A policy perspective for Army dentists performing posterior restorations.

Abstract

This study reviews trends and behaviors in both the civilian and Army dental communities with regard to posterior restorations and choices of material for the restoration, and suggests policy perspectives for Army dentists based on this behavior. Items of research interest include provider experience, type of restorative material used, and the survival time of a posterior restoration. Data are obtained from the Washington Dental Service and the Army Dental Care System. The methodology used to review performance is Data Envelopment Analysis. The study shows that efficient dental providers produce longer lasting restorations regardless of material, and there is no difference in survival rate between amalgam and composite restorations when the restoration is performed by an efficient provider. The study has managerial implications for the improvement of military dental services through increased operational efficiency. The study has policy implications for better allocation of Army health resources and improved dental readiness within the military force structure.

Introduction

The longevity of dental restorations depends on many factors including dental materials, the dentist, and patient hygiene habits. Dentistry is often referred to as a cottage industry, yet the cost of dental services are substantial. In 2001, US national dental expenditures were $65.6 billion, an 8% increase from 2000. (1) Since dental restorations do not last forever, a cycle of restoration replacement is critical within DoD because dental readiness is a requirement for US military force deployment. A systematic review on the literature of the longevity of dental restorations concluded that 50% of all restorations will last 10 to 20 years, although significantly higher and lower survival times have been reported. (2)

Several types of commonly used restorative materials are used for posterior teeth. These include amalgam, composite resin, glass ionomers, gold, and porcelain. Dental amalgam is an alloy of mercury that incorporates silver, tin, copper, and zinc. Amalgam remains a popular dental restorative material because it is versatile, adapts well to use in the wet oral environment, and is relatively inexpensive. Previous studies have found amalgam to be the most cost effective and durable restorative material available. (3-8)

Composite material is a quartz and resin base material that can be matched to the patient's natural tooth color and is seen as more cosmetically pleasing to patients. However, it has been viewed as less reliable for posterior restorations because of increased mastication forces and the potential marginal leakage due to insufficient bonds on large sub-gingival restorations.

Less common restorative materials for posterior teeth include glass ionomers, gold, and porcelain. Glass ionomers are also used in a limited fashion, primarily serving as an interim or temporary restoration. Gold and porcelain based restorations are also options for restoring posterior teeth, but are significantly more expensive. (3-4) Cast gold restorations function well due to similar wear properties to enamel, but laboratory fees significantly increase costs and the restorations generally do not meet the aesthetic concerns of the 21st century. Porcelain restorations meet aesthetic concerns but are expensive and can wear opposing enamel surfaces. The cost of porcelain and gold restorations make them impractical for use within the Army and DoD.

With respect to the two common restorative materials, amalgam has historically been considered the restorative material of choice for most dental providers due to the perception of superior performance and lower cost. However, due to increasing aesthetic concerns of the military population and public concerns over the safety of amalgam restorations due to the perceived effects of mercury, amalgam restorations may no longer be the consumer or provider restorative material of choice.

Supporting these public concerns, the 1999 American Dental Association (ADA) Services Rendered Survey reported that 54.1% of all restorations placed in the US in 1999 were composite resin based. (5) This significant shift toward composite use has not taken place in the military, where more effective and less expensive amalgam is still popular. This investigation evaluates the longevity of amalgam and composite posterior restorations, including the impact of efficiency with respect to Army dental providers.

Background

In the civilian community, amalgams are more frequently placed on posterior teeth. This is because dental insurance companies are more likely to reimburse a patient for an amalgam restoration on a molar, but decline to reimburse for composite restorations because the amalgam restoration is cheaper and fits the standard of care. (6,7) The ADA conducted a nationwide survey of dental fees in 1999 which found that the average cost (based on the 75th percentile) of an amalgam posterior two-surface restoration is approximately $93, while a similar composite restoration costs approximately $139. (8)

Amalgam restorations in permanent teeth have been the most common operative dentistry procedure in the United States. (9-14) Dentists have avoided placing more aesthetic posterior composite restorations because of their perceived inferiority and higher costs to patients, as well as the likelihood of their being refused reimbursement by the dental insurance companies. (11,15-17) Some researchers suggest that amalgam's acceptable record of accomplishment has established a practice guideline that establishes it as the posterior material of choice in restorative dental practice. (18) Recent research suggests that, in fact, improved materials and techniques are resulting in superior composite restorations, with failure rates virtually indistinguishable from those of amalgam. (19) The results of this study are significant as DoD strives to increase the dental readiness of the force structure while minimizing dental costs.

Though composite restorations are gaining popularity in private practice settings, public settings such as the military and public health clinics may be slower to adopt these practices. The perceived durability combined with being less expensive and technique sensitive makes amalgam the chosen restoration material. The Army Dental Care System (ADCS) provides dental services for the 485,000 active duty Soldiers worldwide and their family members overseas. The system can be viewed as providing dental care in a public health arena. The 1999 ADA data on restorative material use is a reflection of private practitioner trends as the data comes from insurance claims. In that study, 54% of all restorations were composite restorations, while only 46% were amalgam. The figure compares composite and amalgam restorations placed by the ADCS versus the US national average.

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The trend shown by private practitioners is not consistent with restorations by Army dental providers. In fiscal year 2002, 60.7% of all restorations placed in the ADCS were amalgam, and 38.1% of posterior restorations were composite. The data clearly documents a practical variance between increased use of posterior composite restorations by private dentists versus the amount used by Army dental providers.

Why has the shift to composite resin experienced in the US civilian sector not been mirrored by military providers? One reason may be that military dental providers still view amalgam as the material of choice. Another reason may be lack of training of providers in posterior composite restorations, a situation which could be addressed in continuing education and residency training.

The results of this study have managerial implications at the clinic level and policy implications at the Army level. Currently, Army practitioners make their own decisions of which material to use based on training and their judgment as to the best material for the particular patient. If composite restoration longevity were to surpass amalgams in repeated studies, the Army may want to review existing policies and initiate a continuing education program on the use of posterior resin restorations.

Data and Statistical Instrument

For the statistical part of the study, data were obtained from the Washington Dental Service, Seattle, WA. This dental insurance claims database contains over 1.5 million patient encounters and over 23,000 contributing dentists. Providers and patients are followed from January 1993 through December 1999. A total of 1,240 dentists in the database met researcher selected screening criteria of performing at least one-hundred posterior restorations over 7 years. The final patient sample size included 279,999 restorations, of which 194,484 were amalgams and 85,515 were composites. DEA-Solver Professional Version 2.0 (SAITECH Decision Support Systems, May 2001) was used as the statistical measuring instrument in the analysis. Data were obtained from the ACDS for the policy part of the study.

Methods

In order to analyze the differing effectiveness of amalgam and composite survival times, this study employs a relatively new technique, data envelopment analysis (DEA). In the DEA methodology, efficiency is defined as a Pareto-optimal allocation of resources. An allocation is Pareto-optimal or Pareto-efficient if production and distribution cannot be reorganized to increase the utility of one or more units without decreasing the utility of other units. Stated another way, efficiency is a simple ratio whose quotient is derived as a function of outputs over inputs where E = fx (O/I). DEA has been successfully applied in numerous examples from many industries, and specifically to the study of health care organizations and professionals. (20-27)

DEA introduces the concept of decision-making units (DMU), in this case the individual dentist, by considering multiple inputs and outputs while identifying the most efficient providers. A DMU is regarded as the entity responsible for converting inputs into outputs and whose performance is to be evaluated. In DEA, Inputs are defined as any factor used as a resource by the DMU for producing something of value. It may also be any environmental factor that bears a strong effect on how the resources are consumed. Outputs are the amount of goods, services, or other outcomes obtained as a result of the processing of resources or any factor that describes the qualitative nature of the resulting outcome. (26-30) The DEA program algorithm is briefly presented by the following equation (28-30):

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

Where

E denotes the efficiency score for each dentist in the set of o = 1 ... n dentists

[y.sub.ro] is the selected output "r" produced by each dentist in the set "o"

[x.sub.io] is the selected input "I" used by each dentist in the set "o"

[y.sub.rj] is the selected output "r" produced by dentist "j"

[x.sub.ij] is the selected input "I" used by dentist "j"

In this formulation, [u.sub.r] and [v.sub.i] are the weights assigned respectively to output "r" (survival time) and input "i", both obtained from DEA. The constant is represented by [c.sub.o].

The output variable includes the survival time of the restoration, while inputs represent provider experience, amalgam, and composite materials. When the aforementioned equation is linearized for conceptual purposes, the efficiency formulation of a dentist can be expressed as:

Efficiency = f [(survival time)/(amalgam + composite + provider experience)]

Efficient dental providers receive an efficiency score of 1.0.

Results

Table 1 displays frequencies for efficient and inefficient providers. Table 2 shows that 122 providers, which constituted approximately 10% of the study population, were found to be efficient. Table 2 suggests a disparity between efficient and inefficient providers. The average material survival time for efficient dentists is 46.47 months, for inefficient dentists it is 41.79 months. Efficient dentists have an average restoration longevity of 4.7 months longer than that of the inefficient providers. An interesting finding is that the average experience for efficient dental providers is approximately 25 years, whereas inefficient providers have approximately 5 years less experience. The difference is significant ([rho] <.001, [chi square] = 18.98). The results suggest that efficient providers are, on average, 17% more experienced than inefficient providers. Efficient providers also performed 44% of their total replacements with composite material, while inefficient providers used composite material only 29% of the time. This suggested that in order to become efficient, inefficient providers should perform more composite restorations.

Post hoc analysis was performed, and iDEAs-W was used to identify theoretical possibilities for improvement of the inefficient population of dental providers. A virtual output/virtual input quotient was calculated to achieve an Iota ([iota]) value by balancing projections of inefficient provider properties along the efficiency frontier. Projections provide information on the relative changes required by each dentist that must be made in order to reach the efficiency frontier.

Iota is obtained by standardizing the total weighted distance by the virtual input. Iota values are a measure of total inefficiency in terms of proportional input reduction. An Iota value less than one ([iota] < 1), indicates inefficiency. A [iota] =.5 indicates that the DMU should be able to decrease input by 50% to be efficient. The theoretical model in this case returned an [iota] = .807, suggesting that only 20% of dentists in this population are capable of achieving efficiency with 5 years additional experience without changing their amalgam based practice pattern.

Discussion

This study suggests that the longevity rate of a restoration is related to the experience of the provider. This is particularly important within the Army because dental health status is critical for individual and unit deployment. The results also suggest that providers who work with amalgam, regardless of severity, are less likely to be efficient than are providers who work with composite restorations. This is significant because amalgam is the compound of choice within the Army. The finding may suggest that less experienced providers may need additional continuing education focused on the placement of posterior resin restorations, since 71% did not use composite material. This is an appropriate area for further study within the Army.

The research suggests a positive correlation between experience and success for procedures. The growing options for dental restoration within private industry will also become a growing trend for Army consumers in the years to come. From a managerial perspective, military dental clinics have not traditionally given patients options. As a result, managers in military dental clinics may encourage dental providers to practice both amalgam and composite material restorations in order to increase efficiency and quality.

Military dentists who wish to improve efficiency are challenged to implement meaningful programs and services that can positively affect military readiness. This study clearly demonstrates that Army dental clinics may be missing an opportunity to improve efficiency by expanding the use of composite restorations. Additionally, it is clear that as the level of efficiency of dental providers increases, the quality and longevity of the dental restoration also increases. Improvements in the training of Army dental providers will provide better patient care and ultimately increase the life of a posterior restoration. This will result in increased military readiness. Therefore, Army dental clinic managers are encouraged to integrate the use of composite restorations and improved provider training in their strategic planning process to ensure operational efficiency and improve military readiness.

Policy Implications

This study suggests that provider experience and practice patterns are key indicators for the success of a posterior restoration. This finding is particularly important within the Army where recent dental graduates compose a large percentage of the general dentistry provider force. These results would suggest the Army should invest additional training funds early in a dentist's career to improve their practice efficiency. Also, it may be appropriate to consider the range of clinical practice, quality of practice, and efficiency of practice. The results also support the use of retention bonuses later in a dentist's career to retain efficient providers.

Military dentistry continues to seek best practices as a method to improve quality and reduce costs. If posterior composite restorations were found to last longer than amalgam, long-term cost savings could be realized by extending the replacement cycle of restorations. Future research in restoration compounds that address the replacement cycle could reduce costs and enhance the deployability of individuals in military units. Since this study shows employment of experienced providers results in 4.7 months of longevity in the restoration and improved dental fitness of the population, the findings stress the importance to the military of hiring experienced dentists. This can be achieved by selective hiring from dental schools or the use of hiring bonuses for dentists in private practice. Additionally, a retention bonus may be a sound economic investment to encourage experienced dentists to remain on active duty.

The data also suggest that dental providers with a more restricted scope of practice (i.e., higher percentage of amalgams regardless of severity) are less likely to be efficient than those dental providers with a broader scope of practice (i.e., higher percentage of composite restorations). While this finding may have different implications within the Army due to unique practice settings, it does suggest that inefficient dental providers should broaden their scope of clinical practice to include both amalgam and composite restorations to become efficient. By providing additional training to dental providers, it is possible to improve the overall rate of efficiency leading to an improved state of dental readiness and lower overall costs.

This study has implications within the Army because military readiness is affected by the choice of dental materials. During the recent mobilization of forces for Operation Iraqi Freedom, approximately 25% of the reserve component Soldiers had emergent dental conditions effecting their deployment. Over half of those emergent conditions were corrected with dental restorations. The prevailing thought is that posterior amalgam restorations should be utilized on this high-risk group. However, the research suggests that composite restorations can last as long or longer than amalgams when performed by an experienced provider.

The results of this study suggest that dental experience is key to restoration survivability. However other factors bear mentioning. The first factor addresses patient preference and the policy implications of preference. As already mentioned, the use of composites has recently exceeded amalgam for the first time in the civilian practice setting. Clearly, patients are interested in composite restorations. Reasoning behind this trend may be explained through Rogers' diffusion of innovation theory. (31) In brief, tenets of the theory suggest that the relative advantage, compatibility, and observability of an innovation (composite resin) will positively increase its adoption by (in this context) dental patients. Many patients and some dental professionals remain concerned about the effects of mercury in amalgam, despite clinical studies dismissing the risk. Thus composite has a perceived advantage of being a safer alternative to amalgam. In addition, the aesthetics, or cosmetic value, of composites versus amalgam is immediately observable to patients and quite compatible with the current societal pressure to maximize one's appearance. In summary, the perceived advantage and concerns over one's appearance have served to create a strong public demand for the use of composite resin and have given patients a viable choice. By offering composite restorations to military beneficiaries, the Army may gain a strategic advantage in recruitment and retention leading to a significant increase in patient satisfaction.

Surprisingly, only 70% of all North American dental schools teach their students how to repair a resin-based composite dental filling. (32) The gaining popularity of this material combined with the similar longevity identified from this study necessitates composite repair practices at all schools. From a policy perspective, the Army may want to ensure similar coverage is offered to all military beneficiaries.

Summary

There have been few long-term studies of the longevity rate of amalgam or composite material and none that have considered the experience of the provider in the longevity rate. (33,34) This study has important implications for the Army because it suggests that experience is a key factor in the longevity rates of composite restorations.

Since experience is such a significant factor in restoration longevity rates, this study has implications for provider selection, training, retention, and specialty pay. Additionally, the study may improve the level of efficiency of practice within military dental clinics as well as improve the deployability of active duty and reserve military members. A 10% increase in efficiency would result in significant cost savings and an improved readiness posture for the military. The impact of a 10% increase in efficiency created by the 4-month increased longevity of restoration is even more important because it represents a long-term system-wide saving that is compounded as newer materials and procedures are used throughout military dental care. More importantly, the financial savings are enhanced by the improved deployability of the active duty and reserve forces.

Portions of this article were included in the presentation "Performance of Dental Providers on Restorations--A DEA Evaluation" at The 16th Triennial Conference of the International Federation of Operational Research Societies, 8-12 July, 2002, hosted by the UK Operational Research Society, University of Edinburgh, Scotland.

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LTC Coppola is an Assistant Professor in the US Army-Baylor University Graduate Program in Health Care Administration, US Army Medical Department Center & School, Fort Sam Houston, TX.

Dr. Harrison is Assistant Professor of Health Administration at the University of North Florida, Jacksonville, FL.

LTC Chaffin is a resident in the US Army-Baylor Graduate Program in Health Care Administration, Fort Sam Houston, TX.

Dr. Burke is Assistant Professor in the School of Information Studies, Florida State University, Tallahassee, FL.

Table 1. Frequencies of provider services for amalgam and composite
restorations between inefficient and efficient providers.

                                   Inefficient Providers

                                  Encounters    Percentage

Total                              216,376
Amalgam                            152,693           71%
Composite                           63,683           29%
Amalgam Severity 2 Surface          61,891        40.59%
Amalgam Severity 3 Surface          61,237        40.10%
Amalgam Severity 4 Surface          29,475        19.30%
Composite Severity 2 Surface        35,639        55.96%
Composite Severity 3+ Surface       28,044        44.03%

                                   Efficient Providers

                                  Encounters    Percentage

Total                               15,607
Amalgam                              8,695           56%
Composite                            6,912           44%
Amalgam Severity 2 Surface           3,787        43.55%
Amalgam Severity 3 Surface           3,096        35.61%
Amalgam Severity 4 Surface           1,812        20.84%
Composite Severity 2 Surface         3,814        55.18%
Composite Severity 3+ Surface        3,098        44.82%

Table 2. Comparison of age, experience, and survival times of
restorations between efficient and inefficient dentists.

                                 Inefficient    Efficient
                                  Providers     Providers

Total Number                        1,118        122
* Provider years of experience      20.25        24.5
Average survival time of
  restoration (months)              41.79        46.47
Mean age of dental provider         46.7         50.9

* Chi-square ([chi square]) = 18.98 [rho] < 0.0001