and abutment/retainer interfaces were examined under 20 different scenarios of axial and lateral occlusal loading.

RESULTS

The results indicate that more displacement occurred in the 2 rather than the 3-unit cantilever fixed partial denture, with the greatest displacement having occurred under lateral loading. The maximum principal stresses observed in the periodontal ligament/bone interfaces were greatest buccocervically, with the highest value being observed in the 2-unit fixed partial denture under lateral loading. The highest maximum principal stresses observed in the retainer/abutment interfaces were located cervically in relation to the distal margin of the retainer of the 2-unit fixed partial denture under axial loading.

CONCLUSIONS

It was concluded that in adopting a cantilever fixed partial denture approach for the replacement of a missing maxillary canine in shortened dental arch therapy, there may be merits, in terms of mechanical behavior, in selecting a double-rather than a single-abutment design. Furthermore, prostheses' displacement and functional stresses may be minimized by reducing lateral loading and avoiding pontic only loading.

Occlusal and TMJ loads in subjects with experimentally shortened dental arches

To determine whether shortened dental arches (SDAs) cause functional overloading of the teeth and the temporomandibular joints, which has been implicated in periodontal diseases and temporomandibular disorders, we investigated the influences of SDA on occlusal and joint loads. Bite force and masticatory muscle electromyograms were recorded in five dentate subjects who clenched maximally on intra-oral appliances, creating symmetrical SDAs experimentally. Muscular forces estimated from the recorded electromyograms were fed into a finite element jaw model for calculating bite forces and joint loads. Comparison between the measured and the calculated bite forces ensured that the joint loads were representative. The bite force on each tooth increased with missing molar occlusions, while joint loads decreased. The bite force per root surface area was always greatest on the most posterior tooth, and these values were most constant. The findings provide no evidence that SDA causes overloading of the joints and the teeth, which suggests that neuromuscular regulatory systems are controlling maximum clenching strength under various occlusal conditions.

Abutment positioning in a cantilevered shortened dental arch: a clinical report and static analysis

This article describes the extension of a shortened dental arch with a cantilever fixed partial denture in a patient who refused to be treated with an implant-supported and retained prosthesis. Orthodontic movement of the distal abutment to enlarge the interabutment span was performed before the final restoration. The mechanical advantage of the enlarged span in a cantilever fixed partial denture is analyzed, discussed, and demonstrated by 2-dimensional static analysis.

New paradigms in prosthodontic treatment planning: a literature review

New treatment modalities have expanded the choices available to prosthodontists and their patients. At the same time, an explosion of data has called into question the validity and efficacy of certain forms of traditional prosthodontic treatment. Together, these factors have greatly complicated the treatment-planning process. The purpose of this article is to provide a framework for the prosthodontic treatment-planning process that incorporates the latest evidence-based information available. A review of the literature was undertaken through a Medline search. Articles published in English from 1975 through 2001 were evaluated; selected articles were chosen for review on the basis of a subjective judgment of their relevancy and significance to the clinician.