▋ Introduction
Antibiotics can be classified into two categories: bacteriostatic and bactericidal.

Bacteriostatic antibiotics: These do not kill bacteria directly but inhibit their growth, allowing the host’s immune system to effectively eliminate the pathogens and resolve the infection.

Bactericidal antibiotics: These act by directly killing the bacteria.

▋ Commonly Used Oral Antibiotics in Dentistry
Bactericidal Antibiotics:

Penicillins: Amoxicillin, Augmentin, Unasyn, Ampicillin.

Cephalosporins: Classified into 1st to 5th generations based on their antimicrobial spectrum. Currently, only the 1st to 3rd generations are available in oral dosage forms in Taiwan (e.g., 1st gen: Cephalexin; 2nd gen: Cefuroxime; 3rd gen: Cefixime).

Bacteriostatic Antibiotics:

Tetracyclines: Tetracycline, Doxycycline, Minocycline.

Macrolides: Erythromycin, Clarithromycin, Azithromycin.

Lincosamides: Clindamycin.

▋ Is Penicillin Allergy Linked to Implant Failure?
Research indicates that Amoxicillin is the antibiotic most likely to cause allergic reactions, with a reported prevalence of 7%–12% in Western populations and 2%–5% in Asian populations (specifically Hong Kong). For patients with a penicillin allergy, many clinical guidelines suggest Clindamycin as a primary alternative.

However, a 2023 review article (Clin Oral Impl Res. 2023;34: 651-661) found that patients who self-reported a penicillin allergy and were prescribed Clindamycin had over three times the risk of implant failure, with a significantly higher incidence of early implant failure (Fig. 1).

Another 2021 study showed that the Clindamycin group, compared to the Amoxicillin group, had:

6.9 times higher risk of infection-related failure after ridge augmentation.

4.5 times higher risk of failure after socket preservation.
Across a total of 2,961 sites (ridge augmentation + socket preservation), the Clindamycin group faced a 5.5 times higher risk of infection (Int J Oral Maxillofac Implants. 2021;36(1):122-25).

The exact mechanism remains unclear. Some studies suggest Clindamycin may exert toxicity on osteoblasts (Arch Orthop Trauma Surg. 2008), while others point to Clindamycin-resistant bacteria, such as Prevotella, as the cause of failure.

▋ Clinical Recommendations and Author’s Perspective
When managing patients who self-report a penicillin allergy for implant-related surgeries, the following strategies are recommended:

A. Detailed Allergy Assessment & Delabeling:
Patients should be categorized into Low Risk or High Risk (Table 1).

Low Risk: Symptoms such as mild diarrhea, non-immediate rash, or vague family history of allergy.

Management: These patients can undergo Penicillin Allergy Delabeling (Fig. 2). Refer the patient to an immunologist for a Penicillin Skin Test or an Oral Amoxicillin Challenge.

Note: Research shows that over 90% of patients who self-report a penicillin allergy are found not to be allergic upon formal testing.

B. Selecting Alternative Antibiotics:

First Choice: Macrolides (e.g., Erythromycin).

Second Choice: Cephalosporins.

Caution: Both Penicillins and Cephalosporins are Beta-lactams, raising concerns about cross-reactivity. However, recent studies show the cross-reactivity rate is less than 1%.

Conclusion
Penicillins remain the gold standard for dental treatments. If a patient “self-reports” an allergy, a referral for formal allergy testing is advised. For patients with a confirmed penicillin allergy undergoing implant or grafting surgery, Erythromycin is suggested as an alternative. These conclusions are based on observational studies; as high-level evidence is still evolving, clinicians should use this information as a reference for their practice.