The introduction of Dr. Victor Sendax’s concept of a mini dental implant (MDI) system ^17,^18,^19,^20,²¹ has produced a major impact in tissue engineering techniques employed in otolaryngology/head and neck surgery, craniomaxillofacial surgery, and oral and maxillofacial reconstructive surgery.

Definition of MDI

In UK MDI training workshops, Peckitt defines MDIs with the following characteristics:

• Implant: titanium alloy or other implantable material

• Implant dimensions (< 2.5 mm in diameter)

• Fused abutment (for additional strength)

• Atraumatic placement (minimal surgery)

Indications for the Use of MDIs

Medical Considerations

Minimal surgery is needed in nearly all patient groups. MDIs have advantages for patient groups in which minimal surgical trauma is an added advantage or quite simply mandatory. MDI placement is often flapless, predictable, and quick. This offers advantages to medically compromised patients (e.g., patients with stable anticoagulation and antiplatelet medication regimens) and those undergoing major reconstructive maxillofacial surgery (Figure 7-1).

FIGURE 7-1 Hematoma after flap surgery and placement of four standard endosseous dental implants in the anterior mandible for the provision of an overdenture.

The knife edged alveolar ridge may require direct exposure for access and trimming of the alveolar crest. However, this can often be achieved with direct exposure and with minimal tissue reflection, which is of distinct benefit to medically compromised patients.

Surgical Considerations

Five-year survival rates for patients with advanced squamous cell carcinoma of the oral cavity are poor and have not improved significantly in the past 30 years.^1,¹³ Current treatment modalities are:

Although there have been significant advances in free flap tissue transfer, especially in the reconstruction of the hemimandible and anterior mandible, the introduction of techniques such as the free fibula flap has an association with both donor and recipient site morbidity, cumulating in the disaster of flap loss and loss of the patient (Figure 7-2).

FIGURE 7-2 Anatomy of Free Fibula Flap.

A free fibula flap is commonly used in the reconstruction of the anterior mandible and body of mandible on the premise that vascularized bone maintains its volume and contour.

Patients with oral cancer are commonly debilitated and are more likely to have higher American Joint Committee on Cancer (AJCC) fitness scores.³ The implications are that this group of patients is more likely to succumb to the consequences of major surgery. Therefore offering patients treatment options involving reduced surgical trauma has distinct advantages (Table 7-1).

TABLE 7-1 AJCC Fitness Scores

AJCC (H) Performance Scale	Definition
H0	Normal activity
H1	Symptomatic and ambulatory
H2	Ambulatory > 50% of time Occasionally needs assistance
H3	Ambulatory < 50% of time Nursing care required
H4	Bedridden May need hospitalization

Moreover, major surgical treatment modalities are costly to the purchasers of healthcare, and if neither cure nor adequate palliation can be achieved at reasonable cost, the value of such treatment protocols requires reappraisal.²²

Logistical Issues

The low cost of MDIs is of special interest to state healthcare systems providing complex composite reconstructive head and neck cancer services. With modern planning techniques, MDI placement is possible at the time of resection and reconstruction with presurgical manufacture of the dental prosthesis. As we shall see, treatment is even possible without the use of flap surgery. This further improves the efficiency of the treatment modality, making treatment possible in a single surgical procedure. The financial implications of this scenario are profound for the patient whose surgery is simplified, for the provider with reduced demand for resources, and for the purchaser with significant reduction in cost (Table 7-2).

TABLE 7-2 Oral Cancer Surgery Costs

Type of Surgery	Annual Cost
Reconstructive surgery	≤18,125,000 ($28, 206,078)
Engineering assisted surgery™	≤10,537,875 ($16,399,014)
Savings	≤7,587,125 ($11,807,064)

Indications: MDI Implants in Oral Rehabilitation?

• For stabilization of any overdenture system

• Craniofacial applications

• Obturator

Anatomical Considerations

Atrophic Ridges

Factors Influencing Functional Dentition

The 1998 Adult Dental Health Survey (Oral Health)²⁶ in the United Kingdom documented that a minimum of 21 teeth are required for functioning dentition (Figure 7-3).

FIGURE 7-3 Proportion of dentate adults who have partial dentures by the number of natural teeth.

In a base sample size of 923 adults with dental prostheses, speaking difficulties (9%), eating difficulties (37%), and other problems (16%) were recorded. An overall incidence of prosthetic problems was documented in 40% of patients sampled (Tables 7-3 to 7-6).

TABLE 7-3 Problems with Speaking with Dentures

Problem with Speaking	Percentage
Loose denture/slips when talking	4%
Alters or slurs speech	3%
Other speaking problems	2%
No problems	93%

Data modified from Adult Dental Health Survey Oral Health in the United Kingdom 1998. Office for National Statistics; London: The Stationery Office.

TABLE 7-4 Problems with Eating with Dentures

Problems with Eating	Percentage
Food sticks under denture plate	12%
Loose/denture/slips when eating	9%
Hurts gums	8%
Cannot chew or bite well	5%
Other eating problems	3%
No problems	74%

36% of patients have eating difficulties.

Data modified from Adult Dental Health Survey Oral Health in the United Kingdom 1998. Office for National Statistics; London: The Stationery Office.

TABLE 7-5 Other Denture Problems

Other Denture Problems	Percentage
Loose dentures	5%
Gets ulcers	3%
Sore gum/plate rubs gums	3%
Denture worn down	1%
Other denture problem	4%
No problems	84%

16% of patients have other denture problems.

Data modified from Adult Dental Health Survey Oral Health in the United Kingdom 1998. Office for National Statistics; London: The Stationery Office.

TABLE 7-6 Prosthetic Outcomes

Prosthetic Outcome	Percentage
Prosthetic problems (incidents)	40%
No problems	60%

Data modified from Adult Dental Health Survey Oral Health in the United Kingdom 1998. Office for National Statistics; London: The Stationery Office.

The implications of this survey imply that conventional prosthetic practice is delivering a quality of service with a 40% complication rate in the United Kingdom, and current primary treatment options require reappraisal in the light of recent technical advances in the sphere of MDI dentistry.

Because stability of the lower denture is now so effective with inexpensive MDIs and outcomes so superior (compared with the tissue-borne full lower denture prosthesis, which is indicated only if dental implant placement is contraindicated), Peckitt now advocates that the MDI-retained lower overdenture is now the primary denture treatment option.²²

MDIs and Complex Maxillofacial Reconstruction

If we consider the 40% prosthetic complication rate for routine edentulous cases, it is clear that more complex cases will present greater problems for the prosthetician, and it is advocated that a simple reliable cost effect system is required. Peckitt argues that MDIs fulfill many of the requirements:

Contraindications to the Use of MDIs

There are few, but include:

Medical	Psychiatric disease
	Chronic facial pain syndromes
	History of infected endocarditis
	Rheumatic fever

Rheumatic fever is not necessarily a contraindication; some cases may be deemed low risk. Treatment should be carried out in conjunction with a cardiology opinion. Echocardiography is a useful investigation in the assessment of risk.

Surgical	Severe jaw atrophy (bone height)
	Grade 4 bone density (not necessarily)
	Heavy occlusion that cannot be relieved
	Gross dental sepsis
	Immediate tooth replacement after extraction may present problems

Peckitt has demonstrated the successful use of MDI implants in severe maxillary atrophy ¹⁶ and in grade 4 bone density in conjunction with bone grafting and platelet rich plasma techniques,¹² with stability at 9 years.

Management of the Complex Reconstruction Case

History

Medical Status

• The patient must be declared medically fit for surgical component.

• A detailed medical examination is mandatory.

Dental

Dental considerations are of prime importance in achieving a satisfactory functional and esthetic result.

• A thorough dental examination is required for every patient.

• Teeth with poor prognosis must be identified and excluded from the treatment plan.

• If radiotherapy is planned, teeth in the immediate radiation field should be extracted.

• Adequate bone width is required.

Investigations

• OPT / lat chin / PA bone density

• I.D. nerve / sinus status

• Implant sites / selection / templates

• Study models / crown bridge

• Putty jig / suck down splint / drill guide

• CT scan for biomodel manufacture mandatory for complex orofacial or panfacial reconstructions

Prosthetic Evaluation

• Existing or conversion

• New prosthesis

What are Current Treatment Modalities and How do They Work?

Treatment planning involves clinical assessment, stabilization, and investigation using noninvasive and invasive techniques. Historically case planning implied a total reliance on the skills and performance of the clinician. In some cases resuscitation and emergency interventions are required to preserve life; in such cases secondary interventions are carried out to complete the treatment plan.

When the timing of an intervention and clinical stability permits planning as a single intervention, this is traditionally two dimensional (2D) with existing imaging technology that is commonly available. The treatment plan must then be replicated and translated into a three- dimensional (3D) patient. These protocols must have an association with a compromised outcome as a function of inaccuracy of plan translation, and it is to be noted that such comparable practice has been abandoned by other industries that have since demonstrated an improvement.

EAS concepts may be used in conjunction with the planning and facilitation of established interventions (i.e., current practice), new surgical procedures and medical devices (in particular MDIs), and customized medical devices.

The Art and Craft of Clinical Practice

Clinical practice has traditionally and proudly been regarded as an art or craft acquired through apprenticeship. However, the reliance on human performance does not lend itself to efficiency and homogeneity of outcome and has been superseded in industry by new reverse engineering planning technology, rapid prototyping, automation, and standardization of the production processes.

Although dental casts of the teeth and jaws have been used successfully for many years in treatment planning, recently new advances in engineering technology have made EAS possible for sister specialties. These advances include:

• The discovery of osseointegration;

• Transmucosal or transcutaneous implant systems (in particular the MDI concept of Dr. Victor Sendax);

• New (bio)engineering materials;

• Advanced computer technology;

• Computer assisted diagnosis, design, and manufacture;

• Rapid prototyping, reverse engineering, and biomodel manufacture;

• New manufacturing processes;

• Customized templates, jigs, and implants;

• Applications in customized tissue engineering.

These developments herald the introduction of new gold standards in healthcare, with an improvement in efficiency and quality already seen in other industries.

Successful Outcome

The parameters of successful outcome are often arbitrary and based on current practice, which does not necessarily portray the best outcome possible and does not take into account recent developments especially in the field of EAS. Best practice is a complex function of many parameters in relation to accepted national standards of outcome. In the United Kingdom, crucial data are not freely available or have not been documented; for many parameters, no national standards have been agreed upon. This has an adverse effect on clinical audit, evidence-based practice, and clinical governance issues.

Performance data related to other aspects of best practice throughout the healthcare industry is deficient, but if one considers the model of quality improvement in the manufacturing industry after advances in computer technology and adoption of automated processes, it is likely that poor performance indicators are related to human factors.

Medical Negligence

EAS technology provides the opportunity for presentation of hard copy evidence for cases of personal injury. The use of anatomical biomodels may protect both the patient and clinician in medical negligence cases. The use of EAS techniques is likely to reduce the incidence of litigation related to human error. The current annual cost of the United Kingdom’s NHS related medicolegal litigation runs at ≤7billion (USD $10.9 billion)/annum. If a 14% reduction in the cost of medical negligence litigation could be achieved by the adoption of EAS technology as the gold standard of duty of care, this would result in a saving of ≤1billion (USD $1.5 billion)/annum in the United Kingdom.

Applications of EAS in Healthcare

Let us therefore examine the effects of EAS on the delivery of healthcare on the available evidence.

Each year in the United Kingdom there are more than 2500 new cases of oral cancer ^14,^15,²⁴ (approximately 1% of all cancer registrations) with an annual mortality of approximately 1400 compared with 1339 deaths from cervical cancer in 1995. Some evidence shows that oral cancer is becoming more common in women and younger patients in the United Kingdom and other countries. Oral cancer is twice as common in men.

Although the incidence of oral cancer was static in the 1980s, now signs show a rising incidence. Four patients die of this disease every day in the United Kingdom.⁴

In the 1960s 15% of patients presented with T3 or T4 tumors; this increased to 28% in the 1980s, which implies that in England and Wales approximately 724 patients presented in 1991 with disease that would probably have been treated with complex composite free flap techniques in the United Kingdom.

In the United States in 2005, new cases of cancer of the oral cavity and pharynx were estimated at 29,370, with an estimated annual mortality of 7320 ² (Table 7-7).

TABLE 7-7 American Cancer Society Oral Cancer Estimates
New Cases and Mortality (2005)

Lymph Node Status and Survival

In a series of 2550 cases of epidermoid carcinoma of the oral cavity and oropharynx, Spiro et al ²⁵ observed a 14% reduction in 5-year survival—from 51% for the clinically negative neck (cN0) to 37% if only one node was histologically diagnosed positive for metastatic tumor,. If multiple unilateral nodes were histologically positive, the 5-year survival was reduced to 24% (i.e., the survival rate was nearly halved). For histologically involved bilateral nodes, the 5-year survival dropped to 5%. This series of patients roughly numbers the new cases that would be expected to present annually in the United Kingdom.

If it is accepted that the majority of deaths in oral cancer are related to local recurrence or direct extension of disease rather than from distant metastasis, it would appear that current treatment modalities are failing in their palliative aims, most commonly within the first 2 years of treatment.

National Cancer Statistics (United Kingdom)⁷

In the United Kingdom in 2005, 4926 persons were diagnosed with an oral cancer. Across countries, the highest incidence for both male and female patients is in Scotland.

In 2006 there were nearly 1700 deaths from oral cancer in the United Kingdom.

The overall age-standardized mortality rate has remained fairly stable between 1971 and 2006 at approximately 3.5 and 1.4 per 100,000 for male and female patients, respectively.

As with the incidence trends, the all-ages oral cancer mortality figure masks the variation in age-specific trends. Mortality rates have more than halved since the 1970s for men in their 70s and 80s. On the contrary, for men in their 40s, 50s, and 60s there has been a small but steady increase. For younger men the rate has remained stable.

The mortality in oral cancer is to be considered in context with epidemiologic data for all cancer registrations and associated mortality in the United Kingdom. The cost to the nation in terms of overall patient mortality is that 62% of patients will die from the disease.

Head and Neck Surgery: Cost of Treatment ¹⁵

Complex Composite Free Flap Techniques

In 1993 at the British Association of Oral and Maxillofacial Surgeons meeting in Cardiff, Lavery estimated the true cost of microvascular free flap transfer at ≤25,000 (USD $38,900) per oral cancer case.

Average Costs of Treatment: One Live Patient at 2 years

The average cost of a 2-year survival episode is documented at ≤85,000 (USD $132,000) for patients treated with complex composite microvascular techniques (assuming a 70% 2-year mortality rate at ≤25,000 (USD $38,900) per case in line with Lavery’s estimation). In a pilot study of seven patients with cancer treated in Doncaster Royal Infirmary with customized titanium implants,¹⁵ zero mortality was recorded at 4.5 years at a cost of ≤14,535 (USD $22,600) per case episode for those patients treated 1994 to 1996.

Complex composite microvascular flap reconstructive techniques are reserved for patients with advanced disease, the majority of which affect the mandible. If the percentage of cases presenting as T3/T4 cases of 28% is accepted, approximately 725 microvascular oral reconstruction episodes per year are carried out in the United Kingdom, at an annual cost of ≤18,125,000 (USD $28,206,000) (assuming the estimated cost of ≤25,000 (USD $38,9000) per episode has remained unchanged since 1993).¹⁵

The cost of free flap surgery in New Zealand has been estimated at NZ $60,000 to NZ $80,000 per case intervention (Izzard: 2007 Auckland Head and Neck Cancer Centre) (Table 7-8).

TABLE 7-8 Cost Comparison: Composite Free Flap Transfer Versus Engineering Assisted Surgery (EAS)

Composite Free Flap Transfer	EAS
≤25,000 (USD $38,900)/case	≤14,535 (USD $22,600)/case (7 patients)
70% expected mortality @ 2 years	0% mortality @ 4 years
Average cost: 2 year survival ≤85,000 (USD $132,000)	Average cost: 2 year survival ≤14,535 (USD $22,600)

Data from Peckitt: EAS Costs 1994-1996. Doncaster Royal Infirmary, United Kingdom, www.maxfac.com/costsavings.html.

Simplification of treatment plans incorporating (EAS techniques has demonstrated a reduction in cost (see Table 7-2) of treatment to ≤14,535 (USD $22,600) per surgical intervention and, in comparison, the national annual total cost of treatment would be ≤10,537,875 (USD $16,399,000) for this option, an annual saving to the nation of ≤7,587,125 (USD $11,807,000) plus an associated improvement in long-term overall mortality figures and statistical significance even on a small sample size.

Research and Development

The palliative care of patients with head and neck cancer is discussed by Lovel,¹¹ who quotes Stjernsward: “No further research is required; the knowledge of what needs to be done exists. The single most useful thing that we can do is to make sure that every patient benefits from that knowledge.”

However, “If surgical treatment is a component of such palliation, it is argued that there is still much to learn” (Peckitt).¹⁵

Treatment Planning: Huge Cost Savings with Biomodels

For the management of complex reconstruction and trauma cases, savings are higher per unit case as a function of the consequences of reduced surgical trauma. Savings of ≤30,000 (USD $46,685) per case intervention are possible ¹ with projections of reduced operating times, less dependency on critical care facilities, earlier discharge from hospital, and enhanced rehabilitation.

EAS: Discussion

New developments in engineering, used for the first time in oral and maxillofacial surgery,^15,²² permit the manufacture of accurate anatomical biomodels of the skeleton from CT scans, using a variety of reverse engineering methods. Biomodels have been used in treatment planning and the design and manufacture of customized titanium implants for the single staged reconstruction of the orofacial region using very simple cost effective interventions. These may carried out without surgery from a second surgical site and obviate the necessity for complex flap surgery.

In our experience, the Sendax MDI system has a pivotal role in complex orofacial reconstruction within the context of EAS. The system is a great example of EAS thinking.

We now have a treatment option that permits endosseous stabilization of a prosthetic device:

• With the advantages of a flapless technique and minimal trauma;

• In cases of compromised osseous width and/or bone volume;

• As a single staged or immediate technique;

• At low cost;

• To produce an excellent quality of prosthetic retention and palliation;

• With simple and economical salvage in the event of implant loss.

Moreover, the Sendax MDI system can be used in conjunction with anatomical biomodels and custom drill guides for precision placement. We have also used the MDI O-ring system in conjunction with customized implant manufacture where conventional MDI placement has been impossible, and we have used this method to replace the whole maxilla and midface in a surgery time of 1.5 hours and with patient discharge at 20 hours (i.e., same-day surgery).

With EAS planning techniques and relatively atraumatic surgical protocols, a single staged orofacial reconstruction, including the dentition, is now possible in most cases, obviating the need for multistaged and increasingly expensive treatment options for patients with a guarded prognosis.

The use of the Sendax MDI system has been so successful in head and neck reconstructive surgery practice in New Zealand that it is rapidly becoming the implant system of choice for this group of patients.

Within oral and maxillofacial surgery, EAS has special relevance in the planning and treatment of complex trauma, facial deformity, craniofacial/skull base surgery, and reconstructive surgery.