Prosthodontic Principles in Dental Implantology

More patients are requesting fixed prosthesis to replace missing teeth. More than 5 million dental implants are placed annually in the United States. This number will decrease in 2020 owing to the coronavirus disease-19 pandemic. The edentulous patient has a decreased quality of life. Prosthodontic rehabilitation/reconstruction of edentulism improves overall quality of life. Patient-reported outcome measures are subjective reports of patients’ perceptions of their oral health status and the impact that it has on their quality of life. This chapter contains a variety of prosthodontic principles for the reader to help satisfy the needs and expectations of the patient.

Key points

  • Since the coronavirus disease 2019 pandemic, several businesses have closed and many people have been left jobless.

  • The current recession will have a negative impact on dentists and dental offices in the United States and worldwide.

  • The modern-day dentist will need to be conservative and may need to implement payment plans as means to encourage patients to invest in implant treatment.

  • Long spanned and/or complex implant cases should have mandatory occlusal-protected appointments.

  • The general practitioner is challenged on a daily basis to make clinical decisions based off of the patient’s anatomy, needs, and wishes, in order, to select the best prostheses.

More than 5 million dental implants are placed annually by dentists in the United States, according to the American Dental Association. Oral health enhances a patients’ quality of life. Pjetursson and colleagues , reported that “the survival rates of implant-supported single crowns and fixed dental prostheses (FDPs) range between 89% and 94% at 10 years.

The current pandemic of coronavirus disease 2019 (COVID-19) has caused >1 million deaths worldwide and >230,000 deaths in the United States, and these numbers are growing every day. On a brighter note, more than 30 million people have recovered worldwide. Coronaviruses are a group of viruses that can cause a variety of respiratory illnesses (ie, pneumonia) that can lead to respiratory failure. SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) was renamed COVID-19 (coronavirus disease 2019). Current medical/ dental literature on the COVID-19 pandemic suggests that dentists, oral surgeons, and otolaryngologists–head and neck surgeons are at high risk of contagion owing to the exposure to saliva, blood, aerosol, and droplets. , This crisis has resulted in people being quarantined in their homes (in attempts to contain the spread of the virus), schools closing, restaurants closing, businesses cutting staff or closing themselves, and ultimately leading to millions of people losing their jobs (income). More than 30 million people in the United States have claimed themselves jobless (unemployed) at the end of April, 2020. The recession in the United States will eventually rebound in a positive direction with time. At the beginning of the pandemic, the effect on dentists and staff were challenging owing to some office closings and the temporary hold on all elective procedures (recommended by state governors), while only focusing on dental emergencies. The dental implant market in the United States and globally will take a hit financially during the pandemic. There will be patients who were able to afford implants (before the pandemic) who will be unaffected, there may be another working class who (once were able) may not be in a position to afford or consider implants as a necessity. The modern-day dentist should be understanding, may have to be more conservative with their patients’ treatment plan, and suggest to them ways of investing in an implant 1 or 2 at a time. The dental office may need to implement down payments or payment plans (before treatment) as a way of encouraging implant care. This consideration can be extended by the doctor that has a heart for providing quality dentistry for their fellow man or woman, that is, the patient. The modern-day dentist or general practitioner (GP) should implement reproducible treatment protocols, which will propel more successful outcomes. The 5 concepts for dental implant success include (1) past medical history, (2) examination and occlusion, (3) dental imaging, (4) fixed verses removable prosthodontics, and (5) surgery, and are reviewed in this article ( Fig 1 ). The goal is to bring forth proven contributions of evidence based dentistry in the complex discipline of dental implantology in a format that will strengthen the decision making process of the GP in the clinical setting. At the end of this article, the reader will be able to make efficient, intelligent, and methodical treatments based off current scientific research (systemic reviews, randomized controlled trials, meta-analysis, and retrospective studies) and the foundation of textbooks on dental implantology. The objective during this challenging time in our profession is to make dental implants affordable for the patient, enhance their ability to function, improve their aesthetics, and improve their overall quality of life. Pictures (from cases) have been included to describe certain topics discussed, is in no way to lead or influence the GP to use a particular treatment. The pictures are to be used as visual aids to bring light to the literature being discussed. Because there are so many variables mentioned in this article, the reader should always consider whatever works for them or more conservative approaches when it comes to their case(s).

Fig. 1
The 5 concepts for dental implant success.
( Courtesy of Ricardo A. Boyce, DDS, FICD. © 2015.)

The first discussion will be on the use of personal protective equipment (PPE) for the safety of the doctor(s), dental hygienist, and staff. The Centers for Disease Control and Prevention and other state and local health department have continued to instruct and respond to the outbreak of the COVID-19 respiratory disease. All patients should be triaged over the phone, queried about any recent travel histories, if they have tested positive for COVID-19 (or awaiting test results), if they have a fever (>100.4°F), chills, shaking, body aches, headache, itchy throat, dry throat, dry cough, shortness of breath, or loss of smell or taste. They should also be asked if their family members or loved ones (having contact) have had the virus. The patients should be instructed to wear some sort of mask or face covering to protect themselves and others before their office visit. Please note that the questions mentioned should be followed up on arrival to the dental clinic. All members of the health care team (dentists, dental hygienists, dental assistants, and receptionist) should be wearing masks and washing their hands throughout the day and be prepared to triage all patients (before any treatment). The temperature should be taken with a contact-free forehead thermometer. Patients should have a review of systems and their vitals (temperature) checked before treatment. Those patients that present to the office (or queried over the phone) with a fever (>100.4°F) and any of the other symptoms mentioned should not be treated and given another appointment at least 2 weeks from the date (or until the patient is cleared from the virus/disease). , The dentist can prescribe acetaminophen (if the patient does not have in their possession or at home) should any fever exist and be instructed to contact their physicians and/or specialists for medical advice (a medical consult can be written). If the patient presents with symptoms of new confusion, dyspnea, severe dysphagia, airway compromise, bluish lips (or face), persistent pain or pressure in the chest, and fever, then emergency medical services should called immediately. Until more is learned about this virus, appointments should be booked to allow social distancing in the reception area and every patient should be treated as if they were COVID-19 positive. The use of air purifiers or air scrubbers (with HEPA filters and UVC light disinfection) can be considered for each treatment room. The rooms to be allowed to be aired out (or with the windows open) in between cases. Dental procedures can be performed if there is absence of contacts and/or symptoms. High-speed handpieces and ultrasonic devices should be minimized; the use of rubber dams are highly recommended. ,

When patients arrive they should be given level 1 masks (if they do not present with one) to wear in waiting room. The goal of the office staff should be to protect all patients and staff. When the procedures are about to start, all staff (in the surgical room) should be wearing N-95 or KN95 or level 3 (depending on the procedure) masks or masks with a face shield or goggles and/or a separate face shield; in addition, a full-length gown should also be worn. The clinician can review a list of guidelines and recommendations from the Centers for Disease Control and Prevention’s website ( ). Good judgment for PPE should be used for the type of procedure, because it can be adjusted for minor follow-up procedures. The dental staff should perform hand hygiene using alcohol-based hand sanitizer and alcohol hand rubs before and after all patient contact, contact with potentially infectious material, and before putting on and upon removal of PPE, including gloves. The recommendation is to wash hands with soap and water for at least 20 seconds. If hands are visibly soiled, use soap and water before returning to alcohol-based hand sanitizer.

The donning (putting on) and doffing (taking off) should be done by those health care workers who are treating and in direct contact with patients. Those dental professionals who work in a hospital or have to consult COVID-19–infected patients (on the floors) may feel more comfortable using a P 100 or N 100 mask instead of an N-95 mask. Any clinician who will be performing implant procedures in the hospital operating room will be practicing surgical scrubbing, gowning, and gloving, and others can obtain a more detailed description of donning and doffing on the Centers for Disease Control and Prevention’s website ( ).

Good oral health is a shared responsibility between the patient and the dental provider. Patients must be informed and motivated to perform their daily home care duties until their next visit (or recall). Prudent safety recommendations for the GP providing care for implants in the ambulatory setting/dental office include but are not limited to (1) placing the patient in an upright position (whenever possible), (2) placement of a 4 × 4 gauze in the area of the oropharynx to protect objects falling (if the office does not have them, a 2 × 2 will be suffice, unfolding it will be even better), and (3) attach dental floss to Hex tools ( Fig. 2 ). In the unlikely case an implant part should accidently be swallowed by the patient, they will need to be directed to the nearest hospital for a chest radiograph.

Fig. 2
Restorative tools with floss attached to prevent aspiration.

The GP often instructs the patient how to maintain their dentition, as well as, having the following extended responsibilities: (1) obtain a good medical history, (2) request a medical consult with the patient’s physician or specialist (when necessary), (3) obtain necessary laboratory tests based on the patient’s past medical history (ie, complete blood count with differential, hemoglobin A1c, international normalized ratio, etc), and (4) inform the patient of their risk factors associated with dental implant placement. An updated list of medical conditions with risk factors for failure or potential complications of implant placement are provided in Box 1 .

Box 1
Risk factors for implant placement

Moderate to severe neutropenia Atypical odontalgia or atypical facial pain
Patients on corticosteroids Radiation therapy to the head and neck
Cancer chemotherapy Myocardial infarction within 6 mo
Patients on IV bisphosphonates Gravid patient
Poorly controlled diabetics Heavy smoking habits
Malignancy/terminal illness Cluster phenomenon
Psychological instability Parafunctional habits
Selective serotonin reuptake inhibitors Proton Pump Inhibitors

There are several documented literatures on the cluster phenomenon and parafunctional habits associated with implant failure. Rose and colleagues stated that “meticulous screening and patient selection can help reduce the risk of failure or potential complications during implant treatment.” Potential complications in the risk factor category include to discomfort, pain, and purulence. Patients with multiple comorbidities and taking multiple medications may be potential risks for implant failure. Systematic reviews and meta-analysis have proved that there is a statistically significant increased implant failure rate with patients on selective serotonin reuptake inhibitors and proton pump inhibitors. If the patient (symptomatic or asymptomatic) asks for the implant to be removed owing to any of the aforementioned reasons (included in Box 1 ), the implant is considered to have failed.

Individual risk assessments are necessary before implant surgery. In light of COVID-19, geriatric patients with serious chronic diseases (ie, pulmonary, cardiac, etc) may be at increased risk of sudden death; therefore, medical consults should be sent to physicians and specialist before implant surgery (now more than ever). As for these older patients, it may be safe and wise to provide alternative prosthodontic treatment in the form of conventional partial dentures and/or complete dentures.

The GP should be skilled enough to handle the implant case and if not then refer the patient to a dental specialist who can execute surgical strategies for the various hard and soft tissue deficiencies, such as (1) anatomic preconditions, (2) lack of keratinized mucosa, (3) local diseases affecting the teeth and implants, (4) mechanical overload, (5) tissue morphology and phenotype, (6) expansion of the floor of the sinus, (7) extraction(s), (8) trauma to orofacial structures, (9) migration of teeth and malpositioning of implants, and (10) iatrogenic factors.

Chiapasco and colleagues listed 5 main methods to augment the local bone volume at deficient sites as follows: (a) osteoinduction by the use of growth factors; (b) osteoconduction where a grafting material serves as a scaffold; (c) distraction osteogenesis, by which a fracture is surgically induced and then pulled apart; (d) guided bone regeneration, which allows spaces maintained by barrier membranes to be filled with bone; and (e) revascularized bone grafts, where vital bone segment is transferred to its recipient bed with its vascular pedicle. There are different regenerative techniques that can be implemented to reconstruct deficient alveolar ridges, namely, lateral, vertical, or combined bone augmentation. The approaches to achieve this reconstruction is by the use of bone blocks, particulated grafts, and/or barrier membranes. There are a variety of biomaterials that can be applied, including autogenous, allogenic, xenogenic, and synthetic bone substitute (resorbable and nonresorbable). The goal is to achieve primary stability of the implant and avoid any micro movement, which could lead to poor revascularization of the graft site.

There are no well-documented series of scientific studies that show the superiority of an implant company over another. The most important biological event (of osteointegration) is in the clinical healing phase of the dental implant is cell adhesion at the interface between it and the host tissue. A meta-analysis and systematic reviews have showed that rough-surfaced implants demonstrated favorable results compared with machined implants. Ogle also stated that “the success and failure is more dependent on patient related, procedural, and prosthetic parameters than implant shape.”

Clinicians interested in short implants (≤6 mm) should be mindful that studies have shown higher rates of prosthetic complications (microrotation and rocking). , The complications and rotational movements seem to decrease when the prostheses were splinted. Meta-analysis of randomized clinical trials reported that long implants show a higher survival rate than extrashort implants (after a 5-year timeframe).

Chen and Buser published a list of protocols for implant placement after extractions: (a) type 1 (immediate implant placement): the implants are placed on the same day as the extraction; (b) type 2 (early implant placement): the implants are placed 1 to 2 months after the extraction; (c) type 3 (delayed implant placement): the implants are placed 3 to 4 months after the extraction; and (d) type 4 (late or conventional placement): 4 to 6 months or greater after implant placement. The patient who presents with infection in the bone may benefit from the delayed or late/conventional to improve the chances of success. In cases where there is difficulty in achieving primary stability (and challenges to stabilize the implant), good clinical judgment would be to consider a conventional loading approach to avoid micromovements to increase the survival rate, which directly impacts the affect the esthetic outcome. Canellas and colleagues showed a statistically significant difference in favor of delayed implant placement in their meta-analysis. Gallucci and colleagues created a comprehensive protocol combining implant placement and loading ( Fig. 3 , highlighting the well documented and insufficiently documented cases):

  • Type 1A: immediate placement and immediate restoration/loading

  • Type 1B: immediate placement and early restoration/loading

  • Type 1C: immediate placement and conventional restoration/loading

  • Type 2A: early placement with soft tissue healing and immediate restoration/loading

  • Type 2B: early placement with soft tissue healing and early restoration/loading

  • Type 2C: early placement with soft tissue healing and conventional restoration/loading

  • Type 3A: early placement with partial bone healing and immediate restoration/loading

  • Type 3B: early placement with partial bone healing and early restoration/loading

  • Type 3C: early placement with partial bone healing and conventional restoration/loading

  • Type 4A: late placement and immediate restoration/loading

  • Type 4B: late placement and early restoration/loading

  • Type 4C: late placement and conventional restoration/loading

Fig. 3
Classification according to implant placement and healing protocol.
( From Gallucci GO, Hamilton A, Zhou W, et al. Implant placement and loading protocols in partially edentulous patients: A systemic review. Clin Oral Implants Res. 2018;29(Suppl 16):126; with permission.)

Gallucci and colleagues stated that type 1C is the most scientifically and clinically validated approach. The most documented approach, type 4C, is the standard of care when treatment modifiers such as bone augmentation, low insertion torque, reduced diameter implants, and patient local and systemic factors are present. The Group 2 ITI Consensus Report reviewed these new implant protocols for descriptive analysis: (a) immediate implant placement, same day as the extraction(s); (b) early implant placement: (soft tissue healing) 4 to 8 weeks or (partial bone healing) 12 to 16 weeks after the tooth extraction(s); and (c) late implant placement: placed after complete bone healing, more than 6 months after tooth extraction. The implant loading protocols defined as follows: (a) immediate loading: dental implants are connected to a prosthesis in occlusion with the opposing arch within 1 week subsequent to implant placement; (b) immediate restoration: dental implants are connected to a prosthesis, held out of occlusion with the opposing arch within 1 week subsequent to implant placement; (c) early loading: dental implants are connected to the prosthesis between 1 week and 2 months after implant placement; and (d) conventional loading: dental implants are allowed a healing period of more than 2 months after implant placement with no connection of the prosthesis.

Morton and colleagues showed the percentage of the survival rates for the new set of protocols (types 1A–4C; see Fig. 3 ). Their consensus statement on this topic revealed a 98% survival rate with type 1A (yellow); a 98% survival rate with type 1B (yellow); a 96% survival rate with type 1C (green); types 2A and 2B both have clinically insufficient documentation (red); a 96% survival rate with type 2C (green); a 98% survival rate with type 4A (yellow); a 98% survival rate with 4B(green); and a 98% survival rate with type 4C(green). The reader should be mindful there is no gold standard for implant placement after extraction(s); however, the implant placement and loading protocol should be planned before surgery.

Establishing proper occlusion can dictate the success of each case. Occlusal treatment at the time of delivery and at follow-up visits cannot be overemphasized. Several studies , have proven that most reported complications (prosthetic or bony) are associated with occlusion. In dental implantology, another form of dental implant complication(s) refer to “a problem with any of the replaceable components of the implant system.” Misch stated that “most common complications of the implant prostheses relate to biomechanical factors, such as porcelain fracture, unretained prostheses (cement or screw), abutment screw loosening, early implant failure after loading, and implant component fracture. The GP is encouraged to implement an occlusal plan to provide an implant-protective occlusion to decrease biomechanical complications and improve clinical longevity. It has been documented that the implant system handles the stress of mastication and occlusal interferences poorly. If occlusal treatment visits are not properly provided for the patient it can result in implant(s) failure. The benefits of implant-protective occlusion are as follows: (1) no premature occlusal contacts or interferences, (2) mutually protected articulation, (3) implant body angle to occlusal load, (4) cusp angle of crowns, (5) cantilever or offset loads, (6) crown height (vertical height), (7) implant crown contour, (8) occlusal contact position, (9) timing of occlusal contacts, and (10) protect the weakest component. The screw could fracture as a result of occlusal overload or torqueing beyond the manufacturer’s recommendation. The sequence of internal mechanical complications of the screw that can lead to failure are as follows: the screw loosening leading → screw bending; the screw bending leading → screw fracturing; and screw fracturing leading → fracturing of the platform of the implant, which could ultimately lead to failure of the implant. It is recommended that all bent screws be replaced by new ones before retorqueing, owing to the high risk of breakage (this can be requested by the manufacturer or the dental laboratory). It is important to note that, after the implant placement, the cover screw, healing cap, and temporary crown should be hand torqued until delivery of the final restoration(s) or prostheses when it will be torqued according to the manufacturer’s recommendation. There are a few times when skillful clinicians may be fortunate enough to remove a broken screw embedded within the implant. If not possible, the implant may have to be buried (leaving it nonfunctional) or be removed (trephination) or a cast post/core and crown be cemented. If a problem like one of these described occur in the office then referral to a specialist would be recommended.

Papaspyridakos and colleagues revealed in their systematic review that “wears” are the most common minor complication and “fracture of the prosthetic material” are the major complication with implant-supported fixed complete dental prostheses for the edentulous patients. They went further to recommend for patients to wear nightguards to prevent any complications of the prostheses. A more current retrospective study (with 1–12 years of follow-up) of implant-supported fixed complete dental prostheses detailed (the annual rate in percentage) of minor complications as (1) wear of the prosthetic material (9.8%), (2) decementation of cement retained implant-supported fixed complete dental prostheses (2.9%), and (3) loss of the screw access filling material (2.7%). The annual rate of major complications from this same study are as follows: (1) fracture of prosthetic material (1.9%), (2) fracture of the occlusal screw (0.3%), and (3) fracture of the framework (0.3%). Moreover, to avoid repairs, remakes, and wasted chair time, a nightguard as a part of the final delivery is recommended. The use of nightguards and orthodontic retainers have been recommended in the partially dentate patient (with implants) to prevent interproximal contact loss, which could lead to peri-implantitis. There are a number of clinical complications published in the literature that may compromise the successful outcome of dental implants (ie, biologic, technical/mechanical, esthetic, or phonetic). , Heitz-Mayfield and colleagues stated that “Bleeding on probing (BOP) has a positive predictive value (7% to 58%) for the diagnosis of peri-implantitis.” Peri-implant mucositis characteristically includes BOP, and/or suppuration, probing depths of less than 4 mm with no evidence of bone loss (is reversible), is considered a precursor to peri-implantitis. A diagnosis of peri-implantitis involves evidence of inflammation, infection, and progressive bone loss (classified as mild, moderate, or severe), if not treated can lead to failure of the implant.

Over the past 2 decades, cone beam computed tomography has proved to become a valuable armamentarium in dental implantology treatment planning ( Fig. 4 ). , This 3-dimensional imaging modality allows the clinicians the ability to access bone density before implant placement, measure the bone height, and width to properly predict the placement of the implant more accurately. This allows the GP (along with the help of the dental laboratory) the ability to develop a more “prosthetically driven” process, to allow the patient the option of receiving a prosthesis on the day of surgery. Moreover, this outcome should never be promised to the patient because of the possibility of complications that can occur somewhere in the case (ie, unsatisfactory aesthetics). It is imperative that the surgeon use cone beam computed tomography scans to assess vital structures in the image of the maxilla and/or mandible. An awareness and knowledge of surgical anatomy is important to the success of the case. Aziz affirmed that “prevention of an inferior alveolar nerve (IAN) injury is directly related to proper and thorough preoperative implant planning. He also stated, “The etiology of IAN injury is usually associated with inadequate planning or overzealous implant placement (ie, miscalculation). This miscalculation can also occur in the area of the maxillary sinuses, the mental foramen, nasopalatine canal, and the lingual concavity of the mandible. There are a variety of virtual systems ( Figs. 5 and 6 ) on the market for the clinician to choose from to plan for the placement of implant(s). The modern-day GP can use software to select the implant company, choose the length of the implant, platform size, draw the nerve (if needed), choose virtual teeth (and abutment), and position (move and rotate) the implant to prevent any perforations and fenestrations ( Fig 6 ).

Fig. 4
( A ) Cone beam computed tomography. ( B ) Axial view of cone beam computed tomography.

Mar 21, 2021 | Posted by in General Dentistry | Comments Off on Prosthodontic Principles in Dental Implantology
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